碳酸盐岩地下储气库多重介质储层强注强采流体多尺度运移机理

The 11 completed sandstone underground gas storages built domestic exist broken structure and small scale of sand body and other unfavorable factors, thus many problems emerged in the process of building process. Fractured carbonate reservoirs have the complete structure, large volume and the advantages of the seepage condition , so it is the ideal goal for building , but the particularity of multi-medium carbonate reservoir heterogeneity and underground gas storage forced injection process determines the complexity of multi-scale fluid transport mechanism . The relevant theoretical research is imminent, there is no precedent in foreign countries . This paper by means of small combined core experiment, flat big core experiments and micro visual etching model experiments , for the carbonate rock hole, holes, seams and complex multiple medium of matrix ,oil gas and water in the reservoir and the medium of multi-scale coupling characteristics ,developing high strength in the process of injection-production fluid physical simulation experimental displacement each rounds, deeply analyze the seepage law of multi-phase fluid macroscopic and microscopic mechanism of injection-production. A prediction model of cave-fracture-pore distribution in the reservoir and a non-darcy flow mathematical model of fluid channeling in the medium of multi-scale were established , deeply study the process of formation of "gas surrounded by oil" or "gas surrounded by water" and the motion law of the gas displacement front, providing strong supports for the efficient operation of the carbonate rock gas storage, laying the theoretical foundation for similar underground gas storage reservoir reconstruction .

国内已建成的11座砂岩地下储气库存在构造破碎、砂体规模小等不利因素导致建库过程中暴露出诸多问题，碳酸盐岩裂缝性油藏具备构造完整、体积大以及渗流条件好等优势，是理想的建库目标，但是碳酸盐岩多重介质储层的非均质性及地下储气库强注强采工艺的特殊性决定了流体多尺度运移机理的复杂性，相关理论研究迫在眉睫，国外亦未见先例。本课题拟通过小岩心组合实验、平板大岩心实验及微观可视化刻蚀模型实验等手段，针对碳酸盐岩孔、洞、缝及基质复杂的多重介质储层以及介质内油、气、水多尺度的耦合特征，开展高强度注采过程中多轮次流体互驱物理模拟实验，深入剖析多相流体宏观和微观注采机理及渗流规律，建立洞穴-裂缝-孔隙在储层中分布的预测模型和流体在介质中窜流的多尺度非达西流数学模型，深入研究“油包气”或“水包气”形成的过程及气驱前缘运动规律，为碳酸盐岩储气库高效运行提供强有力的技术支撑，为类似储层改建地下储气库奠定理论基础。

传统的利用枯竭砂岩气藏改建地下储气库难以满足城市用气季节调峰的迫切需求。我国碳酸盐岩约占沉积岩总面积的55%，具有分布范围广、构造完整、储层物性好、库容量大、埋深适中以及裂缝系统渗流条件好等优势，有利于建成大型碳酸盐岩储气库群。在地下储气库强注强采过程中，碳酸盐岩多尺度、多轮次油气水互驱的运移规律和流动机理难以遵循达西定律，其气水互驱机理及主控影响因素是碳酸盐岩多重介质储层改建地下储气库急待解决的重点和难点问题。本项目自主设计和研发了一套能够模拟碳酸盐岩地下储气库不同地层温度、不同压力系统、多轮次注采的物理模拟实验系统，创建了一套实验方法，并开展了3大类27项基础性实验；针对碳酸盐岩孔、洞、缝及基质复杂的多重介质储层以及介质内油、气、水多尺度的耦合特征，开展了高强度注采过程中多轮次流体互驱物理模拟实验，揭示了碳酸盐岩储气库流体多轮次强注强采的流体宏观分布、渗流特征，评价了多轮次油气水互驱的微观运移规律及运行机理；结合微观渗流实验研究中观察到的水封气、裂缝与基质之间的窜流存在启动压差等现象以及张量理论和等值渗流阻力原理，建立了油、气、水在孔、洞、缝等复杂多重介质中流动的等效连续介质模型。研究成果可为我国西气东输的城市用气调峰工程提供强有力的技术支持，同时对碳酸盐岩地下储气库的运行机理评价具有科学意义。