Based on the seismic and drilling data, casting thin sections, geochemical analysis of oil and rock samples, and hydrocarbon generation history simulation, the hydrocarbon accumulation characteristics and exploration ...Based on the seismic and drilling data, casting thin sections, geochemical analysis of oil and rock samples, and hydrocarbon generation history simulation, the hydrocarbon accumulation characteristics and exploration direction of Termit superimposed marine–continental rift basin are discussed. The Termit basin is superimposed with two-phase rifts(Early Cretaceous and Paleogene). The subsidence curves from two wells on the Trakes slope in the east of the basin show high subsidence rate in the Late Cretaceous, which is believed to be high deposition rate influenced by transgression. However, a weak rift may also be developed. The depositional sequences in the Termit basin were controlled by the Late Cretaceous marine transgression cycle and the Paleogene lacustrine transgression cycle, giving rise to two types of superimposed marine–continental “source-sink” deposits. The marine and continental mixed source rocks developed universally in the whole basinduring the marine transgression period, and are overlaid by the Paleogene Sokor 1 reservoir rocks and Sokor 2 caprocks developed during the lacustrine transgression period, forming the unique superimposed marine–continental basin in WCARS. The early low geothermal gradient in the Termit basin resulted in the late hydrocarbon generated by the source rock of Upper Cretaceous Yogou in Paleogene. Mature source rock of Upper Cretaceous Donga developed in the Trakes slope, so that the double-source-supply hydrocarbon and accumulation models are proposed for the Trakes slope in which formed the oil fields. Due to virtue of the newly proposed hydrocarbon accumulation model and the exploration activities in recent years in the Termit superimposed marine–continental rift basin, an additional effective exploration area of about 2500 km2has been confirmed in the east of the basin. It is believed that potential domains such as Sokor 1, Donga and Upper Cretaceous lithologic traps in the southeast of the basin are key expected targets for exploration and frontier evaluation in future.展开更多
The Eocene Sokor1 Formation is proven oil reservoir rocks in the Termit sub-basin. These sandstone intervals are deeply buried, highly heterogeneous in character and characterized by Low Contrast Low Resistivity (LCLR...The Eocene Sokor1 Formation is proven oil reservoir rocks in the Termit sub-basin. These sandstone intervals are deeply buried, highly heterogeneous in character and characterized by Low Contrast Low Resistivity (LCLR) log responses. Petrophysical and quantitative well-based rock physics interpretations were integrated for property estimations, fluid and lithology typing in reservoir characterization. Six (6) reservoir sandstone intervals were identified, delineated and correlated across five (5) wells. The estimated petrophysical properties showed that the Eocene Sokor1 sandstones have averagely good reservoir properties with sand_5 interval exhibiting exceptional reservoir properties. <i><span style="font-family:Verdana;">V</span><sub><span style="font-family:Verdana;">p</span></sub><span style="font-family:Verdana;">/V</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> vs. AI and </span><i><span style="font-family:Verdana;">μρ</span></i><span style="font-family:Verdana;"> vs. </span><i><span style="font-family:Verdana;">λρ</span></i><span style="font-family:Verdana;"> elastic cross-plots color coded with reservoir properties (</span><i><span style="font-family:Verdana;">V</span><sub><span style="font-family:Verdana;">sh</span></sub></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;"><span style="white-space:nowrap;">Φ</span></span></i><span style="font-family:Verdana;">), show distinct and well separated data clusters signifying hydrocarbon bearing sandstones, brine sandstones and shales/mudstones in the 3D crossplot planes with varying seismic elastic property values in each well thereby, enhancing reservoir characterization and providing information’s about the burial history, reservoir quality and property distribution in the sub-basin. The analys</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> suggests that, although the reservoir interval has averagely good petrophysical properties in all wells, the seismic elastic crossplots show that these properties are much better distributed in wells 2 and 3 than in wells 4, 5 and 9. Therefore, sand_5 reservoir interval in wells 2 and 3 </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> likely to be more hydrocarbon bearing and productive than wells 4, 5 and 9 in the sub-basin.</span></span></span>展开更多
