TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to a centralizer system used for drilling of
wellbore. Particularly, the instant invention relates to an improved centralizer 5 system
with a protection guard for the centralizer. Further, more particularly, the present
invention relates to a centralizer system having a cover shell for protection of the
centralizer during its storage and/or transportation till the installation of the centralizer
system in the wellbore.
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BACKGROUND AND THE PRIOR ART
A centralizer is a device fitted with hinged collar and bowsprings to keep the casing or
liner in the center of the wellbore to help ensure the efficient placement of a cement
15 sheath around the casing string or liner. The casing is a large diameter pipe cemented in
place during the construction process to stabilize the wellbore. The casing forms a major
structural component of the wellbore and serves several important functions such as the
prevention of the formation wall from caving into the wellbore, isolation of the different
formations to prevent the flow or crossflow of formation fluid and providing a means of
20 maintaining control of formation fluids and pressure as the well is drilled. The casing
string provides a means of securing surface pressure control equipment and downhole
production equipment such as the drilling blowout preventer (BOP) or production packer.
Casing is available in a range of sizes and material grades. Further, a casing is usually
manufactured from plain carbon steel that is heat treated to varying strengths, but may be
25 specially fabricated of stainless steel, aluminum, titanium, fiberglass and other materials.
If casing strings are cemented off-center, there is a high risk that a channel of drilling
fluid or contaminated cement will be left where the casing contacts the formation,
creating an imperfect seal. Thus, a centralizer has to be strong enough to counter the
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pressure of drilling stream in the casing string or liner yet have enough spring action so as
not to break or crack with the pressure.
The centralizer is a cage-like steel apparatus which is attached to the casing string as it is
being lowered into the hole after drilling has reached total depth and the drill strin5 g
withdrawn. The centralizers are attached to every third or fourth thread joint knuckle and
serve to keep the casing from resting against the edge of the borehole. This allows the
casing string to be cemented to the borehole without any „thin‟ cement areas. The cement
bonds the casing to the borehole and prevents fluid from being pushed up the borehole,
10 pressurizing the annulus and contaminating upper level strata and aquifers.
The centralizer keeps the casing in the center of the hole and prevents it from lying
against the wall. The most important function of oil and gas well primary cementing is to
isolate the various formations within the well bore. If casing strings are cemented off15
center, there is a high risk that a channel of drilling fluid or contaminated cement will be
left where the casing contacts the formation thereby creating an imperfect seal which can
result in gas or oil migration from one zone to another. Centralizers, thus if are damaged
or dented or cracked, can lead to deterrent in the drilling process.
20 Centralizers either have hinged collars and bows or integral bows and collars which go
around the casing and push it away from the borehole wall in all directions. The hinged
collars and bows help keep the casing or liner in the center of the wellbore. They are used
in the overall process of drilling, or constructing, the well, but not in the actual drilling
part. Once the hole is drilled, pipe called casing is run into it so that the hole doesn‟t
25 collapse, and so whatever fluid comes out of the hole doesn‟t get loose and make a mess
(i.e. blowout). That pipe, or casing, is cemented in place with centralizers holding the
casing in the center of the hole so the pipe is totally encased in a cement sheath, without
the cement all on one side of the pipe.
4
Centralizers for wells have to fulfill two requirements: They should have a high restoring
capability and a low moving force, and they should allow pipe rotation and reciprocation.
There are certain measures which can be taken for modification and assembly of the part5 s
of a centralizer system. The prior art is replete with the teachings of manufacturing the
centralizers that are made with the right kind of material and method.
One such method of manufacturing is disclosed in US 20170183920A1. US „920 teaches
method manufacturing a centralizer which includes:
10  selection of a tubular having a first inner diameter,
 cutting the tubular to form a blank including at least one end collar and ribs
integrally formed therewith and
 swaging at least one end collar such that the first inner diameter is modified to
second inner diameter.
