3-D Seismic Fault Plane Images from Offshore Myanmar, Gulf of Thailand, and Lake Maracaibo: Insight into Regional Stresses and Hydrocarbon Migration Pathways

Pigott, John D.¹; Prapasanobon, Non ²
(1) Conoco-Phillips School of Geology & Geophysics, University of Oklahoma, Norman, OK. (2) PTTP Company Limited, Bangkok, Thailand.

Fault zones play critical roles in petroleum systems, potentially providing conduits and barriers for hydrocarbon migration pathways from source pods and, if associated with fractures, forming significant reservoirs. Insight into the regional stresses responsible for their formation and into the consequent fluid-gas pathways developed may be obtained through 3D seismic images of the fault plane entity.

Through meticulous systematic line by line interpretation of the terminations of horizon reflectors against a consistent vertical displacement zone in the volume, a three dimensional fault plane entity can be constructed. The subsequent 3D visualization product reveals geomorphologic features such as grooves, ridges, and steps similar to those commonly observed in fault zones macroscopically in outcrop and microscopically in slickensides. Such interpretations were performed on 3D seismic volumes from three different regions of the world: normal faults from offshore Myanmar, transtensional faults from the Gulf of Thailand, and transpressional faults from the Maracaibo Basin, Venezuela.

The Offshore Myanmar normal faults reveal grooves and ridges that yield normal dip-slip in an N-S direction. A transtensional fault example from the Gulf of Thailand reveals normal dip-slip motion in a NE-SW direction on the vertical seismic data and reveals oblique normal dip-slip motion in an E-W direction developed by dextral strike-slip motion in a NW-SE direction. The transpressional fault example from Mara¬caibo Basin, Venezuela is manifested as reverse dip-slip motion in a NW-SE direction and reveals an oblique reverse dip-slip in a NWW-SEE direction formed by dextral strike-slip motion in a NE-SW direction.

Seismic attribute maps reveal seismic anomaly patterns on the fault planes parallel to the ridge and groove trends. As the ridges, grooves, and steps are parallel to the direction of fault slip motion, they provide the direction of fault gouge and fault breccia production and if permeable the likely pathways of gas-fluid migration along the fault planes with preference given to the fault plane ridges.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.