鄂南地区上三叠统延长组层序地层特征及其控藏因素分析

Sequence stratigraphic characteristic of Yanchang Formation of Upper Triassic in southern Ordos Basin and its control factors

以层序地层学理论为指导,综合岩心、钻井、测井及地震资料,将鄂尔多斯盆地南部上三叠统延长组划分为4个三级层序和11个四级层序,建立研究区层序地层格架;分析了层序格架内砂体时空展布特征,认识到储集层受到层序界面的控制,基准面旋回上升半旋回的早中期以及下降半旋回的中晚期砂体为优质储集体,建立了研究区层序地层格架内砂体的发育模式;分析了层序格架内的成藏组合,明确了研究区层序格架内的油气藏特征及分布,指出研究区发育"下生上储"型曲流河三角洲油气藏、"上生下储"型辫状河三角洲油气藏和"上生下储"型或"下生上储"型深水重力流油气藏3种油气藏类型,并对其有利勘探目标进行了预测.

According to the theory and approach of sequence stratigraphy and core,drilling,well-logging,seismic data,the Upper Triassic Yanchang Formation of the southern Ordos Basin was divided into 4 third-order sequences and 11 fourth-order sequences,and the sequence stratigraphic framework was established.Based on the analysis of the distribution characteristics of the sandbodies in the sequence stratigraphic framework,it is held that the reservoir is controlled by the sequence boundaries.It is also found that the beneficial reservoirs are the sandbodies in the early to middle stage of rising semi-cycle and the middle to late stage of falling semi-cycle of the base-level cycle.The development mode of the sandbodies in the sequence stratigraphy framework was established.The reservoir-forming combination in sequence stratigraphy framework is analyzed,and the characteristics and distribution of oil and gas reservoirs in the studied area are determined.The study demonstrates that there are three types of the oil-gas reservoirs in this area: 'lower generation and upper storage' meandering river delta oil-gas reservoirs,'upper generation and lower storage' braided river delta reservoirs,and 'upper generation and lower storage' or 'lower generation and upper storage' deep-water gravity flow reservoirs.The beneficial areas in the studied area are forecasted.