Reducing Uncertainty through Multi-Measurement Integration: from Regional to Reservoir scale

Transcription

1 Reducing Uncertainty through Multi-Measurement Integration: from Regional to Reservoir scale Efthimios Tartaras Data Processing & Modeling Manager, Integrated Electromagnetics CoE, Schlumberger Geosolutions

2 Integrated EM Center of Excellence Multi-measurement Integrated Earth Model Dedicated to the integration of seismic, electromagnetic and potential field data to build a uncertainty MT Seismic less uncertain earth models combining all available independent information on the subsurface. FTG Grav From regional scale to reservoir characterization EM 2

3 CSEM-Seicmic Integration to Reduce Uncertainty Structural Imaging Simultaneous Joint Inversion Prospect Ranking Seismically-constrained CSEM inversion Reservoir Characterization Petrophysical Joint Inversion

4 CSEM-Seicmic Integration to Reduce Uncertainty Structural Imaging Simultaneous Joint Inversion Prospect Ranking Reservoir Characterization

5 Simultaneous Joint Inversion Seismic DATA LINK CSEM/MT DATA Velocity Earth Model Model Space Space Property Link Space Simultaneous Joint Inversion Resistivity Model Space Velocity Model Resistivity Model

6 Sunshine Project: Integrated Seismic & EM (SLB + EMGS Multiclient data)?? 35 Blocks 35 Blocks ~ 800km 2 WAZ Seismic data CSEM & MMT data 360 Receivers 51Transmitters Resistivity SALT Velocity

7 Method: Simultaneous Joint Inversion Workflow EM CSEM/MT DATA EM-Modelling CSEM/MT Seismic DATA Vintage RTM Intermediate Resistivity Model EM-Based Interpretation Intermediate Velocity Model SJI FINAL RTM Final Resistivity Model Final Velocity Model

8 CSEM Modeling Inversion Evolution through Iterations Synthetic data, it 0 Ex Amplitude at 0.24Hz Original seismic image Resistivity at it 0

9 CSEM Modeling Inversion Evolution through Iterations Synthetic data, it 97 Ex Amplitude at 0.24Hz Original seismic image Resistivity at it 97

10 EM-based Interpretation Poor imaging Complex salt interpretation LOG(R)? Mismatch between velocity and resistivity New interpretation Structural geological restoration validation RTM LSI validation

11 EM-based Interpretation Structural restoration validation CSEM suggests a thicker salt CSEM Resistivity model

12 Seismic Results before SJI with CSEM WAZ SEISMIC ONLY

13 Seismic Results after SJI with CSEM WAZ SEISMIC + EM

14 CSEM-Seicmic Integration to Reduce Uncertainty Structural Imaging Prospect Ranking Seismically-constrained CSEM inversion Reservoir Characterization

15 CSEM value: Resistivity vs. Hydrocarbon Saturation From Electrical Methods in Geophysical Prospecting by Keller & Frischknecht 1966 CSEM responds well to high HC saturation / high resistivity targets Water in Oil Oil in Water AVO Anomaly CSEM Anomaly Commercial Hydrocarbon? Reduce Risk

16 Important caveats Resistivity changes can be due to Lithology Porosity Saturation Type of pore fluid (HC or water) Not all resistors indicate H/C (volcanics, carbonates, tight sands, etc.) Must understand geology and incorporate all available G&G information But even then... 18

17 CSEM non-uniqueness 1D Transverse resistance Inline - 0.1Hz Target target Thickness T ρ CSEM data are sensitive to the transverse resistance of a resistive layer target Transverse resistance = resistivity x thickness

18 CSEM non-uniqueness Joint interpretation of seismic and CSEM data using well log constraints: an example from the Luva Field, First Break - May Peter Harris, Zhijun Du, Lucy M. MacGregor, Wiebke Olsen, Rone Shu and Richard Cooper 20 20

19 Seismically-constrained 3D CSEM inversion Use available geological information (depth surfaces from seismic, logs, etc.) as apriori information in the inversion scheme: Regularization breaks (aka tear surfaces ): forcing the inversion not to smooth across a certain surface. This is relevant if a significant resistivity change is expected at that discontinuity (e.g., Top Reservoir, Top Salt, Top Basalt, etc.) Locks: penalizing model changes in a certain region of the 3D model. This is mainly relevant to constrain rather homogeneous overburden sections above potential reservoirs or to constrain resistivity anomalies within seismically defined geobodies.

