岩心中硅酸凝胶堵剂突破压力的研究

Breakthrough Pressure of Silicic Gel in Artificial Cores

在不同渗透率k(0.7～1、3～4、11～13μm2)的人造石英砂岩心上,测定了4个配方实验硅酸凝胶堵剂(4%、6%、8%、10%水玻璃+10%盐酸)的突破压力pt。堵剂用矿化度1.12×104mg/L、含Ca2++Mg2+377.8mg/L的注入水配制。堵剂注入岩心后在80℃下密闭放置24h使之凝胶化,测得对水的比突破压力p′t(单位岩心长度的突破压力)的对数值与岩心初始平均渗透率k的对数值之间有线性关系,lgp′t随lgk的增大而降低。设水在岩心内的流动为稳态单相流,导出了lgp′t与lgk之间的线性关系式,利用该式计算了4种实验堵剂的lgp′t～lgk直线斜率。当凝胶化温度升高时(40℃→60℃→80℃),测得的p′t值增大。在岩心渗透率0.7～1μm2,凝胶化温度80℃时,用蒸馏水配制的4种实验堵剂,其突破压力普遍大大低于用注入水配制的4种实验堵剂。图2表4参1。

The breakthrough pressure, p_t, is determined for artificial cores of different permeability, k(0.1—1,3—4,11—13 μm^2), having plugged by four experimental cilicic gelling fluids composed of 4%,6%,8%, and 10% water glass, respectively, plus 10% HCl. The fluids are prepared in a recycled produced water of TSD=1.12×10~4 mg/L and Ca^(2+)+Mg^(2+) concentration 377.8 mg/L. For these cores with the fluids injected and gelated at 80℃ in 24 h under hermitic condition, linear relationships exist between the logarithm of specific breackthrough pressure, p′_t, and logarithm of initial average core permeability, k, while lg p′_t decreases with increasing lg k. Suppose that the flow of water in the cores is an one-phase stead flow, a linear expression of lg p′_t in terms of lg k is deduced and used to determining the slop of strait lines lg p′_t-lg k for four experimental fluids. The p′_t values determined increase when the gelation temperature raises (40℃→60℃→80℃). All the values of breakthrough pressure determined for four experimental fluids prepared in distilled water are much lower than that in recycled produced water on cores of permeability 0.7—1 μm^2 at gelation temperature 80℃.