Geomechanic Effect for Gas Single Phase Reservoir

8/11/2019 Geomechanic Effect for Gas Single Phase Reservoir

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Singgih Suganda, B.Eng., Master Student of Bandung Institute of Technology

Mukhammad Taufan, B.Eng., Master Student of Bandung Institute of Technology*

Ir. Zuher Syihab, M.Sc., Ph.D., Bandung Institute of Technology**

Prof. Ir. Pudjo Sukarno, M.Sc., Ph.D., Bandung Institute of Technology**

Fully Coupled Geomechanics and Its Effect

to the IPR Correlation

for Gas Single Phase Reservoir

Student Paper Contest (SPC)

for Postgraduate Student

2013 APOGCE, Jakarta-Indonesia


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OUTLINE

Introduction

Objective

Background Theory

Modified Fluid Flow for Geomechanic Reservoir

Rock Geomechanic Equations

Base Case Study

Result of Sensitivity Study

Conclusions


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Effect of Reservoir Properties Changing toDry Gas Single Phase IPR

Unrealistically IPR due to

reservoir properties changing

IPR calculation

procedures must be

corrected

Future Single

Phase IPR can be

predicted

GeomechanicAspects


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1

Presenting method to calculate

single phase IPR in Dry Gas Res.by considering Geomechanic

aspects.

To know the effect of Geomechanic

aspects in Gas Single Phase IPR2

3To establish new dimensionless

correlation for Gas Single-

phase IPR with influence of

reservoir Geomechanic effects

OBJECTIVE


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Darcys Law(gravity

assumed to be

neglected)

Conservation of

Mass

Equation of State

(isothermal)

Background Theory(Modified Fluid Flow for Geomechanic Reservoir)

0).(

)(

gg

g

ut

0)]1.([)]1([

ss

s ut

pkuu sg

)(

pcg

1

pcr

1

Gas Flow

Modified


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Strain-Stress-PressureStress Equilibrium

Rock

Equations

Strain Displacement

Background Theory(Rock Geomechanic Equations)


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Stress Equilibrium

Poroelastic theory (shu, 2003) :

0

z

zx

y

yx

x

x

0

z

zy

y

y

x

xz

0

z

z

y

yz

x

xz


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Strain-Stress-Pressure

HookesLaw :

)(2 zyxxx GP

)(2 zyxyy GP

)(2 zyxzz GP


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Strain displacement

There are two basic assumptions in deformation :

Free deformation and Uniaxial deformation (Settari,

2005)

ue zzyyxx

.


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Basic Numerical

Coupled these two equations

will result fluid flow behavior

under Geomechanic effect

Modified Fluid

Flow Eq.

Rock Mechanic

Eq.

General Equation in Geomechanic Reservoir

dt

dp

dp

dcccccp

k msbsbfg

)()1(.

pfuGuG i ).()(2

Numerical Building

These equations are coupled

and combine with other

equations in developed

simulator. And being validate

with commercial simulator

Basic Numerical

Dont forget to underlined

that Porosity & Permeability

are under mean effective

stress function


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1. Construct the base case IPR.(The data is obtained from ARMA/USRMS

05-769 paper, titled: Applying fully coupledgeomechanics and fluid flow model to

petroleum wells (Hunt et. al., 2005),

2. Sensitivity study from base case is theninvestigated for all parameters.

3. Build future IPR, then modified as

dimensionless IPR and plotted in the same

graph.

4. Regression results new dimensionless

future IPR correlation for dry gas reservoir

Base Case Study


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1. PVT data is taken from SPE 16000 Fifth Comparative Solution Project:

Evaluation of Miscible Flood Simulators.

2. Simulation is run till 4000 days (11 years).

Base Case Simulation Result

Fig.Comparison in Average Reservoir Pressure Between

Conventional and Geomechanics Model.

