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依据地震、岩心和测井资料,对陆西凹陷下白垩纪九佛堂组开展层序地层学研究并分析层序格架内岩性圈闭发育情况。结果表明:九佛堂组可划分为1个三级层序,层序内可识别出初次湖泛面和最大湖泛面并划分低位、湖侵和高位体系域;低位体系域发育近岸水下扇和辫状河三角洲,湖侵体系域发育近岸水下扇和曲流河三角洲,而高位体系域发育曲流河、辫状河三角洲和扇三角洲,3个体系域均发育滑塌浊积扇;低位和湖侵体系域各类成因砂体储集物性差,不利于岩性圈闭发育,而高位体系域发育在五十家子庙洼陷和包日温都断裂带曲流河三角洲前缘、辫状河三角洲前缘、扇三角洲前缘的砂体和滑塌浊积扇砂体物性好,前3类砂体可形成砂岩上倾尖灭型岩性圈闭,滑塌浊积扇砂体可形成砂岩透镜体型岩性圈闭。
Based on the seismic, core and well logging data, the sequence stratigraphy of the Lower Cretaceous Jiufotang Formation in Luxi Depression was studied and the lithologic traps in the sequence framework were analyzed. The results show that the Jiufotang Formation can be divided into a third-order sequence, and the first lake flooding surface and the largest lake flooding surface can be identified and divided into low level, lake invasion and highstand system tract; Lower fan and braided river delta, the nearshore system tract develops nearshore subaqueous fan and meandering river delta, whereas the highstand system tract develops meandering river, braided river delta and fan delta, The lowstands and lacustrine sedimentary systems of all kinds of sand bodies have poor reservoir properties, which are not conducive to the lithologic trap development. The highstand systems tract is developed in the Wujiajiazui Sag and the Belt-Wendu fault zone The front of the delta front, braided river delta front, fan delta front sand body and slump turbidite fan sand body have good physical properties. The first three types of sand bodies can form sandstone dip-up type lithologic trap, Sedimentary fan sand bodies can form sandstone lens lithology traps.