Hartowijaya Pty Ltd

Within the framework of the United Nations Economic Commission for Europe (UNECE), member states have formed an Ad Hoc Group of Experts (AHGE) for Coal Mine Methane (CMM), comprised of over 200 individuals from governments, industry, investors, and international and intergovernmental organizations, which meets regularly and addresses mine safety issues and methane emission reduction potential.
At its most recent meeting on 16-17 October 2008, the AHGE discussed misconceptions about CMM projects worldwide, due at least in part to the perceived slow progress of such projects through the project-based “Flexible Mechanisms” of the Kyoto Protocol. There have been several publications addressing the “under-delivery” of carbon credits from CMM projects, raising concerns in the carbon credit market about reliable carbon credit supplies from these projects.

The intent of this guide is to provide assistance to mines in the development and
implementation of management systems to control risk arising from outbursts. The status of this document is as guidance material to the coal industry to assist operating mines in developing effective systems with the primary aim of preserving the life of those who work in conditions which may be prone to outbursts.

In order to achieve this aim the guide provides a set of management elements which must be addressed in order to manage outburst risks in a disciplined and controlled manner. With this in mind the importance of management approaches in addition to technical measures is recognised.

The general nature of the outburst risk is such that it may be continuously variable, not only between mines but also within an individual colliery’s workings. A single, unchanging approach to the management of the risk is, therefore, inappropriate. A degree of discipline is also warranted as a means to detect, and effectively act upon, the often subtle changes in a mine’s operating environment which may be associated with the potential for outbursts.

It is not the intention of this document to detail how any particular aspect of the management of the outburst risk is to be attempted, but rather to give an outline of what elements must be considered in the development of a managed approach to that risk. That managed approach is based on the development, implementation and maintenance of an Outburst Management Plan (OMP) for an affected mine.

In this context the OMP is the collection of measures to be undertaken to assess, detect and control outburst risks at a particular mine and it is intended that working OMP’s are tailored to suit the situation at any individual mine.

The extensive experience of the Coal Mining Inspectorate in the investigation of
outburst events has shown that a degree of certainty is often lacking in knowing that
procedures intended to be undertaken are, in fact, undertaken. In other words, it has become apparent that the management of outburst risk is at least as much a managerial and control issue as it is a technical issue. The best technology available has often been found wanting in the absence of effective systems to control its application.

The preparation of this document has drawn significantly from the model of managerial control represented by the AS3900 (ISO9000) series of quality assurance standards. This underlying model has been modified and supplemented by technically-based processes such as risk management and standards identified as desirable by various working groups formed as a result of fatalities and other outburst events in the Southern District of New South Wales.

 

Coalbed gas content measurements are commonly used in mine safety as well as coalbed methane resource assessment and recovery applications. Gas content determination techniques generally fall into two categories: (1) direct methods which actually measure the volume of gas released from a coal sample sealed into a desorption canister and (2) indirect methods based on empirical correlations, or laboratory derived sorption isotherm gas storage capacity data. Direct gas content determination techniques may be fbrther,subdivided into quick-crushing and extended desorption methods. The quick-crushing methods are primarily used in mine safety applications outside the United States, but have also been used for resource recovery applications. Quick-crushing methods rely on crushing the coal sample soon after collection to release all the desorbable gas, thus significantly shortening the amount of time required for desorption measurements.

However, some data useful for resource recovery applications are lost. Extended desorption techniques are most commonly used for resource assessment and recovery applications where information on desorption rates is useful for reservoir modeling, and for fundamental coalbed methane research. Extended desorption methods allow the gases in the coal sample to desorb under controlled laboratory conditions until a defined low desorption rate cutoff point is reached. The sample may then be crushed to measure the amount of gas remaining within the sample. Direct method techniques for gas content measurement are the focus of this paper.

Keywords: coal; coalbed methane; gas content; coal mine safety; reservoir engineering; unconventional gas reservoirs

William P. Diamond, Steven J. Schatzel

Information Circular 9486: Handbook for Methane Control in Mining

National Institute for Occupational Safety and Health

By Fred N. Kissell, Ph.D.

This document is in the public domain and may be freely copied or reprinted.

This handbook describes effective methods for the control of methane gas in mines and tunnels. It assumes the reader is familiar with mining. The first chapter covers facts about methane important to mine safety, such as the explosibility of gas mixtures. The second chapter covers methane sampling, which is crucial because many methane explosions have been attributed to sampling deficiencies. Subsequent chapters describe methane control methods for different kinds of mines and mining equipment, primarily for U.S. coal mines. These coal mine chapters include continuous miners and longwalls, including bleeders. Coal seam degasification is covered extensively. Other coal mine chapters deal with methane emission forecasting and predicting the excess gas from troublesome geologic features like faults. Additional coal chapters contain methane controls for shaft sinking and shaft filling, for surface highwall mines, and for coal storage silos. Major coal mine explosion disasters have always involved the combustion of coal dust, originally triggered by methane. Thus, a chapter is included on making coal dust inert so it cannot explode. Methane is surprisingly common in metal and nonmetal mines around the world, as well as in many tunnels as they are excavated. Accordingly, a chapter is included on metal and nonmetal mines and another on tunnels. Proper ventilation plays the major role in keeping mines free of hazardous methane accumulations. The ventilation discussed in this handbook, except for the chapter on bleeder systems, deals only with so-called face ventilation, i.e., ventilation of the immediate working face area, not ventilation of the mine as a whole. The omission of whole-mine ventilation was necessary to keep this handbook to a reasonable size and because a huge amount of excellent information is available on the subject.

Author(s):	Kissell-FN
Reference:	Pittsburgh, PA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2006-127, Information Circular 9486, 2006 Jun; :1-184

The measurement of gas content plays an important role in mine safety and mine planning for coal and gas recovery. A number of methods exist to determine gas content; direct and indirect methods. The direct method of fast desorption test is the preferred method of gas content measurement. The indirect methods are based on either empirical correlations or laboratory derived sorption isotherms. Recent research has identified two new, semi-direct methods of estimating total gas content using early stage gas desorption rate measurement. Both techniques, if adopted, can
provide operators with an indication of gas content and particularly whether the content is above or below the outburst threshold limit. A total of 930 samples, were analysed from two local mines, with known gas drainage problems and high degree of variability in both the insitu gas content and composition. Two specific aspects of the analysis included; the relationship of the three gas content components, Q1, Q2 and Q3, and the initial gas desorption rate relative to total gas content. Based on the relationship between desorption rate and total gas content, it was possible for minesite technical staff to provide operational personnel with an estimate of maximum expected total gas content from a particular core sample, based on the initial desorption rate value determined from Q2 field measurement data collected by the drillers or site geologists.

Dennis Black, Naj Aziz, Matt Jurak and Raul Florentin