鄂尔多斯盆地三叠系延长组深水砂岩与致密油的关系*

鄂尔多斯盆地湖盆中部地区三叠系延长组长6油层组中下部和长7油层组中上部大面积发育深水砂岩, 这种砂岩具有厚度大、平行于湖盆长轴方向连续分布的特征。根据沉积结构、构造及接触关系, 将深水砂岩划分为砂质碎屑流成因的砂岩、浊流成因的砂岩、滑塌成因的砂岩及三角洲前缘成因的砂岩等4种沉积类型。在储集层矿物学、岩石学特征研究的基础上, 提出深水砂岩的沉积特征(如粒度细、云母和绿泥石等塑性颗粒含量高、陆源碳酸盐岩岩屑与伊利石杂基发育等)是造成储集层抗压实能力较差、胶结强烈、储集层致密的关键因素；在有利成藏条件分析中提出深水砂岩致密储集层处于油源中心、与烃源岩互层共生是形成大面积非常规致密油资源的重要控制因素。

Relationship between deepwater sandstone and tight oil of the Triassic Yanchang Formation in Ordos Basin

A large area of deep water sandstone was developed during the depositional period between lower-mid Chang 6 and mid-upper Chang 7 intervals of Yanchang Formation of Triassic in the center of Ordos Basin. The large area sandstone had a great thickness and distributed continuously paralleled to the long axis of the basin. According to the sedimentary textures and structures and contact relationship, deepwater sandstone could be divided into four types, i. e., sandy debrite, slump stone, turbidite and delta front sandstones. On the base of reservoir characteristics of mineralogy and petrology, it was put forward that the sedimentary characteristics of deepwater sandstone, such as fine granularity, high content of plastic particles as mica and chlorite, as well as developing terrigenous matrix of carbonate and illite, were key factors that caused intense compaction and cementation in reservoir. Through analysis of favorable reservoir conditions, it was the important controlling factors for the forming of massive unconventional tight oil that deepwater sandstone locating in the center of oil source rock, and syngenetically interbedding with hydrocarbon source rock.