Study On Resistance Characteristics Of Heavy Oil Aeration

Heavy oil as a kind of important energy source occupies an important position in the oil and gas exploration and development as well as the national energy strategic reserve.Due to the high viscosity,high density and poor mobility of heavy oil,conventional transport process is difficult to meet its requirements of safety,economy and high efficiency.Inspired by the fluid aeration resistance reduction,taking into account some remote dispersive wells and offshore platforms which almost perform gas venting or combustion process,if transporting the gas and heavy oil together,heavy oil resistance reduction and energy saving transportation is expected to achieve.For this purpose,the paper puts forward the idea and method of research on the resistance characteristics of heavy oil aeration,discusses the conditions and main influencing factors of resistance reduction of heavy oil aeration,and explores a new method of heavy oil resistance reduction during pipeline transportation,laying a theoretical foundation on promoting the development of heavy oil aeration transportation technology.In this paper,the resistance characteristics and the related problems of the heavy oil aeration transportation were carried out in-depth study by using the combination of numerical simulation and indoor experiment.The effects of aeration medium,gas-liquid ratio and diameter on pressure drop,temperature drop,gas-liquid flow rate,liquid holdup and flow pattern were studied by establishing the sea-tube model using the method of numerical simulation.220#white oil and 440#white oil were used as the simulated oil to test the basic composition of the heavy oil and analyze the variation of the physical properties and the characteristics.Air was selected as an experimental aeration medium,and a suitable aeration system is designed.A small experimental loop device was established to simulate the transportation of heavy oil aeration.The flow behavior of heavy oil aeration was studied systematically,and the changes of the air pressure drop and flow pattern during the flow process were discussed.The comparison and analysis related to pressure drop model were carried out to describe the applicability of the flow aeration experiment of heavy oil.The important conclusions and understandings are as follows:(1)The heavy oil the pressure drop increases gradually and the liquid holdup rate decreases gradually and the slug flow occurs gradually with the increase of the amount of aeration gas.When the aeration medium is gas,the pressure drop turns out to be minimum,while the pressure drop being maxium when the aeration medium is carbon dioxide.The optimum aeration interval of each aeration medium was obtained by comparing the relative size of the aeration pressure drop value,and the optimal aeration ratio of nitrogen and air is 1:1 in the simulation interval.The optimal aeration ratio of carbon dioxide is 0.65:1,and the optimum aeration ratio of gas is 1.2:1.(2)220#and 440#simulated oil both have good Newtonian fluid properties at the test temperature of 10～60 ℃ and the viscosity decreases significantly as the temperature increases in 10～30 ℃.(3)During the aeration experiment range,resistance reduction rate of 220#white oil aeration is mostly less than 20%,and the maximum resistance reduction rate is less than 60%.The reduction rates by use of T type three pass aeration mode are higher than that of Y type three pass aeration mode.In the same aeration mode,the overall resistance reduction rates of 440#white oil are higher,compared with 220#white oil,and the gas-liquid ratio is higher when the resistance reduction rates are same.But reduction effect is better in the lower gas-liquid ratio.(4)Under the experimental conditions,the reduction rate reaches the top value 49.24%under the condition of 220#white oil T type aeration,when the gas-liquid ratio is 24.02.The reduction rate reaches the top value 39.13%under the condition of 220#white oil Y type aeration when the gas-liquid ratio is 4.35.And the reduction rate reaches the top value 33.76%under the condition of 440#white oil Y type aeration when the gas-liquid ratio is 0.96.At the same time,from the simulation results in Chapter 2,it can be seen that the optimum aeration ratio of air is 1:1 in the range of software simulation,and the viscosity of heavy oil is similar to that of simulation oil in this chapter,indicating that liquid viscosity is one of the main factors affecting the optimum aeration ratio.(5)The theoretical calculated values are mainly distributed in the lower pressure drop range,while the experimental values are mainly distributed in the higher pressure drop interval.When the viscosity of the fluid is constant,the data points are mainly distributed in the low gas-liquid ratio range.And the smaller the gas liquid ratio is,the smaller the error between the calculated pressure difference value and the simulated result is,while the higher the viscosity is,the worse the applicability of the model is.(6)Compared with model Ⅰ and model Ⅱ,the Dukeler Ⅱ method is more suitable to describe the flow process of fluid aeration in this paper.It is also proved that Dukeler Ⅱmethod drop formula are in more widely range of viscosity and flow than Dukeler Ⅰ.