Abstract
Due to the laws of physics and multiphase flow, subsea tie back systems are generally limited to approximately 110km as a single pipeline or 150km as dual pipelines after which the production plateaus are shortened and increasing amounts of reserves remain in the ground. This paper presents an overview of an innovative new technology which demonstrates that gas tie-backs can be achieved without the need of compression.
The premise of the technology is to achieve pseudo-dry gas conditions through intermittent in-line separation with segregated transport of the associated liquid phase. Achieving near dry gas conditions in the main production conduit removes hydraulic constraints on line size and turndown, leading to improved recovery for long distance tieback opportunities.
The paper demonstrates this innovative technology and its value proposition by means of a ‘bench-marked’ study of a 200km long gas tie-back in 1,800m (5,900ft) of water. The Computational Fluid Dynamics (CFD) work has demonstrated high separation efficiencies at significant superficial gas velocities, while the required hardware fits within the installation envelope of an ‘In-line’ pipeline tee. This has been coupled to the flow assurance work showing improvements in recoverable reserves, while leading to capital expenditure reductions of upwards of 50% due to the removal of offshore structures.
