鄂尔多斯盆地延长探区石千峰组千5段沉积相分析

Sedimentary facies analysis of Qian-5 member of Shiqianfeng formation in Yanchang block,Ordos basin

延长探区上古生界石千峰组千5段具有较大的天然气勘探潜力,为查明其沉积环境特征及沉积演化规律,在大量钻井、测井及岩心测试分析资料的基础上,识别出千5段典型相标志,并据此分析其沉积微相类型和特征,明确了沉积微相平面展布规律。研究表明,延长探区千5段主要发育辫状河三角洲沉积体系,以靖边-横山-子洲-吴堡一线为界,北部为辫状河三角洲平原亚相,南部则发育辫状河三角洲前缘亚相;水下分流河道改道频繁,在横向上往复迁移,在纵向上多期叠置,形成了大规模的砂岩沉积体,是研究区最有利的储集砂体。

Qian-5 member of upper palaeozoic Shiqianfeng formation in Yanchang block is of great natural gas exploration potential,in order to identify the depositional environmental characteristics and sedimentary evolution regularity,based on large quantities of drilling,logging and core test data,typical sedimentary facies markers were identified,and therefore,the sedimentary micro-facies types and characteristics were analyzed,and then the plane distribution of sedimentary micro-facies was finally clarified.Research results indicated braided river delta sedimentary system was mainly developed in Yanchang block,taking JingbianHengshan-Zizhou-Wubu as a boundary,braided river delta plain subfacies in northern area and braided river delta front subfacies in southern area.The underwater distributary channels changed frequently,laterally moving back and forth and vertically,superimposed with several phases,and then massive sandstone sedimentary bodies were formed,which was considered to be the optimum reservoir rock in Yanchang block.