MIXED GAS-OIL SUBSEA PIPELINES IN OFFSHORE TECHNOLOGY: TECHNICAL AND ECONOMIC ASPECTS

Abstract

The choice of gas separation and transportation mode in offshore
applications may significantly affect the project profitability. Main
alternatives are separation on board the platform with the utilization of
separate subsea pipeline for single-phase gas and oil transportation, and
remote separation with multiphase transportation of the gas-oil mixture in a
single pipeline. In order to assist the project engineers during the feasibility
study phase, the problems relevant technical and economic issues are
analysed in this paper after preliminarily describing the two process
schemes. In particular a computer model is developed in order to simulate
the two-phase flow of the multi-component mixture adopting the Beggs and
Brill model, which showed to be the most reliable approach in this
application. A cost comparison with reference to a hypothetical but realistic
case study is finally carried out to assess the convenience of the multiphase
flow solution. This option appears to be especially attractive when multiplewell
fields exist which can be developed in an integrated manner by
providing a single centralized separation plant.
A Allowance for additional mass (t)
L Liquid production (m3/day x 1000)
STP Standard Temperature and Pressure