Development of new Corrosion Inhibitors
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Pipelines are an essential part of the oil ang gas industry as they are the main means of transportation. As the offshore technology advances, subsea pipelines are being operated in more demanding environments. In field operations where corrosion occur, chemicals called inhibitors can be employed. Corrosion inhibitors (CI) are injected in small amounts with low concentrations to ensure flow assurance and controlling corrosion, especially CO2 corrosion. Currently there are no CIs that functions at elevated temperatures, so the purpose of this master thesis was to synthesize CIs for that purpose. The master thesis was divided into two projects, one screening process to see whether or not it was possible to synthesize CIs below 100, and if the presence of a catalyst would help. The second project was a small experimental design project where three aldehydes and three catalysts was used in different combinations. The goal was to achieve a six-membered ring in these CIs as the theory says that this is crucial for the performance. Two kinds of test were performed to evaluate the chemical performance of the synthesized products; High pressure, high temperature (HPHT), static autoclave testing and kettle-testing. The HPHT Autoclave tests were executed at Schlumberger in Aberdeen. Kettle-testing was done using the Linear Polarization Resistance (LPR) technique. Time (hours) and Corrosion rate (mils per year) were the parameters which were compared among the tests to reveal the best corrosion inhibitor. To characterize the synthesized products infrared (IR) spectroscopy and nuclear magnetic resonance (NMR) was performed. NMR spectra of the products related to structure III show that these compounds do not have the six-membered ring which was the goal for the synthesis. HPHT, static autoclave tests revealed that these products do not perform well as expected considering the NMR results. The same is shown in the Kettle-test where product 24 does not perform well as a CI, with the best inhibition efficiency of 37.7%. Product 12 on the other hand show mixed results, but product 12 injected with formulation with 1% 2-mercaptoethanol (2-ME) tested in a cell with 80% NaCl (3%) brine and 20% kerosene have a performance of 93.6 % efficiency inhibition. There were also some other interesting results from the HPHT, static autoclave test. Product 6 with an average performance of 7.205 mpy, with half the amount of active product in the formulation injected. Further research after this thesis could be on dose response (in context of the HPHT static autoclave test) to find the cut off points in performance in terms of corrosion rate and surface conditions. Further characterization of the products related to structure III is also work that should be done in order to characterize the actual product. It would also be smart to optimize the synthesis ratios and order of executing synthesis steps in order to optimize costs related to the final product(s). Additional testing of the products at Schlumberger (Forus) with Rotating Cylinder Electrode (RCE) is also of interest as this test add medium stress-shear.
Master's thesis in Environmental Technology