An essential part of any scale squeeze management strategy for any oilfield is the capability to accurately and precisely determine the residual scale inhibitor concentration in the produced fluids. These data in combination with ion analysis and well productivity index are essential to determine the lifetime efficiency of scale squeeze treatments. For sub-sea wells comingled in the same flowline this presents a significant challenge due to mixed brine composition in the flowline and the requirements to analyse multiple families of scale squeeze inhibitors in the same sample without interference from the continuously injected wellhead/topside scale inhibitors and any other production chemicals that maybe applied.
In recent years the use of environmentally acceptable polymeric scale squeeze inhibitors has increased. The accurate and precise analysis of polymers has proved to be difficult and a toolbox of advanced scale inhibitor analysis techniques has therefore been developed to improve scale management capability in sub-sea fields.1 This technology is based upon a range of novel analysis techniques, including Liquid Chromatography-Mass Spectroscopy (LC-MS), which have demonstrated the feasibility to detect multiple families of scale inhibitors at low levels with improved confidence along with the potential for squeezing wells co-mingled at the same flowline with different scale inhibitors. This was not considered possible before and recent refinements have been targeted towards the specific challenges on the Norne field, where it was required to detect three different polymeric scale squeeze inhibitors in the same flow line sample in the presence of the continuously applied wellhead and topside polymeric scale inhibitor.
This paper presents brief details of the progress made with new analysis techniques and highlights the application benefits of the implementation of these novel scale inhibitor analysis techniques in the Norne field. Data will be presented from a proof of concept study for squeezing three sub-sea wells co-mingled in the same flowline with three different polymeric scale squeeze inhibitors, namely, a phosphorus containing polyamine, a phosphorus tagged quaternary amine terpolymer and a phosphorus tagged sulphonated copolymer all in the presence of the wellhead/topside sulphonate/carboxylate copolymer. The implications of different detection limits for the three different polymers on the individual well treatment lifetimes and re-squeeze frequency will also be discussed.