TECHNICAL FIELD
[0001] The present subject matter, in general, relates to systems for gravel packing, and,
in particular relates, to an over the top assembly for gravel packing and sealing.
BACKGROUND
[0002] Conventional techniques of drawing petroleum or other hydrocarbons from 5
reservoir rocks present underneath the earth’s surface involve digging of wells. The process of
well completion involves several stages including creation of well casing, bottom-hole
completion, and tubing. In case of reservoirs having soft formation rocks, such as formation
sand, which might cave into the well casing during the hydrocarbon production, the process of
bottom-hole completion involves specific control processes called as gravel packing processes 10
that help in preventing formation sand from getting mixed with the hydrocarbon production.
[0003] Conventionally, a gravel packing process is carried out by an over the top packer
system that enables isolation of formation sand for hydrocarbon production. Usually the gravel is
packed in an annular space between the well casing and the tubing by a top mounted packer tool.
The gravel so packed allows only hydrocarbon fluid such as petroleum oil to pass through and 15
prevents the passage of the formation sand along with the hydrocarbon fluid. The gravel in turn
is prevented from entering the tubing by a porous cylindrical screen part of the tubing placed in
the wellbore for drawing the hydrocarbon fluid. The conventional over the top packer system
also involves a sealing means that seals the annular space between the well casing and the tubing
for preventing the outflow of the gravel packed in the annular space. 20

BRIEF DESCRIPTION OF DRAWINGS
[0004] The detailed description is described with reference to the accompanying figures.
In the figures, the left-most digit(s) of a reference number identifies the figure in which the
reference number first appears. The same numbers are used throughout the drawings to reference 25
like features and components.
[0005] Figure 1a illustrates a schematic layout of over the top assembly, in accordance
with an embodiment of the present subject matter. 3

[0006] Figure 1b illustrates a changeover tool of the over the top assembly, in accordance
with an embodiment of the present subject matter.
[0007] Figure 1c illustrates a landing nipple of the over the top assembly, in accordance
with an embodiment of the present subject matter.
[0008] Figure 1d illustrates a lower part of seal subassembly of the over the top 5
assembly, in accordance with an embodiment of the present subject matter.
[0009] Figure 1e illustrates a middle part of the seal subassembly of the over the top
assembly, in accordance with an embodiment of the present subject matter.
[0010] Figure 1f illustrates a sealing element of the seal subassembly of the over the top
assembly, in accordance with an embodiment of the present subject matter. 10
[0011] Figure 1g illustrates a check nut of the seal subassembly of the over the top
assembly, in accordance with an embodiment of the present subject matter.
[0012] Figure 1h illustrates an upper part of the seal subassembly of the over the top
assembly, in accordance with an embodiment of the present subject matter.
[0013] Figure 2a, 2b, 2c, and 2d illustrates an over the top system including the over the 15
top assembly, in accordance with an embodiment of the present subject matter.
DETAILED DESCRIPTION
[0014] The conventionally known over the top packer systems are used for gravel
packing of well casing of standard sizes of 5-1/2” and 7” outer diameters. An over the top system
generally includes one or more blank pipes, one or more changeover tools, a landing nipple, one 20
or more service tools, a sealing means, and a plug assembly. The one or more blank pipes, the
landing nipple, the one or more changeover tools, and the sealing means of the over the top
system together forms a production tubing of the well completion process. In the over the top
system, the one or more service tool is mounted on top of the production tubing.
[0015] The landing nipple is disposed at the top of the production tubing for connecting 25
the one or more service tools with the production tubing. The landing nipple is a primary well
completion component that is tubular in cross-section and has a substantially large wall
thickness. A crossover tool is mounted on top of the landing nipple for pumping gravel slurry
After packing the desired volume of gravel in the annular portion, the crossover tool is retrieved
from the production tubing. Though the slurry pumping and the subsequent reverse circulation 30
with the help of crossover tool ensures that no gravel lies above the landing nipple, possibilities 4

of escape of gravel from the annular portion always exists in the absence of complete isolation of
the annular portion. Complete isolation is therefore generally achieved by sealing the annular
portion.
[0016] The sealing of the annular portion completes the gravel packing process and
ensures that the gravel packed in the annular portion is retained. A plurality of sealing means is 5
known in the conventional over the top system. For example, the over the top system known in
the art involves sealing of the annular portion with the help of a rubber seal. However, the seal
thus created is prone to failure when high compressive forces act on the rubber material. The
conventional over the top system also involves sealing by externally fitting ring like structures
surrounding the production tubing. For example, a metallic ring circumferentially mounted on 10
the production tubing helps in holding the gravel within the annular portion. However, the
possibility of disengagement of the metallic ring from the tubing is high during the production.
There is also a possibility of leakage of the gravel slurry through a gap that is formed between
the metallic ring and the inner wall of the well casing, which may lead to improper sealing of the
annular portion. 15
[0017] The conventional over the top system also involves sealing the annular portion
with the help of malleable material such as lead, which is circumferentially disposed around the
production tubing and expanded by compressing with the help of a known tool. However, seal
thus obtained is not effective and leak proof. The ineffective sealing is due to disproportionate
expansion of lead affected by uncontrolled compressive forces transmitted by the tool used for 20
sealing. The sealing thus obtained is substantially thin in cross-section, which is not sufficient to
hold the gravel in the annular portion during production. Further, the seal is also continuously
exposed to the gravel slurry during the production that may cause erosion of the seal material.
Moreover, the seal thus obtained is not effective when the production tubing is inclined in nature.
Further, the seal thus obtained does not prevent leakage of hydrocarbons from the production 25
tubing. Any such leakage can further deteriorate the sealing formed in the annular portion.
[0018] The present subject matter provides an over the top assembly for the over the top
system used for gravel packing. In an implementation, the over the top assembly of the present
subject matter can be used for gravel packing of well casing of larger outer diameters, such as 9-
5/8” outer diameter. In an implementation, the over the top assembly of the present subject 30
matter includes a landing nipple mounted to a changeover tool on one side and a seal 5

