thesis LPG HF Final

A REVIEW OF LPG BASED HYDRAULIC FRACTURING AS AN
ALTERNATIVE TO SLICKWATER HYDRAULIC FRACTURING
BY
EMMANUEL UMO
5140150
SEPTEMBER 2014
A dissertation submitted the Department of Geography, Environment and
Disaster Management, Faculty of Business, Environment and Society,
Coventry University in partial fulfilment of the requirements for MSc in Oil
and Gas Management

EMMANUEL UMO 5140150 Page 1
ABSTRACT
Extensive water use for the recovery of natural gas from unconventional reservoirs
has led to concerns around the world over the application of hydraulic fracturing
(HF). Efforts to improve productivity while reducing water consumption has led to
the development of waterless alternatives for HF such as LPG based hydraulic
fracturing. LPG based HF was thus reviewed as an alternative to the more widely
applied slickwater HF. The benefits and challenges of LPG based HF as an alternative
to slickwater HF was investigated via an analysis of a case study of the McCully field
and relevant literature. Results showed that LPG based HF increased effective fracture
length, enhancing productivity with the potential of addressing the concerns
associated with slickwater HF such as high water consumption, water contamination,
vehicle accidents and induced seismicity. Based on these findings, recommendations
on the application of LPG based HF as a waste management strategy and as an
alternative to slickwater HF due to its approach which places it at the highest order in
the waste management hierarchy is discussed. Directions for further research were
also suggested in the study.
KEYWORDS: hydraulic fracturing, LPG, propane, slickwater, shale gas

Table of Contents
ABSTRACT ..............................................................................................................................................................1
LIST OF FIGURES ..................................................................................................................................................5
LIST OF TABLES....................................................................................................................................................6
LIST OF ABBREVIATIONS.................................................................................................................................6
RESEARCH DECLARATION..............................................................................................................................8
ACKNOWLEDGEMENT ......................................................................................................................................9
CHAPTER 1............................................................................................................................................................10
1.0 INTRODUCTION ...........................................................................................................................................10
1.2 JUSTIFICATION.............................................................................................................................................12
1.3 AIM ....................................................................................................................................................................12
1.4 RESEARCH QUESTION ..............................................................................................................................12
1.5 OBJECTIVES...................................................................................................................................................12
CHAPTER 2............................................................................................................................................................13
2.0 LITERATURE REVIEW ...............................................................................................................................13
2.1 CONVENTIONAL AND UNCONVENTIONAL HYDROCARBONS...............................................13
2.2 SHALE GAS.....................................................................................................................................................13
2.3 HYDRAULIC FRACTURING.....................................................................................................................14
2.4 WATER BASED HYDRAULIC FRACTURING.....................................................................................17
2.4.1 SLICKWATER HYDRAULIC FRACTURING ....................................................................................17
2.3.2 LINEAR POLYMER FLUIDS ..................................................................................................................18
2.3.3 CROSS-LINKED GELS .............................................................................................................................19
2.3.4 VISCO-ELASTIC SURFACTANTS (VES) ...........................................................................................19
2.4 CONCERNS WITH WATER BASED HYDRAULIC FRACTURING ...............................................20
2.4.1 WATER CONSUMPTION AND POLLUTION....................................................................................20
2.4.2 AIR POLLUTION........................................................................................................................................21
2.4.3 LAND POLLUTION ...................................................................................................................................21
2.4.4 MAN-MADE EARTHQUAKES...............................................................................................................22
2.5 SWISS CHEESE MODEL .............................................................................................................................22
2.6.0 WATERLESS HYDRAULIC FRACTURING ALTERNATIVES ....................................................22
2.6.1 LPG.................................................................................................................................................................23
2.7 WASTE MANAGEMENT STRATEGIES IN SHALE GAS PRODUCTION....................................25
CHAPTER 3............................................................................................................................................................28
3.0 RESEARCH METHODOLOGY ..................................................................................................................28
3.1 INTRODUCTION ...........................................................................................................................................28
3.2 RESEARCH STRATEGY .............................................................................................................................28
3.3 CASE STUDY APPROACH .........................................................................................................................29
3.4 LITERATURE REVIEW AS A METHOD ................................................................................................30
3.5 DATA COLLECTION....................................................................................................................................30

3.6 DATA ANALYSIS..........................................................................................................................................30
3.6.1 EVALUATION OF SECONDARY DATA ............................................................................................32
3.7 RESEARCH LIMITATIONS ........................................................................................................................32
3.8 ETHICAL ISSUES ..........................................................................................................................................32
3.8 PROJECT FLOW DIAGRAM ......................................................................................................................33
CHAPTER 4............................................................................................................................................................34
4.0 RESULTS DISCUSSION AND ANALYSIS.............................................................................................34
4.1 CASE STUDY ANALYSIS...........................................................................................................................34
4.1.1 BACKGROUND INFORMATION ON MCCULLY FIELD ..............................................................34
4.1.2 WATER BASED HF ...................................................................................................................................34
4.1.3 LPG BASED HF...........................................................................................................................................35
4.1.4 RESULTS AND ANALYSIS AND DISCUSSION ..............................................................................35
4.2 INDUSTRY ANALYSIS AND DISCUSSION .........................................................................................38
4.2.1 WATER CONSUMPTION.........................................................................................................................38
4.2.2 WATER CONTAMINATION...................................................................................................................40
4.2.3 VEHICLE TRAFFIC ...................................................................................................................................42
4.2.5 INDUCED SEISMICITY............................................................................................................................43
4.2.6 CLIMATE CHANGE ..................................................................................................................................44
4.3 SWOT ANALYSIS .........................................................................................................................................45
4.3.1 SWOT ANALYSIS OF WATER BASED HF........................................................................................45
STRENGTHS ..........................................................................................................................................................45
WEAKNESSES ......................................................................................................................................................46
OPPORTUNITIES .................................................................................................................................................48
THREATS................................................................................................................................................................48
4.3.2 SWOT ANALYSIS OF LPG BASED HF ...............................................................................................49
STRENGTHS ..........................................................................................................................................................49
WEAKNESSES ......................................................................................................................................................50
OPPORTUNITIES .................................................................................................................................................50
THREATS................................................................................................................................................................51
SUMMARY.............................................................................................................................................................52
CHAPTER 5............................................................................................................................................................54
5.0 CONCLUSION ................................................................................................................................................54
5.1 – INTRODUCTION........................................................................................................................................54
5.2 – MAIN FINDINGS OF THE STUDY .......................................................................................................54
5.3 LIMITATIONS ................................................................................................................................................55
ETHICS APPROVAL...............................................................................................................................................72
Low Risk Research Ethics Approval .............................................................................................................72
Project Title ...................................................................................................................................................72
Principal Investigator Certification .............................................................................................................72
Principal Investigator .............................................................................................................................72
Student’s Supervisor (if applicable)................................................................................................72

Low Risk Research Ethics Approval Checklist...................................................................................73
Applicant Details.......................................................................................................................................73
Project Details............................................................................................................................................73
Participants in your research .............................................................................................................73
Risk to Participants .................................................................................................................................73
Risk to Researcher ..................................................................................................................................75
Informed Consent of the Participant...............................................................................................75
Participant Confidentiality and Data Protection ........................................................................76
Gatekeeper Risk........................................................................................................................................76
Other Ethical Issues................................................................................................................................76

LISTOF FIGURES
Figure 1.1: Global distribution of Shale Resources
Figure 2.1: illustration showing type of natural gas resources
Figure 2.2: Illustration of well casing for unconventional wells
Figure 2.3: Hydraulic fracturing illustration
Figure 2.4 Summary of water based hydraulic fracturing history
Figure 2.5 Distribution of Shale Plays in the United States
Figure 2.6 Illustration of VES
Figure 2.7 The Potential Impacts of Hydraulic Fracturing on Drinking Water
Figure 3.1 Triangulation of quantitative and qualitative data
Figure 4.1 Comparison of fluid recovery between LPG and Water based fracturing
fluids
Figure 4.2 Comparison of gas production rates of gas wells with LPG based (red bar)
treatment and water based (blue bars) treatments
Figure 4.3 Production rates from different fracturing fluids
Figure 4.4: Baseline US Daily Water Consumption
Figure 4.5: Water Consumption across Shale Plays in the United States and Canada
Figure 4.6: Water Consumption in the Marcellus Shale
Figure 4.7: Daily Water Consumption in Texas
Figure 4.8: methane concentrations near shale gas production areas
Figure 4.9: Comparison of Number of Trucks Required for Hydraulic Fracturing
Figure 4.9.0: Accident rate comparisons between 2 Pennsylvania Shale Gas extracting
Counties
Figure 4.9.1: Illustration of fluid block due to water based hydraulic fracturing
Figure 4.9.2: Illustration of the potential of LPG based hydraulic fracturing
Figure 4.9.3: Annual number of earthquakes in Oklahoma above 3.0 Magnitude

LISTOF TABLES
Table 1: Constituents of Hydraulic Fracturing Fluid
Table 4.1: Reservoir Parameters of the McCully Field
Table 4.2 Comparison of the Properties of Water, Propane and Methane
Table 4.3: Variations in Water Costs in US Shale Gas Development
Table 4.4 Lifetime Methane Emissions Estimate from Some Shale Plays In The
United States
TABLE 4.5: Swot Analysis of Water Based HF
Table 4.6: Swot Analysis of LPG Based HF
LISTOF ABBREVIATIONS
BP British Petroleum
BPM Barrels per Minute
CCTV Closed Circuit Television
CMHEC CarboxyMethyl HydroxyEthyl Cellulose
CMHPG CarboxyMethyl HydroxyPropyl Guar
CRS Crash Report System
DECC Department of Energy and Climate Change
EC European Commission
EIA Energy Information Administration
EOR Enhanced Oil Recovery
EPA Environmental Protection Agency
HEC Hydroxyethyl Cellulose

