Research On Gas-Liquid Two-Phase Flow And Friction Pressure Drop Characteristics Of Coiled Tubing Spiral Section

When the fluid flows inside the coiled tubing,there will be a lot of friction loss,especially in the spiral pipe section,the fluid will generate a secondary flow perpendicular to the main flow direction due to the centrifugal force,which will affect the fluid flow.In operations such as well washing,workover,and underbalanced coiled tubing drilling,the fluid in the coiled tubing presents a gas-liquid two-phase flow.The two-phase flow through the spiral section of the coiled tubing will produce a series of complex flows,making the two-phase flow It is difficult to determine the frictional pressure drop in the spiral section,which makes the calculation of surface pump pressure,wellhead and bottom hole pressure and other related hydraulic parameters difficult.Therefore,it is necessary to study the flow of gas-liquid two-phase flow in the spiral section of coiled tubing.Based on the Flunet software,the Euler model is used in this paper to analyze and study the gas-liquid two-phase flow in the spiral section of the coiled tubing and the characteristics of the frictional pressure drop by computer numerical simulation.The multi-stage repeated continuous winding on the drum Tubing spiral section is simplified as a unit spiral section for modeling and analysis.Four cross sections are selected in the unit spiral section to study the flow characteristics of gas-liquid two-phase flow in the coiled tubing spiral section.The cloud diagram,gas-liquid cross section obtained by numerical simulation The phase cross-section gas content,cross-sectional velocity and other parameters are studied and analyzed,and the two-phase distribution change law in the coiled tubing spiral section,the cross-sectional velocity change law and the secondary flow flow law are obtained.Through the calculation and analysis of the friction pressure drop of the spiral section of the coiled tubing under different inflation rates,different pipe diameters,different curvature ratios and different inlet speeds,the friction pressure of the gas-liquid two-phase flow of the spiral section of the coiled tubing under different conditions is obtained.The law of change of falling.Based on the experimental data obtained by numerical simulation combined with the classical formula method and the knowledge of fluid mechanics,the correlation calculation formula for the frictional pressure drop of the two-phase flow in the coiled tubing spiral section is returned,and it is extended to the multi-layer case.The research results show that as the two-phase flow flows in the spiral section,the gas-liquid separation is more obvious,and the gas phase mainly gathers on the inside of thepipe,and the liquid phase gathers on the outside of the pipe.With the flow of the two-phase flow,the two phases begin to separate The distribution changes under the action of centrifugal force,and finally two obvious symmetrical vortices are formed under the action of the secondary flow.When the fluid flows in the spiral section,the velocity distribution of the inner and outer sides is not uniform.The velocity of the liquid near the inner side of the tube is the lowest,and the velocity of the liquid near the outer side of the tube is the highest.The velocity of the gas phase and the liquid phase along the axial direction show a law of decreasing first and then increasing,and the intensity of the secondary flow increases with the flow.When the gas-liquid two-phase flows in the spiral section of coiled tubing,the friction pressure drop accounts for the main part of the total pressure drop.The friction pressure drop gradient of the gas-liquid two-phase flow in the spiral section has a parabolic relationship with the mass air volume.When the inflation volume is small,the friction pressure drop of the coiled tubing spiral section will continue to rise rapidly with the increase of the mass inflation volume.When the mass inflation volume reaches around 0.8,the friction pressure drop gradient fall with the mass air increasing.The frictional pressure drop gradient under the condition of different masses of air inflation shows an upward trend with the increase of pipe diameter.The frictional pressure drop gradient of the spiral section increases with the curvature ratio.The intensity of the secondary flow increases with the increase of the inlet velocity,so that the friction pressure drop gradient of the gas-liquid two-phase flow in the spiral section becomes larger.Under different mass inflation amounts,the friction pressure drop gradient increases with the inlet The increase in speed increases.At the same time,the correlation calculation formula of the friction pressure drop of the gas-liquid two-phase flow in the spiral section is given,and it is extended to the case of multi-layer winding.