INVESTIGATION OF FINE-SCALE DEFORMATION IN A CLASSIC LARAMIDE STRUCTURE USING INTEGRATED HIGH-RESOLUTION AND CONVENTIONAL 3D SEISMIC METHODS: TEAPOT DOME, WYOMING

Using the classic Laramide structure of Teapot Dome oil field near Casper, Wyoming, USA as a test case, we demonstrate how high-resolution compressional (P) and horizontally polarized shear (SH) wave seismic reflection surveys can overcome the limitations of conventional 3D seismic data in resolving small-scale structures in the shallow subsurface (<100-200 m). The results were integrated with structural mapping and interpretation of 3D seismic data, correlated drill hole logs, and trenching of shallow faults with the aim of investigating the interaction of deeper and shallow faults, as detected using the different methods. The integration of the two high-resolution seismic methods greatly enhances the detection and mapping of fine-scale deformation and stratigraphic features at shallow depth that cannot be imaged by conventional seismic methods. We show that the Cretaceous-age Shannon reservoir, which is the most productive and the shallowest petroleum reservoir at Teapot Dome (depth = 76-198 m), can only be imaged properly with high-resolution seismic methods. The integration of 3D and high-resolution P-wave seismic data enabled us to determine that some of the larger faults propagated from the deep Paleozoic section upward through the shallow Shannon reservoir. Steeply dipping northeast-striking faults are identified in the shallow Shannon section that cut through the Laramide-structure of the dome. The strike of these faults is approximately orthogonal to the hinge line of Teapot Dome. Vertical displacements observed from the seismic and drillhole data across these faults range from 10 to 40 m. Possible positive flower structures, which would suggest some amount of strike-slip transpressional motion, are also observed. Our results support earlier conclusions that the fine-scale faults are Laramide-age structures that were coeval with and helped to facilitate Laramide folding. Our study therefore shows how conventional 3D seismic data exploration requires additional seismic acquisition at smaller scales in order to image deformation in shallow reservoirs. Such imaging becomes critical in cases of shallow reservoirs where it is important to define potential problems associated with compartmentalization of primary production, enhanced oil recovery, or carbon sequestration.