Technology - The Shale Revolution !!!

The ShaleRevolution :
Shale RevolutionCharacteristics Existing Technologies Natural Gas References
Shale, a sedimentary rock is predominantly comprised of strengthened clay sized particles. Shale is deposited as mud in low energy depositional environments as deep water basins and tidal flats where these fine grained clay particles fall out of suspension in these quite water.
Shale is a source rock for hydrocarbon having low permeability. It is a common rock formation across the world. Unconventional gas shale, a natural gas from shale formations, is not new to explorers. The continuous accumulation of tight and low permeable shale acts as both a source and a reservoir for the natural gas shale formations with certain characteristics and under certain conditions produce shale gas. The gas produced by shale is stored within the pore spaces or fractures in the rock itself which does not allow gas to flow easily through it. This led pioneers to traditionally focus on limestone and sandstone which have high permeability.
TECHNOLOGY SHALE GAS

Few years ago, it appeared as though United States was running short of natural gas, prices spikes as there raised a clash between declining production in Oil fields and increasing industrial demands. But now, it is possible to achieve these goals by the new initiated technologies. One such technology is the recovery of Shale.
In its April 2009 report, "Modern shale gas development in United States: A premier "the US department of energy stated that at the US natural gas production rates for 2007 of about 19.3 Tcf, the current recoverable resource estimates that the gas can be supplied to US for the next 90 years. Separate estimates of shale gas resource estimated this supply to 116 years

Electric utilities turned from unblemished gas back to the cheap coal. The suppliers connected building terminals to import liquefied natural gas from Abroad.
Eventually today, coal fire power is again on the declining state, ports for liquefied natural gas are idling below capacity and the nation is awash with gas.
It resulted in threat of carbon regulations that curbed industry's appetite for coal. Then there came to boom to the industry that again rose the natural gas production.
The technology based corporate like USA and China discovered the essence of Shale and today, they are very effectively using shale gas as natural gas, which is very beneficial economically.
The dramatic emergence of shale gas in US, produced gas in excess. This sharply reduced the US price of natural gas by 75% from its peak in mid-2008. The share of shale gas in US gas production has raised from 0 to 8%. A deposit, the Barnett shale in Texas produced 1.1 trillion cubic feet of gas in 2008 and other deposits could be as productive.

Characteristics of shale and shale gas :
Shale a most common sedimentary rock, is a fine grained material of clastic sedimentary rock. The low permeability becomes a natural barrier in the process of extraction of oil and the gas. Shale is composed of tiny flakes of clay materials and the fragments of quartz and calcite. The color it exhibits is grey. The color of shale gas varies with the presence of variable amount of minor constituents in it.
Black shale results from the presence of carbonaceous material in quantity greater than 1% and indicates a reducing environment.
Red, brown and green colors indicate the presence of ferric oxide (hematite – red) , iron hydroxide (glothite – brown) and limonite (limonite – yellow) or micaceous minerals (chlorite , biotite & illite – greens) respectively.
Clay being a major constituent of shale and other mud rocks, has a number of many minerals found in it

Authigenic quartz
Chert
Calcite
Dolamite
Ankerite
Hematite
Albite

Shale As Natural Gas :
Shale gas , a natural gas , is a fossil fuel. Fossil fuels are the remains of plant and animals buried under the earth million of years ago in terms of its chemical makeup. Shale gas is typically a dry gas primarily composed of methane (90% or more) within the shale bed. The potential of shale formation to contain economic quantities of gas can be evaluated by identifying specific source rock characteristics such as –:

Total organic carbon(TOC)
Thermal maturity
Kerogen analysis

Characteristics of shale gas-:

Very high gamma ray activity
High resistivity
Low bulk density
Low Pe

Shale gas, simply a natural gas, produced from shale formation which typically acts as both the reservoir and the source for the natural gas

Natural Gas And Shale Gas :-
Natural Gas is a combustible mixture of hydrocarbon gas, that is primarily formed of methane, and also include ethane, propane, butane and pentane. When burnt, it gives off a great deal of energy. Unlike other fossil fuels, it emits lower levels of potentially harmful byproducts in the air. Natural Gas is Colorless, Shapeless and Odorless in its pure form .
The composition of Natural Gas can vary wide, but below is a chart outlining the typical makeup of Natural Gas before it is refined.

Applications Of Natural Gas :
Very long time ago Chinese discovered the energy in natural gas could be made use of and used to heat water. The natural gas industry, in its infantry, used to light steel lamps, and the occasional house. Due to much improved distribution and technological advancements, gas is being used in ways never thought possible.
Natural gas has applications ranging from home industrial to transportation sector. The uses described here are not totally comprehensive, they may help to show how many things can be done using natural gas .

