南苏丹Melut盆地北部地区岩性油藏成藏条件及勘探启示

Lithologic reservoir forming conditions and its exploration implication in northern Melut Basin,South Sudan

南苏丹Melut盆地北部地区经过十多年的勘探部署,目前剩余构造圈闭少、面积小,难以满足勘探需求,勘探领域需向岩性油藏领域转移。以近200口探井的测井、录井、岩心,以及4 000多km^2三维地震资料为基础,开展了Melut盆地烃源岩、沉积相及断裂特征分析,结果表明:(1)北部地区发育Jamous凹陷、Abyat凹陷、Moleeta凹陷和Ruman凹陷4个生油凹陷,油源条件优越;(2)白垩系Galhak组和古近系Yabus组上段发育三角洲前缘砂泥岩互层沉积,其岩性组合特征有利于岩性圈闭的形成;(3)断裂为Galhak组源内及Yabus组源上岩性油藏的形成提供了油气运移通道。Melut盆地北部地区具备形成岩性油藏的地质条件,该认识指导了Ruman地区Galhak组上倾尖灭、Gasab地区Yabus组构造-岩性等一批岩性油藏的勘探发现,推动了Melut盆地岩性油藏的勘探进程。

After more than ten years of exploration in northern Melut Basin,the remaining structural traps are limited and small,which is difficult to meet the exploration demands,and the exploration field should be transferred to the field of lithologic reservoir. With wire-logging,mud-logging and coring data from near 200 exploration wells and more 4 000 km^2 3D data,the source rock evaluation,sedimentary facies and fault features were researched,the results show that：firstly,the northern Melut Basin consists of Jamous,Abyat,Moleeta and Ruman depressions acting as four active oil kitchens and presents sufficient oil source. Secondly,interbedded sandstone and mudstone of delta front developed in Cretaceous Galhak Formation and Tertiary Yabus Formation,which is favor-able to form lithological traps. Thirdly,faults could enhance the oil charging for Galhak Formation as in-source reservoir and act as migration pathway for upper member of Yabus Formation as above-source reservoir.The research shows that northern Melut Basin has the geologic conditions for forming lithologic reservoirs and guides a series of exploration discoveries of lithologic reservoirs,such as up-dip pinchout lithologic reservoir of Galhak Formation in Ruman area and structural-lithologic composite reservoir of Yabus Formation in Gasab area,which strongly promotes the exploration and deployment of lithologic reservoirs in northern Melut Basin.