Invasion of drilling fluid into natural gas hydrate deposits during drilling might damage the reservoir,induce hydrate dissociation and then cause wellbore instability and distortion of the data from well logging. Add...Invasion of drilling fluid into natural gas hydrate deposits during drilling might damage the reservoir,induce hydrate dissociation and then cause wellbore instability and distortion of the data from well logging. Adding nanoparticles into drilling fluid is an effective method in reducing the invasion of drilling fluid and enhancing borehole stability. However, the addition of nanoparticles might also introduce hydrate formation risk in borehole because they can act as the "seeds" for hydrate nucleation. This paper presents an experimental study of the effect of hydrophilic silica nanoparticle on gas hydrate formation in a dynamic methane/liquid-water system. In the experiment, the ultrapure water with and without1.0 wt%–6.0 wt% concentrations of silica nanoparticles, grain sizes of 20 and 50 nm, were pressurized by methane gas under varied conditions of temperature and pressure. The induction time, the gas consumption, and the average rate of gas consumption in the system were measured and compared to those in ultrapure water. The results show that a concentration of 4.0 wt% hydrophilic SiO_2 particles with a grain size of 50 nm has a relatively strong inhibition effect on hydrate formation when the initial experimental condition is 5.0 °C and 5.0 MPa. Compared to ultrapure water, the hydrophilic nano-SiO_2 fluid increases the induction time for hydrate formation by 194% and decreases the amount and average rate of hydrate formation by 10% and 17%, respectively. This inhibition effect may be attributed to the hydrophilicity,amount and aggregation of silica nanoparticle according to the results of water activity and zeta potential measurements. Our work also elucidates hydrophilic, instead of hydrophobic, nanoparticles can be added to the drilling fluid to maintain wellbore stability and to protect the hydrate reservoir from drilling mud damage, because they exhibit certain degree of hydrate inhibition which can reduce the risk of hydrate reformation and aggregation during gas hydrate or deep water drilling if their concentration can be controlled properly.展开更多
Enhancing corrosion resistance of Mg-Zn alloys with high strength and low cost was critical for broadening their large-scale practical applications. Here we prepared solutionized, peak-and over-aged ZK60 alloys with a...Enhancing corrosion resistance of Mg-Zn alloys with high strength and low cost was critical for broadening their large-scale practical applications. Here we prepared solutionized, peak-and over-aged ZK60 alloys with and without microalloying Ca(0.26 wt.%) to explore the effects of nanoscale precipitates on their corrosion behavior in detail via experimental analyses and theoretical calculations. The results suggested the peak-aged ZK60 alloy with Ca addition showed improved corrosion resistance in comparison with the alloys without Ca,owing to the contribution of Ca on the refinement of precipitates and increase in their number density. Although the precipitates and Mg matrix formed micro-galvanic couples leading to dissolution, the fine and dense precipitates could generate “in-situ pinning” effect on the corrosion products, forming a spider-web-like structure and improving the corrosion inhibition ability accordingly. The pinning effect was closely related to the size and number density of precipitates. This study provided important insight into the design and development of advanced corrosion resistant Mg alloys.展开更多
The adsorption and diffusion behavior of Cl^- on sputtering Fe-20 Cr nanocrystalline(NC) thin film compared with corresponding coarse crystalline(CC) alloy has been studied in HCl + NaCl solution(pH = 2,[Cl^-]=0...The adsorption and diffusion behavior of Cl^- on sputtering Fe-20 Cr nanocrystalline(NC) thin film compared with corresponding coarse crystalline(CC) alloy has been studied in HCl + NaCl solution(pH = 2,[Cl^-]=0.1 mol/L) by electrochemical techniques,X-ray photoelectron spectroscopy(XPS) and the firstprinciples calculations.The XPS results show that adsorption and diffusion of Cl^- in the passive film has been inhibited on NC thin film.Ultra-violet photoelectron spectroscopy(UPS) results show that the work function Φ s of NC thin film(4.7 eV) is higher than that of CC alloy(4.5 eV).The theoretical calculations and valence electron structure analysis were used to understand the effect of nanocrystallization in this work.展开更多
Specially designed Mg-Cu-Al alloys were prepared for the application in fracturing balls.In comparison to Mg-2.5 Cu alloy,Mg-2.5 Cu-6.0 Al alloy exhibits an improved compressive strength of 378 MPa and compressive str...Specially designed Mg-Cu-Al alloys were prepared for the application in fracturing balls.In comparison to Mg-2.5 Cu alloy,Mg-2.5 Cu-6.0 Al alloy exhibits an improved compressive strength of 378 MPa and compressive strain of 27%,combined with a high degradation rate of 383 mm/y.Two kinds of second-phases are found in Mg-Cu-Al alloys,i.e.MgAlCu andβ-Mg_(17)Al_(12)+Al_(2)Cu phases.They form a discontinuous network and act as cathodes for micro-galvanic corrosion,leading to a high degradation rate.Moreover,the addition of Al could improve the strength and ductility simultaneously in Mg-Cu alloys.The enhancement of strength primarily arises from the solid-solution strengthening and second-phase hardening.A high density of basal,non-basal dislocations and stacking faults were activated upon mechanical deformation.This accounts for the good ductility in Mg-Cu-Al alloys.展开更多
基金supported by National Youth Top-notch Talent Support Programthe National Natural Science Foundationof China(41672367,51704266)+2 种基金China Geological Survey Project(DD20160216)Qingdao National Laboratory for Marine Science and Technology Open Fund(QNLM2016ORP0203)Experimental Apparatus Improvement Program of CUG(SJ-201613)
