Northern Territory Gas Plays a Reality
On 14 September 2016 the Northern Territory Government announced a moratorium on hydraulic fracturing of onshore unconventional reservoirs including the use of hydraulic fracturing for exploration, extraction and production.
Two years on, the 135 recommendations in the Scientific Enquiry’s long awaited Final Report has signalled a lifting of the moratorium on fracking by the NT Government and heralded a flurry of activity as the major gas operators prepared to get back on the ground to explore the Territory’s shale gas play.
Whilst shale gas is different to both conventional gas sources and the coal seam gas found in Queensland, the comprehensive Scientific Enquiry drew on experience from other regions to develop the recommendations that the major players like Santos and Origin Energy will need to implement to ensure compliance and the backing of local communities and the public at large.
The strict new requirements placed on the industry have been developed to bring risks down to acceptable levels with water-related risks being the central concern. The Panel of experts responsible for the report examined the risk and potential contamination that spills of wastewater and/or fracturing chemicals could pose to surface and groundwater and noted that the largest spills can come from wastewater containment ponds.
“the largest spills can come from the failure (leakage), or overtopping of wastewater contamination ponds”
Early RFQ’s suggest that around 20-30 megalitres (>125,000 bbl if you’re oilfield or 8 Olympic swimming pools if you’re a layperson) of capacity will be required for each 10 well pad which will be used to store hydraulic fracturing fluid, flowback, drilling fluid and produced water.
Historically, fluid storage at the drill site has been in large in-ground ponds or Turkey’s nest as they are known in the industry. These holes in the ground are lined and provide a reliable way to hold large volumes however they are subject to runoff and in extreme weather events can overtop and flood the surrounding area. Because of the Northern Territory’s tropical and monsoonal climate, rainfall can be significant (2 metres annually) especially in the rainy season so the potential risk of contamination resulting from overtopping was red flagged by the scientific inquiry.
The Panel’s recommendations to mitigate this risk outlined the use of engineered, above ground enclosed tanks reporting that this world leading practice removes the risk of overtopping caused by input of rainwater. The report went on to highlight the use of leak detection systems and bunded areas as an essential component of the comprehensive spill and waste containment management strategy.
“The likelihood of leakage from containment ponds can be mitigated by the use of double lined systems with leak detection.”
The gas companies already have considerable experience using above ground fluid storage tanks and are aware of the benefits that they offer over the traditional Turkey’s nest. Concept Tanks, Australia’s leading provider of modular concrete fluid containment systems, has over 200 tank installations across Australia and specialise in the manufacture and installation of engineered solutions for the oil & gas industry.
The Concept tank’s unique patented modular design delivers a free-standing fluid containment system with storage capacity up to 50 megalitres (over 300,000 bbl)! Tanks can be engineered to include a range of ‘zero to grade’ options including floating covers, leak detection and secondary bunding.
To address the issue of overtopping, Concept tanks utilise engineered floating covers and tank overflow weirs. The floating cover provides a hydraulic barrier between the wastewater contained in the tank and the rainfall.
At the point that the rainfall exceeds the tank freeboard, the rain flows through the tank’s integral overflow weir and downpipes and can then be channelled away via a constructed spillway if required.
Because this system mitigates the potential for overtopping, the freeboard allowance is minimal and therefore the required storage capacity is reduced. This means smaller tanks, smaller footprint, shorter installation times and of course lower cost.
Leak detection and secondary containment were also noted in the report as offering the potential to mitigate the risk of a spill and prevent an uncontrolled release of chemicals to the ground and to waterways.
Concept tanks feature dual liners with leak detection systems that operate on solar power and can provide real-time tank monitoring in remote locations. The use of tanks in conjunction with specially fabricated liners provides a synthetic hydraulic barrier that prevents leakage of potentially harmful contaminants into the surrounding environment.
The LLDPE (Linear Low-Density Polyethylene) geomembranes have superior tensile and puncture resistance properties and are specifically designed for waste containment applications.
It is clear that there will need to be a water tight (every pun intended) solution for wastewater containment to ensure compliance with the regulators and although still in the early stages, the region will ultimately benefit if the operator’s further exploration and appraisal is successful, with all Territorians sharing in the economic prosperity via royalties, important employment opportunities and engagement with local companies and suppliers.
You can view and download Concept Tank’s ‘Zero to Grade’ presentation for more information, visit the website at www.conceptservices.com.au or contact us on 07 3850 4444.
By Andrew Bilton.