CA1118338A - Submersible pumping system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
There is provided a new and improved method and apparatus for use with submersible pumping systems. In this system, a coiled tubing is connected directly to the downhole apparatus and an unarmored power supply cable is maintained within the coiled tubing. The coiled tubing, with the unarmored cable therein, is utilized to lower and retrieve the downhole apparatus without applying tension to the power supply cable.

Description

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 : .

~, ~18;~3~3 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 ~118338 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 , .

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 '~ ~

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.

111~338 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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Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1 An improved downhole 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.

2. The apparatus recited in Claim 1 wherein, said coiled tubing and said cable are substantially concentric.

3. The apparatus recited in Claim 2 wherein, said coiled tubing and said cable are each relatively continuous in length.

4. The apparatus recited in Claim 1 wherein, said operative means comprises a submersible pump system.

5. The apparatus recited in Claim 1 wherein, said coiled tubing is impervious to and protects said cable from materials in said well.