A comparison of inversion techniques for estimating Vp/Vs from 3D seismic data

There are a variety of methods that can be used to extract rock-properties information from seismic data. Three of the methods that can be used, include; 1. AVO analysis, followed by post-stack inversion of the AVO attributes (Goodway, et al.) 2. Prestack inversion of the P-wave data directly to impedance (Hampson et al.) 3. Joint prestack inversion of the P-wave data and converted wave data directly to impedance (Hampson et al.) After each of these inversions has completed one of a variety of rock properties can be calculated. This paper compares the results of estimating Vp/Vs using each of the above mentioned techniques. INTRODUCTION Apache Canada Ltd. began an experiment with multicomponent seismic data in 2004 with an eastern Alberta 3D3C acquired with I/O Vectorseis MEMS geophones. The primary target in this experiment was, and continues to be, Mannville-age channel sands. The channel is easily identifiable on 3D seismic data, though reservoir quality issues remained an issue. It was hoped that the multicomponent seismic data would provide the leverage necessary to aid in drilling gas wells with a higher degree of success. In November 2006, Anderson and Larson showed that that hope appears to have been realized, with look-back success rates improving from 31% with P-wave seismic only, to 65% when integrating the information from the P-wave and converted wave volumes. A project was then undertaken to evaluate the differences in predicting rock properties, specifically Vp/Vs, from seismic data using one of three paths: 1. Amplitude variation with offset (AVO) analysis followed by post-stack inversion of the AVO attributes 2. Prestack inversion of the P-wave gathers directly to impedances 3. Joint prestack inversion of the P-wave gathers and a converted wave volume The procedure and results from that analysis are presented below. A map of the seismic data identifying the relative positions of the wells is provided in Figure 1. POST-STACK INVERSION METHOD The process of estimating Vp/Vs with a post-stack inversion method follows the procedure outlined by Goodway et al. (1997). In this paper, the authors propose starting