Class III tight oil reservoirs have low porosity and permeability,which are often responsible for low production rates and limited recovery.Extensive repeated fracturing is a well-known technique to fix some of these ...Class III tight oil reservoirs have low porosity and permeability,which are often responsible for low production rates and limited recovery.Extensive repeated fracturing is a well-known technique to fix some of these issues.With such methods,existing fractures are refractured,and/or new fractures are created to facilitate communication with natural fractures.This study explored how different refracturing methods affect horizontal well fracture networks,with a special focus on morphology and related fluid flow changes.In particular,the study relied on the unconventional fracture model(UFM).The evolution of fracture morphology and flow field after the initial fracturing were analyzed accordingly.The simulation results indicated that increased formation energy and reduced reservoir stress differences can promote fracture expansion.It was shown that the length of the fracture network,the width of the fracture network,and the complexity of the fracture can be improved,the oil drainage area can be increased,the distance of oil and gas seepage can be reduced,and the production of a single well can be significantly increased.展开更多
Production decline analysis has been considered as an important method to obtain the flow parameters, reservoir properties and original gas in place. Although advanced Blasingame production decline analysis methods fo...Production decline analysis has been considered as an important method to obtain the flow parameters, reservoir properties and original gas in place. Although advanced Blasingame production decline analysis methods for vertical wells, fractured wells and horizontal wells are widely used, limited study has conducted on Blasingame production decline type curves for multi-fractured horizontal well(MFHW). Based on the perpendicular bisection(PEBI) grids, a numerical model was developed and the solution was obtained using control volume finite element method and the fully implicit method. Blasingame production decline-type curves of the infinitely conductive MFHW were plotted through computer programming. A field case was presented to analyse and verify the model developed. Five flow regimes, including early formation linear flow, early radial flow, compound linear flow, transient flow and pseudo-radial flow, are recognized. Fracture spacing is the main factor that affects early radial flow, compound linear flow and transient flow, the distance from the well to the circular boundary affects the pseudo-radial flow, and the type curves are also significantly affected by the formation permeability, fracture number and fracture half-length. The validation of field case suggests that the Blasingame production decline type curves proposed in this work can be applied to the production decline analysis for MFHW in tight gas reservoirs.展开更多
The way of producing needle-shaped wolldstonite pow-der has never been released, the key to the matter is to get high enough length to -width ratio of the particle. With φ 50 mm horizontal disk type jet mill,rue carr...The way of producing needle-shaped wolldstonite pow-der has never been released, the key to the matter is to get high enough length to -width ratio of the particle. With φ 50 mm horizontal disk type jet mill,rue carry out a series of experiments, and discover that select-ing reasonable technological operating condition, with the aim of weak-ening colliding pulverizing effect and reinforcing rubbing pulverizing effect, is helpful to improve effectively the L-W radio.展开更多
A previous study proposed a mathematical model of A-type horizontal cells in the rabbit retina. This model, which was constructed based on the Hodgkin-Huxley model, was described by a system of nonlinear ordinary diff...A previous study proposed a mathematical model of A-type horizontal cells in the rabbit retina. This model, which was constructed based on the Hodgkin-Huxley model, was described by a system of nonlinear ordinary differential equations. The model contained five types of voltage-dependent ionic conductances: sodium, calcium, delayed rectifier potassium, transient outward potassium, and anomalous rectifier potassium conductances. The previous study indicated that when the delayed rectifier potassium conductance had a small value, depolarizing stimulation could change the dynamic state of the model from a hyperpolarized steady state to a depolarized steady state. However, how this change was affected by variations in the ionic conductance values was not clarified in detail in the previous study. To clarify this issue, in the present study, we performed numerical simulation analysis of the model and revealed the differences among the five types of ionic conductances.展开更多
