降低启动压力的表面活性剂体系在朝阳沟油田的应用

Application on Surfactant System of Decreasing Start-up Pressure Gradient in Chao Yanggou Oilfield

针对朝阳沟低渗透油田注水过程中注水压力上升较快、欠注严重的问题,进行了朝阳沟油田降压增注表面活性剂体系的筛选工作,最终确定表面活性剂体系的配方为0.2%石油磺酸盐类表面活性剂T702-40~#+0.5%Na_2CO_3。实验结果表明,该表面活性剂体系与原油间平衡界面张力能够达到2×10^(-2)mN/m,耐温、抗盐性好,与朝阳沟油田注入水和地层水配伍性好,能够使岩石的润湿性发生反转,比水驱提高采收率5%左右。该表面活性剂体系驱替计算得出的可流动渗透率值约比水驱可流动渗透率值大15%,具有明显的降低启动压力的作用,并进行了表面活性剂体系降低启动压力的机理分析。朝阳沟油田朝82-152井区矿场试验结果表明,该表面活性剂体系能够降低启动压力,使油层吸水能力提高,使低渗透储层动用比例提高,7口油井累积增油1768t。

For the characteristics of water injection pressure rising fast and difficultly injecting in the water injecting process in Chao Yanggou low permeability oilfield, the lowering pressure and increasing injecting surfactant system was screened and the recipe of surfactant system was determined as follows： 0.2% Petroleum sulfonate salts surfactant T702-40 surfactant＋ 0.5% NaCO3. The experimental results indicated that the equilibrium interfacial tension between the surfactant system and the Chao Yanggou crude oil could reach 2 x 10-5 mN/m, the surfactant system had good temperature resistance and salinity resistance, and had good compatibility with injecting water and formation water, and could make the rocky wettability reverse, which make the oil recovery be improved by about 5%. The movable permeability value calculated from the surfactant system flooding was 15% bigger than that of water flooding, which could reduce start-up pressure obviously. And the mechanism of surfactant system reducing start-up pressure was researched. Field test results of 82-152 well area in Chao Yanggou oilfield indicated that the surfactant system could reduce start-up pressure, improve reservoir water absorbing capacity, increase producing proportion of low permeability reservoir, and cumulative oil increment of 7 wells was 1768 t.