Study on Online Correction of Polished Rod Dynamometer Cards and Digitalization Application of Pump Dynamometer Cards

The polished rod dynamometer operates under alternating loads and large temperature differences for a long time, inevitably leading to zero drift and temperature drift issues. At the same time, conventional inversion of polished rod dynamometer cards fails to consider the impact of friction loads, resulting in inaccurate production and liquid level calculations from pump dynamometer cards. Based on the oil-filled environment in the sucker rod and tubing during the upstroke of the pumping unit, this paper proposes a rapid identification method for the four characteristic points of the polished rod dynamometer card to obtain a calculation method for friction loads at the velocity reversal points A and C. The gravity of the polished rod string in the liquid column serves as the benchmark for calibrating the polished rod dynamometer card. Combined with basic well data, a one-dimensional wave equation difference calculation method is used to solve for the pump dynamometer card. An approximation algorithm is employed to achieve rapid calibration of the polished rod dynamometer card and inversion of the pump dynamometer card. Calculation and engineering application results indicate that the accuracy of production and liquid level calculations obtained from the pump dynamometer card through online correction of the polished rod dynamometer card exceeds 90%, achieving the goal of engineering digitization applications.