摘要： 湖相滩坝砂体是陆相盆地广泛发育的一类油气储集层,已成为成熟油田岩性油气藏勘探的重要领域。基于层序界面识别与划分、古地貌恢复、物源体系、砂体展布以及成藏条件分析,论证了Melut盆地Ruman凹陷白垩系Gayger-Galhak组的层序地层特征及其对滩坝沉积的控制。结果表明:(1)目的层段发育1个二级层序和SQ1、SQ2、SQ3等3个三级层序,SQ3又可进一步细分为6个准层序组(四级层序)。(2)不同级别的层序分别控制着滩坝沉积的发育位置、平面展布及岩性圈闭的成藏要素,表现为: 二级层序控制滩坝沉积的垂向发育位置,滩坝砂体主要发育于二级基准面下降期;三级层序控制滩坝沉积的发育规模和沉积模式,三级基准面下降半旋回与上升半旋回转换位置发育的潜山隆起周缘型坝砂面积(约10km²)和厚度(10~20m)较大、孔隙度高(20%~25%),而发育于三级基准面上升期的水下潜山台地型坝砂面积(1~4km²)和厚度(2~3m)较小、孔隙度相对较低(15%~20%);四级层序洪泛期沉积的泥岩作为局部盖层,不仅控制着滩坝储盖组合的分布,而且决定了滩坝成因岩性圈闭的有效性。

关键词: Melut盆地, Ruman凹陷, 层序地层, 滩坝沉积, 沉积模式

Abstract: As a widely developed oil & gas reservoir in continental lake basin,lacustrine sandy beach-bar is an important target for lithological oil & gas reservoir exploration. Based on the identification and demarcation of sequence boundaries,palaeogeomorphic reconstruction,analysis of provenance system,sand-body distribution and reservoir-forming conditions,it can be found that the sequence evolution of the Cretaceous Gayger-Galhak Formations controlled the deposition of beach-bar in Ruman area,Melut Basin. Result shows that:(1) One 2^nd-order sequence,three 3^rd-order sequences(SQ1,SQ2 and SQ3)were developed in the target horizons,where SQ3 can be further divided into six Parasequence sets(corresponding to 4^th-order sequences). (2)Different hierachies of sequences controlled the location and lateral distribution of sandy beach-bar,and reservoir-forming factors for lithological traps of beach-bar in different ways. The 2^nd-order sequence controlled the vertical development position of beach-bar,where sand-bodies of beach-bar were mainly developed in the descending stage of relative base-level. The 3^rd-order sequence controlled the lateral distribution of beach-bar,in the transit point between the descending and ascending semi-level of the 3^rd-order sequence,beach bar developed around the Ruman burial hill,with large area(about 10km²),large thickness(10~20m)and high porosity(20%~25%). During the ascending stage of the 3^rd-order sequence,subaqueous burial-hill platform deposition model was developed,with small area(1~4km²),thin thickness(2~3m)and relatively low porosity(15%~20%). The flooding surface of the 4^th-order sequence controlled the distribution of sandy beach-bar reservoir-seal assemble,the flooding mudstone can be considered as local seal,determines the effectiveness of beach-bar lithological trap.

Key words: Melut Basin, Ruman sag, sequence stratigraphy, beach-bar deposition, depositional model

中图分类号: 

• P588