Fig.Comparison in Producer Rate Between

Conventional and Geomechanics Model

Vid. Base Case Simulation is Running Using

Developed Simulator


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0

1000

2000

3000

4000

5000

6000

0 2 4 6 8 10 12 14 16 18 20

Pwf(psi)

Qg (MMSCFD)

IPR Base case Initial Fetkovich

IPR base case geo

IPR - Base Case Study

Conventional Res. Geomechanic Res.

Fig. Base Case IPR Comparison for Geo and Non-Geomechanic Reservoir

Fig. Comparison Of Isochronal Log-Log Plot Analysis Between Non-Geomechanics (Left Side)

And Geomechanics Reservoir (Right Side)


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IPR - Base Case Study Sensitivity

1. Sensitivity analysis is undergone to test the model for its behavior to these

changes of its variables.

2. Sensitivity analysis is conducted by varying : poisson ratio (v), modulusyoung (E), porosity (), and well radius (rw).

3. Geomechanic effect is pressure dependent variable, sensitivity in the future

reservoir condition is highly expected, and it has been performed in this

study.

4. Regression from combination of Pwf/Pres and Qg/Qmax in the same graph,

resulted new dimensionless IPR correlation for dry gas reservoir

0

1000

2000

3000

4000

5000

6000

0 5 10 15 20

Pwf(psi)

Q (MMSCFD)

E = 5x10^5

E = 1x10^5

E = 1x10^6

Base case IPR Geo

0

1000

2000

3000

4000

5000

6000

0 5 10 15 20

Pwf(psi)

Q (MMSCFD)

rw = 0.205

rw = 0.45

Bass case IPR geo

Fig. Modulus Young and Well Radius Sensitivity


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Future IPR Construction

-1000

0

1000

2000

3000

4000

5000

6000

0 5 10 15 20

Pwf

Q (MMSCFD)

Initial condition

future 1 Geo

Future 1 Fetkovich

Future 3 Geo

Future 3 FetkovichFuture 4 Geo

Future 4 Fetkovich

Initial condition fetkovich

Future 2 Geo

Future 2 Fetkovich

Future 5 Geo

Future 5 Fetkovich

Future 6 Geo

Future 6 Fetkovich

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

Pwf/P

res

Qg/Qmax

= 1 0.53

0.47

2

assumptions : Laminar flow, Dry gas

single phase, Pseudo-steady state

condition, No skin, Homogeneous

reservoir, and there is no fluid influx.

2

max

47.053.01

P

P

P

P

Q

Q wfwfg

Fig . Future IPR Result

Fig. Dimensionless IPR from Initial Base Case DataIn Every Future Condition


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Base Case Dimensionless Future IPR

Prod Time

(year)Gp (MMSCF)

QmaxF

(MMSCFD)

PresF

(psi)

PresF/

PresP

QmaxF/

QmaxP

1 1884.3690 14.9029 4577 0.9535 0.8159

2 9693.1070 10.4623 3913 0.8152 0.5728

3 9693.1070 8.3350 3470 0.7229 0.4563

4 12452.2000 6.4304 3143 0.6548 0.3520

5 14519.2600 5.3513 2893 0.6027 0.2930

6 16251.8300 4.5214 2691 0.5606 0.2475

7 17723.9900 3.8995 2526 0.5263 0.2135

8 18894.8700 3.7361 2387 0.4973 0.2045

9 20022.2900 3.3347 2267 0.4723 0.1826

10 21010.2600 2.8939 2163 0.4506 0.1584

11 21886.9600 2.5823 2072 0.4317 0.141412 22737.1400 2.1222 1991 0.4148 0.1162

13 23378.6200 2.0948 1919 0.3998 0.1147

14 24079.1900 1.7506 1854 0.3863 0.0958

Prod Time

(year)Gp (MMSCF)

QmaxF

(MMSCFD)

PresF

(psi)

