酒泉盆地营尔凹陷下白垩统层序地层划分及沉积体系特征

Stratigraphic Sequence Division and the Characteristics of Sedimentary System of Lower Cretaceous in Yinger Depression,Jiuquan Basin

以层序地层学为指导,以营尔凹陷地震、钻测井等资料为基础,结合酒泉盆地以往层序地层研究成果,通过对三级层序测井、录井特征分析和地震剖面上局部削截、上超等三级层序标志的识别,确定了层序边界,将下白垩统划分出1个Ⅰ级层序、3个Ⅱ级层序、7个Ⅲ级层序、18个体系域;在层序地层研究的基础上,总结出营尔凹陷下白垩统下沟组具有近物源、多物源、快速沉降、快速沉积的特点,凹陷缓坡发育大型扇三角洲,凹陷陡坡发育近岸水下扇,并指出南部陡坡一系列近岸水下扇应是下一步油气勘探的有利区带。

Guided by the methods of sequence stratigraphy and based on the seismic data, drilling and well logging data, other people＇s research on the sequence stratigraphy in Jiuquan basin, this paper analyzes the characteristics of the third-order sequence well logging, and recognizes the criterion of the third-order sequence boundary in seismic section, such as local truncation, onlap, and so on. From all this study above, the sequence boundary can be identified, and we recognize 1 first-order sequence, 3 second-order sequences, 7 third-order sequences and 18 system tracts. According to the sequence stratigraphy study, we conclude that the Xiagou Formation of the Lower Cretaceous in Yinger depression has the characteristics of near more provenances, rapid subsidence, and rapid deposition. The mild slope of the depression develops large scale fan deltas, and the steep slope develops nearshore subaqueous fans. Among these, the nearshore subaqueous fan in the south steep slope should be a favorable exploration target.