Micro-bubble Fluid Research Articles

Experimental Investigation on the Impacts of Fracture Roughness and Fluid Composition on the Formation of Bubble Bridges through the Microbubble Fluid Flow.

The colloidal gas Aphron (CGA) drilling fluids are an alternative to ordinary drilling mud to minimize formation damage by blocking rock pores with microbubbles in low-pressure or depleted reservoirs. Fractured formations usually have different characteristics and behavior in contrast to conventional ones and need to be investigated for Aphron applications. In this research, a series of core flood tests were conducted to understand the factors controlling the pore-blocking mechanisms of microbubbles in fractured formations. For the first time, a synthetic metal plug was used to simulate the fracture walls and eliminate the formation matrix effect. This study analyzed the effects of three fluid compositions, considering the polymer and surfactant concentrations at reservoir conditions, including temperature and overburden pressure. Additionally, fracture surface roughness as one of the parameters affecting the microbubble fluid penetration through the fracture path and bubble blockage were studied. The results indicated that microbubble fluid composition would not affect the bubble size or blockage probability. The different stable microbubble fluids resulted in the same pattern and conditions. Besides, fluid penetration would be more challenging if the fracture roughness decreased. Due to the accumulation of bubbles and the fact that some of them were trapped in the fracture's rough surface, the blockage possibility increased. According to the range of roughness for the steel core in previous studies and compared with the roughness of carbonate reservoir rocks, the roughness of fractured reservoir rocks is much higher than that of the steel surface. Accordingly, the observed trend in the experiments showed that when it is possible to form a bubble bridge in steel cores, then in carbonate rocks, we will definitely see blockage with any roughness, provided that other parameters are acceptable.

Mechanistic Study of Micro-bubble Fluid Infiltration through the Fractured Medium.

Drilling in depleted reservoirs has many challenges due to the overbalance pressure. Another trouble associated with overbalance drilling is differential sticking and formation damage. Low-density drilling fluid is an advanced method for drilling these depleted reservoirs and pay zones with different pressures to balance the formation pore pressure and hydrostatic drilling fluid pressure. This study investigated the infiltration of a micro-bubble fluid as an underbalanced drilling method in fractured reservoirs. A novel method has been presented for drilling permeable formations and depleted reservoirs, leading to an impressive reduction in costs, high-tech facilities, and drilling mud invasion. It also reduces mud loss, formation damages, and skin effects during the drilling operation. This paper studied micro-bubble fluid infiltration in a single fracture, and a synthetic metal plug investigated the bridging phenomenon through the fractured medium. Moreover, the effects of fracture size, bubble size, and a pressure differential of fracture ends have been thoroughly analyzed, considering the polymer and surfactant concentrations at reservoir conditions, including the temperature and overburden pressure. In this study, nine experimental tests were designed using the design of experiment, Taguchi method. The results indicated that higher micro-bubble fluid mixing speed values make smaller bubbles with lower blocking ability in fracture (decrease the chance of blocking more than two times). On the other hand, a smaller fracture width increases the probability of bubble bridges in the fracture but is not as crucial as bubble size. As a result, drilling fluid infiltration in fractures and formation damages decreases in the condition of overbalanced drilling pressure differences of about 200 psi.

Experimental investigation on plugging performance of CO2 microbubbles in porous media

