Woodada Gas Field Summary
- The Woodada Gas Field was first discovered in June 1980, with production commencing in May 1982.
- The area surrounding the field was declared a nature reserve known as Lake Logue Nature Reserve in December 1987.
- The Woodada Gas Field has produced some 52.9 billion standard cubic feet of gas (approximately 1.5 billion cubic metres of gas) of gas from the Beekeeper Formation and is shut-in on care and maintenance.
- The Woodada Deep-1 shale gas projects targeted the shales which lies beneath the Beekeeper Formation.
- Woodada Deep-1 exploration well, drilled in April 2012, is a deepening of the Woodada-4 well.
Monitoring of Woodada Gas Field
Gas wells that are no longer in production are suspended prior to being decommissioned. Suspending a gas well involves performing a series of procedures to ensure that the well poses no risk to the public and environment while it is inactive. Suspended wells are routinely pressure monitored on a six-monthly basis until they are fully decommissioned. If monitoring results are not as expected, then further investigation is undertaken to better understand the results and determine if remedial action is required.
Recently, during routine monitoring, a change in pressure readings was observed at the Woodada-14 well which was drilled and suspended in 1994. Further testing indicated that:
- Low pressure gas from the depleted reservoir was slowly entering (20-30 psi) the well bore.
- The integrity of the well head and well casing remained intact and there is no environmental or safety risk.
As a result, AWE is undertaking remedial action in accordance with the regulatory approvals.
The approved Environmental Bridging Document summary provides further details.
Woodada Deep-1 Hydraulic Fracture Stimulation Case Study
The hydraulic fracturing of the Woodada Deep well provides an important case study of how hydraulic fracturing can be conducted safely and efficiently in onshore Western Australia.
In mid-2012, AWE successfully hydraulically fractured two zones with the Woodada Deep-1 well, targeting the Middle Carynginia (2,370 to 2,425 metres) and Upper Carynginia (2,283 to 2,330 metres) shale formations.
Test results – water quality
Gemec Environmental Consultants (Gemec) was engaged by AWE to conduct the water quality monitoring and advise on potential groundwater contamination risks.
Gemec analysed water obtained from the fracturing fluid flowback ponds (it is important to note, these ponds are double fenced and are double HDPE lined to prevent the leakage into groundwater) as well as water from two existing water bores and three purpose designed monitoring stations at varying distances from the Woodada Deep-1 well head.
Gemec therefore conclude that comparison of the data against previous groundwater monitoring events indicates that the hydraulic fracture stimulation operations have had no discernible influence on groundwater conditions in the vicinity of the WDA1 (Woodada Deep-1) site. No chemical of potential concern was identified that had the potential to present a risk of harm to the environment.
AWE was licenced to extract 32,000kL of water from a superficial aquifer to hydraulically fracture its Woodada Deep-1 well. However, it used less than 5,000kL. The total allocation for all users of Superficial Aquifer is 14,600,000kL, so AWE’s use represented less than 0.034% of total annual use.
Hydraulic fracturing of a horizontal well for commercial production would increase this figure to approximately 20,000kL, though AWE will not hydraulically fracture the well for commercial production.
Test results – air quality
AWE also retained Gemec Environmental Consultants to undertake monitoring, testing and reporting of air quality around the fracturing fluid retention ponds to ascertain any impact on surrounding air quality, and therefore on native flora and fauna populations.
Gemec was responsible for installing the sampling equipment and providing independent analysis of the chemical characteristics of the vapour emissions. The readings were conducted immediately after hydraulic fracture flowback fluids were deposited in the retention pond and up to three months later.
The comparison indicates that the concentrations reported at the Woodada Deep site are considered to be minor compared to those reported at the reference locations, which included a remote rural area, an industrial centre with high traffic density and refuelling a car at a service station.
Given the generally minor to trace concentrations reported (at or marginally above the limit of reporting, the vapour emissions emanating from the flowback fluid contained in the retention pond do not present an adverse risk to native fauna in the vicinity. The wind dispersion factor would further reduce concentrations away from the immediate vicinity of the retention pond.
In a human health context, a comparison of the benzene, toluene, ethylbenzene and xylene concentrations reported during the sampling programme with the ATNEPM MILs and those reported in various settings indicate that the concentrations reported at the Woodada site are negligible and do not pose an adverse risk to human health.
Test results – microseismicity
AWE contracted Pinnacle (a Halliburton company) to undertake microseismic testing during the hydraulic fracturing operation.
Pinnacle was primarily contracted to undertake hydraulic fracturing efficiency diagnostics to maximise completion efficiency and production economics for future hydraulic fracturing programs at Woodada Deep-1 and/or future wells.
The testing also provided valuable information on the scale and location of microseismic events from hydraulic fracturing which can be used to interpret the safety of hydraulic fracturing.
Based on the results, Pinnacle reported three significant observations:
- The shallowest (closest to surface) mapped event was 700 metres in vertical distance away from the base of the closest known saline aquifer (Lesueur Sandstone).Why is this important?No aquifer contamination from hydraulic fracture fluid likely due to distance between fracturing zone and the aquifer (Note: The Lesueur Sandstone is 1,186 – 1,485 metres deep and saline and is not used for human/stock consumption).
- All events showed seismic moment magnitude between -3.0 and -1.9, which is typical for hydraulic fracture treatments.Why is this important?The smallest moment magnitude that can be felt by a person at surface is around 2.0 to 3.0. Each unit in moment magnitude is 30 times larger than the one before.Therefore, the largest events detected during the fracture stimulation at Woodada Deep-1 are ~27,000 times smaller than the smallest size of event that could be detected at surface. This is 729 million times smaller than the earthquake near Newcastle, NSW in 1989 which is the smallest known earthquake in Australia to have caused fatalities.
- No linear “out of zone” features in mapped events with abnormally high moment magnitude.Why is this important?It is likely that all events were contained within the targeted Carynginia section.