渤中坳陷沉积演化和上第三系储盖组合分析

SEDIMENTARY EVOLUTION AND NEOGENE RESERVOIR-SEAL ASSEMBLAGE ANALYSIS OF BOZHONG DEPRESSION

渤中坳陷的构造－沉积演化经历裂陷和裂后坳陷两大阶段。早第三纪裂陷阶段发育了沙三段、沙一段和东下段三套优质湖相烃源岩，具有良好的生烃潜力为陷内蕴藏着丰富的油气资源；晚第三纪裂后坳陷阶段以河流平原沉积充填为特征，发育辫状河－曲流河－滨浅湖沉积体系，形成两类有利的储盖组合：Ⅰ类是以明下段广泛发育的河／湖沼泽－滨浅湖相泥岩作盖层，馆陶组厚层砂岩作储层，是非常有利的区域性储盖组合；Ⅱ类是明化镇组和馆陶组曲流河平原相发育的泛滥平原泥岩与曲流河砂体组成的互层状储盖组合。由于这两套储盖组合的存在为渤中坳陷上第三系中浅层油气的聚集创造了非常有利的条件。

Bozhong Depression with vastly thick Tertiary System deposit underwent two evolution stages of structure-deposit: rifting stage and post-rifting depression stage. In the rifting stage three sets of hydrocarbon rocks of Sha-Ⅲ, Sha-Ⅰ,and Lower Dongying Formation were developed, being of very good hydrocarbongenerating potential developed. The depression contains very rich oil and gas resources. The deposit of fluvial plain facies,developing the braided stream to meandering stream and nearshore shallow lacustrine sedimentary system,characterizes the Neogene post-rifting down-warping stage of Bozhong Depression. There are two sets of reservoir-seal assemblages generated in the Neogene system:one is composed of the mudstones of fluvial-lacustrine-marsh to shallow lacustrine facies and the thick-layer sandstone of Guantao Formation,being a very favorable regional reservoir-seal assemblage;the other is a interbedding reservoir-seal assemblage consisting of overflooding plain mudstone and the sandstone of meandering stream. These two sets of assemblages provide a very favorable condition for the oil and gas accumulation in the middle to shallow layer of Bozhong Depression.