subassembly on the other side. In one embodiment, the outer diameter of the over the top
assembly is substantially smaller as compared to the inner diameter of the well casing for
creating an annular portion between the well casing and the over the top assembly. In one
implementation, for drawing out the hydrocarbon from the reservoir rocks, the changeover tool
of the over the top assembly is connected to plurality of blank pipes of the production tubing. In 5
one implementation, the plurality of blank pipes includes a plurality of centralizers that ensures
that the over the top assembly remains in the center of the well casing. The changeover tool acts
as a bridge connecting two components with different dimensions and/or different thread
configurations. In an embodiment, an upper portion of the changeover tool has a threaded portion
for coupling to the landing nipple of the over the top assembly. The landing nipple can have a 10
larger inner diameter as compared to the outer diameter of the plurality of blank pipes that is
connected to a bottom portion of the changeover tool. In an implementation, the upper portion of
the changeover tool is larger in diameter as compared with a lower portion of the changeover
tool to allow for the coupling with the landing nipple and the blank pipes. In one embodiment,
the larger inner diameter of the landing nipple ensures that the outer surfaces of both the upper 15
and lower portions of the changeover tool are provided with a pin type threadform. Thus, a Pin X
Pin thread configuration of the changeover tool is achieved, which reduces the weight of the
changeover tool substantially. This also reduces the maximum outer diameter of the changeover
tool to approximately 5.25”, thus enabling easy handling of the changeover tool while engaging
with the landing nipple. Further, the reduction in weight of the changeover tool also reduces the 20
cost associated with the material used for fabricating the changeover tool.
[0019] In one embodiment, the over the top assembly of the present subject matter
includes the landing nipple. The outer and inner surfaces of the landing nipple is threaded so as
to couple with other members of the over the top assembly. In one embodiment, the landing
nipple is capable of receiving the crossover tool during the gravel packing process. In one 25
implementation, the inner surface of the top portion of the landing nipple is threaded, for
example, with left hand square thread, for engaging with the crossover tool. In an
implementation, the inner surface of the bottom portion of the landing nipple is threaded with
box type thread for engagement with the pin type thread of the outer surface of the changeover
tool. In one implementation, the landing nipple enables the installation of one or more flow 30
control devices, for example, a seal subassembly. In one embodiment, the outer surface of the 6

top portion of the landing nipple is threaded, for example, with buttress thread for engagement
with the seal subassembly of the production tubing. In an implementation, the buttress thread on
the outer surface of the top portion of the landing nipple is provided with a pitch of
approximately 10 threads per inch so as to provide a substantially high strength and withstand
higher forces being transmitted during engagement with the seal subassembly. Further, in one 5
implementation, the left hand square thread on the inner surface of the top portion of the landing
nipple is provided with a pitch of approximately 2 threads per inch ensuring easy assembly and
disassembly of the crossover tool with the landing nipple.
[0020] In one implementation, the over the top assembly of the present subject matter
includes a seal subassembly mounted on top of the landing nipple for effecting proper sealing of 10
the gravel pack and isolation of the annular portion. In one embodiment, the seal subassembly of
the over the top assembly includes a lower part, a middle part, an upper part, and a sealing
element. In one implementation, the lower part of the seal subassembly engages with the top
portion of the landing nipple. The buttress thread with a pitch of 10 threads per inch on the outer
surface of the landing nipple engages with the inner surface of the lower portion of the seal 15
subassembly having similar thread configuration. In one embodiment, the buttress thread has one
flank that is vertical while the other that is inclined with flat top and bottom connecting portions.
The buttress thread enables transmission of large forces between the landing nipple and the lower
part of the seal subassembly. In one embodiment, the buttress thread is unidirectional in nature
transmitting power and motion in one direction. 20
[0021] The engagement between the threaded portions of the lower part of the seal
subassembly and the landing nipple is achieved by providing forces in the downward direction
with the help of an external service tool, for example, a kelly tool installed on top of the seal
subassembly. In one embodiment, the kelly tool is made up of alloy steel with a centrally drilled
hole for allowing fluid to pass through. The kelly tool helps in transmitting motion to the 25
underlying component. In one embodiment, the kelly tool is engaged to the inner surface of one
end of the upper part of the seal subassembly through the left hand square thread provided on the
inner surface of the upper part of the seal subassembly. The engagement between the upper part
of the seal subassembly and the kelly tool ensures that the upper part of the seal subassembly is
tightly fixed to the kelly tool and moves along with the kelly tool for transmitting motion to the 30
other components of the seal subassembly. In one embodiment, the inner tubular surface of the 7

upper part of the seal subassembly has a stepped profile. The upper part of the seal subassembly
has a first inner surface that is threaded to engage with the kelly tool, and has a substantially
larger inner diameter as compared to an adjoining second inner surface that has a non-threaded
surface to accommodate a collar portion of the middle part of the seal subassembly. The second
inner surface has a substantially larger inner diameter as compared to an adjoining third inner 5
surface, which is also not threaded and accommodates a first portion of the middle part of the
seal subassembly. In one embodiment, the non-threaded inner surfaces of the upper part of the
seal subassembly allow sliding movement with respect to the middle part of the seal
subassembly. The sliding movement of the upper part of the seal subassembly helps in achieving
an effective sealing of the annular portion, and achieving a tight fit between the lower part of the 10
seal subassembly and the landing nipple. Further, in one embodiment, the collar of the middle
part of the seal subassembly enables prevents slipping between the sliding middle and the upper
parts while checking the engagement between the landing nipple and the lower part of the seal
subassembly.
[0022] In one embodiment, the outer surface of the other end of the upper part of the seal 15
subassembly has a square thread for engaging with the sealing element. In one embodiment, the
outer surface of the other end of the upper part of the seal subassembly is centrally provided with
a slot that adjoins the threaded surface. In an implementation, the rotation of the middle part of
the seal subassembly is retarded by any known screwing means, for example, an Allen headed
screw that is passed through the slot on the upper part of the seal subassembly, thereby allowing 20
the middle part of the seal subassembly to slide and not rotate inside the upper part of the seal
subassembly.
[0023] In an implementation, the middle part of the seal subassembly includes a second
portion that is provided with a right hand square thread on the outer surface to enable
engagement with the inner surface of the sealing element and a check nut that retards the 25
downward movement of the sealing element. In one embodiment, the middle part of the seal
subassembly includes a third portion that is tapered and threaded on the outer surface towards the
end that is engaged with the inner surface of the lower part of the seal subassembly. In an
embodiment, the middle part of the seal subassembly is fixed with respect to the lower part of the
seal subassembly. In an implementation, the middle part of the seal subassembly includes a 30
plurality of circumferentially disposed seal cups whose one end is attached to the middle part, 8

