Conventional vs Unconventional Reservoirs
Introduction
Reservoirs are critical
utilities in hydrocarbon exploration and production in that they are the
underground storage space for oil and natural gas. But Not all reservoirs are
all the same. They vary widely in geological setting and methods of extraction
and economic viability. A solid knowledge of the contrasts in customary and
uncommon saves is fundamental with regards to improving investigation efforts
and expanding hydrocarbon generation.
Conventional Reservoirs
Conventional reservoirs
are geological formations that permit hydrocarbons to move freely through
interlinked pore spaces in reservoir rocks. The porous reservoir rock,
typically sandstone or limestone, is surrounded by impermeable shale or
mudstone rock that entraps hydrocarbons and inhibits their upward migration.
Typical Characteristics of
Conventional Reservoirs
1. High Permeability:
This allows for rapid production using
conventional drilling and extraction techniques.
2. Natural Pressure Drive:
Most conventional
reservoirs have some relief of pressure from water drive, gas cap drive, which
can push hydrocarbons toward the producing well, or solution gas drive, thus
facilitating recoveries.
3. Well-Defined Traps:
As conventional reservoirs
are structural and stratigraphic traps. These include traps such as anticlines, fault
traps, and salt domes that effectively lock hydrocarbons within the reservoir.
4. Simple Extraction
Techniques:
Due to the high
permeability of conventional reservoirs, relatively simple techniques can be
used for extraction. To produce hydrocarbons efficiently, vertical, or
directional drilling is usually adequate.
5. Economic Viability:
Unlike unconventional
resources, which are likely to have higher drilling and completion costs, the
cost of producing from ‘conventional’ reservoirs is relatively low.
Unorthodox Reservoirs
Hydrocarbons trapped in
topologically challenging formations with low permeability are categorized as
unconventional reservoirs, and their resources often require advanced
extraction techniques. These reservoirs typically consist of organic-rich
rocks, like shale, tight sandstone, and coal beds.
♦ Unconventional
Reservoirs: The Essentials
1. Low Permeability:
These unconventional
reservoirs have very low permeability, limiting the natural flow of
hydrocarbons. Turning these resources into production requires specialized
techniques, namely hydraulic fracturing (fracking) and horizontal drilling.
2. Advanced Extraction
Technologies:
Hydrocarbons flow through
artificial pathways created by horizontal drilling and hydraulic fracturing,
which allow for the extraction of hydrocarbons from unconventional reservoirs.
3. Narco-Hydrocarbon Distribution:
In contrast to
conventional reservoirs where hydrocarbons are contained within clearly defined
traps, unconventional reservoirs contain hydrocarbons interspersed throughout
the rock matrix, which makes extraction more difficult.
4. Higher Development
Costs:
The need for advanced
drilling and stimulation technologies led to the cost of developing
unconventional reservoirs being much higher than conventional.
5. Long-term Production Show:
Unconventional make up for the
initial extra capital required in production lifetimes, as stimulation is
ongoing and recovery increases with time.
Advancements in Technology for Reservoir Development
Recent improvements in
extraction technologies have made the development of both conventional and
unconventional reservoirs much more feasible. Key innovations include:
✔Horizontal Drilling: Allows for more extensive well contact with reservoir rock, increasing
hydrocarbon recovery.
✔Fracture Fracking: Creates fake breaks in formations with low permeability to help oil and gas
flow.
✔Enhanced Oil Recovery
(EOR): Technologies including CO2 award injection, steam flooding, and water
flooding, increase hydrocarbon recovery from both conventional and
unconventional deposits
Environmental Factors
✔Conventional Reservoirs: Conventional has a little smaller environmental footprint, because extraction is done with simpler techniques.
✔Unconventional Reservoirs: Apprehensions about groundwater contamination by salt and seismic upset arise with increased drilling, water consumption, and chemicals.
Implications for the
Economy and Markets
Conventional reservoirs are still seen as the dominant driver of hydrocarbon supply owing to their lower cost and relative simplicity of production.
Conclusion
Conventional reservoirs
are characterized by an abundance of oil and gas that can be easily retrieved,
as opposed to unconventional reservoirs. Conventional Reservoirs have higher
permeability and lower production costs, while Unconventional Reservoirs need
new technologies and higher investments. Still, technological advancements are
closing that gap making both reservoir types essential to feed the world’s needs
for energy.
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