高压油气藏对砂岩力学特性影响的试验研究
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摘要
首先采用声波纵、横波测量方法,进行岩样筛选。然后根据高压油气藏地质构造特征,设计模拟高压油气藏内部孔隙压力变化条件下岩石力学特性测试的方案。在GCTS-1000型三轴压缩试验机上进行高温高压三轴岩石力学测试,结果表明:随着砂岩内部孔隙压力增加,外部围压保持不变的条件下,岩石的强度与围压不呈单调上升的变化趋势,而是随着孔隙压力的增加,净围压减小,岩石强度先随净围压减小而逐渐减小,之后则表现出反常的增大现象。在地压梯度为2.20MPa/(100m)时,产生最低强度值。随着地压梯度的增大,岩石强度值反而升高,形成一个V形曲线。砂岩的弹性模量为一波浪形曲线,上下波动范围最大差值为2909MPa。泊松比的值从低向高;在地压梯度大于2.00MPa/(100m)时,泊松比接近0.5。重复试验揭示了岩石三轴强度特性的这一特殊现象。该结果对于高压油气藏、水泥环和套管系统的真三维套管变形与损坏的模拟有着重要的参考价值,而且是必不可少的基础数据。
Sandstone samples are selected by the compressive wave velocity and the shear wave velocity. Then test scheme has been designed to simulate rock mechanical behaviors under the altering pore pressure of high pressure oil and gas reservoir according to the geological structure. All the triaxial tests have been performed on the triaxial compression test system GCTS–1000 with high temperature and high pressure. The test results show that:rock strength doesn′t increase monotonically with confining pressure while the internal pore pressure is increasing and confining pressure keeps constant;but the rock strength will decrease with the net increasing confining pressure first and increase abnormally then. The minimum value appears when the geostress gradient is equal to 2.20 MPa/(100 m);but the sandstone compressive strength grows up with the increase of geostress gradient. The relationship curve between rock strength and pore pressure is V-shaped. The relationship curve between elastic module and pore pressure appears as a wave shape and the maximum difference among elastic module is 2 909 MPa. In the experiment,the Poisson′s ratio increases gradually and approaches 0.5 when the geostress gradient coefficient is larger than 2.00 MPa/(100 m). This particular phenomenon of sandstone triaxial strength has been observed during repeated tests. The test result is significant to simulate the true three dimensional deformation and failure of the system composed of high-pressure gas and oil reservoir,cement sheath and casing.
Sandstone samples are selected by the compressive wave velocity and the shear wave velocity. Then test scheme has been designed to simulate rock mechanical behaviors under the altering pore pressure of high pressure oil and gas reservoir according to the geological structure. All the triaxial tests have been performed on the triaxial compression test system GCTS–1000 with high temperature and high pressure. The test results show that:rock strength doesn′t increase monotonically with confining pressure while the internal pore pressure is increasing and confining pressure keeps constant;but the rock strength will decrease with the net increasing confining pressure first and increase abnormally then. The minimum value appears when the geostress gradient is equal to 2.20 MPa/(100 m);but the sandstone compressive strength grows up with the increase of geostress gradient. The relationship curve between rock strength and pore pressure is V-shaped. The relationship curve between elastic module and pore pressure appears as a wave shape and the maximum difference among elastic module is 2 909 MPa. In the experiment,the Poisson′s ratio increases gradually and approaches 0.5 when the geostress gradient coefficient is larger than 2.00 MPa/(100 m). This particular phenomenon of sandstone triaxial strength has been observed during repeated tests. The test result is significant to simulate the true three dimensional deformation and failure of the system composed of high-pressure gas and oil reservoir,cement sheath and casing.
