Multiphase Pumping With Twin-Screw Pumps - Understand And Model Hydrodynamics And Hydroabrasive Wear

Abstract

Crude oil and gas production can be enhanced by multiphase pumping from the well subsea to far distant production platforms. The twin-screw pump has proven quite suitable for this application. The positive displacement principle offers efficient multiphase performance within a wide range of gas void fractions and can handle hydroabrasive conditions fairly well, too. The paper reports about modeling the hydrodynamic performance and hydroabrasive wear of twin-screw pumps. The influence of the gas void fraction on the pump capacity can be modeled by the “disc model” and assumptions about the fluid conditions in the internal pump clearances. The model implemented into a computer program will be verified by experimental testing of various pump features with respect to performance, pressure distribution, thermodynamics, and bending deflection of the screw shafts. The phenomena of the hydroabrasive wear will be studied by the rotary clearance tribometer as well as with pump field tests with silica sand/water suspensions. Based on a number of material combinations including hard coating on tungsten carbide basis, the relative suitability of materials as well as the local wear phenomenology will be analyzed. The paper offers a full survey about the hydroabrasive twin-screw pump wear characteristics and steps to predict and achieve satisfactory pump life.