A High-Accuracy VTI Reverse-Time Migration Method

Asoneofthemostaccurateseismicimagingmethods,reverse-timemigration(RTM)has been applied more and more widely in various exploration geophysical settings, es-pecially in the complicated geological structures. Improving the imaging accuracy andcomputational efficiency are two significant but challenging issues for the application ofRTM in oil and gas exploration. A new low-dispersion numerical method for solvingacoustic VTI wave equations has been developed, called nearly-analytic central differ-ence (NACD) method, which uses linear combination of wave displacements and theirgradients to approximate high-order spatial partial derivatives, leading to weak numeri-cal dispersion and high computational accuracy. The theoretical properties of the NACDmethod, including the theoretical error, stability condition and numerical dispersion re-lation, are analyzed in detail. Dispersion analysis and wavefield simulation show thatthe NACD method results in weaker numerical dispersion than the conventional methodssuchasLax-Wendroffcorrection(LWC)schemeandstaggered-grid(SG)finite-differencemethod do, and that the computational cost of the NACD method is lower than that of theLWC and SG method while achieving the same simulation accuracy. Tests on both theimpulse response and the2D prestack Hess acoustic VTI model demonstrate that, theNACD method achieves higher imaging quality than the LWC scheme and SG methoddo, especially when the coarse spatial grid is used. With the ability to be extended toother anisotropic media, this new method can be a promising algorithm for large-scaleanisotropic RTM.