【摘要】 缝洞型碳酸盐岩油藏是指以天然溶蚀孔、洞和多尺度裂缝作为储渗介质的一类复杂油藏。该类油藏的基质致密,一般都需要通过酸压改造来提高单井产量。但目前关于缝洞型油藏导流能力沿缝长方向分布的研究还不完善,现有的酸蚀裂缝导流能力模型都基于固定网格或复杂流场,其不能模拟排量变化或考虑缝洞对导流能力分布的影响。本文首先分析了缝洞型油藏与常规油藏酸压技术目标的差异,然后在经典模型的基础上建立了基于动网格的酸蚀裂缝导流能力数值模型。利用该模型进行了敏感性分析,认为采用高、低浓度组合的方式可以提高有效酸蚀裂缝长度和酸液利用效率;在酸压裂缝遇洞后,需要以其与井筒的距离远近作为依据,选择采用续注关井返排、停泵关井返排和停泵立即返排等不同的应对方案。该研究对于优化缝洞型碳酸盐岩油藏的酸压设计和提高酸液利用效率具有一定指导意义。更多还原

【Abstract】 Fracture-cavity carbonate reservoirs are a kind of complex reservoirs with natural solution pores,holes and multi-scale fractures as accumulation-permeation media.This kind of reservoirs is usually characterized by tight matrix,and it is always required to improve single-well production through acid fracturing treatment.However,there is no existing complete research on the conductivity distribution of fracture-cavity reservoir along the fracture length direction,while the current acid-etched fracture conductivity models are all based on fixed mesh or complex flow field,unable to simulate displacement change or the influences of fracture cavity on conductivity.At first,this study analyzed the differences in acid fracturing technical target between fracturecavity reservoirs and conventional reservoirs.Then,a numerical conductivity model of fracture-cavity reservoir on dynamic mesh was built based on classical models.The sensitivity analysis was carried out using this model.It is considered that the length of effective etched fractures and utilization rate of acid can be enhanced through the combination of high and low concentrations;when the acid-etched fracture encounters with a cave,the corresponding measures such as continuous injection-well shut-flow back,pump off-well shut-flow back and pump off-instant flow back,should be selected on a basis of the distance from the shaft.This study is of a certain guiding significance to optimize the design of acid fracturing of fracture-cavity carbonate reservoirs and improve the utilization rate of acid fluid.更多还原