Objective:To investigate the anti-diabetic effect of the root extract of Annona muricata(AME)in streptozotocin-nicotinamide-induced type 2 diabetic(T2DM)mice.Methods:After 4 weeks of high-fat diet,ICR mice were given ...Objective:To investigate the anti-diabetic effect of the root extract of Annona muricata(AME)in streptozotocin-nicotinamide-induced type 2 diabetic(T2DM)mice.Methods:After 4 weeks of high-fat diet,ICR mice were given 1 g/kg nicotine and 120 mg/kg streptozotocin(STZ)orally to construct a T2DM model.The T2DM mice were randomly divided into five groups:model group,200 mg/kg metformin group and 50,100,200 mg/kg AME groups.Drugs were oral administered continuously for 4 weeks.Fasting blood glucose and body weight were measured weekly.Oral glucose tolerance test(OGTT)and detection of serum glycated hemoglobin(HbA1c)level were performed one week before the end of the experiment.At the end of drug administration,serum total cholesterol(TG),triglycerides(TC),low-density lipoprotein levels(LDL-C)and insulin levels were tested by lipid detection kits;homeostasis model assessment-estimated insulin resistance(HOMA-IR)and HOMA-βindexes were calculated.Liver and kidney tissues were weighed to calculate organ indices and pathological tests were performed.Western blot was performed in the liver to detect adenosine monophosphate-activated protein kinase(AMPK),acetyl coenzyme A carboxylase(ACC),glucose-6-phosphate carboxylase(G6Pase),and phosphoenolpyruvate carboxykinase(PCK1)protein expression.Results:with 200 mg/kg AME significantly reduced fasting blood glucose,HbA1c,TG and LDL-C levels,protected liver and kindey in diabetic mice,decreased the area under the OGTT curve,inhibited ACC and G6Pase protein expressions,and activated AMPK protein expression.Conclusion:AME showed good therapeutic activity against T2DM,and the mechanism may be related to the activation of AMPK and inhibition of ACC and G6Pase proteins.展开更多
Based on the elastoplastic model of cement sheath considering the influence of three-dimensional principal stress and the stress field model of interface crack,a mechanical performance design method of cement sheath i...Based on the elastoplastic model of cement sheath considering the influence of three-dimensional principal stress and the stress field model of interface crack,a mechanical performance design method of cement sheath is established to meet the wellbore sealing requirements during fracturing.This method takes the failure types of the cement sheath,such as tensile failure,plastic yield,interface crack propagation along interface and zigzag propagation into account.Meanwhile,the elasticity modulus and Poisson's ratio quantitative design charts of cement sheath are constructed based on this method,and the safety and risk areas of wellbores are defined,which quantify the yield strength and tensile strength indexes of cement sheath.The results show that decreasing elasticity modulus,increasing yield strength and Poisson's ratio of cement sheath can avoid plastic deformation of cement sheath;increasing the tensile strength of cement sheath can prevent its tensile failure;increasing elasticity modulus and Poisson's ratio of cement sheath is good for shortening the length of the interface crack,but will increase the risk of interface cracks zigzagging into cement sheath.The model calculation and case verification has proved that the method in this paper can give accurate calculation results and is convenient for field application.展开更多
The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,E...The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,Eleusine indica,Potentilla anserine,and Artemisia argyi,according to the classification in Botany,and the thrust-displacement curves and failure patterns of different samples were analysed by comparison to fill the aforementioned gap.Results reveal that the roots can reduce the characteristics of soil brittleness and enhance its capability to resist large deformation,and different root types contribute different effects to the strain-hardening behavior of the root-soil mass.The contribution of the fibrous root system to strength is limited,whilst the tap root system substantially enhances strength and stiffness.Results of failure patterns show that fibrous and tap root systems affect soil solidification and surface cracking reduction.However,the effect of the tap root system depends on the composition of lateral and tap roots:long and rich lateral roots are effective for resisting the creation of cracks,but thick tap roots with few and thin lateral roots may lead to several surface cracks.展开更多
Based on the Boussinesq assumption, derived are couple equations of free surface elevation and horizontal velocities for horizontal irrotational flow, and analytical expressions of the corresponding pressure and verti...Based on the Boussinesq assumption, derived are couple equations of free surface elevation and horizontal velocities for horizontal irrotational flow, and analytical expressions of the corresponding pressure and vertical velocity. After the free surface elevation and horizontal velocity at a certain depth are obtained by numerical method, the pressure and vertical velocity distributions can be obtained by simple calculation. The dispersion at different depths is the same at the O (epsilon) approximation. The wave amplitude will decrease with increasing time due to viscosity, but it will increase due to the matching of viscosity and the bed slope, thus, flow is unstable. Numerical or analytical results show that the wave amplitude, velocity and length will increase as the current increases along the wave direction. but the amplitude will increase, and the wave velocity and length will decrease as the water depth decreases.展开更多
基金the China Research and Pilot Test on Key Technology of Efficient Production of Changqing Tight Oil(Grant No.2021DJ2202).
