The Next Generation of the Purpose Built Intervention Semi-Submersibles: Delivering Subsea Well Intervention Cost Reduction through the Increase of the Operational Efficiency
Authors: Batista João H. G. , Carr David J. 
Published: October 2017

The new scenario for oil pricing, where the "lower for longer" seems to be the new reality, brought the necessity to revise all the costs associated to the subsea oil & gas production. More than just request price reductions on the contracting of the services; operators are now looking for the efficiency of the offered activities.

In the well interventions’ world, the combination of cheaper and, still good in quality, services will not guarantee the lowest overall cost in a campaign. Aspects, such as, the existence of the built for purpose interventions features, experience of the crew in the well intervention operations, integration among services providers, the possibility of having fast change among down-hole conveyance systems, possibility of executing off-line activities and others, are what will bring a true safe, efficient and cost-effective operation.

The third generation of the purpose built intervention semi-submersible (Q7000) is in the final stage of the construction and will be available to the market in 2018, bringing new technology enhancements and lessons learned from more than 15 years of continuous operations of the 1st and 2nd generation of the intervention semi-submersibles (Q4000 and Q5000, respectively).

In order to have better operability in high winds seas and currents, Q7000 will incorporate modern automation, DP Class 3 classification and a customized design. As a vessel able to perform heavy work overs as well, Q7000 will have also a MODU classification, which will give the capability to take hydrocarbon returns to surface, as well as circulated well bore fluids.

What differentiate a purpose built intervention semi-submersible from a typical drilling rig are how the associated intervention equipment is handled and the ability of the unit on offering off-line and parallel activities. In this sense, Q7000 will incorporate features to allow fast change-out among slickline, wireline and coiled tubing units; pipe handling system to increase the agility on the pipe runs; heavy lift subsea crane with active compensation, to allow off-line or parallels subsea activities; main derrick with active and passive compensation system; high capacity service crane, to allow simultaneous crane operations increasing the efficiency with mobilization and demobilization offshore; high capacity in terms of storage, including bulk, liquid and self-sustaining (fuel and potable water) storage; deck with high draft tonnage and a maintenance tower, to allow off-line testing of the subsea intervention package. The paper will give a detailed description of the design, capabilities and operational premises considered in the Q7000 development and will also illustrate, through a comprehensive exposition of the purpose built intervention features, how a purpose built intervention semi-submersible is able to deliver a more efficient and cost-effective subsea well intervention than a conventional drilling rig.