Improving Permeability Modeling in a Large Offshore Carbonate Field Using Near Wellbore Upscaling and

Dynamic Calibration Workflow

Viswasanthi Chandra

PhD Supervisors: Prof. Sebastian Geiger Prof. Patrick Corbett

• Objectives • Field X background • Work done and main results • Key conclusions

Overall aim • Using novel near wellbore upscaling (NWU) workflow to

obtain improved permeability model of Field X Main conclusions • Improved characterisation of key small-scale geological

heterogeneities • Revised permeability model eliminated the K-multipliers Scientific impact • Improved reservoir characterisation and simulation of

carbonates using NWU workflow

• Low relief anticline trap • Thin oil rim, gas cap, deep seated aquifer • Main HC bearing layers: Zone A, Zone B

E-W section: see gas over oil over water. See the two main reservoir layers (Image courtesy: Zoe Watt)

A/B Unconformity

Kh-multipliers required for history match : x20 in Zone A, x10 in Zone B Plus local well K and well PI multipliers

Around 90% of the permeability ‘missing’ !?

- DST K-transform >> core K-transform - Average K in geomodel ~ 20 mD and Ke in

simulation model ~ 200 mD

What was undersampled? How should it be modelled?

Correct the K = Better Simulation Model = Better Production Forecast

OPT = OPTH

OPT1

OPT = OPTH

OPT2

OPT1

OPT = OPTH

OPT3

OPT2

OPT1

OPT = OPTH

Can

be

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us

ing

revi

sed

K-

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All K-multipliers removed

History matched case with K-multipliers

• High resolution process based modeling • Integrates multi-scale geological and

petrophysical data • More realistic representation of subsurface

Bedding Structure Modeling Property Modeling Upscaling

Chandra et al., 2013, SPEREE

• Corroded zones with enhanced micro- and macro-porosity

• Presence of solution enhanced stylolites and associated tension gashes

Solution-enhanced macro- and micro-porosity

Solution-enlarged stylolites and associated tension gashes

Solution-enlarged stylolites

Solution-enhanced stylolites and macro-porosity

• Effective permeability calculated using flow based upscaling

Cross-plot of upscaled poro-perm Cross-plot of upscaled Kv /Kh vs Kh values

Corroded matrix porosity

Leached stylolites and tension gashes in highly Corroded matrix

Geomodel permeability from core K-transform AFTER K-multiplier

K-multipliers in simulator

Modified permeability scenario

K-Transform From NWU

Geomodel porosity

Cumulative oil production curves

• Extending to full field model • Uncertainty and optimisation study • Preliminary observations...

Simulator ECLIPSE IMEX

Wells > 100 producers

Grid 1.2 million cells after coarsening the geomodel

Fine (geomodel) >3 million cells

CPU time 12.12 DAYS !! 11.5 HOURS

Remarks needs further tuning for better convergence of linear iterations

far less convergence issues

• Solution-enhanced porosity features modelled and upscaled using novel NWU workflow

• Core data issues mitigated

• Upscaled global K-transforms and Kv /Kh ratios obtained

• Field X permeability model re-evaluated

• Need for K-multipliers eliminated

• Suggestions for alternative Field X permeability model provided

• Uncertainty and optimisation work in progress

Viswasanthi Chandra

viswa.chandra@pet.hw.ac.uk

Acknowledgements:

Dr. Richard Steele Dr. Paul Milroy Dr. Andrew Barnett Dr. Paul Wright Dr. Alex Asaff