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The energy industry is exploring sustainable chemistry and engineering solutions for exploitation of shale reservoirs. Smectite-rich shale is challenging to drill with traditional water-based drilling fluid (WBDF). The objectives of this study are (i) to investigate acute toxicity of drilling fluids and (ii) to enhance the rheological properties, lubricity, and clay inhibition behavior of WBDF by adding Tween 80 (T80)/ZnO nanoparticles. Acute toxicity results revealed 100% survival rate of white leg shrimp in WBDF waste. At 0.7 g, the optimum concentration of T80ZnO, the plastic viscosity (PV) was improved by 12%; the negative surface charge of nanomaterial might have improved repulsion forces/stability and enhanced viscosity in the drilling fluids. Yield point (YP) was improved by 71%, moreover 10 min gel strength (GS) and 10 s GS were significantly increased by 32 and 54%, respectively. The metal oxide nanosolids induced heat transfer characteristics and ensured gelling and yield strength properties. Lubricity was slightly increased by 7%; the ZnO nanorods between the two sliding contact surfaces (i.e., assuming drill pipe and casing) improved lubricity. Filtrate loss (FL) volume was considerably minimized to 17 and 30% at API and high-pressure, high-temperature (HPHT) conditions, respectively; this observation could be explained by pores plugging in the filter paper. Heated clay swelling inhibition was optimized after addition of 0.6 g of T80ZnO nanoparticles to WBDF. The clay inhibition was enhanced by 9 and 17% when compared to conventional WBDF and fresh water, respectively; this progress might have attributed to the corresponding: (i) pores plugging in the clay and (ii) interparticle pores bridging between existing drilling additives and nanomaterial. The above findings identify that this drilling fluid could attain sustainable environmental and operational success while drilling into montmorillonite/smectite rich-clay and shale rock.

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The world’s energy demand is steadily increasing where it has now become difficult for conventional hydrocarbon reservoir to meet levels of demand. Therefore, oil and gas companies are seeking novel ways to exploit and unlock the potential of unconventional resources. These resources include tight gas reservoirs, tight sandstone oil, oil and gas shales reservoirs, and high pressure high temperature (HPHT) wells. Drilling of HPHT wells and shale reservoirs has become more widespread in the global petroleum and natural gas industry. There is a current need to extend robust techniques beyond costly drilling and completion jobs, with the potential for exponential expansion. Drilling fluids and their additives are being customized in order to cater for HPHT well drilling issues. Certain conventional additives, e.g., filtrate loss additives, viscosifier additives, shale inhibitor, and shale stabilizer additives are not suitable in the HPHT environment, where they are consequently inappropriate for shale drilling. A better understanding of the selection of drilling fluids and additives for hydrocarbon water-sensitive reservoirs within HPHT environments can be achieved by identifying the challenges in conventional drilling fluids technology and their replacement with eco-friendly, cheaper, and multi-functional valuable products. In this regard, several laboratory-scale literatures have reported that nanomaterial has improved the properties of drilling fluids in the HPHT environment. This review critically evaluates nanomaterial utilization for improvement of rheological properties, filtrate loss, viscosity, and clay- and shale-inhibition at increasing temperature and pressures during the exploitation of hydrocarbons. The performance and potential of nanomaterials, which influence the nature of drilling fluid and its multi-benefits, is rarely reviewed in technical literature of water-based drilling fluid systems. Moreover, this review presented case studies of two HPHT fields and one HPHT basin, and compared their drilling fluid program for optimum selection of drilling fluid in HPHT environment.

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