2.3.5.2 Hazard analysis


2.3.5.2.1 Coal seam gas operations

A hazard analysis was conducted for the Clarence-Moreton bioregion based on the proposed CSG operations and associated water management. The assessment of geology and hydrogeology demonstrated that there is no hydraulic connection between the Richmond river basin and the Bremer river basin, where the only existing baseline coal mine (Jeebropilly Mine) is located. Consequently, potential hazards associated with coal mines were not considered in the BA 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 activities were identified and scored in the Clarence-Moreton bioregion; these are all activities identified during the IMEA (Bioregional Assessment Programme, Dataset 1). However, the results are based on a subset of activities with complete scores. The 30 highest ranking hazardous activities and impact modes based on hazard score and hazard priority number 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 impact cause) could result in an effect (change in the quality and/or quantity of surface water or groundwater). There may be multiple impact modes for each activity or chain of events. In order to better understand the impacts of different activities associated with CSG operations on water-dependent assets, 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 context. 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 causal pathways.

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 aquifer 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 extraction that reduces groundwater pressure, or desirable effects such as the reinjection of co-produced water that restores groundwater pressure.

Figure 36

Figure 36 Highest ranked hazards for coal seam gas (CSG) operations ranked by hazard priority number midpoint in the Clarence-Moreton bioregion (based on Ford et al., 2016)

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

Lower-ranking hazards that are in scope are also considered in the bioregional assessment. The full list of identified hazards is included in Bioregional Assessment Programme (Dataset 1).

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)


Component

Life-cycle stagea

Activityb

Impact mode

Causal pathway

Effect

Wells

P

Water and gas extraction

Aquifer depressurisation (coal seam)

Groundwater extraction causal pathway

GW pressure

Wells

P

Water and gas extraction

Aquifer depressurisation (non-target, non-reservoir)

Groundwater extraction causal pathway

GW pressure

Wells

P

Water and gas extraction

Aquifer depressurisation

Groundwater extraction causal pathway

GW flow (reduction)

Wells

D

Pressure concrete durability

Seal integrity loss

Well integrity causal pathway

GW quality

Wells

C

Cementing and casing

Incomplete/compromised cementing/casing (linking aquifers)

Well integrity causal pathway

GW quality

Wells

P

Water and gas extraction

Aquifer depressurisation (fault-mediated)

Groundwater extraction causal pathway

GW pressure

Processing

C

Gas-gathering pipeline networks

Disruption of natural surface drainage

Surface drainage causal pathway

SW volume, SW quality

Pipelines

C

Trunk gas pipelines and associated easements (processing plant to town)

Disruption of natural surface drainage

Surface drainage causal pathway

SW volume, SW quality, GW quantity

Pipelines

C

Gas and water-gathering pipeline networks (well to processing plant)

Disruption of natural surface drainage

Surface drainage causal pathway

SW volume, SW quality, GW quantity

Wells

D

Pressure concrete completion

Incomplete seal

Well integrity causal pathway

GW quality, GW pressure

Wells

C

Hydraulic fracturing

Contaminate non-target aquifer (chemical)

Hydraulic fracturing causal pathway

GW quality

Wells

P

Untreated co-produced water storage, processing and disposal (pilot stage only)

Leaching from storage ponds

Water management causal pathway

GW quality

Wells

E

Abandonment

Bore leakage between aquifers

Well integrity causal pathway

GW composition, GW quality, GW pressure

Wells

C

Hydraulic fracturing

Connecting aquifers

Hydraulic fracturing causal pathway

GW composition, GW quality, GW pressure

Wells

E

Abandonment

Bore leakage to surface

Well integrity causal pathway

SW quality

Wells

C

Cementing and casing

Incomplete/compromised cementing/casing (gas leakage)

Well integrity causal pathway

GW quality

Wells

W

Waste disposal

Surface water contamination

Water management causal pathway

SW quality

Wells

C

Drill cutting disposal

Surface water contamination

Water management causal pathway

SW quality

Pipelines

C

Trunk gas pipelines and associated easements (processing plant to town)

Soil erosion following heavy rainfall

Water management causal pathway

SW quality

Processing

P

Hypersaline brine ponds

Leaking

Water management causal pathway

SW quality, GW quality

Processing

P

Brine storage ponds, pumps and water disposal pipelines

Leaking

Water management causal pathway

SW quality, GW quality

Wells

C

Perforation

Miss perforation target and depressurise aquifers

Well integrity causal pathway

GW pressure, GW quality

Wells

P

Groundwater monitoring bore construction or expansion

Incomplete/compromised cementing/casing (linking aquifers)

Well integrity causal pathway

GW composition, GW quality

Roads and infrastructure

C

Construction of access roads and easements (e.g. for drilling rigs and equipment)

Disruption of natural surface drainage

Surface drainage causal pathway

SW direction, SW volume, SW quality

Processing

C

Water treatment plant (RO, fixed resin, fixed disc, electrochemical, etc.)

Disruption of natural surface drainage

Surface drainage causal pathway

SW volume, SW quality

Processing

C

Treated water pond

Disruption of natural surface drainage

Surface drainage causal pathway

SW volume, SW quality

Processing

C

Hypersaline brine ponds

Disruption of natural surface drainage

Surface drainage causal pathway

SW volume, SW quality

Processing

C

Gas processing plant

Disruption of natural surface drainage

Surface drainage causal pathway

SW volume, SW quality

Processing

C

Brine storage ponds, pumps and water disposal pipelines

Disruption of natural surface drainage

Surface drainage causal pathway

SW volume, SW quality, GW quantity

Wells

C

Hydraulic fracturing

Changing non-target aquifer properties (physical or chemical)

Hydraulic fracturing causal pathway

Aquifer properties

2.3.5.2.2 Hazard handling and scope

A comprehensive list of hazards has been generated for CSG operations as part of the hazards workshop, as described in Section 2.3.5.2.1 . 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 BA perspective are those that extend beyond the development site and that may have cumulative impacts. 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 Clarence-Moreton bioregion 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 effect of an activity such as ‘water and gas extraction’ depends on the impact cause and impact mode. 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:

  • surface water quality
  • surface water direction
  • surface water flow
  • groundwater quality
  • aquifer properties
  • groundwater composition
  • groundwater flow (reduction)
  • groundwater level
  • groundwater pressure.

In Table 17, various impact modes were identified, many of which shared similar causal pathways. 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 impacts on aquifers associated with depressurisation 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. Activities related to well 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.

Last updated:
11 July 2017
Thumbnail images of the Clarence-Moreton bioregion

Product Finalisation date

19 January 2017