An analysis of reservoir conditions and responses in longwall panel overburden during mining and its effect on gob gas well performance

Schatzel, Steven J.; Karacan, C. Özgen; Dougherty, Heather; Goodman, Gerrit V. R.

doi:10.1016/j.enggeo.2012.01.002

Cited by 84 publications

(37 citation statements)

References 8 publications

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“…The zone of maximum GGV production was determined to be located about 60 m (200 ft) behind the face. The majority of surface subsidence was observed to end in that study about 88 m (290 ft) behind the face (Palchik, 2003; Schatzel, Karacan, et al, 2012). It should be noted that borehole completion designs used at the study mine site and at the Northern Appalachian Basin coal mine differ significantly.…”

Section: Discussion and Resultsmentioning

confidence: 75%

“…Karacan et al (2007) performed novel numerical modeling methods and showed a permeability decrease of about two orders of magnitude within the mined coal horizon when moving from the edge to the center of the gob. Schatzel, Karacan et al (2012) gave results on changing permeabilities over an active longwall panel where permeabilities reached at least 63 D in the overburden over the tailgate. Data also showed that maximum permeability in the gob overburden above the gateroads corresponded to maximum compaction above the panel centerline following undermining.…”

Section: Discussion and Resultsmentioning

confidence: 99%

“…In general, the transport network related to GGV performance is produced by mining-induced fractures behind the longwall face. In the United States, key GGV design parameters related to production have been reported (Karacan et al, 2007; Schatzel, Karacan et al, 2012). The operator configured GGVs to be drilled and completed near the mined coal bed, terminating about 15 m (50 ft) into the caved material from the tailgate entry.…”

Section: Introductionmentioning

confidence: 99%

“…In general, the primary gas migration pathways in the gob are paralleling the gateroads on the headgate and tailgate edges or near margin locations (Diamond, Jeran and Trevits, 1994; Schatzel, Karacan et al 2012). Gas migration along these pathways is favored by the high permeability zones found in the overburden paralleling the gateroads due the collapsed rock in the space formerly occupied by the coalbed bordering the gateroad pillars, which still provide some ability for roof support inby the longwall face (Figs.…”

Section: Introductionmentioning

confidence: 99%

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Methane emissions and airflow patterns on a longwall face: Potential influences from longwall gob permeability distributions on a bleederless longwall

2017

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Longwall face ventilation is an important component of the overall coal mine ventilation system. Increased production rates due to higher-capacity mining equipment tend to also increase methane emission rates from the coal face, which must be diluted by the face ventilation. Increases in panel length, with some mines exceeding 6,100 m (20,000 ft), and panel width provide additional challenges to face ventilation designs. To assess the effectiveness of current face ventilation practices at a study site, a face monitoring study with continuous monitoring of methane concentrations and automated recording of longwall shearer activity was combined with a tracer gas test on a longwall face. The study was conducted at a U.S. longwall mine operating in a thick, bituminous coal seam and using a U-type, bleederless ventilation system. Multiple gob gas ventholes were located near the longwall face. These boreholes had some unusual design concepts, including a system of manifolds to modify borehole vacuum and flow and completion depths close to the horizon of the mined coalbed that enabled direct communication with the mine atmosphere. The mine operator also had the capacity to inject nitrogen into the longwall gob, which occurred during the monitoring study. The results show that emission rates on the longwall face showed a very limited increase in methane concentrations from headgate to tailgate despite the occurrence of methane delays during monitoring. Average face air velocities were 3.03 m/s (596 fpm) at shield 57 and 2.20 m/s (433 fpm) at shield 165. The time required for the sulfur hexafluoride (SF6) peak to occur at each monitoring location has been interpreted as being representative of the movement of the tracer slug. The rate of movement of the slug was much slower in reaching the first monitoring location at shield 57 compared with the other face locations. This lower rate of movement, compared with the main face ventilation, is thought to be the product of a flow path within and behind the shields that is moving in the general direction of the headgate to the tailgate. Barometric pressure variations were pronounced over the course of the study and varied on a diurnal basis.

