Abstract
Oil-based drilling fluids (OBDFs) are essential for drilling in challenging environments, particularly those with high-pressure and high-temperature (HPHT) conditions. However, maintaining optimal OBDF performance in such extreme environments requires specialized additives. This study investigates the potential of a novel organoclay (OC), Claytone-3, as a rheological additive to enhance the performance of OBDFs under HPHT conditions. Claytone-3's performance is directly compared to a pre-exisiting OC (MC-TONE) to quantify the improvements offered by this novel additive.
To understand the structural and compositional differences between the two OCs, a comprehensive characterization was conducted. This involved employing several techniques including X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and particle size distribution (PSD). The impact of Claytone-3 on critical mud properties was then rigorously evaluated through a series of experiments designed to simulate downhole conditions. These experiments focused on key aspects of drilling fluid performance, including emulsion stability, sag tendency, rheological properties, and filtration properties. Static and dynamic sag tests were conducted at 275/150°F to evaluate the ability of Claytone-3 to prevent barite sag, a common issue in HPHT wells. Rheological properties including plastic viscosity (PV), yield point (YP), and the PV/YP ratio, were measured at 275°F after hot rolling (AHR) for 16 hours at 275°F and 500 psi differential pressure to assess the fluid's carrying capacity and hole cleaning efficiency. Finally, API filtration tests were performed at 275°F and 500 psi differential pressure to determine the effectiveness of Claytone-3 in minimizing fluid loss and forming a thin, impermeable filter cake.
The results demonstrate that Claytone-3 enhances OBDF performance across all tested parameters. Claytone-3 exhibited a 2% improvement in emulsion stability compared to the reference OC and effectively mitigated both static and dynamic sag, ensuring barite suspension even under challenging HPHT conditions. Furthermore, Claytone-3 yielded a 1% increase in PV, an 11% increase in YP, and a 10% improvement in the PV/YP ratio compared to the MC-TONE formulated fluid, indicating improved carrying capacity and hole cleaning potential. Finally, Claytone-3 demonstrated a 2% reduction in filtrate volume and an 11% reduction in filter cake thickness, contributing to improved wellbore stability.
This study underscores the potential of Claytone-3 as a high-performance rheological additive for OBDFs in HPHT environments. By improving emulsion stability, sag resistance, rheological properties, and filtration control, Claytone-3 offers a promising solution for enhancing drilling efficiency, reducing non-productive time, and mitigating risks associated with HPHT drilling operations.