HF Hydraulic Fracturing
HPG Hydroxy Propyl Guar
IEA International Energy Administration
IPIECA International Petroleum Industry Environmental Conservation
Association
Km Kilometre
LBNL Lawrence Berkeley National Laboratory
LPG Liquefied Petroleum Gas
mg/L Milligrams per Litre
MMcf Million Cubic Feet
NORM Naturally Occurring Radioactive Material
NYSDEC New York State Department of Environmental Conservation
PADEP Pennsylvania Department of Environmental Protection
SPE Society of Petroleum Engineers
TDS Total Dissolved Solids
UK United Kingdom
US United States
USGS United States Geological Survey
VES Visco Elastic Surfactants
VOC Volatile Organic Compounds

RESEARCH DECLARATION
I declare that this report is entirely my own work and that any use of the work of
others has been appropriately acknowledged as in-text citations and compiled in the
reference list. I also confirm that the project has been conducted in compliance with
the University’s research ethics policy. I agree that the project report can be made
available as a Reference Document for other students in the Department of
Geography, Environment and Disaster Management Information Room/Map Library.
Signed: EMMANUEL UMO .......................................... Date: 02/09/2014

ACKNOWLEDGEMENT
I give thanks to the Almighty God for sustaining me and helping me to overcome the
challenges throughout the duration of this research.
Special thanks to my parents, brothers and sisters, friends and flatmates for providing
me with the support required to succeed in this adventure.
I am immensely grateful to my Supervisor Okereke, N. U. for academic support and
guidance during the study and also my lecturer Adrian Wood who provided
immeasurable inspiration for the study.
I am also grateful to the Faculty of Business, Environment and Society for the
enabling atmosphere without which this academic exercise would have been
impossible.

CHAPTER 1
1.0 INTRODUCTION
Shale gas is considered to be a cleaner fuel source compared to other fossil fuels such
as coal and is projected to become constitute 53% of total natural gas production in
the United States (EIA 2014). EIA also projects that the use of natural gas as a fuel for
vehicles will rise nearly 12 percent per year through 2040 (EIA 2014). This indicates
rapid development in the direction of shale gas and shows the importance of natural
gas for global future energy requirements.
Shale gas is obtained from source rocks that have become reservoir rocks due to
available extraction technologies and favourable market prices (Jarvie et al. 2007).
Shale gas reservoirs typically contain large quantities of total organic carbon (TOC) in
fine grained rocks of low permeability (Passey et al. 2010) and are distributed in
every continent of the world EIA (2014), (see figure 1.1).
Figure 1.1: Global distribution of Shale Resources (EIA 2013)
In order to extract unconventional natural gas from shale, multi-stage hydraulic
fracturing (HF) also called fracking, is combined with horizontal drilling and these
have improved recovery rates from 2% to 50% in recent years (King 2010, Rahm
2011).
Water based HF, for example slickwater, linear and cross-linked gels are one of the
reasons for the rapid development of the shale gas industry (King 2010, Rogala 2012,
Ribeiro and Sharma 2013). Due to low cost and water availability, slickwater
fracturing has been the most popular approach used to get commercial production
rates from shale gas reservoirs (Schein 2008). HF is estimated to use between 2-10

million gallons of water (EIA 2014), leading to concerns over the large quantities of
required for shale gas extraction (Boudet 2012).
Although hydraulic fracturing has been in practice since 1947 as a treatment for
vertical wells of low productivity, increased concerns from the use of enormous
volumes of water, chemical additives, leaks from poor well casings and the handling
of HF wastewater (flowback) has generated a lot of controversy (Weinhold 2012,
Finewood and Stroup 2012). According to Weinhold (2012), HF wastewater contains
pollutants that can cause cancer, cardiovascular, respiratory, neurologic, and
developmental damage to human beings. Leaks of flowback during storage, treatment
and disposal have been identified as a potential source of environmental
contamination (Groat and Grimshaw 2012).
While (Entrekin et al. 2011, Fitzpatrick et al. 2011) state that the abstraction of large
quantities of water for HF puts pressure on water resources, opposition toward HF or
‘fracking’ as it is popularly is also based on arguments that it causes the release of
methane into the atmosphere, increasing greenhouse gases (Howarth et al. 2011,
Osborn et al. 2011, Jackson et al. 2013, Vengosh et al. 2014). Others state that the
chemical additives in water based fluids contaminate freshwater sources (Ferrar et al.
2013) and the disposal of flowback via injection well could cause man-made
earthquakes (Seeber et al. 2004). Some researchers have however disagreed with
some of these findings (Cathles et al. 2012).
There has also been evidence from the shale gas industry that water based HF could
damage the shale formation, leading to ineffective stimulation of the reservoir and
low productivity (Palisch et al. 2008). However, waterless alternatives such as liquid
CO2, liquid Nitrogen and LPG have been known to show better well performance
compared to water based HF (Ribeiro and Sharma 2013). Nevertheless, the
characteristics that make LPG excellent for the stimulation of shale gas reservoirs,
logistics and personnel safety concerns seems to be the main drawbacks that have so
far prevented its widespread application (Brino 2011).
Although the selection of fracturing fluids depends on key considerations such as
reservoir geology, presence of formation water (fluid native to the shale formation),
pumping pressure needs and cost (Ribeiro and Sharma 2013), there is an absence of
literature on the application of LPG based HF as an alternative to water based HF is
necessary as a possible waste management strategy. Furthermore, the waste
management strategy of the shale gas industry has largely been directed at
reuse/recycle and disposal rather than elimination and avoidance (Lottermoser 2011).
Finally, the distribution of shale gas resources cuts across all continents of the world,
thus the development and success of waterless alternatives of shale gas extraction in
the United States could be vital for meeting future economic, environmental, climatic
and public expectations across the globe especially in regions where water is a scarce
resource.

1.2 JUSTIFICATION
Several studies have been undertaken on the application of slickwater hydraulic
fracturing for the extraction on shale gas in the United States and Canada, including
its impacts on productivity, the environment and society. However, information on the
application of LPG based hydraulic fracturing has been limited especially as a waste
management strategy and also its potential impacts on the environment and society.
Thus this study is focused on LPG based HF as an alternative to slickwater HF
especially as a waste management strategy. Slickwater was selected for review due to
its position as the most widely applied shale gas well stimulation technique, while
LPG based HF was selected due to its novel approach towards the reduction of
materials employed for the extraction of shale gas and its suitability for the
stimulation of deeper unconventional wells.
1.3 AIM
The aim of this study is to review LPG based HF as an alternative to water based HF
especially as a waste management strategy during the extraction of shale gas.
1.4 RESEARCH QUESTION
The key research question is: whether LPG based hydraulic fracturing is suitable as an
alternative to water based hydraulic fracturing considering the current waste
management strategies in the shale gas industry.
1.5 OBJECTIVES
• To review the concerns associated with water based hydraulic fracturing.
• To review the performance of LPG based hydraulic fracturing for shale gas
extraction using a single case study.
• To determine the application of LPG based hydraulic fracturing as a waste
management strategy for the shale gas industry.

CHAPTER 2
2.0 LITERATURE REVIEW
2.1 CONVENTIONALANDUNCONVENTIONALHYDROCARBONS
Rogner (1997) regards conventional oil and gas as simply petroleum resources that do
not require enhanced recovery methods while Kohl (2007) regards conventional gas
as gas reserves that hold small easy to develop resources whereas unconventional gas
reserves are large and more difficult to develop resources. Thus improvements in
recovery methods and petroleum technology are necessary to make the development
of such resources possible (Bentley 2002).
2.2 SHALE GAS
Shale is an organic rich sedimentary rock containing kerogen, a source rock for
petroleum (Curtis 2002) and has been commercially exploited as a source of natural
gas for centuries (King 2010). However, the rapid growth of shale gas development in
recent years has been driven by advances in petroleum technology, increasing energy
demands and rising gas prices (Rahm 2011).
Hatfield (1997) had earlier predicted that there will be a significant decline in
conventional hydrocarbon resources in the first decade of the 21st century, Campbell
and Laherrere (1998), also stated that there has been a steady decline in the
production of oil and gas from conventional sources since the 1960s. However, both
admitted that the unconventional oil and gas reserves worldwide are still enough to
meet future global energy requirements. The exploitation of shale gas has now made it
possible to transition from the rapidly declining conventional gas resources to
unconventional resources to meet growing energy demands (Kerr 2010). Also
according to Hirsch (2008), since conventional gas production has already peaked,
producing liquid fuels from natural gas ensures that gas is poised to become the next
major fuel source for transportation (Hekkert et al. 2005).
Figure 2.1: illustration showing type of natural gas resources (EIA 2013)

