Fluid Flow
Fluid Flow plays a key role in the oil and gas industry. There are several problems related to Fluid Flow in different processes along the production chain. In general, multiphase mixtures of complex fluids are transported through different geometries, such as pipes, pumps, separators, equipment, devices, among others. The main problems involve the calculation of pressure drop, pipe sizing, flow pattern identification, definition of operational stability boundaries, production monitoring, among others.
In this scenario, the ALFA group has developed several basic and applied studies on the detailed characterization of fluid flows, and these are supported by development agencies and industries. The LABPETRO infrastructure was specifically designed to study fluid flow problems, featuring long horizontal and vertical lengths for piping assemblies.
a. Multiphase flow in Pipes
The flow of complex mixtures in pipes is still an open problem in several conditions. At ALFA, we develop one-dimensional models for gas-liquid, liquid-liquid, and even gas-liquid-liquid flows to predict both pressure drop and volume fractions. These models can be used by the industry and in commercial codes to improve their predictions. Other interesting research subjects are emulsion flows (water in oil or oil in water), detailed experiments using PIV (Particle Image Velocimetry), and multiphase flow with non-Newtonian fluids. The complexity of the models and the physics increase, but render them closer to the real problems of the industry. For this, we build different flow loops to fit the needs of each research subject.
b. Multiphase flow in Pumps
Given the complexity of the fluid produced, it is common for ESPs to work with multiphase mixtures of oil, gas, water, and solids. Multiphase flow within the pump can cause serious operational problems, such as loss of performance, operational instability and reduced equipment run life. Understanding the behavior of ESP pumping multiphase flows is essential for proper sizing of the lifting system, as well as for monitoring production.
The ALFA group has been developing studies applied to ESP, involving its operation with multiphase flows, such as gas-liquid and liquid-liquid (emulsion) flows. For multiphase pumping, the flow visualization is central to understanding the phase behavior. These studies employ state-of-the-art high-speed imaging techniques, Particle Image Velocimetry (PIV), and optical probes to measure population distribution (FBRM). These studies are focused on understanding and modeling the behavior of ESPs under real operating conditions, contributing to the dimensioning of real production systems.
c. Multiphase flow in devices
Real applications involve several devices, such as valves, reductions, expansions, and bends in most lines transporting multiphase flows. The effects of such devices on flow characteristics have been a research subject in recent years. At ALFA, we develop experimental research on multiphase flows (gas-liquid, liquid-liquid, emulsions) flowing through such devices to understand the effect on flow patterns, pressure drop, phase distribution and others for improvement of one-dimensional models in such conditions.
d. Drag reduction
The study of drag reduction is very important for the transport of hydrocarbons through long pipelines. Very dilute solution (in order of parts per million, ppm) of drag reducer agent (DRA) is capable of providing large reductions in turbulent pipe flow pressure drop in comparison to that obtained with the pure solvent at the same flow rate. The reduction in pressure drop along the pipeline leads to larger volumes transported for the same pumping energy, or lower power pumps can be used to carry the same flow rate.
At the ALFA Group, the experiments can run in rheometer and pipe to compare their relative capability to reduce torque and pressure drop, respectively. Despite the different flow mode and turbulence level in both methods, a qualitative correlation between their results can be established. The experiments conducted in a rheometer help to quickly select the best drag reducer agent with small sample volume and good accuracy.
e. Instrumentation
Measurements of multiphase flow characteristics are still an issue in several cases. There are plenty of techniques for this but each has its limitations, both in application or in measurement capability, or they cannot be used in real applications. At ALFA, we develop instrumentation for in-lab measurements as resistive and capacitive probes, but also compare then to innovative non-intrusive techniques, such as dynamic pressure characteristics, and even pipe acceleration. These non-intrusive techniques can be used by companies without for interventions or modifications in their piping layouts.