Thixotropic evaluation of bentonitic clay dispersions modified with nonionic surfactants for organic drilling fluids

The use of nonionic surfactants to modify the surface of bentonite is still quite restricted, although many advantages of that method can be found in the literature, like superior stability and low toxicity. On the other hand, problems involving the fluidity and viscosity of dispersions used in organic drilling fluids have become more and more challenging to colloid science. Therefore, the present study had the purpose of assessing the thixotropic behavior of dispersions of Brazilian bentonite organophilizated with nonionic surfactants for use in organic drilling fluids. Bentonite samples were organophilizated by a combination of two nonionic surfactants, being the process evaluated by X-ray diffraction and thermogravimetric analysis, in which the amount of nonionic surfactants incorporated was quantified. Fluid evaluation followed current standards. The flow curves of the organophilic clays revealed pseudoplastic behavior and the presence of hysteresis, which suggested thixotropy, with a relation between the thixotropy and the apparent viscosity of the final dispersions. Most of the process parameters evaluated showed significant effects on the value of d001 and the overall performance. Factors like clay type and organophilization method also directly affect the thixotropic behavior of dispersions. One of the samples can be considered promising for use in organic drilling fluids.

Comparative Study of Organoclays with Ionic Surfactant

The clays of the smectite group, mainly montmorillonite, are widely used in the production of organoclays due to the small dimensions of the crystals, high cation exchange capacity (CEC), and swelling capacity in water, which lead to a rapid and efficient intercalation of organic compounds used in the synthesis. In this context, this research was intended to make a comparative study of clays organofilized with ionic surfactants through their respective CEC. We selected four samples of bentonites, namely Chocolate (Boa Vista, PB), Brasgel (industrial), Dark Bentonite (Pedra Lavrada, PB) and M400 Bentonite (industrial). The natural samples were characterized through XRD, EDX, TA and GA, and the organofilized ones through XRD. The characterization tests showed that the samples are composed of clay minerals of the smectite group, the CEC values ​​were insignificant changes when comparing the values ​​of natural and activated clays with sodium carbonate. And the levels indicated by the CEC for the ionic surfactant Praepagem HY proved insufficient to transform the organophilic clays, as the nominees for the ionic surfactant Praepagem WB led to adequate results regarding the incorporation of the surfactant in the clay fraction of the studied samples.