scholarly journals Relation between basic coal seam parameters and their gas saturation for Dobrudzha coal field, NE Bulgaria

2021 ◽  
Vol 280 ◽  
pp. 08006
Author(s):  
Nikolay Hristov ◽  
Efrosima Zaneva-Dobranova ◽  
Gergana Meracheva ◽  
Viktoriia Dmytrenko ◽  
Yuriy Vynnykov
Keyword(s):  
Coal Seam ◽  
Energy Resource ◽  
Point Of View ◽  
Coal Seams ◽  
Gas Saturation ◽  
The North ◽  
Geological Conditions ◽  
Petrophysical Model ◽  
Basic Parameters ◽  
Size And Morphology

One of the main natural gas contained in the coal seams is methane. Most of it is adsorbed on the surface of the coal matrix, another is in free state in different in size and morphology pore spaces or dissolved gas in the waters that associate with the coal seams. The form of presence and the degree of gas saturation depends on the rank of the carbonization process, the petrophysical and physicochemical parameters of the environment. Methane in coal seams is accepted to be categorized as an unconventional energy resource. From this point of view, it is of interest in the Dobrudzha coal basin, located in the North-eastern part of Bulgaria. The specific geological conditions of the basin, the limited study, the presence of a thick covering aquifer make it difficult to extract coal by traditional methods. This requires the use of non-popular for the country methods for energy extraction and establishing relation between the basic parameters of coal seams and their gas saturation. The existing geological-geophysical, drilling and laboratory information is combined in a detailed petrophysical model, which extends over the best presented and studied coal seam (m5) from the field. The basic parameters that reflect the amount of adsorbed gas and are the subject of study are the content of moisture, carbon, ash and the degree of carbonization, expressed by the vitrinite and its reflectance.

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

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.

Deep Sinking for Coal in the Wyre Forest Coal-Field

The Geologist ◽  
1861 ◽  
Vol 4 (11) ◽  
pp. 468-469
Author(s):  
George E. Roberts
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
The Other ◽  
Coal Field ◽  
Coal Seams ◽  
North West ◽  
The North ◽  
Western Border ◽  
Shaft Sinking ◽  
Considerable Range

Some other memoranda which I find among my papers relating to this work (for a section of which, with particulars of shaft-sinking, see “Geologist” of last month) may not be unacceptable to your coal-mining readers.The spot where the shaft was sunk was 476 feet above the level of the Severn Valley Railway at Eymoor, and about 510 feet above the ordinary height of the River Severn, from which it was distant about two miles. The coal seam met with and worked at the depth of 176 yards, has in other parts of the coal-field a thickness of four feet. The colliers regard it as a Flying Reed (red?) coal. Two of the thin coal-seams afterwards sunk through were entirely made up of the remains of Sigillariæ; the coal, in consequence, was “long grained” and slaty. These Sigillarian coals have a considerable range through the Wyre Forest field, and in common with most of the other seams, crop out along the western border. At the Baginswood pits, in the north-west corner of the coal·field, the upper coal, two feet four inches in thickness, worked by hand-draw, being only ten yards from surface, is a most interesting seam, made up entirely of compressed Sigillariæ.

scholarly journals Floor failure depth of upper coal seam during close coal seams mining and its novel detection method

2017 ◽  
Vol 36 (5) ◽  
pp. 1265-1278 ◽  
Author(s):  
Wei Zhang ◽  
Dongsheng Zhang ◽  
Dahong Qi ◽  
Wenmin Hu ◽  
Ziming He ◽  
...  
Keyword(s):  
Stress Distribution ◽  
Coal Seam ◽  
Mechanical Model ◽  
Coal Pillar ◽  
Coal Seams ◽  
Geological Conditions ◽  
Floor Failure ◽  
Calculation Results ◽  
Failure Depth ◽  
Close Coal Seams

