Efeito da adição de poliuretana na permeabilidade de pastas leves com incorporador de ar

Abstract

The cementing job has the purpose of sealing permeable zones and providing support for the casing column. Depleted reservoirs or with low fracture pressure require low-density cementitious slurries. Low-density or lightweight cement are also obtained through the incorporation of air by the use of the air incorporating additive (IAR) and its application contributes to the formation of closed pores incorporated throughout the cement slurry. The polyurethane (PU) presents excellent results of fluid loss control, free water, permeability and porosity, contributing to the reduction of gas migration through the cement sheath. The general objective of this thesis is to evaluate the effect of the polyurethane addition on the lightweight slurries permeability with air incorporator. The concentrations of the chosen developer were based on the manufacturer's suggestion. From a calculated density of 15.6 lb/gal (1.87 g/cm3 ) to a standard slurry, slurries with air incorporator and polyurethane were prepared. The experimental design used was the complete factorial 32, in which it was previously performed to better evaluate the effects of the additives used. Density, stability, mechanical strength and permeability tests were performed according to the requirements of the American Petroleum Institute (API) and the Brazilian Association of Technical Standards (ABNT). A reduction in slurry density was observed with increasing concentration of air incorporating additive. The compressive strength decreased with the air incorporation, a fact that was already expected due to the pores formation, but the values are compatible with lightweight slurries. The permeability tests were satisfactory, presenting values below 0.1 mD for 28 days of cure. It was concluded that it is feasible to use air incorporator together with polyurethane in low-density cement slurries and that it is possible to obtain coherent results with low permeability and good compressive strength for the conditions of formations with low fracture gradient.