Gel Kinetics And Thermal Stability Of Temperature-resistant HPAM

In oil field production?partially hydrolyzed polyacrylamide-based polymer gel iswidely used in chemical temporary plugging operation?in order to regulate the flowdirection of injected water?increase the sweep efficiency of displacing liquid andenhance oil recovery for the development of mature oil fields.HPAM gel system is usually composed of polyacrylamide-based polymer?crosslinking agent and other additives.And as organic crosslinking agent?phenol/formaldehyde is commonly used to crosslink with PAM-based polymer. Butthe high toxicity of the phenol/formaldehyde?especially its carcinogenic and noneco-friendliness to reservoir and environment?restricts its application in the temporaryplugging operation. So the development of eco-friendly?low-toxicity and watersoluble organic crosslinker has become the urgent research subject currently.Poor temperature-resistance?which greatly limits the application of HPAM gel inoilfield temporary plugging?is still the most major defects of PAM-based gels.Thedissolved oxygen?bivalent ions and excessive crosslinking will influence gels'long-term thermal stability. What's more?for a crosslinking system?gelation time toosoon or too slow?will cause difficulties to the oilfield operations. Therefore?achievingcontrollability of gelation time and improving the long-term stability of PAM gel areproblems pressing for solutions.In order to develop a new type of organic crosslinker?we investigated thepossibility of substitute for phenol with bisphenol A?a condensation productin ofphenol. In the present work?we firstly synthesized low-toxicity bisphenol A phenolicresin?BPAPR? and tetre-hydroxymethyl bisphenol A ?THMBA? with excellentsolubility?and the reaction conditions of BPAPR are optimized. Secondly?we studiedthe gelation kinetics of HPAM crosslinking with three composite crosslinkers?BPAPR/polyethylene polyamine? BPAPR/HMTA and THMBPA/polyethylenepolyamine? in which polyethylene polyamine and HMTA are the crosslinkingpromoter?while BPAPR and THMBPA as crosslinking main agent?respectively. Andthen we investgated the influence of polyethylene polyamine species?temperature?initial pH?composite crosslinker ratio and salt concentration on the gelation timeand gel strength using bottle testing method? realizing the controllability of thegelation time in the range of10h¹20h at90?¹20?. Thirdly?we examined the long-term temperature-resistant stability of the gel systems under90?and120?inthe laboratory and obtained the excellent gels which can be stbale for90days under90?¹20?. Finally?the reaction process of THMBPA with formaldehyde wasstudied using isobutyramine as the model compound. The result shows that amidegroup of isobutyramine will react with formaldehyde by hydroxymethylation?andthen the hydroxylmethylated isobutyramine react with THMBPA and generates thePh-CH₂-NH-C?=O?-structure?taking off a molecule of formaldehyde and water.