碳酸盐岩储层闭合酸化模拟研究

酸压裂缝生产一段时间后导流能力会逐渐降低，常采用闭合酸化来提高已酸压裂缝的导流能力，闭合酸化模拟对闭合酸化设计意义重大，因此，针对该问题进行闭合酸化建模及数值模拟。首先，基于达西定理、物质平衡原理、酸岩反应动力学建立闭合酸化数学模型；然后通过地质统计学中的序贯高斯模拟算法生成具有非均质性和空间关联性的初始裂缝宽度空间分布和裂缝表面基质渗透率分布；利用有限体积法对模型进行数值求解，用C++编制模拟计算程序；最后基于该模型进行广泛的数值模拟研究，分析酸液分布规律、裂缝表面溶蚀规律、酸液作用距离的影响因素及规律，并形成各种条件下的酸液作用距离图版。研究表明，初始裂缝宽度和裂缝表面粗糙度对裂缝表面溶蚀形态起主导作用，裂缝面溶蚀形态有均匀推进、指进溶蚀和沟槽溶蚀；裂缝宽度越小、粗糙度越大，裂缝表面溶蚀竞争越强烈，越容易形成沟槽，酸液作用距离越远；排量、注酸量正相关于活酸作用距离，酸液传质系数负相关于活酸作用距离；典型的施工排量、酸液用量、常用的酸液类型下，闭合酸化中酸液作用距离为20～60 m。此模型可以预测不同条件下酸液作用距离和酸蚀裂缝表面溶蚀形态，优化闭合酸化参数，为现场闭合酸化施工设计提...

Simulation study of closed fracture acidizing in carbonate formations

The conductivity of acid-fractured fractures will gradually reduce after a period of times. Closed? fracture acidizing is often used to improve the? conductivity of acid-fractured fractures, and closed acidizing simulation is of great significance to the design of closed acidizing. Therefore, in this paper, closed? fracture acidizing modeling and numerical simulations are performed for this problem. Firstly, a mathematical model of closed acidizing was established based on Darcy"s theorem, material balance principle and acid rock reaction kinetics; then the initial spatial distribution of spatially correlated fracture width and matrix permeability distribution on fracture surface were generated by sequential Gaussian simulation algorithm in geological statistics; numerical solution of the model was using the finite volume method and developing the simulation calculation program; finally, an extensive numerical simulation study was conducted based on the model to analyze the feature of acid distribution, the feature of dissolution, the factors and features influencing the acid action distance, and to form a plate of the acid action distance under various conditions. The study shows that the initial fracture width and fracture surface roughness play a dominant role in the fracture surface dissolution morphology, and the fracture surface dissolution morphology has uniform pushing, finger-in dissolution and groove dissolution; The smaller the fracture width and the greater the roughness, the stronger the competition for dissolution on the fracture surface, the easier it is to form grooves, and the farther the distance of the acid action; The rate of acid injection? and? volume are positively correlated with acid action distance, and acid transfer coefficient is negatively correlated with acid action distance. The distance of acid action in closed acidizing is 20-60m under typical rate of injection, acid volume, and commonly used acid type. This model can predict the acid action distance and acid corrosion fracture surface dissolution morphology under different conditions, optimize the closed acidizing parameters, and provide theoretical basis and guidance for the construction design of closed fracture acidizing in the field.