scholarly journals OpenFOAM solver of the methane behaviour near the coal mine tunnelling face and its application

2021 ◽  
Vol 18 (3) ◽  
pp. 418-427
Author(s):  
Chengwu Li ◽  
Yuechao Zhao ◽  
Yonghang He
Keyword(s):  
Effective Stress ◽  
Methane Emission ◽  
Emission Rate ◽  
Friction Angle ◽  
Adsorption Parameters ◽  
Fractured Zone ◽  
Methane Seepage ◽  
Production Safety ◽  
Coal Damage ◽  
Methane Emission Rate

Abstract The methane near a tunnelling face seriously affects production safety in coal mines. A model considering methane seepage, adsorption, desorption and coal damage processes was established in this research. The open field operation and manipulation (OpenFOAM) solver was compiled to numerically solve the established model. The model is validated against data published in a previous theoretical study. The solver was used to investigate the effect of different parameters on methane emission regularity. This solver demonstrates that the effects of the original stress, coal cohesion and coal internal friction angle on the methane emission rate are limited, but their effects on the width of the fractured zone and effective stress are great. The effects of the initial methane pressure and coal adsorption parameters on the methane emission rate are also notable, but their effects on the width of the fractured zone and effective stress are limited.

scholarly journals Comparing facility-level methane emission rate estimates at natural gas gathering and boosting stations

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Timothy L. Vaughn ◽  
Clay S. Bell ◽  
Tara I. Yacovitch ◽  
Joseph R. Roscioli ◽  
Scott C. Herndon ◽  
...  
Keyword(s):  
Natural Gas ◽  
Confidence Intervals ◽  
Methane Emission ◽  
Emission Rate ◽  
National Study ◽  
Aircraft Measurements ◽  
Component Level ◽  
Facility Level ◽  
Unburned Fuel ◽  
Methane Emission Rate

Coordinated dual-tracer, aircraft-based, and direct component-level measurements were made at midstream natural gas gathering and boosting stations in the Fayetteville shale (Arkansas, USA). On-site component-level measurements were combined with engineering estimates to generate comprehensive facility-level methane emission rate estimates (“study on-site estimates (SOE)”) comparable to tracer and aircraft measurements. Combustion slip (unburned fuel entrained in compressor engine exhaust), which was calculated based on 111 recent measurements of representative compressor engines, accounts for an estimated 75% of cumulative SOEs at gathering stations included in comparisons. Measured methane emissions from regenerator vents on glycol dehydrator units were substantially larger than predicted by modelling software; the contribution of dehydrator regenerator vents to the cumulative SOE would increase from 1% to 10% if based on direct measurements. Concurrent measurements at 14 normally-operating facilities show relative agreement between tracer and SOE, but indicate that tracer measurements estimate lower emissions (regression of tracer to SOE = 0.91 (95% CI = 0.83–0.99), R2 = 0.89). Tracer and SOE 95% confidence intervals overlap at 11/14 facilities. Contemporaneous measurements at six facilities suggest that aircraft measurements estimate higher emissions than SOE. Aircraft and study on-site estimate 95% confidence intervals overlap at 3/6 facilities. The average facility level emission rate (FLER) estimated by tracer measurements in this study is 17–73% higher than a prior national study by Marchese et al.

scholarly journals METHANE EMISSION FROM PADDY SOIL IN RELATION TO SOIL TEMPERATURE IN TROPICAL REGION

2016 ◽  
Vol 78 (1-2) ◽  
Author(s):  
Fazli P. ◽  
Hasfalina C. M. ◽  
Mohamed Azwan M. Z. ◽  
Umi Kalsom M. S. ◽  
Nor Aini A. R. ◽  
...  
Keyword(s):  
Soil Temperature ◽  
Methane Emission ◽  
Paddy Soil ◽  
Emission Rate ◽  
Paddy Fields ◽  
Tropical Region ◽  
Emission Pattern ◽  
Short Period ◽  
Methane Emission Rate

Methane (CH4) is 21 times more powerful as a greenhouse gas than carbon dioxide. Wetlands including flooded paddy fields are one of the major sources for this gas. Paddy fields are responsible for producing 25 to 54 Tg of CH4 annually. Methane emission rate could be affected by several factors such as irrigation pattern, fertilizer type, soil organic matter and soil temperature. Among them, soil temperature is a determining factor which deserves to be investigated. This study performed with the aim of understanding the effect of soil temperature on the methane emission rate from paddy soil in a short period of time (hourly) and long term (during rice growing season). The results of this study suggest that soil temperature could control the amount of methane emission and there is a positive and strong correlation in both soil temperature and methane emission pattern in short period of time. However, in case of long term trend, other factors such as water management and plant age decreased this correlation from 0.768 to 0.528.

scholarly journals Global annual methane emission rate derived from its current atmospheric mixing ratio and estimated lifetime

