The present invention relates generally to downhole tools and methods and, more particularly, but without limitation, to tools and methods used to deliver jarring impacts to objects downhole.
Jarring tools are used to jar or shake loose a downhole tool or object that has become stuck or lodged in the well bore. In hydraulic or reciprocating type jars, a metering or timing section inside telescopically arranged inner and outer tubular members resists allowing the jar to extend, which provides sufficient time for the tubing string to be stretched before a hydraulic release mechanism within the jar allows rapid extension and impact within the tool. This creates a large dynamic load on the stuck tool or object. Most hydraulic jars are designed for repetitive or cyclic action to continue jarring the stuck object until it is dislodged. The cyclic firing and resetting or recocking of the jar is accomplished by pushing and pulling the tubing string.
Hydraulic jars are often run on coiled tubing. However, there are several disadvantages to using coiled tubing to run a hydraulic jar. Because of the increased frictional forces at work in a horizontal well bore, it is particularly difficult to push or “snub” coiled tubing into a horizontal well, making it difficult to cycle the jar.
The jarring tool of the present invention offers an improvement in methods and tools for jarring operations using coiled tubing. In accordance with the present invention, the piston of the jarring assembly comprises a cup that is expandable in response to fluid pressure. For example, the jarring piston may be formed of a copper alloy. Alternately, the piston may be formed of an alloy steel. The component forming the hydraulic chamber, including the seal bore, may be formed of simple steel of normal steel hardness, such as AISI 4140.
The seal bore preferably has two sections, a smaller diameter section at the entry and a larger diameter section at the outlet end. In the most preferred embodiment, the seal bore is tapered. The cup is designed to have a small interference fit with the narrow diameter end of the tapered section. The tapered section has a diameter selected to allow the piston cup to expand to the point that is becomes permanently enlarged to the larger diameter end of the tapered section. In this way, when the pressure is released, the cup's enlarged diameter will be enough to maintain the minimum required interference with the straight section of the seal bore on the next cycle. This compensates for any wear or erosion on the lip from the previous cycle.
Because the expansion of the cup as it exits the seal bore reduces the effects of wear on the cup lip from the previous cycle, the enlarged piston cup will maintain the minimum interference in the straight section of the seal bore in the next cycle. Thus, wear on the piston lip is compensated for by repeated expanding its diameter, thus removing the need to use harder, more wear-resistant material to make the cup and seal bore. This provides a relatively thin piston cup which can be pushed through the seal bore using less force, making it easier to reset the jar in every cycle.
Although the jarring tool and method of this invention is particularly useful with coiled tubing, those skilled in the art will appreciate that it can be employed with other tubular well conduits, such as jointed well tubing and drill pipe. Additionally, although this jarring tool is particularly advantageous for up jars, in which the jarring action requires snubbing the coiled tubing, down jars and bidirectional jars will be benefited by employing this inventive jarring assembly.
Turning now to the drawings in general to and to
A fishing tool 28 on the end of the tubing 14 in the wellbore 30 is used to attach a jar 32 to the stuck object 34. The combination of tools connected at the downhole end of the tubing 14 forms a tool string or bottom hole assembly (“BHA”) 36. The bottom hole assembly 36 and tubing 14 combined are referred to herein as the tubing string 38. The bottom hole assembly 36 may comprise a variety of tools including but not limited to a bit, a mud motor, hydraulic disconnect, jarring tools, back pressure valves, and connector tools.
Fluid is introduced into the coiled tubing 14 through a system of pipes and couplings in the reel assembly, designated herein only schematically at 40. In accordance with conventional techniques, the jar 32 is cycled by raising and lowering the section of tubing in the injector assembly 18 repeatedly until the object 34 is dislodged.
In some instances, the jar 32 is connectable directly to the stuck object 34 in the wellbore 30. In other instances, the jar 32 is connected as one member of a bottom hole assembly comprising several tools. When the jar 32 is described as being connectable to a “stationary object downhole,” it is intended to mean that the tool is connectable directly to the object or indirectly to the object through another tool in the tool string, which may have become lodged in the wellbore, or to the fishing tool 28 that is in turn attached to the stuck object 34 in the well.
The coiled tubing injection system 10 illustrated in
Turning now to
Either the mandrel 102 or the housing 104 is attachable to the well conduit 14, and the other is attachable to the fixed object 34 in the wellbore 30. In the particular embodiment shown, the downhole end 106 of the mandrel 102 is attachable to the stuck or stationary object 34, and the uphole end 108 of the housing 104 is attached to the tubing 14. In this way, the housing 104 is moved up or down relative to the mandrel 102. However, it will be appreciated that this arrangement may be reversed, that is, the housing may be attachable to the downhole object (or other tool) and the mandrel attachable to the well conduit.
