Evaluation of the Effect of Phase Sliding on the Density of Multiphase Mixtures in Vertical Pipes
Authors: Ismayilov Gafar Q. , Ismayilova Fidan B. , Habibli Punhana A. 
Published: November 2024

In oil and gas production, mainly during the development of offshore hydrocarbon fields, the extraction, gathering and transportation of oil and gas are often associated with gravitational, vertical upward and downward flows. Thus, such flows are common during the extraction of well product and movement of multiphase mixtures from seabed to the platform and vice versa through the vertical submarine oil and gas pipelines connecting offshore platforms.

Predicting, modeling and analyzing two-phase flows is one of the challenging issues in the oil and gas industry. Thus, due to phase fluctuations, drifts and interactions, combined chaotic and dissipative flows, the study becomes difficult and requires special sensitivity. Therefore, Wire-mesh Sensor (UMS) is used in the study of horizontal gas-liquid two-phase flows. [1]

During the gravitational movement of multiphase flows in vertical pipes, different flow patterns are formed and their physicochemical and rheological properties vary significantly along the flow. The diameter of the pipe, the physical properties of the flowing fluid, the flow rate all together create the structure of the flow patterns. There are two types of flow here, bubble and mist. At low values of velocity and gas-liquid ratio, bubble flow occurs, and at high values, mist flow occurs. Liquid-gas ratios also divide phases into two forms: continuous and dispersed. The dispersed phase is characterized by a low value of the ratio, and the continuous phase is characterized by a high ratio of liquid-gas mixture. [5]

In the paper is given a study on change of the density of a multiphase mixture depending on the phase slippage in the form of a bubble (dispersed) flow.

How the density of the gas-liquid mixture changes during the vertical upward movement of the gas-liquid mixture, taking into account the sliding effect has been studied, a monotonous increase in the density of the mixture depending on the relative velocity of the gas relative to the liquid for different values of gas volumetric flow rate in vertical pipes has been determined.

In the paper, it is also shown that the dispersion of the gas varies depending on the size of the bubbles distributed in the liquid as a result of changes in the mode of motion of the gas-liquid mixture during its movement in a vertical pipe.

As the gas bubbles agglomerate together with the pressure decreases, they also change the flow pattern. It is no coincidence that in many cases, in long vertical pipes, the bubble flow regime is transformed into a slug and then into a churn flow.

As the hydrostatic pressure increases due to the aggravation of the multiphase mixture as a result of phase slippage, the total pressure loss during upward multiphase flow also increases.

In the paper the use of a relatively small diameter vertical pipe to increase the fluid flow rate in order to reduce the slippage effect is also suggested or to form several streams by creating vortices along the length of the pipe during the flow. In this case, the importance of special calculations related to losses and justification of the diameter was noted.