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Monte Carlo simulation and well testing applied in evaluating reservoir properties in a deforming longwall overburden.
Transp Porous Med 2011 Jan; 86(2):415-434
During longwall mining, the intact strata start to deform and fracture as the mining 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.
Coal-gas; Coal-mining; Controlled-environment; Control-systems; Control-technology; Engineering-controls; Gases; Longwall-mining; Mine-gases; Mining-industry; Quantitative-analysis; Statistical-analysis; Underground-mining; Ventilation; Author Keywords: Reservoir; Gob gas venthole; Longwall gobs; Well testing; Monte Carlo method
C. Özgen Karacan, OMSHR, National Institute for Occupational Safety and Health, P.O. Box 18070, Cochrans Mill Road, Pittsburgh, PA 15236, United States
Issue of Publication
Transport in Porous Media