Wannamal West Road / Boonanarring
On Thursday June 6th 2013 I was given a tour and explanation of the 3D Seismic survey being conducted for Empire Oil and Gas NL managed by Terry Grocke.
The project involved recording seismic data over an area of approximately 80 sq.kms with 23 sq.km in the Boonanarring nature reserve. Approx 1,600 shotholes were drilled, 10-15m deep with no casing installed in a grid of holes 50-100m apart in lines spaced at 400m. Each hole was loaded with a 1 or 2kg explosive charge. The small explosions were monitored by nearly 6,000 portable electronic devices, ‘nodes’, capable of the most accurate measurement of acoustic energy, time and position.
To personnel on the surface, detonations were undetectable at any distance greater than about 50m from the shothole. I am convinced each site would be difficult to detect after one year. The nodes were collected and returned to base where the recorded seismic data was downloaded in a mobile ‘harvester’ (caravan full of computer hardware). After preliminary assessment the data will be sent to a specialised contractor for detailed processing which will result in a ‘data cube’ to be analysed and interpreted by geophysicists and geologists to identify possible reservoirs of natural gas or oil.
The zone of interest in this area is typically 3,500 – 4,000m(+) deep. Of particular interest were regions of relatively porous sandstone which may contain gas under pressure. I was told the gas deposits are much deeper than the water rich layers exploited for agriculture and human consumption.
The technique used was explained as being unique to Australia for several reasons. It took advantage of the most advanced technology available.
Empire Oil and Gas seemed to be making a deliberate effort to impress on the authorities and local community its intention to use worlds best practise techniques to assess and develop the gas deposits of the region in the most ecologically sensitive way possible.
The use of helicopters to deliver seismic equipment including portable seismic drilling rigs into the field minimised the environmental footprint.
This equipment was lowered into place using a ‘long-line’. Helicopters needed to land at base only to refuel.
Personnel walked between sites to the predetermined locations. Bentonite clay was the preferred drilling fluid additive. Special mixing techniques had to be developed to adapt this to the airborne system used. All vehicular traffic on the site was restricted and monitored. Dieback spore reduction techniques were also used in drilling.
Currently there are two gas production wells existing at a single site just to the south of Wannamal west road. They are fenced on a footprint of less than a quarter of an acre. Visually less intrusive than a small tank or stock trough. I would be happy to have them on my farm. No sound or smell. I could
not reasonably argue any water aquifers down to the Yarragadee would be damaged.
The gas wells draw from a region around 4000m deep. One well goes straight down, the other goes vertical then horizontally to source. The explanation of their construction was not technical however it was obvious the most modern techniques were used in an effort to construct bores which would be as safe as science could currently demand. I would like a more detailed explanation of the procedures and chemicals used to achieve what I observed and the insurances provided to cover their lifelong safety, and what happens beyond that time. There was no sign that large quantities of water and chemicals had been used. At the end of the well’s life it would be sealed with concrete and the hydrocarbon flow blocked off . I would have liked more details of this process.
The gas flows to the surface under pressure and is piped to the small processing facility. It separates the oil which is stored on site and trucked to market. Water is also extracted and allowed to evaporate in a small lined dam. No sign of smell or oily condensate. No noise or excessive movement. The cleansed gas is piped in a buried line some kilometres to the west and injected into the Dampier to Bunbury pipeline.
My thanks to Empire Oil and Gas NL for providing access to the site.