柴达木盆地石油勘探潜力及勘探方向

通过50多年勘探研究表明,柴达木盆地主要存在第三系、侏罗系两套烃源岩,第三系烃源岩有机质丰度总体偏低,烃转化率较高,有机质热演化程度较低,主要分布在柴西地区。侏罗系烃源岩有机质丰度高,有机质类型为Ⅱ—Ⅲ2型,主要分布在柴北缘地区。盆地内具有碎屑岩和碳酸盐岩两类储层,碎屑岩储层是主要储油层,在纵向上分布于侏罗系、古新统、始新统、下干柴沟组下段、油砂山组,在区域上分布广泛,以河流三角洲、滩坝以及水下扇等不同沉积成因的砂岩类储层为主。盆地石油总资源量为21.5×108t,石油的探明率为15.3%,具有较大的资源发现潜力,综合分析提出了下步勘探的重点预探区带有3个,即柴西南构造岩性区、狮子沟—油砂山深层构造带、柴北缘的潜伏构造带。

Potential and Direction of Petroleum Exploration in Qaidam Basin

For more than 50 years of exploration research, it is revealed that two series of hydrocarbon source rocks of Qaidam Basin are mainly distributed in Tertiary and Jurassic. The hydrocarbon source rock of Tertiary, mainly distributed in the western region of the basin, has higher hygrocarbon conversion rate, but the richness and thermal evolution of its organic matter are poor in general. While the source rock of Jurassic, mainly distributed in the northern margin of the basin, is of rich organic matter and the II- III2 organic matter is the most common type. There are two kinds of reservoir including detrital rock and carbonate rock, of which the detrital reservoir is the main oil-bearing reservoir in the basin. It is vertically distributed in Jurassic, Palaeocene, Eocene, Lower Xiaganchaigou Formation, and Youshashan Formation. Moreover, it is widely distributed in the area, of which the sandstone reservoirs with different sedimentary origins such as fluvial delta, beach, embankment, and sub-water fun are the most common depositional environments. The total oil resources in Qaidam Basin are 2.15 billion tons with the proven rate being 15.3 percent. It shows that a large potential for petroleum resources exploration still exists in the basin. Based on comprehensive analysis, three key pre-prospecting zones are proposed for next exploration, that is, the structural lithologic zone in the southwestern Qaidam Basin, the deep structural belt in Shizigou-Youshashan, the buried structural belt in the northern margin of Qaidam Basin.