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

Abstract

Summary Drilling-fluid design for shale plays aims to deal with the lack of wellbore stability associated with fluid-invasion, shale-swelling, and cuttings-dispersion phenomena. Although oil-based mud can be used to achieve these goals, environmental and economic concerns limit its application. This research evaluates the potential of using silica (SiO2) nanoparticles (NPs) (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 WBM (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 ζ-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-pressure/low-temperature (LP/LT) and high-pressure/high-temperature (HP/HT) conditions. In addition, 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 potassium chloride (KCl)/partially hydrolyzed polyacrylamide (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 high colloidal stability with ζ-potential values less than –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 a nearly flat trend in the cumulative filtrate for the NP-WBM at aged conditions, whereas KCl/PHPA suffered a dramatic increase. Also, NP-WBM preserved 43.97% of its initial cuttings-carrying capacity, whereas 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 cuttings erosion and swelling effect by 24.48 and 35.24%, respectively, compared with 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 environmentally friendly alternative for harsher environments.