In order to determine the reasonable shape of the patching plate for the corrosion defects in the bottom of crude oil storage tank, this paper used finite element analysis to calculate the changes of the stress value in the corrosion defects after repairing different patching plate shapes, and then investigated the stress distribution and the safety factor value of the patching plate, and finally gave the best shape of the patching plate for the bottom of 20 000 m³ crude oil storage tank in Liaohe oil field. The results show that the best shape of the patching plate is a round patching plate. After repairing the corrosion defect, the stress value in the corrosion defect only decreases with the increase of the radius of the patching plate after the repair of the corrosion defect, and does not change with the change of the depth and radius of the defect. With the increase of the radius of the patch plate, the cost and safety of the patch plate will also increase, the specific size of the patch plate should be developed in accordance with the actual situation of the project. The results of the study can give theoretical guidance to the tank bottom repair from a scientific point of view.

Due to the complex submarine environment, submarine pipeline steel often faces serious corrosion risk. Through potentiodynamic polarization technology and AC impedance technology, the effects of hydrostatic pressure, mass concentration of dissolved oxygen and growth days of sulfate reducing bacteria (SRB) on the electrochemical corrosion behavior of X70 pipeline steel in simulated solution in the South China Sea were investigated. Combined with electron microscope characterization technology, the corrosion morphology was analyzed, and the mechanism of the corrosion behavior of X70 steel under the coexistence of three environmental factors was clarified. The results show that the self corrosion current density of X70 pipeline steel in the experimental environment inoculated with SRB is twice that of sterile steel; under the pressure of 0~3.5 MPa, the corrosion degree first intensifies and then slows down; when SRB and dissolved oxygen coexist, the presence of oxygen inhibits the number of facultative anaerobic bacteria SRB, thus inhibiting corrosion.

At present, water injection is often used to extract oil, but CO₂ corrosion often occurs in water?bearing pipelines. Therefore, Computational Fluid Dynamics (CFD) was used to study the distribution of oil and water in straight pipes and bends at different water content (volume) and flow rates, to determine the conditions for the occurrence of CO₂ corrosion in oil pipelines, and the effect of flow rate and water content on the wall shear force was analyzed. The results show that the occurrence of CO₂ corrosion depends on the water content and flow rate in the pipeline. When the water content increases, oil infiltration in the inner wall of the pipe to prevent corrosion; when the water content decreases, the amount of water accumulation increases, resulting in serious CO₂ corrosion. When the flow rate increases, turbulence occurs in the pipeline, so it is difficult to form water accumulation, reducing the risk of corrosion. However, an increase in flow rate will lead to an increase in wall shear, which will destroy the corrosion product film and further accelerate the corrosion rate. In downward elbows, under the action of gravity, water often does not occur in the pipeline, and the risk of corrosion is low; in upward elbows, water is most likely to occur, and the risk of corrosion is high; affected by scouring, the elbow end is corroded seriously. The elbow end is susceptible to the interaction of corrosion and mechanics, so corrosion is serious. The research results have certain guiding significance for the safe operation of oilfield gathering pipelines.