Basic Reservoir Enginnering

1. RESERVOIR
ENGINEERING

2. Overview of Reservoir Engineering
 Outcome:
 Data in put:
 PVT
 Scale
 Reservoir Simulation:
 Natural depletion
 Water Injection
Reservoir Management:

3. There are several laboratory tests that being conducted to
characterize the reservoir fluid. The test results are then being
used as input for Petral software analysis:
 Compositional Analysis
 Constant composition expansion test
 Differential liberation test
 Separator test
 Swelling test for CO2 and N2
Reservoir Fluid Studies

4.  Samples of oil and gas are taken from test separator or from
stock tank. The fluid then combined in laboratory on the basis
of the produced GOR.
 The method is by flashing the sample from reservoir to
atmospheric condition to obtain oil and gas at equilibrium
condition
Compositional Analysis

5. Gas Chromatography
Component Mole % Molecular Density@
Separator Oil Separator Gas Wellstream Weight 60°F
CO2 0.08 1.49 0.91
N2 0.00 0.27 0.16
C1 1.91 60.66 36.47
C2 1.60 15.32 9.67
C3 2.40 10.14 6.95
i-C4 0.81 1.88 1.44
n-C4 2.66 4.82 3.93
i-C5 1.45 1.43 1.44
n-C5 1.57 1.30 1.41
C6 6.81 2.59 4.33
C7+ 80.71 0.09 33.29 218 0.8515
TOTAL 100.00 100.00 100.00
Wellstream composition calculated based on GOR of 130 scf/stb
Result of Compositional Analysis

6.  The objectives of the CCE test are:
 Determine the saturation pressure.
 Compressibility factor of gas phase.
 Total hydrocarbon volume as a function of
pressure.
Constant Composition Expansion Test (CCE)

7. Pressure (psig) Relative Volume Pressure (psig) Relative Volume
5000 0.9453 2516 1.0001
4500 0.9541 2401 1.0243
4000 0.9638 2253 1.0599
3500 0.9746 2090 1.1066
3000 0.9867 1897 1.175
2900 0.9893 1698 1.2655
2800 0.992 1477 1.4006
2700 0.9948 1292 1.5557
2620 0.997 1040 1.8696
2605 0.9974 830 2.2956
2591 0.9978 640 2.9457
472 3.9877
CCE Test Result

8. Reported Reservoir Conditions
Reservoir Pressure 2516 psia
Reservoir Temperature 220 degF
Constant Composition Expansion
Bubble point Pressure 2516.7 psia
Reservoir Characterization & PVT information data

9.  Based on the DL test it is possible to determine
amount of gas in solution, the shrinkage in the
oil volume, density of the remaining oil as a
function of pressure.
Therefore, the gas compressibility factor and specific gravity can
also be determined.
Differential Liberation Test (DL)

10. Pressure
(psig)
Vapor Z-
Factor
Liquid Density
(lb/ft3)
Gas-Oil Ratio
(Mscf/stb)
Oil Relative
Volume
(rb/stb)
Gas
Gravity
Gas FVF
(rb/Mscf)
2516.7 45.11 1.1342 1.7493 0
2350 0.8686 45.669 1.0526 1.7095 0.7553 1.2574
2100 0.8692 46.502 0.9378 1.6535 0.7547 1.407
1850 0.8719 47.331 0.8309 1.6013 0.7565 1.6006
1600 0.8767 48.16 0.7307 1.5523 0.7614 1.8586
1350 0.8836 48.992 0.6361 1.5057 0.7704 2.2164
1100 0.8926 49.835 0.546 1.4609 0.7859 2.7411
850 0.9036 50.699 0.4591 1.4171 0.8121 3.5773
600 0.9167 51.608 0.3732 1.3726 0.8597 5.105
350 0.9324 52.632 0.2824 1.3234 0.9618 8.7518
159 0.9481 53.673 0.196 1.272 1.1726 18.685
0 56.323 0 1.1228 1.8901 0
DE Test Result

11. Differential Vaporization Test (at 2014 psig and 155 °F)
Oil Formation Volume Factor 1.1 bbl/stb
Solution Gas Oil Ratio 1.1342scf/stb
Oil Density 45.11lb/ft3
Reservoir Fluid Viscosity (at 2014 psig and 155°F)
Oil Viscosity 1.33 CP
Reservoir Characterization & PVT information data

12. Tested to determine the changes in volumetric behavior of
reservoir fluid as fluid pass through separator then into stock
tank.
Separator Testing

13. Performed for very specific applications where if a reservoir is to
be depleted under miscible gas injection or a gas cycling scheme
Mole
Fraction
Gas Added
Saturation
Pressure
(psig)
Swell Factor
(Relative
Volume)
0 2519 1
5 2607 1.024
10 2705 1.0504
20 2913 1.1136
30 3159 1.1949
40 3285 1.3031
Mole
Fraction
Gas Added
Saturation
Pressure
(psig)
Swell Factor
(Relative
Volume)
0 2521 1
5 3216.6 1.0117
10 4019 1.0242
20 5784 1.0528
30 8057 1.0879
Swelling Test of (CO2) Swelling Test of (N2)
Swelling Test