Arrow Energy’s proposed Bowen Gas Project is a coal seam gas development covering an area of 8000 km2 in the Bowen Basin in central Queensland. The development comprised approximately 4000 CSG production wells, of which up to one quarter may be hydraulically fractured. The Queensland regulator (Department of Environment and Heritage Protection) requested the IESC’s advice on the draft environmental impact statement (EIS), specifically on whether the EIS sufficiently addressed:
- the potential for hydraulic fracturing to enhance interconnection of groundwater aquifers
- the implications of such interconnection on groundwater quality and level, and
- the potential for interconnection of aquifers and/or coal seam gas contamination in target and non-target aquifers particularly at fault lines, with or without hydraulic fracturing.
The IESC advised that there was a potential for faults to play a role in aquifer interconnection, and that therefore there was a need for additional information to be included in the draft EIS on faulting, and the location of the wells in which hydraulic fracturing was proposed, to determine potential interconnectivity and its implications. Matters that required consideration included:
- more detailed field validation of the parameters used in the numerical groundwater model, and use of the field data in a thorough sensitivity analysis of the role of faults
- site-specific field investigation of fault zones, particularly those which are seismically active or have a high pressure differential
- more detailed consideration of sub-vertical faults and folds, propagation of fractures associated with faults, and behaviour of faults as barriers or conduits to water flow
- an execution plan for hydraulic fracturing near known faults detailing the well numbers, type and location; number of multi-seamed wells to be constructed; grid spacing; potential for multiple fracturing events; and details of chemical mixing and storage facilities.
The Australian Government Department of the Environment subsequently requested IESC advice on the Supplementary Report to the EIS. In its advice provided on 4 June 2014, the IESC noted that the proponent had done significant work to address many of its concerns. These additional investigations had provided data and improved understanding of faults, hydraulic fracturing and fracture propagation. However, the IESC said that it could not be confidently concluded from this research that faults will act as a barrier to groundwater flow due to lack of specific data from the Bowen Basin. The IESC recommended that the project’s groundwater monitoring programme should include a higher density of bores in proximity to known and newly identified faults, and that in these locations monitoring should be carried out in a range of formations to identify the potential influence of faults on groundwater flow due to depressurisation. In relation to hydraulic fracturing, the IESC advised that details should be provided on how hydraulic fracturing and fracture propagation would be monitored and controlled.
To address the issues, the conditions of approval require:
- a peer-reviewed Groundwater Monitoring and Management Plan to include a groundwater monitoring network to detect impacts on surface water, groundwater and changes in connectivity between surface and groundwater. The plan also requires details of a risk based exceedance response including early warning indicators and trigger thresholds.
- the number of wells that can be hydraulically stimulated be limited to 1000
- that wells be constructed, operated and decommissioned in accordance with industry best practice.
The combination of the proponent’s commitment to mitigation and management measures, Queensland’s requirement for an Environmental Authority and the conditions of approval address the concerns raised by the IESC and ensure that impacts to water resources will not be unacceptable.