Technical Program of Trenchless Pipeline Directional Drilling Crossing Unfavorable Stratum

摘要

Trenchless pipeline directional drilling technology has been widely used in pipeline crossing. However, it is always inevitable to cross the unfavorable stratum during the pipeline directional drilling construction, which has become a difficult problem for pipeline directional drilling crossing technology and hinder its development and application. Therefore, unfavorable stratum including high-hardness rock, pebble gravel stratum, sand and soil stratum are researched and their lithologic character is analyzed. The Horizontal Directional Drilling (HDD) technical difficulties under the circumstances of unfavorable stratum are summarized and the possible adverse effects during construction process are predicted. For wellbore collapse, drilling fluid leakage, wellbore instability and low efficiency of breaking rocks, technical program is proposed on the basis of selection of drilling fluid, structure of stratum, drilling methods and method of using well casing. A new method is introduced for directional drilling crossing unfavorable stratum, which can decrease the construction risk in the condition of unfavorable stratum, reduce construction cost and guarantee construction period.