SEMINAR - Jennifer Lewis

Wide-azimuth seismic at the subsalt Jack asset: Is it worth the early investment?

Jennifer L. Lewis
Chevron Energy Technology Company, Houston, USA

April 9th, 2008

For decades, hydrocarbon accumulations beneath the Gulf of Mexico allochthonous salt canopy were largely considered implausible. The paradigm shift that success could be achieved in deepwater subsalt settings began in 1990 with the subsalt Mica discovery. Today, besides an expanding exploration portfolio, industry has the fortunate task of facing the many and variedfocusing on challenges of subsalt appraisal and development. With this transition comes the need for robust and accurate subsurface characterization. Beneath a salt canopy often many thousands of feet thick, this is a challenge from many viewpoints, from drilling and reservoir management to seismic imaging.

Answers to new and increasingly detailed questions are sought in an effort to minimize risk and optimize project value at a Chevron-operated Deepwater Gulf of Mexico field called Jack. The seismic data quality covering the field is typical of many subsalt images. Data at the reservoir level are low frequency (~10 Hz dominant) and contaminated with remnant multiple noise, making characterization of key reservoir uncertainties, e.g., faulting, an onerous undertaking at best. Recently, industry has recognized a step-change improvement in subsurface imaging in deepwater subsalt settings with wide-azimuth (WAz) towed streamer acquisition and processing. IntegratePresented with the opportunity for a similar improvement in the data quality over the Jack field, an integratedd modeling effort was undertakens, which includedincluding simple 1D synthetics, 3D ray tracing, and 2.5D finite difference models. While these analyses , facilitate the understanding comprehension of the advantages as well as the limitations of proposed WAz survey designs, they are not able to directly aid in the determination of the value that the improved data quality may have to the project. To help address the value of information, a parallel reservoir modeling project was conducted to, while simulated reservoir production models address the implications of acquiring a WAz survey prior to development decisions. Together, Tthese models provide an integrated analysis that can be used to means of effectively communicateing the impact and value of a WAz investment early in the appraisal phase of a project.