The commerciality of unconventional field development depends on generating highly productive stimulated reservoir volumes (SRV) in an economical manner, but there is no reliable method to estimate SRV consistently during or immediately after fracturing operations. The SRV achieved during fracturing can be inferred through multiple techniques, including production data analysis, modeling (analytical or numerical, including various treatments of geomechanics), and/or microseismic monitoring, all of which have several limitations. Using production data, we need at least several months of well production history to establish a pseudo-boundary dominated flow regime. Additionally, the production-derived total SRV is a composite of all the stages lumped together, as it is difficult to evaluate the performance of individual fracture stages due to the reservoir heterogeneity. Furthermore, production rates are measured as a total aggregate for all the fractures, while production contributions from each stage cannot be obtained pragmatically for most wells. Full physics modeling, besides being time-consuming and requiring specialized expertise, requires proper reservoir characterization including geomechanical parameters and calibration, which are not routinely captured for most wells, and even when they are acquired, they are difficult to measure accurately. Microseismic, though informative, doesn't indicate actual SRV, and often it is only available for a small percentage of the wells. It is desirable to have a scalable method to estimate SRV evolution consistently during injection using commonly available fracture treatment data for all wells, and it should be practically applicable in a typical unconventional field.

A novel asymptotic analysis of the diffusivity equation has been proposed by other researchers like Datta-Gupta et al. (2011), Yang et al. (2015), and King et al. (2016) to estimate the production drainage volume in unconventional reservoirs based on diffusive time of flight (DTOF). We have extended this methodology to estimate injection SRV (iSRV) quickly from routinely collected fracture treatment data after each stage has been pumped. Further, we have benchmarked stage-wise stimulated reservoir volumes to other available production performance measures or aggregated stage volumes with total well production drainage volume.

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