An accurate estimation of microseismic event locations plays an important role in the success of fluid-injection programs. Wavefield-based elastic time-reverse imaging (TRI) offers a robust approach to locate microseismic events that occur due to induced seismicity. The event location accuracy, though, is greatly dependent on the veracity of the elastic velocity models. In this study, we propose a methodology for microseismic image-domain wavefield tomography using the elastic wave equation and extended source images. Gradients are computed using the adjoint-state method and build on the extended image residuals that satisfy the differential semblance optimization (DSO) criterion. The objective function is designed to optimize the focusing of timereversed microseismic energy at zero lag in extended source images. The function applies a penalty operator to the extended images to annihilate the energy at zero lag and highlight residual energy at non-zero lags caused by backpropagation through erroneous velocity models. Minimizing the objective function leads to a model optimization problem aimed at improving the image-focusing quality. Realistic synthetic experiments demonstrate that one can compute accurate velocity model gradients using the proposed method, which can significantly improve the focusing of imaged events, leading to enhanced fluid-injection programs.
Presentation Date: Monday, October 12, 2020
Session Start Time: 1:50 PM
Presentation Time: 2:40 PM
Location: Poster Station 8
Presentation Type: Poster