As used herein, the terms “up,” “upward,” “upper,” and “uphole” and similar terms refer only generally to the end of the drill string nearest the surface. Similarly, “down,” “downward,” “lower,” and “downhole” refer only generally to the end of the drill string furthest from the well head. These terms are not limited to strictly vertical dimensions. Indeed, many applications for the tool of the present invention include non-vertical well applications.
Throughout this specification, the mandrel 102 and housing 104 as well as the jarring assembly components are described as moving “relative” to one another. This is intended to mean that either component may be stationary while the other is moved. Similarly, where a component is referred to as moving “relatively” downwardly or upwardly, it includes that component moving downwardly as well as the other, cooperative component moving upwardly.
In the preferred embodiment, the housing 104 comprises a top sub 110 which is provided with a internally threaded end or box joint forming the upper end 108 for attachment to the coiled tubing 14 or to another tool in the tool string 36. An upper housing 112 is connected to the downhole end of the top sub 110, and a lower housing 114 is connected to the downhole end of the upper housing. A wiper seal sub 116 connects to the downhole end of the lower housing 114, and a collar or split sub 118 connects to the downhole end of the wiper seal sub, forming the lower end of the housing 104. While this is a preferred assembly for the housing, the components of the housing may vary in number and configuration.
Referring still to
The preferred tool 32 includes a jarring assembly designated generally at 130. The telescopically engaged portions of the housing 104 and the mandrel 102 are configured to form a hydraulic jarring chamber 132 therebetween. The hydraulic chamber 132 includes an upper or low pressure chamber 134, a lower high pressure chamber 136, and a narrow diameter seal bore 138 therebetween. It will be understood that in a down jar version of this tool, the lower chamber will be the high pressure chamber and the upper chamber will be the low pressure chamber.
The jarring impact is created when an impact surface on the housing 104, such as the hammer surface 140 impacts an impact surface on the mandrel 102, such as the anvil surface 142. When the tool is reset or cocked, an impact surface 144 on the housing 104 abuts an impact surface 146 on the mandrel 102, to limit the travel of the housing when being reset. The shape and location of these impact surfaces may vary.
A piston assembly 150 is supported on the upper mandrel 124 for movement inside the hydraulic jarring chamber 132. As shown in
Turning now to
A cup-type piston 170 is slidably supported coaxially around the piston sleeve 152. The piston 170, shown in detail in
The piston assembly 150 further comprises a timing washer 180, shown in detail in
As best seen in
One or more springs 204 are supported between the flanged end 162 of the piston sleeve 152 and uppermost end 206 of the center mandrel 122. These springs are included to accommodate slight variances in tolerances resulting from manufacturing. Thus, the springs should be strong enough to resist any movement in the piston sleeve 152 during operation of the tool.
As the housing 104 is pulled up on the mandrel 102 (towards the left in
When the fluid reaches the end of the spiral channel 190 it exits the piston assembly 150 around the outer diameter of the timing washer 180 and flows up into the upper or low pressure chamber 134 (
The piston assembly 150 also provides an unrestricted flow path for passage of the hydraulic fluid through the piston assembly when it passes through the seal bore 138 (
While a preferred timing or metering mechanism has been shown and described herein, it will be appreciated that the present invention is not so limited. Other metering structures, such as annular flow channels, orifices, tortuous paths of different configuration, may be employed.
Directing attention now to
In the preferred seal bore 138, the bore comprises a smaller diameter section and a larger diameter section. Most preferably, these different diameter sections take the form of a straight section at the entrance end 210 of the bore 138 and a tapered section extending from the straight section to the exit end 212 of the bore. The straight section, designated by the arrow 218, is relatively short compared to the tapered section, designated by the arrow 220. While this straight section is advantageous for manufacturing and assembly, it is not essential to the function of the seal bore.
The straight section 218 has a constant diameter along its length designated as “d1.” The tapered section 220 gradually increases in diameter from the dimension d1 to a slightly larger diameter at the exit end designated as “d2.” By way of example only, if the piston 170 is made from 110 KSI copper allow and is about 0.060 inch thick, and if the straight section is 2.25 inches in diameter (d1) and 0.63 in length, the tapered section 220 may gradually increase in diameter to 2.272 inches in diameter (d1) at the exit end 212 having a length of 2.75 inches, that is, a taper of 0.004 per inch.
The purpose of the tapered section with its slightly increasing diameter is to allow the diameter of the piston cup 174 to permanently expand slightly in response to fluid pressure. As indicated, the piston 170 is designed to permanently expand slightly in response to fluid pressure. More particularly, the piston is designed to permanently expand at a pressure that is lower the operating pressure of the hydraulic fluid. By way of example, the piston may be formed of a metal allow, such as a copper allow, that is slightly resilient so that the fluid pressure will expand the cup to the largest diameter of the seal bore. While the metallic cup may not retain the fully expanded diameter, neither will it resume its smallest original diameter; instead, the cup will maintain a slightly enlarged diameter that is larger than the smaller diameter section of the seal bore. Thus, the present invention includes the use of resilient and non-resilient cup materials that are capable of some permanent expansion.
