高温高压耦合下含不同倾角充填缝砂岩的强度实验研究
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摘要
超深储层中岩石的力学性质十分复杂,在油气勘探中经常会遇到井壁围岩垮塌和压裂施工压力大的难题。为揭示高温高压耦合条件下不同倾角充填缝砂岩的破坏模式和强度特征,通过RTR1500高温高压岩石力学实验机,开展对含充填裂缝类砂岩的抗压强度测试实验,研究不同围压、温度、裂缝倾角和裂缝充填方式对岩石强度的影响规律,并根据实验结果绘制了高温高压耦合的条件下不同裂缝倾角岩样破坏准则图。结果表明:(1)裂缝倾角是影响破坏模式和抗压强度的最主要因素,低、高角度缝岩样破坏模式为剪切破坏,抗压强度不随裂缝倾角变化而变化;斜交缝岩样破坏模式为沿裂缝面的滑移,抗压强度随着裂缝倾角增大先减小后增加,存在最小值。(2)不同充填方式下岩样中的主要微裂缝类型不同,破坏时反应岩石的不同性质。(3)温度增加使岩样的整体强度降低,围压增加岩样强度增加,高温高压耦合会使岩石本体更加破碎,岩样由脆性向塑性转变,并且围压增大会抑制裂缝倾角的作用效果。
The mechanical properties of rocks in ultra-deep reservoirs are very complicated,and well collapse and high pressure of fracturing construction are often encountered in the exploration of oil and gas. In order to reveal the failure damage modes and compressive strength characteristics of sandstone with different crack angles and different filling methods under the conditions of high temperature and high pressure,RTR–1500 triaxial rock testing system was used to carry out the compressive strength test experiment of sandstone cores with different crack angles and different filling methods. The influences law of different confining pressures,temperatures,crack angles and crack filling methods on rock strength were studied in the experiment. According to the experimental results,the diagram of failure criterion of sandstone cores with different crack angles is drawn under the coupling of high temperature and high pressure. The results show that:(1) the fracture dip is the most important factor affecting the failure mode and compressive strength. The failure mode of low and high angle fracture rock samples is shear failure,and the compressive strength does not change with the change of the fracture dip. The failure mode of oblique fracture rock samples is slip along the fracture surface,and the compressive strength decreases first and then increases with the increase of the fracture dip,there is a minimum.(2) The main types of micro-cracks in rock samples are different under different filling methods,which reflects the different properties of rock when it is destroyed.(3) Increasing temperature decreases the overall strength of rock samples,and increasing confining pressure increases the strength of rock samples. Coupling of high temperature and high pressure will make the rock body more fragmented. Rock samples change from brittleness to plasticity,increasing confining pressure will inhibit the effect of fracture dip.
The mechanical properties of rocks in ultra-deep reservoirs are very complicated,and well collapse and high pressure of fracturing construction are often encountered in the exploration of oil and gas. In order to reveal the failure damage modes and compressive strength characteristics of sandstone with different crack angles and different filling methods under the conditions of high temperature and high pressure,RTR–1500 triaxial rock testing system was used to carry out the compressive strength test experiment of sandstone cores with different crack angles and different filling methods. The influences law of different confining pressures,temperatures,crack angles and crack filling methods on rock strength were studied in the experiment. According to the experimental results,the diagram of failure criterion of sandstone cores with different crack angles is drawn under the coupling of high temperature and high pressure. The results show that:(1) the fracture dip is the most important factor affecting the failure mode and compressive strength. The failure mode of low and high angle fracture rock samples is shear failure,and the compressive strength does not change with the change of the fracture dip. The failure mode of oblique fracture rock samples is slip along the fracture surface,and the compressive strength decreases first and then increases with the increase of the fracture dip,there is a minimum.(2) The main types of micro-cracks in rock samples are different under different filling methods,which reflects the different properties of rock when it is destroyed.(3) Increasing temperature decreases the overall strength of rock samples,and increasing confining pressure increases the strength of rock samples. Coupling of high temperature and high pressure will make the rock body more fragmented. Rock samples change from brittleness to plasticity,increasing confining pressure will inhibit the effect of fracture dip.
引文
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[11]LAJTAI E Z.Strength of discontinuous rocks in direct shear[J].Geotechnique,1969,19(2):218-233.
[12]凌建明.节理裂隙岩体损伤力学研究中的若干问题[J].力学进展,1994,25(2):257-264.(LING Jianming.Some problems in damage mechanics of jointed and fractured rock mass[J].Advances in Mechanics,1994,25(2):257-264.(in Chinese))
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[14]车法星,黎立云,刘大安.类岩石材料多裂纹体断裂破坏试验及有限元分析[J].岩石力学与工程学报,2000,19(3):295-298.(CHEFaxing,LI Liyun,LIU Daan,Fracture experiments and finite element analysis for multi-cracks body of rock-like taterial[J].Chinese Journal of Rock Mechanics and Engineering,2000,19(3):295-298.(in Chinese))
[15]YANG S Q,XU T,HE L,et al.Numerical study on failure behavior of brittle rock specimen containing pre-existing combined flaws under different confining pressure[J].Civil and Mechanical Engineering,2015,15(4):1 085-1 097.
