Compact Modular Manifold Design for Reduced Cost and Added Value Subsea Production Systems

Abstract

The focus of this paper is to present and discuss the key attributes of a cluster-type compact modular manifold (cluster type) design using new and innovative methods to integrate existing technologies in a drive to cut CAPEX, OPEX and delivery time. A subsea production manifold plays a central role in the gathering and distribution of production fluids from multiple wells through adjoining rigid or flexible flowlines. Current market trends emphasize is towards standard products in a drive to reduce project risk, delivery and cost. Standardization of the integral components of a manifold can be easily achieved, but it is typical for the manifold package to vary depending project specific requirements. For the majority, standardization will typically mean utilizing an existing design from previous projects, which can lead to redundancies and inefficient design. By looking at a standard modular solution from the outset, a tailored type solution can be effected within a standard format. Thus, the most cost effective ‘fit for purpose’ solution for each project can be designed and delivered as standard product. The approach to generating a modular manifold in standard design format was to take the best in class methods for discrete component manufacture and marry them to similarly designed parts that are scalable both up and down. This evolved into a design which incorporates forged headers with integrated valve blocks and compact horizontal connectors. The resulting compact, cost effective solution that can be delivered in multiple configurations using modular subassemblies. By utilizing this simple design philosophy, a reduction in size and weight compared to a typical conventional manifold can be as much as 50%. Because the modules are "standard parts", there are direct cost and lead time savings that can be passed on to the end user. The significant reduction in size and weight greatly benefits the installation program by allowing better utilization of rear deck space during loadout. This also has a reduction in crane capacity requirement which is a significant logistical factor in deep and ultra-deep waters. By designing a lighter structure, it is possible in many cases to utilize mud mats instead of more robust suction piles, which have significant associated manufacturing and installation costs. The commercial impacts of the modular design have also been considered. Schedule risk is vastly reduced as a result of removing the majority of pressure containing welds, a process which requires elevated control to ensure correct execution. The bolted arrangement also facilitates compliance with local content requirements. Pressure containing parts and parts with critical functionality can be manufactured and tested in an environment controlled by the design authority. Parts can then be packaged and shipped for in-country assembly and SIT allowing significant in-country content with a high degree of integrity.