Coal seam gas operations

The hazard analysis identifies impacts on aquifers as the highest ranked hazards associated with CSG operations in the Maranoa-Balonne-Condamine subregion. The hazard analysis identifies the following potential impacts to aquifers including:

  • injection of treated water into the aquifer
  • hydrostatic depressurisation of the aquifer (target coal seam and non-target aquifers)
  • fault-mediated depressurisation caused by faults opening or closing due to CSG operations
  • aquitard-mediated depressurisation (i.e. an aquitard is absent or the integrity of the aquitard is compromised in some parts of the subregion)
  • connection of previously disconnected aquifers by hydraulic fracturing, incomplete casing of wellheads or incomplete seal integrity.

After impacts on aquifers, the potential impacts associated with storage, processing and disposal of treated water: raised groundwater levels, soil salt mobilisation and leaching from storage ponds were all identified as potentially important in this context.

Figure 29 plots the 30 highest ranked hazards (and associated activities and impact modes), ranked by midpoint of the hazard priority number. This figure shows the range of hazard score and hazard priority number for each of these potential hazards.

‘Disruption to natural surface drainage’ was the most common impact mode in the 30 highest ranked hazards. This impact mode appears 21 times in the IMEA for CSG operations in the Maranoa-Balonne-Condamine subregion, and 7 times in the 30 highest ranked hazards. This is because many of the activities associated with CSG operations (such as site vegetation removal and diverting site drain lines) lead to this impact mode. This impact mode is considered hazardous as it may lead to impacts on surface water volume, direction and quality; in extreme cases, impacts on groundwater quantity were identified as a possible outcome.

The following complete the list of the 30 highest ranked hazards that might potentially impact on water-dependent assets in the Maranoa-Balonne-Condamine subregion for CSG operations:

  • gas leakage into groundwater caused by incomplete or compromised cement casing
  • leaching from storage ponds (untreated co-produced water and hypersaline brine ponds)
  • soil erosion following heavy rainfall, with total suspended solids (TSS), total dissolved solids and surface water flow as the associated stressors.

Details of the hazard analysis are available at Bioregional Assessment Programme (Dataset 1).

Figure 29

Figure 29 Highest ranked hazards (and their associated activities and impact modes) for coal seam gas operations, ranked by midpoint of the hazard priority number

The x-axis shows the hazard priority number and hazard score for potential hazards. The intervals between the highest and lowest hazard priority number are shown in dark blue; the intervals for hazard score are shown in light blue. The same hazard may appear multiple times, as it may arise from a number of different life-cycle stages and activities. Hazards are listed with the syntax [Life‑cycle stage][Activity]:[Impact mode], where life-cycle stages are indicated by (E) for exploration and appraisal, (C) for construction, (P) for production and (D) for decommissioning.

Typology and punctuation are consistent with Dataset 1.

Data: Bioregional Assessment Programme (Dataset 1)

Last updated:
16 October 2018
Thumbnail of the Maranoa-Baloone-Condamine subregion

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