Synthesis And Research Of Thermo-Thickening Additives For Well Cementing

Good cementing quality is a vital guarantee of oil exploitation. In order to guarantee the cementing quality, the key is to improve the property of the cementing cement. Along with the speedy development of oil industry, Oil and gas resources of superficial layer decreases, then oil and gas resources of deep layer has gradually become the focus of exploration and exploitation. The number of deep and ultra-deep well is increased. These wells have a complicated bore frame and their bottom-hole circulating temperature is very high, which always induce the consistency thinning behavior and the poor sedimentary stability of cement slurry system. In order to promote the stability of cement slurry under high temperature, there are two methods can be considered to solve the problem, one is adding superfine material to the cement slurry, the other is enhance the consistency of cement slurry.In this paper, we try to enhance the stability of cement slurry under high temperature by adding polymer additive with thermo thickening property. First of all, the hydrophilic backbone, P(AA-co-AMPS) and thermo sensitive side chains P(DEAA-co-DMAA) were synthesized respectively through free radical copolymerization in aqueous solution, then thermo thickening water soluble graft polymer, P(AA-co-AMPS)-g-P(DEAA-co-DMAA) was prepared through grafting onto technique. The chemical structure information for the polymers was characterized by means of FTIR, 1H NMR, and elemental analysis. The results demonstrate that the structure of synthetic polymer is consistent with the target products. The heat resistance of the polymer was measured by virtue of thermo gravimetric analysis(TGA), the result shows that the decomposition temperature of the polymer is at about 270 ?, the polymer has a good heat resistance. The thermo thickening properties of the graft copolymer solution were investigated by use of R/S-CC Rheometer, The results demonstrate that the polymers in aqueous solution display a significant increase in viscosity with the temperature rising and their thermo thickening behavior is influenced by polymer itself(such as the concentration of the polymer, chemical composition) and external conditions(such as shear rate, salt concentration and pH value). Finally, when the temperature is increased, the hydrodynamic diameter of graft copolymer is prolonged. This result illuminated the thermo association process from the microscopic perspective.The thermothickening graft polymer was added into the slurry system, the application performance of the product was evaluated by virtue of sedimentary stability test, the consistency behavior under high temperature and pressure(HTHP) and compatibility test with other additives. API fluid loss is about 30 m L, this result illustrates that the compatibility of thermo thickening polymer and filtrate reducer is good. Besides, adding the polymer into slurry, let sit for 2 h, the free fluid decreased to 0.2% and the density difference is 0.02 g·cm-3. The results indicate that the thermo-thickening polymer can remarkably promote the stability of cement slurry under high temperature and high pressure.