Ca2+和Mg2+对Cr3+聚合物凝胶性能影响实验研究

Experimental study on influence of Ca2+ and Mg2+ on performance of Cr3+ polymer gel

关键词:  凝胶  Cr³⁺聚合物  溶剂水类型  驱油效果  海上油田 

Key words:  gel Cr³⁺ polymer  solvent water type  displacement effect

摘要:

为进一步探究Ca²⁺和Mg²⁺对弱凝胶调驱效果的作用机理,针对渤海某油藏地质特征和流体性质,以黏度、黏弹性、阻力系数、残余阻力系数以及采收率为评价指标,从增黏性、抗剪切性、耐温性、黏弹性、渗流特性和调驱效果等方面着手,开展了Ca²⁺和Mg²⁺对弱凝胶性能及其调驱效果影响研究。结果 表明,与注入水相比,软化水虽然矿化度较高,但其几乎不含Ca²⁺、Mg²⁺二价阳离子,利用其所配制Cr³⁺聚合物凝胶溶液中的聚合物分子链受阳离子影响较小,聚合物分子聚集体尺寸较大,其增黏性、抗剪切性、耐温性、黏弹性、渗流特性和调驱效果均强于注入水配制Cr³⁺聚合物凝胶。对海上油田注入用水进行软化处理,即除去水中Ca²⁺和Mg²⁺,有利于改善Cr³⁺聚合物凝胶调驱效果,进一步提高原油采收率。 

Abstract:

In order to explore the function mechanism of Ca²⁺ and Mg²⁺ on weak polymer gel displacement, aiming at geological characteristics and fluid property of one reservoir in Bohai Oilfield, this paper studied on the influence of Ca²⁺ and Mg²⁺ on displacement effect of Cr³⁺ polymer gel through evaluating increasing viscosity, shear resistance, temperature tolerance, viscoelasticity, seepage characteristic and displacement effect, with taking viscosity, viscoelasticity, resistance factor, residul resistance factor and oil recovery as evaluation factor. The results show that, compared with injection water, although softened water has higher salinity, it almost doesn’t contain Ca²⁺ and Mg²⁺. Polymer molecular chains of Cr³⁺ polymer gel prepared by softened water suffer less influence of Ca²⁺ and Mg²⁺ divalent catio, and have bigger polymer molecular aggregation size, its increasing viscosity, shear resistance, temperature tolerance, viscoelasticity, seepage characteristic and displacement effect are all stronger than Cr³⁺ polymer gel prepared by injection water. Using softening process for offshore oilfield injection water, which means eliminating Ca²⁺ and Mg²⁺, is good for improving displacement effect of Cr³⁺ polymer gel, and furtherly enhancing oil recovery.