Note: Descriptions are shown in the official language in which they were submitted.
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"SYSTEM FOR DEPLOYING AN ESP WIT~IN A WELLBORE"
BACKGROUND OF THE INVENTION
1. Field ofthe Invention
The present invention relates to electric submergible pumping systems (ESPs)
S used for recovering fluids from subterranean wellbores and, more particularly, systems
and related methods for deploying such ESPs within wellbores.
2. Description of Related Art
Electric subme~ e pumping systems (ESPs) are widely used around the world
for recovering fluids from subterranean wellbores because ESPs have the broadest10 performance capabilities of any artificial lift system. For example, ESPs areco.l..l,ercially available that are sized to efficiently lift from only about 100 bbl/day up
to 95,000 bbl/day; from depths as great as 15,000 ft; and in wells with bottomhole
temperatures of up to 450 degrees F. Typical examples of an ESP suspended in a well
on conventional production tubing are shown in US 3,835,929 and US 4,187,912. For
all of their inherent benefits, ESPs have not been as widely used as desired because of
the relatively high cost and/or lack of availability of suitable workover rigs and derrick
structures to install and remove the ESPs. This situation is especially true for offshore
wells where workover rigs are extremely expensive, as compared to their onshore
equivalents.
To address the issue of the need to use a workover rig, several inventors have
conceived of suspending an ESP from coiled tubing in a well to take advantage of the
relatively low cost and ease of transportati-on of the units used to install and remove
coiled tubing. Coiled tubing is a continuous length of tubing coiled onto a reel or drum.
The drum is driven to the well site where a motorised injector unit is removably mounted
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on the wellhead to feed the tubing into the well. The same drum and injector unit is used
to pull the tubing out of the well. Coiled tubing is widely used for logging deviated
wellbores, well stim~ tion, cementing, perforating, drilling and well cleaning. With an
ESP suspended on coiled tubing, the previously detrimental issues of relatively high cost
5 and lack of availability of workover rigs are elimin~ted. Examples of ESPs suspended
on coiled tubing are shown in US Patents 4,336,415; 4,345,784; 4,374,530; 4,476,923;
4,938,060; and 5,180,014; as well as GB Patent 2,252,777A.
While coiled tubing has many benefits as a means for suspending an ESP within
a wellbore, the coiled tubing rig and injector equipment are often too large and/or too
10 tall to fit on relatively small sites, such as on a small offshore platform or in Arctic rig
enclosures. Therefore, there is a need for a yet more compact and lightweight system
and related methods for deploying an ESP within a wellbore.
SUMMARY OF THE INVENTION
The inventors hereof have s~lcces~fillly tested an ESP suspended on coiled tubing
15 in a well and have developed several novel features that meet the above needs and
overcome the foregoing disadvantages. Specifically, the present invention is a system
and related method for deploying an electric submergible pumping system within a
wellbore. The electric submergible pumping system has an electrical cable operatively
connected thereto. A plurality of sucker rods are connected together to form a sucker
20 rod string, with one end of the sucker rod string connected to the electric submergible
pumping system. The electrical cable is attached to the sucker rod string at a plurality
of spaced locations by ela",pillg or banding. This deployment system permits the use of
relatively inexpensive and manoeuvrable rigs/cranes for the installation, removal and
repair of the electric submergible pumping system rather than having to use conventional
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relatively expensive and larger workover rigs.
BRIEF DESCRIPTION OF THE DRAWING
The drawing is a side elevational view of an electric submergible pumping system
deployed within a wellbore on a sucker rod string in accordance with one pler~lled
5 embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As briefly stated above, the present invention is a system and related method for
deploying an ESP within a wellbore, ~ltilising a sucker rod string in place of jointed
tubing, coiled tubing and cable. This deployment system permits the use of relatively
10 i~ elL~ re and manoeuvrable rigs/cranes for the installation, removal and repair ofthe
ESP rather than having to use conventional relatively expensive and larger workover
rigs. In addition, sucker rods are relatively inexpensive as compared to joined tubing,
coiled tubing and non-torque cable.
To aid in the understanding of the present invention, reference is made to the
15 accolllpanying drawing. As shown in the drawing, a wellbore 10, used for recovering
fluids such as water and/or hydrocarbons, penetrates one or more subterranean earthen
formations 12. The wellbore 10 includes a wellhead 14 removably connected to an
upper portion of a production tubing and/or casing string 16, as is well known to those
skilled in the art. If the casing string 16 extends across a fluid producing subterranean
20 formation 12, then the casing string 16 can include at least one opening or perforation
18 for permitting fluids to enter the interior thereof. An electric submergible pumping
system (ESP) 20 is shown suspended within the casing string 16, and generally
comprises an electric motor 22, an oil-filled motor protector 24, and a pump 26, such
as a centrifugal, gear, vane, turbine or positive displacement pump. The ESP 20 is
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shown in an "up-side down" configuration, commonly known as a "bottom intake
system", with the motor 22 above the pump 26, but it should be understood that aconventional configuration with the motor 22 connected below the pump 26 can be
used, as desired.
