东营凹陷东营三角洲与中央隆起带盐—泥构造形成的关系及其对隐蔽油气藏勘探的意义

Relationship between Dongying delta of Dongying depression and formation of salt-shale structure in central uplift and meaning in exploration of subtle oil/gas reservoir

东营三角洲是一个沿东营凹陷长轴方向发育的典型河控三角洲。在裂陷中期到晚期东营凹陷东部和南部发育的众多三角洲中,东营三角洲发育面积最广、时间最长,对古地形和沉积作用的影响最大。精细的三维地震资料、测井和钻井资料表明,东营三角洲对中央隆起带特别是梁家楼—现河庄构造带盐—泥构造的形成有着重要的意义。根据高分辨率层序地层学和构造分析的基本原理,通过把东营三角洲进积过程和盐—泥构造的上拱作用相结合,认为厚度巨大的三角洲进积体是盐—泥构造形成的一个触发因素。由于盐—泥构造的形成、沉积斜坡突然变陡以及三角洲的不断进积,最终重力滑动和底辟运动导致了生长断裂的形成,进而形成了构造坡折带,而且在三角洲前缘形成了滑塌浊积岩体,并形成了与构造坡折带有关的砂体,如低位扇体系。综上所述,三角洲进积体、盐—泥构造和构造坡折带关系模式的建立对于隐蔽油气藏的勘探有着重要的意义。

Dongying delta is typical river-controlled delta developed along the long axis direction of Dongying sag. Many deltas have been developed in the east and south parts of Dongying sag in mid-latter stage of fault depression, among which the Dongying sag is the broadest developed area, the longest developed time and has the biggest influence on palaeotopography and sedimentary action. The study by using fine 3-D seismic, logging and drilling data showed the Dongying delta of Dongying sag has important meaning for the formation of central uplift zone, especially for the salt-shale structure in Liangjialou-Xianhezhuang structural zone. It is considered, by using the basic principle of high-resolution sequence-stratigraphy and structural analysis and through combining the prograding process of Dongying delta with uppe-bend action of salt-shale structure, that significant thickness of delta prograding body is trigger factor of forming the salt-shale structure.The more important is,because of the formation of salt-shale structure, the sedimentary slope suddenly become steep, adding the progressively prograding of delta. Finally, the gravity slumping and diapir movement lead to form the growth fault and further form the structural slope break zone: on the one hand, slumping turbidite bodies have been formed in delta front; on the other hand, the sand bodies relative to structural slope break, for example the lower fan system, have been formed. Creating the relation mode among the delta prograding body, salt-shale structure and structural slope break has important meaning for exploration of subtle oil/gas reservoir.