Bubble Point Research Articles

Isolation of microbubbles beyond Sparrow's resolution limit in super-resolution ultrasonography using phase patterned waves.

 Objective
Super-resolution ultrasonography (SR-US) provides detailed microvasculature images, improving diagnostic precision. However, it typically depends on tacking microbubbles (MBs) used as contrast agents at low concentration. This process requires acquiring a large amount of acoustic data, leading to longer acquisition times. In this paper, we describe a method that allows for the use of higher concentrations of MBs, which reduces the acquisition time and enables high-speed SR-US. Our approach involves isolating and detecting individual MBs even when they are located close to each other, making it possible to use higher bubble concentrations efficiently.

 Approach
In this study, as introduced in previous research, we use phase patterned waves (PPWs) to isolate MBs by adjusting the intensities of each bubble's point spread function (PSF). The PPWs create high and low sound pressure across the lateral plane, optimizing the variation in PSF intensities for MBs positioned side by side. Unlike conventional irradiation method of ultrasound plane waves, PPWs cause significant sound pressure attenuation with increasing axial distance due to destructive interference. This effect allows us to alternate the PSF intensities for MBs aligned along the axial direction. By estimating the positions of MBs in both the lateral and axial directions and combining them into two-dimensional coordinates, we can accurately determine the final positions of the MBs.

 Main results
We applied PPWs and conventional ultrasound irradiation methods to estimate the positions of two MBs, achieving accuracy within 25% of the wavelength from their actual locations, even when the bubbles were closer than Sparrow's resolution limit. Furthermore, using an overlapped PSF model, we improved the accuracy of the estimated positions to within an average of 15% of the wavelength from their true locations, regardless of the number of overlapping MBs or their relative positions.

 Significance
Isolating MBs using PPWs is expected to enable high concentrations of MBs in SR-US, paving the way for high-speed SR-US.

Liquid–liquid equilibrium studies of n‐butane–bitumen system with application to solvent‐aided in situ bitumen recovery

Abstract Solvent‐assisted recovery methods have gained attention as an alternative to conventional thermal methods which have significant environmental drawbacks and high greenhouse gas emissions. Solvent‐assisted recovery methods can lead to various phase equilibria, such as vapour–liquid equilibrium (VLE) and liquid–liquid equilibrium (LLE), under specific thermodynamic conditions. A thorough understanding of this phenomenon is essential for effectively designing and optimizing these processes. Despite the availability of both VLE and LLE for mixtures of solvent‐bitumen systems, LLE data is scarcer, particularly at conditions close to the solvent's saturation pressure. This study reports on LLE measurements of n‐butane–bitumen mixtures at temperatures ranging from 295 to 372 K. The pressures were set just above the solvent's saturation pressure at each temperature to maintain LLE conditions. We examined both the phase behaviour and thermophysical properties of the mixture. The thermophysical properties of the light phase, including density and viscosity, were recorded. The bubble point pressure, n‐butane content in the light phase, heavy phase onset, and detailed characterization of both the light and heavy cuts were also conducted. The experimental thermophysical data were then modelled using the Peng–Robinson equation of state (PR‐EoS) and modified Pederson model. In conclusion, these findings enhance our understanding of the LLE behaviour of n‐butane–bitumen systems under conditions near the solvent's saturation pressure and find plications in solvent‐aided in situ bitumen recovery processes.

An Experimental Investigation of the Effect of Pressure and Salinity on IFT in Live Oil/Brine Systems

Residual oil saturation in reservoirs is primarily influenced by viscous and capillary forces, with interfacial tension (IFT) being a critical factor in fluid distribution due to capillary pressure. Adjusting IFT is essential for enhancing oil recovery, particularly in waterflooding, which is the most common secondary recovery technique after primary production. The salinity of injected water directly affects the IFT between crude oil and brine, making it a crucial factor in optimizing recovery. However, limited studies have examined IFT using live oil samples under actual reservoir conditions. In this study, a high-pressure, high-temperature (HPHT) drop shape analyzer was used to measure the IFT between live oil and brine under reservoir conditions. Five live oil samples and two sodium chloride (NaCl) brine concentrations (30,000 and 100,000 ppm) were tested at a reservoir temperature of 180 °F. Measurements were conducted above the bubble points of the oils, replicating undersaturated reservoir conditions. The results revealed that the impact of pressure on IFT was more complex than that of salinity. IFT generally decreased with increasing pressure but showed mixed behavior across different samples. Conversely, IFT consistently increased with higher salinity. These findings enhance the understanding of IFT behavior under reservoir conditions, supporting improved reservoir simulations and oil recovery strategies.

