利用二氧化碳的缓慢释放控制聚丙烯酰胺在含柠檬酸铬水溶液中的粘度（英文）

Enhanced Viscosity of Poly（acrylamide）Solution in the Presence of Chromium Citrate Triggered by Release of CO2

部分水解聚丙烯酰胺广泛用在堵水调剖以提高石油采收率等采油工程领域．本文报道了一种可以有效延缓部分水解聚丙烯酰胺在60℃水中与铬离子交联的新技术，首先利用柠檬酸和铬离子之间的络合来有效阻止部分水解聚丙烯酰胺与铬离子之间的交联作用，随着包埋在水溶液中碳酸氢根离子分解释放二氧化碳，溶液的pH值逐渐增加，导致部分水解聚丙烯酰胺电离度增加，因此与铬离子的交联作用也逐渐增强．当部分水解聚丙烯酰胺与铬离子的交联作用大于铬离子与柠檬酸之间络合作用时，溶液的黏度逐渐增加．在封闭条件下，以及由于磷酸二氢钾的缓冲作用，二氧化碳的释放是缓慢进行的，而三聚氰胺与部分水解聚丙烯酰胺氢键相互作用又进一步阻止了羧基的电离，因此部分水解聚丙烯酰胺与铬离子的交联作用可以被延缓到近一个月的时间，完全满足了利用深度堵水调剖方法提高石油采收率的工程技术要求．

Partially hydrolyzed polyacrylamide （HPAM） has been widely used for water shut-off and profile control to enhance oil recovery. Herein, we reported a novel technique by which the crosslinking between HPAM and Cr3＋ in aqueous solutions at 60 ℃ can be delayed effectively. Citric acid was selected as an organic complexing agent of Cr3＋ so that the crosslinking between HPAM and Cr3＋ can be prevented completely. Due to the decomposi- tion of the bicarbonate （HCO3-） embedded in solution, CO2 released from solution and the pH value of solution increased gradually. The degree of ionization of HPAM and its ability to complex with Cr3＋ increased accordingly. When the complexation of Cr3＋ with HPAM is stronger than that with citric acid, the viscosity of the HPAM solution increased signif- icantly. Under the closed condition, together with the existence of potassium dihydrogen phosphate （KH2PO4）, the release of CO2 was very slow and the condition was highly con- trolled so that the ionization of HPAM was prevented initially. Furthermore, the hydrogen bonding interactions between HPAM and melamine embedded in solution previously also postponed the ionization of HPAM. As a result, the crosslinking between HPAM and Cr3＋ can be delayed for almost one month, completely meeting the requirements for deep water shut-off and profile control to enhance oil recovery.