METHOD FOR DETERMINING THE MEAN TIME BETWEEN FAILURES OF ESP UNITS

Electrical submersible pumps are widespread in the oil industry, in particular, for production of watered mixture in periodic pumping mode. Intermittent mode allows reducing energy costs due to application of high-rate equipment with higher efficiency and prompt change of well fluid withdrawal during change of well parameters without changing equipment. This method is also used when producing oil with high gas factor, with stops for gas phase passing and liquid accumulation. However, this method assumes the presence of peak force loads acting on the pump shaft and supports, as a result of which destruction of electric motor winding insulation, crushing of dowels and keyways of impellers, as well as accumulation of residual deformations of shafts and supports take place. In this relation in view of specific features of electrical submersible pumps installations operation, in particular, installations operating in a periodic pumping mode, the identification of factors influencing the operating time of pumping equipment in order to reduce failures is an actual task at the present moment. The accounting of parameters, determining the system operating time, allows preventing the failures in advance. Mean time between failures depends on many parameters of technological mode. The known methods of calculating mean time between failures are of qualitative character only and allow estimating at what moment in time or by what reason the failure will happen. Statistical distributions (exponential, normal, Weibull distributions etc.) on which base the most probable values of operating time depending on the value of the influencing parameter, or within a certain time are determined, cannot be used for evaluation of the effect of several parameters, which are typical for the presented system. The method based on the regression and statistical analysis of the sample of the wells, granted by one of the Western Siberia companies, is presented in the work for considering several parameters, which have the greatest influence on the operating time to failure, as well as the most influencing factors on the electrical submersible pumps installations life time in the periodic mode are determined.