291275_799b7ad1b69841d0bb73d345e7ac8408

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Production Optimization

of an Oil Reservoir

By: Abdollah Esmaeili

National Iranian South Oil Company(NISOC)

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Production

Optimization purposes

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Fig 1- Production Optimization system

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Fig 2- Production Optimization System and its Benefits

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Fig 3 - Production Management Environment

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Fig 4 - Production Optimization in a Fractured Reservoir

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Reservoir geometry

The field is a northwest-southeast, symmetrical anticline,

which has two parts: eastern andwestern parts. The field is about

40 km long and 4 km wide, 8 kmlong and 1.5 km wide, in eastern

and western sides respectively.

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http://slidepdf.com/reader/full/291275799b7ad1b69841d0bb73d345e7ac8408 9/45Fig 12 - Cross-section of reservoir in this oil field

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Well NO.Depth interval

(meter subsea)

Net pay

(meter)

Porosity

(%)

Water

Saturation (%)

1 3333-3661 222.7 11.2 25.1

5 3321-3723 196.9 12.9 20.3

8 3455-3731 150.6 11.3 33.8

9 3311-3751 202.5 12.6 26

10 3491-3899 173.3 12.4 25.3

11 3551-3807 123.1 12.1 38.8

14 3480-3556.5 49.7 11.4 26.7

15 3391-3526 44 12.7 24.7

16 3346-3615 134.5 12.7 24.2

19 3442-3550 75.6 12.2 23.8

22 3419-3730 181.2 11.6 27.2

28 3453.6-3759 94 10.6 33.3

30 3372-3640 75 11.1 20.4

33 3387-3806 184 12.9 15.3

34 3355-3773 19.2 13 20

Table 1 - Petrophysical property of this reservoir

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Well History

In this study,

two producing wells

of this reservoir

will be described

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Well No. 1This well was drilled at 1992 and

production started at this time. The flow

rate of production was 3000 STB/d and

increased to 8000 STB/d at 1993. Duo to

additional gas production the choke size

changed from 7/8"to 5/16" at 2006 and

flow rate decreased to 500 STB/d. Inorder to repair the well (at 2006), a 5"

liner was run and perforated in an

interval from depth 3675 to 3804 meter.

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Casing Configuration of Well No. 1

Casing 9 5/8" shoe @ 2690 MD

Liner 7" from 2555 MD to 3380 MD

Liner 5" from 3260 MD to 3827 MD

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Geographical Coordinate

of

Well No. 1

1, 910, 276 m East

1,039,504 m North

Location of the well is: E 53 S

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Casing Configuration of Well No. 2

Casing 9 5/8" shoe @ 3365.8 MD

Liner 7" from 3308.5 MD to 4160 MD

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Geographical Coordinate

of

Well No. 21,907,175 m East

1,042,098 m NorthLocation of the well is: E 24 S

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Property Well No.1 Well No.2

bubble point pressure (psig) 4398 4398bubble point temperature(oF) 220 220

oil compressibility @Pb pressure (psi-1) 1.45E-5 1.45E-5

FVF(Bo) @ Pb ( bbl/STB ) 1.5131 1.5131

oil gravity (o

API) 34.9 34.9Rs @ Pb pressure (scf/stb) 1053 1053

viscosity @Pb pressure (cp) 0.2892 0.2892

well radius (inch) 3.504 2.496

well radius (ft) 0.292 0.208

average porosity (%) 13 12.5

average Sw (%) 24 25

type of completion cased – hole cased – hole

interval (ft) 11686-11867 12057-12480

formation thickness (ft) 112.5 144

Table 2 - Wells, reservoir and fluid property data

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well No. 1 No. 2

production rate (STB/d) 1000 3000

wellbore flowing pressure( psig) 3893 4582

reservoir pressure (psig) 4230 4837

productivity index (STB/d/psig) 2.97 12

wellhead pressure (psig) 915 1460

GOR (scf/stb) 1030 1020

gas S.G 0.77 0.76

water cut (%) 0 0

choke size (1/64 inch) 24 32

Table 3 - Production condition of the wells No. 1 and No. 2

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Skin factorand

Reservoir permeability

forWells No. 1 and No. 2

which are analyzed by

PANSYS software

well Wells No. 1 Wells No. 2

Skin factor 7.812 6.5913

Permeability

(md)