while the other end is in contact with the inner wall of the well casing. The plurality of seal cups
that is capable of being collapsed in a single direction helps in preventing gravel from rising
above the landing nipple and reaching the sealing element made of lead. The disposal of the seal
cups on the middle part prevents the sealing element from being eroded by coming in contact
with the gravel thereby ensuring that the sealing element does not deteriorate. 5
[0024] In an embodiment, the downward motion of the upper part of the seal
subassembly along with the kelly tool transfers compressive forces to the sealing element. The
presence of check nut on the other end of the sealing element prevents the downward motion of
the sealing element. In an implementation, the sealing element is made of any material that is
malleable in nature and expands on transmission of compressive forces, and does not erode. In 10
an implementation, the substantial travel between the upper part and the middle part of the seal
subassembly ensures that with the to and fro motion of the upper part, the sealing element
expands approximately three times in volume so as to form an effective sealing. Further, in an
embodiment, the sealing element is made of lead. In an embodiment, the transmission of forces
from the kelly tool causing expansion of the sealing element and to the lower part of the seal 15
subassembly for effecting a tight fit with the landing nipple is called as stabbing. The
construction of the upper part of the seal subassembly ensures that substantial travel with respect
to the middle part of the seal subassembly is achieved so as to provide complete and efficient
expansion of the sealing element, thus providing an effective sealing of the annular portion. In
one embodiment, the substantial travel between the upper part and the middle part of the seal 20
subassembly also ensures that effective sealing is achieved even when the over the top assembly
is disposed within an inclined well casing. For example, the seal subassembly of the present
subject matter is effective for the well casing inclination of approximately 40°.
[0025] In an implementation, the seal subassembly of the over the top assembly of the
present subject matter provides an effective sealing between the production tubing and the well 25
casing thereby preventing escape of the gravel packed in the annular portion. In an
implementation, the seal subassembly of the over the top assembly also provides effective
locking of the landing nipple, thereby providing a leak proof production tubing. On completion
of the stabbing process, the kelly tool is retracted easily from the left hand square thread of the
upper part of the seal subassembly. 30 9

[0026] Specific details of several embodiments of the over the top assembly of the
present subject matter is described below with reference to particular components and associated
procedures. In other embodiments, the components and associated methods can have other
arrangements. Some of the details related to structures and processes that are well-known and are
often associated with such over the top assemblies, are not set forth in the following description 5
for brevity and clarity. Moreover, although the following disclosure sets forth several
embodiments of different aspects of the invention, several other embodiments can have different
configurations than those described in the forthcoming section will also be evident to a person
skilled in the art and are intended to be included in the scope herein. As such, the present
disclosure and associated technology can encompass other embodiments with additional 10
elements and/or other embodiments without some of the elements described below with
reference to the Figures.
[0027] Figure 1a illustrates an over the top assembly 100, in accordance with an
embodiment of the present subject matter. The over the top assembly 100 includes a changeover
tool 102, a landing nipple 104, and a seal subassembly 106. In an embodiment, the seal 15
subassembly 106 of the present subject matter includes a lower part 108, a middle part 110, a
sealing element 112, a check nut 114, and an upper part 116. In one implementation, the over the
top assembly 100 includes one or more changeover tools 102 for connecting the components
above the one or more changeover tools 102 to those below. The component below the one or
more changeover tools 102, for example, includes one or more blank pipes (shown in Figure 2a). 20
The one or more changeover tools 102 acts as a bridge connecting the one or more blank pipes
and the landing nipple 104 disposed above the one or more changeover tools 102. In one
implementation, the changeover tool 102 is capable of connecting two components with different
dimensions and/or different thread configurations.
[0028] In one embodiment, the over the top assembly 100 is provided with the landing 25
nipple 104, which has a tubular cross-section of approximately 165 mm outer diameter and a
substantially larger wall thickness of approximately 15 mm. The outer and inner surfaces of the
landing nipple 104 is threaded so as to couple with other components of the over the top
assembly 100. In one embodiment, the landing nipple 104 is capable of receiving a crossover
tool (shown in Figure 2a) during the gravel packing process. In an embodiment, the landing 30 10

