Assessment of combined scale/corrosion inhibitors - A combined jar test/bubble cell

摘要

The formation of calcium carbonate scale and the occurrence of CO_2 corrosion in sweet environments are both widespread phenomena and have been studied extensively in oil and gas industry. Scale and corrosion are part of the main problem encountered in distillation plants or in flow assurance for oil and gas industry. Investigations centred on inhibition tend to focus on reducing scale and corrosion through individual chemical treatments as opposed to inhibiting both processes with one chemical inhibitor. Scope exists for a combined product which is capable of retarding both the effects of scale formation and CO_2 corrosion. This paper presents results from an initial trial that has been conducted to develop a methodology based on a bulk jar scaling test and a bubble cell corrosion measurement. The efficiency of four combined corrosion and scale inhibitors were assessed while both scaling and corrosion processes were occurring on X-65 carbon steel samples. The formation and growth of scale in the bulk was monitored using a turbidity meter and the corrosion rate was assessed through linear polarisation resistance measurement. The four combined products were studied at different concentrations (2, 4 and 5ppm) at 60°C in CO_2- saturated brine. Scanning Electron Microscopy (SEM) was used to examine the surface morphology of the samples after the experiments. According to the results, the combined products act by increasing the induction time of the formation of the calcium carbonate in the bulk, changing the morphology of the crystals and forming a partial protective layer onto the sample. Each chemical reveals a different efficiency in inhibiting the scale and/or the corrosion process.