1. Self-chosen topic: Natural gas-from
extraction to consumption
Ph.D candidate Stamatina Karakitsiou
Department of Physics and Technology, University of Bergen, Norway
February 12, 2016
2. Outline
– Motivation
– Natural gas formation
The genesis of hydrocarbons
Maturation periods
Kerogen
– Natural gas-detection method
– Natural gas-characteristics
– Conventional and unconventional well
– Unconventional method
Hydraulic fracturing
– Natural gas distribution
Liquified natural gas
Pipline transmission system
– Innovation technologies
– Conclusions
2
5. Motivation
– Natural gas has had a tremendous growth as part of the global energy mix,
and today accounts for 21 % of the global primary fuel consumed. Current
reserves are enough to support global conventional gas consumption for the
next 60 years
– The International Energy Agency (IEA) suggests that unconventional oil and
gas could account for as much as 50% of undiscovered global reserves.a
a
World fossil fuel supply based on world production, data from BP’s 2013, statistical review of world energy
6. Natural gas formation-The genesis of hydrocarbons
– Gas is generated from organic matter which accumulates in sedimentary basins
– Only a small part of the organic matter is trapped in sediments (most of it is
oxidised)
– The amount of organic matter that is trapped in the sediments is transformed
into kerogen.a
– kerogen: is defined the organic material which is dehydrated after burial to
about 100 m or more.
a
Yoshihiro Ujlle, Nature vol 272, pp 438-439. 1978
7. Natural gas formation-The genesis of hydrocarbons
– Kerogen is formed within the upper few hundred meters of the sediment
column after the deposition from precursor products like:humus, humid,
fulvic acid
– The organic mater may be derived from: marine organism, algae, plants
derived from land
– The transformation of amino acids, carbohydrates, and other compounds into
kerogen is achieved by the removal of functional groups such as :acid groups,
aldehydes and ketones
– This involves a loss of oxygen from the organic material, also of nitrogen,
water and CO2
– Thus the whole process is taking place in ”anoxic environments”a
a
Robert M. Hazen, Reviews in Mineralogy and Geochemistry, vol 77, pp 449-465, 2013
8. Natural gas formation-Maturation periods
Diagenesis: Is the change of sentiments or existing sedimentary rocks into a
different sedimentary rock during and after rock formation (lithification) this
happens in low temperature and pressures
Catagenesis: Is a term to describe the cracking process which results in the
conversion of organic kerogen into oil a
Metagenesis: Takes place in really high temperatures and pressures. At this
stage of lithogenesis a complex process of mineral recrystallisation occurs. In this
stage minerals have really low porosity. Natural gas is formed
a
Tissot et al, Petroleum formation and occurrence, 1978
9. Natural gas formation-Kerogen
– Being a complex of very large molecules (polymer) kerogen is difficult to anal-
yse but with pyrolisis (350 C◦
-450 C◦
) can then be analysed by means of gas
chromatography and mass spectrometry
– Three main types of kerogen which may be classified as a function of H/C and
O/C ratio
– Type 1: High H/C ratio usually between 1.3 and 1.7 , contains little oxygen
less than 0.1. It will provide mainly oil, with less gas (CH4 and CO2)a
– Type 2: Is a composition between type 1 and type 3 and is most common
for oil
– Type 3: Is derived from organic matter from land plants, such as lignin,
tannins and cellulose. It contains low H/C ratio and high O/C reflecting
the composition of the precursor plant matter. In maturing (through of the
effect of the temperature) this kerosene generates abundant water, CO2 and
methane CH4. Most coals have a composition and structure similar to type
3 kerogen. Type 3 generates mostly gas
a
Robert M. Hazen, Reviews in Mineralogy and Geochemistry, vol 77, pp 449-465, 2013
10. Natural gas formation-Kerogen
a
Figure 3: Diagram (Van Krevelen diagram) showing the primary composition of the different types of
kerogen and the changes as a function of heating (maturation) during progressive burial
a
B.Biju-Duval, Sedimentary geology , Technip, pp 562-577, France, 2002
11. Natural gas formation-Maturation time
a
Figure 4: The maturity of a source rock is a function of the time-temperature index. The geothermal
gradients are most critical during the deepest burial because the maturation is an exponential function of
the temperature. At a certain depth and temperature the maturity may vary greatly and burial curve C will
produce the highest maturity at this depth. Source rocks buried in curve A and B are less mature because
their exposure to greater burial depth has been much sorter.
