Analysis of drag reduction characteristics of water ring transportation in high viscosity oil horizontal pipeline
With the increasing demand for oil resources,conventional crude oil is gradually depleting.The use of heavy oil is becoming a trend as the world possesses abundant reserves of heavy oil,accounting for 70%of the global remaining oil reserves.Heavy oil has immense development potential and vast market prospects.However,it also possesses high viscosity,high molecular weight,and poor fluidity,posing significant difficulties and challenges for its transportation.Therefore,accelerating the research and innovation of heavy oil transportation technology and related theories in China is an objective requirement to adapt to future trend changes,and it is an inevitable choice for the economic and efficient development of heavy oil resources through integrated transportation.This paper adopts the method of water annulus transportation to reduce the resistance of horizontal flow in heavy oil,aiming to explore the characteristics of flow resistance in horizontal pipe under water annulus confinement.It analyzes the effects of inlet water cut(5%—80%),oil flow rate(0.65-1.57m3/h),and water flow rate(0.09-2.13m3/h)on the lubrication and drag reduction effect of water annulus,as well as the influence on the flow pattern of heavy oil.An experimental annular loop for water annulus transportation of heavy oil is independently designed,and an effective roughness is introduced.A predictive correction model for annular flow pressure drop is established to analyze and discuss the flow pattern characteristics and the range of oil-water flow rate during the formation of annular flow.The results indicate that the water annulus formed under certain conditions can effectively reduce the drag in the transportation of heavy oil.The water annulus can effectively lubricate the pipe wall.The revised pressure drop prediction model has a relative error of comparison with the experimental values within±10%,and the RMSE is 0.02.The pressure drop in water annulus transportation accounts for only 0.01-0.24 of the pressure drop in pure oil transportation.When the oil flow rate is high,attention should be paid to the water flow rate to avoid excessive values that may lead to a decrease in the oil transportation efficiency η and drag reduction rate DR.
water ring transportdrag reductionhorizontal tubehigh viscositypressure drop
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