One of the problems connected with the completion of subsea fields located in large water depths concerns the connection between the production line and the subsea structure, especially when the use of rigid line terminating with a spoolpiece is envisaged The installation and connection of a rigid spoolpiece, being an almost state of the art operation with diver assistance, has almost no track record where diverless operation is concerned, except m special cases such as the vertical spool installation (Ref/I/) As a result, a new concept for a remote spoolpiece tie-in system has been developed and it is illustrated in this paper The concept is related to a system able to tie-in rigid spoolpieces up to 20″ in an operative water depth exceeding 2500m The basic philosophy of the system includes fully ROV based operations, standardisation and flexibility by using the same interfaces and being independent from the selected connection system, optimisation of both CAPEX and OPEX by the minimization of permanently subsea installed hardware
The development of marginal fields in deep water, which have the problem of High Pressure / High Temperature production streams, is currently forcing the installation technology towards the use of rigid lines, instead of flexible ones, to transport the well fluid to the receiving facilities in a more cost effective way This also results in requiring expansion spools at subsea tree locations and, possibly, also at the receiving point, h s being a mainfold template, an import riser base or a riser termination end The man problems faced in the presented scenario are large water depth requiring diverless technology, procedure and accuracy for spool installation, and connection system standardisation Beyond these, aspects such as permanently subsea installed hardware minimisation, independence from the surface vessel (1 e no rigid link) and cost optimisation have also to be considered As a result, a new tie-in system for rigid spoolpieces has been designed and details are presented in this paper The basic characteristics of the system can be summarised in (Available in full paper)
The selection of system design data was based on a market survey focused on worldwide field scenarios requiring the installation and tie-in of rigid spools at water depths beyond diver capabilities This resulted in the identification of the following parameters, which have been used as the basis for the design activities (Available in full paper)
On the basis of the identified design data, the functional requirements of the system were then defined as follows
all tie-in interventions shall be performed diverless,
the tie-in system shall be completely reversible at any step of the intervention procedure and shall guarantee full piggability of the pipeline sections concerned with the tie-in operation,
the impact of the tie-in operation on field construction p l w n g shall be optimised to reduce time and costs,
all tools and eqiupment shall be installed, operated and removed by ROV, thus minimising the use of and guaranteeing independence from the surface support vessel,
