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为明确CO_2驱过程中CO_2-地层水-岩石的相互作用对特低渗透砂岩不同尺度孔喉的伤害情况,利用核磁共振技术定量计算驱替后砂岩岩心的孔喉堵塞程度。研究结果表明,实验后产出液的pH值低于实验前的地层水,且离子浓度的变化反映长石和碳酸盐矿物发生了溶解;在驱替时间为60 h,T2值在0.1~10.0 ms内的较小孔喉有11.21%~13.25%被堵塞;反应时间为120 h,较小孔喉平均堵塞程度达到25.25%;而T2值在10.0~1 000.0 ms内的较大孔喉始终未发生明显堵塞。CO_2与矿物的溶解反应对岩心渗透率的伤害明显高于对孔隙度的伤害,且伤害程度与反应时间呈正相关,与CO_2注入压力无明显相关性。
In order to clarify the water-rock interaction between CO_2-formation and CO_2 flooding, the paper deals with the damage of pore throats at different scales in ultra-low permeable sandstone. The degree of pore-throat blockage in sandstone core after flooding is quantitatively calculated by using nuclear magnetic resonance technique. The results show that after the experiment, the pH value of the produced liquid is lower than that of the pre-experimental formation water, and the change of the ion concentration reflects that the feldspar and the carbonate mineral dissolve. When the displacement time is 60 h and the T2 value is 0.1-10.0 The small pore throats of 11.27% ~ 13.25% were blocked in the second time. The reaction time was 120 h, the average small pore throats was 25.25%. The larger pore throats of T2 ~ 10.0 ~ 1 000.0 ms Significant blockage occurred. The dissolution of CO_2 and minerals damages the core permeability obviously higher than that of the porosity, and the degree of injury is positively correlated with the reaction time and has no obvious correlation with CO_2 injection pressure.