鄂尔多斯盆地中部三叠系延长组7段湖相页岩油勘探潜力

Shale oil exploration potential in central Ordos Basin: A case study of Chang 7 lacustrine shale

范柏江 晋月 师良 李亚婷 陈玮常

Bojiang Fan Yue Jin Liang Shi Yating Li Weichang Chen

鄂尔多斯盆地中部延长组7段页岩为浅湖-半深湖相沉积，页岩厚度薄且交互发育砂质纹层甚至薄砂层。在压裂改造层面上，该地区页岩由于砂质含量高似乎是更理想的开发目标。但是，尚没有对该地区的页岩油勘探目标进行过剖析与对比。为了探索浅湖-半深湖相的页岩油勘探目标，基于地球化学测试与分析，开展了两类岩性的生、排烃能力对比，综合判断页岩油资源的勘探潜力。研究表明，页岩的有机质丰度高于砂质纹层页岩；页岩主要由偏腐泥型的有机质构成，砂质纹层页岩由混合型有机质构成；页岩和砂质纹层页岩均处于低-中等成熟的热演化阶段；砂质纹层页岩的生烃能力弱于页岩；页岩与砂质纹层页岩均能有效排烃；砂质纹层页岩、页岩的页岩油含量分别为7.22和9.42 mg/g；砂质纹层页岩与页岩的油饱和度指数相当，且两者都具有可动用性；页岩和砂质纹层页岩均具有页岩油勘探潜力。

The Chang 7 member (the seventh member of Yanchang Formation) lacustrine shale in the central Ordos Basin is largely thin and made up of either pure shale or shale interbedded with sandy laminas or thin sand layers of shallow to semi-deep lake facies.Its high content of sand seems quite ideal for achieving positive stimulation responses through fracturing.A discussion and comparison of shale oil exploration targets in the area is recommended for gaining such response.However, no such efforts have been made so far.To judge the oil potential of the shale, samples are collected from both pure shale and shale interbeded with sandy lamina to compare hydrocarbon generation and hydrocarbon expulsion capacities based on geochemical tests and analyses.The results show that shale mainly composed of sapropelic organic matter has higher organic matter abundance than shale interbeded with sandy lamina composed of mixed organic matters.Both are at a low to moderate maturity stage but shale interbeded with sandy lamina is inferior to pure shale in terms of hydrocarbon generation capacity.Both can effectively expel hydrocarbons.Shale interbeded with sandy lamina contains oil at 7.22 mg/g and pure shale 9.42 mg/g.Both can be economically developed and share similar oil saturation index, indicating great oil potential.

10.11743/ogg20210506