Carbonate reservoirs commonly feature rough-walled fractures with complex geometries and hydraulic properties, posing significant challenges in accurately evaluating the dissolution patterns and conductivities along these fractures during acid stimulation processes in oil, gas, and geothermal production. This study conducts an experimental investigation of acid treatment in carbonate fractures with varying roughness levels to analyze the transition patterns in the dissolution of these rough-walled fractures, particularly focusing on the effects of acid injection rate and fracture roughness. The results reveal that the dissolution patterns progressively change from uniform dissolution and channel dissolution to surface dissolution. This transition occurs either with an increase in the acid injection rate or a decrease in the fracture roughness. In response to these findings, a phase transition model has been developed to incorporate the dissolution pattern transition, taking into consideration the roughness of the fractures. The model is based on the degree of dissolution observed in the etching channels in the flow and longitudinal direction. Further analysis of fracture conductivities, considering different dissolution patterns, indicates that the formation of etching channels post-acidizing in these rough-walled fractures is the primary factor influencing changes in the conductivity of the fracture surfaces. A channel-dissolution coefficient is introduced for the evaluation of the dissolution pattern and fracture conductivity. The critical transition value from uniform to channel dissolution is identified as , and the transition from channel dissolution to surface dissolution is . Analysis comparing fracture conductivities under different dissolution patterns reveals a preference for channel dissolution, which offers enhanced efficiency in acid treatment. For optimal treatment efficacy, it is advised that the channel-dissolution coefficient be maintained between and . These insights offer a comprehensive experimental and theoretical basis for the optimization of acid treatment techniques, aimed at enhancing the productivity of oil, gas, and geothermal operations in carbonate reservoirs with rough-walled fractures.

中文翻译：

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沿粗壁碳酸盐裂缝酸溶解的相变模型


碳酸盐岩储层通常具有具有复杂几何形状和水力特性的粗壁裂缝，这对准确评估石油、天然气和地热生产酸刺激过程中这些裂缝沿线的溶解模式和电导率提出了重大挑战。本研究对不同粗糙度水平的碳酸盐岩裂缝进行酸处理实验研究，以分析这些粗糙壁裂缝溶解的转变模式，特别关注注酸速率和裂缝粗糙度的影响。结果表明，溶解模式逐渐从均匀溶解、通道溶解转变为表面溶解。这种转变随着酸注入速率的增加或断裂粗糙度的降低而发生。针对这些发现，开发了相变模型来纳入溶解模式转变，同时考虑裂缝的粗糙度。该模型基于在蚀刻通道中沿流动方向和纵向观察到的溶解程度。考虑不同溶解模式，对裂缝电导率的进一步分析表明，在这些粗壁裂缝中酸化后蚀刻通道的形成是影响裂缝表面电导率变化的主要因素。引入通道溶解系数来评估溶解模式和裂缝导流能力。从均匀溶解到通道溶解的临界转变值为 ，从通道溶解到表面溶解的转变为 。 比较不同溶解模式下裂缝电导率的分析揭示了通道溶解的偏好，这提高了酸处理的效率。为了获得最佳治疗效果，建议通道溶解系数保持在 和 之间。这些见解为酸处理技术的优化提供了全面的实验和理论基础，旨在提高具有粗壁裂缝的碳酸盐岩储层的石油、天然气和地热作业的产能。