The efficient development and exploitation of shale oil depends on long-distance horizontal wells. As the degreeof cleaning of the wellbore plays a key role in these processes, in this study, this problem is investiga...The efficient development and exploitation of shale oil depends on long-distance horizontal wells. As the degreeof cleaning of the wellbore plays a key role in these processes, in this study, this problem is investigated experimentallyby focusing on the dimensionless cuttings bed height. A method is proposed to calculate the horizontalwellhydraulic extension taking into account the influence of the wellbore cleaning degree on the wellborepressure distribution and assess the effect of a variety of factors such as the bottom hole pressure, the circulatingpressure drop, the drilling pump performance and the formation properties. The analysis shows that the hydraulicextension of horizontal wells decreases with an increase in the cuttings bed height, and the higher the displacementof drilling fluid, the faster the hydraulic extension declines. The annular pressure drop of the horizontalsection increases with the increase of the cuttings bed height, resulting in a higher bottom-hole pressure. Severalarguments are provided to guide the safe drilling of shale oil horizontal wells and overcome the limits of currenttechnological approaches.展开更多
Objective:To observe dynamic changes of levels of monocyte chemotactic protein-1(MCP-1),tumor necrosis factor-α(TNF-α) and interleukin-8(IL-8) in patients with acute pancreatitis and to investigate its evaluation va...Objective:To observe dynamic changes of levels of monocyte chemotactic protein-1(MCP-1),tumor necrosis factor-α(TNF-α) and interleukin-8(IL-8) in patients with acute pancreatitis and to investigate its evaluation value on the severity of acute pancreatitis.Methods:A total of 109 patients with acute pancreatitis admitted were divided into mild acute pancreatitis group(MAP group,42 cases),moderately severe acute pancreatitis(MSAP group,35 cases)and severe acute pancreatitis(SAP group,32 cases).ELISA was used to detect the serum levels of MCP-1,TNF-α and IL-8 of patients at day 1,day 4 and day 7 of admission to hospital.Results:The serum levels of MCP-1,TNF-α and IL-8 from MAP group,MSAP group and SAP group at day 1 of admission to hospital all significantly increased.There was a significant difference between MAP group and control group,MSAP group and MAP group,SAP group and MSAP group(P<0.05).The serum concentrations of IL-8 from MASP group and SAP group obviously increased at day 1,and there was significant difference between MASP group and MAP group,SAP group and MSAP group(P<0.05),while the difference between MAP group and control group was not obvious(P>0.05);The serum concentrations of MCP-1,TNF-α and IL-8 from MAP group all reached the highest level at day 4,which were significantly higher than the detection levels at day 1.In MSAP group and SAP group,the serum concentrations of MCP-1,TNF-α and IL-8 were the highest at day 1,which were significantly higher than the detection levels at day 4 and 7.At each detecting timing,the serum concentrations of MCP-1,TNF-α and IL-8 from MSAP group and SAP group were all higher than those of MAP group and MSAP group,respectively.Conclusions:The dynamic changes of serum levels of MCP-1,TNF-α and IL-8 in patients with acute pancreatitis have their rules,and the change rule of MAP group was different with that of MSAP and SAP group,which showed the reference value for the diagnosis and illness severity evaluation of acute pancreatitis.展开更多
Whether hydraulic fractures could connect multiple gas zones in the vertical plane is the key to fracturing treatment to jointly exploit coalbed methane and tight sandstone gas through integrative hydraulic fracturing...Whether hydraulic fractures could connect multiple gas zones in the vertical plane is the key to fracturing treatment to jointly exploit coalbed methane and tight sandstone gas through integrative hydraulic fracturing in tight sandstone–coal interbedded formations. Laboratory true triaxial hydraulic fracturing experiments were conducted on layered specimens with di erent combination types of natural sandstone and coal to simulate the propagation behavior of hydraulic fractures. The effects of the fracture initiation position, fracturing fluid viscosity and injection rate were discussed. The results showed that di erent fracture morphologies could be found. When initiating from coal seams, three patterns of fracture initiation and propagation were obtained:(1) The main hydraulic fracture initiated and propagated along the natural fractures and then diverged due to the effects of in situ stress and formed secondary fractures.(2) The hydraulic fracture initiated and propagated in the direction of the maximum horizontal stress.(3) Multiple fractures initiated and propagated at the same time. With the same fracturing fluid viscosity and injection rate, the hydraulic fractures initiating in sandstones had greater chances than those in coal seams to penetrate interfaces and enter neighboring layers. Excessively small or large fracturing fluid viscosity and injection rate would do harm to the vertical extension height of the induced fracture and improvement of the stimulated reservoir volume. Compared with operation parameters(fracturing fluid viscosity and injection rate), the natural weak planes in coals were considered to be the key factor that a ected the fracture propagation path. The experimental results would make some contributions to the development of tight sandstone–coal interbedded reservoirs.展开更多
