基于缝间形态表征的酸蚀裂缝导流能力研究

发布时间：2018-03-31 21:29

本文选题：碳酸盐岩　切入点：酸蚀裂缝　出处：《西南石油大学》2017年硕士论文

【摘要】：酸压是指在高于裂缝闭合压力或储层破裂压力的条件下,将酸液挤进地层,在油气储层中形成裂缝,同时裂缝壁面的岩石和酸液发生反应,酸液非均匀地刻蚀裂缝壁面岩石,形成凹凸不平或者沟槽状的刻蚀裂缝,施工结束后裂缝不完全闭合,最后形成具有一定导流能力的人工裂缝,从而改善油气井的渗流状况达到增产的目的。酸压是碳酸盐岩油气藏增产改造的关键技术之一,而酸蚀裂缝的导流能力是评价酸压施工的重要指标。本论文从物理模拟实验入手,分别记录了岩石起裂后、酸液非均匀刻蚀后以及裂缝不完全闭合后的壁面形态,并研究了储层温度、酸液H+浓度以及闭合压力在酸压过程中对岩石壁面以及裂缝缝间形态的影响。利用三维数字化分析发现酸液刻蚀后的裂缝形态与闭合后的最终形态之间不仅仅是单纯的数字相加过程,裂缝闭合过程会导致缝间形态发生一定的形变,通过经典赫兹接触GW模型对裂缝闭合引起的形变量进行了研究和计算,并拟合出形变量与岩石闭合压力的关系式。该关系式定量的揭示了岩石壁面闭合形变量与岩石壁面的关系,使酸蚀后导流通道的开度计算更加准确,对导流能力的预测值也更有实用价值。本论文在利用接触形变量对裂缝开度进行修正,并利用数值模拟的方法对酸蚀裂缝导流能力进行编程计算,并利用CFD仿真模拟岩石壁面渗流流场及压力场得到岩石壁面导流能力,并对两结果进行对比及适用性分析。研究表明CFD仿真计算结果略小于基于立方定律的网格计算结果,是因为编程计算结果对裂缝通道迂曲度的忽视。但由于立方定律网格计算方法适用于大型裂缝壁面,而CFD仿真计算在建模时对壁面的几何形状有一定限制,故适用于小尺寸裂缝导流能力的计算。本论文的研究成果对酸蚀裂缝的表面形态以及酸蚀裂缝导流能力的预测有着重要的指导意义,揭示了前人忽视多年的闭合压力与裂缝形变量的关系,得到闭合压力与导流能力之间的关系。对酸蚀裂缝导流能力的计算更加精确。
[Abstract]:Acid fracturing is the process of squeezing acid into the formation and forming fractures in oil and gas reservoirs under conditions higher than the fracture closure pressure or reservoir fracture pressure. At the same time, the rocks on the fracture wall react with the acid solution, and the acid solution inhomogeneously etches the fractured wall rock. Forming uneven or grooved etched cracks, the cracks are not completely closed after construction, and finally artificial cracks with certain diversion capacity are formed. Acid fracturing is one of the key techniques for the stimulation and transformation of carbonate reservoirs, so as to improve the percolation of oil and gas wells. The conductivity of acid corrosion crack is an important index to evaluate acid compression construction. This paper starts with physical simulation experiments and records the wall morphology of rock after fracture initiation, non-uniform etching of acid solution and incomplete closure of fracture. And studied the reservoir temperature, The effect of H concentration and closing pressure on the rock wall and fracture joint morphology during acid compression is studied. By using 3D digital analysis, it is found that the formation of fracture after etching and the final shape after closure are not only the same as that of the final form after acid etching. Simple digital addition process, The fracture closure process will lead to some deformation of the fracture morphology. The shape variables caused by the fracture closure are studied and calculated by the classical Hertz contact GW model. The relation between the shape variable and the closed pressure of rock is fitted. The relation between the closed shape variable of rock wall and the rock wall is revealed quantitatively, which makes the calculation of the opening degree of the diversion channel after acid erosion more accurate. In this paper, the contact variable is used to modify the crack opening, and the numerical simulation method is used to calculate the conductivity of the acid corrosion fracture. The flow field and pressure field of rock wall are simulated by CFD, and the two results are compared and analyzed. The results show that the results of CFD simulation are slightly smaller than those of grid calculation based on cubic law. But because the cubic law grid method is applicable to the large crack wall, the CFD simulation has some limitations on the geometric shape of the wall. Therefore, it is suitable for the calculation of the conductivity of small size cracks. The research results of this paper have important guiding significance for predicting the surface morphology of acid corrosion cracks and the conductivity of acid corrosion cracks. The relationship between closure pressure and fracture shape is revealed, and the relationship between closure pressure and conductivity is obtained, and the calculation of conductivity of acid corrosion fracture is more accurate.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE357.2

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