Patent Application
20060081401
The field of this invention is downhole isolation devices and particularly those that can be used during drilling or completion to provide a second closure in situations where the tree has not yet been mounted.
Drilling with casing can be accomplished in two different ways. In on instance, a drillable casing shoe is mounted on the end of the casing and rotated down the wellbore. The other way is to lock a drilling bottom hole assembly into a profile bushing near the lower end of the casing string. Using the latter method, more complex drilling equipment can be used, such as downhole motors, directional tools, hole openers, logging or measuring while drilling tools and so on. In many instances, the entire interval can be drilled without removal of the bottom hole assembly. If any of the components of the bottom hole assembly fail or wear out, the bottom hole assembly needs to be unlatched and returned to the surface on drill pipe run in to retrieve the assembly. However, when the bottom hole assembly is removed, there is a risk that the well could kick or blow out. The act of pulling out the bottom hole assembly can cause reduced pressure beneath the bottom hole assembly, also called swabbing, which can induce the well to kick. The annulus around the casing can be closed off with standard casing blowout preventers, but presently there exists no equipment to isolate the casing interior against a well kick or a blowout.
The present invention, in one application, provides a variety of solutions that allow the casing interior to be closed off at least once during removal of the bottom hole assembly. In one embodiment, an internal packer can be triggered on removal of the bottom hole assembly. This packer can be actuated in a variety of ways such as hydrostatically or through a release of gas due to a reaction. Alternatively, a flapper valve can be installed in the casing and held open until removal of the bottom hole assembly at which time a spring can urge it to a closed position to prevent a blowout. Multiple assemblies are contemplated to allow the bottom hole assembly to be removed more than once and still get the blowout protection each time. Upon return of the bottom hole assembly into the casing, the previously set packer can be drilled out or, if a flapper has been used and sprung, then the bottom hole assembly can be simply pushed out of the way.
Other applications of the closure device of the present invention are contemplated. Some of these applications are to control fluid loss during sidetracking, fracturing, and gravel packing. Another application is during perforating to allow the spent gun to be removed with control of the well using the invention in combination with surface blowout prevention equipment. Yet other applications are contemplated to allow a second closure device in the well during a variety of operations to provide control of the well and to meet the requirements of local regulations for redundant closure devices in the event of a blowout.
These and other advantages of the present invention will be more readily appreciated by those skilled in the art from a review of the description of the preferred and other embodiments, the drawings and the claims, all of which appear below.
A sealing device for downhole use, one of which is for casing, when drilling with casing, which allows the casing to be closed off if the bottom hole assembly needs to come out for any reason. In one embodiment, the internal packer is triggered to set in a variety of ways upon removal of the bottom hole assembly. It can be drilled out when the new bottom hole assembly is run in later. In an alternative design, a flapper can be used that is held open for the initial insertion of the bottom hole assembly and is released to spring shut upon removal of the assembly. Multiple flappers or packers or other types of closure devices are envisioned to allow removal of the bottom hole assembly more than once and still retain blowout protection on each removal of the bottom hole assembly. A variety of applications are contemplated some of which are perforation, side tracking, fracturing, and gravel packing, to name a few examples.
The applications for the present invention are diverse. The present invention can be used in applications in casing where a bottom hole assembly is inserted for an operation and subsequently needs removal one or more times. In these situations, the present invention provides a second closure to the surface blowout preventers. The invention can be used in casing for a variety of applications such as perforating, fracturing, side tracking, and gravel packing to name a few. It can also be applied in through tubing applications although the most prevalent use of the invention lends itself to drilling and completion operations where a tree is not mounted and the only other well control device that is mounted is the surface blowout preventers. Use of the invention eliminates the need to kill the well with mud or other fluids. Killing the well can affect its subsequent performance adversely. If there is mud in the well, the present invention, when activated, prevents the formation from absorbing the mud and then coming in as a blowout.
The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.
