RT Journal Article SR Electronic(1) A1 Rampton, David A1 Small, MitchYR 2022 T1 Evaluating an Unconventional Shale Completion with Repeat Crosswell Tomography JF First Break, VO 40 IS 1 SP 67 OP 73 DO https://doi.org/10.3997/1365-2397.fb2022005 PB European Association of Geoscientists & Engineers, SN 1365-2397, AB Abstract Evaluation of hydraulic fracturing relies on indirect inference from measurements that are distorted by distance and noise of various kinds, so reservoir monitoring technology that places the measurement as close to the completion as possible is important. Crosswell tomography is just such a technology, placing source and sensor in the plane of the feature to be analysed, and is an excellent technology for making in situ estimates of subsurface properties in simple geologic settings when source-receiver separation is small and when noise levels are low. Since these conditions are not typical in-field scale surveys of unconventional shales, this study overcomes these deficits by incorporating vertically transverse isotropy in raytracing and applying a strong source effort to increase signal-to-noise. The survey used Schlumberger’s Ztrac source and multicomponent geophones to both generate and record compressional and shear wave energy, matching baseline and repeat surveys within a few days of hydraulic fracturing to detect subtle timelapse changes prior to flowback and fluid diffusion. The result is a unique characterization of fracture creation due to hydraulic fracturing, highlighting an out of zone response and subsequent impact on the bounding limestone layers., UL https://www.earthdoc.org/content/journals/10.3997/1365-2397.fb2022005