Thumbnail Image

Determining Structural Influence on Depositional Sequences in Carbonates Using Core-calibrated Wireline Logs: Mississippian, Mid-continent, U.S.A.

Doll, Preston Lee
Identifying stratigraphic surfaces and correlating depositional packages is problematic in proximal ramp settings where argillaceous carbonates with distinct wireline log signatures are absent due to non-deposition or post depositional erosion. In southern Kansas, packages were defined based on petrophysical similarities as expressed by the neutron and density porosity logs. Based on the examination of core-calibrated wireline logs, depositional packages were established that could be correlated up to 25 miles (~40 km). Examination of the geometry of these packages indicated that they prograded to the south and thinned both landward and basinward. The apparent direction of progradation changed near the Pratt Anticline from southwesterly to southeasterly. Furthermore, packages thinned and terminate against the Pratt Anticline and Central Kansas Uplift. This thinning and apparent change in direction of progradation is interpreted as evidence of syndepositional uplift of both features during Mississippian deposition.Attempts to tie packages in the Bartel #1-16 core in Reno County, Kansas to the Bann #1-14 core in Woods County, Oklahoma were not successful. The predominantly log-based correlation was interpreted to show that most packages in the Bartel #1-16 core terminate before the Kansas-Oklahoma border. The packages/sequences in the Bann #1-14 are interpreted to be younger and more distal as increases in gamma-ray signature interpreted as flooding surfaces become apparent. Establishing a method for correlating depositional packages in proximal settings and understanding the relative ages of packages in a regional context increases our understanding of the complex Mississippian carbonate section. Considering the influence of uplift on the direction of package progradation could be useful in aligning horizontal wellbores to intersect reservoir facies.Full sized cross sections are available as supplementary files.