二氧化碳压裂机理的实验研究及矿场实践  

Experimental study and field test of CO_(2) fracturing mechanism

作　　者：苏伟东 周然[1,2] 叶文勇 李勇[1,2] 杜焰 张承武[1,2] 何鑫岩 SU Weidong;ZHOU Ran;YE Wenyong;LI Yong;DU Yan;ZHANG Chengwu;HE Xinyan(Drilling&Production Technology Research Institute,CNPC Chuanqing Drilling Engineering Company Limited,Deyang,Sichuan 618300,China;National Engineering Laboratory for Exploration and Development of Low Permeability Oil and Gas Fields,Xi’an,Shaanxi 710018,China;Sichuan Yuesheng Energy Group Co.,Ltd.,CNPC Chuanqing Drilling Engineering Company Limited,Chengdu,Sichuan 610066,China)

机构地区：[1]中国石油集团川庆钻探工程有限公司钻采工程技术研究院,四川德阳618300 [2]低渗透油气田勘探开发国家工程实验室,陕西西安710018 [3]四川越盛能源集团有限公司,四川成都610066

出　　处：《天然气勘探与开发》2025年第1期50-56,共7页Natural Gas Exploration and Development

基　　金：中国石油天然气集团有限公司攻关性应用性科技专项(编号:2023ZZ28YJ01)。

摘　　要：为了揭示二氧化碳压裂造缝机理,采用二氧化碳压裂大型物理模拟实验、X射线衍射检测、岩石力学测试、岩样CT扫描及对现场压裂的水击压力响应、井下微地震裂缝监测解释等手段,从小尺寸岩样、大尺寸岩样及大尺度矿场3个尺度开展了实验及试验研究。研究结果表明:(1)超临界二氧化碳在岩石中具有极强的滤失穿透性,其形成的人工裂缝面积远小于常规水力压裂;(2)二氧化碳对地层岩石中的方解石和白云石具有明显的溶蚀作用,并导致岩石杨氏模量值、剪切模量值和抗压强度值减小,岩石脆性指数增大;(3)受二氧化碳浸泡的影响,岩石破裂后所形成的裂缝断面较粗糙、整合性差,即使在没有支撑剂支撑的条件下仍具有较好的导流能力,实现了人工裂缝的自支撑;(4)二氧化碳压裂瞬时停泵压力表现为小幅度长时间的波动,其压力传导特征与常规水力压裂存在着明显的区别;(5)超临界二氧化碳压裂的混合断裂机制较好地解释了二氧化碳压裂物模实验中声发射信号少、矿场压裂试验中微地震事件少的现象,证明了超临界二氧化碳压裂的混合断裂机制理论的合理性。结论认为,在没有支撑剂加入的情况下,二氧化碳形成的人工裂缝能够起到较好的油气增产作用,也由此证明了二氧化碳压裂自支撑理论的合理性。To reveal the fracture initiation mechanism in CO_(2) fracturing,experiments and tests were conducted with small-sized and large-sized rock samples,and large-scale fields through large-scale physical simulation experiment of CO_(2) fracturing,X-ray diffraction(XRD)detection,rock mechanics testing,rock sample CT scanning,and interpretations of water hammer pressure response and downhole microseismic fracture monitoring during on-site fracturing.The results are obtained in five aspects.First,supercritical carbon dioxide(SC-CO_(2))has an extremely strong capability of filtration and penetration in rocks,and the area of the artificial fractures it causes is much smaller than that formed by conventional hydraulic fracturing.Second,CO_(2) has a significant dissolution effect on calcite and dolomite in rocks,leading to a decrease in the Young’s modulus,shear modulus,and compressive strength of rocks,and an increase in rock brittleness index.Third,affected by the CO_(2) soaking,the fracture surface formed after rock rupture is relatively rough and poorly integrated.Such fractures show a good conductivity even without proppants,achieving self-propping of artificial fractures.Fourth,the instantaneous pump-off pressure of CO_(2) fracturing exhibits small-amplitude and long-duration fluctuations,and its pressure conduction behaviors are distinctly different from those of conventional hydraulic fracturing.Fifth,the mixed fracturing mechanism of SC-CO_(2) fracturing provides a good explanation for the phenomena of less acoustic emission signals in physical simulation experiments of CO_(2) fracturing,and fewer microseismic events in field tests,proving the rationality of the mixed fracturing mechanism.It is concluded that the fractures initiated by CO_(2) fracturing,with no proppant added,can achieve good stimulation performance,proving the rationality of the self-propping theory of CO_(2) fracturing.

关 键 词：二氧化碳压裂 造缝机理 大物模实验 岩石力学 溶蚀作用 自支撑 混合断裂 

分 类 号：TE357.7[石油与天然气工程—油气田开发工程]