致密砂岩岩电参数实验方法对比研究

Comparative study on experimental methods of rock-electrical parameters of tight sandstone

岩电参数是电测井资料评价含水饱和度的重要参数,主要通过多种室内实验方法获取,但不同方法所得岩电参数具有差异性。针对岩电参数实验中的关键环节,实验研究了洗盐前与洗盐后、常规抽真空饱和与注CO_(2)置换抽真空饱和、自吸增水法与气驱法岩电参数的差异性。结果表明:洗盐后的岩样孔隙空间变大,模拟地层水赋存连续性增强,岩石的导电能力增强,岩石电阻率测定前需要对岩心进行清洗处理;注CO_(2)置换真空饱和对于特低渗、超低渗岩心饱和程度达标率高,更能反映真实的电阻率值;当岩样为超低渗时,自吸增水法较气驱法线性关系更好,测试点数分布均匀。选取某地区致密砂岩密闭取心井岩样,利用本文优选出的测试实验方法获取岩电参数,进而计算得到的含水饱和度与实测原始含水饱和度吻合度更高。本文研究可以为致密砂岩储层含水饱和度预测和精度保证提供有力支撑。

Rock-electrical parameters are important parameters for evaluating water saturation with electric logging data,which are mainly obtained by a variety of laboratory experimental methods,but the rock-electrical parameters obtained by different methods are different.Aiming at the key links in the experiment of rock-electrical parameters,the differences in rock-electrical parameters before and after salt washing,conventional vacuum saturation and CO_(2)injection displacement vacuum saturation,self-priming water addition method and gas flooding method were experimentally studied.The results show that the pore space of rock samples after salt washing becomes larger,the occurrence continuity of simulated formation water is enhanced,the electric conductivity of rock is enhanced,and the core needs to be cleaned before rock resistivity measurement.The displacement vacuum saturation by CO_(2)injection has a high saturation tallying rate of ultra-low permeability and ultra-low permeability core,which can better reflect the real resistivity value.When the rock sample is ultra-low permeability,the self-priming method is more linear than the gas drive method,and the distribution of test points is uniform.The tight sandstone coring well samples in a certain area are selected,and the rock-electrical parameters are obtained by using the test and experiment method selected in this paper.The calculated water saturation is in better agreement with the measured original water saturation.This study can provide strong support for the prediction and accuracy assurance of water saturation in tight sandstone reservoirs.