岩石非线性细观响应中孔隙液体的影响
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摘要
在细观尺度上对孔隙流体对岩石力学性质的影响进行定量化研究。将孔隙流体带来的非线性应变的影响分为经典应变的影响和非经典弹性单元(NCU)对非经典应变的影响。分析低饱和度和高饱和度时微细观机制的作用,以此分别讨论流体对岩石非线性力学行为和岩石介质宏观刚度的影响。为适应不同饱和度下岩石力学行为,提出一种新的固液相互作用函数关系,对试验数据进行非线性反演,获得不同饱和度时的PM空间图像,分析孔隙流体对PM空间密度(NCU数目)的影响。首次反演杨氏模量、压缩波速度随饱和度变化完整过程。饱和度为0%～20%时,由于液体的激活作用,对于经典部分,动态杨氏模量随饱和度增加而减小;对于非经典部分,随饱和度增大PM空间NCU密度增大,NCU数目增多,非线性增强,杨氏模量下降。当饱和度为20%～80%时,动态杨氏模量不随饱和度变化,PM空间NCU密度也基本保持不变。当饱和度由80%以上增大到全饱和时,杨氏模量、弹性波速度反而随饱和度增加而增大,PM空间NCU数目有所减小,非线性程度下降。饱和岩石的经典和非经典非线性应变比干燥岩石有显著的增长,与模拟的PM空间NCU密度分布结果是一致的。这些数值分析结果与试验结果的规律性基本吻合。该项研究对于储层预测、油藏描述、斜坡附近建筑的安全性、核仓库性能及地球物理反演、资料解释都具有潜在的应用前景。
Quantitative studies of pore fluid influence on the mechanical properties of rocks are carried out on mesoscopic scale. The nonlinear strain is decomposed into a classical part and a nonclassical contribution which is described by nonclassical elastic units(NCU). Based on the analysis of the mechanism on mesoscopic scale,fluid influences on rock mechanical behavior and stiffness under various saturations are discussed. Introducing new forms of macroscopic solid-fluid interaction functions,Preisach-Mayergoyz(PM) space under different saturations are obtained from the inversion of experimental data;and the influences of fluid saturation on PM space density are investigated. The entire variation between Young′s modulus and compressional wave velocity with saturation is studied. When saturation increases from 0% to 20%,the dynamic modulus decreases for classical part,and the PM space density increases for nonclassical part,respectively. Whereas saturation is between 20% and 80%,the dynamic modulus and PM space density barely changes. As saturation increases from 80% to 100%,the dynamic modulus increases and the PM space density decreases,contrary to the low saturation condition. The classical and nonclassical nonlinear strains of saturated rocks are obviously larger than those of dry rocks in accord with the PM space density distribution. These numerical results are generally consistent with the experimental results. This simulation research has potential prospects for the problems such as reservoir prediction and description,safety of constructions near slope area,nuclear storehouse properties,geophysical inversion,and data interpretations.
Quantitative studies of pore fluid influence on the mechanical properties of rocks are carried out on mesoscopic scale. The nonlinear strain is decomposed into a classical part and a nonclassical contribution which is described by nonclassical elastic units(NCU). Based on the analysis of the mechanism on mesoscopic scale,fluid influences on rock mechanical behavior and stiffness under various saturations are discussed. Introducing new forms of macroscopic solid-fluid interaction functions,Preisach-Mayergoyz(PM) space under different saturations are obtained from the inversion of experimental data;and the influences of fluid saturation on PM space density are investigated. The entire variation between Young′s modulus and compressional wave velocity with saturation is studied. When saturation increases from 0% to 20%,the dynamic modulus decreases for classical part,and the PM space density increases for nonclassical part,respectively. Whereas saturation is between 20% and 80%,the dynamic modulus and PM space density barely changes. As saturation increases from 80% to 100%,the dynamic modulus increases and the PM space density decreases,contrary to the low saturation condition. The classical and nonclassical nonlinear strains of saturated rocks are obviously larger than those of dry rocks in accord with the PM space density distribution. These numerical results are generally consistent with the experimental results. This simulation research has potential prospects for the problems such as reservoir prediction and description,safety of constructions near slope area,nuclear storehouse properties,geophysical inversion,and data interpretations.
引文
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[12]SCALERANDI M,AGOSTINI V,DELSANTO P P,et al.Local interaction simulation approach to modeling nonclassical,nonlinear elastic behavior in solids[J].Journal of the Acoustical Society of America,2003,113(6):3049–3059.
[13]VAKHNENKO O O,VAKHNENKO V O,SHANKLAND T J,et al.Strain-induced kinetics of intergrain defects as the mechanism of slow dynamics in the nonlinear resonant response of humid sand stone bars[J].Physical Review(E),2004,70(1):1–4.
