U.S. patent application number 10/904965 was filed with the patent office on 2006-06-08 for downhole tool shock absorber.
This patent application is currently assigned to SCHLUMBERGER TECHNOLOGY CORPORATION. Invention is credited to SCOTT S. CHESSER, BULENT FINCI, RICHARD D. WARD.
Application Number | 20060118297 10/904965 |
Document ID | / |
Family ID | 36572917 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060118297 |
Kind Code |
A1 |
FINCI; BULENT ; et
al. |
June 8, 2006 |
DOWNHOLE TOOL SHOCK ABSORBER
Abstract
Shock absorbers for downhole tools. The shock absorbers
entailing a columnar body having a wall including a plurality of
cells, and a retainer adapted to retain the shock absorber on the
tool body. The retainer also adapted to transfer an impact force to
the shock absorber.
Inventors: |
FINCI; BULENT; (SUGAR LAND,
TX) ; CHESSER; SCOTT S.; (RICHMOND, TX) ;
WARD; RICHARD D.; (LA PORTE, TX) |
Correspondence
Address: |
SCHLUMBERGER OILFIELD SERVICES
200 GILLINGHAM LANE
MD 200-9
SUGAR LAND
TX
77478
US
|
Assignee: |
SCHLUMBERGER TECHNOLOGY
CORPORATION
110 SCHLUMBERGER DRIVE
SUGAR LAND
TX
|
Family ID: |
36572917 |
Appl. No.: |
10/904965 |
Filed: |
December 7, 2004 |
Current U.S.
Class: |
166/242.1 ;
166/244.1; 175/321 |
Current CPC
Class: |
E21B 17/07 20130101;
F16F 7/121 20130101 |
Class at
Publication: |
166/242.1 ;
166/244.1; 175/321 |
International
Class: |
E21B 17/00 20060101
E21B017/00 |
Claims
1. A shock absorber for a downhole tool, comprising: a columnar
body having a wall comprising a plurality of cells.
2. The shock absorber of claim 1, wherein the columnar body
comprises a hollow core.
3. The shock absorber of claim 2, wherein the columnar body is
formed of a material selected from a group consisting of a metal,
an alloy, and a composite.
4. The shock absorber of claim 2, wherein the columnar body is made
of an aluminum alloy.
5. The shock absorber of claim 1, wherein the columnar body is
pre-crushed.
6. The shock absorber of claim 1, wherein the cells contain a
sealant material.
7. The shock absorber of claim 1, further comprising means for
retaining the columnar body on a downhole tool.
8. The shock absorber of claim 7, wherein the means for retaining
the columnar body is adapted to transfer impact loads to the
columnar body.
9. The shock absorber of claim 7, wherein the means for retaining
the columnar body comprises telescoping parts adapted to
accommodate deformation of the columnar body due to impact
loads.
10. The shock absorber of claim 1, wherein the wall is made from a
laminate of corrugated sheets of material.
11. The shock absorber of claim 10, wherein the material comprises
an aluminum alloy.
12. A downhole tool, comprising: a tool body; a shock absorber
having a columnar body, the columnar body having a wall comprising
a plurality of cells; and a retainer adapted to retain the columnar
body on the tool body.
13. The downhole tool of claim 12, wherein the columnar body
comprises a hollow core.
14. The downhole tool of claim 12, wherein the columnar body is
formed of a material selected from a group consisting of a metal,
an alloy, and a composite.
15. The downhole tool of claim 12, wherein the columnar body is
made of an aluminum alloy.
16. The downhole tool of claim 12, wherein the cells contain a
sealant material.
17. The downhole tool of claim 12, wherein the wall is made from a
laminate of corrugated sheets of material.
18. The downhole tool of claim 12, wherein the retainer comprises
telescoping parts adapted to accommodate deformation of the
columnar body due to impact loads.
19. The downhole tool of claim 12, wherein the shock absorber is
disposed on an end of said tool body.
20. The downhole tool of claim 19, wherein the retainer is adapted
to transfer impact loads to the columnar body of said shock
absorber.
21. A method of mounting a shock absorber on a downhole tool,
comprising: disposing said shock absorber at one end of the body of
said downhole tool, said shock absorber having a columnar body with
a wall including a plurality of cells; and retaining said columnar
body on the tool body.
