Laboratory tests were conducted to analyze the ultrasonic velocity response to the pressure change in dry carbonate rocks from the Weyburn oilfield, Canada. Twenty-four samples are from seven wells with helium porosities ranging from 1% to 29%. Thin-section images, SEM and mercury intrusion porosimetry were performed to show their inner structures and pore throat size distributions. P- and S-wave velocities (V_p and V_s) measurements were first done under hydrostatic loading and then while unloading, with confining pressures varying between 3 and 35 MPa. The results indicate that V_p and V_s in these samples follow a linear relation independent of the pressure change. The ratio V_p/V_s is more responsive to pressure change irrespective of the pore volume. One-third of the carbonate samples show abnormal V_p/V_s reduction with the increase in the effective pressure. The pressure dependence of velocities (PDV) of Weyburn carbonate rocks varies widely even for samples from the same formation with similar sedimentary history. Samples with loosely packed crystals and/or relatively large dominant pore diameter have higher PDV. The exponential empirical model V = \(A-C\text{e}^{DP_{\text{e}}}\) was tested; therein, V is the elastic wave velocity, P_e is the effective confining pressure, and A, C and D are the best fitting coefficients determined by curve fitting. The model gives good fits for most of the Weyburn carbonate samples. From a statistical point of view, there is no difference between the V_p- and V_s-derived exponential coefficient D.

进行了实验室测试，以分析对来自加拿大 Weyburn 油田的干燥碳酸盐岩压力变化的超声波速度响应。24 个样品来自 7 个气孔，氦气孔隙率在 1% 到 29% 之间。进行薄片图像、SEM 和压汞孔隙率测定以显示它们的内部结构和孔喉尺寸分布。P 波和 S 波速度（V _p和V _s）测量首先在静水载荷下进行，然后在卸载时进行，围压在 3 到 35 MPa 之间变化。结果表明，这些样品中的V _p和V _s遵循与压力变化无关的线性关系。比例V _p / V _s对压力变化更敏感，而与孔体积无关。随着有效压力的增加，三分之一的碳酸盐样品显示出异常的V _p / V _s降低。即使对于来自具有相似沉积历史的同一地层的样品，Weyburn 碳酸盐岩的速度压力依赖性 (PDV) 也有很大差异。具有松散堆积晶体和/或相对较大的主要孔径的样品具有较高的 PDV。测试了指数经验模型V  =  \(AC\text{e}^{DP_{\text{e}}}\)；其中，V为弹性波速度，P _e为有效围压，A、C、D为曲线拟合确定的最佳拟合系数。该模型非常适合大多数 Weyburn 碳酸盐样品。从统计的角度来看，V _p和V _s导出的指数系数D之间没有差异。