Due to the uneven seabed and heaving of soil during pumping,incomplete soil plugs may occur during the installation of bucket foundations,and the impacts on the bearing capacities of bucket foundations need to be eval...Due to the uneven seabed and heaving of soil during pumping,incomplete soil plugs may occur during the installation of bucket foundations,and the impacts on the bearing capacities of bucket foundations need to be evaluated.In this paper,the contact ratio(the ratio of the top diameter of the soil plug to the diameter of the bucket)and the soil plug ratio(the ratio of the soil heave height to the skirt height)are defined to describe the shape and size of the incomplete soil plug.Then,finite element models are established to investigate the bearing capacities of bucket foundations with incomplete soil plugs and the influences of the contact ratios,and the soil plug ratios on the bearing capacities are analyzed.The results show that the vertical bearing capacity of bucket foundations in homogeneous soil continuously improves with the increase of the contact ratio.However,in normally consolidated soil,the vertical bearing capacity barely changes when the contact ratio is smaller than 0.75,while the bearing capacity suddenly increases when the contact ratio increases to 1 due to the change of failure mode.The contact ratio hardly affects the horizontal bearing capacity of bucket foundations.Moreover,the moment bearing capacity improves with the increase of the contact ratio for small aspect ratios,but hardly varies with increasing contact ratio for aspect ratios larger than 0.5.Consequently,the reduction coefficient method is proposed based on this analysis to calculate the bearing capacities of bucket foundations considering the influence of incomplete soil plugs.The comparison results show that the proposed reduction coefficient method can be used to evaluate the influences of incomplete soil plug on the bearing capacities of bucket foundations.展开更多
In order to improve the properties of corundum based dispersive purging plugs,dispersive purging plug specimens were prepared using tabular corundum(1-0.15 and≤0.15 mm)as the aggregates,tabular corundum(≤0.044 mm)an...In order to improve the properties of corundum based dispersive purging plugs,dispersive purging plug specimens were prepared using tabular corundum(1-0.15 and≤0.15 mm)as the aggregates,tabular corundum(≤0.044 mm)andα-Al_(2)O_(3)micropowder(d_(50)=0.6μm)as the matrix,Secar 71 cement as the binder,introducing different amounts of nano-CaCO_(3),casting into shapes,and firing at different temperatures(1200 or 1600℃)for 4 h.The effects of the nano-CaCO_(3) extra-addition(0,0.5%,1.0%,1.5%and 2.0%,by mass)on the consistency of the castables as well as the properties and microstructure of the dispersive purging plug specimens were studied.The results show that:(1)with the fixed water addition,the consistency of the corundum castables decreases as the nano-CaCO_(3)addition increases;(2)with the increasing nano-CaCO_(3)addition,the bulk density of the specimens fired at different temperatures for 4 h decreases,the apparent porosity,the cold strength and the hot modulus of rupture all increase,the gas permeability does not change significantly;(3)the specimens fired at 1600℃ for 4 h have obviously better cold comprehensive performance than those fired at 1200℃for 4 h;(4)when the nano-CaCO_(3)addition is 1.5%,the comprehensive performance of the specimen is the optimal.展开更多
Major aortopulmonary collateral arteries (MAPCAs) are congenital vessels that arise from the aorta or its first-order branches and are distally connected to the pulmonary arterial vasculature, thereby providing pulmon...Major aortopulmonary collateral arteries (MAPCAs) are congenital vessels that arise from the aorta or its first-order branches and are distally connected to the pulmonary arterial vasculature, thereby providing pulmonary blood flow. MAPCAs are often associated with cyanotic congenital heart disease with decreased pulmonary blood flow. Isolated MAPCAs are rare in patients without congenital heart disease with structurally normal hearts. Sometimes, isolated congenital MAPCAs can occur without any lung disease. Isolated MAPCAs represent the occurrence of collaterals in the absence of underlying heart disease, which commonly presents as heart failure, recurrent respiratory tract infection, and pulmonary artery hypertension. We report a rare case of congestive heart failure in a 6-year-old patient with dual arterial supply to an otherwise normal right lung, with a normal bronchial tree, and a structurally normal heart. The patient was successfully managed by the closure of collaterals by Amplatzer vascular plugs II (AVPII) and Amplatzer Piccolo Occluders.展开更多
A high-quality plug of the abandoned wellbore is considered an essential technical aspect of the oil and gas well abandonment technology system. This paper presents a method of active mechanical excitation to enhance ...A high-quality plug of the abandoned wellbore is considered an essential technical aspect of the oil and gas well abandonment technology system. This paper presents a method of active mechanical excitation to enhance the quality of wellbore plug barriers. An indoor simulation platform is developed, and the effects of different combinations of vibration frequency, amplitude and duration on the properties of the wellbore plug cement material are investigated. It is observed that the optimal combination of excitation parameters occurs at a vibration frequency of 15 Hz, a vibration time of 6 min, and a vibration amplitude of 3 mm. Compared with the condition without the vibration process, the cementing strength, compressive strength, and tensile strength of wellbore cement plug with the optimal mechanical vibration process could increase by 51%, 38% and 20%, respectively, while the porosity decreases by 5%. As determined by scanning electron microscopy of the set cement's microstructure, mechanical vibration effectively eliminates internal porosity and improves the set cement's density. The optimal excitation parameters obtained from the test can guide the design of the vibration plugging tool. The designed vibration plugging tool is simulated in the near field. The cement plug cementation quality tester tests the vibrating and non-vibrating samples, and the cementation ratio is calculated. The test results show that the average cementation ratio of vibrating samples is 0.89375, and that of non-vibrating samples is 0.70625, and the cementation quality is improved by 27%. It is concluded that it not only provides essential data for the design of mechanical vibration plug apparatus, on-site vibration plugs, and the development of operational specifications for vibration plugs, but also provides solid engineering guidance.展开更多
To clean out the smear layer on teeth surface, and protect the teeth medulla, the experiment applied the study observing the cleanup of six groups of surface smear layer of dental caries and the tubule plugs reserving...To clean out the smear layer on teeth surface, and protect the teeth medulla, the experiment applied the study observing the cleanup of six groups of surface smear layer of dental caries and the tubule plugs reserving effect after using of different cavity cleansers with the help of SEM. The result implied that both the acidic preparations and chelator could clean out the smear layer on teeth surface in some way, but the later one could also reserve partial tubule plugs, which reduce the stimulation to the teeth medulla. So the chelator is better cleansers in clinical use.展开更多
Gas hydrates and wax are the major flow assurance problems for the transportation of produced hydrocarbons through pipelines.However,in most research works both these two problems are studied separately.Although simul...Gas hydrates and wax are the major flow assurance problems for the transportation of produced hydrocarbons through pipelines.However,in most research works both these two problems are studied separately.Although simultaneous precipitation or deposition of these compounds in pipelines can lead to different mitigation/prevention strategies,the investi-gations in which both these problems are considered simultaneously appeared only recently.There is no information in the literature on the texture/composition and features of decomposition process of mixed wax/hydrate plugs.At the same time,this information could be useful to understand how to treat the problem of formation of these plugs.In this work,three wax/gas hydrate plugs were collected at quasi-static conditions from a water-in-oil emulsion to study their texture,composition and the features of decomposition process.Powder X-ray diffraction and IR(infrared spectroscopy)analyses showed that the plugs consisted of wax and gas hydrate.Thermovolumetric and DSC(Differential Scanning Calorimetry)experiments showed that the main part of gas hydrate in the plugs at the ambient pressure started to decompose at about 268 K.This temperature was higher than the equilibrium temperature of carbon dioxide hydrate at this pressure,indicating that the gas hydrate in the plugs could be effectively preserved at temperatures below the ice melting point(273.2 K).It was found through observation of the hydrate decomposition process in the plugs under the microscope that the gas in the samples released in small bubbles,while the hydrate particles were not visible at this magnification,indicating that the hydrate was indeed highly dispersed in the samples.A residual wax was jelly-like after decomposition of hydrate in all the cases.Rheological experiments showed that the plugs residues after decomposition of the hydrates had higher yield points and viscosities than the initial waxy crude oil origi-nally used for the experiments.展开更多