Hydraulic fracture is important in unconventional oil and gas exploration.During the propagation of the hydraulic fracture,the crack tip is blunted due to the development of the process zone in the near-tip area.In th...Hydraulic fracture is important in unconventional oil and gas exploration.During the propagation of the hydraulic fracture,the crack tip is blunted due to the development of the process zone in the near-tip area.In this study,the blunting of the hydraulic fracture in polymethyl methacrylate specimens due to multi-timescale stress concentration is investigated.The ratio of the initiation toughness to the arrest toughness of the blunted hydraulic fracture is measured using both the dynamic and the static methods.Results show that a hydraulic fracture can be blunted with the time span of stress concentration from 1 ms to 600 s.It is also shown that the blunting of hydraulic fracture is a highly localized process.The morphology of the blunted crack depends on the stress distribution in the vicinity of the crack tip.展开更多
A multi-casing structure in drilling engineering can be considered as an inhomogeneous body consisting of many different materials. The mechanical behavior of the inhomogeneous body in an infinite domain is very compl...A multi-casing structure in drilling engineering can be considered as an inhomogeneous body consisting of many different materials. The mechanical behavior of the inhomogeneous body in an infinite domain is very complicated. In this paper, a detailed expression about the fictitious stress method of the boundary element method(BEM) is demonstrated for the inhomogeneous body. Then the fictitious stress method is deployed to investigate the stresses for the multi-casing structure under non-uniform loading conditions and an irregular wellbore. Three examples of the multi-casing structure in the borehole imply the high effectiveness of BEM for complex geometries related to the borehole in an infinite formation.The effects of casing eccentricity and the interfacial gap on the stress field are discussed. The eccentric casing takes the potential yield when the eccentric orientation is along the direction of Sh. Under different eccentric orientations, the von Mises stress in the casing increases with increasing degree of eccentricity. The radial stress in the multi-casing structure is always continuous along the radius, but the circumferential stress is discontinuous at the interface. The radial stress decreases and the circumferential stress increases with the increasing of the interfacial gap between the adjacent materials.展开更多
In this paper,a silvered gradient nanostructured(GNS)layer was successfully fabricated on Ti6Al4V surface by means of surface ultrasonic rolling treatment(SURT)combined with silvering process.Surface characteristics,m...In this paper,a silvered gradient nanostructured(GNS)layer was successfully fabricated on Ti6Al4V surface by means of surface ultrasonic rolling treatment(SURT)combined with silvering process.Surface characteristics,mechanical properties,corrosion resistance,antibacterial ability and cytotoxicity of GNS Ag/Ti6Al4V were investigated in comparison with those of coarse-grained(CG)and GNS Ti6Al4V samples.Owing to the greatly enhanced diffusion kinetics of Ag in the GNS layer,surface silvering on GNS Ti6Al4V was achieved at a relatively low temperature(500℃),and the release rate of Ag^(+)was substantially accelerated,which endowed GNS Ag/Ti6Al4V with excellent antibacterial property.Moreover,improved wear and corrosion resistance of GNS Ag/Ti6Al4V can be achieved without cytotoxicity,indicating excellent bioadaptability.展开更多
Biomaterial surfaces with satisfied antibacterial activity and appropriate cytocompatibility are a pressing clinical need for orthopedic and dental implants.Fluorinecontaining biomaterials have been demonstrated to ob...Biomaterial surfaces with satisfied antibacterial activity and appropriate cytocompatibility are a pressing clinical need for orthopedic and dental implants.Fluorinecontaining biomaterials have been demonstrated to obtain antibacterial activity and osteogenic property,while the effect of fluorine chemical compositions on antibacterial property and cytocompatibility is rarely studied.To this end,the coatings with different fluorine chemical compositions on titanium surface were prepared by plasma treatment to verify the antibacterial ability and cytocompatibility of fluorinated surfaces.Their antibacterial ability was evaluated by using Staphylococcus aureus,and the cell compatibility was investigated with MC3T3-E1 cells in vitro.The results show that both fluorocarbon coating and metal fluorides coating exhibited a hydrophilic and nano-scaled roughness.Rather than the fluorocarbon coating,the coating composed of metal fluorides presented satisfied bactericide effect and excellent cytocompatibility.The antibacterial mechanism is associated with the metal fluorides and released fluoride ion.This work would provide novel sight in optimizing the surface modification method of fluorinated biomaterials for biomedical applications.展开更多
基金supported by CNPC Key Core Technology Research Projects (2022ZG06)project funded by China Postdoctoral Science Foundation (2021M693508)Basic research and strategic reserve technology research fund project of institutes directly under CNPC.
