Forward modeling of carbonate fracture reservoir based on time space dual variable grid algorithm

Key words:  carbonate  fracture reservoir  variable timestep  foward modeling  seismic response

Abstract:

The space variable grid method was improved by introducing local variable timestep scheme. Fractures were treated as local heterogeneous bodies, and fracture media was represented by using different size of grid samples. Wave equation was solved directly by finite difference method. Seismic forward modeling of micro fractured reservoir of field carbonate velocity models was realized, and some detailed wave propagation phenomena were gotten. The results show that local variable timestep scheme can realize local refinement calculation in a global timestep, which solves huge computing resource and time consuming problems caused by fine timesteps in the global models. Fracture density and fracture length have much effect on amplitude and polarity of seismic record, and a weak fracture reflection energy always follows reflection wave closely. Subsurface structure affects fracture characteristics a lot. Fracture reflection characteristics of flat strata and undulation strata are quite different. So fracture growing zones can be found according to different fracture reflection characteristics if subsurface structure is known.