The ESP 20 is vperatively connected to a lower end of a length of conventional
sucker rod 28 by way of a threaded connector 30. A string of connected sucker rods 28
acts as a strength member to fully support the weight of the ESP 20; however, as an
alternative, the casing string 16 can include a casing shoe (not shown) whereupon a
lower portion of the ESP 20, such as the pump 26 is landed to transfer the weight of the
10 ESP 20 to the casing string 16. The sucker rods 28 can be of any commercially available
size (i.e. diameter and length) and formed from any material suitable to the wellbore
conditions, as all is well known in the art. For examples, sucker rods are made from
ferrous metals, ceramics, carbon fibres, fibreglass, or combinations ofthese.
An electrical cable 32 is operatively connected to the ESP 20 to provide
15 electrical power to the motor 22, and is operatively connected at the surface to surface
electrical control equipment and a source of electrical power (both not shown), as are
both well known in the art. Commercially available electrical cable 32 typically used
with ESPs 20 does not have sufficient internal strength to support its own freely
suspended weight; therefore, a plurality of bolt-on clamp devices 34 are used to attach
20 the cable 32 to outside of the sucker rods 28. The clamp devices 34 are spaced about
every 10 to about 200 feet apart, and are preferably spaced about every 20 to 100 feet
apart. The clamp devices 34 can be used alone or in conjunction with one or moreplastic or metallic bands or straps 36, as commonly used to band electrical cable to the
outside of production tubing in a well. It should be understood that any form of wrap-
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around tape, string, band, or straps may be used in the practice of the present invention
in conjunction with or apart from the clamp device 34. Further, if the cable 32 includes
its own steel wire strength member or members then the clamp devices 34, straps, bands,
etc. may not be necessary for a successful application of the present invention. In any
5 event, some form of clamp device 34 is desired to prevent the cable 32 from being loose
within the well where movement thereof may cause damage to it by rubbing against the
interior surface of the casing string 16.
The annular production arrangement shown in the drawing has a pump intake 38
located adjacP.nt a lower portion of the well 10 adjacent the perforations 18, as desired,
10 or in any other location and configuration suitable to those skilled in the art. One or
more sealing devices 40 are used to seal the annular space between the interior of the
casing string 16 and the exterior ofthe ESP 20. The sealing devices 40 are preferably
one or more retrievable or permanent elastomeric packing elements or "packers", and
contact the exterior of the ESP 20 above the pump intake 38 but below the fluid
15 discharge opening of the pump 26.
In one prere,led method of the present invention, the ESP 20 is connected to
one end of a first length of sucker rod 28 by way of a threaded male-female coupling 42,
which type of coupling is also used to couple each of the sucker rods 28 together to
form a sucker rod string, as is well known to those skilled in the art. The elevators on
20 a typical workover rig (not shown) fasten to the coupling 42 to suspend the ESP 20,
whereafter the cable 32 is banded or strapped or clamped to the sucker rods 28. The
elevators lower the ESP 20 and the sucker rods 28 into the wellbore 10 as additional
lengths of sucker rods 28 are connected thereto to form the sucker rod string that
suspends the ESP 20. When the ESP 20 is to be retrieved, the workover rig is brought
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to the well site, the elevators connected to the topmost sucker rod 28, and then the
elevators are used to raise the sucker rod string and the ESP, as is well known to those
skilled in the art.
The use of sucker rods to deploy an ESP has many advantages over the use of
5 conventional jointed tubing, coiled tubing and cable. Sucker rods are reusable, have
almost in~efinite life, and are far less expensive per unit length than jointed tubing, coiled
tubing and cable. The use of sucker rods permits the use of relatively small, lightweight,
and inexpensive workover rigs for inst~ tion and retrieval. This is especially important
for small offshore platforms where space and weight considerations are very important.
10 In addition, the time to install and retrieve an ESP by use of sucker rods is less than for
other methods due to the ease of set up and rig down of the workover rig as compared
to larger workover units needed for jointed tubing and coiled tubing units.
Wherein the present invention has been described in particular relation to the
drawing attached hereto, it should be understood that other and further modifications,
15 apart from those from those shown or suggested herein, may be made within the scope
and spirit of the present invention.
