黏土-水悬浮体系热滚老化后的分散性

Dispersion Behavior of Clay-water Suspension System after Heat Rolling Aging

黏土作为钻井液重要的基础材料,黏土-水分散体系热滚老化后的分散行为直接影响到钻井液流变性、失水造壁性和沉降稳定性等性能,尤其对于高温高密度钻井液。通过激光粒度仪对黏土-水分散体系热滚老化后的粒径中值进行研究,考察黏土种类、无机盐和氢氧化钠等因素对黏土-水分散体系的影响。结果表明,随老化温度升高,高岭石、海泡石和凹凸棒石的黏土-水悬浮体系粒径中值稳定,表现出对温度因素不敏感,但高岭石和凹凸棒石粒径要明显小于海泡石。膨润土-水悬浮体系随老化温度升高,温度低于90℃时,黏土水化分散占主导作用,分散度增加;温度在90~180℃时,水化分散和去水化聚结两种因素相对平衡,分散度相对稳定;温度在180~200℃时,去水化聚结占主导作用,分散度降低;氢氧化钠加入并未影响膨润土-水分散体系的分散规律,只是加剧了膨润土的分散程度,温度超过150℃时这种差异性消失。膨润土-无机盐水悬浮体系随老化温度升高,水化分散占主导作用,分散度增加,并在120℃趋于稳定。膨润土高温水化分散和去水化聚结作用均对钻井液尤其是高密度钻井液性能造成不利影响,降低膨润土加量或者使用分散度对温度不敏感的黏土如高岭土等以及加入适量无机盐可以降低这种不利影响。

Clay is a basic material of drilling fluid,dispersion behavior of clay-water suspension system after heat rolling aging has important influences on drilling fluid properties,especially high density drilling fluid,such as rheological property,fluid losing and wall building property,and sedimentation stability.Influencing Factors of particle size distribution of clay-water suspension system was studied by laser particle size analyzer including clay kinds,inorganic salt and sodium hydroxide.The results show that particle size distribution of clay-water suspension system such as kaolin,sepiolite and attapulgite are stable,however,particle size of sepiolite ia bigger than kaolin and attapulgite.With the increasing of aging temperature,particle size distribution of bentonite-water suspension system follow the law:below 90℃,hydration dispersion plays a dominant role,dispersity of bentonite increase;90~180℃,hydration dispersion and dehydration coalescence keep relative balance,dispersity of bentonite is stable;180~200℃,dehydration coalescence plays a dominant role,dispersity of bentonite decrease;addition of sodium hydroxide increased only dispersity of bentonite,dispersity difference disappearedmore than 150℃.With the increasing of aging temperature,particle size of bentonite-inorganicwater suspension system decreased,dispersity of bentonite increase and keep stable more than 120℃.Hydration dispersion and dehydration coalescence both go against the effect of drilling fluid,this disadvantageous effect could be decreased or eliminated by decreasing addition of bentonite,or using clay such as kaolin and attapulgite,or adding inorganic salts.