M Basin in South Sudan is a complex Meso-Cenozoic intracontinental superimposed rift basin formed under the action of oblique rifting in the Central African Shear Zone. The oil and gas resources discovered in M Basin are concentrated in the upper Paleogene reservoir of the North Sub-basin, and few discoveries have been made in other sub-basins. In order to analyze the rules of hydrocarbon accumulation in the basin and reveal the exploration potential of various sub-basins, using the petroleum system theory as a guide and based on the analysis of reservoir elements, this paper carries out the analysis of the geochemical characteristics of crude oils, oil-source rock correlation, and the evaluation of petroleum systems and points out the exploration direction for different petroleum systems. (1) Two sets of source rocks have been formed in the basin, and the lacustrine mudstone in the upper part of the Lower Cretaceous succession is the primary source rock. (2) The petroleum systems in the basin are classified into three known petroleum systems and three predicted petroleum systems. For the Northern Petroleum System in the North Sub-basin, there are two critical periods, namely, the end of the Paleogene and the beginning of the Neogene. The end of the Paleogene is a period of large-scale hydrocarbon charging, and the beginning of the Neogene is a period of continuous oil charging. The near-source lithologic-stratigraphic trap in the lower part is an important zone with great potential for future exploration. (3) To a certain extent, the crude oil of the Southern Petroleum System in the North Sub-basin is genetically related to the two sets of source rocks mentioned above. For this petroleum system, there is only one critical period, namely, the end of the Paleogene. The upper Paleogene structural trap is a favorable zone with great exploration potential. (4) Except for the M Petroleum System in the South Sub-basin, which is speculated to be similar to the Northern Petroleum System in the North Sub-basin, the Cretaceous successions of the petroleum systems in other sub-basins are shallowly buried and only have limited exploration potential. This study not only provides an effective means for the study of petroleum systems, but it also further enriches and develops the connotation of petroleum systems in rift basins.

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.

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 history and results of petroleum exploration in the Santos Basin, Brazil are reviewed. The regularity of hydrocarbon enrichment and the key exploration technologies are summarized and analyzed using the seismic, gravity, magnetic and drilling data. It is proposed that the Santos Basin had a structural pattern of two uplifts and three depressions and the Aram-Uirapuru uplift belt controlled the hydrocarbon accumulation. It is believed that the main hydrocarbon source kitchen in the rift period controlled the hydrocarbon-enriched zones, paleo-structures controlled the scale and quality of lacustrine carbonate reservoirs, and continuous thick salt rocks controlled the hydrocarbon formation and preservation. The process and mechanism of reservoirs being transformed by CO2 charging were revealed. Five key exploration technologies were developed, including the variable-velocity mapping for layer-controlled facies-controlled pre-salt structures, the prediction of lacustrine carbonate reservoirs, the prediction of intrusive/effusive rock distribution, the detection of hydrocarbons in lacustrine carbonates, and the logging identification of supercritical CO2 fluid. These theoretical recognitions and exploration technologies have contributed to the discovery of deep-water super-large reservoirs under CNODC projects in Brazil, and will guide the further exploration of deep-water large reservoirs in the Santos Basin and other similar regions.

以中国石油企业海外项目勘探实践为基础,结合典型国际石油公司案例,提出效益勘探的内涵.认为效益勘探是一种勘探理念和勘探程序,既是过程也是结果,核心是"以效益为中心",将效益前置并贯穿于油气勘探全过程.将海外勘探项目划分为风险勘探、滚动勘探与精细勘探三个阶段,针对不同勘探阶段项目,建立地上风险、地下风险和吸引力这3个一级指标和11个二级指标的效益勘探指标体系.依据风险系数与吸引力的不同匹配,得出项目的4类评价结果组合,提出不同类型勘探项目的投资策略,为勘探新项目获取和在运营项目的优化提供决策支撑.通过动态综合评价项目风险、潜力和价值,视评价结果宜进则进、宜退则退,实现存量资产高质量发展与整体业务可持续发展的兼顾.

