Water invasion is a common phenomenon in gas reservoirs with active edge-and-bottom aquifers.Due to high reservoir heterogeneity and production parameters,carbonate gas reservoirs feature exploitation obstacles and lo...Water invasion is a common phenomenon in gas reservoirs with active edge-and-bottom aquifers.Due to high reservoir heterogeneity and production parameters,carbonate gas reservoirs feature exploitation obstacles and low recovery factors.In this study,combined core displacement and nuclear magnetic resonance(NMR)experiments explored the reservoir gas−water two-phase flow and remaining microscopic gas distribution during water invasion and gas injection.Consequently,for fracture core,the water-phase relative permeability is higher and the co-seepage interval is narrower than that of three pore cores during water invasion,whereas the water-drive recovery efficiency at different invasion rates is the lowest among all cores.Gas injection is beneficial for reducing water saturation and partially restoring the gas-phase relative permeability,especially for fracture core.The remaining gas distribution and the content are related to the core properties.Compared with pore cores,the water invasion rate strongly influences the residual gas distribution in fracture core.The results enhance the understanding of the water invasion mechanism,gas injection to resume production and the remaining gas distribution,so as to improve the recovery factors of carbonate gas reservoirs.展开更多
The physical and chemical properties of soils are closely controlled by the climate factors and thus are significant for paleoclimate reconstruction. In this study, two adjacent soil profiles （LP and LPM） with diffe...The physical and chemical properties of soils are closely controlled by the climate factors and thus are significant for paleoclimate reconstruction. In this study, two adjacent soil profiles （LP and LPM） with different slopes from Yah＇an, Shaanxi Province, were investigated using magnetic methods to determine the impact of topography on magnetic properties of soil. Our results show that although LP and LPM have similar magnetic minerals and grain size distribution, both the average and max- imum magnetic susceptibility （Z） of LP are almost doubled compared to those of LPM. In addition, the ratios of susceptibility enhancement to the background （Ez） for LP and LPM are 2.27 and 2.04, respectively; the ratios of saturation isothermal rem- nant magnetization （SIRM） enhancement （EsIRM） for these two profiles are 1.80 and 1.86, respectively. The slopes of the linear regression trends between frequency-dependent susceptibility （ZFD） and ＂hard＂ isothermal remnant magnetization （HIRM） （ZFD/HIRM）, Anhysteretic remnant magnetization （ARM） and HIRM （ARM/HIRM）, are almost free from the effect of parent material. XFD/HIRMs for LP and LPM are 28.7×10 5 and 28.9×10 5 A m^-1, respectively; ARM/HIRMs are 0.35 and 0.33 for LP and LPM, respectively. These results demonstrate that parameters, ZFD/HIRM, ARM/HIRM, Ez and ESIRM, are affected less by parent material and topography, which are better than the Z for bulk samples to indicate the paleoclimatic conditions （e.g., the paleorainfall） in a large-scale region.展开更多
基金Project(2016ZX05017)supported by the China National Science and Technology Major Project
文摘Water invasion is a common phenomenon in gas reservoirs with active edge-and-bottom aquifers.Due to high reservoir heterogeneity and production parameters,carbonate gas reservoirs feature exploitation obstacles and low recovery factors.In this study,combined core displacement and nuclear magnetic resonance(NMR)experiments explored the reservoir gas−water two-phase flow and remaining microscopic gas distribution during water invasion and gas injection.Consequently,for fracture core,the water-phase relative permeability is higher and the co-seepage interval is narrower than that of three pore cores during water invasion,whereas the water-drive recovery efficiency at different invasion rates is the lowest among all cores.Gas injection is beneficial for reducing water saturation and partially restoring the gas-phase relative permeability,especially for fracture core.The remaining gas distribution and the content are related to the core properties.Compared with pore cores,the water invasion rate strongly influences the residual gas distribution in fracture core.The results enhance the understanding of the water invasion mechanism,gas injection to resume production and the remaining gas distribution,so as to improve the recovery factors of carbonate gas reservoirs.
基金supported by the National Natural Science Foundation of China(Grant Nos.40125013 and 40821091)Q S Liu was supported by the 100-talent Program of the Chinese Academy of Sciences
文摘The physical and chemical properties of soils are closely controlled by the climate factors and thus are significant for paleoclimate reconstruction. In this study, two adjacent soil profiles （LP and LPM） with different slopes from Yah＇an, Shaanxi Province, were investigated using magnetic methods to determine the impact of topography on magnetic properties of soil. Our results show that although LP and LPM have similar magnetic minerals and grain size distribution, both the average and max- imum magnetic susceptibility （Z） of LP are almost doubled compared to those of LPM. In addition, the ratios of susceptibility enhancement to the background （Ez） for LP and LPM are 2.27 and 2.04, respectively; the ratios of saturation isothermal rem- nant magnetization （SIRM） enhancement （EsIRM） for these two profiles are 1.80 and 1.86, respectively. The slopes of the linear regression trends between frequency-dependent susceptibility （ZFD） and ＂hard＂ isothermal remnant magnetization （HIRM） （ZFD/HIRM）, Anhysteretic remnant magnetization （ARM） and HIRM （ARM/HIRM）, are almost free from the effect of parent material. XFD/HIRMs for LP and LPM are 28.7×10 5 and 28.9×10 5 A m^-1, respectively; ARM/HIRMs are 0.35 and 0.33 for LP and LPM, respectively. These results demonstrate that parameters, ZFD/HIRM, ARM/HIRM, Ez and ESIRM, are affected less by parent material and topography, which are better than the Z for bulk samples to indicate the paleoclimatic conditions （e.g., the paleorainfall） in a large-scale region.
