DITZELL, CURTIS L., Ocean Energy Inc., Denver, Colorado; and DOUGLAS B. OSTBY, Barrett Resources Corporation, Denver, Colorado

Abstract: Blind-Thrust Spiro Play - A Case History, Western Arkoma Basin, Oklahoma

This paper presents a case history of the in-fill development of a portion of the Hartshorne South gas field (100+ Bcf), located in the western Arkoma, Basin of southeastern Oklahoma, USA. Development primarily targets the Basal Atoka "Spiro" sandstone where thrust faulting compartmentalized the Spiro into separate, gas-charged reservoirs at 12,000' to 15,000'. Having no surface expression, the ?blind thrusted? Spiro fault blocks require detailed subsurface imaging to identify and define drilling targets. Although the; Hartshorne South gas field was successfully developed during the mid 1980s to early 1990s using 2D seismic for structural imaging, the increased subsurface illumination of a 50 square mile 3D seismic survey was required to locate the undrilled and potentially undrained structures targeted by our in-fill development program.

Interpretation of the 3D volume, integrated with well control and production performance data, identified a previously untested structure that, due to its structural orientation, was largely invisible to the existing, predominately north-south oriented, 2D seismic data. Amplitude analysis, of reservoir!, continuity, aided in the selection of a drill site at the optimum structural location. The Barrett Resources Watts Ranch #1-25 wellbore successfully encountered a productive and originally pressured ?blind-thrust? Spiro reservoir.

AAPG Search and Discovery Article #90921©1999 AAPG Mid-Continent Section Meeting, Wichita, Kansas