Gaomiaozi(GMZ)bentonite is a potential buffer/backfill material for a deep geological disposal of highlevel radioactive waste.It has a wide pore size distribution(PSD)with sizes ranging from several nanometers to more...Gaomiaozi(GMZ)bentonite is a potential buffer/backfill material for a deep geological disposal of highlevel radioactive waste.It has a wide pore size distribution(PSD)with sizes ranging from several nanometers to more than one hundred microns.Thus,properly characterizing the pore structures of GMZ bentonite is a challenging issue.In this study,pressure-controlled porosimetry(PCP),ratecontrolled porosimetry(RCP),and scanning electron microscopy(SEM)were used to investigate the PSD of GMZ bentonite,The results indicate that each method has its limitation,and a combined use of PCP and RCP is suitable to obtain the full-scale PSD of GMZ bentonite.Moreover,we also compared the full-scale PSD with nuclear magnetic resonance(NMR)result.It is found that there is no significant difference in the range of PSD characterization between NMR and mercury intrusion method(PCP and RCP).However,in a ce rtain range,the detection accuracy of NMR is higher than that of mercury injection method.Finally,permeability prediction based on PCP and SEM data was conducted,and both of the two methods were found to be able to predict the permeability.The combined method is effective to obtain the full-scale PSD of GMZ bentonite,which is the key to estimation of the sealing ability of bentonite buffer.展开更多
An important factor to evaluate reservoir quality is the pore-throat size.However,the strong heterogeneity makes it difficult to characterize the pore-throat distribution in tight reservoirs.The field emission scannin...An important factor to evaluate reservoir quality is the pore-throat size.However,the strong heterogeneity makes it difficult to characterize the pore-throat distribution in tight reservoirs.The field emission scanning electron microscope(FESEM),high pressure mercury injection and rate-controlled mercury injection are used to investigate the pore-throat size distribution in tight sandstone reservoirs of Member 7 of the Yanchang Formation in eastern Gansu,Ordos Basin,and studies of the pore throat size controlling on physical property of the tight sandstone reservoirs are also carried out.The result shows that the pore type is mainly dominated by the residual intergranular pore,dissolution pore,micropore and a few micro-fractures;the high-pressure mercury injection experiment indicates that the pore-throat size ranges from 0.0148 μm to 40mm,the pore throat more than 1 mm is less;the ratecontrolled mercury injection experiment reveals that for samples with different physical properties,the pore radius mainly varies from 80 μm to 350 μm;the throat radius exhibits the strong heterogeneity,and is from 0.12 μm to 30μm;the pore-throat size can be effectively characterized by combination of high-pressure and rate-controlled mercury injections,and it varies from 0.0148 μm to 350 μm.The permeability is mainly controlled by the large pore throat(>R_(50))which accounts for a small proportion;in the tight sandstone with the permeability greater than 0.1 mD,the permeability is mainly controlled by the micropore and mesopore;in the tight sandstone with the permeability smaller than 0.1 mD,the permeability is mainly controlled by the nanopore and micropore;the proportion of small pore throat increases with reduction of permeability,it is important that the small pore throat influences the reservoir storage property though its effect on permeability are small.展开更多
基金support of the National Natural Science Foundation of China(Grant Nos.51809263)the Open Fund of Key Laboratory of Deep Earth Science and Engineering(Sichuan University)(Grant Nos.DESE201906 and DESE201907)。
文摘Gaomiaozi(GMZ)bentonite is a potential buffer/backfill material for a deep geological disposal of highlevel radioactive waste.It has a wide pore size distribution(PSD)with sizes ranging from several nanometers to more than one hundred microns.Thus,properly characterizing the pore structures of GMZ bentonite is a challenging issue.In this study,pressure-controlled porosimetry(PCP),ratecontrolled porosimetry(RCP),and scanning electron microscopy(SEM)were used to investigate the PSD of GMZ bentonite,The results indicate that each method has its limitation,and a combined use of PCP and RCP is suitable to obtain the full-scale PSD of GMZ bentonite.Moreover,we also compared the full-scale PSD with nuclear magnetic resonance(NMR)result.It is found that there is no significant difference in the range of PSD characterization between NMR and mercury intrusion method(PCP and RCP).However,in a ce rtain range,the detection accuracy of NMR is higher than that of mercury injection method.Finally,permeability prediction based on PCP and SEM data was conducted,and both of the two methods were found to be able to predict the permeability.The combined method is effective to obtain the full-scale PSD of GMZ bentonite,which is the key to estimation of the sealing ability of bentonite buffer.
基金The work was supported by the Natural Science Foundation of China(No.41672098,No.41602133)the National Science and Technology Major Project of China(No.2011ZX05007-003,2016ZX05006-006)PetroChina Special Projects(2011E-2602).
文摘An important factor to evaluate reservoir quality is the pore-throat size.However,the strong heterogeneity makes it difficult to characterize the pore-throat distribution in tight reservoirs.The field emission scanning electron microscope(FESEM),high pressure mercury injection and rate-controlled mercury injection are used to investigate the pore-throat size distribution in tight sandstone reservoirs of Member 7 of the Yanchang Formation in eastern Gansu,Ordos Basin,and studies of the pore throat size controlling on physical property of the tight sandstone reservoirs are also carried out.The result shows that the pore type is mainly dominated by the residual intergranular pore,dissolution pore,micropore and a few micro-fractures;the high-pressure mercury injection experiment indicates that the pore-throat size ranges from 0.0148 μm to 40mm,the pore throat more than 1 mm is less;the ratecontrolled mercury injection experiment reveals that for samples with different physical properties,the pore radius mainly varies from 80 μm to 350 μm;the throat radius exhibits the strong heterogeneity,and is from 0.12 μm to 30μm;the pore-throat size can be effectively characterized by combination of high-pressure and rate-controlled mercury injections,and it varies from 0.0148 μm to 350 μm.The permeability is mainly controlled by the large pore throat(>R_(50))which accounts for a small proportion;in the tight sandstone with the permeability greater than 0.1 mD,the permeability is mainly controlled by the micropore and mesopore;in the tight sandstone with the permeability smaller than 0.1 mD,the permeability is mainly controlled by the nanopore and micropore;the proportion of small pore throat increases with reduction of permeability,it is important that the small pore throat influences the reservoir storage property though its effect on permeability are small.
