Accurate reservoir modelling through optimized integration of geostatistical inversion and flow simulation. A North Sea case study.

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Julia Nicholson
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Accurate reservoir modelling through optimized integration of geostatistical inversion and flow simulation. A North Sea case study. A. Castoro 1, L de Groot 2, D. Forsyth 3 & R.

1 Accurate reservoir modelling through optimized integration of geostatistical inversion and flow simulation. A North Sea case study. A. Castoro 1, L de Groot 2, D. Forsyth 3 & R. Maguire 1 1 Fugro-Jason UK, 2 GDF SUEZ E&P Nederland B.V., 3 Currently Saudi Aramco, Previously GDF SUEZ E&P Nederland B.V. DEVEX 2009, May, Aberdeen Exhibition and Conference Centre

2 Objectives and workflow Create robust reservoir model fit for prediction of field production and development planning Engineering Data Input structural model, seismic data & well data Geostatistical inversion > 20 reservoir models with range of properties History match & ranking of all reservoir models Prediction runs for well planning and field development Selection & fine tuning of final reservoir models Business Decision 2

3 Outline Models from geostatistical inversion Initial history match and model selection Final models history match Geostatistical vs deterministic models Conclusions 3

4 Geostatistical inversion vs other modelling techniques? Geostatistical reservoir modeling Interpolate between the wells Plausible details Accurate near wells Not elsewhere Deterministic seismic inversion Optimize P-Impedance to minimize synthetic-to-seismic misfit Accurate within seismic bandwidth Unrealistically smooth Only one possibility StatMod MC FJ geostatistical seismic inversion Subsumes geostatistical modeling and deterministic inversion Does both, simultaneously and in a statistically rigorous way Multiple plausible realizations at high detail (e.g. 1ms 25m) Yet also coherent interpretations of the seismic up to the km scale 4

5 Lithotype Reservoir properties A1 A2 A3 A4 A5 A6 A7 A8 B3 Best Good UPPER RESERVOIR Low Non reservoir LOWER RESERVOIR 5

6 Seismic data Near stack seismic A2 Seismic Synt Impedance Estimated wavelet Seismic-well ties and synthetics B3 Seismic Synt Impedance Amplitude Phase 6

7 Deterministic (4ms) Geostatistical vs deterministic inversion Impedance sections Geostatistical (1ms) A8 A5 A2 A1 A7 A6 7

8 Geostatistical inversion honours all inputs Wells are honoured Deterministic Geostatistic Seismic is honoured Geostatistics are honoured Input Output 8

9 Single realization with wells overlaid Blind well validation Wells were not used as a constraint Lithotype Best Good P-Impedance 1.5e+07 Lithology A8 A5 A2 A1 A7 A6 Low Non reservoir 1.1e+07 7e+06 Impedance 9

10 Outline Models from geostatistical inversion Initial history match and model selection Final models history match Geostatistical vs deterministic models Conclusions 10

Model screening: historical field gas production Some models can fail to match historical total field gas production by up to 2 % SM3 / day Model 1 Model 9 Historical

11 Model screening: historical field gas production Some models can fail to match historical total field gas production by up to 2 % SM3 / day Model 1 Model 9 Historical Historical Simulated Simulated Time Model 4 Model 16 Model 1 SM3 Simulated Model 9 Historical Models not matching historical gas production Simulated Model 4 discarded Model 16 Time 11

12 Outline Models from geostatistical inversion Initial history match and model selection Final models history match Geostatistical vs deterministic models Conclusions 12

13 Final models history match (bottom hole pressure) Well A1 Well A2 Well A7 Well A3 Well A6 Well B3 13

14 Outline Models from geostatistical inversion Initial history match and model selection Final models history match Geostatistical vs deterministic models Conclusions 14

15 Geostatistical vs deterministic inversion models Permeability (md) 15

16 Historical Historical Time Historical Pressure (barsa) (barsa) Pressure Time Pressure (barsa) Pressure (barsa) Historical Pressure (barsa) Pressure (barsa) Geostatistical vs deterministic inversion: history match Historical Time Time Time Time 16

17 Outline Models from geostatistical inversion Initial history match and model selection Final models history match Geostatistical vs deterministic models Conclusions 17

Conclusions Creation of multiple equally probable reservoir models given the geophysical and geological data Inverted impedance ( porosity, etc) shown to be reliable by blind well predictions

18 Conclusions Creation of multiple equally probable reservoir models given the geophysical and geological data Inverted impedance ( porosity, etc) shown to be reliable by blind well predictions Geostatistical character and correlations maintained History match achieved without the use of porosity or permeability modifiers without the incorporation of faults not substantiated by evidence from seismic interpretation or well test analysis The reservoir model is considered robust and suitable for use in forward simulation for well planning and field development 18

19 Acknowledgements Thanks to GDF SUEZ E&P Nederland B.V. for permitting this study to be shown Questions? 19

23855 Rock Physics Constraints on Seismic Inversion

23855 Rock Physics Constraints on Seismic Inversion M. Sams* (Ikon Science Ltd) & D. Saussus (Ikon Science) SUMMARY Seismic data are bandlimited, offset limited and noisy. Consequently interpretation of