The effect of inorganic salt precipitation on oil recovery during CO2 flooding: A case study of Chang 8 block in Changqing oilfield, NW China

YUAN Zhou,LIAO Xinwei,ZHANG Kuaile,ZHAO Xiaoliang,CHEN Zhiming

Table 3 Core porosity and permeability tested before and after the experiment.

Experiment No. Displacement fluid Temperature/ °C Displacement pressure difference/MPa Displacement pressure/ MPa Calcium ion mass concentration/ (mg·L-1) Permeability before experiment/ 10-3 μm2 Permeability after experiment/ 10-3 μm2 Permeability change rate/% Porosity before experiment/ % Porosity after experiment/ % Porosity change rate/% 1 Distilled water 20 3 19 0 0.1219 0.1233 1.14848 8.50 8.62 1.41176 2 20 4 20 0.1222 0.1245 1.88216 8.61 8.81 2.32288 3 20 5 21 0.1266 0.1316 3.94944 8.83 9.18 3.96376 4 20 6 22 0.2664 0.2847 6.86936 7.90 8.55 8.22784 5 30 6 22 0.3585 0.3898 8.73082 9.01 10.31 14.42840 6 50 6 22 0.389 0 0.4392 12.90480 11.57 13.66 18.06390 7 80 6 22 0.4032 0.538 0 33.43250 11.68 15.45 32.27740 8 Formation water 20 3 19 10590 0.1294 0.1307 1.00463 8.05 8.10 0.62111 9 20 4 20 0.1299 0.1319 1.53964 8.41 8.49 0.95124 10 20 5 21 0.1316 0.1357 3.11550 8.50 8.59 1.05882 11 20 6 22 0.2225 0.235 0 5.61797 8.96 9.12 1.78571 12 30 6 22 0.3688 0.392 0 6.29067 9.82 10.22 4.07332 13 50 6 22 0.3337 0.3589 7.55169 8.52 9.33 9.50704 14 80 6 22 0.3614 0.4678 29.44100 11.48 14.87 29.52960