In response to the unclear understanding of fracture propagation and intersection interference in zipper fracturing under the factory development model of deep shale gas wells,a coupled hydro-mechanical model for zipp...In response to the unclear understanding of fracture propagation and intersection interference in zipper fracturing under the factory development model of deep shale gas wells,a coupled hydro-mechanical model for zipper fracturing considering the influence of natural fracture zones was established based on the finite element–discrete element method.The reliability of the model was verified using experimental data and field monitoring pressure increase data.Taking the deep shale gas reservoir in southern Sichuan as an example,the propagation and interference laws of fracturing fractures under the influence of natural fracture zones with different characteristics were studied.The results show that the large approaching angle fracture zone has a blocking effect on the forward propagation of fracturing fractures and the intersection of inter well fractures.During pump shutdown,hydraulic fractures exhibit continued expansion behavior under net pressure driving.Under high stress difference,as the approaching angle of the fracture zone increases,the response well pressure increase and the total length of the fractured fracture show a trend of first decreasing and then increasing,and first increasing and then decreasing,respectively.Compared to small approach angle fracture zones,natural fracture zones with large approach angles require longer time and have greater difficulty to intersect.The width of fractures and the length of natural fractures are negatively and positively correlated with the response well pressure increase,respectively,and positively and negatively correlated with the time required for intersection,the total length of hydraulic fractures,and fracturing efficiency,respectively.As the displacement distance of the well increases,the probability of fracture intersection decreases,but the regularity between displacement distance and the response well pressure increase and the total length of fractures is not obvious.展开更多
To obtain the fracture parameters of concrete, fracture tests were conducted with three-point bending beam method aiming at 30 concrete beams with different sizes and different intensity. The concrete specimen with pr...To obtain the fracture parameters of concrete, fracture tests were conducted with three-point bending beam method aiming at 30 concrete beams with different sizes and different intensity. The concrete specimen with prefabricated crack to determine the fracture parameters of concrete were conducted and the fracture performance of the specimen was analyzed. The test results show that, initial fracture toughness is unrelated to the size of specimens; while unstable fracture toughness is related to the size of specimens. As for specimens of bastard size, when concrete intensity is relatively low, unstable fracture toughness increases along with the increase of intensity; when concrete intensity is relatively high, unstable fracture toughness will decrease; when concrete intensity increases continuously, unstable fracture toughness will further increase somewhat. As for specimens of standard size, unstable fracture toughness will increase along with the increase of intensity. Aiming at concrete beam specimens, we conducted two-dimensional non-linear finite element analysis, obtained the stress intensity factor, and carried out contrastive analysis with the experimental results.展开更多
The fatigue performance and fracture mechanism of laser welded twinning induced plasticity（TWIP）steel joint were investigated experimentally based on the evolution of microstructure and micromechanical properties.Th...The fatigue performance and fracture mechanism of laser welded twinning induced plasticity（TWIP）steel joint were investigated experimentally based on the evolution of microstructure and micromechanical properties.The optical microscopy was used to analyze the evolution of microstructure.The variation of composition and phase structure of fusion zone were detected by energy dispersive X-ray and X-ray diffraction spectrometers.The micromechanical behaviors of the various zones were characterized using nanoindentation.The static tensile test and high cycle fatigue test were performed to evaluate the mechanical properties of welded joint and base metal.The microstructures,tensile properties and fatigue strength of base metal as well as welded metal were analyzed.The fatigue fracture surfaces of base metal and welded joint were observed by means of scanning electron microscopy,in order to identify fatigue crack initiation sites and propagation mechanisms.Moreover,the fatigue fracture characteristics and mechanisms for the laser welded TWIP steel joints were analyzed.展开更多
In order to promote the exploration and development of continental shale gas reservoirs in China further,we systematically summarized the geological features of typical continental shale,such as the Ordos Basin.Then,t...In order to promote the exploration and development of continental shale gas reservoirs in China further,we systematically summarized the geological features of typical continental shale,such as the Ordos Basin.Then,the shale gas reservoir characteristics,geochemical charac-teristics and fracturing performance of the Lower Cretaceous Shahai Fm in the Fuxin Basin were analyzed by using the data of TOC contents,rock specific surface,pore size distribution and X-ray diffraction analysis of the whole rock.Based on this,it was compared with the marine/continental shale gas reservoirs from the aspect of geological feature.Finally,the shale gas reservoir and resource potential of the Shahai Fm were evaluated.And the following research results were obtained.First,the formation age of China's continental shale is later,its TOC contents vary in a large range,and its organic matters are mainly of a mixed-humic type.And it is characterized by low thermal evolution degree,low quartz content,high feldspar content,high carbonate content,and comparability of total brittle mineral content to marine shale.Second,shale in the Shahai Fm has shallow burial depth and its mineral composition is dominated by quartz,feldspar and carbonate minerals.Its pores are mainly mesopores with an average porosity of 3.47%.There are diverse reservoir spaces,which is favorable for the accumulation of shale gas.Third,the TOC content of the Shahai Fm shale is mainly above 2%,with a moderate thermal evolution degree of organic matter and high gas content.Fourth,the total brittle mineral content of Shahai Fm shale is up to 60%,indicating a good fracturing performance.Fifth,shale reservoirs in the Shahai Fm can be classified into three categories.Type Ⅰ is target reservoirs of exploration and development,and Type Ⅱ is favorable reservoirs.It is estimated that the amount of shale gas resources are in the range of 232.2-286.2 billion m^(3).It is concluded that the Shahai Fm shale in the Fuxin Basin has both resource potential in geology and fracturing performance in engineering,and its exploration and development prospect is broad.What's more,the potential of commercial shale gas development is great in the sweet-point areas.展开更多
基金Supported by National Natural Science Foundation Joint Fund Project(NO.U21B2071)National Natural Science Youth Foundation of China(NO.52304041)。
文摘In response to the unclear understanding of fracture propagation and intersection interference in zipper fracturing under the factory development model of deep shale gas wells,a coupled hydro-mechanical model for zipper fracturing considering the influence of natural fracture zones was established based on the finite element–discrete element method.The reliability of the model was verified using experimental data and field monitoring pressure increase data.Taking the deep shale gas reservoir in southern Sichuan as an example,the propagation and interference laws of fracturing fractures under the influence of natural fracture zones with different characteristics were studied.The results show that the large approaching angle fracture zone has a blocking effect on the forward propagation of fracturing fractures and the intersection of inter well fractures.During pump shutdown,hydraulic fractures exhibit continued expansion behavior under net pressure driving.Under high stress difference,as the approaching angle of the fracture zone increases,the response well pressure increase and the total length of the fractured fracture show a trend of first decreasing and then increasing,and first increasing and then decreasing,respectively.Compared to small approach angle fracture zones,natural fracture zones with large approach angles require longer time and have greater difficulty to intersect.The width of fractures and the length of natural fractures are negatively and positively correlated with the response well pressure increase,respectively,and positively and negatively correlated with the time required for intersection,the total length of hydraulic fractures,and fracturing efficiency,respectively.As the displacement distance of the well increases,the probability of fracture intersection decreases,but the regularity between displacement distance and the response well pressure increase and the total length of fractures is not obvious.
