Patent Application
20080149350
The field of this invention relates to downhole tools and more specifically valves that are released to actuate by exposure of the release mechanism to produced well fluids.
A frequent occurrence in drilling a well includes a need to circulate out the mud used during drilling with a different weight mud before production is started. In other procedures, the production string with screens is run into the mud and the mud is displaced with production. The problem here is that the mud can clog the production screens.
Previous efforts employed a swelling material sensitive to well fluids to block a fluid passageway have raised concerns about long term reliability of the material to act as a flow barrier over time. The problem with swelling materials as differential pressure seals is that when they swell they also get very soft and their ability to withstand differential pressures is reduced.
The present invention uses such materials but in a manner where the fact that they get soft is a plus to the operation of the tool into which they are incorporated. In essence, the swelling material that is selected is responsive to produced hydrocarbons to release a latch so that the tool can operate. In an embodiment of a circulation sub, a sliding sleeve with o-ring seals is held open against a closure force by a collet latch. The collets become unsupported when exposed to produced hydrocarbons to close a bypass port previously used to displace drilling mud around the production screens. The softening of the material unlocks the collets from a retaining groove so that an energy source, such as a spring, can push the sleeve to straddle a port with o-rings on a shifting sleeve. These and other aspects of the present invention will be more apparent to those skilled in the art from the description of the preferred embodiment below and the associated drawings, while recognizing that the full scope of the invention is to be found in the claims.
A material that reacts to produced hydrocarbons acts as a latch to retain a stored potential energy force. In a specific application, a sliding sleeve valve is held away from a circulating port to allow drilling mud to be circulated out. Later, when the well is put on production, the lock that holds collets in a groove releases as exposure to produced hydrocarbons at a retaining sleeve makes it get soft. This, in turn, allows a spring force to run the collets out of their groove and straddle the circulation port between two o-rings on the shifting sleeve to close the port. The closure of the port directs produced hydrocarbons to screens that had been bypassed when mud was circulated out due to ports being the path of least resistance.
When the production string is run in the hole, the drilling mud is still there. The productions screens 14 or 18 would clog if the production from the formation passed through them forcing the mud in the hole to also go through the screen. In some applications, the drilling mud in the hole is simply displaced by production. In that instance it is desirable to bypass the screens 14 and 18 until the majority of the mud has been displaced and after that time to direct the well production through those very same bypassed screens.
The issue with this technique is to know when the mud is close to fully displaced, which makes it safe for the production to be directed through the screens 14 and 18 with little risk of plugging such screens with drilling mud. The remaining structure in
Those skilled in the art will appreciate that while a configuration showing trapped potential energy released by weakening of the material 48 is illustrated that other applications are envisioned where the exposure to a predetermined well fluid accomplishes the actuation in other ways. The driving force, if stored potential energy is used does not need to be a spring. It could be other forms of stored energy that are unleashed to accomplish tool movement such as pressurized gas or a stack of Belleville washers, to name a few examples. While the preferred embodiment is a bypass for other well equipment that closes when a condition in the well is met, the invention encompasses opening a bypass instead or not even using a bypass and simply moving a part on a tool directly in response to presence of a material. While the locking system is shown as trapped collet heads being liberated on exposure of material 48 to a predetermined fluid, other types of locking devices that are defeated by a softening or dimensional change in material 48 are contemplated within the scope of the invention.
The above description is illustrative of the preferred embodiment and various alternatives and is not intended to embody the broadest scope of the invention, which is determined from the claims appended below, and properly given their full scope literally and equivalently.
