Strap cutter and method

A strap cutter is secured to the top structure on an oil well casing and as the discharge pipe supporting a submersible pump is withdrawn, the cutting head of the strap cutter engages with and cuts the straps which secure the pump power cable to the discharge pipe. The strap cutter is manually guided into place but employs the upward motion of the discharge pipe string to supply the cutting force. The method comprises the use of the upward motion to accomplish the cutting step.

BACKGROUND 
This invention is directed to a strap cutter for the cutting of straps 
between the discharge pipe string and the power cable to the submerged 
electric pump motor as the discharge pipe string is pulled. The method 
comprises the steps involved in this procedure. 
Most subterranean oil must be pumped from the ground. A casing extends from 
the surface down into the oil pool, and is perforated in the oil-producing 
zone to permit the oil to flow into the casing. A common oil recovery pump 
structure, especially found in the older, shallower oil fields, is a 
surface pump jack which pulls a pump rod which extends to a pump cylinder 
in the oil adjacent the bottom of the casing. An advantage of this 
structure is the fact that the motive unit is on the surface, and is 
easily accessible for maintenance. A disadvantage is the length of the 
pump rod string, which becomes very long for greater well depths. 
Submersible pumps are now widely used for the recovery of oil. They 
comprise an electric motor-pump combination which is positioned in the 
lower portion of the casing in the oil pool therein. The discharge pipe 
string is directly connected to the pump to receive the pumped oil, and 
the pipe string also serves as a mechanical support for the pump and its 
motor. Of course, electric power must be supplied to the pump, and this is 
accomplished by a suitably shielded electric power cable which also 
extends down the casing, on the outside of the pipe string. In order to 
support the power cable, it is strapped to the outside of the pipe string 
with steel band straps. 
As the pump is raised for service, the straps are cut. In prior operations, 
the straps have been manually cut with the use of a hand-carried 
conventional wire cutter. As the pipe string is raised, sections are 
removed and set aside in a conventional manner, and the power cable is 
wound up on an adjacent spool. 
The manual cutting of the strapping is dangerous and requires a very low 
pipe string raising speed. Furthermore, the direct manual operation is 
dangerous in this close proximity to the moving equipment. Thus, there is 
need for an improved, safer strap cutter and method. 
SUMMARY OF THE INVENTION 
In order to aid in the understanding of this invention, it can be stated in 
essentially summary form that it is directed to a strap cutter and method 
for cutting strapping which secures submersible pump power cable to the 
side of its discharge pipe string as the string and cable are withdrawn 
from an oil well. The strap cutter comprises a relatively fixed member 
which is manually guided to engage on the strap, and a relatively movable 
shear blade pivoted thereon, with the shear blade securable to a portion 
of the casing-mounted structure, so that as the string is raised, the 
raising motion operates the shear blade to cut the strap. The method 
comprises the steps involved in this cutting method. 
It is thus an object of this invention to provide a strap cutter which 
permits the operating personnel to stand farther away from the pipe string 
combination as it is pulled, with a portion of the strap cutter attached 
to the fixed equipment around the wellhead so that the motion of the pipe 
string combination as it is raised causes the motion which cuts the strap. 
In this way, the operator need only engage the strap cutter onto the strap 
so that raising motion of the pipe string causes cutting action of the 
strap cutter, to reduce operator fatigue and provide enhanced safety for 
the operator. 
It is another object to provide a strap cutting method which employs the 
motion of the pipe string being pulled to cause the cutting of the strap 
to reduce fatigue and enhance safety. 
It is another object to provide a strap cutter wherein the straps on a pipe 
string being pulled for access to a submersible pump can be cut more 
quickly, with proper cutting being accomplished at near maximum pipe 
string pulling speeds, to reduce the time involved in well maintenance. 
It is a further object to provide such a strap cutter which is durable, to 
be of long life and for safe handling, together with an economical 
construction which is of useful general utility. 
Other objects and advantages of this invention will become apparent from a 
study of the following portion of this specification, the claims and the 
attached drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The strap cutter of this invention is generally indicated at 10 in FIGS. 1, 
2, and 3. FIG. 1 illustrates an installation where oil is removed from the 
ground by means of a submersible pump-motor combination submerged in the 
well casing. Well casing 12 extends up out of the ground from a 
subterranean zone of interest. Often a work platform 14 is positioned 
around the casing. A top structure 16 is secured to the top of the casing. 
