The Study On Oilfield Sewage Components's Effect To Its Corrosion Resistance

With the oil production going into the high water exploitation phase, oil production process will produce a large amount of produced water. The produced-water reinjection after simple handing not only reduce environment pollution but also save valued water resources, which is an important way in raising the economic benefit and assuring the sustainable development of oilfield. But with the coursing of the produced-water reinjection system in yihe multi-purpose station, the erosion of the system is serious increasingly. Because of corrosion, the pipes, installments and reinjection well have been damaged many times, which have given rise to much economic cost and even compelled the system to stop work. Aiming at the serious corrosion status of the oilfield produced water, the dissertation mainly includes works as below:1. The failure analysis about water injection pipeline which is corrosion perforation, by means of macroscopic corrosion morphology, micro-corrosion morphology, energy spectrum analysis etc. the author confirms that the main reason of yihe station's produced water corrosiveness is the free carbon dioxide, the dissolved oxygen, Sulfate-reducing bacteria(SRB), pH value, the mineralization etc.2. The static hanging sheets study on oilfield produced water in the laboratory. Static handing experiments can be divided into two parts by handing time: the short duration static handing orthogonal experiments and long-lasting patch test hanging about the main corrosion factors. Orthogonal experimental results show the contribution rate order of corrosion the main corrosion factors: oxygen > carbon dioxide > pH value > mineralization degree etc. Long-lasting patch test hanging results show that the corrosion rate of oilfield produced water increases with the increase of dissolved oxygen; the corrosion rate also increases with the increase of carbon dioxide; the corrosion rate decreases with the increase of pH value.3. The electrochemical study on the main corrosion factors of oilfield produced water. Electrochemical study includes two parts: polarization curves and alternating current impedance. The results of the main factors affect to corrosion rate by electrochemical test are consistent with the hanging patch test results. Through the analysis of polarization curves we can see that the anodic reaction of A3 steel corrosion in the sewage is mainly iron dissolution process, the main cathode reactions are hydrogen corrosion and oxygen corrosion. Through the equivalent circuit simulation to the EIS of oilfield produced water, the results show that equivalent circuit Rs(QRt(R0L)) is the closest to the actual situation.4. According to the study result of oil product water, this paper raise some comprehensive anticorrosive measures fitting in with yihe multi-purpose station. Those measures mainly include water quality modification, adding oxygen scavenger and disinfectant, excluding gases in oilfield produced water, adopting catholic protection, applying metallic coating technology and so on.