Stabilization of Drilling Foams Using Nanoparticles

Abstract Foam is the preferred fluid for underbalanced drilling due to its superior hole-cleaning capacity and reduced liquid requirements. However, it must have reasonable stability to function as a drilling fluid under borehole conditions. Unstable foam loses its viscosity and generates drained liquid that causes slugging flow, resulting in temporary overbalance that can damage the formation. This study aims to improve foam stability of aqueous foam using nanoparticles with unique surface properties. Due to their small sizing and large specific surface area, nanoparticles exhibit unique properties. In addition, their surfaces can be modified to display the desired properties for a given application. In this study, bare (NS1) and coated silicon oxide nanoparticles (NS2, and NS3) have been utilized to enhance the stability of foams. A foam circulating flow loop with horizontal pipe viscometers and a vertical drainage testing cell was used to create foams and analyze their characteristics. At 1000 psi, foams with different nanoparticle concentrations and foam qualities were generated. Their rheology and stability were then investigated. A sonicator and laboratory blender were used to mix nanoparticles with water and anionic surfactant to prepare the liquid phase of foams. The hydrostatic pressure distribution at different column depths as a function of time was measured after trapping a fully generated foam in a vertical test cell. Initially, baseline foams without nanoparticles were tested. Later, two types of nanoparticles (bare and coated) were tested at different nanoparticle concentrations (1 to 3 wt%). Increasing the baseline foam quality (in-situ gas volumetric concentration) from 40 to 60% resulted in a significant increase in apparent viscosity and a reduction in liquid drainage. Nanoparticles containing foam also showed similar trends of property changes with foam quality. Besides this, experiments demonstrated the impact of nanoparticles on the characteristics of foams. The viscosity and stability of foams increased with the addition of nanoparticles. Also, the drainage of foams noticeably decreased while their half-life improved with the concentration of nanoparticles. The effectiveness of nanoparticles is also influenced by their type. Silica nanoparticles that are coated (functionalized) with an amino group (NS2) provide better foam stability than regular nanoparticles (NS1) and nanoparticles treated (coated) with silane (NS3). This study contributes to the formulation of a new generation of drilling foams that can be used in harsh borehole environments where foam instability becomes a major concern.