The field of the invention is a method of placing cement at predetermined locations of an annular space around a tubular string for zonal isolation.
Straddle tools to inflate external casing packers with cement are known and described in U.S. Pat. No. 5,082,062, U.S. Pat. No. 5,186,258, U.S. Pat. No. 5,366,019 and U.S. Pat. No. 5,692,564. Other external casing barriers have also been used such as swelling packers or hydraulically or mechanically compressed packers. These various packer designs present their own series of complications when multiple barriers need to be placed at spaced locations. The swell packers take a long time to reach sealing position while the mechanically set packers are of limited use in deviated boreholes. The hydraulically set packers require balls to be delivered to seat and need ball catchers for the balls once pushed through the seats. The ball seats may also need to be blown out to avoid reducing the size of the production flow passage once production begins.
More recently cement formulations have advanced to the point where commercially available cements can be pumped in a borehole and hold the position where the cement is placed despite the presence of borehole fluids.
The present invention allows for single trip placement of cement rings at predetermined locations on a tubular string where access to the open hole is provided. A straddle tool allows isolation of these access openings in sequence so that cement can be delivered into a surrounding annular space without need to perforate and squeeze cement into the annular gap and the surrounding formation. The cement can be spotted in the tool and once straddling access valves in the string cement can be sequentially delivered preferably in a single trip moving up the hole to define as many zones as needed for the completion before production starts. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined by the appended claims.
A method of providing cement isolators in an annular space about a tubular string in open hole uses a straddle tool that sequentially engages profiles in the tubular string so that prepositioned communication valves to the surrounding annulus can be straddled to force cement out through the straddle tool and into the annular space. The cement is formulated to stay in position and set up. Each valved opening in the string comes with an associated locating profile and another profile for a locking dog to secure the straddle tool in position for forced delivery from the tool and into the valve assembly for delivery into the open hole annulus where a sealing ring of cement will set up for isolation. The operation sequentially put in place as many barriers as there are valve assemblies to straddle and in a single trip generally working in an uphole direction.
Referring to
A wiper plug 68 can be launched ahead of a predetermined volume of cement 70 sufficient to make all the anticipated annular rings with some excess. Well fluid with another dart that is not shown can be pumped behind the cement to bump the plug 68 so that pressure can be built inside the straddle tool 38 to force cement 70 through the various valve assemblies such as 54 as shown in
As shown in
The cement wiper plug ahead of the cement can also free a flapper valve to close to retain the cement instead of using the wiper plug for cement retention. Packer 60 can be set with pressure extended dogs and setting down weight in a manner known in the art. Pressure can also be used to extend dogs 48 to lock the straddle tool 38 to recess 18. Slacking off weight at that time indicates that the dogs 48 have extended for support of the straddle tool 38. Picking up releases dogs 48 to retract and relieving pressure allows valve 40 to close. Return valve 76 closes with a pick up force on the straddle tool 38.
Those skilled in the art will appreciate that the method allows for a single trip creation of annular barriers that stay where they are pumped in the annular space and set up to create multiple barriers as needed. A straddle tool is provided to allow charging the required volume of cement at each location and being able to take returns into the upper annulus through a return valve. This return valve can be configured to be selectively closed if needed for well control purposes. As many barriers as there are exit valve assemblies in the liner or casing string can be made before the straddle tool is removed from the borehole and excess cement is reversed out.
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: