柴达木盆地中南部第三系石油地质条件与勘探前景

柴达木盆地中南部处于盆地西部第三系含油气系统和盆地东部第四系含油气系统之间，第三纪接受了巨厚的湖相沉积。该区具备有利的构造圈闭、泥岩盖层条件，烃源岩以E3^2-N2为主，累计厚度为2000m，具备一定的资源潜力。与盆地西部油田区相比，该区烃源岩厚度变薄、有机质丰度降低、埋藏深度大，有机质热演化多已进入高成熟阶段，砂岩储层不发育、物性差，是制约油气成藏的不利条件。柴达木盆地中南部地区勘探应以找气为主、找油为辅，寻打构造裂缝为主的裂缝性集层是取得勘探突破的一个关键环节。位于甘森湖凹陷边缘的土疙瘩构造是一个可以进行重点评价的目标。

Petroleum geology conditions and exploration perspective in central south Qaidam basin

The central south Qaidam basin lies between the western Tertiary petroleum systerm and the eastern Quaternary petroleum system, and accepted very thick lake facies deposits in the Tertiary. There are good structural trap condition and mudstone cap condition. And the E 2 3-N 1 formations are the main source rocks with an accumulated thickness more than 2000m, so there have good resources potential. Contrast with western oil field area, there have some changes that the source rock thickness becomes thin, the organic matter abundance reduces, the buried depth is deeper and the heat evolution of the organic matter arrives high maturity stage. The unfavourable conditions for oil and gas pooling are the undeveloped sandstone reservoirs, and their poor petrophysical properties. Based on the above analysis, the authors think that the exploration should try to find gas reservoir firstly, and then oil reservoir, and to find reservoirs with structural fractures is the key step. Tugeda structure which lies the margin of Gansenhu sag is the object which needs serious evaluation.