The exploratory potential of the lithological compound oil reservoirs in Sifangtuozi area is great and the benefit reserves in Gaotaizi and Saertu oil reservoirs have already been submitted.However,there exits the weak researches on the strata and sedimentation,the peripheral exploratory progress of the reserves blocks is still slow.Based on the data from 347 exploratory and development wells,combined with the core observation,the classification of the multi-level sequences for Qingshankou Formation and the analysis of the sedimentary microfacies of the braided river delta were carried out.The study shows that according to the identifiable tectonic changed surface,abrupt lithological facies interface and depositional conversion interface etc.,Qingshankou Formation can be divided into one Ⅱ-order sequence (SSQqn),three Ⅲ-order sequences (SQqn1,SQqn2,SQqn3) and twelve V-order sequences (RST);the sedimentary system of the braided river delta,shore shallow lake,hemi-deep lake and deep lake was developed in Qingshankou Formation period,and the former facies is characterized by multi-phrase alternated forward rhythm and backward rhythm,wide braided river belts,frequent diversion of the channels and the mud balled by the sand etc..Integrated with the old wells rechecking,K1qn1 (Well F84,Well F120),K1qn2 (Well F52,Well F79) and Sand GroupV-Ⅷ of K1qn3 (Well F40,Well F81) are designed as the next exploratory targets.%四方坨子地区岩性复合油藏勘探潜力大,已在高台子、萨尔图油层提交了效益储量.因地层及沉积研究薄弱,储量区块外围勘探进展缓慢.以347口探井和开发井资料为基础,结合岩心观察,对青山口组开展多级层序划分和辫状河三角洲沉积微相分析工作.研究发现:依据构造变革面、岩相突变面、沉积作用转换面等可识别界面,青山口组可划分为1个二级层序(SSQqn)、3个三级层序(SQqn1、SQqn2、SQqn3)和12个四级层序(RST);青山口期发育辫状河三角洲—滨浅湖—半深湖、深湖沉积体系,其中辫状河三角洲相具有“多期正反韵律交替叠置、辫状带宽阔、河道频繁迁移改道、砂包泥”等特点.结合老井复查,预测青一段(F84井、F120井)、青二段(F52井、F79井)和青三段V-Ⅷ砂组(F40井、F81井)为下步勘探目标.
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