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Anisotropic Depth Migration in the Colombian Llanos Foothills as a Key to Understanding the Structure in Depth

Vestrum, Rob W.1; Florez, Isabel C.2; Gittins, Jon M.1
1 Seismic data processing, Thrust Belt Imaging, Calgary, AB, Canada.
2 Exploration, Hocol, Bogotá, Colombia.

The objective of the depth imaging was to confirm the existence of the structure in depth, improving the image and obtaining more accurate positioning of the events in order to decide on an appropriate the well trajectory.

We used a collaborative, geologically constrained approach that integrates all available geologic information into the interpretation of the seismic velocity model. Iteratively testing several model interpretations, we arrived at a final velocity model with 20 surfaces describing the structure with its dips and velocities found in all the wells drilled in the vicinity. Close collaboration between the exploration geologist and the service company geophysicist found a velocity model that optimized the seismic imaging. This area has interbedded siliciclastic rocks with high dips and vertical and lateral velocity contrasts, giving a considerable lateral movement in the images in depth when we correct for seismic anisotropy and lateral-velocity heterogeneity.

The final anisotropic-depth-migrated image confirms the structure and moves the imaged structured to the east compared to the time image. The position of the structure and dips were confirmed by two wells drilled in the area, which verifies the accuracy of the seismic-imaging algorithm and the interpretive model-building process in this complex-structured area.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009