Estudo da organofilização da argila paligorsquita para uso em fluido de perfuração não aquoso

Abstract

The petroleum industry accounts for a significant portion of the clay market share, where they are used in drilling fluids as thixotropic agents. It is responsible for some important physicochemical characteristics, which must be controlled so that the fluid can perform its functions properly. Among the important functions of clays in drilling are cooling the bit, waterproofing the geological formation and maintaining solid suspension. In water-sensitive drilling operations, the use of oil-based fluid is often necessary, and in this case, clays lose their thixotropic properties, since their natural state is hydrophilic, they cannot be used without undergoing an organic treatment to make them hydrophobic. Different studies have been carried out to obtain organophilic clays, by different methods, capable of meeting the necessary requirements for their use. In this context, this research aimed to determine the ideal content (maximum point of surfactant adsorption) of palygorskite (Plg) to obtain organophilization using cationic surfactant cetyltrimethyl ammonium bromide (CTAB) at different concentrations. The adsorption tests were carried out in a finite bath, varying the content of Plg and CTAB in the solution. In these tests, parameters such as time, temperature, pH and thermodynamic characteristics were observed. To analyze the results, mathematical models for adsorption processes (Langmuir, Freundlich, Dubinin-Radushkevitch (D-R) and Tempkin) were used. In addition, X-ray fluorescence (FRX), X-ray diffraction (DRX), Thermogravimetric and differential analysis (TG and DTG), measurement of contact angle, and rheological analysis were performed. The collected data showed that an increase in clay content in the dispersion leads to a decrease in surfactant adsorption on clay. However, it was possible to obtain the ideal clay content for the organophilization of Plg at different concentrations of the CTAB surfactant. The data obtained in the experiments fit well with the Freundlich model. The Dubinin-Radushkevitch and Tempkin isotherms confirmed the chemical adsorption of CTAB on clay Plg. X-ray fluorescence identified the main constituents of the Plg sample. X-ray diffraction showed that organophilization does not change its crystal structure. The thermogravimetric and differential analysis allowed observing the main events associated with thermal degradation of Plg. The contact angle test showed that there was a change in wettability after the adsorption process, which is influenced by pH, as was observed in the results of the rheological analysis, confirming its affinity for oil phase due to the increase in rheological parameters.