Vermiculite for enhancement of barite stability in water-based mud at elevated temperature

Abstract

When drilling deep wells and high-temperature high-pressure (HTHP) formations, the solids sagging and inconsistent drilling mud properties are widely encountered and exhibit severe technical and operational challenges. The aim of this work is to provide a new novel solution using “vermiculite” for sagging prevention and enhancing the mud stability. The vermiculite was introduced as anti-sag additive for water-based drilling fluid at elevated temperature. Various quantities of vermiculite were added (0, 1, 2, 3, and 4 lb./bbl) and the mud stability was accordingly evaluated by conducting the static and dynamic sagging measurements. The effects of vermiculite on mud properties were thoroughly investigated by assessing the mud density, alkalinity, rheology, viscoelasticity, and filtration behavior. The practical elevated temperature was simulated experimentally by conditioning the tests up to 250 °F. The results of this work showed an improvement on mud stability as the sag tendency was reduced by adding vermiculite. The amount of 4 lb./bbl vermiculite was enough to mitigate the solids sag at elevated temperature and bring the sag tendency factors to the safe values. The rheological and viscoelastic properties were notably improved with vermiculite. The 14% reduction on plastic viscosity and the increment of yield point by 36% with better gelling structure confirmed the ability of vermiculite to enhance the mud stability. In addition, the 4 lb./bbl-vermiculite contributed to the outperformed filtration performance with less filtrated volume and affinity to formation damage. The vermiculite containing drilling fluid yielded better filter cake characteristics with less thickness, weight, and permeability by 34, 35, and 66%, respectively.