大湾区块陡坡带沙三中亚段砂砾岩体沉积特征及成因探讨

Sedimentary characteristics and genesis of sandy conglomerate of the middle Es3 in the actic region of Dawan Block

辽河坳陷东部凹陷大湾区块陡坡带沙三中亚段沉积时期发育了一套砂砾岩体,由于该区勘探程度较低,前人尚未对该区砂砾岩体进行深入的分析和研究,对其成因及分布规律认识不清,制约了该区的勘探进程。利用岩心观察、岩石薄片、粒度分析、重矿物组合特征以及古地貌恢复等技术手段,对研究区砂砾岩体沉积特征、物源及成因进行研究,结果表明:大湾区块陡坡带沙三中亚段砂砾岩体为近岸水下扇沉积体系,物源来自于东部茨榆坨潜山凸起,同时大湾区块位于茨榆坨潜山凸起倾没端,是主物源的优势倾泻方向,有利于形成规模扇体。在此基础上明确了大湾区块陡坡带沙三中亚段砂砾岩体展布特征,从而为大湾区块陡坡带岩性油气藏勘探寻找有利目标提供了指导。

A set of sandy conglomerate is developed during the deposition of the middle Es3 Formation in the actic region of Dawan Block in the eastern sag,Liaohe depression.Due to the low exploration degree in this area,the sandy conglomerate has not been deeply analyzed and studied,and its genesis and distribution law are not clear,which restricts the exploration process in this area.The sedimentary characteristics,provenance and genesis of the sandy conglomerate in the study area are studied by using core observation,petrographic thin section and grain size analysis,combined with the characteristics of heavy mineral assemblages and palaeogeomorphology restoration and other technical means.The results show that the sandy conglomerate in the study area is deposited by nearshore subaqueous fan,and its provenance is from the eastern Ciyutuo buried hill uplift.At the same time,Dawan Block is located at the pitching end of Ciyutuo buried hill uplift,which is the dominant pouring direction of the main proventsource and conducive to the formation of large⁃scale fan.On this basis,the distribution of sandy conglomerate mass has been defined and the guidance for oil and gas exploration in the actic region of the Dawan Block has been provided.