A new type of shale gas reservoir—carbonate-rich shale: From laboratory mechanical characterization to field stimulation strategy  

作　　者：Zhen-Hui Bi Lei Wang Chun-He Yang Yin-Tong Guo Wu-Hao Guo Han-Zhi Yang 

机构地区：[1]Key Laboratory of Geomechanics and Geotechnical Engineering Safety,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,430071,Hubei,China [2]University of Chinese Academy of Sciences,Beijing,100049,China [3]State Key Laboratory of Coal Mine Disaster Dynamics and Control,Chongqing University,Chongqing,400044,China

出　　处：《Petroleum Science》2024年第5期3047-3061,共15页石油科学（英文版）

基　　金：sponsored by the “National Natural Science Foundation of China” (No. U22B6003), (No. 52104010), and (No. 52104046)。

摘　　要：Recently, a new promising type of marine shale gas reservoir, carbonate-rich shale, has been discovered.But the mechanical properties of this type of shale were still unrevealed and the corresponding reservoir stimulation design was lack of guidance. Using the deep downhole cores of an exploratory carbonate-rich shale gas well, the physical and mechanical parameters and failure mechanism of the whole reservoir section were acquired and evaluated systematically, by performing XRD, tri-axial compression, Brazilian splitting, and fracture toughness tests. A new model was established to evaluate the reservoir brittleness based on fracture morphology and stress-strain curve. Recommended strategy for reservoir stimulation was discussed. Results showed that(1) Carbonate-rich shale possessed high compressive strength and high Young's modulus, which were improved by 10.74% and 3.37% compared to that of siliceous shale. It featured high tensile strength and fracture toughness, with insignificant anisotropy.(2) With the content of carbonate minerals increasing, the shear failure morphology transformed from sparse and wide brittle fractures to diffusely distributed and subtle plastic cracks.(3) The brittleness index order was: siliceous shale, clay-rich shale, carbonate-rich shale, and limestone.(4) The special properties of carbonate-rich shale were rooted in the inherent feature of carbonate minerals(high strength, high elastic modulus,and cleavage structure), resulting in greater challenge in reservoirs stimulation. The above findings would promote the understanding of carbonate-rich shale reservoirs and provide reference for the optimum design of reservoir stimulation.

关 键 词：Carbonate-rich shale Brittleness evaluation Mechanical property Lithological difference Reservoir stimulation 

分 类 号：TE377[石油与天然气工程—油气田开发工程]