Oil Field Engine News

By Staff
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Rotary rig as depicted in an old Oil Well Supply Co. catalog.
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Drilling rig layout.

My good friend Scott Hirshey recently gave me a copy of an old
pamphlet he obtained from the estate of the late Harry Horner, the
well-known oil field engine enthusiast who passed away last year.
The pamphlet, Driiling, Getting Acquainted with Your Company’s
Operations, was written by professor CM. Young and printed by The
Columbia Gas System in 1949. I’ve excerpted portions of the
pamphlet for this issue, as I think it gives a good description of
the cable-tool drilling method under which most of our old oil
field engines labored.

Standard and Rotary Drilling

There are two principal methods of drilling wells; the cable
tool method and the rotary method. In the cable tool method a heavy
drill is dropped upon the rock, which is broken by the blow. In the
rotary method a drill is pressed against the rock with great force
and turned, and the rock is worn away by the concentration of
pressure in a small area.

The Standard Rig

The walking beam is driven by the engine and gives motion to the
tools. As finally developed it was an oak beam 26 feet long,
supported at the middle on a Samson post with one end directly over
the hole. A pitman at the other end is connected to the wrist pin
of the band wheel crank and the band wheel is driven by a belt from
the engine.

On the side of the derrick opposite the band wheel is the bull
wheel on which the drilling cable is wound. On one side of the bull
wheel is a grooved wheel that carries the bull rope, by which the
bull wheel is driven from the band wheel. The other side has a
brake drum for control of the tools when they are run in the
hole.

In order to allow the cable to be fed out as the hole is
deepened it is attached to the walking beam by a temper screw; a
screw allowing six feet of travel through a split threaded box, the
two halves of which are held together by a clamp. When the screw
has been let out its full length of travel, that is, when a
‘screw’ has been drilled, this split box is opened and the
screw is raised through it, and the box is again clamped onto the
screw. This raises the rope clamp by which the temper screw is
attached to the rope.

To make this change the bull rope is thrown onto the bull wheel
and the cable wound up until the tools are supported a little above
the bottom of the hole. Then the rope clamp is moved upward and
tightened on the cable, the bull wheel released and some slack
thrown into the cable, and drilling is carried on again.

When exceptionally heavy strings of casing have to be handled, a
rig with a calf wheel is used. The calf wheel is similar to the
bull wheel but is on the band-wheel side of the derrick and is
driven from the band wheel by chain and sprocket, with the use of
the calf wheel, and with multiple sheaves at the top of the derrick
and in the traveling block that supports the casing, heavy strings
can be handled.

When no calf wheel is used the top of the derrick, called the
water table, carries two sheaves; one for the sand line (which
handles the bailer) and one for the drilling cable. Thus, it will
be seen that the drilling cable runs up from the bull wheel over
the crown pulley and down to the tools. The sand line sheave is set
to one side and the line runs from the bailer up over this sheave
and down to the sand reel, which is commonly driven by friction
from the band wheel.

The sand line and bailer are used in removing cuttings from the
hole. The bailer is a long tube with an upward-opening valve at the
bottom. This valve has a dart, which extends a few inches below the
bottom of the bailer and raises the valve when the bailer reaches
bottom.

The bits are steel forgings made in various sizes and designs to
fit different conditions. The cutting edge is forged to a distinct
edge. The angle of the sides runs from about 90 to 100 degrees,
depending upon the kind of rock that is being drilled. The bit does
not cut the rock, but breaks it.

Since the bit is forged to an edge, the result is that great
pressure is suddenly concentrated on the narrow line on which the
bit strikes the rock. This concentrated pressure is so great that
the strength of the rock is overcome and chips are broken off. Thus
the essence of drilling by the standard method is a series of blows
against the rock.

In order to prevent the accumulation of cuttings on the bottom
of the hole where they would simply be pulverized by following
blows, water is poured into the hole if it is not already present.
The finest cuttings make this water into a mud, which hinders the
settling of the coarse cuttings, and the whole is constantly
stirred up by the up-and-down movement of the tools.

Spudding

When drilling begins, there is not room for tools below the end
of the walking beam, so the walking beam cannot be used. The tools
are hung on the cable and a jerk line is attached to the cable
above the bull wheel and run to the wrist pin on the band wheel
crank. Then when the crank revolves the cable is pulled out of line
and let back again, and the tools are raised and dropped. A
spudding shoe is used to protect the cable, and this is especially
necessary when a wire line is used. The beginning of a hole is
always called ‘spudding in,’ even when a rotary rig is
used.

Conductor Pipe and Drive Pipe

When the hole is started a conductor pipe is set in the ground
and carefully plumbed. This is necessary to keep out the surface
soil and to start the hole in a truly vertical direction. Also
sometimes drive pipe is used. This is a pipe that extends from the
surface to the first solid rock, and because it sometimes has to be
driven down it is called drive pipe. If the material below the
loose surface soil stands well at all, the drive pipe is not
used.

The Rotary Method

Very briefly, it consists of pressing a bit against the rock and
turning it. At the same time a stream of mud is pumped down through
the hollow drill pipe that turns the bit. This mud cools the bit
and carries the cuttings to the surface. Also, because there is a
column of heavy liquid in the hole, gas, oil or water cannot flow
in from the beds passed through and the caving off of fragments of
rock is prevented, or at least hindered.

The bits used after hard rock is met have a set of wheels much
like cog wheels with sharp teeth. These roll around against the
rock and are pressed against the rock by the weight of the drill
pipe. Thus, great pressure is concentrated on the teeth and the
rock is broken by this pressure. The drill pipe is turned at the
surface by a rotary table that is driven by a steam engine or other
motor. The drill pipe slides down through the rotary table and new
lengths are added at the top as needed. Thus drilling is almost
continuous. But the changing of bits, when this is necessary, is a
long job because all of the drill pipe has to be pulled out of the
hole and then run back again. Since it is not necessary to shut out
water, little casing is run until the hole is finished. Drilling is
more rapid than with a standard rig, but the rig costs much more
and much more power is required, as well as a larger crew. It is
the saving in time, which has led to the use of the rotary in those
fields to which it is suited.

I hope you enjoyed this brief description. As ever, anyone
interested in an OFES society membership please write or e-mail at
the address below.

Contact the Oil Field Engine Society at: 1231 Banta’s
Creek Road, Eaton, OH 45320-9701. On the Web at
www.oilfieldengine.com or e-mail at: oilengine@voyager.net

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