The permit (PMP 38154) work program goes on to say that the Pohokura reserves carry a large uncertainty range. "As a result it is imperative that good geological, petrophysical, production and pressure data is gathered in future, in order to assess possibilities for further recovery optimization over the field life."
With total New Zealand gas reserves listed as 1462 petajoules at 1 January 2004 by the Ministry of Economic Development, the addition of the Pohokura reserves will take total reserves to over 2000 PJ.
The Pohokura work program lists in-place volumes in the permit at 1550 million standard cubic feet (scf) of gas and volumes of condensate of 125.9 million stbbl.
Hydrocarbon volumes and reserves in the Mangahewa Formation were estimated using a static and dynamic modeling exercise. The numbers used are April 2004 mean figures.
Volumetric estimates will be updated regularly throughout the development phase and field life. The next expected updates will be at the end of the year following seismic reprocessing and after the initial batch of development wells in 2006.
Production will be from single offshore unmanned wellhead platform with a base case of six wells. A further three wells will be drilled from onshore. The platform will lie in 32m of water and serve as a template for a shallow-water rig. The four conductors used for the production wells will also serve as piles for the platform. Each conductor can hold two wells allowing up to eight wells slots for the platform.
Processing will be undertaken from onshore with the plant having a peak capacity of 220 TJ a day, equivalent to 80 PJ a year (200 MMscf/d of gas and 15,000 stb/d of condensate in the early production period).
No LPG (propane and butane) facilities are included in stage one of the project, though the option is still under consideration for stage two, dependent on market analysis of product pricing. The LPG fractions represent approximately 5.9% of the total Pohokura gas wellstream.
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