Based on seismic and drilling data in the study area,the geological structure and kinematic process of the Termit rift basin were studied using seismic profile interpretation and balanced restoration to find out the d...Based on seismic and drilling data in the study area,the geological structure and kinematic process of the Termit rift basin were studied using seismic profile interpretation and balanced restoration to find out the dynamic mechanism of the basin.(1)The geological structure of the Termit Basin is represented as a narrow rift basin,with development of series of structural styles in extensional,extensional strike-slip and compressional stress setting.On plane,it is narrow in the north and wide in the south,and transitions from graben to half-graben from north to south;it features a graben controlled by the boundary faults in the north and a fault-overlapped half-graben in the south.(2)Before the Cretaceous,a series of hidden faults developed in the West African rift system,which laid the foundation for the development location and distribution direction of the Termit Basin;during the Cretaceous to Paleogene periods,the basin experienced two phases of rifting in Early Cretaceous and Paleogene,which controlled the initial structure and current structural shape of the basin respectively;during the Neogene to Quaternary,the basin was subjected to weak transformation.(3)In the Precambrian,the Pan-African movement gave rise to a narrow and long weak zone within the African plate,which provided the pre-existing structural conditions for the formation of the Termit Basin.In the Early Cretaceous,affected by the South Atlantic rifting,the Pan African weak zone was reactivated,resulting in the first stage of rifting and the basic structural framework of the Termit Basin.In the Paleogene,affected by the subduction and convergence of the Neo-Tethys Ocean,the African-Arabian plate extended in near E-W trending,and the Termit Basin experienced the second stage of rifting.The oblique extension in this period caused intense structural differentiation,and the current structural pattern of alternate uplifts and depressions took shape gradually.展开更多
XRF and EDX analyses were carried out on 18 batches of representative raw samples to determine the distribution of major chemical elements in the petroleum source rocks of Donga and Yogou formations of Termit sediment...XRF and EDX analyses were carried out on 18 batches of representative raw samples to determine the distribution of major chemical elements in the petroleum source rocks of Donga and Yogou formations of Termit sedimentary basin. The chemical composition of these formations is dominated by silicon (Si), aluminum (Al) and iron (Fe). This is consistent with the oxide composition, which is also dominated by silicon oxide (SiO2), aluminum oxide (Al<sub>2</sub>O<sub>3</sub>) and iron monoxide (FeO). No less important chemical elements are calcium (Ca), potassium (K), sulfur (S), titanium (Ti), magnesium (Mg), manganese (Mn) and barium (Ba), as well as some of their oxides. All these major chemical elements are carried by silicate detrital minerals associated with pyrite and goethite and/or clay minerals such as kaolinite and interstratified illite, smectite and chlorite. This trend is illustrated by the values of the Si/Al and SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> ratios.展开更多
基金Supported by CNPC Scientific Research and Technology Development Project (2021DJ3103)CNODC Overseas Rresearch and Development Support Project (2023-YF-01-04)。
文摘Based on the seismic and drilling data, casting thin sections, geochemical analysis of oil and rock samples, and hydrocarbon generation history simulation, the hydrocarbon accumulation characteristics and exploration direction of Termit superimposed marine–continental rift basin are discussed. The Termit basin is superimposed with two-phase rifts(Early Cretaceous and Paleogene). The subsidence curves from two wells on the Trakes slope in the east of the basin show high subsidence rate in the Late Cretaceous, which is believed to be high deposition rate influenced by transgression. However, a weak rift may also be developed. The depositional sequences in the Termit basin were controlled by the Late Cretaceous marine transgression cycle and the Paleogene lacustrine transgression cycle, giving rise to two types of superimposed marine–continental “source-sink” deposits. The marine and continental mixed source rocks developed universally in the whole basinduring the marine transgression period, and are overlaid by the Paleogene Sokor 1 reservoir rocks and Sokor 2 caprocks developed during the lacustrine transgression period, forming the unique superimposed marine–continental basin in WCARS. The early low geothermal gradient in the Termit basin resulted in the late hydrocarbon generated by the source rock of Upper Cretaceous Yogou in Paleogene. Mature source rock of Upper Cretaceous Donga developed in the Trakes slope, so that the double-source-supply hydrocarbon and accumulation models are proposed for the Trakes slope in which formed the oil fields. Due to virtue of the newly proposed hydrocarbon accumulation model and the exploration activities in recent years in the Termit superimposed marine–continental rift basin, an additional effective exploration area of about 2500 km2has been confirmed in the east of the basin. It is believed that potential domains such as Sokor 1, Donga and Upper Cretaceous lithologic traps in the southeast of the basin are key expected targets for exploration and frontier evaluation in future.
