Research On Inner Corrosion Control Of Pipeline And Biodegradation Of Hydrocarbon In Oilfields

Equipment corrosion and environmental pollution caused by leaked crude oil are two main problems in oilfields. 3% NaCl solution was commonly used to investigate CO2 corrosion as simulation medium under static and lower flowing conditions, which was different from on-site corrosive medium at high flow velocity under multiphase containing sand in oilfields. Under those conditions, corrosion inhibitor could not perform effectively and protective coating of anti-erosion wearing and corrosion resistance is widely used to control corrosion. Epoxy resin coating was used to protect erosion wearing inside equipment, which was easy to bubble, harden and lost its performance under high temperature and medium containing hydroxybenzene. However, unmodified bismaleimide (BMI) resins could not be solely used for anti-corrosion coating because of their high crosslinking densities after curing, poor solubility, and narrow processing window; and therefore a new type of anti-erosion wearing coating is anticipated to research. For the increasingly serious petroleum pollute, the biodegradation technology was used more widely because of the advantage of low cost, in-situ degradation and no pollution products. Synergic effect is always the important spot of research in the field of biodegradation of organic pollutants.In this dissertation, corrosive behavior of carbon steel under flowing condition and corrosive solution containing sand, corrosion inhibitor's inhibition performance, and lab comprehensive evaluation of corrosion inhibitor, were investigated by weigh lost method, electrochemical techniques (electrochemical impedance spectroscopy (EIS), linear polarization resistance), surface analysis(scanning electron microscope (SEM), X-ray diffraction (XRD)), etc; by ternary copolymerization of BMI, 1,3-PBO and oleic acid, the curing behavior and some properties of the processibility, toughness and heat resistance were focused on by IR, DSC, TGA, ESEM, etc; properties of adhesive coating of modified epoxy resin with BMI were investigated by friction wear, shear strength, multiphase erosion-wearing testing; by combination of the two analytical techniques, gas chromatography and UV spectrophotometry to evaluate the microorganisms biodegradation of diesel, the biodegradation process of diesel by bacteria Mycobacterium hyalinum (MH) , by fungi Cladosporium, and their synergic effect were studied, respectively. Our aims are to discuss inhibition performance of corrosion inhibitor under high flowing corrosive solution containing sand, establishment lab comprehensive evaluation method and properties of modified coatings under extreme corrosive conditions, mechanism of synergic effect of biodegradation of diesel, which can provide academic explanation and technical support for protection of inner corrosion in pipeline systems and the bioremedy of leaked crude oil. The main conclusions are as follow:Critical flow velocity in uninhibited corrosive solution is between 3m/s and 4m/s at testing conditions. At different flow velocity, corrosion rate is further increased by the entrained sand in the medium. Corrosion inhibitor shows the peak-value-phenomenon in corrosive solution under flowing condition. The optimum concentration is 120mg/L as the flow velocity is less than 3m/s, in contrast with the concentration of 160mg/L when flow velocity is between 4m/s and 5m/s and the concentration of 200mg/L when flow velocity is 7m/s. The optimum concentration is further increased when adding sand. Critical flow velocity is different in inhibited corrosive solution at different concentration. Critical flow velocities are 3m/s, 3.5m/s, 4.5m/s in inhibited corrosive solution at the concentration of 120mg/l, 200mg/l and 280mg/l, respectively. Corrosion rate of medium containing sand at the flow velocity of 7m/s could not effectively controlled by corrosion inhibitor with the concentration of 280mg/l or higher.Compared mixed corroison inhibitor with incumbent corrosion inhibitor by static coupon testing, dynamic high pressure coupon testing, electrochemical techniques, compatability test with incumbent scale inhibitor and demulsifier, and on-site application, all the results have demonstrated that this corrosion inhibitor is a mixed type of absorptive inhibitor, which can effectively inhibit locale corrosion with characteristics of low emulsification and better compatability, and also meet anti-corrosion's requirements. On-site monitoring results show that lab comprehensive evaluation is effective and applicable to settle the discrepancy of lab screening on corrosion inhibitor.By spontaneous reaction between BMI and oxazoline, flexible linkage or chain was introduced into BMI. Oleic acid, which presents long flexible chain and reactive groups (C=C double bond and -COOH), was copolymerized with BMI and 1,3-PBO. By ternary copolymerization of BMI, 1,3-PBO and oleic acid , the processibility and toughness of BMI was improved while keeping their good heat resistance. The results indicates that 1,3-PBO and oleic acid play a role in diluting to BMI at lower temperatures. At higher temperatures, the copolymerization between BMI, oleic acid and 1,3-PBO increases the crosslinking density in the resultant materials. The cured resin still remains high Tg. SEM results confirm that 1,3-PBO and oleic acid could toughen BMI system because of the formation of ester-amide bonds and the long fat chain of oleic acid. By testing tensile-shear strength of epoxy resin coatings at different corrosive media, it gains that BMI-B/EP has the best performance under different conditions except in alkaline medium. Modified epoxy adhesive resins show fine friction property at temperature range from 20℃to 120℃. Testing results under conditions of multiphase corrosive media and high flow velocity at high temperature show that modified epoxy coatings exhibited excellent performances of erosion resistance and high wear resistance than epoxy resin coating.When the mixture of bacteria strain MH and fungi strain Cladosporium is used, the extent of diesel biodegradation is significantly increased by 80% after five days; Diesel pollutants in aqueous solution can be completely removed by synergistic use of these MH and Cladosporium; The observed synergistic effect is closely related to the aromatics-resistance of the fungi strain Cladosporium, which in turn favors the growth of the MH.