15
The problem which still arises in US „920 is the effect of external pressure and storage
and/or transport conditions on the components of the centralizer system, specially the
centralizer unit which may be damaged before reaching the site of the drilling.
20 Further, IN 237022 discloses spring centralizer device for supporting a tubular member
spaced from the wall of a bore, the spring centralizer device having a longitudinal axis,
and comprising first and second mutually spaced collar portions and a plurality of bow
portions disposed there between, wherein the first and second collar portions and the bow
portions are formed from a single piece of special steel material such that the material
25 extends seamlessly from each collar portion through the bow portions.
In the conventional centralizer system, currently available, usually the centralizer gets
damaged due to its presence outside the casing and the constant exposure to friction and
5
tugging in the wellbore. Further, in the conventional centralizer system, the centralizer is
placed as the outermost component attached to the casing by stop collars and hence this
leads to the damage of the centralizer due to the storage conditions, before it reaches the
site of use i.e. the wellbore. Hence, there is also a need to prepare a centralizer system to
be protected during transportation and storage of the centralizer. There exists a need 5 in
the art for the centralizers which are safe, reusable and durable i.e. comprising
components which have a longer life span and thereby making them economical and
beneficial for the manufacturers.
10 The varied nature of centralizer applications and job sites, whether it be for oil and gas, or
water well drilling, means that it can be difficult to find a centralizer that can endure the
harsh transport conditions and still not make the centralizer lose its shape. Further, the
centralizers are attached on the casing at the site of the manufacture and transported to
the onshore drilling site which increases the chances of damage of the centralizers.
15
Therefore, despite the developments in the conventional centralizer system, a need is felt
for more effective, safe, durable, reusable, economical, compact and efficient way of
protecting the centralizer system. So, the present invention is resulted which includes an
effective, safe, durable, economical, compact and efficient improved centralizer system
20 which comprises of the centralizer equipped with a cover shell which is placed as the
outer shell and is either placed attached to the casing or as a separate unit.
SUMMARY OF THE INVENTION
25 The present invention henceforth solves the problem of the damage and short-lived nature
of the centralizer due to exposure to harsh external transport conditions thereby
enhancing the efficiency of the system. The present invention provides an improved and
economical centralizer system to work at optimum and/or adverse conditions, the
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centralizer system comprising: an outermost shell i.e. the cover shell; and the internal
centralizer unit including a centralizer and the central hollow casing. Further, both the
cover shell as well as the internal centralizer are attached to the central hollow casing
using different collars as present on both the ends of the centralizer and is attached with
the help of bolts. The cover shell can be removed as a separate component withou5 t
obstruction to the functioning of the centralizer system.
It is therefore an object of the present invention to provide a compact, safe, reusable and
efficient cover shell in which the centralizer is placed for its safe transportation and
10 storage. The cover shell can be removed at the site of use of centralizer.
Further, another object of the instant invention is to provide a cover shell for the
centralizer which can be easily repaired, serviced and can also be reused. Also another
object of the present invention is to protect the single piece centralizer from occasional
15 failure due to harsh transport conditions and thereby reducing the overall cost of
maintenance of the centralizer system.
Another object of the invention is to prevent the damage caused to the centralizer while
in transit to the drilling site reducing the risk of consequent hampering of the overall
20 drilling process.
Another object of the invention is to meet the long felt need for protection of the
centralizer such that the same remains intact even when the centralizers are stacked on
top of one another while also preventing the loss of spring action or restoring force.
25
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of
the present invention, are descriptive of some of the methods, and are not intended to
7
limit the scope of the invention. The drawings are not to scale (unless so stated) and are
intended for use in conjunction with the explanations in the following detailed
description.
Figure 1 illustrates the design of the cover shell of the centralizer system as disclosed 5 in
the present invention.
Figure 2 shows the cross-sectional view of the centralizer system in which the cover shell
is placed as the outermost layer of centralizer.
10
Figure 3 shows the perspective view of the centralizer system in which the cover shell is
placed as the outermost layer of centralizer.
