Ball-sealer plugging is a cost-effective method for hydraulic fracturing in vertical wells,yet the transport and plugging behavior of ball sealers remains poorly understood.This paper investigates ball-sealer plugging...Ball-sealer plugging is a cost-effective method for hydraulic fracturing in vertical wells,yet the transport and plugging behavior of ball sealers remains poorly understood.This paper investigates ball-sealer plugging using both experimental and numerical approaches.A coupled computational fluid dynamics(CFD) and discrete element method(DEM) model simulates ball transport under field conditions,validated by experiments in inclined pipes.Results show that plugging performance improves with a higher flow rate ratio of the perforation,allowing effective plugging even when the ball is far from the target perforation.There exists a threshold distance between the ball and the perforation under specific conditions.The closer the ball is to the wellbore wall,the higher the likelihood of successful plugging.Low-density balls can enhance plugging performance to some extent.At high flow rates,ball inertia along the wellbore axis increases,reducing the ball's ability to redirect and weakening plugging performance.Ball interactions also affect their positioning and plugging success.In vertical wells with multiple clusters,prioritizing higher flow rates to the first fracturing cluster optimizes overall plugging performance and minimizes excessive plugging in lower,under-stimulated clusters.These findings offer valuable insights for optimizing ball-sealer deployment in well completions,improving operational outcomes.展开更多
Ball-sealer in-stage diversion in horizontal wells is a key technique to realize the uniform stimulation of fractured sections in tight oil and gas reservoirs.So far,however,there are fewer research results on the pro...Ball-sealer in-stage diversion in horizontal wells is a key technique to realize the uniform stimulation of fractured sections in tight oil and gas reservoirs.So far,however,there are fewer research results on the propagation morphologies of multi-cluster fractures after the implementation of different ball-sealer in-stage diversion processes during the fracturing treatment,which results in less theoretical support for the preparation offield ball-sealer in-stage diversion process and measures and impacts its application effects in the fracturingfield.To deal with this situation,this paper established a fully coupled“wellboreeperforationefracture propagation”model of horizontal wells on the basis of the boundary element method.Then,a method for calculating the allocation of ball sealers was proposed.Finally,the number of ball sealers,diversion time and number of diversions during the intra-stage temporary plugging and diversion under the condition of initial heterogeneous stressfield and their effects on the propagation of multi-cluster fractures were simulated.And the following research results were obtained.First,theflow restriction of perforation friction can counterbalance the intake difference caused by the induced stress interference so that the friction difference applied on thefluidflow in each fracture cluster is reduced.Second,when the effect of the heterogeneous distribution of the initial stressfield is taken into consideration,the liquid intake of each fracture cluster changes greatly and even ineffective perforation clusters without liquid incoming appear in the high-stress region.And after the ball is injected,new fractures are initiated from the ineffective perforation clusters.Third,when the initial minimum horizontal principal stress difference(Dsh)is higher than 3 MPa,it is beneficial to reduce the non-uniform propagation of each fracture cluster by increasing the number of ball sealers appropriately in the middle stage of the construction(over half of the total perforations of each stage)or carrying out temporary plugging in the earlyemiddle stage(including ball injection in batches in the earlyemiddle stage).Fourth,when Dsh is lower than 2 MPa,it is necessary to reduce the number of ball sealers or inject balls in the middleelate stage,or the non-uniform propagation of each fracture cluster will be aggravated.展开更多
The flowability of a root canal sealer is clinically important because it improves the penetration of the sealer into the complex root canal system. The purpose of this study was to compare the flowabilities of four r...The flowability of a root canal sealer is clinically important because it improves the penetration of the sealer into the complex root canal system. The purpose of this study was to compare the flowabilities of four root canal sealers, measured using the simple press method （ISO 6876）, and their viscosities, measured using a strain-controlled rheometer. A newly developed, calcium phosphate-based root canal sealer （Capseal） and three commercial root canal sealers （AH Plus, Sealapex and Pulp Canal Sealer EWT） were used in this study. The flowabilities of the four root canal sealers were measured using the simple press method （n= 5） and their viscosities were measured using a strain-controlled rheometer （n=5）. The correlation between these two values was statistically analysed using Spearman＇s correlation test. The flow diameters and the viscosities of the root canal sealers were strongly negatively correlated （p= -0.8618）. The viscosity of Pulp Canal Sealer EWT was the lowest and increased in the following order： AH Plus〈Sealapex〈Capseal （P〈0.05）. All of the tested root canal sealers showed characteristic time- and temperature-dependent changes in their rheological properties. The viscosities measured using the strain-controlled rheometer were more precise than the flowabilities measured using the simple press method, suggesting that the rheometer can accurately measure the rheological properties of root canal sealers.展开更多
