Design And Experimental Research Of High Volume Downhole Oil-Water Separation System For Offshore Oilfield

With the progress of technology, offshore oilfield has entered the large-scale development phase. However, offshore, oilfields have the characteristics of high volume production in single well and high water-oil ratio of crude oil. The characteristics which are in contradiction with the limited water handling capacity of offshore platform restrict the exploitation of offshore oilfields. Downhole oil-water separation (DOWS) technology is an effective method to solve the problem. In the thesis the DOWS of 9-5/8 inches casing completion well is the research object and the target handling capacity is 700m3/d.The structure and classification of DOWS are introduced, the advantages and disadvantages of various type are analysed. Based on the high volume, the design of whole structure of the DOWS, hydrocyclones and channel blocks are completed.The double-cone hydrocylone as the first-step separator and the single-cone hydrocyclone as the second-step separator are simulated by CFD. The best operation parameters are obtained according to the simulation results. The entrance flow is 120m3/d and the split ratio is 0.5 of the double-cone hydrocyclone. The entrance flow is 60m3/d and the split ratio is 0.4 of the single-cone hydrocyclone. The total split ratio is 0.7. The pressure laws of the series structure in same total split ratio and different individual split ratio are obtained.The demulsificaiton rate is the fastest when the demusifier concentration in 0.08%. The effect of demulsificaiton is the best when the demusifier concentration between 0.4% and 0.6%. With the increase of temperature, demulsification effect gradually increased. The oil droplet increased 10 times in 10min, when the demusifier concentration between 0.08% and 0.8%.The test bench for ground experiment of DOWS is built. The experimental scheme is made which offered condition for experiment.