表面亲油纳米二氧化硅改变岩石表面润湿性的研究

Studies on Rock Wettability Alternation Caused by Surface Modified Lipophilic Nanometric Silica Treatment

实验研究了注水井增注用的4种商品表面亲油改性纳米二氧化硅改变岩石表面润湿性的能力.kg为0.01～0.1 μm2的胜利义北砂岩岩心,洗油后浸泡在盐水中使表面亲水,注入0.5～3.0 PV 1.5 g/L的纳米二氧化硅柴油悬浮液,静置不同时间,用自吸吸入法测定岩心相对润湿指数W(水、油润湿指数之比).结果表明,W值随注入量增大按指数关系减小,注入量3 PV时达到稳定值,注入量相同时随静置时间(18～40小时)延长而减小;在注入量2 PV、静置40小时条件下除829外的3种样品使亲水岩心(W=1.7)变亲油(W＜1.0),俄罗斯产品101效果最好,W=0.5.用光学投影法测量并图示了表面亲水岩石薄片依次浸泡在煤油、纳米二氧化硅柴油悬浮液、盐水中时接触角随浸泡时间的变化.在煤油中,大理石和灰岩表面变亲油,纳米二氧化硅处理使接触角略有增大;在盐水中,经101处理的大理石表面亲油性至少维持500小时,其余样品处理的大理石迅速变为亲水,各种样品处理的亲油灰岩表面在盐水中经过～0～70小时(样品101)先后变为亲水.玻璃表面在煤油中仍亲水,不同纳米二氧化硅处理玻璃的效果各不相同:迅速亲油化(101和727),～60小时后变亲油(829),接触角增大但仍亲水(902);处理后的亲油玻璃表面在盐水中迅速变强亲水.纳米二氧化硅不能使石英表面亲油化.图6表4参6.

The ability to alternate rock wettability is studied for 4 commercial surface modified lipophilic nanometric silica （LNS） used for stimulating water injection wells, The Yibei＇s sandstone reservoir cores of kg 0.01-0.1μm^2, deoiled and hydrophilizized in .salt water in 〉40 hrs, are treated by injecting 0.5-3.0 PV of 1.5 g/L LNS suspension in diesel oil and standing in different time duration and then tested by using spontaneous imbibition method for determining relative wettability index, W （ratio of water to oil wet.ability indexes）. It is shown that the W values decrease with increasing the suspension volume injected （SVI） according to a power law and reach their equilibrium when SVI = 3 PV and with increasing time duration of standing （18-40 hrs） at equal SVI; with 3 LNS samples besides one （LNS 829）, the hydrophilic cores of W= 1.7 become lipophilic （ W〈 1.0） at SVI = 2 PV in 40 hrs of standing while Russian LNS 101 appears to be the best, giving W = 0.5. The changes with time of contact angle on platelike hydrophilic rock samples being immersed in kerosene, LNS suspensions, and salt water successively are measured by optical projection method and graphically demonstrated. The hydrophilic surfaces of marble and carbonatestone become lipophilic in kerosene and a slight increase in contact angle on them is observed in LNS suspension; in salt water, the marble surfaces treated by LNS 101 keep lipophilic at least in 500 hrs and those treated by other LNSs become hydrophilic in short time, the carbonatestone surfaces treated by different LNSs become hydrophilic in different time, -0-70 hrs （for 101 ）. The glass surfaces are hydrophilic when immersed in kerosene and the effects of different LNSs are different： become lipophilic in short time （for lot and 727） or in -60 hrs （for 828） or keep hydrophilic with contact angle raised （for 902） ; the LNS treated glass surfaces become highly hydrophilic in salt water. LNSs can not make quartz surfaces lipophilic.