Synthesis and Characterization of Substituted-Ammonium Humic Acid Fluid Loss Additive for Oil-Based Drilling Fluids

Using widely distributed and cheap lignite as starting material, humic acid was modified by octadecylamine, and a new kind of humic acid acetamide was prepared. The optimal reaction conditions of the humic acid acetamide polymer were obtained through laboratory tests as follow: the ratio of of humic acid and octadecylamine was 1:1.5, the reaction temperature was 150 °C, and the reaction time was 16~18 h. The new product was characterized by IR, and the results showed that this substituted-ammonium humic acid was successfully prepared by reacting parts of carboxyl group of humic acid with octadecylamine. HTHP filtration experiments demonstrated that the substituted-ammonium humic acid had good fluid loss properties. As a result, this substituted-ammonium humic acid polymer is an excellent fluid loss additive, and it could meet the requirement of drilling operation under extreme condition.