Median Particle Diameter Research Articles

Influence of soil and hydraulic conditions on the processes of internal erosion, cavity formation and collapse behind coastal structures

Collapse of cavities formed by internal erosion has occurred at the back sides of seawalls and quaywalls all over the world. Here, the process of internal erosion was investigated by conducting prototype-scale experiments. A series of processes of cavity formation and collapse were reproduced considering different grain size distributions and water level conditions. Suction, that is, negative pore water pressure relative to atmospheric air pressure, affected the formation of cavities and the timing and scale of their collapse. The scale of the collapse was large under high suction. The types of hydraulic force also affected the cavity formation. A symmetrical cavity was formed under one-dimensional water level fluctuations, whereas the cavity expanded in size toward the wave-incident boundary under incident waves. Cavity collapse was found to be caused by a decrease in suction accompanied by a rise in groundwater level. The collapse occurred within the area where ground surface displacement was observed, and the maximum ground surface displacement (dmax) was correlated with the ratio of the maximum width of the cavity and its depth (B/L) regardless of the ground height and water level fluctuation range. Countermeasure against the internal erosion using a two-layer filter was systematically studied in a series of sand filtration tests and prototype-scale hydraulic experiments. The filter maintained a sufficient deterrent effect under various hydraulic and dynamic forcing when the uniformity coefficient of the filter (DF60/DF10) was higher than 3.0, and the median particle diameter ratio (DF50/DS50) was less than or equal to 20.

Shear Characteristics of the Interface between Recycled Concrete Aggregates and Various Geosynthetics

To investigate the interface shear characteristics between various geosynthetics and recycled concrete aggregate (RCA), 30 large-scale monotonic direct shear tests were conducted. The main work was to analyse the effect of a biaxial polypropylene geogrid, a glass fiber geogrid, a warp-knitted polyester geogrid, a woven geotextile, and geonet on the interface shear properties of RCA. The test results show that adding a biaxial polypropylene geogrid or a geonet to RCA can improve its interface shear strength. The inclusion of glass fiber geogrids, warp-knitted polyester geogrids, and woven geotextiles decrease the interface shear strength of RCA. The reinforcing RCA with geosynthetics can effectively suppress its shear dilation, and the change in internal friction angle is consistent with the change law of the material interface enhancement coefficient. Finally, the aperture size of a geogrid has a significant effect on the mechanical properties of the geogrid-RCA interface. The interface shear strength increases first and then decreases with an increase in the ratio between aperture size and median particle diameter. It is concluded that there is an optimal range of aperture ratio between a geogrid and RCA.

Factors associated with edentulous patients' willingness about implant-supported complete denture: a multivariate analysis.

The aim of this study was to evaluate the factors influencing edentulous patients' willingness about mandibular implant-supported complete denture. A cross-sectional study was carried out with 117 bimaxillary edentulous patients wearing removable complete dentures (CDs). Patients were assessed concerning denture-related items (number of previous mandibular CDs, previous denture wearing period, dentures maker professional, and regular wearing of previous mandibular dentures) and individual-related aspects, such as mandibular edentulousness period, mandibular bone height, and willingness to the use of mandibular implant-supported complete denture. Masticatory performance was evaluated by the median particle diameter. Mandibular bone height and satisfaction were assessed using a validated method. The Chi-square test was used for data analysis and prevalence ratios were adjusted by using multivariate Poisson regression, both with 95% confidence interval. A total of 78 participants (66.7%) were interested in mandibular implant-supported overdenture (mean age 65.33 ± 9.49). Masticatory performance was not influenced by choosing mandibular implant-supported complete denture. The preference about mandibular implant-supported complete denture was correlated with longer mandibular complete denture experience (p = 0.021) and it was significantly associated with dissatisfaction about retention (p = 0.005). Previous experience with mandibular complete dentures and dissatisfaction about retention influence the willingness about mandibular implant-supported overdenture. Many factors are associated with rehabilitation preferences for edentulous patients and mandibular implant-supported complete denture is one of the available alternatives. Therefore, this study has demonstrated the factors influencing the decision to replace a mandibular conventional complete denture by dental implant treatment based on patient's outcomes. Such finding may be considered as a relevant aspect towards shared decision-making for prosthodontic rehabilitation of edentulous patients.

