51314-4114-Effect of Surface Roughness and Flow on Corrosion Inhibition of Coiled Tubing Steel under Matrix Acidizing Conditions

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Product Number: 51314-4114-SG

ISBN: 4114 2014 CP

Author: Evgeny Barmatov

Publication Date: 2014

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Matrix acidizing well treatment of oil and gas wells is a widely established technique to increase hydrocarbon production by the partial dissolution of reservoir rocks and fine particles which may have been introduced during drilling. Either organic acids such as acetic acid or mineral acids such as HCl or HCl/HF mixtures are injected into the well at high concentrations. For this application corrosion inhibitors are enabling because uninhibited matrix acidizing treatment fluids would induce severe corrosion of downhole equipment. A broad range of organic film-forming corrosion inhibitors have been developed to retard the acid corrosion of low carbon steel coiled tubing through which the acidizing fluids are injected. Depending on the injection rate flow velocity and surface texture parameters may have a profound effect on the rate of material corrosion.In this paper the effect of surface roughness on corrosion behaviour of low carbon steel in 4M hydrochloric acid at 78°C in the presence of corrosion inhibitor molecules has been examined under laminar and turbulent flowing conditions. Glass bead blasted (GBB) low carbon steel and metal coupons with P240 and P1200 grit surface finish were studied. The corrosion rate and cathodic current density of low carbon steel coiled tubing samples were determined by Tafel slopes linear polarization studies and electrochemical impedance spectroscopy under deaerated conditions. A commercially available corrosion inhibitor comprising a mixture of a polymerizable molecule an oily phase and nonionic surfactants was used. The corrosion rate follows the order: GBB > 240 grit >1200 grit. This indicates that under laminar and developed turbulent flow the lowest corrosion rate was found on the polished surface and the highest rate on the GBB surface. The flow has marginal effect on corrosion rate for the P240 and P1200 ground surfaces. However an increase in flow velocity results in a strong increase in corrosion rate for the GBB surface. For both flow regimes the effect of exposure time on corrosion rate open-circuit corrosion potential and the value of electrochemical double layer capacitance were studied.