Experimental and numerical analysis of effective enhancement of wellbore stability in shales with nanoparticles

Abstract One way to reduce wellbore instability in shales is to use agents capable of sealing pores and micro-fractures. The main objectives are 1) to perform pore pressure transmission experiments with test fluids containing nanomaterials, and 2) to develop a model to characterize pore pressure transmission with pore plugging. Pore pressure transmission experiments were performed on two types of shales, Mancos Shale and Eagle Ford Shale, using test fluids containing nanoparticles. An orthogonal test matrix has been developed, which includes different nanoparticle sizes (10 nm, 20 nm, 40 nm), particle types (aluminum oxide, magnesium oxide) and particle concentrations (3 %, 10 %). A mathematical model that incorporates chemical potential, pore plugging, and time-dependent permeability is developed to characterize pore pressure response. The best combinations to decrease pore pressure at the equilibrium state, according to the test matrix, are 10 % 10 nm Al2O3 for Eagle Ford Shale and 10 % 30 nm Al2O3 for Mancos Shale. This nanoparticle-based plugging technique will minimize pore pressure transmission and delay the time to equilibrium, reducing hydration and swelling problems in shale formation. As a result, this research will help to better define drilling fluid properties to enhance wellbore stability in actual wells containing shales.