渤海B气田孔店组砂砾岩储层特征及主控因素分析

Analysis of Characteristics and Main Controlling Factors of Glutenite Reservoir of E1-2k2 Formation in B Gas Field of Bohai Sea

渤海B气田孔店组为断陷湖盆背景下粗粒扇三角洲近源快速沉积体系,发育巨厚的砂砾岩,隔夹层不发育。在陡坡断阶带,形成厚层近源的扇三角洲沉积。依据砂砾岩颜色、岩性组合与垂向发育特征,该区位于扇三角洲前缘亚相,可进一步划分为扇三角洲前缘近端、前缘主体、前缘远端3种类型。储层主控因素主要为古地貌及成岩作用。孔店组沉积时期,主干断裂由于持续活动,可容纳空间巨大,同沉积断裂形成的断阶带控制孔店组地层发育,物源供给充足,湖盆范围有限。古地貌控制了孔店组大型砂砾岩体发育。铸体薄片、扫描电镜观察及X射线衍射分析表明,B气田孔店组储层成岩作用主要有压实作用、胶结作用、溶蚀作用、交代作用。

E1-2k2 formation of B gas field in Bohai Sea is a near source fast sedimentary system of coarse-grained fan delta in the background of faulted lake basin,with a very thick glutenite developed and no interlayer developed.In the fault step belt of steep slope,the fan delta deposit with thick layer and near source is formed.According to the characteristics of glutenite color,lithologic association and vertical development,the area is located in the subfacies of fan delta front,which can be further divided into three types:near front,main front and far front.The main controlling factors of reservoir are paleo-geomorphology and diagenesis.In the period of E1-2 k2 formation deposition,the main fault can accommodate a large space because of its continuous activity.The fault step belt formed by the synsedimentary fault controls the formation development of E1-2 k2 formation;the supply of material resources is sufficient,and the scope of lake basin is limited.Paleogeomorphology controls the development of large-scale glutenite in E1-2k2 formation.Casting thin section,scanning electron microscopy and X-ray diffraction analysis show that the diagenesis of E1-2k2 formation reservoir in B gas field mainly includes compaction,cementation,dissolution and metasomatism.