Seismic Response Models and the AVO Simulation of Coal-Bearing Reservoirs

Abstract

The presence of coal in complex structures featuring sandstone reservoirs seriously hinders reservoir characterization and the identification of fluids in subsurface formations. Coal can strongly obscure the reflections from sandstone, easily leading to false bright spots during exploration; thus, reservoirs and their boundaries cannot be accurately described. Furthermore, sandstone layers intercalated with thin coal seams form complex composite reflections. Therefore, considering the complexity of coal-bearing reservoirs together with the geological evolution of coal and actual logging data, this study systematically analyses the seismic reflections of coal-bearing reservoirs. First, the seismic responses of various coal-bearing reservoir models are established by evaluating multiple well logs of the target layer. Then, by forward-simulating theoretical seismic data, seismic response models comprising different lithological combinations are established. Finally, seismic attributes (such as the amplitude, frequency and phase) of coal-bearing and non-coal-bearing strata are compared, and the seismic responses of typical lithological combinations of coal-bearing reservoirs are summarized. A single-well model test and a comparison between synthetic and seismic data confirm that numerical simulations can be used to forward model the seismic response characteristics of different sand–coal models, thereby eliminating the influences of coal and accurately characterizing sandstone reservoirs.