Improving Anisotropic Velocity Model Calibration in Microseismic Data From the Woodford Shale
P.J. Usher and J. Huang
Event name: Sixth EAGE Shale Workshop
Session: Poster Session 2
Publication date: 28 April 2019
Info: Extended abstract, PDF ( 1.61Mb )
Price: € 20
This study demonstrates a workflow of anisotropic velocity calibration for microseismic monitoring. We search for a layered P and S velocity, along with Thomsen parameters, that minimises travel time residuals with our calibration shots. Due to the limited calibration shots, the travel time residual was minimised for a set of early microseismic events from each stage. The velocity models varied from isotropic, to constant non-zero Thomsen parameters, layered Thomsen parameters that are proportional to 1/VP and finally to a general layered vertical transversely isotropic velocity model. We showed that different levels of model complexity effect event location in the Woodford Shale. With increasing complexity, the event locations become more accurate, cluster around the injection points, and have less artefacts and systematic biases. The calibrated anisotropic model can later be used to characterise the fractures and mineral content of the shale and thus add value to microseismic monitoring. This process can be automated to help remove biases, to quantify velocity model error, and as step towards joint inversion for layered anisotropic velocity and event locations.