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).
Acrylamide
polymers were widely used as oilfield chemical treatment
agents because of their wide viscosity range and versatile functions.
However, with the increased formation complexity, their shortcomings
such as poor solubility and low resistance to temperature, salt, and
calcium were gradually exposed. In this paper, acrylamide (AM)/2-acrylamide-2-methyl-1-propane
sulfonic acid (AMPS) copolymers were synthesized by aqueous solution
polymerization and inverse emulsion polymerization, respectively.
The aqueous polymer (W-AM/AMPS) and the inverse emulsion polymer (E-AM/AMPS)
were characterized by Fourier transform infrared (FTIR) spectroscopy,
nuclear magnetic resonance (1H NMR), transmission electron
microscopy (TEM), scanning electron microscopy (SEM), and particle
size analysis. The rheological properties, filtration properties,
and sodium ion (Na+) and calcium ion (Ca2+)
resistance were investigated. The results showed that E-AM/AMPS not
only had a dissolution speed 4 times faster than that of W-AM/AMPS
but also had superior shear-thinning performance both before and after
aging. The filtration property of the bentonite system containing
2 wt % E-AM/AMPS was also better than that of the bentonite system
containing 2 wt % W-AM/AMPS. In addition, E-AM/AMPS also exhibited
extremely high tolerance for Na+ and Ca2+. The
huge difference between rheological and filtration properties of E-AM/AMPS
and W-AM/AMPS in drilling fluid can be attributed to the differences
in the polymer microstructure caused by the two polymerization methods.
Both FTIR and 1H NMR results showed that more hydrogen
bonds were formed between E-AM/AMPS molecular groups and molecular
chains, which led to a cross-linked network structure of E-AM/AMPS
which was observed by TEM. It was this cross-linked network structure
that made E-AM/AMPS have a high viscosity and allowed it to be better
adsorbed on bentonite particles, thus exhibiting excellent rheological
and filtration behavior. In addition, E-AM/AMPS powder had a high
specific surface area so that it can be dissolved in water faster,
greatly reducing the time and difficulty of configuring drilling fluid.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.