oil reservoir drive mechanisms presentation
TRANSCRIPT
OIL RESERVOIR DRIVE
MECHANISMS Presented by :
Moklesur Rahman Moupiya Mallick
Natra Kamal HazarikaNayan Jyoti Sabhapandit
Nishal GohainParardha Sabhapandit.
4th SEMESTER, PETROLEUM ENGINEERING, DUIET
INTRODUCTIONEach Reservoir is a unique combination of :
GEOMETRIC FORM
Each Drive Mechanism has typical performance characteristics:
ULTIMATE RECOVERY FACTOR
PRESSURE DECLINE RATE
GAS-OIL RATIO
WATER PRODUCTION
GEOLOGICAL ROCK PROPERTIES
PRIMARY DRIVE MECHANISMS
FLUID CHARACTERISTICS
PRIMARY RECOVERY MECHANISMSThe term refers to the production of hydrocarbons from a
reservoir without the use of any process like fluid injection, to supplement the natural energy of the reservoir.
SIX OIL RESERVOIR DRIVING MECHANISMS:
ROCK & LIQUID EXPANSION DRIVE
DEPLETION DRIVE
GAS-CAP DRIVE
WATER DRIVE
GRAVITY DRAINAGE DRIVE
COMBINATION DRIVE
It exists in under saturated oil reservoir (i.e. Pr >Pb )
The only materials present in an under saturated oil reservoir are-* Crude oil * Connate water* Rock
As the reservoir pressure declines, the rock and fluids expand due to their individual compressibilities.
The reservoir rock compressibility is the result of two factors:
• Expansion of the individual rock grains • Formation compaction
ROCK AND LIQUID EXPANSION DRIVE
FLUIDS
ROCKS
ROCKS
ROCKS
ROCKS
ROCKS
ROCKS
WELLBORE
WELLBORE
WELLBORE
Res. Pr Decreases Rocks Expand Pore Volume Reduces Fluids force out of the pore space to the wellbore
PERFORMANCE CHARACTERISTICS
RESERVOIR PRESSURE :
GAS-OIL RATIO:
WATER PRODUCTION :
RECOVERY
EFFICIENCY:
DECLINE RAPIDLY & CONTINUOSLY
REMAINS LOW & CONSTANT
NIL
1 - 10 %, Average 3 %
DEPLETION DRIVE MECHANISM :
Also known as :
SOLUTION GAS DRIVE,DISSOLVED GAS DRIVE & INTERNAL GAS DRIVE
Principal source of energy Gas liberation from the crude oil & the subsequent expansion of the solution gas as the reservoir pressure is reduced.
Production data of a depletion drive
PERFORMANCE CHARACTERISTICS :
RESERVOIR PRESSURE :
GAS-OIL RATIO :
WATER PRODUCTION :
RECOVERY EFFICIENCY :
DECLINE RAPIDLY & CONTINUOSLY
FIRST LOW, THEN RISES TO MAXIMUM & THEN DROPS
NIL
5 - 35 %, Average 20 %
GAS-CAP DRIVE MECHANISM
It can be identified by the presence of a gas cap with little or no water drive
Due to the ability of the gas cap to expand, these reservoirs are characterized by a slow decline inthe reservoir pressure.