a
Knut Bjørlykke, Petroleum Geoscience, From Sedimentary Environments to Rock Physics, pp 339-348,
2010
12. Natural gas formation-Gas window
– During catagenesis thermal cracking is efficient. The molecular weight of
the hydrocarbons decreases with burial. The depth at which the generation
of hydrocarbons occurs is called the oil window. The threshold at which
catagenesis begins varies from 50 C◦
to 150 C◦
and from 500 m to 4000 m,
depending on the geothermal gradients of the sedimentary basins. a
– Metagenesis is the last phase of kerogen evolution in which dry gas
(methane) or thermogenic gas forms by cracking of the previously
formed hydrocarbons and the residual kerogen. This is called the gas win-
dow, generally starting at depths of 3000 m at 120C◦
to 200C◦
.
a
B.Biju-Duval, Sedimentary geology , Technip, pp 562-577, France, 2002
13. Natural gas formation-Strartigraphy
a
Figure 5: Explanation about source rock, reservoir rock and natural gas migration
a
Knut Bjørlykke, Petroleum Geoscience, From Sedimentary Environments to Rock Physics, pp 339-348,
2010
14. Natural gas-detection method-undersea
– A specially designed vessel with air guns shoots highly pressurised air into the
water, which creates a concussion that hits and locally vibrates the sea floor
– This seismic energy transmits through the earth’s crust , and as it encounters
layers of rock with different acoustic properties
– The energy bounces back as a reflection
– It is then recorded by an array of sensors called geophones and hydrophones
– The product of density and velocity is called acoustic impedance Z
– The amount of energy that is reflected depend on the contrast in acoustic
impedance between the rocks. This can be expressed from :Rc=Z1−Z2/Z1+Z2
for layer 1,2
– Easier process to scan in the sea level than in the land
15. Natural gas-characteristics
– Two different types to reach natural
gas
– the first one is derived from thermo-
genesis -convensional method
– The other one belongs to uncon-
ventional hydrocarbons-shale
gas-hydraulic fracking)
– Natural gas chiefly consists of
methane (CH4), but also contains
other hydrocarbons such as ethane,
butane, propane and naphtha
– Natural gas is odourless, colourless
and flammable. It is non-toxic and
lighter than air, utility companies
add a smell with a product called
mercaptan-to make leaks easier to
detect.
Figure 6: Compounds of natural gas a
a
www.statoil.com
10
16. Conventional and unconventional well
A conventional well is one which taps these traditional sedimentary forma-
tions, sometimes also known as traps.a
A conventional well typically is drilled
using the same methodology as Colonel Drake: a vertical hole that employs layers
of steel and cement to separate the well bore from the surrounding freshwater
aquifers.
An unconventional well is different in that it drills deeper to tap the organic
rock that is the actual source of the oil and gas. An unconventional well usually
employs sophisticated methodologies including horizontal drilling.
a
www.pagcoc.org
17. Unconventional methods
Source rocks of shale composition with important subsurface extension
(under the groundwater base), which, during their geological evolution, were
found within the gas window (generally corresponding to depths over 5000 to
6000 m) can unconventionally liberate the remaining in the rock gas by hydraulic a
Hydraulic fracturing (also hydrofracturing, hydrofracking, fracking, or frac-
cing) is a well-stimulation technique in which rock is fractured by a pressurised
liquid. The process involves the high-pressure injection of ’fracking fluid’ (primar-
ily water, containing sand or other proppants suspended with the aid of thicken-
ing agents) into a wellbore to create cracks in the deep-rock formations through
which natural gas, petroleum, and brine will flow more freely. When the hydraulic
pressure is removed from the well, small grains of hydraulic fracturing proppants
(either sand or aluminium oxide) hold the fractures open.
a
Quanshu Li et al, A review on hydraulic fracturing of unconventional reservoir, Petroleum, v 1, pp 8-15,
2015
19. Unconventional methods–defects
The extraction and use of shale gas may potentially affect the environment through
the leaking of extraction chemicals and waste into water supplies.
Figure 8: Hydraulic fracturing in Europe
url
a
a
Timothy Vinciguerra et all, Atmospheric Environment, pp 144-150, 2015
20. Natural gas distribution
The natural gas system is gener-
ally described in terms of:
– Production
– Processing
– Transmission
– Storage
– Distribution
Natural gas uses:
– Source of energy for heating
– Electricity generation
– Fuel for vehicles
– Chemical feedstock in the manufac-
ture of plastics and other commer-
cially important organic chemicals
Figure 9: Process of natural gas
21. Natural gas distribution–Liquified natural gas
– LNG is natural gas (predominantly methane, CH4) that has been converted
to liquid form for easy storage and transport.a
– Natural gas is condensed into a liquid form at close to atmospheric pressure
by cooling it. LNG achieves a higher reduction in volume than compressed
natural gas (CNG) so that the volumetric energy density is 2,4 times greater
than that of CNG.