With shale gas considered to be one of the transition substitutes for conventional oil
(Bartis et al. 2005), it is no surprise that natural gas from shale currently accounts for
over 23% of US natural gas production up from 1% in 2000, it increased to 14% by
2009 and is estimated to reach 49% by 2035 (IEA 2013, EIA 2014). Shale gas is also
considered to be a cleaner source of energy compared to other fossil fuels and is
estimated to become a significant source of energy constituting over 50% of all
natural gas produced by 2040 (EIA 2014).
Nevertheless, the extraction of natural gas from subsurface shale is not without some
challenges. Shale are usually buried 3000 – 7000ft below the earth surface and
development for shale gas production involves a combination of micro-seismic
imaging, horizontal drilling and multi-stage hydraulic fracturing (Rahm 2011).
2.3 HYDRAULIC FRACTURING
Hydraulic fracturing (HF) is a method used to stimulate hydrocarbon reservoirs of low
permeability to achieve commercial rates of production (Arthur et al. 2008). It
involves pumping water at very high pressures along with sand and chemicals into the
well bore. The combination of directional drilling and HF has led to the successful
extraction of oil and gas from low permeability hydrocarbon formations (Andrews et
al. 2009, Kuuskraa and Stevens 2009, EIA 2014). According to Arthur et al. (2008),
the design of HF treatments depends on a lot of factors such as the specific
characteristics of the shale formation (geophysical data and results from core
samples).
Hydraulic fracturing treatment was pioneered in 1947 at the Hugoton Gas Field in
Grant County, Kansas by Stanolind Oil. George P. Mitchell later developed the
modern method of HF of Shale formations using sand and water in the Barnett Shale,
Texas (Backwith 2012). The method has consequently been used to successfully
stimulate over 3 million wells worldwide (EIA 2013).
After the well is drilled, surface casing, conductor casing, intermediate casing and
production casings are put in place to maintain well integrity and protect the
surrounding groundwater resources from contamination (King 2010).
Figure 2.2: Illustration of well casing for unconventional wells (Stuart 2014)

Fracturing fluids (which is typically made up of 99.5% water and sand while chemical
additives consist of only 0.5% of the hydraulic fracturing fluid) are then pumped at
very high pressures into the wellbore to fracture the petroleum bearing formations.
The fluids usually consist of water, sand and chemical with various functions (see
table 1.0). Combined with horizontal drilling (a technique where the well is vertically
drilled hundreds of meters below the land surface and directed horizontally away from
the well bore to the target reservoir), multi stage HF of the shale formation is a
process where charges are set off in strategic sections of the well bore, perforating
through the steel and cement casings to create fissures in the shale formation (see
figure 2.3). Fracturing fluid is then pumped down the well at very high pressures to
expand the fissures. Proppants in the fracturing fluid keep the fissures open creating
pathways for fluid and gas to flow into the wellbore (see figure 2.3). This allows
several wells to be drilled and treated from a single wellhead. Recovered fluids called
flowback rise to the surface as a result of the internal pressures built up in the
reservoir following the HF treatment. The flowback is collected, stored and treated for
disposal (King 2010).
Figure 2.3: Hydraulic Fracturing illustration (Total 2014)
According to Burke et al. (2011), well productivity is greatly enhanced by horizontal
drilling and HF, the method also leads to a reduction in the size of the well pad and
the number of wells drilled. Revenue from mineral rights and job creation are also
some of the positive economic impacts of HF (Vaughan and Pursell 2010).
According to Bello and Wattenbarger (2010), unconventional gas reservoirs now
constitute a major source of US gas production. Due to multi-stage hydraulic
fracturing and horizontal drilling technologies, shale gas is expected to make up 50%
of the total natural gas production in the United States by 2040 (EIA 2013).
According to Samuelson (2012), Zoback et al. (2012), IEA (2013), HF has also
improved the recovery rates of natural gas reserves by over 50%.

Table 1.0: CONSTITUENTS OF HYDRAULIC FRACTURING FLUID (Stuart
2012)
CONSTITUENT COMPOSITION
(%)
EXAMPLE PURPOSE
Water and Sand 99.5 Sand suspension Sand grains act as
proppants to keep
micro fractures open
Acid 0.123 Hydrochloric
acid
Dissolves minerals and
initiates cracks in the
rock
Friction reducer 0.088 Polyacrylamide Minimizes friction
between the fluid and
the pipe
Surfactant 0.085 Isopropanol Increases the viscosity
of the fracturing fluid
Salt 0.060 Potassium
Chloride
Creates a medium for
the transport of brine
Gelling agent 0.056 Guar gum or
Hydroxyethyl
cellulose
Thickens water to
create sand suspension
Scale Inhibitor 0.043 Ethylene glycol Prevents scale deposits
in pipes
pH adjusting agent 0.011 Sodium or
Potassium
Carbonate
Maintains
effectiveness of
chemical additives
Breaker 0.010 Ammonium
persulphate
Allows a delayed
breakdown of gel
polymer chains
Cross linker 0.007 Borates Ensure the viscosity of
fracturing agents at
high temperatures
Iron control 0.004 Citric acid Prevents the
precipitation of metal
oxides
Corrosion inhibitor 0.002 n, n-dimethyl
formamide
Prevents pipe
corrosion
Biocide 0.001 Gluteraldehyde Minimizes the growth
of bacteria that
produce corrosive and
toxic by-products
Oxygen scavenger - Ammonium
bisulphite
Removal of oxygen
from fluid to prevent
corrosion

2.4 WATER BASED HYDRAULIC FRACTURING
To optimize gas production from shales, the choice of HF fluids must take into
consideration the geological properties of the shale formation in order to select the
appropriate fluid type, fluid volume, proppant type, and proppant concentration and
surface pump rates. Although a variety of fracturing agents exist such as water based,
oil based, alcohol based, emulsion based, foam based, acid based and gas based
hydraulic fracturing fluids, water based HF fluids are the most commonly applied HF
agents and these include (Luca 2013),
• Slickwater
• Linear Polymer Fluids
• Cross-Linked Gels
• Visco-Elastic Surfactants
Water based HF fluids have been used to stimulate unconventional gas reservoirs
since water from the Arkansas River was drawn to extract natural gas from the
Hugoton Field in 1956 (Britt et al. 2006). The most commonly applied water based
HF technique is the slickwater treatment (Luca 2013). However shale gas reservoirs
are often susceptible to formation damage from water based hydraulic fracturing
fluids (Bennion et al. 2000, Rogala et al. 2013, Wang et al. 2014, Bottero 2014).
According to Bennion et al. (2000) water trapped in the reservoir prevents maximum
gas recovery rates, while Rassenfoss (2013) adds that water in the shale formation
reduces gas permeability.
2.4.1 SLICKWATER HYDRAULIC FRACTURING
According to Schein (2008), slickwater HF is ‘a fracture treatment that utilizes large
volumes of water to create an adequate fracture geometry and conductivity to obtain
commercial production from low permeability reservoirs.’ According to Palisch et al.
(2008), slickwater fracturing fluids are water based hydraulic fracturing fluids with
chemical additives such as potassium chloride and polyacrylamide which are
introduced to help reduce friction and viscosity.
Figure 2.4 Summary of water based HF history (Sharma et al. 2004)

More recently, slickwater fracturing treatments have made a resurgence since it was
successfully applied by Mitchell Energy to stimulate the Cotton valley Sands in East
Texas in 1997 (Sharma et al. 2004, Palisch et al. 2007). Slickwater hydraulic
fracturing has since become the choice method for stimulating unconventional
reservoirs especially in the Barnett Shale of the Fort Worth Basin, Texas (Arthur et al.
2008). This has led to the practice spreading to other shale formations with similar
characteristics such as the Haynesville shale, Marcellus shale and Devonian Shale.
Others include the Mancos shale of the Uinta basin, Woodford shale of the Ardmore
basin, Eagle ford Shale and Mowry Shale of the Powder River Basin (see figure 2.5).
Figure 2.5 Distribution of Shale Plays in the United States
According to Palisch et al. (2008), over 30% of HF stimulation performed in the
United States in 2004 were slickwater fracturing treatments.
Nitrogen foam fracture treatments were the choice stimulation method for Fayettville
Shale reservoirs up till 2004 due to the high clay content, water availability and low
bottom-hole pressure of the formation. However by 2006, in a bid to cut overhead
costs, slick water treatments were introduced; while 1.8 million gallons of Nitrogen
Foam plus 750,000 pounds of proppant were applied to yield 204 MMcf of natural
gas, 2.8 million gallons of slickwater plus 940,000 pounds of proppant were applied
to yield 326 MMcf of natural gas (Palisch et al. 2008). However, due to its poor
proppant placement characteristics, slickwater HF treatments usually require higher
pumping rates of up to 100 BPM (Ribeiro and Sharma 2013). Another disadvantage
of slickwater treatments is the excessive water requirement which could result in
formation damage and probably social problems from domestic and agricultural users
(Cheng 2010).
2.3.2 LINEAR POLYMER FLUIDS
Polymers such as hydroxypropyl guar (HPG), hydroxyethyl cellulose (HEC),
carboxymethyl hydroxypropyl guar (CMHPG) and carboxymethyl hydroxyethyl
cellulose (CMHEC) are added to water to create a viscous gel that possesses good

proppant carrying and placement capabilities (EPA 2004). The advantages of linear
polymer gels for HF of shales lie in their ability to place proppant in high
permeability formations without the deposition of filter cake (Fisher et al. 2005).
While there is little fluid loss control due to fluid invasion of the shale formation, in
low permeability formations, there is a tendency for gel filter cake deposition on
fracture faces but with better fluid loss control (Palisch et al. 2008)..
2.3.3 CROSS-LINKEDGELS
Hydrated polymer gels created from Guar or HPG are usually crosslinked with Borate
to improve viscosity. An alteration of the fluid pH reverses the cross-linked gel
enabling rapid clean up. The result is a fracturing fluid with good proppant transport
and placement characteristics that improves the permeability and conductivity of the
fractures created (Luca 2013). An added advantage of cross-linked gels is its ability to
withstand temperatures of up to 300 degrees Fahrenheit while maintaining stable fluid
rheology (Halliburton 2011). Low fluid loss is also experienced with the application
of cross-linked gels. Borate cross-linked hydraulic fracturing treatments have been
known to return better well performance than slickwater HF treatments (Burke et al.
2011). However, although water based HF treatments do not perform better than
cross-linked gel HF treatments, the lower implementation costs of slickwater HF has
led to its more widespread application (Britt et al. 2006).
2.3.4 VISCO-ELASTIC SURFACTANTS (VES)
Visco-elastic surfactants are polymer-free fluids that possess enough viscosity for
hydraulic fracturing treatments without the need for polymer additives (Sullivan et al.
2006). Hydrophobic tails of surfactant molecules assemble in a water solution to form
worm-like micelles which mingle to create viscosity.
Figure 2.6 Illustration of VES (Sullivan et al. 2006)
VES could be anionic, cationic or zwitterionic. On contact with reservoir salts or
liquid hydroxcarbons, the viscosity of the VES breaks to allow for effective proppant
conductivity. In dry gas reservoirs however, a photo-electrolyte has to be introduced
to act as a breaker due to its ability to disrupt the worm-like micelles of the surfactants
(Sullivan et al. 2006).

