Development of a Quantitative Approach to Risk Based Flow Assurance

Abstract

Flow Assurance (FA) engineers usually produce a range of technically feasible solutions in response to a particular challenge. Often these solutions are cost neutral. In order for a development manager to select the optimum solution he/she examines the risk profiles associated with the options. To progress a marginal development, explicit understanding of financial risk is imperative, needing a step up from qualitative “gut feel” assessments to a more reasoned and auditable quantitative evaluation of FA risk. As part of Woodside's Next Generation Flow Assurance Strategies initiative, Woodside embarked on a Joint Industry Project (JIP) called RiBFAT, standing for Risk Based Flow Assurance Toolkit. The main objective of this JIP is to develop quantitative risk profiles for FA solutions to the wide range of FA challenges. Phase 1 of the JIP produced a Proof of Concept for a risk based approach to hydrate management, one of the main FA challenges of cold ambient temperature field developments, typified by deepwater. Phase 2 was the conversion of the agreed methodology into fully functioning non-commercial software; completed by the end of 2014. This paper discusses the methodology developed and illustrates how this can be applied to a field development concept in order to compare the risk profiles for alternative FA strategies for hydrate management. The risk profiles cover the life of the asset including additions / modifications to facilities as required to optimise the development of the reserves. Ongoing use of the methodology results in the production of a database of knowledge for each FA challenge, which may be interrogated for benchmarking or assurance purposes, allowing the user to develop greater confidence in a particular proposed strategy. The methodology for addressing risk described in this paper will be extended in the next phase of the JIP to other FA challenges such as slugging, scale, wax and corrosion, building up to a comprehensive toolkit for FA risk assessment, including the database. Concurrently, we plan to document this methodology as the first ever global FA risk assessment recommended practice.

An Overview of Flow Assurance Heat Management Systems in Subsea Flowlines

“…Passive insulation in the operation and design of subsea flowlines is very important because of the unfavorable low temperature and high-pressure conditions; such an environment creates stringent needs for optimal insulation [68][69][70][71]. The passive insulation system of heat management is flowline insulation with materials of low thermal conductivity like polypropylene, polyethylene, polyurethane, extruded polystyrene, fiberglass, mineral wool, rubber, glass-reinforced plastic, Vacuum Insulation Panels (VIPs), and aerogel [50,[72][73][74], to control and reduce the loss of heat from the crude oil to the surrounding [50,75,76]. Some insulation types are dry and wet insulations, flowline burial, Pipe-In-Pipe (PIP), and others [50,77,78] (Figure 4a).…”

“…The multilayer insulation system is a sub-units of the integral insulation technique [85] and comprises various insulation layers [85,138,139]. The usual designs have syntactic foam layer, blown foam layer, and solid layer [76], and individual layer conduct a particular role [85,140].…”

“…For most fields, the goal is to stay above the region of 15 to 40 • C [161]. Therefore, the active heating method is used for many situations in flowlines [49,76], such as the prevention of cooldown and warming up of non-flowing systems like (e.g., during shutdown or startup) [49,168], sustaining and increasing temperature while flowing [49]; decreasing the need for chemical injection [49,76] Compared to passive insulation, active heating can sustain the hydrocarbon fluid temperature beyond the hydrates and wax formations temperatures over long periods [49,76]. Three heating systems exist; Hot Water Circulation (HWC), Electrically Heat-Traced Flowline (EHTF), and Direct Electrical Heating (DEH) as shown in Figure 10a.…”