Definition - What does Double-Entry Well mean?
In trenchless construction, double-entry wells are horizontal wells that are drilled and completed at both ends. That is, the well extends and is accessible from the launch pit to the reception pit at the ground surface. Double-entry wells are constructed using horizontal directional drilling techniques whereby a pilot bore is initially drilled followed by a reamer to enlarge the bore to the required size.
Double entry wells are also known as double-entry completions or dual-entry completions.
Trenchlesspedia explains Double-Entry Well
Once the location of the launch pit is determined, the pilot bore is drilled using a guidance and steering system located on the ground level to ensure that the drill emerges at the desired reception pit location.
Typically, the pilot borehole must be back reamed to a larger size to facilitate installation of the casing. As the reamer is retracted, drill roads are added behind it to maintain a continuous installation throughout the borehole. Back-reaming may also be done in multiple passes if the bore diameter is sufficiently large.