Desenvolvimento de fluidos de perfuração de emulsão inversa à base de ésteres de óleos e gorduras residuais de fritura

Abstract

The biosynthetic based drilling fluids (BBF) at the base of esters have been increasingly used as substitutes for diesel and mineral oil based fluids, due to environmental concerns, as well as having the same characteristics and yields, present a greater biodegradability and much lower toxicity level when compared with petroleum-derived fluids. The success and cost of drilling operations depend primarily on the quality of the fluid used and these exercises, properly, their functions when their rheological properties, such as, plastic viscosity, yield point and gels straights (initial and final) are adjusted for each type of desired situation. The present study aimed at the development of inverse emulsion drilling fluids with low toxicity and high efficiency, using the ester produced through residual oils and fats of frying (OFR) as a continuous phase. A factorial planning 23 was conducted, where the oil/water ratio, the concentrations of oil-wetting agent and emulsifier were varied in two levels with three repetitions at the central point, totaling eleven formulations, was evaluated, through the analysis of variances test (ANOVA), with a confidence level of 95%, as and which additives have influenced in the rheological and thixotropic properties and the electrical and oxidative stability of the fluids produced. Moreover, the thermal stability of fluids was analyzed through thermogravimetric analyses (TG). The rheological behavior and the apparent viscosity of all formulations were also evaluated at three distinct temperatures, 30, 50 and 70 °C and the data were adjusted to the models of Bingham and Herschel-Bulkley. Have been verified the tendency of the apparent viscosity of the fluid to decrease with the increase in temperature. The formulations developed behave like binghamian fluid, so the Bingham model is able to better represent the fluid developed. The analysis of experimental planning revealed that the ratio of oil/water of 75/25, the emulsifier concentration 1,11% wt and 0,16% wt of oil-wetting agent, representative of the F3 formulation, produced the best results for the analyzed properties. The value of 217 V was obtained in the electrical stability test, with an induction period of 39.09 hours. The F3 fluid presented a high thermal stability, with a total mass degradation (100%) at 893.19 °C. The plastic viscosity and the yield point obtained were 0,039 Pa. s and 10,56 Pa respectively. The gel straight values were 9,2 Pa (initial) and 11,7 Pa (final), presenting a thixotropy (∆FG) of 2,5 Pa. The rheological and thixotropic parameters obtained for this formulation are conforming to the studies of other authors, being considered satisfactory.