松辽盆地断陷层系油气成藏的分区特征

ZONED-DISTRIBUTION OF OIL AND GAS ACCUMULATION IN FAULT DEPRESSIONS IN THE SONGLIAO BASIN

受北北东向深大断裂控制,在松辽地区发育了东部、中部、西部3个晚侏罗—早白垩世断陷带,各带构造沉积演化存在显著差别,使得该区油气成藏具有明显的分区性。在中部地区沿孙吴—双辽深断裂发育的一批继承性深断陷中,发育巨厚优质湖相烃源岩和火山岩及砂岩、砂砾岩2类储集体,断陷之上披覆多套巨厚的湖相泥岩,油气藏保存条件良好,且烃源岩持续热演化生烃,由此,在其中央低凸起带、坡折带上的近东西向继承性鼻状隆起带上发育一批大中型油气田。而在东、西部边缘断陷中,烃源岩体积较小,母质类型差,生烃丰度低,油气藏保存条件差,仅发育中、小型油气田。

Controlled by the NNE oriented deep fault rupture, three Late Jurassic-Early Cretaceous fault subsidence zones were developed in the east, middle and west of the Songliao Basin. Evident differences among structure depositional evolutions of these three zones cause distinct zoned-distribution of oil and gas accumulation in this area. In heritage deep sags developed along the Sunwu-Shuangliao deep fault in the central part, large thick lacustrine facies source rocks and volcanic rocks as well as sandstones and grits were developed. The fault sags are overlaid with multiple giant thick lacustrine facies mudstones, providing favorable conditions for oil and gas containing, as well as for continuing thermal evolution. Therefore, a number of middle and large scaled oil and gas fields were developed on the nearly EW strike heritage nose-like dome belt in low uplifts and slope break zones. While in the east and west margin, only small and middle scaled oil and gas fields were developed, due to the small volume of hydrocarbon rocks with lower quality mother matter, low source rock abundance and poor containing condition.