Bubble point pressures for dimethyl ether – methanol, dimethyl ether – 2-methoxyethanol and dimethyl ether - 2-ethoxyethanol at (293.15-313.15) K, and their predictions considering pair interactions for three functional groups, -CH2OCH2-, -CH2OH and -CH2CH2CH2-

Bubble point pressures for dimethyl ether – methanol, dimethyl ether – 2-methoxyethanol and dimethyl ether - 2-ethoxyethanol at (293.15-313.15) K, and their predictions considering pair interactions for three functional groups, -CH2OCH2-, -CH2OH and -CH2CH2CH2-

Air bubble dispersion imaging in whipping cream with specified fat contents by fuzzy phase classification implemented in electrical impedance tomography

The air bubble dispersion in whipping cream during agitation has been imaged by fuzzy phase classification implemented in electrical impedance tomography (fEIT) for internal morphological structure visualization. The fEIT consists of non-linear conductivity reconstruction and fuzzy phase classification to classify into a probabilistic cluster (: oil-in-water phase, : air bubble). In the experiments, probabilistic air bubble cluster of whipping cream with five milk fat (MF) contents were reconstructed by fEIT during agitation to image the air bubble dispersion. The demonstrated the air bubble dispersion within the sensor area caused by agitation. The spatial average was increased and then decreased due to the incorporation and subsequent departure of air bubbles during agitation. The peak time ts, which represents the critical saturation point of air bubbles, was decreased as MF content increased, which was verified by OR measurement and microscope observation. Compared to reconstructed by EIT influenced by the liquid water phase, fat and air bubbles, reconstructed by fEIT successfully imaged air bubble dispersion in whipping cream. Furthermore, fEIT demonstrated comparable performance to OR measurements in evaluating the internal morphological structure of whipping cream during agitation, while providing the advantage of inline measurement.

Phase Behavior of CO2 + 2,2-dimethylbutane and CO2 + 2-methylpentane from 293 K to 363 K and at Pressures up to 11 MPa

This study is a continuation of a series of works concerning the acquisition of new experimental data related to binary mixtures of branched alkanes with CO2. A synthetic method was employed to measure phase transition pressures for the systems CO2 + 2,2-dimethylbutane and CO2 + 2-methylpentane with an adjustable-volume high-pressure cell. To our knowledge, these binary systems were investigated for the first time in this work. Bubble and dew point pressures were obtained by visual detection at constant composition with an expanded uncertainty ranging from (0.04 to 0.08) MPa. Mixtures were investigated at temperatures ranging from (293.15 to 363.15) K with pressures up to 11 MPa. The Peng-Robinson equation of state was used to correlate the experimental data. An accurate representation of the results has been obtained by using classical mixing rules with temperature-dependent binary interaction parameters regressed against experimental data. The predictive model PPR78 has also provided satisfactory results.

Flow boiling of R448 A inside mini-channel: an integrated experimental and computational investigation

This work investigates the heat transfer of low GWP alternative refrigerant mixture R448A inside multiport mini-channel tubes through both numerical and experimental method. The measured heat transfer coefficient through experiments will be analysed to evaluate the effect of mass flux, and heat flux toward the heat transfer coefficient. A correlation will be provided as a basis for comparison with Computational data. A new mass transfer model for non-azeotropic mixture was developed and applied to simulate the boiling mechanism of R448A. The CFD model is validated through comparison with correlation, while the void fraction is compared against flow pattern observation. Finally, through the mass fraction field, the preference of boiling of more volatile components is shown, which result in the elevation of the bubble points, as well as a layer of mass transfer resistance adjacent to the wall penalizing the evaporation process.

