Note: Descriptions are shown in the official language in which they were submitted.
338
This invention is directed at downhole apparatus such as
submersible pumping systems, in general, and to an economical, yet strong
system for lowering and retrieving pumping apparatus, in particular.
There are many known types of apparatus for use with suitable
standard submersible pumping units in known downhole (I.E. petroleum, water
or the like) production facilities. In particular, in the best known prior
art arrangement, the standard submersible pumping unit consists of a pump,
motor protector, and a cable which is run on a production string utilizing a
pulling rig. In this arrangement, a galvanized cable is lowered along side
the production tubing and banded around and to the tubing with cable bands
approximately every fifteen feet for the total pumping depth.
In another system called the cable suspended pump system (CSPS) a
heavily strengthened cable is utilized to run and to retrieve a pumping unit.
In this apparatus installation and removal of the unit is obtained by
spooling the power cable with a compact CSPS service unit.
Workover units are known in the art which are used to inject and
retrieve a continuous string of tubing into a well for use in conjunction
with various fluids which are to be inserted into and/or retrieved from the
well. This device permits a continuous string of tubing to be inserted into
a well which is far superior to the previously used technique of inserting
long, individual sections of pipe or tubing.
The most pertinent prior art which has been discovered by applicant
is listed below in Patent numerical order.
Hoover, United States Patent 2,233,890, issued March 4, 1941~
Eccentric Suspension and Cable Connection for Submersible Motor Pumps. This
patent is directed to a device which provides a motor pump and cable-
connector construction such that the diameter of the pump discharge is not
unduly reduced to allow for the cable-connector.
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Maginniss, United States Patent 2,478,701, issued August 9, 1949,
Electric Motor Operated Actuator Unit. This patent is directed to a self
contained electric motor operated actuator having an electric motor and a
motor driving shaft as well as a co-extensive waterproof housing for the
motor, switch and cable.
Fletcher, United States Patent 2,669,483, issued February 16, 1954,
Device for Transferring Fluids. This patent is directed to a device for
transferring fluids from one point to another having an electrically driven
pump for pumping the fluid through a flexible conduit which is wound on an
electrically driven reel. The flexible conduit includes a plurality of
conductors in the wall thereof.
Voetter, United States Patent 3,162,806, issued December 22, 1969,
Bore Logging Apparatus, etc. This invention is directed to a borehole
logging apparatus in which electrically conductive housing sections are
insulated from one another.
Morgan, United States Patent 3,517,110, issued June 28, 1970,
Flexible Underwater Riser Containing Electrical Conductors and Material
Conduits. This invention is directed to a flexible underwater riser capable
of sustaining high tensile loads and includes a plurality of material
conduits and electrical conductors maintained within a protective sheet and
around a central core member.
Cedenk, United States Patent 3,603,718, issued September 7, 1971,
Electrical Cable Structure. This invention is directed to an electrical
cable structure that is adapted for downhole oilwell use and includes open
channels under the sheath with gas permeable walls for dissipating any
accumulation of hydrocarbon gases.
Busuttil, et al., United States Patent 3,753,206, issued August 14,
1973, Electrical Connector With Coaxial Contacts. This invention is directed
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to a connector having male and female members which include circular or
annular contact portions which can be remotely interconnected in a downhole
operation.
On its broadest aspect, the invention resides in an improved down-
hole apparatus, comprising, operative means to be selectively lowered into
and retrieved from a well, and improved means for lowering and retrieving
said operative means, said improved means comprising, coiled tubing attached
to said operative means and unarmored cable disposed within said coiled
tubing and attached to said operative means.
This invention is developed primarily in order to protect a
standard cable from well fluids by using a coiled tubing string which is used
to pull a submersible pumping unit from the well and including an unarmored
power cable inside the coiled tubing to lower the pump to the desired depth
and retrieve same. All pulling and lowering stress is borne by the coiled
tubing only. On drawings which illustrate the invention,
Figure 1 shows, diagramatically, the apparatus of the instant
invention.
Figure 2 shows, diagramatically, another view of the instant
invention including surface apparatus.
