Development and Evaluation of a New High Temperature Filter Loss Reducer Used in Oil Base Drilling Fluid

An oil base mud filter loss reducer, DR-FLCA(functions at 220℃), was developed through imidization of humic acid by diethylenetriamine followed by hydrophobic modification by octadecyl tri-methyl ammonium chloride. The molecular structure, micromorphology and thermo-stability of DR-FLCA was characterized using IR spectroscopy, SEM and thermogravimetric analysis, and laboratory experiments were conducted to evaluate the effects of DR-FLCA on the rheology, electrical stability and HTHP filtration of high temperature high density oil base drilling fluid. DR-FLCA retains emulsifying capacity because of the imide group, phenolic hydroxyl group and alcoholic hydroxyl group on the molecular chains of DR-FLCA, and the long chain organic ammonium on the molecule chain. The micromorphology of this filter loss reducer is an aggregate of loose thin layers. DR-FLCA decomposes at 248℃. A 2.4 g/cm³ oil base drilling fluid treated with DR-FLCA, after aging at 220℃ for 16 hours, have the following properties:filter loss 8.6 mL, electrical stability 1,154 V, plastic viscosity 69 mPa·s, and yield point 7 Pa, demonstrating better filtration, (secondary) emulsifying, thinning and HTHP (200℃) filtration performances than Baker Hughes' and Halliburton's corresponding products(HTHP filtration are 5.4,8.2 and 6.5 mL), the electrical stability of which also decreases after aging, but the quality of mud cake is slightly poorer than Baker Hughes' and Halliburton's corresponding products.