Comparison of the results of the seismic profiling and WAS-96/RMS seismoacoustic active method in an assessment of the impact of the overlying coal seam edge

In the study, a comparison between the results of seismic profiling and the active seismoacoustic method WAS-96/RMS has been presented. The methods were used to assess the impact of an overlying coal seam edge on the relative stress state of the test heading in the chosen hard coal mine in the Upper Silesian Coal Basin, Poland. The work presents the methodologies of measurement, processing and interpretation of both methods. In the research area there were two edges of the adjacent seams at vertical distances of 70 and 100 m. The obtained results allowed for the development of conclusions regarding the effectiveness of both methods. It was stated, that the seismic profiling method, as well as the WAS-96/RMS method allowed for the identification of anomalies in the area of impact of the overlying coal seams. Based on previous experience, a comparison of the advantages and limitations of the seismic profiling and the WAS- 96/RMS method has also been presented. As a result, it was found that seismic profiling should be the basic method for assessing the impact of the edges and remnants of exploited seams, whereas the WAS-96/RMS method may be used as a complementary method if a confirmation of the rockbursts threat is required.

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The Impact of the Coexistence of Methane Hazard and Rock-Bursts on the Safety of Works in Underground Hard Coal Mines

Energies ◽

10.3390/en14010128 ◽

2020 ◽

Vol 14 (1) ◽

pp. 128

Author(s):

Justyna Swolkień ◽

Nikodem Szlązak

Keyword(s):

Rock Burst ◽

Methane Concentration ◽

High Energy ◽

Hard Coal ◽

Coal Seams ◽

Safety Level ◽

Methane Drainage ◽

Innovative Methods ◽

Hard Coal Mining ◽

The Impact

Several natural threats characterize hard coal mining in Poland. The coexistence of methane and rock-burst hazards lowers the safety level during exploration. The most dangerous are high-energy bumps, which might cause rock-burst. Additionally, created during exploitation, safety pillars, which protect openings, might be the reason for the formation of so-called gas traps. In this part, rock mass is usually not disturbed and methane in seams that form the safety pillars is not dangerous as long as they remain intact. Nevertheless, during a rock-burst, a sudden methane outflow can occur. Preventing the existing hazards increases mining costs, and employing inadequate measures threatens the employees’ lives and limbs. Using two longwalls as examples, the authors discuss the consequences of the two natural hazards’ coexistence. In the area of longwall H-4 in seam 409/4, a rock-burst caused a release of approximately 545,000 cubic meters of methane into the excavations, which tripled methane concentration compared to the values from the period preceding the burst. In the second longwall (IV in seam 703/1), a bump was followed by a rock-burst, which reduced the amount of air flowing through the excavation by 30 percent compared to the airflow before, and methane release rose by 60 percent. The analyses presented in this article justify that research is needed to create and implement innovative methods of methane drainage from coal seams to capture methane more effectively at the stage of mining.

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Methane emissions against the background of natural and mining conditions in the Budryk and Pniówek mines in the Upper Silesian Coal Basin (Poland)

Environmental Earth Sciences ◽

10.1007/s12665-021-10063-4 ◽

2021 ◽

Vol 80 (22) ◽

Author(s):

Marcin Dreger ◽

Sławomir Kędzior

Keyword(s):

Methane Emissions ◽

Geological Structure ◽

Methane Content ◽

Coal Extraction ◽

Hard Coal ◽

Coal Seams ◽

Coal Basin ◽

Related Factors ◽

Upper Silesian Coal Basin ◽

Mining Conditions

AbstractThe paper presents the variability of hard coal output, methane content and methane emissions into coal workings and into the atmosphere from the two most methane-gassy coal mines in Poland. The Budryk mine is one of the youngest mines in Poland, but it is the most methane-gassy as well. In 2016, the total CH4 emissions exceed 140 million of m3. This large increase in methane emissions to mine workings is primarily related to the increase in the depth of coal extraction (up to 1290 m) and, consequently, the rapid increase in the methane content in coal seams (up to 10–12 m3/Mg coaldaf). On the other hand, in the Pniówek mine, methane emission was the highest at the beginning of the study period (1986–1991). During the following years, emission decreased to the values of less than 140 million of m3, which were still one of the largest amounts of emitted methane in the entire Upper Silesian Coal Basin. The coexistence of natural factors, such as the geological structure and gas distribution, as well as mining-related factors, i.e. the depth of mining, the intensity of coal extraction determines the temporal variability of methane emissions in the studied mines.

