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 1980's to early 1990's 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.