The primary problem needed to be solved in mining close coal seams is to understand quantitatively the floor failure depth of the upper coal seam. In this study, according to the mining and geological conditions of close coal seams (#10 and #11 coal seams) in the Second Mining Zone of Caocun Coal Mine, the mechanical model of floor failure of the upper coal seam was built. Calculation results show that the advanced abutment pressure caused by the mining of the upper coal seam, resulted in the floor failure depth with a maximum of 26.1 m, which is 2.8 times of the distance between two coal seams. On this basis, the mechanical model of the remaining protective coal pillar was established and the stress distribution status under the remaining protective coal pillar in the 10# coal seam was then theoretically analysed. Analysis results show that stress distribution under the remaining protective coal pillar was significantly heterogeneous. It was also determined that the interior staggering distance should be at least 4.6 m to arrange the gateways of the #209 island coalface in the lower coal seam. Taken into account a certain safety coefficient (1.6–1.7), as well as reducing the loss of coal resources, the reasonable interior staggering distance was finally determined as 7.5 m. Finally, a novel method using radon was initially proposed to detect the floor failure depth of the upper coal seam in mining close coal seams, which could overcome deficiencies of current research methods.

scholarly journals Theory and Application of Gob-Side Entry Retaining in Thick Three-Soft Coal Seam

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Junchao Shen ◽  
Ying Zhang
Keyword(s):  
Coal Seam ◽  
Engineering Practice ◽  
Coal Seams ◽  
High Resource ◽  
Soft Coal ◽  
Geological Conditions ◽  
Body Construction ◽  
Roadway Support ◽  
Soft Coal Seam ◽  
Engineering Scheme

With the characteristic of less roadway excavation and high resource recovery, gob-side entry retaining (GER) technology is a safe and efficient green mining technology. Many experts and scholars have done extensive research on its principle and application. However, GERs are rarely used in thick soft coal seams. In this paper, based on the geological conditions of a coal mine in China, we propose a novelty approach of GER in thick three-soft coal seam (it means a single seam with a soft roof and a soft floor). The engineering scheme includes roadway expansion, large section roadway support, cutting roof to relieve pressure, and road-inside backfill body construction. The established mechanical and numerical calculation models effectively guide the engineering practice. Field observations showed that all the processes met the requirements of field production. The research results could provide theoretical guidance for the application of GER under similar geological conditions.

Impact of in-seam drilling performance on coal seam gas production and remaining gas distribution

2019 ◽  
Vol 59 (1) ◽  
pp. 328
Author(s):  
Fengde Zhou ◽  
Glen Fernandes ◽  
Joao Luft ◽  
Kai Ma ◽  
Mahmoud Oraby ◽  
...  
Keyword(s):  
Coal Seam ◽  
Gas Production ◽  
Gas Content ◽  
Gas Distribution ◽  
Coal Seams ◽  
Coal Seam Gas ◽  
Gas Saturation ◽  
Drilling Performance ◽  
Permeability Anisotropy ◽  
The Impact

Drilling horizontal wells in low permeability coal seams is a key technology to increase the drainage area of a well, and hence, decrease costs. It’s unavoidable that some parts of the horizontal section will be drilled outside the targeted coal seam due to unforeseen subsurface conditions, such as sub-seismic faulting, seam rolls, basic geosteering tools, drilling practices and limited experiences. Therefore, understanding the impact of horizontal in-seam drilling performance on coal seam gas (CSG) production and remaining gas distribution is an important consideration in drilling and field development plans. This study presents a new workflow to investigate the impact of horizontal in-seam performance on CSG production and gas distribution for coal seams with different porosity, permeability, permeability anisotropy, initial gas content (GC), initial gas saturation and the ratio of in-coal length to in-seam length (RIIL). First, a box model with an area of 2 km × 0.3 km × 6 m was used for conceptual simulations. Reduction indexes of the cumulative gas production at the end of 10 years of simulations were compared. Then, a current Chevron well consisting of a vertical well and two lateral wells, was selected as a case study in which the impact of outside coal drilling on history matching and remaining gas distribution were analysed. Results show that the RIIL plays an increasing role for cases with decreasing permeability or initial gas saturation, while it plays a very similar role for cases with varied porosity, permeability anisotropy and GC. The size and location of outside coal drilling will affect the CSG production and remaining gas distribution.