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Structurally Altered Hard Coal in the Areas of Tectonic Disturbances – An Initial Attempt at Classification

Archives of Mining Sciences ◽

10.1515/amsc-2016-0047 ◽

2016 ◽

Vol 61 (3) ◽

pp. 677-694 ◽

Cited By ~ 4

Author(s):

Katarzyna Godyń

Keyword(s):

Optical Methods ◽

Hard Coal ◽

Original Structure ◽

Coal Seams ◽

Initial Attempt ◽

Near Fault ◽

Upper Silesian Coal Basin ◽

Tectonic Disturbances ◽

Coal Degradation ◽

Tectonic Dislocations

Abstract As regards the exploitation of hard coal seams, the near-fault zones and faults themselves are considered to be particularly dangerous areas, which is due to a high probability of the occurrence of gasogeodynamic phenomena. Tectonic dislocations running across a seam have a destructive impact on coal. Degradation of the coal structure, particularly visible in the microscale, is reflected in the coal’s strength or gas properties. Such “structurally altered” coal is characterized by the presence of numerous fracturings, crushed areas, or dislocations of some of its fragments, and sometimes even the total destruction of the original structure. The present paper provides a detailed analysis and description of near-fault coal obtained from selected seams of the Upper Silesian Coal Basin, completed due to the application of optical methods. Both the type and the degree of changes in the structure of such coal were identified. On this basis, the author attempted to systematize the nomenclature used in relation to selected Upper Silesian hard coal seams, which, in turn, resulted in a proposed classification of the “altered structures” of the near-fault coal.

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A Study of the Laws of Abnormal Gas Emissions and the Stability Controls for Coal Mine Walls in Deeply Buried High-Gas Coal Seams

Advances in Civil Engineering ◽

10.1155/2020/8894854 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Anying Yuan ◽

Hao Hu ◽

Qiupeng Yuan

Keyword(s):

Coal Seam ◽

Water Content ◽

Coal Mine ◽

Gas Diffusion ◽

Hard Coal ◽

Coal Seams ◽

Gas Emissions ◽

Soft Coal ◽

Pressure Water ◽

Gas Coal

At the present time, it is considered to be of major significance to study the gas emission law and stability controls of coal bodies in deeply buried high-gas coal seams. For this reason, in view of the specific problems of gas emissions caused by unstable rib spalling in coal mine walls, comprehensive research methods were adopted in this study, in order to conduct an in-depth examination of micropore structure parameters, gas desorption, diffusion laws, and coal stability levels. The results showed that the development degree of the pores above the micropores, as well as the small pores in soft coal seams, was better than those observed in hard coal seams. In addition, the gas outburst phenomenon was found to have more easily formed in the soft coal seams. The coal body of the No. 6 coal seam in the Xieqiao Coal Mine not only provided the conditions for gas adsorption but also provided dominant channels for gas diffusion and migration. The abnormal gas emissions of the No. 6 coal seam were jointly caused by the relatively developed pores above the small holes in the coal body, rib spalling of coal mine walls, and so on. The research results also revealed the evolution law of mechanical characteristics of the No. 6 coal seam under different water content conditions. It was found that the strength levels of the No. 6 coal seam first increased and then decreased with the increase in water content, and the water content level at the maximum strength of the coal seam was determined to be 7.09%. This study put forward a method which combined the water injection technology of long-term static pressure water injections in deep coal mining holes and real-time dynamic pressure water injections in shallower holes. Field experiments were successfully carried out.