– This makes LNG cost efficient to transport over long distances where pipelines
do not exist.
– Specially designed cryogenic sea vessels (LNG carries) or cryogenic road
tankers are used for its transport.
a
S.Adrew Mclritosh, Moving natural gas across oceans, oilfield review, pp 50–63, 2008
22. Natural gas distribution–Liquified natural gas
– The natural gas extracted from the ground, contains impurities, water and
other associated liquids. So first it is processed to clean it.
– It goes through a series of pipes and vessels where gravity helps separate the
gas from some of the heavier liquids. Other impurities are then stripped out
– The natural gas passes through a water–based solvent that absorbs carbon
dioxide and hydrogen sulphide, these would otherwise freeze when the gas is
cooled and so cause blockagesa
– Next any remaining water is removed, as this would also freeze
– Finally, remaining lighter natural gas liquids, mainly propane and butane
are extracted to be sold separately or used as refrigerant later in the cooling
process
a
S.Adrew Mclritosh, Moving natural gas across oceans, oilfield review, pp 50–63, 2008
23. Natural gas distribution-liquefaction process
– Liquefaction process happens in heat exchangers
– A coolant, chilled by giant refrigerators, absorbs the heat from the natural gas
– It cools the gas to –162 C◦
, shrinking its volume by 600 times a
a
S.Adrew Mclritosh, Moving natural gas across oceans, oilfield review, pp 50–63, 2008
24. Natural gas distribution-liquefaction process
– This process turns natural gas into a clear, colourless, non–toxic liquid that is
much easier to store and to transport
– The LNG is kept in insulated tanks until is ready for loading into specialy
designed LNG ship or carriera
– When the ship arrives at its destination, the LNG is transferred to a re–
gasification plant where is heated, returning to its gaseous state
– The gas is then transported via pipelines to the customer providing energy for
homes and industry
a
S.Adrew Mclritosh, Moving natural gas across oceans, oilfield review, pp 50–63, 2008
25. Natural gas distribution–Pipeline transmission system
– ’Interstate highway’ for natural gas-consists of thousands of miles of high-
strength steel pipe varying in diameter.
– The primary function of the transmission pipeline company is to move huge
amounts of natural gas thousands of miles from producing regions to local
natural gas utility delivery points-called ’city-gate stations’.
– Compressor stations at required distances boost the pressure that is lost
through friction as the gas moves through the steel pipes.a
– Pipeline throughput depends on pipeline diameter and the operating pressure,
taking into account the length of the pipeline and the terrain
– Typical onshore pipeline operating pressure is about 50 to 80 bar
– For offshore pipeline the operating pressure is typically between 100 to 150
bar depending on the material and the age of the pipeline
a
X.Wang. Advanced Natural gas engineering, Esevier
26. Natural gas distribution–pipe-coating materials
Steel pipes are required in the majority of the gas industry of the coating.
Purpose of the coating:
– Purpose of the coating:
Protect the pipe from moisture
Corrosive soils, inside and outside of the pipe
Construction-induced defectsa
– Coating techniques
Specialised coal tar enamel
Fusion bond epoxy
Polyethylene
– Cathodic protection
The pipe has to be designed with enough wall thickness to handle the internal
operation pressure, the bending stress and the external crushing forces
a
www.petrowiki.org
28. Natural gas distribution–important parameters
Concepts of fluid mechanics are required to simulate the fluid flow behaviour inside
the pipeline and its effect on the pipeline. It is used to identify the flow rate and
pressure within the pipeline which depends on several parameters.
Such parameters are: a
– Leakage rate
– Change in density
– Pressure in accordance with time
– Temperature with respect to time
a
McCabe et al. Unit operations of chemical engineering, 1993
29. Natural gas distribution–Pressure effect
Pressure drop
Since the pressure at the beginning point of the pipeline is known, it is needed
only to evaluate pressure drop.
