Significant differential hydrocarbon enrichment occurs in depressions in a petroliferous basin.There are multiple depressions in the Bohai Bay Basin, and each depression as a relatively independent unit of hydrocarbon...Significant differential hydrocarbon enrichment occurs in depressions in a petroliferous basin.There are multiple depressions in the Bohai Bay Basin, and each depression as a relatively independent unit of hydrocarbon generation, migration and accumulation, contains significantly different hydrocarbon generation conditions and enrichment degree. On the basis of previous documents and a large number of statistical data, this work comparatively analyzed the differential hydrocarbon enrichment and its major controlling factors in depressions of the Bohai Bay Basin. The results show that depressions in the Bohai Bay Basin have various hydrocarbon enrichment degrees, and can be categorized into four types, namely enormously oil-rich, oil-rich, oily and oil-poor depressions. In general, the enormously oil-rich and oil-rich depressions are distributed in the eastern part of the basin along the Tan-Lu and Lan-Liao faults, whereas depressions in the western part of the basin are poor in hydrocarbons. Moreover, the vertical distribution of hydrocarbons is also highly heterogeneous, with Pre-Paleogene strata rich in hydrocarbons in the northern and western depressions, Paleogene strata rich in hydrocarbons in the entire basin, and Neogene strata rich in hydrocarbons in the off-shore areas of the Bohai Bay Basin. From early depressions in onshore areas to the late depressions in offshore areas of the Bohai Bay Basin, the source rocks and source-reservoir-cap rock assemblages gradually become younger and shallower, and the hydrocarbon resource abundance gradually increases. Hydrocarbon supplying condition is the key factor constraining the hydrocarbon enrichment for different depressions,while the main source-reservoir-cap rock assemblage, sufficient hydrocarbons and the transportation capacity of faults control the vertical distribution of hydrocarbons. The main factors controlling hydrocarbon enrichment are different for different layers. The hydrocarbon supplying condition of source rocks is the key controlling factor, whereas the source-reservoir configuration, the main sourcereservoir-cap rock assemblages, and the fault transportation are the main factors of hydrocarbon enrichment in the Paleogene, Paleogene and Neogene, respectively.展开更多
The Piranshahr pull-apart basin,situated in the northwestern part of the Zagros Main Recent Fault(MRF),is characterized by two right-stepping segments of the dextral MRF.Here,a combination of finite element modeling t...The Piranshahr pull-apart basin,situated in the northwestern part of the Zagros Main Recent Fault(MRF),is characterized by two right-stepping segments of the dextral MRF.Here,a combination of finite element modeling techniques,especially twodimensional numerical modeling using ABAQUS software,along with field-based structural geological methods are used to assess the geometry and evolution of the pull-apart along the releasing stepovers in this strike-slip system.The utilized numerical approach applies two-dimensional(2D)finite-element modeling related to elastic Newtonian rheology to evaluate the distribution of stress and localization of strain within the pull-apart basin.This study provides valuable insights into the factors controlling the shape,as well as exploring the interaction between the pre-existing structures in this right-lateral strike-slip releasing stepover,pull-apart basin development in strike-slip systems,and stress-strain behavior by studying the impact of boundary conditions and fault overlap on the deformation pattern.The models consider three representative geometries of fault segment interactions,including underlapping,neutral,and overlapping stepovers,positioned at angles of 30°,45°,and 60°.The results indicate that increased overlap creates an extensive and elongated deformation pattern,while decrease overlap leads to block rotation and a narrow deformation pattern.In addition,the degree of overlapping between parallel strike-slip faults influences the stress and strain.The mean normal stress within the transtensional basin,located between the fault segments,exhibits an extensional nature,while the region outside the stepover experiences general compressive mean normal stresses.The Piranshahr transtensional pull-apart basin exemplifies the progressive evolution of underlapping stepovers,resulting in displaying an elongated rhomboidal to trapezoidal-shaped geometry over time.展开更多
In this paper, progress in strain study of blocks and faults by GPS data are discussed, and the concept that active structures between blocks are the main body of crustal strain is clarified. By energy transfer princi...In this paper, progress in strain study of blocks and faults by GPS data are discussed, and the concept that active structures between blocks are the main body of crustal strain is clarified. By energy transfer principle of elastic mechanics, the relation between strain around faults and tectonic force on fault surfaces is set up and main body element model of crustal strain is constructed. Finally, the relation between mechanical evolution of model and seismogenic process of Kunlun earthquake （Ms=8.1） is discussed by continuous GPS data of datum stations. The result suggests that the relatively relaxed change under background of strong compressing and shearing may help to trigger moderate-strong earthquakes.展开更多
