High-temperature core drilling fluid technology of Well Songke-2

The completion depth of Well Songke 2 is 7108.88 m. At the time 38h after the well completion, the bottom hole temperature was 241℃. Three kinds of drilling fluids were investigated in laboratory according to the formation and temperature conditions, and they respectively are the potassium chloride-polysulfonate system which is resistant to temperature of 180℃, the polymer drilling fluid which is resistant to 230℃ and formate-polymer drilling fluid which is resistant to 250℃. The experimental data show that these drilling fluids have good high temperature stability and low HTHP filtration loss. Through detecting the quality of drilling fluid real time, the predicted problems could happen through over-temperature detection, which make indoor experiments to guide in-site maintenance in the project construction, ensure the stability performance at high temperature interval, and guarantee the coring operation smoothly. In addition, the drilling fluid of each system achieves a safe and smooth transition during the conversion, without any waste slurry, which greatly saves the cost. The logging and casing running before cementing could be successfully completed at one time, which further proves that the drilling fluid used has good high temperature stability.