| dc.description.abstract | The capabilities of different types of nanoparticles (NPs) had been exploited to develop a water-based drilling fluid having better characteristics for harsh drilling conditions. More specifically, the objectives of this work are to: 1) investigate the effectiveness of using different oxide NPs: ferric oxide (of sizes< 50 nm), magnetic iron oxide (of average particle size 50 –100 nm), silica NPs (size =12 nm), and zinc oxide NPs (of sizes < 100 nm) on the rheological properties and filter cake characteristics of Ca-bentonite-based drilling fluid at downhole conditions, 2) conduct a sensitivity analysis of the rheological properties of these drilling fluids and investigate the effect of charge potential, 3) determine the optimum concentration of NPs, and 4) evaluate the effect of different drilling fluid additives on the performance of NPs/Ca-bentonite fluids by formulating and testing a complete bentonite-based drilling fluid formula.
A reduction of 43% in the fluid loss volume was achieved when using 0.5 wt% of ferric oxide NPs with 7 wt% Ca-bentonite suspension compared to that without NPs. However, using silica or zinc oxide NPs at different concentrations resulted in an increase in the fluid loss volume and filter cake thickness. The inductively coupled plasma (ICP) analysis of the filtrate fluids and the scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) of the filter cakes revealed the replacement of the cations dissociated from the Ca-bentonite by ferric oxide NPs at the investigated conditions, which promoted the formation of rigid clay platelet structure. Furthermore, using 0.5 wt% of NPs provided less agglomeration, as shown by the SEM images, and less filter cake permeability. Moreover, the produced filter cake consisted of two layers, as indicated by the computed-tomography (CT) scan. Increasing the concentration of NPs resulted in an increase in the fluid loss and filter cake thickness. At high NP concentration (2.5 wt%), a new layer of the agglomerated NPs generated in the filter cake close to the surface of formation, which adversely affected the cake characteristics. The ferric oxide and magnetic iron oxide NPs/Ca-bentonite fluids were found to have stable rheological properties at different NP concentrations and temperatures (up to 200°F). Additionally, thermally aging these fluids at 350°F for 16 hours showed minor changes in their rheological properties, which confirmed their applicability in drilling downhole environments.
The ferric oxide NPs improved the filter cake and filtration properties of Ca-bentonite-based drilling fluids in the presence of polymer and other additives under both static and dynamic filtration (at 100 rpm). The best filter cake characteristics were obtained when using a NP concentration of 0.3-0.5 wt%. Furthermore, the formulated NPs/Ca-bentonite-based drilling fluids could withstand downhole conditions up to 500 psi and 350°F and produced a filter cake that has 0.151-in. thickness, 6.9 ml filtrate loss volume, and 0.428 µd permeability at this conditions. Moreover, it was noticed that the ultrasonication for at least one hour and bentonite hydration for 16 hours are recommended for better preparation of the formulated ferric oxide NPs/Ca-bentonite-based drilling fluid. | en |
