A Method for Diagnosing Formation Fluid Leakage During the Operation of Sucker Rod Pumps and a Device for Its Implementation

Abstract

The operation of oil sucker rod pumps (SRP) is known to be one of the most common and basic methods of oil production, especially for marginal wells. However, rapid wear of the plunger pair, tubing and sucker rods caused by friction, leading to a decline in equipment performance, as well as to labor intensity of replacement and repair of deep-well pumps, determines the relevance of developing methods for diagnosing the technical condition of sucker rod pumping units (SRPU) and formation fluid (FF) leakage during the operation of SRPU as an indicator of the technical condition of SRPU in particular. As one of the controlled parameters, leakage value is important for the operational control of well performance and increasing the efficiency of oil production. The authors consider the impacts of well product leakage both in the pump itself (the "cylinder-plunger" clearance, valves) and on the path of the pump product from the cylinder to the orifice (through threaded connections of the tubing string (TS) of the well, through possible pipe breakdowns caused by wear due to rubbing against the rods, etc.). In the existing literature, formulas are given for calculating the amount of fluid leakage through the clearance between the working surfaces of the plunger and the cylinder of a SRP during laminar flow in the clearance (laminar regime is the most probable), with the clearance as the main parameter, cubed. However, this formula requires determining the size of the clearance directly, which is an extremely difficult (impossible) task in an operating SRPU. And results of determining leakage from dynamometer cards and piezograms have low accuracy. In view of the above, the paper proposes a new method and a device for its implementation, which involves measuring the pressure on the well flow line and at two points of the tubing string (TS) of the well, one of which is located at the TS orifice, and the second lower at a distance of half the height of the cylinder of the pump being used, the FF leakage from downhole pumping equipment being calculated by the algorithms given in the text. It is shown that the proposed diagnostic method makes it possible to more accurately and reliably, in comparison with the existing methods, determine the formation fluid leakage during the operation of SRPU.