Shale oil reservoir is generally characterized by well-developed bedding planes,and multi-cluster fracturing is the most effective technique to achieve stable shale oil production.In this paper,a multi-cluster fractur...Shale oil reservoir is generally characterized by well-developed bedding planes,and multi-cluster fracturing is the most effective technique to achieve stable shale oil production.In this paper,a multi-cluster fracturing model for a horizontal well in shale with high-density bedding planes is established.The fracture morphology,fracture geometry,fracturing area and multiple fracture propagation mechanism are analyzed under simultaneous fracturing,sequential fracturing,and alternative fracturing.Results show that in the case of small cluster spacing and three clusters,the growth of the middle fracture is inhibited and develops along the bedding planes under both simultaneous fracturing and alternative fracturing.For sequential fracturing,the increase in the interval time between each fracturing advances the post fracturing fracture deflecting to the pre-existing fractures through the bedding planes.The reactivation of the bedding planes can promote the extension of the fracturing area.Increasing the injection rate and the number of clusters promotes the activation of bedding planes.However,it is preferable to reduce the number of clusters to obtain more main fractures.Compared with modified alternating fracturing and cyclic alternating fracturing,alternating shut-in fracturing creates more main fractures towards the direction of the maximum in-situ stress.The fracturing efficiency for high-density layered shale is ranked as simultaneous fracturing>alternative fracturing>sequential fracturing.展开更多
The authors regret Acknowledgements Firstly,the authors wish to acknowledge the academic support from Ruhr University Bochum during the first author's(Xiao Yan)research stay from 2018.11 to 2020.10,including the s...The authors regret Acknowledgements Firstly,the authors wish to acknowledge the academic support from Ruhr University Bochum during the first author's(Xiao Yan)research stay from 2018.11 to 2020.10,including the soft code implement and debug support from Vladislav Gudzulic and academic advising from Günther Meschke.展开更多
The asymmetric separation has a crucial effect on the performance of the scramjet.In this study,the asymmetric separation and combustion in both rectangular and circular scramjets are investigated numerically,and the ...The asymmetric separation has a crucial effect on the performance of the scramjet.In this study,the asymmetric separation and combustion in both rectangular and circular scramjets are investigated numerically,and the effect of injection scheme is analyzed.The characteristics of the flow field are analyzed based on sufficient code verification.In the rectangular scramjet,the separation tends to occur in the corner due to the corner boundary-layer effect.The separation is asym-metric and only two corners have serious separation.The fuel penetration depth in the separation zone increases and the combustion is intensified.When the injection scheme is uniform,both the combustion and separation become weak.In the circular scramjet,the separation and combustion are basically axisymmetric in the scramjet with one-row injection scheme.The asymmetric combustion becomes obvious in cases with multi-row injection scheme.When the injection orifices distribute intensively on the top and bottom sides,the strongest and weakest separations occur near these two sides respectively.When the distribution of orifices becomes uniform,the direction of separation cannot be predicted.For multi-row cases,the nonuniform injection scheme could result in violent combustion and asymmetric flow structures compared with the uniform injection scheme.展开更多
A numerical method using AUSMDV scheme and k-ω SST turbulence model with an explicit compressibility correction was developed,and a 3-D numerical simulation of a supersonic flow field with a vertical sonic jet of hyd...A numerical method using AUSMDV scheme and k-ω SST turbulence model with an explicit compressibility correction was developed,and a 3-D numerical simulation of a supersonic flow field with a vertical sonic jet of hydrogen was performed.Good agreement between numerical results and experimental data validated the reliability of the numerical method.Whereafter,two parameters,mass-weighted average total pressure and mixing efficiency,were defined to evaluate the mixing performance of different injection schemes.Based on the numerical method and evaluation criterion,the mixing characteristics of different injection schemes were studied in detail.It was found that for the mixing field of supersonic transverse jet,the near-field mixing is controlled by convection transport while the far-field mixing is controlled by mass diffusion;the circular-hole injection causes a loss of total