High-Temperature, High-Performance Water-Based Drilling Fluid Helps Operator Drill First Exploratory Well in Environmentally Sensitive Area

This paper presents the design and execution of a high-temperature, high-performance water-based drilling fluid (HPWBF) to overcome challenges associated with handling limitations of oil-based waste in the area. The exploratory well targeted Formation Palermo Aike, an asset that is expected to have a high impact on the expansion of natural resources for the country to about 10 BBOE. This could make it the second most important unconventional resource after Formation Vaca Muerta in the country. The approach to this challenge involved the design of a drilling fluid that would enable the operator to acquire core samples and conduct electric logging in a pilot hole. This would lead to the flawless drilling of a horizontal well within a promising hydrocarbon-bearing formation section. Fluid qualification involved extensive and unique laboratory testing to address unknown shale formations, temperatures as high as 185°C (365°F), and pore pressures expected to reach 1.9 SG (15.9 ppg). Success criteria included the maintenance of wellbore stability. Specific goals included resistance to barite sag and the maximization of fluid stability for extended static periods during logging at anticipated high bottom hole temperatures. The vertical 8 ¾-in. pilot hole was drilled for approximately 670 m (2,198 ft) with 1.83 SG (15.3 ppg) fluid density. Core plugs were retrieved from 3,438 m (11,276 ft) to 3,474 m (11,394 ft). The 8 ¾-in. curve section was drilled for 635 m (2,080 ft) with 1.83 SG fluid density, landing at 90 degrees inclination. Lubricity was crucial to build angle, and the inherent lubricious nature of the fluid helped achieve the coefficient of friction (COF) target. The 6 1/8-in. lateral section was drilled for approximately 1,080 m (3,543 ft) with 1.83 SG fluid density. Fluid maintenance was difficult in water evaporation due to the high temperatures (164°C / 327°F). The engineered high-temperature HPWBF allowed the evaluation of Palermo Aike formation and helped retrieve quality cores for the evaluation of the producing formation. The team performed five logging runs with the well in static conditions for almost five days (116 hours) without any signs of fluid or formation instability. The logs allowed the collection of a large amount of geological information to establish areas with the greatest potential for production. They also provided insights into future targets for hydraulic fractures. The pilot, curve, and lateral sections were drilled with excellent performance for inhibition, fluid stability, and hole cleaning. The high-temperature, HPWBF was formulated with a novel dual function, high-temperature polymer that provides viscosity and filtration control. This new polymer allows for the removal of thermally labile biopolymers found in conventional high-performance WBFs without the addition of clay-based viscosifiers. Advanced lab testing was performed to evaluate the stability and pumpability of the fluid in long static conditions at bottom-hole temperature (BHT) as high as 185°C (365°F).