Session: 04-03-04 Thermo-Mechanical

Paper Number: 104359

104359 - Deepwater Rcm and Sri Design of Production Rigid Flowline Loops 

This paper presents a thermomechanical design for deepwater production rigid flowlines. This design considers that the subsea wells are tied-in to rigid flowline production loops in a daisy chain arrangement. The production loops are connected to a Floating Production Storage Offloading (FPSO) unit via risers.

Complex reservoir characteristics and the staggered nature of production wells across the fields, typically result in complex operating loading for production flowlines, with numerous potential start-up and operating scenarios. Moreover, due to daisy-chain arrangements and challenging bathymetries there are typically various locations along the flowline routes, such as end-termination and in-line flowline structures, which necessitate rigorous control of flowline displacements.

The Residual Curvature Method (RCM) and Subsea Rock Installation (SRI) were selected for the lateral buckling and walking control schemes for this design. The RC sections and the rock berms are strategically placed along the routes to work in unison to control the response of the flowlines and ensure the integrity of the flowline systems. The RC sections form engineered lateral buckles and contribute to controlling the flowline displacements. The rock berms control the flowline displacements, including the feed-in into the engineered lateral buckles and enhance their reliability. Additionally, the RC sections and rock berms allow flexibility in the design process since it is relatively easy to relocate, even late in the design phase.

Numerous potential start-up and operating scenarios introduce uncertainties in flowline designs which impose a risk on their reliability and robustness. In order to eliminate this risk in a cost-effective manner, production loops can be pre-conditioned. The pre-conditioning operation involves utilising the FPSO’s hot oil circulation facilities to heat up the production loops gradually and in a controlled manner, during the hot-commissioning, to initiate the engineered lateral buckles and structurally condition the rigid flowline loops.

This paper presents a novel thermomechanical design for production rigid flowline loops which involves the deployment of deepwater RCM and SRI. It focuses on the RCM engineering which is required to ensure that the design satisfies all the code criteria for any as-landed angle of the RC sections; i.e. irrespectively of the level of rolling of the RC section during installation. This design accounts also for the effect that the cooldown of thick insulated pipelines, from the as-laid temperature to the ambient seawater temperature, has on the pipeline response just after pipelay and though-life.  Moreover, this paper presents the effect of soil berm formation on the initial formation as well as the through-life performance of the engineered lateral buckles which are triggered by the RC sections. Furthermore, this paper investigates the through-life response of the engineered lateral buckles at locations of relatively high transverse slope. Finally, it presents a comparative study which demonstrates the lower carbon footprint of RCM compared to that of sleepers.

Presenting Author: Nikolaos Chatzimanolis Subsea7

Presenting Author Biography: Nikolaos Chatzimanolis is a mechanical engineer (CEng, MEng & MSc) who specialises in subsea pipeline design and installation. Nikolaos joined Subea7 in 2011 from BPP-Tech, an engineering consultancy which provides services in the offshore energy industry. Nikolaos has worked in many projects in various roles, from installation analysis engineer and pipelines design engineer to project lead engineer and currently rigid pipeline design discipline manager. Nikolaos has presented the “Walking Behaviour and Mitigation Strategies of the Deepwater Tullow TEN Project Swaged Pipe-in-Pipe Flowlines” in ISOPE 2018 and authored the “Upheaval Buckling Analysis of Subsea Trenched and Buried Pipeline Accounting for Slurry” which he presented in SPT 2022.

Authors:

Nikolaos Chatzimanolis Subsea7
Hossein Jalali Subsea7
Arek Bedrossian Subsea7
Min Xie Subsea7
Mark Lewis Subsea7