Technologies for the safe and efficient drilling of ultradeep wells in the areas with intrusive rocks in the Shunbei Oilfield

In the Shunbei Oilfield, the areas with irruptive rocks have many formations that tend to suffer collapse and mud loss easily, the Paleozoic rocks are of poor drillability and the direction detector in Ø120.6 mm hole is vulnerable, which decreases the rate of penetration (ROP) and increases the drilling cycle. By analyzing wireline logging, mud logging and testing data, this paper established the three-pressure profile, selected the setting positions and optimized the completion hole size from 120.6 mm to 143.9 mm. In view that igneous rocks tend to suffer mud loss and intrusive rocks tend to suffer collapse, the mud loss control and collapse prevention technologies and countermeasures were prepared. The separate-layer ROP improvement technology of nonplane-tooth PDC bit was matched by investigating the characteristics of rock strength. By researching the building capacity of screw and designing the hole trajectory of “high first and then low”, bending screw, directional drilling bit, MWD instrument and inverted drill string were optimized so as to satisfy the requirements of actual directional drilling at 175 ℃. Based on researches and applications, an efficient drilling technology with wellbore stabilization and ROP improvement as the core was developed. It has been applied on site in 6 wells. Thanks to its application, the drilling cycle is shortened by 26.5 d and the domestic record of deepest Ø143.9 mm onshore horizontal well (8 220 m) is set up.