鄂尔多斯盆地陇东地区三叠系延长组储层特征及影响因素分析

以三角洲-湖泊沉积体系为主的陇东地区三叠系延长组主产油层组长3、长6、长7和长8储层岩石类型主要有长石砂岩、岩屑长石砂岩及岩屑砂岩,成分成熟度普遍较低,结构成熟度中等-较好;经历了压实作用、胶结作用和溶解作用,孔隙类型以粒间孔、次生溶孔为主。纵向上,长3油层组储层物性最好;平面上,东北部储层物性明显优于西南部。优质储层多出现在三角洲前缘水下分流河道和河口坝中,碎屑组成、粒级、填隙物含量和成岩作用均对储层性能有重要影响。在陇东地区延长组中识别出简单韵律、复合韵律2大类6种类型储层物性垂向分布模式,而高频基准面旋回的升降控制着本区储层物性韵律的分布规律。

THE INFLUENTIAL FACTORS AND CHARACTRISTICS OF TRIASSIC YANCHANG FORMATION RESERVIOR IN LONGDONG AREA, ORDOS BASIN

Chang 3, Chang 6, Chang 7 and Chang 8 Triassic Yanchang formations are the main producing oil layers in Longdong area, Ordos basin. The reservoir-rock types in these formations are arkose, lithic arkose and litharenite with delta and lacustrine facies. Their compositional maturity is low and textural ma turity is medium. The clastic rocks experienced compaction, cementation and dissolution, thus producing intergranular pores and secondary solution pores. In profile, the physical properties of Chang 3 reservoirs are the best and in plane, the physical properties of reservoirs in the northeast are obviously better than that in the southwest. Favorable reservoirs mostly occur in the sand bodies in delta-front underwater distributary river channel and river mouth bars. All the composition of clasts, grade scale, content of interstitial materials and diagensis have important effects on the reservoir properties. Six vertical distributional models of reservoir are identified in Yanchang formation in Longdong area. The ascend and descend of base-level cycle with high frequency are main factors which control the distribution of reservoir physical properties.