Abstract: As shale oil-gas exploration and development advances rapidly, astronomical cycle theory has attracted much attention in the prediction of shale oil-gas reservoirs. Deep-water shale is extremely insensitive to well-logging/mud-logging and seismic response, so it restricts the application of traditional methods in shale lithofacies evolution and sweet spot prediction, thus severely restricting the research on stratigraphic correlation and evolution regularity of deep-water shale. The research on the high-frequency evolution regularity of deep water shale and the prediction of shale oil-gas sweet spots were carried out from the perspective of astronomical cycle, which can provide a new viewpoint for solving above-mentioned difficulties in hydrocarbon exploration. Based on the climate changes on the scale of ten thousand to hundreds of thousands of years at the earth surface controlled by astronomical cycle, the paper analyzes the sedimentary evolution mechanism driving the development of shale sweet spots within the thickness range of several meters to tens of meters. Moreover, the three application cases of astronomical cycle theory in prediction of shale oil-gas reservoirs are elaborated as below. (1) Based on deep machine learning, the sedimentary autogenetic cycle was accurately identified and eliminated, the paper establishes an astronomical cycle framework with the accuracy of about 1 m in the Eocene deep-water shale area of Dongying sag, and it is proposed that the precessional cycle controls the lithofacies cycle of meter-level organic-rich carbonate-bearing/carbonate-rich shale, and the peak stage of long eccentricity corresponds to the favorable sweet spot interval. (2) Astronomical cycle controls the evolution of the sand-mud reservoir in the Middle Eocene sand-interbedded shale oil reservoirs of Zhanhua sag. The long, short eccentricty and precessional cycle co-control the stage and frequency of interbedded sand, mineral composition of shale and cyclicity of organic content. The research results can provide new ideas for the prediction of sand-interbedded shale sweet spot intervals. (3) An integrated stratigraphic framework of sequence-astronomical cycle in the transition zone of coarse to fine grains and the shale depositional zone of the lake basin was established, and it is proposed that ordered changes in the lithofacies type and scale of coarse and fine grains are subject to the systematic domain level, and the astronomical cycle controls the lithofacies cycles of several meters to tens of meters within the domain. The research results can help solve the difficulty in prediction of coarse and fine sane rocks encountered when drilling horizontal wells, thus providing support for the integrated exploration and development of conventional and unconventional reservoirs. With the further and continuous exploration and development of shale oil and gas, the distribution of shale oil sweet spots is analyzed from a new perspective of astronomical cycle, which will help improve the optimization accuracy of sweet spot intervals before horizontal well drilling.

Key words: astronomical cycle, shale oil and gas, reservoir, high-frequency evolution, prediction

摘要： 随着页岩油气勘探开发蓬勃发展,天文旋回理论在页岩油气储层预测中受到广泛关注。由于深水泥页岩对测井/录井、地震响应极不敏感,限制了传统方法在泥页岩岩相演化及甜点预测中的应用,制约了深水泥页岩的地层对比及演化规律研究。从天文旋回角度开展深水泥页岩高频演化规律研究以及页岩油气甜点预测,可为解决上述勘探难题提供新视角。基于天文旋回控制下的地表万年至数十万年尺度的气候变化,分析其驱动泥页岩甜点在数米至数十米厚度变化范围内的沉积演化机理,阐述了天文旋回理论在页岩油气储层预测中的3个应用实例。① 基于深度机器学习,实现了沉积自旋回的精准识别与剔除,建立了东营凹陷始新统深湖泥页岩区精度约为1 m的天文旋回格架,发现岁差周期控制着米级富有机质含(富)灰页岩岩相旋回,长偏心率的峰值阶段对应着有利甜点段。② 天文旋回控制着沾化凹陷中始新统夹砂型页岩油储层的砂-泥一体化储层演化,长偏心率、短偏心率和岁差旋回协同控制着砂岩夹层的期次、频率以及泥页岩矿物组分和有机质含量的旋回性。研究结果可为夹砂型页岩甜点段预测提供新思路。③ 建立了湖相盆地从粗粒、细粒砂岩过渡区至泥页岩沉积区的层序-天文旋回一体化地层格架,提出粗粒、细粒砂岩岩相类型和规模的有序变化受体系域级别控制,天文旋回约束了体系域内部数米至数十米级别的岩相旋回。研究结果可助力解决水平井同时钻遇粗粒、细粒砂岩的预测难题,服 务于常规-非常规储层一体化勘探开发。随着后续页岩油气勘探开发不断深化,从天文旋回新视角分析页岩油气甜点的分布规律,将有助于提高水平井钻前的甜点层段优选精度,助力细粒沉积学和非常规油气地质学发展。

关键词: 天文旋回, 页岩油气, 储层, 高频演化, 预测