Patent ID: 8026198

Claim:
A water-based drilling fluid for use in drilling wells through a formation containing a shale which swells in the presence of water, the drilling fluid comprising: an aqueous based continuous phase; a weighting material; and a shale hydration inhibition agent (SHIA) selected from the group consisting of (a) propylamine derivatives having the formula: R—Y—(CH 2 ) n —NH 2 wherein n=3; Y═O or N; R=one or more —CH 3 groups or a morpholino group; (b) hydrogenated poly(propyleneimine) dendrimers (HPPID) having a core with the formula N(-A-N*)3 and branches with the formula —H 2 or -(AN*H 2 ) 2 wherein A=(CH 2 ) 3 and N* is the growth point where two additional branches are attached; and (c) polyamine twin dendrimers (PTD) having a core with the formula H 2 N—(CH 2 ) x —NH 2 wherein 2≦x≦6, and branches B with the formula —(CH 2 —CH 2 —CH 2 —NH 2 ), wherein the core and the branches are arranged as: (B) 2 n . . . —(B) 8 —(B) 4 —(B) 2 —[H 2 N—(CH 2 ) x —NH 2 ]—(B) 2 —(B) 4 —(B) 8 — . . . (B) 2 n wherein n is the dendrimer growth generation number and n<10; wherein the SHIA is present in a sufficient amount to reduce shale swelling.