Reservoir Characterization in the Sacroc Unit of the Kelly-Snyder Field, Horseshoe Atoll, Permian Basin, Texas, Via Probabilistic Clustering and Prediction Procedures Using Limited Well Log and Core Data

Eric Eslinger¹ and Reinaldo Gonzalez^2
1Eric Geoscience, Inc., Glenmont, NY
²Advanced Resources International, Houston, TX

Reservoir quality (RQ) and flow units were defined using well log and whole core data from 24 wells in the Kelly-Snyder Field, a complex carbonate oil field (SACROC Unit) in the Permian Basin. Twenty-two of the wells were from a small "central study" area, including one that had whole core through most of the ~ 900 ft limestone interval of the Pennsylvanian-Permian aged Canyon and Cisco Formations. Two additional cored wells outside of the study area were also used.

The goal of the study was to provide input into a 3D geostatistical reservoir model. Major problems were: 1. limited wells with core porosity and permeability; 2. the fact that most wells inside and outside of the study area had only neutron (NPHI) and gamma ray (GR) logs, and 3. the unavailability of core description information.

The overall problem was attacked using a probabilistic clustering procedure which permits estimation of "missing" well logs where only NPHI and GR logs exist, and also estimation of porosity and permeability profiles in non-cored wells. Porosity and permeability profiles were generated for all wells; credibility was established using a series of "hold-out" tests. Flow unit reservoir quality was defined and its continuity evaluated as a function of reservoir geometry. A vertical cyclicity (defined by interpreted "sharp" 3rd to 4th order sequence boundaries) was observed that is semi-pervasive throughout the study area. The differences in porosity and permeability between the "good" RQ flow units (11-13 % porosity) and the "poor" RQ flow units (<5% porosity), plus the sharpness of the boundaries between them and their lateral continuity indicate that substantial vertical compartmentalization exists that could impact on-going secondary and tertiary recovery efforts.

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