Print this pageTriangle Zone Geometry of the Frontal Quachitas in the Wilburton Area, Arkoma Basin, Oklahoma: Implications for Fault Sealing in the Wilburton Gas Field
CEMEN, IBRAHIM; ZUHAIR AL-SHAIEB; ATA SAGNAK; RODNEY FELLER; and SALEEM AKTHAR
The Wilburton gas field, situated in the central part of the Arkoma basin, produces mainly from the lower Atokan Spiro Sandstone. In the Wilburton area, we constructed seven balanced structural cross sections, prepared a top structure contour map of the Spiro Sandstone and developed pressure-depth profiles for the Spiro reservoirs.
The cross-sections suggest the presence of a well developed triangle zone between the mildly compressed Arkoma basin and frontal Ouachitas fold-thrust belt. This zone is floored by the Lower Atokan detachment and flanked by the Choctaw fault to the south and the Carbon fault to the north. The south-dipping Choctaw fault contains several south-dipping imbricate fan thrust faults in its hanging wall. The footwall of the Choctaw fault contains several duplex structures formed by hinterland dipping imbricate thrust faults, splaying in a break-forward sequence of thrusting from the Springer detachment (floor thrust). The duplexes join to the Lower Atokan detachment (roof thrust) in the Atoka Formation. The Lower Atokan detachment continues in the Atoka Formation northward and displaces the Red Oak Sandstone before reaching a shallower depth and forming the Carbon fault as a north-dipping backthrust below the San Bois syncline. When restored to their position at the time of the Spiro deposition by using the key-bed restoration method, the cross-sections indicate about 60% shortening in the Wilburton area.
In the duplex structures, the Spiro reservoirs that were brought to structurally higher positions by the thrust faults generally exhibit higher pressure-depth gradients. Therefore, we suggest that the thrusting in the wilburton area was formed after the Spiro Sandstone reservoirs were charged, and the duplex structures might have provided seals for the reservoirs. The top Spiro structure contour map suggests that the duplexes are separated by tear faults which may have served as lateral seals.