Green drilling fluid additives for a sustainable hole-cleaning performance: a comprehensive review

Drilling fluids are the core of drilling operations, and they are responsible for many roles, such as lubricating drill string, cooling down drilling equipment, maintaining wellbore integrity, and transporting cuttings to the surface. High-energy demands have caused the oil and gas production rates to increase by orders of magnitude, which is accompanied by increased usage of different drilling fluids, including oil-based muds (OBM) and water-based muds (WBM). Large amounts of fluids used without caution can cause severe consequences to the environment if not well monitored. Therefore, the field has been exploring the utilization of biodegradable and environmentally friendly additives (green). These green formulations can promote a safer alternative to the currently available commercial additives, meet sophisticated drilling requirements, and ensure resource sustainability. A comprehensive overview of the literature has been conducted in this review, starting with a background on oil and gas reservoir types and cuttings transportation mechanisms, followed by a discussion on various recent green fluids or additives emerging in the field. In addition, an economic comparison has been conducted to assess the feasibility of the reviewed green formulations. Finally, the review ends with a summary and future prospective on the topic. In conclusion, this review suggests the development of multifunctional drilling fluids with good hole-cleaning properties, utilizing additives studied for different functions (e.g., filtration). Enhancement of rheological properties achieved through the addition of these additives indicates their suitability for hole-cleaning applications, which must be confirmed through additional studies. Consequently, filling the existing gap in the literature is by triggering research topics in this area.