| System efficiency is an important technical indicators to evaluate the energy consumption of well pumping unit. Simulation evaluation method on the extreme efficiency of oil well pumping system is the theoretical basis to analyse energy consumption, energy-saving potential and to guide energy saving optimization. Beam pumping system is the dynamical system of electro-mechanical and hydraulic integrated system, therefore, the dynamics model is the important subject of this field. At present, the beam pumping system has two shortcomings: the ground device is simplified as a single degree of freedom rigid system and the simulation model of the longitudinal vibration of the sucker rod pumping is built based on linear hypothesis. Considering above shortcomings, the two simulation models are built, which are simulation model of multi-freedom torsional vibration of ground device and the mathematical model of longitudinal vibration of sucker rod string. Simulation model of instantaneous transmission efficiency of machine nodes is built based on system dynamics simulation. Simulation optimization model of the system extreme efficiency is built based on above models. The results have theoretical value and practical significance.Based on traditional model, the simulation model of double-disk torsional vibration of belt driving system has been established. The new simulation model has following features: the difference between belt tight and loose side stiffness is considered, the time varying characteristics of belt equivalent stiffness and pulley equivalent rotational inertia is considered. The simulation model of the longitudinal vibration of elastic belt is built, considering belt distribution quality. Then, the simulation model of belt instantaneous transmission efficiency is built. The simulation results show that the nonlinear characteristic is found in the results of belt longitudinal vibration model. Meanwhile, that negative torque fluctuation which influences motion law of suspension point and longitudinal vibration of sucker rod pumping causes belt transmission efficiency fluctuation, reduces average efficiency of belt transmission significantly and increases the big belt wheel speed fluctuation.Based on traditional simulation model of longitudinal vibration of sucker rod string, the simulation model of the longitudinal vibration of the combined sucker rod is built, the rod is equipped with shock absorber and damper. Considering the influence of the coulomb damping, power law damp and the speed nonlinear term of pump load, the discrete systems model of the longitudinal vibration of sucker rod is built. The simulation results show that the combined sucker rod systems composed of shock absorber and linear damper are linear systems with the assumption of a linear system, the shock absorber has obvious damping effect in the deep well or flexible rod pumping system.Considering the elasticity of belt-gearbox transmission system, the mathematical model of multiple degrees of freedom torsional vibration of ground device of beam pumping system is built. The simulation accuracy of the motion law of suspension point and suspension indicator diagram are improved.Based on mathematical model of multiple degrees of freedom torsional vibration of ground device and mathematical model of sucker longitudinal vibration multiple degrees of freedom discrete systems, the mathematical model of the dynamics simulation of beam pumping system is built by ordinary differential equations. Overall simulation based on numerical integration method is obtained, which solves the problems that integral method is not uniform with the finite difference method.Based on the dynamic simulation of the beam pumping system, simulation model of force and energy parameters, cell efficiency and system efficiency has been built. Based on multiphase flow computational model of the wellbore nodal forces, simulation model of production supply coordination and optimal model of system efficiency extremes of the pumping wells have been built. The computer software of Simulation and Optimization of Beam Pumping System Dynamics and System Efficiency Limit has been developed, simulation evaluation of system efficiency levels, system efficiency extremes and saving potential have been obtained. |
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