VISCOELASTIC PROPERTIES OF SATURATED SANDSTONES UNDER FATIGUE LOADING
(1. School of Earth and Space Science，University of Science and Technology of China，Hefei，Anhui 230026，China；
2. School of Mechanical Engineering，Beijing Institute of Petrochemical Technology，Beijing 102671，China；
3. Geophysical Research Institute of Geophysical Prospecting，China National Petroleum Corporation，Zhuozhou，Hebei 072750，China；4. CAS Key Laboratory for Mechanical Behavior and Design of Materials，University of Science and Technology of China，Hefei，Anhui 230027，China)
Abstract：Experiments are performed by Metravib dynamic mechanical analyzer under sine wave loading as to imitate the seismic wave(travelling wave). The static load is fixed to 100 N，and the constant dynamic load of the sine wave is 60 N，so that the total loading force is controlled under yield stress. Temperature is controlled between －50 ℃—125 ℃，and the heating speed is 1 ℃/min. At frequency of 5—90 Hz，pump-oil saturated arkoses and Pengshan sandstones are tested under uniaxial cyclic loading. The variations of travelling wave energy attenuation，imaginary modulus，Young?s modulus and elastic wave velocity with temperature or frequency are obtained. The energy attenuation peak and the imaginary modulus peak shift to higher temperatures when the frequency increases；and the energy attenuation and imaginary peak values increase for the travelling wave. These phenomena are caused by thermal relaxation mechanism. The Young?s modulus and elastic wave velocity increase with frequency increase and decrease with temperature increase. These are obvious frequency dispersion，and the dispersion weakens when temperature decreases. The experimental results are similar to the low-frequency resonance standing wave experimental results. Thus the thermal relaxation regularities generally exist in saturated porous rocks. The results are the experimental and theoretical foundation for the study of time-temperature equivalence，and are very instructive for the study of theoretical rock physics model. This investigation is very helpful to the interpretation of seismic，acoustic wave，and seismic prospecting data.
[1] XI D Y，LIU X Y，ZHANG C Y. The frequency(or time)-temperature equivalence of relaxation in saturated rocks[J]. Pure and Applied Geophysics，2007，164(11)：2 157–2 173.
[2] 席道瑛，陈运平，陶月赞，等. 岩石的非线性弹性滞后特征[J]. 岩石力学与工程学报，2006，25(6)：1 086–1 093.(XI Daoying，CHEN Yunping，TAO Yuezan，et al. Nonlinear elastic hysteric characteristics of rocks[J]. Chinese Journal of Rock Mechanics and Engineering，2006，25(6)：1 086–1 093.(in Chinese))
[3] BATZLE M L，HAN D H， HOFMANN R. Fluid mobility and frequency-dependent seismic velocity direct measurements[J]. Geophysics，2006，71(1)：1–9.
[4] WHITE J E. Computed seismic speeds and attenuation in rocks with partial gas saturation[J]. Geophysics，1975，40(2)：224–232.
[5] GIST G A. Interpreting laboratory velocity measurements in partially gas-saturated rocks[J]. Geophysics，1994，59(7)：1 100–1 109.
[6] PRIDE S R，HARRIS J M，JOHNSON D L，et al. Permeability dependence of seismic amplitudes[J]. The Leading Edge，2003，22(6)：518–525.
[7] SPENCER J W. Stress relaxations at low frequencies in fluid saturated rocks：attenuation and modulus dispersion[J]. Journal of Geophysical Research，1981，86(B3)：1 803–1 812.
[8] BATZLE M，WANG Z J. Seismic properties of pore fluids[J]. Geophysics，1992，57(11)：1 396–1 408.
[9] BATZLE M， HOFMANN R，HAN D H，et al. Fluids and frequency dependent seismic velocity of rocks[J]. The Leading Edge，2001，20(2)：168–171.
[10] XI D Y，LIU B，LIU W，et al. The dependence of relaxation attenuation of saturation rock on time and temperature[J]. Chinese Journal of Geophysics，2000，43(6)：873–880.
[11] XI D Y，LIU B，TIAN X Y. Anisotropy and nonlinear viscoelastic behavior of saturated rocks[J]. Chinese Journal of Geophysics，2002，45(1)：101–111.
[12] 席道瑛，张程远，刘小燕. 储层砂岩的各向异性[J]. 石油地球物理勘探，2001，36(2)：187–192.(XI Daoying，ZHANG Chengyuan，LIU Xiaoyan. Anisotropy in reservoir sandstone[J]. Oil Geophysical Prospecting，2001，36(2)：187–192.(in Chinese))
[13] 席道瑛，谢 端，易良坤，等. 温度对岩石模量和波速的影响[J]. 岩石力学与工程学报，1998，17(增)：802–807.(XI Daoying，XIE Duan，YI Liangkun，et al. Effects of temperature on rock?s modulus and wave velocity[J]. Chinese Journal of Rock Mechanics and Engineering，1998，17(Supp.)：802–807.(in Chinese))
[14] 杜 赟，席道瑛，徐松林，等. 多孔岩石波传播的热弛豫模型修正[J]. 地球物理学报，2009，52(12)：3 051–3 060.(DU Yun，XI Daoying，XU Songlin，et al. The modification of thermal relaxation mechanism for wave propagation in porous rocks[J]. Chinese Journal of Geophysics，2009，52(12)：3 051–3 060.(in Chinese))
[15] XI D Y，XU S L，DU Y，et al. Wave propagation analysis of porous rocks with thermal activated relaxation mechanism[J]. Journal of Applied Geophysics，2011，73(3)：289–303.
[16] 席道瑛，程经毅，席 军. 饱和砂岩滞弹性弛豫热激活过程机制探讨[J]. 石油地球物理勘探，1998，33(3)：348–354.(XI Daoying，CHENG Jingyi，XI Jun. Research on the heating activation mechanism of viscoelastic relaxation in fluid-saturated sandstone[J]. Oil Geophysical Prospecting，1998，33(3)：348–354.(in Chinese))
[17] 易良坤，席道瑛，刘小燕. 孔隙介质热激活弛豫波动理论[J]. 岩石力学与工程学报，2003，22(5)：803–809.(YI Liangkun，XI Daoying，LIU Xiaoyan. Wave theory with heat effects in porous media[J]. Chinese Journal of Rock Mechanics and Engineering，2003，22(5)：803–809.(in Chinese))
2011, Vol. 30 
