Abstract: Use of Microresistivity Image Logs in Detailed Reservoir Architecture Reconstruction of Bartlesville Sandstone, Glenn Pool Field, Northeastern Oklahoma

Liangmiao Ye

The Glenn Sandstone, a fluvial-dominated deltaic system equivalent to the Pennsylvanian Bartlesville Sandstone, has produced for 90 years as the main pay zone of the Glenn Pool field. However, 70% of OOIP remains despite post-primary recovery attempts because of the complex reservoir heterogeneity. Detailed reservoir architecture is critical for further reservoir management. This study is focused on a 160-acre block in the southern part of the field, in which the 130-ft thick Glenn Sandstone is divided into six discrete genetic intervals (DGIs) descending from DGI A to F.

Analysis of microresistivity image logs, calibrated to detailed core description, revealed features including bed boundary, cross stratification and cross strata set boundaries, scour surfaces, mud drapes, and fractures etc. Orientation of these architectural elements permitted a detailed reservoir architecture reconstruction in the vicinity of the Self No. 82 well. (1) Structural dip azimuth averages 153° and dip angle 4°. (2) DGI C is dominated by lateral accretion bar deposits. Lateral accretion surface dip azimuth shows progressive upward rotation from 200° to 146°. Comparison of azimuthal orientations for cross strata and lateral accretion surfaces indicates that the well is located in downstream side of a lateral accretion bar. Average vertical spacing of lat ral accretion surfaces is 1.08 ft, and their average structure-corrected dip angle is 6°. The "exact" spatial configuration of lateral accretion mud drapes within the bar is developed and it is inferred that 19 lateral accretion mud drapes are present between Self No. 82 and 81. (3) DGI D is a 22-ft thick complex of splay sandstones. The image color proportion analysis indicates that only a 4-ft interval appears to have been washed by water flooding. This in turn suggests thin mudstones deposited between splay sandstone depositional events serve to vertically compartmentalize reservoirs. Orientation patterns reveal DGI D is actually consist of four splay units, with dispersal direction being, in descending order, 120°, 315°, 70°, and 210°, respectively. (4) 15-ft DGI E splay sandstone is made of two splay units with dispersal direction being 180° (upper) and 30° (lower) respectively. (5) DGI A and B are channel-fill sandstone facies represented by subaqueous medium-scale cross strata sets with numerous mud drapes.

Integration of core study and log facies analysis has resulted in high resolution facies/subfacies architecture models for each DGI, which provide the basis for reservoir simulation and proposed management plan.

AAPG Search and Discovery Article #90957©1995 AAPG Mid-Continent Section Meeting, Tulsa, Oklahoma