Based on the analysis of the fluid inclusion homogenization temperature and apatite fission track on the northern slope zone of the Bongor Basin in Chad,this paper studied the time and stages of hydrocarbon accumulati...Based on the analysis of the fluid inclusion homogenization temperature and apatite fission track on the northern slope zone of the Bongor Basin in Chad,this paper studied the time and stages of hydrocarbon accumulation in the study area.The results show that:(1)The brine inclusions of the samples from the Kubla and Prosopis formations in the Lower Cretaceous coexisting with the hydrocarbon generally present two sets of peak ranges of homogenization temperature,with the peak ranges of low temperature and high temperature being 75–105℃ and 115–135℃,respectively;(2)The samples from the Kubla and Prosopis formations have experienced five tectonic evolution stages,i.e.,rapid subsidence in the Early Cretaceous,tectonic inversion in the Late Cretaceous,small subsidence in the Paleogene,uplift at the turn of the Paleogene and Neogene,and subsidence since the Miocene,in which the denudation thickness of the Late Cretaceous and after the turn of the Paleogene and Neogene are~1.8 km and~0.5 km,respectively.The cumulative denudation thickness of the two periods is about 2.3 km;(3)Using the brine inclusion homogenization temperature coexisting with the hydrocarbon as the capture temperature of the hydrocarbon,and combining with the apatite fission track thermal history modeling,the result shows that the Kubla and Prosopis formations in the Lower Cretaceous on the northern slope of the Bongor Basin have the same hydrocarbon accumulation time and stages,both of which have undergone two stages of hydrocarbon charging at 80–95 Ma and 65–80 Ma.The first stage of charging corresponds to the initial migration of hydrocarbon at the end of the Early Cretaceous rapid sedimentation,while the second stage of charging is in the stage of intense tectonic inversion in the Late Cretaceous.展开更多
The features of the unconformity,fault and tectonic inversion in the eastern Doseo Basin,Chad,were analyzed,and the genetic mechanisms and basin evolution were discussed using seismic and drilling data.The following r...The features of the unconformity,fault and tectonic inversion in the eastern Doseo Basin,Chad,were analyzed,and the genetic mechanisms and basin evolution were discussed using seismic and drilling data.The following results are obtained.First,four stratigraphic unconformities,i.e.basement(Tg),Mangara Group(T10),lower Upper Cretaceous(T5)and Cretaceous(T4),four faulting stages,i.e.Barremian extensional faults,Aptian–Coniacian strike-slip faults,Campanian strike-slip faults,and Eocene strike-slip faults,and two tectonic inversions,i.e.Santonian and end of Cretaceous,were developed in the Doseo Basin.Second,the Doseo Basin was an early failed intracontinental passive rift basin transformed by the strike-slip movement and tectonic inversion.The initial rifting between the African and South American plates induced the nearly N-S stretching of the Doseo Basin,giving rise to the formation of the embryonic Doseo rift basin.The nearly E-W strike-slip movement of Borogop(F1)in the western section of the Central African Shear Zone resulted in the gradual cease of the near north-south rifting and long-term strike-slip transformation,forming a dextral transtension fault system with inherited activity but gradually weakened in intensity(interrupted by two tectonic inversions).This fault system was composed of the main shear(F1),R-type shear(F2-F3)and P-type shear(F4-F5)faults,with the strike-slip associated faults as branches.The strike-slip movements of F1 in Cretaceous and Eocene were controlled by the dextral shear opening of the equatorial south Atlantic and rapid expanding of the Indian Ocean,respectively.The combined function of the strike-slip movement of F1 and the convergence between Africa and Eurasia made the Doseo Basin underwent the Santonian dextral transpressional inversion characterized by intensive folding deformation leading to the echelon NE-SW and NNE-SSW nose-shaped uplifts and unconformity(T5)on high parts of the uplifts.The convergence between Africa and Eurasia caused the intensive tectonic inversion of Doseo Basin at the end of Cretaceous manifesting as intensive uplift,denudation and folding deformation,forming the regional unconformity(T4)and superposing a nearly E-W structural configuration on the Santonian structures.Third,the Doseo Basin experienced four evolutional stages with the features of short rifting and long depression,i.e.Barremian rifting,Aptian rifting–depression transition,Albian–Late Cretaceous depression,and Cenozoic extinction,under the control of the tectonic movements between Africa and its peripheral plates.展开更多