BACKGROUND The success rate of conservative endodontic management for root fracture varies greatly based on different methods used.It has been rarely reported that calcium silicate-based materials are applied in root ...BACKGROUND The success rate of conservative endodontic management for root fracture varies greatly based on different methods used.It has been rarely reported that calcium silicate-based materials are applied in root fracture treatment.CASE SUMMARY A 38-year-old male patient presented with spontaneous pain from the upper left anterior teeth for 1 wk.The spontaneous pain was subsequently relieved,but pain on mastication persisted for 3 d.The patient had a dental trauma from a boxing match 15 years ago.Cone beam computed tomography showed that the maxillary left central incisor had oblique fracture lines and a radiolucent lesion around the fracture line.The tooth was diagnosed with an oblique root fracture with no healing and symptomatic apical periodontitis.In the following conservative endodontic management,the coronal and apical fragments of the canal both were chemo-mechanically prepared and obturated using a single cone gutta-percha with iRoot SP(Innovative BioCreamix Inc,Vancouver,Canada),a new calcium silicate-based bioceramic root canal sealer.At follow-ups at 1,6,12,and 24 mo,the patient was asymptomatic and the radiolucency around the fracture line was healing radiographically.CONCLUSION Conservative root canal treatment is an alternative treatment in some cases of oblique root fracture with no healing.The application of bioceramic sealers and single core obturation techniques may also be essential to obtain an excellent outcome.展开更多
Background: One of the ideal properties of a root canal sealer is to have a good sealing ability, especially at the apical third of the root. Objective: To evaluate the comparison of the apical leakage between obturat...Background: One of the ideal properties of a root canal sealer is to have a good sealing ability, especially at the apical third of the root. Objective: To evaluate the comparison of the apical leakage between obturation using bioceramic sealer (BS) and polydimethylsiloxane sealer (PS). Materials and Methods: Thirty-six mandibular premolars were equally divided into two groups and were obturated with single cone technique. The sealers used for Group I and Group II were BS and PS respectively. After obturation, the samples were incubated (37°C, 24 h), sealed with two coats of nail polish except for 2 mm from the apex, submerged in the Indian ink for 7 days, decalcified, dehydrated, and made transparent according to Robertson technique. Dye penetration was evaluated under stereomicroscope. Samples without dye penetration were given score 0, dye penetration ≤ 0.5 mm were given score 1, 0.51 - 1 mm were given score 2, and >1 mm were given score 3. Result: The largest proportion distribution in BS group was at the score 1 (55.6%), whereas in PS group was at the score 2 (44.4%). Conclusion: Bioceramic sealer showed similar apical leakage to polydimethylsiloxane sealer. Clinical Relevance: Based on this study, bioceramic sealer can be recommended to be used as sealer with low level of apical leakage as well as polydimethylsiloxane sealer.展开更多
This study examined the adhesive strength of two self-adhesive methacrylate resin-based sealers（MetaSEAL and RealSeal SE） to root dentin and compared them with RealSeal and AH Plus in properties. A total of 48 extra...This study examined the adhesive strength of two self-adhesive methacrylate resin-based sealers（MetaSEAL and RealSeal SE） to root dentin and compared them with RealSeal and AH Plus in properties. A total of 48 extracted human single-rooted teeth were used to prepare the 0.9-mm thick longitudinal tooth slice（each per tooth）. Standardized simulated canal spaces of uniform dimensions were prepared in the middle of radicular dentin. After treated with 5.25% sodium hypochlorite（NaOCl） and 17% EDTA, tooth slices were allocated randomly to four groups（n=12） in terms of different sealers used： MetaSEAL, RealSeal SE, RealSeal, and AH plus groups. The simulated canal spaces were obturated with different sealers in each group. There were 10 slabs with 20 simulated canal spaces（n=20） used in each group for push-out testing. The failure modes and the ultrastructures of fractured sealer-dentin interfaces were examined. The remaining 2 slabs in each group underwent partial demineralization for observation of the ultrastructure of resin tags. The results showed that the push-out bond strength was 12.01±4.66 MPa in MetaSEAL group, significantly higher than that in the other three groups（P0.05）. Moreover, no statistically significant differences were noted in the push-out bond strength between RealSeal SE（5.43±3.68 MPa） and AH Plus（7.34±2.83 MPa） groups and between RealSeal SE and RealSeal（2.93±1.76 MPa） groups（P0.05）. Mixed failures were predominant in the fractured sealer-dentin interfaces in MetaSEAL and AH Plus groups, while adhesive failures were frequently seen in RealSeal SE and RealSeal groups. In conclusion, after complete removal of the smear layer, MetaSEAL showed superior bond ability to root dentin. The RealSeal SE is applicable in clinical practice, with its adhesive strength similar to that of AH Plus. The self-adhesive methacrylate resin-based sealer holds promise for use in endodontic treatment.展开更多
In the staged multi-cluster fracturing of shale gas horizontal wells, ball sealers are used to ensure uniform fluid distribution among clusters, a strategy that is both cost-effective and operationally beneficial. Des...In the staged multi-cluster fracturing of shale gas horizontal wells, ball sealers are used to ensure uniform fluid distribution among clusters, a strategy that is both cost-effective and operationally beneficial. Despite these advantages, comprehending the ball sealers' dynamics within the wellbore and their plugging behavior at perforations is still challenging. This complexity results in prediction difficulties regarding their diversion efficiency. To address this, our study utilized a semi-resolved CFD-DEM model based on kernel approximation to simulate the behavior of medium-sized ball sealers in single and multiple cluster scenarios. Our findings from a single cluster scenario reveal that the plugging probability is co-determined by velocity gradients in the fluid ingestion area near the perforation, backflow region, and inertial forces of the ball sealers. As the critical flow rate is achieved, the plugging probability negatively correlated with fluid viscosity and displacement, and positively correlated with the perforation flow ratio (PFR), the difference in particle-fluid density, ball sealer’s diameter, and the ball sealer’s offset from the pipeline center. Temporary plugging control efficiency was used to evaluate the flow balance effect among multiple clusters. The results indicate that an increased number of ball sealers enhances the fault tolerance during the temporary plugging process. Nevertheless, excessive ball sealers might undermine the temporary plugging control efficiency, as perforations with lower fluid inflow rates are unexpectedly plugging. Higher differences in fluid injection rates between clusters led to increased efficiency in temporary plugging control. Premature deployment of ball sealers cannot effectively plug perforations with marginally higher fluid inflow rates, but instead accidently plug intermediate clusters with lower fluid inflow rates. These findings offer a theoretical basis for optimizing the design of ball sealers.展开更多
The purpose of this study was to evaluate the physical properties and bioactivity potential of epoxy-based dental sealers modified with synthesized bioactive glass(BAG),hydroxyapatite(HA)and fluorine substituted hydro...The purpose of this study was to evaluate the physical properties and bioactivity potential of epoxy-based dental sealers modified with synthesized bioactive glass(BAG),hydroxyapatite(HA)and fluorine substituted hydroxyapatite(FHA)nanoparticles.The synthesized powders were incorporated at 10%and 20%into the epoxy-based dental sealer.The setting time,flow and solubility and microhardness of the modified and unmodified samples were examined.The bioactivity was evaluated using FESEM-EDX and elemental mapping,ATR-FTIR and XRD.The flow value of all of the experimental groups except the FHA modified samples,was greater than 20 mm.Concerning solubility,no specimens exhibited more than 1%weight loss.The solubility value of the FHA groups was statistically significant lower than other groups(p≤0.001).The mean hardness values of all of the modified samples were significantly higher than the unmodified group(p≤0.001).Regarding bioactivity,in vitro study revealed that after 3 days immersion in SBF a compact and continuous calcium phosphate layer formed on the surface of epoxy sealers containing BAG and HA nanoparticles.Based on these results,the addition of BAG and HA nanoparticles did not adversely alter the physical properties of epoxy sealers.Additionally,they improved the in vitro bioactivity of the epoxy sealer.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.52274035)。
文摘Ball-sealer plugging is a cost-effective method for hydraulic fracturing in vertical wells,yet the transport and plugging behavior of ball sealers remains poorly understood.This paper investigates ball-sealer plugging using both experimental and numerical approaches.A coupled computational fluid dynamics(CFD) and discrete element method(DEM) model simulates ball transport under field conditions,validated by experiments in inclined pipes.Results show that plugging performance improves with a higher flow rate ratio of the perforation,allowing effective plugging even when the ball is far from the target perforation.There exists a threshold distance between the ball and the perforation under specific conditions.The closer the ball is to the wellbore wall,the higher the likelihood of successful plugging.Low-density balls can enhance plugging performance to some extent.At high flow rates,ball inertia along the wellbore axis increases,reducing the ball's ability to redirect and weakening plugging performance.Ball interactions also affect their positioning and plugging success.In vertical wells with multiple clusters,prioritizing higher flow rates to the first fracturing cluster optimizes overall plugging performance and minimizes excessive plugging in lower,under-stimulated clusters.These findings offer valuable insights for optimizing ball-sealer deployment in well completions,improving operational outcomes.
基金supported by the National Science and Technology Major Project"Post-fracturing fracture parameter evaluation of horizontal wells of shale gas"(No:2016ZX05060001-032).
文摘Ball-sealer in-stage diversion in horizontal wells is a key technique to realize the uniform stimulation of fractured sections in tight oil and gas reservoirs.So far,however,there are fewer research results on the propagation morphologies of multi-cluster fractures after the implementation of different ball-sealer in-stage diversion processes during the fracturing treatment,which results in less theoretical support for the preparation offield ball-sealer in-stage diversion process and measures and impacts its application effects in the fracturingfield.To deal with this situation,this paper established a fully coupled“wellboreeperforationefracture propagation”model of horizontal wells on the basis of the boundary element method.Then,a method for calculating the allocation of ball sealers was proposed.Finally,the number of ball sealers,diversion time and number of diversions during the intra-stage temporary plugging and diversion under the condition of initial heterogeneous stressfield and their effects on the propagation of multi-cluster fractures were simulated.And the following research results were obtained.First,theflow restriction of perforation friction can counterbalance the intake difference caused by the induced stress interference so that the friction difference applied on thefluidflow in each fracture cluster is reduced.Second,when the effect of the heterogeneous distribution of the initial stressfield is taken into consideration,the liquid intake of each fracture cluster changes greatly and even ineffective perforation clusters without liquid incoming appear in the high-stress region.And after the ball is injected,new fractures are initiated from the ineffective perforation clusters.Third,when the initial minimum horizontal principal stress difference(Dsh)is higher than 3 MPa,it is beneficial to reduce the non-uniform propagation of each fracture cluster by increasing the number of ball sealers appropriately in the middle stage of the construction(over half of the total perforations of each stage)or carrying out temporary plugging in the earlyemiddle stage(including ball injection in batches in the earlyemiddle stage).Fourth,when Dsh is lower than 2 MPa,it is necessary to reduce the number of ball sealers or inject balls in the middleelate stage,or the non-uniform propagation of each fracture cluster will be aggravated.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2011-0014231)supported by the National Research Foundation of Korea funded by Ministry of Education, Science and Technology (2009-0086835)+1 种基金supported by a grant from the Kyung Hee University in 2013 (KHU-20131045)supported by Grant No. 04-2009-0032 from the SNUDH Research Fund
文摘The flowability of a root canal sealer is clinically important because it improves the penetration of the sealer into the complex root canal system. The purpose of this study was to compare the flowabilities of four root canal sealers, measured using the simple press method （ISO 6876）, and their viscosities, measured using a strain-controlled rheometer. A newly developed, calcium phosphate-based root canal sealer （Capseal） and three commercial root canal sealers （AH Plus, Sealapex and Pulp Canal Sealer EWT） were used in this study. The flowabilities of the four root canal sealers were measured using the simple press method （n= 5） and their viscosities were measured using a strain-controlled rheometer （n=5）. The correlation between these two values was statistically analysed using Spearman＇s correlation test. The flow diameters and the viscosities of the root canal sealers were strongly negatively correlated （p= -0.8618）. The viscosity of Pulp Canal Sealer EWT was the lowest and increased in the following order： AH Plus〈Sealapex〈Capseal （P〈0.05）. All of the tested root canal sealers showed characteristic time- and temperature-dependent changes in their rheological properties. The viscosities measured using the strain-controlled rheometer were more precise than the flowabilities measured using the simple press method, suggesting that the rheometer can accurately measure the rheological properties of root canal sealers.
文摘BACKGROUND The success rate of conservative endodontic management for root fracture varies greatly based on different methods used.It has been rarely reported that calcium silicate-based materials are applied in root fracture treatment.CASE SUMMARY A 38-year-old male patient presented with spontaneous pain from the upper left anterior teeth for 1 wk.The spontaneous pain was subsequently relieved,but pain on mastication persisted for 3 d.The patient had a dental trauma from a boxing match 15 years ago.Cone beam computed tomography showed that the maxillary left central incisor had oblique fracture lines and a radiolucent lesion around the fracture line.The tooth was diagnosed with an oblique root fracture with no healing and symptomatic apical periodontitis.In the following conservative endodontic management,the coronal and apical fragments of the canal both were chemo-mechanically prepared and obturated using a single cone gutta-percha with iRoot SP(Innovative BioCreamix Inc,Vancouver,Canada),a new calcium silicate-based bioceramic root canal sealer.At follow-ups at 1,6,12,and 24 mo,the patient was asymptomatic and the radiolucency around the fracture line was healing radiographically.CONCLUSION Conservative root canal treatment is an alternative treatment in some cases of oblique root fracture with no healing.The application of bioceramic sealers and single core obturation techniques may also be essential to obtain an excellent outcome.
文摘Background: One of the ideal properties of a root canal sealer is to have a good sealing ability, especially at the apical third of the root. Objective: To evaluate the comparison of the apical leakage between obturation using bioceramic sealer (BS) and polydimethylsiloxane sealer (PS). Materials and Methods: Thirty-six mandibular premolars were equally divided into two groups and were obturated with single cone technique. The sealers used for Group I and Group II were BS and PS respectively. After obturation, the samples were incubated (37°C, 24 h), sealed with two coats of nail polish except for 2 mm from the apex, submerged in the Indian ink for 7 days, decalcified, dehydrated, and made transparent according to Robertson technique. Dye penetration was evaluated under stereomicroscope. Samples without dye penetration were given score 0, dye penetration ≤ 0.5 mm were given score 1, 0.51 - 1 mm were given score 2, and >1 mm were given score 3. Result: The largest proportion distribution in BS group was at the score 1 (55.6%), whereas in PS group was at the score 2 (44.4%). Conclusion: Bioceramic sealer showed similar apical leakage to polydimethylsiloxane sealer. Clinical Relevance: Based on this study, bioceramic sealer can be recommended to be used as sealer with low level of apical leakage as well as polydimethylsiloxane sealer.
