Abstract

Over 1300 earthquakes less than magnitude 3 occurred in the vicinity of the War-Wink field between 1976 and 1979. Accurately located earthquakes occur from the Ellenburger Formation to the Delaware Mountain Group. Most of the earthquakes appear to be associated with anomalously high fluid pressures that approach lithostatic pressure. The high fluid pressures are developed in Mississippian to Wolfcampaian -aged strata overlying the anticline controlling the field location. There is some spatial and temporal correlation between earthquakes and oil field development and production from the Wolfcamp. However, the pattern of seismicity and geologic information imply that the earthquakes are also associated with differential compaction and fluid migration, and reservoir production may only have speeded up deformation. The deepest earthquakes occur along pre-existing faults in the carbonate gas reservoirs and appear to have no direct relation to oilfield operations.