鄂尔多斯盆地长7页岩油与北美地区典型页岩油地质特征对比

摘要

The Chang 7 shale oil in the Yanchang Formation of Ordos Basin was studied using X-ray diffraction, scanning electron microscopy,high pressure mercury penetration, and gas isothermal adsorption. The formation was compared with typical shale oil in North America from four aspects including geological conditions, source rock characteristics,mineral composition, and reservoir space types. The results showed that both the Chang 7 shale oil and the typical shale oil in North America were deposited in a low energy environment, and the stable sedimentary environment was beneficial to shale oil accumulation. The organic matter type and maturity of source rocks in Chang 7 and North America are similar. The TOC content of Chang 7 shale oil is 2% to 18%,which is higher than that of the Eagle Ford shale. Thus,the Chang 7 source rocks are considered to have a great potential for oil production. The brittle mineral content of Chang 7 shale oil is 69.73%,only 1.27% lower than the typical shale oil in North America,indicating that the shale of Chang 7 formation is amenable to fracturing. Compared with the typical shale oil in North America,the Chang 7 shale oil has poor porosity and permeability(0.5%-2.1%and (0.000 4-0.03)×10-3μm2,respectively).Micro-cracks and organic pores were well developed in typical shale oil in North America,while the organic pores in Chang 7 shale oil are scattered, and the reservoir space is mainly composed of intergranular pores,intragranular pores and micro-cracks.It can be concluded that the Chang 7 shale oil has the same oil accumulation pattern and mineral composition as the typical shale oil in North America.How-ever,the Chang 7 shale oil has poor physical properties and a dense reservoir. Therefore, it has great resource potential and high development difficulty.%为研究鄂尔多斯盆地长7页岩油勘探开发潜力,基于X射线衍射、场发射扫描电镜氩离子抛光、高压压汞、气体等温吸附等测试结果,与北美地区典型页岩油从地质背景、烃源岩特征、矿物组分和储集空间类型4个方面进行了对比.结果表明,长7页岩油与北美地区典型页岩油处于稳定的沉积环境中,有利于页岩油成藏.长7烃源岩有机质类型和成熟度与北美相似,TOC含量达到2%~18%,甚至高于鹰滩组页岩油,生油潜力大.长7页岩油脆性矿物总量达到69.73%,仅比北美页岩油低1.27%,可压性强.长7页岩油较北美典型页岩油而言,物性较差,孔隙度和渗透率分别为0.5%~2.1%和(0.0004~0.03)×10-3μm2.北美典型页岩油微裂缝和有机质孔发育良好,而长7页岩油有机质孔多呈孤立状分布,储集空间以粒间孔、粒内孔和微裂缝为主.可见,长7页岩油与北美地区典型页岩油成藏规律及矿物组分相似,但长7页岩油物性差,储集空间细小,因此在具有较大资源潜力的同时亦具有较高的开发难度.