摘要
基于超声波速度测试的煤样脆性指数计算方法具有无损的特点,但究竟基于何种弹性参数计算方法效果更佳是值得深入探究的问题.为此,本文通过测试10组煤样沿0°、45°和90°三个方向的纵、横波速度,基于动杨氏模量和动泊松比(动弹性参数法),以及拉梅常数(拉梅常数法)分别计算两种脆性指数(BI(E_(d),υ_(d))和BI(λ,μ))及其误差(εBI(E_(d),υ_(d))和εBI(λ,μ)),以及脆性指数各向异性值(ABI(E_(d),υ_(d))和ABI(λ,μ)).进一步从脆性表征、计算精度和各向异性刻画三个方面对比分析两种方法的结算结果,分析表明:两种方法计算的煤样脆性指数相关性较高,但BI(E_(d),υ_(d))的变异系数显著高于BI(λ,μ),即具有更高的离散度;计算误差εBI(E_(d),υ_(d))的均值高于εBI(λ,μ),但除了个别煤样的εBI(E_(d),υ_(d))值较大外,绝大部分煤样的εBI(E_(d),υ_(d))值较低,在可接受范围内;个别煤样的ABI(λ,μ)为显著的负值,限制了该型脆性指数计算法在煤各向异性评价方面的适用性.综合而言,除了脆性指数为相对值(0~100)外,基于动弹性参数的脆性指数计算法性能更优,能够为煤层气储层脆性评价提供理论方法支撑.
It is a nondestructive method to calculate the Brittleness Index( BI) of coal samples by elastic parameters obtained from ultrasonic test data. However,which BI calculated by the elastic parameters perform best in the real production requires further analysis. Therefore,in this paper,we test the ultrasonic velocities of ten coal samples along three directions( 0°,45° and 90°),and then calculate two different brittleness indexes,brittleness index calculation errors( ε), and brittleness index anisotropy values( ABI) by the dynamic Young’s modulus and dynamic Poisson’s ratio( dynamic elastic parameter method),and Lame constants( Lame constant method),respectively. Thereafter,the calculation results are compared from the aspects of brittleness index characterization,calculation accuracy,and brittleness index anisotropy description.The comparison results show that the brittleness indexes calculated by the two methods are in a high correlation. The Variation Coefficients( VC) of the brittleness index calculated by the dynamic elastic parameter method are higher than those calculated by the Lame constant method,indicating a higher dispersion of the former.The average values of the brittleness index calculation error for the dynamic elastic parameter method are higher than those for the Lame constant method, while the brittleness index calculation errors calculated by the dynamic elastic parameter method are,with the exception of high values of individual coal samples,still within the acceptable range. The ABIof one test sample calculated by the Lame constant method has a significantly negative value,limiting the applicability of this method in analyzing the ABIcharacteristics of coal samples. Generally, except the brittleness index being expressed in a relative value( 0 ~ 100),the BI calculated by the dynamic elastic parameter method is more adaptable to characterizing the tested coal samples, and thus, can provide theoretical basis for production coal-bed methane reservoir brittleness evaluation.
作者
吴海波
董守华
张平松
黄艳辉
WU HaiBo;DONG ShouHua;ZHANG PingSong;HUANG YanHui(State Key Laboratory Mining Response and Disaster Prevention and Control in Deep Coal Mines,Anhui University of Science and Technology,Huainan 232001,China;School of Earth and Environment,Anhui University of Science and Technology,Huainan 232001,China;School of Resources and Geosciences,China University of Mining and Technology,Xuzhou 221116,China;State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing 102249,China)
出处
《地球物理学进展》
CSCD
北大核心
2021年第3期1138-1144,共7页
Progress in Geophysics
基金
安徽省自然科学基金(1908085QD169)
国家自然科学基金(41902167)
油气资源与探测国家重点实验室开放基金(PRP/open-2005)联合资助。
关键词
煤样
超声波速度
脆性指数
各向异性
变异系数
Coal sample
Ultrasonic velocity
Brittleness Index(BI)
Anisotropy
Variation Coefficients(VC)
