68th EAGE Conference and Exhibition, Vienna 1 Impact of Time Lapse Processing on 4D Simultaneous Inversion The Marlim Field Case Study C. Reiser * 1, E. A. Thedy 2, P. S. Johann 2, A. Castoro 1 and P. Lee 3 1 CGG UK, 2 Petrobras, 3 CGG Brazil

68th EAGE Conference and Exhibition, Vienna 2Overview 1. 1.Introduction 2. 2.Objective of this study 3. 3.Seismic Processing 4. 4.Seismic Preconditioning D Simultaneous Inversion 6. 6.Results 7. 7.Conclusions

68th EAGE Conference and Exhibition, Vienna 3 Geological Settings Discovered in 1985 About 150 development wells Pressure maintained by water injections Sand rich turbidite system of Tertiary age Average thickness 60m Average porosity around 30% Oil density API EW Abreu et al. (1998) Bruhn et al. (1998) MARLIM

68th EAGE Conference and Exhibition, Vienna 4 Geological Settings Discovered in 1985 About 150 development wells Pressure maintained by water injections Sand rich turbidite system of Tertiary age Average thickness 60m Average porosity around 30% Oil density API EW Abreu et al. (1998) Bruhn et al. (1998) MARLIM

68th EAGE Conference and Exhibition, Vienna 5 Time Lapse Seismic: Two surveys acquired using different geometries Pre-development in 1986 Monitor in sqkm for the test area 7.5 sec Record Length Acquisition Sample Interval 4ms (1986) and 1ms (1997) 1986: 25m by 75 m bin size 1997: 25m by 25m bin size RMS amplitude over a 200ms window around 800ms

68th EAGE Conference and Exhibition, Vienna 6Overview 1. 1.Introduction 2. 2.Objective of this study 3. 3.Seismic Processing 4. 4.Seismic Preconditioning D Simultaneous Inversion 6. 6.Results 7. 7.Conclusions

68th EAGE Conference and Exhibition, Vienna 7Objectives  Main objectives Better understanding of the reservoir in terms of: Fluid distribution mapping Discrimination between production and injection effect.  Key issues to address: Not optimum 4D acquisition Attenuate different acquisition footprints Reduce seismic differences unrelated to production  Methodology Develop the 3D Simultaneous Elastic Inversion scheme An estimate of reliable elastic attributes

68th EAGE Conference and Exhibition, Vienna 8Overview 1. 1.Introduction 2. 2.Objective of this study 3. 3.Seismic Processing 4. 4.Seismic Preconditioning D Simultaneous Inversion 6. 6.Results 7. 7.Conclusions

68th EAGE Conference and Exhibition, Vienna 9 Reservoir oriented workflow Time alignment Enhancement of the S/N ratio and the resolution Enhancement of the S/N ratio and the resolution Quantitative and qualitative reservoir properties Acquisition footprint removal Acquisition footprint removal Seismic, wavelets and initial model Multiple attenuation STRATIGRAPHIC INVERSION PROCESS PRECONDITIONING SEQUENCE (Adapted to specific needs) Random noise Random noise attenuation Vp Density Vs RhoLambda

68th EAGE Conference and Exhibition, Vienna 10 Seismic Processing Two 4D processing sequences used for the inversion Few items: Independent – un-parallel seismic processingIndependent – un-parallel seismic processing 1986: DMO stack and Post-Stack migration 1997: Pre Stack migration Different Velocity fields Parallel seismic processingParallel seismic processing Bin regularisation to the 1997 survey (12.5 by 25 m) Same velocity field for both vintage. Parallel PSTM migration Post stack pre-conditioning

68th EAGE Conference and Exhibition, Vienna 11 Seismic Processing – Independent Full Stack Base 86 Full Stack Monitor 97

68th EAGE Conference and Exhibition, Vienna 12 Seismic Processing – Parallel Full Stack Base 86 Full Stack Monitor 97

68th EAGE Conference and Exhibition, Vienna 13 Seismic Processing – Time lapse impact Base Monitor Angle Stacks Differences ParallelIndependent

