Estudo de algumas propriedades reológicas e teores de carbonato e bicarbonato após cura em câmara úmida e autoclave de três argilas esmectíticas tratadas com carbonato de sódio da localidade de Bravo, distrito de Boa Vista, município de Campina Grande, Paraíba.

Abstract

This work of laboratory aims continue a series of research work, which has been developing, using the smectites clays light green, red and mixed couloured from Bravo, District of Boa Vista,Campina Grande, Paraîra, with purpose to study the effects of treatment of cure in some rheological properties of these clays, keeping in mind its applicability as tixotropic fluids for perfuration of oil well. Inicially, the analysis of the rheological properties was done investing from the determination of the apparent plastic viscosités and filtrate volume in the clays under it natural form. The rheological properties of the clays were observed by the treatment of sodium carbonate at the proportion of lOOmeq per 100g of dry clay without treatment of cure. The processes of cure treatment were done in a humid chamber and autoclave keeping the concentration of sodium carbonate and relative humidity constant and changing the temperature and time. The dialysis effect was investigated with the use of C02 at all conditions studied. The use of dialysis process has the purpose to eliminate either soluble compounds or parcially soluble of calcium and magnesium compounds or parcially soluble of calcium and magnesium compounds formed by double exchange chemical reaction by the • 2 + 2-1- + treatment with sodium compounds (montmorilonite, Mg ,Ca ,Na , K+, H30+)+ Na2C03 - montmorilonite (Na + ) + MgC03 + CC>2 compounds (montmorilonite, Mg ,Ca ,Na , K+, H30+)+ Na2C03 - montmorilonite (Na + ) + MgC03 + CC>2 + H20 + K2C03) that are able to be dissolved into clays aqueous dirpèrsion so this will spoil the colloid properties of the montmorilonite, mainly the plastic viscosité. The use of CC>2 has the objective to observe the maximun point that its action will damage rheological properties of the clays in this study. Carbonates and Bicarbonates existing in the 6% solids suspension were determined. These values were used to find correlation in filtrate volume and apparent and plastic viscosites by simple and multiple linear regression analysis. results obtained from technological tests showed that light green, red and mixed coloured clays, after the treatment, presented rheological properties adequated to be used in the perforation of oil wells. However, the effects,of dialysis has considerable influence in the improvement of the rheological properties to the treatment of the clays without the cure process and after the cure process in chamber and autoclave where the clay are treated with sodium carbonate to adequade to proportion after autoclave process.; The use of CC^,however , has considerable influence on the rheological properties, once it being soluble, presented the tendency to floculate the system and consequently to damage the rheological properties. With relation to correlations obtained showing to be of limited validity, even to the rcdused number of observations taken; so were obtained correlations coeficients approximately one taking that there exists linear relation between amounts of carbonates and carbonates plus bicarbonates with apparent and plastic viscosites and the filtrate volume in some of the cure conditions.