柴达木盆地油气勘探新思路

柴达木盆地有大量储油构造和良好的盖层条件,却缺乏足够的理想储集层,寻找裂隙性储集层分布区,很可能是实现该区油气勘探突破的关键。根据对柴达木盆地油泉子构造的野外考察,其南北两翼为陡倾的共轭膝褶带,根据最大有效力矩准则,共轭膝褶带间的夹角为110°,所夹持的背斜具有箱状平顶的几何特征。膝褶带外岩层近水平,带内岩层近直立,局部倒转,普遍顺层剥离、张开和剪切,形成层间张裂隙和切割层理的小型低角度逆冲断层。边界断层和膝褶带内断裂普遍充填石膏脉,局部油浸,表明膝褶带一度为高压流体活动的水压致裂带,有利于油气运移和聚集。由于该构造微向北倒,近核部南侧的膝褶带肩部成为高点,建议在该高点布一深井,探明可能的岩性油气聚集带,并控制北翼主膝褶带的总体产状,然后沿该主膝褶带布一斜井,以期发现与膝褶带相关的裂隙型油藏。图10表1参19

A new idea for petroleum exploration in Qaidam Basin

Searching for fissure-type oil and gas traps is probably the key of petroleum exploration in Qaidam Basin, where oil seeps and anticlines are abundant but without enough ideal reservoirs. A field research of the Youquanzi anticline shows that there are conjugate kink zones on its northern and southern limbs. The angle between the zones is 110°, and the anticlines in between are of box-shape. The bedding outside the zones is sub-horizontal and the inside bedding is sub-vertical with locally overturned. The zones develop interlayer dilation fractures and small-scale thrusts filled with fiber gypsum and locally with oil, indicating that the zones were once filled with high-pressure fluids. The shoulder of the southern kink zone near the core is the culmination of the structure. Drills should be arranged along the culmination, and then an oblique drill along the main kink zone is expected to obtain fissure-type traps.