Synthesis And Performance Of Salt-tolerance Fluid Loss Additive With Weak Retarded For Well Cementing

Designing and mixing oil well cement slurry, which possesses superior comprehensive performance, is a pivotal step to ensure the quality of well cementing. As the geological environment faced by oil or gas well is becoming more and more complex, such as high temperature, frozen soil, seepage and salt formation, the property of cement slurry is also need to be improved synchronously. Since the property of oil cement is limitative, improving the performance of cement slurry can be achieved by adding additives, such as fluid loss additive and retarder. However, the fluid loss additive is suitable for low temperature condition, cannot be applied to higher salt content water circumstance.While for fluid loss additive can be used under the condition of high temperature, there are still some side effects, for instance, causing long waiting setting time at low temperature and sedimentation at high temperature, which are bad for cementing quality.To overcome those defects, functional groups of fluid loss additive are optimized in this paper. N,N-dimethylacrylamide(DMAA), maleic anhydride(MA),2-acrylamido-2-methylpropanesulfonate(AMPS) and N-vinyl pyrrolidone (NVP) with ring structure are chosen as copolymerization monomers. Besides, the polymerization conditions and monomer ratio are optimized by the API fluid loss and setting time of cement slurry. Ultimately, the best comprehensive properties of salt tolerance fluid loss additive SRSTF with weak retarded are derived. Infrared and nuclear magnetic resonance spectra of SRSTF confirmed that four monomers all have been introduced to its chain successfully. Thermo-gravimetric experiment shows that the initial decomposition temperature of SRSTF polymer is 277? and it possesses prominent thermal stability.API fluid loss of fresh water and semisaturation salt-water cement slurries can be controlled below 100 ml by adding SRSTF, whose ability is stable in a wide range of temperature. At 30?, setting time of cement slurry and strength growth of cement stone both are influenced mildly by SRSTF. The cement slurry prepared with SRSTF possesses suitable thickening time, smooth thickening curve, good stability and liquidity. Moreover, the SRSTF is compatible with other admixtures and satisfied with different temperature and different salt concentration under the condition of cementing process requirement. Thus, it is concluded that the SRSTF fluid loss additive has a good practicability.