Transportation sector – Uses of natural gas in transportation sector, ranging from cars and trucks to heavy duty service vehicles. In Canada and some European countries, ‘clear air’ natural gas buses are quite popular and more vehicles are now running in dual fuel, allowing owners to switch blue gasoline or natural gas, depending on the situation , needs and circumstances. The Russian jupoler is working and applying the effort in designing an aircraft that would be able to fly on a combination of natural gas and hydrogen.
Industry and production – In industrial sector, the use of natural gas is divided between production and energy. Anti freeze and plastic are made using natural gas. Natural gas I food processing industries is basically used to power up their plants but petroleum refining and waste treatment are big consumers of natural gas.
Residential uses – Many home appliances including furnaces, barbecues, fireplace logs, pool and spa heaters and fire pits run on natural gas home includes residential heating 51% of American homes choose natural gas as the main source of heat. Natural gas air conditioning is not popular as an electrical alternative, but it does exist.

Natural Gas Use By Sector In Vehicles :

Existing Technologies / Methodologies for Extraction :
In 1990, the pioneers introduced a new technology. Due to low permeability, (most have a matrix
permeability of 10-4-10-8 mD) a tight shale deposit could be cracked by injecting water at high
pressure. On stopping the water injection the pores closed again. This led engineers pump water
mixed with sand. The sand being kept permeable the cracks partially opens on stopping the water
injection thus leading to the increase in gas flow. Vertical drilling into a deposit of 20 meters can
yield only to a production zone of 20 meters. Older shale gas wells were vertical while more recent
wells are primarily horizontal older shale gas wells werevertical while more recent were are
primarily horizontal and therefore new techniques have facilitated horizontal drilling and
hydraulic fracturing. Regardless of the said permeability of the reservoir rock, the rock can be
damaged by the drilling machine when a well is to be drilled out of the reservoir rock, casing of
that particular region is set and cemented. Damage of these rocks mainly occurs is the drilling
process and complete fluid leaks into the reservoir and plug up the pores and pore throats due to
which its permeability decreases .when the pores of these reservoirs rocks are plugged, the
permeability is Reduced and the fluid flow in this damaged portion of the reservoir may
substantially reduce. Due to the above reason the damage can be severe in naturally fractured
reservoir like coal seams. Hydraulic fracturing is the process of pumping a fluid into a wellbore
with very high injection rate for the formation to be accepted in a radial flow pattern.
.

The different applications of hydraulic fracturing are :

Increasing the flow rate of oil or gas from the low permeability reservoirs.
Increase the flow rate of oil or gas wells that have been damaged.
Connect the natural fractures or cleats formation to the wellbore.
Decrease the pressure drop around the well to minimize sand production.
Decrease the pressure drop around the well to minimize problems with asphalting

or paraffin deposition.

Increase the area of drainage or the amount of formation in contact with the

wellbore

Connect the full vertical extent of a reservoir to a slanted or horizontal well
Thanks to the advancements in drilling technology, including horizontal drilling and effective rock fracturing that supported the producers at last unlock the vast reservoir of gas trapped underground in impermeable strata of shale

Types of shale :

The Kajrahat Formation : Black shale :
The oldest black shale, located in the lower part of the Kajrahat Formation, is up to 12.5m
thick. The youngest black shale unit, the Bijaigarh Shale, is up to 70 m hick, which occurs
sandwiched between the Lower and Upper Kaimur sandstone. From the Prior petrographic studies,
it has been observed that of the three shale units, the black shale interval in the Kajrahat Formation
probably has the most compelling indications of microbial mat formation at the sediment surface.
Features like thin carbonaceous fragments that apparently have been contorted, folded, and rolled
up during transport point to the presence of cohesive carbonaceous films. This cohesive nature is
consistent with microbial surface binding. The basal contacts of some of the black shale beds with
underlying gray shale show inclined carbonaceous lamina and clay drapes suggestive of False
cross-lamination (produced when the lateral expansion of a mat through time is intermittently
interrupted by pulses of sediment. In addition, some samples of the Kajrahat Formation black shale
show even parallel lamina that reflect physical sedimentation, such as settling and current
reworking. Thus, microbial mat colonization appears to have been intermittent and/or spatially
limited and prone to interruption when sedimentation rates were too high or sedimentation pulses
persisted for longer time periods. The lamina style itself bears strong resemblance to wavy-crinkly
lamina observed in other occurrences of Proterozoic carbonaceous shale that have been studied
in some depth for microbial mat features.
Types of Shale :

The Rampur Shale :
The Rampur Shale at the mid-level of the Vindhyan Super group, containing abundant evidence of intermittent
erosion of unconsolidated mud, occurs at the base of the Rohtas Limestone and is up to 55 m thick. Many thin
sections show a wavy lenticular fabric that on first glance closely resembles microbial mat laminated
carbonaceous shale from the Belt Basin. However, what initially appears as wavy clay drapes that separate
carbonaceous salty lamina looks upon closer inspection like stacked up clay-rich fragments that were soft when
deposited and were squeezed together when compacted. This impression is reinforced when a cut parallel to
lamination is made. If a laminated shale is cut parallel to bedding, multiple lamina are intercepted because of
slight irregularities and when ground this surface shows a pattern that resembles the isoclines of a topo graphic
map. In contrast, when wavy lenticular laminated Rampur Shale specimens are ground parallel to lamination we
see a surface that is strewn with shale particles. At higher magnification one sees that the shale does indeed
consist of discrete shale particles and that these fragments are compacted and deformed. In plain view the
irregular shaped shale particles are clearly visible at higher magnification other samples show layers of gray
shale with irregular carbonaceous fragments that are up to 10 millimeters in size. In thin section these fragments
are quite thin (0.1-0.2 mm) and may show deformation and folded over portions). This mechanical behavior
suggests a within-fragment cohesiveness that one should not expect if this material originated as a simple
mixture of clays, silt, and organic matter. Such behavior is however, consistent with binding by microbial
surface films. Intervals of the Rampur Shale that contain these fragments also show wavy anatomizing
carbonaceous lamina interspersed with clay drapes. In close-up view these bear striking resemblance to the
lamina pattern in other examples of Proterozoic carbonaceous shale of microbial mat origin. In the Rampur
Shale indications of surface binding by microbial mats appear to be less abundant than in the Kajrahat
Formation black shale interval. The abundance of Rampur shale that consist of compacted shale fragments
Suggests an overall more energetic environment when compared to black shale in the Kajrahat formation.

