Based on systematically summarizing the achievements of previous ion-matched waterflooding researches,the diversity and synergy of oil recovery enhancement mechanisms and the interaction between mechanisms are examine...Based on systematically summarizing the achievements of previous ion-matched waterflooding researches,the diversity and synergy of oil recovery enhancement mechanisms and the interaction between mechanisms are examined according to two classification standards,and the influence of behaviors of different ions on different mechanisms and oil displacement efficiency are investigated.Ionic strength is proposed to characterize the behavior differences of univalent and divalent ions,the relationships between ionic strength,effective concentration,and mechanisms are established to characterize the ion behavior behind various mechanisms,and evaluate the performance of ion-matched injection water.The mechanisms of enhancing oil recovery by ion-matched waterflooding include:(1)The ion-matched water can reduce the ion strength and match the ion composition of formation water,thereby reducing the difference between the effective concentration of univalent ions and divalent ions on the surface of carbonate rocks,and improving the effective concentration of potential determining ions(especially SO42-).(2)It can improve wettability,oil-water interface properties,pore structure and physical properties of the reservoir,and finally enable the establishment of a new ionic equilibrium conducive to waterflooding while breaking the original equilibrium.In this study,experiments such as relative permeability curve,interfacial tension,and core-flooding were carried out on carbonate core samples from the Cretaceous Mishrif Formation reservoirs in Halfaya Oilfield,Middle East,a method for injection water evaluation was established and the injection water suitable for these reservoirs was selected:6 times diluted seawater.Compared with ordinary seawater,oil displacement efficiency can be increased by more than 4.60%and compared with the optimum dilution of formation water,oil displacement efficiency can be increased by 3.14%.展开更多
Based on comprehensive analysis of core,cast thin section,logging and seismic data,the sedimentary and reservoir architectures of the MB 1-2 sub-member of Mishrif Formation in Halfaya Oilfield,Iraq,are studied.The MB ...Based on comprehensive analysis of core,cast thin section,logging and seismic data,the sedimentary and reservoir architectures of the MB 1-2 sub-member of Mishrif Formation in Halfaya Oilfield,Iraq,are studied.The MB 1-2 sub-member of Mishrif Formation has three types of microfacies,lagoon,bioclastic shoal,and tidal channel,and facies architecture controlled by sequence stratigraphy.In the 4th-order sequence,the lagoon facies aggradated vertically,and the bioclastic shoals in lenticular shape embed in the background of lagoon,the end of the sequence is incised by the"meandering river"shape tide channel,which represents the depositional discontinuity.Three types of reservoirs including tidal channel grainstone to packstone reservoirs,bioclastic shoal grainstone to packstone reservoirs and dissolved lagoon wackestone reservoirs are developed.The reservoir architectures within tidal channel and bioclastic shoal are strickly controlled by grainy facies,whereas the dissolved lagoon reservoirs controlled by both facies and dissolution are related to the sequence boundary.The reservoir sections occur mainly in the 4 th sequence highstand systems tract(HST)and are separated by barriers formed in the transgressive systems tract(TST).Complicated facies architecture and dissolution modification resulted in strong heterogeneity within the reservoir,which showed the characteristics of"attic type"architecture.The results of this study can guide the development of similar reservoirs in the Middle East.展开更多
基金Supported by the China National Science and Technology Major Project(2017ZX05030-001).
文摘Based on systematically summarizing the achievements of previous ion-matched waterflooding researches,the diversity and synergy of oil recovery enhancement mechanisms and the interaction between mechanisms are examined according to two classification standards,and the influence of behaviors of different ions on different mechanisms and oil displacement efficiency are investigated.Ionic strength is proposed to characterize the behavior differences of univalent and divalent ions,the relationships between ionic strength,effective concentration,and mechanisms are established to characterize the ion behavior behind various mechanisms,and evaluate the performance of ion-matched injection water.The mechanisms of enhancing oil recovery by ion-matched waterflooding include:(1)The ion-matched water can reduce the ion strength and match the ion composition of formation water,thereby reducing the difference between the effective concentration of univalent ions and divalent ions on the surface of carbonate rocks,and improving the effective concentration of potential determining ions(especially SO42-).(2)It can improve wettability,oil-water interface properties,pore structure and physical properties of the reservoir,and finally enable the establishment of a new ionic equilibrium conducive to waterflooding while breaking the original equilibrium.In this study,experiments such as relative permeability curve,interfacial tension,and core-flooding were carried out on carbonate core samples from the Cretaceous Mishrif Formation reservoirs in Halfaya Oilfield,Middle East,a method for injection water evaluation was established and the injection water suitable for these reservoirs was selected:6 times diluted seawater.Compared with ordinary seawater,oil displacement efficiency can be increased by more than 4.60%and compared with the optimum dilution of formation water,oil displacement efficiency can be increased by 3.14%.
基金Supported by the China National Science and Technology Major Project(2016ZX05004-002)
文摘Based on comprehensive analysis of core,cast thin section,logging and seismic data,the sedimentary and reservoir architectures of the MB 1-2 sub-member of Mishrif Formation in Halfaya Oilfield,Iraq,are studied.The MB 1-2 sub-member of Mishrif Formation has three types of microfacies,lagoon,bioclastic shoal,and tidal channel,and facies architecture controlled by sequence stratigraphy.In the 4th-order sequence,the lagoon facies aggradated vertically,and the bioclastic shoals in lenticular shape embed in the background of lagoon,the end of the sequence is incised by the"meandering river"shape tide channel,which represents the depositional discontinuity.Three types of reservoirs including tidal channel grainstone to packstone reservoirs,bioclastic shoal grainstone to packstone reservoirs and dissolved lagoon wackestone reservoirs are developed.The reservoir architectures within tidal channel and bioclastic shoal are strickly controlled by grainy facies,whereas the dissolved lagoon reservoirs controlled by both facies and dissolution are related to the sequence boundary.The reservoir sections occur mainly in the 4 th sequence highstand systems tract(HST)and are separated by barriers formed in the transgressive systems tract(TST).Complicated facies architecture and dissolution modification resulted in strong heterogeneity within the reservoir,which showed the characteristics of"attic type"architecture.The results of this study can guide the development of similar reservoirs in the Middle East.
