Ahuroa Underground Gas Storage Facility

The Ahuroa underground gas storage (AGS) facility is located in Taranaki, New Zealand. Opened in May 2011, it is the first such facility to be developed in the country. It has an extraction capacity of 45 terajoules a day (TJ/d).

The project was developed by Contact Energy (Contact) and Origin Energy (Origin) with an investment of $170m. Origin owns a majority stake in Contact and is the operator of the facility.

The Ahuroa gas field was converted for use as the storage facility. Origin acquired the field in addition to the Tariki, Waihapa, Ngaere and Rimu-Kauri fields from Swift Energy in 2007.

The storage facility will provide flexibility of operations for Contact. It will enable the company to store gas during periods of low demand and extract it during periods of high demand or high price. The facility will thus insulate Contact’s operations against gas price fluctuations.

AGS can be expanded by adding a second injection and extraction train which can increase capacity to 100TJ/d. It can have a maximum injection / extraction capacity of up to 160TJ/d.

Contact plans to store gas received from a number of sources, including the Pohokura field and future LNG imports, in the Ahuroa storage facility.

Construction and infrastructure of the Ahuroa underground gas storage complex

Development of the facility presented many engineering and construction challenges. Contact was able to leverage the expertise of Origin Energy for the development.

The development was completed in two phases with the first phase commencing in December 2008 to inject gas into the depleted Ahuroa reservoir.

The reservoir is located 3km underground in the Tariki sandstone formation. It was studied and deemed excellent for storage due to its high reservoir quality and integrity.

The size of the reservoir was also ideal for meeting the market requirements. The reservoir is monitored by down hole gauges which are fed into the dynamic reservoir model to monitor the performance.

Installation of a new injection compressor was commenced in July 2009 and completed in September 2009. The compressor was commissioned in October 2009.

Phase two of the project included drilling of three new injection / production wells. The first well, Ahuroa-3, was spud in November 2009.

The second well, Ahuroa-4 was spud in December 2009 and the third well, Ahuroa-5 ST,1 was spud in February 2010. A coiled tubing rig was used to carry out well testing operations.

The second phase also included constructing a new extraction facility capable of extracting 45TJ/day. The construction started in March 2010 and was completed in February 2011. A gas-to-gas exchanger and low temperature separator coalescer vessel were also installed in phase two.

Connection

Gas stored in the AGS facility can be supplied to any of the thermal generation plants of Contact including the new 200MW peaking power station located near the facility at Stratford.

Contractors involved in the AGS facility

Drilling of wells and design of the facility was undertaken by Origin.

The front end design and engineering, procurement and construction contract for the project was awarded to a joint venture (JV) of Transfield Worley and Hawkins Infrastructure.

The Transfield Worley Hawkins JV subcontracted Fitzroy Engineering to design and supply the low temperature separator vessel, flare knock out drum and hot oil heater. Fitzroy was also responsible for upgrading the burner system and installing piping.

EnergyWorks was contracted to install a gas compressor and carry out piping works. The scope of work included venting, fuel gas piping and structural works.

Engineering Control Limited supplied automated control solutions including DeltaV PCS and Hima SIS systems for the facility.