First Break - Volume 38, Issue 6, 2020

Distributed Acoustic Sensor (DAS) is increasingly recognized as a viable alternative to downhole geophone arrays for the acquisition of borehole seismic (VSP – Vertical Seismic Profile) or DAS-VSP data. When acquiring surface seismic data in the field, simultaneously acquired DAS-VSP data in an available well or wells can provide full well VSP imaging and significantly enhance surface seismic data processing. Borehole seismic data can provide higher resolution structural images around the borehole as the receivers are located inside a borehole and near the reservoir. In addition, the formation velocity, deconvolution operator, absorption, attenuation (Q value), anisotropy parameters and other reservoir formation information in a certain range around the wellbore can be obtained directly from the VSP data. These can be used to significantly enhance the surface 3D seismic data processing, such as velocity model calibration and modification, static correction, deconvolution, demultiple processing, high frequency restoration, anisotropic migration, and Q-compensation or Q-migration.

In this project, Q-migration was conducted with the enhanced Q-field data volume obtained from the joint inversion of both the near surface 3D Q-field data volume from uphole data and the mid-deep layer Q-field data volume from VSP data. The Q-migration results show much sharper and more focused faults and fracture zones. A new 3D formation top structural model was built with much finer details based on the Q-migration data, and three new borehole locations were recommended to the client. The final drilling results on these three new boreholes are very successful with high volume of commercial oil flow.