The Situation

The client requested for a drilling fluid formulation to drill an exploration well with expected bottom hole static temperature (BHST) up to 453˚ F based on temperature gradient in the area. Besides the ultra-high BHST, high CO2 and H2S was also expected, which raised a concern of logging operation failure over prolonged period of time.

The Solution

After extensive lab work, M-I SWACO proposed conversion of current conventional non-aqueous fluid (NAF) system into the RHADIANT ultra-high temperature drilling fluid by the addition of new MUL† XT high-temperature emulsifier, and ONE-TROL† HT and ECOTROL† HT fluid loss control agents while drilling high temperature section.

The Results

The RHADIANT fluid, with Sarapar-147 base fluid, confirmed the expected performance, delivered excellent filtration control and filtercake quality with stable rheological properties while drilling the 6-1/8” interval. No drilling or lost circulation problems were encountered and drilling performance was up to the expectations. The trips were smooth and the open hole wireline loggings (seven run in total) were performed with minimal issues for over 90 hrs of static condition comparing with wells with the same temperature range.

The Details

As reduction in rheological properties were observed after the conversion in the pilot test, it was decided to treat the system with
the high temperature chemicals gradually in 3 – 4 batches, along with VERSAGEL† HT viscosifier in order to keep the fluid within specification and to avoid any sudden changes in mud behavior. The entire circulating system was converted successfully to RHADIANT fluid approximately 1,320 ft before TD with 7 ppb MUL XT emulsifier, 4 ppb ONE-TROL HT agents, and 2 ppb ECOTROL HT agents. Before trip and logging phase, active system was treated with lime to counteract any CO2 influx.