The tight oil/gas reservoirs in China have showed the great exploration prospects and high production potential, with the characteristics of low porosity, low permeability, and significant heterogeneity in formation rocks. It remains a challenge to sort out the relations between reservoir wave responses and rock physical properties, and the further studies on the wave response patterns of tight reservoirs are in an urgent demand. The shear modulus and S- (shear) wave attenuation of rocks are affected by the properties of pore fluid and confining pressure. The ultrasonic wave experiments are performed on eight partially-saturated tight sandstone samples at different confining pressures, and we estimate S-wave attenuation with the spectral-ratio method. Results show that S-wave attenuation decreases with increasing confining pressure, and the water saturation case shows more loss compared to the oil saturation case, while the gas saturation case gives the lowest attenuation. We observe the S-wave relaxation peak at an intermediate water saturation for the gas-water partial-saturation case in general. S-wave attenuation increases with increasing porosity or permeability. Based on the measured rock physical properties, and combined with the Voigt–Reuss–Hill (VRH) average, differential effective medium (DEM) model and squirt-flow model, a tight rock attenuation model is proposed for analyzing the attenuation characteristics of fluid-saturated rocks at different confining pressures. The model reasonably describes the S-wave attenuation characteristics. The model predictions of S-wave attenuation show apparent pressure- and fluid-sensitivity at full saturation and partial saturation conditions. For sample TS1-19 at full saturation with different confining pressures, the S-wave peak attenuation predicted by the model ranges from 11.6 to 69.5, and decreases with confining pressure, while the relaxation frequency shifts to high frequency end. For the partial saturation condition of the sample, the predicted S-wave peak attenuation ranges from 15.5 to 39.8 at a confining pressure of 30 MPa and increases with water saturation, while the relaxation frequency shifts to low frequency end. For all the samples at 30MPa confining pressure, the predicted S-wave attenuation ranges from 5.6 to 38.6. At the full-saturation case, the predicted S-wave attenuation increases with porosity and decreases with confining pressure. For the partial saturation case, the S-wave attenuation predicted with the model and the Voigt and Reuss bounds generally increases with water saturation, whereas the experimentally-measured attenuation exhibits the peak attenuation at an intermediate saturation.

我国致密油气藏具有低孔、低渗、地层岩石非均质性明显等特点，显示出良好的勘探前景和较高的生产潜力。理清储层波响应与岩石物性之间的关系仍然是一个挑战，迫切需要进一步研究致密储层的波响应模式。岩石的剪切模量和横波衰减受到孔隙流体和围压性质的影响。对不同围压下的8个部分饱和致密砂岩样品进行了超声波实验，并利用谱比法估算了横波衰减。结果表明，横波衰减随着围压的增加而减小，含水饱和情况比含油饱和情况损失更大，而含气饱和情况衰减最小。一般而言，我们在气水部分饱和情况下观察到中间含水饱和度处的横波弛豫峰。横波衰减随着孔隙度或渗透率的增加而增加。基于实测岩石物性，结合Voigt-Reuss-Hill（VRH）平均值、微分有效介质（DEM）模型和喷流模型，提出了致密岩石衰减模型，用于分析流体衰减特性。不同围压下的饱和岩石。该模型合理地描述了横波的衰减特性。横波衰减的模型预测显示在完全饱和和部分饱和条件下明显的压力和流体敏感性。对于完全饱和状态下不同围压的TS1-19样品，模型预测的横波峰值衰减范围为11.6~69.5，且随围压的增加而减小，而弛豫频率向高频端移动。对于样品的部分饱和条件，预测围压30 MPa下横波峰值衰减范围为15.5~39.8，且随含水饱和度的增加而增大，而弛豫频率向低频端移动。对于30MPa围压下的所有样品，预测的横波衰减范围为5.6至38.6。在全饱和情况下，预测的横波衰减随着孔隙度的增加而增加，并随着围压的增加而减少。对于部分饱和情况，模型预测的横波衰减以及 Voigt 和 Reuss 界通常随着水饱和度的增加而增加，而实验测量的衰减在中间饱和度处呈现峰值衰减。