The Boris Oil Field in the Gulf of Mexico – a Geophysical Case Study

Abstract

The Boris oil field was discovered in 2001 in Green Canyon block 282 in the deep water mini-basin area of the Gulf of Mexico. The Boris discovery was followed by the drilling of the Boris North appraisal well in 2002. First oil from the Boris field was produced in early 2003 with recoverable reserves estimated at 10 to 35 million barrels of oil equivalent. The Boris reservoir shows up as a bright seismic amplitude anomaly in Pliocene-age sand. Seismic reprocessing for robust amplitude fidelity and the use of Kirchhoff prestack time migration were the main geophysical tools that led to the discovery of the field. The Boris reservoir is steeply dipping at a depth of approximately 4500m. The original seismic data across the Boris field consisted of post-stack time migrated data that showed a broad, poorly defined amplitude with poor conformance to structure. After careful amplitude processing was input to prestack time migration, a bright well-defined amplitude ?appeared? on the seismic data with an excellent down-dip fit to structure. Concurrent with the reprocessing, a lithology and fluid prediction project was undertaken. Nearby well control was used to define rock property trends such as Vp versus depth, Vp versus Vs, and Vp versus density. The rock property trends were used to stochastically model the AVO response and the results were compared to the measured AVO response on the reprocessed seismic data. The results of the modelling showed that the fluid type at Boris was consistent with hydrocarbons. The Boris discovery well was drilled within three months of completing this reprocessing.