Figure 4 shows the vertical cross sectional view of the centralizer system in which cover
15 shell is placed as the outermost layer of the centralizer.
Persons skilled in the art will appreciate that elements in the figures are illustrated for
simplicity and clarity and may have not been drawn to scale. For example, the
dimensions of some of the elements in the figure may be exaggerated relative to other
elements to help to improve understanding of various exemplary embodiments of the
20 present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to
depict the same or similar elements, features, and structures.
25 DETAILED DESCRIPTION OF THE EMBODIEMENTS
The following description with reference to the accompanying drawings is provided to
assist in a comprehensive understanding of exemplary embodiments of the invention as
defined by the claims and their equivalents. It includes various specific details to assist in
8
understanding but these are to be regarded as merely exemplary. Accordingly, person
skilled in the art will recognize that various changes and modifications of the
embodiments described herein can be made without departing from the scope and spirit
of the invention. In addition, descriptions of well-known functions and constructions are
omitted for clarity and conciseness. The terms and words used in 5 the following
description and claims are not limited to the bibliographical meanings, but, are merely
used by the inventor to enable a clear and consistent understanding of the invention.
Accordingly, it should be apparent to the person skilled in the art that the following
description of exemplary embodiments of the present invention are provided for
10 illustration purpose only and not for the purpose of limiting the invention as defined by
the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents
unless the context clearly dictates otherwise.
15
The present invention provides an improved centralizer system wherein a cover shell is
attached to the casing in external frame/as separate unit and is removable. The cover shell
is attached to the casing such that it does not cause any obstruction to the mobility and/or
rotation of the centralizer or centering device. Further, the improved and economical
20 centralizer system includes the cover shell which is attached to the casing using the bolts
without causing any obstruction to the centralizer.
In the conventional centralizer system, the centralizer or centering device is placed as the
outermost component of the centralizer system or centering device. The centralizer is
25 always attached to the casing and remains in contact with open atmosphere and is
attached to the casing via collar portions. The centralizer is thus damaged due to exposure
to excessive load during transportation which results in reduction of spring action.
Maintenance and repair of such outside placed centralizer is a challenge.
9
Figure 1 illustrates the conventional centralizer system with a outer cover shell in
according to the present invention. The centralizer in the said arrangement is placed as
the outer component and is attached to the casing using set screws. Figure 1 shows the
centralizer system (100) having a centralizer or centering device (101) and central 5 l casing
(102). The centralizer (101) is present outside the central casing (102) in order to help
ensure the efficient placement of the casing (102) in the wellbore. Figure 1 explains the
construction and placement of the centralizer (101) and the casing of the centralizer
system (100), explaining the arrangement of the cover shell (103). The centralizer or the
10 centering device (101) and central casing (102) of the improved centralizer system (100)
is connected through the collar portions (105A and 105B) using set screws.
The centralizer system (100) includes the centralizer (101) which is attached to the
central casing (102) with collar portions (105A and 105B) present at the upper and lower
15 end of the centralizer. The collar portions (105 A) and (105 B) of the centralizer (101)
are used to attach the single piece centralizer to the central casing with the help of the set
screws.
Fig. 2 illustrates the cross-sectional view of the centralizer system in which the cover
20 shell is placed as the outermost layer of centralizer. Figure 2 shows the arrangement of
the improved centralizer system (100) with cover shell which includes the centralizer
(101) and casing (102). Figure 2 explains the construction of the centralizer (100),
explaining the arrangement for the cover shell in the centralizer system (100) which
includes that the central casing (102) is at central position and above it is the centralizer
25 (101) with the help of collar portion (105A) and the centralizer is covered with the outer
cover shell (103).
10
Figure 3 shows the perspective view of the centralizer system in which the cover shell
(103) is placed as the outermost layer of centralizer system (100). The central casing
(102) is at middle position in order to place it in the wellbore. The outer cover shell (103)
completely protects the centralizer (101) at its position. The abovementioned
arrangement is in such way that the centralizer is not damaged and easily protected. 5 The
outer cover shell (103) can be reused for protection, transportation and storage of
centralizer (101).