A Numerical Study of Particle Migration in Porous Media During Produced Water Reinjection

Abstract The clogging phenomenon often occurs during the reinjection of produced water due to the suspended particles, which will deteriorate the development efficiency. Many experimental and analytical methods have been introduced to solve this problem; however, few numerical approaches have been proposed to investigate the particle migration in the produced water reinjection process. Moreover, it is hard to obtain a clear understanding directly from the particle scale when the injected particles have different sizes. This paper employs a coupled lattice Boltzmann method and discrete element method (LBM-DEM) to study the aforementioned process. The method was validated by reproducing the Drafting–Kissing–Tumbling (DKT) process. Simulations of migration of injected particles with different sizes through porous media were conducted and three clogging scenarios had been identified. We investigated the impact of injected particle size distribution and porous media on particle migration and concluded the results in the polydisperse aspect. From the simulation, we can conclude that mix clogging is the scenario we should try to avoid. Besides, both critical ratio of particle diameter of porous media to median particle diameter of injected particles (D/d50) and critical standard deviation value exist. The particle size range should be as small as possible in economical limits and the D/d50 value should be larger than the critical value. Our results can provide a good guide for the produced water pretreatment, which can improve oil recovery.

A self-penetration torpedo anchor with vibrational shearing

As the depths at which marine facilities are constructed increase, mooring systems have become more complex, expensive, and difficult to install, making it necessary to develop new types of anchors to replace conventional drag-type anchors. In this paper, a new anchor concept based on the application of sediment fluidization technology is proposed. The proposed self-penetration torpedo anchor has a design similar to that of a torpedo anchor but is equipped with a specially designed mechanical vibrational unit. Laboratory tests were carried out to assess the penetration behavior, holding performance, and pullout behavior of the proposed torpedo under self-induced vibration. To evaluate the effect of installation on the anchorage force, the anchoring forces were measured over different rest times following vertical arrival at designated penetration depths. It was demonstrated that the anchor is able to automatically enter deep beds at moderate penetration speeds and that it has a high holding index, with an anchoring force that can recover more than 83.2% of its holding capacity following 7 d of rest in a silty bed with median particle diameters d50 of 31 μm. Furthermore, unlike conventional torpedo anchors the anchoring force and penetration depth of the self-penetration torpedo anchor are not limited by water depth or drop height. Because the proposed torpedo can be more easily extracted through the application of vibration, problems arising from an inability to pull the anchor out can be more readily avoided.

Particle Size Distribution Models for Metallurgical Coke Grinding Products

Six different particle size distribution (Gates–Gaudin–Schuhmann (GGS), Rosin–Rammler (RR), Lognormal, Normal, Gamma, and Swebrec) models were compared under different metallurgical coke grinding conditions (ball size and grinding time). Adjusted R2, Akaike information criterion (AIC), and the root mean of square error (RMSE) were employed as comparison criteria. Swebrec and RR presented superior comparison criteria with the higher goodness-of-fit and the lower AIC and RMSE, containing the minimum variance values among data. The worst model fitting was GGS, with the poorest comparison criteria and a wider results variation. The undulation Swebrec parameter was ball size and grinding time-dependent, considering greater b values (b > 3) at longer grinding times. The RR α parameter does not exhibit a defined tendency related to grinding conditions, while the k parameter presents smaller values at longer grinding times. Both models depend on metallurgical coke grinding conditions and are hence an indication of the grinding behaviour. Finally, oversize and ultrafine particles are found with ball sizes of 4.0 cm according to grinding time. The ball size of 2.54 cm shows slight changes in particle median diameter over time, while 3.0 cm ball size requires more grinding time to reduce metallurgical coke particles.

Optical Properties and Biochemical Indices of Marine Particles in the Open Mediterranean Sea: The R/V Maria S. Merian Cruise, March 2018

