裂缝性碳酸盐岩酸化模拟研究

发布时间：2018-08-19 10:51

【摘要】：基质酸化作为油气井增产和注水井增注的重要措施,在石油天然气勘探开发中具有重要作用。碳酸盐岩储层中往往都会有微裂缝的存在,并且由于地质情况复杂多变,微裂缝的形态和分布也是非常复杂的。虽然生产过程中多数的微裂缝几乎不对储层流体的流动作贡献,但酸化作业可能使其中某些微裂缝与井相互连通形成高渗通道。然而,以往的学者在对碳酸盐岩储层中的酸化过程进行模拟和计算时,往往未考虑微裂缝的存在,或是将裂缝考虑为规则的形状,明显与实际不符。另外,碳酸盐岩酸化存在一个最优注酸速率,在该速率下,突破(breakthrough)时所需的酸液量最少。所以,为了深入认识裂缝性碳酸盐岩酸化的特点,优选施工参数,急需寻求一种更好更切合实际的理论或方法来模拟裂缝性碳酸盐岩中的酸液流动反应过程。本文首次将有限单元法用于研究双重尺度模型,并通过有限元网格对裂缝性碳酸盐岩求解域进行精细网格划分,模拟了酸液在其中的流动反应过程。通过模拟结果讨论了注酸速率、裂缝长度、裂缝方位角和裂缝离井的距离等因素对酸化效果的影响,并进行了实例计算。具体研究工作如下： (1)系统调研了国内外裂缝性碳酸盐岩酸化的数学模型和模拟方法,在此基础上全面总结了碳酸盐岩酸化的特点以及裂缝对其的影响,深入研究了各种模型和方法的不足与优点。 (2)为研究酸液在含微裂缝的储层中的流动反应规律,将微裂缝假设为高孔高渗几何形态特殊的区域,通过双重尺度模型表征酸液流动反应的物理化学过程。 (3)通过有限元软件生成裂缝性碳酸盐岩物理模型,并将得到的单元、节点信息转换为可编程计算的数据形式。按照有限元的理论对数学模型离散化处理,建立了对应的可用于计算机模拟计算的数值模型。 (4)用Matlab编写了计算程序,模拟了酸液在裂缝性碳酸盐岩中的流动反应过程,讨论了注酸速率、酸液用量、裂缝长度、裂缝方位角和裂缝与井的距离等因素对酸化效果的影响。 (5)根据具体油田资料生成离散裂缝网络模型,在整个油藏尺度上进行了单井酸化模拟,深化了理论研究的实际意义。本论文完成的研究内容以及所取得的系列初步研究成果,实现了对裂缝性碳酸盐岩储层的酸化模拟的研究,探讨了裂缝参数对酸化效果的影响,证明了有限单元法用以酸化模拟的可行性,是数值模拟发展的一个重要方向,为多孔介质内的精细酸化模拟提供了一个新的尝试。
[Abstract]:As an important measure for increasing oil and gas production and injection, matrix acidification plays an important role in oil and gas exploration and development. Microfractures often exist in carbonate reservoirs, and the morphology and distribution of microfractures are very complicated because of the complex geological conditions. Although most of the microfractures in the production process make little contribution to the fluid flow in the reservoir, acidizing operations may make some of the microfractures and wells connected to each other to form high permeability channels. However, in the simulation and calculation of acidizing process in carbonate reservoirs, previous scholars often did not consider the existence of micro-fractures or the shape of fractures as regular, which is obviously not in accordance with the actual situation. In addition, there is an optimal rate of acid injection for acidification of carbonate rocks, at which the amount of acid needed to break through (breakthrough) is the least. Therefore, in order to deeply understand the characteristics of fractured carbonate rock acidification and optimize construction parameters, it is urgent to find a better and more practical theory or method to simulate the process of acid flow reaction in fractured carbonate rock. In this paper, the finite element method (FEM) is used to study the dual scale model for the first time. The fluid reaction process of acid in the solution domain of fractured carbonate rock is simulated by the finite element method (FEM). The effects of acid injection rate, fracture length, fracture azimuth angle and fracture distance from well on acidizing effect are discussed. The specific research works are as follows: (1) the mathematical models and simulation methods of fractured carbonate rock acidification at home and abroad are systematically investigated, and on this basis, the characteristics of carbonate acidification and the influence of fractures on it are summarized. The shortcomings and advantages of various models and methods are studied in depth. (2) in order to study the flow response of acid in reservoirs containing micro-fractures, the micro-fractures are assumed to be special areas with high porosity and high permeability. The physical and chemical process of acid flow reaction is characterized by a dual scale model. (3) the physical model of fractured carbonate rock is generated by finite element software and the unit node information is converted into programmable data form. According to the finite element theory, the mathematical model is discretized, and the corresponding numerical model can be used for computer simulation. (4) the calculation program is written with Matlab. The flow reaction process of acid in fractured carbonate rock is simulated. The acid injection rate, acid dosage, fracture length are discussed. The influence of fracture azimuth and the distance between fracture and well on acidizing effect. (5) according to the specific oilfield data, the discrete fracture network model is generated, and the acidizing simulation of single well is carried out on the whole reservoir scale. It deepens the practical significance of theoretical research. The research content and series of preliminary research results achieved in this paper have realized the study of acidizing simulation of fractured carbonate reservoir and discussed the influence of fracture parameters on acidizing effect. The feasibility of the finite element method for acidizing simulation is proved, which is an important direction in the development of numerical simulation and provides a new attempt for fine acidification simulation in porous media.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE357.2

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