Methodology of calculation of fluid partition coefficient in wells equipped with electric submersible pumps under conditions of self-flowing through the annular space

Aim. This article is devoted to the study of the phenomenon of self-flowing through annulus in wells equipped with electric submersible pumps (ESP). The main task of the study is to find dependences for determining the fluid partition coefficient between the annular space and tubing during self-flowing taking into account the influence of ESP performance degradation.

Methods. The authors applied a complex approach including theoretical analysis, laboratory studies, numerical modelling and processing of data obtained from a real well. Within the framework of the experimental part, bench tests were carried out, which allowed to establish new dependences of the liquid partition coefficient on the flowing gas content. The developed algorithm for estimating the fluid partition coefficient provides an opportunity to quantify the redistribution of phase flows, which is important for optimising the operation of downhole equipment. Numerical simulation allowed to identify the key parameters influencing the occurrence of selfflowing through annulus, as well as to simulate the behaviour of the system under different operating conditions.

Results. Experimental data confi rmed the existence of a relationship between the gas content in the flow and the gas-liquid mixture (GLM) distribution between the annulus and the tubing. The modelling results indicate that it is possible to estimate the fluid partition coefficient for given boundary conditions. Analysis of highly discrete telemetry data and multiphase flowmeter measurements from Western Siberian fields confirmed the reliability of the developed model.

Conclusion. Implementation of the obtained solutions and optimisation of electric submersible pumps operation can help to prevent abnormal operation modes and improve the overall efficiency of mechanised hydrocarbon production. The proposed methodology can be used to develop new recommendations for well operation, which is of practical importance for the oil and gas industry.

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