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Influence of Valleys Terrain on Pressure of Fully Mechanized Working Faces in Shallow Coal Seams

Shock and Vibration ◽

10.1155/2021/8880041 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

YingJie Liu ◽

Qingjie Qi ◽

Anhu Wang

Keyword(s):

Coal Seam ◽

Coal Mining ◽

Rock Fracture ◽

Mine Pressure ◽

Overburden Rock ◽

Coal Seams ◽

Valley Bottom ◽

Key Stratum ◽

Seam Mining ◽

The Impact

The absence of a key stratum during overburden rock movement is crucial to the mining pressure of fully mechanized coal mining faces. Using physical and numerical simulations, the 21304 mechanized mining in Daliuta and Huojitu coal mining faces 1−2 appeared twice during a pressure frame accident analysis. The results indicate that a lack of key overlying strata is crucial to the mining of lower coal seams, particularly for the upper sections of a single key stratum of coal. When the key stratum of the upper coal seam is absent, a stable masonry structure is formed after mining. It is easy to form stable stacked strata at the bottom of a coal seam. When developing gullies in deep terrains, the formation of the key stratum will be an upper rock fracture affected by the impact, resulting in a partial absence of the key stratum. When the key stratum is absent, the mining of upslope working faces and the probability of dynamic strata pressure increase with the overburden on the working face and mining of downslope faces. The face mine pressure development laws on the upper and lower coal seam mining were similar, mainly manifesting as “slope section >valley bottom section >back slope section.”

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

The APPEA Journal ◽

10.1071/aj18049 ◽

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.

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Effect of Mining Thickness on Overburden Movement and Underground Pressure Characteristics for Extrathick Coal Seam by Sublevel Caving with High Bottom Cutting Height

Advances in Civil Engineering ◽

10.1155/2018/6871820 ◽

2018 ◽

Vol 2018 ◽

pp. 1-15 ◽

Cited By ~ 1

Author(s):

Yongkang Yang ◽

Yanrong Ma ◽

Chunxu Ji ◽

Tianhe Kang ◽

Xingyun Guo

Keyword(s):

Theoretical Analysis ◽

Coal Seam ◽

Main Roof ◽

Coal Seams ◽

Sublevel Caving ◽

Normal Circumstance ◽

Seam Mining ◽

Cutting Height ◽

The Impact ◽

Pressure Characteristics

Because the coal seam is particularly thick and the mining intensity is large, the mining of extremely thick coal seams often causes a wide range of disturbed fractures, which in turn induces the phenomenon of strong underground pressure such as induced support crushing and water inrush. Through theoretical analysis, laboratory similarity simulation test, and other methods, this paper studies the effect of mining thickness on overburden movement and underground pressure characteristics for extremely thick coal seams by sublevel caving with high bottom cutting height. Some conclusions can be drawn as follows: (i) under the “beam-hinged cantilever beam rocks” structure theory, the rock pillar thickness which needs to be controlled increases linearly as a function of mining thickness is achieved, and the reason of increased of support resistance in full-mechanized caving mining in extremely thick seams is explained in the theory; (ii) based on the results of the theoretical analysis and the lab simulation tests, the law of the abutment pressure peak is inverse to the full-seam mining thickness, and the distance between abutment peak and working face is proportional to the full-seam mining thickness, that is to say that the damage range of overlying strata increased; (iii) there are three working states of loading support in extrathick coal seams, such as normal circumstance, lower main roof pressure, and higher main roof pressure, meanwhile these states keep changing; (iv) under the guarantee of stope safety conditions, due to lower support strength, it will benefit the special thick seam top-coal caving under normal circumstance; (v) increasing the supporting strength can balance the impact loading under the lower main roof pressure, guaranteeing valid support for roof strata; (vi) by releasing high pressure, due to lower production, lower recovery rate of coal and other measures guarantee the stability of the stope support in the case of the higher main roof pressure.

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Methane emissions and demethanation of coal mines in the Upper Silesian Coal Basin between 1997 and 2016

Environmental & Socio-economic Studies ◽

10.2478/environ-2019-0002 ◽

2019 ◽

Vol 7 (1) ◽

pp. 12-23 ◽

Cited By ~ 1

Author(s):

Marcin Dreger ◽

Sławomir Kędzior

Keyword(s):

