Filtração e invasão de fluidos de perfuração: estudo comparativo, caracterização da torta e modelagem

Abstract

Filtration and invasion of drilling fluids are phenomena that occur during the process of drilling oil wells. It is necessary to know the filter cake behavior, which is formed in order to prevent unwanted invasion of filtrate, which can cause irreversible damage for the reservoir rock, making impossible the well to produce oil. The goals of this work were: to study filtration and invasion of drilling fluids, under static and dynamic conditions, characterize the mudcake, obtain comparative results between different fluids (water base mud and emulsion) and model static filtration. For this, experiments were conducted in a high temperature/high pressure cell filtration, using filter paper as filter medium. The cake formed from the filtration of these fluids was characterized according to parameters such as porosity, permeability, compressibility, thickness, shear strength and friction factor. In a comparison between different fluids, it was observed that the water-based mud provided a mudcake more permeable and more porous than emulsion mudcake. Thus, water-based mud allowed more filtrate passed through the filter medium. The factors relevant to the estimation of the friction factor were determined. It was concluded that the compressibility index of the filter cake was a factor which had great influence on the estimation of this parameter. The model allowed the prediction of static filtration, slowness and mudcake thickness curves as a function of time.