Wells – Processes – Cleaning or unloading well
Patent
1998-05-28
2000-11-28
Bagnell, David
Wells
Processes
Cleaning or unloading well
1663331, 166222, 1663344, E21B 2110
Patent
active
061522287
DESCRIPTION:
BRIEF SUMMARY
The invention relates to apparatus and a method for circulating fluid in a borehole.
It is common practice to install liners within a borehole which has been drilled. After installation of the liners it is generally necessary to clean out the inside of the liner to wash away any debris or other contaminants.
Generally, the liner is in the form of a cylindrical tube which has a relatively small internal diameter compared with the diameter of casing lining the borehole immediately above the liner. To clean out effectively inside the liner, high flow velocities are generally required to create turbulence to aid the cleaning out process. Generally, the clean out procedure is carried out by first passing cleaning liquid through a "work string" inserted into the liner, to exit from the work string at the lower end of the liner at a high flow rate so that the cleaning fluid flows turbulently up the annulus between the inside of the liner and the outside of the work string and then into the casing above the liner.
Generally, the "work string" is made up of a number of lengths of drill pipe, or other tubulars, threadedly connected together to form the work string, which may also be referred to as the "drill string".
However, because of the difference in volume between the liner and the casing above the liner, after the cleaning fluid passes the top of the liner and enters the relatively large volume of the casing, the flow velocity of the cleaning fluid in the casing above the liner is greatly reduced and any cleaning action becomes negligible.
Hence, it is generally necessary after passing cleaning fluid through the liner to then pass further cleaning fluid from the work string into the casing at a location above or adjacent the top edge of the liner, so that a high flow rate and hence turbulence of the cleaning fluid can be obtained in the casing. Therefore, it is generally necessary to have some device at or adjacent to the top end of the liner which can be operated downhole to either circulate fluid through the length of the work string to the lower end of the liner or which can direct cleaning fluid at high flow rates out of the work string into the casing above the liner, at or adjacent the top edge of the liner.
One such device that is known for carrying out this operation comprises a hollow body member and in order to change the direction of flow between the bottom of the liner and the top edge of the liner, spherical balls are dropped down the work string to open or close valves in the device.
However, there are a number of disadvantages associated with this apparatus. In particular, the length of time associated with the spherical balls falling from the surface to the device through a work string which is perhaps a few thousand feet in length can take 25 to 30 minutes. Hence, there is a problem with coordinating the arrival of the spherical ball at the apparatus to coincide with the arrival of the required cleaning fluid at the apparatus. It is also necessary to ensure that the increasing and decreasing flow velocities associated with the liner and the casing clean out are coordinated with the arrival of the spherical ball at the apparatus. in a borehole comprises a tubular assembly having a through passage between an inlet and a first outlet, the inlet and the first outlet being adapted for connection in a work string, a second outlet extending generally transversely of the assembly; outlet and a second position permitting fluid flow through the second outlet; and an engagement mechanism actuable between an engaged configuration, in which the obturating member is maintained in one of the first and the second positions, and a disengaged configuration, in which the obturating member can move to the other of the first and the second positions; formation in the borehole to engage or disengage the engagement mechanism.
Preferably, the obturating member of the apparatus is coupled to the shoulder.
Preferably, the formation in the borehole may be a shoulder portion in the borehole, but can be provided by any fo
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patent: 4637471 (1987-01-01), Soderberg
patent: 4991653 (1991-02-01), Schwegman
patent: 5082062 (1992-01-01), Wood et al.
Bagnell David
Browning Clifford W.
Specialised Petroleum Services Limited
Walker Zakiya
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