VES has been utilised in the oil and gas industry for over 2 decades due to its property
as a fracturing fluid of very high zero-sheer viscosity, since proppant transport and
placement does not require the viscosity of other widely applied fracturing fluids
(Samuel et al. 1997, Gupta 2011). The low surface tension of VES ensures that no
clay control additives and flowback surfactants are required. Other advantages to
applying VES fracturing treatments for the stimulation of unconventional gas
reservoirs include; no requirement of hydrated polymers, no requirement of bio-
polymers and no requirement of biocides (Gupta 2011).
2.4 CONCERNS WITH WATER BASEDHYDRAULIC FRACTURING
2.4.1 WATER CONSUMPTION ANDPOLLUTION
According to Wiseman (2009), Entrekin et al. (2013), 2-7 million gallons of water is
required for the hydraulic fracturing (HF) of a single well, requiring about 400 to
1600 trucks (Hayes 2009). This could impact the development of the shale gas
industry in arid, semi-arid or drought prone areas (Gregory et al. 2011).
Such large quantities of water used for HF could lead to reduction in volume of
surface water, which could lead to temperature changes, also sedimentation could
affect dissolved oxygen level and overall water quality which could adversely impact
aquatic life (Kargbo et al. 2010, Mittal 2011), it could also increase the chances of
extended periods of drought in the region (Entrekin et al. 2013). According to BP
(2014), water use for hydraulic fracturing competes directly with its use for
agriculture and domestic purposes. Osborn et al. (2011), states that increase in the
concentration of pollutants in groundwater and surface water from methane, HF
wastewater and drilling fluids could cause the contamination of freshwater resources
(see figure 2.7). exposure to NORMs from flowback water could expose personnel to
radiation hazards (Bame and Fehler 1986, Arthur et al. 2008). Thus alternative
methods of HF are required to address the concerns associated with water abstraction
and use for shale gas production.

Figure 2.7: The Potential Impacts of Hydraulic Fracturing on Drinking Water (EPA
2011)
2.4.2 AIR POLLUTION
According to (Whiting and Chanton 2001, Howarth et al. 2012), hydraulic fracturing
activities could lead to the release of methane and volatile organic compounds
(VOCs) from equipment. The global warming potential of methane is considered to
be about 25 times more than that of CO2 and its release through HF activities could
increase the chances of climate change through the accumulation of greenhouse gases
(GHG) in the atmosphere (Howarth et al. 2011). Nevertheless Cathles et al. (2012) do
not agree with those findings and contend that methane emissions from HF activities
are over estimated. This lack of consensus on the impact of HF on climate change
indicates that studies in this regard are still inconclusive.
2.4.3 LAND POLLUTION
Land pollution by shale gas development could be as a result of road construction,
installation of pipelines and land preparation for well pad construction which could
result in deforestation and soil erosion causing irreversible damage to the landscape
(Forman and Lupberger 2012). Noise and vibration, plus competition for water
resources could also lead to the loss of biodiversity (Pimm and Askins 1995).
According to Kargbo et al. (2010), HF could lead to “disruption and alteration of sub
surface hydrological conditions including the disturbance and destruction of aquifers.”

2.4.4 MAN-MADE EARTHQUAKES
Ellsworth (2013) noted that earthquakes from hydraulic fracturing are often at 2.0
magnitude or less on the Richter scaleand can be regarded as non-destructive.
However, the disposal of flowback water into injection wells is suspected to have
induced a 5.7 magnitude earthquake in Oklahoma in 2011 (Keranen et al (2013).A 2.3
Magnitude earthquake was also recorded in Blackpool following the hydraulic
fracturing of Preese Hall Well 1 by Cuadrilla (de Pater and Baisch, 2011, Eisner et al.
2012). Nevertheless, although the Department for Energy and Climate Change
(DECC) concluded that it was not felt, a risk assessment was recommended (Green et
al. 2012).
2.5 SWISS CHEESE MODEL
Although originally intended as an accident model, the Swiss Cheese Model (SCM)
by introducing the human element into the occurrence of adverse events (Reason
1998), opened the way for it to be applied in a variety of safety critical industries.
According to Reason et al. (2006), holes as a result of errors inherent in the system
can either be eliminated by regulations or changes in design. On the other hand, holes
as a result of active errors represent those human activities that increase the potential
for the occurrence of adverse events (see figure 2.8). Strategies aimed at removing
both active and latent errors from the safeguards in the system could reduce the
occurrence of adverse events. Although critics of SCM point out the absence of detail
on the nature, origin or size of the errors in the safeguards (Shappell and Wiegman
2000, Luxhoj and Kauffeld 2003), the chemical additives, water quantity for example
could represent latent errors in the system while industry practices such as well
stimulation, water management and well integrity could represent active conditions in
the system due to human activity. Without a clear understanding of the safeguards and
errors in the system, shale gas extraction through hydraulic fracturing could lead to
conditions that are unproductive and unsafe for the environment and society.
Figure 2.8: Illustration of the Swiss Cheese Model (SCM) showing latent and active
failures (Reason 1998)
2.6.0 WATERLESS HYDRAULIC FRACTURINGALTERNATIVES

Fracturing for shale gas is becoming a future reality until the transition into renewable
energy sources. However, due to the enormous water requirements of the hydraulic
fracturing process, the hazards involved in handling the chemical components of the
fracturing fluids and the hazards of the flowback which could various forms of TDS,
NORM and VOC, the development of waterless alternatives has evolved to address
these problems (Vermylen and Zoback 2011). Some of the waterless alternatives
currently in use for HF include liquid CO2, liquid Nitrogen and Liquefied Petroleum
Gas (LPG). Nevertheless, CO2, liquid Nitrogen and LPG are known to have some
disadvantages such as ice formation hindering gas flow, surface pumping pressure
requirements and explosion hazards respectively for deeper wells (Rogala 2010).
2.6.1 LPG
According to Tudor et al. (2009), using LPG based HF has been known since the
father of reservoir engineering Morris Muskat stated in 1953 that ‘complete removal
of hydrocarbons from reservoirs can easily be achieved by displacing them with
LPG’. LPG based HF requires less surface pressure to create fractures in the shale
formation since it is less dense compared to water (Boettler 2012). Slickwater is
widely applied due to its relative cost effectiveness and ability to penetrate natural
fractures in the shale formation improving conductivity (Pucknell 2013). Fracturing
with LPG has several advantages which include;
The reduction in water use and risk of environmental pollution, improvement in well
productivity, no formation damage due to the compatibility of LPG with the shale
formation and the high possibility for the recovery of LPG at the wellhead for re-use.
Nevertheless, LPG based HF has some disadvantages such as;

EXPENSIVE
The requirement for more surface pressure pumps to increase downhole pressure
especially in deeper reservoirs and also specialized storage systems before LPG is
utilized as a formation fracturing agent. A highly pressurized system is also required
to blend LPG to gel slurry with proppant and nitrogen. High pressure pumps are
further required to pump the gelled LPG-Proppant slurry into the wellbore to
stimulate the reservoir. Speight (2013) states that HF with LPG based gel could attract
extra well completion costs. Brino (2012) states that it could attract high initial costs.
New York State Department of Energy Conservation (NYSDEC) stated in 2011 that
LPG is a patented technology belonging to Gasfrac, it’s probably costly to apply due
to LPG cost, unavailability and infrastructural deficiencies. At $1.3 to $2.6 per gallon
is much more expensive than water (EIA 2014).
Nevertheless Clark et al. (2012), Goodman (2012) observed that excess supply of
LPG due to the rapid expansion of US shale gas production could result in lower
prices of LPG and other natural gas liquids (NGL). Although Rivard et al. 2014
maintains that HF with slickwater seems to be the most cost effective technique of
shale gas extraction. But despite the complexity of the fractures it generates, it is only
suitable with shales of low clay content and other non-water sensitive reservoirs.
EXPLOSIVE
LPG based HF consists of components that are considered to be highly explosive and
flammable. Propane is heavier than air and tends to pool at ground level potentially
creating an explosive atmosphere. This requires additional sensors and monitors (24
hour infra-red and cctv monitors) to detect leaks. A 2011 explosion and fire resulted
in the hospitalisation of 3 workers including one individual that sustained second
degree burns. A flash fire at a facility also injured 13 workers. A third incident led to
a 2 weeks cessation of operations.
TRANSPORTATION
Large quantities of LPG are still required to implement LPG based HF treatments.
Although switching from water based HF could reduce truck traffic since the ratio is
at 1:5, LPG requires about 80 trucks to complete 20+ HF treatment of a well pad. This
means the risks of vehicle accidents from massive truck movements are not
completely eliminated.
UNAVAILABILITY
However, Showstack (2014) mentions that the current propane shortage in the US will
likely not support widespread utilisation of LPG based HF activities for shale gas
development.
FLARING
Recovery and recycle of LPG is hazardous and difficult requiring large compressors
with high energy requirements that could increase pollution of the atmosphere (Giles
and Lui 2014) (GHG, climate change). Due to adequate infrastructure for the recovery
of LPG, Flaring the returned gaseous LPG as a waste management strategy could
have some long term environmental and health impacts. Total quantity of water used
for the liquefaction of LPG could still be high (McNally 2013).
DATA SCARCITY