22. The method of claim 21, wherein the wall of said columnar body
is made from a laminate of corrugated sheets of material.
23. The method of claim 21, wherein retaining the columnar body
comprises disposing a retainer on the tool body, said retainer
adapted to accommodate deformation of the columnar body due to
impact loads.
Description
BACKGROUND OF INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates generally to shock absorbers. More
particularly, the invention relates to shock absorbers for use with
downhole apparatus.
[0003] 2. Background Art
[0004] In the oil and gas field, downhole apparatus or tools are
used to perform various subsurface operations, generally in a
wellbore. Downhole tools comprise any one of various apparatus used
in subsurface measurements, exploration, production, and monitoring
operations as known in the industry. Typical downhole tools are
configured with elongated or tubular-type bodies to facilitate
their deployment and transport through subsurface formations. In
applications where there are multiple tool bodies, the tool bodies
are joined together to form a tool string (e.g., a
multi-measurement tool string). A typical downhole operation
involves lowering the downhole tool(s) into the wellbore on the end
of a drill pipe or wireline or coiled tubing. As the downhole tool
is lowered into the wellbore, the bottom of the tool may strike a
ledge on the wall of the wellbore or the bottom of the wellbore.
The tool body at the bottom of the downhole tool absorbs impact
loads when the tool bottom strikes the wall or wellbore bottom. In
cases where the bottom of the tool body contains an instrument, it
is desirable to provide a shock absorbing mechanism at the tool
bottom to protect the instruments from shock and impact loads.
[0005] Myriad types of shock absorbers are used in industry for a
multitude of applications. U.S. Pat. No. 6,472,043 describes a
shock absorber for use in aerospace applications and automotive
crash testing. The shock absorber entails a honeycomb block with a
plurality of cylindrical cells arranged in parallel. A need remains
for improved shock absorption mechanisms for subsurface
applications.
SUMMARY OF THE INVENTION
[0006] In one aspect, the invention relates to a shock absorber for
a downhole tool. The shock absorber including a columnar body
having a wall comprising a plurality of cells. In one embodiment,
the columnar body includes a hollow core. The columnar body may be
formed of a metal, an alloy, or a composite. The shock absorber
includes means of retaining the columnar body on a downhole tool.
The means of retaining the columnar body is preferably configured
to transfer impact loads to the columnar body.
[0007] In another aspect, the invention relates to a downhole tool.
The downhole tool including a tool body, a shock absorber having a
columnar body, the columnar body having a wall comprising a
plurality of cells, and a retainer adapted to retain the columnar
body on the tool body.
[0008] In another aspect, the invention relates to a method of
mounting a shock absorber on a downhole tool. The method comprising
disposing the shock absorber at one end of the body of the downhole
tool, the shock absorber having a columnar body with a wall
including a plurality of cells; and retaining the columnar body on
the tool body.
[0009] Other features and advantages of the invention will be
apparent from the following description and the appended
claims.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1A is a schematic of a shock absorber according to an
embodiment of the invention.
[0011] FIG. 1B is an enlargement of the honeycomb cell structure
shown in FIG. 1A.
[0012] FIG. 1C shows the honeycomb cell structure of FIG. 1B filled
with sealant material.
[0013] FIG. 1D illustrates a technique of forming a shock absorber
according to an embodiment of the invention.
[0014] FIG. 2 is a force versus displacement curve for a shock
absorber in accord with the invention.
[0015] FIG. 3 shows a retainer for a shock absorber according to an
embodiment of the invention.
[0016] FIG. 4 shows a downhole tool incorporating a shock absorber
according to an embodiment of the invention.
DETAILED DESCRIPTION
[0017] FIG. 1A illustrates a shock absorber 100 according to one
embodiment of the invention. The shock absorber 100 can be mounted
on a downhole tool and used to absorb shock and impact loads that
would otherwise be absorbed by the downhole tool or tool
components. The shock absorber 100 includes a columnar body 102
having end faces 104, 106. The columnar body 102 can be formed
solid or with a hollow core. If a solid columnar body 102 is used,
the crush load of the body should be determined to ensure that the
necessary protection is provided to the tool. The shock absorber
100, not the tool, should deform in response to impact loads. In a
preferred embodiment, the columnar body 102 is hollow, i.e., has
cavity 105.
