Velocity dispersion and fluid substitution in sandstone under partially saturated conditions  

作　　者：Ma Xiao-Yi Wang Shang-Xu Zhao Jian-Guo Yin Han-Jun Zhao Li-Ming 

机构地区：[1]State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum (Beijing), Beijing 102249, China

出　　处：《Applied Geophysics》2018年第2期188-196,361,362,共11页应用地球物理（英文版）

基　　金：supported by 973 Program "Fundamental Study on the Geophysical Prospecting of the Deep-layered Oil and Gas Reservoirs"(No.2013CB228600)

摘　　要：The elastic moduli of four sandstone samples are measured at seismic （2-2000 Hz） and ultrasonic （1 MHz） frequencies and water- and glycerin-saturated conditions. We observe that the high-permeability samples under partially water-saturated conditions and the low-permeability samples under partially glycerin-saturated conditions show little dispersion at low frequencies （2-2000 Hz）. However, the high-permeability samples under partially glycerin-saturated conditions and the low-permeability samples under partially water-saturated conditions produce strong dispersion in the same frequency range （2-2000 Hz）. This suggests that fluid mobility largely controls the pore-fluid movement and pore pressure in a porous medium. High fluid mobility facilitates pore-pressure equilibration either between pores or between heterogeneous regions, resulting in a low-frequency domain where the Gassmann equations are valid. In contrast, low fluid mobility produces pressure gradients even at seismic frequencies, and thus dispersion. The latter shows a systematic shift to lower frequencies with decreasing mobility. Sandstone samples showed variations in Vp as a function of fluid saturation. We explore the applicability of the Gassmann model on sandstone rocks. Two theoretical bounds for the P-velocity are known, the Gassmann-Wood and Gassmann-Hill limits. The observations confirm the effect of wave-induced flow on the transition from the Gassmann-Wood to the Gassmann-Hill limit. With decreasing fluid mobility, the P-velocity at 2-2000 Hz moves from the Gassmann-Wood boundary to the Gassmann-Hill boundary. In addition,, we investigate the mechanisms responsible for this transition.四件沙岩样品的有弹性的 moduli 被测量在地震(22000 Hz ) 并且超声(1 MHz ) 频率和浸透水、浸透甘油的条件。我们观察到在部分浸透水的条件下面的高渗透的样品和在部分浸透甘油的条件下面的低渗透的样品在低频率(22000 Hz ) 显示出很少分散。然而，在部分浸透甘油的条件下面的高渗透的样品和在部分浸透水的条件下面的低渗透的样品在一样的频率范围(22000 Hz ) 生产强壮的分散。这建议那液体活动性大部分在多孔的媒介控制毛孔液体运动和毛孔压力。高液体活动性便于在毛孔之间或在异构的区域之间的毛孔压力使平衡，导致 Gassmann 方程是有效的一个低频率的领域。相反，低液体活动性甚至在地震频率生产压力坡度，并且这样分散。后者显示系统的移动与减少的活动性降低频率。沙岩样品在 V <sub 显示出变化 > p </sub> 作为液体的功能浸透。我们在沙岩岩石上探索 Gassmann 模型的适用性。为 P 速度的二理论界限被知道， Gassmann 木头和 Gassmann 山限制。观察从 Gassmann 木头在转变上证实导致波浪的流动的效果到 Gassmann 山限制。与减少的液体活动性，在 2-2000 Hz 的 P 速度从 Gassmann 木头边界搬到 Gassmann 山边界。另外，，我们调查为这转变负责的机制。

关 键 词：SANDSTONE SATURATION P-WAVE DISPERSION Gassmann fluid substitution 

分 类 号：TF3[冶金工程—冶金机械及自动化]