nipple 104 is engaged with the seal subassembly 106 for sealing the gravel pack created during
the gravel packing process.
[0029] In an embodiment, the lower part 108 of the seal subassembly 106, on one end is
connected to the landing nipple 104. In an embodiment, the inner diameter of the lower part 108
is substantially equal to the outer diameter of the landing nipple 104. The substantially similar 5
diameters ensure that the engagement of both the components create a tight fit. In an
embodiment, the lower part 108 of the seal subassembly 106, on the other end is engaged with
the middle part 110 of the seal subassembly 106. The lower part 108 of the seal subassembly has
two different inner diameters. A first inner diameter of the lower part 108 is substantially similar
to the outer diameter of the landing nipple 104, while a second inner diameter of the lower part 10
108 is substantially similar to the outer diameter of one end of the middle part 110.
[0030] In an embodiment, the middle part 110 is engaged with the lower part 108 on one
end, while on the other end is provided with a non-threaded outer surface. The check nut 114 that
arrests the motion of the sealing element 112 is engaged on the threaded outer surface of the
middle part 110 adjoining the end of the sealing element 112 that is encompassing the middle 15
part 110. In one embodiment, the middle part 110 includes the collar (shown in Figure 1e) that
has a substantially larger diameter than the outer diameter of the body of the middle part 110. For
example, the outer diameter of the collar is approximately 10 mm larger than the outer diameter
of the body of the middle part 110. In an embodiment, the upper part 116 of the seal subassembly
106 is engaged on one end with the sealing element 112. 20
[0031] In an embodiment, the inner diameter of the sealing element 112 engaging with
the upper part 116 is substantially larger than the inner diameter of the sealing element 112
engaging with the middle part 110. In one embodiment, the upper part 116 is slidably connected
to the middle part 110. In an embodiment, the inner diameter of the upper part 116 receiving the
middle part 110 is substantially larger than the outer diameter of the middle part 110 to allow 25
free sliding movement of the upper part 116 over the middle part 110. In an embodiment, the
seal subassembly 106 can be mounted with the other components of the over the top assembly
100 at any time during the gravel packing process.
[0032] Figure 1b illustrates the changeover tool 102 of the over the top assembly 100 of
the present subject matter. In an embodiment, an upper portion 118 of the changeover tool 102 is 30
threadably connected to the landing nipple 104 of the over the top assembly 100 that has a 11

substantially larger inner diameter as compared to the outer diameter of the one or more blank
pipes (shown in Figure 2a) that is connected to a lower portion 120 of the changeover tool 102.
For discussion, the upper portion 118 and the lower portion 120 may be also referred to as a first
end 118 and a second end 120. In an implementation, the upper portion 118 of the changeover
tool 102 is larger in diameter as compared with the lower portion 120 of the changeover tool 102. 5
In one embodiment, the larger inner diameter of the landing nipple 104 ensures that the outer
surfaces 122, 124 of both the upper and lower portions 118, 120 of the changeover tool 102 are
provided with a pin type threadform. The Pin X Pin thread configuration of the changeover tool
102 thus achieved substantially reduces the overall weight of the changeover tool 102. The
maximum outer diameter of the changeover tool 102 is also reduced to approximately 5.25”. 10
Thus, easy handling of the changeover tool 102 while engaging with the landing nipple 104 is
provided. Further, the substantial reduction in weight of the changeover tool 102 also reduces the
cost associated with the material used for fabricating the changeover tool 102.
[0033] Figure 1c illustrates the landing nipple 104 of the over the top assembly 100 of
the present subject matter. In an embodiment, the landing nipple 104 is of tubular cross-section. 15
In an implementation, the inner surface 134 of the second end 128 of the landing nipple 104 is
threaded. In one embodiment, the inner surface 134 is provided with a box type thread for
engagement with the pin type thread of the outer surface 122 of the changeover tool 102. In one
embodiment, the inner surface 132 of the first end 126 of the landing nipple 104 is threaded. For
example, the inner surface 132 is provided with left hand square thread of 2 threads per inch for 20
approximately 200 mm. The left hand square thread provided in the inner surface 132 of the
landing nipple 104 facilitates easy engagement and disengagement with the crossover tool
(shown in Figure 2a).
[0034] In one implementation, the landing nipple 104 also facilitates installation of one
or more flow control devices, for example, the seal subassembly 106. In one embodiment, the 25
outer surface 130 of the first end 126 of the landing nipple 104 is threaded. For example, the
outer surface 130 is provided with buttress thread for engaging with the seal subassembly 106 of
the over the top assembly 100. In an embodiment, the buttress thread on the outer surface 130 of
the first end 126 of the landing nipple 104 is provided with a pitch of 10 threads per inch for
approximately 300 mm. The substantially high pitch of the buttress thread provided on the outer 30
surface 130 enables achieving a leak proof joint with substantially high strength for withstanding 12

higher compressive forces transmitted during engagement with the seal subassembly 106. In one
embodiment, the buttress thread provided on the outer surface 130 of the landing nipple 104
helps in transmitting motion and power in a single direction. For example, in the direction of
engagement of the seal subassembly 106 with the landing nipple 104. In an embodiment, the
buttress thread on the outer surface 130 ensures that the engagement formed between the seal 5
subassembly 106 and the landing nipple 104 is permanent. In one embodiment, a plurality of
centralizers 136 is disposed on the circumference of the landing nipple 104. The plurality of
centralizers 135 ensures that the landing nipple 104 remains aligned with a central axis 137 of
the over the top assembly 100.
[0035] Figure 1d illustrates the lower part 108 of the seal subassembly 106 of the present 10
subject matter. In an embodiment, the lower part 108 engages with the landing nipple 104 of the
over the top assembly 100. The engagement between the bottom portion 138 of the lower part
108 and the first end 126 of the landing nipple 104 is achieved by the threaded inner surface 142
of the bottom portion 138 of the lower part 108. In an embodiment, the lower part 108 has a
non-threaded outer circumference with an inner diameter substantially larger than the outer 15
diameter of both the adjoining components. In one embodiment, the lower part 108 has a first
inner diameter 144 substantially larger than a second inner diameter 145. The first inner diameter
144 encompasses the first end 126 of the landing nipple when engaged and is approximately 165
mm. The second inner diameter 145 engages with the middle part 110 and is approximately 148
mm in diameter. In an embodiment, the lower part 108 has a top portion 140 capable of being 20
engaged with the middle part 110. The top portion 140 is provided with a threaded inner surface
146 for engagement with the middle part 110. For example, the inner surface 146 is provided
with a round 8 non-upset type thread.
[0036] Figure 1e illustrates the middle part 110 of the seal subassembly 106 of the
present subject matter. In an implementation, the middle part 110 of the seal subassembly 106 25
acts as the power transmitting component of the over the top assembly100. The middle part 110
includes a bottom portion 147, a middle portion 149, and a top portion 152. The bottom portion
147 of the middle part 110 is threadably engaged with the top portion 140 of the lower part 108.
In an embodiment, the bottom portion 147 of the middle part 110 has an outer surface 148
provided with the round 8 non-upset type thread for engagement with the inner surface 146 of 30
the top portion 140 of the lower part 108. The middle portion 149 of the middle part 110 is 13