A rich data set on particulate matter optical properties and parameters (beam attenuation coefficient, volume concentration, particle size and PSD slope), accompanied by measurements of biochemical indices (particulate organic carbon, particulate nitrogen and their stable isotopic composition) was obtained from the surface to deep waters across the Mediterranean Sea, in March-April 2018. A decrease of beam attenuation coefficients, total particle volume concentrations, particulate organic carbon and nitrogen concentrations was noted towards the eastern Mediterranean Sea (EMed) in comparison to the western Mediterranean Sea (WMed). LISST-derived optical properties were significantly correlated with water mass characteristics. Overall, the most turbid water mass identified in the Mediterranean Sea was the Surface Atlantic water (AW), and the most transparent was the Transitional Mediterranean Water (TMW) in the Cretan Sea, whereas a general decrease in particulate matter concentration is observed from the WMed towards the EMed. Relatively depleted δ13C-POC values in the particle pool of the open Mediterranean Sea can be attributed to contribution from terrestrial inputs, mainly via atmospheric deposition. Throughout the entire water column, a significant positive correlation between particle beam attenuation coefficient and particulate organic carbon concentration is observed in the open Mediterranean Sea. Such relationship suggests the predominance of organic particles with biogenic origin. POC concentration and particle median diameter D50 are significantly and negatively correlated both in the WMed and the EMed Sea, confirming that small particles are POC-rich. At depth, a prominent decrease of most measured parameters was observed, with the exception of particle median diameter that increased substantially in the EMed towards the deep sea, suggesting potentially enhanced aggregation processes. The low particle size distribution slope ξ observed in the EMed, corresponding to larger particle populations, supports the above notion. Basin-wide Rayleigh-type isotopic fractionation in vertical profiles of δ15N-PN across the Mediterranean Sea, underlines the differences in the trophic characters of the two sub-basins and highlights the role of circulation changes on biogeochemical parameters and the redistribution of particulate matter as a source of nutrients in the water column.

Analysis of complex erosion models and their implication in the transport of Pisha sandstone sediments

Coarse sediment of the Yellow River in the complex erosion area of the Pisha sandstone region of the Ordos Plateau is deposited on the downstream riverbed, posing a threat to the flood control safety of the river. The objectives of the present study were to analyze the mechanisms of combined erosion and sediment yield under the synergistic action of multiple dynamics, employing the indoor artificial rainfall-wind-freezing-thawing cycle solid model test to explore the temporal and spatial variation of the coarse sediment production and the transportation process. In this study, complex erosion indoor tests were carried out through the artificial rainfall-wind-freezing-thawing cycle solid model. The enrichment rate (ER), fractal dimension, and median diameter (d50) of soil particles were used to quantify the size distribution characteristics of sediment particles under different erosion dynamics. The coarse sediment was first transported in the process of soil erosion because of the special texture and terrain characteristics of Pisha sandstone soil. Moreover, the degree of heterogeneity of sediment under complex erosion was larger than that under water erosion. The effect of wind could aggravate the instability of the erosion dynamic system. Under the combined action of freezing-thawing, wind, and water, the particle size composition changed greatly, and the erosion energy was extremely unstable. The effect of complex erosion created conditions for the coarse sediment transportation. Under the freezing-thawing-wind-water combined action, the particle size of eroded sediment was the coarsest, and that of water erosion was the smallest. We concluded that the reason why the Pisha sandstone area has become the core area of the concentrated source of coarse sediment in the Yellow River is related not only to the special nature of the Pisha sandstone soil itself but also to the effect of complex erosion.

Investigation of the growth and removal of particles in coal-fired flue gas by temperature management

Flue gas generated from coal combustion is the primary source of air pollution. Temperature is an essential parameter for the treatment process of flue gas pollutants. In this study, a field-scale demonstration setup was used to investigate the effect of temperature on particle growth and removal by using actual flue gas. The ionic migration in heat exchanger was also studied, and a temperature management method was established. Results showed that the temperature had a substantial influence on particle growth and removal, the outlet particle median diameter increased from 0.116 µm to 0.155 µm, and the outlet particle mass concentration decreased from 7.05 mg/Nm3 to 4.49 mg/Nm3 when the flue gas temperature difference was 2.9–4.6 K. Changing the boiler load from 100% to 65% led to the increase in the particle removal efficiency from 78.06% to 80.33%. This increment was mainly related to the changes in temperature. In addition, when the temperature difference increased from 2.9 K to 4.6 K, the concentration of the ions in the sample significantly increased, and the removal amount of mercury was enhanced by 2.57 times. The pollutant in the flue gas was effectively removed by the temperature management installation between the wet flue gas desulfurization and wet electrostatic precipitator.

Natural Ventilation Characterization in a Classroom under Different Scenarios.

The COVID-19 pandemic has pointed to the need to increase our knowledge in fields related to human breathing. In the present study, temperature, relative humidity, carbon dioxide (CO2) concentration, and median particle size diameter measurements were taken into account. These parameters were analyzed in a computer classroom with 15 subjects during a normal 90-minute class; all the subjects wore surgical masks. For measurements, Arduino YUN, Arduino UNO, and APS-3321 devices were used. Natural ventilation efficiency was checked in two different ventilation scenarios: only windows open and windows and doors open. The results show how ventilation affects the temperature, CO2 concentration, and median particle diameter size parameters. By contrast, the relative humidity depends more on the outdoor meteorological conditions. Both ventilation scenarios tend to create the same room conditions in terms of temperature, humidity, CO2 concentration, and particle size. Additionally, the evolution of CO2 concentration as well as the particle size distribution along the time was studied. Finally, the particulate matter (PM2.5) was investigated together with particle concentration. Both parameters showed a similar trend during the time of the experiments.

Raman spectroscopy and X‐ray diffraction responses when measuring health‐related micrometre and nanometre particle size fractions of crystalline quartz and the measurement of quartz in dust samples from the cutting and polishing of natural and artificial stones

AbstractAround 560 000 workers in Great Britain are potentially exposed to respirable crystalline silica (RCS), which can cause disabling diseases, such as silicosis and lung cancer. These experiments assessed the performance of a new Raman spectroscopy method for measuring RCS, in samples of pure quartz powder with different median aerodynamic particle diameters and stone dusts from variety of natural and artificial stones. The relationship between the Raman response and particle size was characterised by measuring subfractions of the respirable quartz standard A9950 collected using the Sioutas impactor. Bulk samples of quartz standards A9950 and Quin B that provided the highest median particle size diameters were also measured. Health‐related thoracic and respirable particle size fractions, and the environmental monitoring fractions of PM10, PM2.5, PM1 and PM0.5, were also collected during the powered cutting and polishing of sandstone and diorite (granite), engineered and sintered stones. All Raman spectroscopy results were compared with those from X‐ray diffraction (XRD), which was used as the reference technique. The Raman spectroscopy response closely followed the predicted crystallinity of RCS for different particle diameters. Raman spectroscopy obtained slightly higher percentages than XRD for particle size fractions below 1 μm. The Raman spectroscopy and XRD results were highly correlated for the thoracic, respirable and impactor fractions. The coefficients of determination were between 0.98 and 0.95. The slope coefficients for the correlation were 1.11 for the respirable fraction and 1.07 for the thoracic fraction. Raman spectroscopy is a promising alternative to XRD for measurement of RCS with a much lower limit of detection of 0.21 μg compared with 1 μg.

Glycogen supercompensation is due to increased number, not size, of glycogen particles in human skeletal muscle.

What is the central question of this study? Glycogen supercompensation after glycogen-depleting exercise can be achieved by consuming a carbohydrate-enriched diet, but the associated effects on the size, number and localization of intramuscular glycogen particles are unknown. What is the main finding and its importance? Using transmission electron microscopy to inspect individual glycogen particles visually, we show that glycogen supercompensation is achieved by increasing the number of particles while keeping them at submaximal sizes. This might be a strategy to ensure that glycogen particles can be used fast, because particles that are too large might impair utilization rate. Glycogen supercompensation after glycogen-depleting exercise can be achieved by consuming a carbohydrate-enriched diet, but the associated effects on the size, number and localization of intramuscular glycogen particles are unknown. We investigated how a glycogen-loading protocol affects fibre type-specific glycogen volume density, particle diameter and numerical density in three subcellular pools: between (intermyofibrillar) or within (intramyofibrillar) the myofibrils or beneath the sarcolemma (subsarcolemmal). Resting muscle biopsies from 11 physically active men were analysed using transmission electron microscopy after mixed (MIX), LOW or HIGH carbohydrate consumption separated by glycogen-lowering cycling at 75% of maximal oxygen consumption until exhaustion. After HIGH, the total volumetric glycogen content was 40% [95% confidence interval 16, 68] higher than after MIX in typeI fibres (P < 0.001), with little to no difference in typeII fibres (9% [95% confidence interval -9, 27]). Median particle diameter was 22.5(interquartile range 20.8-24.7)nm across glycogen pools and fibre types, and the numerical density was 61% [25, 107] and 40% [9, 80] higher in the subsarcolemmal (P < 0.001) and intermyofibrillar (P < 0.01) pools of typeI fibres, respectively, with little to no difference in the intramyofibrillar pool (3% [-20, 32]). In LOW, total glycogen was in the range of 21-23% lower, relative to MIX, in both fibre types, reflected in a 21-46% lower numerical density across pools. In comparison to MIX, particle diameter was unaffected by other diets ([-1.4, 1.3]nm). In conclusion, glycogen supercompensation after prolonged cycling is exclusive to typeI fibres, predominantly in the subsarcolemmal pool, and involves an increase in the numerical density rather than the size of existing glycogen particles.

Effect of constituent particle polydispersion on VSSA-based equivalent particle diameter: Theoretical rationale and application to a set of eight powders with constituent particle median diameters ranging from 9 to 130 nm

Volume Specific Surface-Area (VSSA) has been identified as a relevant and alternative method to electron microscopy (EM) to determine whether a material is or not a nanomaterial. VSSA is an integral measurement method that provides an indirect representation of particle size. When this conversion into particle diameter is carried out, constituent particles are supposed to be monodisperse, which can be considered far from reality, materials being composed of polydisperse constituent particles. The way particle polydispersion affects the VSSA of a material, and thus the equivalent particle diameter deduced, is investigated in this paper. In particular, the specific case of normally-distributed, spherical constituent particles, is considered. A theoretical study has led to the introduction of a correction polydispersion-based factor. From experimental VSSA data obtained for eight powders covering a range of constituent particle median diameters from 9 to 130 nm, the VSSA-based constituent particle median diameters were compared to the median constituent particle size obtained from electron microscopy analysis, considered as the reference method. Integrating constituent particle polydispersion through the use of the correction factor improves the accuracy of particle size stemming from the VSSA approach, the relative discrepancies being within ±20% from the reference diameter.

Investigation on mixed particle classification based on imaging processing with convolutional neural network

For the classification of mixed particle with imaging method, the traditional processing techniques tend to extract the particle features from binary images, where particles can be classified by combining feature design corresponding to the particle type and classifiers, such as BP neural network and Support Vector Machine (SVM). However, the accuracies of these methods would be seriously influenced by particle agglomeration and imprecise feature design. In the work, the convolutional neural network (CNN) was introduced to extract the particle features in the image, where the particle localizations were obtained by implementing the region proposal network (RPN). Meanwhile, the particle segmentation at pixel level was achieved by a developed classifier and a fully convolutional network. A series of experiments were performed to a flowing mixed particle system consisting of spherical, elongated and irregular particles, and it showed that both the average accuracy and recall rate of SVM method were up to 87% with artificial feature design, while they were increased to 97% and 93% with CNN, respectively. For the median diameter (Dn50) of irregular particles, the latter method can also reduce the analysis error by more than 11%. It revealed that some shortages like imprecise feature design in traditional methods can be covered, and an end-to-end classified system can be formed to provide a more effective way for online analysis of flowing mixed particles.

Performance of submerged semi-circular breakwater under solitary wave in consideration of porous media

Submerged breakwater as the main structure of coastal engineering to protect coast is widely laid on the seabed because of its significant wave-dissipation performance. To reveal the interaction mechanism between waves and submerged breakwater, the hydrodynamic characteristics of a wave passing over different solid breakwaters were numerically and experimentally studied. Compared with the previous research, considering breakwater made up of porous media and the effects of extreme waves generated by hurricanes or tsunamis, this paper systematically investigates the effects of the semi-circular porous medium breakwater on the breaking solitary wave run-up based on a numerical model with the immersed boundary (IB) method. The computational capability of this model is verified firstly. Then, depending on the model, a series of cases are carried out to research the effects of different breakwaters on the run-up of solitary waves. The results show that the influence of porous breakwater on wave propagation is more significant than that of the solid breakwater. With the increase of the gravel particle median diameter, the maximum run-up height and the horizontal hydrodynamic force on the breakwater decrease, while the vertical hydrodynamic force on the breakwater increases. Increasing the size of the breakwater is beneficial to reducing the wave run-up height and the forces on the sloping beach. Compared with the single breakwater, the impact of the tandem breakwater on the wave propagation is more significant.

Local dynamics of pharmaceutical powder fluidization using high speed long distance microscopy and particle image velocimetry

The local dynamics of fluidized pharmaceutical carrier powders in a turbulent channel flow was studied using particle image velocimetry (PIV) and High-speed, long-distance microscopy (HS-LDM). Four different lactose powders which have been used as a drug carrier in dry powder inhalers were used in this study. These powders have median powder particle diameters ranging between 61 and 121 µm. Air flow velocities ranging between 13.3 m/s and 66.7 m/s were examined. In addition, the effect of grid blockage ratio (ranging from ~25% to ~40% of the area of channel cross-section) was also investigated. Results show that the high-speed, long-distance microscopy (HS-LDM) technique was able to capture the mean velocity of the particles, and the results corresponded well with the PIV measurements. Results from the high-speed, long-distance microscopy (HS-LDM) method also demonstrate that the span of particle velocity closely follows that of the particle size distribution both for cohesive and non-cohesive powders. This study contributes towards an improved understanding of pharmaceutical carrier dynamics in turbulent channel flows and demonstrates how advanced image processing can be used to capture local particle dynamics.

