Thermal and Pore Pressure History of the Haynesville Shale in North Louisiana: A Two-Dimensional Numerical Study

Torsch, William; Nunn, Jeffrey

In North Louisiana, the Upper Jurassic Haynesville shale has a basinward southwest dip and is located at depths ranging from 10,500 ft in the northeast to 14,000 feet in the southwest with local minimums on the Sabine and Monroe Uplifts. Formation thickness ranges from 100 to 400 feet. The shale's pore pressure and temperature history varies across the basin due to local structural highs, lateral changes in basal heat flow, and updip migration of fluid. Using well data, two-dimensional models across the North Louisiana Salt Basin were created to estimate temperature, pore pressure, and fluid flow versus time. Disequilibrium compaction from rapid sedimentation in the low permeability (nDarcy) Haynesville Shale has resulted in significant overpressures ranging from about 7000 psi to 12000 psi. Hydrocarbon generation resulted in a maximum pore pressure increase of more than 500 psi at 88 Ma. However, models created with and without hydrocarbon generation produced nearly identical results for present day pore pressure indicating that disequilibrium compaction is the most significant mechanism in generating overpressure. Fluid migration updip to the Sabine Uplift within the Haynesville Shale and underlying Smackover Limestone has resulted in abnormally high fluid pressures on the Sabine Uplift. Model results including lateral pressure transfer are consistent with present-day pore pressures from well test information. While model results do did predict pore pressures in excess of fracture pressures, computed pore pressures are closest to fracture pressures on the Sabine Uplift following uplift and erosion in the mid-Cretaceous.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013