2014 ◽  
Vol 32 (3) ◽  
pp. 277-283 ◽  
Author(s):  
G. R. Sonnemann ◽  
M. Grygalashvyly
Keyword(s):  
Methane Emission ◽  
Reasonable Agreement ◽  
Reaction Rate ◽  
Emission Rate ◽  
Annual Growth Rate ◽  
Mixing Ratio ◽  
Atmospheric Lifetime ◽  
Lower Limits ◽  
Methane Emission Rate

Abstract. We use the estimated lifetime of methane (CH4), the current methane concentration, and its annual growth rate to calculate the global methane emission rate. The upper and lower limits of the annual global methane emission rate, depending on loss of CH4 into the stratosphere and methane consuming bacteria, amounts to 648.0 Mt a−1 and 608.0 Mt a−1. These values are in reasonable agreement with satellite and with much more accurate in situ measurements of methane. We estimate a mean tropospheric and mass-weighted temperature related to the reaction rate and employ a mean OH-concentration to calculate a mean methane lifetime. The estimated atmospheric lifetime of methane amounts to 8.28 years and 8.84 years, respectively. In order to improve the analysis a realistic 3D-calculations should be performed.

Relationship between Methane Emission and Strata Behavior at Island Coal Face

2012 ◽  
Vol 524-527 ◽  
pp. 662-667
Author(s):  
Xin Xian Zhai ◽  
Fu Lin Wang
Keyword(s):  
Coal Mine ◽  
Methane Emission ◽  
Emission Rate ◽  
Main Roof ◽  
Control Measures ◽  
Emission Rates ◽  
Coal Face ◽  
Coal Wall ◽  
Strata Behavior ◽  
Methane Emission Rate

According to the practical conditions of the island coal face in No.2 Coal Mine of Pingdingshan Coal Company Ltd., China, the strata behaviors and methane emission were monitored and their two relationships were analyzed. The results indicate that strata behavior at coal face affects its methane emission rates at coal wall and goaf，which the quantity of methane emission rate at coal face is largely increasing after main roof weighting. So through the monitor of periodic roof weighting time, larger methane emission rate at coal face can be predicted. Then the related methane control measures can be taken timely.

Spatial and temporal variation of 13C-signature of methane emitted by a temperate mire ecosystem

2021 ◽  
Author(s):  
Janne Rinne ◽  
Patryk Łakomiec ◽  
Patrik Vestin ◽  
Per Weslien ◽  
Julia Kelly ◽  
...  
Keyword(s):  
Spatial Variation ◽  
Temporal Variation ◽  
Methane Emission ◽  
Trophic Status ◽  
Emission Rate ◽  
Temporal Behavior ◽  
Emission Rates ◽  
Spatial Differences ◽  
Mire Ecosystem ◽  
Methane Emission Rate

<p>The net methane emission of any mire ecosystem results from a combination of biological and physical processes, including methane production by archaea, methane consumption by bacteria, and transport of methane from peat to the atmosphere. The complexity of spatial and temporal behavior of methane emission is connected to these.</p><p><sup>13</sup>C-signature of emitted methane offers us a further constraint to evaluate our hypothesis on the processes leading to the variation of methane emission rates. For example, assuming the spatial variation in methane emission rate at microtopographic scale is due to variation in trophic status or variation in methane consumption, will lead to differences in the relation of methane emission rate and its <sup>13</sup>C-signature, expressed as δ<sup>13</sup>C.</p><p>We have measured the methane emission rates and δ<sup>13</sup>C of emitted methane by six automated chambers at a poor fen ecosystem over two growing seasons. The measurements were conducted at Mycklemossen mire (58°21'N 12°10'E, 80m a.s.l.), Sweden, during 2019-2020. In addition, we measured atmospheric surface layer methane mixing ratios and δ<sup>13</sup>C to obtain larger scale <sup>13</sup>C-signatures by the nocturnal boundary-layer accumulation (NBL) approach. All δ<sup>13</sup>C-signatures were derived using the Keeling-plot approach.</p><p>The collected data shows spatial differences of up to 10-15 ‰ in 10-day averages of δ<sup>13</sup>C-signatures between different chamber locations. Temporal variations of 10-day average δ<sup>13</sup>C-signatures from most chamber locations reached over 5 ‰, while the temporal variation of NBL derived δ<sup>13</sup>C-signature was slightly lower.</p><p>The observed spatial variation in the δ<sup>13</sup>C-signature was somewhat systematic, indicating, especially in the middle of the summers, the main control of spatial variation of methane emission to be the trophic status. The temporal changes, measured at different locations, indicate spatial differences in the temporal dynamics at the microtopographic scale. The temporal behavior of larger scale NBL δ<sup>13</sup>C-signature does not fully correspond to the behavior of the chamber derived average δ<sup>13</sup>C-signature.</p>

scholarly journals Is there a relationship between genetic merit and enteric methane emission rate of lactating Holstein-Friesian dairy cows?

animal ◽  
2015 ◽  
Vol 9 (11) ◽  
pp. 1807-1812 ◽  
Author(s):  
L.F. Dong ◽  
T. Yan ◽  
C.P. Ferris ◽  
D.A. McDowell ◽  
A. Gordon
Keyword(s):  
Dairy Cows ◽  
Methane Emission ◽  
Emission Rate ◽  
Genetic Merit ◽  
Holstein Friesian ◽  
Enteric Methane ◽  
Methane Emission Rate

