Knowledge Management System of Institue of Mechanics, CAS
|Alternative Title||Study on Trans-Scale Gas Transport Model and its Applications in Shale|
|Thesis Advisor||林缅 研究员|
|Place of Conferral||北京|
|Keyword||页岩气 跨尺度 数字岩心 REV 分馏|
Since the beginning of the 21st century, unconventional oil and gas has achieved strategic breakthroughs, and shale oil and gas has become an important new field for oil and gas resources. Shale gas has large reserves and wide distributions, with a very large development potential. However, the multiple flow spaces (organic matter/inorganic matter), multi-fluid (viscous/slip/diffusion) features, and hydraulic fracturing in shale make gas migration a complex multi-scale system. Conventional flow simulation is no longer applicable to unconventional shale gas reservoirs, and a set of trans-scale simulation methods for shale gas transport is imminent. In this paper, multi-level trans -scale research from microscale to macroscale is carried out for shale gas.
Firstly, a three-dimensional coupled model of organic matter and inorganic matter in micro-scale shale is established based on the nano-resolution scanned image. The gas transport mechanism of shale micro-pore space is revealed, and the interface coupling effect between organic matter and inorganic matter in shale is studied. And the parallel schemes for different computational sizes are proposed and the accuracy of the model is optimized. The influence of microscopic parameters on shale gas flow is analyzed in depth, and the dominant microscopic parameters affecting shale permeability are clarified, which provides a solid theoretical foundation for larger scale simulations.
Secondly, statistical methods are introduced to remove the parameters that have weak influence on shale permeability. An equivalent model for accurately and quickly calculating micro-scale permeability is proposed, which greatly improves the computational efficiency at micro-scale. Based on multi-scale scanning images, a statistical coupling model of ~100 micrometer scale is established, and an organic matter distribution system covering multi-scale information is formed. For the shale, the concept of organic matter representative element volume (oREV) was creatively proposed, and the microscopic and macroscopic bridges of shale gas flow were established. The determination and flow calculation method for oREV are formed, and the characterization parameters of oREV-scale shale are obtained.
Finally, we apply the trans-scale approach to shale gas exploration and development. Use oREV to connect micro information and macro simulations. On the one hand, for the carbon isotope fractionation problem of methane generated in the field of geochemistry, the oREV-scale two-component gas convection-diffusion-adsorption model was successfully established, and the microscopic mechanism of carbon isotope fractionation of methane was clarified. A perspective gas content calculation methods, based on fractionation numerical simulation and isotope logging data is proposed. And a new evaluation method for "sweet spot" is also formed. On the other hand, considering the variation of permeability and adsorption amount in shale gas production process, the numerical simulation theory of multi-stage fracturing horizontal well in shale gas reservoir based on oREV parameter is formed, which is based on unstructured PEBI grid. A multi-stage fracturing horizontal well finite volume simulator was used to analyze the effects of microscopic pore parameters and reservoir parameters on macro gas production. The trans-scale calculation method of gas production and gas content proposed in this paper provides a new supplement for the exploration and development of shale gas reservoirs. With the rise of multi-scale measurement technology and digital core technology for shale in recent years, the rapid development of trans-scale methods will have an important impact on the future exploration and development of oil and gas reservoirs.
|曹高辉. 页岩气跨尺度渗流模型及其应用研究[D]. 北京. 中国科学院大学,2019.|
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