Bay gas survey to start soon

Peter Gaston Uncertainty over New Zealand's gas reserves is the impetus for a seismic survey due to start off the Hawke's Bay coast in the next few weeks.
The $15 million survey, covering 100,000sq km, extending from Castle Point on the Wairarapa coast to Te Kaha in the Bay of Plenty, will be done by the Norwegian-based Multiwave Geophysical, a multinational seismic acquisition company, for Crown Minerals.
Crown Minerals general manager Dan Feeley said the faster-than-anticipated depletion of the Mauri gas field, and uncertainty over the level of reserves, had placed pressure on the availability of gas for electricity generation.
The survey was part of an initiative to promote gas exploration in some of the country's under-explored sedimentary basins.
The Taranaki basin was relatively well explored and the likelihood of finding new nationally significant gas accumulations was decreasing as exploration continued.
However, there was no modern industry-standard marine seismic information north of Hawke Bay.
Data acquired during the survey will be made freely available to exploration companies when exploration permits.
The tendering process for East Coast permits will begin in the middle of the year and the data will help reduce the single biggest barrier to attracting new explorers to New Zealand. Mr Feeley said frontier basin such as the East Coast were critical to increasing New Zealand's petroleum reserves and reducing the dependency on the Taranaki Basin, and particularly the Maui field.
Crown Minerals had selected several relatively under-explored frontier basins, such as the East Coast for evaluation over the next few years.
The confirmed presence of hydrocarbons, proximity to existing infrastructure and potential markets had influenced the decision to do the first of the survey off the East Coast.
He said the survey would be done by the Singapore-based Pacific Titan, a 65-metre vessel. It would tow a single acoustic streamer, up to 12km long. The polyurethane-covered streamer is 50mm in diameter, and will be towed at a depth of 6 m. Computer-controlled depth controllers, about a metre in width will be spaced at 300m along its length.
The sound from an array of compressed-air guns will used during the survey. The sound-waves from the guns will pass through rock formations along the sea bed and will be picked up on a series of microphones.
During the survey a series of warning pulses will be used to deter marine animals.
Because of the large distance between the Pacific Titan and the tail buoy on the end of the streamer, and the potential for snagging , a Napier-based chase vessel will be used. The Pacific Titan will move at 5knots and with its streamer will take 90 minutes to pass a given point.
The seismic lines the vessel makes will be up to 660km long and spaced between 10 and 100km apart.
American-based Westech Energy struck gas at two sites in the Wairoa area in the late 1990s.