provided with a threaded outer surface 150. In an embodiment, the outer surface 150 of the
middle portion 149 is provided with a right hand square thread of 8 threads per inch pitch for
engagement with check nut (shown in Figure 1g). The top portion 152 of the middle part 110
ends with the collar 154 having substantially larger diameter than the top portion 152. In an
embodiment, the outer diameter of the collar is approximately 10 mm larger than the outer 5
diameter of the top portion 152. The top portion 152 including the collar 154 is encompassed
within the upper part (shown in Figure 1h) in the seal subassembly 106. In one embodiment, the
top portion 152 of the middle part 110 is provided with a centrally disposed key way 151 along
the central axis 137 of the over the top assembly 100. The key way 151 is provided for locking
the rotation of the middle part 110 with respect to the upper part (shown in Figure 1h). 10
[0037] Figure 1f illustrates the sealing element 112 of the seal subassembly 106. In an
embodiment, the sealing element 112 has a first end 156 and a second end 158. The sealing
element 112 is tubular in cross-section and is made of a malleable material such as lead. In one
embodiment, the sealing element 112 is made of 99% lead and 1% impurity of tin and/or
antimony. In an implementation, all the components of the over the top assembly 100 except the 15
sealing element 112 is made of alloy steel of 40Cr4Mo3 composition. The malleable property of
the sealing element 112 enables the sealing element 112 to expand in the space available.
However, the effective expansion or sealing is achieved by the seal subassembly 106 of the
present subject matter. The sealing element 112 has a first inner diameter 160 substantially larger
than a second inner diameter 162. The second inner diameter 162 of the sealing element 112 is 20
non-threaded and encompasses the middle portion 149 of the middle part 110 when engaged.
The first inner diameter 160 of the sealing element 112 has a threaded profile for engaging with
the upper part (shown in Figure 1h). In an implementation, the first inner diameter 160 of the
sealing element 112 is provided with right hand square thread of 8 threads per inch pitch. In one
embodiment, the threaded first inner diameter 160 of the sealing element 112 is substantially 25
smaller in depth as compared to the non-engaging second inner diameter 162 of the sealing
element 112 so that the lead on the non-engaging portion of the sealing element 112 expands
upon transmission of compressive forces to the first end 156 of the sealing element 112. In one
embodiment, the substantially smaller second inner diameter 162 ensures more lead is available
for expansion in the portion surrounding the second inner diameter 162 than in the portion 30
surrounding the first inner diameter 160. 14

[0038] Figure 1g illustrates the check nut 114 of the seal subassembly 106 of the present
subject matter. In an embodiment, the check nut 114 of the seal subassembly 106 has a tubular
cross-section and has an inner diameter larger than the outer diameter of the middle part 110.
The check nut 114 has a first end 164 adjoining the sealing element 112. The check nut 114 is
engaged with the middle part 110 for preventing the expansion of the sealing element 112 along 5
the longitudinal direction of the central axis 137. The presence of check nut 114 ensures that the
sealing element 112 necessarily expand in a direction transverse to the longitudinal direction of
the central axis 137 when substantial amount of compressive forces are transmitted to the sealing
element 112. The check nut 114 has an inner surface 166 provided with a threaded profile for
engagement with the outer surface 150 of the middle portion 149 of the middle part 110. In an 10
embodiment, the inner surface 166 of the check nut 114 is provided with a right hand square
thread of 8 threads per inch pitch to effect engagement with the middle portion 149 of the middle
part 110. It will be apparent to a person skilled in the art that the check nut 114 can be replaced
with any known fastening means with similar characteristic features in an alternative
embodiment of the present subject matter. 15
[0039] Figure 1h illustrates the upper part 116 of the seal subassembly 106 of the present
subject matter. In an implementation, the upper part 116 of the seal subassembly 106 is a motion
and power transmitting member of the seal subassembly 106. In one embodiment, the upper part
116 includes a top portion 168 and a bottom portion 170. In one embodiment, the upper part 116
also includes a first inner surface 174, a second inner surface 176, and a third inner surface 178. 20
In an implementation, the first inner surface 174 has a diameter substantially larger than the
second inner surface 176, while the second inner surface 176 has a diameter that is substantially
larger than the third inner surface 178. The stepwise construction of the upper part 116 of the
seal subassembly 106 enables the upper part 116 to receive components of three different outer
diameters. In one embodiment, the upper part 116 has two outer diameters. A first outer diameter 25
substantially smaller than a second outer diameter is provided in the bottom portion 170 of the
upper part 116 for engaging with the sealing element 112. In an embodiment, the first outer
diameter is tapered at an angle of approximately 75° with respect to the second outer diameter
and forming a tapered intersection between the first outer diameter and the second outer
diameter. In an embodiment, the bottom portion 170 is provided with an outer surface 172 with a 30 15

