页岩吸附油定量评价模型——以松辽盆地北部白垩系青山口组一段为例

Quantitative evaluation model of shale oil adsorption:A case study of the first member of Cretaceous Qingshankou Formation in northern Songliao Basin,NE China

以松辽盆地北部白垩系青山口组一段页岩为例,在研究成熟度演化对干酪根吸附-溶胀的控制作用的基础上,考虑页岩样品中具有吸附油的黏土孔表面积以及地层温度的影响,通过开展自然演化干酪根样品的溶胀油实验和由泥页岩分离获得的黏土样品的吸附油实验,提出一种综合干酪根吸附-溶胀和黏土孔吸附的页岩吸附油量评价模型,并分别建立了干酪根吸附-溶胀油量和矿物吸附油量评价图版。结果表明:①青山口组一段页岩成熟度增加,干酪根吸附-溶胀油能力(Mk)降低,在Ro值为0.83%~1.65%时,Mk值约为50~250 mg/g;②页岩中黏土以吸附沥青质为主,黏土孔的吸附油能力(Mc)为0.63 mg/m^(2),黏土孔壁中平均约15%的表面被吸附油占据;③中—低成熟阶段,页岩吸附油主要受有机碳含量的控制,而当Ro>1.3%时,页岩吸附油量以黏土吸附为主;④与地层原位对比,地表室温评价结果高估吸附油量为8%~22%,平均约15%。该评价模型能够揭示不同成熟度页岩油的赋存机制,为地层温度条件下页岩油的储量评估提供了一种新的途径。

A quantitative evaluation model that integrates kerogen adsorption and clay pore adsorption of shale oil was proposed,and the evaluation charts of adsorption-swelling capacity of kerogen(Mk)and adsorbed oil capacity of clay minerals(Mc)were established,taking the 1st member of Cretaceous Qingshankou Formation in the northern Songliao Basin as an example.The model and charts were derived from swelling oil experiments performed on naturally evolved kerogens and adsorbed oil experiments on clays(separated from shale core samples).They were constructed on the basis of clarifying the control law of kerogen maturity evolution on its adsorption-swelling capacity,and considering the effect of both the clay pore surface area that occupied by adsorbed oil and formation temperature.The results are obtained in four aspects:(1)For the Qing 1 Member shale,with the increase of maturity,Mk decreases.Given Ro of 0.83%-1.65%,Mk is about 50-250 mg/g.(2)The clay in shale adsorbs asphaltene.Mc is 0.63 mg/m^(2),and about 15%of the clay pore surface is occupied by adsorbed oil.(3)In the low to medium maturity stages,the shale oil adsorption is controlled by organic matter.When Ro>1.3%,the shale oil adsorption capacity is contributed by clay pores.(4)The oil adsorption capacity evaluated on the surface at room temperature is 8%-22%(avg.15%)higher than that is held in the formations.The proposed evaluation model reveals the occurrence mechanisms of shale oils with different maturities,and provides a new insight for estimating the reserves of shale oil under formation temperature conditions.