This paper, named "Deep Water Tie-in", describes a tie-in concept for large diameter pipelines The concept is developed for use at large water depths where diving is both costly and dangerous. The concept is developed for a typical Gravity Base (GBS) platform situated in 300 metres water depth. The tie-in of pipelines with a diameter of up to 40″ is achieved through a tie-in arrangement system pre-installed in the platform substructure The main components are an atmospheric tie-in tunnel, seal tube and J-tube for pipeline pull cable The paper describes each of these components in more detail before it embarks on a step by step account of the pipeline tie-in procedure. In order to establish design loads on the sealtube and identify the optimum pipeline approach, computer analyses have been carried out It is shown that a curved pipeline approach or a dogleg are both feasible from a load on anchor or stress in pipeline point of view However, a straight pipeline approach causes loads and stresses too high for practical design purposes. In order to evaluate the advantages of the proposed tie-in arrangement, the paper ends with an outline of alternative tie-in concepts
This paper describes a deep water tie-in concept suitable for large diameter pipelines. The concept has been developed by Aker Engineering Bergen A/S (Previous Bergen Engineering A/S) for a typical Gravity Base Structure (GBS) situated in 300 metres water depth. Aker Engineering Bergen A/S has during the last few years performed several studies with regards to the tie-in of pipelines at deep waters
The tie-in of pipelines up to 40″ diameter is achieved through a tie-in arrangement system pre-installed in the platform substructure This so that the tie-in of the pipelines to the platform riser systems can be achieved in a safe and practical manner with emphasis on flexibility and back-up possibilities.
The tie-in of the large diameter pipelines are to be performed within a dry tie-in chamber through a seal tube system constructed as an integrated part of the GBS structure This tie-in arrangement has the following main advantages compared to alternative methods
The entire riser is installed within the riser shaft and protected against environmental loads and dropped objects
Straight forward inspection and maintenance of the riser and corrosion protection system performed by the platform crew
Pipeline or pipeline section pull-in directly from a lay barge.
Tie-in weld is performed in dry one-atmospheric Condition
No diving required. Pull-in will be assisted by ROV
Flexibility with regards to sizing of future pipelines, The pre-installed tie-in arrangement can accommodate a range in pipeline sizes
Possible to reverse tie-in in order to change pipelines.
In order to evaluate the advantages of the proposed tie-in arrangement, alternative tie-in concepts have been outlined