GAS CONTENT OF A COAL SEAM FACE AREA DURING THE HIGHPERFORMANCE EXTRACTION SECTION OPERATION

Coal, a solid fuel in its natural state has been identified as one of the world's major fossil fuels. It is a compact, stratified mass of mummified plant debris interspersed with smaller amounts of inorganic matter buried in sedimentary rocks. The use of coal as an energy source can be dated back to the prehistoric times. Methane is associated with many if not all coal seams, and is the dreaded “fire damp” responsible for many pit explosions. Coal mines are designed to vent as much methane as possible. It is present in the pores of coal under pressure, released during mining operations and can be extracted through vertical well bores. This paper highlights the fact that pipeline- quality methane can be extracted economically from coal seems before and during underground mining operations. The stimulation method involves hydraulic fracturing of the coal seam by using water, sand and, a gelling agent in a staged and alternating sand/and no sand sequence. The purpose is to create new fractures in the coal seam(s). The cleating of the coal helps to determine the flow characteristics of the coal formation and is vital in the initial productivity of a coal-methane well. The simple calculation of gas-in-place is achieved by multiplying the gas content of the coal by net coal thickness, the density, and the aerial extent of the drainage. The method is claimed to be suitable for use in Nigeria and potential sites for coal bed methane extraction in Nigeria are identified.

Download Full-text

Study on Reservoir Properties and Critical Depth in Deep Coal Seams in Qinshui Basin, China

Advances in Civil Engineering ◽

10.1155/2019/1683413 ◽

2019 ◽

Vol 2019 ◽

pp. 1-7

Author(s):

Guiqiang Zheng ◽

Bin Sun ◽

Dawei Lv ◽

Zhejun Pan ◽

Huiqing Lian

Keyword(s):

Coal Seam ◽

Step Change ◽

Gas Content ◽

Burial Depth ◽

Critical Depth ◽

Coal Seams ◽

Reservoir Properties ◽

Qinshui Basin ◽

Geological Conditions ◽

Change Characteristics

Coalbed methane (CBM) reservoir properties and relationship of properties with burial depth were studied based on the data derived from 204 deep CBM production wells in Qinshui Basin, China. Through the study, it is found that permeability and porosity decrease with the increase of burial depth and the decreasing trend shows step-change characteristics at a critical burial depth. They also show divisional characteristics at certain burial depth. Gas content, geostress, and geotemperature increase with the increase of burial depth, and the increasing trend shows step-change characteristics and also have divisional characteristics at certain burial depth. Based on the previous study on the reservoir property changes with burial depth, three series of critical depth using different parameters are obtained through simulating the critical depth using the BP neural network method. It is found that the critical depth is different when using different parameters. Combined the previous study with the normalization of three different parameter types, the critical depth in Qinshui Basin was defined as shallow coal seam is lower than 650 m and transition band is 650–1000 m, while deep coal seam is deeper than 1000 m. In deep coal seams, the geological conditions and recovery becomes poor, so it can be defined as unfavorable zones. Therefore, other development means, for example, CO2 injection, need to be used to accelerate the deep coal methane development.

Download Full-text

Quantitative Evaluation of Coal Seam Gas Content Estimate Accuracy

10.2118/29577-ms ◽

1995 ◽

Cited By ~ 3

Author(s):

Matthew J. Mavor ◽

Timothy J. Pratt ◽

Charles R. Nelson

Keyword(s):

Coal Seam ◽

Quantitative Evaluation ◽

Gas Content ◽

Coal Seam Gas

Download Full-text

Study on Well Logging Technology with Methods of Evaluating Gas Content of Coal-Bed Methane Reservoir

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1003.183 ◽

2014 ◽

Vol 1003 ◽

pp. 183-187

Author(s):

Huai Jie Yang ◽

He Ping Pan

Keyword(s):

Statistical Analysis ◽

Coal Seam ◽

Well Logging ◽

Langmuir Equation ◽

Gas Content ◽

Coal Bed ◽

High Yield ◽

Coal Bed Methane ◽

Analysis Method ◽

Statistical Analysis Method

In this study, the well logging response of CBM reservoir have been analyzed, and discussing the factors that affect the gas content of coal seam. The well logging technology has been employed in connection with log data and gas content. Take one oilfield’s well logging data for example, statistical analysis method and Langmuir equation method are selected to calculate the gas content of one coal seam, the two calculated results are basically the same, the highest value are about 26 cm3/g, is a high-yield coal seam.

