Evaluation of Intermittent-Flow Behavior Upstream of Electrical Submersible Pumps

Abstract

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 173958, “Experimental Evaluation of Behavior of Intermittent Flow in Scenario of Application of Electrical Submersible Pump,” by Roberto da Fonseca Jr., Paulo Vinicius S.R. Domingos, and Diogo Cunha dos Reis, Petrobras, prepared for the 2015 SPE Artificial Lift Conference—Latin America and Caribbean, Salvador, Brazil, 27–28 May. The paper has not been peer reviewed. This work experimentally investigates the behavior of an intermittent multiphase liquid/gas flow that takes place upstream of an electrical submersible pump (ESP). On the basis of the results and associated interpretation, a flow-homogenizer device was designed, built, and tested. Classical ESPs, which, in essence, are composed of a series of radial/ centrifugal impeller/diffuser pairs, are not tailored to work in scenarios with high gas-void-fraction (GVF) values. The apparatus was assembled to avoid the development of intermittent flow. Introduction In the oil industry, multiphase flow occurs during the production and transport of oil and gas at wells and in the lines that connect wells to platforms. During well production, the flow from the reservoir to the production platform undergoes depressurization. Consequently, a portion of the liquid hydrocarbon dissociates and becomes gaseous during production. Multiphase flows are characterized by the existence of several flow patterns. When gas and liquid flow in a pipe at the same time, several flow configurations may exist. These patterns depend on operating variables—namely, the velocity of the liquid and gas, fluid properties, and some geometrical aspects such as pipe diameter and angle. Hydrodynamic aspects of the flow change dramatically as each flow pattern prevails. Despite the large number of flow patterns, this work focuses on intermittent flow. In this flow pattern, the liquid in the pipe is nonuniformly distributed axially. Plugs or slugs of liquid that fill the pipe are separated by gas zones, which contain a stratified liquid layer flowing along the bottom of the pipe. The liquid in the slug may be aerated by small bubbles, which are concentrated toward the front of the slug and the top of the pipe. The intermittent pattern is usually subdivided into slug and elongated-bubble patterns. In principle, the flow behaviors of slug and elongated-bubble flow appear to be the same, with regard to the flow mechanism; therefore, there is no particular advantage in distinguishing between them.