交替注入工艺对深层海相碳酸盐岩酸蚀裂缝导流能力的影响研究

Influence of Alternate Injection Process on Conductivity of Acid-Etched Fractures in Deep Marine Carbonate Rocks

元坝气田长兴组属于高温、超深的碳酸盐岩储层,具有低孔低渗的特征,需要酸化改造才能投产。储层高温导致酸岩反应速率快,常规酸压改造的酸蚀缝长较短,且裂缝壁面多呈均匀刻蚀,导致后续导流能力下降快,严重影响开发改造效果。针对以上改造难点,开展了室内多级交替注入酸压模拟实验,采用雷诺相似准则,基于工程参数对实验交替注入参数进行优化调整,测试了不同交替级数下岩板刻蚀形态及导流能力。实验结果表明,三级交替注酸后的岩板非均匀刻蚀程度最强烈,其表面形成了酸蚀沟槽;扫描高程及标准偏差直观反映了不同交替级数酸蚀裂缝的高程波动及粗糙度,三级交替酸蚀裂缝轮廓的起伏程度和粗糙度最大;裂缝导流能力评价结果验证了三级交替注酸具有最优的裂缝导流能力。优化后的多级交替注入酸压工艺应用于元坝长兴组储层改造,现场应用表明三级交替注入工艺可以提高元坝长兴组气藏产能,为低渗储层改造提供了有效的技术手段。

The Changxing Formation in the Yuanba gas field is a high temperature,ultra-deep carbonate reservoir with low porosity and low permeability,which requires acid reformation before it can be put into production.The high temperature of the reservoir leads to a fast reaction rate of acid rock,and the acid-etching seam length of conventional acid-pressure transformation is short and the fracture walls are mostly uniformly etched,resulting in a rapid decrease in subsequent flow-conducting capacity,which seriously affects the development and transformation effect.To address the above difficulties,an indoor multi-stage alternate injection acid pressure simulation experiment was carried out to optimize the experimental alternate injection parameters based on the Reynolds similarity criterion,and to test the etching pattern and flow conductivity of the rock slab under different alternate stages.The results show that the non-uniform etching of the slab after the three-stage alternate acid injection is the strongest,and the surface of the slab forms acid etching grooves;the scanning elevation and standard deviation visually reflect the elevation fluctuation and roughness of the acid etched fractures at different alternate levels,and the undulation and roughness of the three-stage alternate acid etched fracture profile are the largest;the evaluation results of the fracture inflow capacity verify that the three-stage alternate acid injection has the best fracture inflow capacity.The optimized multi-stage alternate acid injection process was applied to the reservoir reformation of the Changxing Formation in Yuanba,and the field application showed that the three-stage alternate injection process could improve the gas reservoir capacity of the Changxing Formation in Yuanba,providing an effective technical means for the reformation of low-permeability reservoirs.