Evaluation of Using Fly Ash as a Weighing Material for Oil-Based Drilling Fluid

Innovation and sustainability are essential in the fast-changing oil and gas business. Fly ash, a byproduct of coal combustion in power plants and factories, has become a valuable resource in many industries, changing the concept of waste materials. Fly ash is essential to sustainable development and environmental care due to its unique qualities and multiple applications. In the drilling industry, a well-designed drilling fluid is essential and this requires the use of various additives that serve specific functions to achieve a successful borehole. This study investigates the use of fly ash as a weighing material in oil-based mud, with the intent to develop an economically acceptable drilling fluid system using industrial waste. The study compared fly ash to three commonly used weighing materials in the drilling industry: calcium carbonate (CaCO₃), barite (BaSO₄), and ilmenite (FeTiO₃). Drilling fluids were prepared using these weighing materials at various weights, and their properties (density, electrical stability, rheological features, and filtration properties) were measured using API-recommended methods. The rheology and filtration tests were conducted at elevated temperatures (350 °F). The results indicate that fly ash has the potential to be a useful weighing material in drilling operations. It can increase the fluid density up to 10 ppg without affecting the rheological properties at 350 °F. Additionally, the electrical stability of the drilling fluid was enhanced compared to the other used weighing materials. The addition of fly ash also improved rheological characteristics such as plastic viscosity, yield point, and gel strength without affecting HPHT filtration properties. The carrying capacity was improved by 53 and 86% over calcium carbonate and barite, respectively. Overall, the findings suggest that fly ash can be a viable alternative to other weighing materials in the recommended density range.