Erosion-corrosion mitigation using chemicals

Abstract

The presence of entrained sand in oil and gas production is becoming increasingly prevalent as wells age and this is leading to erosion-corrosion in C02-saturated conditions becoming a major mechanism of material attack. Its understanding, prediction and control are key challenges to sound facilities design. The use of carbon steel in conjunction with corrosion inhibitors in preventing erosioncorrosion has been observed as an economically viable solution for oil and gas piping systems. In order to produce highly effective corrosion inhibitors, it is important to understand how inhibitors act on each of the components of erosion-corrosion. Although research into corrosion inhibition has been extensively conducted, there is less documentation of inhibitors in retarding erosion-corrosion. This thesis has attempted to construct a quantitative structure relationship between erosion, corrosion and their synergistic effects to investigate erosion-corrosion and inhibition mechanisms with four fully formulated CO2 inhibitors (CGO, CRO, CRW8 and CRW9) along with some mechanistic studies involving single components from inhibitor formulations. Two experimental set-ups were used: a rotating cylinder electrode (RCE) and a submerged impinging jet (SIJ). In both experimental methodologies, gravimetric measurement, cathodic polarisation, Linear Polarisation and AC impedance techniques were used to ascertain the extent of corrosion as a function of conditions and inhibitor dosing/type. Both RCE and SIJ test samples were studied using surface analysis techniques such as scanning electron microscope (SEM), Light microscope, Energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). In this thesis, through integration of electrochemical analysis and gravimetric measurements the damage has been identified as being associated with mechanical erosion, electrochemical corrosion or interactive electrochemical/mechanical processes. The role that inhibitors can play in reducing damage in addition to that caused by corrosion, namely by erosion and their synergistic action has been shown. Under both configurations. erosion-corrosion interactions play a major role in damage with corrosion being a controlling parameter. The thesis has made substantial advances in the understanding of the extent to which corrosion inhibitors could be used to control erosion-corrosion damage and in understanding the mechanisms of how this can be achieved