Mine Site Greenhouse Gas Mitigation

The Role of Hydrogeology, in situ Stress and Temperature Logs in the Distribution and Delineation of Coal Seam Gas Regimes

Mine Site Greenhouse Gas Mitigation » Mine Site Greenhouse Gas Mitigation

Published: June 15Project Number: C21061

Get ReportAuthor: Agnes Burra | University of Queensland

This thesis explores mechanisms that determine coal seam gas (CSG) distribution and methods for its delineation. Understanding the distribution of gas content and composition underpins exploration and forecasting, as well as estimation of fugitive emissions from coal mines. Coal seam gas origins are variable, and thermogenic hydrocarbon accumulations are often supplemented by inorganic carbon dioxide and microbial methane in many reservoirs. The generation of these gases is dependent on geological and hydrogeological parameters relating to reservoir geometry and permeability.


Specifically, this thesis examined:

· Hydro-geochemical controls on gas distributions and the apparent vertical zonation of gas reservoirs in the Sydney Basin, Australia;

· The role of in situ stress in regulating water and gas migration (and/or accumulation); and

· Utilisation of wireline temperature logging to enhance existing gas and geological exploration methods.


The Sydney Basin is a coal-bearing sedimentary basin in eastern Australia. It is bounded by a series of highlands in the north, west and south and drains towards the centre and then to the east of the basin. Coal seam gas occurrence is laterally extensive and comprises layers of biogenic and thermogenic hydrocarbons and carbon dioxide. The zonation of these gases is regular and cross-cuts regional bedding dip; however, the sequence of gases varies with geographical position within the basin. Inland areas host a CO2-rich zone between the shallow biogenic and deep thermogenic hydrocarbon layers, whereas coastal locations are devoid of CO2, even in the vicinity of igneous intrusives.


Gas contents typically increase with depth and peak at around 600-800m, below which volumes decrease to the base of the coal-bearing sequences. Carbon isotope data mirror this trend; both δ13C-CH4 and δ13C-CO2 increase with depth down to 800m, and then stabilise. These results confirm the respective biogenic and thermogenic hydrocarbon origins; however, carbon dioxide results are more complex. Conventional interpretation of CO2 origin is limited to deep-seated magmatic sources; however, many of the δ13C-CO2 values in the basin are outside of the traditionally assigned range. Investigations reveal that meteoric water enriched with positive cations (such as fresh rainwater in highland recharge areas) routinely dissolve carbonate mineralisation and transport bicarbonate down-gradient. Groundwater chemistry evolves along flow paths from fresh to saline composition and this causes  re-precipitation of minerals. In some areas, the bicarbonate saturated waters can get trapped and, due to partial-pressure and groundwater salinity changes, liberate CO2 gas which then adsorbs to the coal matrix. Saline groundwaters in coastal regions preclude the development of CO2-rich gas accumulations, instead hosting extensive hydrocarbon reservoirs.


Groundwater infiltration and gas migration are dependent on permeability that primarily occurs via fractures and coal cleats. Horizontal stress is critical in determining whether the cleat or fracture sets stay open and form conduits. Reinterpretation of existing data showed that differential horizontal stress magnitude varies with depth in zones regardless of the host formation lithology or stratigraphy; similar to that exhibited by the gas compositional layering. This means that the horizontal stress isotropy varies between zones; displaying higher values in the shallower and deeper parts of the strata (associated with biogenic and thermogenic gas reservoirs, respectively), and lower values in the middle section around 600-850m that hosts the mixed gas zone. This results in more fracturing in the middle zone and is intensified by the pore pressure overcoming the effective vertical stress. The upwelling, deep formation waters interact with the meteoric influx and result in the development of a peak gas horizon in this zone.


The observations show that the vertically zonal nature of the stress environment controls the hydrogeological setting, which in turn facilitates the gas distribution. Therefore, groundwater monitoring methods, such as wireline temperature logging, could be utilised for mapping gas distribution. This tool is used to discern downward and upward flow and identify along-bedding flow and for approximation of permeability. The changes in temperature gradients identify flow type boundaries that coincide with changes in gas characteristics. This is particularly pertinent where gas compositional changes occur; in a case study presented as part of this investigation, surface meteoric influx discernible from the temperature logs coincide with the shallow biogenic methane zone, which is underlain by a highly compartmentalised and isolated strata interval of some 100-300m thickness hosting high concentrations of CO2 gas. In an adjacent and less compartmentalised region, the biogenic methane zone persists to deeper horizons but with increasingly less infiltration evident with depth concomitant with increasing CO2 compositions.


This case study provides proof of concept for the utilisation of temperature logs towards enhancing coal seam gas exploration and optimising production and estimation processes.


Health and safety, productivity and environment initiatives.


Open Cut

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

Recently Completed Projects

C19024Establishing Ecologically Sustainable Mine Water Release Criteria In Seasonally Flowing Streams

Extreme rainfall conditions in the Fitzroy Catchment over an approxi...

C25030Coal Mine Open Pit Final Void Closure And Relinquishment - Addressing Uncertainty In Coal Mine Environmental Planning

This report addresses uncertainties faced by coal mine operators whe...

C27046Estimation Of True Deformation Vector From Slope Radar Monitoring

Slope deformation radar monitors are now widely used in open cut coa...

Open Cut

Coal Preparation

Maximising throughput and yield while minimising costs and emissions.

Recently Completed Projects

C27004Improving Coal Flotation With Oscillatory Air Supply

This report provides detailed information on coal flotation with os...

C25018Improving Solids Recovery And Moisture Reduction In Ultrafine Coal Dewatering

This report provides detailed information on fine coal dewatering in...

C27028Lab Froth Flotation Testing Guide With Coal Quality

Correct outcomes from laboratory froth flotation testing in coal bor...

Coal Preparation

Technical Market Support

Market acceptance and emphasising the advantages of Australian coals.

Recently Completed Projects

C26039Nanoporosity In Cokes: Their Origin, Control And Influence On CO2 Reactivity

This project using the outcomes of previous project C24060, examine...

C28063A Comprehensive Technical Review Of High-Efficiency Low-Emission (HELE) Pulverised Coal Combustion Technologies For Power Generation

Research and development has been undertaken worldwide to realise co...

C28064Carbon Structure Transformation During Coking Of Australian Coking Coals: Better Understanding The Coke Formation

Carbon structures of coke that are formed during the plastic layer a...

Technical Market Support

Mine Site Greenhouse Gas Mitigation

Mitigating greenhouse gas emissions from the production of coal.

Recently Completed Projects

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...

C26004CFD Modelling Of Reverse Thermal Oxidisers For VAM Abatement - CFD Modelling Of Fixed-Bed RTO Devices

The project is part of a larger multi‐phase program of study a...

C27058Technological Assessment Of A Recycle Reactor For VAM Abatement

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

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