非洲是中国第二大原油进口来源地,加强中非油气合作对建立多元稳定的油气供给市场、保障中国能源安全具有重要意义,有必要进一步深化加强中非油气合作,不断提高中非油气合作的质量与规模.具体措施包括:充分发挥苏丹、安哥拉等合作模式优势,推进中国企业进入非洲油气市场,扩大非洲市场份额;加强成熟探区"三新领域"勘探力度,推动现有项目滚动挖潜与高效勘探;加大在传统产油大国投资布局,建立更加稳定的非洲油气供给市场;加大对安哥拉深海盐下勘探开发投资力度,提高中安合作份额油比重,同时积极进入非洲东西海岸新兴资源国海上勘探,寻找陆上成熟探区接替新领域;积极参与非洲炼化与LNG业务,全面升级中非油气合作的质量与规模,建议积极进入安哥拉及埃及炼化产业,延伸业务价值链,提高项目营收能力,布局莫桑比克与坦桑尼亚LNG业务,打造中国LNG进口新渠道.

近30年来,全球发现常规大油气田的难度加大,海上和非常规油气成为勘探热点.一些国家石油公司先后崛起,成为陆上大油气田发现的主力军,跨国石油公司是海上深水大油气田发现的主力军,世界资源争夺更加激烈.中国石油天然气集团有限公司跨国勘探开发经过27年的快速发展,经历了滚动勘探开发、大型风险勘探开发、多元化快速发展3个阶段,已在全球建成五大油气合作区,2019年海外权益油气产量超过1×108t油当量,降低了我国油气综合对外依存度6.7％,为保障国家能源安全做出了重要贡献.面对更加激烈的国际竞争、复杂的投资环境、苛刻的合同条件等挑战,中国石油需加大新项目开拓力度,以"一带一路"为重点,加大深水常规油气勘探开发项目投入,慎重进入非常规项目,加大科技投入,加强勘探资产运作,提高勘探项目创效性,建立风险勘探基金,加强多公司联合作业.

说到中非油气合作,自然就会想到"苏丹模式"和"安哥拉模式"."苏丹模式"彰显了中国企业技术实力,为中国企业进入非洲市场起到了示范和引领作用.以贷款换石油的"安哥拉模式",创新了中非油气合作模式,促进了中非合作与互利共赢. 然而,随着非洲资源国成品油需求的变化、陆上盆地勘探程度的提高及海洋勘探与液化天然气(LNG)业务的兴起,我们需要进一步调整和优化中非油气合作领域与方向.特别是"十四五"期间,中国产业发展将由规模增长向质量提升转变,提高中非油气合作质量与规模,对保障中国"十四五"能源安全、推动能源产业高质量发展具有重要意义.

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.

本文通过对苏丹—南苏丹Muglad盆地盆地结构、构造演化、构造特征、主要圈闭类型、不同类型反向断块圈闭形成机制等研究,深入探讨了Muglad盆地构造对油气成藏的控制作用.研究表明,反向断块圈闭是Muglad盆地最主要的圈闭类型,而主力产油区块1、2、4区主要发育两种类型的反向断块圈闭.一种是古隆起及斜坡区应力调节作用下的反向断块圈闭,该类型反向断块圈闭构造背景相对稳定,加之斜坡或古隆起区有利于油气聚集,是研究区最有利的成藏构造.另一种为凯康槽两侧同沉积断裂带内因中非剪切带走滑扭动作用形成的局部反向断块圈闭,该类型反向断块圈闭受凯康槽边界断裂多期强烈活动影响具有保存难、不易成藏的特点.另外,凯康槽两侧盆地结构及构造演化差异进一步决定了油气平面富集差异.凯康槽东侧Shelungo、Bamboo和Unity隆起带的发育及相对稳定的构造背景为油气富集创造了良好的圈闭和保存条件;而凯康槽西侧不发育类似的隆起带,由西部斜坡和西部断阶带组成.西部斜坡反向断层不发育,西部断阶带多期强烈活动使得凯康槽西侧油气发育程度整体不如东侧.受西部断阶带的多期改造,西部斜坡区具有多层系成藏的特点.

