SUBSEA MULTIPHASE PUMPING SYSTEM X GAS LIFT: AN EXERGO-ECONOMIC COMPARISON

Abstract

This paper presents a methodology for an exergetic comparison between two artificial lift
systems: a gas lift and a twin-screw multiphase pump system, and a standalone offshore
platform. A software (Hysys.Process v2.1) was used to simulate an offshore platform with
the artificial lift methods and calculate all properties (including exergy) of the material
and energy streams. The twin-screw multiphase pump behavior was simulated with a
thermodynamic model developed recently (NAKASHIMA (2000) and NAKASHIMA,
OLIVEIRA and CAETANO (2002)). The operational conditions of the PETROBRAS 7-
MRL-72D-RJS well operating with cited systems were predicted by an internal study
conducted in PETROBRAS (BARUZZI et al. (2001a) and partially published in BARUZZI
et al. (2001b)). The comparisons cover the range of 2000 to 2020, the same range adopted
in the study. Results show that in general the production costs are lower when the multiphase
pump is used. The main advantages of this method over the gas lift is the absence of
material (gas) recycle and a better energy management.