Recent Patents on Thin Coal Seam Mining Equipment

2020 ◽  
Vol 13 (2) ◽  
pp. 99-108
Author(s):  
Yanxiang Wang ◽  
Daolong Yang ◽  
Bangsheng Xing ◽  
Tingting Zhao ◽  
Zhiyi Sun ◽  
...  
Keyword(s):  
Coal Seam ◽  
Underground Space ◽  
Mining Method ◽  
Mining Equipment ◽  
Coal Seams ◽  
Thin Coal Seam ◽  
Recoverable Reserves ◽  
Working Face ◽  
Geological Conditions ◽  
Seam Mining

Background:: China's thin and extremely thin coal seam resources are widely distributed and rich in reserves. These coal seams account for 20% of the recoverable reserves, with 9.83 billion tons of industrial reserves and 6.15 billion tons of recoverable reserves. Objective: Due to the complex geological conditions of the thin coal seam, the plow mining method cannot be effectively popularized, and the drum mining method is difficult to be popularized and applied in small and medium-sized coal mines, so it is necessary to find other more advantageous alternative mining methods. Methods: The equipment integrates mining operations, conveying operations, and supporting operations, and is suitable for mining short and extremely thin coal seam with a height of 0.35m-0.8m and width of 2m-20m. It has the advantages of the low body of the shearer, no additional support on the working face, and small underground space. The mining efficiency of thin coal seam and very thin coal seam can be improved and the mining cost can be reduced. Results: Thin coal seam shear mining combines mining, conveying, and supporting processes together and has the advantages of a low fuselage, no extra support required for the working face, and feasibility in a small underground space. Conclusion: The summarized mining method can improve the mining efficiency of thin and extremely thin coal seams, reduce mining costs, and incorporate green mining practices, which take both mining economy and safety into account.

Gas Disaster Governance of Rock Cross-Cut Coal Uncovered in Extremely Inclined Outburst Coal Seam

2014 ◽  
Vol 962-965 ◽  
pp. 1147-1152 ◽  
Author(s):  
Hong Qing Zhu ◽  
Bei Fang Gu ◽  
Min Bo Zhang ◽  
Cheng Yi Yang ◽  
Xiang Shen
Keyword(s):  
Coal Seam ◽  
Computational Formula ◽  
Coal Seams ◽  
Minimum Thickness ◽  
Thick Coal Seam ◽  
East Region ◽  
Drilling Parameters ◽  
Geological Conditions ◽  
Outburst Coal Seam ◽  
Rock Pillars

Due to the complex geological conditions of Nanshan mine east region, the outburst predict index overrun frequently in the process of high-dipping extremely thick coal seam rock cross-cut coal uncovering, this text designed and optimized the front explore borehole parameter to ascertain conditions of coal seam; Optimized gas drainage drilling parameters to improve the rate of extraction, reduced the blank tape; On the basis of the theory of mechanics, derivate the computational formula of minimum safety rock pillars, identified with the minimum thickness safety of rock pillars. Through the above measures, guaranteed debunking coal seams quickly and safely.

Application on Gob-Side Entry Retaining Technology with Coal Gangue Bag Packing in Medium-Thick Coal Seams

2013 ◽  
Vol 446-447 ◽  
pp. 1364-1368
Author(s):  
Hong Biao Wang ◽  
Chao An ◽  
Shan Dong Zhang
Keyword(s):  
Coal Seam ◽  
Coal Gangue ◽  
Coal Seams ◽  
Medium Thickness ◽  
Basic Parameters ◽  
Production Smoothing ◽  
Selection Of

The key point of production smoothing in coalmine is regular continuing excavate, the gob-side entry retaining technology with coal gangue bag packing not only solve the continuing excavate problem, but also facilitate the meticulous mining. The selection of the waste filling technique and the determination of basic parameters of filling body are the keys to whether gob-side entry retaining technology success or not. Due to the thicker thickness in medium-thickness coal seam and the higher height of crossheading, it is propose that the gob-side entry retaining technology need to be improved much higher. Therefore, the determination of basic parameters of filling body is particularly important.

scholarly journals Control of the Internal and External Staggered Distance of Coal Mining Face to the Water-Conducting Fissures in the Overlying Strata of the Near Coal

