Velocity Model Calibration And Interpretation Of Fracture Imaging For Downhole Microseismic Monitoring

The velocity model in downhole microseismic monitoring plays a vital role in the location accuracy of the microseismic events.In the traditional way,the layers of the velocity model are divided by the sonic logging curve,then the velocity value in each layer is calibrated by the perforation shot.However,when the number or depth of the layers has errors,the final velocity model would have some mistakes.To avoid the influence of incorrect layer information,we propose to build the initial velocity model by the uniform but fine interval layer velocity model,then the layer depths and values are calibrated by the perforation shot at the same time.Without the knowledge of the origin ti me,we use the differential arrival times to invert the P-wave and S-wave velocity values in each fine interval layer under Total Variation(TV)regularization.Then the interior point method is used to solve the matrix.The synthetic tests shows that the velocity model is recovered well by one perforation shot in the case of lots of receivers.When the number of receivers is less,the velocity model can be recovered well by multiple perforation shots.The noise has less impact in this method.Real tests shows that this method is well applicable in the oil/gas production.The Liao he Oilfield is in the late stage of oil and gas development,the hydraulic fracturing technology can help to increase the production.In this paper,we deals with the actual data processing of microseismic monitoring in the Liaohe Oilfield,and have a precise interpretation of the fracture geo metric characteristics.It provides the detailed guidance information for the hydraulic fracturing,pro motes the application and accumulates data of microseimic monitoring in the oil/gas production.