Capillary Number Correlations for Gas-Liquid Systems

Pore-Scale Investigation of Dynamic Immiscible Displacement in Layered Media using Synchrotron X-ray Microtomography

Understanding the dynamics of immiscible fluid in a porous media is critical in many chemical and environmental engineering processes. However, the geological heterogeneity effect on multiphase flow behavior remains unclear. Here, the dynamics of immiscible fluid displacement and entrapment were experimentally demonstrated at pore-level using time-lapse synchrotron X-ray microtomography. A drainage-imbibition experiment was designed using an unconsolidated layered sand pack that comprised coarse sand and fine sand zones. There were significant differences between the two zones, with regard to the temporal variations in fluid saturation and morphological evolution of nonwetting fluid (oil) during imbibition. Highly connected oil clusters in the coarse zone broke up into many small fragments, whereas the cluster in the fine zone remained connected while spanning multiple pores. To further understand the impacts of pore size and connectivity on multiphase fluid dynamics, a new approach that tracks the temporal variation of immiscible fluid in individual pores was conducted. The surface area at the oil-water interface increased during imbibition, which is expected to facilitate mass transfer and surface interactions. Understanding immiscible fluid displacement in layered porous media at the pore-level could lead to more effective environmental remediation.

Droplet Impact on Suspended Metallic Meshes: Effects of Wettability, Reynolds and Weber Numbers

Liquid penetration analysis in porous media is of great importance in a wide range of applications such as ink jet printing technology, painting and textile design. This article presents an investigation of droplet impingement onto metallic meshes, aiming to provide insights by identifying and quantifying impact characteristics that are difficult to measure experimentally. For this purpose, an enhanced Volume-Of-Fluid (VOF) numerical simulation framework is utilised, previously developed in the general context of the OpenFOAM CFD Toolbox. Droplet impacts on metallic meshes are performed both experimentally and numerically with satisfactory degree of agreement. From the experimental investigation three main outcomes are observed—deposition, partial imbibition, and penetration. The penetration into suspended meshes leads to spectacular multiple jetting below the mesh. A higher amount of liquid penetration is linked to higher impact velocity, lower viscosity and larger pore size dimension. An estimation of the liquid penetration is given in order to evaluate the impregnation properties of the meshes. From the parametric analysis it is shown that liquid viscosity affects the adhesion characteristics of the drops significantly, whereas droplet break-up after the impact is mostly controlled by surface tension. Additionally, wettability characteristics are found to play an important role in both liquid penetration and droplet break-up below the mesh.

Study on the Impacts of Capillary Number and Initial Water Saturation on the Residual Gas Distribution by NMR

The determination of microscopic residual gas distribution is beneficial for exploiting reservoirs to their maximum potential. In this work, both forced and spontaneous imbibition (waterflooding) experiments were performed on a high-pressure displacement experimental setup, which was integrated with nuclear magnetic resonance (NMR) to reveal the impacts of capillary number (Ca) and initial water saturation (Swi) on the residual gas distribution over four magnitudes of injection rates (Q = 0.001, 0.01, 0.1 and 1 mL/min), expressed as Ca (logCa = −8.68, −7.68, −6.68 and −5.68), and three different Swi (Swi = 0%, 39.34% and 62.98%). The NMR amplitude is dependent on pore volumes while the NMR transverse relaxation time (T2) spectrum reflects the characteristics of pore size distribution, which is determined based on a mercury injection (MI) experiment. Using this method, the residual gas distribution was quantified by comparing the T2 spectrum of the sample measured after imbibition with the sample fully saturated by brine before imbibition. The results showed that capillary trapping efficiency increased with increasing Swi, and above 90% of residual gas existed in pores larger than 1 μm in the spontaneous imbibition experiments. The residual gas was trapped in pores by different capillary trapping mechanisms under different Ca, leading to the difference of residual gas distribution. The flow channels were mainly composed of micropores (pore radius, r < 1 μm) and mesopores (r = 1–10 μm) at logCa = −8.68 and −7.68, while of mesopores and macropores (r > 10 μm) at logCa = −5.68. At both Swi= 0% and 39.34%, residual gas distribution in macropores significantly decreased while that in micropores slightly increased with logCa increasing to −6.68 and −5.68, respectively.