Mapping rocks onshore
Adam Vonk’s PhD research has involved mapping where sedimentary rocks are found in the Taranaki region in New Zealand, to see how this information can help identify new fossil fuel reserves. He explains that there is quite a lot of information and research about offshore resources. However, only a little is known about onshore sedimentary rocks and how this gives clues to finding fossil fuel resources. Petroleum companies and the New Zealand government have produced a book about the geology of the Taranaki basin, but Adam found that it did not describe how the offshore and onshore geology are related to each other.
Adam explains that, by examining onshore rocks and determining their history, it is possible to predict what sort of rocks may be found beneath the land surface and how this information provides clues about offshore rock layers. This information explains how rocks are distributed, and this allows oil companies to have a better idea of likely places to explore for fossil fuels.
Jargon alert
Each field of science has its own language – here are a few of the terms Adam uses:
Sedimentary rocks – rocks formed from the deposition, consolidation and compression of fine particles (sediments of various sizes) that came from pre-existing rock, which can be igneous, sedimentary or metamorphic in origin.
Hydrocarbon – an organic compound made up of hydrogen and carbon. Fuels such as oil and natural gas are hydrocarbons.
Stratigraphic – studying the layers of rocks. A geological layer is called a strata, and stratigraphy looks at these layers to determine how old they are and what they are made from.
Monograph – a detailed book on a specific topic
Points of interest
The last large-scale mapping of the Taranaki onshore region was undertaken during World War II in an effort to find fuel to help with the war.
To drill an onshore hole, it costs around 5 million dollars, and it costs 50 million for an offshore hole.
Transcript
ADAM VONK
My sort of thesis is involved in mapping sedimentary rocks and understanding sedimentary rocks and how they relate to, sort of, petroleum and hydrocarbon resources in New Zealand. There’s been a lot of workers, sort of, work in small areas of Taranaki. The last mapping projects and stratigraphic studies which occurred in Taranaki was back in the 1940s, 1950s, when they were encouraged to search for oil to help the war effort. But since then, there’s been no real sort of geological investigation on land. Offshore in Taranaki basin, where the oil and gas occurs, there’s been quite a lot of geological investigation by petroleum companies and government departments such as GNS, and they’ve put together a monograph of Taranaki basin, which was published in 1996. But the onshore geology and how that relates to the offshore was very poorly understood, I think. And so that’s where my research came in. It incorporates a lot of those previous studies into one larger study and encompasses a broad section of rocks and integrates all of that data together.
The Taranaki area is quite unique in the fact that we can actually examine, look at, take photographs of and whack with a hammer, rocks that occur onshore. Now those rocks are actually dipping into the subsurface of Taranaki basin, which is the area under the volcano and the area under the sea out to the west. By understanding the history of those rocks onshore, we can actually predict what types of rocks might be occurring in the subsurface of Taranaki. The main reason for predicting that subsurface geology is to gain a better understanding of how those rocks are distributed in order for oil companies to explore, run seismic lines over and drill holes into to find petroleum and hydrocarbons. The cost of drilling a petroleum well is – onshore on Taranaki might be, you know, upwards of 5 million dollars, offshore approaching maybe 50 million for one well. You don’t really want to be just spending that money on all these holes that turn out to be dry; you want to actually have as much information as you can in order to get the best return on your investment.
Acknowledgements: Archives New Zealand / Te Rua Mahara o Te Kāwanatanga Lloyd Homer – GNS Science Rosalie Pollack – GNS Science NZ Geographic Jun Tsuda Glen Morse Duncan Rimmer