Bubble points and densities of H2 (up to ∼ 5%) in CO2-rich binary systems

Bubble points and densities of H2 (up to ∼ 5%) in CO2-rich binary systems

Bubble point pressure measurement and prediction of VLE and VLLE for dimethyl ether - 2-butoxyethanol and dimethyl ether - water - 2-butoxyethanol at (293.15 to 313.15) K

Bubble point pressure measurement and prediction of VLE and VLLE for dimethyl ether - 2-butoxyethanol and dimethyl ether - water - 2-butoxyethanol at (293.15 to 313.15) K

A Review of the Study of Fluid Phase Behavior at the Confined Scale of Shale Reservoirs: A Theoretical and Experimental Perspective.

The fluids within the pores of shale reservoirs are influenced by nanoscale confinement effects, causing the phase behavior and flow characteristics of the oil and gas systems to deviate from bulk properties. Consequently, conventional phase theory and experimental methodologies are inadequate for studying such confined fluids. The phase characteristics and underlying microscopic mechanisms of oil and gas within confined spaces remain unclear, posing a substantial barrier to the efficient and rational development of shale reservoirs. This paper reviews current theoretical and experimental research on fluid phase behavior under nanoscale confinement in shale reservoirs. It provides a comprehensive discussion of four categories of research techniques, including mathematical models, numerical simulations, indirect measurement experiments, and direct observation experiments, detailing their principles, primary applications, and advantages and limitations. Furthermore, it compares the relationships and differences among these techniques and offers an outlook on the future development of research into the shale fluid phase behavior. Analyses indicate that various research methods can be employed to investigate the phase behavior of fluids at the confined scale of shale reservoirs. However, due to the influence of factors such as research techniques, target materials, and experimental conditions, there is no consensus on the critical pore size responsible for confinement effects, the shift in the critical properties, and the variations in bubble and dew points. The current research adopts the research idea of "theoretical exploration through mathematical modeling, mechanism revelation via numerical simulation, regularity reflection through indirect measurement experiments, and phenomenon demonstration through direct observation experiments" and forms a relatively complete research system of the confined fluid phase behavior of shale reservoir. However, the system still has some limitations and challenges, necessitating further optimization and refinement in future research.

Hydrophilic Polyphenylene Sulfide/Cellulose/Polyphenylene Sulfide Composite Membrane with High Bubble Point Pressure and High Oxygen Purity for Alkaline Water Electrolysis

Hydrophilic Polyphenylene Sulfide/Cellulose/Polyphenylene Sulfide Composite Membrane with High Bubble Point Pressure and High Oxygen Purity for Alkaline Water Electrolysis

Prediction of Formation Compressibility and Secondary Gas Cap Development from Seabed and Downhole Tidal Pressure Signals in the Lancaster Field

The Lancaster Field is the first, and to date only, fractured basement reservoir development on the United Kingdom Continental Shelf. The field produces under natural depletion and at the depth of the wells was initially under-saturated by approximately 300 psi. Reservoir pressure has declined during production and, due to the lack of a gas export route, regulatory approval for ongoing production below the bubble point has been made conditional on no incremental liberated gas being produced to the surface. Estimation of the potential size of any secondary gas cap that develops is a key part of the surveillance required to meet this condition. In this paper we show how analysis of the seabed and downhole tide pressure signals can be used to estimate the pore volume compressibility for the fractured basement reservoir at initial conditions and how the observed changes in the seabed to downhole attenuation can be related to changes in the fluid compressibility and hence gas saturation. The gas saturations predicted from this analysis are compared to those derived from reservoir simulation modelling and show reasonable agreement.

Effect of Reefs and Faults on Oil Reservoir Performance - Case Study: Carbonate Reservoir, Southern Iraq

The study area is located in an unstable region within the Mesopotamian basin of the Arabian plate. It is surrounded by several oil fields that produce hydrocarbons from NW-SE-trending anticline formations, which are compatible with the direction of the Zagros folded axis. The study area is characterized by the presence of bubble point pressure discrepancy at the same productive reservoir unit, which raised several doubts about the faults or reefs that led to this phenomenon and the future impact on the development strategy of the study area. The study aimed to assess how faults and reef affect the development plan for carbonate oil reservoir. The process involves three steps tailored to fit the specific characteristics of the research area before the development strategy of oil production. The first step was creating a seismic model to identify any irregular amplitudes of reflected events and abrupt discontinuities, which could indicate either a reef or a fault. This was followed by creating a geological model based on faults and reef, developing a reservoir model, and conducting historical matching. The study proved the presence of a fault and excluded the presence of a reef. Four development plan scenarios were created for a 20-year period based on the probabilities of the fault and reef. The study found that case four had the most favorable results among all the cases. This case showed a production plateau that lasted for seven years with slight fluctuations.

Temperature, Compositional and Geological Controls on the Formation of Pervasively Saturated Hydrocarbon Accumulations

Abstract Pervasively-saturated hydrocarbon reservoirs is a term used to describe non-conventionally trapped hydrocarbon systems that have greater hydrocarbon saturations than conventionally trapped reservoirs and are typically more aerially extensive. In this paper, we develop a physical model of the geological controls that lead to the formation of this hydrocarbon reservoir system based on pressure, temperature and compositional data. We first focus on the attributes of pervasively-saturated reservoirs (e.g. the association of the updip regional waterline with early to mid-maturity source rocks and lack of oil, gas contacts). Next, we discuss in detail the geological settings of the Leduc, Montney and Viking formations to illustrate the differences between conventionally trapped reservoirs and pervasively-saturated reservoirs in terms of pressure, temperature and fluid composition. Finally, we use pressure, temperature and composition data to understand the phase behavior of the reservoir to build a working model that describes the formation of pervasively-saturated reservoir systems. We show that: capillary pressures cannot lead to the observed high hydrocarbon saturations in low porosity reservoirs; pervasively-saturated Viking reservoirs were, at one time, migration pathways for bubble point oils and dewpoint gases buoyantly migrating from the deep basin; maturation of organic matter during burial leads to hydrolytic disproportionation of organic matter which desiccates the reservoir system and when the water saturation becomes low enough, leads to a loss of hydrocarbon buoyancy and stationary hydrocarbon fluids. Uplift and erosion places the saturated hydrocarbon fluids at greater pressures for their temperature than conventionally trapped reservoir systems, because pressure is controlled by the temperature and the composition of the hydrocarbon fluids. We close with two applications involving the sequestration of CO2 that take advantage of the high reservoir pressures to show that the injected CO2 has little to no buoyancy with respect to the original fluids in place. These results suggest these fluids are unconditionally stable which contrasts with saline aquifer CO2 storage applications where the fluids are unconditionally unstable and will always buoyantly migrate away from the point of injection.

Phase Behavior and Flowing State of Water-Containing Live Crude Oil in Transportation Pipelines

To address the challenges and risks associated with the declining crude yield, an optimization project for the surface production facilities at ZY Oilfield is underway. Upon the completion of this project, the oilfield’s export pipelines will transport water-containing live crude oil. To ensure pipeline transportation safety, it is essential to clarify the phase behaviors and flow state of water-containing live oil. For this purpose, the VLLE characteristics of water-containing live oil were analyzed with Aspen HYSYS V12 software and validated through PVT tests. Additionally, the pressure variations in multiphase flow pipelines under different operating conditions were calculated using the Beggs and Brill–Moody–Eaton method with Pipephase 9.6 software. The results indicated that the bubble point pressure and vapor fraction of water-containing live oil were higher than those of dehydrated dead crude within the operating temperature range. Liquid–gas flow was likely to occur in the presence of low soil temperatures, low oil output, low outlet pressure, high outlet temperatures, or small water fractions, particularly at the pipeline ends. Moreover, the optimized technological processes for stations and pipeline operations were proposed. The findings offer a new approach for the safe transportation of low-output live oil and provide valuable insights for optimizing surface production in aging oilfields.

High-Performance Composite Separator with a Porous Bicontinuous Structure for Alkaline Water Electrolysis.

Alkaline water electrolysis is considered an optimal technology for large-scale production of green hydrogen because of its economic and mature characteristics. The separator plays a crucial role in the alkaline water electrolysis process, as it fulfills the functions of gas separation and electrolyte transport. Nevertheless, the development of advanced separators with low ohmic resistance, high gas barrier ability, and good durability simultaneously remains a major challenge. Here, we first fabricated a series of high-performance composite separators with a porous bicontinuous structure by employing a nonsolvent-induced phase separation technique using a "weak solvent" (a solvent with a low affinity toward the membrane-forming polymer). The unique porous bicontinuous structure endows the membranes with high porosity, narrow pore size distribution with nanopores, and good hydrophilicity. As a result, the composite separator exhibits not only a low area resistance (0.13 Ω·cm2) but also a high bubble point pressure (5.1 bar). The composite separator also displays excellent durability in both long-term electrolysis and alkaline-aging tests.

Reservoir Fluid PVT High-Pressure Physical Property Analysis Based on Graph Convolutional Network Model

In this paper, the high-pressure physical property analysis of reservoir fluid PVT (pressure–volume–temperature) was studied to improve the accuracy and efficiency of reservoir fluid property prediction. Due to the limitations of traditional laboratory measurement and theoretical model prediction methods, the graph convolutional network (GCN) model was introduced in this paper, and the enhanced ChebNet model was used to analyze the complex relationship between the high pressure physical property parameters. The key parameters such as bubble point pressure, volume coefficient, and crude oil viscosity were accurately predicted by using Chebyshev polynomial approximation and the matrix product optimization ChebNet model, which was constructed to represent the high pressure physical property parameters and their relationships. The experimental results showed that compared with linear regression, linear discrimination, random forest, and ordinary ChebNet models, the enhanced ChebNet model introduced in this paper presented significant advantages in evaluation indicators, and the AUC value reached the optimal value. This paper provides a new perspective and method for reservoir fluid PVT high-pressure physical property analysis and explores a new possibility for the application of graph convolutional networks in oil and gas exploration and development.

Experimental study of bubble flow dynamics in an asymmetric hierarchical porous structure

Porous media have been widely used for liquid–gas separation, benefiting from the strong capillary force generated by micro/nanoscale pores. Understanding the flow characteristics at the pore scale is important for the design of porous structures. In this study, the flow mechanisms of an isolated bubble in an asymmetric hierarchical pore were investigated by high-speed flow visualization and microscopic particle image velocimetry (Micro-PIV). The influence of the hierarchical pore on the flow field in the liquid and the dynamics of bubble penetration was investigated using isopropyl alcohol as the test liquid and polydimethylsiloxane micromodels. The critical pressure for the bubble to break through the pore was determined. The results show that the presence of secondary microstructure can increase the critical bubble point pressure by 79.7%. Meanwhile, the attack angle of the microstructure affects the critical pressure differently by changing the pinning effect, the curvature of the bubble as well as the flow field. The results of this work could provide guidance for optimizing the design of porous media for efficient gas–liquid separation.

The migration mechanism of oil under natural depletion development for shale oil in Ordos Basin

The primary driving energies during the natural depletion development process in shale oil are rock and fluid elastic energy, as well as dissolved gas energy. The release times of these energies significantly affect the flow feature of oil, gas, and water in the pore throat space, thereby impacting the oil recovery. This study elucidated the microscopic migration mechanisms of oil under various driving energies through physical simulation experiments utilizing self-developed nuclear magnetic resonance (NMR) technology and high-temperature high-pressure micro-visualization methods (HTHPMF). Additionally, the contribution of different driving energies to recovery in the natural depletion development process was quantitatively characterized using the new material balance model and numerical simulation. The findings indicated that: (1) The oil flow in pore space exhibited three distinct stages of exploitation during the natural depletion development., namely the elastic drive stage, the transition stage, and the dissolved gas drive stage, with about 70% oil coming from the macro-pores. (2) The elastic energy of rock and oil, as well as dissolved gas energy in the transition stage were mainly driving energies during the nature depletion development process. Continuous dissolved gas drive stage was found to be unfavorable for reservoir development. (3) The reasonable bottomhole flowing pressure should be controlled to be near the bubble point pressure so as to maximize the utilization of various driving energies. This study provided a basis for formulating a reasonable production system for shale reservoirs during the nature depletion development process.

Large eddy simulation of spray evaporation characteristics of alcohol-based fuels based on modified evaporation model with UNIFAC

Large eddy simulation of spray evaporation characteristics of alcohol-based fuels based on modified evaporation model with UNIFAC