钻屑法测定瓦斯含量存在问题分析及改进

Analysis on Problems Existed in Gas Content Measurement with Drilling Cuttings Method and Improvement

针对传统钻屑法测定瓦斯含量精度不高的问题,分析了该测定方法的特点和影响因素,根据煤岩力学理论提出了瓦斯含量测定的修正方案。研究发现,受煤的孔隙结构和解吸能力等特性影响,钻屑法瓦斯含量测定方法不适合于低阶煤;钻屑质量与钻孔深度之间存在非线性关系,其决定因素是地应力控制下的煤岩扩容效应。通过引入煤岩扩容理论,提出了钻屑结构计算方法和气体补偿理论,现场瓦斯含量测定结果显示,与传统测定方法相比,修正方法的测试精度可提高8%~15%,有效降低了测试误差。

According to a low gas content accuracy measured with a conventional drilling cuttings method,the paper analyzed the features and influence factors of the measuring method.According to the coal and rock mechanics theory,a revised plan of the gas content measurement was provided.The study results found that with the influences of the coal pore structure,desorption capacity and other features,the gas content measuring method with the drilling cuttings method could not be suitable for the low rank coal.There was a nonlinear relationship between the drilling cuttings quality and the drilling depth and the decisive factor would be the coal and rock volume expansion effect under the control of the geostress.With the introduction of the coal and rock volume expansion theory,the drilling cuttings structure calculation method and the gas compensation theory were provided.The site gas content measured results showed that in comparison with the conventional measuring method,the measuring accuracy of the revised method could be improved by 8% ~15% and the measuring error could be effectively reduced.