A New Prospective of US Gulf of Mexico from a Large Scale Seismic Reimaging Project

Abstract

Abstract

We will present a multiclient seismic reimaging project that covers more than 50,000 square kilometers. The project area is located in the most prolific deep water basin centered on Green Canyon, Walker Ridge, Keathley Canyon and Garden Banks. Input seismic data included vintage narrow azimuth (NAZ), modern wide azimuth (WAZ) and latest full azimuth long offset seismic data (FAZ). Existing seismic coverage in the area are piece meal in nature, having different vintages of data acquisition and processing with different velocity models and anisotropy parameters. This makes large scale regional studies of the deep water basin more difficult: Horizons are discontinuous at survey boundaries, they are at differing depths, with different frequency content, different amplitudes and different wavelet characteristics. The objective of the project is to produce a most advanced prestack depth migration volume over an extremely large area using one unified earth model, therefore solving all the problems mentioned above.

A team of 38 petro-technical experts assembled to work on the project, including petrophysicists, rock physicists, seismic interpreters and seismic processing specialists. We have examined close to 600 wells in the coverage area for inclusion in a joint inversion with prestack seismic data for velocity and anisotropy parameter determination. Check shot data, sonic logs, lithological markers (top salt and base salt, for example) as well as paleo tops are used. In addition, full tensor gravity data over 800 US OCS blocks were utilized to assist in salt interpretation. Full azimuth tomography, full waveform inversion and deghosted RTM are the latest geophysical technologies that have been applied to this project.

For the first time, we can successfully track key subsalt horizons over very long distances, enabling operators to carry their successes from one mini-basin to another mini-basin. We see significant improvement in subsalt structural integrity, stratigraphic definition, seismic illumination and conformance of velocity model to geology. We now believe that evaluations in the area will be more reliable and afford further successes.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016