Relative scarcity of data with regards to the long term health and environmental
impacts of LPG based HF. Scarcity of data on the long term performance of LPG
based HF treatments.
WATER CONTAMINATION
The issue of water contamination due to chemicals in HF fluids and methane
migrations from well casing and cementing failures ( Adair 2011, Mair 2012, King
2013, Davies 2014) are not addressed with LPG based HF due to the proprietary
chemicals that form part of the LPG gel components.
2.7 WASTE MANAGEMENTSTRATEGIES IN SHALE GAS
PRODUCTION
The combination of HF and horizontal drilling for shale gas extraction has resulted
in a surge in natural gas production in the United States from less than 1% of its total
gas production in the early 2000s to 40% in 2012 (Nicot and Scanlon 2014).
However, the quantity of water used for hydraulic fracturing (HF) and the potential
for surface water, groundwater and environmental contamination has led to concerns
over to shale gas production (Jackson et al. 2013, Vidic et al. 2013). Traffic
congestion, noise, emissions, road damage and additional expenses are also some of
the impacts of water use for shale gas extraction (Slutz et al. 2012). Water use for HF
in 2012 is estimated to be approximately between 2 million to 7 million bbl/well (EIA
2013), with 10% to 40% returned as flowback (Boschee 2014). According to Slutz et
al. (2012), HF wastewater management consequently accounts for 5 to 15% of shale
gas drilling and completion expenses in the shale gas industry. According to Boschee
(2014) the 3 major waste management strategies in the shale gas industry are;
(i) Reuse of flowback/produced water.
(ii) Recycle of flowback/produced water.
(iii) Disposal of flowback/produced water.
Based on the EC Waste Framework Directive (EC 2008), waste is defined as ‘any
substance or object which the holder disposes of or is required to dispose of.’ The
waste hierarchy is the European waste management model which can be applied to
the shale gas industry to address concerns that have come from material use and waste
generation and management (see figure 2.8). According to Hansen et al. (2002), ‘the
waste management hierarchy is a principle designed to protect the environment and
conserve resources through an approach established in the waste policy and
legislation.’ The most preferred strategy in the waste management hierarchy follows
the order of avoidance or reduction, reuse, recycle and disposal (Ansari 2012).

Figure 2.9: The Waste Hierarchy (adapted from Hultman and Corvellec 2011)
REDUCE/AVOIDANCE; involves active measures that are taken to reduce or
minimise the quantity of waste generated through design, application and operations
that will not lead to the generation of waste (Hultman and Corvellec 2011).
REUSE; on the other hand involves activities that channel materials and resources
towards repeating their initial functions without extensive processing (Hultman and
Corvellec 2011). The reuse of flowback/produced water usually involves treatment
(on-site or off-site) for the removal of TDS, hydrocarbons and NORMS via a simple
process that costs between $1.00/bbl to $2.00/bbl on average in the United States
(Slutz et al. 2012). In the Marcellus Shale, Pipelines and trucks are utilised to
transport HF wastewater to treatment facilities off-site, although on-site treatment for
reuse is also practiced (Nicot and Scanlon 2014).
RECYCLE; refers to the processing of waste materials for use. The recycle of HF
wastewater from shale gas wells involves the conversion of the flowback/produced
water to distilled water via a patented process (Hayes and Severin 2012). The
recycling process costs between $3.50/bbl and $6.25/bbl (Slutz et al. 2012).
RECOVERY; involves the recapture of energy from the waste stream during
incineration.
DISPOSAL; may involve pre-treatment to reduce the size or negative impact before
being used as landfill. According to Wilson and VanBriesen (2012), Lutz et al.
(2013), Nicot and Scanlon (2013), the use of injection wells to dispose
flowback/produced water is the most common practice in the Barnett, Eagle Ford, and
Bakken Shales despite the presence of treatment facilities with the capacity to remove
high concentrations (50,000 mg/L) of total dissolved solid (TDS). This indicates that
the disposal of HF wastewater greatly depends on the location of the shale formation.
Thus according to Zaman and Lehmann (2013), waste consumes scarce resources and
energy, pollutes the environment and is costly to manage. With the waste
management strategies of the shale gas industry focused on reuse, recycle or disposal
(Slutz et al. 2012), there is need for improved strategies to cope with the concerns of
industry and society. Although Lottermoser (2011) does not see the concept of high
order management of mine wastes as an opportunity for economic gains, strategies
aimed at the reduction of water expenses from sourcing, transportation, storage,
treatment and disposal could increase profitability of shale gas development. Wilson
(1996) proposed a strategy that involves legislation to guide operators up the waste
management hierarchy from disposal to prevention and avoidance. The waste
management strategy applied should be required to take into consideration the
AVOIDANCE
REUSE
RECYCYCLE
RECOVERY
DISPOSAL

impacts on the society, environment, economic benefits and sustainability (Ansari
2012). A good HF wastewater management strategy can address the concerns of the
environment, society, government regulators and industry. Strategies that lead to the
avoidance or reduction of water use for HF could provide long term social benefits
(Horner et al. 2011).

CHAPTER 3
3.0 RESEARCH METHODOLOGY
3.1 INTRODUCTION
This chapter details the procedures and activities that are carried out to achieve
success with the research project. This will ensure that the research project is
replicable, will point to directions for further research and is of high academic and
ethical standards. According to Somekh and Lewin (2011), the practice of research
involves building on existing knowledge while identifying research gaps, then linking
ideas from data obtained with clear interpretation.
The aim of reviewing LPG based HF as an alternative to water based HF was
achieved through a systematic procedure set out in the methodology. A mixed
research method was the approach used for data collection and analysis. The entire
study will be based on secondary data accessed from peer reviewed publications,
company reports, authoritative online resources and government data records.
Although the researcher may be faced with complex and unfamiliar data and also the
absence of some required variables while working with secondary data sets, it is
important to note that the use of secondary data affords the researcher an opportunity
to save time and costs (Bryman et al. 2012). Another advantage of secondary data is
that it allows the researcher to have access to high quality data within the limited time
available for the research project, while providing time for more in-depth analysis and
possibility of new interpretations from the data obtained (Bryman 2012). The
relevance of this study is to fill the research gap left by the limited information on
LPG based HF as alternative water based HF. According to Biggam (2008), research
can only be considered trustworthy if the methods of data collection and study
approach are clearly detailed. Thus the approach for the entire study is detailed in this
chapter.
3.2 RESEARCH STRATEGY
According to Bryman (2012), a quantitative research strategy adopts a deductive
approach whereas a qualitative research strategy follows an inductive approach.
Based on the objectives of the research, a combination of both strategies was
employed to achieve the aim and objectives of the study. This will involve the
application of phenomenology. According to Wilding and Whiteford (2005), the
phenomenological approach explains patterns of an event as they happen in relation to
the subject matter without depending on theories, preconceptions and assumptions for
understanding. In this study it will allow the researcher to experience phenomena
from the point of view of active participants of the shale gas industry (Bryman 2012).
Using deductive reasoning, the research shall generate data from the case study
observed to arrive at a framework for eliminating or reducing the use of water for
shale gas extraction (Kitchin and Tate 2000).
This research adopts a mixed method approach, combining the merits of both
quantitative and qualitative research methods. A combination of the two methods
results in what is referred to as triangulation (see Figure 3.1).

