Study Of Multiphase Flow Characteristics And Parameters Measurement In Small Diameter Pipe

With the continuous development of horizontal wells, the dynamic monitoring of oil fields is facing more challenges for multiphase flow measurements. In this study, two experimental test facilities and related measurement systems were desined and developed for the investigations of horizontal and vertical multiphase flow in20mm diameter pipe. The high-speed camera, quick closing valve, conductance sensor, turbine flowmeter and differential pressure sensor were used to study the multiphase flow characteristics and their influence on parameters measurements. Some pioneer works on developing new measurement techniques were also explored.For horizontal oil-water two-phase flow, a flow pattern map was established from the flow images of the visualization; an investigation of turbine flow meter as well as conductance sensor’s responses to the complex multiphase was carried out, and some analyses of oil-water slippage law and the impact of the oil-water spatial structure on the conductance sensor were explored. It was found that the inclined flow with angle of less than5degree has relatively smaller impact on the turbine flow meter than the oil cut. Due to the flow pattern variation under low flow rate condition, the change of turbine flow meter’s response caused by oil cut is complex; only when the flow becomes uniform dispersed flow under high flow rate condition, the turbine meter’s response behaves are more sensitive with the increase in oil cut. For different oil water space structure and slippage between stratified flow and dispersed flow, different dynamic flow models and electric models were adopted to calculate the water cut from water holdup, respectively. In addition, methods of measuring the flow characteristics with image processing technology were developed, and two-phase interface position and the size of the droplets in the dispersed flow can be obtained.A PIV (particle image velocimetry) experimental system was developed to measure the velocity field in stratified flow and the droplets velocity in dispersed flow. The successful results revealed that the oil-water two-phase flow velocity field is significantly different from that of single phase flow.For multiphase vertical flow, some flow pattern maps were also established from the flow images on air gas water flow. Then the turbine flow meter and conductance sensor response characteristics on oil water flow, gas water flow and oil water gas flow were discussed. It was found that the average turbine flowmeter value shows a good linear relationship with the oil-water total flow rate. The increase of the gas flow rate slightly increases average turbine flow meter value. The response fluctuations of turbine flow meters and conductance sensor occur in slug flow. Large size bubble will causes transient decrease of turbine flowmeter value and transient increase of conductance sensor value. With the oil cut increase the turbine flowmeter value will slightly increase, and conductance sensor and turbine flowmeter response fluctuation intensity will both increase.Numerical simulation shows attractive potential on dynamic research of multiphase flow. The VOF (volume of fluid) multiphase numerical model was used to simulate the horizontal two-phase flow and the vertical multiphase flow. For the oil-water two-phase horizontal flow, the numerical results of water holdup and velocity field coincide with the experimental results. In addition, the influences of flow rate, water cut and oil physical parameters on water holdup were analyzed in relative details with the help of numerical simulation.