柴达木盆地西部地区第三系湖相藻(蓝细菌)灰岩储层成因类型

Genetic Types of Tertiary Lacustrine Algal(Cyanobacteria) Limestones Reservoirs in Western Qaidam Basin

柴达木盆地西部地区第三系湖相藻 (蓝细菌 )灰岩储层的成因类型主要包括两类 :滨湖亚相的藻 (蓝细菌 )坪灰岩和浅湖亚相的藻 (蓝细菌 )丘灰岩。滨湖亚相的藻 (蓝细菌 )坪灰岩和浅湖亚相的藻 (蓝细菌 )丘灰岩具有完全不同的沉积特征、岩石类型和储层特征。柴达木盆地第三系藻 (蓝细菌 )灰岩储层分布较广 ,是柴达木盆地第三系碳酸盐岩储层中最重要的油气储层。目前柴达木盆地第三系藻 (蓝细菌 )灰岩储层主要见于西部地区的跃西、跃东、七个泉、狮子沟、花土沟、尖顶山、南翼山和大风山等地区 ,层位上从下干柴沟组上段 (E23 )至上油砂山组 (N22 )均有分布。E23 和N1的藻 (蓝细菌 )灰岩主要分布于英雄岭凹陷以西 (西南 )地区 ,N12 和N22 的藻 (蓝细菌 )灰岩主要分布于英雄岭凹陷以东(东北 )地区 ,这与柴达木盆地的湖水进退、沉积中心的迁移及盆地演化有着密切的关系。滨湖亚相藻 (蓝细菌 )坪灰岩储层的储集空间以次生溶孔和溶缝为主 ,溶孔和溶缝的形成与大气淡水的淋滤作用有关。浅湖亚相藻 (蓝细菌 )丘灰岩储层的储集空间以次生溶孔和溶缝为主 ,同时也发育原生枝管状钙藻 (绿藻门的松藻科 )的藻管孔 ,溶孔和溶缝的形成与晚期沿断裂带大气淡水的溶解作用及有机酸的溶解作用有关。

Genetic types of tertiary lacustrine algal(cyanobacteria) limestones reservoirs in the western Qaidam basin mainly include:algal(cyanobacteria) flat limestones in littoral lake and algal(cyanobacteria) mound limestones in shallow lake.There are of completely different sedimentation characteristics,lithological types and reservoir featares.Tertiary algal(cyanobacteria)limestones reservoirs in the western Qaidam basin are characterized by widespread distribution and being the most important in the carbonate reservoirs.Tertiary algal(cyanobacteria)limestone reservoirs in the western Qaidam basin have been found in Yuexi, Yuedong,Qigequan, Shizigou, Huatugou, Jiandingshan, Nanyishan and Dafengshan regions etc., and distributed from E^2 3 to N^2 2. Algal(cyanobacteria)limestones reservoirs in E^2 3 and N 1 distributed mainly in the west(southwest) region of Yingxionglingdepression, those in N^1 2 and N^2 2 distributed mainly in east(northeast) region of Yingxionglingdepression. Distribution of algal(cyanobacteria)limestones in the western Qaidam basin is mainly controlled by lake level changes,migration of sedimentation center and basin evolution.Reservoir spaces of algal(cyanobacteria)flatlimestones in littoral lake are predominant with secondary disolution pores and disolution fissures .They are possibly controlled by atmospheric water leaching.Reservoir spaces of algal(cyanobacteria)moundlimestones in shallow lake are predominant with secondary disolution pores and disolution fissures,and also developed primary algal tube pores.They are possibly controlled bydisolution along rupture zones and organic acid disolution.