Challenges and lessons learnt from Northern Territory (NT) Orphan Well project

Abstract

The Orphan Well project evolved from recommendations in the Final Report of the NT Hydraulic Fracturing Inquiry (HFI). The purpose was to assess wells that were drilled under petroleum permit or licence, and which had subsequently been surrendered by the titleholder and are now the responsibility of the NT Government. The project’s objective was to confirm the current status of these wells and to put forward recommendations for remedial works and/or monitoring for wells assessed to have an integrity risk. The assessment primarily focusses on the risk of fugitive methane gas. Two petroleum engineers were employed to undertake the project of assessing 113 orphan wells scattered over 1.4 million km² of the NT. As it is a requirement to rehabilitate the land after petroleum activities have ceased, access to orphan wells is often not maintained; therefore, logistical consideration was undertaken. The project involved an initial desktop study of well history (construction) followed by a field site inspection. The drilling of these wells date back to the 1960s. These older wells can often have less detail in the well records including survey location, and being pre-GPS, may include location errors of several kilometres. Remote helicopter travel was used to undertake fieldwork and to locate these wells. The site inspections commenced in February 2022 and as at 31 December 2022 on ground field inspections were delivered to 96 wellsites. This paper provides insight as to how the Orphan Well team developed its processes in both desktop study and site investigations.