Synthesis Of Comb-like Polymer And Study Of Its Interaction With Montmorillonite

Nowadays, the threat of an oil shortage is more obvious due to increasing demand. With the development of oil industry, the exploration of oilfield shifts to deep strata, thus drilling fluids that can be used in demanding situation such as high temperature and high salt concentrations, are needed to be studied. Traditionally, most copolymers used at high temperature are linear random copolymers, polymerized by monomers which could resist high temperature and high salt. However, the effect of copolymer structure on reducing the fluid loss was ignored. Comb-like copolymer was polymerized by macromer technology in this study. We found that drilling fluids can not only have good filtration properties but also satisfying flow behavior with the addition of such a comb-like copolymer. The interactions between copolymer and clay dispersion was also studied.The present dissertation includes three topics.1. Preparation and characterization of comb-like copolymerComb-like copolymer with large side chains was polymerized using macromer technology. The macromer (PEGM-MA) was synthesized by direct esterification of maleic anhydride (MA) and polyethylene glycol methyl ether (PEGM). According to the molecular design, polymer was then prepared through a copolymerization reaction under a certain temperature after mixing macromer, acrylamide (AM) and 2-acrylamido-2-methyl-propane sulfonic acid (AMPS) together in aqueous solution. Fourier transform infrared spectroscopy (FTIR) indicates the presence of three monomers and confirms the comb-like structure. The Element analysis demonstrates the proportion of structural units in the copolymer. The average viscosimetric molecular weight of the copolymer, calculated from intrinsic viscosity, was about 8～9×104. Thermo gravimetric-differential scanning calorimetry (TG-DSC) method shows that comb-like copolymer have a good property of high temperature resistance.2. Evaluation of filtration control properties about comb-like copolymer in different mud The filtration experiments were carried out based on the standard, GB/T16783.1-2006. Good filtration properties can be found in fresh water mud, salt water mud and saturated saline-water mud with the addition of such a comb-like copolymer. All mud were aged at high temperature. Compared with Driscal D, the influence of the comb-like copolymer on viscosity and yield stress was small.3. Study on the interactions between comb-like copolymer and montmorilloniteThe effects of side chain length and density of comb-like copolymers on clay suspensions were investigated systematically by adsorption, rheology and zeta potential analysis. And the governing dispersing mechanism was elucidated. The backbone of the copolymer preferentially adsorb onto montmorillonite surfaces through hydrogen bonding, which forms between the amide group and surface hydroxyl groups situated at clay platelet edges, with the PEO "teeth" extending into the solution. The adsorbed amount and zeta potential increase with comb-like copolymer concentrations until a plateau is reached. Meanwhile, the adsorbed amount increases with the addition of electrolytes. Rheological experiments reveal that the long side chain copolymer has higher dispersion power than the shorter ones. It might be attributed to the stronger steric hindrance of the long side chain of polymer. To conclude, comb-like copolymer is an efficient dispersant for aqueous montmorillonite suspensions.