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Publication on East Coast will help explorers - 07/07/1998

Ten years of research and bore fruit this week with the release of a major publication on the geology and prospectivity of the East Coast region -- New Zealand's newest commercial petroleum area.

It is the most comprehensive study available on this interesting and unusual sedimentary basin -- the term geologists use to describe an area containing oil-bearing rocks. The factors making the East Coast basin unusual are its large size (75,000sqkm), its tectonic setting (it sits over the boundary of the Australian and Pacific plates), and the way oil and gas commonly bubble up to the surface.

The two-volume publication represents a mammoth effort by scientists at the Institute of Geological & Nuclear Sciences Limited. Though some of the information has been published independently over the past 10 years, it is the first time all the relevant information on this region has been presented in one publication.

'' It provides a highly detailed evaluation of the entire area which extends from Marlborough to East Cape and offers onshore and offshore drilling prospects,'' co-author Brad Field said.

'' It's a one-stop-shop for any company interested in finding out where the most likely target areas are for finding oil and gas.''

Parts of the publication have already been used by exploration companies prospecting in the East Coast region.

Work on compiling the material started 10 years ago and up to 20 scientists with various specialities have contributed. '' Some of the contributors are world experts,'' Field said.

Field and co-author Chris Uruski, both petroleum geologists, drew not only on published petroleum industry information, but included many unpublished studies. The result is an unprecedented reference for oil exploration companies.

The pair believe the publication will boost the already strong level of interest in the East Coast region from exploration companies worldwide.

The first wells were drilled in the region in 1870s and geologists have been compiling information on the area for more than a century. The area features New Zealand's highest concentration of oil and gas seeps -- where oil and gas literally bubble up through the ground. There are about 300 seeps between East Cape and southern Wairarapa.

For many years there were doubts that commercial quantities of oil and gas would be found because it was thought the right source rocks were not present. Opinion started to change in the 1980s as research by geologists and geophysicists showed all the ingredients were present, Uruski said.

The publication has identified seven possible oil and gas bearing structures lying offshore -- each as big as the huge Maui field in Taranaki. Industry studies have confirmed a number of the structures are ''world-class'' and have encouraging hydrocarbon potential, Uruski said.

As well as the seven Maui-sized structures, the publication identifies another 20 to 30 smaller mostly offshore structures that are conducive to oil exploration.

Uruski said the East Coast region was still greatly under-explored compared with other hydrocarbon areas worldwide. Proof of its commercial rank came earlier this year with the gas discovery north of Wairoa by the Enerco-Westech joint venture. IndoPacific NZ Ltd is exploring both north and south of the Wairoa discovery, and other companies have permit blocks over parts of the region.

Called Cretaceous-Cenozoic geology and petroleum systems of the East Coast region, New Zealand the publication includes detailed coverage of subsurface structures, surface geology, neotectonics, basement rocks, and tectonic evolution. The section on petroleum geology includes hydrocarbon and source rock geochemistry, modelling of hydrocarbon generation and prospectivity, and should help pinpoint likely hydrocarbon areas for explorers.

It was funded through the government's Foundation for Research, Science and Technology and is available from the Institute for $120.