对焉耆盆地基底的认识

根据重力、磁力、电法、钻探、盆地周边地质资料，结合地震解释，将中、新生代焉耆盆地基底构造划分为四种样式，即叠瓦式、对冲式、背冲式、基底凸起式；将基底岩性分为四种类型，即南缘主要为元古界深变质岩，北缘主要为海西期花岗岩，四十里城次凹主要为中－上石炭统浅变质岩，焉南断裂以北主要为中泥盆统浅变质岩，基底岩相带呈东西向展布、南北向分带；将基底结构分为两种类型，即种马场断裂以南为塔里木地台型基底，以北为海西期褶皱基底。北部海西褶皱基底塑性强、不稳定，在沉积盖层中易形成背斜型圈闭；受深部热流影响沉积盖层中的有机质成熟度较高，因而使得盆地北部油气富集程度高，目前已发现的油气田均集中在北部。

ON BASEMENT OF YANQI BASIN.

Based on gravity, magnetic, electric, drilling and geologic data of peripheral basin, basement of Yanqi basin in Mesozoic and Cenozoic were classified into four structural types: imbricate, ramp, back thrust and basement arch. The lithology includes Proterozoic catametamorphic rock in south margin, granite in Hercynian period in northern margin, Mid Upper Carboniferous epimetamorphic rock in Sishilicheng sub sag and Mid Devonian epimetamorphic rock to the north of Yannan fault. The lithofacies belt extends from east to west, and is zoned axially. The basement is of Tarim platform to the south of Zhongmachang fault and of Hercynian fold to the north. The latter probably form anticlinal trap in the caprock due to its higher compressibility and unstability. The caprock has higher organic maturity resulting from deeper geothermal flow, so oil and gas are enriched in northern Yanqi basin, which is evidenced by the fact that the discoveries so far took place in northern Yanqi basin.