Caracterização e avaliação da viabilidade técnica de carboximetilceluloses para uso como redutor de filtrado em fluidos de perfuração.

Abstract

The purpose of this work is to evaluate the influence of the physical and chemical properties of carboxymethylcelluloses (CMC) on filtration properties of polymeric drilling fluids. The study was accomplished in three stages. In the first stage, the CMC samples were characterized by measurements of purity, pH, viscosity and degree of substitution, using the classification of the rheological behavior regarding to the uniformity of substitution and spectroscopy tests by the Fourier Transform Infrared Region (FTIR), X-ray Diffraction (XRD) and Thermogravimetric Analysis (TGA). On the second stage, the CMC samples were evaluated according to the standards PE- 2POC-00727-0 and API Specification 13A. Finally, in the third and last step, six CMC samples were selected to be evaluated as a fluid loss additive in polymeric fluids. According to the results obtained from the characterization, the CMC samples presented different degrees of polymerization as a function of the increase of the viscosity values from 30 to 142cP and degrees of substitution (0.71-0.87), besides different uniformities (thixotropic and pseudoplastic behavior). According to the tests in the standard PE-2POC-00727-0, from the twelve samples studied, only CMC7 sample was considered to be faulty. In this way, all the other samples could be used in the aqueous fluid in order to control filtration losses considering this standard. However, no CMC sample was approved in API Specification 13A, which prevents the polymer samples studied from being used as low viscosity CMC in drilling fluids. The samples 3, 4, 5, 9, 10 and 11 were not only able to give the polymeric fluids the reduction of the filtrate volume, but it was also possible to obtain lower filtrate volumes than that obtained from the filtration of the formulated fluid with commercial CMC. Thus, in view of the results obtained it is concluded that the CMCs studied have potential to be used as fluid loss additive in drilling fluids and the performance of this function can be optimized by selecting samples with a lower viscosity, a higher degree of substitution and more uniformly substituted, considering the use in an aqueous medium with low ionic strength.