Delineating the Gas Reservoir With the C-wave Diodic Effect Correction In Qaidam Basin, Northwest China

The C-wave imaging may be degraded by the diodic effect introduced by the gas cloud though C-waves have been commonly used to image through gas cloud. This diodic effect may be compensated with a velocity perturbation method which decouples the diodic moveout into two parts: the base velocity and the velocity perturbation. In this paper, the velocity perturbation is written with base velocity and the PS velocity of positive and negative offset. And the relation between velocity perturbation and gas reservoir is discussed. A land 2D3C seismic dataset is analyzed from the Sanhu area in the Qaidam basin, northwest China and significant diodic effects are observed in the data. The perturbation approach is applied to this data and the resultant C-wave imaging and the details of the reservoir structure are significantly improved. The characterization of the reservoir boundary using velocity perturbation is well consistent with the real reservoir.