页岩岩屑高精度波速测量的仪器与方法

Instruments and methods with high-precision for wave velocity measurement on shale debris

压裂改造是页岩气开发的关键技术,岩石的脆性评价是储层可改造性的重要参数之一。实验室中通常利用岩芯柱进行波速测量,获得杨氏模量和泊松比以评价页岩的脆性系数。但规则的页岩岩芯很难获得。为此,利用非规则的页岩岩屑,设计并提出了一套基于脉冲回声法的岩屑高精度波速测量的仪器和方法。分析了影响岩屑波速测量精度的主要因素,引入了新针式高频声波探头和新数字信号分析方法,利用脉冲回声法,通过提高采样率和信噪比、使用自相关的方法来提高精度,形成了一套页岩岩屑高精度波速测量的仪器与方法。同时试验结果也与规则岩芯测量结果进行了对比,证实了此仪器与方法的可靠性。

Hydraulic fracturing is the key technology for shale gas development. Brittleness is one of the most important parameters to evaluate the fracability of shales. One of the most commonly used methods in laboratory is the measurement of wave velocity of pillar core,to obtain Young＇s modulus and Poisson＇s ratio, so as to evaluate the rock brittleness coefficient. However, it is difficult to obtain regular shale core samples. Therefore, in this study, we develop a new device and a novel method with high precision to measure the velocity of shale debris based on pulse echo. Major factors that influence the measurement precision of shale debris wave velocity are analyzed. This study also proposes a new pin-type high frequency sound wave probe and a digital signal processing data analysis method. The measurement precision is improved by increasing sampling frequency and signal,to-noise ratio as well as using the autocorrelation method and pulse echo method. The comparison between results from regular core and debrisconfirms the reliability of the proposed procedure.