Study On V-cone Measurement Technology Of Injection CO₂ Fluid In Certain Oil Field

V-cone flowmeter is a new type of differential pressure flowmeter.Compared with traditional differential pressure flowmeter,it offers better accuracy,wider rangeability,installation flexibility.Certainoilfield enhances oil recovery by injecting supercritical CO₂,and V-cond flowmeter is used to measure the flow of supercritical CO₂.Under actual operating conditions,the state of CO₂ is not necessarily supercritical and there are many different installation conditions.In this paper,the influence of CO₂ state and different installation conditions is analyzed by numberical simulation.Compared with the calculation accuracy of the three meshing methods,hexahedral mesh has the highest precision and the minimum number of grids,and the residual accuracy is equal to 10^-5.The grid independent solution is equal to 112 million by analyzing the relationship between the number of grids and pressure difference.The numerical simulation results show that the discharge coefficient is 0.705⁰.808.The experimental results show that the outflow coefficient is 0.7177⁰.7257,and the average deviation of numerical simulation is 12.03%.It is proved that the numerical simulation method is reasonable.According to the actual working report of oil field,the simulation pressure is 17MPa,the simulation temperature of liquid CO₂ is 5?and 15?and the simulation temperature of supercritical CO₂ is 38?and 48?respectively.Under four kinds of operation conditons,the discharge coefficient of V-cond flowmeter is 0.8⁰.835,and the maximum deviation of discharge coefficient is 0.0026.With the installation of upstream single elbow on V-cond flowmeter,the maximum and minimum relative deviation of discharge coefficient are 1.08%and 0.28%respectively;with the installation of upstream double elbows on the same plane,the maximum and minimum relative deviation of discharge coefficient are 3.76%and 1.17%respectively;with the installation of upstream double elbows on two vertical planes,the maximum and minimum relative deviation of discharge coefficient are 1.23%and 0.09%respectively.It is recommended to choose single elbow installation or different plane double elbow installation.With the installation of downstream valve,the maximum and minimum relative deviation of discharge coefficient are 0.66%and 0.2%respectively.The discharge coefficient may be large or small,and the relative deviation is less than 1%.The installation of downstream valve will not have a significant effect on performance of V-cone flowmeter.With the installation of upstream expander,the pressure fluctuation is small by placing the expander at a distance of 30D.the discharge coefficient is 0.805⁰.835,and the relative deviation is-0.6%⁰.3%.Pressure fluctuation is obvious under the condition of expander installation,and longer straight pipe is reserved for the actual installation.