文摘Invasion of drilling fluid into natural gas hydrate deposits during drilling might damage the reservoir,induce hydrate dissociation and then cause wellbore instability and distortion of the data from well logging. Adding nanoparticles into drilling fluid is an effective method in reducing the invasion of drilling fluid and enhancing borehole stability. However, the addition of nanoparticles might also introduce hydrate formation risk in borehole because they can act as the "seeds" for hydrate nucleation. This paper presents an experimental study of the effect of hydrophilic silica nanoparticle on gas hydrate formation in a dynamic methane/liquid-water system. In the experiment, the ultrapure water with and without1.0 wt%–6.0 wt% concentrations of silica nanoparticles, grain sizes of 20 and 50 nm, were pressurized by methane gas under varied conditions of temperature and pressure. The induction time, the gas consumption, and the average rate of gas consumption in the system were measured and compared to those in ultrapure water. The results show that a concentration of 4.0 wt% hydrophilic SiO_2 particles with a grain size of 50 nm has a relatively strong inhibition effect on hydrate formation when the initial experimental condition is 5.0 °C and 5.0 MPa. Compared to ultrapure water, the hydrophilic nano-SiO_2 fluid increases the induction time for hydrate formation by 194% and decreases the amount and average rate of hydrate formation by 10% and 17%, respectively. This inhibition effect may be attributed to the hydrophilicity,amount and aggregation of silica nanoparticle according to the results of water activity and zeta potential measurements. Our work also elucidates hydrophilic, instead of hydrophobic, nanoparticles can be added to the drilling fluid to maintain wellbore stability and to protect the hydrate reservoir from drilling mud damage, because they exhibit certain degree of hydrate inhibition which can reduce the risk of hydrate reformation and aggregation during gas hydrate or deep water drilling if their concentration can be controlled properly.
基金the support of the National Natural Science Foundation of China (Grant Nos.51901174,52005389)the China Postdoctoral Science Foundation (Nos.2020M673383,2020M673389)the Fundamental Research Funds for the Central Universities (xzy012020001)。
文摘Enhancing corrosion resistance of Mg-Zn alloys with high strength and low cost was critical for broadening their large-scale practical applications. Here we prepared solutionized, peak-and over-aged ZK60 alloys with and without microalloying Ca(0.26 wt.%) to explore the effects of nanoscale precipitates on their corrosion behavior in detail via experimental analyses and theoretical calculations. The results suggested the peak-aged ZK60 alloy with Ca addition showed improved corrosion resistance in comparison with the alloys without Ca,owing to the contribution of Ca on the refinement of precipitates and increase in their number density. Although the precipitates and Mg matrix formed micro-galvanic couples leading to dissolution, the fine and dense precipitates could generate “in-situ pinning” effect on the corrosion products, forming a spider-web-like structure and improving the corrosion inhibition ability accordingly. The pinning effect was closely related to the size and number density of precipitates. This study provided important insight into the design and development of advanced corrosion resistant Mg alloys.
基金supported by the National Basic Research Program of China (No.2014CB643303)the National Natural Science Foundation of China (Nos.50801063 and 51271187)
文摘The adsorption and diffusion behavior of Cl^- on sputtering Fe-20 Cr nanocrystalline(NC) thin film compared with corresponding coarse crystalline(CC) alloy has been studied in HCl + NaCl solution(pH = 2,[Cl^-]=0.1 mol/L) by electrochemical techniques,X-ray photoelectron spectroscopy(XPS) and the firstprinciples calculations.The XPS results show that adsorption and diffusion of Cl^- in the passive film has been inhibited on NC thin film.Ultra-violet photoelectron spectroscopy(UPS) results show that the work function Φ s of NC thin film(4.7 eV) is higher than that of CC alloy(4.5 eV).The theoretical calculations and valence electron structure analysis were used to understand the effect of nanocrystallization in this work.
文摘Specially designed Mg-Cu-Al alloys were prepared for the application in fracturing balls.In comparison to Mg-2.5 Cu alloy,Mg-2.5 Cu-6.0 Al alloy exhibits an improved compressive strength of 378 MPa and compressive strain of 27%,combined with a high degradation rate of 383 mm/y.Two kinds of second-phases are found in Mg-Cu-Al alloys,i.e.MgAlCu andβ-Mg_(17)Al_(12)+Al_(2)Cu phases.They form a discontinuous network and act as cathodes for micro-galvanic corrosion,leading to a high degradation rate.Moreover,the addition of Al could improve the strength and ductility simultaneously in Mg-Cu alloys.The enhancement of strength primarily arises from the solid-solution strengthening and second-phase hardening.A high density of basal,non-basal dislocations and stacking faults were activated upon mechanical deformation.This accounts for the good ductility in Mg-Cu-Al alloys.
基金supported by the National Natural Science Foundation of China(61722403,92061113,and 12004131)the Interdisciplinary Research Grant for Ph Ds of Jilin University(101832020DJX043)。
基金supported by the National Natural Science Foundation of China(52125205,11974317,11674290,U20A20166,U1704138,52192614,61805015,and 61804011)the National Key R&D Program of China(2021YFB3200302 and 2021YFB3200304)+5 种基金Natural Science Foundation of Beijing Municipality(Z180011 and 2222088)Shenzhen Science and Technology Program(KQTD20170810105439418)the Fundamental Research Funds for the Central UniversitiesHenan Science Fund for Distinguished Young Scholars(212300410020)Key Project of Henan Higher Education(21A140001)the Zhengzhou University Physics Discipline Improvement Program。