Last data update: Sep 23, 2024. (Total: 47723 publications since 2009)
Records 1-7 (of 7 Records) |
Query Trace: Goodman GVR [original query] |
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Large-scale explosion propagation testing of treated and non-treated rock dust when overlain by a thin layer of coal dust
Perera IE , Harris ML , Sapko MJ , Dyduch Z , Cybulski K , Hildebrandt R , Goodman GVR . Min Metall Explor 2021 38 (2) 1009-1017 To prevent coal dust explosion propagations, rock dust needs to be lifted and suspended in the air with the coal dust during an explosion. The addition of anti-caking agents prevents caking of rock dust in the presence of water. Mining and rock dusting processes can frequently create alternating layers of rock dust and float coal dust on mine surfaces. For this test series, a thin layer of coal dust was distributed on top of a layer of either treated or non-treated rock dust in the Experimental Mine Barbara, Poland. The experimental results compare the effectiveness of treated and non-treated rock dusts to attenuate a propagating coal dust explosion initiated with either strong or weak methane explosions. Experimental results indicate that the treated rock dust performs better than non-treated rock dust in arresting a propagating explosion, especially in the presence of moisture. |
Analyses of geological and hydrodynamic controls on methane emissions experienced in a Lower Kittanning coal mine
Karacan CÖ , Goodman GVR . Int J Coal Geol 2012 98 110-127 This paper presents a study assessing potential factors and migration paths of methane emissions experienced in a room-and-pillar mine in Lower Kittanning coal, Indiana County, Pennsylvania. Methane emissions were not excessive at idle mining areas, but significant methane was measured during coal mining and loading. Although methane concentrations in the mine did not exceed 1% limit during operation due to the presence of adequate dilution airflow, the source of methane and its migration into the mine was still a concern. In the course of this study, structural and depositional properties of the area were evaluated to assess complexity and sealing capacity of roof rocks. Composition, gas content, and permeability of Lower Kittanning coal, results of flotation tests, and geochemistry of groundwater obtained from observation boreholes were studied to understand the properties of coal and potential effects of old abandoned mines within the same area. These data were combined with the data obtained from exploration boreholes, such as depths, elevations, thicknesses, ash content, and heat value of coal. Univariate statistical and principal component analyses (PCA), as well as geostatistical simulations and co-simulations, were performed on various spatial attributes to reveal interrelationships and to establish area-wide distributions. These studies helped in analyzing groundwater quality and determining gas-in-place (GIP) of the Lower Kittanning seam. Furthermore, groundwater level and head on the Lower Kittanning coal were modeled and flow gradients within the study area were examined. Modeling results were interpreted with the structural geology of the Allegheny Group of formations above the Lower Kittanning coal to understand the potential source of gas and its migration paths. Analyses suggested that the source of methane was likely the overlying seams such as the Middle and Upper Kittanning coals and Freeport seams of the Allegheny Group. Simulated groundwater water elevations, gradients of groundwater flow, and the presence of recharge and discharge locations at very close proximity to the mine indicated that methane likely was carried with groundwater towards the mine entries. Existing fractures within the overlying strata and their orientation due to the geologic conditions of the area, and activation of slickensides between shale and sandstones due to differential compaction during mining, were interpreted as the potential flow paths. |
An analysis of reservoir conditions and responses in longwall panel overburden during mining and its effect on gob gas well performance
Schatzel SJ , Karacan CÖ , Dougherty H , Goodman GVR . Eng Geol 2012 127 65-74 NIOSH conducted a cooperative research study to provide direct measurements of changing reservoir conditions in longwall panel overburden. The field measurements documented changes in permeabilities, methane concentrations, fluid pressures, and the effects of adjacent gob gas ventholes (GGVs) on NIOSH boreholes drilled in the study panel. Three different stratigraphic horizons were monitored by the NIOSH boreholes. Results indicated that the gob gas venthole fracture network formed 24 to 46m (80 to 150 ft) ahead of the mining face. Overburden permeabilities within the same overburden test zones were ~1md prior to undermining, increasing to hundreds or thousands of md during undermining. Permeabilities measured seven months after undermining showed additional increases. The relationship between changing reservoir conditions, longwall face position, and surface movement is discussed. Recommendations are made to optimize GGV performance by evaluating changes in subsidence produced by mining, resulting in rock stresses that substantially influence induced fracture permeability. Mechanisms to account for the observed changes in reservoir conditions are reported. |
A CART technique to adjust production from longwall coal operations under ventilation constraints
