A Novel Rheological Additive for High-Performance Oil-Based Drilling Fluids in High-Pressure and High-Temperature Conditions

Drilling operations in high-pressure and high-temperature (HPHT) environments present significant challenges to drilling fluid performance. Oil-based drilling fluids (OBDFs) play a critical role in ensuring wellbore stability, controlling formation pressure, and facilitating efficient drilling operations in such challenging environments. However, maintaining optimal OBDF performance in HPHT conditions requires careful formulation and the incorporation of high-performance additives. This study focuses on evaluating the performance of a novel organoclay (OC), Claytone-II, as a rheological additive in OBDFs under HPHT conditions. Claytone-II's potential to enhance drilling fluid properties is assessed through a comparative analysis with a commercially available OC (MC-TONE). A comprehensive characterization of both OCs, involving techniques such as X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and particle size distribution (PSD), was conducted to understand the structural and compositional differences contributing to their performance. To assess the potential of Claytone-II, its performance was rigorously compared to MC-TONE through a series of experiments simulating downhole HPHT conditions. Claytone-II's impact on key OBDF properties, including emulsion stability, sag resistance, rheological properties and filtration characteristics were evaluated. Static sag tests were evaluated at 275°F in both vertical and inclined (45°) wellbore configurations. Moreover, dynamic sag was measured at 150°F to simulate fluid behavior during circulation. Furthermore, rheological and filtration properties were determined at 275°F after hot rolling (AHR) the samples for 16 hours at downhole conditions (275°F and 500 psi differential pressure). The results demonstrate that Claytone-II offers significant improvements across all evaluated parameters. It exhibited enhanced emulsion stability (8% increment), effectively mitigating the separation of oil and water phases under HPHT conditions. Furthermore, Claytone-II demonstrated superior sag resistance, preventing the settling of weighting agent (barite) and ensuring consistent drilling fluid density even at high temperatures. Moreover, plastic viscosity (PV), yield point (YP), and the PV/YP ratio improved by 7.5%, 14%, and 6% increments respectively. This indicates that Claytone-II improved the fluid's carrying capacity and hole cleaning efficiency, crucial for removing drilling cuttings and maintaining wellbore stability. Finally, Claytone-II contributed to better filtration control by reducing fluid loss (8% increment) and forming a thinner, more impermeable filter cake (12.5% increment), which is essential for preventing formation damage and maintaining wellbore integrity. This study highlights the potential of Claytone-II as a high-performance rheological additive for OBDFs in demanding HPHT environments. Its superior performance compared to a commercial counterpart is demonstrated through enhanced emulsion stability, sag resistance, optimized rheological properties, and improved filtration control. By mitigating risks associated with HPHT drilling, Claytone-II offers a promising solution for enhancing drilling efficiency and improving the overall success of HPHT drilling projects.