The countless, dynamic, production environments of the oil industry continually drive the demand for more effective scale control while increasing environmental concerns push forward the development of environmentally friendly, preferably bio-degradable production chemicals. This constant chemical evolution presents innumerable challenges for the detection of these new polymeric scale inhibitors at threshold levels in produced waters.
Part of the SWELL II JIP focus is on developing new analytical techniques for residual scale inhibitor concentrations which provide accurate, repeatable and reliable results. These methodologies focus both on automated HPLC-based and solid phase extraction techniques. The objective of these methodologies is to analyse for the “active” scale inhibitor as opposed to some analysable moiety.
High Performance Liquid Chromatography (HPLC)
From the project, a number of methodologies have been developed which include the use of Gel Permeation, Reversed Phase and Ion Chromatography as well as utilising a number of different detection techniques including Evaporative Light Scattering (ELSD), Charged Aerosol Detector (CAD), UV/Vis and Conductivity.
The project also involves extensive screening of HPLC columns for their applicability to retain a series of generic scale inhibitor species. Sponsors have found it beneficial to have a selection of columns screened, under a number of experimental conditions using a series of generic scale inhibitor species to gain knowledge to feedback to their own laboratories.
Solid Phase Extraction (SPE)
Residual scale inhibitor analysis in produced waters, particularly for the sulphonated co-polymers is recognised as an ongoing challenge for many offshore production environments. Although methods have been well documented, there are a number of known difficulties when assaying residual ppm and sub ppm levels of sulphonated polymers where separation of the inhibitor from the brine phase can be a time consuming, labour intensive and often difficult operation.
The SWELL II JIP also involves the development of appropriate solid phase extraction (SPE) techniques which demonstrate near 100% retention of sulphonated polymers from brines of different salinities and therefore negate the requirement for dialysis. Present advances made in the separation and assay of these and other polymeric species including the ability to obtain reliable separation and, when required, concentration using SPE methods as well as the utility of a variety of different detection systems. Extensive validation tests in a range of high salinity brines demonstrates the limits of detection and repeatability at ppm and sub ppm level for a variety of different polymers including PVS, VS-Co and more conventional polyacrylate as well as phosphorous containing polymers.