In order to find out whether the method based on water or the one based on mercury saturation is better for calculating the fractal dimension of the pore structure of low permeability reservoirs, this paper takes the 41 core plunger sample of Upper Triassic Xujiahe Formation reservoir as an example to calculate the fractal dimension of the pore structure by two methods separately. The results show that the fractal dimension calculated by mercury saturation corresponds with the displacement pressure, sorting coefficient and other pore structure parameters well, the displacement pressure increases while the sorting coefficient decreases with the increase of fractal dimension. So the fractal dimension calculated by this method can quantitatively describe the parameters and the complexity of reservoir pore structure. While on the other hand, the fractal dimension calculated by water saturation corresponds with the displacement pressure, with poor sorting of coefficient and other pore structure parameters, to analyze this phenomenon. It is hoped that the mercury injection data obtained by conventional mercury injection techniques can be used to calculate the fractal dimension of reservoir pore structure if possible.%为对比基于含水饱和度和汞饱和度2种方法计算低渗透碎屑岩储层孔隙结构分形维数的优劣性,分别采用2种方法对川中地区须家河组41块储集岩的毛细管压力曲线进行分形维数计算.结果表明:采用汞饱和度计算的孔隙结构分形维数与排驱压力、分选因数等表征储层孔隙结构的参数相关性较好.随着岩样分形维数增大,排驱压力增大、分选因数减小,相关性明显.采用含水饱和度计算的孔隙结构分形维数与排驱压力、分选因数等相关性较差.在条件许可时,可利用恒速压汞实验计算储集岩孔隙结构分形维数.
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