Integrated Technology of Efficient Wellbore Cleaning and Pre-calibration for Ultra-deep and Large Displacement Wells

Ultra-deep and large displacement wells have complex wellbore trajectory, large well deviation and long stable deviation section. The conventional casing program is a combination of ϕ244.5 mm casing and ϕ177.8 mm liner, and there is a need to pre-calibrate the depth while drilling for perforation during the scraping and washing stage. Normally, two trips of string are used to achieve the functions of wellbore cleaning and pre-calibrating while drilling, resulting in low wellbore cleaning efficiency and long operation cycle. Through the integration and optimization of multi-functional cleaning tools, variable gauge casing scratcher, logging tools while drilling and diverter valve tools, the integrated string structure of efficient wellbore cleaning and pre-calibrating depth is designed. Hydraulic simulation, string safety evaluation and process flow optimization were carried out to realize the integrated function of one-trip high-efficiency cleaning of composite wellbore and pre-calibration while drilling. Compared with the conventional two-trip scheme, the efficiency was increased by 30%. The technology has been successfully applied in three ultra-deep and large displacement wells in East China Sea, and the downhole tools work normally. Compared with the conventional technology of the same well type, the single well is shortened by 43.6 hours on average, which has a significant effect on speed-up and efficiency improvement.