Wells – Processes – Placing or shifting well part
Reexamination Certificate
2000-02-03
2001-09-11
Dang, Hoang (Department: 3672)
Wells
Processes
Placing or shifting well part
C166S187000, C166S191000
Reexamination Certificate
active
06286603
ABSTRACT:
It is common practice to pass a work-pipe down into a borehole, from the ground surface. The work-pipe may be designed to serve one of many different functions, for example to convey samples taken at various depths to the surface.
The invention relates to borehole packers, of the kind used to seal the annular gap a between the work-pipe and the borehole wall or casing.
The purpose of a borehole packer is to bridge and seal the annular, radial, gap between the work-pipe and the borehole. Generally, the construction of the work-pipe, and the placement of the packers on the work-pipe, is done at the ground surface, prior to a lowering the work-pipe and packers, as an assembly, down the borehole. The on-site engineer determines the depth at which he wishes to take the water sample; he arranges the work-pipe so as to include a water-draw-off sampling-port at the desired depth; then he arranges for packers to be placed above and below that depth.
Usually, the process of lowering the assembly of work-pipe and packers into the borehole requires that the packers be deflated at that time. The packers are inflated, from the ground surface, once the packers are deployed at the desired depth. One technique is to employ, in the packer, bentonite or other material that swells upon contact with water. An example of that is shown in USA patent publication U.S. Pat. No. 5,195,583. The bentonite is slowacting enough that the packer remains slim during lowering, but swells to fill the annular gap over the next several hours or days. However, a bentonite packer basically cannot be removed, once deployed, as there is no way of deflating the bentonite packer.
Deflatable packers generally include a means for pressurising the packer from the surface, and deflation involves releasing that pressure, again from the surface. An example of that is shown in USA patent publication U.S. Pat. No. 5,392,853. The packers having been deflated, the work-pipe and packers can be withdrawn from the borehole, whereupon the borehole can be sealed up, and the work-pipe and packers can be re-used in a different borehole.
Deflatable packers have not, traditionally, been of a simple nature. The invention is aimed at providing a deflatable packer that is simple to deploy, is versatile in accommodating onsite requirements, is easy to operate, is robust in construction, is economical to produce, and is trouble-free in service.
Other examples of relevant prior art structures are contained in USA patent publication U.S. Pat. No. 5,048,605.
GENERAL FEATURES OF THE INVENTION
The packers have to be attached to the work-pipe at the ground surface, prior to the assembly of work-pipe and packers being lowered down the borehole The packers must therefore be securely attached with respect to the work-pipe. Traditionally, this requirement has been met by building the packer mechanically into the work-pipe, as a component of the work-pipe. If not built-in, at least the traditional packer has included a structural component whereby the packer could be mechanically attached, e.g with screw fasteners or the like, to the structure of the work-pipe.
One of the problems with traditional built-in packers is that the packer cannot be moved along (i.e up/down) the work-pipe to a new location; rather, the work-pipe has to be rebuilt if the packer needs to be moved Another problem with the built-in packer is that the packer itself is manufactured and assembled, as a unit, in-factory, but the packers are assembled into the work-pipe in the field, i.e at the borehole site. The packer has to be designed and manufactured to suit the dimensions and other details of the fittings already present on the work-pipe, such as screw-threads, port sizes, etc. It is, unfortunately, all too common to find, for instance, when the attempt is made to screw the packer into the work-pipe, that the screw-threads are the wrong size.
The present invention provides a packer in which the packer is secured to the work-pipe, not by mechanical connection, but by the action of a rubber inner-bladder, which encircles the work-pipe. The packer structure includes solid components, but these components do not come into contact with the work-pipe. In the invention, there is no need for mechanical connections, such as screw threads, between the packer and the work-pipe. The solid components of the packer are mounted, not directly from the work-pipe, but indirectly from the work-pipe, via the inner bladder.
The only information that is needed in order to custom-make the packer to suit the on-site work-pipe, then, is the diameter of the work-pipe. The inner bladder comprises a length of stretchy rubber tubing, which is arranged to be of a diameter that is slightly smaller than the work-pipe, so the inner bladder will grip the work-pipe.
In order to allow the packer to be moved along the work-pipe, for assembly and positioning purposes in the field, a vacuum source is provided, and vacuum is applied around the outside of the inner bladder. The vacuum sucks the inner bladder outwards, and thereby increases the clearance diameter inside the inner bladder. With the inner bladder held dear of the work-pipe, the packer can be moved along the work-pipe. Once the packer is in position, the vacuum is released, and the inner bladder then relaxes, and contracts. The inner bladder grips the work-pipe along its length. Only a small degree of residual stretch is needed for the packer to be secured very firmly to the work-pipe.
In practice, if more security is needed than is given by the bladder alone, suitable abutment clamps can be secured around the work-pipe, above and below the packer. The abutment clamps make sure that the packer, even if it is knocked during assembly and installation, cannot move along the work-pipe.
The vacuum source is provided for moving the packers around on the work-pipe, prior to lowering the assembly of work-pipe and packers down the borehole. Generally, the vacuum source is not used again, once the work-pipe and packers have been assembled and installed to their final working depths, in the borehole.
The packer also includes an outer bladder, which is able to be expanded by the application of pressure inside. An operable pressure source is provided, and once the packer or packers are in place on the work-pipe, the pressure source is connected. When the assembly of work-pipe and packers has been lowered into position, the pressure source is operated, which expands the outer bladder, and expands it far enough to bridge the gap between the work-pipe and the casing of the well or borehole. Thereafter, until the time comes for the assembly of work-pipe and packers to be removed from the borehole, the pressure source stays operated, maintaining pressure on the outer bladder.
Preferably, the inner bladder is also subjected to pressure, whereby the grip of the inner bladder upon the work-pipe is enhanced. If only the outer bladder is pressurised, there can be a chance that the in-ground water pressure will dislodge the inner bladder from the work-pipe.
To remove the assembly from the borehole, the pressure is removed, whereby the outer bladder collapses inwards, and breaks contact with the walls of the borehole. Generally, the vacuum would not be applied while the assembly is down the hole (although it could be, to make sure the outer bladders are well-collapsed before an attempt is made to remove the assembly from the borehole); once the assembly is out of the borehole, vacuum can then be applied to the packers, to enable them to be repositioned on, or removed from, the work-pipe, as required.
As mentioned, a major benefit of the packer as described herein is that it can be moved along to a new position on the work-pipe, without breaking the work-pipe; but this cannot be done with a deflatable packer that has been mechanically built into the work-pipe. Another major benefit of the packer as described herein is that a correct size of deflatable packer can be supplied from the factory, simply upon knowing the diameter of the work-pipe; but when the packer was built into the wo
Anthony Asquith & Co.
Dang Hoang
Solinst Canada Limited
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