Fihure 4 shows the vertical cross sectional view of the centralizer system in which the
10 cover shell (103) is attached to the central casing (102) using bolts. And the centralizer
(101) forms the mid component of the entire system in the instant case and is attached to
the central casing (102) using nut bolts.
The centralizer (101) is used in the overall process of drilling, or constructing, the well,
15 but not in the actual drilling part. Once the hole is drilled, pipe called casing is run into it
so that the hole doesn‟t collapse, and so whatever fluid comes out of the hole doesn‟t get
loose and make a mess (i.e. blowout). That casing (102) or pipe is cemented in place with
centralizers holding the casing in the center of the hole so the pipe is totally encased in a
cement sheath, without the cement all on one side of the pipe.
20
Further, as per the present invention the cover shell is attached to the central casing
through the stop collars using bolts. The nuts and bolts that may be used for attaching the
cover shell to the central casing may be made up of Teflon, stainless steel, aluminum,
alloy steel, silicon bronze, brass or any other material generally used for manufacturing
25 bolts.
The cover shell may be attached to the central casing using the same stop collar which is
used for attachment of the centralizer to the central casing or using a separate stop collar.
11
The cover shell and the centralizer are attached to the central casing in such a fashion that
the removal of the cover shell at the site of use of the centralizer does not hinder or
obstruct the attachment of the centralizer to the casing.
Thus, the present invention provides a compact, effective, durable, safe, r5 eusable
economical and efficient improved centralizer wherein the cover shell is attached to the
central casing protecting the centralizer. The present invention prevents the reduction of
spring force resulting in bad cementing job by protecting the centralizer from the external
pressure that is exerted upon it during loading and unloading of the same while
10 transportation to the cementing site.
The accompanying drawings are illustrative of particular examples for enabling methods
of the present invention, are descriptive of some of the methods, and are not intended to
limit the scope of the invention. The drawings are not to scale (unless so stated) and are
15 intended for use in conjunction with the explanations in the following detailed
description.
The figures and the description above provide details of one particular design which is
also specific to the design and configuration of the improved centralizer with removable
20 cover shell being considered. It would be obvious to person skilled in the art that, based
on the concepts, ideas and issues described herein, several variations of the proposed
design for the design and configuration of the base engine considered, as well as, for
engines with distinctly different design and configuration, will be possible without
deviating from the scope of this invention.
25
Although the embodiments herein are described with various specific embodiments, it
will be obvious for a person skilled in the art to practice the embodiments herein with
modifications. However, all such modifications are deemed to be within the scope of the
12
invention. It is also to be understood that the description is intended to cover all of the
generic and specific features of the embodiments described herein and all the statements
of the scope of the embodiments which as a matter of language might be said to fall there
between.

We claim:
1. An improved centralizer system to work at optimum and/or adverse conditions, the
improved centralizer system comprising:
an outer cover shell; 5 and
an internal unit including a centralizer and a central casing wherein the centralizer
is present external to the central casing and is attached through collar portions
which are present at both the sides of the centralizer.
10 2. The improved centralizer system as claimed in claim 1, wherein the cover shell is
attached to the casing through the collar portion using bolts.
3. The improved centralizer system as claimed in claim 1, wherein the cover shell
forms the outermost layer/component of the centralizer system.
15
4. The improved centralizer system as claimed in claim 1, wherein the cover shell is
easily removable from the centralizer.
5. The improved centralizer system as claimed in claim 1, wherein the cover shell is
20 attached to the central casing using set screws without obstruction to the
centralizer.
6. The improved centralizer system as claimed in claim 1, wherein the cover shell
does not hinder the free movement/rotation of the centralizer or the centering
25 device.
14
7. The improved centralizer system as claimed in claim 1, wherein the outer diameter
of the centralizer system is in the range of 6 to 36 inches and the inner diameter is
within 2.65 to 30 inches.