Borehole gravity survey in the Dry Piney oil and gas field, Big Piney-La Barge area, Sublette County, Wyoming

Abstract

This study presents formation density and porosity profiles calculated from a borehole gravity survey made by the U.S. Geological Survey in the Dry Piney oil and gas field in W. Wyoming. Borehole gravity measurements were used in the Dry Piney unit primarily to determine the in situ density of large volumes of rock that extend tens to hundreds of feet outward from the drill hole. Remote sensing of geologic structure was not an objective of the Dry Piney survey. Proven and potential applications of borehole gravity surveys include detection of irregularly distributed porosity, detection of gas and oil zones behind casing, evaluation and recalibration of conventional types of well logs, vertical density profiling for gravity map interpretation and for seismic modeling and analysis, remote detection of geologic structures such as salt domes and ore bodies, large-volume determination of reservoir porosity for reserve estimates, monitoring of reservoir fluid conditions for production evaluation, and porosity evaluation of unconsolidated materials for ground-water and engneering studies. 16 references.