20 Seismic Geobody-driven Constrained EM inversion Lovatini et al., EAGE 2012

21 Seismic Geobody-driven Constrained EM inversion Lovatini et al., EAGE 2012

22 Example 3D constrained inversion Setup Overview Constrained Constrained Unconstrained Constrained Lock Tear surface Lock +Tear surface

23 Example 3D constrained inversion Results Overview (Vertical Resistivity) Constrained Constrained Unconstrained Constrained Lock Tear surface Lock +Tear surface

24 CSEM-Seicmic Integration to Reduce Uncertainty Structural Imaging Prospect Ranking Reservoir Characterization Petrophysical Joint Inversion

25 Petrophysical Joint Inversion (PJI) Seismic Inversion CSEM Inversion PJI Petrophysical Properties

26 EM for Reservoir Characterization Petrophysical Joint Inversion Acoustic Impedance Geophysical Properties properties Shear Impedance Resistivity 3D AVO Inversion 3D CSEM Inversion Bulk modulus Rock model Properties Shear modulus Density Rock model calibration Water Saturation Geophysical Petrophysical Porosity Properties properties Volume of Shale Petrophysical Joint Inversion

27 PJI Case Study: Barents Sea - West Loppa Here STUDY AREA Input data from the Barents sea: Schlumberger Multiclient seismic library Emgs Multiclient CSEM library Scope of work: Phase 1 CSEM Inversion Phase 2 Seismic Inversion Phase 3 Petrophysical Joint Inversion 31 10/2 6/20 14

28 Barents Sea - Survey Map CSEM survey (white) Seismic survey (yellow) Petrophysical modeling - Porosity model - Water saturation model (biphase water/gas) Bathymetry [m] Two procedures are tested: - PI - Petrophysical Inversion of AI & Density - PJI - Petrophysical Joint Inversion of AI & Resistivity 32 10/2 6/20 14

29 Barents Sea CSEM Inversion Workflow CSEM input data preconditioning and qualitative imaging analysis Starting Model Horizontal resistivity 3D resistivity model building Well log and seismic input Anisotropic 1D inversions Mesh and resistivity population Starting Model Vertical resistivity 3D CSEM anisotropic Inversion & QC Unconstrained Seismically Constrained Reliability Testing

30 Barents Sea Seismic Inversion Workflow Seismic input data analysis and preconditioning Well-based analysis Wavelet extraction Low-frequency model building Inversion around the well Density Inversion on whole cube AI

31 Tertiary Anomaly Petrophysical model of the Tertiary anomaly after: - Geological interpretation Reference: Guerra et al A multi-measurement integration case study from West Loppa area in the Barents Sea. First Break Volume Geophysical evidences Seismic data co-rendered with: Poisson s ratio Vertical resistivity (contour lines) 41 10/2 6/20 14

32 Petrophysical Joint Inversion Data Input Cubes Acoustic Impedance Density Resistivity Subvolume Geometry: Top (from sea level): -617 m Base: -1247m X width: 7428 m Ywidth: 4779 m The resistive anomaly is focused within the gas channel by applying the transverse resistive principle Reference: Constable S Ten years of marine CSEM for hydrocarbon exploration. Geophysics, vol. 75, no. 5; P. 75A67 75A /2 6/20 14

33 PJI Results Z SLICE Porosity and Water saturation model Petrophysical Inversion Single Meausurement Seismic Porosity Water saturation Petrophysical Joint Inversion Multiple Meausurements Seismic and Electromagnetics Porosity Water saturation Consistent results for porosity, but integrating multiple measurements the estimated water saturation model improves showing the role of the resistivity attribute to discriminate fluids Miotti et al. SEG 2013

34 Conclusions CSEM limitations are now well understood Data processing, modeling and visualization tools have improved significantly in recent years Integration with seismic and geology allows to obtain maximum value out of CSEM data This integration can take place at the basin, prospect or reservoir scale using appropriate technologies. 47

35 Acknlowledgements We thank EMGS and Schlumberger for access to their CSEM and seismic Multiclient libraries. 48