鄂尔多斯盆地麻黄山西地区三叠系延长组7段页岩油储层特征及控制因素

Characteristics and controlling factors of shale oil reservoirs in the seventh member of Triassic Yanchang Formation, western Mahuangshan area, Ordos Basin

齐荣 朱峰 何发岐 姜龙燕 尹超 邵隆坎

QI Rong ZHU Feng HE Faqi JIANG Longyan YIN Chao SHAO Longkan

中国石化 华北油气分公司 勘探开发研究院, 郑州 450006 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 中国石化 华北油气分公司, 郑州 450006

Research Institute of Exploration and Development, North China Oil and Gas Branch, SINOPEC, Zhengzhou, Henan 450006, China Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China North China Oil and Gas Branch, SINOPEC, Zhengzhou, Henan 450006, China

鄂尔多斯盆地三叠系延长组7段(简称长7段)页岩油资源丰富，但湖盆边缘和湖盆中心页岩油储层特征存在显著差异。目前，湖盆边缘麻黄山西地区页岩油储层研究程度较低，制约了该区页岩油的勘探进展。通过扫描电镜、高压压汞、低场核磁共振、氮气吸附和微米CT等分析手段，结合岩心观察和薄片鉴定等资料，对该区长7段页岩油储层特征进行精细刻画，同时利用碳氧同位素及常量、微量元素分析了优质储层发育机制。结果表明：麻黄山西地区长7段页岩油储层岩性主要为细砂岩、粉砂岩和泥页岩，长英质和黏土矿物含量较高，长英质矿物普遍达到50%以上；储层储集空间类型多样，不同岩性之间孔隙发育具有差异性，其中细砂岩以粒间孔和黏土矿物晶间孔为主，孔径集中分布于1~2 μm；粉砂岩(主要为泥质粉砂岩) 发育无机孔隙和有机质孔，主孔径分布在3 nm和500 nm附近；泥页岩以有机质黏土复合体孔隙和微裂缝为主，小于10 nm和数十纳米的孔径均有发育。储层物性与孔隙结构分析表明，夹层型细砂岩储层为优质储层类型，成岩压实过程中减孔约26%~33%，其储层砂体中部受成烃流体改造作用显著，现今孔隙度普遍大于5%；而夹层型砂体边缘和纹层型储层因胶结物的大量沉淀，物性相对较差。

The seventh member of the Triassic Yanchang Formation (Chang 7) in the Ordos Basin is abundant in shale oil resources. However, there are significant differences in reservoir characteristics between the basin margin and the basin center. Currently, research on shale oil reservoirs in the western Mahuangshan area at the basin margin remains insufficient, which has constrained shale oil exploration in this area. In this study, a detailed characterization of the shale oil reservoirs of Chang 7 member in this area was conducted using scanning electron microscopy (SEM), high-pressure mercury injection, low-field nuclear magnetic resonance (NMR), nitrogen adsorption, and micro-CT, combined with core observations and thin-section identification. Additionally, carbon and oxygen isotope and major and trace element analyses were conducted to investigate the development mechanism of high-quality reservoirs. The results showed that: (1) The shale oil reservoir in the Chang 7 member of the western Mahuangshan area is mainly composed of fine sandstone, siltstone, and mud shale. The mineral composition is characterized by high contents of felsic and clay minerals, with felsic minerals generally exceeding 50%. (2) The reservoir exhibits diverse space types, and the pore development differs among lithologies. In fine sandstone, intergranular pores and clay mineral intercrystalline pores are dominant, with pore sizes mainly distributed in the 1 to 2 μm range. In siltstone (mainly argillaceous siltstone), both inorganic pores and organic matter pores are developed, with dominant pore sizes near 3 nm and 500 nm. Mud shale is mainly composed of pores with organic-clay composites matter and microfractures, developed with pores below 10 nm and those in the range of tens of nanometers. (3) Analysis of reservoir physical properties and pore structure indicated that interbedded-type fine sandstone reservoirs represent the high-quality reservoir type. During compaction diagenesis, the porosity was reduced by approximately 26% to 33%. Hydrocarbon-generating fluids significantly modified the central parts of the sandstone bodies of reservoirs, and the current porosity generally exceeds 5%. In contrast, the edges of sandstone bodies and laminated-type reservoirs experienced substantial cement sedimentation, resulting in relatively poor physical properties.

https://doi.org/10.11781/sysydz2025040791