The drilled hole in the ground before casing and screen are installed.
The borehole is the open cylindrical hole the rotary rig produces as it drills. Borehole diameter is always larger than the inside diameter of the finished well casing — the difference becomes the annulus that gets grouted or filled with gravel pack. Typical Utah residential boreholes are 8 to 10 inches; agricultural boreholes are commonly 14 to 22 inches.