AIM: To investigate donor site's area histological and immunohistochemical knee cartilage appearances after resurfacing iatrogenic defects with biosynthetic plugs orautografts. METHODS: Thirty New Zealand White ra...AIM: To investigate donor site's area histological and immunohistochemical knee cartilage appearances after resurfacing iatrogenic defects with biosynthetic plugs orautografts. METHODS: Thirty New Zealand White rabbits were used in this study. A full-thickness cylindrical defect of 4.5 mm(diameter) × 7 mm(depth) was created with a hand drill in the femoral groove of every animal. In Group A(n = 10) the defect of the donor site was re-paired with a biosynthetic osteochondral plug, in Group B(n = 10) with an osteochondral autograft, while in Group C(control group of 10) rabbits were left untreated. RESULTS: Twenty-four weeks postoperatively, smooth articular cartilage was found macroscopically in some trocleas' surfaces; in all others, an articular surface with discontinuities was observed. Twenty-eight out of 30 animals were found with predominantly viable chondrocytes leaving the remaining two-which were found only in the control group- with partially viable chondrocytes. However, histology revealed many statistical differences between the groups as far as the International Cartilage Repair Society(ICRS) categories are concerned. Immunofluoresence also revealed the presence of collagen Ⅱ in all specimens of Group B, whereas in Group A collagen Ⅱ was found in less specimens. In Group C collagen Ⅱwas not found. CONCLUSION: The matrix, cell distribution, subchondral bone and cartilage mineralization ICRS categories showed statistically differences between the three groups. Group A was second, while group B received the best scores; the control group got the worst ICRS scores in these categories. So, the donor site area, when repairing osteochondral lesions with autografting systems, is better amended with osteochondral autograft rather than bone graft substitute implant.展开更多
Purpose: To determine if there were differences in quality of life (QOL) within the first year following EVAR for patients undergoing internal iliac embolization depending on the type of device used. Methods: Patients...Purpose: To determine if there were differences in quality of life (QOL) within the first year following EVAR for patients undergoing internal iliac embolization depending on the type of device used. Methods: Patients who underwent endovascular AAA repair were identified using a Vascular surgery database at a tertiary care center from 2002-2008. The Radiology Information System and Image Viewer were then used to identify patients who underwent preprocedural embolization prior to endovascular aneurysm repair. Nine patients had embolization with nester coils, 9 had embolization with the amplatzer vascular plug, a type of nitinol based self expanding device. Another group of 8 patients who did not undergo preprocedural embolization was used as a comparator group. These patients were contacted via telephone and answered questions regarding QOL post procedure. The Australian Vascular QOL was the tool used to measure QOL. Differences in QOL were tabulated between the groups of patients. Results: Of the 9 patients who underwent embolization with amplatzer plug, the median QOL score was 60 (p value 0.575), the median QOL for the nester coil group was 52.5 and the comparator group was 58. Separate analysis was done dividing patients into two groups, with and without comorbidities without statistical significance. Conclusion: Patients who underwent preprocedural embolization using amplatzer plugs compared to coils had higher overall QOL scores although the difference was not significant.展开更多
Purpose:Evaluation of the patency and position of perforated lacrimal punctal plugs implanted for treating punctal stenosis together with quantitative assessment of the precorneal tear film using anterior segment opti...Purpose:Evaluation of the patency and position of perforated lacrimal punctal plugs implanted for treating punctal stenosis together with quantitative assessment of the precorneal tear film using anterior segment optical coherence tomography(AS-OCT).Methods:In a prospective study,the lower punctum of 54 eyes of 29 patients implanted with perforated punctal plugs were examined using AS-OCT during the early postoperative period.Preoperative tear meniscus height(TMH)and tear meniscus area(TMA)were evaluated.Postoperatively,the patency of the plug,its position,TMH and TMA were evaluated,and the results were correlated with postoperative epiphora.Munk scale was used for epiphora grading.Results:Using AS-OCT,48(88.9%)plugs were found in proper position while 6(11.1%)were rotated.The lumen of the plugs was completely patent in 47(87%)plugs,partially obstructed in 2(3.7%)plugs and completely occluded in 5(9.2%)plugs.There was a statistically significant postoperative decrease of TMH and TMA(P<0.001)and postoperative epiphora Munk score(P<0.001).Conclusion:AS-OCT is a valuable,reliable,and noninvasive investigative tool that can detect the proper positioning,patency,and contents of the implanted perforated lacrimal punctal plugs in addition to measurement of TMH and TMA.展开更多
As an independent sand control unit or a common protective shell of a high-quality screen,the punching screen is the outermost sand retaining unit of the sand control pipe which is used in geothermal well or oil and g...As an independent sand control unit or a common protective shell of a high-quality screen,the punching screen is the outermost sand retaining unit of the sand control pipe which is used in geothermal well or oil and gas well.However,most screens only consider the influence of the internal sand retaining medium parameters in the sand control performance design while ignoring the influence of the plugging of the punching screen on the overall sand retaining performance of the screen.To explore the clogging mechanism of the punching screen,this paper established the clogging mechanism calculation model of a single punching screen sand control unit by using the computational fluid mechanics-discrete element method(CFD-DEM)combined method.According to the combined motion of particles and fluids,the influence of the internal flow state on particle motion and accumulation was analyzed.The results showed that(1)the clogging process of the punching sand control unit is divided into three stages:initial clogging,aggravation of clogging and stability of clogging.In the initial stage of blockage,coarse particles form a loose bridge structure,and blockage often occurs preferentially at the streamline gathering place below chamfering inside the sand control unit.In the stage of blockage intensification,the particle mass develops into a relatively complete sand bridge,which develops from both ends of the opening to the center of the opening.In the stable plugging stage,the sand deposits show a“fan shape”and form a“V-shaped”gully inside the punching slot element.(2)Under a certain reservoir particle-size distribution,The slit length and opening height have a large influence on the permeability and blockage rate,while the slit width size has little influence on the permeability and blockage rate.The microscopic clogging mechanism and its law of the punching screen prevention unit are proposed in this study,which has some field guidance significance for the design of punching screen and sand prevention selection.展开更多
Conformance control and water plugging are a widely used EOR method in mature oilfields.However,majority of conformance control and water plugging agents are unavoidable dehydrated situation in high-temperature and hi...Conformance control and water plugging are a widely used EOR method in mature oilfields.However,majority of conformance control and water plugging agents are unavoidable dehydrated situation in high-temperature and high-salinity low permeability reservoirs.Consequently,a novel conformance control system HPF-Co gel,based on high-temperature stabilizer(CoCl_(2)·H_(2)O,CCH)is developed.The HPF-Co bulk gel has better performances with high temperature(120℃)and high salinity(1×10^(5)mg/L).According to Sydansk coding system,the gel strength of HPF-Co with CCH is increased to code G.The dehydration rate of HPF-Co gel is 32.0%after aging for 150 d at 120℃,showing excellent thermal stability.The rheological properties of HPF gel and HPF-Co gel are also studied.The results show that the storage modulus(G′)of HPF-Co gel is always greater than that of HPF gel.The effect of CCH on the microstructure of the gel is studied.The results show that the HPF-Co gel with CCH has a denser gel network,and the diameter of the three-dimensional network skeleton is 1.5-3.5μm.After 90 d of aging,HPF-Co gel still has a good three-dimensional structure.Infrared spectroscopy results show that CCH forms coordination bonds with N and O atoms in the gel amide group,which can suppress the vibration of cross-linked sites and improve the stability at high temperature.Fractured core plugging test determines the optimized polymer gel injection strategy and injection velocity with HPF-Co bulk gel system,plugging rate exceeding 98%.Moreover,the results of subsequent waterflooding recovery can be improved by 17%.展开更多
Pipeline isolation plugging robot (PIPR) is an important tool in pipeline maintenance operation. During the plugging process, the violent vibration will occur by the flow field, which can cause serious damage to the p...Pipeline isolation plugging robot (PIPR) is an important tool in pipeline maintenance operation. During the plugging process, the violent vibration will occur by the flow field, which can cause serious damage to the pipeline and PIPR. In this paper, we propose a dynamic regulating strategy to reduce the plugging-induced vibration by regulating the spoiler angle and plugging velocity. Firstly, the dynamic plugging simulation and experiment are performed to study the flow field changes during dynamic plugging. And the pressure difference is proposed to evaluate the degree of flow field vibration. Secondly, the mathematical models of pressure difference with plugging states and spoiler angles are established based on the extreme learning machine (ELM) optimized by improved sparrow search algorithm (ISSA). Finally, a modified Q-learning algorithm based on simulated annealing is applied to determine the optimal strategy for the spoiler angle and plugging velocity in real time. The results show that the proposed method can reduce the plugging-induced vibration by 19.9% and 32.7% on average, compared with single-regulating methods. This study can effectively ensure the stability of the plugging process.展开更多
Fault fractures usually have large openings and considerable extension. Accordingly, cross-linked gel materials aregenerally considered more suitable plugging agents than water-based gels because the latter often unde...Fault fractures usually have large openings and considerable extension. Accordingly, cross-linked gel materials aregenerally considered more suitable plugging agents than water-based gels because the latter often undergo contaminationvia formation water, which prevents them from being effective over long times. Hence, in this study, aset of oil-based composite gels based on waste grease and epoxy resin has been developed. These materials havebeen observed to possess high compressive strength and resistance to the aforementioned contamination, therebyleading to notable increase in plugging success rate. The compressive strength, thickening time, and resistance toformation water pollution of these gels have been evaluated indoors. The results show that the compressivestrength of the gel can reach 11 MPa;additionally, the related gelation time can be controlled to be more than3 h, thereby providing a safe construction time;Invasion of formation water has a small effect on the gel strengthand does not shorten the thickening time. All considered performance indicators of the oil-based gel confirm itssuitability as a plugging agent for fault fractures.展开更多
This paper aims to improve the corrosion resistance of dispersive purging plugs.White fused corundum particles and fine powder,α-Al_(2)O_(3) micropowder,Cr_(2)O_(3) micropowder,Guangxi clay and zircon powder were use...This paper aims to improve the corrosion resistance of dispersive purging plugs.White fused corundum particles and fine powder,α-Al_(2)O_(3) micropowder,Cr_(2)O_(3) micropowder,Guangxi clay and zircon powder were used as the main raw materials.The mass ratio of white fused corundum particles and fine powder was fixed at 85:15,and 0,1%,2%,or 3%(by mass)of zircon fine powder was added to replace the same amount of white fused corundum fine powder.The corundum porous material was prepared by the particle stacking pore-forming method at 1650℃for 3 h.The effect of the zircon addition on the properties and microstructure of porous materials was investigated.The results show that:after adding zircon,the permeability of the porous material increases,the cold and hot strengths increase obviously,and the expansion rate after firing decreases.When the addition of zircon is 2%,the comprehensive performance of the specimen is optimal with the smallest linear change rate and the highest permeability.展开更多
The use of biopsy plugs to sample fish muscle tissue for mercury analyses is a viable alternative to lethal sampling; however, the practice has yet to be widely implemented in routine monitoring due to concerns about ...The use of biopsy plugs to sample fish muscle tissue for mercury analyses is a viable alternative to lethal sampling; however, the practice has yet to be widely implemented in routine monitoring due to concerns about variability of mercury concentrations in fish muscle tissues. Here we examine distribution of mercury in fillets of four fish species(Walleye, Northern Pike, Smallmouth Bass and Lake Trout), suitability of left/right side of fillet for biopsy sampling, and appropriateness of re-using a biopsy punch. The results showed that average mercury concentrations in left and right fillets of fish are similar.Mercury concentrations in biopsy plug samples, taken from the anterior dorsal area of the fish fillet, were statistically equivalent to the mercury concentrations in homogenized fillets. There was no discernible cross contamination between samples when a biopsy punch was reused after washing in hot soapy water, and as such, biopsy punches can be recycled during sampling to reduce the sampling cost. If a tissue mass collected from a specific site on the fillet is insufficient, then we suggest sampling corresponding locations on the other fillet rather than sampling two adjacent sites on one fillet to obtain more tissue. The results presented here can improve the accuracy of fillet biopsy plug sampling,minimize fish mortality for mercury monitoring, and reduce labor and material costs in monitoring programs.展开更多
Plugs are crucial for initiating crop production in greenhouses, soil, and controlled environment agriculture (CEA). Vegetable, fruiting, ornamental, and other horticultural crops that utilize plugs for production hav...Plugs are crucial for initiating crop production in greenhouses, soil, and controlled environment agriculture (CEA). Vegetable, fruiting, ornamental, and other horticultural crops that utilize plugs for production have demonstrated superior transplant establishment rate, plant health, and total yield. The APS Laboratory for Sustainable Food at Florida Gulf Coast University investigated the quality of plugs grown based on different concentrations and fertigation sources using synthetic and organic sources. We carried out the growth of “Rex Butterhead” Lettuce (Latuca sativa) plugs with five different fertigation treatments, 1) full-strength synthetic starter fertilizer solution;2) half-strength synthetic starter fertilizer solution;3) full-strength organic starter fertilizer solution;4) half-strength organic starter fertilizer solution, and 5) no fertilizer for control. Fertilizer treatments were formulated following manufacturer recommendations. The seeds were sown in Oasis<sup>®</sup> Horticubes and saturated every day with the different fertilizer treatments. The plugs were cultivated for 15 days in a controlled environment until two leaves after the cotyledons had developed. After 15 days, we collected data which included wet weight (g), dry weight (g), leaf area (cm<sup>2</sup>), and chlorophyll concentration (mg/cm<sup>2</sup>). In addition, we derived data including the Leaf Area Index (LAI, cm<sup>2</sup>/cm<sup>2</sup>) and Specific Leaf Area (SLA, cm<sup>2</sup>/g). Descriptive statistics were used to describe the biomass data. A Tukey’s HSD test was carried out to understand the differences between the fertilizer sources. We determined there was a statistically significant difference (P = 7.34E−29) in the measured plug growth parameters due to the various fertigation sources. We found that all fertilizer treatments produced viable plugs except for the control treatment. Of all the treatments, we concluded the half-strength organic treatment produced the more vigorous plugs with the greatest wet weight (g) and largest total leaf area (cm<sup>2</sup>) which was statistically significantly different. Results from this study may inform growers about appropriate fertilizer options for plug production.展开更多
Using the visualized experimental device of temporary plugging in hydraulic fractures, the plugging behaviors of temporary plugging particles with different sizes and concentrations in hydraulic fractures were experim...Using the visualized experimental device of temporary plugging in hydraulic fractures, the plugging behaviors of temporary plugging particles with different sizes and concentrations in hydraulic fractures were experimentally analyzed under the conditions of different carrier fluid displacements and viscosities. The results show that the greater the carrier fluid viscosity and displacement, the more difficult it is to form a plugging layer, and that the larger the size and concentration of the temporary plugging particle, the less difficult it is to form a plugging layer. When the ratio of particle size to fracture width is 0.45, the formation of the plugging layer is mainly controlled by the mass concentration of the temporary plugging particle and the viscosity of the carrier fluid, and a stable plugging layer cannot form if the mass concentration of the temporary plugging particle is less than 20 kg/m^(3)or the viscosity of the carrier fluid is greater than 3 mPa·s. When the ratio of particle size to fracture width is 0.60, the formation of the plugging layer is mainly controlled by the mass concentration of the temporary plugging particle, and a stable plugging layer cannot form if the mass concentration of the temporary plugging particle is less than 10 kg/m^(3). When the ratio of particle size to fracture width is 0.75, the formation of the plugging layer is basically not affected by other parameters, and a stable plugging layer can form within the experimental conditions. The formation process of plugging layer includes two stages and four modes. The main controlling factors affecting the formation mode are the ratio of particle size to fracture width, carrier fluid displacement and carrier fluid viscosity.展开更多
The excellent mechanical properties of supramolecular gel could adapt to the complex reservoir environment and had broad application prospects in the field of oil and gas drilling and production engineering.In this pa...The excellent mechanical properties of supramolecular gel could adapt to the complex reservoir environment and had broad application prospects in the field of oil and gas drilling and production engineering.In this paper,a supramolecular gel based on hydrophobic association and hydrogen bonding was prepared by micellar copolymerization,which could be used to plug fractures and pores in formations.Supramolecular gel was a gel network system with high performance characteristics formed by self-assembly of non-covalent bond interaction.The rheological properties,mechanical mechanics,temperature resistance and swelling ability of supramolecular gel were studied.The results showed that the supramolecular gel had a dense three-dimensional network structure with open and interconnected pore structures,which could exhibit good rheological properties and strong viscoelastic recovery ability.The mechanical properties of the supramolecular gel were excellent,it had a tensile stress of 0.703 MPa and an elongation at break of 1803%.When the compressive strain was 96%,the compressive stress could reach 14.5 MPa.Supramolecular gel also showed good temperature resistance and swelling properties.At the aging temperature of 135℃,supramolecular gels still maintained good gel strength,and it only took 12 h to reach the equilibrium swelling ratio of 35.87 in 1%NaCl solution.It was also found that supramolecular gel in low concentration saline(1%NaCl solution)showed relatively faster swelling than high concentration saline(25%NaCl solution).The swelling process of the supramolecular gel was non-Fick diffusion(typeⅡ).This indicated that the organic/inorganic permeability network was well formed.Therefore,the diffusion rate of small molecules could be guaranteed to be equal to the relaxation rate of large molecules before and after the phase transition temperature.In addition to the diffusion of water molecules,the swelling process of the supramolecular gel was also affected by the relaxation of gel network and polymer chain segment,the interaction between water molecules and polymer network and the groups of polymer network and other factors.Supramolecular gel particles could be used as plugging materials for drilling fluids,which had excellent ability to plug formation fractures and pores.The plugging ability of the supramolecular gel was up to 6.7 MPa for 0.5 mm fracture width,and 9.6 MPa for porous media with 5 mD permeability.Compared with HT-PPG gel particles commonly used in oil fields,supramolecular gel particles had better plugging ability on fractures and porous media.The development and application of supramolecular gel had far-reaching significance for promoting the functional application of polymer materials in drilling and production engineering.展开更多
The application of the wellhead suction anchor in the second production test of natural gas hydrates(NGHs)in the South China Sea(SCS)was met with success.This design incorporates a central conductor guide pipe,which d...The application of the wellhead suction anchor in the second production test of natural gas hydrates(NGHs)in the South China Sea(SCS)was met with success.This design incorporates a central conductor guide pipe,which distinguishes it from traditional suction foundations.However,this addition resulted in a relatively high penetration resistance and a shallower penetration depth at the self-weight penetration stage.To mitigate this issue,the current study proposes an optimized design where the end of the suction foundation is sharpened.The installation characteristics of the traditional suction foundation and new suction foundation during self-weight penetration into sand are studied through laboratory tests and theoretical analysis.The flat and sharpened bottom shapes are considered in the traditional and new suction models.The effects of the initial penetration velocity on the initial penetration depth and soil plug and impact cavity characteristics are systematically studied.The results show that the self-weight penetration depth of the foundation with a sharpened bottom is 44.5%deeper than that of the foundation with a flat bottom.There are cavities around the foundation at the self-weight penetration stage,and the penetration depth is overestimated by 15%-30%.Finally,a model for predicting the penetration depth of the new suction foundation is proposed.展开更多
The effective plugging of artificial fractures is key to the success of temporary plugging and diverting fracturing technology,which is one of the most promising ways to improve the heat recovery efficiency of hot dry...The effective plugging of artificial fractures is key to the success of temporary plugging and diverting fracturing technology,which is one of the most promising ways to improve the heat recovery efficiency of hot dry rock.At present,how temporary plugging agents plug artificial fractures under high temperature remains unclear.In this paper,by establishing an improved experimental system for the evaluation of temporary plugging performance at high temperature,we clarified the effects of high temperature,injection rate,and fracture width on the pressure response and plugging efficiency of the fracture.The results revealed that the temporary plugging process of artificial fractures in hot dry rock can be divided into four main stages:the initial stage of temporary plugging,the bridging stage of the particles,the plugging formation stage,and the high-pressure dense plugging stage.As the temperature increases,the distribution distance of the temporary plugging agent,the number of pressure fluctuations,and the time required for crack plugging increases.Particularly,when the temperature increases by 100℃,the complete plugging time increases by 90.7%.展开更多
基金financially supported by the National Science Fund for Distinguished Young Scholars of China(Grant No.51825904)the Research on the Form,Design Method and Weathering Resistance of Key Components of Novel Floating Support Structures for Offshore Photovoltaics(Grant No.2022YFB4200701).
文摘Due to the uneven seabed and heaving of soil during pumping,incomplete soil plugs may occur during the installation of bucket foundations,and the impacts on the bearing capacities of bucket foundations need to be evaluated.In this paper,the contact ratio(the ratio of the top diameter of the soil plug to the diameter of the bucket)and the soil plug ratio(the ratio of the soil heave height to the skirt height)are defined to describe the shape and size of the incomplete soil plug.Then,finite element models are established to investigate the bearing capacities of bucket foundations with incomplete soil plugs and the influences of the contact ratios,and the soil plug ratios on the bearing capacities are analyzed.The results show that the vertical bearing capacity of bucket foundations in homogeneous soil continuously improves with the increase of the contact ratio.However,in normally consolidated soil,the vertical bearing capacity barely changes when the contact ratio is smaller than 0.75,while the bearing capacity suddenly increases when the contact ratio increases to 1 due to the change of failure mode.The contact ratio hardly affects the horizontal bearing capacity of bucket foundations.Moreover,the moment bearing capacity improves with the increase of the contact ratio for small aspect ratios,but hardly varies with increasing contact ratio for aspect ratios larger than 0.5.Consequently,the reduction coefficient method is proposed based on this analysis to calculate the bearing capacities of bucket foundations considering the influence of incomplete soil plugs.The comparison results show that the proposed reduction coefficient method can be used to evaluate the influences of incomplete soil plug on the bearing capacities of bucket foundations.
文摘In order to improve the properties of corundum based dispersive purging plugs,dispersive purging plug specimens were prepared using tabular corundum(1-0.15 and≤0.15 mm)as the aggregates,tabular corundum(≤0.044 mm)andα-Al_(2)O_(3)micropowder(d_(50)=0.6μm)as the matrix,Secar 71 cement as the binder,introducing different amounts of nano-CaCO_(3),casting into shapes,and firing at different temperatures(1200 or 1600℃)for 4 h.The effects of the nano-CaCO_(3) extra-addition(0,0.5%,1.0%,1.5%and 2.0%,by mass)on the consistency of the castables as well as the properties and microstructure of the dispersive purging plug specimens were studied.The results show that:(1)with the fixed water addition,the consistency of the corundum castables decreases as the nano-CaCO_(3)addition increases;(2)with the increasing nano-CaCO_(3)addition,the bulk density of the specimens fired at different temperatures for 4 h decreases,the apparent porosity,the cold strength and the hot modulus of rupture all increase,the gas permeability does not change significantly;(3)the specimens fired at 1600℃ for 4 h have obviously better cold comprehensive performance than those fired at 1200℃for 4 h;(4)when the nano-CaCO_(3)addition is 1.5%,the comprehensive performance of the specimen is the optimal.
文摘Major aortopulmonary collateral arteries (MAPCAs) are congenital vessels that arise from the aorta or its first-order branches and are distally connected to the pulmonary arterial vasculature, thereby providing pulmonary blood flow. MAPCAs are often associated with cyanotic congenital heart disease with decreased pulmonary blood flow. Isolated MAPCAs are rare in patients without congenital heart disease with structurally normal hearts. Sometimes, isolated congenital MAPCAs can occur without any lung disease. Isolated MAPCAs represent the occurrence of collaterals in the absence of underlying heart disease, which commonly presents as heart failure, recurrent respiratory tract infection, and pulmonary artery hypertension. We report a rare case of congestive heart failure in a 6-year-old patient with dual arterial supply to an otherwise normal right lung, with a normal bronchial tree, and a structurally normal heart. The patient was successfully managed by the closure of collaterals by Amplatzer vascular plugs II (AVPII) and Amplatzer Piccolo Occluders.
基金The authors wish to acknowledge the Open Foundation of Cooperative Innovation Center of Unconventional Oil and Gas,Yangtze University(Ministry of Education&Hubei Province),(Item No.UOGBX2022-04,UOG2022-26,UOGBX2022-05)the National Natural Science Foundation of China"New method and control mechanism of surface rotary steering drilling"(Item No.51974035,U1262108,U1762214)the key R&D program of Hubei Province"Development and application of multi-dimensional power integrated drilling tools for intelligent drilling"(Item No.2020BAB055)for the financial support to this paper。
文摘A high-quality plug of the abandoned wellbore is considered an essential technical aspect of the oil and gas well abandonment technology system. This paper presents a method of active mechanical excitation to enhance the quality of wellbore plug barriers. An indoor simulation platform is developed, and the effects of different combinations of vibration frequency, amplitude and duration on the properties of the wellbore plug cement material are investigated. It is observed that the optimal combination of excitation parameters occurs at a vibration frequency of 15 Hz, a vibration time of 6 min, and a vibration amplitude of 3 mm. Compared with the condition without the vibration process, the cementing strength, compressive strength, and tensile strength of wellbore cement plug with the optimal mechanical vibration process could increase by 51%, 38% and 20%, respectively, while the porosity decreases by 5%. As determined by scanning electron microscopy of the set cement's microstructure, mechanical vibration effectively eliminates internal porosity and improves the set cement's density. The optimal excitation parameters obtained from the test can guide the design of the vibration plugging tool. The designed vibration plugging tool is simulated in the near field. The cement plug cementation quality tester tests the vibrating and non-vibrating samples, and the cementation ratio is calculated. The test results show that the average cementation ratio of vibrating samples is 0.89375, and that of non-vibrating samples is 0.70625, and the cementation quality is improved by 27%. It is concluded that it not only provides essential data for the design of mechanical vibration plug apparatus, on-site vibration plugs, and the development of operational specifications for vibration plugs, but also provides solid engineering guidance.
文摘To clean out the smear layer on teeth surface, and protect the teeth medulla, the experiment applied the study observing the cleanup of six groups of surface smear layer of dental caries and the tubule plugs reserving effect after using of different cavity cleansers with the help of SEM. The result implied that both the acidic preparations and chelator could clean out the smear layer on teeth surface in some way, but the later one could also reserve partial tubule plugs, which reduce the stimulation to the teeth medulla. So the chelator is better cleansers in clinical use.
文摘Gas hydrates and wax are the major flow assurance problems for the transportation of produced hydrocarbons through pipelines.However,in most research works both these two problems are studied separately.Although simultaneous precipitation or deposition of these compounds in pipelines can lead to different mitigation/prevention strategies,the investi-gations in which both these problems are considered simultaneously appeared only recently.There is no information in the literature on the texture/composition and features of decomposition process of mixed wax/hydrate plugs.At the same time,this information could be useful to understand how to treat the problem of formation of these plugs.In this work,three wax/gas hydrate plugs were collected at quasi-static conditions from a water-in-oil emulsion to study their texture,composition and the features of decomposition process.Powder X-ray diffraction and IR(infrared spectroscopy)analyses showed that the plugs consisted of wax and gas hydrate.Thermovolumetric and DSC(Differential Scanning Calorimetry)experiments showed that the main part of gas hydrate in the plugs at the ambient pressure started to decompose at about 268 K.This temperature was higher than the equilibrium temperature of carbon dioxide hydrate at this pressure,indicating that the gas hydrate in the plugs could be effectively preserved at temperatures below the ice melting point(273.2 K).It was found through observation of the hydrate decomposition process in the plugs under the microscope that the gas in the samples released in small bubbles,while the hydrate particles were not visible at this magnification,indicating that the hydrate was indeed highly dispersed in the samples.A residual wax was jelly-like after decomposition of hydrate in all the cases.Rheological experiments showed that the plugs residues after decomposition of the hydrates had higher yield points and viscosities than the initial waxy crude oil origi-nally used for the experiments.
文摘AIM: To investigate donor site's area histological and immunohistochemical knee cartilage appearances after resurfacing iatrogenic defects with biosynthetic plugs orautografts. METHODS: Thirty New Zealand White rabbits were used in this study. A full-thickness cylindrical defect of 4.5 mm(diameter) × 7 mm(depth) was created with a hand drill in the femoral groove of every animal. In Group A(n = 10) the defect of the donor site was re-paired with a biosynthetic osteochondral plug, in Group B(n = 10) with an osteochondral autograft, while in Group C(control group of 10) rabbits were left untreated. RESULTS: Twenty-four weeks postoperatively, smooth articular cartilage was found macroscopically in some trocleas' surfaces; in all others, an articular surface with discontinuities was observed. Twenty-eight out of 30 animals were found with predominantly viable chondrocytes leaving the remaining two-which were found only in the control group- with partially viable chondrocytes. However, histology revealed many statistical differences between the groups as far as the International Cartilage Repair Society(ICRS) categories are concerned. Immunofluoresence also revealed the presence of collagen Ⅱ in all specimens of Group B, whereas in Group A collagen Ⅱ was found in less specimens. In Group C collagen Ⅱwas not found. CONCLUSION: The matrix, cell distribution, subchondral bone and cartilage mineralization ICRS categories showed statistically differences between the three groups. Group A was second, while group B received the best scores; the control group got the worst ICRS scores in these categories. So, the donor site area, when repairing osteochondral lesions with autografting systems, is better amended with osteochondral autograft rather than bone graft substitute implant.
文摘Purpose: To determine if there were differences in quality of life (QOL) within the first year following EVAR for patients undergoing internal iliac embolization depending on the type of device used. Methods: Patients who underwent endovascular AAA repair were identified using a Vascular surgery database at a tertiary care center from 2002-2008. The Radiology Information System and Image Viewer were then used to identify patients who underwent preprocedural embolization prior to endovascular aneurysm repair. Nine patients had embolization with nester coils, 9 had embolization with the amplatzer vascular plug, a type of nitinol based self expanding device. Another group of 8 patients who did not undergo preprocedural embolization was used as a comparator group. These patients were contacted via telephone and answered questions regarding QOL post procedure. The Australian Vascular QOL was the tool used to measure QOL. Differences in QOL were tabulated between the groups of patients. Results: Of the 9 patients who underwent embolization with amplatzer plug, the median QOL score was 60 (p value 0.575), the median QOL for the nester coil group was 52.5 and the comparator group was 58. Separate analysis was done dividing patients into two groups, with and without comorbidities without statistical significance. Conclusion: Patients who underwent preprocedural embolization using amplatzer plugs compared to coils had higher overall QOL scores although the difference was not significant.
文摘Purpose:Evaluation of the patency and position of perforated lacrimal punctal plugs implanted for treating punctal stenosis together with quantitative assessment of the precorneal tear film using anterior segment optical coherence tomography(AS-OCT).Methods:In a prospective study,the lower punctum of 54 eyes of 29 patients implanted with perforated punctal plugs were examined using AS-OCT during the early postoperative period.Preoperative tear meniscus height(TMH)and tear meniscus area(TMA)were evaluated.Postoperatively,the patency of the plug,its position,TMH and TMA were evaluated,and the results were correlated with postoperative epiphora.Munk scale was used for epiphora grading.Results:Using AS-OCT,48(88.9%)plugs were found in proper position while 6(11.1%)were rotated.The lumen of the plugs was completely patent in 47(87%)plugs,partially obstructed in 2(3.7%)plugs and completely occluded in 5(9.2%)plugs.There was a statistically significant postoperative decrease of TMH and TMA(P<0.001)and postoperative epiphora Munk score(P<0.001).Conclusion:AS-OCT is a valuable,reliable,and noninvasive investigative tool that can detect the proper positioning,patency,and contents of the implanted perforated lacrimal punctal plugs in addition to measurement of TMH and TMA.
文摘As an independent sand control unit or a common protective shell of a high-quality screen,the punching screen is the outermost sand retaining unit of the sand control pipe which is used in geothermal well or oil and gas well.However,most screens only consider the influence of the internal sand retaining medium parameters in the sand control performance design while ignoring the influence of the plugging of the punching screen on the overall sand retaining performance of the screen.To explore the clogging mechanism of the punching screen,this paper established the clogging mechanism calculation model of a single punching screen sand control unit by using the computational fluid mechanics-discrete element method(CFD-DEM)combined method.According to the combined motion of particles and fluids,the influence of the internal flow state on particle motion and accumulation was analyzed.The results showed that(1)the clogging process of the punching sand control unit is divided into three stages:initial clogging,aggravation of clogging and stability of clogging.In the initial stage of blockage,coarse particles form a loose bridge structure,and blockage often occurs preferentially at the streamline gathering place below chamfering inside the sand control unit.In the stage of blockage intensification,the particle mass develops into a relatively complete sand bridge,which develops from both ends of the opening to the center of the opening.In the stable plugging stage,the sand deposits show a“fan shape”and form a“V-shaped”gully inside the punching slot element.(2)Under a certain reservoir particle-size distribution,The slit length and opening height have a large influence on the permeability and blockage rate,while the slit width size has little influence on the permeability and blockage rate.The microscopic clogging mechanism and its law of the punching screen prevention unit are proposed in this study,which has some field guidance significance for the design of punching screen and sand prevention selection.
基金This work has been Sponsored by CNPC Innovation Found(Grant No.2021DQ02-0202)Besides,the authors gratefully appreciate the financial support of the Science Foundation of China University of Petroleum,Beijing(Grant No.2462020XKBH013)Financial supports from the National Natural Science Foundation of China(Grant No.52174046)is also significantly acknowledged.
文摘Conformance control and water plugging are a widely used EOR method in mature oilfields.However,majority of conformance control and water plugging agents are unavoidable dehydrated situation in high-temperature and high-salinity low permeability reservoirs.Consequently,a novel conformance control system HPF-Co gel,based on high-temperature stabilizer(CoCl_(2)·H_(2)O,CCH)is developed.The HPF-Co bulk gel has better performances with high temperature(120℃)and high salinity(1×10^(5)mg/L).According to Sydansk coding system,the gel strength of HPF-Co with CCH is increased to code G.The dehydration rate of HPF-Co gel is 32.0%after aging for 150 d at 120℃,showing excellent thermal stability.The rheological properties of HPF gel and HPF-Co gel are also studied.The results show that the storage modulus(G′)of HPF-Co gel is always greater than that of HPF gel.The effect of CCH on the microstructure of the gel is studied.The results show that the HPF-Co gel with CCH has a denser gel network,and the diameter of the three-dimensional network skeleton is 1.5-3.5μm.After 90 d of aging,HPF-Co gel still has a good three-dimensional structure.Infrared spectroscopy results show that CCH forms coordination bonds with N and O atoms in the gel amide group,which can suppress the vibration of cross-linked sites and improve the stability at high temperature.Fractured core plugging test determines the optimized polymer gel injection strategy and injection velocity with HPF-Co bulk gel system,plugging rate exceeding 98%.Moreover,the results of subsequent waterflooding recovery can be improved by 17%.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.51575528)the Science Foundation of China University of Petroleum,Beijing(No.2462022QEDX011).
文摘Pipeline isolation plugging robot (PIPR) is an important tool in pipeline maintenance operation. During the plugging process, the violent vibration will occur by the flow field, which can cause serious damage to the pipeline and PIPR. In this paper, we propose a dynamic regulating strategy to reduce the plugging-induced vibration by regulating the spoiler angle and plugging velocity. Firstly, the dynamic plugging simulation and experiment are performed to study the flow field changes during dynamic plugging. And the pressure difference is proposed to evaluate the degree of flow field vibration. Secondly, the mathematical models of pressure difference with plugging states and spoiler angles are established based on the extreme learning machine (ELM) optimized by improved sparrow search algorithm (ISSA). Finally, a modified Q-learning algorithm based on simulated annealing is applied to determine the optimal strategy for the spoiler angle and plugging velocity in real time. The results show that the proposed method can reduce the plugging-induced vibration by 19.9% and 32.7% on average, compared with single-regulating methods. This study can effectively ensure the stability of the plugging process.
基金“Research and Application of Key Techniques for Drilling and Completion of Bozhong 19-6 Condensate Gas Field Development-Phase I”sub topic 4“Research on Leakage Prevention and Plugging Techniques for Fault and Buried Hill Reservoirs”,a Project of China National Offshore Oil (China)Co.,Ltd. (Project No.YXKY-2020-TJ-03).
文摘Fault fractures usually have large openings and considerable extension. Accordingly, cross-linked gel materials aregenerally considered more suitable plugging agents than water-based gels because the latter often undergo contaminationvia formation water, which prevents them from being effective over long times. Hence, in this study, aset of oil-based composite gels based on waste grease and epoxy resin has been developed. These materials havebeen observed to possess high compressive strength and resistance to the aforementioned contamination, therebyleading to notable increase in plugging success rate. The compressive strength, thickening time, and resistance toformation water pollution of these gels have been evaluated indoors. The results show that the compressivestrength of the gel can reach 11 MPa;additionally, the related gelation time can be controlled to be more than3 h, thereby providing a safe construction time;Invasion of formation water has a small effect on the gel strengthand does not shorten the thickening time. All considered performance indicators of the oil-based gel confirm itssuitability as a plugging agent for fault fractures.
基金This work was sponsored by the National Natural Science Foundation of China(No.52172029)the Natural Science Foundation of Henan(No.202300410473).
文摘This paper aims to improve the corrosion resistance of dispersive purging plugs.White fused corundum particles and fine powder,α-Al_(2)O_(3) micropowder,Cr_(2)O_(3) micropowder,Guangxi clay and zircon powder were used as the main raw materials.The mass ratio of white fused corundum particles and fine powder was fixed at 85:15,and 0,1%,2%,or 3%(by mass)of zircon fine powder was added to replace the same amount of white fused corundum fine powder.The corundum porous material was prepared by the particle stacking pore-forming method at 1650℃for 3 h.The effect of the zircon addition on the properties and microstructure of porous materials was investigated.The results show that:after adding zircon,the permeability of the porous material increases,the cold and hot strengths increase obviously,and the expansion rate after firing decreases.When the addition of zircon is 2%,the comprehensive performance of the specimen is optimal with the smallest linear change rate and the highest permeability.
文摘The use of biopsy plugs to sample fish muscle tissue for mercury analyses is a viable alternative to lethal sampling; however, the practice has yet to be widely implemented in routine monitoring due to concerns about variability of mercury concentrations in fish muscle tissues. Here we examine distribution of mercury in fillets of four fish species(Walleye, Northern Pike, Smallmouth Bass and Lake Trout), suitability of left/right side of fillet for biopsy sampling, and appropriateness of re-using a biopsy punch. The results showed that average mercury concentrations in left and right fillets of fish are similar.Mercury concentrations in biopsy plug samples, taken from the anterior dorsal area of the fish fillet, were statistically equivalent to the mercury concentrations in homogenized fillets. There was no discernible cross contamination between samples when a biopsy punch was reused after washing in hot soapy water, and as such, biopsy punches can be recycled during sampling to reduce the sampling cost. If a tissue mass collected from a specific site on the fillet is insufficient, then we suggest sampling corresponding locations on the other fillet rather than sampling two adjacent sites on one fillet to obtain more tissue. The results presented here can improve the accuracy of fillet biopsy plug sampling,minimize fish mortality for mercury monitoring, and reduce labor and material costs in monitoring programs.
文摘Plugs are crucial for initiating crop production in greenhouses, soil, and controlled environment agriculture (CEA). Vegetable, fruiting, ornamental, and other horticultural crops that utilize plugs for production have demonstrated superior transplant establishment rate, plant health, and total yield. The APS Laboratory for Sustainable Food at Florida Gulf Coast University investigated the quality of plugs grown based on different concentrations and fertigation sources using synthetic and organic sources. We carried out the growth of “Rex Butterhead” Lettuce (Latuca sativa) plugs with five different fertigation treatments, 1) full-strength synthetic starter fertilizer solution;2) half-strength synthetic starter fertilizer solution;3) full-strength organic starter fertilizer solution;4) half-strength organic starter fertilizer solution, and 5) no fertilizer for control. Fertilizer treatments were formulated following manufacturer recommendations. The seeds were sown in Oasis<sup>®</sup> Horticubes and saturated every day with the different fertilizer treatments. The plugs were cultivated for 15 days in a controlled environment until two leaves after the cotyledons had developed. After 15 days, we collected data which included wet weight (g), dry weight (g), leaf area (cm<sup>2</sup>), and chlorophyll concentration (mg/cm<sup>2</sup>). In addition, we derived data including the Leaf Area Index (LAI, cm<sup>2</sup>/cm<sup>2</sup>) and Specific Leaf Area (SLA, cm<sup>2</sup>/g). Descriptive statistics were used to describe the biomass data. A Tukey’s HSD test was carried out to understand the differences between the fertilizer sources. We determined there was a statistically significant difference (P = 7.34E−29) in the measured plug growth parameters due to the various fertigation sources. We found that all fertilizer treatments produced viable plugs except for the control treatment. Of all the treatments, we concluded the half-strength organic treatment produced the more vigorous plugs with the greatest wet weight (g) and largest total leaf area (cm<sup>2</sup>) which was statistically significantly different. Results from this study may inform growers about appropriate fertilizer options for plug production.