[16]潘建武.含单一天然弱面岩石试样的力学特性研究[硕士学位论文][D].焦作:河南理工大学,2010.(PAN Jianwu.Study on the mechanical properties of rock specimens with a single natural weak plane[M.S.Thesis][D].Jiaozuo:Henan Polytechnic University,2010.(in Chinese))
[2]HOEK E,BROWN E T.Underground excavations in rock[M].London:Institution of Mining and Metallurgy,1980:30-70.
[3]邓林,邓荣贵,付小敏,等.泥巴山隧道流纹岩加卸围压力学特性研究[J].岩石力学与工程学报,2009,28(增1):3 150-3 155.(DENGLin,DENG Ronggui,FU Xiaomin et al.Study on mechanical properties of rhyolite under loading and unloading conditions in niba mountain tunnel[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(Supp.1):3 150-3 155.(in Chinese))
[4]CLEARY M.Effects of depth on rock fracture[C]//Rock at Great Depth.Rotterdam:A.A.Balkema,1989:1 153-1 163.
[5]何满潮,谢和平,彭苏萍,等.深部开采岩体力学研究[J].岩石力学与工程学报,2005,24(16):2 803-2 813.(HE Manchao,XIEHeping,PENG Suping,et al.Study on rock mechanics in deep mining engineering[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(16):2 803-2 813.(in Chinese))
[6]SINGH J.Strength of rocks at depth[C]//Rock at Great Depth.Rotterdam:A.A.Balkema,1989:37-44.
[7]周宏伟,谢和平,左建平.深部高地应力下岩石力学行为研究进展[J].力学进展,2005,35(1):91-97.(ZHOU Hongwei,XIEHeping,ZUO Jianping.Development in researches on mechanical behaviors of rocks under the condition of high ground pressure in the depths[J].Advances in Mechanics,2005,35(1):91-97.(in Chinese))
[8]谢和平,高峰,鞠杨.深部岩体力学研究与探索[J].岩石力学与工程学报,2015,34(11):2 161-2 179.(XIE Heping,GAO Feng,JU Yang.Research and development of rock mechanics in deep ground engineering[J].Chinese Journal of Rock Mechanics and Engineering,2015,34(11):2 161-2 179.(in Chinese))
[9]陈景涛,冯夏庭.高地应力下岩石的真三轴试验研究[J].岩石力学与工程学报,2006,25(8):1 537-1 543.(CHEN Jingtao,FENGXiating.True triaxial experimental study on rock with high geostress[J].Chinese Journal of Rock Mechanics and Engineering,2006,25(8):1 537-1 543.(in Chinese))
[10]尹土兵,李夕兵,宫凤强,等.温压耦合作用下岩石动态破坏过程和机制研究[J].岩石力学与工程学报,2012,31(增1):2 815-2 816.(YIN Tubing,LI Xibing,GONG Fengqiang,et al.Study of dynamic failure processes and mechanism of rock subjected to coupling temperature and pressure[J].Chinese Journal of Rock Mechanics and Engineering,2012,31(Supp.1):2 815-2 816.(in Chinese))
[11]LAJTAI E Z.Strength of discontinuous rocks in direct shear[J].Geotechnique,1969,19(2):218-233.
[12]凌建明.节理裂隙岩体损伤力学研究中的若干问题[J].力学进展,1994,25(2):257-264.(LING Jianming.Some problems in damage mechanics of jointed and fractured rock mass[J].Advances in Mechanics,1994,25(2):257-264.(in Chinese))
[13]高峰,钟卫平,黎立云等.节理岩体强度的分形统计分析[J].岩石力学与工程学报,2004,23(21):3 608-3 612.(GAO Feng,ZHONG Weiping,LI Liyun,et al.Fractal and statistical analysis of strength of jointed rocks[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(21):3 608-3 612.(in Chinese))
[14]车法星,黎立云,刘大安.类岩石材料多裂纹体断裂破坏试验及有限元分析[J].岩石力学与工程学报,2000,19(3):295-298.(CHEFaxing,LI Liyun,LIU Daan,Fracture experiments and finite element analysis for multi-cracks body of rock-like taterial[J].Chinese Journal of Rock Mechanics and Engineering,2000,19(3):295-298.(in Chinese))
[15]YANG S Q,XU T,HE L,et al.Numerical study on failure behavior of brittle rock specimen containing pre-existing combined flaws under different confining pressure[J].Civil and Mechanical Engineering,2015,15(4):1 085-1 097.
[16]潘建武.含单一天然弱面岩石试样的力学特性研究[硕士学位论文][D].焦作:河南理工大学,2010.(PAN Jianwu.Study on the mechanical properties of rock specimens with a single natural weak plane[M.S.Thesis][D].Jiaozuo:Henan Polytechnic University,2010.(in Chinese))