Abstract
To overcome the negative impact on the rheological and filtration loss properties of drilling fluids caused by elevated temperature and salts contamination, which are common in ultradeep or geothermal drilling operations, it is imperative to develop highly efficient additives used in the water-based drilling fluid. In this study, a zwitterionic copolymer P (AM/DMC/AMPS/DMAM, ADAD) was synthesized by using acrylamide (AM), cationic monomer methacrylatoethyl trimethyl ammonium chloride (DMC), anionic monomer 2-acrylamide-2-methyl propane sulfonic acid (AMPS), and N,N-dimethylacrylamide (DMAM) through free radical copolymerization. The copolymer was characterized by 1H Nuclear Magnetic Resonance (NMR), Fourier transform infrared spectroscopy (FTIR), elemental analysis, thermogravimetric analysis (TGA), and zeta potential. The rheological behavior, filtration properties, and the performance exposure to salt or calcium contamination in water-based drilling fluid were investigated. The bentonite/polymer suspension showed improved rheological and filtration properties even after aging at 160 °C or a high concentration of salt and calcium. The filtration loss can be greatly reduced by more than 50% (from 18 mL to 7 mL) by the inclusion of 2.0 wt% copolymer, while a slight increase in the filtrate loss was observed even when exposed to electrolyte contamination. Particle size distribution and zeta potential further validate the idea that zwitterionic copolymer can greatly improve the stability of base fluid suspension through positive group enhanced anchoring on the clay surface and repulsion force between negative particles. Moreover, this study can be directed towards the design and application of zwitterionic copolymer in a water-based drilling fluid.
Highlights
The utilization of drilling fluids, a vital part and the lifeblood of a drilling operation, has never been more important than it is today in light of the deep wells drilling for exploration of fossil fuels and geothermal energy [1,2]
A zwitterionic copolymer was synthesized by using AM, cationic monomer methacrylatoethyl trimethyl ammonium chloride (DMC), anionic monomer AMPS, and N,N-dimethylacrylamide (DMAM) through free radical copolymerization
The −CH2−CH−CO− and −CH−CO− in Acrylamide, AMPS, or DMC and DMAM were at the regions of 1.22−1.85 and 1.85−2.45 ppm, respectively
Summary
The utilization of drilling fluids, a vital part and the lifeblood of a drilling operation, has never been more important than it is today in light of the deep wells drilling for exploration of fossil fuels and geothermal energy [1,2]. Most copolymers used in water-based drilling fluid are sensitive to high temperatures and high concentrations of electrolytes in solutions, which could severely affect the viscosity and filtration loss properties To overcome these problems, copolymers with thermal and electrolytes resistant monomers or inflexibility groups, such as 2-acrylamide-2-methylpropanesulfonic acid (AMPS) and other monomers with the SO3− group, have received considerable attention [24]. To obtain a water-based drilling fluid with enhanced rheological and filtration properties which can withstand high-temperature and high-salinity, polymeric additives with versatile functional groups are still desperately needed In this present study, a zwitterionic copolymer was synthesized by using AM, cationic monomer methacrylatoethyl trimethyl ammonium chloride (DMC), anionic monomer AMPS, and N,N-dimethylacrylamide (DMAM) through free radical copolymerization. The product of the optimal formulation was noted as PADAD; the optimal monomer mole ratio was 4:1:4:1 of AM, DMC, AMPS, and DMAM
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