Princess: A Deep-Water Sub-Salt Discovery in the Gulf of Mexico

Alice Hobson Ellis, John Stachowiak, Aafke Bouma, Bret Hampton, K.V.K. Prasad, Mike Rainey, and Dorine Bosman
Shell Exploration and Production Company, New Orleans Louisiana

Princess is a sub-salt discovery consisting of several stacked, hydrocarbon-bearing intervals located in the Mars Basin, Gulf of Mexico. This paper will try to: 1) describe Princess and its relationship to the prolific Mars Basin, 2) portray the challenges associated with characterizing the subsurface in a sub-salt setting and 3) provide an overview of the approach taken to appraise and develop this field.

Princess is located in 3700 feet of water, on the northern flank of the Mars Basin, adjacent to the Ursa field. Shell is the operator with partners British Petroleum, ExxonMobil and ConocoPhillips. The discovery well targeted poorly imaged, sub-salt traps and it penetrated several levels of pay in stacked, Upper Miocene turbidite reservoirs.

There is a wide range in post-discovery well volumes because 1) there was no seismic image of the penetrated reservoirs, 2) there is considerable upside potential in deeper, untested stratigraphy and 3) a waterflood as a secondary recovery mechanism is being considered. A staged development concept, allowing for these uncertainties, was chosen to simultaneously appraise and develop the field with very challenging extended reach wells.

Since the discovery, the subsurface understanding has improved significantly with the drilling of appraisal and development wells and the acquisition of seismic data designed to improve sub-salt imaging.

First production was established late 2003, 3 ½ years after discovery. Three wells are currently producing via a sub-sea tieback to the Ursa Tension Leg Platform. This subsea system still has the flexibility to cater for many different outcomes as appraisal of the various intervals continues.

AAPG Search and Discovery Article #90032©2004 GCAGS 54th Annual Convention, San Antonio, Texas, October 10-12, 2004