Characterization of Fluvial-Dominated Deltaic Reservoirs in a Mature Oil Field: Glenn Pool Field, Northeastern Oklahoma

Liangmiao Ye, Dennis R. Kerr

Glenn Pool field, located on the Northeastern Oklahoma Platform, has produced for 90 years from the Glenn Sand, a fluvial-dominated deltaic system equivalent to the Pennsylvanian Bartlesville Sandstone. About 70 percent of OOIP remains as a result of the complex reservoir architecture. This study has focused on a 160 acre block (82 wells drilled to date) in the southern part of the field.

Detailed reservoir architecture is critical for improving production performance. Through detailed well log correlation, the 120-140 ft thick Bartlesville Sandstone is subdivided into six discrete genetic intervals (DGI) descending from A to F. Core and log facies studies show that DGI A through E are likely to be delta plain fluvial channel-fill and crevasse splay deposits, and F channel-mouth bar deposits. Channel-fill facies is characterized by upward-fining texture and reduction in scale of physical sedimentary structures, and it is subdivided into: lower channel-fill subfacies, well to moderately sorted medium-grained sandstone with medium-scale cross stratification; middle channel-fill subfacies, moderately sorted, lower medium-grained to poorly sorted, silty fine-grained sandst ne with low-angle parallel stratification and ripple lamination or ripple lamination superimposed on cross stratification; and upper channel-fill subfacies, mudstone to silty claystone. Splay facies is characterized by fine- to medium-grained sandstone with ripple lamination and upward-coarsening texture. Channel-mouth bar facies is characterized by well sorted, generally massive, upper medium- to lower coarse-grained sandstone. Lab core measurements have shown that the porosity and permeability are strongly DGI-related. Descending from DGI A to F, porosity increases from about 8 percent to about 22 percent, permeability increases from less than 0.1 md to more than 300 md. Initial results suggest that within a given DGI, petrophysical properties are facies/subfacies related.

Analysis of a microresistivity image log, which was acquired in a project cooperative well--Uplands Resources Self No.82, permitted a detailed architecture reconstruction. At location of Self No.82, DGI C is made up of lateral accretion bar deposits. Comparison of azimuthal orientations for cross strata and lateral accretion surfaces indicates a downstream location. From spatial orientation of lateral accretion surfaces, it is predicted that 19 lateral accretion mud drapes are present between Self No.82 and Self No.81 (270 ft apart). Based on orientation patterns, in the vicinity of Self No.82, DGI D is divided into 4 splay units and DGI E is divided into 2 splay units. Image color proportion analysis indicates that of 22 ft DGI D splay deposits, only a 4 ft interval has been contacte by water flooding.

The facies architecture model is being incorporated with results of crosswell tomography and reservoir simulation for the development and implementation of a reservoir management plan.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995