Download Full-text

The Studies on Gas-Bearing Characteristics of Deep Coal Seams in Yanchang Oil and Gas Province, China

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.962-965.213 ◽

2014 ◽

Vol 962-965 ◽

pp. 213-216

Author(s):

Guo Ping Jiang

Keyword(s):

Coal Seam ◽

Layer Thickness ◽

Oil And Gas ◽

Single Layer ◽

Gas Content ◽

Coal Bed ◽

Coal Seams ◽

Resource Potential ◽

Gas Bearing ◽

Average Layer Thickness

In this paper, four general directions are described to make evaluations and their resource potential; those are coal structure and coal level, gas content of deep coalbed, the coalbed thickness and distribution and the buried depth of coalbed. Coalfields of the study area are mainly Permian and Carboniferous coal seam of Shanxi Formation coal and Benxi group 11 # coal, coal seam depth 1370-1812m. No. 3 coal-seam average layer thickness of 1.6 m, the monolayer most 2 m thick; No. 11 coal-seam in the average layer thickness of 3 m, single-layer thickness of 4.5 m. Predict the amount of coal resources of 17.3 one hundred million t. Predict coal-bed methane resources of 27.68 billion cubic reserve abundance of 104 million square / km2 in. The exploration results show that this region has good development prospects.

Download Full-text

Nitrogen Injection To Flush Coal Seam Gas Out Of Coal: An Experimental Study

Archives of Mining Sciences ◽

10.1515/amsc-2015-0067 ◽

2015 ◽

Vol 60 (4) ◽

pp. 1013-1028 ◽

Cited By ~ 7

Author(s):

Lei Zhang ◽

Naj Aziz ◽

Ting Ren ◽

Jan Nemcik ◽

Shihao Tu

Keyword(s):

Coal Seam ◽

Clean Energy ◽

Gas Content ◽

Coal Seams ◽

Coal Seam Gas ◽

Gas Recovery ◽

Nitrogen Injection ◽

Gas Desorption ◽

Effective Role ◽

Study Laboratory

Abstract Several mines operating in the Bulli seam of the Sydney Basin in NSW, Australia are experiencing difficulties in reducing gas content within the available drainage lead time in various sections of the coal deposit. Increased density of drainage boreholes has proven to be ineffective, particularly in sections of the coal seam rich in CO2. Plus with the increasing worldwide concern on green house gas reduction and clean energy utilisation, significant attention is paid to develop a more practical and economical method of enhancing the gas recovery from coal seams. A technology based on N2 injection was proposed to flush the Coal Seam Gas (CSG) out of coal and enhance the gas drainage process. In this study, laboratory tests on CO2 and CH4 gas recovery from coal by N2 injection are described and results show that N2 flushing has a significant impact on the CO2 and CH4 desorption and removal from coal. During the flushing stage, it was found that N2 flushing plays a more effective role in reducing adsorbed CH4 than CO2. Comparatively, during the desorption stage, the study shows gas desorption after N2 flushing plays a more effective role in reducing adsorbed CO2 than CH4.

Download Full-text

Reasons and Control Countermeasures of Special Soft Coal Roadway Deformation in Liangbei Coal Mine

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.671-674.1144 ◽

2013 ◽

Vol 671-674 ◽

pp. 1144-1149

Author(s):

Le Tuan Cheng ◽

Jia Lin Zhang ◽

Zheng Sheng Zou ◽

Qing Bo Li

Keyword(s):

Coal Seam ◽

Coal Mine ◽

Mining Area ◽

Gas Content ◽

Deformation And Failure ◽

Gas Outburst ◽

Soft Coal ◽

Coal Roadway ◽

Roadway Stability ◽

Roadway Deformation

B1 coal seam located at -550m level in Liangbei Coal Mine is a typical "three-soft" seam. The coal roadway with a depth of 610-750m lies under the critical softening depth of the roadway, and its support difficulty coefficient is 1.5-2.0. The coal has poor air permeability, high gas content and high gas pressure, so danger degree of the gas outburst is relatively strong. The coal seam was destroyed in a disastrous state by more than 100 boreholes for gas outburst prevention during the excavation. This results in the difficulty in the roadway support. Engineering geological characteristics of the coal roadway at 11 mining area are introduced. Based on the engineering geo-mechanics method, the reasons of deformation and failure of the coal roadway are analyzed. In view of problems in excavation and support, as well as the type of the coal roadway deformation mechanism, the borehole parameters are optimized for the gas outburst prevention, and bolt-net-cable coupling support with high convex steel-belt is used to control the coal roadway stability at 11 mining area. Practice shows that the effect is fine.

