Methane in situ explosion fracturing(MISEF)technology improves deep reservoir permeability by generating multiple radial fractures around the wellbore,with fracture propagation significantly influenced by in situ stre...Methane in situ explosion fracturing(MISEF)technology improves deep reservoir permeability by generating multiple radial fractures around the wellbore,with fracture propagation significantly influenced by in situ stress and bedding structures.However,limited experimental studies on the combined effects of triaxial stress and explosive loading,along with detailed characterization of explosive damage,hinder further optimization of this technology.This study introduces an experimental method to simulate MISEF under triaxial stress,using CH4-O2 detonation to generate controllable explosive loads.Bedding shale samples are fractured in a pseudo-triaxial core holder.Micro-computed tomography(μ-CT)and nuclear magnetic resonance(NMR)are used to quantify three-dimensional(3D)fracture characteristics and pore structure evolution.LS-DYNA simulations are employed to elucidate fracture propagation and dynamic behavior.The results show that detonation produces explosive loads with overpressures of 69.929-84.338 MPa and pressure rise rates of up to 555.624 MPa/ms,exhibiting an oscillation-attenuation characteristic.μ-CT reveals 3-5 radial fractures,with 3D fracture volume and surface area decreasing as triaxial stress rises.Hoop stress inhibits fracture propagation more than axial stress.NMR analysis shows that explosive loading converts bound fluid to movable fluid,while in situ stress suppresses this process.With increasing triaxial stress,micropore(T2<10 ms)changes are minimal,while meso/macropore and fracture(T2>10 ms)NMR signals decrease significantly.Higher triaxial stress reduces water overpressure of stress loading chambers and vibrational displacement at sample boundaries.Numerical simulations indicate that explosive loading generates hoop tensile stress,which drives the formation of radial fractures.Triaxial stress increases hoop compressive stress,suppressing fracture propagation.Fractures initiate along bedding planes,forming cross-shaped or T-shaped patterns.展开更多
Methane in-situ explosion fracturing(MISEF)enhances permeability in shale reservoirs by detonating desorbed methane to generate detonation waves in perforations.Fracture propagation in bedding shale under varying expl...Methane in-situ explosion fracturing(MISEF)enhances permeability in shale reservoirs by detonating desorbed methane to generate detonation waves in perforations.Fracture propagation in bedding shale under varying explosion loads remains unclear.In this study,prefabricated perforated shale samples with parallel and vertical bedding are fractured under five distinct explosion loads using a MISEF experimental setup.High-frequency explosion pressure-time curves were monitored within an equivalent perforation,and computed tomography scanning along with three-dimensional reconstruction techniques were used to investigate fracture propagation patterns.Additionally,the formation mechanism and influencing factors of explosion crack-generated fines(CGF)were clarified by analyzing the morphology and statistics of explosion debris particles.The results indicate that methane explosion generated oscillating-pulse loads within perforations.Explosion characteristic parameters increase with increasing initial pressure.Explosion load and bedding orientation significantly influence fracture propagation patterns.As initial pressure increases,the fracture mode transitions from bi-wing to 4–5 radial fractures.In parallel bedding shale,radial fractures noticeably deflect along the bedding surface.Vertical bedding facilitates the development of transverse fractures oriented parallel to the cross-section.Bifurcation-merging of explosioninduced fractures generated CGF.CGF mass and fractal dimension increase,while average particle size decreases with increasing explosion load.This study provides valuable insights into MISEF technology.展开更多
It was aim to investigate the interfacial microstructure and shear performance of Ti/Cu clad sheet produced by explosive welding and annealing. The experimental results demonstrate that the alternate distribution of i...It was aim to investigate the interfacial microstructure and shear performance of Ti/Cu clad sheet produced by explosive welding and annealing. The experimental results demonstrate that the alternate distribution of interfacial collision and vortex of flyer layer forms in the interface a few of solidification structure. TEM confirms that the interfacial interlayer contains obvious lattice distortion structure and intermetallic compounds. It interprets the explosive welding as the interfacial deformation and thermal diffusion process between dissimilar metals. The interfacial shear strength is very close to the Cu matrix strength, which is determined by the mixture of the mechanical bonding and metallurgical bonding. Several cracks exist on the shear fracture owing to the intermetallic compound in the interfacial solidifi cation structure and also the probable welding inclusion.展开更多
In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosi...In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.展开更多
基金the National Key Research and Development Program of China(Grant No.2020YFA0711800)Jiangsu Provincial Innovation Capacity Building Program(Jiangsu Safety Emergency Equipment Technology Innovation Center(Grant No.BM2022013)the National Natural Science Foundation of China(Grant No.12372373).
