鄂尔多斯盆地富县地区二叠系下石盒子组1段源-汇格局与砂体分布

Source-to-sink pattern and sand body distribution in the first member of Permian Lower Shihezi Formation in Fuxian area, Ordos Basin

方旭蕾 王琳霖 齐荣 高辉 杨飞 刘璐 苏娟

FANG Xulei WANG Linlin QI Rong GAO Hui YANG Fei LIU Lu SU Juan

1. 长江大学 地球科学学院, 武汉 430100; 2. 中国石化 石油勘探开发研究院, 北京 102206; 3. 中国石化 华北油气分公司 勘探开发研究院, 郑州 450006

1. College of Earth Science, Yangtze University, Wuhan, Hubei 430100, China; 2. Petroleum Exploration & Production Research Institute, SINOPEC, Beijing 102206, China; 3. Research Institute of Exploration and Development, Huabei Oilfield Company, SINOPEC, Zhengzhou, Henan 450006, China

鄂尔多斯盆地东南部富县地区作为上古生界天然气勘探的重要接替阵地，其主力勘探层段——二叠系下石盒子组1段(盒1段)受复杂构造—沉积作用影响显著，导致沉积充填的源—汇分布格局与砂体分布规律仍不明确。因此，深入开展多物源体系下的沉积充填交汇关系、砂体成因类型及其分布规律研究对该地区天然气的高效勘探与规模增储具有重要意义。基于野外露头和岩心观察，结合岩石薄片、重矿物以及测井资料的综合分析，系统开展了富县地区盒1段沉积物源分析，并总结了砂体成因类型、结构特征及其分布与演化规律。富县地区盒1段沉积期主要发育南部陆源碎屑充填区及南北陆源碎屑混源充填区。在盒1段共识别出9种岩相类型和3类岩相组合，其中主要砂体成因类型为辫状河相辫状河道充填和心滩砂坝两类。沿物源方向，岩相组合由指示南物源区下切、加积、侧积沉积充填作用逐渐演化为南北物源混源区侧积充填作用。盒1段经历了从沉积初始阶段洪水期富陆源粗碎屑供给到沉积晚期枯水期泥质沉积为主的沉积演化过程。其中，盒1-1、盒1-3小层沉积期是辫状复合河道砂体发育的有利阶段，尤其是盒1-1小层沉积期，优势砂体主要发育于富县地区中东部南物源沉积充填区及北部的物源混合充填的主力区。

The Fuxian area in the southeastern Ordos Basin is a crucial area for natural gas exploration in the Upper Paleozoic. The primary exploration target, the first member of the Permian Shihezi Formation (He 1 Member), is significantly influenced by complex tectonic and sedimentary processes, resulting in an unclear understanding of the source-to-sink distribution pattern and sand body distribution. Therefore, in-depth research on the sedimentary fillings, the genetic types of sand bodies, and their distribution patterns under multiple provenance systems is of significant importance for efficient natural gas exploration and large-scale storage enhancement in this region. The study employed field outcrop survey, core analysis, thin-section observation, heavy mineral analysis, and well logging data to systematically analyze the sedimentary provenance of the He 1 Member in the Fuxian area. The study summarized the genetic types, structural characteristics, and the distribution and evolution patterns of sand bodies. During the sedimentary periods, the He 1 Member in the Fuxian area primarily developed a terrigenous clastic debris filling zone in the southern region and a mixed-provenance terrigenous clastic debris filling zone in the northern and southern region. Nine lithofacies types and three lithofacies assemblages were identified within the He 1 Member, with the main sand body genetic types being braided river facies channel filling in braided rivers and channel bars. Along the provenance direction, lithofacies assemblages evolved from incision, aggradation, and lateral accretion in the southern provenance zone to lateral accretion in the mixed-provenance zone of the northern and southern region. The He 1 Member experienced a sedimentary evolution process from terrigenous coarse clastic debris sedimentation during flood periods at an initial stage to muddy sedimentation during low water periods at a later stage. In addition, the sedimentary periods of He 1-1 and He 1-3 sublayers were favorable stages for the development of braided composite channel sand bodies, especially during the sedimentary period of the He 1-1 sublayer. The dominant sand bodies were mainly developed in the southern provenance sedimentary filling area in the central and eastern Fuxian area and the primary mixed-provenance filling area in the northern Fuxian area.

中国石化科技部项目“鄂南富县区块古生界天然气成藏规律与精细评价”(P22070)资助。

https://doi.org/10.11781/sysydz2025020284