含油多孔介质二维弥散特性初步研究

Study on Characteristics of 2-D Hydrodynamic Dispersion in Oil-Contaminated Porous Medium

为了研究含油多孔介质的二维水动力弥散特性,控制砂土中柴油和机油含油率为0、1%、2%,作为供试的含油多孔介质,采用自己设计的二维水动力弥散试验装置测定示踪剂(氯化钙)的穿透曲线,并定量确定了含油砂土的有效孔隙度、纵向弥散度、横向弥散度以及砂土中孔隙水的流速。试验结果表明,有效孔隙度随石油含量的增加而减小,而且含柴油砂土的有效孔隙度减小比含机油砂土更加显著;在纵向上,示踪剂浓度峰值的到达时间和峰值浓度的大小主要取决于孔隙水流速的大小,孔隙水流速越大,示踪剂达到浓度峰值的时间越短,且峰值浓度越大;含机油砂土的纵向弥散度小于清洁砂土,而含柴油砂土的纵向弥散度大于清洁砂土;不同含油率砂土的纵向弥散度变化范围为0.133～0.370cm,横向弥散度变化范围为9.83×10-3～4.64×10-2 cm,纵向弥散度均大于其横向弥散度。

In order to study the characteristics of 2-D hydrodynamic dispersion in oil-contaminated porous medium, sand with 0, 1.0%, 2. 0% of diesel and engine oil were taken as the porous medium. And then, a self-designed two-dimensional hydrodynamic dispersion apparatus was used to measure the breakthrough curves of a tracer （CaC12）. The effective porosity, longitudinal dispersivity, transverse dispersivity and pore water velocity of each sand sample were determined quantificationally. The results show that the ef- fective porosity of the sand decreases with the increase of oil content, and the decrease induced by diesel is greater than that by engine oil. In the longitudinal direction, both the peak-reaching time of tracer con- centration and the peak concentration depend mainly on the pore water velocity. The greater the pore water velocity is, the shorter the peak-reaching time of tracer concentration is, and the higher the peak concentration is. The longitudinal dispersivity of sand contaminated by engine oil is smaller than that of pure sand, while the longitudinal dispersivity of diesel-contaminated sand is bigger than that of pure sand. The longitudinal dispersivity values of coarse sand with different oil contents range from 0. 133~0. 370 cm, while the transverse dispersivity values, which are smaller than the longitudinal dispersivity values, range from 9. 83 ×10^-3to 4.64×10^-2cm.