Abstract: A New Integrated Tectonic Synthesis of the Piceance Basin: Implications for Fractured Reservoir Detection and Characterization

Thomas E. Hoak

Detailed reservoir characterization of Piceance Basin thin-skinned structural traps reveals the importance of fracture-controlled gas production. Production trends in Parachute, Rulison, White River Dome, Divide Creek and Shire Gulch fields lie parallel to thin-skinned and basement-involved structural trends. A complete understanding of basin fracture genesis can he achieved through determination of the regional tectonic evolution. To understand the evolution of thin-skinned aid basement-involved structures, high-resolution aeromagnetic data, seismic data, remote sensing imagery analysis, and production history analyses have been integrated with conventional subsurface and surficial dynamic structural analyses. By examining the timing relationships between structural elem nts, it Was possible to determine the overall basin evolution and use this information to better define and predict fractured reservoir production trends and the occurrence of fractured reservoir conditions Several important observations have emerged from this study.

Examination of structural trends in rocks ranging in age from the Precambrian through Holocene show the importance of pre-existing anisotropies in partitioning younger tectonic strain. Because of this strain partitioning, many Laramide structures show complex reactivation histories that obscure older Precambrian and Paleozoic tectonic events. An excellent example of this reactivation and partitioning is provided by NW-trending Precambrian-age structures on the Uncompahgre Uplift that were reactivated during Pennsylvanian-age deformation (Ancestral Rockies) and Laramide events. Both phases are typified by extensional tectonics, however, the Pennsylvanian-age orogeny reactivated Precambrian-age faults and related structure& Laramide contraction overprints the two older phases.

Because of its importance to reservoir engineering problems such as hydraulic stimulation design and drainage efficiency calculations for fractured reservoirs, the modern stress state throughout the basin has been determined and data suggest that there is significant variability in principal stress orientations throughout the basin.

Preliminary results suggest that stress variability may be controlled by local anisotropies.

A wide variety of data sets have been used to construct an integrated tectonic analysis of the Piceance Basin. This interpretation demonstrates the complex evolution of multiply-reactivated tectonic structures and the relationship between production trends, structure, and fractured reservoirs. Most importantly, the integrated exploration approach demonstrates the power of an integrated basin analysis as a deterministic tool for understanding and predicting fractured reservoir conditions in advance of drilling.

AAPG Search and Discovery Article #90959©1995 AAPG Rocky Mountain Section Meeting, Reno, Nevada