超深碳酸盐岩断缝体储层酸压裂缝与天然裂缝-溶洞相互作用机理

海相超深层碳酸盐岩油气（≥6000m）是我国油气资源未来最重要的发展领域之一。针对四川、塔里木盆地开发中存在强应力干扰下断裂-溶洞-裂缝沟通差、酸压改造体积小、压裂效率低等难题，围绕高温高应力储层人工裂缝与多尺度天然缝洞相互作用机理认识不清的关键科学问题，研制微型双悬臂梁I型裂缝拉伸装置，利用环境扫描电镜及数字图像表征方法，揭示微观下动态裂缝激活区中的缝-洞断裂力学特征；建立流-固-热耦合时不同尺度、形态与分布特征的断-缝-洞数值模型，研究靶向酸压裂缝扩展穿透机理，提出三维空间下酸压裂缝与断裂-溶洞-裂缝相互作用准则，形成酸蚀缝洞连通扩展控制技术，通过室内真三轴全程酸压模拟实验验证，揭示酸压裂缝遇到断-缝-洞后停滞、贯穿和转向连通成网的相互作用机理，掌握复杂应力下酸压裂缝扩展路径和沟通模式，解决超深层酸压改造酸蚀裂缝短、缝洞连通差、导流下降快的工程难题，实现海相超深层致密油气长效开发。

Ultra-deep marine carbonate oil and gas (≥6,000m) are parts of the most critical development areas of China's oil and gas resources in the future. However, the poor crack-karst-fracture communication, insufficient acid fractured volume, and low fracturing efficiency under the substantial stress interference in Sichuan and Tarim Basin development are not uncommon problems. Moreover, the interaction mechanism between artificial fractures and multi-scale natural fractures, and that between fractures and caverns in high-temperature and high-stress reservoirs is still unclear. In this way, a miniature double-cantilever I-type fracture stretching device was developed, characterized by environmental scanning electron microscopy and digital imaging. Consequently, the fracture-cavern fracture mechanics characteristics in the dynamic fracture activation zone were revealed successfully at the microscopic level..Furthermore, a crack-fracture-cavern numerical model based on the fluid-solid-thermal coupling theory with different scales, shapes, and distribution characteristics was established. What is more, the targeting of acid-fracturing fracture propagation and interaction mechanism was studied. Besides, the acid fracturing fracture and crack-karst-fracture interaction criterion in three-dimensional space were proposed..Additionally, the connecting-expanding controlling theory of acid-etched fracture-wormhole was formed. It was verified by true tri-axial full-scale acid fracturing simulation experiment. The results revealed the interaction mechanism when the acid fractures encountered a crack-karst-fracture structure, which can be divided into three modes of trapped, penetrating, turning, and connecting to form a network. Then, the propagation path and communication mode of acid fracturing fractures under complex in-situ stress conditions can be grasped. As a result, the practical engineering problem in ultra-deep acid fracturing will be solved, such as the short length of acid-etched fractures, poor fracture-cavern connection, and rapid declination of formation flow conductivity. Finally, long-term and efficient development of marine ultra-deep tight oil and gas will be achieved.