Abstract

In North Avant Field, the Bartlesville sandstone has had a long history of primary and secondary oil production. Recent interest and attempts to use horizontal wells, both as producers and injectors, has spurred interest in the permeability anisotropy character of the meandering-fluvial reservoir interval. This study utilizes data taken from wells in a 160-acre tract. Data include five cores that are described in terms of architecture and are analyzed for permeability anisotropy using conventional core-plug and probe permeameter measurements.

Meandering-fluvial facies architectural elements include three facies: channel-fill, splay and floodplain. The channel-fill facies is subdivided into the lower subfacies made up of trough cross-stratified fine sandstone, a middle subfacies composed of lateral-accretion surfaces and very fine sandstone, and an upper subfacies of very fine sandstone to mudstone. Using a probe permeameter, selected core segments were measured for permeability in the horizontal direction around the core periphery and perpendicular to architectural elements such as cross-stratification (lower channel-fill subfacies) and lateral-accretion surfaces (middle channel-fill subfacies).

Based on core-plug data only the lower and middle channel-fill subfacies have sufficient porosity and permeability to be of interest as reservoirs. Macroscopic heterogeneities, such as mud and micaceous and carbonaceous debris drapes on lateral-accretion surfaces in the middle channel-fill subfacies, would suggest that permeability anisotropy should exist with minimum values perpendicular to such surfaces and intermediate and maximum values in the inclined stratal planes. Characterization of this relationship is the focus of this research effort. Facies and subfacies affect permeability. We find the lower channel-fill subfacies show slight permeability anisotropy. The middle channel-fill subfacies also shows anisotropy; lateral-accretion surfaces influence permeability anisotropy as a result of its proximity, thickness and continuity.