Synthesis Of Thermoviscosifying Polymer And Its Effect On Stability Of Cement Slurry

The oil well cement slurry is prone to sedimentation under high temperatures,which will undermine cementing quality and safety seriously.The traditional stabilizers have the disadvantage of thickening cement slurry under low temperatures while thinning under high temperatures.Therefore,this study aims to develop a thermoviscosifying polymer as a novel stabilizer.The thermoviscosifying polymer whose viscosity increases upon increasing temperature can match the temperature change in downhole.And the thermoviscosifying polymer provides a new method to improve the stability of oil well cement slurry.Through combining the long-chain-alkyl hydrophobic monomer HW-18 with AM and AMPS,this study has synthesized a thermoviscosifying polymer for cement slurry.Then,according to the application condition,the tolerances for alkali,salt and high temperatures and high-temperature rheologic characteristics of thermoviscosifying polymer were detected.In order to reveal the mechanism of viscosity enhancement,this study determined the structure and weight of thermoviscosifying polymer molecular,investigated heat absorption and hydrophobicity of thermoviscosifying polymer in different temperatures,and observed its micro morphology in aqueous solution.Finally,guided by the API standard,the effects of thermoviscosifying polymer on the thickening time,water loss,compressive strength,consistency and stability of cement slurry were tested.The experimental results show that the optimal initiator dosage is 0.6%,the optimal ratio of oxidizing and reducing agents is 1.4:1,and the optimal monomer ratio of AM,AMPS and HW-18 is 3:1:1.The molecular chain of thermoviscosifying polymer can form the spatial network to increase the viscosity.With the increasing temperature,the solubility of polymer will increase and molecular chain will further extend,resulting in the thermoviscosifying phenomenon.The thermoviscosifying polymer possesses high tolerances for alkali,salt andhigh temperatures,which is suitable for cement slurry.Thermoviscosifying polymer has little effect on the thickening time,water loss and compressive strength of oil well cement.Thermoviscosifying polymer can thicken cement slurry under high temperatures,which significantly improves the stability of cement slurry.The thermoviscosifying polymer can protect the cement slurry from instability,overcome the technical defect of thinning under high temperatures like traditional stabilizers,which contributes to the cementing quality and the development of oil and gas resources in China.