Seismic Imaging of Imbricate Structures in Southwest China: A Case Study

The hydrocarbon prospects of the Western China Thrust Belt require solving a most challenging problem in seismic imaging --- irregular topography associated with a rugged terrain, complexity of the near-surface that includes high-velocity layers and outcrops with significant lateral velocity variations, complexity of the overburden, and the complexity of the target imbricate structures themselves. We present a case study that demonstrates a workflow to solve this challenging problem: (1) The near-surface model is estimated by nonlinear traveltime tomography that accounts for topography, and resolves lateral and vertical velocity variations. The near-surface corrections are based on wavefield datuming rather than shot-receiver statics. (2) The subsurface overburden model is estimated by prestack time migration combined with powerful interactive tools to pick rms velocities that are structurally consistent and laterally consistent, and the substratum model is estimated by half-space velocity analysis. (3) The subsurface image is obtained by prestack depth migration of shot gathers from topography.