Database and combined modelling packages applied by expert team
The NSW government chose Schlumberger Water Services as the Independent Expert to manage and complete the Study. To take on the complex project and meet the challenge, Schlumberger first created a custom relational database to manage the datasets collected from federal, state, and local governments; industry partners; and others. The final database contained more than 30 million records.
The Petrel software platform was then used to construct a 19-layer 3D geological model representing all strata from ground level to 2,000-m depth over the catchment. Several coal seams were mapped as individual layers, enabling a higher degree of interpretation and 3D visualization for these areas. Based on the Petrel model, the team created linked dynamic numerical models for both the surface water and groundwater systems using LASCAM and MODFLOW software—collectively known as “the Model.”
The Model, calibrated to historical records, is able to incorporate and assess a wide range of potential future coal-resource-development activities. It is a robust predictive tool that can be updated with new data, recalibrated as necessary, and used to assess alternative scenarios and the effects of changing other inputs and assumptions such as climate change.
Based on the position of the coal seams identified, seven different scenarios were conceived for future coal resource development. These included possible future open-pit and underground coal mines, as well as extensive areas where coal seam gas extraction might occur. The Model was required to assess the potential impact of each of these scenarios until the year 2100.
To address the need for communication with stakeholders, Schlumberger released interim Study reports at key milestones. Each milestone was presented to the various stakeholders at two separate community presentation and discussion forums.
Potential impacts quantified and areas of concern identified
The comprehensive data management, analyses, and model construction
enabled prediction of the potential short- and long-term cumulative effects of
mining and coal seam gas developments on water resources for the entire Namoi
catchment. The Schlumberger project team identified sub-regional areas where
water resources were most at risk and quantified the potential magnitude of
impact for different coal resource development options. They also evaluated the
sensitivity of the results to different inputs and the level of confidence in
Areas of the catchment were identified where water resources were at
high, medium, or low risk to coal and gas developments. With this information,
stakeholders, industry, and the government can focus on specific and much
smaller areas of concern rather than spreading resources across the whole of
the catchment. Stakeholders were also made more aware of the quantitative risks
associated with each type of coal resource development.
Furthermore, in the course of the Study, Schlumberger identified a
number of data gaps and evaluated their relative importance. A future
investigation and monitoring program was proposed to provide robust
catchment-specific data inputs that can be used to reduce the uncertainties and
enhance confidence in predictions.