Field Trials of Nitrogen Injection Into UIS Directional Boreholes to Enhance Gas Drainage in Low Permeable Seams

Underground » Ventilation, Gas Drainage and Monitoring

Published: November 18Project Number: C24019

Get ReportAuthor: Ting Ren, Gongda Wang, Frank Hungerford, Jia Lin, Patrick Booth, Jan Nemcik, Alex Remennikov and Naj Aziz | University of Wollongong

Pre-gas drainage is widely used as an effective method to control gas and coal outburst in underground coal mines. However difficulties of reducing gas content below threshold limit values (TLV) within a given drainage lead time have been encountered in some coal mines in QLD and NSW, especially in carbon dioxide abundant coal seams. By injecting an alien gas such as nitrogen into the coal seam, the gas drainage performance can be improved. In this study, field trials of nitrogen injection enhanced gas drainage were conducted. This study aims to conduct field trials using underground inseam (UIS) directional boreholes to demonstrate the use of nitrogen flushing to accelerate gas drainage rate to enable statutory threshold values to be met in hard-to-drain or low permeable seams.

For the design and implementation of field trials, extensive laboratory studies of the Bulli coal characteristics were conducted using coal samples collected from the top, middle and bottom of the Bulli seam of the planned trial sites at Metropolitan and Appin mines. All samples have a large volume of pores with a diameter up to 6nm while the micro-pores account for most of the pore space and surface area. Permeability changes of the cores are measured under different confining stress mimicking the field geo-stress conditions. The permeability of the coal samples was found in the order of 5~0.01mD under a confining pressure condition from 2MPa to 8MPa. From the permeability tests, we conclude that the coal seam at the proposed trial area is comparatively tight and less permeable under current stress conditions at Metropolitan Colliery. Nitrogen flushing tests are conducted in laboratory using core samples and these tests indicated that a ratio of 3~10 units nitrogen is required to displace 1 unit of CO2.

Numerical reservoir simulations are conducted by the COMSOL Multiphysics software. A binary gas transport model has been developed to simulate the nitrogen flushing process of coal seam gas. The simulations involved an improved permeability and fully-coupled model considering the competitive adsorption of binary gas and its influence on the coal matrix-cleat interaction, and the mechanical response to binary gas state change under in-situ stress condition by constraining core displacement. This model was fully validated by laboratory nitrogen flushing tests. The residual gas content of the core and the gas composition variations of the production gas flow matched well with the simulation results. The simulations demonstrated that coal seam permeability played a vital role in governing the nitrogen flushing process.

This project has demonstrated that nitrogen flushing with UIS boreholes can be used to accelerate gas drainage in hard-to-drain or low flow boreholes. This is a promising technology for stimulating gas recovery from tight coal seams. The field trial has established a work procedure that can be referred to and used in future field work. Future work should consider a full scale field demonstration project using a group of boreholes from a drainage stub and a continued supply of nitrogen source from surface or underground. Outcomes from this project are also useful for other options of seam gas drainage such as surface in-seam (SIS) holes with nitrogen flushing.


Health and safety, productivity and environment initiatives.

Recently Completed Projects

C26059Proof Of Concept Of The Electronic Spark Test Apparatus On Existing Known Power Supplies

This project continued a long running research program into an elect...

C25001Ventilation And Gas Management - Underground Coal Mines

This planning guideline has been prepared to assist mine operators t...

C27010A Clinical, Radiological And Occupational Review Of Coal Mine Dust Lung Disease In Queensland

The aim of this project was to review recently diagnosed cases of Co...


Open Cut

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

Recently Completed Projects

C26034Coking Properties Deterioration In Small Samples

Accurate evaluation of coking coal parameters at the exploration sta...

C23029Alternative And Sustainable Explosive Formulations To Eliminate Nitrogen Oxide Emissions

This technical report describes the technology of a novel mining exp...

C25005Site Based Trials Of Alternative Explosive Formulations To Eliminate Nitrogen Oxide Emissions

This report documents the outcomes of Phase 3 of this project and b...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C26009Improved Precision Of Determining Coal In Urban Dust

Dust samples collected in coastal locations using High Volume Air Sa...

C26015Novel Characterisation Of Coal Petrography For Improving The Dewatering Of Fine Coals Using Chemicals

This project aimed to develop alternatives to existing mechanical de...

C26014Low Cost Online Measurement Of Particle Size And Density For Diagnostics Across The Fine Coal Circuit

This project has developed a novel prototype optical system for prof...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C26045Mineralogy Effects On The 3D Porosity Evolution Of Coke And Coke Reactivity

CRI/CSR CO2 combustion data are key metrics of coke quality and perf...

C25049Fusibility Of Coal Blends And Minerals In Coking

The CSIRO optical reflected light imaging CGA (Coal Grain Analysis) ...

C25045Stage Two - Assessment Of In Situ High-Temperature Strength Of Cokes

Stage I of this project established a reliable and repeatable proces...

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

C27058Technological Assessment Of A Recycle Reactor For VAM Abatement

Underground coal mining emits high volumes of methane, diluted in ve...

C27008Selective Absorption Of Methane By Ionic Liquids

The connection of a ventilation air methane (VAM) abatement plant di...

C24061Proof-Of-Concept Photocatalytic Destruction Of Methane For Coal Mining Fugitive Emissions Abatement

Australia's fugitive emissions in 2015 were 41 Mt CO2-e (representin...

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