pressure comparable to the slot injection,but can induce a much higher mixing efficiency because of its 3-D flow characteristic;the variation of injection angle under circular-hole injection mainly affects the near-field mixing degree,and among the five injection angles studied in the present paper,angle 120° is the optimal one;with the increase of the ratio between injector space and diameter,the induced mixing efficiency increases while the caused loss of total pressure can grow greatly;the two-stage injection method designed through reducing the injector area to keep the same hydrogen mass flowrate can induce a much higher mixing efficiency while only a bit larger loss of total pressure when compared to the single-stage injection,and hence the two-stage injection is superior to the single-stage injection.The research results can direct the design of the fuel injection method in the combustor of scramjet engine.展开更多
A tunable dual-wavelength fiber ring laser with a Fabry-Perot laser diode is proposed and demonstrated. The dual-wavelength outputs have the optical side-mode-suppression-ratio (SMSR) over 31 dB. The wavelength tuning...A tunable dual-wavelength fiber ring laser with a Fabry-Perot laser diode is proposed and demonstrated. The dual-wavelength outputs have the optical side-mode-suppression-ratio (SMSR) over 31 dB. The wavelength tuning range can be up to 9 run.展开更多
Based on the features of surfactant flooding, a mathematical model for surfactant flooding is established. The adsorption-retentlon, convection diffusion of surfactant and influence of concentration change upon relati...Based on the features of surfactant flooding, a mathematical model for surfactant flooding is established. The adsorption-retentlon, convection diffusion of surfactant and influence of concentration change upon relative permeability curve are included in the model. The novel description of adsorption quantity of surfaetant and relative permeability curve are presented, which enhance the coincidence between mathematical model and field practice, the relative errors of main development indexes arc within 6%. The model is applied to the numerical research of the surfactant flooding in the untabulated beds of Xingl-3 surfactant flooding pilot site of No. 4 Oil Production Company of Daqing Oilfield, the influences of surfaetant concentration, injection quantity, slug combination mode upon the development effect and economic benefit are quantitatively analyzed, the injection scheme is optimized as follows： surfaetant concentration is 0.5%, slug volume is 0.02 PV, slug combination mode is 2 slugs. After the implementation of scheme in oilfield, the cumulative increase of oil is 2186.0 t, up to nearly 30%.展开更多
基金the financial support from Intergovernmental International Science and Technology Innovation Cooperation Key Project(2022YFE0128400)National Natural Science Foundation of China(42307209)+2 种基金Shanghai Pujiang Program(2022PJD076)State Energy Center for Shale Oil Research and Development(33550000-22-ZC0613-0365)Natural Science Foundation of Qinghai Province(No.2024-ZJ-717).
文摘Shale oil reservoir is generally characterized by well-developed bedding planes,and multi-cluster fracturing is the most effective technique to achieve stable shale oil production.In this paper,a multi-cluster fracturing model for a horizontal well in shale with high-density bedding planes is established.The fracture morphology,fracture geometry,fracturing area and multiple fracture propagation mechanism are analyzed under simultaneous fracturing,sequential fracturing,and alternative fracturing.Results show that in the case of small cluster spacing and three clusters,the growth of the middle fracture is inhibited and develops along the bedding planes under both simultaneous fracturing and alternative fracturing.For sequential fracturing,the increase in the interval time between each fracturing advances the post fracturing fracture deflecting to the pre-existing fractures through the bedding planes.The reactivation of the bedding planes can promote the extension of the fracturing area.Increasing the injection rate and the number of clusters promotes the activation of bedding planes.However,it is preferable to reduce the number of clusters to obtain more main fractures.Compared with modified alternating fracturing and cyclic alternating fracturing,alternating shut-in fracturing creates more main fractures towards the direction of the maximum in-situ stress.The fracturing efficiency for high-density layered shale is ranked as simultaneous fracturing>alternative fracturing>sequential fracturing.
文摘The authors regret Acknowledgements Firstly,the authors wish to acknowledge the academic support from Ruhr University Bochum during the first author's(Xiao Yan)research stay from 2018.11 to 2020.10,including the soft code implement and debug support from Vladislav Gudzulic and academic advising from Günther Meschke.
