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Mining Publication: Time-Lapse Analysis of Methane Quantity in the Mary Lee Group of Coal Seams Using Filter-Based Multiple-Point Geostatistical Simulation
Keywords: Alabama Degasification Quantitative analysis
Original creation date: August 2013
Authors: C Karacan, RA Olea
Peer Reviewed Journal Article - August 2013
Go to Web Page
NIOSHTIC2 Number: 20042826
Math Geosci 2013 Aug; 45(6):681-704
Coal seam degasification and its success are important for controlling methane, and thus for the health and safety of coal miners. During the course of degasification, properties of coal seams change. Thus, the changes in coal reservoir conditions and in-place gas content as well as methane emission potential into mines should be evaluated by examining time-dependent changes and the presence of major heterogeneities and geological discontinuities in the field. In this work, time-lapsed reservoir and fluid storage properties of the New Castle coal seam, Mary Lee/Blue Creek seam, and Jagger seam of Black Warrior Basin, Alabama, were determined from gas and water production history matching and production forecasting of vertical degasification wellbores. These properties were combined with isotherm and other important data to compute gas-in-place (GIP) and its change with time at borehole locations. Time-lapsed training images (TIs) of GIP and GIP difference corresponding to each coal and date were generated by using these point-wise data and Voronoi decomposition on the TI grid, which included faults as discontinuities for expansion of Voronoi regions. Filter-based multiple-point geostatistical simulations, which were preferred in this study due to anisotropies and discontinuities in the area, were used to predict time-lapsed GIP distributions within the study area. Performed simulations were used for mapping spatial time-lapsed methane quantities as well as their uncertainties within the study area.
The systematic approach presented in this paper is the first time in literature that history matching, TIs of GIPs and filter simulations are used for degasification performance evaluation and for assessing GIP for mining safety. Results from this study showed that using production history matching of coalbed methane wells to determine time-lapsed reservoir data could be used to compute spatial GIP and representative GIP TIs generated through Voronoi decomposition. Furthermore, performing filter simulations using point-wise data and TIs could be used to predict methane quantity in coal seams subjected to degasification. During the course of the study, it was shown that the material balance of gas produced by wellbores and the GIP reductions in coal seams predicted using filter simulations compared very well, showing the success of filter simulations for continuous variables in this case study. Quantitative results from filter simulations of GIP within the studied area briefly showed that GIP was reduced from an initial ~73 Bcf (median) to ~46 Bcf (2011), representing a 37 % decrease and varying spatially through degasification. It is forecasted that there will be an additional ~2 Bcf reduction in methane quantity between 2011 and 2015. This study and presented results showed that the applied methodology and utilized techniques can be used to map GIP and its change within coal seams after degasification, which can further be used for ventilation design for methane control in coal mines.
Cover page for Time-Lapse Analysis of Methane Quantity in the Mary Lee Group of Coal Seams Using Filter-Based Multiple-Point Geostatistical SimulationPeer Reviewed Journal Article - August 2013
Go to Web Page
NIOSHTIC2 Number: 20042826
Math Geosci 2013 Aug; 45(6):681-704
See Also
Degasification and Production of Natural Gas From an Air Shaft in the Pittsburgh Coalbed
Degasification System Selection for U.S. Longwall Mines Using an Expert Classification System
Development of a Statistical-Analytical Approach for Assessing Coal Bump Potential
Directionally Controlled Drilling To Horizontally Intercept Selected Strata, Upper Freeport Coalbed, Greene County, Pa.
Drainage of Methane From the Overlying Pocahontas No. 4 Coalbed From Workings in the Pocahontas No. 3 Coalbed
In Situ Estimation of Roof Rock Strength using Sonic Logging
In-depth Survey Report: Control Technology for Environmental Enclosures - The Effect of Wind Speed Upon Aerosol Penetration Into an Enclosure at Clean Air Filter, Defiance, IA
Methane Gas Content of the Mary Lee Group of Coalbeds, Jefferson, Tuscaloosa, and Walker Counties, Ala.
Rotary Drilling Techniques Used in the Beckley Coalbed
Use of Vertical Boreholes for Assisting Ventilation of Longwall Gob Areas
Page last reviewed: July 13, 2016
Page last updated: July 11, 2016
Content source: National Institute for Occupational Safety and Health, Mining Program
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