Construction technology of large-scale directional crossing in medium-coarse sand formations

The formations crossed in Fuhe ϕ1016 pipeline project mainly included medium-coarse formations and gravel sand formations, which had abundant groundwater and no cementation, poor integrity and bore wall stability, so large-diameter directional drilling construction in such formations was a high risk procedure. Based on this investigation, this project adopted four-stage broaching procedure through fully analyzing construction horizons, geological conditions and combined with previous construction experience, the drilling mud adopted high quality composite bentonite special for non-excavation operation with polymer cellulose added for treatment improvement. The practice showed that careful analysis of formation data, rational design of construction procedure, mud parameter optimization and selection, as well as real-time control to the construction process can effectively improve the one-time success rate of horizontal directional drilling in similar formation construction.