Flow Modelling Across Faults

SPE YP Technical Showcase Event 28 May 2013

Wahab Ahmed

Faults-Introduction

Fault Pattern

Fault Zone Properties – Fault Permeability, Fault Thickness

Fault Transmissibility Multiplier Calculation

Fault Threshold Pressure – Constant Fault Threshold Pressure , Variable Fault Threshold Pressure

Wrap-up – Conclusions , References

Agenda

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Fault

Fault Fault is a fracture, fissure or joint along which there have been relative displacement

Normal Faults Normal fault is one in which the hanging wall falls down relative to the foot wall due to tensional

stress

Reverse Faults Reverse fault is one in which the hanging wall moves up relative to the foot wall due to

compression

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Fault Pattern

Parallel Fault or Bookshelf Model

Graben or Rift Fault

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North Sea Examples

(After Glennie, 1990)

Thistle Field (from Williams

and Milne,1991)

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Fault Zone

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Factors affecting Fault zone seal

Fault zone architecture

Burial and Fault History and Juxtaposition of lithologies

Local facies

Pressure difference across fault

Reservoir fluid type and saturation

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Fault Zone Properties

Fault Permeability

-Vshale vs Permeability relationship , Explicit ,SGR &

Vclay methods (Manzocchi ,Sperrevik methods)

Fault Thickness

- Estimation from Fault Displacement

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Manzocchi Algorithm

D=Fault Displacement in m

SGR=Shale Gouge Ratio

K=Permeability in mD

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Sperrevik Algorithm

Fault rock clay content (Vf)

Maximum rock burial depth and (Zmax)

Depth at time of deformation (Zf)

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Fault Thickness

Displacement to Thickness Ratio

Two Algorithms

tf= D/66 (Hull, 1988)

tf=D/170 (Walsh,1998)

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Transmissibility Calculation

Transmissibility in X direction

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Fault Transmissibility Multiplier

K1

K2

K2

K1 Kf

L1 L2

L2 L1

tf

Trans12

Trans1-f Transf-2

Transfault

Assumptions:

Intersection Area=1

No Grid block dips

1D single phase flow

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Field Case Study-Gulfaks

5 Injectors in the west flank

5 Producers in the eastern flank

Injectors Control=Voidage replacement

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Effect of Fault Permeability on Fault

Transmissibility multiplier

Fault Permeability=1mD Fault Permeability=10mD

Fault Permeability=100mD

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Effect of Fault Permeability on Flow

Simulation

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Fault Transmissibility multiplier (Manzocchi

Vs Sperrevick Correlation)

Manzocchi Method for Fault

Permeability from SGR

Sperrevik method for Fault

Permeability from SGR

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Manzocchi Vs Sperrevick Correlation effect

on Flow Simulation

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Effect of Fault Thickness on Fault

Transmissibility multiplier

Thickness to

Displacement Ratio=100

Thickness to

Displacement Ratio=66

Hull’s Correlation

Thickness to

Displacement Ratio=170

Walsh Correlation

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Effect of Fault Thickness on Flow Simulation

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Fault Threshold Pressure

Constant Fault Threshold Pressure

- same value across the fault

Variable Fault Threshold Pressure

- different values for each cell connection across fault

Pressure=2500 psi Pressure=2550 psi

Fault Threshold Pressure=100 psi

No Flow

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Variable Fault Threshold Pressure

Vshale Pressure

(bar)

0 0

0.5 100

1 200

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Transmissibility Multiplier for Fault Threshold

Pressure Cases

Fault Permeability=1 mD Fault Permeability=10 mD

Fault Thickness to Displacement Ratio=66

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Constant vs Variable Fault Threshold

Pressure -1mD Case

Early breakthrough

for Variable Fault

Threshold Pressure

Case & gentle

increase in water

cut

Difference in water

cut is significant for

lower values of

Fault Permeability

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Constant vs Variable Fault Threshold

Pressure -10mD Case

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Conclusion

Fault zone Thickness and Permeability are important for

flow modelling

Fault Permeability affects are more significant between 1mD

and 10 mD – Manzocchi algorithm gives low values of Fault Transmissibility multiplier as

compare to Sperrevik

Fault Displacement is used to predict fault thickness

– Fault Transmissibility will be higher for higher value of Fault Displacement to

Thickness ratio

Fault Threshold pressure prevents the flow across fault interface

– Early water breakthrough and gentle increase will be observed for variable fault

threshold pressure case as compare to constant fault threshold pressure

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References

1. Manzocchi, T. et al. (1999). “Fault transmissibility multipliers for flow simulation models”, Petroleum Geoscience, Vol. 5,

pp. 53-63

2. Sperrevik, S. et al. (2002). “Empirical estimation of fault rock properties”, In: Hydrocarbon Seal Quantification (edited

by Koestler, A.G and Hunsdale, R), NPF Special Publication 11, pp 109 -125.

3. Fisher, Q.J. et al. (Jan. 2006). ”Microstructural and Petrophysical Properties of Fault Rocks from the Snorre Field”,

Rock Deformation Research Group, report 9454

4. Jonas Cordazzo , Clovis Raimundo Maliska , Antonio Fabio Carvalho da Silva Interblock Transmissibility Calculation

Analysis for Petroleum Reservoir Simulation Department of Mechanical Engineering, Federal University of Santa

Catarina . Brazil , pp 5 -7

5. Reservoir Structure Course material of IPE Heriot Watt University by Dr J Couple

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Questions