Study On Hydrocyclones In Series For Purification

With the development of oil field exploitation,the water oil ratio of oil field is rising,which makes the exploitation difficulty and cost increase gradually.How to increase the separation efficiency of oil-water mixture and the production income under the condition of high water cut has become a technical problem to be solved urgently.The downhole oil-water separation and Reinjection Technology(DOWS)with hydrocyclone as the key separator came into being.This technology can separate and lift the oil to the surface and reinject the water into the foundation underground in the same oil well,so as to reduce the invalid water circulation and surface sewage treatment pressure.Two kinds of well-done hydrocyclones which can be used downhole are selected and analyzed in this paper with names as guide cone hydrocyclone and reverse cone hydrocyclone.The influence of the inlet flow and split ratio on the velocity,pressure,concentration and separation efficiency of the two hydrocyclones is analyzed.The results show that the performance of guide cone hydrocyclone is better when the inlet speed is in the range of0.3m/s-1.5m/s.At this time,the pressure drop ratio is not higher than 1.5,the oil at the overflow is more concentrated and the efficiency increases from 96.8%to 98.3%.When the inlet speed is in the range of 1.5m/s-3.5m/s,the reverse cone hydrocyclone is the better one.At this time,the pressure drop ratio is not higher than 1.5,and the oil phase at the overflow is relatively concentrated,and the efficiency increases with the inlet speed The speed increased from 97.0%to 98.4%.Therefore,reverted cone hydrocyclone is selected as the primary separator for concentrator and the guide cone one is used as the secondary separator for purification.Based on principle of structure similarity and adaptable structure,optimization of structure parameters are obtained,when two kinds of hydrocyclone are working as primary concentrator and secondary purifier respectively.The best parameters of primary concentrator are getted that main diameter is 35mm,total length 344mm and reverted cone 4°.When the main diameter of secondary purifier is 42,total length 815mm and so on.the Maximum separation efficiency is reached.Then primary concentrator and secondary purifier internal velocity?pressure and separation characteristics are analyzed,and the feasibility and efficiency of two kinds monomers with different structure is testified by numerical simulation.In view of the structure of the underflow of the first stage reverse cone hydrocyclone and the inlet of the second stage guide cone hydrocyclone,along with considering the limitation of the radial space size of the oil well,three kinds of connection transition are designed in this paper to guide the fluid flow.They are named as the frog,the butterfly and chopsticks structure.And the chopsticks one is selected as the optical one because it can bring steady fluid.The flow field characteristics and separation performance of the hydrocyclones in series are studied in this paper under the conditions of flow rate of 2m~3/h?7m~3/h,primary separation ratio of 10%?30%and secondary separation ratio of 3%?20%.Results showed that the best separation efficiency which can be up to 99.9%under the condition of the inlet flow rate as5m~3/h,and the separate ratio as 20%and 10%.Up to 99.9%.