鄂尔多斯盆地延长组深水重力流岩相发育特征及其储集性

鄂尔多斯盆地陇东地区长7、长6油层组广泛发育深水重力流，基于对长7-长6段共计852.7 m岩心的精细分析并结合测井、录井等数据，总结分析了湖盆重力流沉积岩相的类型、成因、特征和发育规律。综合岩石类型、沉积构造和发育规模，共识别出8种岩相类型，分别是：滑动砂岩相(Sl)、滑塌砂岩相(Ss)、滑塌泥岩相(Sm)、中-薄层块状含砾砂岩相(Sc)、中-薄层块状纯净砂岩相(Sp)、厚层块状含砾砂岩相(St)、块状含砾泥岩相(Mc)、中-薄层具层理砂岩夹泥岩相(Tb)。按照Shanmugam基于重力流沉积过程的分类方法，Sl是滑动成因，Ss、Sm是滑塌成因，St、Sp、Sc、Mc是碎屑流成因，Tb是浊流成因。不同岩相发育规模差别较大，从累计厚度和发育频次上看，St、Sp规模最大。砂岩岩相可构成良好储层，St储层质量最好，其次为Sp、Sc，但Sp、Sc的发育规模远大于St，综合认为在实际勘探中Sp、Sc是重力流储层最有利的勘探目标。

LITHOFACIES CHARACTERISTICS OF GRAVITY FLOW DEPOSITS AND THEIR IMPACTS ON RESERVOIR QUALITY IN THE YANCHANG FORMATION,ORDOS BASIN

During the periods of Chang 7 and Chang 6 Members in Late Triassic, gravity flows developed widely in the deep water of Longdong area of the Ordos Basin. Based on the detailed study of 852.7m cores in addition to loggings and testing data, this paper classified the types of lithofacies, then summarized the sedimentary characteristics, forming process, distribution scale and reservoir quality of each lithofacies. Eight types of lithofacies are recognized, i.e., sliding sandstone (Sl), slumping sandstone (Ss), slumping mudstone (Sm), thin- to medium-bedded massive conglomeratic sandstone (Sc), thin- to medium-bedded massive pure sandstone (Sp), thick-bedded massive conglomeratic sandstone (St), massive conglomeratic mudstone (Mc), and thin- to medium-bedded sandstone with beddings (Tb), belonging to slides-dominated lithofacies (Sl); slumps-dominated lithofacies (Ss, Sm); sandy debris flow-dominated lithofacies (Sc, Sp, St); muddy debris flow-dominated lithofacies (Mc); and turbidity current-dominated lithofacies(Tb) respectively according to Shanmugam's classification. The distribution scale of different lithofacies varies greatly, St and Sp are the largest in terms of accumulated thickness and depositional frequency. All the sandstone lithofacies can be good reservoir, and lithofacies St is the best, followed by Sp and Sc. However, the distribution scale of Sp and Sc is much larger than St. It is generally believed that Sp and Sc are the most favorable targets in exploration of gravity flow reservoirs.