Influência do tratamento de cura em câmara úmida e climatizada nas propriedades reológicas e nos teores de carbonatos e bicarbonatos das argilas esmectíticas do distrito de Boa Vista, município de Campina Grande, PB.

Abstract

Two samples of smectite policationic clays of type mixed and chocolate colour proceeding from Bravo, District of Boa Vista, Campina Grande, Paraíba were studied. The samples were submitted to characterization and technological tests, in orderto optimise the rheological properties byusingcure treaitment, keeping in mind its applicabi lity as tixotropic agent for perforation of oil wells. Especial enphases was given to the exchange of natural cations by treating with sodium carbonate in order to observe the formation of tixotropic gels. The clays were submitted to three processes of cure treatment. First process was to submit the samples to be cured in the humid cham ber at 100% of R.H. and room temperature, the second cure process was done in the climatized chamber at 90% of R.H. and 40ºC, 50ºC, 70ºC and 90ºC the third process was carried out under the same conditions of the second process following the dialysis. In these processes the samples were studied before and after treatment with sodium carbonate in different concentrations of 50, 100 and 150 meq of sodium carbonate per lOOg of dry clay for periods of 1,5, 3, 6, 9, 12, 15, 18, 21 and 24 hours of cure. The results showed the following variables effects; time, sodium carbonate concentration, temperature and rei ative humidity in the apparent and plastic viscosities and volume of the filtrate and from the volume of the filtrate the quantities of carbonates and bicarbonates are determined m ali the conditions studied for three cure processes. With the results from the results from the three cure processes were deter mined the relationship existing between the amount of carbonates, bicarbonates and carbonates plus bicarbonates with rheological properties by simple and multiple linear regression analysis. It was verified that clays of type mixed and chocolate colour are composed of the same clayminerals. The studies showed that the clays of type mixed given values of rheological properties in the specification of the three cure processes when treated conveniently. Although was observed that the cure carried out in the climatized chamber at 90% of R.H. and 50C and 709C (second process) and the conditions of 90% of R.H. and 409C and 509C following the dialysis (third process) showed more adequated to be used as tixotropic agent in fluids for perforation of oil welis and for those clays of chocolate colour were also obtained values of rheological properties in the specifications of the three cure processes of treatment with maximum temperature of 509C, when treated conveniently. It was noticed that the cure in the cl imati zed chamber at 90% of R.H. and 40ºC and 50ºC (second process)showed more adequated. It was verified also that the amount of carbonates would not af fect rheological properties of both samples while that amount of bicarbonates affected. Most of the results investigated from regression analysis showed an unagreement with proposed mathematical model.