RELIABILITY ANALYSIS OF SUBMERSIBLE CENTRIFUGAL PUMPS IN OIL COMPANIES

Abstract

Background In the event of failure of any of the submersible units, it is necessary to carry out underground repairs - killing the well with process fluid, removing the submersible from the well, installing the arc submersible part in it, starting the installation, developing the well (removing the process fluid from it) and removing the installation of the submersible centrifugal electric pump to the operating mode. The duration of underground repairs reaches several days, the costs for its implementation are comparable to the cost of the submersible centrifugal electric pump, and the losses from the downtime of the well during this period significantly exceed it. Therefore, for the consumer, the most important indicators are the reliability of the submersible centrifugal electric pump unit. Aims and Objectives The article is devoted to the analysis of the reliability of installations of submersible centrifugal pumps in a number of oil companies. The mean time to failure of the submersible part of the submersible centrifugal pumps is taken as the most important indicator of submersible centrifugal pumps reliability, which exists as a single assembly unit only during the run into the well before the first lift (failure). Methods The average operating time to structural and technical failure of the submersible part of the new submersible centrifugal pumps unit, based on the results of control operation, was determined as follows. It was assumed that the operating time to failure of the loaded parts obey the Weibull distribution law. The analysis was carried out on 22 samples of control operation of the 9 most common submersible centrifugal pumps units in oil companies: Tatneft, Bashneft, Rosneft-Samaraneftegaz and Nizhnevartovskneftegaz. The samples consisted of 1-89 submersible centrifugal pumps units with the number of failures 0-31. 6 of them (2 in OAO NK Tatneft, 3 in OAO NK Bashneft, 1 in OAO Rosneft-Samaraneftegaz) had statistics sufficient to check the correspondence of the theoretical distribution law to the statistical one with acceptable reliability (the number of monitored submersible centrifugal pumps units is at least 25 and the number of objects with credited failures is at least 12). Results The average operating time for the four associations to structural and technological failure of the submersible part of a typical submersible centrifugal pumps unit is 64.5-81.9% of the corresponding average operating time for new submersible centrifugal pumps units. Considering that the aggregate of typical installations includes a significant proportion of repaired and mixed (equipped with new and repaired units) installations, this fact can be interpreted as evidence of the low quality of repair of units by the consumer. The data obtained in Oil companies: Tatneft and Bashneft fully agree with this conclusion. The data of Oil company Nizhnevartovskneftegaz do not contradict this conclusion either. The high values obtained in Oil company Rosneft-Samaraneftegaz are most likely the result of insufficiently thorough identification of the reasons for the rise of the submersible centrifugal pumps during control operation, as a result of which some of the failures for operational reasons are interpreted as failures for structural and technological reasons.