文摘The Eocene Sokor1 Formation is proven oil reservoir rocks in the Termit sub-basin. These sandstone intervals are deeply buried, highly heterogeneous in character and characterized by Low Contrast Low Resistivity (LCLR) log responses. Petrophysical and quantitative well-based rock physics interpretations were integrated for property estimations, fluid and lithology typing in reservoir characterization. Six (6) reservoir sandstone intervals were identified, delineated and correlated across five (5) wells. The estimated petrophysical properties showed that the Eocene Sokor1 sandstones have averagely good reservoir properties with sand_5 interval exhibiting exceptional reservoir properties. <i><span style="font-family:Verdana;">V</span><sub><span style="font-family:Verdana;">p</span></sub><span style="font-family:Verdana;">/V</span><sub><span style="font-family:Verdana;">s</span></sub></i><span style="font-family:Verdana;"> vs. AI and </span><i><span style="font-family:Verdana;">μρ</span></i><span style="font-family:Verdana;"> vs. </span><i><span style="font-family:Verdana;">λρ</span></i><span style="font-family:Verdana;"> elastic cross-plots color coded with reservoir properties (</span><i><span style="font-family:Verdana;">V</span><sub><span style="font-family:Verdana;">sh</span></sub></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;"><span style="white-space:nowrap;">Φ</span></span></i><span style="font-family:Verdana;">), show distinct and well separated data clusters signifying hydrocarbon bearing sandstones, brine sandstones and shales/mudstones in the 3D crossplot planes with varying seismic elastic property values in each well thereby, enhancing reservoir characterization and providing information’s about the burial history, reservoir quality and property distribution in the sub-basin. The analys</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> suggests that, although the reservoir interval has averagely good petrophysical properties in all wells, the seismic elastic crossplots show that these properties are much better distributed in wells 2 and 3 than in wells 4, 5 and 9. Therefore, sand_5 reservoir interval in wells 2 and 3 </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">is</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"> likely to be more hydrocarbon bearing and productive than wells 4, 5 and 9 in the sub-basin.</span></span></span>
基金Supported by the National Natural Science Foundation of China Enterprise Innovation and Development Joint Fund Project(U19B6003-01)Scientific research and technology development project of China National Petroleum Corporation(2021DJ3103).
文摘Based on seismic and drilling data in the study area,the geological structure and kinematic process of the Termit rift basin were studied using seismic profile interpretation and balanced restoration to find out the dynamic mechanism of the basin.(1)The geological structure of the Termit Basin is represented as a narrow rift basin,with development of series of structural styles in extensional,extensional strike-slip and compressional stress setting.On plane,it is narrow in the north and wide in the south,and transitions from graben to half-graben from north to south;it features a graben controlled by the boundary faults in the north and a fault-overlapped half-graben in the south.(2)Before the Cretaceous,a series of hidden faults developed in the West African rift system,which laid the foundation for the development location and distribution direction of the Termit Basin;during the Cretaceous to Paleogene periods,the basin experienced two phases of rifting in Early Cretaceous and Paleogene,which controlled the initial structure and current structural shape of the basin respectively;during the Neogene to Quaternary,the basin was subjected to weak transformation.(3)In the Precambrian,the Pan-African movement gave rise to a narrow and long weak zone within the African plate,which provided the pre-existing structural conditions for the formation of the Termit Basin.In the Early Cretaceous,affected by the South Atlantic rifting,the Pan African weak zone was reactivated,resulting in the first stage of rifting and the basic structural framework of the Termit Basin.In the Paleogene,affected by the subduction and convergence of the Neo-Tethys Ocean,the African-Arabian plate extended in near E-W trending,and the Termit Basin experienced the second stage of rifting.The oblique extension in this period caused intense structural differentiation,and the current structural pattern of alternate uplifts and depressions took shape gradually.
文摘XRF and EDX analyses were carried out on 18 batches of representative raw samples to determine the distribution of major chemical elements in the petroleum source rocks of Donga and Yogou formations of Termit sedimentary basin. The chemical composition of these formations is dominated by silicon (Si), aluminum (Al) and iron (Fe). This is consistent with the oxide composition, which is also dominated by silicon oxide (SiO2), aluminum oxide (Al<sub>2</sub>O<sub>3</sub>) and iron monoxide (FeO). No less important chemical elements are calcium (Ca), potassium (K), sulfur (S), titanium (Ti), magnesium (Mg), manganese (Mn) and barium (Ba), as well as some of their oxides. All these major chemical elements are carried by silicate detrital minerals associated with pyrite and goethite and/or clay minerals such as kaolinite and interstratified illite, smectite and chlorite. This trend is illustrated by the values of the Si/Al and SiO<sub>2</sub>/Al<sub>2</sub>O<sub>3</sub> ratios.
