M-I SWACO has released the ENVIROTHERM* NT water-base drilling fluid, which is designed for high-temperature, high-pressure (HTHP) wells, including those in shale plays, environmentally sensitive areas or projects that experience high temperatures and require a water-base drilling fluid system.

The ENVIROTHERM NT drilling fluid is a next generation, environmentally acceptable water-base system that is stable in the presence of contamination from soluble calcium, salts and acid gases. It can be used at temperatures in excess of 450 degF (232 degC) and densities up to 19.0 lbm/galUS (2.3 g/cm3). The drilling fluid has been field proven under severe conditions over 350 degF (177 degC), exhibiting stable properties while drilling and also during prolonged static conditions experienced during tripping, logging and testing operations.

In an HTHP tight gas reservoir in Hungary, an operator was faced with acid gas contamination (CO2 and H2S) and environmental limitations that put constraints on cuttings disposal and oil-base drilling fluid usage. The ENVIROTHERM NT system was used to safely drill to TD. The HTHP fluid loss was controlled while the rheology was actually lower than what the lab tests had shown. The reduced rheology helped minimize the equivalent circulating density (ECD) for the extremely high mud weight of 19.0 lbm/galUS (2.3 g/cm3).

The water-base drilling fluid is simple and easy to manage, requiring minimal dilution for HTHP environments, ensuring the fluid is maintained within specification, maximizing hole stability, drilling efficiency and cost effectiveness. It can be easily converted from a low to a high temperature system with no rheology increase or loss of other properties.

Tags: M-I SWACO