C_(12)NBr对黄原胶/Cr(Ⅲ)凝胶体系粘弹性的影响

Effect of C_(12) NBr on the Viscoelasticity of Gel Containing X anthan Gum/Cr(Ⅲ)

以三价铬离子(Cr3+,Cr(Ⅲ))为交联剂制备的黄原酸(XC)凝胶在油田开发过程中具有许多用途,应用RS75型流变仪测定了含有和不含有阳离子表面活性剂C12NBr(十二烷基-氧丙基-β-羟基-三甲基溴化铵)时凝胶体系粘弹性的变化规律.结果表明,XC凝胶体系不符合理想的线性粘弹性模型,储能模量(G')和耗能模量(G″)在切力较低时变化甚微,切力较高时两者皆降低,但降低的幅度不同,因而G'～τ(应力)和G″～τ曲线出现交点,此交点随C12NBr浓度增大而降低.结合等温线的研究表明,C12NBr能结合到XC分子上,破坏凝胶的网络结构.然而,在一定条件下其复合粘度(η)随频率和切力的变化出现最低值现象的机理还有待进一步探讨.

Water based gels,comprising Xanthan gum(XC)cross linked with cross lin king agen t,such as trivalent chromic ions(Cr (Ⅲ)),are now finding widesp read use for near well-bore water and gas shut-off in the oil industry.The st udy on the rheolo gy of gel is very important to understand and to improve the i n-situ appli-cation of the gels technology.In this paper the viscoelasticity of the systems of XC cross-linked with C r(Ⅲ)in the presence of dode-cyl-oxypropyl-a-hydroxyl-trimethyl-ammonium bro mide(C 12 NBr )has been investigated.The viscoela sticity measurements were performe d on a RS 75controlled stress rheometer(Haake Co.)operating in an oscillati ng mode.Determination of the G' and G″vs shear stress was performed at a fixed frequency of 1.0Hz and the moduli vs frequency relationsbip were determ ined at a fixed shear stress of 1Pa.For the XC aqueous solution,the storage(i.e .,elastic)modulus G' could not be measured under the experimental condition. For the cross linking system G' value increased it was and always la rger than t he G″value at shear stress less than 0.5P a,i.e.,the gelling system has more sol id or elastic properties.The elasticity of gel is weakened and its vis cosity is enhanced in the presence of C 12 NBr.The main effect of the a ddition of C 12 NBr to XC gel is to destroy the network structure of the gel.It is resulted from the binding between C 12 NBr and XC,i.e.,c ross linking agent Cr (Ⅲ)was replaced by C 12 N + .This is t estified by binding isotherom of C 12 NBr on XC.