Coring-lnduced Fractures: Indicators of Hydraulic Fracture Propagation in a Naturally Fractured Reservoir

Abstract

ABSTRACT Efficient hydraulic fracture treatment of low-permeability reservoirs depends on reliable prediction of the stimulation fracture strike, which generally is parallel to the maximum horizontal stress. Coring-induced fractures can be used to predict the strike of stimulation fractures if coring-induced fractures are aligned with the maximum horizontal stress. Our study (1) determines the orientation of coring-induced fractures in East Texas and (2) compares the strike of coring-induced fractures to indicators of stress direction and stimulation fracture strike. We used descriptions of 565 fractures in 1,802 ft (549 m) of core from seven wells in the Lower Cretaceous Travis Peak Formation, a low-permeability sandstone and shale unit approximately 2,000 ft (609 m) thick that produces gas in much of East Texas. Fracture imaging logs were available from three study wells. Stimulation fracture azimuth was independently determined by monitoring microseismicity during fracture treatment. Mean strike of coring-induced petal and petal-centerline fractures is parallel to the east-northeast azimuth of maximum horizontal stress determined from core strain recovery, borehole breakouts, and strike of fractures created in stress tests and hydraulic fracture treatments. Natural and coring-induced fractures are not parallel, but the difference in strike is generally small (<10 degrees). Petal and petal-centerline fractures are useful for predicting the strike of stimulation fractures. Their usefulness is limited by the precision of core orientation methods.