Nano-laponite/polymer composite as filtration reducer on water-based drilling fluid and mechanism study

In drilling deep complex formations, most drilling fluid additives have
insufficient temperature and salt tolerance, resulting in the decline of
drilling fluid performance. This study used 2-acrylamide-2-methylpropane
sulfonic acid, acrylamide, dimethyl diallyl ammonium chloride, and
modified nano-laponite to synthesize a nanocomposite filtrate reducer
(ANDP) with excellent temperature and salt resistance, which can maintain
the performance of drilling fluid. The structure of ANDP was analyzed by a
transmission electron microscope and an infrared spectrometer. The thermal
stability of ANDP was studied by thermogravimetric analysis. The
performance of ANDP was evaluated in a water-based drilling fluid. The
mechanism was analyzed per clay-particle size distribution, Zeta
potential, filter cake permeability, and scanning electron microscopy
imaging. The results show that ANDP has good thermal stability and
expected molecular structure. The filtration of freshwater drilling fluid
after aging at 200°C is 10.4 mL and that of saturated brine drilling fluid
is 6.4 mL after aging at 150°C. Mechanism analysis suggests that the ANDP
increases the thickness of clay particle hydration layer and maintains the
colloidal stability of the drilling fluid. ANDP inhibits the agglomeration
of clay particles and significantly reduces the filtration by forming
dense mud cake.