基金granted by the Important National Science&Technology Specific Projects(grants No.2011ZX05006-003 and 2016ZX05006-003)the National Natural Science Foundation(grant No.41372132)
文摘Significant differential hydrocarbon enrichment occurs in depressions in a petroliferous basin.There are multiple depressions in the Bohai Bay Basin, and each depression as a relatively independent unit of hydrocarbon generation, migration and accumulation, contains significantly different hydrocarbon generation conditions and enrichment degree. On the basis of previous documents and a large number of statistical data, this work comparatively analyzed the differential hydrocarbon enrichment and its major controlling factors in depressions of the Bohai Bay Basin. The results show that depressions in the Bohai Bay Basin have various hydrocarbon enrichment degrees, and can be categorized into four types, namely enormously oil-rich, oil-rich, oily and oil-poor depressions. In general, the enormously oil-rich and oil-rich depressions are distributed in the eastern part of the basin along the Tan-Lu and Lan-Liao faults, whereas depressions in the western part of the basin are poor in hydrocarbons. Moreover, the vertical distribution of hydrocarbons is also highly heterogeneous, with Pre-Paleogene strata rich in hydrocarbons in the northern and western depressions, Paleogene strata rich in hydrocarbons in the entire basin, and Neogene strata rich in hydrocarbons in the off-shore areas of the Bohai Bay Basin. From early depressions in onshore areas to the late depressions in offshore areas of the Bohai Bay Basin, the source rocks and source-reservoir-cap rock assemblages gradually become younger and shallower, and the hydrocarbon resource abundance gradually increases. Hydrocarbon supplying condition is the key factor constraining the hydrocarbon enrichment for different depressions,while the main source-reservoir-cap rock assemblage, sufficient hydrocarbons and the transportation capacity of faults control the vertical distribution of hydrocarbons. The main factors controlling hydrocarbon enrichment are different for different layers. The hydrocarbon supplying condition of source rocks is the key controlling factor, whereas the source-reservoir configuration, the main sourcereservoir-cap rock assemblages, and the fault transportation are the main factors of hydrocarbon enrichment in the Paleogene, Paleogene and Neogene, respectively.
基金the financial support provided by (Shahid Beheshti University)
文摘The Piranshahr pull-apart basin,situated in the northwestern part of the Zagros Main Recent Fault(MRF),is characterized by two right-stepping segments of the dextral MRF.Here,a combination of finite element modeling techniques,especially twodimensional numerical modeling using ABAQUS software,along with field-based structural geological methods are used to assess the geometry and evolution of the pull-apart along the releasing stepovers in this strike-slip system.The utilized numerical approach applies two-dimensional(2D)finite-element modeling related to elastic Newtonian rheology to evaluate the distribution of stress and localization of strain within the pull-apart basin.This study provides valuable insights into the factors controlling the shape,as well as exploring the interaction between the pre-existing structures in this right-lateral strike-slip releasing stepover,pull-apart basin development in strike-slip systems,and stress-strain behavior by studying the impact of boundary conditions and fault overlap on the deformation pattern.The models consider three representative geometries of fault segment interactions,including underlapping,neutral,and overlapping stepovers,positioned at angles of 30°,45°,and 60°.The results indicate that increased overlap creates an extensive and elongated deformation pattern,while decrease overlap leads to block rotation and a narrow deformation pattern.In addition,the degree of overlapping between parallel strike-slip faults influences the stress and strain.The mean normal stress within the transtensional basin,located between the fault segments,exhibits an extensional nature,while the region outside the stepover experiences general compressive mean normal stresses.The Piranshahr transtensional pull-apart basin exemplifies the progressive evolution of underlapping stepovers,resulting in displaying an elongated rhomboidal to trapezoidal-shaped geometry over time.
基金National Natural Science Foundation of China (40274023) and National Program for Key Science & Technology Projects (2004BA601B01-02-01).
文摘In this paper, progress in strain study of blocks and faults by GPS data are discussed, and the concept that active structures between blocks are the main body of crustal strain is clarified. By energy transfer principle of elastic mechanics, the relation between strain around faults and tectonic force on fault surfaces is set up and main body element model of crustal strain is constructed. Finally, the relation between mechanical evolution of model and seismogenic process of Kunlun earthquake （Ms=8.1） is discussed by continuous GPS data of datum stations. The result suggests that the relatively relaxed change under background of strong compressing and shearing may help to trigger moderate-strong earthquakes.
