Study on the Split-Type Subsea Manifold Engineering Technology

Subsea manifold is a flow-routing subsea hardware (subsea flow router) that connects between subsea trees and flowlines. It is used to optimize the subsea layout arrangement and reduce the quantity of risers connected to the platform, the new engineering technology of subsea manifold to be studied in this paper. From the perspectives of safety, economy, constructability, installation, operability and maintainability, it is proposed to divide the subsea manifold into three parts: manifold module, protection structure module and foundation module, thus forms the new split-type subsea manifold engineering. On the basis of analyzing the functional requirements of subsea manifolds, the method of manifold design and piping stress check is given herein. The protection structure design mainly involves protection against dropped object impact, fishing nets and dropped object. The structure design and strength checking method of dropped objects impact and trawl-board impact are also given. There are mainly two types of foundation for subsea facilities: mudmat and suction pile. Mudmat is more cost effective, hence it is the preferred solution. The design calculation method of mudmat is given (including vertical bearing capacity, torsional resistance, sliding resistance, overturning resistance, settlement calculation, skirt penetration capacity). Finally, the three modules are combined to form a new split-type subsea manifold design, which has been successfully implemented in South China Sea, providing a reference for the application of the new split-type subsea manifold.