Through a case analysis,this study examines the spatiotemporal evolution of microseismic(MS)events,energy characteristics,volumetric features,and fracture network development in surface well hydraulic fracturing.A tot...Through a case analysis,this study examines the spatiotemporal evolution of microseismic(MS)events,energy characteristics,volumetric features,and fracture network development in surface well hydraulic fracturing.A total of 349 MS events were analyzed across different fracturing sections,revealing significant heterogeneity in fracture propagation.Energy scanning results showed that cumulative energy values ranged from 240 to 1060 J across the sections,indicating notable differences.Stimulated reservoir volume(SRV)analysis demonstrated well-developed fracture networks in certain sections,with a total SRV exceeding 1540000 m^(3).The hydraulic fracture network analysis revealed that during the midfracturing stage,the density and spatial extent of MS events significantly increased,indicating rapid fracture propagation and the formation of complex networks.In the later stage,the number of secondary fractures near fracture edges decreased,and the fracture network stabilized.By comparing the branching index,fracture length,width,height,and SRV values across different fracturing sections,Sections No.1 and No.8 showed the best performance,with high MS event densities,extensive fracture networks,and significant energy release.However,Sections No.4 and No.5 exhibited sparse MS activity and poor fracture connectivity,indicating suboptimal stimulation effectiveness.展开更多
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
Non-point source(NPS)pollution has been the major cause of water quality degradation.However,there are still shortcomings in the current monitoring methods for NPS pollution,such as small monitoring range,error of mon...Non-point source(NPS)pollution has been the major cause of water quality degradation.However,there are still shortcomings in the current monitoring methods for NPS pollution,such as small monitoring range,error of monitoring data,time-consuming and laborious monitoring process.Although the established method,field experiment plots,was used effectively in the first and second national pollution source census in China.However,when the results obtained by monitoring experimental plots are extrapolated to a field or larger scale,there are considerable uncertainties because of the characteristics of large spatial and temporal variation of farmland.To optimize the farmland surface runoff monitoring methods,an online monitoring system for continuous cropping based on a serial pipeline was developed,which takes diversion trench,online flowmeter and dynamic acquisition device as the main body.Compared with the current farmland monitoring methods,this system can realize more precise automatic monitoring of water quantity and quality,and lower costs.This innovative method will provide greater confidence in the actual monitoring of NPS pollution from farmland and wider practical application.This new method could prove particularly valuable for the next national pollution source census in China.展开更多
基金supported by Yunlong Lake Laboratory of Deep Underground Science and Engineering Project(No.104024008)the National Natural Science Foundation of China(Nos.52274241 and 52474261)the Natural Science Foundation of Jiangsu Province(No.BK20240207).
文摘Through a case analysis,this study examines the spatiotemporal evolution of microseismic(MS)events,energy characteristics,volumetric features,and fracture network development in surface well hydraulic fracturing.A total of 349 MS events were analyzed across different fracturing sections,revealing significant heterogeneity in fracture propagation.Energy scanning results showed that cumulative energy values ranged from 240 to 1060 J across the sections,indicating notable differences.Stimulated reservoir volume(SRV)analysis demonstrated well-developed fracture networks in certain sections,with a total SRV exceeding 1540000 m^(3).The hydraulic fracture network analysis revealed that during the midfracturing stage,the density and spatial extent of MS events significantly increased,indicating rapid fracture propagation and the formation of complex networks.In the later stage,the number of secondary fractures near fracture edges decreased,and the fracture network stabilized.By comparing the branching index,fracture length,width,height,and SRV values across different fracturing sections,Sections No.1 and No.8 showed the best performance,with high MS event densities,extensive fracture networks,and significant energy release.However,Sections No.4 and No.5 exhibited sparse MS activity and poor fracture connectivity,indicating suboptimal stimulation effectiveness.
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supported by Key S&T Special Project of Yunan Province(202202AE090034,202402AE090024)National Natural Science Foundation of China(42107410,42477441)+1 种基金Hebei Financial Aid Program for Introduced Overseas Scholars(C20230337)Local Science and Technology Development Fund Projects Guided by the Central Government in Hebei Province(246Z3607G).
文摘Non-point source(NPS)pollution has been the major cause of water quality degradation.However,there are still shortcomings in the current monitoring methods for NPS pollution,such as small monitoring range,error of monitoring data,time-consuming and laborious monitoring process.Although the established method,field experiment plots,was used effectively in the first and second national pollution source census in China.However,when the results obtained by monitoring experimental plots are extrapolated to a field or larger scale,there are considerable uncertainties because of the characteristics of large spatial and temporal variation of farmland.To optimize the farmland surface runoff monitoring methods,an online monitoring system for continuous cropping based on a serial pipeline was developed,which takes diversion trench,online flowmeter and dynamic acquisition device as the main body.Compared with the current farmland monitoring methods,this system can realize more precise automatic monitoring of water quantity and quality,and lower costs.This innovative method will provide greater confidence in the actual monitoring of NPS pollution from farmland and wider practical application.This new method could prove particularly valuable for the next national pollution source census in China.
