Key points are not available for this paper at this time.
Abstract Extended reach wells are drilled to develop the remaining oil in shallow formation just around 600~1400m in China Bohai oilfield. The formation there is terrestrial sediment and heterogeneity is strong, moreover, only water-based drilling fluid can be used as Bohai Bay is an internal bay with weak self-cleaning ability. For these reasons, precise well trajectory control, wellbore cleaning, casing running and cementing are challenges in this region. Facing the problems above, a set of safe and efficient drilling technology for shallow extended reach wells has been developed. Firstly, well profile is optimized referring previous drilling experience, secondly, well trajectory is redesigned using software and directional drilling tools with high buildup rate are selected for precise well trajectory control; thirdly, drilling fluid properties are continuously improved to maintain wellbore cleaning and smooth; Lastly, innovative floating while rotating casing running method and cementing technology are employed to reduce the friction in casing running and avoid leakage during cementing job. The design build rate is about 4 degree/100ft, while the natural inclination reduction rate of formation is serious using classic directional drilling tools that fail to meet this requirement. Thus, uniform wall thickness Positive Drive Motor with 1.5 bend angle and Rotary Steering System of push-the-bit type are selected in surface and second spud drilling to ensure adequate build rate with assistance of software which can track and modify well trajectory while drilling. Water based environmental protection drilling fluid with low viscosity and high shear force are developed to remove cuttings bed and reduce ECD. Meanwhile, the inhibition and plugging of drilling fluid are enhanced to avoid hydration expansion of mudstone. The tripping and back reaming efficiency have been improved by 20%. The drag and torque of casing running in different ways are calculated, innovative floating while rotating casing running method is proposed comprehensively considering the rig capacity and the torsional strength of the casing. Low density cementing slurry system and slurry column structure are optimized to reduce ECD while cementing and cementing quality is excellent. From 2019 to 2021, these technologies have been successfully applied in 7 extended reach wells, with an average drilling efficiency of 97.1%, and the field applications show that the ROP has been improved by 40% while well construction time has been reduced by 28.4% compared with previous operation. Moreover, the horizontal displacement to vertical depth ratio of W1H well is as high as 3.23, breaking the record of Bohai oilfield.
Xie et al. (Mon,) studied this question.