The Development and Application of High-Temperature and High-Performance Water Base Drilling Fluid on the well Shunbei 801X

The well 801X in Shunbei area is a key exploratory well located in the Shuntuoguole block in Tarim Basin. This well has total depth of 9,145 m, maximum well angle of 71° and horizontal displacement of 1,075.77 m. To deal with the high temperature high pressure problems encountered during drilling, a high performance water based drilling fluid with density of 2.0 g/cm³ was developed by high temperature additive selection and drilling fluid parameter optimization. Laboratory experimental results have shown that this drilling fluid can function normally at temperatures up to 200 ℃. It has good rheology at high temperatures and can effectively plug the microfractures developed in the shale formations. Filtration rate of this drilling fluid at 180 ℃ was 13.8 mL, and the mud cake was thin and tough. This drilling fluid can also stand the contamination from CO₃^2-, HCO₃^- and salt water. Field application has shown that this drilling fluid had stable properties in drilling the high temperature formations, and its properties were easy to maintain. Tripping of drilling tools was done smoothly, and no downhole troubles were encountered. The well was safely drilled in high rate of penetration. In well testing, the converted oil and gas equivalent was 1,007.6 t. The development of this drilling fluid has provided a useful reference for the optimization of drilling fluids for subsequent drilling operations in the Shunbei block.