Abstract: The invention relates to a drilling fluid resulting from a combination of calcium carbonate, starch, calcium oxide, xanthan gum, and essentially a cationic surfactant, where the cationic surfactant is constituted by the following components: calcium nitrate, diethanolamine (DEA), and glacial acetic acid. Also disclosed is a method for producing the cationic surfactant, a process for obtaining the drilling fluid, as well as a method for measuring the free calcium of the reaction when the fluid is in wellbore operation.