The Determination of the Methane Content of Coal Seams Based on Drill Cutting and Core Samples from Coal Mine Roadway

Abstract

The determination of methane content of coal seams is conducted in hard coal mines in order to assess the state of methane hazard but also to evaluate gas resources in the deposit. In the world’s mining industry, natural gas content in coal determination is usually based on direct methods. It remains the basic method in Poland as well. An important element in the determination procedure is the gas loss that occurs while collecting a sample for testing in underground conditions. In the method developed by the authors, which is a Polish standard, based on taking a sample in the form of drill cuttings, this loss was established at a level of 12%. Among researchers dealing with the methane content of coal, there are doubts related to the procedures adopted for coal sampling and the time which passes from taking a sample to enclosing it in a sealed container. Therefore, the studies were designed to evaluate the degree of degassing of the sample taken in the form of drill cuttings according to the standard procedure and in the form of the drill core from a coal mine roadway. The results show that the determinations made for the core coincide with the determinations made for the drill cutting samples, with the loss of gas taken into account.

Increasing Safety in an Underground Coal Mine through Degasification by Vertical Wells—Influence of the Relationship between the Permeability of Carbon and the Filter Cake of the Bentonite Suspension

“…Figure 3 shows the underground mining gallery in the coal layer crossing the vertical well, and the laboratory tests on the Pastora layer coal samples. A new methodology to avoid gas loss while samples are collected by drill cutting was developed by [25]. The coal properties used in this study are shown in Table 1.…”

Low-Temperature Response Characteristics of Coalbed Methane Desorption under High and Low Destruction Degrees

“…Coal seam gas content is a key parameter in the exploration and development of coalbed methane resources, which can effectively predict the occurrence of protrusion, examine the effectiveness of regional antisurge, and evaluate the degree of coal mine gas hazard. – The methods of coal bed gas content determination are divided into direct method – and indirect method. , The process of the indirect method to determine coal seam gas content is complicated, the measurement period is long, and the success rate is low, so the direct method is mostly used to measure coal seam gas content underground in China. The direct method of measuring coal seam gas content mainly includes three parts: determination of gas desorption in underground coal samples, determination of residual gas in a laboratory, and extrapolation of gas loss during sampling, of which the first two parts can be measured according to relevant requirements, and the results are real and reliable.…”

Experimental Study on Gas Loss Derived from Positive Pressure

“…The desorption and residual can be accurately determined in the laboratory, while the loss can only be calculated by some theoretical methods, and the calculation consequences will directly dominate the accuracy of the gas content. The sampling method has a significant impact on the loss determination results . The larger the particle size is, the smaller the loss is .…”

“…The sampling method has a significant impact on the loss determination results. 7 The larger the particle size is, the smaller the loss is. 8 The traditional loss calculation method is based on the law of gas desorption under normal pressure, 9 which is contradictory to the positive pressure sampling environment in engineering applications, and hence, this method is prone to leading to excessive error in both theory and practical applications.…”