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页岩储层超临界二氧化碳压裂裂缝形态研究
引用本文:苏建政,李凤霞,周彤.页岩储层超临界二氧化碳压裂裂缝形态研究[J].石油与天然气地质,2019,40(3):616-625.
作者姓名:苏建政  李凤霞  周彤
作者单位:中国石化 石油勘探开发研究院, 北京 100083
基金项目:国家科技重大专项(2017ZX05049003-005;2017ZX05049006-007)
摘    要:目前超临界CO2压裂技术尚不成熟,裂缝形成与扩展机理尚不明确。为深入认识超临界CO2压裂裂缝延伸规律及空间形态,基于位移间断边界元方法,通过引入Pen-Robinson方程来实现超临界CO2压裂过程的模拟。结合室内物理模拟实验,初步探讨了页岩储层水力压裂与超临界CO2压裂裂缝扩展形态的差异。研究结果表明,由于超临界CO2的扩散性及良好的渗透能力,通过增加围岩孔隙压力,从而减少了地应力对裂缝扩展的约束,使裂缝起裂压力低于水力压裂。超临界CO2压裂时产生的体积应变增量与压后裂缝破坏程度比水力压裂更高,使得在裂缝形态复杂程度高于水基压裂液。同时,超临界CO2压裂裂缝断面复杂、不平整,裂缝表面粗糙度比水力压裂更大。

关 键 词:裂缝扩展  裂缝形态  天然弱面  超临界二氧化碳  水力压裂  页岩储层
收稿时间:2019-03-20

Hydraulic fracture propagation behavious and geometry under supercritical CO2 fracturing in shale reservoirs
Su Jianzheng,Li Fengxia,Zhou Tong.Hydraulic fracture propagation behavious and geometry under supercritical CO2 fracturing in shale reservoirs[J].Oil & Gas Geology,2019,40(3):616-625.
Authors:Su Jianzheng  Li Fengxia  Zhou Tong
Affiliation:Petroleum Exploration and Production Research Institute, SINOPEC, Beijing 100083, China
Abstract:The supercritical CO2 fracturing technology is yet to be improved,and the mechanisms of fracture generation and propagation are still not clear at present.In order to get an in-depth understanding of hydraulic fracture propagation behaviors and geometry under supercritical CO2 fracturing,we introduced the Pen-Robinson equation to simulate the process of supercritical CO2 fracturing,based on the displacement discontinuity boundary element method.Combined with lab physical simulation experiments,the differences of hydraulic fracture propagation behaviors and geometry between conventional fracturing with water-based fluid and fracturing with supercritical CO2 in the shale reservoir were discussed.The results show that the pressurization in the pores of surrounding rocks will function to reduce the constraint of in-situ stress on fracture propagation,thanks to the diffusivity and good permeability of supercritical CO2,and in turn the initiation pressure for fractures is lower than that of conventional fracturing.The incremental volumetric strain generated during and the failure of fractures after supercritical CO2 fracturing are higher than those under conventional fracturing,thus the fracture geometry under supercritical CO2 fracturing is more complex than that under fracturing with water-based fluid; meanwhile,the fracture plane under supercritical CO2 fracturing is more complex and uneven,and has higher tortuosity than that under conventional fracturing with water-based fluid.
Keywords:fracture propagation  fracture geometry  natural weak plane  supercritical CO2  hydraulic fracturing  shale reservoir  
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