CUBE - A New Technology for the Containment of Subsea Blowouts

Abstract

Young Technology Showcase After the Macondo incident, the oil industry started a significant review of its capabilities to respond to a subsea well blowout and launched some specific development projects. Eni decided to participate in the principal joint industry projects launched on this topic, and also started internal activities aimed at the development of new containment methods. Two years after Macondo, it is clear that the major containment method of a subsea blowout relies on the use of a capping stack. This can be deployed in water depths as deep as 3000 m and equipped with multiple outlets that allow liquid and gaseous hydrocarbons to be routed to surface. However, in some cases well capping cannot be applied when a) well-integrity issues arise, this may happen when the capping stack causes a substantial pressure increase at the wellhead, with a potential rupture of the casing and the lateral dispersion of well fluids; b) the blowout preventer (BOP) stack is not accessible because of mechanical problems (status of wellhead/BOP or irremovable debris); c) the blowout does not come directly from the well (i.e., from nearby sea lines or mud line). On the basis of these and similar considerations, it is quite clear that the containment of a blowout event cannot only rely upon the use of a capping stack and other methods must be available. Eni has been working in the last 2 years on a new concept with the support of TEASistemi, a research company of the University of Pisa, developing an alternative to the capping technology. This system is based on the use of an open-sea containment system, which is able to perform at least partial gas/liquid separation. After separation, most of the liquid hydrocarbons plus a minor amount of seawater are pumped to surface. The gas phase can be sent to surface through a separate riser or can be discharged at sea. In order to prevent hydrate formation within the separation system, there must be a low separator-residence time. The system conceived by the authors of this paper has been patented in June 2010 (De Ghetto and Andreussi, 2010) and the first tests were performed in September 2010 at the TEASistemi Laboratory in Pisa. Of course the concept of subsea phase separation is not new for the oil industry, but up to now it has not been adopted for the containment of subsea blowouts. The reason probably being that up to the Macondo incident, it was believed that subsea collection and transmission to surface of blowout fluids could be easily accomplished by some type of containment dome. Unfortunately, the Macondo incident showed that this is not always the case and that the use of a containment dome presents a number of potential problems which need to be faced, such as the formation of hydrates, the poor control of the system, and finally, issues associated with large fluxes of seawater into the dome.