Development Of A Self-matching Oil Well Cement Retarder

An oil cement retarder SY was synthesized by the copolymerization of Acrylic Acid(AA), Sodium methallyl sulfonate (MAS), a vinyl monomer LN(containing hydrophilic long chain) and Trimethylallylammonium chloride(TMAAC) via free radical copolymerization, in which Ammonium sulfate (APS) was used as initiator. Through the orthogonal experiment and single factor method the optimum reaction conditions were determined, and the results are as follows:the ratio of AA:MAS:LN:TMAAC on mole is 4:1:0.15:0.5, monomer weight concentration is 30%, the initiator concentration (Ammonium persulfate) is 5%, the solution pH value is 5, the reaction temperature is 80? and reaction time is up to 16h. The structure of the copolymer was characterized through Fourier transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance ('HNMR) spectroscopy. The results show that the retarder SY contains all functional groups of side chains; Thermal gravimetric analysis demonstrates that the thermal stability of SY is excellent and can be used in a wide temperature range.The retarding properties, dosage and temperature sensitivity and compatibility with other additives of the retarder SY synthesized under optimal conditions were studied after added to the oil cement slurry. The results indicate that:the retarder SY can be used at the high temperature of 200?; the thickening time can reach 400 min when the dosage is 4%, the dosage of the retarder S Y has good linear relationship with thickening time and the thickening time is adjustable in 90?200?; the temperature sensitivity coefficient and dosage sensitivity coefficient is less than 5.0% and 1.68 respectively, which both meet the industry standards; the retarder SY has a good adaptability with other different brands of oil well cement and compatibility with other commonly used additives; the retarder SY has little effect on cement strength and has certain dispersing effect, which improves the rheology of cement slurry.The application performance of the retarder SY used in different density slurry system was studied. The three kinds of high-density slurry system of 2.10,2.20 and 2.30 g/cm3 were optimized. The thickening time can be adjusted among 270?355 min at 150?, the strength of cement reaches 10.8 MPa when the curing temperature is 120? for 48 hours. Subsequently, the three kinds of low-density slurry system of 1.30,1.38 and 1.50 g/cm3 were obtained. The thickening time can be adjusted in 322-360 min at 150 ?, the strength of cement reaches 10.5 MPa when the curing temperature is 120? for 24 hours. When the dosage of retarder SY meets the requirement of the thickening time at 180? and temperature difference is 60?, the thickening time is between 313?362 min and the strength of cement reaches 16.1 MPa when the curing temperature is 120?for 24 hours.The mechanism of oil well cement retarder S Y was investigated through X-ray diffraction, scanning electron microscopy, low field nuclear magnetic resonance and complexometric titration. The results show that the retarder SY polymer is adsorbed on the surface of the cement particles via adsorption groups and form a low permeable bundle layer; the formation of Ca(OH)2 crystal is retarded by the complexation of Ca2+ with strong anionic groups such as -SO3- and -COO-; which can delay the hydration rate of cement. Electrostatic compatibility will occur after the mutual combination of positive and negative ions in the early stage of hydration, which will increase the adsorption of the retarder SY and delay the thickening time. The saturated solubility of Ca(OH)2 will be improved after the addition of the retarder SY, as a result, the time of crystal formation will be extended and the ability of retarding be improved.In conclusion, the retarder SY has the strong ability of temperature resistance, retarding properties and compatibility with different brands of cement and additives and broad application temperature range, which shows its good practical application prospect.