[0018] In one embodiment, a wall 108 of the columnar body 102 has a
honeycomb structure 108a. As shown in FIG. 1B, the honeycomb
structure 108a is composed of cells 110 defined by webs 112. The
webs 112 extend longitudinally between the end faces (104, 106 in
FIG. 1A) of the columnar body (102 in FIG. 1A). The thickness of
the webs 112 may be constant or vary between the end faces 104,
106. In the illustration, the cross-sectional shape of the cells
110 is hexagon. However, the invention is not limited to this
shape. For example, the cross-sectional shape of the cells 110
could be a triangle, square, octagon, or other appropriate
shapes.
[0019] Returning to FIG. 1A, the magnitude of the impact loads that
can be absorbed by the shock absorber 100 depends on the geometry
of the cells (110 in FIG. 1B), the cell density of the honeycomb
structure 108a, the thickness of the webs (112 in FIG. 1B), the
thickness of the wall 108, and the properties of the material used
in making the columnar body 102. The columnar body 102 is made of a
material capable of absorbing impact energy and maintaining its
chemical integrity in a subsurface environment. The material could
be a metal or an alloy or a composite. Preferably, the material has
a high strength-to-weight ratio. One example of a material suitable
for use in making the columnar body 102 is an aluminum alloy. The
aluminum alloy may be anodized to increase its ability to withstand
subsurface exposure.
[0020] FIG. 1C shows the cells 110 of the honeycomb structure 108a
filled with a sealant material 114 according to another embodiment
of the invention. The sealant material 114 could be any suitable
material, such as a curable material (e.g., epoxy). The sealant
material 114 should be able to maintain its chemical integrity in a
subsurface environment. Filling the cells 110 with the sealant
material 114 can enhance the mechanical properties of the columnar
body (102 in FIG. 1A) while minimizing the surface area exposed to
attack from external fluids and chemicals.
[0021] Embodiments of the columnar body 102 can be formed by
laminating corrugated sheets of material (116 in FIG. 1D) and
shaping the laminate into a columnar body. After shaping the
laminate, a sealant material, such as epoxy, could be pumped into
the voids (118 in FIG. 1D) formed by the laminated corrugated
sheets to form the structure shown in FIG. 1C. Depending on the
sealant material(s) used, the material can be applied at room
temperatures as known in the art. If the sealant material is too
viscous, a viscosity-reducing (or thinning) agent may be added to
the sealant as needed and the structure can be heat treated to cure
the sealant material. The temperature, pressure, and duration of
the curing process depend on the sealant material. The use of a
sealant material forms an additional bond between the corrugated
sheets, making the columnar body 102 more robust as desired.
[0022] The invention is not limited to forming the columnar body
102 by laminating corrugated sheets of material and shaping the
laminate. The columnar body 102 could also be formed by extrusion.
The webs 112 could be solid or may have a foamed (porous)
structure. The foamed webs could be made by known metal foaming
processes. One such process involves compacting a mixture of metal
powder and foaming agent and heat-treating the compacted body near
the melting point of the metal. The metal expands and develops
pores during the heat treatment. Other techniques may be used to
form the columnar bodies to implement the invention as known in the
art.
[0023] FIG. 2 shows a force vs. displacement curve for a shock
absorber having a columnar body with a honeycomb structure. This
honeycomb structure is made from corrugated sheets of aluminum
alloy, available from Hexcel Corporation, Stamford, Conn. The
columnar body has an outer diameter of 2.25 in (5.72 cm) and an
inner diameter of 1.7 in (4.32 cm). The crush strength of the
columnar body is 1350.+-.203 psi (9,310.+-.1400 kPa). The lower
limit of the crush strength 1,147 psi (7,910 kPa) amounts to a
crush force of approximately 2,000 lbf (8,896 N). This means that
the shock absorber would elastically absorb loads smaller than
2,000 lbf (8,896 N) and plastically deform at 2,000 lbf (8,896 N)
or higher. When the columnar body (102 in FIG. 1A) is made of a
metal or alloy, the columnar body could be pre-crushed (based on
the desired load to plastically deform the absorber) to eliminate
peak load.
[0024] A retainer is used to retain the shock absorbers 100 of the
invention on the downhole tools. Those skilled in the art will
appreciate that there are a variety of ways one can mount and
retain the shock absorbers of the invention on a downhole tool. A
desirable feature of the retainer is that it should accommodate
crushing of the shock absorber due to absorption of impact loads.
