Study on the Influence of nanoparticles in the filtrate characteristics and filtrate cake formation of a water based drilling fluid
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In an overbalanced drilling process, the drilling fluid enters into the porous formation creating a layer of filter cake along the borehole. The extent of the filter cake build-up depends much on the particle sizes of the colloids in the drilling fluid, pressure difference and the pore sizes of the formation. The morphological structure of the filter cake together with the filtration characteristics of the drilling fluid determines the formation damage. A proper understanding of the filtration properties and appropriate control of the drilling fluid filtration is advantageous as it could help in mitigating the formation damage and the differential sticking that could occur during a drilling process. In the proposed work, the effect of nanoparticles in controlling the filtrate and its influence in changing the structure of the filtrate cake will be studied. All experiments will be conducted in accordance with the recommended API RP 131 practices. Owing to a larger surface area to volume ratio, nanoparticles added to a drilling fluid is expected to minimize the fluid loss along with the formation of a thin filter cake having low permeability and porosity. Effect of nanoparticle morphology, one having spherical (alumina particles with mean diameter 20nm) and another having a cylindrical structure (multi-wall carbon nano tubes) will be studied. A water based drilling fluid containing Barite and Bentonite as weighing and viscosifier respectively will be used to prepare the basemud sample. Appropriate amounts of nanoparticles will be added to this mud to study the influence of this complex mixture on the filtrate characteristics. A systematic study on the stability of the drilling fluid suspended with nanoparticles and the influence of it on the preparation methodology at varying particle concentrations will be reported. Ceramic disks with varying porosity will be used to study the influence of drilling fluid particle sizes on the pore sizes in the formation. The structure of the filter cake will be studied using Scanning Electron Microscopy (SEM). The thickness, porosity, and permeability of the filter cake will be measured and will be correlated to obtain the optimum nanoparticle loading that would be beneficial for the drilling applications.