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 October 2009 Attribute-Assisted Seismic Processing and Interpretation

- + Acknowledgements PEMEX Exploración y Producción, for providing data and permission to publish this work, especially to Juan M. Berlanga, Proyecto Aceite Terciario 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

- + Outline Introduction Curvature - definitions Application to Chicontepec Basin Conclusions 24

- + Chicontepec, Mexico (Salvador, 1991) 23

- + Data: Availability and Quality 3D Seismic volume anticline Reverse fault Normal fault Footprint syncline fault 22

- + Outline Introduction Curvature - definitions Application to Chicontepec Basin Conclusions 21

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

- + Osculating circle on 2D curve (movie)

- + Sign convention for 2D curvature attributes R xz Flat Plane k 2D =0 Anticline k 2D >0 Syncline k 2D <0 Dipping Plane k 2D =0 19 Plane: k 2D = 0 Anticline: k 2D > 0 Syncline: k 2D < (lago argentina)

- + Circles in perpendicular planes tangent to a quadratic surface n |k max |=1/R min |k min |=1/R max ψ min + - k 2 =k max In this case k 1 = k min 18

- + Fold axis limb syncline anticline k min =k 1 =0 syncline Graphical representation of k max and k min + - k max =k 2 <0 k min =k 2 =0 k max =k 1 >0 k max =k 2 <0 anticlinal and synclinal folds 17

- + k pos anomaly k 1 anomaly syncline anticline flat plane dipping plane k 2 anomaly k neg anomaly The principal curvatures k 1 and k 2 vs. k pos and k neg k 1 > 0k 2 = 0 k 1 = 0k 2 < 0 See Roberts (2001) for definitions + - Trough Hinge Limb Asymmetric fold 16

- + Osculating circle on rotated curve (movie)

- + k1k1 k pos k pos & k 1 k pos The principal curvatures k 1 and k 2 vs. k pos and k neg k1k1 k1k1 k pos ≈ k 1 We recommend using principal curvatures k 1 and k 2 instead of k pos and k neg 15

- + Definition of shape index, s Principal curvatures s=-1.0 Bowl s=0.0 Saddle Dome s=+1.0 s=-0.5 Valley Ridge s= k 1 < 0 and k 2 < 0 k 1 = 0 and k 2 < 0 k 1 > 0 and k 2 < 0 k 1 > 0 and k 2 = 0 k 1 > 0 and k 2 > 0

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

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

- + k 2 anomalies k 1 anomalies second principal curvature anomalies (k 2 - blue) delineate the two troughs of the fold first principal curvature anomalies (k 1 - red) delineate the hinge of the fold no significant coherence anomalies Fold - Anticline Trough Hinge Limb Trough 11

- + k2k2 k2k2 k2k2 k2k2 k1k1 k1k1 k1k1 k1k1 Anticline feature k1k1 k2k2 10 Trough Hinge Trough

- + Anticline feature flexures Hinge Trough local hinge k1k1 k2k2 Opacity Amplitude 0 1 Neg 0.0 Pos flexures 9

- + Fault plane hanging wall dragged down footwall dragged up footwall dragged up k1k1 k2k2 k2k2 Reverse fault feature – case1 coherence Fault plane seperation drag on footwall 8

- + k1k1 k2k2 Reverse fault feature – case 2 coherence Fault plane footwall flat footwall dragged up Fault plane hanging wall dragged down No seperation No drag on footwall 7

m Fault: Vertical section with interpretation coherence k1k1 k1k1 k1k1 k1k1 k2k2 k2k2 Only coherence Coherence k1 and k2 Coherence k1 and k2 Coherence & k1 k1k1 k2k2 coherence 6

- + Fault: Seismic volume with interpretation coherence k1k1 k1k1 k2k2 k2k2 k1k1 k2k2 k1k1 k1k1 k2k2 k2k2 Opacity Amplitude 0 1 Neg 0.0 Pos coherence dome 5

- + Fault planes k2k2 down thrown side Up thrown side k1k1 Normal fault coherence 4

- + Fault: Vertical section with interpretation coherence k1k1 k1k1 k2k2 k2k2 k1k1 k1k1 k2k2 k2k2 k1k1 k1k1 k2k2 k2k2 k1k1 k2k2 Opacity Amplitude 0 1 Neg 0.0 Pos coherence 3 k2k2 k2k2 Switch

- + Fault: Seismic volume with interpretation k1k1 k2k2 Opacity Amplitude 0 1 Neg 0.0 Pos coherence k1k1 k1k1 k2k2 k2k2 Bowl k1k1 k1k1 k2k2 k2k2 fault processing footprint 2

- + 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 k 1 and k 2 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

- + Questions?