Based on seismic and drilling data, core samples, geophysical attributes and previous researches (including fossils and geochemical analysis results published), this paper analyzes the depositional system of Termit Mesozoic and Cenozoic rift basin by focusing on source-sink study, and discusses its controlling effects on hydrocarbon accumulation. (1) This paper established late Cretaceous Yogou "fluctuated falling sea level source-sink depositional model" and Paleogene Sokor 1 "fluctuated rising lacustrine level source-sink depositional model" of Termit basin. Marine and continental facies, post-rift and rift, regression and transgression, "lower larger scale post-rift sediment range" and "upper smaller scale rift sediment range", which all indicate the specialty and hydrocarbon significances of the basin. (2) During the late stage of Late Cretaceous, meandering river delta prograded basinward, gradually turning from marine facies to transitional facies, thus inverse cycle was developed. A large amount of continental organic matters were transported to the slope and center area of the basin during the late Yogou Formation and formed the main source rock of the basin. The delta front sandstone developed in this period interbedded with source rock, where hydrocarbon could accumulate in; Major provenance areas locate in the eastern and southern part of the basin, and the lithologic traps developed in these slope area had good exploration potential; (3) during the early stage of Paleogene rift period, the faults were reactivated. The basin gradually evolved from Madama fluvial facies to lacustrine environment. Braided river delta retrograded, and normal cycle was developed, which was different from that of Late Cretaceous. During the rift climax and the maximum flood period, thick layers of mudstone were deposited. They became regional cap rocks of the basin, and formed the main reservoir and cap rock assemblage with the underlying delta sandstone of Sokor 1 formation. Combined with activated faults connecting the late Cretaceous source rocks, they jointly formed the dominant play of this area. The main provenances locate in the western and eastern part of the basin during this period, and large quantity of hydrocarbon could accumulate in both sides.

东尼日尔盆地群属于西非裂谷系.基于地震、钻井、井壁取心和地球化学分析数据等资料，针对下组合新层系Donga组，从沉积体系分析入手，探讨其成藏组合和勘探潜力.Donga组为晚白垩世海侵背景下发育的一套正旋回沉积层序，下粗-中上部细，顶部发育薄层碳酸盐岩.该层序在东尼日尔盆地群跨多个盆地广泛发育和连续沉积，预示着晚白垩世盆地群形成了暂时统一盆地.海侵事件显著影响了晚白垩世的沉积体系，控制了其含油气系统发育和油气成藏.Donga组广泛沉积的泥岩为有效烃源岩和盖层.Donga组主要发育侧向对接供烃“上生下储”和“自生自储”成藏模式.储层是Donga组成藏主控因素，盆地群埋藏适中、近物源的北部和东南部边缘相带储层发育，具备较好勘探潜力.

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 km2 has 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.

中非走滑裂谷盆地群是在中非剪切带影响下形成的中、新生代陆相裂谷盆地,构造复杂多样且勘探程度较低,成藏规律认识不清制约了该区的油气勘探发现.基于盆地构造、沉积、成藏组合特征和已发现油气田解剖,总结盆地油气富集规律和主控因素,并分析了勘探潜力和方向.研究认为,中非走滑裂谷盆地群在早白垩世以来经历了多期伸展、走滑和反转等构造活动,对沉积地层、构造特征和油气成藏具有较强的控制作用;受储盖组合和构造演化的影响,中非走滑裂谷盆地群不同盆地的油气发现和成藏组合有较大差异,总体表现为"西富东贫、下稀上稠"的特点;油气富集的主控因素是有效生烃灶、构造活动和断层;西部Doba盆地油气最为富集,发育多套成藏组合,上、下白垩统均已经获得规模发现,未来主要勘探方向包括下白垩统岩性圈闭和基岩圈闭,中部Doseo盆地上白垩统缺乏有效盖层,主要勘探目标为下白垩统砂泥岩组合,圈闭类型为走滑形成的断背斜、断块圈闭,基岩潜山是潜在的勘探目的层;东部的Salamat盆地尚未证实有效的成藏组合,勘探潜力有限.

The Lower Cretaceous AG2 Formation is the main source rock and dominant oil-bearing layer of Sufyan sag, Muglad Baisn, Sudan. This paper based on the study of lithology, log facies, seismic facies and seismic attribute, studied the AG2 depositional system of Sufyan sag. And analyzed its tectonic features, paleogeomorphology, paleoclimate and provenances, built the sedimentary model of rifting period. The Sufyan is a graben, faulted in the north and south part at the initial rift period, as the basin evolution and water level fluctuation, the north part of sag became gentle slope environment and the south was steep slope yet in AG2 Period. There are Babanusa uplift and Central Africa locate at the northern part of Sufyan sag, which are the extra-provenance of Muglad Basin, and divided with Nugara sag by Tomat small uplift in south direction, and developed the inner-provenance. From the drill data and core data, most of the sandstone is fine-grained and well sorted in northern part of the sag, we find turbidite of medium grained sandstone in the downthrow side, which means the gravity current and the long-distance sediment transportation. We built the AG2 meandering river delta depositional model of northrn part, and judge the north provenance is the dominant one. The drill data shows high sand gross ratio and fine-grained sediment of southern part, and found its near sediment supply and periodicity, we built braided-river delta model of the south sediment supply system. The depositional model of the south is similar with the fan-delta, but has weak sediment supply and subsea sediment transportation characteristics. The south and west are the secondary provenance. This paper compiled two sediment facies maps of AG2 in two periods, built three-dimensional depositional model, and suggest the middle structure area of the sag are favorable prospecting area, which have good reservoir and near the source rock.

The primary reservoir-seal assemblage (RSA) of the Bentiu-Aradeiba formations in the Muglad Basin,Sudan is becoming over-explored,which significantly reduces inventory of drillable prospects and makes further exploration more difficult.Based on our reservoir forming study and recent drilling data,we propose that there are four novel exploration domains in the basin,i.e.,the secondary oil reservoir in shallow formations,lithological oil reservoir,buried basement hill oil reservoir,and gas reservoir below source rocks.The four domains are characterized as follows:the fault step zones and palaeo-uplifts of the Kaikang sub-basin are the favorable targets for the secondary oil reservoir in shallow formations;the Fula,Bamboo and Sufyan depressions and Neem South slope are potential candidates for the lithological oil reservoir;the basement hills blanketed by AG2 and/or AG4 source rocks in the center and slope of depressions should be the first choice for buried basement hill oil reservoir;and finally,the AG5 structural prospects distributed in the Neem area,the Fula-Moga and Sharaf-Abu Gabra structural zones and the central structural zone of the Sufyan depression,could be selected as favorable targets for the large-middle-scale natural gas reservoir below source rocks.