松辽盆地大情字井区青山口组二段风暴沉积及意义

Storm deposition and significance of the second member of Qingshankou Formation in Daqingzi well area,Songliao Basin

松辽盆地大情字井区青山口组二段(青二段)钻井揭示其砂体分布规律极为复杂,随着勘探程度的不断深入,早期“深湖型”三角洲沉积、浅水三角洲沉积等地质认识与生产实践之间的系列矛盾问题日益突出。为解决上述问题,围绕大情字井区开展了系统岩心观察和岩心数据分析。岩心观察显示青二段存在大量指示风暴沉积特征的风暴岩,岩性和粒度分析揭示研究区沉积具牵引流和重力流双重属性,表明青二段除发育三角洲沉积之外,同时还发育风暴沉积。经分析认为,研究区发育的风暴岩根据垂向沉积序列可划分为Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ共5种类型,又根据不同类型风暴岩的沉积过程和搬运距离,近一步在平面上划分为原地风暴岩、近源风暴岩和远源风暴岩3类,其中原地风暴岩以Ⅰ型为主,Ⅱ型、Ⅲ型、Ⅳ型均为近源风暴岩,Ⅴ型为远源风暴岩。综合风暴岩的沉积特征,结合其剖面、平面展布,建立了研究区风暴沉积模式,从而形成大情字井区青二段三角洲前缘沉积与风暴沉积共同作用的认识,合理解释了实际钻遇砂体的复杂分布规律。研究成果可为该区后期油气高效勘探部署开发提供实际指导,亦可为相似油田区域沉积模式提供总结参考。

Drilling of the second section of the Qingshankou Formation in the Daqingzi well of the Songliao Ba⁃sin revealed a highly complex distribution pattern of sand bodies.With the continuous deepening of exploration,a series of contradictions between geological understanding and production practice such as early“deep lake type”delta sedimentation and shallow water delta sedimentation have become increasingly prominent.To solve the above problems,the author conducted systematic core observation and core data analysis.Core observation shows that there are a large number of storm rocks indicating the characteristics of storm sedimentation in the Qing-2 section.Lithology and particle size analysis reveal that the sedimentation in the study area has dual attri⁃butes of traction flow and gravity flow,indicating that in addition to the development of delta sedimentation,the Qing-2 section also develops storm sedimentation.After analysis and research,the storm rocks developed in the study area can be divided into five types based on the vertical sedimentary sequence:I,II,III,IV,and V.Fur⁃thermore,according to the sedimentary process and transportation distance of different types of storm rocks,they will be further divided into three types on the plane:In-situ storm rocks,near source storm rocks,and far source storm rocks.Among them,in-situ storm rocks are mainly classified as Class I,II,III,and IV are all near source storm rocks,and Class V is far source storm rocks.Based on the sedimentary characteristics of storm rocks and their planar distribution,a sedimentary model of storm rocks in the study area was established,thus forming an understanding of the joint effect of delta front sedimentation and storm sedimentation in the Qing'er section of the Daqingzijing area,and reasonably explaining the distribution pattern of actual drilled sand bodies.The research results can provide practical guidance for the efficient exploration and development of oil and gas in the later stage,and can also provide model guidance for sedimentation in similar oilfield areas.