镇北-环县地区长4+5油层组致密砂岩沉积相

Research on sedimentary facies of tight sandstone of Chang 4+5 oil reservoirs of Triassic Yanchang Formation in Zhenbei-Huanxian area,Ordos Basin,China

鄂尔多斯盆地镇北-环县地区上三叠统延长组长4+5油层组致密砂岩勘探潜力巨大,但沉积相类型和特征复杂,严重制约勘探布署与开发成效。作者综合利用岩心、测井和测试分析资料并总结了前人研究成果,通过沉积相识别标志的研究,分析了长4+5油层组沉积相特征,结果表明,镇北-环县地区长4+5油层组主要为独特的河控-湖泊辫状河三角洲沉积体系。建立了辫状河三角洲沉积模式,结合取心段沉积微相分析,认为研究区最有利的储集砂体为水下分流河道及河口坝沉积。

The tight sandstone of Chang 4 ＋ 5 oil reservoirs of Triassic Yanchang Formation in the Zhenbei-Huanxian area is known for a great potential of oil and gas exploration.However,the types and characteristics of the sedimentary facies are complicated to some extent.This will undoubtedly limit the exploration arrangement and exploitation efficiency.Based on the core data,logging data and the testing and analyzing results of the previous researches,further studies for the sedimentary facies of Chang 4＋5 oil reservoirs have been done by studying the identified symbols of sedimentary facies.This suggests that the main sedimentary face of the oil reservoirs is a unique river-controlled lake braided delta depositional system,and the depositional model of braided delta is constructed.With the microfacies analysis of the cored intervals,the authors consider that the underwater distributary channel and debouch bar deposits are the most favorable reservoir sand bodies in the study area and this achievement will provide important geological evidences for the oil and gas exploration.