Silica and Graphene Oxide Nanoparticle Formulation to Improve Thermal Stability and Inhibition Capabilities of Water-Based Drilling Fluid Applied to Woodford Shale

Abstract

Abstract Drilling fluid design for shale plays aims to prevent wellbore instability problems associated with fluid invasion, shale swelling, and cuttings dispersion. Although oil-based mud (OBM) can be used to achieve these goals, environmental and economic concerns limit its application. This research evaluates the potential of using silica nanoparticles (SiO2-NPs) and graphene nanoplatelets (GNPs) as drilling fluid additives in a single formulation to improve shale inhibition and long-term stability of water-based mud (WBM) against temperature effects. The design of the nanoparticle water-based mud (NP-WBM) followed a customized approach that selects the additives according to the characteristics of the reservoir. Characterization of Woodford shale was completed with X-ray diffraction (XRD), cation exchange capacity (CEC), and scanning electron microscopy (SEM). The aqueous stability test and zeta-potential measurements were used to assess the stability of the NPs. NP-WBM characterization included the analysis of the rheological properties measured with a rotational viscometer and the evaluation of the filtration trends at low-temperature/low-pressure (LTLP) and high-temperature/high-pressure (HTHP) conditions. Additionally, dynamic aging was performed at temperatures up to 250°F for thermal stability evaluation. Finally, chemical-interaction tests such as cutting dispersion and bulk swelling helped to analyze the effect of introducing NPs on the inhibition capabilities of the WBM. Conventional KCl/PHPA fluid was used for comparison purposes. The results of this investigation revealed that SiO2-NPs and GNPs acted synergistically with other additives to improve the filtration characteristics of the WBM with only minor effects on the rheological properties. NPs exhibited a high colloidal stability with ζ-potential values below-30 mV, which warrants their dispersion within the WBM at an optimal concentration of 0.75 wt.%. The high thermal conductivity of NPs played a key role in promoting an almost flat trend in the cumulative filtrate for the NP-WBM at aged conditions, whereas KCl/PHPA suffered a drastic increase. Also, NP-WBM preserved 43.97% of its initial cutting carrying capacity, while KCl/PHPA experienced a severe reduction of 95.24% at extreme conditions (250°F). Despite the high illite content of the Woodford shale, the NP-WBM exhibited superior inhibition properties that reduced cutting erosion and swelling effect by 24.48% and 35.24%, respectively, compared to the KCl/PHPA fluid. Overall, this investigation supports the potential use of nanomaterials to enhance the inhibition capabilities and the long-term stability of WBM for unconventional shales, presenting an eco-friendly alternative for harsher environments.