引文
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[12]周思孟.复杂岩体若干岩石力学问题[M].北京:中国水利水电出版社,1998.[ZHOU Simeng.Several rock mechanics problems of complex rock matrix[M].Beijing:China Water Power Press,1998.[in Chinese]]
[13]陈勉.我国深层岩石力学研究及在石油工程中的应用[J].岩石力学与工程学报,2004,23[14]:2455–2462.[CHEN Mian.Review of study on rock mechanics at great depth and its applications to petroleum engineering of China[J].Chinese Journal of Rock Mechanics and Engineering,2004,23[14]:2455–2462.[in Chinese]]
[14]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]:91–99.[ZHOU Hongwei,XIE Heping,ZOU Jianping.Review of rock mechanics at great depth and high terrestrial stress[J].Mechanics Development,2005,35[1]:91–99.[in Chinese]]
[15]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]:2803–2813.[HE Manchao,XIE Heping,PENG Suping,et al.Rock mechanics study on exploitation at great depth[J].Chinese Journal of Rock Mechanics and Engineering,2005,24[16]:2803–2813.[in Chinese]]
[2]韩林,刘向君,孟英峰,等.加载途径对深部孔隙性砂岩力学特性的影响[J].岩石力学与工程学报,2008,27[3]:596–600.[HAN Lin,LIU Xiangjun,MENG Yingfeng,et al.Effect of loading paths on mechanical properties of deep porous sandstone[J].Chinese Journal of Rock Mechanics and Engineering,2008,27[3]:596–600.[in Chinese]]
[3]周青春,李海波,杨春和,等.南水北调西线一期工程砂岩温度、围压和水压耦合试验研究[J].岩石力学与工程学报,2005,24[20]:3639–3646.[ZHOU Qingchun,LI Haibo,YANG Chunhe,et al.Experimental study on thermo-mechanical coupling of sandstone for west route of South-to-North water Transfer Project[J].Chinese Journal of Rock Mechanics and Engineering,2005,24[20]:3639–3646.[in Chinese]]
[4]王学滨.孔隙压力对岩样全部变形特征的影响[J].沈阳建筑大学学报[自然科学版],2005,21[6]:625–629.[WANG Xuebin.Effect of pore pressure on complete deformational characteristics of rock specimen[J].Journal of Shenyang Jianzhu University[Natural Science],2005,21[6]:625–629.[in Chinese]]
[5]吴景浓.地壳岩石的渗透性状及孔隙水对岩石力学性质的影响[J].华南地震,1990,10[1]:77–82.[WU Jingnong.Permeability of rock in crust and the influence of water at aperture on the character of rock mechanics[J].South China Journal of Seismology,1990,10[1]:77–82.[in Chinese]]
[6]邢福东,朱珍德,刘汉龙,等.高围压高水压作用下脆性岩石强度变形特性试验研究[J].河海大学学报[自然科学版],2004,32[2]:184–187.[XING Fudong,ZHU Zhende,LIU Hanlong,et al.Experimental study on strength and deformation characteristics of brittle rocks under high confining pressure and hydraulic pressure[J].Journal of Hohai University[Natural Sciences],2004,32[2]:184–187.[in Chinese]]
[7]孟召平,李明生,陆鹏庆,等.深部温度、压力条件及其对砂岩力学性质的影响[J].岩石力学与工程学报,2006,25[6]:1177–1181.[MENG Zhaoping,LI Mingsheng,LU Pengqing,et al.Temperature and pressure under deep conditions and their influences on mechanical properties of sandstone[J].Chinese Journal of Rock Mechanics and Engineering,2006,25[6]:1177–1181.[in Chinese]]
[8]谢守益,徐卫亚,贾赟,等.饱和多孔白垩岩的孔隙力学性质研究[J].岩石力学与工程学报,2007,26[4]:804–810.[XIE Shouyi,XU Weiya,JIA Yun,et al.Study on pore mechanics character of saturated and porous Cretaceous rock[J].Chinese Journal of Rock Mechanics and Engineering,2007,26[4]:804–810.[in Chinese]]
[9]王学滨,潘一山.考虑围压及孔隙压力的岩石试件应力与应变关系解析[J].地质力学学报,2001,7[3]:265–270.[WANG Xuebin,PAN Yishan.Analyzing the relationship of stress and strain considering the confinement pressure and pore pressure of rock[J].Journal of Geomechanics,2001,7[3]:265–270.[in Chinese]]
[10]郭中华,朱珍德,余湘娟,等.灰岩强度特性的三轴压缩试验分析[J].河海大学学报[自然科学版],2002,30[3]:93–95.[GUO Zhonghua,ZHU Zhende,YU Xiangjuan,et al.Analysis of stress-strain relationships for limestone by triaxial test[J].Journal of Hohai University[Natural Science],2002,30[3]:93–95.[in Chinese]]
[11]陈颙.地壳岩石的力学性能——理论基础与试验方法[M].北京:地震出版社,1988.[CHEN Yu.Mechanical properties of crest rock—theoretical foundation and experimental methods[M].Beijing:Earthquake Press,1988.[in Chinese]]
[12]周思孟.复杂岩体若干岩石力学问题[M].北京:中国水利水电出版社,1998.[ZHOU Simeng.Several rock mechanics problems of complex rock matrix[M].Beijing:China Water Power Press,1998.[in Chinese]]
[13]陈勉.我国深层岩石力学研究及在石油工程中的应用[J].岩石力学与工程学报,2004,23[14]:2455–2462.[CHEN Mian.Review of study on rock mechanics at great depth and its applications to petroleum engineering of China[J].Chinese Journal of Rock Mechanics and Engineering,2004,23[14]:2455–2462.[in Chinese]]
[14]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]:91–99.[ZHOU Hongwei,XIE Heping,ZOU Jianping.Review of rock mechanics at great depth and high terrestrial stress[J].Mechanics Development,2005,35[1]:91–99.[in Chinese]]
[15]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]:2803–2813.[HE Manchao,XIE Heping,PENG Suping,et al.Rock mechanics study on exploitation at great depth[J].Chinese Journal of Rock Mechanics and Engineering,2005,24[16]:2803–2813.[in Chinese]]
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