Figure 3.1 Triangulation of quantitative and qualitative data (adapted from Bryman
2012)
The quantitative data collection, presentation and analysis was necessary to illustrate
the trends in the shale gas industry while the qualitative data collection, presentation
and analysis provided context, evidence and discussions towards achieving the
research aim and objective. Quantitative data was sourced from information in the
public domain such as verifiable and authoritative sources such as IEA, EIA, USGS,
SPE and www.fracfocus.org. According to Eisenhardt (1989), the case study approach
attempts to understand the dynamics of a situation by focusing on a particular
phenomenon. Flyvbjerg (2006) regards the case study approach as suitable for
conducting an in-depth study that could lead to the creation of theories for further
research. A case study hereby provides a clear direction which leads to valid and
reliable conclusions. Thus a case study approach will be most suitable for conducting
a review of LPG based HF as an alternative to water based HF.
A case study combined with a detailed review of recent literature on the subject
matter from authoritative sources was used to obtain secondary data. Journal articles
were consulted, reports from authoritative organisations, publications from
government agencies, newspaper publications and other scholarly materials formed
the basis of knowledge for the research project.
According to Vartanian (2010), the use of secondary data involves the analysis of any
data to answer research questions different from that which the data was collected for.
However, the use of secondary data has some limitations; since the research design is
different from that of the present research and the data had already been collected, the
data may not satisfy the research questions of the present study and adequate
information about research design and data collection techniques may not be provided
(Bryman 2012). Qualitative data was sourced from published peer reviewed materials,
reports and relevant books. According to Denzin and Lincoln (2005), despite the lack
of faith in qualitative enquiry, it is a veritable research method that can be used to
draw valid conclusions.
3.3 CASE STUDY APPROACH
The case study approach used for this research is based on the detailed and systematic
examination of a case of incidents under review (Flyvbjerg 2006) This approach
illuminates the events of the particular phenomena under study through detailed
examination (Creswell et al. 2011). The researcher used a single case study approach
analytically comparing records and evidence from the McCully Field, New
QUALITATIVE
DATA
QUANTITATIVE
DATA
Results and
Discussion
Data AnalysisData Analysis
Data Collection Data Collection

Brunswick, Canada with the current shale gas extraction practice in the United States.
Both countries were considered because their shale gas development is similar and
some of the shale plays under development cut across both countries. Both countries
are located in North America and are poised to be major producers and exporters of
shale gas by 2035 according to EIA (2013).
3.4 LITERATURE REVIEWAS AMETHOD
Literature review is an important part of research where existing knowledge is
investigated in order to find the opportunity for the researcher to enter into a wider
conversation (Okoli and Schabram 2010). This concept according to (Okoli and
Schabram 2010), regards literature review as “a systematic, explicit, and reproducible
design for identifying, evaluating, and interpreting the existing body of recorded
documents”. Similarly, (Bryman et al. 2012), sees the practice of reviewing literature
as process that involves the definition of variables and keywords, reviewing literature
based on the these keywords, analysing and discussing the findings from past studies.
Literature reviews perform a variety of functions such as mapping, consolidating and
evaluating the knowledge available in a particular subject and identifying research
gaps that need to be filled in order to further contribute to knowledge (Okoli and
Schabram 2010).
3.5 DATA COLLECTION
In order to carry out an effective examination of hydraulic fracturing in the United
States, the researcher focused on the factors influencing HF techniques in the United
States with suggestions towards improvement strategies. The researcher used the
records obtained from applying LPG Gel as a fracturing treatment at the McCully
field in New Brunswick Canada. The collection of secondary data was obtained from
reputable sources such as SPE publications, peer reviewed journal articles, reports
from reputable websites. The productivity obtained from the study of the McCully
field and also from several shale plays in the United States. The unconventional gas
regulations policies were obtained from the United States Geological survey (USGS)
and the Philadelphia Department of Environmental Protection (PADEP). This was to
ascertain the role of government in the influencing of the methods used for the shale
gas extraction. It also used data from EIA to analyse the trends in natural gas
production especially in the United States in order to predict the possible future of
both technologies.
The USGS, PADEP, IEA and EIA websites and reports provided information on what
projects were on stream presently and what projects are being planned for
development.
However for comparison, the best practice for shale gas extraction was collected from
IPIECA and ICF international guidelines on shale gas extraction and hydraulic
fracturing (IPIECA 2009, ICF 2006).
3.6 DATA ANALYSIS
The study covers shale gas development in the United States and Canada and the
trends of water use for hydraulic fracturing between 2009 and 2014. The research

involved the analysis of shale gas production over the last ten years and the impact
that water use for shale gas extraction has had on the environment. Microsoft Excel
was used to plot charts covering the issues identified in the literature review, while
qualitative data was used to interpret the data as well as assist with the analysis. Based
on the information from the literature review, a framework was developed for the
review of LPG based HF as an alternative to slickwater HF (see figure 3.2), thus the
data analysis and discussion covered;
 Water consumption
 Water contamination
 Vehicle Traffic
 Productivity
 Induced Seismicity
 Climate Change
Figure 3.2 Framework for the review of LPG based HF as an alternative to slickwater
hydraulic fracturing

3.6.1 EVALUATION OF SECONDARYDATA
The evaluation of the sources of the secondary data was carried out by comparative
analyses of similar data from other sources to identify inconsistencies in the trends
and also to accomplish the aim and objectives of the study (Bryman et al. 2012). The
evidence from the case study was also critically analysed to provide answers to the
research questions. Secondary data was collected from reports and publications from
government agencies, authoritative organisations and reputable operators to ensure the
quality of the research material. Nevertheless, the evaluation of the quality of the
secondary data ensures the researcher some control over the limitations of using
secondary data (Bryman et al. 2012).
3.7 RESEARCH LIMITATIONS
A major challenge of the research was the poor availability of data with regards to the
use of LPG based HF for shale gas extraction. This is mainly due to the method still
not widely applied.
This made it difficult to analyse trends of the productivity and potential environmental
impacts of the method. However, this was addressed by making inferences from
secondary data obtained from authoritative literature and also the case study
undertaken for the research. The problem of generalizing with information from the
McCully field was overcome by diligent examination of related literature and drawing
parallels with gas fields of similar characteristics. Although according to McNabb
(2004) Single-Case Study projects have typical limitations associated with the results
which could probably only be applied to the case study under consideration, and this
hamper the ability of the researcher to infer or generalise from the findings. Despite
these limitations, the case study is considered a suitable approach towards achieving
the aim and objective of this study since it provides an opportunity for a systematic,
in-depth and thorough investigation of the subject matter (Somekh and Lewin 2011).
Thus the case study under consideration for this project could be used to represent
expectations from the shale gas industry.
Finally, time and resource constraints limited the scope of the research. Several
themes within the selection of fracturing fluids for shale gas extraction such as
energized fracturing fluids, cost benefit analysis of waterless fracturing fluids and
water based fracturing fluids were intended to be covered. To overcome these
limitations, objectives were framed and analysis carried out to capture diverse topics
in order to present a more comprehensive comparison of LPG based HF with water
based HF.
3.8 ETHICALISSUES
Since the study was based around secondary data analysis, the risk was categorised as
low. Nevertheless, great effort was taken to ensure that a balanced and unbiased
position was maintained throughout the research, while plagiarism was avoided by
ensuring that all sources of information consulted or used in the research were
properly referenced (Bryman 2012). The validity and reliability of the results obtained
from the study is related to the actions of the researcher (Somekh and Lewin 2011).
Thus extra effort was applied towards maintaining academic and professional
integrity and ethical standards throughout the study.

3.8 PROJECTFLOW DIAGRAM
Figure 3.3: Project flow diagram
RESEARCH AIM AND OBJECTIVES
DATA COLLECTION
LITERATURE REVIEW
CASE STUDY
DATA ANALYSIS & DISCUSSION
QUALITATIVE ANALYSIS
QUANTITATIVE ANALYSIS
CONCLUSION AND
RECOMMENDATIONS

CHAPTER 4
4.0 RESULTS DISCUSSION ANDANALYSIS
4.1 CASE STUDY ANALYSIS
4.1.1 BACKGROUNDINFORMATION ON MCCULLYFIELD
The McCully field consists of the Hiram Brook and Frederick Brook Sands and
shales. Discovered in 2000 by Corridor Resources. Table 4.1 shows the field
parameters. Both the Hiram Brook and Frederick Brook shales are part of the Lower
Carboniferous Albert Formation located at New Brunswick, Canada.
Table 4.1: Reservoir Parameters of the McCully field (LeBlanc 2011)
Reservoir Depth 1800m
Gross Thickness Up to 870m
Net Pay Up to 95m
Temperature 400C – 600C
Porosity 4% - 8%
Water Saturation <10% - 30%
Permeability 0.01mD – 1.8mD
Reservoir Pressure 20 MPa – 35MPa
4.1.2 WATER BASED HF
Production from 29 production wells of the Hiram Brook shale and 1 production well
from the Frederick brook shale commenced in 2007 after the construction and
commissioning of a gas plant. The unconventional gas wells were initially stimulated
with water based HF treatments. This involved the perforation and plugging of each
stage before the next. After perforations have been completed, all the fractured zones
were drilled out for the commencement of clean up. This resulted in extensive periods
of clean up due to the length of time required to recover flowback water from the gas
wells, also the small fracture lengths created by the water based fracture treatments
plus the poor water handling capacity of the shale formation yielded low productivity.
Phase trapping or water blocking the fracture zones and reducing gas permeability
was suspected (LeBlanc et al. 2011).
Table 4.2 Comparison of the properties of water, propane and methane (LeBlanc et al.
2011)
FLUID VISCOSITY (100
Fahrenheit)
SURFACE
TENSION
DENSITY
(Kg/M3)
Water 1.93 72.8 1.00
Propane 0.083 7.6 0.51
Methane 0.0116 0 0.66