Referring now to the Figure 1, there are shown the basic components
of the submersible pumping system contemplated by the instant invention. In
this apparatus the submersible pumping system comprises a standard pump 10 at
the end of the production string. Pump lO is seated on a casing seating
shoe 12 at the desired pump depth. This arrangement permits the intake of
pump 10 to be isolated from the discharge end of the pump, e.g. discharge
head 11. In addition, this arrangement permits the casing to cool the motor
14 without coming in contact with the unarmored cable 16 described hereinafter.
Discharge head 11 is connected to pump 10 in the standard fashion
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and joined to seating shoe 12 as noted above. In addition, protector 13 is
joined to the outlet of discharge head 11 by a suitable bolted arrangement
which is known in the art. Seating shoe 12 is fastened to the production
tubing or string 17 in the usual fashion as well. Protector 13 is colmected
to discharge head 11 at the output portion thereof and is disposed within the
production tubing 17. Protector 13 provides the typical function, i.e.
isolation of motor 14 from any well fluids and, also, allows the internal
motor pressure to equalize with ambient pressure.
Motor 14 is similar to any conventional submersible pump motor with
the exception that the shaft thereof is taken from the bottom rather than the
top. Motor 14, therefore, permits the coil tubing 15 and power cable 16 to
enter motor 14, concentrically, at the top. Motor 14 which is used to drive
pump 10 is connected to the upper end of protector 13 in the usual manner.
Therefore, motor 14 is also located in the production tubing 17.
The upper end of motor 14 is connected to coil tubing 15 which is
of a known type in the oil field equipment art. Tubing 15 is fastened to
motor 14 in any desirable manner. One such connection is shown in Figure 2.
In addition, unarmored cable 16 is attached to the upper end of motor 14.
Unarmored cable 16 is disposed within coil tubing 15 and is protected thereby.
Consequently, cable 16 can be of the unarmored variety which is significantly
less expensive than galvanized ~or otherwise armored) cable. In addition, the
unarmored cable 16 is vastly easier to operate and manipulate.
Coil tubing 15 exhibits extremely high tensile strength and has
been successfully used in the oil industry, both onshore and offshore, for
some time. Coil tubing 15 is available in different sizes, i.e. outer and
inner diameters. Consequently, coil tubing 15 will accomodate Yarious sizes
of unarmored cables 16.
Unarmored cable 16 is, in this invention, installed inside the coil
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tubing 15. This combination can be provided on spools of 6,000 to 15,000
feet which are ready to be run into the well.
Coil tubing 15 provides the tensile strength for pulling the unit
and also protects cable 16 against damage without exposing the cable to well
fluids, especially gas under well pressure~ All~of the submersible pumping
system is inserted through the typical bore hole or the like represented by
casing 18. Casing 18 has been inserted into a suitable production area
wherein pump 10 can pump well fluid from the bottom of the casing through
production tubing 17 to the surface as is known in the art.
As shown in Figure 1, pump 10 has the bottom intake which is set
below the casing seating shoe 12 rather than being located above protector 13
and motor 14. Although not shown, pump 10, protector 13 and motor 14 can be
seated on the top of any size liner 18 and will operate identical to any
submersible pumping installation currently known.
It should be understood that the casing seating shoe 12 is a
seating element which is run on the bottom of the permarlent producing string
17. This seating shoe serves to carry the weight of the submersible pumping
unit and, as well, to seal off the casing between the pump intake and
discharge head 11. In addition, fluid discharge head 11 is made to fit above
pump 10 and to seat into seating shoe 12. The weight of the fluid in the
producing string 17 and the complete submersible pumping unit (including the
weight of coiled tubing 15 and cable 16) maintains pump 10 in place, and
therefore, the well is maintained under control. A surface check valve ~see
Figure 2) can be used in order to prevent the production string from being
exposed to surface or formation pressures. In addition, the surface check
valve arrangement permits a pump to be changed in a "dead" production string.
In a conventional system, it has been shown that most downhole
electrical cable failures were directly or indirectly related to mechanical
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338
damage inflicted during running into or removal of the apparatus from the well.
