Structure Optimization And Experimental Research Of Multicup Isoflux Oil-water Separator

The increase of oilfield water content leads to increasing energy consumption in liftingand gathering system and more work in ground engineering construction and renovation,therefore water has received more and more attention. Based on “Key Technology to EnhanceOil Recovery in High Water Cut Oil Field” project of PetroChina Company Limited, a newtype of gravity oil-water separator—multicup isoflux oil-water separator—is devised.Multicup isoflux theory and shallow tank theory are used in the separator. Through theoreticalanalysis and experimental research, the structure of separator is optimized, then apply theoptimized separator in injection-production in the same well and produced water treatmentand field experiment is carried out.The separation principle, structure and working process of separator are first introducedin this dissertation, and the upward movement and coalescence process of oil droplets in thesettling cups are analyzed. The flow process of fluid in the separator is researchedtheoretically and simulated by Fluent. Both the flow resistance of center tube and localresistance coefficient of liquid inlet hole are determined. Then design calculation software ofseparator is compiled. A large number of calculations are carried out, in the premise of isoflow,distribution of liquid inlet holes in center tube is provided under the condition of differentflow rates.The separation effect of oil-water separator is mainly decided by the shape of settlingcup.24kinds of settling cups with different shapes are designed and the best one is picked outthrough laboratory experiment. The research shows that the smaller the dip angle of settlingcup bottom is, the more likely it is to form continuous oil film moving upward along declinededge, and the separation effect is better; the more the edges are, the larger the contact area ofcup bottom is, and the effect is better. Among the24kinds of settling cups, the crown-shapeone with cusp and a battle has the best separating effect, it has cylinder,46.5mm long cup and12edges, its dip angle of settling cup bottom is30°, the upside part inosculates with the ridgeon the bottom of the above one. The cup is with oil wet material and a battle that is the samein shape with cup bottom.In order to solve the problem that sand settling in separator leads to poor separationeffect, sand drainage experiment of separator is carried out. Punching in the bottom of settlingcup can help remove sand, liquid inlet hole also has this function. Synthesizes the effect ofsediment sand and oil separation, the diameter of sand drainage outlet is3mm and the outlet number is four. The outlets in the up-cup stagger those in the down-cup, and both themstagger liquid inlets. Compared with separator without outlet, drawdown speed of liquid levelis reduced by only2.6%when the water content is95%.In order to further improve the efficiency of oil-water separation, oil wet filter material isadded in settling cup, which can improve relative permeability of water and reduce therelative permeability of oil so that improve the effect of oil-water separation. Throughlaboratory experiment, settling cup that adding coated quartz sand with the thickness of14mmhas the best effect, compared with crown-shape settling cup with cusp and a battle, liquid flowcan increase by59%, when the water content is95%.Apply the optimized multicup isoflux oil-water separator in injection-production in thesame well and produced water treatment, and field experiment is carried out.Injection-production in the same well is realized by two pumps, one is placed underlayerfor exploiting and the other uplayer for reinjecting. This system is consisted of extractionpump, packed piston, bridge type packer, injection pump and downhole oil-water separator.Test this technology in ten wells, the average producing fluid volume reduces from103.48t/ddown to32.5t/d, fell70.79t/d; Water content reduces from95.29%to95.29%, fell by7.97%,which have a remarkable energy saving effect.In the field experiment of produced water treatment, applying coalescence equipmentand additive that can enlarge the oil droplets size to further improve the separation efficiency.In the premise of separation efficiency and effect, the treatment capacity of crown-shapesettling cups that adding coated quartz sand with the thickness of14mm is49.3times that offield settling tank. After the coalescence equipment is applied, the treatment capacity is187.4times that of field settling tank. Adding additive can improve the size of oil droplets, S1hasthe best effect among the five kinds of tested agents when concentration is20mg/L.Recommended dosing sites are transfer station and wellhead, central processing station is notrecommended.Appling multicup isoflux oil-water separator in oil field can reduce the load of groundproduced water treatment system, decrease the production cost and fixed investment, improvethe oil recovery and realize sustainable development in oil field.