Find the rocks and the fluids will follow -- AVO as a tool for lithology classification

摘要

Full-stack seismic interpretation continues to be the primary means of subsurface interpretation. However, the underlying impact of amplitude variation with offset (AVO) is effectively ignored or overlooked during the full-stack interpretation process. Recent advances in well-logging and rock physics techniques highlight the fact that AVO is a useful tool not only for detection of fluid anomalies, but also for the detection and characterization of lithology. We evaluated an overview of some of the key steps in the rock physics assessment of well logs and seismic data, and highlight the potential to move toward a new convention of interpretation on so-called lithology stacks. Lithology stacks may come in a variety of forms but should form the focus of interpretation efforts in the early part of the exploration and appraisal cycle. Several case studies were used to highlight that subtle fluid effects can only be extracted from the seismic data after careful assessment of the lithology response. These case studies cover a wide geography and variable geology and demonstrate that the techniques we tested are transferable and applicable across many different oil and gas provinces. The use of lithology stacks has many benefits. It allows interpretation on a single stack rather than many different offset or angle stacks. A lithology stack provides a robust, objective framework for lithostratigraphic interpretation and can be calibrated to offset wells when available. They are conceptually simple, repeatable, and transferable, allowing close cooperation across the different subsurface disciplines.