Practice and understanding of drilling technology in ultra deep Well Xingang 1

Well Xin’ gang 1 is the deepest ultra deep exploration well of Dagang oilfield with designed depth of 6 700 m. Because of ultra deep depth and several pressure systems existing, the difficulty of well structure design is extremely large. The Well Xin’ gang 1 is characterized by deep buried targets formation, super hard lithology, low ROP, and large sets of basalt in Dongying and Shahejie formation could easily lead to well collapse and leak. The cementing quality is difficult to be ensured because the long open hole interval of 2 380 m in the third spudding and large temperature difference between upper and lower hole. Besides, the high downhole temperature challenges to the performances of drilling fluid, and complicated geological lithology of build-up and hold interval requires a tough task of well trajectory control. Aiming to these difficulties, Mountains of work has been done from the aspects of well structure program optimal design, anti-high temperature drilling system selection, ultra-deep well trajectory control, ultra deep well cementing, ROP improving and safety operation. Based on these efforts the well finally was completed successfully, which accumulated a wealth of experience about ultra deep well drilling technology in Dagang oilfield.