Theoretical And Experimental Research Of Low Shear Wellhead Choke Valve Used In Oil And Gas Exploration

In the exploration and crude oil gathering and transportation process, both the wellhead product dehydration and waste water treatment are facing the problem that improving efficiency of oil-water separation. There are many factors influencing the efficiency of oil-water separation. Among which droplet diameter is the most important. Wellhead choke valve, as an key component in process of adjusting the flow and pressure of wellhead product, generate the most serious problem in cause of its working process accompanied by intense shear and emulsification, resulting in breakup of dispersed droplets, increasing the difficulty of oil-water separation. Therefore, the research and development of low shear valve technology and devices is of great significance.The basic theory of droplet breakup, mechanism of droplet breakup in throttling element and research and development of foreign low shear throttling product were introduced in this paper. The auther took part of design ideas of similar products as reference, and proposed conceptual design of low shear choke valve. Then completed the structure scheme comparsion and basic design of the basic structure after combining with structure of conventional choke product. In this paper, the flow field in valve was simulated by Fluent, the computational fluid dynamics (CFD) software, and the relationship of tangential orifices diameter, angle, distance from cage axis and necking diameter with the energy dissipation rate and distribution of dispersed phase was discussed, then accomplished the detail design of the key element according to the simulation result. Finally the entire drawings of product and the assistance work of manufacturing were accomplished.Low shear choke valve evaluation device to assess the performance of designed throttle were designed and manufactured. The valve was tested under different pressure drop and compared with conventional axial flow valve. The results proved that low shear valve can significantly increase the settling velocity of oil droplet under high pressure drop situation, and realize low shear rate. For example, the oil content of water layer after separation for10min reduced by57.5%in low shear valve experiment under the pressure drop of0.5MPa, compared to conventional axial flow valve.Although the oil-water mixture with low concentration used in experiment failed to represent wellhead product, the research results of in this paper provided a technical reference for the industrial application of low shear valve, and offered experience for the further structure improvement.