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In subsea oil and gas production, a transition away from complete gas hydrate avoidance to riskbased hydrate management has the potential to offer cost savings and improved viability for new developments. Rigorous characterization of hydrate formation probability (via the measurement of statistically significant numbers of independent hydrate formation events) represents a critical step towards accurate quantification of hydrate blockage risk. Such characterization is especially pertinent when deploying low dosage kinetic hydrate inhibitors (KHIs) which, unlike thermodynamic hydrate inhibitors (THIs), affect hydrate formation kinetics rather than thermodynamic stability envelopes. Here we demonstrate the use of a 2nd generation, Peltiercooled, high pressure, stirred, automated lag time apparatus (HPS-ALTA) to efficiently measure hydrate formation under conditions simulating a methane dominant natural gas asset. Over 2,500 hydrate formation events were measured using a low salt content brine, enabling the production of smooth, high resolution hydrate probability distributions in the presence of three inhibitor chemical additives and combinations thereof (a corrosion inhibitor, a KHI and a conventional THI). Beyond enabling rapid, high fidelity testing of potential inhibitor interactions, the results explicitly demonstrate the ability to effectively manipulate formation probability boundaries via a 2 combination of thermodynamic and kinetic inhibition effects. Such hybrid inhibition strategies can be used to achieve long induction times at operationally relevant formation temperatures (over 2 days at 2.5 °C in this study) and may be more beneficial and/or cost-effective than strategies focused on complete hydrate avoidance.

The European ALARA Network regularly organises workshops on topical issues in radiation protection. In light of the Fukushima accident, the most recent workshop questioned the application of the ALARA principle in emergency exposure situations. This memorandum presents the conclusions and recommendations of this workshop. One of the outcomes is that the process of optimisation in emergency exposure situations should be flexible enough to be able to modify or refine decisions over the course of an accident. In the urgent phase, decisions must be made in a very time-constrained environment, based on scarce, uncertain and sometimes unreliable information. In this phase, optimisation and protection strategies are therefore developed and applied on the basis of conservative assumptions or 'reasonably foreseeable worst-case scenario' which could lead to an overestimation of the consequences. In the intermediate phase, knowledge of the situation improves, and more time is available to make the decision. This is reflected by adopting a less conservative approach, and transitioning to a more appropriate optimisation adapted as effectively as possible to the various exposure situations. When the situation is eventually stabilized (transition phase), there is time to shape the measures taken previously to reflect local conditions in the affected territories. In every phase, consideration should be given to the stakeholders, so that their needs and requirements can be incorporated as effectively as possible.

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.

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