【摘要】 蒙古国塔南凹陷南屯组中发育大量远岸水下扇沉积,综合岩石学特征、重矿物组合及地震资料分析,确定其为盆地陡坡物源供给形成,属于罕见的陡坡远岸水下扇.在总结陡坡远岸水下扇地震、测井及岩心特征的基础上,将其划分为供给水道、内扇、中扇、外扇4种亚相及若干微相,不同相带特征差异显著.陡坡远岸水下扇主要沿中央断层呈串珠状展布,并在低水位体系域、水进体系域及水退体系域中均有发育,其形成和演化受物源供给、古地形及构造运动3方面因素共同控制.其储集物性整体较差,但在周围高压暗色泥岩的配合下,往往可以形成大量岩性油气藏和构造—岩性复合油气藏,受非连续沉积及层内非均质性影响,陡坡远岸水下扇油藏通常具有含油层数多、单一油层厚度薄、不同油层之间含油性差异大的特点.更多还原

【Abstract】 The strata of Nantun Formation in Ta’nan sag of Mongolia developed a great number of offshore subaqueous fan deposits,which has been determined to have been formed by the supplying source of steep slope of the basin according to the synthetically analysis of the petrologic characteristics,the heavy mineral assemblages and the seismic data,and it is also found out that this subaqueous fan is a kind of infrequent steep-slope offshore subaqueous fan.On the basis of the summary of the seismic,logging and core features,the offshore subaqueous fan can be divided into four kinds of sub-facies(supply channel,inner fan,middle-fan,and outer fan respectively)and several micro facies,and there are significantly different characteristics between different facies belts.The steep-slope offshore subaqueous fan spread along the central fault in the form of string beadings and developed in low stand system tract,transgressive system tract and regressive system.The formation and evolution of the steep-slope offshore subaqueous fan were commonly controlled by three factors,namely,sediment supply,ancient landform and tectonic movement.Despite its poor reservoir properties,amounts of lithologic reservoirs and tectonic-lithologic combined reservoirs often formed in the system owing to the surrounding high pressure dark mudstone.It was influenced by the incontinuous deposition as well as the inner heterogeneity of layers.The reservoirs of the steep offshore subaqueous fan usually are featured with more oil layers,thin single oil layers and different oiliness levels in different layers.更多还原