文摘Class III tight oil reservoirs have low porosity and permeability,which are often responsible for low production rates and limited recovery.Extensive repeated fracturing is a well-known technique to fix some of these issues.With such methods,existing fractures are refractured,and/or new fractures are created to facilitate communication with natural fractures.This study explored how different refracturing methods affect horizontal well fracture networks,with a special focus on morphology and related fluid flow changes.In particular,the study relied on the unconventional fracture model(UFM).The evolution of fracture morphology and flow field after the initial fracturing were analyzed accordingly.The simulation results indicated that increased formation energy and reduced reservoir stress differences can promote fracture expansion.It was shown that the length of the fracture network,the width of the fracture network,and the complexity of the fracture can be improved,the oil drainage area can be increased,the distance of oil and gas seepage can be reduced,and the production of a single well can be significantly increased.
基金Project(2013CB228005)supported by the National Basic Research Program of China
文摘Production decline analysis has been considered as an important method to obtain the flow parameters, reservoir properties and original gas in place. Although advanced Blasingame production decline analysis methods for vertical wells, fractured wells and horizontal wells are widely used, limited study has conducted on Blasingame production decline type curves for multi-fractured horizontal well(MFHW). Based on the perpendicular bisection(PEBI) grids, a numerical model was developed and the solution was obtained using control volume finite element method and the fully implicit method. Blasingame production decline-type curves of the infinitely conductive MFHW were plotted through computer programming. A field case was presented to analyse and verify the model developed. Five flow regimes, including early formation linear flow, early radial flow, compound linear flow, transient flow and pseudo-radial flow, are recognized. Fracture spacing is the main factor that affects early radial flow, compound linear flow and transient flow, the distance from the well to the circular boundary affects the pseudo-radial flow, and the type curves are also significantly affected by the formation permeability, fracture number and fracture half-length. The validation of field case suggests that the Blasingame production decline type curves proposed in this work can be applied to the production decline analysis for MFHW in tight gas reservoirs.
文摘The way of producing needle-shaped wolldstonite pow-der has never been released, the key to the matter is to get high enough length to -width ratio of the particle. With φ 50 mm horizontal disk type jet mill,rue carry out a series of experiments, and discover that select-ing reasonable technological operating condition, with the aim of weak-ening colliding pulverizing effect and reinforcing rubbing pulverizing effect, is helpful to improve effectively the L-W radio.
文摘A previous study proposed a mathematical model of A-type horizontal cells in the rabbit retina. This model, which was constructed based on the Hodgkin-Huxley model, was described by a system of nonlinear ordinary differential equations. The model contained five types of voltage-dependent ionic conductances: sodium, calcium, delayed rectifier potassium, transient outward potassium, and anomalous rectifier potassium conductances. The previous study indicated that when the delayed rectifier potassium conductance had a small value, depolarizing stimulation could change the dynamic state of the model from a hyperpolarized steady state to a depolarized steady state. However, how this change was affected by variations in the ionic conductance values was not clarified in detail in the previous study. To clarify this issue, in the present study, we performed numerical simulation analysis of the model and revealed the differences among the five types of ionic conductances.
