MISKIMINS, JENNIFER L., Colorado School of Mines, Dept. of Petroleum Engineering, Golden, CO

ABSTRACT: Present-Day Stress States Near Faults, North LaBarge Field, Sublette County, Wyoming

North LaBarge field is located in the Green River basin in southwest Wyoming. The field produces hydrocarbons from the Mesaverde sandstones (Cretaceous) at a depth of around 2,000 ft (610 m). Maximum horizontal stress orientations determined from borehole breakouts vary from the regional N-S trend to E-W. 3-D seismic verified the locations of the LaBarge thrust, four major strike-slip, and a reverse fault. A horsetail splay termination of a strike-slip fault is inferred.

This study utilized fourteen wells. Integration of density logs determined overburden stresses. G-function analysis of hydraulic fracture treatments determined minimum horizontal stress magnitudes. A combination of minimum horizontal stress magnitudes and pore pressures determined maximum horizontal stress magnitudes. Comparison of the overburden stress gradients with the minimum horizontal stress gradients indicates that horizontal hydraulic fractures are not occurring.

Combining stress magnitudes and orientations developed 3-D stress profiles for six wells. Analysis of these profiles indicates that fracture closure stresses are increased by proximity to faults. The type of fault present also influences horizontal stress orientations. Analysis of the stress profiles in the horsetail splay area suggests that a horizontal well may intersect numerous open fractures, thus resulting in a significant increase in reserves. Variations in horizontal stress orientations indicate that precautions should be taken during waterflood operations. Placement of producers and injectors in line with the same stress field orientation should be avoided to decrease the chances of early water breakthrough and increase sweep efficiency.

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid