柴西地区第三系藻灰(云)岩的岩石类型与分布特征

Lithological types and distribution features of Tertiary algal limestone in Chaixi area, Qaidam Basin

利用 2 0余口取心井的 40 0余块铸体薄片以及相关的岩矿分析测试资料 ,研究柴达木盆地西部跃进、花土沟和南翼山等地区的藻灰 (云 )岩的岩石学特征、分布规律和形成条件。柴西地区藻灰 (云 )岩主要分布于 3个层段 ,N12 藻灰 (云 )岩呈薄层夹于浅灰绿至紫褐色砂岩和泥岩中 ,陆源碎屑含量较高 ;N2 藻灰岩与其它各种岩类呈极薄互层状分布 ,陆源碎屑含量普遍高 ;E3 2 藻灰 (云 )岩分布于厚层碳酸盐岩中 ,厚度较大 ,陆源碎屑含量低、云质含量较高。 70 %以上的藻灰 (云 )岩孔喉半径小于 5 .0 μm ,藻纹层灰 (云 )岩、藻叠层灰 (云 )岩和藻团块灰 (云 )岩溶蚀作用普遍较强 ,储集性质和含油性普遍较好 ;一些藻泥晶灰 (云 )岩溶孔也较发育 ,可作为储集层。藻灰岩最发育的时期是区域构造较稳定期 ,形成于生长逆断层上盘水体较清的水下古隆起高部位。图 3表 2参

Tertiary of Chaixi area in Qaidam Basin developed algal laminated, algal stromatalite, algal masses and algal micrite limestones. The former three algal limestones are good hydrocarbon bearing reservoirs,and the dissolution porosity of a little algal micrites developed, which also formed hydrocarbon bearing reservoirs. The distribution features of algal limestones,which mainly distributed in E 3 2, N 1 2 and N 2 strata, are different. E 3 2 algal limestones,distributied in thick carbonate rock, are lower continential clastic and higher dolomite contents. The N 1 2 algal limestones are thinner interbeded with light gray to brown sandstone and mudstone with higher continential clastic contents and the N 2 algal limestones are even thinner interlaminate with other rocks, and its continential clastic contents are very high. The distribution features of the algal limestone are controlled by regional structure activities, lake horizotal face changes and paleogeology environments.