Petrophysical analysis of the lower Lance Formation, Washakie Basin, Wyoming.

摘要

The Upper Cretaceous Lance Formation in the Washakie Basin has the potential to be a high volume gas producer. Sandstones in the Lance Formation are currently secondary targets that produce gas within a small geographical area. A better understanding of the petrophysical parameters for the Lance Formation may permit the expansion of the limited productive area by improving wireline log interpretation of the Lance Formation.Several problems are evident when petrophysical analysis of the Lance Formation is attempted. (1) There are no published values for the formation water resistivity (Rw) from the Lance Formation (2) values for the cementation factor (m), saturation exponent (n), and tortuosity factor (a) are not readily available (3) the characteristics (resistivity and porosity) of gas producing Lance sandstone and (4) 100% water saturated resistivity (Ro) is unknown.To address the petrophysical problem, several hypothesis were proposed. (1) The Rw determined using log analysis can be confirmed by sampling Lance Formation water (2) the cementation exponent determined by Pickett Plot can be used in the Archie equation to facilitate the evaluation of potential gas-bearing areas in the basin and (3) The controls of Lance Formation gas production include thick sandstones, structure, faulting of anticlinal folding.