To further improve carbon dioxide enhanced oil recovery CO2-EOR efficiency in heterogeneous reservoirs, the use of CO2 microbubbles as a temporary blocking agent is attracting widespread interest due to their significant stability. This study aims to investigate the plugging performance of CO2 microbubbles in both homogeneous and heterogeneous porous media through a series of sandpack experiments. First of all, CO2 microbubble fluids were generated by stirring CO2 gas diffused into polymer (Xanthan gum (XG)) and surfactant (Sodium dodecyl sulfate (SDS)) solution with different gas: liquid ratios. Then, CO2 microbubbles fluids were injected into single-core and dual-core sandpack systems. The results show that the rheological behaviors of CO2 microbubble fluids in this study were followed the Power-law model at room temperature. The apparent viscosity of CO2 microbubble fluid increased as the gas: liquid ratio increased. CO2 microbubbles could block pore throat due to the “Jamin effect” and increase the resistance in porous media. The blocking ability of CO2 microbubbles reached an optimal value at the gas:liquid ratio of 20% in the homogeneous porous media. Moreover, the selective pugging ability of CO2 microbubbles in dual-core sandpack tests was significant. CO2 microbubbles exhibited a good flow control profile in the high permeability region and flexibility to flow over the pore constrictions in the low permeability region, leading to an ultimate fractional flow proportion (50%:50%) in the dual-core sandpack model with a permeability differential of 1.0:2.0 darcy. The fractional flow ratio was considerable compared with a polymer injection. At the higher heterogeneity of porous media (0.5:2.0 darcy), CO2 microbubble fluid could still establish a good swept performance. This makes CO2 microbubble fluid injection a promising candidate for heterogeneous reservoirs where conventional CO2 flooding processes have limited ability. This finding would be helpful in developing the utilization of CO2 microbubbles in EOR operation by better understanding their plugging mechanism in porous media.

Numerical and experimental investigation of micro-bubble fluid infiltration in porous media

The current limited availability of the easy access crude oil reservoirs shifted the focus of the petroleum industry towards the production of heavy oil and depleted reserves. Micro-bubble fluids (colloidal gas aphrons) have been recently used as part of water and oil based drilling fluids and have proven to effect the reduction of formation damages. However, this study presents a micro-bubble transient flow model using a finite difference method of modified implicit in pressure, explicit in saturation and the forward difference, one-point upstream weighting method for surfactant concentration calculation. The saturation and pressure profile for each phase, the concentration profile for surfactant and non-adsorbing tracer, effluent, and pressure drop history can be determined by the model. According to the pressure drop history, the micro-bubble fluid apparent viscosity can be obtained. Accordingly, the proposed model was validated with some experimental tests which were designed by the Taguchi method.

Mathematical modeling of the colloidal gas aphron motion through porous medium, including colloidal bubble generation and destruction

Recently, micro-bubble (colloidal gas aphrons) has been widely applied as a drilling fluid, especially for depleted reservoirs, or as a mobility control agent for enhanced oil recovery methods. Our study is focused on transient micro-bubble flow in the homogeneous porous medium. There is one idea that the micro-bubble fluid viscosity and its mobility depend on the bubble density in the fluid, and this is the concept of the bubble population balance models. This study presents an improved micro-bubble transient flow model using motion equation coupled with the bubble population balance equation, to model generation, convection, and destruction of gas bubbles along the porous medium. The presence of micro-bubbles controls the invasion of the fluid to the porous medium.

Modeling of micro-bubble surfactant multi-layer drilling fluid stability based on single bubble behavior under pressure and temperature in a deviated gas well

Micro-bubble surfactant multi-layer (MBSML) drilling fluids are included in the drilling operation of low pressure reservoirs. These fluids contain tiny dispersed micro-bubbles coated with two surfactant layers. For the stability evaluation of these fluids in operational conditions, surfactant type, concentration, pressure and temperature effects on the size of micro-bubble fluid, should be scrutinized. For investigating these variables, a diffusion model for solute transport in micro-bubble fluids was proposed with the mass transfer concept. The model included mass transfer resistance of fluid phases and interfaces. It was observed that the bubble sizes decrease as a result of adding surfactant to the fluid. However, there were pressure, temperature and surfactant concentration thresholds for the bubble stability.

Oxygen supersaturated fluid using fine micro/nanobubbles.

Microbubbles show peculiar properties, such as shrinking collapse, long lifetime, high gas solubility, negative electric charge, and free radical production. Fluids supersaturated with various gases can be easily generated using microbubbles. Oxygen microbubble fluid can be very useful for oxygen delivery to hypoxic tissues. However, there have been no reports of comparative investigations into adding fluids containing oxygen fine micro/nanobubbles (OFM-NBs) to common infusion solutions in daily medical care. In this study, it was demonstrated that OFMNBs can generate oxygen-supersaturated fluids, and they may be sufficiently small to infuse safely into blood vessels. It was found that normal saline solution is preferable for generating an oxygen-rich infusion fluid, which is best administered as a 30-minute intravenous infusion. It was also concluded that dextran solution is suitable for drug delivery substances packing oxygen gas over a 1-hour intravenous infusion. In addition, normal saline solution containing OFMNBs was effective for improving blood oxygenation. Thus, the use of OFMNB-containing fluids is a potentially effective novel method for improving blood oxygenation in cases involving hypoxia, ischemic diseases, infection control, and anticancer chemoradiation therapies.

