The wellbore instability
caused by the penetration of drilling
fluids into the formation is a vital problem in the drilling process.
In this study, we synthesized a polymer/graphene oxide composite (PAAN-G)
as a fluid loss additive in water-based drilling fluids. The three
monomers (acrylamide (AM), 2-acrylamide-2-methyl-1-propane sulfonic
acid (AMPS),
N
-vinylpyrrolidone (NVP)) and graphene
oxide (GO) were copolymerized using aqueous free radical polymerization.
The composition, micromorphology, and thermal stability properties
of PAAN-G were characterized by Fourier transform infrared (FT-IR)
spectroscopy and thermogravimetric analysis (TGA). According to the
American Petroleum Institute (API) standards, the influence of PAAN-G
on the rheological and filtration properties of bentonite-based mud
was evaluated. Compared with PAAN, PAAN-0.2G has more stable rheological
properties at high temperatures. The experimental results showed that
even at a high temperature of 240 °C, PAAN-G can still maintain
a stable fluid loss reduction ability. In addition, PAAN-G is also
suitable for high-salt formations; it can still obtain satisfactory
filtration volume when the concentration of sodium chloride (NaCl)
and calcium chloride (CaCl
2
) reached 25 wt %. Besides,
we discussed the fluid loss control mechanism of PAAN-G through particle
size distribution and scanning electron microscopy (SEM).