In order to overcome serious instability problems
in hydratable shale formations, a novel electropositive
wellbore stabilizer (EPWS) was prepared by a new
approach. It has good colloidal stability, particle size distribution,
compatibility, sealing property, and flexible
adaptability. A variety of methods including measurements
of particle size, Zeta potential, colloidal stability, contact
angle, shale stability index, shale dispersion, shale swelling,
and plugging experiments were adopted to characterize the
EPWS and evaluate its anti-sloughing capacity and flexible
adaptability. Results show that the EPWS has advantages
over the conventional wellbore stabilizer (ZX-3) in particle
size distribution, colloidal stability, inhibition, compatibility,
and flexible adaptability. The EPWS with an average
particle size of 507 nm and an average Zeta potential of
54 mV could be stable for 147 days and be compatible with
salt tolerant or positive charged additives, and it also
exhibited preferable anti-sloughing performance to hydratable
shales at 77, 100, and 120 C, and better compatibility
with sodium bentonite than ZX-3 and KCl. The EPWS can
plug micro-fractures and pores by forming a tight external
mud cake and an internal sealing belt to retard pressure
transmission and prevent filtrate invasion, enhancing
hydrophobicity of shale surfaces by adsorption to inhibit
hydration. The EPWS with flexible adaptability to temperature
for inhibition and sealing capacity is available for
long open-hole sections during drilling.