天然气工业2025，Vol.45Issue(9)：114-124,11.DOI:10.3787/j.issn.1000-0976.2025.09.010
孔隙流体及压力对CO2压裂裂缝特性的影响
Influence of pore fluid and pressure on the behaviors of fractures induced by CO2 fracturing:A case study on the Triassic Chang 6 tight sandstone reservoir in the Ordos Basin
摘要
Abstract
In the process of reservoir fracturing,the injected fluid can alter the pore fluid pressure and effective rock stress,thereby influencing the propagation behaviors of hydraulic fractures.Taking the Triassic Yangchang Chang 6 tight sandstone reservoir in the Ordos Basin as the research object,this paper studies the effects of different fluids(ScCO2,N2,water,etc.)injected into reservoir pores and different pressure conditions on the morphology of hydraulic fractures in tight sandstone reservoirs by using a high-temperature and high-pressure pseudo triaxial fracturing experimental system,combined with core CT scanning and three-dimensional fracture reconstruction technology.And the following research results are obtained.First,under the same condition as slickwater fracturing with the same pore fluid,injecting ScCO2 and N2 can both reduce the fracture initiation pressure of rocks,with ScCO2 having the greatest impact,which reduces the initiation pressure by 24.04%compared with the samples without pore fluid.Second,compared with the sample without pore fluid,the fracturing sample with pores filled with water has a higher fracture initiation pressure(about 1.1%higher).Third,compared with slickwater fracturing with three kinds of pore fluid respectively,ScCO2 fracturing achieves the lowest fracture initiation pressure and the most complex fracture propagation morphology,with an average fractal dimension increase of 1.85%.Fourth,the higher the pressure of the CO2 injected into the rock pores,the more complex the fracture propagation morphology after ScCO2 fracturing.ScCO2 has the lowest viscosity,so it is easy to flow in pores to communicate natural fractures and search for weak rock planes,thus stimulating fracture propagation.In addition,high pore pressure leads to a decrease in the effective rock stress,thereby reducing the fracture initiation pressure and inducing the formation of a complex fracture network.In conclusion,to perform fracturing stimulation of unconventional reservoirs,it is recommended to inject a certain amount of CO2 into the tight reservoir to increase the pore pressure to 60%-80%of the effective reservoir stress,and then conduct ScCO2 fracturing to enhance the fracturing effect.This method provides theoretical and methodological support for the efficient CO2 fracturing of unconventional oil and gas reservoirs.关键词
超临界CO2/致密砂岩储层/孔隙流体/起裂压力/水力压裂/裂缝形态/三维裂缝重构/分形维数Key words
Supercritical CO2/Tight sandstone reservoir/Pore fluid/Fracture initiation pressure/Hydraulic fracturing/Fracture morphology/3D fracture reconstruction/Fractal dimension分类
能源科技引用本文复制引用
王海柱,Stanchits Sergey,余星,石明亮,王斌,薛小佳,陈文斌,陶亮,张国新,Cheremisin Alexey..孔隙流体及压力对CO2压裂裂缝特性的影响[J].天然气工业,2025,45(9):114-124,11.基金项目
国家自然科学基金杰出青年科学基金项目"油气井流体力学与工程"(编号:52425402)、国家自然科学基金国际(地区)合作与交流项目"非纯CO2压裂干热岩裂缝扩展机理及造储方法研究"(编号:W2412078)、国家自然科学基金青年科学基金项目"粗糙迂曲缝内超临界CO2微细支撑剂携带机理研究"(编号:52204021)、中国石油大学(北京)科研启动基金项目"页岩复杂缝网内微细支撑剂铺置与压嵌规律研究"(编号:2462022BJRC002). （编号:52425402）
