Risk-informed rig selection for well abandonment operations in Australia

AGR’s Well Management was contracted to support the abandonment of a series of subsea wells. The client needed to look at the most effective method of carrying out the abandonment drilling campaign and ensure that all of the Australian regulator requirements were met.

The Challenge

In order to source and contract a rig for the operations, the following needed to be considered:

• A light intervention vessel could do some of the work but it would need a Mobile Offshore Drilling Unit (MODU) to carry out other areas
• A jack-up could carry out all of the work or the remainder of the work that the intervention vessel could not complete. However a jack-up could have a higher risk of waiting on weather as it moved between the wells
• A semi-submersible could carry out all of the work or the remainder of the work that the intervention vessel could not complete. The semi-sumbersible could kedge between wellheads so would not be affected by the weather, however there would be an additional cost that may not be offset by the possible time saved
• The abandonment had to comply to internationally recognised standards for zonal isolation etc

Key iQx capabilities

• P1™ (now PLANS) output a detailed analysis of the time & cost estimation for the many permutations of intervention vessel, jack-up and semisubmersible
• The probabilistic cost evaluation took into account weather conditions, exchange rates, and rig rates among other elements to deliver a simple comparison and allow the client to make an informed choice on the best vessel for the operations.

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