Effects of water and gas injection and viscosity on volumetric fraction, pressure gradient and phase inversion in upward-vertical three-phase pipe flow

The natural and artificial presence of water and gas is common in the offshore oil production scenario. In the last years, several studies on two-phase flows of viscous oils proved that the water and gas addiction is very efficient in the frictional and gravitational pressure-gradient reduction. In recent works, the oil-water-gas three-phase flow showed promising results in the total pressure-gradient reduction. However, the works on three-phase flow are not as conclusive as those on two-phase flow. In order to better understand the phenomenology of the upward-vertical three-phase flow, new experimental data are presented in a wide range of flow rates of gas, water and oil with three different viscosities (100 mPa s, 220 mPa s and 325 mPa s). The gains obtained by gas (air) and water injection were quantified by pressure-gradient reduction factors. A new flow-pattern classification in three-phase flows is proposed as a function of water and gas superficial velocities. Furthermore, analyzes were performed about the volumetric fractions, the slip between the liquid phases and the applicability of the drift-flux model in three-phase flow. The results indicate that the total pressure gradient in three-phase flow can be considerably lower than in single-phase and two-phase flows; therefore, a profound understanding of oil-water-gas three-phase flow is in order if one intends to improve the oil production in vertical wellbores.