Catcher Sub

(1) Technical Field

This invention pertains to catcher subs connected in well flow conduits in which a ball seals to permit pressurization of fluid in the conduit above the ball. The invention especially pertains to a catcher sub from which the ball is expended only after pressure in the conduit is increased and later reduced.

(2) Background Information

A number of catcher subs are available for use in well conduits which permit pressurization of fluid in the conduit to operate pressure operated well tools in the conduit above the catcher sub. Very high fluid pressures, often in excess of 5,000 psi, are required to operate the pressure operated well tools and often pressures in excess of the very high operating well tool operating pressures are required to shear pins and expend a sealing ball and seat downwardly from the catcher sub. When pins are sheared by high well conduit pressures, a pressure shock wave is released to travel downwardly in the conduit from the catcher sub into open producing formations below, probably causing damage to the formations which will require expense and time to repair.

The improved catcher sub of this invention includes a collet slidably mounted in the catcher housing. The collet is moveable from an up contracted position to a down expanded position by applying pressure on a ball which seals on the collet when it is in contracted position. Pressure on the sealing ball high enough to operate pressure operated tools in the conduit above will not operate the catcher sub to expend the ball and produce a formation damaging pressure shock wave as the collet is held and supported in contracted position and not moved by ball down force from high pressure on the ball. The application of higher pressure operates the catcher sub to not hold and support the collet in up contracted position, permitting lower pressure applied thereafter to move the collet to expanded position. When the inside diameter of the expanding collet increases to that of the ball, downward flow will move the ball through the collet and expend it from the catcher sub.

FIG. 1 is a half sectioned drawing in elevation showing one form of the improved catcher sub of this invention before operation to expend the ball.

FIG. 2 is a drawing of the cross-section along line 2--2 in FIG. 1.

FIG. 3 is a drawing similar to FIG. 1 showing the improved catcher sub after operation to expend the ball.

FIGS. 4A and 4B together are a half sectioned drawing in elevation of another form of the improved catcher sub, which includes an internal profiled recess and shows this catcher sub ready to receive an operating ball.

The improved catcher sub 10 shown in FIG. 1 has a through flow passage 10a and includes a connector 11 having a thread 11a and a surface 11b sealingly engageable by seals. A housing 12 is connected to connection 11 and in the housing are bores 12a and 12b each of which is sealingly engageable by seals. An annular piston 13 surrounds the lower portion of the connector. A resilient seal 14 on the piston sealingly engages seal bore 12a in the housing and a resilient seal 15 in the piston sealingly engages seal surface 11b on the connector and the piston is releasably positioned in the down position by shearable member 16. A longitudinally moveable sleeve 17 in the housing is biased to move upwardly by compressed spring 18 and has an internal groove 17a and bores 17b and 17c, which are sealingly engageable by seals. A longitudinally moveable collet 19 in mandrel 20 has fingers 19a (see also FIG. 2) and bonded on each finger is a resilient seal segment 19b. Each finger also has a camming surface 19c. A ring 21 around the collet holds the collet fingers in contracted position and seal segments 19b sealingly engaging each other to form an annular resilient seal ring. Another resilient seal 22 on the ring sealingly engages sleeve bore 17b. A number of lugs 23, each having a camming surface 23a and an underbore 23b, are held in contracted position by bore 17b in the sleeve, with surfaces 23a contacting camming surfaces 19c on each collet finger (see also FIG. 2).

A resilient seal 24 sealingly engages sleeve bore 17c, sealing the sleeve to mandrel 20. Spring 18 is compressed on mandrel shoulder 20a by sleeve 17, which is retained in the down position by piston 13, which is in turn releasably positioned by shearable member 16. An adapter ring 25 is connected to the lower end of housing 12 and a resilient seal 26 sealingly engages body bore 12b sealing the mandrel to the body. A guide ring 27 is connected on the mandrel below the adapter ring.

In use, improved catcher sub 10 is installed in a well flow conduit below a tool such as a packer, which is operated by pressurizing the conduit. The well flow conduit is then lowered into the well. Before the conduit is pressurized, a ball B in the conduit above the catcher sub falls or is pumped downwardly to land and seal on the annular resilient seal ring formed by seal segments 19b on the contracted collet fingers closing the conduit for pressurization--see FIG. 1. Pressure, up into the 5,000 psi range, sufficient to operate the pressure operated tool may now be applied in the conduit and flow passage 10a. This pressure acts on piston seals 14 and 15 moving the piston upwardly shearing shearable members 16. Down force on the collet produced by pressure on the ball is transmitted through collet camming surface 19c and lug camming surface 23a to the lugs and into mandrel 20. After the pressure operated tool has operated, pressure in the conduit is reduced to about 150 psi, which reduces frictional forces between surfaces 19c and 23a and the lugs and sleeve bore 17b. Compressed spring 18 now exerts force sufficient to move sleeve 17 upwardly over seals 22 and 24. The sleeve is moved upwardly by the spring until sleeve groove 17a is adjacent the lugs. The down force of the sealed ball on the collet from low pressure in the conduit, will move the collet downwardly out of ring 21 and cam the lugs to expand into groove 17a and permit the collet fingers 19a to expand into overbores 23b in the lugs as shown in FIG. 3. Expansion of the collet disengages seal segments 19b and increases the inside diameter to greater than the outside diameter of ball B, permitting the ball to move downwardly in passage 10a and be expended out of the catcher sub.

Another form of the improved catcher sub of this invention is depicted in FIGS. 4A and 4B. Improved catcher sub 28 is the same structure as improved catcher sub 10 and is operable in exactly the same way. The sleeve 29 and housing 30 in catcher sub 28 have been lengthened sufficiently to include profiled recesses 31.

If after a ball seals on contracted collet 19 in catcher sub 28, pressure in the conduit is increased and reduced and sleeve 29 is not moved upwardly by spring 18 preventing the collet from expanding, a tool can be lowered in the well conduit and operated to lock in recesses 31. Considerable upward force may then be applied to the tool locked in sleeve 29 to move the sleeve upwardly and allow the collet to expand and the ball be expended.