Rock physics of low-porosity sandstones for seismic reservoir characterization.

摘要

In the U.S., gas production from low-porosity sandstones, generally defined as sandstone formations of porosity below 15%, has played an important role in the past and is likely to be crucial for the future domestic gas supply. According to the U.S. Geological Survey, low-porosity gas sands contain more that one-third of the estimated U.S. gas reserves. For these reasons, it is very important to improve seismic reservoir characterization in low-porosity gas sands.; In the past decade, rock physics has been mainly focused on high-porosity clastic reservoirs. The rock physics of low porosity sandstones has been relatively neglected, yet various technical problems related to low porosity sands remain unsolved. There is a number of geologically dependent interpretation problems related to the complex depositional, diagenetic and structural histories of low porosity, low permeability sandstones. In low porosity sandstones, many grain-contact rock physics models are not valid. Fluid effects are not apparent, so fluid monitoring from seismic is very difficult. Another important issue is estimating reservoir quality from logs and seismic.; The objective of this thesis is to develop a consistent rock physics methodology for seismic reservoir characterization of low-porosity sandstone reservoirs. The research is data-driven and based on rational rock physics. Data at different scales, from laboratory measurements to seismic images are integrated into a unified methodology. The proposed work is subdivided into seven work tasks: Task 1. Geology background. Task 2. Data organization and quality control. Task 3. Analysis of rock physics trends from log and core data. Task 4. Laboratory measurements and analysis. Task 5. Effective medium model development. Task 6. Upscaling of rock physics transforms. Task 7. Application of rock physics to real seismic.; The basic-science contribution and novelty of this study is that for the first time we linked rock physics theory to field well log and seismic data for low-porosity sandstones. Our work went beyond conventional reservoir characterization. We used rock physics methodology to map porosity and permeability from seismic. We developed a procedure for using rock physics for advanced seismic reservoir characterization of low porosity sandstones.