Method of drilling a shale formation with a drilling fluid composition

A method of drilling a shale formation, the method comprising:

• drilling the subterranean geological formation to form a wellbore therein;
• and
• injecting a drilling fluid composition into the wellbore during the drilling,
• wherein during the injecting the drilling fluid composition is circulated in the wellbore at a pressure that is higher than the static pressure of the shale formation:
• wherein the drilling fluid composition comprises:
• an aqueous base fluid;
• 0.01 to 5 wt. % of polyamine-functionalized activated carbon (AC-PAD);
• 0.1 to 10 wt. % of a shale material;
• 0.01 to 2 wt. % of a thickener;
• 0.1 to 10 wt. % of a fluid loss control additive;
• 0.01 to 5 wt. % of an adsorbent;
• and
• 1 to 20 wt. % of a borehole stabilizer;
• wherein each wt. % is based on a total weight of the drilling fluid composition;
• wherein the AC-PAD is uniformly disposed on surfaces of the shale material;
• and
• wherein the shale material has an average pore size of 5 to 400 nanometers (nm).