低产抽油机井动态参数仿真模型与提高系统效率的途径

综合考虑柱塞运动规律、阀球运动规律、阀隙瞬时流量与油井流入特性等因素的影响，建立了流体进泵规律与泵筒内瞬时压力的仿真模型，以此为依据改进了抽油杆柱纵向振动底部边界条件的仿真模型，进而建立了基于抽油杆柱纵向振动与流体进泵规律耦合的抽油机井示功图动态仿真模型；基于流体瞬时进泵规律，建立了抽油泵充满系数、漏失系数的仿真模型，从而改进了排量系数计算模型。对比仿真结果表明，所建立的系统动态参数仿真模型具有通用性，可以提高低沉没度供液不足油井示功图、排量系数与系统动态参数的仿真精度。仿真优化算例表明：①大泵径、长冲程与低冲数的抽汲参数设计原则仍然适用于低产抽油机井的节能设计，但最低冲数存在界线，同时最低冲数界限也限制了泵径上限；最低冲数界限随泵间隙的增加而增加；②对于严重供液不足油井，通过合理降低冲程与冲数，可以确保在油井产液量下降率低于5%的条件下，使系统效率最高提高近120%；③在油井产液量一定、下泵深度相同的条件下，优化冲程、冲数与泵径组合可以显著提高系统效率，仿真算例的系统效率变化范围为9.43%~17.48%；④在油井产液量与流压一定条件下，综合优化下泵深度、冲程、冲数与泵径可以显著提高系统效率，优化算例的系统效率由10.56%提高到31.49%。

Dynamic parameter simulation model of low-production pumping well and the ways to improve system efficiency

Through comprehensively considering the influences of piston motion law, valve ball movement law, instantaneous flow rate of valve clearance, oil-well inflow performance and so on, this study establishes the simulation model on the laws for pumped fluid flow and the instantaneous pressure in pump barrel. Accordingly, the simulation model on the bottom boundary condition of longitudinal vibration of sucker rod stem is improved. Further, this study sets up the dynamic simulation model of dynamometer card for pumping well based on the coupling between the longitudinal vibration of sucker rod stem and the laws for pumped fluid flow. As per the laws of instantaneously pumped fluid flow, a simulation model on the fullness and leakage coefficients of oil pump is established to improve the calculation model of discharge coefficient. Through comparing the simulation results, it is shown that the created system dynamic parameter simulation model is generic, able to improve the simulation precision of the dynamometer card, discharge coefficient and system dynamic parameters of oil wells with low submergence depth and insufficient liquid supply. The simulation optimization cases show that (1)the design principle of swabbing parameters for large pump diameter, long stroke and low stroke frequency is also applicable to the energy-saving design of low-production pumping well, but there is a limit of minimum stroke frequency. Meanwhile, minimum stroke frequency also limits the upper limit of pump diameter, and the limit of minimum stroke frequency increases with the increasing pump clearance. (2)For oil wells with insufficient fluid supply, when the liquid-production drop rate is less than 5%, the system efficiency can be increased up to 120% by reducing the stroke and stroke frequency reasonably. (3)Under the condition of certain liquid production and equivalent pump depth for oil wells, system efficiency can be improved significantly by optimizing stroke, stroke frequency and pump diameter, and the system efficiency of simulation case varies from 9.43% to 17.48%. (4)Under the condition of certain liquid production and flow pressure, comprehensive optimization of pump depth, stroke, stroke frequency and pump diameter can significantly improve system efficiency, and the system efficiency of the optimized case is increased from 10.56% to 31.49%.