高含水含蜡原油的粘壁特性试验

高含水期油田采用不加热集输工艺时,由于输送温度低,管道中往往出现凝油粘壁现象,导致管道流通面积减小,井口回压升高,集输能耗增大。基于传统冷指装置设计了可实现试验介质循环的试验装置,探究了油温、油壁温差、含水率、剪切强度及试验时间对高含水含蜡原油凝油粘壁特性的影响。结果表明:凝油粘壁和多相蜡沉积不是同一种沉积行为。当油水混合液的温度低于起始粘壁温度时会出现严重的粘壁行为,高含水含蜡原油的粘壁温度低于纯油凝点,含水率越高,起始粘壁温度越低。油壁温差和油温对粘壁行为的影响分温度区间,原油凝点以下的粘壁行为主要受油温控制,凝点以上的粘壁行为受温差影响更大。不发生乳化的油水混合液,水相的存在弱化了粘壁行为;反之,水相的存在强化了粘壁行为。搅拌或管流流动对粘壁凝油主要起剪切剥离作用。凝油粘壁厚度随时间的持续存在极限值,并不会无限增长。(图10,表2,参29)

Test on wall-adhering behavior of high water-cut waxy crude oil

When the unheated gathering and transportation technology is adopted in oil fields at high water cut stage,the phenomenon of congealable oil adhering to the wall often occurs inside the pipeline due to the low transportation temperature,and this may lead to the reduced pipeline flow area,the back pressure rise at the wellhead and the increased energy consumption of gathering and transportation.On the basis of the traditional cold finger device,an experimental device was designed to realize the circulation of test medium.With this device,the effects of oil temperature,oil-wall temperature difference,water cut,shear strength and test time,on the wall-adhering behavior of high water-cut waxy oil-were investigated.The results show that the congealable oil wall-adhering and the multiphase wax deposition are not the same deposition behavior.Serious walladhering occurs when the temperature of oil-water mixture is lower than the initial wall-adhering temperature.The walladhering temperature of high water-cut waxy crude oil is lower than the pour point of pure oil.The higher the water cut is,the lower the initial wall-adhering temperature will be.The effects of oil-wall temperature difference and oil temperature on the wall-adhering behavior are distinguished from temperature intervals.The wall-adhering behavior below the crude pour point is mainly controlled by the oil temperature,while the wall-adhering behavior above the pour point is more affected by the temperature difference.For the unemulsified oil-water mixture,the presence of water phase weakens the wall-adhering behavior.On the contrary,the presence of water phase enhances the wall-adhering behavior.Stirring or pipeline fluid flow mainly exerts shear stripping effect on wall-adhering congealable oil.The thickness of congealable oil adhering to the wall will definitely reach the limit value with time,instead of increasing indefinitely.