钻井用节流阀抗冲蚀性能的实验评价

发生井喷事故时主要依靠节流阀来控制井内流体的流速,因而要求其具有较强的抗冲蚀能力,但目前的节流阀抗冲蚀能力评价大多都停留在有限元分析或流体流场模拟计算阶段,无实测数据,未进行定性、定量评价,给选型和使用都带来了较大的困难。为此,采取远程控制阀开启度调整实验压力和流体流速、氮气注入压力略高于实验压力来保证气体有效混入形成三相流体的实验思路,闭环模拟了不同流速、不同流体组分、不同压力条件下的井喷对孔板、圆柱和楔形3种节流阀的冲蚀情况。实验结果表明:①抗冲蚀能力依次为圆柱节流阀楔形节流阀孔板节流阀;②在实验压力范围内,楔形节流阀阀芯出现轻微蚀痕,下游短节发生单边冲蚀,抗冲蚀能力较弱;③当孔板节流阀开度约1/8时,实验泵压多次跌落回4 MPa,其阀芯后端受到严重冲蚀。进而依据实验结果,提出了改变楔形节流阀阀芯形状、优选材质、在孔板节流阀的阀芯侧面增加密封件等改进思路。结论认为,所形成的三相流体抗冲蚀评价方法可应用于类似结构节流阀的评价。

Experimental evaluation on the anti-erosion performance of throttle valves for drilling

When a blowout accident happens, throttle valve is the key device to control the flow velocity of fluid in a well, so its erosion resistance shall be stronger. At present, however, the evaluation on the anti-erosion performance of throttle valves mostly focuses on finite element analysis or fluid field simulation calculation, with neither measured data nor qualitative and quantitative evaluation, which brings great difficulties to the selection and application of throttle valves. In this paper, an experimental idea was adopted of adjusting the experimental pressure and fluid velocity based on the remote control of valve opening and keeping the nitrogen injection pressure slightly higher than the experimental pressure to ensure that the gas is effectively mixed to form three-phase fluid. Closed-loop simulation was performed on the erosion of blowout on three kinds of throttle valves (orifice-type throttle valves, cylindrical throttle valves and wedge-shaped throttle valves) under different flow velocities, different fluid components and different pressures. And the following experimental results were obtained. First, from the viewpoint of erosion resistance, three kinds of throttle valves are ranked as a cylindrical throttle valve ＞a wedge-shaped throttle valve ＞an orifice-type throttle valve. Second, within the experimental pressure range, a wedge-shaped throttle valve has slight erosion marks on the valve core and unilateral erosion on the downstream nipple, indicating that its erosion resistance is weak. Third, when the opening of an orifice-type throttle valve is 1/8, the experimental pump pressure drops back to 4 MPa for many times, and the rear end of the valve core is seriously eroded. Finally, according to the experimental results, the improvement ideas of changing the core's shape of a wedge-shaped throttle valve, optimizing the material and adding seals on the side of an orifice-type throttle valve were put forward. In conclusion, the three-phase fluid erosion resistance evaluation method can be used to evaluate throttle valves of similar structure.