渗透率级差对油层实际气液比的影响

Effect of Permeability Ratio on Real Proportionalty of Oil Layers

为揭示低渗透非均质油藏实际气液比的变化规律,提高气液交替泡沫驱措施成功率,室内进行填砂管物理模拟试验,按气/液体积流量1∶1的比例交替注入空气及质量分数为0.1%的起泡剂溶液(0.1 PV起泡剂+0.1 PV氮气交替注入),注采达到平衡后(压力恒定或注入速度等于产出速度),观察不同渗透率级差的高、低渗管的产气量、产液量以及气液比变化规律,研究渗透率级差对泡沫驱油层气液比的影响规律。研究结果表明:当渗透率级差在1.0数14.6的范围内,随着级差的增大,高渗管的载气速率和载液速率逐渐增高,而低渗管逐渐降低,但变化幅度不大,泡沫驱能有效改善地层非均质性。当渗透率级差在14.6数38.4的范围内,随着级差的增大,高渗管的载气速率和载液速率急剧上升,而低渗管的载液速率和载气速率急剧下降,其中高渗管气液比稳定在1∶1,能理想发泡,低渗管实际气液比开始偏离此数值,起泡效果不理想,低渗管主要降低油水界面张力来提高单管采收率。当渗透率级差在38.4数88.3的范围内,大量的气、液沿着高渗层流动,气液比稳定在1∶1左右,而低渗管载气速率仅为1.68 m L/h,载液速率仅为0.04 m L/h,实际气液比严重偏离1∶1。此时,低渗管处于泡沫驱启动极限,产生严重的所谓"气走气路、水走水路"的现象。图9表3参10。

In order to reveal the change law of the actual gas-liquid ratio of low-permeability heterogeneous reservoirs,and improve the success rate of gas-liquid alternating foam flooding measures,the indoor physical simulation test of sand filling pipe was carried out by alternately injecting air and a foaming agent solution with 0.1% mass fraction(0.1 PV foaming agent + 0.1 PV nitrogen alternately)according to the ratio of gas/liquid volume flow 1∶1. After the equilibrium was reached,the pressure being constant or the injection speed being equal to the output speed,the gas production,liquid production and gas-liquid ratio change of high and low permeability pipes with different permeability grades was observed,and the effect of the permeability difference on gas-liquid ratio of the foam flooding was probed. The experimental results showed that when the permeability difference was in the range of 1.0- 14.6,the carrier gas velocity and carrier fluid velocity of the high-permeability pipe gradually increased with the increase of the grade difference,while the low-permeability pipe gradually decreased,but the change was not distinct,and the foam drive could effectively improve the formation heterogeneity. When the permeability difference was in the range of 14.6-38.4,the carrier gas velocity and the carrier fluid velocity of the high-permeability pipe rose sharply with the increase of the permeability difference, while the carrier liquid velocity and the carrier gas velocity of the low-permeability pipe decreased sharply,at the same time,the gas-liquid ratio of the high-permeability pipe was stable at 1∶1,which was ideal for foaming,while that of the low-permeability pipe deviated from this value,the foaming effect being not ideal,the enhanced oil recovery of the low-permeability pipe mainly realized by decreasing the oil-water interfacial tension. When the permeability difference was in the range of 38.4-88.3,a large amount of gas and liquid flowed along the high permeability pipe,and the gas-liquid ratio of the high-permeability pipe was stable at about 1∶1,while the carrier gas velocity of the low permeability pipe was only 1.68 mL/h,and the carrier liquid velocity was only 0.04 mL/ h,and the actual gas-liquid ratio deviated significantly from 1∶1,at this time,the low-permeability pipe was at the limit of the foam drive,resulting in a serious phenomenon of so-called "air-moving gas path,water walking water path".