g as m aterial b alance. o utline : volumetric depletion reservoir. water drive mechanism. burns et...
TRANSCRIPT
GAS MATERIAL BALANCE
OUTLINE:
Volumetric depletion reservoir. Water drive mechanism. Burns et al method. Gas material balance exercise.
VOLUMETRIC DEPLETION RESERVOIR
The term volumetric depletion reservoir applies to the performance of a gas reservoir in which water influx due to pressure decline is insignificant.
Volume of the hydrocarbon remains constant and can be calculated by the following equation.
As the pressure decline from the initial reservoir pressure for a given volume of production Gp material balance equations can be written.
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
VOLUMETRIC DEPLETION RESERVOIR
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
VOLUMETRIC DEPLETION RESERVOIR
The assumption that hydrocarbon pore volume is constant is problematic.
Connate water saturation expansion. Grain pressure increases due to fluid pressure
reduction.
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
VOLUMETRIC DEPLETION RESERVOIR
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
VOLUMETRIC DEPLETION RESERVOIR
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
WATER DRIVE RESERVOIR
If the reduction in reservoir pressure leads to water influx into the reservoir material balance equation is modified.
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
WATER DRIVE RESERVOIR
is the fraction of the hydrocarbon which is flooded by the water.
The effect of water influx is to maintain the pressure. Material balance equation for water drive mechanism in gas
reservoir is a non linear equation. A mathematical model needs to be defined to interpret history
matching and prediction. Aquifer fitting. If the aquifer is the same size of reservoir then a simple
mathematical model can be applied.
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
WATER DRIVE RESERVOIR
If the production history of the reservoir is available Burns et al proposed the following method.
Step1: Depletion material balance ( apparent gas in place).
Step 2: corrected value of the gas in place can be calculated by the following formula:
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
WATER DRIVE RESERVOIR
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
EXERCISE:
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
EXERCISE:
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
SOLUTION:
GIIP:
Gas pressure at the centroid
Temperature Ei
Z factor calculation at GWC
EGWCGas pressure
gradient
Gas water contact depth
pressureTemperatur
e
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
SOLUTION: Pressure at GWC:
Temperature at GWC:
Z factor: 0.888
Gas formation factor at GWC:
Gas pressure gradient:
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
SOLUTION:
Gas pressure at centroid:
Temperature at centroid:
GIIP:
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
SOLUTION:
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
SOLUTION:
Step1: calculate cumulative gas production until the pressure reduced to 1200 psi.
When P=1200 psi, Z=0.832.
Step2: cumulative gas production in the build up period:
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
SOLUTION:
Step3: Cumulative gas production in plateau period:
Step4:Time in which reservoir can produce at the rate of 100 MMscf/d:
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
SOLUTION:
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development
SOLUTION:
Fundamentals of Reservoir Engineering, L.P. Dake , Shell Learning and Development