A modified mechanistic model is formulated to predict the pressure drop in horizontal slug flow for two-phase flow (viscous liquid and air). The model is evaluated by using accurate PDVSA INTEVEP experimental data for liquid with viscosity of 480 cP. A comparison between the modified model and experimental data shows that the absolute average relative error in pressure drop prediction is less than 6%.
Venezuela has the world largest heavy oil reserves. PDVSA has launched several projects to develop the technology for optimum exploitation and production schemes. Special attention have been focused on multiphase flow along the production system, which includes horizontal & multilateral wells, vertical wells (tubing & annular flow), pipelines and production networks.
Multiphase flow is characterized for the existence of flow patterns. There are different types of them, where the most common one is called slug flow, see Fig 1. Therefore, proper production system design requires of reliable pressure drop models for slug flow. Current pressure drop models for slug flow, have been developed and validated for low viscosity oils. Fluid properties affect the slug flow characteristics as well as the behavior of the pressure losses. Available pressure drop models estimate the pressure gradient with average errors about 30% as can be seen in Fig 2. This uncertainty might affect CAPEX and OPEX up to 10%.
The interest of this work is to develop a rigorous pressure drop model that can be applied for both light and heavy oils. The model should be validated initially with lab data and then with field data. Due to the lack of high quality laboratory data for pressure drop in heavy oils, PDVSA INTEVEP built a multiphase production laboratory.
The experimental facility and the slug flow model will be described next.
Experiments were carried out in a 2-in test loop facility at PDVSA INTEVEP. Lube oil (480 cP) and air were testing fluids.