We developed an automated and robust technology for measurement of corrosion inhibitors residuals in oilfield samples and fuels. Our method can process ca. 60 to 100 samples per hour and works on field samples without need for purification, regardless of typical interferences, such as varying pH, condensate, solids, high TDS, or high brine. The method is very sensitive and very specific to most common corrosion inhibitors used, such as aromatic quats, pyrolidines, pyrimidines, pyridines.
Corrosion inhibitors residuals are used as a proxy for the efficacy of the corrosion inhibition program. Field samples are collected regularly and the concentration of corrosion inhibitors is measured.
The most common technique used is a so called “wet” method, which is essentially a series of manual extractions of corrosion inhibitors with chloroform or dichloromethane to partition the corrosion inhibitors and purify them in a stepwise fashion, followed by reacting corrosion inhibitors with a dye and measuring UV absorbance of this dye complex. This method has been used for decades and is still used daily by most oil and gas chemical service companies supplying producers with corrosion inhibition programs. This method is very laborious where maximum of around 35 samples per 8-hour shift is measured, it uses toxic chemicals, and is not very accurate.
Alternatives include use of expensive instruments, such as HPLC, HPLC/MS, LC, LC/MS, GC, NMR. fluorometers. While all these techniques are very feasible, the field samples cannot be measured directly. The samples must be first purified by use of expensive columns. The operation of such instruments requires highly trained operators with scientific background and are very expensive to maintain, not to mention their initial cost. It usually takes about 30 minutes to do a measurement and thus, these instruments are predominantly used as R&D tools.
We use a well-established technique – fluorescence spectrophotometry to measure the concentration of corrosion inhibitors. We are able to do the measurements very accurately, reliably with high reproducibility without purification and essentially in any field interference matrix. We are able to couple any generic fluorometer with an autosampler, which together with using our analytical method yields in a high throughput system able to reliably analyze up to 100 samples per hour. While fluorometer with an autosampler costs around $40,000 from any major analytical instruments manufacturer, this instrument coupled with our method is very simple to use, does not require specialized knowledge, and doesn`t use toxic chemicals.
Our method can be further modified to potentially develop a hand-held device to reliably measure corrosion inhibitors concentration directly in the field, or can be modified to be used as an in-line system attached to a pipeline to measure corrosion inhibitors in pre-set intervals.
While this is not something we focused on, with the right technology commercialization partner, we can revisit this technology to develop these systems.