Smart Spacer Fluid Modified with Iron Oxide Nanoparticles for In-Situ Property Enhancement was developed for Cleaning Oil Based Drilling Fluids and Characterized Using the Vipulanandan Rheological Model

Abstract During the installation of oil and gas production wells, it is critical to have a successful cementing operation. The quality of the cementing job strongly depends on the cleaning efficiency of the spacer fluid in removing not only the drilling fluid with the cuttings but also the filter cakes during the drilling operation. Based on the depth applications, different types of spacer fluids are used in the oil gas industry. In this experimental study modifying the smart spacer fluid properties in-situ was investigated. Optimization of spacer formulation was carried by having material properties such as density, rheology and cleaning efficiency as the variables. In this study, using the maximum shear stress tolerance of the spacer fluid determined using the Vipulanandan rheological model was investigated to quantify the cleaning efficiency of the spacer fluid. In this study, the effects of pressure, temperature and magnetic field strength on the electrical resistivity and rheological properties of a sensing smart spacer fluid modified with iron oxide nanoparticles (nanoFe2O3) were investigated. The temperature was varied from 25°C to 75°C. The magnetic field strength was varied from 0 T to 0.6 T. The nanoFe2O3 contents (particle size of 30 nm and surface area of 38 m2/gm) in the spacer fluid were varied up to 1% by the weight of spacer fluid to enhance the sensing and rheological properties of the spacer fluid. The initial resistivity of the spacer fluid without any nanoFe2O3 at 25°C was 0.2 Ωm. Addition of 1% nanoFe2O3 increased the electrical resistivity by 3.5%. Adding nanoFe2O3 enhanced the piezoresistive behavior of the smart spacer fluid. The electrical resistivity changed by 0.7, 5 and 12% for the spacer fluids with 0,0.5% and 1% nanoFe2O3 respectively for a maximum pressure of 500 psi. Increase in the magnetic field strength improved the rheological properties while increasing the temperature decreased the rheological properties of the spacer. The rheological properties of the spacer fluids were characterized by high strain rate to determine the nonlinear behavior of the shear thinning spacer fluid. The spacer fluid rheology was modelled using Bingham-plastic model, Herchel Bulkley model and Vipulanandan model. The electrical resistivity was used as sensing parameter to monitor the percentage of oil cleaning efficiency of the spacer fluid. Based on the new Vipulanandan rheological model, the yield stress (τo) of the modified spacer fluid increased by 6% to 100% depending on the oil content, nanoFe2O3 content, temperature and magnetic field strength. The maximum shear stress tolerance (τmax) for the spacer fluid increased from 49.4 Pa to 65.5 Pa, 33% increase at the temperature of 25°C with 1% addition of nanoFe2O3. The cleaning efficiency of the spacer fluid in removing oil based drilling fluid contamination was 79.8% without the addition of nanoFe2O3. With the addition of nanoFe2O3 the cleaning efficiency increased from 79.8% to 99.4%, 20% increase in the efficiency. The maximum shear stress tolerance (τmax) correlated well with the cleaning efficiency. Also the change in the electrical resistivity of the spacer fluid after cleaning correlated well with the cleaning efficiency and hence can be used for in-situ monitoring of the cleaning operation.