缝洞性碳酸盐岩多段酸压水平井压力动态研究

The flow process of multiple-acidized-fractured horizontal wells in carbonate formation is very complex because carbonate formation possesses special pore structures, and knowing about the property parameters of acidized fractures and the connection conditions of natural fractures and vugs is the premise of efficient development of a single horizontal well, therefore it is in urgent need of deep study on the porous flow theory of multiple-acidized-fractured horizontal wells in carbonate formations. Based on the fundamental theory of porous flow mechanics, according to the practical geological traits of carbonate formations, a series of flow models of multiple-acidized-fractured horizontal wells will be established in fractured, porous-vuggy, fractured-vuggy, cavernous carbonate formations respectively, and these models will fully consider more practical circumstance of acidized-fractures, such as, non-equidistance between the neighbor fractures, unequal half-length for each fracture, unequal half-height for each fracture, and unequal arbitrary angle; The mathematical models will be solved using the theory of point source function and the method of orthogonal transformation, and then we will plot the pressure dynamics curves using some programs; Presetting multi-groups of changing formation parameters and well parameters, we can simulate the changing characteristics of pressure dynamics and accordingly reveal the porous flow laws and hydrodynamic behavior characteristics of multiple-acidized-fractured horizontal wells in carbonate formations; At the same time we will conduct the research on the differences of pressure dynamics caused by different parameters of acidized fractures, different formation types and different inter-porosity flow manners. The research results will provide some new porous flow models for carbonate formations, and promote the development of the mechanics for flow in underground porous media, and lay the foundation in theory for efficient development of acidized-fractured horizontal wells.

碳酸盐岩储层具有独特的孔隙结构，水平井多段酸压后的渗流过程极其复杂，弄清酸压缝的特性参数及与天然缝洞体的沟通情况是单井高效开发的前提，急需深度研究其渗流理论。本项目从渗流力学基本原理出发，根据碳酸盐岩储层实际地质特征，且充分考虑酸压裂缝呈非等间距、非等半长、非等缝高、非等任意倾角的实际情况，分别建立裂缝型、孔洞型、裂缝孔洞型及洞穴型碳酸盐岩多段酸压水平井的渗流模型；利用点源函数理论、正交变换等数学方法对模型进行求解，再编程绘制压力动态特征曲线，预设多组变化的储层参数和井参数，模拟压力动态变化特征，揭示缝洞性碳酸盐岩多段酸压水平井的渗流规律和水动力学行为特征；同时开展不同酸压裂缝参数、不同储层类型和不同窜流方式条件下的压力动态差异性研究。研究成果将为碳酸盐岩储层提供新的渗流模型，促进地下渗流力学理论的发展，为水平井酸压后的高效开发奠定理论基础。

碳酸盐岩储层具有独特的孔隙结构，水平井多段酸压后的渗流过程极其复杂，弄清酸压缝的特性参数及与天然缝洞体的沟通情况是单井高效开发的前提，急需深度研究其渗流理论。因此，本项目从渗流力学基本原理出发，根据碳酸盐岩储层实际地质特征，开展了缝洞性碳酸盐岩多段酸压水平井的基础渗流理论研究。完成的主要研究内容有：建立了一系列缝洞性碳酸盐岩储层多段酸压水平井渗流模型；利用点源函数理论、正交变换等数学方法对模型进行了求解；研究了碳酸盐岩储层多段酸压水平井生产压力动态特征；开展了5口井的现场应用分析，验证了理论研究成果。取得的主要研究进展有：建立并求解了综合考虑非等裂缝半长、非等裂缝缝高、任意倾角的多级多段压裂水平井渗流模型，编程绘制了一系列井底压力动态特征曲线，揭示了多级多段压裂水平井渗流规律；建立并求解了裂缝型碳酸盐岩储层多段酸压水平井缝网渗流模型，编程绘制了受天然裂缝特性参数控制的井底压力动态特征曲线，揭示了缝网渗流规律；建立并求解了孔洞型碳酸盐岩储层多段酸压水平井渗流模型，编程绘制了受天然溶蚀孔洞特性参数控制的井底压力动态特征曲线，揭示了渗流规律；建立并求解了裂缝孔洞型碳酸盐岩储层多段酸压水平井缝网渗流模型，编程绘制了受天然裂缝和天然溶蚀孔洞特性参数控制的井底压力动态特征曲线，揭示了渗流规律。项目研究成果为碳酸盐岩储层提供了新的渗流模型；揭示了缝洞性碳酸盐岩储层多段酸压水平井的渗流规律和水动力学行为特征；深化认识了缝洞发育程度及流体在基质、天然裂缝和溶蚀孔洞之间窜流的特征；揭示了流体在人工裂缝和天然裂缝之间流动的不稳定压力瞬态变化规律，为碳酸盐岩储层水平井酸压后的高效开发奠定了坚实的理论基础。本项目的研究还扩大了现代数学理论方法在工程技术领域中的应用，在一定程度上促进了地下油气藏渗流力学理论的发展，无疑具有重大的科学意义和价值。