关键词: 深部煤层气, 勘探开发, "甜点"预测, 岩石力学地层, 裂隙(缝)

Abstract: Sweet spot prediction is a key and difficult area for deep coalbed methane (CBM) exploration and development, which will restrict whether the large-scale efficient development of deep CBM can be achieved. The conventional sweet spot prediction method is to study the geological or engineering sweet spots separately. The sweet spot prediction/evaluation system based on the geology and engineering integration concept needs to be established urgently. The urgent task is to find an effective theoretical method for realizing the organic unity of geological and engineering sweet spots of deep CBM. The rock mechanical stratigraphy has the inherent attributes and innate advantages of connecting the geology and reservoir engineering of CBM, which provides a new method for overcoming the technical difficulties in the integrated prediction of deep CBM sweet spots. By summarizing the development characteristics of the geological and engineering sweet spots of deep CBM and the difficulties and challenges faced in sweet spot prediction, this paper discussed and analyzed the methodology of rock mechanical stratigraphy for the integrated prediction of deep CBM sweet spots, and carried out the application research of deep CBM sweet spot prediction based on rock mechanical stratigraphy. The research results show that the development law of natural fractures in deep coal reservoirs under the control of rock mechanical stratigraphy is a key constraint for predicting the geological sweet spots of deep CBM, while the development law of fracturing induced fractures under the control of rock mechanical stratigraphy, physical changes in reservoir rocks, and reservoir stimulation are the key factors for evaluating the deep CBM engineering sweet spots. With rock mechanical stratigraphy as a method mechanism, it is possible to realize the organic connection between sedimentary diagenesis, rock mechanical characteristics, geological structure and geostress field characteristics, geological accumulation response, reservoir engineering response, and integrated prediction of deep CBM sweet spots. The application and practice of rock mechanical stratigraphy in the fracture characteristic analysis and high permeability zone prediction of coal reservoir, coal-rock fracture behavior analysis and production zone selection, and fracturing and drainage optimization of CBM reservoir have preliminarily proved that it will be expected to be a technical tool to solve difficulties in the integrated prediction of deep CBM sweet spots.

Key words: deep coalbed methane, exploration and development, sweet spot prediction, rock mechanical stratigraphy, fracture