Seismic interpretation of Pennsylvanian Atokan strata using three-dimensional seismic inversion data, Wilburton Gas Field, Arkoma Basin, southeastern Oklahoma.

摘要

Scope and Method of Study. The Arkoma Basin is a very prolific foreland basin that is actively being explored and drilled today. The structure and depositional setting of the Spiro Sandstone plays a major role in the productivity. Seismic inversion data provides a direct correlation to rock properties and can be used to aid in better reservoir characterization. This study will investigate whether seismic inversion data can be used as a crucial piece of data that can be as influential as well logs in determining areas to drill in the Arkoma Basin. Where well log and core data are limited, this study could provide vital information on what the projected porosity would be in the Spiro Sandstone in a specific structural position. Correlating acoustic impedance values to porosity will lead to more efficient drilling.;Findings and Conclusions. The findings for this thesis can be broken into three different areas based on the relationship to acoustic impedance; structure, porosity, and thickness. Structure: Areas of tighter anticlinal shaped folds may correlate to lower acoustic impedance values due to fracture porosity. Horizon contour maps provided additional insight as to where areas of greater compression are occurring, which may cause an increase in fracture density. The absolute value of acoustic impedance was unaffected by structural position. Core analysis is necessary to determine if open fractures exist as well as thin sections to determine if the porosity preserved is primary or secondary. Porosity: Acoustic impedance and porosity showed a good linear correlation. Higher porosities were seen in areas of lower acoustic impedance. In areas where the Spiro Sandstone experienced facies changes, the acoustic impedance value was a good predictor of porosity. Thickness: Inversion data resolved two distinct units that were originally mapped as a package in seismic; Spiro Sandstone and Wapanucka Limestone. Isochron maps were produced to predict thickness changes in the Spiro Sandstone. These maps were checked with well log thicknesses and showed a correlation of 0.707. Acoustic impedance values did not show any correlation to thickness values.