Making use of the Resources available.
New Plymouth has a proud history of Oil Exploration and Extraction extending back into the mid 1860's with the first onshore wells, followed by New Zealands first Oil refinary opening in 1913.
Early European settlers in New Plymouth were complaining about an oily scum on Ngamotu Beach which stained their dresses and coated their boots. Rainbow hued slicks often covered the water around the Sugar Loaf Islands.
The Taranaki Basin
An area of approx 300,000km2 covering both onshore and offshore geological structures off of the West Coast of New Zealand.
Hydrocarbon products found in this area include Oil, Gas & Condensate. There have been approx 400 exploration and production wells drilled within the basin which is far fewer than in comparable fields around the world.
How Oil & Gas Form:
Oil and gas are made of carbon and hydrogen compounds. They occur naturally in the earth’s crust at shallow to moderate depths (1–12 kilometres). The formation and trapping of oil and gas requires the combination of a number of significant events, involving the presence of a suitable source rock, its burial, and the preservation of hydrocarbons. Oil and gas formed when organic material (land plants and marine plankton) was laid down in peat swamps, estuaries and shallow seas. Sediments buried this material, preserving it from decay. A good reservoir rock must be both porous (with gaps to store oil and gas) and permeable (the spaces must be connected). This allows oil and gas to move through the reservoir rock and be extracted. Oil and gas exploration focuses on finding these trap features (known as prospects). The first step is to examine the surface geology to decide if the right types of rock are present. The next stage is usually to undertake seismic surveys, which bounce sound waves off underground rock layers. This tells geologists what the rock structures below the ground are like – and whether there are places where oil and gas may be trapped.
Taranaki's Oil & Gas Basin:
A sedimentary basin is a depression in the earth’s crust into which sediments have been deposited over millions of years. The sedimentary basins in New Zealand that are likely to contain oil and gas are young (less than 80 million years old), and most have many faults that offset the rock layers. New Zealand’s key sedimentary basins started forming after the breakup of Gondwana, about 85 million years ago, and the opening of the sea floor in the Tasman Sea. Rivers, eroding the nearby land, transported sediments containing organic material into these basins. This allowed shoreline sands to be deposited, followed by marine silts and mud many kilometres thick. These sands were compacted by the weight of the overlying sediment. Being both porous and permeable, they made ideal reservoir rocks. Impermeable overlying silts, mud and carbonates formed seals. In most New Zealand basins, oil and gas formed only over the past 20 million years. During this period the New Zealand land mass was uplifted and eroded. Sediments kilometres deep were deposited, and rock layers were moved by faults, which produced many underground structural traps (places where rocks containing petroleum are capped and sealed by impermeable rocks). Around New Zealand, there are eight sedimentary basins, onshore and underlying the continental shelf, with known or potential hydrocarbons. In addition, there are several deep-water basins offshore. Commercial quantities of oil and gas have only been produced from structural traps in the Taranaki Basin. In the Taranaki and East Coast basins, the most promising traps consist of structures formed by rock compression.
Cross Section of Taranaki Basin
This cross-section of the rock layers in the Taranaki Basin, north-west of the Taranaki coastline, shows sedimentary rock layers, which can be up to 7 kilometres thick. The vertical lines are faults that have offset the rock layers. Faults may act as upward routes for oil and gas trying to rise to the surface. Faults also offset underlying rock layers, creating gaps between permeable and impermeable rocks, where oil and gas can be trapped. Sedimentary basins such as this are the most likely places in New Zealand to find oil and gas in the future.
Current Production fields are:
Offshore: Maui (gas-condensate and oil), Tui Area (oil), Pohokura (gas-condensate), Maari-Manaia (oil), Kupe (gas-condensate).
Onshore: Kapuni (gas-condensate), McKee (oil and gas), Tariki-Ahuroa (gas-condensate), Waihapa-Ngaere (oil and gas), Ngatoro (oil and gas), Kaimiro (oil and gas), Mangahewa (gas-condensate), Rimu-Kauri (oil and gas), Cheal (oil), Turangi (gas).
To complete this Earthcache you will need to:
- go to the "Reference Points" and look for information associated with the History of Taranaki Oil Production, (it is only a short walk between these points),
- answer the following questions,
Location 1. S 39° 03.653 E 174° 02.465
- How many cubic meters of Oil were produced?
- and Between what Period?
- What is the Casing number cast into the Crank Counterbalance (at approx. knee height)?
Location .2. S 39° 03.675 E 174° 02.176
- How many productive wells were there in the Moturoa Oilfields prior to 1955?
- When did New Zealand Oil Refineries have a successful strike in the Moturoa Oilfields?
- Take a photo from Location .1. showing the Port today and the activity of the once "Moturoa Oilfields, (optional, but would be very much appreciated)
Please ensure that you email the answers to the questions above to the cache owner and post the optional photos with your online log.
You can log this cache straight away after you have emailed your answers to the cache owner, no need to wait for confirmation. Please include the name of this Earthcache in the email - you'd be surprised how many people forget.
References Include:
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