Vertical Connection Used as Tie-in System for Rigid Pipeline

Abstract

Abstract An attractive alternative to the use of flexible pipe flowlines is the use of rigid pipe flowlines. This is especially true in deep water giant fields or marginal fields, where the distance from floating production units to the wells is often several kilometers. Deepwater diverless tie-ins have a significant impact in the overall economics of the field development, and the selection of the tie-in method is a part of the critical path. This paper describes the studies conducted to evaluate and select a diverless tie-in system for the connection between the manifolds and rigid pipelines, and between rigid pipelines and flexible risers. Introduction In previous developments of deep water fields in the Campos Basin, Brazil, in water depths up to 1000 m, flexible flowline between christmas-trees or manifolds and floating production units have been used as a standard. The use of flexible pipelines allowed for rapid development of new fields, and the ability to recover and re-use flexible pipelines reduced their capital cost. Several connections systems has been used, including horizontal pull-ins, lay-away installations, and most recently the Vertical Connection System(VCS), addressed in ref. 1. Field development in Brazil is now moving into deeper waters and more marginal fields, requiring longer flowlines. As the flow line length increases the cost effectiveness of flexible pipelines is reduced when compared to rigid pipelines. In a new scenario of Albacora field, two(2) subsea production manifolds will be connected to rigid pipelines. Nating in flexible risers. The use of rigid pipelines requires a new diverless connection system to be selected. To evaluate alternative tie-in methods for rigid pipelines at the manifolds and risers, a study was performed to select the most economical and feasible tie-in system. Consideration was given to the resources available in Brazil, the operational experience and the technical soundness of the system, and the ability to meet the project schedule and budget Scenario In Albacora Field - phase I1 (fig. l), four (4) subsea production manifolds and one (1) subsea water injection manifold will be tied in to the production unit, the FPSO P-3 1 Vidal de Negreiros. Each production manifold will receive the production of eight (8) wells. The schematic of the production manifolds (fig. 2) shows the following:One (1) 8" ID production header,One (1) 8" ID service header,One (1) 4" ID production test header,One(1) 4" ID gas lift header. To allow pig passage (required to prevent paraffin formation) the production header and the service header are connected in a pigging loop, as well as the production test header and the gas lift header.