Why flexibility and responsiveness is essential to managing water from the coal seams
Flexibility and adapting to change are key ingredients to success in managing projects using water extracted from the coal seams. The Santos GLNG project is leading the way in ensuring that its Queensland CSG project will establish a best practice approach to management of water extracted from coal seams. Philippa Kassianos reports.
The development of the coal seam gas (CSG) industry in Queensland has unlocked a potential water resource for rural communities. Coal seam gas production involves the depressurisation, (through the release of water) of the coal seam. The Santos GLNG Project will produce 344 gigalitres of water over the life of the project (up to 40 years).
However, there are several challenges that the industry faces in successfully using this resource. The overarching challenge involves adopting a flexible approach to managing water which is variable in production rate and quality. Other challenges include working within a land and climatic environment which can vary dramatically from season to season in addition to an evolving complex legislative and regulatory environment.
In recognising this context, the Santos GLNG Project reflects the principles of best practice rural management – an adaptive approach which provides a portfolio of options which can be used for the storage, treatment and use of water from the coal seams. This adaptive approach seeks to meet Santos GLNG’s three key management principles for managing water from coal seams:
- Minimise the impacts to the environment;
- Provides ongoing and tangible benefits to the local community; and,
- A sustainable approach to water management – benefits that can outlast the availability of water from coal seam gas.
So what are the variables that affect water from the coal seams? And how does this approach work for the seasonal use of water by our rural communities?
The variable nature of management of water from the coal seams
The variable nature of management of water from the coal seams is due to constant change around: water production rates; water quality; seasonal and demand variations. The adaptive management approach recognises the nature of these changing variables and has enabled the development of a system and uses which respond to these variables.
The Santos GLNG Project will produce 344 gigalitres of water over the life of the project (up to 40 years). The expected volume of water has been forecast through exploration and appraisal activities and reservoir modelling. However, the rate of water production from coal seams i.e. the shape of the water curve, is likely to vary as the location and timing of wells is optimised. Santos GLNG has planned and designed infrastructure and beneficial uses for managing water from coal seams with additional capacity to deal with possible variability in water production from coal seams.
The quality of water from coal seams varies between CSG fields (for example between Santos Roma CSG Field and Fairview CSG field) and can vary within fields (for example the salinity of water from coal seams in the Fairview CSG field gradually changes from west to east).
Santos GLNG’s focus is on treatment of the water to a suitable quality for its intended beneficial use. The treatment process is generally a desalination process (reverse osmosis), with some post treatment (called amendment) to make the water suitable for its specific end use.
Santos GLNG has planned and designed infrastructure to manage water from coal seams to enable transfer of water between treatment facilities to manage this variability.
Extensive operational monitoring is undertaken to ensure that the water meets the required standards prior to use. Regular audits are also undertaken by Santos GLNG and the government to ensure that their required standards are met.
A water management system for water from the coal seams needs to be capable of operating during periods of extreme weather conditions, for example managing water from coal seams to avoid overflow from storages during high rainfall events. In addition to seasonal variations (e.g. crops need more water in summer), there are short and medium term variations in demands arising from farming practices. As water from coal seams is a constant supply, these varying demands need to be managed.
Dealing with the variables to benefit the community
The Santos GLNG Water Management Strategy deals with these variables by adopting a portfolio of water uses which are specific to the regions we operate in: Roma, Fairview and Arcadia. The portfolio of uses was developed through the assessment of potential uses against local conditions including local environmental settings (geology, topography, soil types), local land uses and local demands.
For example, the planned portfolio of water uses in the Roma CSG field includes:
- Roma town drinking water (Managed Aquifer Recharge project): the injection of treated water from coal seams into the Gubbermunda sandstone from which Roma draws most of its town water supply – depleted over the past 100 years from agricultural and town water usage. Injection of treated water from coal seams will provide the town with an additional 50 years of drinking water supply.
- Irrigation of cattle forage crops: Santos GLNG has undertaken partnerships with local landholders to establish irrigation infrastructure and use treated water from coal seams to irrigate forage crops that will enhance beef production.
- Dust suppression: as required, the use of treated water from coal seams for dust suppression on local dirt roads and for construction purposes.
This portfolio approach enables Santos GLNG to respond to seasonal variations. For example, injection (for drinking water) can be maximised during periods of high rainfall when dust suppression is not required and irrigation demands are low (between crop cycles or during winter for summer crops). Conversely this portfolio approach enables irrigation to be maximised during periods of low rainfall, by reducing injection rates.
This portfolio approach is an example of one of the flexible approaches that Santos GLNG has adopted to manage the range of variables expected in water management.
What is adaptive management?
Santos GLNG’s water team has developed an adaptive management system that deals with the variables expected in water from coal seam production and provides flexibility in the water gathering network, treatment, beneficial uses and brine management.
