Emulsions of glycerol in olefin: A critical evaluation for application in oil well drilling fluids

Abstract

Drilling in ultra-deep waters presents a series of difficulties and specificities, related to well depth, water depth, high pressures and saline formations found in the pre-salt basins. In addition, there is still a need to use fluids that meet environmental legislation for cleaning and disposal of cuttings in the sea. In view of these requirements, the invert emulsion fluids, of brine in olefin, are promising and have been extensively used for this application. These fluids need to maintain their rheological properties throughout the drilling, also considering the temperature variation, in order to minimize the formation of hydrates, interaction with clay areas, interaction with saline zones and damages to the permeable rock. The hypothesis of this research is that the substitution of brine by glycerol in the drilling fluid can lead to the following advantages: (a) maintenance of rheological properties; (b) mitigation of interactions with clay and saline areas; (c) no formation of hydrates, due to absence of water in the fluid; and (d) introduction of a new economic effectiveness for glycerol waste disposal. For this, crude glycerol was used to replace saturated NaCl brine in the invert emulsion drilling fluid. The interaction with saline and clay-rich zones was investigated by evaluating the interaction of the dispersed phase and the continuous phase using clay and salt plugs. Among the main results, crude glycerol obtained as a by-product of biodiesel was compatible with commercial additives used in drilling fluids based on brine in olefin emulsions, demonstrating feasibility of immediate application in drilling fluids, in view of the maintenance of rheological properties, reduction of filtrate volume and lower reactivity with salt and clay areas. Thus, the article presents a new composition of drilling fluid for ultra-deep waters, with the potential to minimize damage to the rock formation, through the use of a waste from the biodiesel production industry, without the need of previous treatments.