Estimation of Gas Loss in Methodology for Determining Methane Content of Coal Seams

Szlązak, N.; Obracaj, D.; Korzec, Marek

doi:10.3390/en14040982

Cited by 23 publications

(19 citation statements)

References 18 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The indirect method has many parameters, resulting in cumulative error and a long measurement period; the direct method is the primary method to measure the CSGC, which is widely applied both in China and the United States [6][7][8]. The error of this method comes from the calculation of the gas loss amount [9][10][11][12]. In China, the core tube sampling method is recommended to obtain the coal core samples (CCS) [13].…”

Section: Introductionmentioning

confidence: 99%

Temperature Variation Law of Core Tube Wall during Coring in Different Strength Coal Seams: Experiment and Modelling

et al. 2022

View full text Add to dashboard Cite

Temperature is the primary factor affecting the law of coal gas desorption. When the core method is used to measure the coal seam gas content (CSGS), the temperature of the coal core sample (CCS) will increase. The heat generated by the core bit cutting and rubbing the coal during coring is transferred to the CCS through the core tube, resulting in the temperature rising of the CCS. Because the CCS entering the core tube during coring is a dynamic process, the temperature of CCS is difficult to measure. To solve this problem, the temperatures of the core tube wall during coring in the Jiulishan coal mine (JLS), Guhanshan coal mine (GHS) and Zhaogu coal mine (ZG) at the core depth of 20 m were measured by the self-designed temperature measuring device. The thermodynamic models of the core bit and the core tube during coring were established. The reliability of the model was verified by comparing the numerical simulation results with the field measurement results. The verified model was used to predict the temperature changes of the core tube wall during coring in different strength coal seams and different core depths. The results show that the temperature change of the core tube wall was divided into a slowly temperature rising stage Ⅰ, a fast temperature rising stage Ⅱ and a slowly temperature rising and slowly temperature falling stage Ⅲ, which correspond to the process of pushing the core tube, drilling the CCS and early stage and later stage of withdrawing the core tube, respectively. The maximum temperature of the core tube wall appears in the first 3 min of withdrawing the core tube, and increases with the core depth increasing. The temperature of the measuring point at the end of drilling the CCS and the maximum temperature during coring linearly increase with the core depth. The temperature heating rate of the core tube is negatively linear, with the coal seam strength during pushing the core tube wall process. However, the temperature heating rate of the core tube wall is positively linear with the coal seam strength during drilling the CCS process. This study can provide a basis for further research on the dynamic distribution characteristics of temperature in the CCS during coring, which is of profound significance to calculate the gas loss amount and CSGC.

show abstract

Section: Introductionmentioning

confidence: 99%

Temperature Variation Law of Core Tube Wall during Coring in Different Strength Coal Seams: Experiment and Modelling

et al. 2022

View full text Add to dashboard Cite

show abstract

“…Coalbed methane desorption amount and desorption time show a typical curve (Figures , , and ) rather than a linear relationship. It is generally believed that the more seriously the coal body is damaged, the larger the exposed area is, and the smaller the particle is, the faster the desorption rate is. , The change of gas from adsorption state to free state is fast and continuous. With decreasing pressure difference, the gas is released in a law of deceleration (not uniform deceleration) all the time until it is in equilibrium with the ambient pressure.…”

Section: Resultsmentioning

confidence: 99%

Methodology for Lost Gas Determination from Exploratory Coal Cores and Comparative Evaluation of the Accuracy of the Direct Method

Ahmad

et al. 2021

ACS Omega

View full text Add to dashboard Cite

In the coal exploration of China, the commonly used direct method within 120 min has potential errors in lost gas calculation of deep coal seam for its complex geological conditions. The exploration of deep coal resources by drilling holes in Huainan of Eastern China offered an opportunity to starting research into developing a new method. A developed method with error analysis was constructed to estimate the lost gas using the total desorption process obtained from exploratory coal cores. The accuracy of the direct method was also evaluated comparatively. The result shows that the desorption curve of tested coal samples matches the fitted curve equation. Desorption temperature and the tectonic coal with associated pore characteristics significantly affect the variation of the adsorption characteristics and the estimation of lost gas. The direct method obviously underestimates the lost gas, and methodology using a new lost gas estimation procedure with additional residual gas allows for achieving relatively accurate results of the determination of gas content in coal seams. The calculated result of the new method is about 1.00–1.41 times that of the direct method. The error analysis of desorption results allowed us to determine the dependence between the time (retrieval time and desorption time) and determination method. The time used for desorption in the tank is allowed to extend to less than 400 min or more than 1000 min, which is very potentially important to accurately get the coalbed gas content for coring samples, especially deep exploratory cores for field application.

show abstract

“…According to this procedure the gas loss is 12%. The estimation of gas loss in methodology for determining methane content of coal seams has been presented previously by the authors [1].…”

Section: Methodology For the Determination Methane Content Of Coalmentioning

confidence: 99%

“…The determination of this parameter in Polish mines is conducted based on the direct method, and the sample for analysis is taken in the form of drill cuttings from a borehole performed in the coal seam. The methodology of conducting the determination has been presented previously by the authors [1] and has been adopted as the national standard [2]. The research basis for the method, its scope of application and uncertainty of measurement according to the method have also been presented by the authors [1,3].…”

Section: Introductionmentioning

confidence: 99%

“…The methodology of conducting the determination has been presented previously by the authors [1] and has been adopted as the national standard [2]. The research basis for the method, its scope of application and uncertainty of measurement according to the method have also been presented by the authors [1,3]. In the world mining industry, the methane content of coal seams is mostly determined using direct methods, which are more accurate than indirect methods [4][5][6][7].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

2021

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Estimation of Gas Loss in Methodology for Determining Methane Content of Coal Seams

Cited by 23 publications

References 18 publications

Temperature Variation Law of Core Tube Wall during Coring in Different Strength Coal Seams: Experiment and Modelling

Temperature Variation Law of Core Tube Wall during Coring in Different Strength Coal Seams: Experiment and Modelling

Methodology for Lost Gas Determination from Exploratory Coal Cores and Comparative Evaluation of the Accuracy of the Direct Method

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

Contact Info

Product

Resources

About