The Gunnison Discovery—Garden Banks Block 668

Jeff Pan¹ and Jim Fulcher^2
1 Kerr McGee, Houston, TX
² Nexen,

In April 2000, Kerr-McGee Oil and Gas Corporation and its partners Nexen Inc. and Cal Dive International drilled the discovery well of the Gunnison Field in Garden Banks block 668 (GB 668). GB 668 is located about 150 miles to the south of Houston and it is in the 3,200 feet water depth.

The prospect generation and evaluation in the Gunnison mini-basin was primarily based on 2-D seismic data prior to 1998. In mid-1998, the 3D seismic data became available. Mapping of the re-processed GPI 3D data in 1999 produced eight levels of amplitude-supported targets. Several of the amplitudes conform to down-dip structural limits and exhibit positive AVO response. These features significantly reduced the risk of the prospect. Geopressure analysis was deployed to mitigate the seal risk factor of the shallow targets. Trap was considered the primary risk for the deep targets due to the difficulty of seismic imaging near salt flank.

The Gunnison Field was discovered just before midnight on Easter Sunday 2000 as GB 668 #1 well penetrated the first of twelve pays. After 10 delineation wells, the Greater Gunnison Field was sanctioned in October 2001. The ranges of field size, extent of area, column heights, thickness and fluid quality were all addressed by the exploration and development teams. Thirty-two months after the discovery, on December 11, 2003, Gunnison Field achieved its first production. The field is now ramping up to its peak daily production rate of 30,000 barrels of oil and 180 million cubic feet of gas.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005