Before the discovery of Fula oilfield,previous studies consider that there developed source rock of semi-deep to deep lacustrine in Abu Gabra Formation,Fula depression,which were comprehensively evaluated to be good to very good source rocks but with lower thermal evolution degree,and the other main factors controlling the formation of oil pools were uncertainty,so Fula depression were considered lack of the oil and gas exploration potential.Based on detailed study of gravity data,seismic data and well data,analysis stratigraphic sequence,structure development and evolution,sedimentary facies combined with lithofacies,log-facies and seismic facies,this study reveals that the development of structure and deposition in Fula depression were controlled by shear-extensional regional tectonism.There developed a certain and effective hydrocarbon generation sag of the Abu Gabra Formation in Lower Cretaceous.Three favorable source-reservoir-seal assemblages and 4 reservoir-forming zones are identified.The rollover anticline-faulted nose zone in the middle structure belt,the faulted noses zones in west margin of south sub-depression,in the south faulted step belt and in east margin of the north sub-depression are evaluated prospect reservoir plays.Fula 1 rollover anticline and Fula 2 faulted nose are regarded as the best of prospect targets.These study results play an important role on oil and gas exploration and development in Fula depression.This research methods and exploration strategy can provide references for early petroleum exploration and basin analysis.

Fula sub-basin is a passive rift sag formed by the extensional stress resulted from Central Africa Shear Zone.It is an asymmetric half-graben,which develops fault steps to the west and is overlapped to the east.The western escarpment is a long and narrow structure of about 400 km2,controlled by a long-lived boundary fault.Due to complicated structure,steep stratum and varied sedimentary facies,there are many challenges for exploration in the escarpment,such as the seismic data acquisition and processing,integrated G&G study,drilling technology,etc.The integrated G&G study and exploration practice proved that the strategy of early deployment of 3D seismic acquisition and applying progressive exploration and development can efficiently decide reserves,reduce risks and enhance exploration benefits.Optimizing the seismic acquisition parameters and infilling shot points to improve the local fold times in the main part of the structure according to the conditions of subsurface and surface is beneficial to enhancing the seismic data quality.Timely adjusting the drilling technology can improve the drilling efficiency and the quality of borehole condition,which is helpful to discover pay zones and protect reservoirs.

Muglad Basin,southern Sudan,is a passive rift basin resulted from the extensional tectonics of the dextral shear stress field in the Central African Trans-current Slip Zone.Fula Sag of 5000km~2 is located in northeastern Muglad.Fula Transform Zone in the middle structural zone is formed during the first rifting phase in Early Cretaceous.During the second rifting phase in Late Cretaceous,faults reactive and the zone is finalized.During the third rifting phase in Paleogene,the tectonic framework of the zone isn't changed and only small accommodation faults are developed.The effect of the zone to hydrocarbon accumulation exists in the whole reservoir-forming process.The transfer zone may form structures or traps that are prone to hydrocarbon migration and accumulation.It controls the distribution of organism-rich sendiments or sandbodies by dividing the depositional area into isolated subsags.The dense faults in the zone provide channel for hydrocarbon migration and accumulation.

Located in the south of central transitional zone of the Fula sub-basin,northeastern Muglad Basin,Sudan,the Fula N is a structural-hydrodynamic heavy oil pool with shallow burial depth,loosely cemented reservoir,high porosity and permeability,and active bottom water.These features make the CHOPS(cold heavy oil production with sand) a suitable technology for the development of the pool.Matching technologies,such as completion with bigger size casing and long sand pocket and protection of interbedded shale in thick oil layer during perforation,are adopted,achieving an average daily production of more than 100 m3 from single well.In wells with severe sand problem,the production technology known as "limited sand control" is used to reduce the ope-ration cycle and cost,and enhance the economic returns.

