Análise de propriedades mecânicas de pastas de cimento aditivadas com Óxido de Magnésio e Látex SBR

Abstract

Leaks through the cement sheath have been a persistent and chronic problem in the oil industry for decades. Thus, several additives are used to strengthen the cement matrix and provide better adaptation of the slurry to the well scenario. Drying shrinkage caused by water loss and gel consolidation is a serious disadvantage of Portland cement. This shrinkage is capable of creating microcracks when the stresses are greater than the tensile strength of the cement, which significantly increases the permeability of this material. Magnesium Oxide (MgO) is an additive able of reducing drying shrinkage through structural substitutions in the cement matrix. SBR Latex is a widely used additive to prevent gas migration as it reduces fluid loss, increases acid resistance and improves the microstructural bonds of cement. Based on this, this work evaluates the influence of MgO and SBR latex additives using experimental design. The results confirm the effects of MgO and SBR latex in reducing scenarios favorable to leaks and point to a strong influence of MgO in reducing drying shrinkage and gel formation. They indicate that MgO has low influence on compressive strength in the early stages of curing but has an important influence throughout curing and also has a strong influence on the shear strength of the slurry. They show that SBR Latex is an additive able of reducing compressive strength by increasing the elasticity of the slurry and that it has little practical influence on the shear stresses. From the results obtained it's possible establish better conditions for formulating slurries that use MgO and/or SBR látex applicable in oil well cementing operations.