Research Of Corrosion Prevention Technology For Injection-production System In Chaheji Oil Field

Chaheji Oilfield has been developed for more than 30 years. As it has entered into the medium-high water cut development stage in recent years, composite water cut and salinity of produced water keep increasing sharply, acompanied by existence of quantities of corrosive substances, which can intensify the corrosion and scaling of injection-production system and seriously affect the normal operation of oilfied. In this paper, the corrosion and scaling mechanism and influential factors in key blocks of Chaheji Oilfield, such as Cha 4, Cha 9 block, were studied. Based on the analysis of produced water, injected water and scaling product and forecast of the corrosion and scaling by software, it was determined that corrosion stype in Chaheji Oilfield was mainy carbon dioxide corrosion, and Cl-,SO42-,SRB could aggravate corrosion; the scale formed in oilwell was mainly carbonate and that formed in water injection system was mainly product of corrosion. Based on those above-mentioned problems, the corrosion and scaling inhibitor fomulation, which was suitable for the corrosion and scaling control in oilwell shaft of key corrosive blocks, and the corrosion and bacteria inhibitor formulation, which was to aim at water injection system, were both established through agentia screening combination. The method of determining the stype of corrosion and scaling according to the molar ratio of Ca2+/HCO3- was also founded. Field application showed that iron content decreased obviously in oilwell produced fluid, and the inhibition rate of corrosion was 83.2% and that of scaling was 95% on the average in injection-production system. The pump inspection period of oilwell extended to 1.7 times longer than that of before, and the corrosion rate in-situ was controled in less than 0.07mm/a.