A fracture propagation model of radial well fracturing is established based on the finite element-meshless method.The model considers the coupling effect of fracturing fluid flow and rock matrix deformation.The fractu...A fracture propagation model of radial well fracturing is established based on the finite element-meshless method.The model considers the coupling effect of fracturing fluid flow and rock matrix deformation.The fracture geometries of radial well fracturing are simulated,the induction effect of radial well on the fracture is quantitatively characterized,and the influences of azimuth,horizontal principle stress difference,and reservoir matrix permeability on the fracture geometries are revealed.The radial wells can induce the fractures to extend parallel to their axes when two radial wells in the same layer are fractured.When the radial wells are symmetrically distributed along the direction of the minimum horizontal principle stress with the azimuth greater than 15,the extrusion effect reduces the fracture length of radial wells.When the radial wells are symmetrically distributed along the direction of the maximum horizontal principal stress,the extrusion increases the fracture length of the radial wells.The fracture geometries are controlled by the rectification of radial borehole,the extrusion between radial wells in the same layer,and the deflection of the maximum horizontal principal stress.When the radial wells are distributed along the minimum horizontal principal stress symmetrically,the fracture length induced by the radial well decreases with the increase of azimuth;in contrast,when the radial wells are distributed along the maximum horizontal principal stress symmetrically,the fracture length induced by the radial well first decreases and then increases with the increase of azimuth.The fracture length induced by the radial well decreases with the increase of horizontal principal stress difference.The increase of rock matrix permeability and pore pressure of the matrix around radial wells makes the inducing effect of the radial well on fractures increase.展开更多
Complex hydraulic fracture networks are critical for enhancing permeability in unconventional reservoirs and mining indus-tries.However,accurately simulating the fluid flow in realistic fracture networks(compared to t...Complex hydraulic fracture networks are critical for enhancing permeability in unconventional reservoirs and mining indus-tries.However,accurately simulating the fluid flow in realistic fracture networks(compared to the statistical fracture net-works)is still challenging due to the fracture complexity and computational burden.This work proposes a simple yet efficient numerical framework for the flow simulation in fractured porous media obtained by 3D high-resolution images,aiming at both computational accuracy and efficiency.The fractured rock with complex fracture geometries is numerically constructed with a cell-based discrete fracture-matrix model(DFM)having implicit fracture apertures.The flow in the complex fractured porous media(including matrix flow,fracture flow,as well as exchange flow)is simulated with a pipe-based cell-centered finite volume method.The performance of this model is validated against analytical/numerical solutions.Then a lab-scale true triaxial hydraulically fractured shale sample is reconstructed,and the fluid flow in this realistic fracture network is simu-lated.Results suggest that the proposed method achieves a good balance between computational efficiency and accuracy.The complex fracture networks control the fluid flow process,and the opened natural fractures behave as primary fuid pathways.Heterogeneous and anisotropic features of fluid flow are well captured with the present model.展开更多
Recently, quasimolecular dynamics has been successfully used to simulate the deformation characteristics of actual size solid materials. In quasimolecular dynamics, which is an attempt to bridge the gap between atomis...Recently, quasimolecular dynamics has been successfully used to simulate the deformation characteristics of actual size solid materials. In quasimolecular dynamics, which is an attempt to bridge the gap between atomistic and continuum simulations, molecules are aggregated into large units, called quasimolecules, to evaluate large scale material behavior. In this paper, a 2-dimensional numerical simulation using quasimolecular dynamics was performed to investigate laminar composite material fractures and crack propagation behavior in the uniform bending of laminar composite materials. It was verified that under bending deformation laminar composite materials deform quite differently from homogeneous展开更多
