Patent Application
20110132599
The field of this invention is well completions and more particularly completions that allow multi-zone completions that call for fracturing, gravel packing and isolation in a single trip.
In the past in the case of a broad pay zone or multi pay zone to be completed the procedure was to break it into sections. The fracturing and gravel packing equipment is run into cased and perforated hole along with an isolation packer. The packer would be set to isolate the lowermost zone and the isolated zone would then be fractured below that packer. Thereafter, gravel would be delivered outside screens through a crossover to fill the annular space around the screen with gravel. After that the packer would remain in the zone just gravel packed along with the screens with gravel on their exterior as the crossover and associated wash pipe were pulled out through the already set packer. After that zone was isolated, fractured, and gravel packed another trip in the hole with a similar assembly as used for the lowest zone would be run in for doing the same for the next zone up. This process continued until all zones or sections of a continuous zone were completed.
This technique required many trips in and out of the wellbore and that translated into very high expenses for rig time. One of the reasons that this staged procedure was used was that to do it another way where an entire interval could be isolated and fractured and gravel packed at once required packers to then be set in the annulus after gravel packing. The packers that had been available were not known for reliable sealing against the inside wall of casing if the annular space was full of gravel.
More recently packer designs have evolved and sealing in an annulus that is full of gravel is possible. An example of such a packer is U.S. Pat. No. 6,896,049. Other packer designs are illustrated in U.S. Pat. Nos. 6,782,946; 5,988,276; 6,009,951; 7,100,690; 5,184,677 and 6,513,600.
Packers that push gravel out of the way for a metal to metal seal in cased hole have been suggested in a multi-zone completion method described in US Publication 2008/0164026. The issue with the metal to metal seal packers is the high force required to push the gravel aside while a complex crossover is still in the hole.
The present invention seeks to build on the technique of multiple zone fracturing and gravel packing by creating a barrier between producing zones that are gravel packed together by injecting fluid into the gravel packed annulus that forms a barrier between or among the zones. The injected material is a sealing material that is known in the art and some examples are discussed in U.S. Pat. Nos. 5,942,031 and 4,797,159. In the preferred embodiment the material is placed in the same trip as the gravel packing and the wash pipe with a shifting tool integrated into it is used to inject the chemical into the desired locations between zones to create barriers. The chemical can be stored inside the outer assembly and the shifter associated with the wash pipe can sequentially evacuate the chambers with the chemical into the annular space to create a barrier or barriers as required. These and other features of the present invention will be more readily apparent to those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings with the understanding that the full scope of the invention is determined by the appended claims.
A plurality of zones is gravel packed together and then isolated from each other in the gravel annulus by formation of a barrier in the gravel annulus. The screen assembly carries a series of chambers internally that are located between the producing zones generally in the area of blank pipe between the zones. The wash pipe has a shifter associated with it so that extraction of the wash pipe after gravel packing will serially shift pistons that reduce chamber volume where the chemical is stored. The chemical will exit through a rupture disc and nozzle and will commingle with the gravel and make an impervious annular barrier.
The chemical composition of the material that creates the barriers 24 is also known in the art; however, it is its application into the system described that is part of the claimed invention. The barriers created substantially isolate adjacent zones 10 and 12 in the annulus 28 and as an option can also be fully impervious barriers.
One way to discharge the seal material to make a barrier 24 is shown in
An alternative way to create barriers at discrete locations would be to expose openings 50 in the blank pipe sections 38 and then pull out the wash pipe 36 and run in with a straddle tool to straddle each opening 50 and pump the barrier chemical from the surface through the various ports 50. Doing so does add another trip into the well with the straddle tool and further requires proper placement of the tool and delivery of a predetermined volume of the barrier chemical to the site.
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.
