Avaliação do desempenho de ejetores em poços de petróleo em campos maduros

Abstract

In the Oil industry, artificial elevation methods become indispensable for wells with low productivity history. The implantation of these methods especially the pump ones arises new challenges related to the production of gas in contact with the pump. Therefore, gas separators are installed at the bottom of the well to ensure that the gas is directed to the annulus making the pump method viable to the well. However, it is necessary to release the confined gas in the annular, since it can cause an increase in the pressure of the coating so as to generate a back pressure at the pressure of the production line, and thus, the ejector, which is an equipment which has been studied with the function of using a high velocity main fluid to suck a secondary fluid, is connected to the wellhead to promote the releasement of the gas from the annulus. Therefore, the present analysis is part of a larger project which has been directed to the study of ejectors, and this research is focused on the dimensioning of parameters in the ejector (length and radius of the throat) seeking a greater efficiency for mature fields. The study was carried out in three stages: The search for literatures which produced a greater understanding of the studied instrument; The use of essential data (suction chamber geometry, nozzle geometry and diffuser sizing) from earlier studies of this project in order to find a higher efficiency ejector; Finally, the use of a CFD computational tool, in the commercial simulator ANSYS CFX, to design and simulate the fluid dynamics of the ejector. At this step several analysis were made based on different lengths and diameters of the throat in order to generate pressure graphs for a posterior analysis of the ejector type that fits as the most efficient. Therefore, among all tests performed, the dimensioning of the ejector in the throat area seeking the best configuration to raise efficiency has enabled different combinations of diameter and length, guaranteeing for the users a dimensioning without the need of an exclusive arrangement.