The Study Of Dynamometer Card's Indirect Measurement Method

Dynamometer card is one of important means of determining the working status of pumping wells, so study on the measurement method of the dynamometer card is an extremely noted subject in all oil field of the whole nation and even the whole world. In order to determine the working status, of the supervisory system of pumping wells that has been developed, Force sensors is generally used to gather the signal of greaser's polish rod load, load and other signals through the measurement of the measuring cell. However, because of measuring cell is always in the stretching procedure of alternate load over a long period of time, it is easy to lead to a change in elasticity or even out of work. In addition, the equipment is prone to deficiency, resulting in decreased reliability, increased maintenance workload and rose cost. This will not only affect the working conditions of some oil wells' correctly analyze, judge, but also should not meet the requirement of field in digital administration.Owing to the small number of measurement times of measured dynamometer card, the short life of sensors, the high measurement cost, slow information feedback and other shortcomings, a indirect measurement method of the dynamometer card by electric current method was proposed in this paper. Based on the law of conservation of energy and the analysis of the detailed movement of beam pumping unit by complex vector analysis, mathematical model of electric current, polish rod load and point of suspension displacement was established. This model was a multivariate nonlinear function of polish rod load, electric current, correspondence time, phase voltage, power factor, power rating, electrical efficiency, structure angle of pumping units and so on. An accurate determination was made about current data in a stroke by comprehensive use criterion of the minimum time interval between points, scope of numerical value and so on.Using Delphi7 coding, adopting C/S pattern, the system software of dynamometer card's indirect measurement method was developed; the software successfully connects with the fifth production in the space of long-distance supervising system. It can transfer information in any time which is uploaded from long-distance supervising system, descript dynamometer card curves, electric current curves and capacity factor curves, facilitate the real-time monitoring of working conditions of pumping wells .The experiment of 20 oil wells in well site showed that the dynamometer card's shape alternation is correspondence to actual measurement dynamometer card's which is drafted by this system, and the average proportional error is less than 9.87%, relative error of largest and the smallest loading is no more than 10%, which illustrate that the equivalency dynamometer card matches the actual measurement dynamometer card and it can be achieved by using real-time data of current to real time monitor conditions of pumping wells. The results of the study provide a theoretical basis for the establishment and the regulation of working system, and the down hole remedial operation.