文摘This study examined the adhesive strength of two self-adhesive methacrylate resin-based sealers（MetaSEAL and RealSeal SE） to root dentin and compared them with RealSeal and AH Plus in properties. A total of 48 extracted human single-rooted teeth were used to prepare the 0.9-mm thick longitudinal tooth slice（each per tooth）. Standardized simulated canal spaces of uniform dimensions were prepared in the middle of radicular dentin. After treated with 5.25% sodium hypochlorite（NaOCl） and 17% EDTA, tooth slices were allocated randomly to four groups（n=12） in terms of different sealers used： MetaSEAL, RealSeal SE, RealSeal, and AH plus groups. The simulated canal spaces were obturated with different sealers in each group. There were 10 slabs with 20 simulated canal spaces（n=20） used in each group for push-out testing. The failure modes and the ultrastructures of fractured sealer-dentin interfaces were examined. The remaining 2 slabs in each group underwent partial demineralization for observation of the ultrastructure of resin tags. The results showed that the push-out bond strength was 12.01±4.66 MPa in MetaSEAL group, significantly higher than that in the other three groups（P0.05）. Moreover, no statistically significant differences were noted in the push-out bond strength between RealSeal SE（5.43±3.68 MPa） and AH Plus（7.34±2.83 MPa） groups and between RealSeal SE and RealSeal（2.93±1.76 MPa） groups（P0.05）. Mixed failures were predominant in the fractured sealer-dentin interfaces in MetaSEAL and AH Plus groups, while adhesive failures were frequently seen in RealSeal SE and RealSeal groups. In conclusion, after complete removal of the smear layer, MetaSEAL showed superior bond ability to root dentin. The RealSeal SE is applicable in clinical practice, with its adhesive strength similar to that of AH Plus. The self-adhesive methacrylate resin-based sealer holds promise for use in endodontic treatment.
基金supported by National Natural Science Foundation of China(grant No.U21B2071)Youth Program of National Natural Science Foundation of China(grant No.52104039)Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(grant No.2020CX030201).
文摘In the staged multi-cluster fracturing of shale gas horizontal wells, ball sealers are used to ensure uniform fluid distribution among clusters, a strategy that is both cost-effective and operationally beneficial. Despite these advantages, comprehending the ball sealers' dynamics within the wellbore and their plugging behavior at perforations is still challenging. This complexity results in prediction difficulties regarding their diversion efficiency. To address this, our study utilized a semi-resolved CFD-DEM model based on kernel approximation to simulate the behavior of medium-sized ball sealers in single and multiple cluster scenarios. Our findings from a single cluster scenario reveal that the plugging probability is co-determined by velocity gradients in the fluid ingestion area near the perforation, backflow region, and inertial forces of the ball sealers. As the critical flow rate is achieved, the plugging probability negatively correlated with fluid viscosity and displacement, and positively correlated with the perforation flow ratio (PFR), the difference in particle-fluid density, ball sealer’s diameter, and the ball sealer’s offset from the pipeline center. Temporary plugging control efficiency was used to evaluate the flow balance effect among multiple clusters. The results indicate that an increased number of ball sealers enhances the fault tolerance during the temporary plugging process. Nevertheless, excessive ball sealers might undermine the temporary plugging control efficiency, as perforations with lower fluid inflow rates are unexpectedly plugging. Higher differences in fluid injection rates between clusters led to increased efficiency in temporary plugging control. Premature deployment of ball sealers cannot effectively plug perforations with marginally higher fluid inflow rates, but instead accidently plug intermediate clusters with lower fluid inflow rates. These findings offer a theoretical basis for optimizing the design of ball sealers.
基金supported by International Campus of Tehran University of Medical Sciences(IC-TUMS)and health Services grant No.9423684001.
文摘The purpose of this study was to evaluate the physical properties and bioactivity potential of epoxy-based dental sealers modified with synthesized bioactive glass(BAG),hydroxyapatite(HA)and fluorine substituted hydroxyapatite(FHA)nanoparticles.The synthesized powders were incorporated at 10%and 20%into the epoxy-based dental sealer.The setting time,flow and solubility and microhardness of the modified and unmodified samples were examined.The bioactivity was evaluated using FESEM-EDX and elemental mapping,ATR-FTIR and XRD.The flow value of all of the experimental groups except the FHA modified samples,was greater than 20 mm.Concerning solubility,no specimens exhibited more than 1%weight loss.The solubility value of the FHA groups was statistically significant lower than other groups(p≤0.001).The mean hardness values of all of the modified samples were significantly higher than the unmodified group(p≤0.001).Regarding bioactivity,in vitro study revealed that after 3 days immersion in SBF a compact and continuous calcium phosphate layer formed on the surface of epoxy sealers containing BAG and HA nanoparticles.Based on these results,the addition of BAG and HA nanoparticles did not adversely alter the physical properties of epoxy sealers.Additionally,they improved the in vitro bioactivity of the epoxy sealer.
