Intra-stage multi-cluster temporary plugging and diverting fracturing(ITPF)is one of the fastest-growing techniques to obtain uniform reservoir stimulation in shale gas reservoirs.However,propagation geometries of mul...Intra-stage multi-cluster temporary plugging and diverting fracturing(ITPF)is one of the fastest-growing techniques to obtain uniform reservoir stimulation in shale gas reservoirs.However,propagation geometries of multiple fractures during ITPF are not clear due that the existing numerical models cannot capture the effects of perforation plugging.In this paper,a new three-dimensional FEM based on CZM was developed to investigate multiple planar fracture propagation considering perforation plugging during ITPF.Meanwhile,the fluid pipe element and its subroutine were first developed to realize the flux partitioning before or after perforation plugging.The results showed that the perforation plugging changed the original distribution of the number of perforations in each fracture,thus changing the flux partitioning after perforation plugging,which could eliminate the effect of stress interference between multiple fractures and promote a uniform fluid distribution.The standard deviation of fluid distribution in the perforation plugging case was only 8.48%of that in the non-diversion case.Furthermore,critical plugging parameters have been investigated quantitatively.Specifically,injecting more diverters will create a higher fluid pressure rise in the wellbore,which will increase the risk of wellbore integrity.Comprehensively considering pressure rise and fluid distribution,the number of diverters should be 50%of the total number of perforations(N_(pt)),whose standard deviation of fluid distribution of multiple fractures was lower than those in the cases of injecting 10%N_(pt),30%N_(pt)and 70%N_(pt).The diverters should be injected at an appropriate timing,i.e.40%or 50%of the total fracturing time(tft),whose standard deviation of the fluid distribution was only about 20%of standard deviations in the cases of injecting at20%tftor 70%tft.A single injection with all diverters can maintain high bottom-hole pressure for a longer period and promote a more uniform fluid distribution.The standard deviation of the fluid distribution in the case of a single injection was 43.62%-55.41%of the other cases with multiple injection times.This study provides a meaningful perspective and some optimal plugging parameters on the field design during IPTF.展开更多
The purpose of closure of small dry tympanic membrane perforations is to restore the continuity of the tympanic membrane in order to improve hearing and decrease the incidence of middle ear infections. Small and cost ...The purpose of closure of small dry tympanic membrane perforations is to restore the continuity of the tympanic membrane in order to improve hearing and decrease the incidence of middle ear infections. Small and cost effective procedures like Chemical Cauterization and Fat Plug Myringoplasty have been found to be effective in healing small central perforations with significant hearing improvement. A study was carried out in 69 patients with central perforations in the Department of ENT, Gauhati Medical College & Hospital for the duration of 1 year from August 11 to July 12. Out of 69 patients, 36 underwent Chemical Cauterization and 33 Fat Plug Myringoplasty. Pre-and post-operative hearing assessments of each patient were done and statistically analyzed. The success rate was found to be 83.33% and 90.9% respectively. In both groups, there was statistically significant hearing improvement with a P value 0.01. From our study, it was found that the two procedures are simple, reliable and also lessened the morbidity of the patient. Thus we recommend the use of these two official procedures for the treatment of central perforations of tympanic membrane less than 5 mm.展开更多
Oblique perforation of thick metallic plates by rigid projectiles with various nose shapes is studied in this paper. Two perforation mechanisms, i.e., the hole enlargement for a sharp projectile nose and the plugging ...Oblique perforation of thick metallic plates by rigid projectiles with various nose shapes is studied in this paper. Two perforation mechanisms, i.e., the hole enlargement for a sharp projectile nose and the plugging formation for a blunt projectile nose, are considered in the proposed analytical model. It is shown that the perforation of a thick plate is dominated by several non-dimensional numbers, i.e., the impact function, the geometry function of projectile, the non-dimensional thickness of target and the impact obliquity. Explicit formulae are obtained to predict the ballistic limit, residual velocity and directional change for the oblique perforation of thick metallic plates. The proposed model is able to predict the critical condition for the occurrence of ricochet. The proposed model is validated by comparing the predictions with other existing models and independent experimental data.展开更多
This study conducted temporary plugging and diversion fracturing(TPDF)experiments using a true triaxial fracturing simulation system within a laboratory setting that replicated a lab-based horizontal well completion w...This study conducted temporary plugging and diversion fracturing(TPDF)experiments using a true triaxial fracturing simulation system within a laboratory setting that replicated a lab-based horizontal well completion with multi-cluster sand jetting perforation.The effects of temporary plugging agent(TPA)particle size,TPA concentration,single-cluster perforation number and cluster number on plugging pressure,multi-fracture diversion pattern and distribution of TPAs were investigated.A combination of TPAs with small particle sizes within the fracture and large particle sizes within the segment is conducive to increasing the plugging pressure and promoting the diversion of multi-fractures.The addition of fibers can quickly achieve ultra-high pressure,but it may lead to longitudinal fractures extending along the wellbore.The temporary plugging peak pressure increases with an increase in the concentration of the TPA,reaching a peak at a certain concentration,and further increases do not significantly improve the temporary plugging peak pressure.The breaking pressure and temporary plugging peak pressure show a decreasing trend with an increase in single-cluster perforation number.A lower number of single-cluster perforations is beneficial for increasing the breaking pressure and temporary plugging peak pressure,and it has a more significant control on the propagation of multi-cluster fractures.A lower number of clusters is not conducive to increasing the total number and complexity of artificial fractures,while a higher number of clusters makes it difficult to achieve effective plugging.The TPAs within the fracture is mainly concentrated in the complex fracture areas,especially at the intersections of fractures.Meanwhile,the TPAs within the segment are primarily distributed near the perforation cluster apertures which initiated complex fractures.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52174045,No.52104011)Natural Science Foundation of Xinjiang Uygur Autonomous Region(2022D01B77)。
