渤海古近系混合沉积发育特征与沉积模式

陆源碎屑与湖相碳酸盐混合沉积在渤海海域古近系普遍发育，已经成为重要的油气勘探目标.基于90余口已钻井，结合地震、测井以及相关分析化验资料，以渤海海域古近系钻遇的混合沉积为研究对象，开展了沉积特征与成因背景分析，建立了混合沉积发育模式.研究表明:渤海古近系混合沉积发育近岸混积扇、近岸混积滩坝、远岸混积滩坝3种沉积相、7种沉积亚相和14种沉积微相.近岸混积扇以发育混积沟道为典型特征，岩性为含生屑的砂砾岩或中粗砂岩，为陡坡扇三角洲环境短源水道废弃后与生物碎屑间歇性间互沉积；近岸混积滩坝，为近源搬运沉积的陆源碎屑与盆内碎屑之间的混合沉积，典型沉积特征为发育高陆源碎屑含量的各种粒屑滩或坝；远岸混积滩坝为典型的以富含生物碎屑为主的混合沉积，陆源碎屑含量低，一般为盆内低隆或孤立潜山之上原地生长生物与少量供给的陆源碎屑发生的混合沉积.混合沉积发育模式和规模受古气候与古水体环境、古构造与水动力、陆源碎屑物质供给、古地貌条件等共同控制，其中古地貌特征起主导作用.混合沉积发育模式的建立，对混积型储层预测和油气勘探具有重要意义. 

Sedimentary Features and Development Pattern of Mixed Deposition of Paleogene System in Bohai Sea Area

The mixed deposition of terrigenous siliciclastic and lacustrine carbonates is pervasively developed in Paleogene system of Bohai Sea area. Based on drilling, sesimic, well logging and lithological testing data of 90 wells in the mixed deposition of Paleogene system of Bohai Sea area, sedimentary features and forming background were analyzed and the mixed deposition development model was established. Our research indicates that three types of sedimentary facies, including mixed fan, nearshore mixed bar, and offshore mixed bar, which could be further divided into seven types of sub facies and fourteen types of micro facies, are developed in Paleogene strata of the interest area. Nearshore mixed fan, which is normally associated with delta facies and formed near the intrabasinal local provenance of the steep slope zone, is featured with mixed deposited gully with bioclastic sandy conglomerate, and medium-coarse and medium sandstones is featured with the sedimentary facies of which is abandoned fan delta short axial source channel and bioclastic interval deposition. Nearshore mixed bar, which is generally formed near the intrabasinal local provenance of the lake bay, is featured with the mixed deposition of near source transportation sediments and intrabasinal clastic sediments. The typical sedimentary nearshore mixed bar is featured with grained clast bars of high terrigenous clastic content. Offshore mixed bar, which is developed on low uplift or isolated buried hill, is featured with rich bioclastic mixed deposits, low terrigenous clastic content, in-situ development of biology and low supply of terrigenous siliciclastics mixing. The pattern and scale of the mixed deposition are controlled by the interation of paleoclimate environment, paleotectonic activity, hydrodynamic condition, terrigenous siliciclastic supply, with the ancient landform as the most dominant factor. The establishment of the mixed depositional model could play a significant role in the future reservoir prediction and oil exploration.