Core Work--Critical Piece of the Reservoir Puzzle: DEB (Wolfcamp) Field, Gaines County, Texas

David Entzminger¹, Lyn Canter¹, Mark Sonnenfeld¹, Jay Blaylock¹, and Scott Haberman^2
1Whiting Petroleum Corp., Denver, CO
²Lago Petroleum Consulting, Denver, CO

Wolfcamp production in many Central Basin Platform fields, including DEB(1952), is commonly attributed to reefal porosity. Field development assumed faulting ceased prior to Wolfcamp time. Our work demonstrates production from stacked carbonate shoals, yet significant water volumes cycle through underlying porous buildup facies. 3D seismic faults cut through the Wolfcamp section and impact waterflood performance.

Two cores (>600’) were described in detail yielding 8 facies (from deepest marine to shallow platform interior): 1. crinoidal lime wackestone; 2. crinoidal-fusulinid lime wacke/packstone; 3. bioclastic-intraclastic-skeletal lime wacke/packstone; 4. bioclastic lime packstone; 5. bryozoan-fusulinid-platy algae lime boundstone; 6. coarse-grained, skeletal lime pack/grainstone; 7. coarse-grained fusulinid-bioclastic-coated grain lime pack/grainstone and grainstone; and 8. foram-dasyclad-peloid lime packstone. Main pay f.6-7 were deposited as aggradational, high energy platform-margin shoal complexes. Significant porosity and permeability also occurs in f.5 boundstones, positioned about 40-50’ below the main pay zone in the water leg. A reciprocal relationship exists between the development of f.5 buildups and overlying shoals; where the buildup is thick and well-developed, shoal pay facies thin. The most extensively developed buildups exhibit significant secondary porosity development with well-connected vugs, cavities, and solution-enlarged fractures contributing to excessive water production through coning.

Log correlations are challenging, but key surfaces and stacking patterns defined through core and tied to 3D seismic assist in uncored areas. Core-based insights enhance platform-to-basin correlations by relating disconformities recognized in core to emerging periplatform plays represented by sediment gravity flow deposits.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas