Gas-liquid Ratio Research Articles

Gas and slurry flow behaviors in a CO2‐mineralization spray tower reactor

AbstractThe spray tower reactors have provided an important solution for the scale‐up of mineralization processes with industrial solid waste to absorb CO2. In this study, numerical simulations were employed to investigate the fluid flow behaviors in a mineralization spray tower reactor (MSTR), and the average relative error of simulation and experimental results was 7.5%. The results showed that at a high liquid–gas ratio (L/G > 100 L/m3), the fluid flow behavior was dominated by the slurry flow, which was only hindered by the gas flow to a certain extent at the gas inlet. Further analysis revealed that the accumulation of slurry at the center and wall of the reactor, as well as the bias flow of flue gas, were the main reasons for the insufficient gas–liquid contact, which led to a lower CO2 absorption efficiency. The relationship between fluid flow behavior and CO2 absorption efficiency could improve the understanding of the MSTRs.

Research progress on the influencing factors and enhancement mechanism of CH4/CO2 mixture separation process by hydrate‐based technology: A review

AbstractThe separation of mixed gas by hydrate method can realize the efficient separation of CO2 gas from biological gas. However, the long period, slow rate, and low selectivity of hydration reaction have become the critical problems restricting the efficient separation of the gas mixture by hydrate method. In this review, the formation characteristics of CH4/CO2 mixed gas hydrate are systematically summarized, and the kinetic process and influencing factors of CH4/CO2 mixed gas hydrate formation are comprehensively analyzed. On this basis, the influence mechanism and law of temperature, pressure, gas–liquid ratio, gas component ratio, additives, and other factors on the CH4/CO2 mixed gas hydrate formation progress were described in detail, and the enhancement mechanism of CH4/CO2 mixed gas hydrate formation under the influence of different factors was analyzed. Finally, the shortcomings and future development directions of the purification and separation technology of CH4/CO2 mixed gas by hydrate method are pointed out. Further research is needed to understand the kinetic mechanism and enhancement mechanism of the CH4/CO2 mixture separation process by hydrate method. The relative results will provide valuable guidance for the separation of mixture gas by a hydrate‐based method.

Investigation of Gas-liquid Separation Experiment of Electric Pump Drainage and Gas Extraction Unit in High Gas-liquid Ratio Gas Wells

Given the prominent problem of water in the Tarim basin of China with high formation temperature and large water production, a preferred scheme of electric pump drainage and gas extraction unit for gas fields with a high gas-liquid ratio is proposed by the mechanical principle and structural design method. Then, the corresponding electric pumps were developed, and the drainage and gas extraction scheme of a permanent magnet electric pump unit with gas-liquid separation in the way of an inverted deflector is designed. Through indoor experiments simulating the downhole gas-liquid ratio environment, the gas-liquid separation ability and adaptability of the design scheme under different good conditions are verified. The results obtained demonstrate that the cable connection process can meet the requirements of high-pressure resistance (≥25 MPa), and the gas-liquid separation effect is very good in vertical wells by adopting the inverted deflector scheme. The separation effect exceeded 90% under different working conditions (production from 30 to 150 m3/day and inhalation gas-liquid ratio from 50% to 95% and even higher) in the experiment with high gas content. The results will promote the gas recovery rate of high gas-liquid ratio gas fields and improve extraction efficiency.

Experimental Study on Enhanced Oil Recovery Effect of Profile Control System-Assisted Steam Flooding.

Steam flooding is an effective development method for heavy oil reservoirs, and the steam flooding assisted by the profile control system can plug the dominant channels and further improve the recovery factor. High-temperature-resistant foam as a profile control system is a hot research topic, and the key lies in the optimal design of the foam system. In this paper, lignin was modified by sulfonation to obtain a high-temperature-resistant modified lignin named CRF; the foaming agent CX-5 was confirmed to have good high-temperature foaming ability by reducing the surface tension; the formula of the profile control system (A compound system of CRF and CX-5, abbreviated as PCS) and the best application parameters were optimized by the foam resistance factor. Finally, the effect of PCS-assisted steam flooding in enhanced oil recovery was evaluated by single sand packing tube flooding, three parallel tube flooding, and large-scale sand packing model flooding experiments. The results show that CX-5 has a good high-temperature foaming performance; the foam volume can reach more than 180 mL at 300 °C, and the half-life is more than 300 s. The optimal PCS formulation is 0.3 wt% CRF as an oil displacement agent + 0.5 wt% CX-5 as a foaming agent. The optimal gas-liquid ratio range is 1:2 to 2:1, and the high pressure and permeability are more conducive to the generation and stability of the foam. Compared with steam flooding, PCS-assisted steam flooding can improve oil recovery by 9% and 7.9% at 200 °C and 270 °C, respectively. PCS can effectively improve the heterogeneity of the reservoir, and increase the oil recovery of the three-parallel tube flooding experiment by 28.7%. Finally, the displacement results of the sand-packing model with large dimensions show that PCS can also expand the swept volume of the homogeneous model, but the effect is 9.46% worse than that of the heterogeneous model.

Thermodynamic performance analysis of a novel integrated energy cascade system of liquid air energy storage and two-stage organic Rankine cycles

Liquid air energy storage can enhance the absorptive capacity for renewable energy due to its high energy storage density and extensive application scenarios. This paper proposes an integrated cascade energy system including liquid air energy storage, two-stage organic Rankine cycle, organic Rankine cycle, liquid natural gas regasification and absorption heat pump/chiller to use waste heat and liquid natural gas's cold energy fully and improve the round-trip efficiency. The waste heat of liquid air energy storage and the cold energy of liquid natural gas could increase the temperature and condense the working fluid of organic Rankine cycles. The system's thermodynamic model in design and off-design conditions are established. The charge and discharge minimum loads of liquid air energy storage are 82.5 % and 33.5 %, respectively. The round-trip efficiency of liquid air energy storage obtains a maximum of 49.6 % and a minimum of 29 % in the load ranges. Based on the load changes, the effects on the organic Rankine cycle are discussed, and four control strategies are proposed to absorb the waste heat and cold energy efficiently under off-design conditions. Besides, the organic Rankine cycles are affected by the mass flow of liquid natural gas and split ratio, which are discussed, and its underlying causes are analyzed. The results show that the integrated cascade energy system's round-trip efficiency reaches a maximum of 80.3 % in design conditions and a minimum of 62.7 % in off-design conditions, increasing by 61.9 % and 116.2 %, respectively.

End-to-end machine-learning for high-gravity ammonia stripping: Bridging the gap between scientific research and user-friendly applications

The removal and recovery of ammonia from wastewater are critical processes for achieving global environmental sustainability and promoting circular economic development. High-gravity technology is an advanced solution to achieve ammonia stripping from wastewater. This study used machine-learning (ML) techniques to provide more comprehensive insights on various influencing factors, including the operating parameters, wastewater characteristics, and design parameters of rotating packed beds. Bayesian auto-optimization combined with a boosting algorithm effectively overcame the challenges of modeling complex datasets with small sample sizes, multidimensional data, missing values, and skewed distributions. Accurate ML based predictive models for the ammonia removal efficiency (η) and mass transfer coefficient (KLa) were developed, the performance on the training set was R2 = 0.98 and R2 = 0.89, and on the testing set was R2 = 0.98 and R2 = 0.82. The developed model revealed that the stripping stage and gas-liquid ratio were the most influential features for predicting η, whereas the liquid flow and high-gravity factor were the most important features for predicting KLa. The well-trained model was then deployed in an online software application that could provide both predictive and auto-update functions for operators and managers, ensuring that practitioners could use the model. The end-to-end machine-learning approach used in this study—that is, covering data collection, model development, and application—could improve the availability of research results, providing valuable references for the further advancement of technology in the field of environmental.

Distribution law of Taylor bubble/liquid slug length in oil–gas–water slug flow and the measurement of gas/liquid flow rates based on thermal diffusion

A novel online, non-separation, non-intrusive method based on thermal diffusion is proposed to measure the gas and liquid flow rates of oil–gas–water slug flow in this paper. Temperature fluctuations of a heated pipe wall induced by Taylor bubbles (TB) and liquid slugs (LS) are presented, and velocities and lengths of TB and LS are measured based on these temperature fluctuations. Meanwhile, the number of slug units required to calculate the average TB/LS length is analyzed, and the effect of gas/liquid superficial velocity, oil cut, and gas–liquid ratio on the TB/LS length distribution are respectively presented. The length ratio of TB and LS is found to be linearly and positively correlated with the gas–liquid ratio, which is independent of gas/liquid superficial velocities and oil cuts. Moreover, a simple and reliable model is built to directly associate the TB/LS velocity and length with the gas/liquid flow rates. Experimental results indicate that this proposed method is effective and accurate with root-mean-square errors of 0.025 and 0.052 m3/h for the calculated gas and liquid flow rates, respectively. The flow rate method based on thermal diffusion is simple, cheap, and radiation-free, and it provides a potential solution for the gas/liquid flow rate measurement of oil–gas–water three-phase flows.

Experimental investigation on the thermal and flow performance of a thermodynamically-balanced packed bed humidification system

In this paper, a packed bed humidification system filled with corrugated wire mesh was experimentally investigated to obtain a better humidification performance. To thermodynamically balance the simultaneous heat and mass transfer process, multiple water injection bypasses were fabricated at different packing heights based on the entropy generation minimization method. In addition to the inlet water temperature, the influences of the liquid–gas ratio and injection ratio on the humidification capacity, energy effectiveness, and pressure drop were respectively studied and discussed. The experimental and comparison results demonstrated that the established humidification device was robust and superior. It was summarized that raising the number of injections can significantly elevate the humidification capacity, and synchronously magnify the pressure drop for all the cases, while the effectiveness behaved a reverse trend. Additionally, a higher value of the inlet water temperature could increase the humidification capacity and effectiveness, as well as the pressure drop. And, an elevation amplitude of the humidification capacity emerged as 35.51% for the double water injections with a maximum value of 1.48 × 10−2 kgs−1 once the liquid–gas ratio increased from 1 to 1.36, while the value was 39.13% as the injection ratio raised from 0.33 to 0.7. Furthermore, it was illustrated that increasing the mass flow rate of the liquid will reduce the effectiveness when the heat capacity rate ratio is larger than 1, and the effectiveness can reach 0.97 at Twi = 70 °C. In the process of thermodynamic balancing, the increase in the pressure drop of humid air should receive more attention for the designer and researcher related to the packed bed humidifier.

Flow and plugging behavior of foams in fractures of fractured reservoirs

The development of fractured reservoirs can benefit from the use of foams, as they can enter fractures to increase the flow resistance of high-permeability zones, thereby redirecting fluid flow toward low-permeability zones. This can reduce the leak-off of working fluids during flow and improve the reservoir stimulation efficiency. The fracture visualization models applicable to micro-scale foam flow are developed to fully reveal the flow and plugging behavior of foams in micro-fractures. The models are accompanied by the implementation of the micro-fracture foam flow experiments. The experiment results show that with the increasing flow rate and foaming agent concentration, foams become smaller, more homogeneous, stable, and capable of plugging micro-fractures. However, both significantly large and small gas-liquid ratios degrade these properties of foams. For optimal results, a gas/liquid flow rate of 100–150 μL/min, a gas-liquid ratio of 2–4, and a foaming agent concentration of higher than 0.75 wt% are recommended. During foam flow, foams preferably enter wider fractures, where they accumulate and become trapped, plugging the flow channels. This results in a diversion of the subsequent foams towards narrower fractures, leading to more effective plugging of the fractures.

Study on effective phase interfacial area at different injection angles of hydro-jet cyclone

In contrast to conventional tower-type mass transfer equipment, the hydro-jet cyclone exhibits superior mass transfer capabilities. This study presents a novel investigation into the effective phase interfacial area (ae) of the hydro-jet cyclones across five unique injection angles. The investigation employs a combination of CFD simulations and experimental analysis utilizing a CO2-NaOH system. The results indicate that the 45° upward incidence angle yields the most favorable flow field characteristics for efficient mass transfer when liquid–gas ratio ranges from 0.18 to 0.27. The ae values of the hydro-jet cyclones range from 1846 to 5358 m2·m−3, representing an approximate fivefold increase compared to the rotating packed tower. Empirical formulas for ae are proposed for both vertical incidence and upward 45° incidence angles. This significant enhancement in ae offers the advantage of reducing the equipment volume of the hydro-jet cyclone, leading to substantial cost savings in terms of investment and auxiliary devices.

Research and Practice of Heavy Oil Hydraulic Pump Lifting Technology in Bohai Bay K Oilfield

In the early stage of heavy oil reservoir development in Bohai Bay K Oilfield, crude oil viscosity is high, conventional lifting processes have poor adaptability, and production energy consumption is high; Entering the stage of ultra-high water cut development, the company implemented carbon dioxide huff and puff, the difficulties in lifting matching brought about by the integrated wellbore requirements of injection and production, high gas-liquid ratio lifting, and enhanced corrosivity of the produced fluid. It conducted research on concentric dual/single pipe hydraulic lifting technology for heavy oil reservoirs, and conducted field practice. The research results and field practice show that the hydraulic pump lifting technology has good adaptability for both heavy oil sand production wells and heavy oil carbon dioxide huff and puff wells, effectively reducing the energy consumption of heavy oil lifting, significantly extending the pump inspection cycle of heavy oil sand production wells, significantly improving the lifting adaptability of carbon dioxide huff and puff wells, and has high promotion value in similar reservoirs and single wells.

Numerical Simulation and Experimental Investigation of Variable Mass Flow in Horizontal Wellbores: Single-Phase and Multiphase Analysis

Considering the current limitations and restricted scope of existing experiments, as well as the absence of corresponding numerical simulation verifications and comparisons, and the lack of actual case studies of variable mass flow calculation and comparison, this study focuses on high production oilfields in the Mideast and South China Sea. The objective is to investigate single-phase and multiphase variable mass flow through numerical and experimental simulations. The study develops linear regression equations to establish the relationship between the mixture pressure drop caused by side flow and the velocities of the main flow, as well as the ratio between side and main flow velocities. Actual calculations using these equations are provided. The comprehensive analysis reveals that, for a fixed total flow rate, an increase in the side versus main injection velocity ratio leads to an increase in pressure loss before and after the injection hole. In single-phase flow, the friction factor for side hole flow is generally higher than that for only axial main flow, with the same total flow rate. In multiphase flow, when the gas-liquid ratio (GLR) is relatively large, the side flow has minimal impact on pressure drop, while at lower GLR values, the side flow significantly increases the pressure drops. When predicting the pressure drop for single-phase variable mass flow in horizontal wellbores, it is appropriate to consider only the mixture pressure drop caused by the closest hole to the calculation section, assuming the injection hole flow rates are approximately equal. In terms of predicting the productivity of single-phase variable mass flow, it is crucial to consider the mixture pressure drop. Neglecting the mixture pressure drop can lead to relatively larger productivity prediction results, with potential production rate errors exceeding 50%. The accuracy of the prediction is influenced by the ratio of mixture pressure drop to production pressure differential, and the pressure along the external zone of the screen pipe is higher when considering the mixture pressure drop compared to when it is neglected. Additionally, the flow rate along the external zone of the screen pipe becomes more non-uniform when the mixture pressure drop is considered. Furthermore, the findings from the single-phase and multiphase flow experiments suggest that significant deviations in production rates may occur in scenarios with low gas-liquid ratio (GLR), highlighting the need for further investigation in this area.

Prediction of Liquid Holdup in Horizontal Gas Wells Based on Dimensionless Number Selection

Abstract Pressure gradient prediction is crucial in gas well analysis. The experiment is the most effective method of understanding the flow characteristics in horizontal gas wells. The greatest difference between experimental and high-pressure conditions is gas density, which could cause the established multiphase correlations unreliable when they are applied to high-pressure gas wells. Similarity numbers are widely employed in predicting flow behavior. Nevertheless, few studies focused on this area. In addition, gas wells are characterized as high gas–liquid ratio; the majority empirical correlations were developed for oil wells, which have more consideration in low gas–liquid ratio, influencing the precision of gas well models. An experimental examination of gas–liquid flow has been carried out in this study. First, the experimental test matrix was designed to meet each flow pattern. Next, the effect of gas velocity, liquid velocity, pipe diameter, water-cut, and inclined angle on liquid holdup was explored. Subsequently, the similarity numbers suggested have been investigated and assessed for pressure scaling up. Finally, a comprehensive model was established, which was developed to forecast pressure gradient in gas wells. Field data were supplied to assess the new correlation. The results demonstrated that the Duns–Ros and the modified Duns–Ros dimensionless numbers were improper for pressure scaling up, whereas the Hewitt–Robert Number performs best. Based on the field data, the new correlation with Hewitt–Robert Number was superior to extensively employed pressure drop correlations, showing that it can deal with predicting pressure gradient in gas wells.

The Effect of Ambient Pressure and Gas–Liquid Ratio on the Spray Characteristics of an Effervescent Atomizer

The Effect of Ambient Pressure and Gas–Liquid Ratio on the Spray Characteristics of an Effervescent Atomizer

Research on heat and mass transfer characteristics of a counterflow wet cooling tower using a new type of straight wave packing

In this paper, a new type of straight wave packing is developed for the purpose of improving the heat and mass transfer characteristics of counterflow wet cooling towers. Experimental studies and numerical simulations are carried out to explore the effects of inlet air velocity, water drenching density, gas-liquid ratio and packing height on the heat and mass transfer characteristics of cooling towers. According to research, the novel packing's cooling efficiency increased by 14.4% when compared to the conventional straight wave packing. This is a more substantial effect, and it offers a new plan for the cooling tower's heat transfer that can direct engineering practice. Combined with the analysis of the actual tower operating conditions, it is found that the higher the height of the packing, the easier it is to meet the cooling task, and the smaller the reasonable gas-liquid ratio and air volume required, the maximum air volume can be saved by 30%.

Laboratory tests and field pilot of foam-assisted deoxidized-air flooding in a low-permeability sandstone reservoir

Foam-assisted deoxidized-air flooding is a promising technique for improving oil recovery, particularly in low-permeability oil reservoirs. However, significant differences in displacement efficiency have been observed. A comprehensive program including field pilot analysis in Wuliwan oil reservoir, a low-permeability reservoir in China, and laboratory experiments was initiated to investigate the displacement mechanism of foam-assisted deoxidized-air flooding. We carried out a series of laboratory experiments of foam-assisted deoxidized-air flooding with different gas–liquid ratios at different water cut stages, while using nuclear magnetic resonance technology to monitor the distribution of crude oil in pores. The results revealed that increasing gas–liquid ratio enhanced oil recovery during the high water cut stage, but reduced it during the middle water cut stage. The differences in oil recovery at different water cut stage appear to be linked to changes of the displacement mechanism. We indeed observed that oil was produced from a wide range of pores at the high water cut stage, but only from the macropores at the middle water cut stage. The field pilot analysis supported our conclusion based on the experimental findings, that foam-assisted deoxidized-air flooding using an appropriate gas–liquid ratio can efficiently lower water cut and enhance oil production at different water cut stages. The combination of laboratory and field pilot tests used here can serve as a template for future studies in other oil reserves.

Investigation of the plugging capacity and enhanced oil recovery of flexible particle three-phase foam

In the later stage of water flooding in reservoirs, the oil production decreases. The stability of three-phase foam system is strong, enhancing oil displacement effects of ultrahigh water cut reservoirs. In this paper, the flow state of the foam system was studied by using a microscopic visualization model. Second, sandpack flooding experiments were performed to analyze the optimal plugging conditions of three-phase foam through resistance factors. Finally, single and parallel sandpack flooding experiments were carried out to analyze plugging effect and production conditions under different injection systems and permeability ratios. The research shows that three-phase foam is more stable and capable of plugging. The stable residual resistance factor after injection of the three-phase foam system is 172.75. When the foam and particles are injected simultaneously, the gas–liquid ratio is 1:1, the formation permeability is 5526.5 mD, and the plugging effect of three-phase foam is the best. The oil recovery increases by 24.9% after the injection of three-phase foam system. The three-phase foam system combines Jamin effect of foam and dynamic plugging characteristics of flexible particles. The highest oil recovery factor of 80.87% is achieved at a permeability ratio of 9.99. Three-phase foam flooding has broad application prospects.

Laboratory Test of Fluid Physical Property Parameters of Well Fluid Containing CO2

Change regulation of the physical properties of fluid is key to accurately predicting multiphase fluid flow in the production wellbore of CO2 flooding reservoirs. Given the characteristics of significant changes in pressure, temperature, and CO2 content in the whole wellbore of production wells in CO2 flooding reservoirs, this paper systematically studied the change rules of volume factor, viscosity, density, and solubility of well fluid for pressure 5~30 MPa, temperature 20~120 °C, and CO2 content 10~90% through single degassing PVT experiments. According to the experimental results, the volume factor of crude oil increases first and then decreases with the pressure increase. At the bubble point pressure (20 MPa), the volume factor of crude oil can reach 1.89 at high temperatures. The volume factor can be increased from 1.28 to 1.44 at 8 MPa when the temperature increases from 20 °C to 120 °C. Under the bubble point pressure, the increase in pressure increases the solubility of CO2, and the viscosity of crude oil decreases rapidly. In contrast, above the saturation pressure, the increase in pressure increases the viscosity of crude oil. Under the freezing point temperature (24 °C), the viscosity of crude oil decreases sharply with increase in temperature. In contrast, above the freezing point temperature, the viscosity change of crude oil is not sensitive to temperature. The wellbore temperature has a significant impact on the density of the well fluid. At 5 MPa, the temperature increases from 20 °C to 120 °C, which can reduce the density of high CO2 crude oil from 0.93 g/cm3 to 0.86 g/cm3. The solubility of CO2 in crude oil is sensitive to pressure. When the pressure increases from 5 MPa to 15 MPa at 20 °C, the solubility increases by 36.56 cm3/cm3. The results of this paper support the multiphase fluid flow law prediction of CO2 flooding production wells with a high gas–liquid ratio.

Enhancing NOx removal in a high-gravity rotating packed bed with gaseous ClO2 oxidation-absorption: Kinetic, mass transfer, and cost analysis

The application of ClO2(g) for NO oxidation presents a promising approach to improving air pollution control technology. In this study, an integration of ClO2(g) with absorption using a high-gravity rotating packed bed (HiGee RPB) was proposed for NOx removal. The results showed that ClO2(g) has a comparable oxidation efficiency (close to 100%) to O3 in converting NO to NO2, while the dosage of ClO2(g) required was two times smaller than that of O3. The gas-phase oxidation kinetic analysis between ClO2(g)-NOx, using an ideal plug flow model, simulated the potential amount of NOx species produced in a short reaction distance in the pipeline. Furthermore, at higher gas-liquid ratios and in high-gravity fields, the effective mass transfer interfacial area for NO2 absorption was mainly controlled by the liquid film rather than droplet behavior, resulting in decreased absorption capacity. The empirical model for predicting the gas-side mass transfer coefficient confirmed that the interaction between mass transfer performance and chemical absorption was independent. Therefore, selecting the appropriate absorbent is a key factor in achieving high-loading NO2 concentrations after oxidation by ClO2(g). Another interesting finding is that balancing system energy consumption and the target treated NOx concentration played a critical role in enhancing the NOx absorption capacity. The cost analysis showed that substituting existing scrubbers with RPB processes could facilitate NOx absorption capacity (g-NOx/kWh) with cost-effectiveness. Overall, this study provides valuable insights into the development of effective and efficient NOx removal technologies, and future research in this area can build on these findings.

The structure design and offshore oilfield experiment study of industrial compact flotation unit

The Compact Flotation Unit is widely used in the offshore oilfield produced water treatment based on the characteristics of relatively small footprint and high oil removal efficiency, but the structure details of the Compact Flotation Unit have been rarely described up to now. Few literature is talking about the Compact Flotation Unit design process and systematically analyzing the influence of operating parameters on the oil removal efficiency, especially on the large-capacity industrial-level Compact Flotation Unit products. In this paper, the working principle and structure design process of the Compact Flotation Unit from Beijing Institute of Petrochemical Technology cooperated with China National Offshore Oil Corporation Research Institute were systematically introduced. Furthermore, the single-stage Compact Flotation Unit from Beijing Institute of Petrochemical Technology of industrial scale with a treatment capacity of 120 m³/h was manufactured and tested on floating production storage and offloading unit located in the South China Sea. When the inlet average oil content was 280.3 mg/L, the outlet average oil content was 39.9 mg/L, and the corresponding average oil removal efficiency was 85.8%. The flow split ratio, back pressure, and inlet flow rate have a significant impact on the oil removal efficiency, while the effect of the gas-liquid ratio and outlet water recycle ratio are not sensitive. The main reason can be attributed to the dissolved gas components in the produced water. A large quantity of microbubbles is generated after depressurization which directly participates in the flotation process. Besides that, the single-stage Compact Flotation Unit prototype can tolerate the fluctuation of inlet flow rate and oil content.