考虑酸蚀效应的缝洞交互行为研究  

Fracture and vug interaction behavior considering acid etching effect

作　　者：史宏伟 赵海峰[1] 甘贵鹏 徐凯强 SHI Hongwei;ZHAO Haifeng;GAN Guipeng;XU Kaiqiang(College of Petroleum Engineering,China University of Petroleum(Beijing),Beijing City,102249,China)

机构地区：[1]中国石油大学(北京)石油工程学院,北京102249

出　　处：《油气地质与采收率》2024年第6期168-178,共11页Petroleum Geology and Recovery Efficiency

基　　金：国家自然科学基金面上项目“一种复杂缝网的能量断裂准则及其在致密砂岩压裂模拟中的应用”(11672333)。

摘　　要：缝洞型碳酸盐岩储层具有低孔、低渗透和非均质性强的特点,酸压是该类储层增产改造的主要技术手段,酸压改造的关键在于高效沟通缝洞储集体。由于受到非均质性和随机分布孔洞的影响,酸压过程中裂缝扩展路径复杂,缝洞交互规律认识不清。为此,开展室内实验,研究碳酸盐岩酸蚀前后孔隙度、渗透率和力学性质变化规律。实验结果表明:酸岩反应对岩石力学参数影响显著,以质量分数为15%胶凝酸为例,酸蚀作用后,岩心孔隙度、渗透率增加,岩心抗压强度、弹性模量分别降低了42%和60%,泊松比增加了25%。通过在经典内聚力模型中引入岩石物理力学演化方程,建立了一种考虑酸岩反应的裂缝扩展模型,将该模型与常规水力裂缝扩展模型和室内酸压物理模拟实验对比,验证了该模型的有效性和正确性。利用建立的模型研究了孔洞尺度、注液排量、水平地应力差对裂缝扩展路径的影响,结果表明:①人工裂缝倾向于贯穿小孔洞、绕过中型孔洞、沟通大型孔洞。②当水平地应力差超过5 MPa,注液排量超过0.057 m3/s时,有助于裂缝与孔洞沟通。③酸岩反应能明显提高缝洞沟通效率,注液排量为0.1 m^(3)/s时酸压裂缝扩展面积是常规水力压裂的2倍。因此,改造高应力差碳酸盐岩储层时,为了提高缝洞沟通效率、改善酸压效果,应适当提高注液排量。Fractured-vuggy carbonate reservoirs are characterized by low porosity,low permeability,and strong heterogeneity.Acid fracturing is the primary technical means to increase the production of this kind of reservoir,and the key to fracturing reconstruction is to communicate fractured-vuggy reservoir efficiently.However,due to the influence of heterogeneity and randomly distributed vugs,the fracture propagation paths are complicated during acid fracturing,and the law of fracture-vug interaction is not clear.Therefore,laboratory experiments were carried out to study the changes in porosity,permeability,and mechanical properties of carbonate rocks before and after acid etching.The experimental results showed that acid-rock reaction significantly influences rock mechanics parameters.With a 15%mass fraction of gelled acid as an example,core porosity and permeability increase;the compressive strength and elastic modulus of cores decrease by 42%and 60%,and Poisson’s ratio increases by 25%after acid etching.Then,the rock’s physical and mechanical evolution equation was introduced into the classical cohesive model,and a fracture propagation model considering acid-rock reaction was established.The model was compared with the conventional hydraulic fracture propagation model and the laboratory physical simulation experiment of acid fracturing,and the effectiveness and correctness of the model were verified.Finally,the model was used to study the effects of horizontal in-situ stress difference,vug size,and injection displacement on fracture propagation path.The simulation results showed that①Artificial fractures tend to penetrate small vugs,bypass medium vugs,and communicate with large vugs.②It is helpful for the communication between fractures and vugs when the horizontal stress difference exceeds 5 MPa and the injection displacement exceeds 0.057 m^(3)/s.③The acid-rock reaction can significantly improve the fractured-vuggy communication efficiency,and the fracture propagation area by acid fracturing is twice that by

关 键 词：碳酸盐岩储层 酸压 缝洞交互行为 酸岩反应 内聚力单元 数值模拟 

分 类 号：TE357[石油与天然气工程—油气田开发工程]