Hydraulic fracture modelling is a key component of a shale reservoir well placement strategy as it provides an indication of the typical lengths and heights of stimulated fractures and of the changes to the stress env...Hydraulic fracture modelling is a key component of a shale reservoir well placement strategy as it provides an indication of the typical lengths and heights of stimulated fractures and of the changes to the stress environment in which these are propagating.However,spatial and stratigraphic variations in the stress and geomechanical properties of shales make accurate modelling a challenging task.For the UK Bowland Shale,stacked horizontal wells targeting multiple stratigraphic intervals could be used to avoid large offset faults in a geologically complex area.However,it is not known how these intervals may respond to hydraulic fracturing and predicting the height and length of hydraulic fractures is necessary in order to assess the likelihood of vertical fracture interference across landing zones or propagation towards major faults.In the case of the former,intervals of high effective stress may be key to containing fractures within their desired target.Using a planar hydraulic fracture simulator,and a 3D geomechanical model incorporating dipping stratigraphy,the issue of predicting hydraulic fracture geometry in the Bowland Shale was assessed through a series of modelling exercises using well Preese Hall-1 and horizontal pseudo-wells.When pre-defined landing zones were targeted,narrow and long transverse fractures around 1 km from the well were simulated.When the simulation design mimicked perforation clusters placed at 12 m intervals along horizontal pseudo-wells,the effects of stress shadowing were acute and resulted in irregular fracture geometries.Furthermore,high effective stress intervals performed efficiently as barriers to vertical hydraulic fracture propagation,reinforcing the feasibility of using stacked production for the Bowland Shale.The modelling results were then used to discuss the possible placement of horizontal wells in a mapped,100 km2 region around well Preese Hall-1,where up to 13 sites could be positioned,with a horizontal well length of around 1.5 km.Finally,by drawing on a wellestablished analogue for the Bowland Shale,it was estimated that up to 195 Bcf of gas could be produced from the 13 locations in the area if three stratigraphic intervals are produced from one location.展开更多
Objective To investigate the effect of computer aided 3D simulation technique for treating complicated foot and ankle fractures precisely.Methods From November 2007 to August 2009,255 patients with complicated foot an...Objective To investigate the effect of computer aided 3D simulation technique for treating complicated foot and ankle fractures precisely.Methods From November 2007 to August 2009,255 patients with complicated foot and ankle fractures展开更多
Reliable prediction of the shale fracturing process is a challenging problem in exploiting deep shale oil and gas resources.Complex fracture networks need to be artificially created to employ deep shale oil and gas re...Reliable prediction of the shale fracturing process is a challenging problem in exploiting deep shale oil and gas resources.Complex fracture networks need to be artificially created to employ deep shale oil and gas reserves.Randomly distributed minerals and heterogeneities in shales significantly affect mechanical properties and fracturing behaviors in oil and gas exploitation.Describing the actual microstructure and associated heterogeneities in shales constitutes a significant challenge.The RFPA3D(rock failure process analysis parallel computing program)-based modeling approach is a promising numerical technique due to its unique capability to simulate the fracturing behavior of rocks.To improve traditional numerical technology and study crack propagation in shale on the microscopic scale,a combination of high-precision internal structure detection technology with the RFPA^(3D) numerical simulation method was developed to construct a real mineral structure-based modeling method.First,an improved digital image processing technique was developed to incorporate actual shale microstructures(focused ion beam scanning electron microscopy was used to capture shale microstructure images that reflect the distri-butions of different minerals)into the numerical model.Second,the effect of mineral inhomogeneity was considered by integrating the mineral statistical model obtained from the mineral nanoindentation experiments into the numerical model.By simulating a shale numerical model in which pyrite particles are wrapped by organic matter,the effects of shale microstructure and applied stress state on microcrack behavior and mechanical properties were investigated and analyzed.In this study,the effect of pyrite particles on fracture propagation was systematically analyzed and summarized for the first time.The results indicate that the distribution of minerals and initial defects dominated the fracture evolution and the failure mode.Cracks are generally initiated and propagated along the boundaries of hard mineral particles such as pyrite or in soft minerals such as organic matter.Locations with collections of hard minerals are more likely to produce complex fractures.This study provides a valuable method for un-derstanding the microfracture behavior of shales.展开更多
