旋转掀斜斜坡区构造-沉积演化特征及油气地质意义--以渤海湾盆地歧口凹陷板桥斜坡为例

Rotate-tilt slope zone structures-sedimentary evolution and petroleum geologic significance:A case study of Banqiao Slope of Qikou Sag,Bohai Bay Basin

为明确旋转掀斜斜坡区构造—沉积演化特征及其对岩性油气藏的控制作用,以渤海湾盆地歧口凹陷板桥斜坡区为例,运用地震、测井及岩心薄片等资料,分析了板桥斜坡构造演化特征、不同构造阶段沉积特征及其与岩性油气藏成藏的关系。认为板桥斜坡古近纪经历了"整体沉降—旋转掀斜"2个阶段,古地貌具有"早缓—晚陡"的特征,古构造经历早期单斜—晚期箕状的演化过程。E_(3s3)-E_(3 s_1~x)以构造整体沉降为主,古地貌平缓,沧县隆起物源向整个斜坡区大面积输送,发育大型辫状河三角洲沉积,前缘砂体在现今缓坡区叠置连片;E_(3s_1~z)-E_3 d发生旋转掀斜,斜坡区主体发生构造反转,形成现今箕状格局。板桥斜坡大面积缓坡为岩性圈闭形成提供构造背景,早期古地貌平缓有利于缓坡区优质砂体叠置连片,晚期旋转掀斜有利于上倾尖灭岩性圈闭形成。板桥斜坡中、低缓斜坡区E3sx1三角洲前缘水下分支河道有利砂体叠置连片,储集物性好,与油源断层匹配,是岩性油气藏勘探有利地区。据此,在缓坡区新落实多个岩性圈闭发育带,部署完钻的12口井相继获得高产油气流,圈闭钻探成功率高达85%。

In order to illustrate rotate-tilt slope zone structures,sedimentary evolution and it＇s controls on lithological reservoir,a case study in Banqiao Slope of Qikou Sag was presented,based on the seismic data,well-log information,core and core slice,analyzed the evolution characteristics of Banqiao Slope tectonic,sedimentary characteristics of different construction phase and its relationship with lithological reservoir.Banqiao Slope experienced two stages,average settlement and rotate-tilt.Effected by tectonic evolution,palaeogeomorphology was featured by early gentle slope and later steep slope,tectonics of E_（3s3）-E_（3 s_1~x） episode showed whole settlement,with gentle palaeogeomorphology,provenances from Cangxian Lift were deposited in large areas,developed braided-river delta sedimentation.Slope rotate-tilted at the episode of E_（3s_1~z）-E_3 d,the main structure of slope reversed,developing dustpan-shaped tectonics,with the characteristics of rotate-tilted slope controlling sandbodies,faults in source rocks and lithologic traps controlling reservoir,advantageous phase accumulation and high productivity.Sand bodies developed by sub-water channel of delta front were overlapped and distributed widely in middle and low slopes at the time of E_（3s_1~x）,with good reservoir properties.Matched with faults in source rocks,they are the favorable exploration area of lithological reservoirs.According to those,some lithologic traps were found in gentle slope areas,12 wells have been drilled,and attained high yield flow of oil and gas,drilling success rates can reach 85%.