文摘The efficient development and exploitation of shale oil depends on long-distance horizontal wells. As the degreeof cleaning of the wellbore plays a key role in these processes, in this study, this problem is investigated experimentallyby focusing on the dimensionless cuttings bed height. A method is proposed to calculate the horizontalwellhydraulic extension taking into account the influence of the wellbore cleaning degree on the wellborepressure distribution and assess the effect of a variety of factors such as the bottom hole pressure, the circulatingpressure drop, the drilling pump performance and the formation properties. The analysis shows that the hydraulicextension of horizontal wells decreases with an increase in the cuttings bed height, and the higher the displacementof drilling fluid, the faster the hydraulic extension declines. The annular pressure drop of the horizontalsection increases with the increase of the cuttings bed height, resulting in a higher bottom-hole pressure. Severalarguments are provided to guide the safe drilling of shale oil horizontal wells and overcome the limits of currenttechnological approaches.
基金supported by Health and Family Planning Commission of Hainan Province,China,Scientific Research Project(Grant No.14A210207)
文摘Objective:To observe dynamic changes of levels of monocyte chemotactic protein-1(MCP-1),tumor necrosis factor-α(TNF-α) and interleukin-8(IL-8) in patients with acute pancreatitis and to investigate its evaluation value on the severity of acute pancreatitis.Methods:A total of 109 patients with acute pancreatitis admitted were divided into mild acute pancreatitis group(MAP group,42 cases),moderately severe acute pancreatitis(MSAP group,35 cases)and severe acute pancreatitis(SAP group,32 cases).ELISA was used to detect the serum levels of MCP-1,TNF-α and IL-8 of patients at day 1,day 4 and day 7 of admission to hospital.Results:The serum levels of MCP-1,TNF-α and IL-8 from MAP group,MSAP group and SAP group at day 1 of admission to hospital all significantly increased.There was a significant difference between MAP group and control group,MSAP group and MAP group,SAP group and MSAP group(P<0.05).The serum concentrations of IL-8 from MASP group and SAP group obviously increased at day 1,and there was significant difference between MASP group and MAP group,SAP group and MSAP group(P<0.05),while the difference between MAP group and control group was not obvious(P>0.05);The serum concentrations of MCP-1,TNF-α and IL-8 from MAP group all reached the highest level at day 4,which were significantly higher than the detection levels at day 1.In MSAP group and SAP group,the serum concentrations of MCP-1,TNF-α and IL-8 were the highest at day 1,which were significantly higher than the detection levels at day 4 and 7.At each detecting timing,the serum concentrations of MCP-1,TNF-α and IL-8 from MSAP group and SAP group were all higher than those of MAP group and MSAP group,respectively.Conclusions:The dynamic changes of serum levels of MCP-1,TNF-α and IL-8 in patients with acute pancreatitis have their rules,and the change rule of MAP group was different with that of MSAP and SAP group,which showed the reference value for the diagnosis and illness severity evaluation of acute pancreatitis.
基金the support from the National Science and Technology Major Projects of China(Grant No.2016ZX05066)Major Program of National Natural Science Foundation of China(Grant No.51490650)PetroChina Innovation Foundation(No.2018D-5007-0307)
文摘Whether hydraulic fractures could connect multiple gas zones in the vertical plane is the key to fracturing treatment to jointly exploit coalbed methane and tight sandstone gas through integrative hydraulic fracturing in tight sandstone–coal interbedded formations. Laboratory true triaxial hydraulic fracturing experiments were conducted on layered specimens with di erent combination types of natural sandstone and coal to simulate the propagation behavior of hydraulic fractures. The effects of the fracture initiation position, fracturing fluid viscosity and injection rate were discussed. The results showed that di erent fracture morphologies could be found. When initiating from coal seams, three patterns of fracture initiation and propagation were obtained:(1) The main hydraulic fracture initiated and propagated along the natural fractures and then diverged due to the effects of in situ stress and formed secondary fractures.(2) The hydraulic fracture initiated and propagated in the direction of the maximum horizontal stress.(3) Multiple fractures initiated and propagated at the same time. With the same fracturing fluid viscosity and injection rate, the hydraulic fractures initiating in sandstones had greater chances than those in coal seams to penetrate interfaces and enter neighboring layers. Excessively small or large fracturing fluid viscosity and injection rate would do harm to the vertical extension height of the induced fracture and improvement of the stimulated reservoir volume. Compared with operation parameters(fracturing fluid viscosity and injection rate), the natural weak planes in coals were considered to be the key factor that a ected the fracture propagation path. The experimental results would make some contributions to the development of tight sandstone–coal interbedded reservoirs.
