塔东地区上奥陶统层序地层特征

通过大量的地震、钻井、录井、测井等资料分析，针对塔里木东部地区(简称塔东地区)上奥陶统进行了层序地层和沉积学方面的研究，结果表明，塔东地区上奥陶统可识别出1个二级层序、3个三级层序，自下而上分别是层序SQ1、SQ2和SQ3。层序SQ1识别出TST体系域，为一套深水盆地沉积，发育深水盆地、浊流沉积；层序SQ2可三分为LST、TST和HST体系域，LST体系域发育海退背景下的陆架边缘三角洲沉积，TST体系域为快速水进期，发育海相泥岩沉积，HST发育高水位滨岸沉积；SQ3发育浅海沉积，主要为三角洲—滨岸沉积体系。地层层序发育和沉积相分布受控于构造运动、沉积物源供给和相对海平面升降3个因素。3套层序的划分明确了塔东地区上奥陶统潜在的源岩层、储层和盖层的分布，其中层序SQ1为有利的烃源岩层、SQ2陆架边缘三角洲是潜在的有利储层，SQ3发育的滨岸砂岩为已经证实的油气藏。

SEQUENCE STRATIGRAPHIC FEATURES OF THE UPPER ORDOVICIAN IN EAST TARIM BASIN

Based upon the seismic, drilling, wireline logging data and others from various data sources, this paper studied the sequence stratigraphy and sedimentary facies of the Upper Ordovician in East Tarim Basin. The results suggest that the Upper Ordovician deposits consist of one 2nd-order sequence and three 3rd-order sequences, SQ1, SQ2 and SQ3 from bottom to top. The sequence of SQ1 is a transgressive system tract, consisting of deep basin sediments and turbidites. The sequence SQ2 can be further divided into three system tracts, i.e. the LST, TST and HST. The LST consists of shelf edge deltas upon a regression background. The TST is resulted from a fast transgression stage, in which prevailed marine mudstone sedimentation. The HST consists of high stand shoreface deposits. The SQ3 sequence is dominated by shallow marine sedimentation, characterized mainly by deltaic and shoreface sediments. Sequence stratigraphy and sedimentation of the region are controlled by the joint action of tectonic movement, sediment supply and eustatic fluctuation. In the sequence of SQ1, there developed high quality source rocks. The SQ2 sequence is considered a potential reservoir and the SQ3 sequence has been proved a good reservoir for petroleum accumulation.