Innovative Field Development Solutions:
Enabling Technologies for Long Subsea Oil Tiebacks Alessandro Radicioni, Giorgio Arcangeletti, Annalisa Di Felice, Amerigo D’Amico, Enrico La Sorda, SAIPEM S.p.A. Introduction In a market scenario dominated by low oil prices, operators are keen to find new architectural solutions for field development that bring about a reduction in the CAPEX and OPEX. In this context, developing new floating facilities and the related subsea network for a production of around 50kbopd is overly expensive. Today, the preferred solution appears to be a subsea tieback to an existing facility. Traditionally, the industry has developed tiebacks within a range of 10 to 30km. Looking towards the future, the target tieback length could increase to 50km or more (see Fig. 1) but several challenges have to be overcome to make it technically feasible and economically viable, mainly: • flow assurance linked to hydraulic, thermal and operability requirements, especially in transient conditions (see next section). • technologies needed to overcome the flow assurance challenges, especially considering the long distances from the wells to the topside facilities. • the necessary topside equipment integration and/or modifications. The long distance between the oil production wells and the treatment facilities generally requires the use of subsea pumps that have to be installed in the correct position based on the fluid characteristics and the well flowing conditions along with the chosen transport line diameter. Moreover, wet insulated or PiP and heated lines become necessary. By increasing the step-out distance, other elements of the traditional architecture may reach their technical and/or economical limits. For example, conventional chemical distribution and subsea facility control using hydraulic systems will have to be rethought, switching to 44 | MED OIL & GAS
Fig.1 – Example of an ultra-deep water long tieback field architecture
the subsea chemical distribution and all electric concept. Optimizing the development of these types of tiebacks considering all these challenges is not an easy exercise but it is one that offshore O&G industry players are trying to do. To offer the best response, considering all the aspects involved such as system design, selection and procurement of the main technologies, fabrication and installation challenges etc., SAIPEM launched an in-house project whose aim was to design, develop and optimize the subsea field scheme. This project is based on SAIPEM’s extensive experience in challenging URF EPCI projects and on technologies that SAIPEM has already developed or is developing. Identification of technology requirements and their relative status along with the potential development plan is an essential part of this initiative.
To achieve the project’s aim, several case studies were selected and investigated to define the best development schemes with the aim of identifying and developing technologies to be used as building blocks for long subsea tiebacks and to generalize the results achieved. The goal was to build the main innovative elements of subsea field architecture to propose to Clients in order to fulfill specific project requirements and constraints, and to make the exploitation of new reservoirs profitable, maximizing the use of existing facilities. Some key or new technologies were identified and included in specific R&D programs aimed at developing proprietary technologies, or at entering into agreements with potential partners (i.e. Siemens for the Control System) in order to gain a commercial advantage in that market segment.
