German-Australian Demonstration of the Application of Lotem Measurement in Coal Mining

Underground » Geology

Published: April 97Project Number: C4029

Get ReportAuthor: Keeva Vozoff, O Engels, Greg Poole, S Lintker | Harbourdom Consulting, BHP Coal, DMT

The primary objective of the project was to show that it is possible to obtain important information about drainage and fluid content of coal seams from surface electromagnetic (LOTEM) measurements combined with reflection seismic data resistivity logs. If this can be done with sufficient resolution to map undrained zones ahead of mining, it will reduce the need for in-seam measurements of all kinds, thus reducing costs. Computer modelling showed it should be possible because of the large changes in the electrical properties of the coal seam as it is mined and drained.

A second objective of the project was to demonstrate the effectiveness of distributed multichannel electromagnetic (EM) data acquisition, and new field procedures designed around that principle. The concept is to apply seismic-like procedures to EM acquisition and processing in order to reduce the cost of acquiring EM data.

To test the concepts in a real situation, two surveys were carried out a year apart (May 1995 and May 1996) at exactly the same surface positions over an active longwall in the Appin Colliery. Between the two surveys the mine and drainage zones had shifted laterally by one longwall width, 250m.

In parallel with this project there was another in Europe, using exactly the same technology, to monitor movement of the water table in a closed anticline used to store gas in the summer. In that project, which was funded by the European Union, DMT was one of four participants and HarbourDom GmbH the prime subcontractor.

The main objectives in that project were to demonstrate and develop the distributed multichannel EM system concept. Whilst there has been no direct interchange of data, technical information has been exchanged between the two projects.

To plan the survey it was necessary to numerically model the effects on our measurements of changes in subsurface distribution of petrophysical properties. It was assumed for modelling purposes, that the only changes taking place were the 250m lateral shift of the mine and drainage zones, and that changes lay entirely within the Bulli seam itself.

The modelling predicted changes in our responses of up to 25% between the two surveys, which should have been easily observed with the anticipated performance of our equipment and data processing procedures.

The first results, from the 1995 survey, showed there was a serious design fault in the equipment which badly affected measurements when the receiver spread was too close to the transmitter. However, because of the survey procedures used we were able to use the data taken when transmitter and receivers were far enough apart, about 25-30% of the total.

The result from the second year's survey was that the effects we observed in the useable data were 4-5 times larger than predicted by the models. The likely explanation, supported by subsequent modelling, is that petrophysical properties changed (resistivities increased) not only in the seam itself, but also in a much thicker stress relief zone overlying the seam.

This was also observed in the seismic reflection records, with reflectors in the overlying 100-200m 'breaking up' as the longwall moved. New modelling done to explain our results shows that the effects can be explained by a zone of increased resistivity about 200m thick. What is less clear at this time is how the effects we are looking for can be used in the presence of the much larger effects which occur.

In terms of the second objective, data were acquired at a rate much greater than that of any other electromagnetic data acquisition system of this scale, that is with transmitter-receiver separations of 100's to 1000's of metres, and there are clear ways to improve production still further. The major limitation at present is in the time required for data processing and interpretation.


The Survey

A new distributed multichannel electromagnetic system was used to monitor changes in subsurface electrical properties due to mining and seam drainage. This was done through repeated surveys one year apart over the Appin Colliery near Appin, NSW.

By repeating measurements at the identical closely-spaced surface positions, and by recording very large volumes of data and applying statistical processing, it was expected that we would be able to observe the 15-25% changes in responses predicted by computer modelling. The model assumed that the only changes in physical properties taking place were within the (Bulli) seam itself.

Engineering faults in the equipment led to a loss of about 75% of the data. From the remaining data it was seen that the changes from survey to survey were 5-10 times greater than predicted in the modelling. Such changes can be explained if the electrical resistivity increases by 1-2 orders of magnitude in a zone 200m thick overlying the active region of longwall mine and drainage.

This is consistent with changes seen in reflection seismic profiles, in which reflectors break up and vanish in a zone of that dimension.


We conclude that the changes we were looking for are still there but there is little point in looking for them until the larger changes in the overlying region can be predicted.

