Rheological Performance of Potassium Formate Water-Based Muds for High-Temperature Wells

Abstract

Drilling mud plays a crucial role during drilling operation as they not only enhance efficient transport of drilled-cuttings from the drill bit to the surface, but also maintain their rheological properties especially in harsh environments to suspend drilled-cuttings when drilling operations stop. Although water-based muds are known to be environmentally friendly and less expensive as compared to oil-based and synthetic-based muds, they exhibit poor performance with less stability when circulating in high-temperature wells particularly with shale formations. Water-based mud systems with potassium brine have proven better results in shale formations; nonetheless, very little is known about their performances in high-temperature environments. This study examines the performance of water-based muds with synthetic polymers and potassium formate brine as additives in high-temperature conditions up to 300 ℉. The drilling muds were formulated using the Taguchi Design of Experiment (TDOE) approach. The muds were prepared and tested in laboratory conditions under the guidelines of safety and drilling fluid testing using the American Petroleum Institute (API) standard. The experimental data obtained showed that the combinations of synthetic polymers and potassium formate brine were able to stabilize the rheology of the water-based muds at elevated temperatures. The usage of potassium formate brine at concentrations of 3.2, 6.7, and 10% aided in stabilizing the drilling mud’s rheological properties after dynamic aging at 300 ℉. Rheological properties such as plastic viscosity and yield point were also found to be almost identical for both static and dynamic aging conditions. Therefore, this study serves as optimization guide to design water-based muds applicable to high-temperature formations.