Influência de umectante aniônico na reologia e espessura do reboco de fluidos hidroargilosos.

Abstract

Absence of monitoring physical and chemical properties of drilling fluids such as viscosities, gel strength, water loss and filter-cake, may cause problems during well perforation, e.g., differential sticking (defined as the stuck pipe). To solve this problem it is necessary to treat the drilling fluid with dispersant and surfactant. The aim of this work is to study the influence of dispersant additives and an anionic surfactant over the rheological properties and filter-cake thickness of the drilling fluids. Two samples of sodium bentonite clays called Brasgel PA and Verde-lodo, three samples of dispersant additives, called Hexa (without surfactant), Hexa T (with surfactant) and Spersene, and one sample of anionic surfactant were studied. Determination of apparent and plastic viscosities and the water loss before and after treatment with additives of the drilling fluids were performed according to the Petrobras standard. A new methodology to measure filter-cake thickness, based on API standard, and using an extensometer equipment were development. The results show that values of the apparent viscosity, water loss and filter-cake thickness were reduced when additives concentration was increased. Besides that it is shown the importance of using dispersant and surfactant agents simultaneously in formulating additives for drilling fluids to prevent or solve thick filter-cake problems.