Structural Compartmentalization in a Decapitated Anticline: The example of the Divide Creek Fractured Reservoir, Piceance Basin

T. E. Hoak and A. L. Klawitter

Integrated analysis of high-resolution aeromagnetic and remote sensing data, confirmed by field geology, seismic and production data, demonstrates reservoir compartmentalization within the Divide Creek Field, southeast Piceance Basin. Topographic constraints and Federal land use restrictions, limit the ability to collect extensive seismic data across this complex structure and precludes complete characterization of subsurface structure by direct methods. Integrated analysis of airborne aeromagnetic data with TM (thematic mapper) and SAR (synthetic aperture radar) data, permit the resolution of the 3D complexity of this fold and its associated reservoir not easily defined using conventional 2D seismic.

The Divide Creek Anticline is a decapitated pop-up anticline. The pop-up anticline that originally formed along a deeper, Eagle Valley Evaporite detachment surface has been "decapitated" along a shallower Mancos-level detachment that translates the shallows pop-up anticlinal axis to the west. The fold is further segmented by normal faults trending axis-perpendicular to its axis that create distinct reservoir compartments. Processing of aeromagnetic data using multiple bandpass filters demonstrates three detachments in the fold, and the 3D geometry of the detachments. Understanding timing of these structures is critical for constraining fracture genesis and gas migration models.

Oriented fracture data from surficial studies, aeromagnetic data, remote sensing imagery, and subsurface core delineate three primary trends. These trends correspond to axis- parallel, axis-perpendicular and an older oblique regional fracture sets. This fracture permeability has made Divide Creek Field the most prolific Piceance Basin tight gas sand field.

Integration of aeromagnetics, remote sensing and high-resolution seismic represent a potent exploration tool for deciphering structural dynamics and fracture geometries in complex regions. Given the global abundance of such complex structures, the example of the Divide Creek Anticline represents a classic analog for exploration models in complex, folded regions.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California