歧口凹陷北塘次凹沙三段物源—沉积体系分析

Provenance and sedimentary system research of the third member of Shahejie formation in Beitang sub-sag of Qikou sag

为明确歧口凹陷北塘次凹物源体系砂体展布、确定勘探目标区带,根据布格重力异常、古地貌和地震资料等分析物源口分布及运移方向;根据轻重矿物特征分析物源波及范围;利用砂体分散体系分析物源与砂体分布,构建物源—沉积体系.结果表明:研究区沙三段发育西部及北部物源,包括西部葛沽、塘沽、军粮城,以及北部汉沽、大神堂和涧南等6个子物源,其中大神堂、涧南、塘沽与军粮城子物源供给强度大、波及范围广,是北塘次凹主要物源供给区;受物源体系影响,北部发育冲积扇—辫状河三角洲—远岸水下扇沉积体系,西部发育扇三角洲—远岸水下扇体系,多种沉积体系相互匹配,形成北塘次凹"满盆皆砂"的砂体分布格局;三角洲前缘与远岸水下扇主水道微相区砂体是油气聚集成藏优质储层,为下一步油气勘探有利目标区.

In order to determine the exploration target area in Beitang sub-sag of Qikou sag,the provenance and sand body distribution should be identified.Based on the Bouguer gravity anomality as well as palaeo-geomorphology and seismic data,the source amount distribution and the migration direction were analyzed.According to the characteristics of light and heavy minerals,spread scope of different provenances were researched.By studying provenance sand dispersion and sand body distribution,provenance-sedimentary system was constructed.Western and northern provenanc were found in 3rd section of Eogene Shahejie formation(Es3).Six sub sources were divided,including western Gegu,Tanggu,Junliangcheng,as well as northern Hangu,Dashentang and northeast corner of Jiannan source.Among them,Dashentang,Jiannan,Tanggu and Junliangcheng sub source were more intensive,making them the main provenance.Affected by the source system,alluvial fan,braided river delta and far shore water fan sedimentary system can be seen in the north of Beitang sub sag,while the fan delta,far shore water fan system can be found in the west.Various sedimentary systems match each other,forming 'full of sand' of Beitang sub-sag.Delta front and far shore subaqueous fan main channel microfacies sandbodies area is the hydrocarbon reservoir forming high quality reservoirs,is the favorable target areas for further oil and gas exploration target area.