柴达木盆地南翼山湖相碳酸盐岩油气藏特征及形成条件

柴达木盆地南翼山油气田是一个由浅层油藏和中深层凝析气藏组成的湖相碳酸盐岩油气藏的典型例子.共有4套烃源岩,整个地层剖面以泥质岩为主,泥晶碳酸盐岩次之.油气储层为碳酸盐岩,主要有泥质泥晶云岩、泥质泥晶灰岩、泥晶灰岩、藻灰岩等,储集空间主要为晶间孔、粒间孔、溶蚀孔、裂缝和溶洞,储层厚度一般2～5m,平面分布相当稳定.地面至地下构造裂缝均很发育,在油气分布区的中深层存在明显的地震波速度降低现象和异常高压.裂缝充填物方解石的裂变径迹测试表明,裂缝在油气生成运移之前已赋存在.生物标志化合物的分析表明油气均来自大于4300m的烃源岩. 

CHARACTERISTICS AND FORMING CONDITIONS OF LAKE-FACIES CARBONATE-ROCK OIL AND GAS POOLS IN THE NANYISHAN STRUCTURE OF THE QAIDAM BASIN

As a typical example of lake-facies carbonate-rock oil and gas pools consisted by shallow oil pools and medium-deep gas condensate pools,Nanyishan oil and gas field in the Qaidam Basin has altogether four sets of hydrocarbon source rocks. The whole stratigraphic profile is dominated by argillite,micritic carbonate rock comes second. The reservoirs of hydrocarbon are carbonate rocks,including argillaceous micritic dolostone,argillaceous micritic limestone,micritic limestone,algal limestone,etc. The storage spaces are mainly intercrystal pores,intergranular pores,solution openings,fissures and karst caves. The reservoirs,which have the thickness of 2-5m in general,have rather stable plane distribution. Tectonic fractures are all well-developed from surface to underground. The clear reducing of seismic-wave velocity and abnormal high-pressure are observed in the medium-deep layers of hydrocarbon-distributive areas. The fission-track testing of fracture-infilling calcite revealed that fractures occurred before the generation and migration of hydrocarbon. The analysis of biomarkers showed that hydrocarbon come from source rocks deeper than 4 300m.