3. Contents
• Petroleum Reservoir
• Conventional Reservoir
• Unconventional Reservoir
• Comparison between Conventional and Unconventional Reservoirs
• Shale Gas
• Shale Oil
• Gas Hydrates
• Gas Hydrated resources in World
• Coalbed Methane
• Extraction Techniques
• Unconventional reservoir in Pakistan
• Conclusion
• References
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4. Petroleum Reservoir
“ Petroleum reservoir can be defined as an accumulation
or pool of hydrocarbons in subsurface within porous or
fractured rock formation.’’
Petroleum reservoirs can be categorized as ;
1) Conventional reservoir
2) Unconventional reservoir
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6. Conventional Reservoir
“ Conventional reservoir contains gas that can easily flow
naturally. In this reservoir, gas and oil can be migrated from
source rock.”
By using traditional techniques they can be extracted such as ;
1) Drilling
2) Pumping
3) Compression techniques
It all depends on the cost, ease of its development and production
rate.
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7. Unconventional Reservoirs
“ Unconventional reservoir term can be used to refer
reservoirs with “ low permeability” and “ low porosity”.
• Unconventional gas is an natural gas that cannot be
produced at an economic rate.
• Gas can not flow easily because of low permeability,
hence, require stimulation techniques.
• Unconventional reservoir are quite challenging in its
extraction due to low permeability and porosity.
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10. Conventional Reservoir
i. Consisting of gas that can
easily flow.
ii. It shows ease in its
development and extraction
iii. Not to much costly .
iv. Migration is in flow from
source to reservoir rock.
v. Can be profitably extracted
by direct methods.
Unconventional Reservoir
i. Consisting of gas that can not
flow easily, usually trapped.
ii. It’s extraction is challenging.
iii. To much costly
iv. It do not migrate from source
to reservoir rock.
v. Can be extracted by advanced
techniques that are costly.
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11. Conventional
Reservoir
• Conventional reservoirs
are ;
1. Sandstones
2. Limestone
3. Dolomites
Unconventional
Reservoir
• Unconventional reservoirs
includes;
1. Shale gas
2. Tight sands
3. Coal bed methane
4. Tar sands
5. Methane hydrates
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12. Shale gas
• Shale gas is an natural occurring gas that is formed and trapped in shale.
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13. Shale oil
Shale oil is an oil that is preserved in shale in association with;
• Siltstones
• Carbonates .
Tight Gas
An unconventional reservoir that contains tight gas or oil trapped in
pores of;
• Siltstones
• Sandstones.
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14. Gas Hydrates
• Gas hydrates are the gas molecules that come in contact with the ice
molecules. When subjected to warm environment it will convert into water
and natural gas.
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17. Coalbed Methane (CBM)
Coalbed methane is an methane gas or natural gas that is extracted
from coal.
Coalbed methane can be referred as ;
• Coal-mine methane ( CMM)
• Coalbed gas ( CBG)
• Coal seam gas ( CSG)
Formation
• CBM is formed in the process of coalification, which is the
conversion of plant remains into coal.
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20. Extraction of Unconventional
Resources
HORIZONTAL DRILLING
“ Horizontal drilling is used to provide greater
access to the gas trapped in deeper gas producing
formation.”
Mostly there held a vertical well drilling to target
the formation but, for unconventional reservoir to
reach the desire depth, drill bit is turned to bore
a well horizontally usually used in shale bearing
formations.
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22. Hydraulic Fracturing
• Hydraulic fracturing is a technique in which sand, chemicals and
water ( a pressurized liquid ) collectively used and are pumped
into well to unlock the trapped gas in shale formations.
• This is done by the hydraulic pressure , that results in opening of
the cracks or fractures in the rocks that allows natural gas to flow
out easily through the fractures.
• It must be used among with the horizontal drilling, so that the
hydraulic fracturing enables the desired amount of gas extraction
at reasonable cost.
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24. Directional Drilling
• Directional drilling is the process of drilling
which controls the direction of boring to target
more than one location.
• By directional drilling, multiple wells can be
drilled at different targeted locations.
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28. Conclusion
• Detailed study on Conventional and Unconventional
reservoirs, concludes about the extracting techniques
that are quite costly as compared to Unconventional
extraction techniques. Besides this, unconventional
reservoir shows its importance because these reservoirs
are unexplored at many places and conventional
reservoirs do not seems to fulfill the industrial as well as
domestic needs. It is believed that unconventional
reservoirs may overcome the need of present day
economically and in future too.
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29. References
• Collett, T.S., A.H. Johnson, C.C. Knapp, and R. Boswell, 2009,
Natural gas hydrates: A review, in T. Collett, A. Johnson, C. Knapp,
and R. Boswell, (eds.), Natural Gas Hydrates-Energy Resource
Potential and Associated Geologic Hazards, AAPG Memoir 89, p.
146-219.
• Grevemeyer, I., A. Rosenberger, and H. Villinger, 2000, Natural gas
hydrates on the continental slope off Pakistan: constraints from
seismic techniques: Geophysical Journal International, v. 140, p.
295-310.
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