Hydraulic fracturing and permeability enhancement are effective methods to improve low-permeability coal seams.However,few studies focused on methods to increase permeability,and there are no suitable prediction metho...Hydraulic fracturing and permeability enhancement are effective methods to improve low-permeability coal seams.However,few studies focused on methods to increase permeability,and there are no suitable prediction methods for engineering applications.In this work,PFC2D software was used to simulate coal seam hydraulic fracturing.The results were used in a coupled mathematical model of the interaction between coal seam deformation and gas flow.The results show that the displacement and velocity of particles increase in the direction of minimum principal stress,and the cracks propagate in the direction of maximum principal stress.The gas pressure drop rate and permeability increase rate of the fracture model are higher than that of the non-fracture model.Both parameters decrease rapidly with an increase in the drainage time and approach 0.The longer the hydraulic fracturing time,the more complex the fracture network is,and the faster the gas pressure drops.However,the impact of fracturing on the gas drainage effect declines over time.As the fracturing time increases,the difference between the horizontal and vertical permeability increases.However,this difference decreases as the gas drainage time increases.The higher the initial void pressure,the faster the gas pressure drops,and the greater the permeability increase is.However,the influence of the initial void pressure on the permeability declines over time.The research results provide guidance for predicting the anti-reflection effect of hydraulic fracturing in underground coal mines.展开更多
During the past years,the recovery of unconventional gas formation has attracted lots of attention and achieved huge success.To produce gas from the low-permeability unconventional formations,hydraulic fracturing tech...During the past years,the recovery of unconventional gas formation has attracted lots of attention and achieved huge success.To produce gas from the low-permeability unconventional formations,hydraulic fracturing technology is essential and critical.In this paper,we present the development of a three-dimensional thermalhydraulic-mechanical numerical simulator for the simulation of hydraulic fracturing operations in tight sandstone reservoirs.Our simulator is based on integrated finite difference(IFD)method.In this method,the simulation domain is subdivided into sub domains and the governing equations are integrated over a sub domain with flux terms expressed as an integral over the sub domain boundary using the divergence theorem.Our simulator conducts coupled thermal-hydraulic-mechanical simulation of the initiation and extension of hydraulic fractures.It also calculates the mass/heat transport of injected hydraulic fluids as well as proppants.Our simulator is able to handle anisotropic formations with multiple layers.Our simulator has been validated by comparing with an analytical solution as well as Ribeiro and Sharma model.Our model can simulate fracture spacing effect on fracture profile when combining IFD with Discontinuous Displacement Method(DDM).展开更多
基金Supported by the National Natural Science Foundation of China(51827804)CNPC Strategic Cooperation Science and Technology Major Project(ZLZX2020-01-05)Open Fund of State Key Laboratory of Rock Mechanics and Engineering(SKLGME021024).
文摘A fracture propagation model of radial well fracturing is established based on the finite element-meshless method.The model considers the coupling effect of fracturing fluid flow and rock matrix deformation.The fracture geometries of radial well fracturing are simulated,the induction effect of radial well on the fracture is quantitatively characterized,and the influences of azimuth,horizontal principle stress difference,and reservoir matrix permeability on the fracture geometries are revealed.The radial wells can induce the fractures to extend parallel to their axes when two radial wells in the same layer are fractured.When the radial wells are symmetrically distributed along the direction of the minimum horizontal principle stress with the azimuth greater than 15,the extrusion effect reduces the fracture length of radial wells.When the radial wells are symmetrically distributed along the direction of the maximum horizontal principal stress,the extrusion increases the fracture length of the radial wells.The fracture geometries are controlled by the rectification of radial borehole,the extrusion between radial wells in the same layer,and the deflection of the maximum horizontal principal stress.When the radial wells are distributed along the minimum horizontal principal stress symmetrically,the fracture length induced by the radial well decreases with the increase of azimuth;in contrast,when the radial wells are distributed along the maximum horizontal principal stress symmetrically,the fracture length induced by the radial well first decreases and then increases with the increase of azimuth.The fracture length induced by the radial well decreases with the increase of horizontal principal stress difference.The increase of rock matrix permeability and pore pressure of the matrix around radial wells makes the inducing effect of the radial well on fractures increase.
基金supported by the Natural Sciences and Engineering Research Council of Canada(NSERC)with NSERC/Energi Simulation Industrial Research Chair program,NSERC Discovery 341275,and CRDPJ 54389419.
