摘要
水平井分段压裂是页岩气藏开发的主要技术手段。然而,页岩纳米孔与微裂缝的毛管自吸作用往往导致压裂液返排困难,滞留压裂液对页岩气解吸—扩散—渗流过程潜在损害严重。为深化页岩气藏压裂液返排与及其水相圈闭损害动态变化的认识,利用川东龙马溪组页岩样品,在岩心柱尺度上实验模拟增产改造时压裂液自吸—返排过程,讨论了孔隙结构、裂缝发育情况、返排压差及时间影响自吸—返排效果的机理。结果表明:孔隙半径越小,毛管力越大,页岩自吸速率越大,水相返排效果越差;自吸诱发页岩产生裂缝,增大了气相渗流通道,促进了滞留水相返排;返排压差、返排时间与水相返排效果呈正相关关系,在返排压差0.2MPa和1.0MPa条件下先后各返排12h,水相最大返排率约为46%,最大渗透率恢复率约为67%。分析表明:页岩气藏潜在水相圈闭损害严重,滞留水相的返排有利于增强页岩气渗流能力。
Horizontal well staged fracturing is the main technical means of shale gas reservoir reformation. The flowback rate of fracturing fluid is low in shale gas reservoir.The retained fracturing fluid in nanopore and microcraek seriously affects the desorption-diffusion-permeability of shale gas.Spontaneous imbibition and flowback experiment swere carried out on the shale of Longmaxi Formation in the eastern Sichuan Ba- sin to reveal the characteristics of fracturing fluid flowing back and the change of aqueous phase trapping damage.The effects of pore structure, fracture, flowback pressure and time on spontaneous imbibition and flowback behavior were evaluated.Results show that,the smaller the pore radius, the greater the capillary force,the higher the spontaneous imbibition rate and the poorer the flowbaek effect.Aqueous phase sponta- neous imbibition can induce cracks in shale, which increased the channel of permeability and promoted a- queous phase flowback.Flowback pressure and flowback time have a positive correlation with the flowback effect of aqueous phase,and after 24 hours of flowback,the maximum flowback rate is 46~ and permeabili- ty recovery rate is 67~.This paper draws the conclusion that, the potential aqueous phase trapping damage of shale gas reservoirs is severe, and reduce aqueous phase in shale benefits to improve permeability of shale gas.
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2017年第6期819-827,共9页
Natural Gas Geoscience
基金
国家自然科学基金项目(编号:51674209)
国家科技重大专项"彭水地区常压页岩气开发技术与政策研究"(编号:2016ZX05061003)
非常规油气层保护四川省青年科技创新研究团队项目(编号:2016TD0016)联合资助
关键词
页岩气
页岩
气藏
储层损害
水相圈闭
压裂液
Shale gas
Shale
Gas reservoir
Formation damage
Aqueous phase trap
Fracturing fluid
