Efeitos de tratamento de cura em algumas propriedades reológicas de argilas esmectíticas de Boa Vista, visando sua aplicação como fluidos tixotrópicos para perfuração de poços de petróleo.

Abstract

A study of the effects of cure-treatment on some rheological propert ies of esmectite clays, which may be used as thixotropric fluid in petroleum drilling, was made on two samples of lightgreen and red colour smectite clays obtaind from the Bravo loca lity of Boa Vista district of Campina Grande, Paraiba. They were submited to characterization analysis and techno 1ogica 1 tests.Four processes of cure treatment were used in a chamber of controlable climate where the relative humidity, the temperature, the time and the sodium carbonate concentration could be varied. The range of the relative humidity studiet was 50% until 30%, and the range of the temperature varied from kO°C to 90°C. With two of the processes the effect of dialysis before and after the cure treatment was also verified. The amounts of carbonate and bicarbonate were also determined for the clay sample suspensions of 6% solid content and submited to the cure treatment of 90% re lative humidity at hO°C temperature and 90% relative humidity at 90°C temperature. On the basis of these data the correlations of the rheological properties like apparent viscosity, plastic vis cosity and filtered volume were found out. The study showed that the light-green clay becomes ex^ cellent in rheological properties after the adequate cure treatment. Thus this clay found abundantly can be utilised althoug it is considered improper to be used. It was found out that the red clay when treated proprtly also presented rhelogical properties with in the limits of specifications. It was verified that the two clay samples behaved rheologicaly differently when submited to the similar cure treatment, inspite of the fact that both the clays are basically of same mineral. The minimum and maximum contents of carbonate and bicar bonate necessary to obtain the specific rheological properties of the clays were also established in the present work.