文摘Complex hydraulic fracture networks are critical for enhancing permeability in unconventional reservoirs and mining indus-tries.However,accurately simulating the fluid flow in realistic fracture networks(compared to the statistical fracture net-works)is still challenging due to the fracture complexity and computational burden.This work proposes a simple yet efficient numerical framework for the flow simulation in fractured porous media obtained by 3D high-resolution images,aiming at both computational accuracy and efficiency.The fractured rock with complex fracture geometries is numerically constructed with a cell-based discrete fracture-matrix model(DFM)having implicit fracture apertures.The flow in the complex fractured porous media(including matrix flow,fracture flow,as well as exchange flow)is simulated with a pipe-based cell-centered finite volume method.The performance of this model is validated against analytical/numerical solutions.Then a lab-scale true triaxial hydraulically fractured shale sample is reconstructed,and the fluid flow in this realistic fracture network is simu-lated.Results suggest that the proposed method achieves a good balance between computational efficiency and accuracy.The complex fracture networks control the fluid flow process,and the opened natural fractures behave as primary fuid pathways.Heterogeneous and anisotropic features of fluid flow are well captured with the present model.
文摘Recently, quasimolecular dynamics has been successfully used to simulate the deformation characteristics of actual size solid materials. In quasimolecular dynamics, which is an attempt to bridge the gap between atomistic and continuum simulations, molecules are aggregated into large units, called quasimolecules, to evaluate large scale material behavior. In this paper, a 2-dimensional numerical simulation using quasimolecular dynamics was performed to investigate laminar composite material fractures and crack propagation behavior in the uniform bending of laminar composite materials. It was verified that under bending deformation laminar composite materials deform quite differently from homogeneous
基金a James Watt Scholarship from Heriot-Watt University(HWU)and the receipt of a British University Funding Initiative(BUFI)studentship award(grant number GA/16S/024)from the British Geological Survey(BGS)which provides the funding for the PhD project upon which this work is based.The PhD forms part of the Natural Environment Research Council(NERC)Centre for Doctoral Training(CDT)in Oil and Gas(grant number NE/M00578X/1)The BGS is thanked for providing access to well data,Schlumberger are thanked for the provision of Techlog software and Halliburton are thanked for the provision of GOHFER software under academic license to HWU.Jingsheng Ma acknowledges NERC grant number NE/R018022/1 for financial support.
文摘Hydraulic fracture modelling is a key component of a shale reservoir well placement strategy as it provides an indication of the typical lengths and heights of stimulated fractures and of the changes to the stress environment in which these are propagating.However,spatial and stratigraphic variations in the stress and geomechanical properties of shales make accurate modelling a challenging task.For the UK Bowland Shale,stacked horizontal wells targeting multiple stratigraphic intervals could be used to avoid large offset faults in a geologically complex area.However,it is not known how these intervals may respond to hydraulic fracturing and predicting the height and length of hydraulic fractures is necessary in order to assess the likelihood of vertical fracture interference across landing zones or propagation towards major faults.In the case of the former,intervals of high effective stress may be key to containing fractures within their desired target.Using a planar hydraulic fracture simulator,and a 3D geomechanical model incorporating dipping stratigraphy,the issue of predicting hydraulic fracture geometry in the Bowland Shale was assessed through a series of modelling exercises using well Preese Hall-1 and horizontal pseudo-wells.When pre-defined landing zones were targeted,narrow and long transverse fractures around 1 km from the well were simulated.When the simulation design mimicked perforation clusters placed at 12 m intervals along horizontal pseudo-wells,the effects of stress shadowing were acute and resulted in irregular fracture geometries.Furthermore,high effective stress intervals performed efficiently as barriers to vertical hydraulic fracture propagation,reinforcing the feasibility of using stacked production for the Bowland Shale.The modelling results were then used to discuss the possible placement of horizontal wells in a mapped,100 km2 region around well Preese Hall-1,where up to 13 sites could be positioned,with a horizontal well length of around 1.5 km.Finally,by drawing on a wellestablished analogue for the Bowland Shale,it was estimated that up to 195 Bcf of gas could be produced from the 13 locations in the area if three stratigraphic intervals are produced from one location.
文摘Objective To investigate the effect of computer aided 3D simulation technique for treating complicated foot and ankle fractures precisely.Methods From November 2007 to August 2009,255 patients with complicated foot and ankle fractures
基金supported by the Central Program of Basic Science of the National Natural Science Foundation of China(No.72088101)"The theory and application of resource and environment management in the digital economy era"+1 种基金The National Natural Science Foundation of China(No.41941018)Scientific research and technological development program of RIPED,"major research of basic geologic and synergy research of engineering practice on Gulong shale oil"(No.2021ycq01).