Several international oil companies had conducted petroleum exploration, but failed to make any commercially viable discoveries in the Doseo Basin for over 30 years. In this article, an integrated analysis, based on t...Several international oil companies had conducted petroleum exploration, but failed to make any commercially viable discoveries in the Doseo Basin for over 30 years. In this article, an integrated analysis, based on the latest seismic and drilling data combined with exploration practice and tectonic, sedimentary as well as petroleum-geological characteristics of the basin, has been conducted with the aim to disclose the key factors of hydrocarbon accumulation and enrichment and then to find the potential petroleum plays. The Doseo Basin in Chad is a Meso-Cenozoic lacustrine rift basin developed on the Precambrian crystalline basement in the Central African Shear Zone. It is a half graben rift controlled by the strike-slip fault at the northern boundary, and can be divided into two sub-basins, an uplift and a slope. The basin experienced two rifting periods in the Cretaceous and was strongly inverted with the erosion thickness of 800–1000 m during the Eocene, and then entered the depression and extinction period. Structurally, a large number of normal faults and strike-slip faults are identified in the basin, and the boundary faults are inverted faults with normal at first. The main structural styles include inverted anticlines, fault noses, complex fault-blocks and flower structures. The Lower Cretaceous is the main sedimentary strata, which are divided into the Mangara Group, Kedeni, Doba and Koumra Formations from bottom to up. Two transgressive-regressive cycles developed in the Lower Cretaceous indicates with mainly lacustrine, fluvial, delta, braided-delta, fan-delta sandstone and mudstone. The effective source rock in the basin is the deep-lacustrine mudstone of the Lower Cretaceous containing the type Ⅰ and type Ⅱ;organic matters. Furthermore, Inverted anticlines and fault-complicated blocks comprise the main trap types and the Kedeni Uplift is the most favorable play, followed by the Northern Steep Slope and Southern Gentle Slope. Lateral sealing capacity of faults controls the hydrocarbon abundance.展开更多
基金Supported by the PetroChina Science and Technology Project(2023ZZ0703)National Natural Science Foundation of China(42072229,41102131).
文摘Based on the analysis of the fluid inclusion homogenization temperature and apatite fission track on the northern slope zone of the Bongor Basin in Chad,this paper studied the time and stages of hydrocarbon accumulation in the study area.The results show that:(1)The brine inclusions of the samples from the Kubla and Prosopis formations in the Lower Cretaceous coexisting with the hydrocarbon generally present two sets of peak ranges of homogenization temperature,with the peak ranges of low temperature and high temperature being 75–105℃ and 115–135℃,respectively;(2)The samples from the Kubla and Prosopis formations have experienced five tectonic evolution stages,i.e.,rapid subsidence in the Early Cretaceous,tectonic inversion in the Late Cretaceous,small subsidence in the Paleogene,uplift at the turn of the Paleogene and Neogene,and subsidence since the Miocene,in which the denudation thickness of the Late Cretaceous and after the turn of the Paleogene and Neogene are~1.8 km and~0.5 km,respectively.The cumulative denudation thickness of the two periods is about 2.3 km;(3)Using the brine inclusion homogenization temperature coexisting with the hydrocarbon as the capture temperature of the hydrocarbon,and combining with the apatite fission track thermal history modeling,the result shows that the Kubla and Prosopis formations in the Lower Cretaceous on the northern slope of the Bongor Basin have the same hydrocarbon accumulation time and stages,both of which have undergone two stages of hydrocarbon charging at 80–95 Ma and 65–80 Ma.The first stage of charging corresponds to the initial migration of hydrocarbon at the end of the Early Cretaceous rapid sedimentation,while the second stage of charging is in the stage of intense tectonic inversion in the Late Cretaceous.