For example, the retainer can include telescoping parts that allow
the length of the retainer to change as the shock absorber is
crushed. Another desirable feature in a retainer is for it to
transfer impact loads to the shock absorber.
[0025] FIG. 3 shows a retainer 300 for the shock absorber 100
according to one embodiment of the invention. The retainer 300
includes a lower body 302 and an upper body 304. The lower body 302
includes a base 306 and a hub 308 extending from the base 306. The
shock absorber 100 is mounted on the base 306 and about the hub
308. Lateral motion of the shock absorber 100 is limited by the hub
308. Retention slot 310 and alignment slot 312 are provided inside
the hub 308. The upper body 304 includes a tab 314 that can be
inserted in the alignment slot 312 and the retention slot 310. When
the tab 314 is in the alignment slot 312, the lower body 302 can be
slipped onto or separated from the upper body 304. For clarity of
illustration, FIG. 3 does not show a key slot or groove in the
lower body 302 configured to guide the tab 314 into position within
the retention slot 310. Some embodiments can be configured with
multiple slots 310, 312 and/or tabs 314.
[0026] When the tab 314 is in the retention slot 310, the upper
body 304 is coupled to the lower body 302. The tab 314 can move
within the retention slot 310, allowing movement of the lower body
302 relative to the upper body 304 when the shock absorber 100 is
crushed. The lower body 302 transfers impact loads to the shock
absorber 100. Vertical motion of the shock absorber 100 is limited
by a shoulder 316 on the upper body 304. An embodiment can also be
implemented with spring means disposed between the upper body 304
and lower body 302, abutting against the shoulder 316 on the upper
body and the top of the lower body (not shown). The spring means
would absorb some of the impact load and aid in maintaining the
body 302 from twisting or uncoupling from the upper body 304. In
one embodiment, the upper body 304 also includes threads 318 for
engaging the downhole tool. Other configurations for engaging the
upper body 304 to a downhole tool may also be (e.g., snap-fit
mechanisms, fasteners, clamps, welding) used to implement the
invention as known in the art. Alternatively, the downhole tool can
also be pre-formed with its end adapted to accept the lower body
302 and shock absorber 100 (not shown).
[0027] FIG. 4 shows a downhole tool 400 having tool bodies 402
joined together to form a tool string. The tool bodies 402 are
configured to perform a downhole operation, such as formation
testing. A shock absorber 100 of the invention is disposed at the
bottom of the downhole tool 400 using, for example, the retainer
300 (shown in FIG. 3). The downhole tool 400 with the shock
absorber 100 is lowered into a wellbore 404 using, for example, a
wireline 406 or other suitable conveyance mechanism as known in the
art. As the downhole tool 400 is lowered, the retainer 300 may
strike a ledge on the wall of the wellbore 404 or the bottom of the
wellbore 404. Impact loads applied to the retainer 300 are
transferred to the shock absorber 100 retained in the retainer 300.
The shock absorber 100 absorbs the impact loads, thereby protecting
instruments in the downhole tool 400 from damage.
[0028] A process for mounting a shock absorber 100 on a downhole
tool 400 according to the invention entails disposing the shock
absorber at one end of the downhole tool body (shown in FIG. 4),
the shock absorber having a columnar body 102 with a wall including
a plurality of cells as described herein. The columnar body is then
retained on the tool body as described herein. The shock absorbers
100 of the invention are not limited to external use. The shock
absorbers 100 can also be implemented on tools configured for
transport through other tools or conduits. One such application
entails the disposal of a shock-absorber-equipped run-in tool in a
drill collar, at the earth surface, for transport through the
collar to a desired subsurface location within the drill string
(See e.g., U.S. Pat. No. 6,577,244).
[0029] While the invention has been described with respect to a
limited number of embodiments, those skilled in the art, having the
benefit of this disclosure, will appreciate that other embodiments
can be devised which do not depart from the scope of the invention.
For example, shock absorber embodiments of the invention may also
be formed in quadrants or sectors of a cylindrical surface of
revolution which, when juxtaposed together, would comprise or
constitute a columnar body (not shown). It will also be appreciated
that the present invention is applicable to, and can be implemented
in, any field where shock absorption is desired; it is not limited
to downhole tools or subsurface applications.
* * * * *