Abstract: Reservoir Distribution and Exploration Potential of the Spiro Formation in the Choctaw Trend, Arkoma Basin, Oklahoma and Arkansas

Jonathan S. Gross, Sheree A. Thompson, Brenda L. Claxton, Matthew B. Carr

In the Arkoma basin, the distribution of reservoir quality sandstones in the Spiro Formation can be explained by integrating three technologies: (1) well log correlations using sequence stratigraphic principles; (2) a thermal-maturation study using surface and subsurface vitrinite reflectance values in a regional three dimensional data set; and (3) petrographic analysis of the reservoir. Parasequence stacking patterns on logs, isopach maps, and results from core studies were integrated to interpret depositional environments. In Pittsburg and Latimer counties, Oklahoma, along the Choctaw Fault Trend, the thrusted Spiro is predominantly a barrier island deposit composed of reservoir-quality, progradational and aggradational sandstones. However, to the east from Leflore County, Oklahoma, through Yell County, Arkansas, along the structural trend, the Spiro is composed predominantly of tight, non-productive retrogradational sandstones. Petrographic observations of the progradational Spiro show that sands in the west are medium to fine grained, but in the east they are very fine grained. Chlorite coats, which inhibit quartz cementation, are present only in the west. To examine the relationship between thermal maturity and porosity, vitrinite reflectance data were calibrated to commercial gas production and petrographic data, and a thermal basement was established. The vitrinite data indicate that the Spiro in the west is within the gas window (approx. 1.5% R_o), but in the east, it is overmature (>2.5% R_o). The term overmature applies to reservoirs t at have insufficient porosity for commercial production due to destructive diagenesis caused by thermal stress. The simultaneous multidisciplinary approach is economically significant because exploration analysis cycle time is decreased, and decisions can be made with more reliability.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994