Modeling offshore steady flow field data using drift-flux and black-oil models

Abstract

The flow of oil in pipes is, in general, a multiphase flow where water, oil, gas, emulsions and sediments are transported in a co-current flow. Various complex phenomena, including mass transfer between phases, phase slip, friction pressure drop, variable geometry, compression, heat transfer and other thermodynamic effects make the flow modeling quite complex. Mixture models considering simplified empirical correlations derived from experimental observations, such as friction pressure drop and drift-flux models, are becoming increasingly used in the oil industry because of their good accuracy and simplicity. Fluid characterization is complex because it deals with multicomponent systems; therefore, empirical approaches such as black-oil models have been widely used. Modeling oil flows in real systems also requires suitable computer tools to solve equations that often need to be discretized in space and time and solved iteratively. In this paper, a stationary flow model based on a drift-flux formulation and a black-oil fluid model is developed. We present a method to integrate numerically the stationary equations and test the accuracy of a few drift-flux and two-phase multiplier correlations using steady state field data. Specifically a high pressure, three-phase flow system in deep water consisting of an offshore oil well with a 8,000m length, 6in diameter pipeline-riser system located at Tupi oilfield (Santos basin, Brazil) is used as a case study. Results show that the proposed method, as well as the fluid and flow models adopted, is suitable for the analysis of stationary oil flows in real production systems.