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhiyuan Jin ◽  
Tao Peng
Keyword(s):  
Coal Seam ◽  
Coal Mining ◽  
Coal Mine ◽  
Calculation Formula ◽  
Coal Seams ◽  
Coal Face ◽  
Geological Conditions ◽  
Mining Face ◽  
Seam Mining ◽  
Water Proof

In Northwest China, rainfall is low, water resources are scarce, and the ecological environment is fragile. For shallow-buried and close-spaced coal seams with a thickness of upper coal bed >60∼70 m, the water-conducting fissures of the overlying rock will not penetrate the water-isolating layer after the upper coal seam is mined; the internal and external gap angles of the water-conducting fissures are not generated from the water-isolating layer. We set out to explore the critical internal and external dislocations for the second significant development of water-conducting fissures in the overlying rock after coal mining under control. A calculation model for the critical internal and external staggered distances of coal mining face in shallow-buried and close-spaced coal seams is established, the calculation formula is given, and the calculation formula for the critical seam mining ratio under the condition of internal staggered mining mode is given. Numerical simulation performed by UDEC methods: taking the overburden strata in the shallow-buried and close-spaced coal seam mining area of Shigetai Coal Mine as a prototype, it was verified that the critical internal and external offsets of the coal mining face in shallow-buried and close-spaced coal seams have a significant effect on the overlying water flow cracks in the mining of the lower coal seam. For the feasibility of developmental control, according to the engineering geological conditions of Shigetai, through the calculation method of external staggered distance, it is concluded that the distance of the open cut of the lower coal face and the upper coal face is only 21∼27 m, which is much smaller than the water barrier. It does not produce the critical distance of the water-conducting cracks. Therefore, in the process of mining the lower coal seam, the water-proof layer will produce water-conducting cracks, lose its water-proof performance, and cause water loss. This is also the cause of the water inrush accident in Shigetai Coal Mine.

Labor safety and control of the working area state in the penals while mining steep coal seams by shield aggregates

2020 ◽  
pp. 47-64
Author(s):  
V.V. Zberovskyi ◽  
◽  
R.А. Ahaiev ◽  
K.K. Sofiiskyi ◽  
B.М. Dehlin ◽  
...  
Keyword(s):  
Coal Seam ◽  
Physical And Mechanical Properties ◽  
Dynamic State ◽  
Coal Seams ◽  
Gas Dynamic ◽  
Geological Conditions ◽  
Labor Safety ◽  
Sudden Outburst ◽  
District Change ◽  
And Control

In this article, circumstances and factors which can lead to a degraded labour protection and occurrence of emergency in a district are reviewed and analyzed on the example of an accident occurred at sudden coal-and-gas outburst in the panel face № 42-1146 m of the Tovstyi-Zakhid seam m3 in the Central Mine of the Toretsvukhillia Mining Company. In this article, state of equipment and its location in the district in accordance with the requirements of the safety rules, records of devices which monitor gas-dynamic state of the coal seam and operation of the shield aggregate are considered. Mining and geological conditions of the seam bedding and technological conditions of the district location within the working horizon; methane content in the air of the roadways in the district; change of coal physical and mechanical properties in the area of possible geological disturbance; results of control of the coal seam gas-dynamic state analyzed by acoustic emission parameters; and other risk factors that led to emergencies were studied. The decisions made for controlling possible area with geological disturbance impact which was detected in the horizons of 916 m and 1026 m on the basis of mining-graphic materials and data of geological study in the mining roadways adjacent to the panel No. 14 in the district 42-1146 m were analyzed. The order and sequence of the works established for eliminating consequences of the coal and gas sudden outburst and detecting zone with disturbed coal and outburst cavity were considered. On the basis of the results obtained, conclusions were made and actions were elaborated on preventing accidents at mining steep prone-to-outburst coal seams by the shield aggregates. It is recommended to continue the scientific research for the purpose of detecting zone with possible impact of discontinuous geological disturbance and plicate disturbed zones in the coal seams by the changed hardness of coal in the adjacent panel, and developing certain local measures on preventing gas-dynamic phenomena at mining steep prone-to-outburst seams by the shield aggregates. The objective of this work was to analyze state of the working area and labor protection and to study the conditions and factors which had led to the accident with serious consequences and emergency condition of the panel.

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