文摘Reliable prediction of the shale fracturing process is a challenging problem in exploiting deep shale oil and gas resources.Complex fracture networks need to be artificially created to employ deep shale oil and gas reserves.Randomly distributed minerals and heterogeneities in shales significantly affect mechanical properties and fracturing behaviors in oil and gas exploitation.Describing the actual microstructure and associated heterogeneities in shales constitutes a significant challenge.The RFPA3D(rock failure process analysis parallel computing program)-based modeling approach is a promising numerical technique due to its unique capability to simulate the fracturing behavior of rocks.To improve traditional numerical technology and study crack propagation in shale on the microscopic scale,a combination of high-precision internal structure detection technology with the RFPA^(3D) numerical simulation method was developed to construct a real mineral structure-based modeling method.First,an improved digital image processing technique was developed to incorporate actual shale microstructures(focused ion beam scanning electron microscopy was used to capture shale microstructure images that reflect the distri-butions of different minerals)into the numerical model.Second,the effect of mineral inhomogeneity was considered by integrating the mineral statistical model obtained from the mineral nanoindentation experiments into the numerical model.By simulating a shale numerical model in which pyrite particles are wrapped by organic matter,the effects of shale microstructure and applied stress state on microcrack behavior and mechanical properties were investigated and analyzed.In this study,the effect of pyrite particles on fracture propagation was systematically analyzed and summarized for the first time.The results indicate that the distribution of minerals and initial defects dominated the fracture evolution and the failure mode.Cracks are generally initiated and propagated along the boundaries of hard mineral particles such as pyrite or in soft minerals such as organic matter.Locations with collections of hard minerals are more likely to produce complex fractures.This study provides a valuable method for un-derstanding the microfracture behavior of shales.
基金This work was supported by National Natural Science Foundation of China(52130409,52121003,52004291,51874314).
文摘Hydraulic fracturing and permeability enhancement are effective methods to improve low-permeability coal seams.However,few studies focused on methods to increase permeability,and there are no suitable prediction methods for engineering applications.In this work,PFC2D software was used to simulate coal seam hydraulic fracturing.The results were used in a coupled mathematical model of the interaction between coal seam deformation and gas flow.The results show that the displacement and velocity of particles increase in the direction of minimum principal stress,and the cracks propagate in the direction of maximum principal stress.The gas pressure drop rate and permeability increase rate of the fracture model are higher than that of the non-fracture model.Both parameters decrease rapidly with an increase in the drainage time and approach 0.The longer the hydraulic fracturing time,the more complex the fracture network is,and the faster the gas pressure drops.However,the impact of fracturing on the gas drainage effect declines over time.As the fracturing time increases,the difference between the horizontal and vertical permeability increases.However,this difference decreases as the gas drainage time increases.The higher the initial void pressure,the faster the gas pressure drops,and the greater the permeability increase is.However,the influence of the initial void pressure on the permeability declines over time.The research results provide guidance for predicting the anti-reflection effect of hydraulic fracturing in underground coal mines.
文摘During the past years,the recovery of unconventional gas formation has attracted lots of attention and achieved huge success.To produce gas from the low-permeability unconventional formations,hydraulic fracturing technology is essential and critical.In this paper,we present the development of a three-dimensional thermalhydraulic-mechanical numerical simulator for the simulation of hydraulic fracturing operations in tight sandstone reservoirs.Our simulator is based on integrated finite difference(IFD)method.In this method,the simulation domain is subdivided into sub domains and the governing equations are integrated over a sub domain with flux terms expressed as an integral over the sub domain boundary using the divergence theorem.Our simulator conducts coupled thermal-hydraulic-mechanical simulation of the initiation and extension of hydraulic fractures.It also calculates the mass/heat transport of injected hydraulic fluids as well as proppants.Our simulator is able to handle anisotropic formations with multiple layers.Our simulator has been validated by comparing with an analytical solution as well as Ribeiro and Sharma model.Our model can simulate fracture spacing effect on fracture profile when combining IFD with Discontinuous Displacement Method(DDM).