Development And Application Of T-junction Pipe Separator For High Water Cut Production Streams

In the late stage of oilfield development,in order to improve oil recovery,the water content of the produced stream in some oilfields is as up to 90%.Traditionally,the mixture with a high water cut is delivered to oil-water separation treatment station after measurement.The separated water is usually transported to the sewage treatment station and processed to reach the qualification of injection water.After that,water injection station pumps the injected water back to the injection well.However,two main defects such as the high consumption of energy and operating cost can be found in this process.In order to improve the efficiency,it was put forward that a new pre-water-separation process could achieve on-site separation and on-site reinjection.Therefore,a combined T-junction pipe separator was proposed,and used as the preprocess separating water from mixture at the well site in front of the oil-water gathering and transferring process(metering station),which omits 4 technical processes including central treatment station,sewage station,water injection station,and water injection well.The combined T-junction pipe separator has the advantages of simple structure,compact size,light weight,low pressure drop loss and so on,which makes the metering station be reconstructed easily as well.It can be applied to oil field and offshore platform to reduce the cost of transportation.In this paper,the influence of different structure parameters,operation parameters and physical parameters on oil-water two-phase separation of T-junction pipe separator for high water comtent produced stream was studied by simulation,laboratory experiments and theoretical analysis.The field test of the short radius treatment system was carried out in the Block 90 of Shengli Oilfield.In the aspect of numerical simulation,the influence of structural parameters on oil-water separation was analyzed.The results show: The longer the fully developed section is,the better the separation effect is;the increase of the branch pipe spacing effectively reduces the oil content of the water outlet;the branch pipe height has less influence on the oil content of the water outlet.The number of branches is 3,which usually meets the separation requirements.In addition to the structural parameters,the effects of different operating parameters and physical parameters on the separation of oil and water from high water-bearing production fluids were analyzed.The results show: The oil content of the water outlet increases at higher flow velocities and split ratios,and the separation efficiency decreases as the mixture flow rate increases,but increases as the split ratio increases.The critical diameter of the oil droplets in oil-water separation is 400 ?m.When the oil droplet diameter is lower than this value,the separation effect will be important.In the aspect of laboratory experiment,a multi-phase flow separation experiment system was built,and the separation performance of the T-junction pipe separator was studied based on the system.In the experimental range,under different mixing velocities,inlet oil content and split ratios,the phase distribution and flow in each horizontal pipe section and branch pipe were recorded and observed.The experimental data of the oil outlet rate and separation efficiency of the water outlet of the T-tube separator under different operation parameters are obtained by sampling.In the aspect of theoretical analysis,the T-junction separator is used to separate the twophase flow and the special structure of the double-outlet,and the static model of the distribution box and the static pressure model of the confluence box are corrected.The corrected parallel tube group flow prediction model is used to calculate the branch pipe flow,and the calculated data is compared with the experimental data.The average relative error of the branch pipe flow is less than 5%.The size design criteria of the T-junction separator were proposed,and the structural dimensions of the T-junction separator under different oil droplet sizes were designed according to the Stokes settlement formula.Finally,the problem of long process flow,high energy consumption and high operating cost for high water-containing production stream gathering and transportation process.A shortprocess treatment scheme of produced liquid consisting of T-junction separator,column spine cyclone separator and cyclone air flotation device is proposed.A large number of laboratory experiments and numerical simulations were carried out according to the physical property parameters and processing requirements of the on-site production streams.The structural dimensions of the T-junction separator,column spine cyclone separator and cyclone air flotation device were designed.