利津洼陷及周边地区沙四上亚段沉积相

SEDIMENTARY FACIES IN UPPER SHA-4 MEMBER IN LIJIN LOW AND ITS SURROUNDING AREAS

利津洼陷及周边地区沙四上亚段发现了多种类型油气藏尤其是滩坝油气藏，由于缺乏对沉积相类型及平面分布系统研究，影响了下一步油气勘探。为了查明该地区的沉积相类型，搞清滩坝的沉积特征、平面分布及与其他沉积相之间的空间分布关系，以沉积学、层序地层学理论为指导，综合运用岩心观察、测井、录井和地震等分析方法，在利津洼陷沙四上亚段识别出扇三角洲、近岸水下扇、滨浅湖滩坝和半深湖－深湖泥四种主要沉积相类型。根据层序地层学研究结果，将沙四上亚段细分为1个层序3个体系域（LST、TST、HST）7个准层序组，对各准层序组内的沉积相展布进行了研究，以低位域滩坝最为发育，湖侵域、高位域滩坝发育差，但高位域发育碳酸盐滩坝，扇三角洲、近岸水下扇在各种层序组内均有发育，并指出下一步应尽可能向洼陷内或深洼区寻找有利的滩坝砂体。

Several types oil and gas reservoirs are discovered in Upper Sha-4 Member of Lijin Low and its sur- rounding areas, especially beaches and bars reservoirs. Lack of study on sedimentary facies types and areal distri- bution system prevents further exploration. Thus, in order to identify sedimentary facies types in this area and un- derstand spatial distribution, areal distribution and spatial distribution relationship with other sedimentary facies. Based on theory of sedimentology and sequence stratigraphy, four main sedimentary facieses are identified in Upper Sha-4 Member of Lijin Low by integrating core observation, electric logging, mud logging and seismic methods, in- cluding fan-delta, inshore underwater fan, shore shallow-lake beaches and bars and half deep lake-deep lake mud. Based on the results of sequence stratigraphy, Upper Sha-4 Member is divided into one sequence, three system tracts [ LST, TST, HST ） and 7 parasequence groups. Then, sedimentary facies extension in each parasequence group is analyzed. Results show that beaches and bars in lower zones is most developed and lake erosion area and higher zones are poorly developed. However, carbonate beaches and bars in higher zones develop in high position zones, and fan delta and inshore underwater fan all develop in all sequence groups, suggesting next step exploration should focus on favorable bar sandbodies in sag or deep sag areas.