利用物理模拟实验,开展了特低渗透油藏水驱后氮气驱油的效果及特征研究.结果表明:氮气驱可在水驱波及区内提高原油采收率3.4％左右,见气前与低气液比阶段是油井的主要采油期,后续注气压力梯度为注水压力梯度的1/4 ～ 1/3；多个油层合注合采时,氮气驱波及程度低,低渗透层不具备吸气能力,气体完全进入高渗透层；气窜在高渗透层形成后,剩余油主要分布于低渗透层.选用SCT-1复合凝胶体系对已形成气窜的高渗透层进行封堵,调节高渗透层与低渗透层的吸气能力,封堵后的高渗透层吸气能力变弱,低渗透层剩余油被有效开发.注气封堵结合可有效抑制气窜,提高氮气驱波及程度.%With the help of the physical simulation experiments, the effects and characteristics of subsequent nitrogen displacement after the water flooding in ultra-low permeability oil reservoirs are investigated and studied. The results show that the displacement recovery factor can be enhanced by 3. 4% or so within the water swept area. The oil production is mainly conducted during the periods of non-gas and low gas-liquid ratio, the pressure gradient of subsequent gas injection is 1/4-1/3 of that of the water flooding; when commingling of the injection and production of many oil layers, the swept degree of the nitrogen flooding is rather low, there is no ability of gas inhalation for the low-permeability oil reservoirs, while the case is just on the contrary for those high-permeability ones; after the gas channeling is conducted in the high-permeability oil reservoirs, the remained oil is mainly distributed in the low-permeability ones. The gas-crossed high-permeability reservoirs are plugged by SCT-1 combined gel system to adjust the inhalation abilities of the above two kinds of reservoirs. Finally the ability of the high-permeability reservoirs becomes weaker, and in the meantime the remained oil in the low-permeability reservoirs is effectively devel-oped. To sum up, the combination between the gas injection anrl plugging can effectively inhibit the gas channeling and improve the swept degree of the nitrogen flooding.
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