Pressure drop specifies the differences between pressure at start point and pressure
at the end point
∆P = Pstartpoint − Pendpoint (1)
Due to steady state flow inside the pipe, the pressure drop can be calculated by
using the below formula a
∆P =
fρV 2
L
2Di
+ ρgH (2)
where f is Darcy-Weisbach friction factor which can be found by using the Moody
Diagram. H,L and D are height differences between the desired points for single
phase fluids, length of the of the pipeline and inner diameter of the pipeline,
respectively.
a
McCabe et al. Unit operations of chemical engineering, 1993
30. Natural gas distribution–Moodys’s diagram
a
Figure 10: Moody diagram (Moody, 1944)
a
McCabe et al. Unit operations of chemical engineering, 1993
31. Natural gas distribution–Temperature effect
– Similar to the pressure, the temperature must be evaluated in order to see
how this change influence the steady flow through a pipeline
– Each system exchanges work and heat with its surroundings
– At onshore pipelines the changes at the ambient temperature have to been
taken into account
– At offshore pipelines the seawater temperature is criticala
Figure 11: Under water pipelines , North Sea, Statoil
a
McCabe et al. Unit operations of chemical engineering, 1993
32. Natural gas distribution-Temperature effect
– There are three modes of heat transport
– 1) Conduction heat transfer: If a temperature gradient exists through
a solid or a stationary fluid. For a cylindrical tube, the value of conduction
heat transfer flux ( ˙Qcone,cal) is expressed by below formula:
˙Qcone,cal = −2π · L · K ·
T1 − T2
ln(r2
r1
)
with K the convection heat transfer coefficient (3)
– 2) Convection heat transfer: Occurs when a moving fluid is in touch with
a liquid surface or even between particles of a moving fluid. The convection
heat transfer flux in the case of an interaction between a moving fluid and a
solid surface is defined by:
˙Qcond = h·As˙T h the conventional heat transfer coefficient and As the contact surface area (4)
33. Natural gas distribution-Temperature effect
– 3) Thermal radiation: This case happens when there is no contact be-
tween surfaces. For this mode to be significant compared to convection and
conduction modes the temperature must be high
– Different temperatures create a difference in pressure which must be consider
in the pipeline system onshore and offshore.
Figure 12: Simulation of different temperatures through a gas pipeline
34. Innovation technologies-”smart well”
– ’smart-well’ :Below-ground wireless communication in the gas industry
– Advancements in horizontal well drilling and hydraulic fracturing helped to
meet this demand
– The most common ”smart well” system system currently utilise fiber-optic
cables and in well valves operated hydraulically to retrieve measurements and
optimise production from the well
– The problem of high pressure and temperature has limited the industry-wide
adoption of such technologies
– At the moment they use them only in shallow shale gas wells
– Advances in measurement–while–drilling (MWD) technology have driven two
wireless downhole technologies: 1) pressure wave telemetry and 2)
electromagnetic (EM) telemetrya
a
N.G. Franconi et al, review:Wirelss communication in oil and gas wells, vol 2, pp 996-10005, 2014
35. Innovation technologies-”smart well”
– Pressure wave telemetry :The pressure waves are generated through a
water hammer, which are produced when a fluid is forced to stop or change
direction suddenly.
– The data are analysed into the pressure waves through a variety of analog and
digital modulation techniques
– Pressure-wave transducers on the casing head convert the pressure waves to
voltage that are interpreted by embedded processors and used by operators
during the directional drilling process
– Electromagnetic telemetry :Involve the use of the drill string to propa-
gate EM waves that can be measured on the surface of the eartha
a
N.G. Franconi et al, review:Wirelss communication in oil and gas wells, vol 2, pp 996-10005, 2014
36. Innovation technologies -’Zeolites membrane-in natural gas purifi-
cations’
– Natural gas has to be purified from CO2 and a zeolite membrane is proposed
for this
– Zeolite which is a mineral has pores in the nanoscale, and the specific type of
zeolite which called Sapo-34 has 0.38 nm pores
– Sapo-34 can function under a wide range of pressures and it can take temper-
atures up to 700 degrees Celsius
– Sapo-34 can be synthesized as a very thin layer of interlocking crystals 1-5
microns thick and this layer act as membranea
a
H.SHI, Synthesis of Sapo-34 zeolite membrane with the aid of crystal growth inhibitors for CO2–CH4,
New. J. Chem, vol 38, pp 5276–5278, 2014
37. Innovation technologies -’Zeolites membrane-in natural gas purifi-
cations’
– An actual natural gas well can be simulated by feeding mixtures of carbon
dioxide and methane from the left side
– CO2 is much smaller then CH4 thus it can permeate through the membrane
exiting at the bottom-permeate flow
– CH4 being very large it is retained in the original gas mixture -retentate gas
flow– at the right
– A 50– 50 mixture of CO2 and CH4 is converted to 1:99 mixture
– The current technology captures CO2 with a liquid chemical which absorbs
it-very energy intensive
– Sapo-34 environmental friendly–cost effective
38. Conclusions
– Natural gas process combines all the natural sciences- in a high
technology level
– Natural gas is a fossil fuel with the less emissions in CO2 but
it can still creates an environmental disaster if science is not
applied properly