基金Funded by the National Natural Science Foundation of China(No.51279111)The Non-profit Industry Financial Program by the Ministry of Water Resources in2012(No.201201038)
文摘To obtain the fracture parameters of concrete, fracture tests were conducted with three-point bending beam method aiming at 30 concrete beams with different sizes and different intensity. The concrete specimen with prefabricated crack to determine the fracture parameters of concrete were conducted and the fracture performance of the specimen was analyzed. The test results show that, initial fracture toughness is unrelated to the size of specimens; while unstable fracture toughness is related to the size of specimens. As for specimens of bastard size, when concrete intensity is relatively low, unstable fracture toughness increases along with the increase of intensity; when concrete intensity is relatively high, unstable fracture toughness will decrease; when concrete intensity increases continuously, unstable fracture toughness will further increase somewhat. As for specimens of standard size, unstable fracture toughness will increase along with the increase of intensity. Aiming at concrete beam specimens, we conducted two-dimensional non-linear finite element analysis, obtained the stress intensity factor, and carried out contrastive analysis with the experimental results.
基金Item Sponsored by National Natural Science Foundation of China(51374151,21201129)Science and Technology Major Project of Shanxi Province of China(20111101053)Natural Science Foundation of Shanxi Province of China(2011011020-2)
文摘The fatigue performance and fracture mechanism of laser welded twinning induced plasticity（TWIP）steel joint were investigated experimentally based on the evolution of microstructure and micromechanical properties.The optical microscopy was used to analyze the evolution of microstructure.The variation of composition and phase structure of fusion zone were detected by energy dispersive X-ray and X-ray diffraction spectrometers.The micromechanical behaviors of the various zones were characterized using nanoindentation.The static tensile test and high cycle fatigue test were performed to evaluate the mechanical properties of welded joint and base metal.The microstructures,tensile properties and fatigue strength of base metal as well as welded metal were analyzed.The fatigue fracture surfaces of base metal and welded joint were observed by means of scanning electron microscopy,in order to identify fatigue crack initiation sites and propagation mechanisms.Moreover,the fatigue fracture characteristics and mechanisms for the laser welded TWIP steel joints were analyzed.
基金Project supported by the National Major Science and Technology Projects of China Project“Evaluation method and expert system for commercial shale gas production zone”(No.:2017ZX05035004-003).
文摘In order to promote the exploration and development of continental shale gas reservoirs in China further,we systematically summarized the geological features of typical continental shale,such as the Ordos Basin.Then,the shale gas reservoir characteristics,geochemical charac-teristics and fracturing performance of the Lower Cretaceous Shahai Fm in the Fuxin Basin were analyzed by using the data of TOC contents,rock specific surface,pore size distribution and X-ray diffraction analysis of the whole rock.Based on this,it was compared with the marine/continental shale gas reservoirs from the aspect of geological feature.Finally,the shale gas reservoir and resource potential of the Shahai Fm were evaluated.And the following research results were obtained.First,the formation age of China's continental shale is later,its TOC contents vary in a large range,and its organic matters are mainly of a mixed-humic type.And it is characterized by low thermal evolution degree,low quartz content,high feldspar content,high carbonate content,and comparability of total brittle mineral content to marine shale.Second,shale in the Shahai Fm has shallow burial depth and its mineral composition is dominated by quartz,feldspar and carbonate minerals.Its pores are mainly mesopores with an average porosity of 3.47%.There are diverse reservoir spaces,which is favorable for the accumulation of shale gas.Third,the TOC content of the Shahai Fm shale is mainly above 2%,with a moderate thermal evolution degree of organic matter and high gas content.Fourth,the total brittle mineral content of Shahai Fm shale is up to 60%,indicating a good fracturing performance.Fifth,shale reservoirs in the Shahai Fm can be classified into three categories.Type Ⅰ is target reservoirs of exploration and development,and Type Ⅱ is favorable reservoirs.It is estimated that the amount of shale gas resources are in the range of 232.2-286.2 billion m^(3).It is concluded that the Shahai Fm shale in the Fuxin Basin has both resource potential in geology and fracturing performance in engineering,and its exploration and development prospect is broad.What's more,the potential of commercial shale gas development is great in the sweet-point areas.