Karacan CO , Goodman GVR . Saf Sci 2011 50 (3) 510-522 Methane emissions in longwall coal mines can arise from a variety of geologic and production factors, where ventilation and degasification are primary control measures to prevent excessive methane levels. However, poor ventilation practices or inadequate ventilation may result in accumulation of dangerous methane-air mixtures. The need exists for a set of rules and a model to be used as guidelines to adjust coal production according to expected methane emissions and current ventilation conditions. In this paper, hierarchical classification and regression tree (CART) analyses are performed as nonparametric modeling efforts to predict methane emissions that can arise during extraction of a longwall panel. These emissions are predicted for a range of coal productivities while considering specific operational, panel design and geologic parameters such as gas content, proximate composition of coal, seam height, panel width, cut height, cut depth, and panel size. Analyses are conducted for longwall mines with and without degasification of the longwall panel. These models define a range of coal productivities that can be achieved without exceeding specified emissions rates under given operating and geological conditions. Finally, the technique was applied to longwall mines that operate with and without degasification system to demonstrate its use and predictive capability. The predicted results proved to be close to the actual measurements to estimate ventilation requirements. Thus, the CART-based model that is given in this paper can be used to predict methane emission rates and to adjust operation parameters under ventilation constrains in longwall mining. |
Monte Carlo simulation and well testing applied in evaluating reservoir properties in a deforming longwall overburden
Karacan CO , Goodman GVR . Transp Porous Media 2011 86 (2) 445-464 During longwall mining, the intact strata start to deform and fracture as the raining face progresses. Gob gas ventholes (GGVs) are drilled from the surface over a longwall panel before mining to capture methane from the fractured zone. Due to fracturing and bedding-plane separations, reservoir properties change extensively. This poses a major problem for venthole designers and methane control engineers and may become a safety and health concern for underground work force due to unexpected methane emissions: it is difficult to predict the location of major strata separations and their temporal magnitudes to best locate the ventholes. Measurements obtained at different times during longwall mining may not be helpful for this purpose as strata deformation is a dynamic process and the results from different tests may not be lumped together to analyze the data collectively. This article uses a combination of Monte Carlo (MC) simulation and well testing methods to analyze multiple data sets obtained from a GGV at different longwall face locations. The aim was to determine the magnitude of average strata separation before conducting well test analyses to determine the properties of a deformed reservoir. MC simulation was used to process cross-correlated and uncertain data distributions obtained from measurements to generate a set of normally distributed values for each data type. These values were further used to project the amount of strata separation to the timing of well test. Finally, well-test analyses were used to interpret test data and to evaluate reservoir properties. |
Probabilistic modeling using bivariate normal distributions for identification of flow and displacement intervals in longwall overburden
Karacan CO , Goodman GVR . Int J Rock Mech Min Sci 2011 48 (1) 27-41 Gob gas ventholes (GGV) are used to control methane emissions in longwall mines by capturing it within the overlying fractured strata before it enters the work environment. In order for GGVs to effectively capture more methane and less mine air, the length of the slotted sections and their proximity to top of the coal bed should be designed based on the potential gas sources and their locations, as well as the displacements in the overburden that will create potential flow paths for the gas. In this paper, an approach to determine the conditional probabilities of depth-displacement, depth-flow percentage, depth-formation and depth-gas content of the formations was developed using bivariate normal distributions. The flow percentage, displacement and formation data as a function of distance from coal bed used in this study were obtained from a series of borehole experiments contracted by the former US Bureau of Mines as part of a research project. Each of these parameters was tested for normality and was modeled using bivariate normal distributions to determine all tail probabilities. In addition, the probability of coal bed gas content as a function of depth was determined using the same techniques. The tail probabilities at various depths were used to calculate conditional probabilities for each of the parameters. The conditional probabilities predicted for various values of the critical parameters can be used with the measurements of flow and methane percentage at gob gas ventholes to optimize their performance. Published by Elsevier Ltd. |
Reservoir diagnosis of longwall gobs through drawdown tests and decline curve analyses of gob gas venthole productions
Dougherty HN , Karacan CO , Goodman GVR . Int J Rock Mech Min Sci 2010 47 (5) 851-857 During longwall mining, fracturing and relaxation in the gob creates new and highly permeable flow paths. Methane inflow from the gob into the mining environment is influenced by the magnitude of fracturing and the extent to which the fractures stay open during mining. Singh and Kendorski [1] evaluated the disturbance of rock strata resulting from mining and described a caved zone that extends from the mining level to 3–6 times the seam thickness, a fractured zone that extends from the mining level to 30–58 times the seam thickness, and a bending zone where there is no change in permeability that extends from 30 times the seam thickness to 50 ft below ground surface. The characteristics of fracturing and the subsidence of overburden were revealed through predictive techniques and field studies [2], [3], [4], [5], [6]. It was concluded that rock failure leading to increased hydraulic conductivity in the gob was initiated by high compressive stresses ahead of the face with the fractures subsequently opened by tensile stresses behind the face [7]. | Gas, particularly methane that is contained within the gob, will be released over time as mining progresses and is a big contributor to ventilation emissions if not controlled. Relaxation of the roof rocks, ventilation pressure and the associated fracture connectivity allow gas to flow from all surrounding gas sources toward the mine workings, which eventually may create an unsafe condition for the underground workforce. |
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