Risks of Coal Seam and Shale Gas Extraction on Groundwater and Aquifers in Eastern Australia

Abstract

In the developed world there are growing concerns about water security due to the increase in exploration and production of coal seam and shale gas in peri-urban areas using both the hydraulic fracturing (fracking) technique of gas production and the method of extraction of naturally occurring groundwater by pumping it from coal formations to release coal seam gas (CSG). In Australia there is a competing prerequisite to maintain and increase the natural resource base as well as the need to protect and sustain the supply of potable and agricultural groundwater in peri-urban areas. One identified issue for this chapter is whether the increasing popularity of fracking in peri-urban and semi-rural areas in New South Wales (NSW) and Queensland poses a risk to the quality of groundwater supply as well as its contamination. The other main issue is whether the extraction of groundwater from coal seams where fracking is not needed has a major impact on groundwater depletion; and, if so, investigating the appropriate risk assessment and risk management approaches.

One problem at hand is that fracking is a technique designed to produce gas from coal seams and shale strata. The process involves pumping water, sand and chemicals under high pressure into layers of coal or shale to create fissures or cracks that force gas to the surface where it is collected and processed. The technique impacts on water supplies in two main ways: It requires large quantities of water at the pumping stage and it is alleged to produce vast amounts of contaminated groundwater containing chemicals known collectively as BTEX, methane gas and excessive amounts of salt. Attractors to this method of gas exploration and production are twofold. The drilling technique invented and developed by George Mitchell in 1980s and 1990s made drilling previously inaccessible strata reachable and cheap. The other attraction is that in the United States of America (USA), since 2008 the domestic price of ‘Henry Hub’ gas has fallen from $12 per million BTUs in 2008 to $4 per million BTUs in 2012. The impact of this 66 % fall in price has relieved the USA’s reliance on imported carbon based fuels momentously, but has had a deleterious impact on groundwater supplies.

The evidence based on the development of drilling sites using fracking in NSW and Queensland peri-urban areas so far, suggests that environmental concerns may not be given as much consideration as they ought, in particular because compliance with environmental risk assessments is not specific enough. In this chapter, we explore the above issues and report on a methodology to assess the potential risk to groundwater supplies in NSW and Queensland using an environmental risk model for CSG extraction in combination with the ‘triple-bottom line’ (TBL) process for community consultation informed by the Global Reporting Initiative (GRIG4) guidelines.