基金the support from the China National Science and Technology Major Project"Changning-Weiyuan shale gas development demonstration project"(2016ZX05062)the support from the China National Petroleum Corporation:"Research on Influencing Factors of Gas Hydrate Sand Production and Experimental Design"(No.CPETQ201921)。
文摘Hydraulic fracture is important in unconventional oil and gas exploration.During the propagation of the hydraulic fracture,the crack tip is blunted due to the development of the process zone in the near-tip area.In this study,the blunting of the hydraulic fracture in polymethyl methacrylate specimens due to multi-timescale stress concentration is investigated.The ratio of the initiation toughness to the arrest toughness of the blunted hydraulic fracture is measured using both the dynamic and the static methods.Results show that a hydraulic fracture can be blunted with the time span of stress concentration from 1 ms to 600 s.It is also shown that the blunting of hydraulic fracture is a highly localized process.The morphology of the blunted crack depends on the stress distribution in the vicinity of the crack tip.
基金supported by the China National High Technology Research and Development Program 863 (Grant No. 2013AA064503)The China Scholarship Council
文摘A multi-casing structure in drilling engineering can be considered as an inhomogeneous body consisting of many different materials. The mechanical behavior of the inhomogeneous body in an infinite domain is very complicated. In this paper, a detailed expression about the fictitious stress method of the boundary element method(BEM) is demonstrated for the inhomogeneous body. Then the fictitious stress method is deployed to investigate the stresses for the multi-casing structure under non-uniform loading conditions and an irregular wellbore. Three examples of the multi-casing structure in the borehole imply the high effectiveness of BEM for complex geometries related to the borehole in an infinite formation.The effects of casing eccentricity and the interfacial gap on the stress field are discussed. The eccentric casing takes the potential yield when the eccentric orientation is along the direction of Sh. Under different eccentric orientations, the von Mises stress in the casing increases with increasing degree of eccentricity. The radial stress in the multi-casing structure is always continuous along the radius, but the circumferential stress is discontinuous at the interface. The radial stress decreases and the circumferential stress increases with the increasing of the interfacial gap between the adjacent materials.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51801064,51961012 and 52001122)Jiangxi Outstanding Young Talents Program(No.20192BCB23014)Jiangxi Key Research and Development Program(No.20203BBE53050).
文摘In this paper,a silvered gradient nanostructured(GNS)layer was successfully fabricated on Ti6Al4V surface by means of surface ultrasonic rolling treatment(SURT)combined with silvering process.Surface characteristics,mechanical properties,corrosion resistance,antibacterial ability and cytotoxicity of GNS Ag/Ti6Al4V were investigated in comparison with those of coarse-grained(CG)and GNS Ti6Al4V samples.Owing to the greatly enhanced diffusion kinetics of Ag in the GNS layer,surface silvering on GNS Ti6Al4V was achieved at a relatively low temperature(500℃),and the release rate of Ag^(+)was substantially accelerated,which endowed GNS Ag/Ti6Al4V with excellent antibacterial property.Moreover,improved wear and corrosion resistance of GNS Ag/Ti6Al4V can be achieved without cytotoxicity,indicating excellent bioadaptability.
基金This study was financially supported by the National Natural Science Foundation of China(No.52001122,51801064 and 51961012)Jiangxi Outstanding Young Talents Program(No.20192BCB23014),and Jiangxi Key Research and Development Program(No.20203BBE53050).
文摘Biomaterial surfaces with satisfied antibacterial activity and appropriate cytocompatibility are a pressing clinical need for orthopedic and dental implants.Fluorinecontaining biomaterials have been demonstrated to obtain antibacterial activity and osteogenic property,while the effect of fluorine chemical compositions on antibacterial property and cytocompatibility is rarely studied.To this end,the coatings with different fluorine chemical compositions on titanium surface were prepared by plasma treatment to verify the antibacterial ability and cytocompatibility of fluorinated surfaces.Their antibacterial ability was evaluated by using Staphylococcus aureus,and the cell compatibility was investigated with MC3T3-E1 cells in vitro.The results show that both fluorocarbon coating and metal fluorides coating exhibited a hydrophilic and nano-scaled roughness.Rather than the fluorocarbon coating,the coating composed of metal fluorides presented satisfied bactericide effect and excellent cytocompatibility.The antibacterial mechanism is associated with the metal fluorides and released fluoride ion.This work would provide novel sight in optimizing the surface modification method of fluorinated biomaterials for biomedical applications.
