钙离子对部分水解聚丙烯酰胺冻胶失水的作用机制研究

冻胶失水导致的体积收缩会缩短油田调剖堵水作业的有效期,因此冻胶失水问题需要引起足够的重视。考察了CaCl_2对部分水解聚丙烯酰胺/铬(HPAM/Cr)冻胶失水规律的影响,研究了CaCl_2对HPAM/Cr冻胶微观形貌、HPAM流体力学半径、黏度的影响;并通过红外光谱技术分析了CaCl_2对HPAM/Cr冻胶失水的作用机理。实验结果表明,高浓度CaCl_2会促进HPAM/Cr冻胶失水,而低浓度CaCl_2具有抑制HPAM/Cr冻胶失水的作用;冻胶容水孔洞减少是高浓度CaCl_2加剧HPAM/Cr冻胶失水的内在原因;HPAM流体力学半径越小,HPAM/Cr冻胶失水越严重,低浓度CaCl_2具有提高HPAM流体力学半径的作用;低浓度CaCl_2能够降低HPAM的黏度损耗速率;Ca~(2+)可与HPAM分子羧基中的C—O发生交联反应,该反应是低浓度CaCl_2能够提高HPAM流体力学半径、降低HPAM黏度损耗速率以及抑制HPAM/Cr冻胶失水的根本原因。明确了CaCl_2对冻胶失水的作用机理,可为今后研制抗盐高稳定性冻胶提供理论参考和支持。

Study on mechanism of Ca2+on the syneresis of HPAM gel

Volume shrinkage caused by gel syneresis will shorten the validity of water shutoff treatment in oilfield, so the issue of gel syneresis needs to be taken more attention. In this paper, the effect of CaCl₂ on the syneresis of partially hydrolyzed polyacrylamide/Chromium (HPAM/Cr) gel, the microstructure of HPAM/Cr gel, and the hydrodynamic radius and viscosity of HPAM were investigated. Besides, the mechanism of CaCl₂ on the syneresis of HPAM/Cr gel was studied by infrared spectroscopy. The experiment results indicate that: the CaCl₂solution with high concentration promotes the syneresis of HPAM/Cr gel, while the one with low concentration inhibits the syneresis of HPAM/Cr gel; the decrease in the number of the hole holding the water is the reason why CaCl₂exacerbates the syneresis of gel; smaller HPAM hydrodynamic radius leads to more serious syneresis, and the CaCl₂solution with low concentration can improve the HPAM hydrodynamic radius; the CaCl₂solution with low concentration decreases the viscosity loss rate of HPAM; Ca₂₊ can crosslink with the C-O of the carboxyl in HPAM, which is the basic reason why the CaCl₂solution with low concentration can improve the HPAM hydrodynamic radius, decrease the viscosity loss rate, and inhibit the syneresis. In this paper, the mechanism of CaCl₂ on the syneresis of HPAM/Cr gel is clarified, which can provide theoretical reference and support for the future development of the salt-resistant gel.