Understanding the Wilcox 1 and Wilcox 2 Reservoir Distribution at Jack (It’s Possible That You Don’t Know Jack!)

Mooney, R. Tom¹, Morgan D. Sullivan¹, Larry Zarra² (1) Chevron Energy Technology Company, Houston, TX (2) Chevron USA, Houston, TX

The 2004 Jack oil discovery encountered more than 350 feet of net pay oil sands in the Wilcox (Upper Paleocene) in approximately 7,000 feet of water in the Gulf of Mexico. Core was taken in the Wilcox 1 which was interpreted to represent true unconfined, basin-floor sheets. The following year, Jack 2 was drilled approximately a mile away and core was taken in both the Wilcox 1 and Wilcox 2. As in the Jack 1 well, the Wilcox 1 cores were interpreted as unconfined sheets, but the Wilcox 2 core was interpreted as confined channel deposits. Common core recognition criteria were used to interpret, and differentiate between, unconfined sheet elements and confined channel elements.

Sub-salt seismic data are generally poor, and lack the resolution to effectively characterize the Jack reservoirs. Consequently, the core analysis, log correlation, and depositional models were used to characterize the Wilcox 1 & 2 reservoirs at Jack. Both channel and sheet elements are part of a larger 3D body, a distributary lobe. The distributary lobe depositional model is the result of previous outcrop research and subsurface analogs. Using the interpreted elements and previously derived aspect ratios (width to thickness ratios) we were able to provide dimensions and reservoir distributions for each element, as well as for the larger distributary lobes.

In 2006, the Jack 2 well was successfully tested and sustained a flow rate of more than 6,000 barrels of crude oil per day.