Borehole
Definition
A borehole is the raw, drilled opening created by the drill bit and rig as it penetrates subsurface material. In well drilling, the borehole diameter is typically sized to accommodate the well casing with space for a grout seal between the casing and the borehole wall — standard residential boreholes in Northern Idaho run 6 to 8 inches in diameter. The borehole may pass through sediment, clay, gravel, and basalt rock formations before reaching the target aquifer. As drilling proceeds, cuttings returning to the surface are examined by the driller to identify formation changes and confirm when the aquifer zone has been reached. In hard rock environments common in parts of Northern Idaho, the bedrock section of the borehole is typically left open (uncased), with casing running only through the unconsolidated overburden above.
Frequently Asked Questions
Why Borehole Matters
How Trident Drilling Company Uses It
Trident Drilling selects borehole diameter based on the intended casing size and anticipated aquifer conditions for each project site. In Northern Idaho's mixed geology — sediment zones near the Rathdrum Prairie Aquifer and basalt formations in other areas — Trident monitors borehole cuttings throughout drilling to confirm formation type and identify aquifer entry depth, using that data to inform real-time drilling decisions.