罗攀,孙晓,贺沛,马春晓,郭兴,穆景福,刘保录
LUO Pan,SUN Xiao,HE Pei,MA Chunxiao,GUO Xing,MU Jingfu,LIU Baolu

• 1:陕西延长石油(集团)有限责任公司研究院
• 2:陕西省二氧化碳封存与提高采收率重点实验室
• 3:中国石油长庆油田公司第十二采油厂

摘要(Abstract)：

CO_2压裂技术以压裂液流动性好、不伤害储层、返排快、易于形成复杂缝网等优势而备受关注。与清水压裂相比，CO_2黏度、密度和压缩性与清水存在很大不同，且CO_2物性受地层温度和压力的影响较大。基于Helmholtz自由能建立了热物性状态方程，完全可以满足CO_2压裂中所能面临的热物性计算需求。对比研究了液态CO_2压裂、超临界CO_2压裂及清水压裂的液体热物理性质、裂缝起裂压力、简单双翼裂缝的扩展和天然裂缝性储层中的复杂裂缝网络的扩展。结果表明：相比于超临界CO_2压裂，清水压裂由于滤失小、增压速度相对快，更易形成较简单的裂缝网络，尤其是简单的双翼裂缝；超临界CO_2的增压范围略大于液态CO_2，两种相态的CO_2大于清水的增压范围，CO_2压裂更有利于张裂缝和剪切裂缝的混合扩展，形成复杂的裂缝网络。研究成果对CO_2压裂和清水压裂的取舍和设计具有一定指导意义。
CO_2 fracturing technology has received much attention for its advantages of good fluidity, low damage to reservoir, fast fracturing flowback and easy formation of complex fracture network. Compared with fresh water in fracturing, the viscosity, density and compressibility of CO_2 are quite different from those of fresh water, and the physical properties of CO_2 are much affected by formation temperature and pressure. Based on Helmholtz free energy, thermophysical state equation is established, which can fully satisfy calculation requirements of thermophysical properties in CO_2 fracturing. Comparative study of liquid thermophysical properties, fracture initiation pressure, the propagation of simple double-wing fractures and propagation of complex fracture networks in natural fractured reservoirs are performed for liquid CO_2 fracturing, supercritical CO_2 fracturing and fresh water fracturing. The results show that, compared with supercritical CO_2 fracturing, fresh water fracturing is easier to form relatively simple fracture network, especially simple double-wing fracture, for its low filtration and relatively high pressure increase speed. The pressurization area of supercritical CO_2 is slightly larger than that of liquid CO_2, and pressurization area of CO_2 in these 2 phases is larger than that of fresh water. CO_2 fracturing is more conducive to mixed propagation of tensile fractures and shear fractures, forming complex fracture network. The research results have guiding significance for selection and design between CO_2 fracturing and fresh water fracturing.

关键词(KeyWords)： CO_2压裂;清水压裂;CO_2物性;裂缝模拟;裂缝起裂压力;裂缝网络
CO_2 fracturing;fresh water fracturing;physical properties of CO_2;fracture simulation;fracture initiation pressure;fracture network

Abstract:

Keywords:

基金项目(Foundation): 陕西延长石油（集团）有限责任公司科技项目“低渗致密油气藏CO_2压裂技术攻关”（ycsy2021ky-A-01）

作者(Author): 罗攀,孙晓,贺沛,马春晓,郭兴,穆景福,刘保录
LUO Pan,SUN Xiao,HE Pei,MA Chunxiao,GUO Xing,MU Jingfu,LIU Baolu

DOI: 10.19597/j.issn.1000-3754.202205062

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