DOES THE HDD REAMING PASS REMOVE EXTREME ALIGNMENT DOG-LEGS - CASE HISTORY

摘要

In 2008 Pembina Pipelines completed the construction of a pipeline project to supply oil pipeline services to Canadian Natural Resources Limited's (CNRL's) Horizon Mine in the Oil Sands of northern Alberta. Near the middle of the project on a section of 24 inch pipeline a Horizontal Directional Drill (HDD) was required due to access, environmental and land constraints encountered during the summer 2007 construction phase.The geotechnical investigation determined the profile of the directional drill would pass through clay and clay till and the resultant HDD length would be approximately 440 metres. Upon completion of the pilot hole and review of the detailed alignment, it was determined that the pipe might be overstressed if pulled in based on the pilot hole alignment. The as-built pilot hole alignment contained several locations with drill radius significantly smaller than the design radius.It is commonly thought that reaming passes can remove some misalignment of the pilot hole in soft formations. A survey was taken during the final 36 inch ream and a subsequent pass of the steering tool through the HDD bore was carried out after the 36 inch ream. This survey demonstrated the reaming pass may not remove severe dog legs.This paper will detail the field alignment investigation along with associated stress analysis. The paper clearly demonstrates reaming passes may not always remove pilot hole misalignment in soft ground formations. Lengthy time delays were required to carry out detailed stress calculations that ultimately demonstrated that the Pine Creek HDD was acceptable.