Methane Emission ◽

Methane Emissions ◽

Coal Extraction ◽

Hard Coal ◽

Coal Seams ◽

Coal Basin ◽

Upper Silesian Coal Basin ◽

Near Future ◽

Research Period ◽

Modern Technologies

Abstract Between 1997 and 2016 we observed important changes in hard coal extraction and methane emission in the Upper Silesian Coal Basin. Hard coal extraction in the near future will be very dangerous because it will be necessary to reach deeper methane-rich coal seams. Permanent monitoring of the volume of emitted and captured methane is necessary to combat the methane hazard. The predictability of gaseous hazards are important in order to keep underground work safe. We gathered and analysed data from three coal companies: Katowice Coal Holding, the Coal Company, Jastrzębie Coal Company and in the whole of the Upper Silesian Coal Basin for the last twenty years and this allowed us to notice changes and CH4 trends in ventilation emission and demethanation. There is a decrease in the extraction of hard coal from year to year. At the same time there is an increase in the total methane emissions which forces actions aimed to effective contracting the methane hazard. Specifically, methane emission has been increasing for years, making hard coal extraction very dangerous. We observed increases in CH4 vent emission and volume of methane coming from underground drainage systems. Much more methane is released during hard coal extraction at deeper mine levels. Throughout the entire research period the methane hazard increased. Therefore, the development of modern technologies for methane capturing should contribute to improvement of hazardous conditions for coal mining in the basin.

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The Seismic Source Parameters of Tremors Provoked by Long-Hole Destress Blasting Executed During the Longwall Mining of a Coal Seam Under Variable Stress Conditions

Pure and Applied Geophysics ◽

10.1007/s00024-020-02603-z ◽

2020 ◽

Vol 177 (12) ◽

pp. 5723-5739

Author(s):

Łukasz Wojtecki ◽

Maciej J. Mendecki ◽

Iwona Gołda ◽

Wacław M. Zuberek

Keyword(s):

Longwall Mining ◽

Source Parameters ◽

Seismic Source ◽

Hard Coal ◽

Coal Seams ◽

Coal Basin ◽

Rockburst Hazard ◽

Seismic Source Parameters ◽

Upper Silesian Coal Basin ◽

Destress Blasting

AbstractThe underground mining of coal seams in the Upper Silesian Coal Basin is carried out at great depths and mostly in the presence of remnants or edges of other surrounding coal seams, i.e. under the condition of high stress level in the rock mass. Therefore, this mining is accompanied by rockburst hazard and suitable preventive action is required. Long-hole destress blasting plays an important role and is commonly applied in rockburst prevention in underground hard coal mines. Estimated blasting effectiveness is important when designing rockburst prevention. It is commonly estimated on the basis of the seismic energy of a provoked tremor. The seismic source parameters have already been considered for this purpose. Additional information about the effects of long-hole destress blasting could be contemplated in the planning of active rockburst prevention. The seismic source parameters of tremors provoked by long-hole destress blasting have been calculated and are presented in this article. Destress blasts were performed during the longwall mining of coal seam no. 506 in one of the hard coal mines in the Upper Silesian Coal Basin. They were executed from the longwall face, in order to destress the rock mass ahead of it. Parameters of the blasts were variable and they were modified according to geological and mining conditions and the observed level of rockburst hazard. The seismic source parameters have been determined for tremors provoked directly after firing explosives and for tremors occurring in the waiting time, and they have been compared with each other.

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The influence of distant coal seam edges on seismic hazard during longwall mining

Journal of Seismology ◽

10.1007/s10950-020-09959-8 ◽

2020 ◽

Author(s):

Łukasz Wojtecki ◽

Iwona Gołda ◽

Maciej J. Mendecki

Keyword(s):

Coal Seam ◽

Longwall Mining ◽

Mining Area ◽

Simultaneous Increase ◽

Coal Seams ◽

Upper Silesian Coal Basin ◽

Longwall Panel ◽

Mining Works ◽

Seam Mining ◽

Mining Tremors

Abstract Underground coal seam mining has been carried out in the Upper Silesian Coal Basin, Poland, for many years and with a simultaneous increase in exploitation depth. Frequently, coal seams are not fully extracted due to numerous reasons which lead to their edges and remnants remaining in the rock mass. Even in the case of the full extraction of a coal seam, mining usually ends at the border of a protecting pillar to protect underground or surface objects, sometimes at the border of the mining area, or some distance from the old goaf or high throw fault. Extraction of subsequent coal seams in an analogous range results in a cluster of coal seam edges remaining. In the vicinity of the mentioned remainders, the disrupted stress distribution is expected. The infraction of the aforementioned equilibrium repeatedly results in the occurrence of strong mining tremors. The observations from the studied coal seam no. 408’s longwall panel indicated that mining works are able to disturb the present stress-strain equilibrium in the area of the edges of other coal seams, even if they are located at a greater vertical distance away. The seismological parameters and distributions have been applied for this purpose.

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