Calibration of curvature & coherence anomalies Example from Chicontepec, Mexico

1. Attribute-Assisted Seismic Processing and Interpretation http://geology.ou.edu/aaspi Calibration of curvature & coherence anomalies Example from Chicontepec, Mexico Ha T. Mai, Kurt J. Marfurt University of Oklahoma, Norman, USA Sergio Chávez-Pérez Instituto Mexicano del Petróleo Seventy-Ninth SEG Annual Meetinh, Houston, Texas 25-30 October 2009

2. Acknowledgements • PEMEX Exploración y Producción, for providing data and permission to publish this work, especially to Juan M. Berlanga, ProyectoAceiteTerciario del Golfo • Schlumberger for providing OU with licenses to Petrel • Sponsors of the Attribute Assisted Seismic Processing and Interpretation (AASPI) consortium at the University of Oklahoma: 25

3. Outline • Introduction • Curvature - definitions • Application to Chicontepec Basin • Conclusions 24

4. Chicontepec, Mexico (Salvador, 1991) 23

5. Data: Availability and Quality • 3D Seismic volume anticline Footprint Normal fault syncline Reverse fault fault 22

6. Outline • Introduction • Curvature - definitions • Application to Chicontepec Basin • Conclusions 21

7. Definition of curvature (2D) x k2D= 0 Flat plane k2D > 0 Anticline n P τ k2D = 0 R Dipping plane k2D < 0 Osculating circle Syncline Curvature k2D = 1/R z Curve 20

8. Osculating circle on 2D curve (movie)

9. Sign convention for 2D curvature attributes + • Anticline: k2D > 0 • Plane: k2D = 0 • Syncline: k2D < 0 k2D=0 k2D>0 k2D=0 k2D<0 Flat Plane Anticline Dipping Plane - R Syncline x (lago argentina) 19 z

10. Circles in perpendicular planes tangent to a quadratic surface + |kmax|=1/Rmin |kmin|=1/Rmax n ψmin In this case k1 = kmin - k2 =kmax 18

11. Graphical representation of kmax and kmin + anticlinal and synclinal folds kmax=k1>0 kmax=k2<0 kmin=k1=0 kmin=k2=0 limb Fold axis syncline kmax=k2<0 kmin=k1=0 anticline - syncline 17

12. The principal curvatures k1 and k2 vs. kposand kneg Asymmetric fold k1 > 0 k2 = 0 + k1 anomaly kposanomaly k1 = 0 k2 < 0 k2 anomaly kneganomaly Hinge Limb Limb Trough anticline dipping plane - syncline flat plane See Roberts (2001) for definitions 16

13. Osculating circle on rotated curve (movie)

14. The principal curvatures k1 and k2 vs. kposand kneg kpos kpos kpos ≈ k1 kpos ≈ k1 kpos& k1 k1 k1 We recommend using principal curvatures k1and k2 instead of kpos and kneg 15

15. Definition of shape index, s Bowl s=-1.0 k1< 0 and k2 < 0 Valley s=-0.5 k1= 0 and k2 < 0 Saddle s=0.0 Principal curvatures k1> 0 and k2 < 0 Ridge s=+0.5 k1> 0 and k2 = 0 Dome s=+1.0 14 k1> 0 and k2 > 0

16. Outline • Introduction • Curvature - definitions • Application to Chicontepec Basin • Folds • Reverse faults • Normal faults • Conclusions c 13

17. Shape index on faults & flexures valley/bowl ridge valley bowl s=-1.0 fault saddle bowl ridge dome valley fault 0.2 anticline anticline fault Valley s=-0.5 syncline Pos curvedness Saddle s=0.0 saddle dome bowl valley saddle Amplitude 0.0 Ridge s=+0.5 plane 0.0 -1.0 -0.5 0.0 +0.5 +1.0 Neg Shape index 1 0 Dome s=+1.0 Opacity 12

18. Fold - Anticline k1 anomalies Hinge Trough Trough Limb Limb k2 anomalies second principal curvature anomalies (k2 - blue) delineate the two troughs of the fold first principal curvature anomalies (k1 - red) delineate the hinge of the fold no significant coherence anomalies 11

19. Anticline feature k1 k1 k2 k1 k2 Hinge Hinge Trough Trough k2 10

20. Anticline feature flexures k1 Trough Hinge flexures Trough local hinge flexures Pos Amplitude 0.0 k2 Neg 1 0 Opacity 9

21. Reverse fault feature – case1 k2 k1 footwall dragged up hanging wall dragged down drag on footwall k2 footwall dragged up seperation coherence Fault plane Fault plane 8

22. Reverse fault feature – case 2 k1 footwall flat hanging wall dragged down No drag on footwall k2 footwall dragged up No seperation coherence Fault plane Fault plane 7

23. Fault: Vertical section with interpretation coherence coherence k1 coherence 1000m k1 Only coherence k1 k2 Coherence k1 and k2 Coherence & k1 k2 6

24. Fault: Seismic volume with interpretation k1 coherence coherence k1 k2 coherence Pos k1 Amplitude 0.0 k2 dome k2 Neg 1 0 Opacity 5

25. Normal fault down thrown side k1 k2 Up thrown side coherence Fault planes 4

26. Fault: Vertical section with interpretation k1 coherence coherence coherence k1 k2 k1 k2 Pos Switch Amplitude 0.0 k2 k2 Neg 1 0 k1 k2 Opacity 3

27. Fault: Seismic volume with interpretation k1 coherence processing footprint fault coherence k2 k1 Bowl Pos k1 Amplitude 0.0 k2 k2 Neg 1 0 Opacity 2

28. Conclusions • Coherence: - not sensitive to smooth folding • - discontinuous in the vertical section • - accurately locate the discontinuity • Curvature - sensitive to folds and flexures • - more continuous on the vertical section • - bracket fault drags with k1 and k2 anomalies but does not give the exact fault location • The shape index provides an accurate 3D image of deformation when seen on either vertical or horizontal planes. • Co-rendering curvature (or the shape index) with coherence along with the seismic amplitude data provides a superior interpretation product allowing one to visualize the deformation style (reverse, normal, strike-slip) on time slices, and to highlight pop-up blocks, antithetic faulting, fault drag, and roll-over anticlines important to hydrocarbon exploration. 1

29. Questions?