Based on seismic,drilling,and source rock analysis data,the petroleum geological characteristics and future exploration direction of the oil-rich sags in the Central and West African Rift System(CWARS)are discussed.Th...Based on seismic,drilling,and source rock analysis data,the petroleum geological characteristics and future exploration direction of the oil-rich sags in the Central and West African Rift System(CWARS)are discussed.The study shows that the Central African Rift System mainly develops high-quality lacustrine source rocks in the Lower Cretaceous,and the West African Rift System mainly develops high-quality terrigenous organic matter-rich marine source rocks in the Upper Cretaceous,and the two types of source rocks provide a material basis for the enrichment of oil and gas in the CWARS.Multiple sets of reservoir rocks including fractured basement and three sets of regional cap rocks in the Lower Cretaceous,the Upper Cretaceous,and the Paleogene are developed in the CWARS.Since the Late Mesozoic,due to the geodynamic factors including the dextral strike-slip movement of the Central African Shear Zone,the basins in different directions of the CWARS differ in terms of rifting stages,intervals of regional cap rocks,trap types and accumulation models.The NE-SW trending basins have mainly preserved one stage of rifting in the Early Cretaceous,with regional cap rocks developed in the Lower Cretaceous strata,forming traps of reverse anticlines,flower-shaped structures and basement buried hill,and two types of hydrocarbon accumulation models of"source and reservoir in the same formation,and accumulation inside source rocks"and"up-source and down-reservoir,and accumulation below source rocks".The NW–SE basins are characterized by multiple rifting stages superimposition,with the development of regional cap rocks in the Upper Cretaceous and Paleogene,forming traps of draping anticlines,faulted anticlines,antithetic fault blocks and the accumulation model of"down-source and up-reservoir,and accumulation above source rocks".The combination of reservoir and cap rocks inside source rocks of basins with multiple superimposed rifting stages,as well as the lithologic reservoirs and the shale oil inside source rocks of strong inversion basins are important fields for future exploration in basins of the CWARS.展开更多
New height precise Earth Geopotential Model EGM08 made it possible to develop the value of the geoidal geopotential W0. This value is independent on Earth’s tides and others disturbances, therefore it can be used as ...New height precise Earth Geopotential Model EGM08 made it possible to develop the value of the geoidal geopotential W0. This value is independent on Earth’s tides and others disturbances, therefore it can be used as basic quantity for many applications. Value W0 represents mean sea surface. W0 was developed from data of satellite altimetry which monitores actual ocean’s surface. This value is one of the four fundamental geodetic constants. This value has been accepted worldwide and is included to the International Earth Rotation and Reference Systems Service Conventions (IERS Conventions) 2003, 2007. This value defines in principle parameters of level ellipsoid which best fit to the surface defined by W0. The body of this level ellipsoid produces normal gravity. We developed other important parameters for determination of the density deviations (VTT technology), i.e. values of normal gravity ge at the equator and gp at the pole on the elipsoid E0 and the value of parameter β. All parameters above used for development of VTT technology are supplied by GPS/leveling data that enable to create so-called density deviation maps at any place in the World. In comparison with gravity anomalies, the density deviations represent more precise density anomalous places in the Earth’s crust. A construction of density deviation map is applied at two from geologically different regions—the Western Carpathians and the Central African Rifts.展开更多
基金Supported by the National Natural Science Foundation Project(92255302)National Science and Technology Major Project(2016ZX05029005)Scientific Research and Technological Development Project of PetroChina(2021DJ31).
文摘Based on seismic,drilling,and source rock analysis data,the petroleum geological characteristics and future exploration direction of the oil-rich sags in the Central and West African Rift System(CWARS)are discussed.The study shows that the Central African Rift System mainly develops high-quality lacustrine source rocks in the Lower Cretaceous,and the West African Rift System mainly develops high-quality terrigenous organic matter-rich marine source rocks in the Upper Cretaceous,and the two types of source rocks provide a material basis for the enrichment of oil and gas in the CWARS.Multiple sets of reservoir rocks including fractured basement and three sets of regional cap rocks in the Lower Cretaceous,the Upper Cretaceous,and the Paleogene are developed in the CWARS.Since the Late Mesozoic,due to the geodynamic factors including the dextral strike-slip movement of the Central African Shear Zone,the basins in different directions of the CWARS differ in terms of rifting stages,intervals of regional cap rocks,trap types and accumulation models.The NE-SW trending basins have mainly preserved one stage of rifting in the Early Cretaceous,with regional cap rocks developed in the Lower Cretaceous strata,forming traps of reverse anticlines,flower-shaped structures and basement buried hill,and two types of hydrocarbon accumulation models of"source and reservoir in the same formation,and accumulation inside source rocks"and"up-source and down-reservoir,and accumulation below source rocks".The NW–SE basins are characterized by multiple rifting stages superimposition,with the development of regional cap rocks in the Upper Cretaceous and Paleogene,forming traps of draping anticlines,faulted anticlines,antithetic fault blocks and the accumulation model of"down-source and up-reservoir,and accumulation above source rocks".The combination of reservoir and cap rocks inside source rocks of basins with multiple superimposed rifting stages,as well as the lithologic reservoirs and the shale oil inside source rocks of strong inversion basins are important fields for future exploration in basins of the CWARS.
基金supported by Grant No.BD 12000020 of the Brno University of Technology.
文摘New height precise Earth Geopotential Model EGM08 made it possible to develop the value of the geoidal geopotential W0. This value is independent on Earth’s tides and others disturbances, therefore it can be used as basic quantity for many applications. Value W0 represents mean sea surface. W0 was developed from data of satellite altimetry which monitores actual ocean’s surface. This value is one of the four fundamental geodetic constants. This value has been accepted worldwide and is included to the International Earth Rotation and Reference Systems Service Conventions (IERS Conventions) 2003, 2007. This value defines in principle parameters of level ellipsoid which best fit to the surface defined by W0. The body of this level ellipsoid produces normal gravity. We developed other important parameters for determination of the density deviations (VTT technology), i.e. values of normal gravity ge at the equator and gp at the pole on the elipsoid E0 and the value of parameter β. All parameters above used for development of VTT technology are supplied by GPS/leveling data that enable to create so-called density deviation maps at any place in the World. In comparison with gravity anomalies, the density deviations represent more precise density anomalous places in the Earth’s crust. A construction of density deviation map is applied at two from geologically different regions—the Western Carpathians and the Central African Rifts.