PresF/

PresP

QmaxF/

QmaxP

1 1873.96518 14.68934 4562 0.9504 0.9618

2 6394.98138 10.17555 3864 0.8050 0.6663

3 9552.55706 7.88285 3417 0.7119 0.5161

4 12173.47170 6.22692 3095 0.6448 0.4077

5 14167.89910 5.17778 2851 0.5940 0.3390

6 15852.68840 4.39993 2654 0.5529 0.2881

7 17279.20130 3.78759 2494 0.5196 0.2480

8 18513.90360 3.30370 2359 0.4915 0.2163

9 19509.78460 3.19868 2244 0.4675 0.2094

10 20554.82160 2.59331 2143 0.4465 0.1698

11 21403.39200 2.30826 2055 0.4281 0.151112 22165.94640 2.08236 1977 0.4119 0.1363

13 22851.54710 1.87303 1907 0.3973 0.1226

14 23484.47950 1.72980 1844 0.3842 0.1133

0

0.2

0.4

0.6

0.8

1

1.2

0.2 0.4 0.6 0.8 1

QmaxF/Qmax

P

PresF/PresP

Base Data Geomechanic Effects

Base Data Non-Geomechanic Effects

Fig . Comparison Dimensionless Future IPR Relationship for Base Case Data


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- Each point in graph above represents the IPR curves at future reservoirconditions.

- Regression results new-correlation to predict future IPR for Gas single phase

reservoir by considering geomechanics factor.

-

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

QmaxF/QmaxP

PresF/PresP

Base case data

rw = 0.205

rw = 0.45

porosity 0.1

porosity 0.3

Poisson ratio 0.15

Poisson ratio 0.35

Mod Young = 1x10^5

Mod Young = 1x10^6

Dimension x 1.5

Dimension x 0.5

kh = 0.5h=x2.0

h=x0.5

kh = 2.0

kh = 0.1

kh = 10

= 0.833(

)2 + 0.145(

) 0.084

Result of Sensitivity Study

084.0145.0833.0

2

Prmax

max

presentres

futureres

presentres

futureres

esentg

Futureg

P

P

P

P

Q

Q

Fig. Dry Gas Future IPR Under Geomechanics Effect


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Non-Geomechanic Reservoir Comparison

R = 0.996

0

0.2

0.4

0.6

0.8

1

0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1

QmaxF/QmaxP

PresF/PresP

Geomechanics Reservir

Non-Geomenchanics Reservoir

Poly. (Geomechanics Reservir)

= 0.833(

)

2

+ 0.145(

) 0.084

At the beginning of production process, the ratio from AOF in geomechanic

reservoir has a lower value at the same value of ratio pressure reservoir

Fig. Comparison Sensitivity Result of Dimensionless Future IPR


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Applying Dimensionless IPR Correlation

Combining both equations, we will can easily predict the IPR curve in every condition of

reservoir. Example, if we have geomechanic reservoir with data:

- Pr = 3900 psi. Pwf = 1000 psi; Qg = 12.1 MMSCFD;

- By varying of bottomhole pressure will result:

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 5 10 15 20

Pwf(psi)

Qg (MMSCFD)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0 5 10 15 20

Pwf(psi)

Qg (MMSCFD)

Intial Condition

Future 1

Future 2

Fig. Initial & IPR Prediction Using Proposed IPR Dimensionless Correlation

2

max

47.053.01

P

P

P

P

Q

Q wfwfg084.0145.0833.0

2

Prmax

max

presentres

futureres

presentres

futureres

esentg

Futureg

P

P

P

P

Q

Q


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Geomechanics aspects affect deliverability of gas reservoir, hence

IPR need to be corrected to accommodate the impact ofgeomechanics.

Effect of geomechanic aspects to gas single-phase IPR will makethe AOF increase and ascend the IPR curve.

The geomechanic aspects made reservoir pressure and production

rate of gas reservoir higher than the conventional reservoir.

New dimensionless future IPR correlation for single phase gas

reservoir under influence of geomechanic aspects has beengenerated and the trend is polynomial second order.


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Geomechanic Effect for Gas Single Phase Reservoir