Report 1 AVO Possibilities With Least Squares Migration

Application of least-squares Kirchhoff migration (LSM) to synthetic reverse vertical seismic profile data (RVSP) demonstrates that LSM reduces the migration artifacts, improves the image resolution and produces a more accurate image than the standard migration, but cannot completely recover the model reflectivity for AVO analysis because of the limited data coverage. The influence of incomplete data on the recovery of reflectivity is discussed and a method using comparable image points as the basis for AVO migration/imaging is proposed. INTRODUCTION Amplitude variation with offset (AVO) can provide direct detection of hydrocarbon reservoirs. There are various means for extracting AVO information from seismic data. One approach is AVO migration (de Bruin and Berkhout,1992; Mosher, etc., 1996). The goal of AVO migration is to provide migrated images with amplitudes estimating the reflector reflectivities. Least squares migration (Nemeth, 1996; Schuster, 1992 and 1997) is capable of reducing migration artifacts and therefore produces better migrated images. In this progress report, we test the possibility of obtaining true reflectivity images by applying least squares migration to synthetic seismic data. The standard Kirchhoff migration operator is the adjoint of the forward modeling operator. The image obtained by standard Kirchhoff migration is a filtered version of the true reflectivity model and contains migration artifacts. Least-squares migration (LSM) tries to find a model that minimizes the data misfit function in an iterative way. It is believed that LSM can reduce migration artifacts, and therefore make better reflectivity estimates.