The top structure 16 is conventional, and may carry valving, flanges, and 
the like. Sometimes it is called a "Christmas tree." 
When a submersible pump is to be installed or removed, tower 18 is brought 
to the wellhead. Usually, tower 18 is a portable structure and is used for 
servicing wells already in production. Similarly, cable reel 20 is a 
portable structure, optionally on a truck or trailer frame, and is brought 
to the site as required. The work platform 14 may also be portable, 
brought to the site with tower 18. 
The submersible pump-motor combination is positioned down in well casing 12 
and is supported on the pipe string 22 which serves both as a discharge 
pipe for the pump and as a support for the pump-motor combination. In 
order to supply electric power to the electric motor, electric power cable 
24 extends down into the well casing, together with pipe string 22. In 
order to support the power cable 24, straps are placed to embrace both the 
pipe string 22 and electric power cable 24. One of the straps is indicated 
at 26 and such straps are placed regularly along the length of the pipe 
string. Straps 26 are positioned from 12 to 24 inches apart along the 
length of pipe string 22 in order to prevent motion of electric power 
cable 24 and to support it. The straps 26 are of conventional steel 
strapping material, and are applied by conventional strapping techniques. 
As the pipe string 22 is withdrawn from casing 12 for servicing the 
pump-motor combination, the straps 26 must be successively cut upon 
withdrawal of the pipe string. Strap cutter 10 performs this function. 
Strap cutter 10 has body 28 which serves as the main structural body of 
the strap cutter. Body 28 has a handle 30 extending therefrom on the end 
away from the pipe string. Crossbar 32 is positioned at the upper forward 
corner of body 28, in line with the inside edge of fixed shear blade 34. 
Fixed shear blade 34 is secured to or formed as part of body 24 and 
extends downwardly at the forward edge of the body 28. Shear blade 34 is 
sufficiently narrow in the front to back direction, that is, axially of 
the handle 30, that it can engage in the substantially triangular space 
which is created as the strap 26 engages around the cylindrical pipe 
string 22 and electric power cable 24. 
Movable shear blade 38 is pivoted on pivot pin 40 on the side of body 28. 
The shear edge of movable shear blade 38 is positioned so that it can 
swing from the angularly outward open position illustrated in FIG. 2 to a 
point where it, moves past the edge of the fixed shear blade in shearing 
relationship. Spring 42, engaged between movable shear blade 28 and body 
28 urges the movable shear blade to the open position illustrated. Stop 
pin 43 is fixed in body 28 and engages an elongated stop slot 44 in the 
movable shear blade to limit the motion of the shear blade in the open and 
closed directions. 
Operating cable 46 is a flexible member which is connected to movable shear 
blade 38 behind pivot pin 40 and at its lower end has a connector 48 by 
which the cable can be attached to a fixed portion of the wellhead or 
adjacent work platform. The mechanical structure is arranged so that when 
the cable is pulled, the shear is actuated. 
When pipe string 24 is being pulled, an operator stands on the platform 
adjacent wellhead 16. He attaches connector 48 as illustrated and holds 
the strap cutter 10 so that its fixed shear blade 34 is positioned in 
space 36. As the pipe string rises, a strap is engaged in the opening 
behind shear blade 34 and strap cutter 10 is pulled upward by the upward 
motion of the pipe string. When operating cable 46 tightens, it swings 
shear blade 38 in the clockwise direction, cutting strip 26 which is 
engaged between the shear blades. Thus, strap shearing is accomplished 
without slowing the upward motion of the pipe string and without a worker 
having to engage a hand tool on the strap and apply cutting force. Thus, 
operating speed and safety are both enhanced. The method of this invention 
comprises the steps achieved by the use of this strap cutter in using it 
in the manner that is described. 
This invention has been described in its presently contemplated best mode 
and it is clear that it is susceptible to numerous modifications, modes 
and embodiments within the ability of those skilled in the art and without 
the exercise of the inventive faculty. Accordingly, the scope of this 
invention is defined by the scope of the following claims.