大庆扶余油层致密储层孔隙结构及非均质性研究

扶余油层是大庆油田的主力产油层之一，发育的致密储层为非常规油气聚集的重要场所，但是孔隙结构较为复杂，非均质性极强。为了研究扶余油层不同类型致密砂岩储层的孔隙结构及其非均质性，本文应用分形几何理论，在高压压汞实验资料的基础上，结合物性测试以及矿物分析对矿物组分的测定，选取扶余油层K1q3、K1q4的8块样品进行分析，根据压汞曲线形态的差异、孔喉半径及排驱压力特征划分出3类储层：低排驱压力微-微细喉道型、中排驱压力-微喉道型、高排驱压力-吸附喉道型。计算致密砂岩储层孔隙结构的分形维数并讨论其地质意义。结果发现：各类储层均呈现两段式分形特征，得到两个分形维数：D1范围为2.9908～2.9956，平均为2.9933，D2范围为2.5738～2.6664，平均为2.6101。大庆扶余油层孔喉结构的复杂程度及非均质性对致密储层的储集空间和储层的渗流能力具有较强的控制作用，分形维数越大，孔喉结构越复杂，非均质性越强。

Study on Pore Structure and Heterogeneity of Tight Reservoir in Fuyu Oil Reservoirs, Daqing

In order to study the pore structure and fractal characteristics of different types of tight sandstone reservoirs in Fuyu oil layer, we selected 8 samples from Fuyu oil layer K1q3 and K1q4 for analysis based on the experimental data of high pressure mercury injection, combined with physical property test and mineral analysis to determine mineral components. Three types of reservoirs were classified according to the shape difference of mercury injection curve, pore throat radius and displacement pressure characteristics: low displacement pressure-micro throat type, medium displacement pressure-micro throat type, and high displacement pressure-adsorption throat type. The fractal dimension of pore structure of tight sandstone reservoir was calculated and the influences of reservoir physical characteristics, pore throat structure parameters and quartz and calcite content on the fractal dimension were discussed. The results showed that all types of reservoirs presented two-stage fractal characteristics, and two fractal dimensions were obtained: D1 ranged from 2.9908 to 2.9956, with an average of 2.9933; D2 ranged from 2.5738 to 2.6664, with an average of 2.6101. The complexity and heterogeneity of pore throat structure in Fuyu oil reservoir in Daqing have a strong control on the tight reservoir space and seepage capacity. The larger the fractal dimension is, the more complex the pore throat structure is and the stronger the heterogeneity is.