A non-aqueous wellbore fluid comprises a non-aqueous continuous phase with one or more organic salts having the formula ((R1-Q)pX)mZn, one or more oligomeric organic salts based on linked ((R1-Q)pX)mZn subunits, or a combination thereof dissolved therein. X is a negatively charged functional group. R1 is an organic group comprising a principal straight chain and one or more side chains which branch from and are shorter than said principal straight chain. Q is a covalent bond or a polar linkage group which connects a terminal atom of the principal straight chain of the organic group R1 to the functional group X. p is a positive integer which is the number of organic groups R1 which are connected to the functional group X. Z is a cation. m and n are positive integers which ensure that the organic salts are charge neutral. The one or more organic salts increase the electrical conductivity of the wellbore fluid.