文摘Intra-stage multi-cluster temporary plugging and diverting fracturing(ITPF)is one of the fastest-growing techniques to obtain uniform reservoir stimulation in shale gas reservoirs.However,propagation geometries of multiple fractures during ITPF are not clear due that the existing numerical models cannot capture the effects of perforation plugging.In this paper,a new three-dimensional FEM based on CZM was developed to investigate multiple planar fracture propagation considering perforation plugging during ITPF.Meanwhile,the fluid pipe element and its subroutine were first developed to realize the flux partitioning before or after perforation plugging.The results showed that the perforation plugging changed the original distribution of the number of perforations in each fracture,thus changing the flux partitioning after perforation plugging,which could eliminate the effect of stress interference between multiple fractures and promote a uniform fluid distribution.The standard deviation of fluid distribution in the perforation plugging case was only 8.48%of that in the non-diversion case.Furthermore,critical plugging parameters have been investigated quantitatively.Specifically,injecting more diverters will create a higher fluid pressure rise in the wellbore,which will increase the risk of wellbore integrity.Comprehensively considering pressure rise and fluid distribution,the number of diverters should be 50%of the total number of perforations(N_(pt)),whose standard deviation of fluid distribution of multiple fractures was lower than those in the cases of injecting 10%N_(pt),30%N_(pt)and 70%N_(pt).The diverters should be injected at an appropriate timing,i.e.40%or 50%of the total fracturing time(tft),whose standard deviation of the fluid distribution was only about 20%of standard deviations in the cases of injecting at20%tftor 70%tft.A single injection with all diverters can maintain high bottom-hole pressure for a longer period and promote a more uniform fluid distribution.The standard deviation of the fluid distribution in the case of a single injection was 43.62%-55.41%of the other cases with multiple injection times.This study provides a meaningful perspective and some optimal plugging parameters on the field design during IPTF.
文摘The purpose of closure of small dry tympanic membrane perforations is to restore the continuity of the tympanic membrane in order to improve hearing and decrease the incidence of middle ear infections. Small and cost effective procedures like Chemical Cauterization and Fat Plug Myringoplasty have been found to be effective in healing small central perforations with significant hearing improvement. A study was carried out in 69 patients with central perforations in the Department of ENT, Gauhati Medical College & Hospital for the duration of 1 year from August 11 to July 12. Out of 69 patients, 36 underwent Chemical Cauterization and 33 Fat Plug Myringoplasty. Pre-and post-operative hearing assessments of each patient were done and statistically analyzed. The success rate was found to be 83.33% and 90.9% respectively. In both groups, there was statistically significant hearing improvement with a P value 0.01. From our study, it was found that the two procedures are simple, reliable and also lessened the morbidity of the patient. Thus we recommend the use of these two official procedures for the treatment of central perforations of tympanic membrane less than 5 mm.
文摘Oblique perforation of thick metallic plates by rigid projectiles with various nose shapes is studied in this paper. Two perforation mechanisms, i.e., the hole enlargement for a sharp projectile nose and the plugging formation for a blunt projectile nose, are considered in the proposed analytical model. It is shown that the perforation of a thick plate is dominated by several non-dimensional numbers, i.e., the impact function, the geometry function of projectile, the non-dimensional thickness of target and the impact obliquity. Explicit formulae are obtained to predict the ballistic limit, residual velocity and directional change for the oblique perforation of thick metallic plates. The proposed model is able to predict the critical condition for the occurrence of ricochet. The proposed model is validated by comparing the predictions with other existing models and independent experimental data.
基金Supported by the National Natural Science Foundation of China(51974332).
文摘This study conducted temporary plugging and diversion fracturing(TPDF)experiments using a true triaxial fracturing simulation system within a laboratory setting that replicated a lab-based horizontal well completion with multi-cluster sand jetting perforation.The effects of temporary plugging agent(TPA)particle size,TPA concentration,single-cluster perforation number and cluster number on plugging pressure,multi-fracture diversion pattern and distribution of TPAs were investigated.A combination of TPAs with small particle sizes within the fracture and large particle sizes within the segment is conducive to increasing the plugging pressure and promoting the diversion of multi-fractures.The addition of fibers can quickly achieve ultra-high pressure,but it may lead to longitudinal fractures extending along the wellbore.The temporary plugging peak pressure increases with an increase in the concentration of the TPA,reaching a peak at a certain concentration,and further increases do not significantly improve the temporary plugging peak pressure.The breaking pressure and temporary plugging peak pressure show a decreasing trend with an increase in single-cluster perforation number.A lower number of single-cluster perforations is beneficial for increasing the breaking pressure and temporary plugging peak pressure,and it has a more significant control on the propagation of multi-cluster fractures.A lower number of clusters is not conducive to increasing the total number and complexity of artificial fractures,while a higher number of clusters makes it difficult to achieve effective plugging.The TPAs within the fracture is mainly concentrated in the complex fracture areas,especially at the intersections of fractures.Meanwhile,the TPAs within the segment are primarily distributed near the perforation cluster apertures which initiated complex fractures.