基金National Natural Science Foundation of China(No.81460591)Hainan Medical University Training Fund(HY2018-09)。
文摘Objective:To investigate the anti-diabetic effect of the root extract of Annona muricata(AME)in streptozotocin-nicotinamide-induced type 2 diabetic(T2DM)mice.Methods:After 4 weeks of high-fat diet,ICR mice were given 1 g/kg nicotine and 120 mg/kg streptozotocin(STZ)orally to construct a T2DM model.The T2DM mice were randomly divided into five groups:model group,200 mg/kg metformin group and 50,100,200 mg/kg AME groups.Drugs were oral administered continuously for 4 weeks.Fasting blood glucose and body weight were measured weekly.Oral glucose tolerance test(OGTT)and detection of serum glycated hemoglobin(HbA1c)level were performed one week before the end of the experiment.At the end of drug administration,serum total cholesterol(TG),triglycerides(TC),low-density lipoprotein levels(LDL-C)and insulin levels were tested by lipid detection kits;homeostasis model assessment-estimated insulin resistance(HOMA-IR)and HOMA-βindexes were calculated.Liver and kidney tissues were weighed to calculate organ indices and pathological tests were performed.Western blot was performed in the liver to detect adenosine monophosphate-activated protein kinase(AMPK),acetyl coenzyme A carboxylase(ACC),glucose-6-phosphate carboxylase(G6Pase),and phosphoenolpyruvate carboxykinase(PCK1)protein expression.Results:with 200 mg/kg AME significantly reduced fasting blood glucose,HbA1c,TG and LDL-C levels,protected liver and kindey in diabetic mice,decreased the area under the OGTT curve,inhibited ACC and G6Pase protein expressions,and activated AMPK protein expression.Conclusion:AME showed good therapeutic activity against T2DM,and the mechanism may be related to the activation of AMPK and inhibition of ACC and G6Pase proteins.
基金Supported by Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance(2020CX040000)Sichuan Science and Technology Program(2020JDTD0019)+1 种基金National Natural Science Foundation of China(52004231)Research Project of Dagang Oilfield(NO.DGYT-2018-JS-244).
文摘Based on the elastoplastic model of cement sheath considering the influence of three-dimensional principal stress and the stress field model of interface crack,a mechanical performance design method of cement sheath is established to meet the wellbore sealing requirements during fracturing.This method takes the failure types of the cement sheath,such as tensile failure,plastic yield,interface crack propagation along interface and zigzag propagation into account.Meanwhile,the elasticity modulus and Poisson's ratio quantitative design charts of cement sheath are constructed based on this method,and the safety and risk areas of wellbores are defined,which quantify the yield strength and tensile strength indexes of cement sheath.The results show that decreasing elasticity modulus,increasing yield strength and Poisson's ratio of cement sheath can avoid plastic deformation of cement sheath;increasing the tensile strength of cement sheath can prevent its tensile failure;increasing elasticity modulus and Poisson's ratio of cement sheath is good for shortening the length of the interface crack,but will increase the risk of interface cracks zigzagging into cement sheath.The model calculation and case verification has proved that the method in this paper can give accurate calculation results and is convenient for field application.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA23090402)the National Natural Science Foundation of China(Nos.41790442,41825018)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0904)。
文摘The influence of different types of roots on the soil is complex and still remains unclear.Four in-situ extrusion tests were conducted on two types of root systems,namely fibrous and tap root system,for three plants,Eleusine indica,Potentilla anserine,and Artemisia argyi,according to the classification in Botany,and the thrust-displacement curves and failure patterns of different samples were analysed by comparison to fill the aforementioned gap.Results reveal that the roots can reduce the characteristics of soil brittleness and enhance its capability to resist large deformation,and different root types contribute different effects to the strain-hardening behavior of the root-soil mass.The contribution of the fibrous root system to strength is limited,whilst the tap root system substantially enhances strength and stiffness.Results of failure patterns show that fibrous and tap root systems affect soil solidification and surface cracking reduction.However,the effect of the tap root system depends on the composition of lateral and tap roots:long and rich lateral roots are effective for resisting the creation of cracks,but thick tap roots with few and thin lateral roots may lead to several surface cracks.
基金National Natural Science Foundation of China.(Grant No.19572077)
文摘Based on the Boussinesq assumption, derived are couple equations of free surface elevation and horizontal velocities for horizontal irrotational flow, and analytical expressions of the corresponding pressure and vertical velocity. After the free surface elevation and horizontal velocity at a certain depth are obtained by numerical method, the pressure and vertical velocity distributions can be obtained by simple calculation. The dispersion at different depths is the same at the O (epsilon) approximation. The wave amplitude will decrease with increasing time due to viscosity, but it will increase due to the matching of viscosity and the bed slope, thus, flow is unstable. Numerical or analytical results show that the wave amplitude, velocity and length will increase as the current increases along the wave direction. but the amplitude will increase, and the wave velocity and length will decrease as the water depth decreases.
