220.127.116.11.1 Coal seam gas operations
A analysis was conducted for the based on the proposed CSG operations and associated water management. The assessment of geology and demonstrated that there is no hydraulic connection between the Richmond river basin and the Bremer river basin, where the only existing coal mine (Jeebropilly Mine) is located. Consequently, potential hazards associated with coal mines were not considered in the for the Clarence-Moreton subregion. The hazard analysis for the Clarence-Moreton bioregion was completed during a one-day workshop in May 2015 with experts from CSIRO and the Office of Water Science.
A total of 226 CSG-related were identified and scored in the Clarence-Moreton bioregion; these are all activities identified during the (Bioregional Assessment Programme, ). However, the results are based on a subset of activities with complete scores. The 30 highest ranking hazardous activities and based on and midpoints are shown in Figure 36. In Table 17, the 30 highest ranked potentially hazardous activities are explained in more detail, and grouped according to different criteria as explained herein:
Impact mode: refers to the manner in which a hazardous chain of events (initiated by an could result in an (change in the quality and/or quantity of or ). There may be multiple impact modes for each or chain of events. In order to better understand the impacts of different activities associated with CSG operations on , those activities were grouped according to different impact modes. ‘Disruption of natural surface water drainage’ was the most frequently identified hazard in the top 30 hazards (9 times), with ‘Soil erosion following heavy rainfall’ being potentially important in this . Disruption of natural surface drainage was identified as hazardous as it may lead to impacts on the direction, volume or quality of surface water.
Causal pathway: describes the logical chain of events – planned or unplanned– between coal resource development to changes in groundwater or surface water, and then to impacts on water-dependent assets. This category (column 5 in Table 17) further simplifies the groupings from the ‘Impact mode’ category into major .
Effects: refers to potentially undesirable changes (impacts) caused by CSG activities on the quality or quantity of a groundwater or surface water resource (column 6 in Table 17). Impacts relating to groundwater manifest themselves as changes to groundwater quality, groundwater pressure or properties whereas those relating to surface water may affect the flow regime, surface water quality and volume. Out of the 226 potentially hazardous activities, 118 are related to surface water and 47 are related to groundwater with some relating to both. An activity can have undesirable effects such as water and gas that reduces groundwater pressure, or desirable effects such as the reinjection of co-produced water that restores groundwater pressure.
The x-axis shows the hazard priority number and hazard score. The interval between the highest and lowest hazard priority number are shown in dark blue, and the hazard score intervals are shown in light blue. The same hazard may appear multiple times, as it may arise from a number of different life cycles and activities. Life-cycle stages are indicated by (E) for exploration and appraisal, (P) for production, (D) for decommissioning and (C) for construction.
Table 17 Top 30 hazardous coal seam gas (CSG) activities and associated impact modes and causal pathways for the Clarence-Moreton bioregion
aLife-cycle stages are indicated by (C) for construction, (E) for exploration and appraisal, (P) for production, (D) for decommissioning and (W) for work-over.
bThe activities are listed in order of their ranking (Figure 36)
18.104.22.168.2 Hazard handling and scope
A comprehensive list of has been generated for CSG operations as part of the hazards workshop, as described in Section 22.214.171.124.1 . This section describes the scope of subsequent work, which addresses only a subset of the full list of hazards.
The hazards of primary focus from a perspective are those that extend beyond the development site and that may have s. This is consistent with the regional focus of BA, and it is where BA will add value beyond site-specific environmental impact statements (EIS). Ultimately, however, BAs need to be able to address all identified hazards by considering the scope, modelling, other literature or narratives, and specifying where science gaps may exist.
BAs are constrained by considering only impacts that can happen via water; thus, hazards such as dust, fire or noise are out of scope and are addressed by site-based risk management unless there is a water-mediated pathway.
Leading practice is assumed and accidents are considered to be covered adequately by site-based risk management procedures and are beyond the scope of BA; for example, the failure of a pipeline is covered by site-based risk management.
Hazards that pertain to the development site and with no off-site impacts are important to acknowledge but will typically be addressed by site-based risk management procedures.
For CSG operations, the following hazards are considered out of scope in the because they are covered by site-based risk management and regulation and do not have plausible cumulative effects on water in the subregion:
- abandonment practice
- hazards addressed by site management and where no water-mediated pathway exists (e.g. dust, fire or noise)
- containment failure due to construction or design
- disruption of surface drainage network for site-based infrastructure, plant and facilities, roads, creek crossings
- equipment/infrastructure failure (e.g. pipeline failures)
- leaching/leaking from storage ponds and stockpiles
- spillages and disposals (e.g. diesel, mud, cuttings or fluid recovery)
- vegetation clearance and subsequent soil erosion following heavy rainfall.
The hydrological of an such as ‘water and gas extraction’ depends on the and . For example, ‘depressurisation’ (impact cause) that causes ‘subsidence’ (impact mode) may affect ‘surface water direction’ (hydrological effect) and ‘aquitard leaks’ (impact cause) that cause ‘non-target, non-reservoir aquifer depressurisation’ (impact mode) affects ‘groundwater pressure’ (hydrological effect).
Hydrological effects associated with CSG operations that are considered to be in scope in the Clarence-Moreton bioregion are:
In Table 17, various impact modes were identified, many of which shared similar . Consequently, four major causal pathway groups that cover the entire top 30 potential hazards associated with CSG operations in the Clarence-Moreton bioregion were identified:
- ‘Subsurface depressurisation and dewatering’ causal pathway group. The hazard analysis identifies on aquifers associated with of the Walloon Coal Measures (the aquifer which hosts the CSG resources) as the highest ranked hazard associated with CSG operations in the Clarence-Moreton bioregion. For example, the hazard analysis identifies the following ways in which aquifers may be impacted: depressurisation of the Walloon Coal Measures (an intended activity conducted to reduce the hydrostatic pressure in the coal seams) and depressurisation of overlying aquifers (non-CSG target and non-reservoir).
- ‘Subsurface physical flow paths’ causal pathway group. related to construction and abandonment also rate as high-priority hazards and are identified seven times in the top 30 during different phases of the CSG life cycle (e.g. exploration, construction or production). Examples of potential impact modes associated with well construction and abandonment include the loss of seal integrity due to the sustained pressure on concrete and incomplete cementing and casing, which could potentially link aquifers and aquitards. Hydraulic fracturing is only identified twice in the top-ranking 30 hazards. Potential hazards related to hydraulic fracturing that were identified include the contamination of non-target aquifers as well as a change of their hydraulic properties.
- ‘Operational water management’ causal pathway group. This causal pathway group includes impact modes that relate to hazards resulting from activities such as the disposal of waste water.
- ‘Surface water drainage’ causal pathway group. The potential impact modes associated with the construction of infrastructure include activities such as the construction of pipelines, access roads and gas processing plants. These were classified as high-priority hazards.
Product Finalisation date
- 2.3.1 Methods
- 2.3.2 Summary of key system components, processes and interactions
- 2.3.3 Ecosystems
- 2.3.4 Baseline and coal resource development pathway
- 2.3.5 Conceptual modelling of causal pathways
- Contributors to the Technical Programme
- About this technical product