The Bijaigarh Shale:
The Bijaigarh Shale shows the discrete flattened shale particles in cuts perpendicular to bedding, and fragment strewn
Surfaces in cuts parallel to bedding. Its features indicate the erosion of a mud substrate by strong currents.The majority
of thin sections from the upper third of the Bijaigarh shale show features that closely resemble those observed in
microbial mat laminated Proterozoic black shale, whereas, many thin sections are either entirely characterized by wavy
crinkly anastomosing carbonaceous lamina that alternate with clay drapes of variable thickness and continuity, or
show carbonaceous layers of this type interspersed with beds of non-laminated shale. These shale beds are texturally
comparable to microbial mat-produced Proterozoic black shale. The prior petro graphic observations indicates the
presence of cohesive carbonaceous surface films, suggesting microbial mat binding of the mud surface. The reflected
light and SEM studies of polished sections of Bijaigarh Shale from the upper third of the unit also show that fine
crystalline early digenetic pyrite is largely confined to carbonaceous lamina and displays a wavy anatomizing texture
as well . This has also been observed in the pyritic faces of microbial mat shale from the Middle Proterozoic Belt Basin.
This faces of the Bijaigarh Shale also contains abundant clusters of phosphatic spheres that seem to fill in and accrete
around original spherical structures of a few microns diameter.In places multiple spheres are encased in a single
phosphatic overgrowth. In the lower two thirds of the Bijaigarh Shale, wavy
anatomizing laminated carbonaceous shale seem absent. This portion of the succession is instead dominated by massive
to evenly laminated carbonaceous shale that closely resembles their physically deposited Phanerozoic counterparts.
That microbial mat can have an important impact on the preservation and modification of siliciclastic sediment surfaces
Is increasingly being recognized. In the absence of grazing metazoans many Precambrian sediment surfaces, including
Muddy substrates, were probably covered with microbial mats and biofilms when a favorable balance existed between
Sedimentation rate, availability of moisture, and an energy source. Yet, whereas microbial mats were a major producer
of biomass in the Precambrian, not all carbonaceous shale of that age necessarily represent in situ microbial mats.
Although there are indications for microbial mat colonization of mud surfaces in all of the three carbonaceous shale
pictured here, there is also evidence in all instances of shale faces that either mimic microbial mat style lamination or
are evenly laminated and quite comparable to Phanerozoic non- mat carbonaceous shale.

References
Liu Honglin, Wang Hongyan, Liu Renhe, Zhaoqun，Lin Yingji , 2009 International coal bed and shale gas symposium, Shale gas in China : New Important Role of Energy of role in 21st century
Modern shale gas Development in the US ,A Primer , April 2009 , US Department of Energy, Ground Water Protection council , National Energy Technology Laboratory Strategic Centre for Natural Gas and Oil.
J Schieber , S Sur & S Banerjee , 2007, 7(e) Benthic microbial mats in black shale units from the Vndhyan Supergroup , Middle Proterozoic of India: The challenges of recognizing the genuine article.
Evaluation of Impacts of Underground Sources of Drinking Water by Hydraulic Fracturing of Coalbed Methane Reservoirs, APP . A-23 , June 2004 , Appendix A, Department of Energy – Hydraulic Fracturing White paper
Mike P. Jackson , October 2007 , The Future of Natural Gas in India : A study of major Consuming Sector.
Shale Revolution (editorial) Nature460, 551-552 (30 July 2009) | doi:10.1038/460551b; Published online 29 July 2009
Total Energy Consumed in the US – 2007 , EIA – Annual Energy Outlook 2009
J. Daniel Arther , SPE, Brian Bohm & Davd Cornue,2009 , Environmental Considerations of Modern Shale Gas Development.
Rick Lewis , David Ingraham , Marc Pearcy,2004 , New Revolution Techniques for Gas Shale Reservoirs , Reservoir Symposium 2004
Swaminathan S Anklesaria Aiyar (article), Shale Gas: Could it be a new energy source? , 9th August 2009 , Times Of India
Ministry of Petroleum & Natural Gas , Government of India , http://petroleum.nic.in/conserv.htm
Types of Shale :