Anisotropic Depth Imaging Case Studies from Australia's North West Shelf

Abstract

This paper demonstrates the increase in confidence of depth prediction and structural imaging achieved using anisotropic pre-stack depth migration of 3D surface seismic data. Using examples of anisotropic travel time derived models updated with hybrid grid-based reflection tomography, this paper provides evidence of improved imaging from two data examples in Australia?s North West Shelf. The data examples described contain various imaging challenges, including short scale lateral velocity heterogeneity, carbonates, gas affected overburden zones, HRDZ?s (Hydrocarbon Related Diagenetic Zones) and reservoir level fault shadows. This paper will describe the work flow approach used and the geological considerations given to derive an appropriate earth model for each dataset. Evidence is presented to show how the velocity models converge to minimal residual moveout with each iteration of reflection tomography. Comparisons between data formed with time domain imaging and anisotropic depth imaging are made for the two surveys considered.