Abstract

Maximum horizontal stress (SHmax) in five Frontier Formation wells in the western Green River Basin (Moxa Arch) was inferred from wellbore breakouts, coring-induced fractures, circumferential acoustic velocity analysis (CVA), anelastic strain recovery (ASR), differential strain curve analysis (DSCA), axial point-load tests (APT), and circumferential monitoring of induced microseismicity (CMS) caused by industrial hydraulic fractures. Defining SHmax in these wells is challenging because wellbore breakouts and coring- induced fractures, which are commonly among the most reliable methods of measuring stress directions, are not well developed, and stress directions from the combined results of several techniques are highly scattered. Some wellbore breakouts, velocity anisotropy, and strength anisotropy data support north-trending SHmax, which is consistent with predictions of previous studies. Other breakout results and ASR and some velocity measurements yield eastward, northeastward, or bimodal northeastward and eastward azimuths for SHmax direction. According to CMS analysis, the growth direction of hydraulic fractures in three wells was east-west or northeast-southwest. We speculate that the scattered measured stress azimuths reflect (1) interference of natural fractures with measurements of stress directions and/or the direction of hydraulic fracture growth and (2) spatially variable stress directions and low deviatoric horizontal stresses caused by the proximity of the study area to the margin of the Cordilleran extensional province and to the midcontinent compressional province.