Preparation And Characterization Of AMPS/DMAM/FA/AM Copolymer Acting As Filtrate Reducer For Well Cementing At High Temperature And High Pressure Stratum

In this paper AMPS/DMAM/ FA/AM water-soluble copolymer was synthesized by adopting oxidation-reduction initiating system. Factors effecting the performance of the cement slurry such as the influence factors in the process of preparation for the copolymer, the production structure, the solution quality and as well as the copolymer quality were discussed. Designed and optimized the AMPS/DMAM/ FA/AM pair-functional cement slurry system at high temperature and high pressure stratum, studied the performance and function mechanism of the different system and different density of the cement slurry at high temperature and high pressure. Successfully developed the pair-functional cement slurry system which was fit to the high temperature and high pressure strata of the Ying-qiong Basin in the South China Sea by the synthesized filtrate reducer, the performance of the cement slurry system was nearly as the same as the foreign kindred productions. Eventually perfectly finished the sub-program of "The research and development of pair-functional gas channeling inhibiting cement slurry system at high temperature and high pressure strata"from one of "The Tenth Five-Year"Scientific Research Programs of China National Offshore Oil Corporation —"The study on the cement process technology at high temperature and high pressure strata of the Ying-qiong Basin in the South China Sea". The program for which we were responsible had been checked and accepted by the experts from China National Offshore Oil Corporation in 2004. The experts said that "The development of pair-functional gas channeling inhibiting cement slurry system & pair-functional pad fluid system had been in the probationary phase, the integrated performance of the systems could satisfy the cement operation requirement of the Ying-qiong Basin in the South China Sea, and to some extent, the systems could substitute for the importing additives entirely." 1.According to the requirement of the cement slurry at high temperature and high pressure stratum and the relationship of the structure and performance of the macromolecule, selected AMPS,DMAM,FA,AM for co-polymerization. Studied the influence factors for the production intrinsic viscosity and the monomer transformation ration in the process of AMPS/DMAM/ FA/AM synthesis. The experiment results show that: ①The pH of the synthesizing reaction system is the most striking effecting factor to the production intrinsic viscosity and the monomer transformation ration. The production intrinsic viscosity and the transformation ration would increase along with the increasing of pH in the solution. In the condition of this experiment, the polymerizing reaction needs to be continued in alkalinity, and pH=11 would be perfect. ②The effecting of the concentration of initiating agent to production intrinsic viscosity and the monomer transformation ration is less than pH. The transformation ration would increase rapidly and the intrinsic viscosity of the dilute solution of the production would increase too while the concentration of the initiating agent increasing. ③The adding quantity of the DMAM monomer would effect a lot for the monomer transformation ration, and while increasing the adding quantity of the DMAM monomer, the monomer transformation ration would increase obviously; It has no obvious influence to the production intrinsic viscosity. Generally 1.0~6.0% of the adding quantity for the DMAM monomer would be favorable, and the quantity should be reduced according to the increasing of pH in the reaction system. 2.The synthesis production was checked by Elementary Analysis, Infra-red Spectroscopy, Nuclear Magnetic Resonance and Thermal Analysis methods. Elementary Analysis had confirmed that the content of every element in the copolymer was the same as the content that calculated by theory. Infra-red Spectroscopy had indicate that Functional Group Signature-apex of every monomer had appeared, 1H-NMR Spectrum Figure had the structure units of AMPS, FA,DMAM and AM, so that we could affirm that the copolymer was the objective synthesis production of these four monomers. DSC & TG analysis result indicated that the decomposed temperature of the tetra-copolymers was 360℃, and this copolymers had excellent thermal stability. 3. Studied the viscosity behavior of the copolymer under different conditions, the experiment results showed that: The apparent viscosity of the copolymer sample would increase along with the increasing for its concentration; The influence for the apparent viscosity of the copolymer by the univalent and divalent cationic ion separately and both of them was as follows: The apparent viscosity would decrease obviously while increasing the concentration of salt (NaCl), and then would keep in stable; In the solution of CaCl2 or CaCl2/NaCl, the apparent viscosity would decrease smoothly along with increasing the concentration of CaCl2 or CaCl2/NaCl;The copolymer had anionic group, but it would counteract the influence to the molecular structure by introducing DMAM monomer, and the copolymer had perfect divalent-ion-resisting performance; After high temperature aging, the apparent viscosity of the copolymer would increase along with the increasing of the aging temperature; The copolymer had excellent high temperature-resisting performance; The apparent viscosity of the sample would increase along with the increasing of the shear velocity. As a word, introducing the hydrolysis-resisting group and the temperature-resisting group to the copolymer's chain benefited not only the viscosity increasing ability of the copolymer in the distilled water and salt solution, but also the rheological behaviors of the copolymer solution. 4. Studied the performance of the copolymer in the general oil well cement slurry under different synthesis conditions, the results showed that the synthesis condition played an important role for the filtrate reduce capacity of the copolymer. The fluid loss capacity and the apparent viscosity of the copolymer would be stronger when increasing the adding amount of the initiating agent; The cement slurry filtration would decrease along with adding a little DMAM monomer; The cement slurry filtration would decrease and the apparent viscosity would increase while increasing the adding amount of the copolymer. The copolymer also has an excellent filtrate reduce capacity in salt solution, and has perfect salt-resisting performance. Whenadding a small amount of the copolymer to the latex cement slurry, the results showed that the latex cement slurry had an extremely low filtration and free fluid quantity. The copolymer also has an excellent filtrate reduce capacity at high temperature up to 150 ℃, and has a favorable compatibility with other oil well cement slurry additives. 5. Studied the pair-functional cement slurry system that satisfied the cement operation requirement at high temperature and high pressure stratum in the South China Sea. The pair-functional cement slurry system prepared by the filtrate reducer HS-3L that synthesized in this paper and other matched additives can increase the gas tongue resistance perfectly and meantime avoid cement slurry weightlessness, it has a favorable function to reduce the cement slurry filtration. The pair-functional gas channeling inhibit cement slurry system at high temperature and high pressure stratum developed by the filtrate reducer HS-3L has perfect performances as follows: High cement slurry resistance while gas cutting; Be able to delay the cement slurry weightlessness; Temperature resisting capacity could be up to 230℃at bottom hole; The density of the cement slurry is up to 2.35g/cm3; The filtration is less than 50ml; The percentage of the free fluid is less than 0.5%; The thickening time could be adjusted; Perfect rheological property; Favorable capacity to resist the cement slurry pollution; High intensity and so on. The system could satisfy the cement operation requirement at high temperature and high pressure stratum of the Ying-qiong Basin in the South China Sea entirely, and meantime has high cost performance.