鄂尔多斯盆地大牛地气田中奥陶统马家沟组裂缝特征及成因

Characteristics and genesis of fractures in Middle Ordovician Majiagou Formation, Daniudi Gas Field, Ordos Basin

彭先锋 邓虎成 何建华 雷涛 张烨毓 胡笑非

PENG Xianfeng DENG Hucheng HE Jianhua LEI Tao ZHANG Yeyu HU Xiaofei

成都理工大学 能源学院, 成都 610059 四川省能源投资集团有限责任公司, 成都 610095 油气藏地质及开发工程国家重点实验室(成都理工大学), 成都 610059 中国石化 华北油气分公司 勘探开发研究院, 郑州 450006 四川省科源工程技术测试中心, 成都 610073

College of Energy, Chengdu University of Technology, Chengdu, Sichuan 610059, China Sichuan Energy Industry Investment Group CO., LTD., Chengdu, Sichuan 610095, China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, Sichuan 610059, China Exploration and Development Research Institute, North China Oil and Gas Company, SINOPEC, Zhengzhou, Henan 450006, China Sichuan Keyuan Testing Center of Engineering Techonology, Chengdu, Sichuan 610073, China

鄂尔多斯盆地大牛地气田天然气潜力巨大，但中奥陶统马家沟组风化壳岩溶储层发育多种裂缝，成因复杂。为探明该储层裂缝特征，应用岩石学和测井技术，从裂缝发育频率、有效性、期次、赋存层位、形态、倾角等方面，比较了陡坎成因裂缝与构造裂缝的差异性；并通过弹性理论和断裂力学理论分析了裂缝端部区域的应力分量，探讨了陡坎裂缝的成因。陡坎成因裂缝以垂直缝、高角度斜交缝为主；裂缝延展方向和裂缝形态不规则，裂缝面不平整，具有上宽下窄、尾端无分叉特征；缝间有溶蚀现象，裂缝呈未—半充填状态，裂缝有效性高。陡坎成因裂缝受控于古地貌陡坡地形的坡度、岩层倾角、初始裂缝密度及岩石力学性质等因素；与构造裂缝相比，陡坎成因裂缝更有利于油气的运移。研究陡坎成因裂缝特征及成因，有助于进一步认识风化壳岩溶储层的展布规律，落实大牛地气田下一步勘探开发有利区。

The Daniudi Gas Field in the Ordos Basin has great natural gas potential, but a variety of fractures with complex origins was developed in the weathering crust karst reservoirs in the Middle Ordovician Majiagou Formation. In order to study the characteristics of fractures in the reservoirs, petrology and logging techniques were used to compare the differences between the fractures caused by steep ridges and structural fractures in terms of fracture development frequency, effectiveness, period, occurrence layer, shape, dip angle, etc. With elastic theory and fracture mechanics theory, the stress component at the end of fractures was analyzed, and the cause of the steep ridge fractures was discussed. Results show that the fractures caused by steep ridges are mainly vertical fractures and high-angle fractures. The fracture extension direction and fracture shape are irregular, and the fracture surface is uneven, with the characteristics of wide top and narrow bottom, and no bifurcation at the tail end. There is dissolution between the fractures, which is in a non- to semi-filled state, and the effectiveness of the fractures is high. The steep ridge fractures were controlled by factors such as ancient steep slope angle, rock layer inclination, initial fracture density and rock mechanical properties. Compared to structural fractures, the steep ridge fractures are more favorable for hydrocarbon migration. Studying the characteristics and causes of steep ridge fractures will help to further understand the distribution of weathered crust karst reservoirs, and identify favorable areas for the next exploration and development of the Daniudi Gas Field.

国家自然科学基金“断层及相关裂缝形成演化过程的断—损耦合机理研究” 41672133

https://doi.org/10.11781/sysydz202201041