DSB显著提高羧酸盐驱油体系抗钙镁离子能力的研究

测定了工业品级的天然混合长链烷基羧酸盐(SDC)以及与3-(N,N-二甲基十二烷基胺)-2-羟基-丙磺酸(DSB)复配驱油体系的界面张力(ITFmin), 分别得出其抗钙镁离子的能力为400和5000 mg/L. 选择试剂级十二烷基羧酸钠与DSB复配, 测定了不同配比溶液的表面张力值和临界胶束浓度cmc, 结合长链烷基脂肪酸与钙离子的溶度积Ksp, 分析了对不溶性长链烷基羧酸盐形成的影响. 根据现场驱油体系配方, 计算了两者在溶液中的摩尔配比为4:1时的十二烷基羧酸盐在胶束中的摩尔分数xm1为0.51, 相互作用参数βm值为-3.11, 反映了两者有较强的相互作用. 采用量子化学方法, 对由1个十二烷基羧酸分子、1个DSB分子及1个二价钙离子组成的模型复合物进行了能量计算和电荷分布计算, 得出在长链烷基羧酸盐和DSB两者混合胶束的界面层中存在负电荷空穴, 提出二价金属离子被络合的模型, 合理地解释了实验事实.

Investigation in Extremely Improved Ability of Resisting Ca2+ and Mg2+ for Alkyl Carboxylates Flooding System with Adding DSB

The natural mixed carboxylates(abbreviated as SDC) can be used to extremely improve the ability of resisting Ca2+ and Mg2+ when adding 3-(N,N-dimethyldodecylammonio)-2-hydroxy-propanesulfonate(abbreviated as DSB). SDC and SDC-DSB flooding system are tolerant to Ca2+ and Mg2+ up to 400 mg/L and 5.0×103 mg/L respectively. Their IFTmin are 10-3 mN/m, and the oil recovery reach 20% by using the core flood experiment. The surface tension and the critical micelle concentrations were measured for the systems of the sodium dodecanoate and DSB. By analysis the solubility product(Ksp) of fatty acid salt, we can know that the concentration of Ca2+ and Mg2+ ions in solution is increased along with the decrease of concentration of free fatty acid group. The interaction parameter βm between sodium dodecanoate and DSB can be calculated as -3.111, which reflects more strong reaction force. The mole fraction xm1 of sodium dodecanoate in the mixed micelles is 0.51. By the software Gaussian 03, we calculated the minimum energy for compound of DSB/dodecyl acid/Ca2+, and obtained the charge of dominating atom in this compound. These results show there are probably many “negative-charge hole” in the surface layer of micelle, thus, the Ca2+ and Mg2+ in solution can combined in the surface layer of micelles. So we can explain why the alkyl carboxylates flooding system extremely improved the ability of resisting to Ca2+ and Mg2+ with adding DSB.