Time Constraints on Seepage Through Fractured Regions on the Vestnesa Ridge off the W-Svalbard Coast

2021 ◽  
Author(s):  
Hariharan Ramachandran ◽  
Andreia Plaza-Faverola ◽  
Hugh Daigle ◽  
Stefan Buenz
Keyword(s):  
Fluid Flow ◽  
Effective Stress ◽  
Gas Hydrate ◽  
Fluid Pressure ◽  
Fracture Network ◽  
The Arctic ◽  
Stability Zone ◽  
Methane Seepage ◽  
Carbonate Formation ◽  
Hydrate Stability

<p>Evidences of subsurface fluid flow-driven fractures (from seismic interpretation) are quite common at Vestnesa Ridge (around 79ºN in the Arctic Ocean), W-Svalbard margin. Ultimately, the fractured systems have led to the formation of pockmarks on the seafloor. At present day, the eastern segment of the ridge has active pockmarks with continuous methane seep observations in sonar data. The pockmarks in the western segment are considered inactive or to seep at a rate that is harder to identify. The ridge is at ~1200m water depth with the base of the gas hydrate stability zone (GHSZ) at ~200m below the seafloor. Considerable free gas zone is present below the hydrates. Besides the obvious concern of amount and rates of historic methane seeping into the ocean biosphere and its associated effects, significant gaps exist in the ability to model the processes of flow of methane through this faulted and fractured region. Our aim is to highlight the interactions between physical flow, geomechanics and geological control processes that govern the rates and timing of methane seepage.</p><p>For this purpose, we performed numerical fluid flow simulations. We integrate fundamental mass and component conservation equations with a phase equilibrium approach accounting for hydrate phase boundary effects to simulate the transport of gas from the base of the GHSZ through rock matrix and interconnected fractures until the seafloor. The relation between effective stress and fluid pressure is considered and fractures are activated once the effective stress exceeds the tensile limit. We use field data (seismic, oedometer tests on calypso cores, pore fluid pressure and temperature) to constrain the range of validity of various flow and geomechanical parameters in the simulation (such as vertical stress, porosity, permeability, saturations).</p><p>Preliminary results indicate fluid overpressure greater than 1.5 MPa is required to initiate fractures at the base of the gas hydrate stability zone for the investigated system. Focused fluid flow occurs through the narrow fracture networks and the gas reaches the seafloor within 1 day. The surrounding regions near the fracture network exhibit slower seepage towards the seafloor, but over a wider area. Advective flux through the less fractured surrounding regions, reaches the seafloor within 15 years and a diffusive flux reaches within 1200 years. These times are controlled by the permeability of the sediments and are retarded further due to considerable hydrate/carbonate formation during vertical migration. Next course of action includes constraining the methane availability at the base of the GHSZ and estimating its impact on seepage behavior.</p>

A record of seafloor methane seepage across the last 150 million years

2020 ◽  
Author(s):  
Davide Oppo ◽  
Luca De Siena ◽  
David Kemp
Keyword(s):  
Organic Carbon ◽  
Sea Level ◽  
Methane Emission ◽  
Temporal Correlation ◽  
Biogenic Methane ◽  
Methane Seepage ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Rapid Generation ◽  
Extinction Events

<p>Methane seepage at the seafloor is a source of carbon in the marine environment and has long been recognized as an important window into the deep geo-, hydro-, and bio-spheres. However, the processes and temporal patterns of natural methane emission over multi-million-year time scales are still poorly understood. The microbially-mediated methane oxidation leads to the precipitation of authigenic carbonate minerals within subseafloor sediments, thus providing a potentially extensive record of past methane emission. In this study, we used data on methane-derived authigenic carbonates to build a proxy time series of seafloor methane emission over the last 150 My. We quantitatively demonstrate that variations in sea level and organic carbon burial are the dominant controls on methane leakage since the Early Cretaceous. Sea level controls variations of methane seepage by imposing smooth trends with cyclicities in the order of tens of My. Organic carbon burial shows the same cyclicities and instantaneously controls the volumes of methane released thanks to the rapid generation of biogenic methane. The identified fundamental (26-27 My) cyclicity matches those observed in the carbon cycle associated with plate tectonic processes, the atmospheric CO<sub>2</sub>, the oceanic anoxic events, and mass extinction events. A higher (12 My) cyclicity relates to modulations of Milankovitch eccentricity cycles and to variations in global tectonics. These analogies demonstrate that the seafloor methane seepage across the last 150 My relates to a large spectrum of global phenomena and thus has key implications for a better understanding of methane cycling at the present day. Temporal correlation analysis supports the evidence that the modern expansion of hypoxic areas and its effect on organic carbon burial may lead to higher seawater methane concentrations over the coming centuries.</p>

Sign in / Sign up

Export Citation Format

Share Document