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.
Oil and gas pipelines (X52 steel) in the marine environment are highly susceptible to corrosion. The effects of different dissolved oxygen concentration, pH, and hydrostatic pressure on the corrosion behavior of X52 pipeline steel in the marine environment was analyzed using electrochemical testing technology and observation of corrosion morphology. The results show that the corrosion of the pipeline slowed down as the ambient pH increased, while the corrosion of the pipeline steel increased as the dissolved oxygen content and hydrostatic pressure increased. The corrosion behavior of pipeline steel under different conditions is controlled by anodic activation of dissolution, and all appear local pitting corrosion phenomenon.
With the wide application of clean energy, improving the transportation efficiency of gas pipeline has become a hot issue, among which, it is very important to reduce the friction resistance in the pipeline transportation process. In order to explore the application effect of triangular riblet in the drag reduction of gas pipeline, ANSYS?FLUENT software was used to numerically simulate the turbulent flow in smooth pipeline and riblet pipeline. The results show that: in the near wall area, the velocity profile of ribbed pipe and smooth pipe has a big difference, and the difference is small in the mainstream area. The drag reduction effect of riblet structure is mainly based on the near?wall surface. The riblet structure pushes the vortex away from the wall surface, filling the rib bottom with low?speed fluid, reducing momentum exchange near the wall surface and friction resistance. Compared with the smooth wall surface, the riblet structure with the size of s＝h＝0.516 5 mm has a drag reduction effect of 4.38%.
Pipeline transportation is the main means to transport oil and gas and other important materials, and the damage of buried pipelines by earthquake is difficult to repair. Based on the nonlinear dynamic theory, the ANSYS finite element software was used to establish the pipeline?soil model, and then the nonlinear contact model between pipeline and soil was established. Finally, different seismic waves were applied to the buried pipeline and compared. The results show that the upper and lower parts of the pipeline have large displacements under the influence of seismic waves; as the input seismic waves gradually increase, the displacement of the lower part of the pipeline decreases, but it is still greater than the displacement on both sides of the pipeline. It can be seen that the upper and lower parts of the pipeline will be greatly affected when an earthquake occurs.
Soil collapse in natural disasters seriously threatens to the stability of buried pipelines. In order to study the stability of buried pipelines in the suspended collapse area, based on the finite element method,the displacement, strain and stress of buried elbows with different wall thickness and outer diameter in the suspended state were studied. Based on the eigenvalue buckling theory, the ultimate length that the buried elbow can withstand when the soil collapses under certain conditions was studied. The results show that reducing the buried depth, increasing the outer diameter and wall thickness can effectively reduce the displacement of pipeline in soil collapse. The stress and strain of the pipeline occur in the center of the collapse area and the fixed ends of the two sides; the increase of the outer diameter and wall thickness of the pipeline can inhibit the occurrence of local excessive stress to a certain extent. The ultimate length of the buried elbow in the goaf is about 87 m, and improving the outer diameter and wall thickness of the pipeline can enhance the buckling resistance of the buried elbow in the process of soil collapse.
In order to study and determine the optimal compounding system that can improve the stability of heavy oil emulsion in Liaohe Oilfield and the law of emulsion stability under different conditions, a focused beam reflectometer(FBRM) and rheometer were used to pass four factors and three levels. Orthogonal experiment with three indexes explored the change law of droplet average particle size, dispersion degree and emulsion viscosity, and investigated the influence of external factors on the stability of emulsion under compound system. The results show that the compound emulsifiers with the mass fractions of OBS?50, AEO15/OS?15, OP?15, and sodium with mass fraction of 4.0%, 4.0%, 1.4% and 1.4%, respectively, are the most beneficial to improve Stability of heavy oil emulsion in Liaohe Oilfield; there is a positive synergy between average particle size and dispersion, and an inverse relationship with the viscosity of the emulsion; the increase in temperature, volume ratio of oil to water will weaken the stability of the emulsion; stirring rate, ore The increase of the degree of chemical conversion can improve the stability of the emulsion; when the mass fraction of the mineralized NaCl is 0.2% to 1.0%, the stability of the emulsion can be greatly improved, and the quality fraction of the emulsion can be further improved. The lifting effect is not obvious.