Download Full-text

Model of Prediction of Gas Emission based on Gas Content Uncertainty in Coal Mine using Geostatistical Simulation and Monte Carlo Method

10.21203/rs.3.rs-607234/v1 ◽

2021 ◽

Author(s):

Shokofe Rahimi ◽

Majid Ataee-pour ◽

Hasan Madani

Keyword(s):

Monte Carlo ◽

Coal Seam ◽

Ventilation System ◽

Prediction Method ◽

Simulation Method ◽

Worker Safety ◽

Gas Content ◽

Geostatistical Simulation ◽

Gas Emission ◽

Factors Affecting

Abstract It is very difficult to predict the emission of coal gas before the extraction, because it depends on various geological, geographical and operational factors. Gas content is a very important parameter for assessing gas emission in the coal seam during and after the extraction. Large amounts of gas released during the mining cause concern about adequate airflow for the ventilation and worker safety. Hence, the performance of the ventilation system is very important in an underground mine. In this paper, the gas content uncertainty in a coal seam is first investigated using the central data of 64 exploratory boreholes. After identifying the important coal seams in terms of gas emission, the variogram modeling for gas content was performed to define the distribution. Consecutive simulations were run for the random evaluation of gas content. Then, a method was proposed to predict gas emission based on the Monte Carlo random simulation method. In order to improve the reliability and precision of gas emission prediction, various factors affecting the gas emission were investigated and the main factors determining the gas emission were identified based on a sensitivity analysis on the mine data. This method produced relative and average errors of 2% and 0.57%, respectively. The results showed that the proposed model is accurate enough to determine the amount of emitted gas and ventilation. In addition, the predicted value was basically consistent with the actual value and the gas emission prediction method based on the uncertainty theory is reliable.

Download Full-text

Investigation of Large-Diameter Borehole for Enhancing Permeability and Gas Extraction in Soft Coal Seam

Geofluids ◽

10.1155/2020/6618590 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Yongwen Wang ◽

Wanjun Yan ◽

Zhongjiu Ren ◽

Zhiqiang Yan ◽

Ziwen Liu ◽

...

Keyword(s):

Coal Seam ◽

Shear Failure ◽

Large Diameter ◽

Gas Content ◽

Gas Extraction ◽

Extraction Area ◽

Damage Area ◽

Soft Coal ◽

Coal Deformation ◽

Soft Coal Seam

The efficiency of gas extraction from the soft coal seam with ultralow permeability is low. Gas extraction with large-diameter borehole is proposed to deplete gas content for preventing gas outburst disaster in this study. The fractures around the large borehole will enhance the permeability in the damage area to promote gas extraction. We established a damage-stress-seepage coupling model for large-diameter borehole gas extraction in soft coal seam. This mathematical model contains governing equations of gases sorption and transport, coal deformation, and damage, reflecting the coupling responses between gas and coal seam. The model is solved by the finite element method to simulate the gas drainage large-diameter borehole through roadway. Distributions of elastic modulus, damage area, and maximum principal stress in soft coal seam with different borehole diameters including 94 mm, 133 mm, 200 mm, and 300 mm are analyzed. The gas pressure, gas content, and effective extraction area in soft coal seam are discussed. Results show that the shear failure zone appears around the large-diameter borehole, and its permeability rises sharply. This opens up the gas transport channel and is conducive to the rapid extraction. It is confirmed that gas extraction using large-diameter borehole (300 mm) can greatly improve the efficiency of the gas preextraction in soft coal seam by increasing gas extraction rate. These provide a foundation for guiding the operation of gas extraction with large borehole from the soft coal seam in the field.

Download Full-text