基金Supported by the PetroChina Science and Technology Project(2021DJ3103)。
文摘The features of the unconformity,fault and tectonic inversion in the eastern Doseo Basin,Chad,were analyzed,and the genetic mechanisms and basin evolution were discussed using seismic and drilling data.The following results are obtained.First,four stratigraphic unconformities,i.e.basement(Tg),Mangara Group(T10),lower Upper Cretaceous(T5)and Cretaceous(T4),four faulting stages,i.e.Barremian extensional faults,Aptian–Coniacian strike-slip faults,Campanian strike-slip faults,and Eocene strike-slip faults,and two tectonic inversions,i.e.Santonian and end of Cretaceous,were developed in the Doseo Basin.Second,the Doseo Basin was an early failed intracontinental passive rift basin transformed by the strike-slip movement and tectonic inversion.The initial rifting between the African and South American plates induced the nearly N-S stretching of the Doseo Basin,giving rise to the formation of the embryonic Doseo rift basin.The nearly E-W strike-slip movement of Borogop(F1)in the western section of the Central African Shear Zone resulted in the gradual cease of the near north-south rifting and long-term strike-slip transformation,forming a dextral transtension fault system with inherited activity but gradually weakened in intensity(interrupted by two tectonic inversions).This fault system was composed of the main shear(F1),R-type shear(F2-F3)and P-type shear(F4-F5)faults,with the strike-slip associated faults as branches.The strike-slip movements of F1 in Cretaceous and Eocene were controlled by the dextral shear opening of the equatorial south Atlantic and rapid expanding of the Indian Ocean,respectively.The combined function of the strike-slip movement of F1 and the convergence between Africa and Eurasia made the Doseo Basin underwent the Santonian dextral transpressional inversion characterized by intensive folding deformation leading to the echelon NE-SW and NNE-SSW nose-shaped uplifts and unconformity(T5)on high parts of the uplifts.The convergence between Africa and Eurasia caused the intensive tectonic inversion of Doseo Basin at the end of Cretaceous manifesting as intensive uplift,denudation and folding deformation,forming the regional unconformity(T4)and superposing a nearly E-W structural configuration on the Santonian structures.Third,the Doseo Basin experienced four evolutional stages with the features of short rifting and long depression,i.e.Barremian rifting,Aptian rifting–depression transition,Albian–Late Cretaceous depression,and Cenozoic extinction,under the control of the tectonic movements between Africa and its peripheral plates.
基金Supported by the China National Science and Technology Major Project (2016ZX05029005)CNPC Scientific Research and Technology Development Project (2021DJ31)。
文摘Several international oil companies had conducted petroleum exploration, but failed to make any commercially viable discoveries in the Doseo Basin for over 30 years. In this article, an integrated analysis, based on the latest seismic and drilling data combined with exploration practice and tectonic, sedimentary as well as petroleum-geological characteristics of the basin, has been conducted with the aim to disclose the key factors of hydrocarbon accumulation and enrichment and then to find the potential petroleum plays. The Doseo Basin in Chad is a Meso-Cenozoic lacustrine rift basin developed on the Precambrian crystalline basement in the Central African Shear Zone. It is a half graben rift controlled by the strike-slip fault at the northern boundary, and can be divided into two sub-basins, an uplift and a slope. The basin experienced two rifting periods in the Cretaceous and was strongly inverted with the erosion thickness of 800–1000 m during the Eocene, and then entered the depression and extinction period. Structurally, a large number of normal faults and strike-slip faults are identified in the basin, and the boundary faults are inverted faults with normal at first. The main structural styles include inverted anticlines, fault noses, complex fault-blocks and flower structures. The Lower Cretaceous is the main sedimentary strata, which are divided into the Mangara Group, Kedeni, Doba and Koumra Formations from bottom to up. Two transgressive-regressive cycles developed in the Lower Cretaceous indicates with mainly lacustrine, fluvial, delta, braided-delta, fan-delta sandstone and mudstone. The effective source rock in the basin is the deep-lacustrine mudstone of the Lower Cretaceous containing the type Ⅰ and type Ⅱ;organic matters. Furthermore, Inverted anticlines and fault-complicated blocks comprise the main trap types and the Kedeni Uplift is the most favorable play, followed by the Northern Steep Slope and Southern Gentle Slope. Lateral sealing capacity of faults controls the hydrocarbon abundance.
