Author(s)

F. E. Trevisan & M. G. Prado

Abstract

Artificial lift systems are extensively used in the petroleum industry in order to enhance or even initiate the production of oil wells that present insufficient energy to produce naturally. The Electrical Submersible Pump (ESP) is one of the many existing artificial lift techniques and consists of assembling several diffuser type centrifugal pumps in series. It is common in petroleum field applications to have an inflow of natural gas into the pump intake, which compromises pump performance and reliability. Trying to better understand the interaction between the gas and liquid inside centrifugal pumps is still a challenge and the current investigation tries to help understand this subject. This research describes the development of a visualization prototype built using original ESP components, applying minimal mechanical and geometrical modifications, with the intent of acquiring visual evidence of the flow patterns that occur inside the pump. Because of these minimal changes to the original pump geometry, the prototype was proven to operate according to the original pump catalogue performance, implying that its hydraulic behaviour was maintained. Water-air two phase experiments were conducted at different rotational speeds (15, 20, 30 Hz) and non-slip void fractions (up to 5%) while the liquid rate was kept constant at 60% of the maximum rate at the defined shaft speed. High speed video footage was gathered, as well as differential pressure measurements. The authors identified four water-air flow patterns inside the impeller channels: Dispersed Bubbles, Agglomerated Bubbles, Gas Pocket and Segregated Gas. By comparing the images with the differential pressure data, it

Keywords

centrifugal pump, flow visualization, two-phase flow, surging, flow patterns