Fula sag is located in northwestern Muglad basin of Sudan Republic in Central Africa. The rift sag dominated by Mesozoic deposits was formed under the setting of shear stress field in Central African shear belt. Its fault activity can be divided into three phases, namely Early Cretaceous, Late Cretaceous and Paleogene, which form two groups of faults in trends of N-S and NW-SE. The frame of Fula structure is controlled by N-S fault and the growth of second-rank structural belt within this sag by NW-SE fault. It is indicated from the structural controlling effects in Fula sag on its oil-gas reservoirs that the structural trans-zone could be as the hydrocarbon enrichment zone, the multi-cycle structural subsidence may shape the favorable reservoir-caprock assembages and the structural slope could be the favorable area of hydrocarbon accumulation.

苏丹六区项目是CNPC与苏丹政府签订的第一个勘探开发项目,也是中国石油(CNPC)首次在海外独自承担风险、进行大规模油气勘探开发项目.苏丹六区是一个复杂的含油气区块,经过中国石油人的艰苦努力,从2001年开始,在短短的5年时间,在该区块先后共发现七个油田,探明石油地质储量是原作业者的7倍,取得了较好的效益.文中论述了该区块的勘探开发历程与石油地质特征,总结了海外复杂地区风险勘探开发的主要经验:加强地震野外采集与室内处理技术一体化攻关,提高空间采样和覆盖次数,努力提高资料质量;开展石油地质综合研究,针对该区地质特点,加强圈闭优选与断层封闭性评价,快速评价钻探;勘探开发一体化,在评价勘探的同时,开始开发早期方案编制工作;为加速开发已发现的油田,针对六区稠油油田特点,采用"携砂冷采"的方式,通过一年的生产,取得了开发此类油田的经验.

苏丹穆格莱德盆地Fula油田主要为较浅的白垩系Aradeiba组、Bentiu组的普通稠油油藏和Abu Gabra组的稀油及天然气藏.主体区块Fula North断块Bentiu组油藏为一垒块上的断背斜块状油藏,具有倾斜的油水界面.Aradeiba组为浅湖沉积的层状薄砂岩的高孔、高渗储层,Bentiu组为辫状河沉积的厚层块状砂岩的高孔、高渗储层, Aradeiba组和Bentiu组油藏埋藏浅,砂岩胶结疏松、物性好、易出砂、地层压力低,原油具有密度大、粘度高、酸值高和油稠等特点.Abu Gabra组的层状油气藏为三角洲前缘沉积砂岩、厚度薄、中孔、中渗、物性差,具有断块小、储层相变快、油气高度低等特点.Abu Gabra组油藏的形成主要受侧向封堵条件、储层的储集性等地质条件控制;有效的生、储、盖组合、泥岩的侧向封堵是Darfur群、Bentiu组油藏最主要的控制因素.

穆格莱德盆地福拉凹陷是一个在中非走滑断裂带控制下发育而成的中、新生代内陆断陷湖盆。自早白垩世至第四纪发育了3个各具特点的沉积旋回，早白垩世沉积的AG组湖相富含有机质的泥岩、页岩分布广泛，评价为好—极好烃源岩；早白垩世后期至晚白垩世发育了多套储盖组合；该凹陷构造格局简明，自南而北表现出“东断西超”→“不对称地堑”→“西断东超”的变化特点，发育有5个二级构造带(南部断阶带、南部次凹、中部构造带、北部次凹及北部断阶带)；构造圈闭发育，以滚动背斜及断鼻为主，且成带分布，形成了4个主要的成藏模式；具有较大的油气资源背景及良好的勘探前景，预测3～5a内在福拉凹陷可探明石油地质储量1.1×108～1.7×108t，可建成年产原油300×104～500×104t的生产能力。

位于非洲的M盆地为前寒武系基底上发育起来的中、新生代内陆断陷盆地.该盆地主要由EW向和NW向两大构造体系组成,前者控制盆地构造的总体发育方向.依据断裂规模,控盆作用及形成、活动时间,此盆地的断裂可分为5个级别.与盆地三大演化阶段相匹配,盆地内发育5个期次的断裂构造,长期继承性发育的构造带是油气聚集的有利场所;后期(第三、第四纪)发育的断层对早期油藏有破坏作用,后期形成的圈闭不具成藏条件.由于断层发育,油气以垂向运移为主,发育较早(AM组沉积前)的断层具有封闭作用.