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For over a decade, being able to accurately predict the risk of calcium naphthenate deposition has been one of the goals of production chemistry studies for development of new fields. In order to fulfill this challenge, many studies have been performed both within the company and through collaborations in JIPs. These studies have also shown specific behaviours of acidic crude oil / water separation depending on processing conditions. They have also permitted the improved detection and quantification of tetraprotic acids that are one of the main building blocks of these deposits. In this work, we will show how these findings have been incorporated into a workflow used to quantify naphthenate deposition risk. In particular, we will try to illustrate how the "other" naphthenic acids of the crude oil can behave as an efficient natural inhibitor of the deposits, and why, even if tetraprotic acids are detected in quite a large number of oils, only a limited number of fields have faced large scale issues related to calcium naphthenate deposits, due either to "good" process design or good fortune. "Simple" physicochemistry tests turn out to be very powerful tools in order to assess the macroscopic behavior of the naphthenic acids, and their influence on the risk analysis. IntroductionWith the growth of petroleum products consumption, oil companies have to face not only the production of more difficult oils but they also have to develop fields in more and more difficult places (deep off shore, artic, …). There is a great need for flow assurance studies to be as accurate as possible both from a project perspective, in order not to over design for CAPEX concerns, as well as from an operational perspective, to be able to cope with scale issues. These studies should ensure efficient and reliable operation of the installations. When the developments are made on floating units, such as FPSO, the volume and the weight for surface installations have to be limited. As an example, optimizing the footprint of separators while keeping a good efficiency is a much greater need for FPSO than for traditional inland developments. This is also the case with additives as all the logistics involved are more difficult to organize: for example, in the case of acidic oils, limiting the use of acetic acid, to maintain low pH, is desirable both for logisitic and safety issues.

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