Abstract
Equivalent viscous damping coefficient is an important parameter of wave equation for sucker rod string. In this paper, based on the principle of equal friction loss, when the viscous energy consumption and the local damping energy consumption are taken into account, effects of equivalent viscous damping coefficients are obtained. Through deducing energy consumption equation of oil and energy consumption equation of the coupling, theoretical formula for equivalent damping coefficient of sucker rods is received. Results show that the smaller the K is (K is the ratio of sectional area of tubing to sucker rod), the larger the proportion of damping coefficient caused by viscous energy consumption in the equivalent damping coefficient of sucker rod system is. When K< 0.095, the proportion of damping coefficient caused by viscous energy consumption is more than 90%. Reducing the sudden change of cross-section area at sucker rod coupling has remarkable effect on reducing damping force of the sucker rod system. The research provides a theoretical basis for the application and design of sucker rod and tubing.
Highlights
Equivalent viscous damping coefficient is an important parameter of wave equation for sucker rod string
By calculating the friction loss caused by the viscous resistance of the sucker rod string in a cycle, the damping coefficient formula suited for various flow patterns is derived based on the principle of equal friction loss [18]
On the basis of the sucker rod string wave equation, Sun Renyuan et al proposed the equivalent viscous damping coefficient formula which was related to the actual pump dynamometer cards by using the numerical integration method and established the corresponding iterative algorithm to calculate the equivalent viscous damping coefficient [21]
Summary
Sucker rod equipment is widely used in artificial lift wells [1,2,3]. Its failure modes are various, such as pump leakage, pump blockage, sucker rod facture, sucker rod eccentric wear, and so on. By calculating the friction loss caused by the viscous resistance of the sucker rod string in a cycle, the damping coefficient formula suited for various flow patterns is derived based on the principle of equal friction loss [18]. On the basis of the sucker rod string wave equation, Sun Renyuan et al proposed the equivalent viscous damping coefficient formula which was related to the actual pump dynamometer cards by using the numerical integration method and established the corresponding iterative algorithm to calculate the equivalent viscous damping coefficient [21]. The influence of sucker rod and tubing size on the equivalent viscous damping coefficient is analyzed, which provides a theoretical basis for sucker rod and tubing matching application
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