The runoff and soil loss were assessed <em>in situ</em> at the scale of 2.12 m<sup>2</sup> plots during the rainy season of 2010 to better understand the determinants and magnitude of the massi...The runoff and soil loss were assessed <em>in situ</em> at the scale of 2.12 m<sup>2</sup> plots during the rainy season of 2010 to better understand the determinants and magnitude of the massive soil loss and land subsidence (donga) in the sub-humid zone of Africa in Karimama, North Benin. The experimental design was a split plot with two factors: the topography in 3 modalities (upstream, center and downstream of the donga) was assigned as main plot factor and the degree of degradation of dongas in 2 modalities (beginner dongas and advanced dongas) was assigned as subplot factor. Runoff water was collected through a storage system composed of two tanks. Data were collected on 36 plots (9 plots per donga × 4 dongas). The runoff varies significantly from one site to another for the rainy episode of October 10, 2010. It is twice as high in land use areas (5.87 mm) as in W Park (2.32 mm;l.s.d. = 1.81 mm). From upstream to downstream, runoff and soil loss increased from 2.4 mm to 85.3 mm and 80 g<span style="white-space:nowrap;">·</span>m<sup>-2</sup> to 197 g<span style="white-space:nowrap;">·</span>m<sup>-2</sup>, respectively. Runoff is high in the early dongas (7.60 mm) and low in the advanced dongas (5.68 mm) in contrast to lower soil loss in the early dongas (34 g<span style="white-space:nowrap;">·</span>m<sup>-2</sup>) and high in the advanced dongas (237 g<span style="white-space:nowrap;">·</span>m<sup>-2</sup>). The low value of soil loss with respect to the magnitude of the phenomenon suggests the probable occurrence of other soil loss mechanisms to be elucidated.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
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
文摘The runoff and soil loss were assessed <em>in situ</em> at the scale of 2.12 m<sup>2</sup> plots during the rainy season of 2010 to better understand the determinants and magnitude of the massive soil loss and land subsidence (donga) in the sub-humid zone of Africa in Karimama, North Benin. The experimental design was a split plot with two factors: the topography in 3 modalities (upstream, center and downstream of the donga) was assigned as main plot factor and the degree of degradation of dongas in 2 modalities (beginner dongas and advanced dongas) was assigned as subplot factor. Runoff water was collected through a storage system composed of two tanks. Data were collected on 36 plots (9 plots per donga × 4 dongas). The runoff varies significantly from one site to another for the rainy episode of October 10, 2010. It is twice as high in land use areas (5.87 mm) as in W Park (2.32 mm;l.s.d. = 1.81 mm). From upstream to downstream, runoff and soil loss increased from 2.4 mm to 85.3 mm and 80 g<span style="white-space:nowrap;">·</span>m<sup>-2</sup> to 197 g<span style="white-space:nowrap;">·</span>m<sup>-2</sup>, respectively. Runoff is high in the early dongas (7.60 mm) and low in the advanced dongas (5.68 mm) in contrast to lower soil loss in the early dongas (34 g<span style="white-space:nowrap;">·</span>m<sup>-2</sup>) and high in the advanced dongas (237 g<span style="white-space:nowrap;">·</span>m<sup>-2</sup>). The low value of soil loss with respect to the magnitude of the phenomenon suggests the probable occurrence of other soil loss mechanisms to be elucidated.
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.
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.
