This paper presents field results and lessons learned from an FPSO, Offshore Brazil where a scale and corrosion inhibitor has been applied subsea to control both the deposition of scale and associated corrosion.

The paper outlines the problems encountered when the initial scale inhibitor formulation was deployed in the field related to materials compatibility with the subsea manifold and the steps taken to develop and monitor an improved formulation. Problems that can affect product application in a subsea environment, including deposition of suspended solids within the chemical, hydrate formation, incompatibility of the chemicals with umbilical material and produced fluid, will all be addressed. The laboratory methods used to select the product along with measurement methods used in the field are also discussed. The validation of the laboratory selection methods in the field required the development of a monitoring program to establish base line control and to assess the degree of protection from scale deposition and corrosion across the process.

The use of novel real time scale monitoring, as well as water chemistry tracking proved vital to the understanding of the efficiency of flow assurance within the processes and how treatment rates of the scale inhibitor and corrosion inhibitor could be optimised.

This paper will outline in detail the particular issues associated with chemical injection to a subsea facility, many of which are currently being developed in the Gulf of Mexico, offshore West Africa and Brazil. This case study is a good example of lessons learned and sharing of best practice from another oil basin.

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