PERFORMANCE EVALUATION OF SYNTHETIC DRILLING FLUID WITH FLAT RHEOLOGY
Deepwater drilling; Synthetic-base drilling; Rheological modifiers; Flat rheological
Synthetic-base drilling fluids with flat rheology were prepared from the synthesis of new rheological modifiers. The stability of these fluids in offshore deepwater drilling has been acquired by the development of chemical additives that promote the maintenance of rheological properties independent of temperature variation the fluid is subjected (flat rheological profile). The rheological modifiers were synthesized from the condensation reactions between dimer acid and three different amines, separately: Diethanolamine, Poly(propylene glycol) bis(2-aminopropyl ether) and Trimethylolpropane tris[poly(propylene glycol), amine terminated] ether in the presence of N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine, at 25°C. The products obtained were characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (13C NMR). The results confirmed the amidation reaction between the reagents from the observation of the characteristic signal of the carbonyl group of amides in the FTIR and 13C NMR spectra. The solubility of rheological modifiers was verified in water, olefin and brine saturated with NaCl. In water, DAG+DEA showed affinity with the aqueous medium, DAG+BPGA400 and DAG+TPGA440 showed affinity with the non-polar medium because of the introduction of lipophilic chains of BPGA400 and TPGA440. To evaluate rheological modifiers in synthetic-base drilling fluid, electrical stability tests and viscosity curves were performed at ambient pressure (~1 bar) and at pressure of 344 bar. At ambient pressure all fluids exhibited flat rheological profile. However, stable emulsions and temperature and pressure independent rheological profile were obtained using the rheological modifier acquired from the reaction between the dimer acid and diethanolamine.