threaded profile for engaging with the sealing element 112. For example, the outer surface 172 of
the bottom portion 170 is provided with a right hand square thread of 8 threads per inch pitch.
[0040] In an embodiment, the third inner surface 178 of the upper part 116 is provided
with a non-threaded profile for receiving the top portion 152 of the middle part 110. In one
embodiment, the second inner surface 176 of the upper part 116 is provided with a non-threaded 5
profile for receiving the collar 154 of the middle part 110. In an embodiment, the bottom portion
170 of the upper part 116 is provided with a slot 180 adjacent to the tapered intersection between
the first outer diameter and the second outer diameter of the upper part 116. The slot 180 is
provided to receive any known screwing means, for example, an Allen headed screw of with a
threaded length of approximately 20 mm can be received through the slot 180 for locking the 10
rotational movement of the top portion 152 of the middle part 110 received in the third inner
surface 178 of the upper part 116.
[0041] In an embodiment, the second inner surface 176 of the upper part 116 is
substantially larger in depth than the thickness of the collar 154 received in the second inner
surface 176. The substantially larger depth of the second inner surface 176 than the thickness of 15
the collar 154 ensures that the upper part 116 has a substantially larger travel of the difference
between the depth of the second inner surface 176 and the thickness of the collar 154 during the
to and fro sliding motion of the upper part 116 with respect of the middle part 110.
[0042] In one embodiment, the first inner surface 174 of the upper part 116 has a
threaded profile to engage with a service tool used for stabbing the seal subassembly 106. The 20
service tool, for example, is a kelly tool (not shown in the Figure) that is threadably engaged
within the first inner surface 174 of the upper part 116. In one embodiment, the first inner
surface 174 of the upper part 116 is provided with a left hand square thread of 4 threads per inch
pitch. As a result of the threaded engagement of the upper part 116 with the kelly tool, the
operation of the kelly tool causes the upper part 116 slide on top of the middle part 110 causing 25
the stabbing of the lower part 108 with the landing nipple 104 thereby achieving a permanent
tight fit. The to and fro sliding motion of the upper part 116 with respect of the middle part 110
also causes the sealing element 112 to expand transversely with respect of the central axis 137.
[0043] Figure 2a, 2b, 2c, and 2d illustrates the over the top system 200-1, 200-2, 200-3,
200-4 (collectively referred to as 200) including the over the top assembly 100 of the present 30
subject matter. In an implementation, a slurry pumping operation of the over the top system 200 16

is shown in Figure 2a, while a reverse circulation operation of the over the top system 200 is
shown in Figure 2b. Figure 2c depicts the retraction of service tool from the over the top system
200, while Figure 2d depicts the sealing operation of the over the top system 200 having the over
the top assembly 100 including the seal subassembly 106 of the present subject matter.
[0044] In an implementation, the over the top system 200 of the present subject matter is 5
used for the gravel packing operation. The first stage of the gravel packing operation involves
implementation of a bottom hole assembly 236 including the service tool for gravel packing, for
example, the crossover tool 202 inside a well casing 204. The slurry pumping operation involves
pumping gravel slurry 212, 228 into the bottom hole assembly 236 by the crossover tool 202. In
one implementation, the slurry pumping operation by the crossover tool 202 is also called as 10
squeezing. In one implementation, the gravel slurry 212, 228 is a combination of gravel 212 and
a carrier fluid 228 that carries the gravel 212. The carrier fluid 228 is also called as gravel
packing fluid, a clean, water based fluid that is used for carrying the gravel 212 into the bottom
hole assembly 236. In an embodiment, the slurry pumping operation involves application of
appropriate pump pressure necessary for forcing the gravel slurry 212, 228 into the bottom hole 15
assembly 236.
[0045] In an implementation, the over the top system 200 has a plug assembly 222 at the
bottom of the bottom hole assembly 236. The plug assembly 222, for example, includes a bull
plug 224 and a bridge plug 226. The bull plug 224, for example, is a tool that is located at the
bottom of the bottom hole assembly 236 and enables isolation of the lower part of the wellbore. 20
In one embodiment, the bull plug 224 is installed temporarily to isolate the lower part of the
wellbore from the slurry pumping operation that is taking place above. After installation of the
bull plug 224, the crossover tool 202 is mounted to the first end 126 of the landing nipple 104. In
an implementation, the inner surface 132 of the first end 126 of landing nipple 104 and the outer
surface of bottom portion of the crossover tool 202 have a left hand square thread for enabling 25
proper engagement between the crossover tool 202 and the landing nipple 104.
[0046] In one embodiment, the crossover tool 202 includes a plurality of downwardly
facing packer cups 234 made of rubber that ensures that the flow of gravel slurry 212, 228
remains downward direction all the time. In one embodiment, the plurality of packer cups 234 is
disposed in such a manner that they are in contact with the inner wall of the well casing 204. The 30
crossover tool 202 has an inner hole 214 through which the gravel slurry 212, 228 is forced 17

downward. The forced gravel slurry 212, 228 is vented out of a crossover port 216 and enters an
annular portion 206 between the bottom hole assembly 236 and the well casing 204. The
crossover tool 202 ensures that the gravel slurry 212, 228 forced out of the crossover port 216 is
gushed inside the annular portion 206 that is vacant. In one embodiment, the gushing gravel
slurry 212, 228 permeates through a plurality of perforations 218 provided on the well casing 5
204 and prevents the seeping in of formation sand 220 into the well casing 204. The presence of
retrievable bull plug 224 ensures that no hydrocarbon from the reservoir rocks is drawn into the
bottom hole assembly 236 during the slurry pumping operation of the over the top system 200.
Further, the bottom hole assembly 236 includes one or more screens 208 for preventing the
permeation of gravel 212 along with the hydrocarbons into the bottom hole assembly 236. 10
However, the pores on the one or more screens 208 allow the carrier fluid 228 to pass through. In
one embodiment, the carrier fluid 228 that passes through the one or more screens 208 moves
upward through one or more blank pipes 210, the changeover tool 102, and the landing nipple
104 into the crossover tool 202. In an implementation, the bottom portion of the crossover tool
202 is disposed with a circular valve 230, which is kept open to allow the entry of returning 15
carrier fluid 228 into the crossover tool 202 during the slurry pumping operation. The carrier
fluid 228 that enters the crossover tool 202 is ejected out through a plurality of return ports 232
disposed on the top portion of the crossover tool 202.
[0047] In an implementation, the reverse circulation operation of the over the top system
200 involves pumping of the gravel slurry 212, 228 into the annular portion 206. In one 20
embodiment, the gravel slurry 212, 228 pumped through the annular portion 206 is retrieved
back through the inner hole 214 of the crossover tool 202. In an implementation, the reverse
circulation involves circulating the gravel slurry 212, 228 opposite to the normal direction of
circulation within the well casing 204. In an implementation, the reverse circulation can be
effective in drawing out the gravel slurry 212, 228 to the surface faster than the normal 25
circulation at a given flow rate, as the inner volume of the crossover tool 202 is considerably less
when compared with the volume of the annular portion 206 that is outside. When the gravel
slurry 212, 228 enters the annular portion, the plurality of packer cups 234 are forced
downwards. Due to the difference in the volume between the inner hole of the crossover tool 202
and the outer annular portion 206, the gravel slurry 212, 228 entering the annular portion 206 30
flushes out by fluidizing the excess gravel 212 dispensed above the landing nipple 104. The 18

