Abstract
High performance (HP) water-based drilling fluids are particularly advantageous compared to conventional water-based systems because they provide faster penetration rates, enhanced hole cleaning, greater shale inhibition, and improved wellbore stability. Most high performance water-based drilling fluids only tolerate operating temperatures up to 300°F because they depend on biopolymer-based viscosifiers. Deeper exploration in extreme high temperature reservoirs (>300°F) requires new drilling fluid technologies. A new high performance, high temperature water-based drilling fluid that is both thermally and rheologically stable at 400°F was developed to meet these demands.
A novel synthetic polymer was developed for use in a new HP water-based mud (WBM). The new fluid system was hot rolled at 150°F for 16 hours to condition the fluid before testing. The conditioned fluids were subjected to dynamic or static aging conditions, with temperatures ranging from 300 to 400°F. The viscosity and pH values were determined with a direct indicating viscometer and pH meter, respectively. The Anton Paar viscosity was measured using the CC. 27 cup and bob geometry. The fluid loss properties of the fluids were determined by high pressure/high temperature (HP/HT) filtration at 350°F according to the API recommended practice.
This paper provides an overview of the current high performance drilling fluid chemistry, as well as the detailed study of the high temperature, high performance water-based drilling fluid formulated with 10.0 to 17.0 lbm/gal densities that exhibits a stable rheological profile. For example, a 14.0 lbm/gal formulation aged at 150°F for 16 hours provided a plastic viscosity (PV) of 29 cp and a yield point (YP) of 22 lbf/100 ft2. After static aging for 48 hours at 400°F, the fluid provided a PV of 27 cp and YP of 24 lbf/100 ft2. The new fluid maintains viscosity, adequate suspension, low shear strengths, shale stability, and filtration control up to 400°F, and the fluid is resistant to contamination.
This clay-free system uses a novel synthetic polymer viscosifier and filtration control agent, enabling the removal of thermally labile biopolymers without the addition of clay-based viscosifiers; it is environmentally acceptable for both land and offshore drilling and can be formulated with either chloride containing or non-chloride containing salts. The new fluid formulation provides reliable thermal stability that can function in extreme high temperature wells, while preserving the benefits of HP water-based drilling fluids.
