DOWNHOLE TOOL SHOCK ABSORBER
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.
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1. Field of the Invention
The invention relates generally to shock absorbers. More particularly, the invention relates to shock absorbers for use with downhole apparatus.
2. Background Art
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.
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 INVENTIONIn 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.
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.
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.
Other features and advantages of the invention will be apparent from the following description and the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
In one embodiment, a wall 108 of the columnar body 102 has a honeycomb structure 108a. As shown in
Returning to
Embodiments of the columnar body 102 can be formed by laminating corrugated sheets of material (116 in
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.
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.
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).
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
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.
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.
Type: Application
Filed: Dec 7, 2004
Publication Date: Jun 8, 2006
Applicant: SCHLUMBERGER TECHNOLOGY CORPORATION (SUGAR LAND, TX)
Inventors: BULENT FINCI (SUGAR LAND, TX), SCOTT CHESSER (RICHMOND, TX), RICHARD WARD (LA PORTE, TX)
Application Number: 10/904,965
International Classification: E21B 17/00 (20060101);