基于天文周期等时格架预测细粒沉积岩相展布——以鄂尔多斯盆地富县地区三叠系长7段为例

Prediction of fine-grained sedimentary lithofacies distribution based on astronomical cycle isochronous lattice: a case study of Triassic Chang 7 member of Fuxian area, Ordos Basin

何发岐 朱建辉 齐荣 武英利 缪九军 姜龙燕 王东燕 陈现

HE Faqi ZHU Jianhui QI Rong WU Yingli MIAO Jiujun JIANG Longyan WANG Dongyan CHEN Xian

1. 中国石化 华北油气分公司, 郑州 450006; 2. 中国石化 石油勘探开发研究院 无锡石油地质研究所, 江苏 无锡 214126

1. SINOPEC North China Company, Zhengzhou, Henan 450006, China; 2. Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China

预测陆相不同类型岩相厚度分布是陆相页岩油富集区带优选评价的基础工作，以此开展的不同类型岩相含油条件、储集条件以及可动条件的研究，对靶区优选和水平井段方向部署有着重要的作用。以岩心观察与测井判识为基础，开展测井资料的频谱分析，引入稳定的天文轨道时间周期，进行时空调谐，建立钻井对比的高频层序等时格架，定量计算每个层序旋回内不同类型岩相厚度的平面变化趋势，认识岩相展布规律。针对鄂尔多斯盆地南部富县地区三叠系延长组7段的研究表明，自然伽马测井曲线包括了若干组天文周期信息，其中可以识别出6个完整的稳定405 kyr长偏心率天文周期旋回，以R203井长7段全岩心段观察和测井相特征分析为基础，合理建立高频等时格架进行井间对比。结果表明，泥页岩和纹层页岩主要发育长73亚段到长72亚段的底部旋回地层，细砂岩、粉砂岩在长72亚段中上部到长71亚段底部的Ⅳ—Ⅴ旋回地层中最为发育；井间横向对比表明，早期旋回的泥页岩和纹层页岩岩相广泛分布，旋回Ⅰ时期主要分布在研究区西南部，旋回Ⅱ时期分布在西部和东—东北部，中部地区局部较厚，而Ⅳ—Ⅴ旋回地层的细砂岩厚度分布由北东—南西的沉积体系控制，平面上呈北—北东往南—南西展布，往西南延伸到ZF27—ZF32井一线，形成了长7段3种源储组合类型。其中纹层页岩与细砂岩岩相配置组合为长73亚段中上部与长72亚段中上部—长71亚段下部层系组合，平面上主要分布在富县地区的中部—北、北东部；页岩岩相厚度发育较好的为长73亚段，平面上主要分布在富县地区的北东—东部、西南部区域。

Predicting the thickness distribution of different types of continental lithofacies is a fundamental task for selecting and evaluating continental shale oil-rich zones. Research on oil-bearing conditions, reservoir characteristics, and mobility of different types of lithofacies plays an important role in target area selection and the deployment of horizontal well sections. Based on core observation and logging identification, spectrum analysis of logging data was carried out. Stable astronomical orbital time cycles were introduced to perform spatio-temporal tuning. A high-frequency sequence isochronous lattice for drilling well comparison was established and the planar thickness variation trends of different types of lithofacies in each sequence cycle were quantitatively calculated, providing insights into lithofacies distribution patterns. Research on the 7th member (Chang 7) of Triassic Yan-chang Formation in the Fuxian area of the southern Ordos Basin showed that the natural gamma logging curves contained several sets of astronomical cycle information, among which 6 complete stable 405 kyr long eccentricity astronomical cycles could be identified. Based on the observation of the whole core section of Chang 7 member in well R203 and logging facies characteristics analysis, a reasonable high-frequency isochronous lattice was established for well-to-well comparison. The results showed that mud shale and laminated shale mainly developed in the bottom cyclic strata from Chang 73 to Chang 72 sub-member, and the fine-grained sandstone and siltstone were mostly developed in strata of cycles Ⅳ to Ⅴ from the middle and upper parts of Chang 72 to the bottom of Chang 71. Lateral comparison between wells showed that the mud shale and laminated shale lithofacies in the early cycles were widely distributed. During cycle Ⅰ period, these facies were mainly distributed in the southwest of the study area, and during cycle Ⅱ period, they were distributed in the west and east-northeast, with thicker storage in the central area. The fine-grained sandstone thickness distribution in strata of cycles Ⅳ to Ⅴ was controlled by a northeast-southwest sedimentary system, with a planar distribution from the north-northeast to the south-southwest, further extending to the southwest along wells ZF 27 to ZF 32. Three types of source and reservoir combinations were formed in Chang 7 member. The combination of laminated shale and fine-grained sandstone lithofacies occurred from the middle and upper parts of Chang 73 and Chang 72 sub-members to the lower part of Chang 71 sub-member, primarily distributed in the central-north, north, and northeast parts of the Fuxian area. The shale lithofacies thickness was well developed in Chang 73 sub-member, mainly distributed in the northeast, east, and southwest regions of the Fuxian area.

中国石化科技部项目(P22179)和中国石化重大项目(P23229)联合资助。

https://doi.org/10.11781/sysydz202405927