Comparing the Performance of 5-Spot and Inverted 9-Spot Patterns by Reservoir Simulation using CMG Suite


Note: Reservoir simulation is a must for a petroleum engineer. During the past 10 years, I focus on experimental studies of EOR processes. I have been waiting for a formal training on reservoir simulation for years. This spring, our PE program opens a course on reservoir simulation using CMG suite, which is easy for a beginner, and has a special component STARS to simulate the enhanced oil recovery processes, especially conformance control using superabsorbent polymer (also called “preformed particle gel” in literatures). In this post and the next, I will show the CMG reservoir simulation results to compare the performance of 5-spot and inverted 9-spot patterns using black oil model, which is part of team project for that reservoir simulation course.

INTRODUCTION

The objective is to study and compare the performance of five-point and nine-point patterns. The tasks included are:

  1. Construct models for a reservoir model with five-spot and inverted nine-spot patterns using CMG;
  2. Run reservoir simulations for both models;
  3. Compare the simulation results by Dec. 31, 2020 for recovery, water cut, average reservoir pressure, oil production rate, gas-oil ratio, cumulative oil production, oil saturation, and pressure distribution between 5-spot and inverted 9-spot patterns.

RESERVOIR DESCRIPTION

A conceptual petroleum production unit with 400 m*400 m*20 m in size is to be simulated. The unit is approximated into 20 * 20 regular grids in horizontal layers and each cell is 20 m in length; and 3 layers in the vertical direction (as 8m, 8m, and 4m respectively).

The grid top, grid thickness, porosity, and permeability in x, y, and z directions are listed in Table 1.

Table 1. Reservoir Properties

Grid Top

(m)

Grid Thickness

(m)

Porosity

(fraction)

Kx

(mD)

Ky

(mD)

kz

(mD)

3120 8 0.2 200 200 20
3128 8 0.2 200 200 20
3138 4 0.2 200 200 20

Some other information about the reservoirs could be found below:

  • Rock Compressibility: 6e-7 1/k Pa, Reference Pressure: 1379 k Pa
  • Reference Pressure: 34000 k Pa @Reference Depth: 3170 m
  • Constant Bubble Spot Pressure: 30000 k Pa
  • Water-Oil Contact: 3250 m
  • Gas-Oil Contact: 2990 m

Black-oil model is chosen, and PVT data is listed in Table 2 and relative permeability is listed in Table 3.

Table 2. PVT Data for Reservoir Fluids in Conceptual Petroleum Production Unit

MODEL BLACKOIL

PVT EG 1

**$

p        Rs        Bo        Eg      viso      visg

700       6.8     1.121      5.77      1.11   0.01262

1600     17.29     1.173     12.41      0.96   0.01349

2270     21.85     1.179     17.08      0.95   0.01371

3160     26.91     1.182     23.98      0.88   0.01401

4640     33.99     1.214     35.33      0.83   0.01434

6430     41.66     1.217     48.84      0.79   0.01485

8500     52.16     1.245     65.49      0.74   0.01535

12490     70.89     1.295     96.05       0.7   0.01657

17280     93.19     1.343    132.78      0.59   0.01849

20960    107.78     1.386    159.54      0.54    0.0204

34470    201.68      1.49    257.76       0.3   0.02741

48260    359.65     1.596    357.98      0.23   0.03456

68950    596.61     1.755    613.66       0.2   0.05281

DENSITY OIL 830.0

DENSITY GAS 1.330

DENSITY WATER 1153.0

CO 1.1360e-6

CVO 3.0120e-5

BWI 1.01

CW 4.3510e-7

REFPW 102.0

VWI 1.290

CVW 0.0

**$ Property: PVT Type  Max: 1  Min: 1

PTYPE CON            1

Table 3. Relative Permeability Data for Conceptual Petroleum Production Unit

*SWT

**

SW     KRW    KROW    PCOW

0.200  0.0000  1.0000  195.84

0.229  0.0001  0.7407   95.20

0.255  0.0003  0.6829   60.00

0.308  0.0012  0.5722   22.00

0.334  0.0023  0.5194   18.80

0.412  0.0102  0.3715   12.60

0.464  0.0219  0.1526    8.43

0.557  0.0416  0.0822    4.40

0.606  0.0721  0.0000    1.32

0.647  0.1448  0.0000    0.00

0.700  0.1780  0.0000    0.00

0.800  0.2604  0.0000    0.00

1.000  1.0000  0.0000    0.00

*SLT

**

SL     KRG    KROG    PCOG

0.200  1.0000  0.0000 3891.60

0.316  0.6784  0.0000  579.60

0.435  0.6215  0.0000  372.40

0.562  0.5456  0.0000  242.50

0.614  0.3939  0.0020   60.80

0.702  0.1399  0.0280   37.21

0.812  0.0515  0.1721   13.65

0.875  0.0297  0.3395   10.45

0.906  0.0226  0.4395    9.00

0.937  0.0173  0.5500    7.51

0.969  0.0131  0.6702    5.90

1.000  0.0000  1.0000    0.00

BASIC MODEL SETUP

Based on the reservoir conditions, a black oil model with 20*20*3 grid blocks are created by Builder, a CMG component. Each grid block in layer 1 (top layer) and layer 2 (mid layer) is 20 m* 20 m*8 m, and each grid block in layer 3 (bottom layer) is 20 m* 20 m*4 m.

FIVE-SPOT PATTERN

Injector (Well-2) and producer (Well-1) are defined in the diagnosed corner cells in Fig. 1, the grid top model for five-spot pattern. The producer started working on Jan. 1, 1995 at liquid production rate is 30 m3 per day. The water injection rate is 30 m3 per day. Layers 1, 2, and 3 are perforated for both producer and injector. Constraints for producer are: minimum bottom hole pressure as 1500 k Pa and maximum liquid production rate as 100 m3/day for operation, and maximum water cut is 0.95 for monitor and shut-in conditions; and constraints for injector are: maximum bottom hole pressure is 80000 k Pa, and maximum water injection is 2000 m3/day for operation.

Fig. 1 Grid Top Model for Five-Spot Pattern

INVERTED NINE-SPOT PATTERN

Injector (Well-2) and one producer (Well-3) are defined in the diagnosed corner cells, and another two producers (Well-1, 4) are defined in another two diagnosed corner cells at phase 90 degrees in Fig. 2, the grid top model for inverted nine-spot pattern.

The producer started working on Jan. 1, 1995 at liquid production rate is 30 m3 per day. The water injection rate is 90 m3 per day. Layers 1, 2, and 3 are perforated for both producer and injector; and well constraints are same with five-point pattern.

Fig. 2 Grid Top Model for Inverted Nine-Spot Pattern

(to be continued)

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5 Responses to Comparing the Performance of 5-Spot and Inverted 9-Spot Patterns by Reservoir Simulation using CMG Suite

  1. Pingback: Determination of Perforation and Production Strategy for Single Well with Aquifer using CMG « Zinan Li's Blog

  2. Eduardo says:

    Thanks.
    Do you know how to monitor average pressure in CMG?
    As far as I can see from the Builder, when you input constraints, there is no parameter called average pressure. Can we define it?

    • lizinan says:

      Of course you can monitor average pressure in CMG. Now I do not have the software with me. You can have a try to check the pressure under field mode.

  3. mirza says:

    how we can define nominal pressure injector and rate injector?

    • lizinan says:

      Thank you for your comments. To be honest I do not understand your question very well. Maybe you can try to edit or input the well information in the Builder module.

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