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Integration of vertical and in-seam horizontal well production analyses with stochastic geostatistical algorithms to estimate pre-mining methane drainage efficiency from coal seams: Blue Creek seam, Alabama.

Authors
Karacan-CÍ
Source
Int J Coal Geol 2013 Jul; 114:96-113
NIOSHTIC No.
20042498
Abstract
Coal seam degasification and its efficiency are directly related to the safety of coal mining. Degasification activities in the Black Warrior basin started in the early 1980s by using vertical boreholes. Although the Blue Creek seam, which is part of the Mary Lee coal group, has been the main seam of interest for coal mining, vertical wellbores have also been completed in the Pratt, Mary Lee, and Black Creek coal groups of the Upper Pottsville formation to degasify multiple seams. Currently, the Blue Creek seam is further degasified 2-3 years in advance of mining using in-seam horizontal boreholes to ensure safe mining. The studied location in this work is located between Tuscaloosa and Jefferson counties in Alabama and was degasified using 81 vertical boreholes, some of which are still active. When the current longwall mine expanded its operation into this area in 2009, horizontal boreholes were also drilled in advance of mining for further degasification of only the Blue Creek seam to ensure a safe and a productive operation. This paper presents an integrated study and a methodology to combine history matching results from vertical boreholes with production modeling of horizontal boreholes using geostatistical simulation to evaluate spatial effectiveness of in-seam boreholes in reducing gas-in-place (GIP). Results in this study showed that in-seam wells' boreholes had an estimated effective drainage area of 2050 acres with cumulative production of 604 MMscf methane during ~2 years of operation. With horizontal borehole production, GIP in the Blue Creek seam decreased from an average of 1.52 MMscf to 1.23 MMscf per acre. It was also shown that effective gas flow capacity, which was independently modeled using vertical borehole data, affected horizontal borehole production. GIP and effective gas flow capacity of coal seam gas were also used to predict remaining gas potential for the Blue Creek seam.
Keywords
Underground-mining; Coal-mining; Coal-gasification; Ventilation; Analytical-processes; Methanes; Methane-control; Safety-engineering; Safety-measures; Longwall-mining; Models; Author Keywords: History matching; Black Warrior basin; Coal mine methane; Degasification; Geostatistical simulation
Contact
C. Ozgen Karacan, NIOSH, Office of Mine Safety and Health Research, Pittsburgh, PA 15236
CODEN
IJCGDE
CAS No.
74-82-8
Publication Date
20130730
Document Type
Journal Article
Email Address
cok6@cdc.gov
Fiscal Year
2013
NTIS Accession No.
NTIS Price
Identifying No.
B20130520
ISSN
0166-5162
NIOSH Division
OMSHR
Priority Area
Mining
Source Name
International Journal of Coal Geology
State
PA
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