Reservoir Simulation（Petroleum engineering）

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EG552B/EG552H

Reservoir Simulation Assignment 1

Introduction

Your task is to build a reservoir simulation model of an oil field using Petrel, then use

the model to investigate the development plan and run some sensitivities as described

below.

Data

The reservoir is a square tilted fault block containing single interior fault. The areal size

of the fault block is 5000 ft x 5000 ft. You should build a model with 25 x 25 grid blocks

in the X and Y directions (25 x 200 ft = 5000 ft). The model should have 8 layers.

The top reservoir depth is defined by these points:

X (ft) Y (ft) Depth (ft)

0 0 4350

5000 0 4420

0 5000 4880

5000 5000 4910

The gross thickness of each layer is 20 ft. Total gross thickness is 8 x 20 ft = 160 ft.

The net thickness of each layer is 17 ft. Total net thickness is 8 x 17 ft = 136 ft.

Porosity and permeability are defined in the supplied files FIELD_PORO.INC and

FIELD_PERMX.INC. Assume PERMY = 0.5*PERMX. For vertical permeability, use

kv/kh = 0.05.

The coordinates of the fault are as follows:

X (ft) Y (ft)

3200 0

3100 1250

3000 2500

2900 3750

2800 5000

The fault is vertical and has no throw but acts as a transmissibility barrier with a

transmissibility multiplier of 0.1.

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Some other reservoir data are given below:

Oil Water Contact Depth 4820 ft

Datum Depth 4700 ft

Initial Reservoir Pressure at Datum 2165 psia

Rock and fluid properties are as follows:

Rock (formation) compressibility 3.5E-6 psi-1

Oil surface density 52 lb/scf

Water surface density 64 lb/scf

Gas surface density 0.075 lb/scf

Water formation volume factor 1.02 rb/stb

Water viscosity 0.488 cP

Water compressibility 2.8E-6 psi-1

Pressure (psia)

GOR (Mscf/stb)

Oil Formation Volume Factor (rb/stb)

Oil Viscosity (cP)

Gas Formation Volume Factor (rb/Mscf)

Gas Viscosity (cP)

1000 0.294 1.173 0.998 2.376 0.0146

1250 0.387 1.216 0.897 1.798 0.0168

1500 0.480 1.260 0.797 1.430 0.0191

1750 0.573 1.304 0.697 1.186 0.0214

1860* 0.614 1.323 0.652

2000 0.614 1.320 0.661 1.022 0.0236

2250 0.614 1.315 0.676 0.915 0.0253

2500 0.614 1.310 0.691 0.849 0.0265

* Bubble point pressure

Relative permeability and capillary pressure data are as follows:

Sw Krw Krow Pc (oil-water) (psi)

0.20 0.0000 1.0000 7.25

0.30 0.0103 0.6477 4.16

0.40 0.0360 0.3844 3.01

0.50 0.0746 0.2000 2.39

0.60 0.1252 0.0834 2.00

0.70 0.1871 0.0221 1.73

0.80 0.2597 0.0013 1.53

0.85 0.3000 0.0000 1.45

0.90 0.5333 0.0000 1.37

1.00 1.0000 0.0000 0.00

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Sg Krg Krog Pc (gas-oil) (psi)

0.00 0.00 1.0 0

0.05 0.00 0.9 0

0.65 0.8 0.0 0

0.80 1.0 0.0 0

Development Plan

It is planned to develop the field using:

 two production wells

 one water injection well

 one gas injection well.

There is no export facility for gas, therefore all produced gas must be re-injected into

the reservoir. Reservoir pressure will be further supported by water injection.

The location of the wells is as follows:

X (ft) Y (ft)

Producer 1 2500 2100

Water Injector 3700 4100

Gas Injector 700 700

The location of the second production well is not yet decided. One of your tasks is to

select an optimum location for this well.

All wells are vertical through the reservoir and should be connected to all 8 reservoir

layers. Use a skin factor of +2.0 for production wells and -1.0 for injection wells.

The following production and injection constraints must be honoured:

Maximum water injection 10,000 stb/d

Maximum gas injection 10,000 Mscf/d

Maximum gas production* 10,000 Mscf/d

Producer Minimum BHP 1500 psia

Water Injector Maximum BHP 2500 psia

Gas Injector Maximum BHP 2500 psia

* All produced gas is to be re-injected therefore gas production cannot exceed gas

injection capacity.

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Procedure

Build the model using Petrel with the data above.

Insert three wells in the locations given.

Run the model for 10 years using the three wells. Make a note of some key results:

 Oil initially in place (STOIIP).

 Gas initially in place.

 Cumulative oil production over 10 years.

 Recovery factor over 10 years.

 Cumulative water production over 10 years.

 Cumulative gas production over 10 years.

 Cumulative water injection over 10 years.

 Cumulative gas injection over 10 years.

Examine the model results in the 3D viewer. Look at the areas which are swept by

water and gas.

Choose a suitable location for the second production well. Drilling constraints mean

that the second production well must be more than 200 ft away from any fault or

reservoir boundary.

Run the model including the second production well and compare results with the first

case. With two production wells, the maximum gas production should be 5000 Mscf/d

per well.

Run some further cases to optimise the location of the second producer. You should

aim to maximise the oil recovery over 10 years.

Now, using the 4-well development plan with the optimised location for the second

producer, run the following sensitivity cases.

 Oil-water contact 4790 ft

 Layer 4 permeability 1000 mD

 kv/kh 0.4

 Fault transmissibility 0

For each sensitivity case, make a note of the key results. Which variable has the

largest impact on oil recovery? Why?

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Report

Follow the reservoir simulation report writing guidelines.

The section Introduction and Background should contain a brief description of the

reservoir model you have constructed.

The Simulation Procedure section should describe the initial model run with 3 wells,

the optimisation process and the sensitivity cases.

The Results section should contain:

A statement or table of fluids initially in place: oil (STOIIP), gas and water.

A plan view of the model showing the location of the wells including the optimum

location selected for the second producer.

A statement or table of recovery factor, cumulative oil, gas and water production for

these cases:

 The initial simulation run with 3 wells.

 The final optimised 4 well case. You do not need to present results from the

intermediate non-optimum runs.

 The four sensitivity cases.

For these same cases you should include a graph (one for each case) with three lines

showing:

 Oil production rate vs time

 Water cut vs time

 GOR vs time

You should discuss the results of the sensitivities and explain (qualitatively) the

behaviour of the reservoir in each case. State which variable has the largest impact

on recovery and explain why.

Discuss how the oil recovery from the reservoir could be further improved. What

additional actions do you recommend?