Study On The Synthesis Of Multi-copolymerized Retarder With High Temperature Resistance For Cementing

Retarder is an important cement additive in adjusting the thickening time of a cement slurry for safe placement into a wellbore at given well-hole conditions.At present,many retarders exhibit less effective as bottom-hole temperature increase,limited operating temperature range and harmful effect on compression strength of cement stone,and so on.Focusing on those problems,this paper has chosen reasonable reactive monomers based on molecular structure design and has synthesized a new cement retarder with high temperature resistance by aqueous solution polymerization.At the same time,in terms of current weakness regarding on evaluation method of retarding effect,a new kind of evaluation method has been put forward.The main research and achievements of this paper are as follows:(1)In the light of the shortcomings of evaluation method of retarding effect,a new method was proposed to evaluate the retarding effect.During the process of cement hydration,the change of conductivity of cement is different from the contents of retarder.Experimental results showed that this method is simple,easy to operate,and can be used as a new method to evaluate the effect of retarder on cement hydration.(2)Aiming at inefficacy of cement retarder at high temperature and limited adaptation temperature range,molecular structure design of retarder is taken into the fact that the mechanism of polymer is closed related to cement hydration process,synthetic cement retarder is applied for high temperature.AMPS(2-acrylamido-2-methylpropanesulfonic acid)was chose as molecular backbone,hydroxy carboxylic acid group as main retarding group,and a new cationic monomer was also been introduced into molecular structure of retarder.A new retarder with high temperature resistance(HW-1)was synthesized using the method of free radical solution polymerization.On the basis of orthogonal testing and single factor analysis methods,the optimum conditions for the synthesis of retarder((HW-1))are as follows:monomer ratio AMPS/IA/AA/DM to 37:8:8:6,reaction temperature 60?,initiator dosage 0.5%,monomer concentration 30%,pH value 4,reaction time 4h,stirring speed 300rpm.(3)The molecular structure and performance analysis of the retarder(HW-1)are verified by FT-IR and 1H-NMR analysis.The results indicated that the retarder(HW-1)is successfully synthesized.The thermal analysis results showed that the synthesized polymers had high temperature resistance(no significant mass loss and heat loss before 350 ?).Based on the study of hydration heat,setting time of cement slurry,conductivity,XRD and SEM of cement stone,it can be concluded that both adsorption action and complexation reaction of the retarder(HW-1)in the cement slurry are contributed to retarding effect.Performance evaluation results showed that the performance of retarder(HW-1)is in line with industry standard SY/T 5504.1-2005.Compared to other commonly used retarder,the retarder(HW-1)has higher temperature resistance,can effectively adjust the thickening time at 75??18?range.(4)Experimental results showed that the synthetic retarder HW-1 has no adverse effects on the rheology,fluid loss,compress strength,stability and anti-gas channeling performance of the latex cement slurry system.Under large temperature difference of 60?90?,the top compress strengths of cement stone meet the petroleum and gas industrial requirements(?7MPa/24-48h).