Photo: Valaris MS-1 rig; Source: Valaris

Western Gas gearing up to drill Australian well as environment plan gets regulator’s approval

Western Australian company Western Gas has secured the regulator’s acceptance of its environment plan to manage drilling activities for the Sasanof-1 exploration well on the North West Shelf.

Western Gas reported last week that it has received acceptance from Australia’s National Offshore Petroleum Safety and Environmental Management Authority (NOPSEMA) for its environmental plan for the Sasanof-1 exploration well off Western Australia.

The environment plan was submitted to Australian authorities in July 2021 when the company also secured a drilling rig for the well. The formal contract award for the Valaris – owned MS-1 semi-submersible rig was announced in November.

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Following an agreement from September 2021, Western Gas finalised the sale of 25 per cent of Western Gas (519P) Pty Ltd – the holding company for WA-519-P – with Global Oil and Gas Limited in November. As previously reported, the acquisition will enable Global to fund 50 per cent of the drilling cost for the Sasanof-1 exploration well.

The well is located in exploration permit WA-519-P, in Commonwealth waters, about 207 km northwest of Onslow. According to Western Gas, the Sasanof prospect is on-trend and updip of the liquids-rich, low CO2 Mentorc gas and condensate field and nearby the giant gas fields of Scarborough and Io-Jansz in the Carnarvon Basin.

Sasanof amplitudes on merged 3D seismic showing Mentorc field and Western Gas’ Sasanof prospect outline; Source; Western Gas

ERC Equipoise (ERCE) has determined Sasanof has an estimated 2U Prospective Resource of 7.2 Tcf gas and 176 million bbls condensate (P50), with a 32 per cent chance of success. The high case 3U prospective resource estimate is for 17.8 Tcf gas and 449 million bbls condensate (P10).

The Sasanof prospect is a large, seismic amplitude supported, structural-stratigraphic trap in the high-quality reservoir sands at the top of the Cretaceous top Lower Barrow Group formation on the Barrow Delta within the Exmouth Plateau.

Western Gas explained that the Safety Case Revision for the Sasanof-1 well and the Well Operations Management Plan (WOMP) were submitted to NOPSEMA in early December 2021 for assessment and are currently being assessed by the Australian regulator.  

Will Barker, Western Gas Executive Director, remarked: “Regulator acceptance of the environment plan for Sasanof is a major achievement for the Western Gas team and our service providers, XODUS and AGR. It reflects a collaborative and focused effort and gives us the confidence to progress through the final stages of regulatory approvals and detailed planning for the well.”

Source: Western Gas

Sasanof-1 will be a vertical well and drilled to a total depth of approximately 2,500 metres in 1,070 metres of water, providing a low cost, high impact exploration well in a known and proven hydrocarbon province.

Western Gas confirmed that drilling activities are scheduled to start in March/April 2022 using the MS-1 rig, following its relocation from nearby activities on the North West Shelf. The company further added that drilling costs are still estimated at $20-25 million as previously stated.

It is worth noting that Sasanof-1 will be Western Gas’ first well drilled from its exploration portfolio surrounding the existing Equus gas project that contains a discovered resource of 2 Tcf and 42 MMbbl. According to the company, the Equus gas project has a historic exploration drilling success rate of 88 per cent with 15 discoveries from 17 wells.