【作者】 刘涛；

【导师】 刘伟；

【作者基本信息】 成都理工大学 ， 石油与天然气工程， 2024， 硕士

【摘要】 全球碳酸盐岩油气资源储量丰富,已经成为各国油气资源勘探开发的重要领域。川渝茅口组碳酸盐岩储层具有埋藏较深、非均质性强、储层类型多样等特点,常规酸化压裂技术难以达到理想的改造效果。本文以川渝茅口组碳酸盐岩储层为研究对象,通过开展岩石力学实验、酸蚀裂缝导流能力实验、裂缝刻蚀酸岩反应数值模拟以及酸化压裂物理模拟实验等工作,对川渝茅口组碳酸盐岩储层的酸化压裂工艺进行了深入研究,取得了如下成果与认识:(1)通过岩石抗压强度测试、抗拉强度测试、断裂韧性测试以及储层地应力大小测试分析了不同岩性碳酸盐岩的力学特性,并通过脆性指数、断裂韧性指数、水平应力系数以及缝洞发育程度建立了川渝茅口组碳酸盐岩可压性评价模型,结果表明,川渝茅口组不同岩性碳酸盐岩试样的可压裂性指数位于0.65～0.73之间,可压性较好,采用合适的压裂工艺改造后均可形成较为复杂的裂缝网络。(2)通过酸蚀裂缝裂缝导流能力实验、裂缝刻蚀酸岩反应数值模拟,分析了不同酸液体系的酸蚀裂缝导流能力和刻蚀能力。结果表明,单一酸液中胶凝酸对裂缝的刻蚀能力更强,酸蚀裂缝导流能力较高。组合酸液中,胶凝酸和转向酸组合对裂缝非均匀刻蚀能力最强,能够在高闭合压力下保持较高的导流能力。(3)开展了全直径碳酸盐岩酸压物理模拟实验,研究了碳酸盐岩天然缝洞发育程度以及不同压裂工艺对裂缝扩展的影响。结果表明,天然缝洞发育会对人工裂缝产生较大影响,当近井地带发育天然裂缝时,人工裂缝沿天然裂缝方向扩展。相比单一液体,多种液体组合压裂能够明显改善压裂施工的改造效果。通过增加压裂施工的交替级数能够大幅度提高改造面积以及酸压裂缝的复杂程度。(4)综合分析不同酸液体系的刻蚀效果和导流能力、不同储层缝洞发育特征下各压裂工艺的改造效果,优选了适合不同类型碳酸盐岩储层的压裂施工方案。缝洞发育储层采用压裂液和胶凝酸多级交替酸压工艺,适当增加交替级数以激活更多天然缝洞体,同时强刻蚀提高缝洞网络导流能力。缝洞欠发育储层采用压裂液和胶凝酸多级交替配合转向酸的复合酸压工艺,在造长缝的同时兼顾提高裂缝的导流能力。基于优化的酸压工艺对不同类型碳酸盐岩储层开展了现场施工应用,施工过程顺利,排采效果显著,研究结果为川渝茅口组不同类型碳酸盐岩储层的压裂施工设计提供了思路。更多还原

【Abstract】 Globally,carbonate reservoirs are rich in oil and gas resources,and have become an important field for the exploration and development of oil and gas resources in various countries.The carbonate reservoirs of the Maokou Formation in the Sichuan and Chongqing regions are characterized by deep burial,strong heterogeneity,and diverse reservoir types.Conventional acid fracturing techniques often fail to achieve desired improvement effects.In this thesis,we take the carbonate reservoir of the Maokou Formation in the Sichuan and Chongqing regions as the research object and investigate the acid fracturing process by carrying out rock mechanics experiments,acid corrosion fracture conductivity testing experiments,numerical simulation of acid rock reactions,and acid fracturing physical simulation experiments.The results achieved are as follows:(1)Through rock compressive strength testing,tensile strength testing,fracture toughness testing,and reservoir stress testing,we analyze the mechanical properties of different lithologies of carbonate rocks.We establish a compressibility evaluation model based on the brittleness index,fracture toughness index,horizontal stress coefficient,and degree of fracture development for the Maokou Formation in the Sichuan and Chongqing regions.The results indicate that the compressibility index of different lithologies of carbonate rocks from the Maokou Formation in the Sichuan-Chongqing region ranges from 0.65 to 0.73,indicating good compressibility.A complex network of fractures can be formed after applying appropriate fracturing techniques.(2)Through acid corrosion fracture conductivity testing experiments and numerical simulation of acid rock reactions,we analyze the etching capabilities of different acid fluid systems.The results indicate that in a single acid solution,gelled acid exhibits stronger etching capabilities on fractures and higher fracture conductivity.In composite acid solutions,the combination of gelled acid and diverting acid shows the strongest ability for non-uniform fracture etching,maintaining high conductivity even under high closure pressure.(3)Conduct full-scale physical simulation experiments on acid fracturing of carbonate rocks to investigate the extent of natural fissure development and the impact of different fracturing techniques on fissure propagation.The results indicate that the development of natural fissures significantly influences the propagation of artificial fractures,particularly in the near-wellbore zone where natural fissures are prevalent,leading to the propagation of artificial fractures along the direction of natural fissures.Compared to single-fluid treatments,the use of multiple-fluid combinations for fracturing substantially improves the effectiveness of fracturing operations.Increasing the alternating frequency of fracturing operations significantly enhances the treatment area and the complexity of acid-fractured fissures.(4)A comprehensive analysis of the etching and conductivity capabilities of different acid fluid systems,the fissure development characteristics of various reservoirs,and the modification effects of different fracturing techniques leads to the selection of optimal fracturing procedures tailored for different types of carbonate reservoirs.For reservoirs with well-developed fissures,a multi-stage alternating acid-fracturing process using fracturing fluid and gelled acid is preferred,with the addition of multiple stages to activate more natural fissure bodies while simultaneously enhancing fissure network conductivity through strong etching.For reservoirs with underdeveloped fissures,a composite acid-fracturing process employing multi-stage alternating fracturing fluid and gelled acid combined with diverting acid is recommended,aiming to create extended fractures while improving the conductivity of the fissures.Based on optimized acid-fracturing techniques,we conduct field applications on various types of carbonate reservoirs.The construction process proceeds smoothly,with significant trial production results.The research findings provide insights for the design of fracturing operations in different types of carbonate reservoirs within the Maokou Formation of the Sichuan and Chongqing regions.更多还原