[14]席道瑛,杜赟,易良坤,等.液体对岩石非线性弹性行为的影响[J].岩石力学与工程学报,2009,28(4):687–696.(XI Daoying,DU Yun,YI Liangkun,et al.Influence of fluid to nonlinear elastic behavior of rock[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(4):687–696.(in Chinese))
[15]BATZLE M L,HAN D H,HOFMAN R.Fluid mobility and frequency-dependent seismic velocity:direct measurements[J].Geophysics,2006,71(1):1–9.
[16]MAVKO G,MUKERJI T,DVORKIN J.岩石物理手册:孔隙介质中地震分析工具[M].徐海滨,戴建春译.合肥:中国科学技术大学出版社,2008:171–175.(MAVKO G,MUKERJI T,DVORKIN J.The rock physics handbook:tools for seismic analysis in porous media[M].Translated by XU Haibin,DAI Jianchun.Hefei:University of Science and Technology of China Press,2008:171–175.(in Chinese))
[2]MCKAVANAGH B,STACEY F D.Mechanical hysteresis in rocks at low strain amplitudes and seismic frequencies[J].Physics of the Earth and Planetary Interiors,1974,8(3):246–250.
[3]BAKULIN V N,PROTOSENYA A G.Nonlinear effects in travel of elastic waves through rocks[R].Moscow:USSR Academy of Sciences,1982:314–316.
[4]席道瑛,刘斌,田象燕.饱和岩石的各向异性及非线性黏弹性响应[J].地球物理学报,2002,45(1):101–111.(XI Daoying,LIU Bin,TIAN Xiangyan.Anisotropy and nonlinear viscoelastic behavior of saturated rocks[J].Chinese Journal of Geophysics,2002,45(1):101–111.(in Chinese))
[5]CARMELIET J,VAN DEN ABEELE K E A.Application of the Preisach-Mayergoyz space model to analyze moisture effects on the nonlinear elastic response of rock[J].Geophysical Research Letters,2002,29(7):1144–1147.
[6]VAN DEN ABEELE K EA,CARMELIET J,JOHNSON P A,et al.Influence of water saturation on the nonlinear elastic mesoscopic response in Earth materials and the implications to the mechanism of nonlinearity[J].Journal of Geophysical Research,2002,107(B6):2121–2131.
[7]PREISACH F.über die magnetische Nachwirkung[J].Zeitschrift für Physik a Hadrons and Nuclei,1935,94(5/6):277–302.
[8]MAYERGOYZ I D.Mathematical models of hysteresis[J].Geophysical Research Letters,1986,56(15):1518–1521.
[9]GUYER R A,MCCALL K R,BOITNOTT G N,et al.Quantitative implementation of Preisach-Mayergoyz space to find static and dynamic elastic moduli in rock[J].Journal of Geophysical Research,1997,102(B3):5281–5293.
[10]薛彦伟,席道瑛,徐松林.岩石非经典非线性频率效应的细观研究[J].岩石力学与工程学报,2005,24(增1):5020–5025.(XUE Yanwei,XI Daoying,XU Songlin.Study of nonclassical nonlinear frequency effect on meso-scale in rocks[J].Chinese Journal of Rock Mechanics and Engineering,2005,24(Supp.1):5020–5025.(in Chinese))
[11]GUYER R A,MCCALL K R,VAN DEN ABEELE K.Slow elastic dynamics in a resonant bar of rock[J].Geophysical Research Letters,1998,25(10):1585–1588.
[12]SCALERANDI M,AGOSTINI V,DELSANTO P P,et al.Local interaction simulation approach to modeling nonclassical,nonlinear elastic behavior in solids[J].Journal of the Acoustical Society of America,2003,113(6):3049–3059.
[13]VAKHNENKO O O,VAKHNENKO V O,SHANKLAND T J,et al.Strain-induced kinetics of intergrain defects as the mechanism of slow dynamics in the nonlinear resonant response of humid sand stone bars[J].Physical Review(E),2004,70(1):1–4.
[14]席道瑛,杜赟,易良坤,等.液体对岩石非线性弹性行为的影响[J].岩石力学与工程学报,2009,28(4):687–696.(XI Daoying,DU Yun,YI Liangkun,et al.Influence of fluid to nonlinear elastic behavior of rock[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(4):687–696.(in Chinese))
[15]BATZLE M L,HAN D H,HOFMAN R.Fluid mobility and frequency-dependent seismic velocity:direct measurements[J].Geophysics,2006,71(1):1–9.
[16]MAVKO G,MUKERJI T,DVORKIN J.岩石物理手册:孔隙介质中地震分析工具[M].徐海滨,戴建春译.合肥:中国科学技术大学出版社,2008:171–175.(MAVKO G,MUKERJI T,DVORKIN J.The rock physics handbook:tools for seismic analysis in porous media[M].Translated by XU Haibin,DAI Jianchun.Hefei:University of Science and Technology of China Press,2008:171–175.(in Chinese))
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