低渗透压力条件下砂岩渗透性质的CT试验

Permeability experiment of sandstone under low seepage pressures by X-ray CT test

运用岩石高压三轴加载装置和渗透压加载装置,对砂岩进行固定应力变渗透水压力试验,同时借助SOMATOMPLUS螺旋CT扫描机进行实时观测。通过试验结果分析,推出了基于CT数的岩石空隙率公式,从CT尺度上分析了岩石空隙率、渗透速度、渗流速度、微孔隙直径、渗透率等随渗透水压力的变化规律。结果表明:岩石的渗透参数随渗透压力的增加而增大,渗透参数随渗透压力的变化呈对数关系,这是由于渗透水压力使岩石内部空隙发生变形,这一变形为弹性变形;而渗流速度与渗透水压力呈线性关系,符合宏观尺度渗流的达西定律。

The seepage experiment of a sandstone sample under constant compression was conducted in the laboratory using triaxial loading apparatus, seepage pressure loading apparatus and medical SOMTOM - PLUS CT scanner. By analyzing the results of this experiment, the porosity formula of rock represented by CT number was proposed in CT scale. Based on this porosity formula, we worked out the porosity, the real flow rate in porous rock, the specific discharge, permeability and the diameters of micro - pore with increasing seepage pressures. The results showed that the seepage parameters increase with the ascendant of seepage pressures. Logarithm relations between the seepage parameters and seepage pressures were proposed. The seepage pressures make the micro - pores within rock enlarged. This deformation within rock is elastic due to seepage pressures before macro - crack occurs.The relation between the specific discharges and seepage pressures are linear and consistent with the Darcy law in macro- scale.