Accurate extraction of valve opening and closing points based on the physical meaning of surface dynamometer card

The extraction of valve opening and closing points is the basis for the identification and quantitative analysis of pumping well dynamometer cards, and it is important for the failure diagnosis and production evaluation of pumping wells. In light of the working principle of sucker rod pump and the physical meaning of surface dynamometer card, this paper discusses theoretically valve opening and closing points and presents an accurate method of extracting the valve opening and closing points of surface dynamometer cards. After the top and bottom dead centers are determined on displacement-time curve and the loading history curve is dealt with by parition and de-noising (smooth de-noisng, curve fitting and iteration de-noising), methods of exhaustion and comparison are applied to find optimal solutions and to determine the opening points of travel valve and set valve. The opening points of the valves are determined by the same method. A corresponding computer program is developed and analyses of 1 000 examples indicate that this approach is effective.