The adaptive scheme management is dependent on five key areas, described in further detail below:
- Predictive modelling
- Extensive monitoring and trend analysis
- Comparison of results against trigger levels and early warnings (preset by modelling)
- Planned responses for when a monitoring trigger is reached
- Reporting on performance against plan
From the outset of the Santos GLNG Project, an extensive program of predictive modelling was undertaken to determine the optimal way to operate CSG water management infrastructure (e.g. water balance modelling) and to understand potential impacts (e.g. groundwater modelling, seepage modelling for irrigation projects) in order to develop appropriate mitigation measures.
To complement this modelling program, Santos GLNG also developed an extensive surface and groundwater monitoring program in place whichincludes operational monitoring and environmental monitoring. Operational monitoring includes monitoring of water production rates, key water quality parameters, pond water levels, pipeline flows, reverse osmosis plant inflows and outflows. Environmental monitoring includes monitoring for early detection of any impacts to regional groundwater levels and quality, surface water resources quality and flow and soils.
In addition, Santos GLNG has, as part of its irrigation projects, a monitoring program which tracks the impacts of irrigated (and treated) water from coal seams on the soil. The sustainability of our irrigation projects and soil monitoring programs is independently reviewed by experts from Queensland universities including UQ, USQ and CQU and by overseas experts with 12 years’ experience in irrigation using water from coal seams.
Our groundwater and surface water monitoring results are available to the public through – www.santoswaterportal.com.au – the Santos GLNG Project Water Portal.
The modelling and monitoring programs provide Santos GLNG with an accurate picture of what is expected (modelling) and what is happening in real time (monitoring). This comparison enables water management via a series of planned responses in the event that the predictive measured performance start to trend differently – in areas such as water production, pond water levels, pipeline flows, and desalination plant flows.
For example, if a water management pond for water extracted from the coal seams is filling up faster than expected the planned responses include:
- Determine whether it’s as a result of increased water production from coal seams or a bottle neck in the treatment process or similar;
- Re-run modelling to predict the impact of the storage filling up faster than expected; and,
- Investigate remedial actions, including different management practice or developing additional infrastructure (pond capacity/treatment/beneficial use capacity).
Planned response flow charts have been developed and are used as ‘operating rules’ for each component of the water management infrastructure for water extracted from coal seams and beneficial uses.
All of the above systems and programs are included in an annual CSG Water Production and Performance Report. These annual reports (one for each region we are working in) are produced to report on performance against plan and highlight areas for improvement.
Santos has invested in water management from the outset of the Santos GLNG Project. This investment has enabled the ability to have a flexible and responsive adaptive management system. This system meets the key principles of our water management strategy as follows:
- Developing a sustainable approach to water management
The Santos GLNG Project has adopted an adaptive management approach to water from coal seams. An adaptive approach – similar to that used by farmers to respond to changing environmental conditions – allows the project team to have a range of beneficial use options available and therefore respond quickly and efficiently. This will enable the reuse of 90 per cent of the Santos GLNG Project water for the benefit of rural communities.
- Minimising impacts to the environment
Santos GLNG has invested in understanding the water environment (groundwater, surface water and CSG water) specific to the Maranoa region. This investment is through extensive modelling, feasibility and research, which is available online at www.glng.com.au as part of the two and a half year environmental impact assessment process. Further investment is continuing in an extensive water monitoring program which provides the team with critical real time data on the water being extracted, treated, stored and used. The Santos GLNG Project water portal (www.santoswaterportal.com.au) provides the community with the results of this ongoing water monitoring program with results from over 100 locations in the Maranoa region.
- Bringing benefits to the local community
Santos is purifying the water from coal seams so that it can be used beneficially by the community and local landholders. The portfolio of water uses, that are relevant to the local area including the irrigation of forage crops; and recharging Roma’s town water supply for up to 50 years represent a beneficial outcome for the Roma community which will be a positive testament to the adaptive approach taken by the Santos GLNG Project.
Team Leader – Water Studies
Santos GLNG Project
Philippa is a civil engineer with a specialisation in water engineering and management. She has been with Santos for the last three years as Team Leader – Water Studies. In this role, Philippa is responsible for the development of coal seam gas (CSG) water management planning and water resource management for the Santos GLNG Project and Santos Eastern Australian CSG fields.
Prior to joining Santos, Philippa worked as a consultant for URS, PB and Water Solutions in senior water engineering positions. Philippa has over 11 years’ experience in a wide range of water engineering fields, including CSG water management, groundwater studies, water balance modelling, flood investigations, hydrology, hydraulics and water supply design.
Philippa is a graduate of the Queensland University of Technology and is a Registered Professional Engineer of Queensland (RPEQ) and a Member of the Institution of Engineers Australia.