Determination of Multiple Scale Inhibitor Residuals in Single Produced Waters: A Case History from the North Sea Differentiating Four Chemistries

摘要

With wet tree developments now outweighing dry tree developments in the North Sea, the challenge of accurate surveillance of scaling in wells is increasing. Often, multiple wells feed into manifolds which themselves feed into comingled systems. The need to differentiate multiple scale inhibitor molecules in the same sample of produced water is now essential in order to monitor the scale health of any given well in that system. Accurate surveillance can save potentially millions of dollars of deferred oil production, intervention vessel hire and chemical and operational costs. This paper details a case history from the North Sea where the subsea field was located 21 km from the host platform. The field comprised three wet tree wells that each required scale inhibitor squeezing, and the flowline itself also had a scale inhibitor injected at the manifold. Commingling occurred at a manifold and with no test line all fluids were produced to the same dedicated separator on the host platform, which was the further point upstream where sampling could occur. Details are given on the selection methodologies employed to determine the most appropriate chemistry for each squeeze application, as well as for subsea injection to the manifold. The primary aim was differentiation of all the chemistries from one another. The paper shows how squeeze treatment volume and frequency were optimized, leading to increased production up-time and deferment of chemical costs. It also shows the accurate detection of scale inhibitor to very low levels, providing confidence that the wells remained protected with no scaling or loss of production. All chemistries selected were also done so with the environmental classification in mind, which led to a significant improvement in environmental profile and impact footprint.