Abstract

Scale inhibitor (SI) analysis is an extremely important part of scale management and it is essential to have reliable methods for the accurate and precise measurement of scale inhibitor residuals in produced fluids in order to prevent wells from scaling. This information enables key decisions on the efficiency of scale squeeze and continuous chemical injection treatments especially in remote environments.

In remote fields, such as in desert and extreme winter environments, the ability to be able to monitor scale squeeze residuals on-site would offer significant potential to improve scale management capability through provision of rapid data which otherwise might not be available for several weeks due to long sample transport times to the laboratory.

Since conventional scale inhibitor analysis methods are not suited for on-site analysis this has led to the development of a toolbox of technology options including suitable scale inhibitor squeeze chemistry coupled with advanced, on-site, "near on-line" scale inhibitor detection procedures including Fluorescence (F) and Time Resolved Fluorescence (TRF).

In this paper, two field examples for on-site TRF analysis of polymeric scale squeeze inhibitors from remote wells in harsh environments will highlight the benefits of quick and timely scale inhibitor residual information. In the example from remote desert wells, a comparison of TRF and High Performance Liquid Chromatography (HPLC) analysis of the polymer residuals will show the accuracy and precision of the TRF method at low SI levels.

In addition, an example for the proof of concept of detection of three different F Tagged sulphonated polymers in the presence of a phosphonate squeeze inhibitor and continuously injected untagged polymer will demonstrate the ability of "near on line" fluorescence techniques to improve scale management where four subsea wells are co-mingled in the same flow line.

This paper concludes that fluorescence techniques are particularly suited to tagged polymers and naturally fluorescent molecules whereas Time Resolved Fluorescence provides the ability to detect untagged scale inhibitors like sulphonated copolymers, phosphonates and phosphate esters. The two techniques can be used individually or in combination with each other and, in addition, offer the advantage of being able to detect polymeric and phosphonate scale inhibitors to minimum inhibitor concentration (MIC) of 1-2ppm and <1ppm respectively which offers potential to extend treatment lifetimes.

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