fluidized excess gravel 212 enters the crossover port 216 and flushed out through the inner hole
214 of the crossover tool 202.
[0048] In an implementation, the reverse circulation operation is followed by retraction
of the crossover tool 202 that is mounted on top of the landing nipple 104. In one embodiment,
the crossover tool 202 is disassembled from the landing nipple 104 by disengaging the tool 202 5
from the landing nipple 104 after ensuring that no gravel 212 remain on top of the landing nipple
104. The left hand square thread on the inner surface 132 of the first end 126 of the landing
nipple 104 with pitch of approximately 2 threads per inch enable easy dismantling of the
crossover tool 202 from the landing nipple 104. Though the slurry pumping and the subsequent
reverse circulation stages has ensured that no gravel lies above the landing nipple 104, 10
possibilities of escape of gravel 212 from the annular portion 206 always exists in the absence of
complete isolation of the annular portion 206. This is achieved by the sealing operation of the
over the top system 200.
[0049] In one implementation, the sealing operation of the over the top system 200
includes a seal subassembly 106 mounted on top of the landing nipple 104 to effect sealing of the 15
gravel 212 within the annular portion 206. In an implementation, the seal subassembly 106 of the
over the top assembly 100 engages with the landing nipple 104 in such a fashion that a
permanent tight fit is formed between the lower part 108 of the seal subassembly 106 and the
landing nipple 104. The stabbing of the lower part 108 of the seal subassembly 106 and the
landing nipple 104 is achieved with the help of the kelly tool (not shown in the Figure). 20
[0050] The kelly tool is mounted on top of the upper part 116 of the seal subassembly
106 in such a manner that the bottom portion of the kelly tool is detachably engaged to the top
portion 168 of the upper part 116 of the seal subassembly 106. The engagement between the
threaded portions of the lower part 108 of the seal subassembly 106 and the landing nipple 104 is
achieved by transmitting compressive forces in the downward direction by the operation of the 25
kelly tool. In one embodiment, the kelly tool is made up of alloy steel with a centrally drilled
hole for allowing fluid to pass through. The kelly tool helps in transmitting motion to the
underlying component(s). The engagement between the upper part 116 of the seal subassembly
106 and the kelly tool ensures that the upper part 116 of the seal subassembly 106 is tightly fixed
to the kelly tool and moves along with the kelly tool for transmitting power and motion to the 30
other components of the seal subassembly 106. 19

[0051] The construction of the upper part 116 of the seal subassembly 106 ensures that
substantial travel with respect to the middle part 110 of the seal subassembly 106 is achieved so
as to provide complete and efficient expansion of the sealing element 112, thus providing an
effective sealing of the annular portion 206. In an embodiment, the middle part 110 of the seal
subassembly 106 is circumferentially provided with a plurality of seal cups 238 that is 5
downwardly disposed facing the gravel 212 inside the annular portion 206. The plurality of seal
cups 238 collapses only in the downward direction facing the gravel 212 and thus prevents the
gravel 212 from moving in an upward direction towards earth surface. The presence of the
plurality of seal cups 238 also ensures that the sealing achieved by the expansion of lead
disposed on the sealing element 112 is not exposed to the gravel 212 thereby preventing the 10
sealing element 112 from erosion. Thus, the presence of the plurality of seal cups 238 helps in
achieving a sealing having a longer life.
[0052] Although the subject matter has been described in considerable detail with
reference to certain embodiments thereof, other embodiments are possible. It is to be understood
that the appended claims are not necessarily limited to the features described herein. Rather, the 15
features are disclosed as embodiments of the over the top assembly.

I/We claim:
1. A seal subassembly (106) for an over the top assembly (100) of an over the top
system (200-1, 200-2, 200-3, 200-4), the seal subassembly (106) comprising:
a lower part (108) having a bottom portion (138) capable of being engaged with a
first end (126) of a landing nipple (104) of the over the top assembly (100); 5
a middle part (110) having a bottom portion (147) threadably engaged with a top
portion (140) of the lower part (108); and
an upper part (116) having a first inner surface (174), wherein the first inner surface
(174) has a threaded profile and substantially larger diameter than a second inner surface
(176) capable of receiving a collar (154) of the middle part (110), and a third inner surface 10
(178) having a substantially smaller diameter than the second inner surface (176) for
receiving a top portion (152) of the middle part (110), wherein the second inner surface
(176) is substantially longer than the thickness of the collar (154) to allow to and fro sliding
movement of the upper part (116) with respect to the middle part (110).
15
2. The seal subassembly (106) as claimed in claim 1, wherein the bottom portion (138)
of the lower part (108) has an inner surface (142) capable of being engaged with an outer
surface (130) of the first end (126) of the landing nipple (104), wherein both the outer surface
(130) and the inner surface (142) are provided with buttress thread of 10 threads per inch
pitch. 20

3. The seal subassembly (106) as claimed in claim 1, wherein the upper part (116) has
a top portion (168) having an inner surface (174) provided with a left hand square thread for
engaging with a kelly tool.
25
4. The seal subassembly (106) as claimed in claim 1, further comprises a sealing
element (112) engaged with a threaded outer surface (172) of a bottom portion (170) of the
upper part (116).
21

5. The seal subassembly (106) as claimed in claim 4, wherein the bottom portion (170)
has a slot (180) adjoining the threaded outer surface (172) for preventing the rotation of the
middle part (110) slidably connected to the upper part (116).

