Woodford shale deposition and its relationship to the paleotopography and environmental setting of pre-Woodford carbonate successions: Arkoma Basin, Leflore County, Oklahoma.

摘要

The Arkoma Basin is an east trending surface feature that extends from south-central Oklahoma to northeast Arkansas near Batesville. It is one of three basins that include shallow-marine carbonate rocks widely known as the Hunton Group. This interval is a reservoir for natural gas in western Arkansas and eastern Oklahoma. The purpose of this study is to determine how the paleotopographic surface of the Hunton is related to the overlying deposit of the Woodford Shale within the Arkoma Basin of eastern Oklahoma.; Approximately 4,450 natural gas electric logs were collected from wells drilled in the area. They included Induction/Resistivity logs, Density/Neutron logs and Temperature logs. Four stratigraphic horizons were utilized. These horizons include Spiro sand, distinct markers within the Fayetteville Shale, Wapanucka Limestone, Cromwell Sandstone, Woodford Shale, Hunton carbonate and the Sylvan Shale. These formations and/or markers were categorically identified on each available log. Focusing on the very high Gamma Ray response signature of the Woodford Shale, the low Gamma Ray response of the Hunton carbonate and the strong Gamma Ray response of the Sylvan Shale, a distinct contact between the three interfaces illustrates a shale-carbonate-shale sequence. Isopach maps were created for the Woodford Shale and Hunton carbonate interfaces along with two cross-sections to illustrate the relationship between the two.; The results indicate that the Pre-Woodford surface does exhibit regional, erosional patterns highlighted by the deposit of the Woodford Shale Three distinct east-west features contributed to the understanding and prediction of where the Hunton carbonate rocks would be thick and where they would be thin.; In conclusion as more geologists continue to move toward the study of Silurian-Devonian carbonates, there is now more research presented that validates the existence of multiple Hunton thick-thin-thick patterns within the study area.