In order to investigate the problem of long-term strength retrogression in oil well cement systems exposed to high pressure and high temperature(HPHT)curing conditions,various influencing factors,including cement sour...In order to investigate the problem of long-term strength retrogression in oil well cement systems exposed to high pressure and high temperature(HPHT)curing conditions,various influencing factors,including cement sources,particle sizes of silica flour,and additions of silica fume,alumina,colloidal iron oxide and nano-graphene,were investigated.To simulate the environment of cementing geothermal wells and deep wells,cement slurries were directly cured at 50 MPa and 200?C.Mineral compositions(as determined by X-ray diffraction Rietveld refinement),water permeability,compressive strength and Young’s modulus were used to evaluate the qualities of the set cement.Short-term curing(2e30 d)test results indicated that the adoption of 6 m m ultrafine crystalline silica played the most important role in stabilizing the mechanical properties of oil well cement systems,while the addition of silica fume had a detrimental effect on strength stability.Long-term curing(2e180 d)test results indicated that nano-graphene could stabilize the Young’s modulus of oil well cement systems.However,none of the ad-mixtures studied here can completely prevent the strength retrogression phenomenon due to their inability to stop the conversion of amorphous to crystalline phases.展开更多
High quality cubic diamond crystals were grown using the temperature gradient method at high pressure and high temperature(HPHT),in a new FeNi alloy as solvent.The crystals were grown at relatively low temperatures su...High quality cubic diamond crystals were grown using the temperature gradient method at high pressure and high temperature(HPHT),in a new FeNi alloy as solvent.The crystals were grown at relatively low temperatures suitable for the growth of {100} faces.An increase in the radial growth rate,and inhibition of the axial growth caused the growth of large,high quality cubic diamond single crystals at high growth rates.For example,over 33 h,the radial growth rate was 0.22 mm/h,while the axial growth rate was only 0.08 mm/h;the growth rate by weight was also increased to 7.3 mg/h.The yellow color of our crystal samples was more uniform than samples from Sumitomo Corporation of Japan and Element Six Corp.The Raman FWHW of the 1332 cm 1 peak in our diamond sample was smaller than the Element Six Corp.sample,but larger than that of the Sumitomo Corp.sample.The nitrogen content of our diamond samples was 240 ppm,which was much higher than the Sumitomo and Element Six samples because of the higher growth rate of our diamond samples.展开更多
基金Financial support comes from China National Natural Science Foundation(Grant No.51974352)as well as from China University of Petroleum(East China)(Grant Nos.2018000025 and 2019000011)。
文摘In order to investigate the problem of long-term strength retrogression in oil well cement systems exposed to high pressure and high temperature(HPHT)curing conditions,various influencing factors,including cement sources,particle sizes of silica flour,and additions of silica fume,alumina,colloidal iron oxide and nano-graphene,were investigated.To simulate the environment of cementing geothermal wells and deep wells,cement slurries were directly cured at 50 MPa and 200?C.Mineral compositions(as determined by X-ray diffraction Rietveld refinement),water permeability,compressive strength and Young’s modulus were used to evaluate the qualities of the set cement.Short-term curing(2e30 d)test results indicated that the adoption of 6 m m ultrafine crystalline silica played the most important role in stabilizing the mechanical properties of oil well cement systems,while the addition of silica fume had a detrimental effect on strength stability.Long-term curing(2e180 d)test results indicated that nano-graphene could stabilize the Young’s modulus of oil well cement systems.However,none of the ad-mixtures studied here can completely prevent the strength retrogression phenomenon due to their inability to stop the conversion of amorphous to crystalline phases.
基金supported by the Natural Science Foundation of the Education Department of Henan Province (2009A430014)
文摘High quality cubic diamond crystals were grown using the temperature gradient method at high pressure and high temperature(HPHT),in a new FeNi alloy as solvent.The crystals were grown at relatively low temperatures suitable for the growth of {100} faces.An increase in the radial growth rate,and inhibition of the axial growth caused the growth of large,high quality cubic diamond single crystals at high growth rates.For example,over 33 h,the radial growth rate was 0.22 mm/h,while the axial growth rate was only 0.08 mm/h;the growth rate by weight was also increased to 7.3 mg/h.The yellow color of our crystal samples was more uniform than samples from Sumitomo Corporation of Japan and Element Six Corp.The Raman FWHW of the 1332 cm 1 peak in our diamond sample was smaller than the Element Six Corp.sample,but larger than that of the Sumitomo Corp.sample.The nitrogen content of our diamond samples was 240 ppm,which was much higher than the Sumitomo and Element Six samples because of the higher growth rate of our diamond samples.