基金supported by the National Natural Science Foundation of China(Nos.11925207,12002381)the Scientific Research Plan of National University of Defense Technology in 2019,China(No.ZK19-02)+1 种基金the Postgraduate Scientific Research Innovation Project of Hunan Province,China(No.CX20200084)the Equipment Pre-research Foundation of Key Laboratory,China(No.6142703200311)。
文摘The asymmetric separation has a crucial effect on the performance of the scramjet.In this study,the asymmetric separation and combustion in both rectangular and circular scramjets are investigated numerically,and the effect of injection scheme is analyzed.The characteristics of the flow field are analyzed based on sufficient code verification.In the rectangular scramjet,the separation tends to occur in the corner due to the corner boundary-layer effect.The separation is asym-metric and only two corners have serious separation.The fuel penetration depth in the separation zone increases and the combustion is intensified.When the injection scheme is uniform,both the combustion and separation become weak.In the circular scramjet,the separation and combustion are basically axisymmetric in the scramjet with one-row injection scheme.The asymmetric combustion becomes obvious in cases with multi-row injection scheme.When the injection orifices distribute intensively on the top and bottom sides,the strongest and weakest separations occur near these two sides respectively.When the distribution of orifices becomes uniform,the direction of separation cannot be predicted.For multi-row cases,the nonuniform injection scheme could result in violent combustion and asymmetric flow structures compared with the uniform injection scheme.
文摘A numerical method using AUSMDV scheme and k-ω SST turbulence model with an explicit compressibility correction was developed,and a 3-D numerical simulation of a supersonic flow field with a vertical sonic jet of hydrogen was performed.Good agreement between numerical results and experimental data validated the reliability of the numerical method.Whereafter,two parameters,mass-weighted average total pressure and mixing efficiency,were defined to evaluate the mixing performance of different injection schemes.Based on the numerical method and evaluation criterion,the mixing characteristics of different injection schemes were studied in detail.It was found that for the mixing field of supersonic transverse jet,the near-field mixing is controlled by convection transport while the far-field mixing is controlled by mass diffusion;the circular-hole injection causes a loss of total pressure comparable to the slot injection,but can induce a much higher mixing efficiency because of its 3-D flow characteristic;the variation of injection angle under circular-hole injection mainly affects the near-field mixing degree,and among the five injection angles studied in the present paper,angle 120° is the optimal one;with the increase of the ratio between injector space and diameter,the induced mixing efficiency increases while the caused loss of total pressure can grow greatly;the two-stage injection method designed through reducing the injector area to keep the same hydrogen mass flowrate can induce a much higher mixing efficiency while only a bit larger loss of total pressure when compared to the single-stage injection,and hence the two-stage injection is superior to the single-stage injection.The research results can direct the design of the fuel injection method in the combustor of scramjet engine.
文摘A tunable dual-wavelength fiber ring laser with a Fabry-Perot laser diode is proposed and demonstrated. The dual-wavelength outputs have the optical side-mode-suppression-ratio (SMSR) over 31 dB. The wavelength tuning range can be up to 9 run.
基金Project supported by the Natural Science Foundation of Heilongjiang Province (Grant No : A2004-11)
文摘Based on the features of surfactant flooding, a mathematical model for surfactant flooding is established. The adsorption-retentlon, convection diffusion of surfactant and influence of concentration change upon relative permeability curve are included in the model. The novel description of adsorption quantity of surfaetant and relative permeability curve are presented, which enhance the coincidence between mathematical model and field practice, the relative errors of main development indexes arc within 6%. The model is applied to the numerical research of the surfactant flooding in the untabulated beds of Xingl-3 surfactant flooding pilot site of No. 4 Oil Production Company of Daqing Oilfield, the influences of surfaetant concentration, injection quantity, slug combination mode upon the development effect and economic benefit are quantitatively analyzed, the injection scheme is optimized as follows： surfaetant concentration is 0.5%, slug volume is 0.02 PV, slug combination mode is 2 slugs. After the implementation of scheme in oilfield, the cumulative increase of oil is 2186.0 t, up to nearly 30%.
