Once the gas is found, it flows up through the well to the surface of the ground and into pipelines. The gas is then transported to a gas processing plant to be cleaned. The gas is purified into natural gas so that it can be used as fuel for homes and businesses.
Other hydrocarbon compounds, like butane and propane, are separated during this process and they can be used in a number of ways. The ‘LPG' you find in BBQ cylinders is a mixture of propane and butane and can be used for heating or cooking.
Carbon dioxide (CO2) gas is also removed from the gas during processing and this is purified and stored as a liquid before being transported to customers around the North and South Islands.
Vector's Kapuni Gas Treatment Plant was New Zealand's first natural gas treatment plant. It processes natural gas for North Island gas-fuelled power stations and thousands of industrial, commercial and domestic gas customers across the North Island. At Kapuni, the gas from the wells is passed through a special solution which removes the carbon dioxide.
The gas is then dried and cooled to –27°C (much colder than your freezer). At this temperature, the propane and butane in the gas become liquids and these can be separated and stored in large tanks (this is Liquefied Petroleum Gas or LPG). The remaining gas is sent into the pipelines which take it all around the North Island.
How is liquid CO2 used?
Carbon dioxide (CO2) is commonly used as a raw material for: production in fire extinguishers; carbonation of soft drinks; freezing of food products such as poultry, meats, vegetables and fruit; chilling meats prior to grinding and refrigeration; and maintenance of ideal atmospheric conditions during transportation of food products to market.
Kapuni is the largest manufacturer of liquid CO2 in New Zealand, supplying twothirds of New Zealand's needs.So the carbon dioxide in your fizzy drink probably comes from Kapuni, which means that it has come from a well 3,500 metres under the ground and is about 35,000,000 years old!
Green power/harnessing energy
Kapuni Gas Treatment Plant has a Cogeneration plant which burns some of the gas produced at the plant to provide electricity and steam for the treatment plant and other customers as well.
The Cogeneration plant produces all the steam and electricity the gas processing plant needs to operate.
- Kapuni is the largest gas processing plant in New Zealand.
- Kapuni operates 24 hours a day, 365 days a year.
- The three highest towers at the plant are nearly 30 metres high.
- Kapuni processes about 1,500,000 cubic metres of natural gas every day. That's about 600 Olympic-sized swimming pools full of gas.
- Seven trucks collect 100 tonnes of LPG every day: enough to fill over 11,000 BBQ LPG cylinders.
- The plant has been operating since 1970.
- 60 people work at Kapuni.