文摘Methane in situ explosion fracturing(MISEF)technology improves deep reservoir permeability by generating multiple radial fractures around the wellbore,with fracture propagation significantly influenced by in situ stress and bedding structures.However,limited experimental studies on the combined effects of triaxial stress and explosive loading,along with detailed characterization of explosive damage,hinder further optimization of this technology.This study introduces an experimental method to simulate MISEF under triaxial stress,using CH4-O2 detonation to generate controllable explosive loads.Bedding shale samples are fractured in a pseudo-triaxial core holder.Micro-computed tomography(μ-CT)and nuclear magnetic resonance(NMR)are used to quantify three-dimensional(3D)fracture characteristics and pore structure evolution.LS-DYNA simulations are employed to elucidate fracture propagation and dynamic behavior.The results show that detonation produces explosive loads with overpressures of 69.929-84.338 MPa and pressure rise rates of up to 555.624 MPa/ms,exhibiting an oscillation-attenuation characteristic.μ-CT reveals 3-5 radial fractures,with 3D fracture volume and surface area decreasing as triaxial stress rises.Hoop stress inhibits fracture propagation more than axial stress.NMR analysis shows that explosive loading converts bound fluid to movable fluid,while in situ stress suppresses this process.With increasing triaxial stress,micropore(T2<10 ms)changes are minimal,while meso/macropore and fracture(T2>10 ms)NMR signals decrease significantly.Higher triaxial stress reduces water overpressure of stress loading chambers and vibrational displacement at sample boundaries.Numerical simulations indicate that explosive loading generates hoop tensile stress,which drives the formation of radial fractures.Triaxial stress increases hoop compressive stress,suppressing fracture propagation.Fractures initiate along bedding planes,forming cross-shaped or T-shaped patterns.
基金funded by the National Key Research and Development Program of China(No.2020YFA0711800)the National Science Fund for Distinguished Young Scholars(No.51925404)+2 种基金the National Natural Science Foundation of China(No.12372373)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX24_2909)the Graduate Innovation Program of China University of Mining and Technology(No.2024WLKXJ134)。
文摘Methane in-situ explosion fracturing(MISEF)enhances permeability in shale reservoirs by detonating desorbed methane to generate detonation waves in perforations.Fracture propagation in bedding shale under varying explosion loads remains unclear.In this study,prefabricated perforated shale samples with parallel and vertical bedding are fractured under five distinct explosion loads using a MISEF experimental setup.High-frequency explosion pressure-time curves were monitored within an equivalent perforation,and computed tomography scanning along with three-dimensional reconstruction techniques were used to investigate fracture propagation patterns.Additionally,the formation mechanism and influencing factors of explosion crack-generated fines(CGF)were clarified by analyzing the morphology and statistics of explosion debris particles.The results indicate that methane explosion generated oscillating-pulse loads within perforations.Explosion characteristic parameters increase with increasing initial pressure.Explosion load and bedding orientation significantly influence fracture propagation patterns.As initial pressure increases,the fracture mode transitions from bi-wing to 4–5 radial fractures.In parallel bedding shale,radial fractures noticeably deflect along the bedding surface.Vertical bedding facilitates the development of transverse fractures oriented parallel to the cross-section.Bifurcation-merging of explosioninduced fractures generated CGF.CGF mass and fractal dimension increase,while average particle size decreases with increasing explosion load.This study provides valuable insights into MISEF technology.
基金Funded by the National Natural Science Foundation of China(Nos.U1332110 and 50971038)the Project of"Liaoning Bai Qian Wan Talents Program"of China(No.2013921071)
文摘It was aim to investigate the interfacial microstructure and shear performance of Ti/Cu clad sheet produced by explosive welding and annealing. The experimental results demonstrate that the alternate distribution of interfacial collision and vortex of flyer layer forms in the interface a few of solidification structure. TEM confirms that the interfacial interlayer contains obvious lattice distortion structure and intermetallic compounds. It interprets the explosive welding as the interfacial deformation and thermal diffusion process between dissimilar metals. The interfacial shear strength is very close to the Cu matrix strength, which is determined by the mixture of the mechanical bonding and metallurgical bonding. Several cracks exist on the shear fracture owing to the intermetallic compound in the interfacial solidifi cation structure and also the probable welding inclusion.
基金funded by the National Natural Science Foundation of China (Grant No.11972018)sponsored by the Defense Pre-Research Joint Foundation of Chinese Ordnance Industry (Grant No. 6141B012858)。
文摘In this study, 40 Cr Mn Si B steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A midexplosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40 Cr Mn Si B steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thickness and the number of the circumferential divisions. The results show that as the tempering temperature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface.
