As energy markets evolve, the supply mix diversifies, and the push for a net zero energy system accelerates, the competitiveness of oil and gas has become increasingly important. A focus upon the total cost of ownership across the field lifecycle has begun to emerge as a driving factor within subsea oil and gas project evaluation, with greater emphasis on cost-effective operations. Acknowledging that the life of field begins within the engineering, procurement, construction, and installation phase of a project allows the operator to influence through life activities to greatest effect and achieve a balanced optimization of capital and operational expenditure.

Intervention is a key activity for maintaining and optimizing a subsea wells performance, from initial installation, through the producing life, and finally during decommissioning. As completion technologies continue to evolve, opportunities emerge for optimization of the systems used to intervene upon subsea wells. One of the largest areas of opportunity is the simplification of a technique to permit operations from a more efficient rig or vessel. This paper explores some of the solutions available today which allow historically rig based activities to be performed from vessels. These include riser based intervention systems, hydraulic intervention solutions, well abandonment technologies, and subsea workover control systems.

An evaluation of the presented techniques against alternative approaches is shared, to aid the reader in selecting the optimal solution for an application. Guidance is provided to assist in identifying the key decision criteria, complete with the capabilities and limitations of each solution.

The conclusions identify that designing a subsea production system with the flexibility to accommodate life of field activities can deliver reduced total cost of ownership to operators. A key part of this is consideration of optimized intervention techniques which can leverage simpler vessels for deployment and operation. By reducing the vessel specification, broad benefits can be realized including reduced asset day rate, reduced operational duration, and increased asset availability globally. This permits improved scheduling and reduced mobilization costs, in some cases enabling intervention activities which otherwise would not be economical.