| The use of polyacrylamide as enhanced-oil agents has faced a big problem that is these agents can not provide excellent thermal stability and salt tolerance,and are not suitable to the hostile reservoir environment. Polyacrylamide /phenol /formaldehyde organic cross-linking system has excellent thermal stability and salt tolerance because of importing the benzene in polymer chains and so becomes one of the most popular enhanced-oil agents.The paper has studied the kinetics and mechanisms of the Polyacrylamide / phenol / resorcin / formaldehyde organic cross-linking system in order to satisfy the different cross-linking rates in different well conditions.On the first place ,the paper determined the Mη and Mw of polyacrylamide by the measurement of viscosity and the method of static light scattering, the resulrs are 3.013*107and 1.514*107.The polyacrylamide purification grade is determined by element analysis and the concentration of C is 36.94%,the concentration of H is 6.96%,the concentration of N is 10.39%,and the concentration of the S is 0.The paper used propionamide as model compound and designed seven reaction routes to study the kinetics and mechanisms of Polyacrylamide/phenol/ resorcin /formaldehyde cross-linking system,including ①phenol/formaldehyde system ②resorcin / formaldehydesystem(3)propionamicie / formaldehyde system ④phenol/ resorcin / formaldehyde system ⑤ propionamide / phenol/formaldehyde system(6)propionamide/ resorcin / formaldehyde system⑦ propionamide / phenol/ resorcin /formaldehyde system. We charactered the reaction process by HPLC. The rate constant of phenol/formaldehyde system is k1 = 1.0728 10-5 L/mol*s; The rate constant of resorcin / formaldehyde system is k2=7.65*10-5 L/mol*s and of the propionamide / formaldehyde system is k3=6.8778*10-6L/mol*s. The rate constants of phenol/ formaldehyde systems are ten times the rate constant 7.11*10-6 L/mol*s reported by the paper of Malhotra (Malhotra H.C ,1976)on the condition of 80°C , pH=6.00 . The cross-linking mechanisms concluded by the kenitics study of the seven route as following :phenol+formaldehyde= hydroxymethylphenol k1resorcin + formaldehyde= hydroxymethylphenol k2propionamide +formaldehyde=hydroxymethyl propionamide k3hydroxymethylpropionamide+ hydroxymethylphenol= crossing-linking production K k2>k1>k3,and the third step is the decided step. |
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