301.265 25.2824

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Fig 17 - Flow correlation matching for well No. 1

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Fig 18 - Flow correlation matching for well No. 2

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Fig 19 - IPR and TPR curves for well No. 1

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Fig 20 - IPR and TPR curves for well No. 2

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Reservoir pressure effects

For analysis the reservoir pressure depletion,assume that the gradient of pressure decline in

the reservoir is 40 psig/year.

Figure 35-a to 35-b show the effect of the

reservoir pressure depletion on the IPR curves

and production rates for the wells No.1 and

No.2, for two conditions:

1) When the wells produce by casing 8.535"2) When the well No.1 produce by tubing size

4.276" and well No.2 produce by tubing size

2.99"

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Figure 35-a- Effect of reservoir depletion of the well No.1 (Casing 8.535")

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Figure 37-a- Effect of reservoir depletion of the well No.2 (Casing 8.535")

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Reservoir

pressure

psia

q (Casing size

=8.535") STB/d

q (Tubing size

=4.276") STB/d

4811 2300 4500

4771 0 4050

4731 0 3700

4691 0 2550

Table 4- Effect of reservoir depletion in the

production rate of the well No.1

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Reservoirpressure

psia

q (Casing size=8.535")

STB/d

q (Tubing size

=2.99") STB/d

4204 800 1850 4164 0 1750

4124 0 1625

4084 0 1500

4044 0 1315

4004 0 1125

Table 5- Effect of reservoir depletion in the

production rate of the well No.2

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Mature oil fieldA mature oil field

is an oil field that

is considered fullydeveloped.

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There may be infillopportunities but in

general the fielddevelopment plan can

be considered

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Challenges in these wells Decline in oil production

Decline in reservoir pressure

Extra Produced Water

Extra Produced Gas

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Important

Question:How we can solve

this problems?

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These are major

challenges,

which requires:

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- a transfer of up todate technology in

enhanced oil

recovery techniques

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Enhanced

recovery with

gas injection

orwater injection

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- development ofgas resources to be

injected into old oil

fields

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- and huge capitalinvestment in

developing new oil

fields

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Gas injection Projects

These projects consist of three main parts:

Upstream

Midstream

Downstream

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Immiscible gas injection

in oil reservoirs

Gas injection Projects

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Conclusions

1. Well analysis is an excellent method for indicating how

to optimize the well overall performance and obtain the

objective flow

rate on the oil wells.

2. According to result of tubing size analysis, production

rate of these wells via casing 8.535" is at unstable state.

3. Gas injection can be a good method to improve oil

production and increase reservoir pressure in these wells

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Recommendations

1. Selecting a multiphase flow correlation to simulate thewell behavior (especially vertical segment) is very

important and crucial, so accurate and reliable data

must be used to build the well model.

2. An economic study should be made to analysis the

profitability and the limitation of the variables which

affect the production rate.

3. In order to optimize any one of the production systemscompletely, it is recommended to analyze the other

parameter such as: performance of the perforation,

performance of the surface facility.

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Recommendations…

5. In order to increase the production rate of this

reservoir, it is recommended to analyze the all

existing flowing wells.4. Artificial lift performance study is recommended

for future work of these wells.

6. A basic requirement for well analysis is the ability

to determine the correct inflow performancerelationship of the well, thus it is required well test

data with the high quality.

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Acknowledgement

I wish to thank the Heads of Research

and Technology Department in National

Iranian South Oil Company (N.I.S.O.C)

and Heads of Research and Technology

Department in National Iranian OilCompany (N.I.O.C) for their helps and

supports in connection with this study

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THANK YOU

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291275_799b7ad1b69841d0bb73d345e7ac8408

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