基金Supported by National Natural Science Foundation of China (U21A20105)Science and Technology Innovation Fund of PetroChina (2020D-5007-0208)。
文摘Using the visualized experimental device of temporary plugging in hydraulic fractures, the plugging behaviors of temporary plugging particles with different sizes and concentrations in hydraulic fractures were experimentally analyzed under the conditions of different carrier fluid displacements and viscosities. The results show that the greater the carrier fluid viscosity and displacement, the more difficult it is to form a plugging layer, and that the larger the size and concentration of the temporary plugging particle, the less difficult it is to form a plugging layer. When the ratio of particle size to fracture width is 0.45, the formation of the plugging layer is mainly controlled by the mass concentration of the temporary plugging particle and the viscosity of the carrier fluid, and a stable plugging layer cannot form if the mass concentration of the temporary plugging particle is less than 20 kg/m^(3)or the viscosity of the carrier fluid is greater than 3 mPa·s. When the ratio of particle size to fracture width is 0.60, the formation of the plugging layer is mainly controlled by the mass concentration of the temporary plugging particle, and a stable plugging layer cannot form if the mass concentration of the temporary plugging particle is less than 10 kg/m^(3). When the ratio of particle size to fracture width is 0.75, the formation of the plugging layer is basically not affected by other parameters, and a stable plugging layer can form within the experimental conditions. The formation process of plugging layer includes two stages and four modes. The main controlling factors affecting the formation mode are the ratio of particle size to fracture width, carrier fluid displacement and carrier fluid viscosity.
基金This research is financially supported by the National Natural Science Foundation of China(Grant 52074327,52288101)the Natural Science Foundation of Shandong Province,China(ZR2020QE107).
文摘The excellent mechanical properties of supramolecular gel could adapt to the complex reservoir environment and had broad application prospects in the field of oil and gas drilling and production engineering.In this paper,a supramolecular gel based on hydrophobic association and hydrogen bonding was prepared by micellar copolymerization,which could be used to plug fractures and pores in formations.Supramolecular gel was a gel network system with high performance characteristics formed by self-assembly of non-covalent bond interaction.The rheological properties,mechanical mechanics,temperature resistance and swelling ability of supramolecular gel were studied.The results showed that the supramolecular gel had a dense three-dimensional network structure with open and interconnected pore structures,which could exhibit good rheological properties and strong viscoelastic recovery ability.The mechanical properties of the supramolecular gel were excellent,it had a tensile stress of 0.703 MPa and an elongation at break of 1803%.When the compressive strain was 96%,the compressive stress could reach 14.5 MPa.Supramolecular gel also showed good temperature resistance and swelling properties.At the aging temperature of 135℃,supramolecular gels still maintained good gel strength,and it only took 12 h to reach the equilibrium swelling ratio of 35.87 in 1%NaCl solution.It was also found that supramolecular gel in low concentration saline(1%NaCl solution)showed relatively faster swelling than high concentration saline(25%NaCl solution).The swelling process of the supramolecular gel was non-Fick diffusion(typeⅡ).This indicated that the organic/inorganic permeability network was well formed.Therefore,the diffusion rate of small molecules could be guaranteed to be equal to the relaxation rate of large molecules before and after the phase transition temperature.In addition to the diffusion of water molecules,the swelling process of the supramolecular gel was also affected by the relaxation of gel network and polymer chain segment,the interaction between water molecules and polymer network and the groups of polymer network and other factors.Supramolecular gel particles could be used as plugging materials for drilling fluids,which had excellent ability to plug formation fractures and pores.The plugging ability of the supramolecular gel was up to 6.7 MPa for 0.5 mm fracture width,and 9.6 MPa for porous media with 5 mD permeability.Compared with HT-PPG gel particles commonly used in oil fields,supramolecular gel particles had better plugging ability on fractures and porous media.The development and application of supramolecular gel had far-reaching significance for promoting the functional application of polymer materials in drilling and production engineering.
基金financially supported by the Key-Area Research and Development Program of Guangdong ProvinceChina(Grant No.2022B0101100001)+3 种基金the Marine Economic Development Special Program of Guangdong province(Six Major Marine Industries):Research and Demonstration of Critical Technologies for Comprehensive Prevention and Control of Natural Disaster in Offshore Wind FarmsChina(Grant No.29[2023])the Guangxi Key Laboratory of Disaster Prevention and Mitigation and Engineering SafetyChina(Grant No.2020ZDK002)。
文摘The application of the wellhead suction anchor in the second production test of natural gas hydrates(NGHs)in the South China Sea(SCS)was met with success.This design incorporates a central conductor guide pipe,which distinguishes it from traditional suction foundations.However,this addition resulted in a relatively high penetration resistance and a shallower penetration depth at the self-weight penetration stage.To mitigate this issue,the current study proposes an optimized design where the end of the suction foundation is sharpened.The installation characteristics of the traditional suction foundation and new suction foundation during self-weight penetration into sand are studied through laboratory tests and theoretical analysis.The flat and sharpened bottom shapes are considered in the traditional and new suction models.The effects of the initial penetration velocity on the initial penetration depth and soil plug and impact cavity characteristics are systematically studied.The results show that the self-weight penetration depth of the foundation with a sharpened bottom is 44.5%deeper than that of the foundation with a flat bottom.There are cavities around the foundation at the self-weight penetration stage,and the penetration depth is overestimated by 15%-30%.Finally,a model for predicting the penetration depth of the new suction foundation is proposed.
基金supported financially by the Beijing Natural Science Foundation Project(No.3222030)the National Natural Science Foundation of China(No.51936001,No.52274002 and No.52192622)+1 种基金the PetroChina Science and Technology Innovation Foundation Project(2021DQ02–0201)Award Cultivation Foundation from Beijing Institute of Petrochemical Technology(No.BIPTACF-002).
文摘The effective plugging of artificial fractures is key to the success of temporary plugging and diverting fracturing technology,which is one of the most promising ways to improve the heat recovery efficiency of hot dry rock.At present,how temporary plugging agents plug artificial fractures under high temperature remains unclear.In this paper,by establishing an improved experimental system for the evaluation of temporary plugging performance at high temperature,we clarified the effects of high temperature,injection rate,and fracture width on the pressure response and plugging efficiency of the fracture.The results revealed that the temporary plugging process of artificial fractures in hot dry rock can be divided into four main stages:the initial stage of temporary plugging,the bridging stage of the particles,the plugging formation stage,and the high-pressure dense plugging stage.As the temperature increases,the distribution distance of the temporary plugging agent,the number of pressure fluctuations,and the time required for crack plugging increases.Particularly,when the temperature increases by 100℃,the complete plugging time increases by 90.7%.