The tapered section 220 is selected to achieve the desired permanent reformed diameter of the piston cup, which is a function of the diameter of the straight section 218 of the seal bore 138. This is because the purpose of the expansion is to maintain a lip diameter that will provide a minimum interference fit in the straight section of the bore. Thus, the exit diameter is calculated according to the following formula:
With continuing reference to
Rupture of the cup 174 may be prevented by providing bypass recesses at the entrance end 210 to allow the hydraulic fluid to flow around the lip of the cup until the a substantial portion of the cup is inside the bore. For example, in the preferred embodiment, a plurality of longitudinal grooves 230 is provided around the entrance 210 to the bore 138 and extending a distance into the straight section 218. As the piston 170 moves into the seal bore 138 and the lip engages the wall of the bore, fluid can still pass through the grooves 230 around the lip. This prevents the full pressure of the operating fluid from acting on the cup until the cup is substantially inside the bore. How far into the seal bore the cup needs to advance to prevent rupture will vary with the pressure and the cup material. Thus, as used herein, “substantially” means that the cup has advanced far enough into the seal bore so that rupture of the cup is prevented.
Having described the structure of the tool 32, its use and operation now will be explained. Referring again to
As the piston assembly 150 moves through the seal bore 138, fluid pressure below the piston assembly increases rapidly until the piston assembly enters the lower or high pressure chamber 136. At this point, there is a sudden release of the pressure, causing the housing to complete its travel to the fully extended or fired position (
To reset the tool 32, the tubing string 14 is snubbed downwardly, which forces the housing 104 to move downwardly on the mandrel 102, that is, to the right as seen in
Now it will be appreciated that as the piston cup 174 moves up and down through the seal bore 138 repeatedly, the lip 176 will be worn away. However, due to the expandable nature of the cup 174 and the increasing diameter of the seal bore 138, the cup is also repeatedly being plastically expanded to compensate for this wear.
Turning now to
This embodiment includes a bidirectional jarring assembly designated generally at 330. The bidirectional jarring assembly includes a pair of piston assemblies 350A and 350B positioned in a hydraulic chamber 332. The hydraulic chamber 332 includes an upper chamber 334, a lower chamber 336, and a narrow diameter seal bore 338 therebetween. The seal bore 338 of this embodiment is adapted for two-way operation, as explained more fully below. The upper and lower hydraulic chambers 334 and 336 function alternately as high and low pressure chambers, depending on the jar direction.
Each of the piston assemblies 350A and 350B is similar to the piston assembly 150 of the jar 32 (
The seal bore 338 will now be described with reference to
Now it will be apparent that the up jar piston assembly 350A will function similarly to the previously described embodiment. The piston assembly 350A will produce an up jar when it passes downwardly through the up seal bore 338 from the position shown in
Referring still to
The piston cup of the jar assembly 350B creates a seal with the seal bore as the cup enters the end 368. The cup expands as it moves through the tapered section 362 (to the left in
Having described the structure of the tool 300, its use and operation will now be explained. Referring again to
To initiate an up jar stroke, the operator pulls upwardly on the tubing string 14 at the surface thereby exerting an upward pull on the attached jar housing 304. As the mandrel 302 is fixed to the stuck object, this pulling action causes the piston assemblies 350A and 350B to move downwardly through the seal bore 338 (to the right in
As previously described, as the up jar piston assembly 350A is forced downward (to the right) through the seal bore 338, fluid is forced through its restricted flow path of the up jar to create the sudden pressure release as it exits the seal bore. During the same stroke, the down jar piston assembly 350B moves “backwards” through the seal bore 338, allowing the fluid to pass through its unrestricted flow path.
Next, to initial a reverse or down jar, the tubing 14 is snubbed downwardly, which forces the housing 304 to move downwardly on the mandrel 302 from the position shown in
This bidirectional embodiment can be operated to provide repeated jars in either an up or down direction, or alternately may be operated to provide jarring impacts in alternating directions. To fire the jar repeatedly in one direction only, the jar assembly is reset by returning the tool to the neutral or centered position shown in
The embodiments shown and described above are exemplary. Many details are often found in the art and, therefore, many such details are neither shown nor described. It is not claimed that all of the details, parts, elements, or steps described and shown were invented herein. Even though numerous characteristics and advantages of the present inventions have been described in the drawings and accompanying text, the description is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of the parts, within the principles of the invention to the full extent indicated by the broad meaning of the terms. The description and drawings of the specific embodiments herein do not point out what an infringement of this patent would be, but rather provide an example of how to use and make the invention. Likewise, the abstract is neither intended to define the invention, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way. Rather, the limits of the invention and the bounds of the patent protection are measured by and defined in the following claims.