Research On The Erosion And Preservation Of The Oily Wastewater Reinjection System In Longdong Oil Field

Longdong oil field belongs to low permeable reservoir and its exploitation needs injection with water, which lead to the producing of much wastewater.The reinjection of the water after treatment not only reduce environment pollution but also save valued water resources,which is an important way in raising the economic mileage and assuring the continuous exploit ion of oil field. But with the coursing of the oily wastewater reinjection system in Longdong oil field, the erosion of the system is serious increasingly. Because of corrosion, the valves,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. Above all, the eroding problem has influenced seriously the work of the system water treatment and reinjection and impacted the production of the whole oil field. So, probing the main reason causing the eroding of water system in oil field and suggesting an appropriate technology of preservation have important sense for the continuous development of the oil field.This article clearly grasps the corrosion actuality of the wastewater system in Longdong oil field through going over material and researching on-site. On the basis of above mentioned, some metallic corrosion theories are questioned which include theory of metallic electrochemical corrosion, polarization circumstances and depolarization theory as well as some different corrosion mechanic and soon.Carbon dioxide, SRB and mineralization are decided three main factors in influencing corrosion through the analysis on the water quality of Longdong oil field. Static and dynamic tests are designed to analyze the influencing level on erosion of the three main factors. The result of the experimentproves that the aseptic wastewater makes feeble erosion on metal, but the existence of SRB accelerates the erosion process, with the increase of SRB from 7.5X102个 /ml to 1.2 X 104个/ml, the corrosion rate raise to 0.0908 mm/a from 0.0103 mm/a,So SRB is the most important factor in influencing erosion of the system. The influence of carbon dioxide on erosion is also very obvious. The corrosion rate will rise to 0.3755mm/a from 0.116mm/a when the concentration of carbon dioxide rises to l00mg/L from 10 mg /L. The verified result has demonstrated that the De waard model could be used in Longdongoil field to forcast the corrosion rate of the CO₂ corrosion. Only under 40g/L the mineralization has been researched, with the descending of the mineralization value, the corrosion rate will also fall. Furthermore, this paper discusses some other factors in influencing erosion.Aiming at the erosion factors influencing wastewater system of Longdong oil filed and combinating the existing anticorrosive technology o internal and foreign countries, this paper raise some comprehensive anticorrosive measures fitting in with Longdong oil field. Those measures mainly include appending corrosion inhibitor and disinfectant, excluding gases in wastewater, adopting catholic protection, applying metallic coating technology, selecting corrosion-resistant materials and so on.