The natural energy available to produce crude oil comes from :
• Expansion of the gas-cap gas• Expansion of the solution gas as it
is liberated
PERFORMANCE CHARACTERISTICS :
DECLINE SLOWLY & CONTINUOSLY
RISES CONTINUOSLY IN UP DIP WELLS
NIL
20-40%, Average 25 %
WATER DRIVE MECHANISM
Many reservoirs are bounded by water bearing rocks called AQUIFERS
The reservoir may be outcropped at one or more places where it may be replenished by surface water as shown in the figure
BOTTOM WATER occurs directly beneath the oil and EDGE WATER occurs off the flanks of the structure at the edge of the oil as illustrated in the figure
WATER DRIVE is the result of water moving into the pore spaces originally occupied by oil, replacing the oil and displacing it to the producing wells
PERFORMANCE CHARACTERISTICS :
REMAINS HIGH & IS SENSITIVE TO THE RATE OF OIL, GAS & WATER PRODUCTION
REMAINS LOW IF THE PRESSURE IS HIGH
DOWN DIP WELLS PRODUCE WATER EARLY & WATER PRODUCTION INCREASES35-80%, Average 50 %
GRAVITY DRAINAGE DRIVE MECHANISM
This mechanism occurs as a result of difference in densities of the reservoir fluid
The fluids in petroleum reservoirs have all been subjected to the forces of gravity, as evidenced by the relative positions of the fluids, i.e., gas on top, oil underlying the gas and water underlying oil as shown in the figure
If the reservoir fluids are in equilibrium, then the gas-oil & oil-water contacts should be essentially horizontal
PERFORMANCE CHARACTERISTICS :
DECLINES RAPIDLY & CONTINUOSLY
REMAINS HIGH IN UP DIP WELLS & LOW IN DOWN DIP WELLS
ABSENT OR NEGLIGIBLE
40-80%, Average 60 %
In operating a gravity-drainage reservoir, it is essential that the oil saturation in the vicinity of the wellbore must be maintained as high as possible
There are two basic reasons for this requirement :
• A high oil saturation means a higher oil flow rate• A high oil saturation means a lower gas flow rate
In order to have maximum conservation of the reservoir gas in a gravity-drainage mechanism, wells should be located as structurally low as possible
COMBINATION DRIVE MECHANISM
This drive mechanism is most commonly encountered where both water & free gas are available in some degree to displace the oil towards the producing wells
Here, two combinations of driving force can be present :
• Depletion drive & a weak Water drive
• Depletion drive with a small gas cap & a weak Water drive
PERFORMANCE CHARACTERISTICS :
DECLINE RAPIDLY
REMAINS LOW IN DOWN DIP WELLS
NEGLIGIBLE
DEPLETION DRIVE < % < WATER DRIVE
CHARACTERISTIC COMPARISON TABLE
SL.
NO.
DRIVE
MECHANISMS
CHARACTERISTICS RESRVOIR PRESSURE
GAS-OIL RATIO
WATER PRODUCTION
RECOVERY EFFICIENCY
1. Rock and liquid expansion
Decline rapidly &
continuously
Remains low & constant
Nil
1-10% Average 3%
2.
Depletion
drive
Decline rapidly &
continuously
First low, then rises to maximum & then
drops
Nil
5-35% Average 20%
3.
Gas-cap drive
Decline slowly &
continuously
Rises continuously in up dip wells
Nil
20-40% Average 25%
4.
Water drive
Remains high & is sensitive to the rate of
oil, gas & water
production
Remains low if the pressure is high
Down dip wells produce water early & water
production increases
35-80% Average 50%
5. Gravity
drainage drive
Decline rapidly &
continuously
Remains high in up dip wells & low in
down dip wells
Absent or Negligible
40-80% Average 60%
6.
Combination drive
Decline rapidly Remains low in down dip wells
Negligible
Greater than Depletion drive & less than Water
drive
CONCLUSION
After studying the six driving mechanisms under primary recovery, it is clear that each drive mechanism has typical performance characteristics in terms of Ultimate Oil Recovery, Pressure decline rate, Gas-oil ratio and Water production. These driving mechanisms provide the natural energy necessary for recovery of the oil from the reservoir and without the use of any external processes like fluid injection etc..
SOURCES & REFERENCES
Reservoir Engineering Handbook by Tarek Ahmed
INTERNET
OUR SPECIAL THANKS TO :
Master Pranjit Borah, 4th semester, Petroleum Engineering, DUIET
Master Manas Kalita, 4th semester, Electronics & Communication Engineering, DUIET
Master Jyotirmoy Sharma, 2nd semester, Mechanical Engineering, DUIET