--> Structural Models Constrained by Geophysical Data Provide Additional Insight to the Subsurface in Southern Colorado, U.S.

AAPG Annual Convention and Exhibition

Datapages, Inc.Print this page

Structural Models Constrained by Geophysical Data Provide Additional Insight to the Subsurface in Southern Colorado, U.S.

Abstract

Onshore structurally complex areas combined with large amount of igneous intrusions can be difficult to discern at depth with seismic data alone. The majority of the CO2 fields of Southern Colorado are located in an area where seismic imaging is remarkably limited due to the presence of high-velocity volcanic rocks the complex structure of the area. In this study, we present the combination of seismic and non-seismic methods to produce a series of 2D geophysical models that reveal basin architecture not easily noticeable through seismic data alone. All datasets were analyzed independently and later integrated into a 3D earth model. 2D geologic cross-sections were built based on the combination of surface outcrops, seismic and well data and constrained by magnetic and gravity data. To increase the confidence of the models, an unconstrained joint inversion of the EM and MT data was ran independently. Subsequently, the cross-sections were incorporated into the EM models constraining the inversions. The airborne EM data was inverted to produce a 3D resistivity model and the potential fields data was also inverted to produce a 3D model. The interpretation of combined data sets provide a better understanding of the overall structure of the area revealing two major structural styles. A SW-NE trend, believed to be related to the Proterozoic growth of the North American continent, and a younger NW-SE trend related to the Laramide orogeny with some reactivation of deep basement faulting. The integration of the modeling inversion results reveal a robust basement architecture, outlining a conductive sedimentary basin overlying a resistive Precambrian basement. The models also reveal a conductor beneath a resistive, and outcropping, basement layer along the westernmost thrust fault that forms the Sangre de Cristo Mountains. This basement has been historically thought to be persistent at depth. However, this conductor might be suggesting the existence of an underlying sedimentary basin overthrusted by this basement. The integration of these datasets significantly improves the understanding of the structural complexities of area, lowering the level of uncertainty. This multi-measurement interpretation approach can significantly enhance the overall understanding of a basin and can also aid in hydrocarbon exploration in regions where seismic exploration is difficult.