The accurate and precise analysis of scale inhibitors plays an important role in making key decisions on the efficiency of scale-squeeze and continuous-chemical-injection treatments. Numerous techniques exist for scale-inhibitor analysis, ranging from the simpler methods to more-complex techniques such as high-pressure liquid chromatography (HPLC) and mass spectroscopy (MS). This paper presents a state-of-the-art review of scale-inhibitor-analysis techniques and describes how these techniques can be used to provide cost-effective scale management.

Introduction

Inorganic-scale deposition is a major problem encountered during production of oil and gas and is often managed by the use of chemical scale inhibitors to prevent scale from forming in the system through continuous chemical injection or by periodic batch squeeze treatments. In most cases, scale prevention through chemical inhibition is the preferred method of maintaining well productivity. Scale-inhibitor squeeze treatments provide one of the more-common and -efficient methods for preventing the formation of carbonate and sulfate scales in the near-­wellbore region, tubing, and topside facilities of production wells.

For any scale-management strategy where squeeze treatments are deployed, the objective will be to achieve the longest possible treatment lifetime to maximize oil production and minimize the number of costly well interventions, especially in complex production scenarios. In order to achieve the required longevity for squeeze treatments, it is essential to use a scale inhibitor that is fit for purpose for the proposed squeeze application (i.e., good scale-inhibition performance, nondamaging, good retention/release properties, and readily and selectively detected to low levels in produced fluids). Indeed, the accurate and precise detection of the scale inhibitor in the produced fluids to low levels at or below the minimum inhibitor concentration (MIC) is a key factor to enable long treatment lifetimes and prevent wells from scaling.

The development of subsea and deepwater fields has placed even more focus on improving the detection of scale-­inhibitor residuals in produced water, especially for commingled well streams where there is a need to detect more than one type of scale inhibitor in the same water sample.

One major goal of this paper is to outline the various common techniques and their suitability for assaying scale-inhibitor residuals by highlighting the benefits and illustrating the limitations and sources of interference for each method.