Resolving the K-2 Salt Structure in the Gulf of Mexico: An Integrated
Approach Using Full Tensor Gravity Gradiometry and Pre-Stack Depth
Imaging
John O'Brien1, Arnold Rodriguez1, David
Sixta1, Mark Davies2, and Phill Houghton2
1 Anadarko Petroleum Corporation, Woodlands, TX
2 ARKeX Ltd, Cambridge, United
Kingdom
K-2 is a subsalt field underlying a massive salt body in the deepwater
Gulf of Mexico. Prestack depth
migration has played a vital role in exploring
and appraising this field. The technique however is not without problems and
fails to image the Base of Salt and subsalt section in an area where the Top of
Salt has a pronounced structural peak; as a result seismic data is unable to
determine the updip extent of the field.
To locate the Base of Salt in the seismic “no-data” zone we performed an
inversion of Full Tensor Gravity Gradiometry data (FTG) constrained with well
information and Prestack Depth
Migration results, where these provide a reliable
image. FTG is a powerful geophysical technique that provides a superior
measurement of the
earth's
gravitational field compared to that obtained with
conventional gravity surveys. This integrated analysis proved to be a potent
technique capable of discriminating between the initial candidate
interpretations for the Base of Salt configuration, even at subsea depths
greater than 20,000 ft. It indicates that the salt has an asymmetric keel that
is approximately 6,000 ft. deep and that the termination of the sedimentary
subsalt reflections delineates the truncation of the pay sands against the salt
keel.
These results have major implications for the field appraisal program. They indicate that we can confidently identify the updip extent of the pay sands and they also resolve the need for further delineation drilling in this part of the field.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005