摘要
页岩气井水力压裂施工后会有大量的压裂液滞留在储层中,页岩吸水后不仅会改变储层中流体的赋存状态,还会对储层渗透率产生一定的影响。为此,以涪陵地区某页岩气区块龙马溪组储层段岩心为研究对象,开展了页岩吸水实验,并评价了页岩岩心渗透率在吸水过程及液体扩散过程中的变化情况。结果表明:页岩岩心吸水量随着伊/蒙混层质量分数及有机碳质量分数的升高而增大;平行层理方向的岩心吸水能力强于垂直层理方向的岩心;岩心在蒸馏水中的吸水量最大(0.0373 g/cm^(2)),在3%KCl溶液中次之(0.0241 g/cm^(2)),在滑溜水中最小(0.0158 g/cm^(2));页岩岩心在吸水初期渗透率迅速下降,然后迅速升高,最后逐渐稳定,在吸水实验结束后,表面产生了明显的微裂缝,最终的渗透率明显高于初始渗透率;页岩岩心吸水1 h后,其渗透率在液体扩散过程中逐渐升高,并且液体扩散初期渗透率的提升幅度较大。研究结果认为,页岩气储层滑溜水压裂液滞留可以诱导储层产生微裂缝,提高地层渗透率,从而有利于页岩气井产能的提高。
After the hydraulic fracturing of shale gas wells,a large amount of fracturing fluid will stay in the reservoir.After the shale absorbs water,it will not only affect the occurrence of fluid in the reservoir,but also have a certain influence on the reservoir permeability.Therefore,taking the Longmaxi Formation rock sample of a shale gas block in Fuling area as the research object,the experiment on influence factors of shale absorption capacity was carried out,and the influence of shale absorption process and liquid diffusion process on permeability was evaluated.The results show that the water absorption per unit area of shale core increases with the increase of mineral content and organic matter content of mixed layer of montmorillonite and illite;the water absorption capacity of cores with parallel bedding is stronger than that of cores with vertical bedding;the water absorption of the core is the largest in distilled water(0.037,3 g/cm^(2)),the second in 3% KCl solution(0.024,1 g/cm^(2)),and the smallest in slippery water(0.015,8 g/cm^(2)).The permeability of shale core decreases rapidly at the initial stage of water absorption,then increases rapidly,and finally stabilizes gradually.After the water absorption experiment,obvious micro cracks appear on the surface of shale core,and the final permeability is significantly higher than the initial permeability.The permeability of shale core increases gradually in the process of liquid diffusion after absorbing water for one hour,and the increase range of permeability is larger at the initial stage of diffusion.The research results show that the slippery hydraulic fracturing fluid retention in shale reservoir can induce micro fractures in the reservoir and improve the formation permeability,which is beneficial to improve the productivity of shale gas wells.
作者
姜桂芹
王国勇
JIANG Guiqin;Wang Guoyong(Post-Doctoral Research Station of CNPC Great Wall Drilling Engineering Co.,Ltd,Beijing 100101,China;Energy Department of CNPC Greatwall Drilling Company,Panjin 124010,China)
出处
《断块油气田》
CAS
CSCD
北大核心
2021年第4期530-534,共5页
Fault-Block Oil & Gas Field
基金
国家科技重大专项“陆相页岩气渗流规律与采气工艺技术”(2017ZX05039)。
关键词
页岩气储层
吸水特性
影响因素
渗透率
微裂缝
shale gas reservoir
water absorption characteristics
influencing factors
permeability
micro-cracks
