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

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 wit h 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 suit able 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 ro ck volume expansion effect under the control of the geostress. With the introduction of the coal and rock volume expansion theory, the drilling cuttings structure calculat ion method and the gas compensation theory were provided. The site gas content measured results showed that in comparison with the conventional measuring metho d, the measuring accuracy of the revised method could be improved by 8% ~ 15% and the measuring error could be effectively reduced.