Gilsonite "Natural asphalt" and other asphaltic type materials penetrate shale pore spaces as a drill bit penetrates a formation.

 It is assumed that a plastic-flow mechanism will allow the asphaltite to extend into the pores of the shale, thus, reducing fluid loss or mud invasion with a tendency to bond the shale and prevent sloughing.
Optimizes lubrication, especially at higher temperatures.
Inhibits hydration of the clay fraction in shale and claystone.
Reduces wellbore damage, especially vibration induced formation damage resulting from the stick-slip phenomenon.