Lignin Graft Copolymer as a Drilling Mud Thinner for High Temperature Well

A study was conducted on graft copolymerization of Kraft lignin with 2-propenamide (acrylamide). Copolymerization process was carried out by a free radical reaction using methanol as the reaction medium, ferrous ion as the catalyst and benzoyl peroxide as the initiator. The formulation of lignin-acrylamide graft copolymer (PLA) was verified by infrared (IR) spectroscopy and Differential Scanning Calorimetry (DSC) analyses. Thermogram observations showed that there were two Tg values indicating that the yield was a copolymer. The performance of the PLA as a polymeric thinning agent for aqueous bentonite mud was evaluated. The rheological performances of the copolymer were compared with a commercial thinner (lignosulfonate). At the optimum dosage of 0.3% of the total mud volume, the PLA acted more effectively as a thinner and also as an agent for controlling the filtration loss than that of the lignosulfonate. Unlike the commercial lignosulfonate, the newly formulated thinner (PLA) showed better thinning performance at a high temperature of 190 °C. Furthermore, the PLA was more tolerant than lignosulfonate towards salt contamination.

Keywords: graft copolymerization, free radical reaction, rheological performances, high temperature well