Pulsatory rise of microbubble swarm along a vertical wall

Based on the experimental finding that microbubble swarms dramatically promote heat transfer from a vertical heated wall, despite their potentially adiabatic nature, tests of microbubble fluid mechanics in the isothermal state are performed to clarify the unique motion characteristics of microbubble swarms. At constant bubble flow rate, the microbubble swarm shows a significant pulsatory rise along a vertical flat wall, particularly for small bubbles. Particle tracking velocimetry applied to the microbubbles shows that a two-way interaction between the microbubbles and the liquid flow self-excites the pulsation during their co-current rise. The sequence consists of the following processes: (i) increase in the bubble number density close to the wall as a result of the liquid velocity gradient driven by the microbubbles themselves; (ii) wave generation inside the microbubble swarm to induce the pulsatory rise of the swarm; and (iii) amplification of the waves, which results in void-bursting motion in the final stage.

Blood oxygenation using microbubble suspensions

Microbubbles have been used in a variety of fields and have unique properties, for example shrinking collapse, long lifetime, efficient gas solubility, a negatively charged surface, and the ability to produce free radicals. In medicine, microbubbles have been used mainly as diagnostic aids to scan various organs of the body, and they have recently been investigated for use in drug and gene delivery. However, there have been no reports of blood oxygenation by use of oxygen microbubble fluids without shell reagents. In this study, we demonstrated that nano or microbubbles can achieve oxygen supersaturation of fluids, and may be sufficiently small and safe for infusion into blood vessels. Although Po(2) increases in fluids resulting from use of microbubbles were inhibited by polar solvents, normal saline solution (NSS) was little affected. Thus, NSS is suitable for production of oxygen-rich fluid. In addition, oxygen microbubble NSS effectively improved hypoxic conditions in blood. Thus, use of oxygen microbubble (nanobubble) fluids is a potentially effective novel method for oxygenation of hypoxic tissues, for infection control, and for anticancer treatment.

J055015 トロコイドギヤによる非ニュートン流体のポンピング機構の可視化([J05501]混相流の多次元ビジュアリゼーション～流動場の光・電磁場・超音波センシング～)

Flow inside a Trochoid gear pump for microbubble fluids is visualized using Kalliroscope flakes to grasp the effect of adding microbubbles on the flow structure. Upon taking phase-statistics for the time serial images, average brightness and standard deviation varying with Reynolds number are obtained. At Re = 2000, the turbulence occurs due to jets of counter flow in enclosed unit. The turbulence is, however, alleviated by the addition of microbubbles: turbulent component is weakened by adding microbubbles. Critical Reynolds number for turbulent flow transition is increased by adding microbubbles. It indicates that the pump volume efficiency may be improved by keeping the laminar flow state in the enclosed unit even at higher Reynolds numbers than in single phase conditions.

Milliseconds microfluidic chaotic bubble mixer

In this study, we report a rapid microfluidic mixing device based on chaotic advection induced by microbubble–fluid interactions. The device includes inlets for to-be-mixed fluids and nitrogen gas. A side-by-side laminar flow segmented by monodisperse microbubbles is generated when the fluids and the nitrogen are co-injected through a flow focusing micro-orifice. The flow subsequently enters a series of hexagonal expansion chambers, in which the hydrodynamic interaction among the microbubbles results in the stretch and fold of segmented fluid volumes and rapid mixing and homogenization. We characterize the performance of the microfluidic mixer and demonstrate rapid mixing within 20 ms. We further show that bubbles can be conveniently removed from the mixed fluids using a microfluidic comb structure on completion of the mixing.