4.1.3 LPG BASED HF
To overcome these problems, LPG based fracture treatments were introduced in 2009
due to the viscosity of propane and its surface tension and density makes it more
compatible with the natural gas (methane) found in the formation (table 4.2).
LPG based HF treatments require an average of 170,000 gallons of fracturing fluid
and 200,000 pounds of proppant compared to 2 to 7 million gallons of fracturing fluid
and 5 million pounds of proppant used in water based HF treatments (Tudor et al.
2009).
4.1.4 RESULTS ANDANALYSIS AND DISCUSSION
Figure 4.1 Comparison of fluid recovery between LPG and Water based fracturing
fluids (LeBlanc 2012)
As shown in figure 4.1, 100% of injected propane was recovered in about 15 days
compared to flowback from water based HF which required 150 – 450 days. This
extended flow back period indicates that the rate of gas flow during production will be
significantly reduced due to the presence of water in the well bore.
Figure 4.2: Illustration of fluid block due to water based hydraulic fracturing (Tudor
2012)
The illustration of results from studies conducted at the McCully gas field is shown in
figure 4.2. This reveals the impact of water based fluids on the fractures created by
hydraulic fracturing. On the other hand, gas well stimulation using LPG based
treatments have the potential to produce more effective fractures as shown in figure
4.3. According to Leblanc (2011), productivity is enhanced by up to 77% using LPG

gel as fracturing treatment. Blackbrush also claims that the recovery of propane after
hydraulic fracturing treatments leaves the cost difference of LPG gel against water at
10% to 15% (Tudor 2012).
Water based HF such as slickwater treatments have poor proppant transport and
placement characteristics that result in inefficient formation stimulation (Benedictis et
al. 2013). Friction reducers used in slickwater fracturing are also known to damage
the shale formation by inhibiting gas permeability in natural fractures (Sun et al.
2011).
Figure 4.3: Illustration of the potential of LPG based hydraulic fracturing (Tudor
2012)
As shown in figure 4.3, If gas production rate is a key measurement of successful
development and operation of shale gas reservoirs (Bottero 2014), a better recovery
from shale gas reservoirs is anticipated with the use of LPG gel based HF treatments
since it reduces the chances of formation damage that is frequent with the use of water
based fracturing treatments. This will lead to long term profits for the operator of the
gas field.
Figure 4.4 Comparison of gas production rates of gas wells with LPG based (red bar)
treatment and water based (blue bars) treatments (LeBlanc 2012)
Figure 4.4 shows that LPG based HF yielded (272 m3 gas/m3) on average 4 times the
rate of water based HF in the McCully Field indicating a better well performance.

Although Morsy et al. (2013) reported a recovery rate of approximately 9.5% for both
water based and LPG based hydraulic fracturing treatments for the Morgan Heavy Oil
Field of North East Alberta Canada, those similar recovery rates only suggests that
LPG is probably unsuitable for use in the enhanced recovery of heavy oils and the
results from the McCully Field show excellent performance in shale gas reservoirs.
Figure 4.5 Production rates from different fracturing fluids (Ribeiro and Sharma
2013)
Nevertheless, according to Ribeiro and Sharma (2013), energized fluids based on
CO2 and Nitrogen could outperform LPG based fluids (see figure 4.5), however, they
must only constitute 50% of the fracture fluid in order to preserve their viscosity and
proppant transport capabilities and are suitable mostly for shallow wells (Ribeiro and
Sharma 2013). The results from figure 4.6 still shows that LPG based HF perform
better than slickwater while the energized fluids still utilize water. The effective
proppant transport and placement properties of waterless HF fluids such as LPG based
HF thus give LPG HF the potential to yield better rates of productivity than water
based HF fluids.

4.2 INDUSTRYANALYSIS ANDDISCUSSION
4.2.1 WATER CONSUMPTION
Figure 4.6: Baseline US Daily Water Consumption (USGS 2009)
Water Quantity
Figure 4.6 illustrates the average daily water consumption in the United States. Shale
Gas extraction falls under Mining indicating that the quantity of water used for HF is
minimal compared to other categories of users. 2-7 million gallons of water are
required for the HF of a single well while conventional gas wells in comparison
require about 1 million gallons of water per well (Ferrar et al. 2013, Nicot and
Scanlon 2012).
Figure 4.5: Water Consumption across Shale Plays in the United States and Canada
(USGS 2010, EIA 2014, Freyman 2014)
0
1
2
3
4
5
6
7
8
WATER VOLUME (MILLION
GALS/WELL)

Figure 4.7 shows the variation in water consumption in some shale plays in the United
States. HF in the Marcellus Shale is estimated to use about 18.7 million gallons of
water per day (Vidic et al. 2013). Although the water volume recorded for the
Marcellus Shale appears to be enormous, it represents only about 7% the total water
usage in the Pennsylvania (EPA 2013) as illustrated in Figure 4.6. It is apparent from
this chart that water use for HF constitutes a small amount of what is used in the
region. However, the disposal of wastewater from shale gas operations suggests a
permanent removal of water from the hydrological cycle. This goes against the
preferred order of waste management proposed by EU (2008), indicating that some
studies are required to investigate the long term impacts of this activity on regional
water availability.
Figure 4.8: Water Consumption in the Marcellus Shale (EIA 2013)
Although the US EPA (2012) stated that between 2008 and 2011 only 13% of water
for HF of the Marcellus Shale was derived from flowback or produced water, recent
records from the Pennsylvania Department of Environmental Protection (PADEP)
show that 87% of flowback and produced water are currently being recycled (Vidic et
al. 2014). This seems to agree with the industry practice identified by Lottermoser
(2011).
Figure 4.8 also shows the consumption of water from the mining category to be 1%.
However, for a region prone to drought, this could lead to competition with farmers
who require water the most for irrigation and aquaculture. This could result in conflict
if water requirements for HF lead to an increase in the price of water locally.
DOMESTIC
74%
RECREATIONAL
12%
GAS WELLS
7%
MANUFACTURI
NG
5%
MINING
2%
WATER USE IN THE MARCELLUS
REGION

Figure 4.7: Daily Water Consumption in Texas (USGS 2009)
4.2.2 WATER CONTAMINATION
Osborn et al. (2011) in a study of water wells in Pennsylvania and New York found
methane concentrations to be higher in drinking water wells dug within 1 Km of shale
gas wells (see figure 4.8). Although this suggests a relationship between HF and water
contamination, King (2012) noted the absence of baseline data in the studies.
Information from micro seismic monitoring, the depth of the shale gas fractures
suggest that fracture zones occur too deep and methane migrations are unlikely to
travel above 600 meters of the fracture zones which makes it out of reach of the
underground water resources (Muehlenbachs 2011, Flewelling et al. 2013). Studies by
Vidic et al. (2013), Molofsky et al. (2013), also suggest that the geochemical
characteristics of the region are possibly the reasons for these methane concentrations
in shallow aquifers. Methane migration from the subsurface such as coal seams,
glacial till, and black shale as well as the flammability of water from shallow aquifers
has been observed before shale gas development activities in the Marcellus Shale
(Eaton 2013), it is therefore essential that baseline conditions are established before
drilling takes place in order to ascertain actual gas migration pathways (Vidic et al.
2013). This is consistent with the information uncovered in the literature review
concerning the lack of agreement with sources of water contamination.
Toxic Substances
While poor well casing and cementing has been identified as one of the pathways that
methane could stray into shallow aquifers (Kissinger et al. 2013), well blowouts,
leaks and spills of poorly treated or untreated HF wastewater increases the risk of
ground and surface water contamination with potentially toxic substances Vengosh et
al. (2014). However, these are regular occurrences in the shale gas industry and
mitigations have mostly been able to control the hazards (Eaton 2013). Nevertheless,
chloride concentrations over 250 mg/L detected 1.7 Km downstream of a

Pennsylvania treatment facility that handles HF wastewater was found to be 2-10
times higher than other Pennsylvania streams they studied (Warner et al. 2013).
Figure 4.8: Methane concentrations near shale gas production areas (Osborn et al.
2011)
The discharge of poorly treated wastewater from shale gas developments in the
Marcellus Shale was suspected to introduce contaminants into surface water systems
including private water wells, thereby reducing their quality Warner et al. (2013).
Vengosh et al. (2014) identified several modes for the contamination of water
resources by shale gas extraction activities as follows;
1. Contamination of shallow aquifers with fugitive methane.
2. Contamination of surface water and shallow aquifers from spills, leaks and
disposal of poorly treated HF waste water.
3. The accumulation of radioactive and toxic substances near disposal, spill or
drilling sites.
Flowback water usually contains toxic elements such as arsenic, selenium, radium,
strontium, barium from uranium source rocks depending on the geochemical
characteristics of the shale play (Lutz et al. 2013). Total Dissolved Solids (TDS) from
flowback and produced water ranging from 25,000 mg/L in the Fayettville shale to
over 180,000 mg/L in the Marcellus shale have the potential to increase the salinity of
water resources if spilled or leaked into groundwater systems (Vengosh et al. 2014).
High concentrations of toxic substances in storage ponds on the surface near drilling
sites are a major contamination hazard (Vengosh et al. 2014). Through spills, leaks
and run-off from the storage ponds, these substances can pollute the soil, contaminate
surface water systems and shallow aquifers with radionuclides, salts, benzene, ethyl
benzene, toluene and xylene. The disposal of untreated or inadequately treated
hydraulic fracturing wastewater is also a major threat to surface and groundwater
resources. The frequency of contamination through this identified pathways often
correlate with the density of shale gas extraction activities of a given area (Thyne
2008). According to Rahm and Riha (2012), due to the challenges that result from the
storage, transportation, treatment and disposal of flowback and produced water from
hydraulic fracturing, poor water management practices have the potential to impact

water quality and quantity. The application of LPG based HF methods could thus
present a way of avoiding the problems associated with water use for hydraulic.
4.2.3 VEHICLE TRAFFIC
Figure 4.9 illustrates the comparison between the number of trucks required for water
based HF and the number of trucks required for LPG based HF. One million gallons
(3,800 m3) of water requires 200 trucks (Williams 2012). On average about 30% of
the water injected for HF returns as flowback (Halliburton 2014) and is categorized as
industrial waste which needs proper storage, treatment and disposal requiring a further
80 to 320 trucks. LPG based HF in comparison requires 80 trucks to transport propane
for use as a fracturing agent, also no flowback water requiring disposal trucks is
obtained (Tudor et al. 2012).
Figure 4.9: Comparison of Number of Trucks Required for Hydraulic Fracturing
This makes LPG based HF a possible alternative towards addressing the concerns
associated with large water requirements of water based HF. According to the New
York State Department of Energy and Conservation (NYSDEC), a typical non-
conventional well requires about 1,800 to 3,950 trucks (NYSDEC 2011). This implies
that the truck traffic is 3 times higher than the requirement for conventional wells.
The number of trucks required for water based HF increases the risks of traffic
congestion, noise, dust, vibrations and road accidents which all pose a negative
impact on community infrastructure such as bridges and roads requiring extra
maintenance (Williams 2012). A reduction in the number of trucks on the road could
be a strategy towards eliminating some failures due to human activity as identified by
the Swiss Cheese Model (SCM) highlighted in the literature review (Reason 1998).
Not only will this approach reduce the possibility of road accidents, it could also
reduce infrastructure maintenance costs.
0
200
400
600
800
1000
1200
1400
1600
1800
2000
WATER BASED LPG BASED
DRILLING
FRAC
DISPOSAL
TOTAL NUMBER OF TRUCKS

