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3-D Tomography of Marcellus Shale Using Microseismic Data


By picking and inverting the arrival time of P wave, fast S wave and slow S wave, we performed 3D tomography on the microseismic data recorded using a downhole array deployed in the Marcellus Shale. Microseismic events are carefully selected to have a uniform distribution in the reservoir in order to better represent reservoir. Iterative method is applied to have a full coupling between the event location and velocity model. Shear wave splitting delay time is measured by using the correlation of waveform on horizontal and vertical components of the sondes. Three velocity structures of the reservoir are produced: P wave velocity, isotropic S wave velocity and the shear wave splitting anisotropy percentage. These velocity structures provided the detailed information of the heterogeneity of the reservoir velocity as well as anisotropy. Microseismic event locations are improved by using these updated velocity models compared with the initial 1D model upscaled from sonic log data.