A Study of a Subsea Chemicals Storage & Injection-Station
Abstract
Total and Doris have announced that they want to challenge the way of thinking of how to supply subsea field developments with chemicals. With a Subsea Chemicals Storage & Injection-station (SCS&I) the chemicals are injected much closer to their injection points compared to a conventional solution, where they are injected from a topside facility. This reduces the response time of hydrate inhibitors which leads to a shorter well shutdown/start-up operation. Also, dosing of production chemicals can be done more accurately, and valuable space topside is made available for other equipment.
This thesis challenges some of the design solutions proposed by Total and Doris for the SCS&I-station. The main topics investigated in this thesis are; total storage volume and tank design, system architecture, distribution schematics and an economic assessment of the SCS&I-station.
The research method used in this thesis is Concept Scoring. This research method enables screening of several concepts, and singles out the most suited concept for its designated application. Preferred architecture systems of the SCS&I-station and pressure-balanced tank design was found by applying this Concept Scoring. It was concluded that the best suited pressure-balanced tank design was the bladder tank. Interestingly, this deviates from the piston tank design proposed by Total and Doris.
It was found that methanol occupies approximately 60% of the total storage tank volume of the SCS&I-station. This means that the impact methanol has on the total storage capacity required is large. The economic assessment indicated that a solution with methanol stored and injected topside is more beneficial compared to a subsea storage solution.