Figure 4.9.1: Accident rate comparisons between 2 Pennsylvania Shale Gas extracting
Counties (Muehlenbachs and Krupnick 2013)
Figure 4.8 shows results of accident data from Crash reporting System (CRS) and data
from PADEP on shale gas wells developed in Pennsylvania (Muehlenbachs and
Krupnick 2013). The results show a 2% rise in road accident rates for every new shale
gas well drilled in Pennsylvania, a relationship between counties with more than 20
shale gas wells and accidents involving heavy trucks associated with shale gas
extraction operations was also found (Muehlenbachs and Krupnick 2013). These
results suggest a negative impact of increased vehicular traffic that could be more
significant as the shale gas industry experiences growth especially if the current trend
of predominant application of water based HF continues. While the use of LPG based
hydraulic fracturing could reduce truck traffic by 80% to 90%, alternatives to truck
delivery of fluid and other materials to well sites such as pipelines could be a better
control measure in line with the Swiss Cheese Model (SCM). The use of brine water
from on-site formation sources, in a closed-loop system coupled with sand delivery by
railway is also a strategy used by Apache and Encana to minimize truck traffic by
60% to 80% in Canada’s Horn River Basin (Rogala et al. 2013).
4.2.5 INDUCEDSEISMICITY
Figure 4.9.4 shows the increase in the number of earthquakes of 3.0 Magnitude and
above recorded in Oklahoma. This coincides with the growth of the shale gas
industry. Although Thompson (2011) stated that with the volume of fluid injected into
the wellbore, the limited penetration distance of the fractured zone and the limited
hydraulic fracture treatment time, hydraulic fracturing induced seismicity may seem
unlikely, and with over 30,000 disposal wells in operation in the United States, the

number associated with induced seismicity may be regarded as insignificant.
Nevertheless, the USGS (2011) published that induced seismicity is possible. LPG
based HF treatments may however eliminate the need for disposal wells since it will
not occasion the need for disposal wells. This could potentially reduce the number of
seismic activity recorded as a result of shale gas extraction activities
Figure 4.9.4: Annual number of earthquakes in Oklahoma above 3.0 Magnitude
(USGS 2012)
4.2.6 CLIMATE CHANGE
With perhaps 40 times more water required for shale gas production compared to
unconventional natural gas, shale gas could potentially release more methane into the
atmosphere compounding climate change problems. Figure 4.4 shows methane
emissions associated with flow back water from hydraulic fracturing stimulation
reservoirs in some shale plays in the United States.
Table 4.3 Lifetime Methane Emissions Estimate from Some Shale Plays in the United
States (Howarth et al. 2011)
Shale Play Lifetime Methane Emissions
Haynesville (Louisiana) 3.2
Barnett (Texas) 1.1
Piceance (Colorado) 1.3
Uinta (Utah) 0.6
Although the lifetime of methane in the atmosphere is shorter compared to CO2 (IPCC
2010), it is 22 to 43 times more potent as a greenhouse gas than CO2 (Howarth et al.
2011). Over a 20 year period, methane emissions from HF could present a larger
greenhouse gas footprint than coal and unconventional gas production. While flaring
of the methane is important to prevent fires at the well site, the potential for negative
impacts on the atmosphere is increased with the release of VOCs, NOs, SO2 which
degrade local air quality (Broderick et al. 2011). Nevertheless, Burnham et al. (2011)
argue that based on industry reports, a significant amount of methane is captured or
0
20
40
60
80
100
120
140
EARTHQUAKES
YEAR

flared during HF and also the scarcity of data of fugitive methane emissions make
those assertions inconclusive.
Although Pollack et al. (2012) maintains that Propane, Butane and Pentane are not
Greenhouse Gases and have short lifetimes in the atmosphere, and results from
studies by Howarth et al. (2011) may suggest that the application of LPG based HF
could potentially reduce methane emissions from shale gas extraction, the recovery
and recycle of LPG is hazardous and difficult, requiring large compressors that use a
lot of energy which could still release large amounts of CO2 into the atmosphere
(Giles and Lui 2014). Also the total quantity of water used for the liquefaction of LPG
could still be high, negating the efforts of water reduction (McNally 2013).
Inadequate infrastructure for the recovery of LPG could result in flaring or venting of
the returned LPG which could lead to some long term environmental and health
impacts. While controls may be in place for propane management such as site
monitors, flares and pipeline tie-ins (Tudor et al. 2009), to achieve the long term
climate change benefits of using LPG based hydraulic fracturing for shale gas
extraction efforts should be directed at further research on the potential impacts of
LPG based hydraulic fracturing treatments.
4.3 SWOTANALYSIS
The shale gas industry faces with many challenges. The strengths, weaknesses,
opportunities, and threats that influence each HF technique is critically assessed in
order to present a balanced review of the techniques used for shale gas extraction.
A SWOT analysis of both water based HF techniques and LPG based HF techniques
are conducted due to their influence on future practice and trends on the shale gas
industry. Data from literature review, case studies, company reports, statistical
reports, government regulations and policies were used to conduct the SWOT
analysis. The findings intend to present guidance towards assessing and assisting the
shale gas industry in making informed choices regarding HF techniques applied for
shale gas extraction.
4.3.1 SWOT ANALYSIS OF WATER BASED HF
STRENGTHS
Water Availability
Water use for HF in 2012 is estimated to be approximately 4.37 gal/Mcf of shale gas
produced. According to Slutz et al. (2012), HF wastewater management accounts for
5 to 15% of shale gas drilling and completion expenses in the shale gas industry.
According to Nicot and Scanlon (2012), it is quite important to develop less water-
intensive methods of extracting natural gas to reduce dependence on water and also
enhance shale gas production in areas with limited water availability. Also efforts
should be made to ensure that water for HF do not compete with domestic and
agricultural users.

Cost Effectiveness
Water based HF methods especially Slickwater treatments are usually applied as cost
cutting measures during well completions (Palisch et al. 2008). Although several
studies (Morsy et al. Rogala et al. 2013, Sharma et al. ) have reported the
disadvantages of water based HF treatments, its continued applications due to
economic reasons suggests that water use for HF will still be utilised for shale gas
extraction in future.
Creation of Complex Fractures
Due the viscosity of water, the stimulation of unconventional reservoirs with water
based treatments has the ability to penetrate natural fractures resulting in fracture
complexity (Cipolla et al. 2008). This penetration of pre-existing fractures and faults
helps to improve the network conductivity of the fractures created enhancing
productivity (Pucknell 2013, Palisch et al. 2008). This remains a positive attribute
which lends support to the application of water based HF treatments.
Widespread Application
As an abundant natural resource, water is usually easily obtained from surface and
groundwater systems for hydraulic fracturing of unconventional reservoirs. Palisch et
al. (2008) and Zoback et al. (2012) maintain that multi-stage HF with slickwater in
horizontal wells is a good technique for the extraction of shale gas in commercial
quantities. Consequently, slickwater HF has experienced widespread application for
the stimulation of unconventional low permeability shale formations since success
was established in the Cotton Valley Sands in the late 1990s (Handren and Palisch
2009. Also, according to Sharma et al. (2004) hybrid HF treatments which combines
slickwater pad followed with linear or cross-linked gel (water based) treatments result
in well stimulations of longer fracture length than applying only slickwater
treatments. As a result, the number of operators who select water based treatments
remain higher than others in the shale gas industry.
WEAKNESSES
Incompatibility with the Formation (Wettability)
Studies have reported that shale gas reservoirs are often susceptible to formation
damage from water based HF fluids (Bennion et al. 2000, Rogala et al. 2013, Wang et
al. 2014, Bottero 2014). According to Rassenfoss (2011) water trapped in the shale
formation reduces gas permeability hindering optimal production rates (Bennion et al.
2000). Nevertheless, this depends on the geologic characteristics of the formation and
commercial production rates are often achieved in non-water sensitive shale
formations after water based HF treatments.
Large Volumes of Water Required
Using reports from the Marcellus Shale, 2-7 million gallons of water are required for
the HF of a single well (Ferrar et al. 2013), whereas conventional gas wells require
about 1 million gallons of water per well in comparison. HF in the Marcellus Shale is
estimated to use about 18.7 million gallons of water per day (USGS 2009). Although
this constitutes only about 0.2% of the total annual water withdrawals in Pennsylvania
(Vidic et al. 2013), it could become a problem in arid and semi-arid areas due to

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