Dimer fatty acid and fatty amide effects on the properties of synthetic-based drilling fluids

Abstract

This paper mainly deals with the analysis of chemical modification on a dimer of fat acid to evaluate the effect on synthetic drilling fluids. The performance of drilling fluids in the deepwater fields is negatively impacted by the elevation of rheological parameters. A required property of the drilling fluid is a minimal sensitivity of the rheological properties with respect to temperature, leading to a flat-rheology system. A proposed fatty amide was synthesized via condensation reaction between saturated dimer fatty acid and diethanolamine. In this reaction, it was used N,N′-dicyclohexylcarbodiimide as coupling agent and 4-dimethylaminopyridine as catalyst. The synthesized material was characterized by FTIR, 13C NMR, solubility tests and surface tension. Next, the precursor dimer fatty acid and the synthesized fatty amide were initially applied on a visual stability test in invert emulsion systems before application in synthetic drilling fluids. Spectroscopic analyses confirmed that fatty amide was successfully synthesized. Surface tension measurements showed that both dimer fatty acid and the fatty amide amide have not surfactant properties. However, when both products were applied in synthetic drilling fluids, electrical stability and HPHT filtration tests proved the ability to stabilize emulsion systems, probably, as network agents. In addition, the drilling fluids containing dimer fatty acid and fatty amide presented minimal viscosity sensitivity in the temperature range of 4–49 °C, at ambient pressure and 344 bar, leading to flat-rheology synthetic drilling fluids.