Nautec provided well site supervision and field engineering support throughout the three well abandonment campaigns. Throughout each activity, regular Pre-Job Safety Meetings and Health Safety and Environment briefings were conducted. Supervision activities included rig up/downs, wireline intervention, fishing, tubular retrieval and cementing activities. Engineering services included well abandonment program review, risk assessment and mitigation, engineering calculations (cementing, mud compressibility & thermal fluid expansion), well control readiness and end of well reports.
The operational challenges included the use of heavy weighted (18.1 ppg) drill mud with elevated wellbore temperatures (Flow-line temperature ~92°C), and barite sag. As a result of high surface temperatures and pressures, frequent rig equipment failures further compounded the challenge. Due to the weighted drill mud and high temperatures, specially formulated cement plugs and tuned spacers were used in order to form an adequate and effective well barrier.
In each well, excess tubing and casing was removed and replaced with approved cement plug barriers that satisfied the South Australian – Department of State Development authorities.
The well abandonment program was completed with no incident or accidents; run to schedule and close to the original budget.
Nautec carried out Engineering Design; Well Abandonment and Operational Supervision / Engineering as part of its well site and well engineering support services to Geodynamics Limited in support of their plans to plug and abandon the Cooper Basin Geothermal Project.