oa Introducing a Priori Information in Non-Linear Slope Tomography: An Application to Minagish Seismic Survey

Slope tomography allows velocity model estimation from locally coherent events. These events can be<br>picked in the migrated prestack depth or time domains, and then de-migrated into the observation<br>space-time domain, providing us with kinematic invariant data. When locally coherent events are<br>picked directly in the observation space-time domain, the kinematic invariants carry the exact<br>acquisition geometry.<br>Kinematic invariants describe locally coherent events by their position and slopes in the un-migrated<br>prestack time domain. Non-linear 3D slope tomography based on the concept of kinematic invariants<br>provides a powerful tool for velocity model building. Several iterations of residual move-out (RMO)<br>picking, prestack depth migration and velocity updates are avoided, unlike conventional approaches<br>based on a linear update where residual depth errors have to be re-picked several times.<br>Because kinematic invariants do not relate to a particular depth velocity model, a priori information can<br>be easily inserted into the initial tomography velocity model to assess different geological assumptions.<br>This capability is illustrated on land Minagish dataset in Kuwait for which RMO has been picked from<br>prestack time migrated gathers. Tomography and imaging results have been produced for two different<br>a priori velocity models. A first model was built by 1D Dix inversion of time migration velocities while<br>the second model was built using velocity information from wells. The updated “wells” model<br>successfully combines two velocity components: the a priori high vertical resolution component that<br>cannot be resolved by tomography and a lower vertical resolution component that maximizes the stack<br>power of the depth migrated seismic data.