Thomas L. Cogswell

ExxonMobil Corporation, Houston, TX

ABSTRACT: Diana Basin Development – A Pragmatic Approach to the Exploitation of Two Deepwater GOM Fields

The Diana basin is an intraslope salt withdrawal basin 160 miles due south of Galveston, Texas in the East Breaks and Alaminos Canyon offshore surveys of the western Gulf of Mexico. The water depth ranges from 4600 to 5000'. ExxonMobil and BP initially acquired leases in the Diana/Hoover area in the late 1980's.

The Diana #1 discovery well was drilled in 1990 based on 2D seismic. A proprietary 3D survey was shot over the area in 1992, and two additional delineation wells were drilled at Diana in 1996. Though the 1990 discovery of the Diana accumulation was in itself significant and development plans were underway, the 1997 discovery of the Hoover oil field ~12 miles to the east dramatically changed the scope of the project. It was quickly seen that plans for a facility at Diana were not as attractive as a host facility at Hoover with Diana as a subsea tieback. A large and diverse multi-disciplinary team of ExxonMobil, BP, and contractor/vendor experts was assembled into the Diana/Hoover Integrated Project Team. The project was fully funded in early 1998. Technical experts from all branches of the ExxonMobil and BP organizations have contributed in every phase of the project.

The Hoover DDCV (Deep Draft Caisson Vessel) combined production and drilling facility was commissioned in the spring of 2000, and first oil from the Diana field was produced May 31^st of that year. The Hoover development wells are being drilled with the Ensco 26 from the DDCV. Development of three smaller accumulations in the area as subsea tiebacks is also underway.

In light of the extreme expense and difficulty of operations in deepwater, the strategic objective is to optimally develop the resource with the least number of wells possible. The majority of the wells in the Diana and Hoover field development plans, as well as in the smaller satellite accumulations, are horizontal open-hole gravel pack (OHGP) completions. These wells access a larger portion of the reservoir than conventional wells, and provide high deliverabilty with minimum pressure drawdown to mitigate water coning.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado