Page 84 - AGL Sustainability Report 2011

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Environment
AGL Energy Limited 82
Watermanagement
Produced water
Deep groundwater is brought to the surface (or
‘produced’) as an unavoidable by-product of coal seam
gas exploration and production activities.
Approach
Community and government stakeholders are increasingly focused
on the potential loss of water resources and contamination of
ground or surface water arising from the activities of Australia’s coal
seam gas industry. At AGL, water management is a key component
of coal seam gas exploration and production projects, and all of
AGL’s coal seam gas activities are designed to have a minimal impact
on the environment and to protect water resources.
The extraction of gas from coal formations involves the drilling of
gas production wells into the earth (typically several hundred to
around one thousand metres deep), stimulating the coal formation,
and allowing gas to flow to the surface. Before the gas can be
brought to the surface, water that exists within the coal formation
must first be removed so that the gas can ‘flow’ and be extracted.
This is known as dewatering.
The quantity of coal seam gas produced water varies depending on
the location of the project and also the stage of the production cycle
of any given well. Some locations, due to the inherent characteristics
of the geology, produce greater volumes of coal seam gas water per
well than similar scale projects located elsewhere.
As a project moves from the exploration stage to the production
stage, the number of wells increases substantially. The total volume
of water removed from the coal formations increases in the initial
years then decreases again as the wellfield reaches maturity.
Currently, only AGL’s Camden Gas Project in New South Wales is
in commercial production stage. Into the future, as some of AGL’s
exploration projects move into production stage (such as the Hunter,
Gloucester and Galilee gas projects), the volume of coal seam gas
produced water from AGL’s operations will increase.
The quality of the coal seam gas water also varies depending on the
location. AGL operates the Camden Gas Project (Sydney Basin), and
has exploration underway in the Hunter (Sydney Basin), south of
Gloucester (Gloucester Basin) and near Longreach (Galilee Basin).
Produced water varies from low salinity (for example in the Galilee
Basin) to moderate salinity in some locations such as in the Hunter
and at Camden and Gloucester. The salinity of produced water is
generally less than one-third that of seawater. It is safe to use for
a variety of purposes (most of which require some blending or
treatment to reduce the salinity hazard).
In FY2011, AGL developed a Produced Water Management
Strategy, in recognition of the need to protect surface water and
groundwater resources and to reuse water sustainably across AGL’s
coal seam gas operations. The long-term objective of the Strategy
is to substantially increase the proportion of produced water that is
beneficially reused for environmental, industrial/commercial, mining
and/or primary production purposes. During FY2012, produced
water management plans will be developed and implemented for
each of the four AGL-operated coal seam gas projects.
Industry best practice well construction techniques are used to
prevent shallow aquifers from being connected to the deep coal
seam gas water bearing zones. AGL has dedicated groundwater
monitoring networks to test the water level and the water quality
characteristics of shallow aquifers used for water supply, to identify
any changes during coal seam gas exploration and production
programs. Surface water monitoring is also in place where there are
sensitive creek/river receptors nearby.
Groundwater monitoring networks were initially established in
the Hunter Gas Project during FY2009, and during FY2011, the
monitoring networks were expanded to cover groundwater and
surface water at the Gloucester and Galilee exploration areas,
and the vicinity of the proposed natural gas storage facility at
Tomago. Further monitoring bores were also drilled for the Hunter
Gas Project during FY2011. Fifty-nine dedicated groundwater
monitoring bores and nine surface monitoring locations are now
operational across these four projects (Hunter, Gloucester, Galilee
and Tomago). Additional monitoring locations are planned for these
projects and at Camden and Camden North in coming years.
Results to date from AGL’s dewatering program at the Hunter and
Camden gas projects suggest that groundwater in deep coal seams
in the coal seam gas project areas is isolated from water resources
in shallow aquifers and streams, and no water level declines or
water quality impacts have occurred due to AGL’s exploration or
production activities.
Produced water
1,2
Galilee Gas Project
Hunter Gas Project
Gloucester Gas Project
Camden Gas Project
154,192kL
310kL
527 kL
2,987kL
Legend
Volume produced water FY11
Notes
1 Produced water comprises natural groundwater generated from coal seams during fow testing and production dewatering. It does not include other water streams (drill
water, fracture stimulation/fowback water and brine water) that usually require separate water management.
2 Monitoring data for water production levels is provided for Gloucester, Hunter and Galilee gas projects. Produced water data for Camden Gas Project is calculated from
recorded volumes removed from the well sites.