Summary
This study presents a successful empirical approach based on the integration of numerous multidisciplinary measurements to optimize completion methodologies and future field development strategies for stacked lateral wellbores, and essentially to high-grade exploratory Wolfcamp landing zones from 3D seismic data. Specifically, we measured mineralogical and geomechanical shale properties directly from 3D surface seismic data lengthwise along lateral well trajectories at individual frac stages which were monitored real-time using microseismic acquisition. Linear regression analyses for calibration show strong correlations between inverted seismic P-wave impedance versus microseismic data and fracture pressure responses, shale mineralogy compositions, and geomechanical properties calculated from core data.
The method was recently tested in the prolific oil-bearing Wolfcamp shale-oil play of the Midland Basin, West Texas, on three horizontal laterals drilled in a "chevron pattern", two of which in the deeper Wolfcamp B formation and the third in the Wolfcamp A. Real-time microseismic monitoring was used to observe the hydraulic fracturing treatments and the resulting heights and lateral extent. Although identical pumping schedules were initially intended for all three laterals stimulated in a "zipper sequence", with geometric stage placement, it became apparent during the treatments that microseismic height growth varied significantly across the given laterals within individual stages.
The results of our combined analysis showed that microseismic fracture height variability is most influenced by changes in shale stratigraphy and subsequent mineralogy composition, without a definitive relationship with treatment injection rates. Optimal fracture heights were observed in landing areas with significant volume of calcite, characteristic of high Young's modulus and closure stress, variables which in turn were estimated from 3D seismic. For validation, production history of said laterals and numerous others in the field confirms a strong correlation between seismic P-wave impedance and initial 120 day cumulative oil in landing zones where high volume of calcite and hence brittleness exists.
