湖泊岸线带直坝和斜坝:形成机制与沉积特征

Lakeshore Oblique and Orthogonal Bars:Sedimentary Features and Formation Mechanism

湖浪、环流和沿岸流等湖流对滩坝砂的形成和分布起到了重要的控制作用。为研究湖流对滨浅湖滩坝砂的改造作用及坝体边缘砂体的分布规律和沉积特征,以青海湖现代沉积和松辽盆地南部青山口组滩坝砂为基础,对上述问题进行了讨论。研究发现,青海湖和松辽盆地青山口组滩坝砂的边缘发育大量直坝和斜坝沉积。直坝和斜坝分别垂直或斜交于湖岸线生长,砂体具有狭长分布的特点,二者的形成主要受向岸浪和反射离岸浪的控制。直坝和斜坝常发育交错层理、平行层理及透镜状层理等浅水构造。直坝和斜坝砂体在坝体边缘呈群带状展布,平面上容易形成岩性油气藏。直坝和斜坝的研究对于完善陆相盆地滩坝砂的沉积模式和拓展我国陆相盆地岩性油气藏的勘探领域都具有重要的价值。

Lake currents,such as lake wave,alongshore current and circulation,control the formation and distribution of lakeshore bars.Based on seismic sedimentological case study of modern sedimentation in Lake Qinghai and lakeshore bars of Qingshankou Formation in Songliao Basin,the above issue is studied.A large number of oblique bars and orthogonal bars were developed on the edge of lakeshore bars in Lake Qinghai and Qingshankou Formation of Songliao Basin.Oblique bars and orthogonal bars respectively were developed vertically or obliquely to the shorelines,their sand body is spread as narrow belts,and their formation is controlled by the onshore wave and offshore wave.The bars are characterized by shallow water sedimentary structures,such as wave cross bedding,parallel and linsen bedding,and inverted and composite facies sequences.As the study shows,the bars perform fine petrophysics to easily develop into native lithologic and stratigraphic reservoirs.The study of oblique and orthogonal bars is valuable to improve the knowledge of sedimentary pattern of beach-bars of terrestrial basin and to expand exploration field of lithologic reservoirs.