The well was designed to allow it to be suspended for utilisation in the future development. However, the client decided to permanently abandon the well during operations. Further to this a thief zone not present in the offset wells was encountered, resulting in a lower 7” liner top of cement than was necessary for well abandonment. This required an alternative solution in a short timeframe to reliably plug and abandon the well in accordance with regulatory requirements.
- Large thief zone encountered that was not present in offset wells
- Short timeframe to mobilise equipment and personnel for the challenging operation
- Limited availability of section milling equipment in Australia requiring mobilisation of equipment from around the globe
- Integration of casing swarf recovery equipment with the rig equipment
- Abandonment design to be suitable for a well situated in a potential CO2 storage site
- Victorian bushfires active whilst operational, heavily impacting logistics
- Bespoke arrangements and expertise required to minimise impact on equipment and personnel
- Risk identification and management: AGR identified the risk associated with the thief zone and potentially low top of cement ahead of time and actively engaged service partners to confirm equipment and personnel were available to abandon the well as required. This was critical in ensuring there was sufficient lead time to mobilise equipment and personnel for the challenging operation
- Technical expertise: AGR’s knowledge of current best practice and industry standards was key in engineering the necessary abandonment solution to comply with regulatory requirements. This included section milling operations, casing swarf recovery and installation of an open hole inflatable bridge plug to isolate the thief zone and enable a balanced cement plug to be set and verified across the full cross section of the wellbore
- Logistical expertise: To execute the engineered solution, equipment was required to be mobilised from around the globe due to limited availability locally. AGR worked closely with the service partners to provide them with logistical expertise and ensure equipment was mobilised without delays despite the short timeframe.
The operations were successfully executed in January 2020. Abandonment objectives of the well were achieved without incident, all environmental commitments met and with no downtime waiting on equipment despite the short timeframe. The well was accepted as permanently abandoned by the regulator NOPSEMA.
- Logistical challenges overcome with no impact to the critical path of operations. Equipment was mobilised from four different countries in addition to multiple locations locally for the section milling operation.
- Effective recovery of casing swarf during section milling operations without incident and all environmental commitments met.
- Plug and abandonment of the well successfully executed including section milling 7” liner, isolating the thief zone with an inflatable bridge plug and installing CO2 corrosion resistant cement plugs, satisfying all regulatory requirements for permanent abandonment of the well.