The localization is carried out by means of the analysis of the travel times of the generated compressional and shear seismic waves from the unknown event position to a set of geophones, usually located in a nearby monitoring well. Vaca Muerta Formation, Neuquén, Argentina), requires the accurate location of the induced microseismic events.
The study and interpretation of hydraulically stimulated regions, such as certain unconventional hydrocarbon reservoirs (e.g. The results show that the proposed strategy is capable of estimating layered VTI velocity models suitable to accurately locate microseismic events during a hydraulic stimulation in the Vaca Muertashale formation. We test the proposed strategy on field data and estimate a set of velocity models that honor the observed data, which we validate carrying out a simulated microseismic event location. To avoid local minima and other convergence issues, we minimize the resulting objective function using very fast simulated annealing (VFSA). This leads to a constrained non linear inverse problem that consists of minimizing the discrepancies between the observed and calculated P and S-wave arrival time differences. Assuming layered modelswith weak anisotropy, we make use of the information provided by well logs and perforation shots of known position to estimate the layer velocities, depths and anisotropy. We provide well-calibrated VTI velocity models useful to locate microseismic events in the VacaMuerta shale formation, Neuquén, Argentina.
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