68th EAGE Conference and Exhibition, Vienna 14 Seismic Processing Base Monitor repeatability analysis Parallel Independent PRECONDITIONING LowHigh NO PRECONDITIONING

68th EAGE Conference and Exhibition, Vienna 15Overview 1. 1.Introduction 2. 2.Objective of this study 3. 3.Seismic Processing 4. 4.Seismic Data Preconditioning D Simultaneous Inversion 6. 6.Results 7. 7.Conclusions

68th EAGE Conference and Exhibition, Vienna 16 Reservoir oriented workflow Monitor Data pre-conditioning Invariant reference Base Geostatistical Filtering 3D Simultaneous Inversion Geostatistical Filtering Initial Model Building Inversion of Invariant reference Inversion of Base Mapping and Interpretation With flow model Inversion of Monitor

68th EAGE Conference and Exhibition, Vienna 17 Application of the Geostatistical decomposition 1986 Data, 32 ° stackCOMMON PART 1997 Data, 32 ° stack Data 1997 Data Common Part Hz Signal / Noise

68th EAGE Conference and Exhibition, Vienna 18Overview 1. 1.Introduction 2. 2.Objective of this study 3. 3.Seismic Processing 4. 4.Seismic Preconditioning D Simultaneous Inversion 6. 6.Results 7. 7.Conclusions

68th EAGE Conference and Exhibition, Vienna 19 Simultaneous Elastic Inversion in a Stratigraphic Framework <  ? Difference Simulated Annealing Model Perturbation V p, V s,  and  t Initial Model Final Model tt 100ms ~2ms 100ms Initial Layered Model Synthetic Angle Stacks Structural Framework Real Angle Stacks

68th EAGE Conference and Exhibition, Vienna 20Overview 1. 1.Introduction 2. 2.Objective of this study 3. 3.Seismic Processing 4. 4.Seismic Preconditioning D Simultaneous Inversion 6. 6.Results 7. 7.Conclusions

68th EAGE Conference and Exhibition, Vienna 21 Reservoir characteristics – well logs information

68th EAGE Conference and Exhibition, Vienna 22 Reservoir characteristics – well logs information Vp (m/s) Vs (m/s) GR (API)

68th EAGE Conference and Exhibition, Vienna 23 Initial Model Data for Initial Model: 17 wells 17 wells 6 with real shear velocity 6 with real shear velocity 6 horizons 6 horizons Model in Vp, Vs and Density Model in Vp, Vs and Density

68th EAGE Conference and Exhibition, Vienna 24 Inversion Results and Well Data Random Line, Sequence 2 - Base IP Random Line, Sequence 2 - Monitor IP

68th EAGE Conference and Exhibition, Vienna 25 Inversion Results: Comparisons Independent processing Parallel Processing Internal faults - Flow barrier ? Orange = Increase of Ip between base and Monitor

68th EAGE Conference and Exhibition, Vienna 26 Inversion Results: Comparisons Independent processing Parallel Processing

68th EAGE Conference and Exhibition, Vienna 27Overview 1. 1.Introduction 2. 2.Objective of this study 3. 3.Seismic Processing 4. 4.Seismic Preconditioning D Simultaneous Inversion 6. 6.Results 7. 7.Conclusions

68th EAGE Conference and Exhibition, Vienna 28Conclusions Data pre-conditioning was helpful in ensuring a reliable input for inversion Geostatistical decomposition attenuated acquisition footprints Reprocessing with parallel sequences improves repeatability and the resolution of the 4D effect though often not practical (technically / economically) true 4D acquisition should reduce some of the 4D noise Simultaneous Elastic Inversion Better comparison with the flow model (saturation variation) with the P impedance differences Some 4D differences unrelated to production history have been observed The 4D differences from the parallel processing appear to be more realistic and their distribution more consistent with the known geology

68th EAGE Conference and Exhibition, Vienna 29Acknowledgements The authors would like to thank Petrobras for granting permission to publish these results. A Thanks to CGG London and CGG do Brazil