Polyacrylamide (PAM)-coated nanosand that may be a relative permeability modifier (RPM) and that is applied to treat a wellbore in a subterranean formation. The treatment may be for excess water production. The PAM-coated nanosand is PAM-hydrogel-coated nanosand. The PAM-coated nanosand os nanosand coated with PAM hydrogel. The PAM hydrogel includes crosslinked PAM in water. Application of the PAM-coated nanosand may reduce water production from the subterranean formation into the wellbore. The PAM hydrogel of the PAM-coated nanosand may expand in a water zone of the subterranean formation to restrict water flow into the wellbore. The PAM hydrogel of the PAM-coated nanosand may contract in an oil zone of the subterranean formation so not to significantly restrict crude oil flow into the wellbore.