1
25-044
Improving Gas Management and Ventilation Performance at
Longwall Mines with Potentially High Gas Emission Rates
Steven J. Schatzel
NIOSH, Pittsburgh, PA
Berk Tulu
NIOSH, Pittsburgh, PA
K. Vaibhav Raj
NIOSH, Pittsburgh, PA
James Addis
NIOSH, Pittsburgh, PA
ABSTRACT
The National Institute for Occupational Safety and Health
(NIOSH) is conducting research to enhance methane
control and mine ventilation practices at coal mines, as a
method to mitigate hazardous work conditions. NIOSH
researchers conducted case studies to investigate the effec-
tiveness of existing systems and improve performance to
decrease the potential for unplanned or excessive methane
emissions. At one mine, drainage was influenced by hydro-
fracking inefficiencies where two of the six wells showed
good frack development. Methane content was variable,
from 300 ft3/t to 600 ft3/t. This paper also summarizes over-
burden movement during undermining and the estimated
quantities of gas transported to the mine using FLAC3D
and CFD modeling. The findings from this research effort
highlight considerations based on specific mine conditions
that may also be applicable to most longwall mines utilizing
methane control systems.
INTRODUCTION
Problem Statement
Although the focus of this research is coal mines with rela-
tively high methane emission rates, methane control meth-
ods are common and necessary in a significant portion of
the industry. One half of the longwall panels listed on the
2023 Coal Age longwall census rely on some form of gas
extraction method (Coal Age, 2023). The international
market for produced coal has influenced U.S. coal opera-
tors’ decisions on staffing and support for mine operations.
Operators have lean staffing models and many have out-
sourced some ventilation support. Typically, few personnel
are present to manage methane control systems, focusing
mainly on maintenance and compliance with established
practices.
Deeper reserves are being pursued in many US coal
basins which typically increases gas in place and in situ gas
pressures. The industry uses the systems and configurations
that have been developed for the mine site, despite poten-
tially increased rates of emissions or overall larger volumes
of gas in dimensionally greater longwall gobs. The goal of
the current NIOSH research is to evaluate methane control
and ventilation methods at the candidate mines, provide
enhancements where performance improvements are pos-
sible and to share these findings with industry partners for
improved mine safety for workers and operators.
TECHNICAL APPROACH
In general, the assessment of gas emissions and migration to
underground mines have been a long-discussed topic due to
its potential impact on miners safety (Schatzel et al., 2008).
The advent of longwall mining to extract coal seams pro-
duced a new consideration in that full extraction mining
created caved, fractured, and bending regions in the strata
of the overburden where methane is produced from nearby
coal seams. Gob regions are critical in methane generation
from coal seams, as they are formed due to ground move-
ment associated with the longwall mining process. These
areas, created as the roof collapses behind the advancing
longwall, allow methane to be released from the fractured
coal and surrounding strata into the mine atmosphere. One
term used to describe this region of overburden that pro-
duces emissions is the gas emission zone which has been
largely defined through empirical studies in differing coal
basins of Europe (Karacan, 2023 Qu et al., 2022).
25-044
Improving Gas Management and Ventilation Performance at
Longwall Mines with Potentially High Gas Emission Rates
Steven J. Schatzel
NIOSH, Pittsburgh, PA
Berk Tulu
NIOSH, Pittsburgh, PA
K. Vaibhav Raj
NIOSH, Pittsburgh, PA
James Addis
NIOSH, Pittsburgh, PA
ABSTRACT
The National Institute for Occupational Safety and Health
(NIOSH) is conducting research to enhance methane
control and mine ventilation practices at coal mines, as a
method to mitigate hazardous work conditions. NIOSH
researchers conducted case studies to investigate the effec-
tiveness of existing systems and improve performance to
decrease the potential for unplanned or excessive methane
emissions. At one mine, drainage was influenced by hydro-
fracking inefficiencies where two of the six wells showed
good frack development. Methane content was variable,
from 300 ft3/t to 600 ft3/t. This paper also summarizes over-
burden movement during undermining and the estimated
quantities of gas transported to the mine using FLAC3D
and CFD modeling. The findings from this research effort
highlight considerations based on specific mine conditions
that may also be applicable to most longwall mines utilizing
methane control systems.
INTRODUCTION
Problem Statement
Although the focus of this research is coal mines with rela-
tively high methane emission rates, methane control meth-
ods are common and necessary in a significant portion of
the industry. One half of the longwall panels listed on the
2023 Coal Age longwall census rely on some form of gas
extraction method (Coal Age, 2023). The international
market for produced coal has influenced U.S. coal opera-
tors’ decisions on staffing and support for mine operations.
Operators have lean staffing models and many have out-
sourced some ventilation support. Typically, few personnel
are present to manage methane control systems, focusing
mainly on maintenance and compliance with established
practices.
Deeper reserves are being pursued in many US coal
basins which typically increases gas in place and in situ gas
pressures. The industry uses the systems and configurations
that have been developed for the mine site, despite poten-
tially increased rates of emissions or overall larger volumes
of gas in dimensionally greater longwall gobs. The goal of
the current NIOSH research is to evaluate methane control
and ventilation methods at the candidate mines, provide
enhancements where performance improvements are pos-
sible and to share these findings with industry partners for
improved mine safety for workers and operators.
TECHNICAL APPROACH
In general, the assessment of gas emissions and migration to
underground mines have been a long-discussed topic due to
its potential impact on miners safety (Schatzel et al., 2008).
The advent of longwall mining to extract coal seams pro-
duced a new consideration in that full extraction mining
created caved, fractured, and bending regions in the strata
of the overburden where methane is produced from nearby
coal seams. Gob regions are critical in methane generation
from coal seams, as they are formed due to ground move-
ment associated with the longwall mining process. These
areas, created as the roof collapses behind the advancing
longwall, allow methane to be released from the fractured
coal and surrounding strata into the mine atmosphere. One
term used to describe this region of overburden that pro-
duces emissions is the gas emission zone which has been
largely defined through empirical studies in differing coal
basins of Europe (Karacan, 2023 Qu et al., 2022).