陆相断陷淡水湖盆页岩油富集条件及勘探潜力

Enrichment conditions and exploration potential of shale oil in continental faulted freshwater lacustrine basins： A case study of the Paleogene Hetaoyuan Formation in the Nanyang Sag， Nanxiang Basin

王良军 李连生 朱颜 李艳然

Liangjun WANG Liansheng LI Yan ZHU Yanran LI

南襄盆地南阳凹陷核三段页岩油获得峰值日产5.21 ~ 19.17 t工业油流，研究页岩油富集对页岩油勘探具有重要意义。通过岩心、测井、薄片、扫描电镜、生排烃模拟和激光共聚焦等分析手段，研究了南襄盆地淡水湖相页岩油的形成条件、赋存特征、富集条件和勘探潜力。研究结果表明，页岩主要发育在核三段晚期至核二段，最大累计厚度可达1 400 m。页岩层有机质总有机碳含量（）介于0.18 % ~ 1.58 %，平均值为0.84 %，游离烃含量（）介于0.15 ~ 1.23 mg/g，有机质类型以Ⅱ型为主，镜质体反射率（）介于0.5 % ~ 1.0 %，处于中等热演化程度。岩相主要为纹层状-层状混合质页岩、纹层状长英质页岩和纹层状云灰质页岩3种类型。以纹层混合质页岩为主，页岩储集空间类型主要为基质孔隙和裂缝。基质孔隙主要为黏土矿物粒间孔、晶间孔、溶蚀孔，同时发育少量有机质孔隙。页岩基质孔隙度介于0.2 % ~ 5.4 %，平均值为3.1 %，具有储集性中等可动性、可压性好的特点。采用容积法计算总资源量达2.01 × 10 t。确定有利区勘探面积72.1 km²。

Commercial oil flow with peak daily production ranging from 5.21 to 19.17 t has been achieved in shale oil exploitation in the 3rd member of the Hetaoyuan Formation （also referred to as the He 3 Member） in the Nanyang Sag， Nanxiang Basin. Therefore， investigating shale oil enrichment in this sag is significant for exploration. Using methods including core observation， log response analysis， thin section observation， scanning electron microscopy （SEM）， hydrocarbon generation and expulsion simulation， and confocal laser scanning microscopy （CLSM）， we investigate the formation conditions， occurrence characteristics， enrichment conditions， and exploration potential of freshwater lacustrine shale oil in the Nanxiang Basin. The results indicate that shales in the Nanyang Sag primarily occur in the upper part of the He 3 Member to the He 2 Member， with a maximum cumulative thickness reaching up to 1 400 m. The shale layers in the sag exhibit total organic carbon （） content ranging from 0.18 % to 1.58 %， with an average of 0.84 %， and free hydrocarbon （） content from 0.15 to 1.23 mg/g. Their organic matter is dominated by Type Ⅱ1， with vitrinite reflectance （） values ranging from 0.5 % to 1.0 %， indicating moderate thermal maturity. The lithofacies of the shales consist principally of lamellar to laminated mixed shales， lamellar felsic shales， and lamellar dolomitic calcareous shales， with lamellar mixed shales predominating. The main storage spaces within the shales include matrix pores and fractures. The matrix pores are dominated by intergranular pores in clay minerals， intercrystalline pores， and dissolved pores， along with a small quantity of organic pores. These pores contribute to matrix porosity ranging from 0.2 % to 5.4 %， with an average of 3.1 %. The shale layers in the sag thereby exhibit moderate reserving properties， moderate shale oil mobility and good fracability. Calculations using the volumetric method reveal total shale oil resources in the sag reaching up to 2.01 × 10⁸ t， with the identified exploration area of play fairways covering 72.1 km².

10.11743/ogg20250109