A separation of the galvanized armor and/or a crushing of the jacket
insulation allows gas to intrude between the jacket and the insulation.
Upon wlthdrawal from the well, the gas trapped during pumping operations
expands and causes the jacket to blow out at the damaged points. A jacket
separation allowing entry of well fluid to the insulator typically results in
deterioration of the insulation and, thus, a subsequent cable failure. By
using unarmored cable 16 within coiled tubing 15, the cable is protected
against any mechanical damage and is, therefore, pro~ected from the well
fluid.
Referring now to Figure 2, there is shown an illustrative diagram
of the instant invention including the surface apparatus. In this figure,
elements which are similar to components shown in Figure 1 bear similar
reference numerals.
The downhole apparatus includes motor 14 which is connected to coil
tubing 15 and unarmored cable 16. The connection is effected by means of
reducing nipple 19 and swage nipple 20. Connector 21 is shown in partial
section to illustrate the adaptation of the plug arrangement relative to the
motor head.
The combination of tubing 15 and cable 16 is connected by means of
any suitable apparatus such as reducing nipple 22 which is connected to well-
head 23. Wellhead 23 is any standard apparatus and includes the various
gauges, valves and the like as shown. In addition, tubing 15 and cable 16
are shown, in dashed outline, passing through wellhead 23. Tubing 15 is
connected to connector 24 while cable 15 passes therethrough. A suitable
power connector or fitting 25 is arranged to connect to the upper end of
tubing 16 via leakproof connector 24 when placed in final position.
Unarmored cable 16A (the above-ground portion of cable 16) is fed through
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fitting 25 to junction box 29 of a type which is typical in the art.
Junction box 29 is connected to switchboard 27 by means of surface cable 28
in the usual manner. Switchboard 27 is connected, electrically, to trans-
formers 26 in any standard and suitable fashion.
In the apparatus shown in Figure 2, pump 10, protector 13 and
motor 14 can be seated on any size liner and operate in identical fashion to
any submersible pumping installation known in the art. Nevertheless,
irrespective of the location of the motor, pump and protector, the apparatus
shown in Figure 1 can be considered to be similar to the apparatus shown in
Figure 2 for purposes of the instant invention. Each of the illustratedcombinations operates in substantially the same manner. That is, the down-
hole apparatus is selectively inserted and/or retrieved by means of the coil
tubing 15 as described above.
The apparatus shown in Figure 2 relating to the surface portion of
the system is standard in the art and a detailed analysis and description
thereof is believed superfluous in this description.
It should be understood that the coil tubing 15 can be packed-off
by any conventional wellhead packoff apparatus (see Figure 2) similar to
known pumping units. However, cable 16 will be mechanically packed at the
surface by use of wellhead electrical feed through connectors. The apparatus
shown and described herein is readily inserted and retrieved from boreholes
using various types of equipment. However, there is available to the industry
a continuous string, coiled tubing unit which is portable and can be used on
land or offshore. These units are fully available and are used in the oil
industry so that new or unproven techniques and devices are not required.
It should also be understood that other improvements within the
scope of this invention will be discoverable by those skilled in the art.
For instance, connectors 24 and 25 and cable 16A can be constructed in one
piece.
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Thus, there is shown and described a pumping system which is
designed to reduce the cost of running and retrieving a submersible pump
apparatus by eliminating the expense and utilization of a workover rig~
production tubing string, flat cable, all bands, guards and splices typically
used in conjunction with a standard pumping unit. This large expense has
been avoided by using; a standard, unarmored power cable which is installed
inside a standard continuous coiled tubing which will also be used to run
and retrieve the pump and related apparatus. The coiled tubing serves the
purpose of protecting the cable from abrasion and tension damage in the well
fluid. Consequently, the system provides an economical method and apparatus
for use in fluid production apparatuses. The system shown and described
herein is designed to minimize the production expense, minimize downtime and
to provide a new, unique and economical method of fluid production from a
downhole well. The description included herein is intended to be illustrative
only. The scope of the invention is limited only by the claims appended
hereto.
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