Although many technical aspects of the project were successful, the main objective of demonstrating a capability to monitor a seam drainage was not attained, for two reasons. One is that the initial model, in which changes were assumed to take place only in the seam itself, was too simple.

From our results we learned that a very thick zone above the seam also changes, but do not yet know whether those changes are predictable. Since the changes also affect the reflection seismic results, it is possible that further study will suggest ways to predict their effects.

The method is in fact very sensitive but will of course require a better equipment design if it is to be used. A variety of other changes to hardware and software are also necessary if it is to be used in commercial applications.


Health and safety, productivity and environment initiatives.

Recently Completed Projects

C27039True Triaxial Strength Of Coal Measure Rocks And Its Impact On Roadway Stability And Coal Burst Assessment

Rocks in the ground are subject to a range of stresses. The stresses...

C3063Underground Vehicle Design Standards And Statutory Implications

The Australian underground diesel vehicle fleet has evolved since di...

C3064Conveyor Belting And Lagging Shear Characteristics - Drive Drum Slip

The primary aim of this project was to investigate the relationsh...


Open Cut

Safety, productivity and the right to operate are priorities for open cut mine research.

Recently Completed Projects

C26029Geological Controls On Fluorine And Phosphorus In Bowen Basin Coals

Increasing global restrictions on fluorine in product coal prompted ...

C28033Raw Ash To Yield Relationships

Correct outcomes in yield predictions for product ash from coal bore...

C27038Establishing Self-Sustaining And Recognisable Ecological Mine Rehabilitation

In recent years an increasing interest has been placed on mining ope...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27064Dry Beneficiation Using FGX And X-Ray Sorters

Conventional dry processing methods engage a single beneficiation de...

C26010Multi-Sloped Screening Efficiency With Changing Strokes, Frequencies, Feed Solids And Feed Rates-Pilot Plant Study

Optimising multi-sloped screens is often described as an art and the...

C28059Impact Of Water Quality In Coal Handling And Preparations Plants

The objective of this project was to deliver a concise reference do...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C23052Novel Stone Dust Looping Process For Ventilation Air Methane Abatement

This multi‐phase project is concerned with the mitigation of m...

C27054Optimisation Of A Thermal Flow Reversal Reactor For Ventilation Air Methane Mitigation

Ventilation air methane (VAM) generally accounts for 50-85% of the t...

C28076Selective Absorption Of Methane By Ionic Liquids (SAMIL) - Phase 2 Demonstration In A Packed Bed Reactor

An alternative approach to high temperature oxidation of ventilation...

Mine Site Greenhouse Gas Mitigation

Low Emission Coal Use

Step-change technologies aimed at reducing greenhouse gas emissions.

Recently Completed Projects

C17060BGasification Of Australian Coals

Four Australian coals were trialled in the Siemens 5 MWth pilot scale ga...

C17060AOxyfuel Technology For Carbon Capture And Storage Critical Clean Coal Technology - Interim Support

The status of oxy-fuel technology for first-generation plant is indicate...

C18007Review Of Underground Coal Gasification

This report consists of a broad review of underground coal gasification,...

Low Emission Coal Use

Mining And The Community

The relationship between mines and the local community.

Recently Completed Projects

C16027Assessing Housing And Labour Market Impacts Of Mining Developments In Bowen Basin Communities

The focus of this ACARP-funded project has been to identify a number...

C22029Understanding And Managing Cumulative Impacts Of Coal Mining And Other Land Uses In Regions With Diversified Economies

The coal industry operates in the context of competing land-uses that sh...

C23016Approval And Planning Assessment Of Black Coal Mines In NSW And Qld: A Review Of Economic Assessment Techniques

This reports on issues surrounding economic assessment and analysis ...

Mining And The Community


National Energy Research,Development & Demonstration Council (NERDDC) reports - pre 1992.

Recently Completed Projects

1609-C1609Self Heating of Spoil Piles from Open Cut Coal Mines

Self Heating of Spoil Piles from Open Cut Coal Mines

1301-C1301Stress Control Methods for Optimised Development...

Stress Control Methods for Optimised Development and Extraction Operations

0033-C1356Commissioned Report: Australian Thermal Coals...

Commissioned Report: Australian Thermal Coals - An Industry Handbook