The Perth Basin Baseline Monitoring Study
The Perth Basin Baseline Monitoring Study provides a valuable reference point for measuring the environmental impact of onshore oil and gas activities.
When considering environmental impacts of onshore oil and gas activities, two of the most important factors to consider are groundwater and air quality.
Water covers 71% of the earth’s surface, but 96.5% of that is found in oceans and seas. Only 2.5% is fresh water, and almost 99% of that is ice.
Pure, fresh water found in underground aquifers is therefore of enormous importance, and communities, governments and resource companies are keenly interested in the health of our groundwater supplies.
Methane is one of the most potent greenhouse gases on earth and it has increased by about 150% since 1760, when the Industrial Revolution began.
It’s also one of the main components of natural gas, so it’s vitally important that gas exploration and production is done properly to avoid additional large amounts of methane being released into the atmosphere.
What’s the current situation with water and methane in the Perth Basin?
During 2015 and 2016 a large study was conducted in the northern Perth Basin between Gingin and Dongara, where gas exploration and production have been under way for almost 50 years.
The aim of the study was to firstly figure out the best way to actually monitor and measure groundwater and methane levels on a regional scale and then to take some measurements. The results will help provide important baseline groundwater and methane monitoring data for the northern Perth Basin and protocols for use by all groundwater users.
The study was conducted collaboratively by the Commonwealth Scientific and Industrial Research Organisation (CSIRO), the Department of Mines, Industry Regulation and Safety (DMIRS) (then the Department of Mines and Petroleum, or DMP) and the University of Western Australia (UWA). Four onshore gas companies jointly funded the study – Latent Petroleum, AWE Limited, Origin Energy and Norwest Energy.
The current state of groundwater
Researchers primarily analysed groundwater data gathered by licensed groundwater users and provided to the Department of Water (now titled Department of Water and Environmental Regulation).
The study concluded that groundwater levels have remained reasonably consistent across the area since 2007. The two major aquifers in the area – the Leederville-Parmelia Aquifer and the Yarragadee Aquifer require more data to make a firm conclusion about the local groundwater level trends.
Researchers identified 1,896 registered bores in the area, but only a few came with water-level data, salinity data or both. Only 231 could be specifically linked to an aquifer. Within the permit areas, the study found that most of the available groundwater data has been provided through water sampling conducted by the resources sector. To gain a comprehensive understanding CSIRO recommends more monitoring of the key aquifers in the Perth Basin. This monitoring and data contribution could be assisted by a range of other groundwater users such as agriculture.
Over time the number of bores being measured has decreased, but of the bores being measured, more data has been collected.
CSIRO has recommended that more water-level loggers and monitoring bores are installed so the aquifers can be more accurately assessed.
The current state of methane
The study measured methane at and near the earth’s surface. Researchers covered about 2,300km throughout the northern Perth Basin and found that methane concentration was about 1.77 parts per million(ppm) across most of the area.
This is similar to levels found at the CSIRO greenhouse gas monitoring station at Cape Grim in Tasmania. Cape Grim is considered to be one of the cleanest air sources in the world and is regularly used by scientists as a reference point.
Researchers recommended that further studies are done to measure how methane is impacted by production facilities, towns, lakes, petroleum wells, cattle and microbes in the area. Stage 2 of the study is being planned and funding is being finalised.