Estudo da formação e estabilidade de tortas de filtração na perfuração de poços de petróleo

Abstract

During the drilling overbalanced operation, drilling fluid tends to invade the reservoir and may compromise productivity of the well. This study aims the better knowledge about the filtration process of drilling fluids as well as the mudcake formation. To perform the experiments were used a HTHP filtration cell. This cell allows evaluate the static and dynamic filtration process compatible with the conditions found during the drilling wells. Initially were evaluated the capacity of the filtration cell to provide filtration data for emulsion because were made a change in initial project of cell. Thereafter were compared kinds of fluids, like water based mud, oil based mud without emulsion and oil based mud with emulsion. Were used filter paper and three types of rock being high permeability sandstone, medium permeability sandstone and low permeability limestone as filter media. We performed experiments to determine mudcake parameters like porosity, permeability and shear strength of mudcake. The results obtained allowed evaluate the mudcake effect and interactions between drilling fluids with rocks. I was found that using filter paper the water based mud produced a greater amount of filtrate. Using rocks like filter media the oil based mud allowed greater volume of filtrate. In emulsion the water droplets emulsified limited the amount of filtrate obtained by obstruction of the pores formed by solid particles and the pores of rocks. Were considerate environments with and without shear rate. The shear rate impose on system created a destructive interference on mudcake occurring erosion. In this experiments were observed the rock effect on mudcake and amount ok filtrate. The higher the permeability of rock, the greater the amount of filtrate obtained.