Australia offshore well inventory characterisation and decommissioning cost saving opportunities through cap rock restoration and rigless/riserless techniques
Christopher Murphy A and Stuart A. Higgins A BA Curtin University Oil and Gas Innovation Centre, Perth, Australia.
B Corresponding author. Email: stuart.higgins@curtin.edu.au
The APPEA Journal 61(2) 445-449 https://doi.org/10.1071/AJ20118
Accepted: 26 March 2021 Published: 2 July 2021
Abstract
This research utilises the Geoscience Australia and NOPIMS public database to characterise the national inventory of active offshore oil and gas (O&G) wells and, through representative examples of dry and wet completions, establish the current well decommissioning cost opportunities associated with using riserless and rigless techniques to restore cap rock. These techniques have been successfully applied in the Gulf of Mexico (GoM) and this study explores the potential savings and barriers to adoption in the Australian offshore operating and regulatory context. Third party studies (Bills 2018; Wood Mackenzie 2020) have reported Australian O&G decommissioning cost estimates in the range of USD 33–49 billion over the next 30–40 years. The well decommissioning contribution to the total project cost has been estimated at 49% (OGUK 2020). This cost is materially significant to the economic life of the asset, the operator’s financial liability and a significant cost burden to the Federal Government through Petroleum Resource Rent Tax (PRRT) offsets. In this context there is a paucity of detail and transparency for well decommissioning cost estimates, to establish whether there are cost saving opportunities whilst still maintaining an acceptable level of risk both during plug and abandonment (P&A) operations and in the longer term when relinquished back to the Federal Government. This study illustrates how and to what extent the Australian offshore Federal well inventory could be decommissioned using cap rock restoration and rigless/riserless techniques and proposes a staged strategy to realise a progressive cost reduction of 21–41% over the base estimate of circa USD 4.08 billion benchmarked with OGUK (2019). This significant cost reduction aligns with the OGTC (2019) technology roadmap target of 35% supported in part by the pursuit of a rigless and riserless well decommissioning philosophy.
Keywords: Australian offshore wells, cap rock restoration, cost estimate, regulation, rigless, riserless, safety case, well abandonment, well decommissioning, well barrier philosophy, well data base.
Christopher Murphy is a Senior Research Fellow with Curtin University Oil and Gas Innovation Centre, Australia. He graduated in 1979 with a BSc Honours in Mining Engineering from Leeds University, UK. Christopher has over 41 years of experience in the oil and gas business and has extensive knowledge of well construction and well and small offshore facilities decommissioning. Christopher was previously Head of Wells and Production Technology for British Gas and Vice President – Global Marine Solutions for Wild Well Control. The latter position saw him personally involved with over 400 well decommissioning projects and 60 small platform decommissioning operations in the GoM and internationally. He is an SPE member and coauthor of a US patent related to blind annulus isolation in subsea well decommissioning, patent number US 2013/0269948 A1. |
Stuart Higgins graduated from Monash University in 1988 with a BEng(Hon) in Mechanical and was also awarded a PhD in 2000 from Monash University. Stuart’s professional career has spanned 25+ years with Oil & Gas Operator specific field development expertise spanning appraise, select, FEED, execute, operate and decommissioning phases covering multiple asset types and international regions. Developments have included subsea, pipeline, fixed and floating deep water greenfield and brownfield assets from Mauritania, Mediterranean, North West Shelf, Browse basin and the Gulf of Mexico. Joining Curtin University in 2015 as an Associate Professor, he has managed and delivered the Master of Subsea Engineering and MSc (Global Subsea) programs and is the Curtin Oil and Gas Innovation Centre Deputy Director – delivering industry based research currently focusing on (1) well decommissioning and (2) the marine environmental impact of NORM and Mercury contamination for decommissioned pipelines. He is a member of SPE and SUT Perth and board member of Subsea Energy Australia (SEA). |
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