碳酸盐岩酸压裂缝导流能力影响因素

Influencing Factors of Carbonate Rock Acid Fracturing Conductivity

酸化压裂是碳酸盐岩储层开发的重要技术手段,酸液注入方式、压裂裂缝开度与酸蚀蚓孔形态等直接影响酸蚀裂缝导流能力。以奥陶系岩下碳酸盐岩储层为研究目标,在建立裂缝开度表征方法基础上,开展不同酸液体系、不同注酸方式、不同裂缝开度及不同缝面形态对酸压裂缝导流能力的影响研究,明确影响酸压裂缝导流能力的主控因素。实验结果表明:主体酸加入稠化、清洁剂后对溶蚀率与酸蚀后裂缝导流能力影响不大;单一注酸与交替注酸方式对酸压裂缝导流能力影响较小,但对残酸返排影响较大,交替注酸方式可降低返排压力70%;裂缝开度越大,酸蚀后裂缝导流能力越大,但提高导流能力倍数越小;裂缝开度>12μm易形成“窜流”酸蚀蚓孔,利于酸蚀通道建立;微裂缝开度与裂缝发育联通是影响酸蚀蚓孔与导流能力的主控因素,次之为微孔发育与联通与储层矿物分布形态。综合酸压工艺推荐先压裂、后酸化、交替注酸的方式。

Acid fracturing is an important technique for carbonate rock reservoir development.Acid injection method,fracture opening and wormhole shape directly affect the fracture conductivity of acid fracture.Taking the ordovician subrock carbonate reservoir as the research target,based on the establishment of fracture opening characterization method,the influence of different acid systems,different acid injection methods,different fracture opening and different fracture surface morphology on acid fracture conductivity was studied,and the main controlling factors affecting acid fracture conductivity were identified.The experimental results show that the main acid adding thickening and cleaning agent has little effect on the dissolution rate and the conductivity of the fracture after acid etching.Single acid injection and alternating acid injection have little effect on acid fracture conductivity,but a large effect on acid flowback.Alternating acid injection can reduce the reflux pressure by 70%.The larger the fracture opening is,the larger the fracture conductivity is after acid etching,but the smaller the multiple of improving the conductivity is.Fracture aperture>12μm is easy to form“crossflow”acid wormhole,which is conducive to the establishment of acid etching channel.The connection between microfracture opening and fracture development is the main factor affecting acid wormhole and conductivity,followed by micropore development and fracture development and mineral distribution.The comprehensive acid fracturing process is recommended by fracturing first,acidizing later and acid injection alternately.