Synthesis and properties of an improved agent with restricted viscosity and shearing strength in water-based drilling fluid

Abstract

To realize good cutting carrying ability and excessive viscosity limitation in water-based fluid, a new amphoteric hydrophobic association polymer (PAADDC) consisting of acrylamide (AM), 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS), diallyl dimethyl ammonium chloride (DMDAAC), 3-[N-(2-methacroyloylethyl)N, N-dimethylammonio]-propane sulfonate (DMAPS) and hexadecyl dimethyl allyl ammonium chloride (C16-DMAAC) was synthesized by free radical copolymerization. The molecular structure of PAADDC was characterized by Fourier transform-infrared spectroscopy (FT-IR) and nuclear magnetic resonance (1H NMR), while the molecular weight of polymer was determined by static light scattering (SLS). PAADDC, an improved agent with restricted viscosity and shearing strength for water-based drilling fluid was evaluated for its rheological properties. The results indicated that rheological parameters (apparent viscosity (AV), plastic viscosity (PV), yield point (YP) and ratio of YP and PV (RYP)) increased with the dosage of PAADDC before and after thermal aging experiments at 100 °C for 16 h, and decreased with thermal temperature range from 60 °C to 180 °C. According to the comparative experiments on shearing strength improvement, viscosity restriction and shearing shrength sustainability, PAADDC performs better than conventional viscosifiers. The observations of environmental scanning electron microscope (ESEM) and atomic force microscopy (AFM) demonstrated that a continuous three-dimensional network was formed in PAADDC squeous solution, which was the main reason for the excellent improvement of shearing strength. In field application, the well Yaoping 16 well was drilled successfully with PAADDC in drilling fluid.