Synthesis Of Fluid Loss Additive With Starch By Grafting Method

The grafted starch copolymers as fluid loss additive gets more attention due to itssalt resistance and highly using temperature. The grafted copolymers of ST-AM,ST-AA and ST-AS were prepared by grafted copolymerization method in our work.The optimization of synthetic conditions was evaluated by the orthogonal testand the single factor test. The best reaction temperature, reaction time, dosages ofalkali and initiators to ST-AM, ST-AA and ST-AS were95℃,65℃and95℃,6h,5hand5h,5%,30%and30%,10%,0.48%and6%, respectively.All the three products prepared in the experiments have good rheologicalproperties and filtration reducing capability in various drilling fluid. The dosages ofST-AM, ST-AA and ST-AS were determined in different drilling fluid. In freshwaterdrilling fluid, the best dosages of ST-AM, ST-AA and ST-AS were1.0%. In4%brinedrilling fluid and saturated brine ones were1.5%.All the grafted copolymers showed good salt resistance ability under differentconcentrations of NaCl. The ST-AM with adsorbing group has better salt resistancethan the ST-AA and ST-AS, which contains only hydration groups. As far as the usingtemperature to be concerned, the ST-AM and ST-AS have good filtrate reducercapability when the aging temperature is below130℃. However, the ST-AA canmaintain good properties until the aging temperature reach140℃.The groups in the three products were characterized by FT-IR. The resultsshowed that the specific peak of C=C in monomers disappeared, and the peaks ofclosely related groups clearly appeared. It concluded that all the monomers havereacted completely and were successfully grafted onto the starch’s structure. Theresult of thermal analysis showed that all the products had good thermal stability.