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Section: Discussion and Resultsmentioning

confidence: 75%

Section: Discussion and Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Methane emissions and airflow patterns on a longwall face: Potential influences from longwall gob permeability distributions on a bleederless longwall

2017

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“…Such research can also serve as a theoretical basis for mine gas extraction [21][22][23][24]. Regarding problems of high gas pressure, gas content, and stress levels related to deep mining, comprehensive methods including theoretical analyses of production data and field trials and numerical simulation methods-such as those of protective seam mining, hydrofracturing, and gas extraction-have been proposed as ways to reduce protected seam gas content and pressure [25][26][27][28]. Due to the limited thickness, low mining productivity, and low gas content of thin coal seams in the coal seam group, using thin coal seams as protective seams can improve the safety of mining coal seams [29,30].…”

Section: Introductionmentioning

confidence: 99%

Gas Permeability Evolution Mechanism and Comprehensive Gas Drainage Technology for Thin Coal Seam Mining

2017

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Abstract:A thin coal seam mined as a protective coal seam above a gas outburst coal seam plays a central role in decreasing the degree of stress placed on a protected seam, thus increasing gas permeability levels and desorption capacities to dramatically eliminate gas outburst risk for the protected seam. However, when multiple layers of coal seams are present, stress-relieved gas from adjacent coal seams can cause a gas explosion. Thus, the post-drainage of gas from fractured and de-stressed strata should be applied. Comprehensive studies of gas permeability evolution mechanisms and gas seepage rules of protected seams close to protective seams that occur during protective seam mining must be carried out. Based on the case of the LongWall (LW) 23209 working face in the Hancheng coal mine, Shaanxi Province, this paper presents a seepage model developed through the FLAC3D software program (version 5.0, Itasca Consulting Group, Inc., Minneapolis, MI, USA) from which gas flow characteristics can be reflected by changes in rock mass permeability. A method involving theoretical analysis and numerical simulation was used to analyze stress relief and gas permeability evolution mechanisms present during broken rock mass compaction in a goaf. This process occurs over a reasonable amount of extraction time and in appropriate locations for comprehensive gas extraction technologies. In using this comprehensive gas drainage technological tool, the safe and efficient co-extraction of thin coal seams and gas resources can be realized, thus creating a favorable environment for the safe mining of coal and gas outburst seams.

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Variations in surface fractal characteristics of coal subjected to liquid CO ₂ phase change fracturing

et al. 2020

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An analysis of reservoir conditions and responses in longwall panel overburden during mining and its effect on gob gas well performance

Cited by 84 publications

References 8 publications

Methane emissions and airflow patterns on a longwall face: Potential influences from longwall gob permeability distributions on a bleederless longwall

Methane emissions and airflow patterns on a longwall face: Potential influences from longwall gob permeability distributions on a bleederless longwall

Gas Permeability Evolution Mechanism and Comprehensive Gas Drainage Technology for Thin Coal Seam Mining

Variations in surface fractal characteristics of coal subjected to liquid CO ₂ phase change fracturing

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An analysis of reservoir conditions and responses in longwall panel overburden during mining and its effect on gob gas well performance

Cited by 84 publications

References 8 publications

Methane emissions and airflow patterns on a longwall face: Potential influences from longwall gob permeability distributions on a bleederless longwall

Methane emissions and airflow patterns on a longwall face: Potential influences from longwall gob permeability distributions on a bleederless longwall

Gas Permeability Evolution Mechanism and Comprehensive Gas Drainage Technology for Thin Coal Seam Mining

Variations in surface fractal characteristics of coal subjected to liquid CO 2 phase change fracturing

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Variations in surface fractal characteristics of coal subjected to liquid CO ₂ phase change fracturing