6. The seal subassembly (106) as claimed in claim 4, wherein the upper part (116) 5
slidably moves to and fro over the middle part (110) and transmits compressive forces to a
first end (156) of the sealing element (112).

7. The seal subassembly (106) as claimed in claim 1 or 6, further comprises a check
nut (114) for arresting a downward movement of the sealing element (112) due to the 10
compressive forces acting on the first end (156) of the sealing element (112).

8. The seal subassembly (106) as claimed in claim 1, wherein the to and fro sliding
movement of the upper part (116) forms a tight fit between the lower part (108) and the
landing nipple (104). 15

9. The seal subassembly (106) as claimed in claim 1, wherein the middle part (110)
includes a plurality of circumferentially disposed seal cups (238).

10. An over the top assembly (100) for an over the top system (200-1, 200-2, 200-3, 20
200-4), the over the top assembly (100) comprising a seal subassembly (106) as claimed in
any one of the preceding claims 1 to 9.

11. The over the top assembly (100) as claimed in claim 10, further comprises a landing
nipple (104) having a first end (126), wherein an inner surface (132) of the first end (126) is 25
provided with a left hand square thread of 2 threads per inch pitch capable of being engaged
with a crossover tool (202).

12. The over the top assembly (100) as claimed in claim 10 or 11, further comprises at
least one changeover tool (102) for securely connecting the at least one landing nipple (104) 30
to a bottom hole assembly (236) of the over the top system (200-1, 200-2, 200-3, 200-4). 22


13. The over the top assembly (100) as claimed in claim 12, wherein the at least one
changeover tool (102) has a first end (118) engaging with the second end (128) of the landing
nipple (104), and a second end (120) for engaging with at least one blank pipe (210) of the
bottom hole assembly (236) having an outer diameter substantially lesser than the outer 5
diameter of the first end (118).

14. The over the top assembly (100) as claimed in claim 13, wherein the first end (118)
has an outer surface (122) provided with a pin type thread configuration for engaging with
the inner surface (134) of the second end (128) of the landing nipple (104) provided with a 10
box type thread configuration, and wherein the second end (120) of has an outer surface
(124) provided with a pin type thread configuration for engaging with the at least one blank
pipe (210).

15. An over the top system (200-1, 200-2, 200-3, 200-4) for packing a plurality of 15
gravel (212) in an annular portion (206) between a well casing (204) and a centrally running
production tubing of a well used for extracting hydrocarbons from reservoir rocks, the over
the top system (200-1, 200-2, 200-3) comprising an over the top assembly (100) as claimed
in any one of the claims 10 to 14.
Date- 23-September-2013 20
KONPAL RAE
IN/PA -1228
Agent for the Applicant

25
To,
The Controller of Patents
The Patent Office at New Delhi

30
23


ABSTRACT

OVER THE TOP ASSEMBLY FOR GRAVEL PACKING AND SEALING
5
A seal subassembly (106), over the top assembly (100), and over the top system (200) are
described. The seal subassembly (106) comprises a lower part (108) having a bottom portion
(138) capable of being engaged with a first end (126) of a landing nipple (104); a middle part
(110) having a bottom portion (147) threadably engaged with a top portion (140) of the lower
part (108); and an upper part (116) having first, second and third inner surfaces. The first 10
inner surface (174) has a substantially larger diameter than the second inner surface (176),
which has a substantially larger diameter than the third inner surface (178). The second inner
surface (176) is capable of receiving a collar (154) of the middle part (110) and is
substantially longer than the collar (154) to allow to and fro sliding movement of the upper
part (116) with respect to the middle part (110). 15

To be Published with Figure 1a
PD010211IN-SC
FORM 5
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
DECLARATION AS TO INVENTORSHIP
(See section 10(6) and rule 13(6)
1. APPLICANT(S)
NAME NATIONALITY ADDRESS
OIL & NATURAL GAS
CORPORATION LIMITED
Indian Centralised Patent Cell, ONGC,
Room No 271, KDMIPE, 9,
Kaulagarh Road,
Dehradun Uttarakhand 248195,
India

hereby declare that the true and first inventor(s) of the invention disclosed in the
complete specification filed in pursuance of our application numbered
2805/DEL/2013 dated 23 September 2013 is/are
2. INVENTOR(S)
NAME NATIONALITY ADDRESS
RAKUNDLA, Snehal Indian WSS, ONGC, Chandkheda,
Ahmedabad- 380005, India
BEG, Mirza Arif Indian WSS, ONGC, Chandkheda,
Ahmedabad- 380005, India
MISHRA, Nirmal Kumar Indian WSS, ONGC, Chandkheda,
Ahmedabad- 380005, India
VAJPEYI, Priyanshu Indian WSS, ONGC, Chandkheda,
Ahmedabad- 380005, India
NANDAN, Alok Indian WSS, ONGC, Chandkheda,
Ahmedabad- 380005, India

3. DECLARATION TO BE GIVEN WHEN THE APPLICATION IN INDIA IS
FILED BY THE APPLICANT(S) IN THE CONVENTION COUNTRY:-

I/We the applicant(s) in the convention country hereby declare that our right to apply
for a patent in India is by way of assignment from the true and first inventor(s).
Dated this 22 September 2014

Signature: