Abstract A new thermal-hydro-mechanical-chemical coupled acid fracturing model is proposed to analyze the effective acid penetration distance during acid fracturing. To improve the computational efficiency of the model, we used a simple three-dimensional displacement discontinuity method. Additionally, a finite-volume method was used to calculate the flow field. Temperature- and chemical-field models were also established based on energy- and material-conservation criteria, respectively. Subsequently, a new full implicit solution was established to solve the problem of rock deformation, stress interference, temperature, and acid–rock reaction coupling. The results show that the greater the injection rate, the greater is the effective acid penetration distance. To ensure that this distance is as large as possible, the injection speed should be maximized in the acid-fracturing process. Similarly, a high acid concentration results in a larger effective acid penetration distance. Therefore, the original concentration of the acid may be moderately increased, which is the simplest and most straightforward way to achieve a high acid penetration distance. If increasing the viscosity does not reduce the transfer rate of H+ and the order of the acid–rock reaction, the effective acid penetration distance is reduced. Therefore, the inter-dependence of multiple fields during construction optimization should be considered. In addition to construction and fluid parameters, reservoir parameters also have a significant effect on the effective acid penetration distance and acid-fracturing process. Reservoir temperature influences the effective acid penetration distance, fluid-temperature distribution in the fracture, and etching width. Finally, a high reservoir temperature results in a rather small effective acid penetration distance.

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酸压裂有效渗酸距离计算的全耦合模型

摘要 提出了一种新的热-水-力-化学耦合酸压裂模型，用于分析酸压过程中的有效酸渗透距离。为了提高模型的计算效率，我们使用了一种简单的三维位移不连续性方法。此外，使用有限体积法来计算流场。还分别基于能量守恒和材料守恒标准建立了温度和化学场模型。随后，建立了新的全隐式求解方法来解决岩石变形、应力干扰、温度和酸岩反应耦合问题。结果表明，注入速率越大，有效酸渗透距离越大。为了确保这个距离尽可能大，酸压过程中应尽量提高注入速度。类似地，高酸浓度导致更大的有效酸渗透距离。因此，可以适度增加酸的原始浓度，这是实现高酸渗透距离的最简单直接的方法。如果增加粘度不会降低 H+ 的转移速率和酸岩反应的顺序，则有效酸渗透距离会降低。因此，在施工优化过程中应考虑多个领域的相互依存关系。除了施工和流体参数外，储层参数对酸液有效渗透距离和酸压过程也有显着影响。储层温度影响有效酸渗透距离，裂缝中的流体温度分布和蚀刻宽度。最后，高储层温度导致相当小的有效酸渗透距离。