ASX-listed oil producer and explorer Triangle Energy has received a stamp of approval from the Australian offshore regulator for a revised environment plan (EP), covering offshore operations at an oil field off the coast of Australia.
The National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) has accepted Triangle’s five-year update of the environment plan for the Cliff Head offshore operations within production license WA-31-L .
This oil field is located off the Western Australian coast and the production phase involves transferring oil and produced formation water (PFW) from the Cliff Head Alpha (CHA) offshore wellhead platform (WHP) to the Arrowsmith Stabilisation Plant (ASP) via a production pipeline.
After the PFW is removed from the product stream at the ASP, the crude oil is stabilized and then transferred to road tankers and transported for refining. This update to the Cliff Head operations EP considers only the offshore components of the development, which occur beyond the Commonwealth-state boundaries.
These activities entail the CHA: an unmanned wellhead platform to accommodate the well heads and support equipment along with eight well heads with the current arrangement of five production wells with electrical submersible pumps (ESPs) to enable artificial lifting of the produced fluid – crude oil and water – and three water injection wells.
In addition, the EP covers an insulated subsea production pipeline, which transports the produced fluids from CHA to the onshore ASP; an insulated subsea water injection pipeline from ASP to the three injection wells at CHA; and a subsea power and communication cable, and chemical supply umbilical running from ASP to CHA. The EP also covers pipeline inspection, maintenance, and repair activities. Furthermore, the production pipeline transports the produced fluids from the CHA to the ASP where oil is separated from the produced formation water, which is then transported via the water injection pipeline to the injection wells, where it is injected into the geological formation that hosts the hydrocarbon reservoir.
While the offshore components of the pipelines that lie within Commonwealth waters are approximately 4.9 km in length, the offshore components of the pipelines that lie within state waters – between the state waters limit and the mean low water mark – are around 6.9 km. The Cliff Head oil field is located in the Perth Basin about 270 kilometres north of Perth and 12 kilometres off the coast of Dongara in Western Australia.
Moreover, Triangle anticipates that the Cliff Head field offshore operations will transition to the non-production phase within the five years covered by the EP, with cessation of production currently slated for mid-2024.
The company’s progress and planning for decommissioning operations are outlined in the EP, however, future decommissioning activities, including plug and abandonment of wells, will be conducted under separate EPs.
In November 2021, Triangle Energy slashed the estimated cost of decommissioning for the Cliff Head field-related infrastructure by nearly $8 million following a decision to use a hydraulic workover unit instead of a jack-up rig.