Solid Circulation Study in a 1.5 MWth Cold Flow Model of Chemical Looping Combustion

Solid circulation in chemical looping combustion (CLC) is very important and affects the mass and heat balance and autothermal operation of a CLC system. A key task in developing CLC technology is to control the solid circulation. In this work, the solid circulation characteristic of a 1.5 MWₜₕ CLC cold flow model is reported. The solid circulation between the fuel reactor and the simplified air reactor riser is controlled by the overflow method. Three kinds of quartz sands are selected as fluidized particles, and their median particle diameters are 392, 249, and 122 μm, respectively. A reasonable pressure profile is obtained in the 1.5 MWₜₕ CLC cold flow model. The effects of operational parameters, including the fuel reactor gas velocity, loop seal gas velocity, simplified riser gas velocity, particle size, and static bed height, on the solid circulation and hydrodynamic characteristics are measured and analyzed. The maximum solid circulation rate can approach 130 kg/(m²·s), and this value satisfies the requirements of mass and heat balance in the CLC system. The static bed height in the fuel reactor should be higher than the overflow port to prevent it from becoming a constraint factor on the solid circulation rate. An overflow model is developed to predict the solid circulation rate, and the relative errors between the predicted result and the experimental data are within 25%.

A risk assessment methodology of aluminum dust explosion for polishing process based on laboratory tests

The secondary dust explosion ignited by the primary explosion energy often causes greater damage to the just destroyed carrier. Therefore, the study of explosion risk as well as the risk reduction effect with suppression is key guard against the secondary and derivative explosions. A novel risk assessment methodology is presented based on Monte Carlo theory for numerically fitting pressure’s uncertainty changes and Crystal ball simulation for calculating explosion risk and its distribution probability of hazardous explosive dust. Taking the aluminum dust of a polishing process as an example, the fitted results show that the tested explosion pressure in laboratory presents the shape of lognormal distribution with average pressure of 0.27 MPa on the condition of 500 g/m3 aluminum dust with median particle diameter at 35 μm. The simulated results show that the risk possibility of myringorupture injury, pneumorrhagia injury, and structure damage all approaches 100% because of the high explosion pressure considering the potential percentage of injury or damage at 50%. However, the risk possibility reduces to 14.27%, 0.13%, and 42.05% with suppressants of ammonium dihydrogen phosphate at 10%, respectively. The proposed method of risk assessment for dust explosion and its suppression provides scientific basis for strategy optimization of dust explosion protection and safe production of fine explosive dust related industry.

Experimental Study on Hydraulic Conductivity and Resistance in Silty Sediments

Hydraulic conductivity k as a function of void ratio e and particle diameter for silty sediment was experimentally investigated, and an empirical formula for the estimation of hydraulic conductivity was proposed. Seepage resistance for flow in silty sediment was deliberated. Based on the findings of the study, it was concluded that hydraulic conductivity k could be expressed as an exponential function of void ratio e and median particle diameter d50 {3.1 μm &lt; d50 &lt; 87 μm and 0.26 &lt; e &lt; 4}. It was further found that the formula of seepage resistance factor (?), a form of friction factor, varies linearly with Reynolds number (Re) for silty sediments. A family of such λ-Re curves for various particle diameter d50 is presented.

CO2-responsive preformed gel particles with interpenetrating networks for controlling CO2 breakthrough in tight reservoirs

Horizontal well re-fracturing of tight reservoirs triggers complex fractures, which induces severe gas channeling and low sweeping efficiency in CO2 flooding due to the significance difference in permeability between matrix and fractures. Herein, novel CO2-responsive preformed gel particles with interpenetrating networks (IPN-ASSAP) was synthesized to mitigate CO2 breakthrough. To reveal the plugging efficiency and EOR potential of IPN-PAASP, the change in particle size distribution, microstructure, strength, and rheology were characterized, followed by core flooding experiments. Experimental results indicated that after IPN-ASSAP contacted with CO2, the median diameter and strength of particles were enhanced due to protonation reaction of IPN-PAASP. Moreover, after IPN-PAASP was injected into fractured core, injection pressure increased from 5.0 kPa to 0.342 MPa with plugging efficiency of 99 %. During water flooding and CO2 flooding, the crude oil in fracture was displaced with oil recovery of 17.1 %. After plugging was formed, injected CO2 entered matrix, and recovery factor increased by 23.1 %. All the experiment results indicated that IPN-PAASP is a promising candidate for fracture plugging during CO2 flooding.