湖泊碎屑岩沙坝成因机制及构型表征研究进展*

湖泊碎屑岩沙坝因波浪和沿岸流的反复冲刷,成熟度较高,显示出巨大的油气勘探潜力,已成为隐蔽油气藏勘探的重点。作者在大量文献调研的基础上,总结了近年来前人在滩坝定义、沉积特征、主控因素、成因机制及内部构型研究中的重要进展,在此基础上提出了沙坝演化阶段及沉积构型的新认识。结果表明,沙坝完整的演化历程主要包括4个阶段,分别是弱波浪作用阶段、动荡水流—冲洗回流阶段、风成阶段及沼泽化阶段。影响沙坝发育的控制因素多样,其中物源和风场是沙坝发育的根本因素,两者分别影响了沙坝发育的物质来源和能量供给;而风场所决定的水动力是影响沙坝储集体发育的最直接因素;构造运动和层序演化则控制沙坝的分布位置及保存程度;各因素综合作用决定了坝的形态、发育规模及保存状况。依据前人构型理论,将沙坝构型按照正序方案依次划分为6级,对构型表征方法和沙坝3~5级构型定量表征进行了初步探索,以期为滩坝砂体勘探开发提供理论和实践支持。

Research progresses of the genetic mechanism and architecture characterization on lake bars

Due to the repeated washing of waves and longshore currents,the bar reservoir has a high maturity,showing great oil and gas exploration potential,and has become the focus of subtle oil and gas reservoir exploration. Based on literature review,we summarize the recent research progresses of bar definitions,sedimentary characteristics,main controlling factors,genetic mechanisms and internal architectures,and propose a new understanding of bar evolution stage and sedimentary architecture. The results show that the bar evolution mainly includes weak wave action stage,turbulent current swash-backwash stage,aeolian stage and swampiness stage. Many factors affect the bar development,in which provenance is the clasts supplier and wind field is the energy engine. Hydrodynamic force induced by the wind strongly affects the development of bar reservoirs. Tectonic movement and sequence evolution control the distribution position and preservation of the bar. The above-mentioned factors work together to determine the morphology,scale,and preservation of the bar. According to the architectural theories,bar architecture is divided into six levels. In this architecture classification,we define composite sand body as level 5,single sand body as level 4 and accretive body as level 3,which are in reservoir scale. We explore the qualitative and quantitative characterization of the bar architecture level 3 to level 5 to provide theoretical support for beach-bar reservoir exploration and development.