A look at these two types of drives.
Most all drilling machines
manufactured today are top-head drives. Many oil-drilling rigs manufactured
today are leaning toward top-head drives, mostly because they are safer.
However, top-head drives are much slower than kelly drives, also known as
rotary table drives.
Top-head drives are slower, but much safer in that most don’t include free-fall
cable hoists with a brake to stop the hoist. Free-fall cable hoists are fast,
but if not properly operated, can drop the tools, harming and in some cases,
killing those in the way. If a top-head drive does have a cable hoist, it
usually is a power-up, power-down hoist, which is slower, but much
In the past, kelly drives were most popular for seismograph (shot hole)
drilling because they drilled fast. I’ve known drillers to drill a 200 foot
hole in 20 minutes hole to hole. Seismograph drillers only had to drill the
hole and move to the next hole and drill again. A shooter would come to the
hole right after it was drilled to insert the explosive.
These drillers were like race car drivers; they would race to see who was the
fastest. The last rig would move to the front of the line to continue drilling.
I’ve seen six rigs drilling a line. Sometimes these rigs could be seen drilling
cross country for miles.
A shot-hole driller friend was the scorekeeper – and referee – because everyone
knew that he was the fastest, drilling a 200-foot hole to hole in 20 minutes.
If the ground was reasonably level, the drillers would move with the mast up.
When the rig got to the next hole, the driller would drop the portable mud pan
and start drilling with air until his help filled the mud pit with water and
mixed mud. When the mud was mixed, the driller would switch from air to mud,
and continue drilling.
Most of the drillers had two water trucks, one on site and one going after more
water. On some locations, the Bureau of Land Management required a third water
truck just in case there was a fire.
In winter, it usually was windy, and with the chill factor, could get to 40
degrees F below zero. The drillers all had hot boxes, propane heaters that circulated
antifreeze through the engines at night and on weekends. They had the mud pumps
encased in a metal shield with the truck exhaust inside to keep the pump from
freezing. They had to drain the mud pumps, hoses and all mud lines every night.
Each morning, they had to use propane torches to thaw out lines and valves that
The water trucks had hot boxes, and the engine exhaust ran through the middle
of the water supply tank and the automatic vacuum suction cut-off device, and
exited at the 2-inch water valve on the rear.
I was a George E. Failing field salesperson during this time. I visited the
drillers on site in Montana one winter day. The chill factor was 40 degrees F
below zero, so I rolled my window down only about an inch, and announced that I
would see them in the spring!
Porky's Hole Thoughts: Kelly Drive vs. Top-head Drives
July 1, 2012