Numerical Simulation Research Of Internal Flow Fields In Pump Units Under Changeable Periods Movements Of Pumping Rod

Artificial lift methods have always been continuously significant in petroleum industry. Most of artificial lift methods are following the principle of symmetrical cycle, also known as periodic oil pumping. However, these methods are often accompanied with the systematic problem of high energy consumption and low efficiency. In the process of studying how to enhance the efficiency of rod pumping system, research methods are usually used such as pumpage variable changing,pump structure alteration,adjustments of submergence pressure,etc. But these factors can not improve the efficiency of sucker rod pumps fundamentally.Scientifically-proven facts show that it can effectively improve the efficiency of sucker rod pumps through changing the operating pump conditions. The original conditions are under the principle of symmetrical cycle which can be altered to changeable periods by controlling on the ground. But there are not basis of experimental supporting the effectiveness of changeable periods. In this paper, the author uses FLUENT,one of computational fluid dynamics softwares,to study the factors of pumping efficiency under varied forms of rod motion by simulating the movements of pump units.Both pumping methods of units and forms of rod movements have effects on the efficiency of artificial lift methods. In this article,the author uses FLUENT to simulate the internal flow fields of pump units,to establish the numerical analytical models which are quite available and suitable for pumping efficiency study,to achieve the control of movements of pistons and ball valves in oil pump though adopting the dynamic mesh technique and UDF(User Defined Function) programme. Firstly, the author analyzes the influences of different working conditions in terms of submergence depth, stroke and rate of pump to efficiency under symmetrical cycle. Secondly, the author changes the pumping methods,in which ratio of upward pump speed to downward pump speed is set as 1.5 and 2 from this paper,basing on the symmetrical cycle to analyze the influences to efficiency of different kinds of submergence depth,stroke length and time of pump. Through the analyses of efficiency by changing the pumping method and movement parameters,it can be realized that changeable periods actually improve the efficiency comparing with symmetrical cycle under same actual working conditions such as submergence depth,stroke length and time of cycle.This paper can clearly provide simulative evidence supporting that changeable periods could enhance the efficiency of artificial lift in actual working conditions through analyses mentioned above.