陇东地区延长组长6-长7段浊积岩分布规律

Turbidite Distribution of Yanchang 6-7 in Longdong Area in Ordos Basin

采用井-震结合的方法将鄂尔多斯盆地陇东地区延长组长6-长7段划分为1个长期基准面旋回和5个中期基准面旋回。研究区延长组长6-长7段浊积岩主要发育在中期基准面旋回下降半旋回的中晚期和上升半旋回的早期,分布于辫状河三角洲前缘前端斜坡及平原区古地形低洼处,其展布范围随长期基准面的下降逐渐向湖盆中部迁移,这种分布特征主要受控于4个因素:盆地及周缘大地构造背景在宏观上控制着浊积岩的发育;区域构造活动为浊积岩的发育提供了一定的触发机制;基准面旋回的变化控制着浊积岩的发育及分布范围;前三角洲地区古地貌决定三角洲前缘浊积体运移方向和沉积位置。陇东地区浊流沉积具有优越的成藏条件,是长庆油田增储上产的重要接替领域。

Chang 6-Chang 7 members of Yanchang formation in Longdong area in Ordos basin are divided into a large scale base-level cycle and five medium scale base-level cycles by well-seismic integrated method. It is shown that in view of time the turbidites of the members are distributed in the middle-late period of the decline hemicycle and early period of rising hemicycle of medium scale base- level cycles, and in view of space they are distributed in the basin slopes in front of braided river delta and the lowland of ancient topography in the basin plain with the distribution range migrating to the central basin gradually as the large scale base-level declines. The distributions of turbidites in the study area are controlled by four factors： The tectonic settings of the basin and peripheral areas control turbidite development from the macro level; the regional tectonic activities provide trigger mechanisms for turbidite development; the changes of base level cycle control the formation and distribution of turbidite; the ancient topography of prograding delta area determines the flow direction of turbidity currents in delta front and the depositional position. The turbidite deposit in Longdong area is of prime conditions for petroleum accumulation, being as an significant succeeding domain for incremental reserves and production in Changqing oil field in the future.