Wells – Processes – Cleaning or unloading well
Reexamination Certificate
1999-01-22
2001-06-26
Novosad, Christopher J. (Department: 3671)
Wells
Processes
Cleaning or unloading well
C166S229000
Reexamination Certificate
active
06250387
ABSTRACT:
The present invention relates to apparatus for cleaning the interior bore of well bore tubulars, such as is found in the oil and gas production industries. A distinctive aspect of the invention lies in its provision of a means for filtering or screening well fluid while down-hole.
It is considered desirable when drilling for oil or gas to maintain a clean interior in the casing or liner of the drilling well. For this purpose, well cleaning equipment is well known and comes in a variety of different forms, including casing scrapers, brushes and circulation tools. Such equipment is used to free the well tubing from debris particles such as, cement lumps, rocks, congealed mud, and so on.
Indeed well clean-up apparatus is used in an attempt to clean the casing or other well tubing of even smaller debris particles such as oxidation lumps, metal debris, scale, slivers, shavings and burrs for example.
It is now common practice to run dedicated well cleaning apparatus after cementing the liner and prior to completion. Tools have also been provided in the art which are intended to perform a cleaning operation in wellbore completions.
However, in the present invention it is recognised that during the extraction of known cleanup tools from the well, additional debris can be dislodged, such as from the wall of the casing, thereby negating much of the cleaning work already performed. In fact, the dislodgement of debris or particles during the extraction of the tool can render futile the processes of filtering and fine-screening that may have gone before. This problem is particularly prevalent as such cleanup tools, known to the art, typically have their cleaning members biased outwardly to ensure adequate pressure of the cleaning members on the walls of the casing or liner. While this is of assistance during the cleaning process, it has been a disadvantage during the extraction of the tool from the well.
It is also recognised in the present invention that tools suited to the cleaning of well tubulars are not generally also equipped to clean the well fluid. It is usual therefore that debris dislodged from the casing or liner walls is not then fully removed from the well by circulation. Rather, the debris may remain suspended in well fluid down-hole, having detrimental effects during subsequent production stages.
An object of the present invention is to obviate or at least mitigate this problem associated with known clean up tools and their use.
A further object of the present invention is to provide apparatus suitable for providing a means of trapping and collecting debris in a well-bore.
In the art there are tools commonly referred to as junk catchers. These tools are of varying design; some being suitable for running on a pipe string, other on coiled tubing, and yet others on wireline. A notable aspect of such tools, however, is that while they invariably provide a cage or some other catchment area for collecting debris or the like down-hole, they are not adapted to filter properly the well fluid. More particularly, junk catchers and or junk subs known in the art have not been arranged to encourage the circulation of well fluid through a filter in a manner that is pro-actively designed to screen debris or other particles out of the fluid.
According to the present invention there is provided a down-hole tool for collecting loose debris particles in a well bore, the tool comprising a body connectable in a work string, diversion means for diverting well fluid passing the tool through the tool body, and a filtration means for filtering debris particles from at least some of the well fluid.
The work string may be a pipe string, coiled tubing or a wireline.
It should be understood that the diversion means may be formed wholly or partially integral with the tool body. Preferably the diversion means comprises a barrier having an outer diameter that corresponds with the internal diameter of an adjacent tubular in the well bore to the extent that there is negligible fluid by-pass outside the tool body, and one or more flow paths that direct fluid passing through the tool body to the filtration means. It is possible to design the tool such that it filters the well fluid when the fluid moves in only one direction relative to the tool, that is in either an up-hole direction or a down-hole direction. This may be achieved by providing a plurality of flow paths in the tool body, the flow paths being associated with respective one-way valves whereby when the fluid passes through the tool body in a first relative direction it does so through a first set of the flow paths having one way valves that so permit, and when the fluid passes through the tool body in a second and opposite relative direction it does so through a second set of the flow paths having one way valves that so permit, but wherein only one of the first and second set of flow paths is adapted to divert the fluid through the filtration means.
The valve means may be balls moveable within respective flow paths under the influence of fluid flow or pressure, wherein the balls are sized to land in sealing engagement with a restricted area in the flow paths for blocking further passage of fluid in a particular direction in the respective flow path.
The barrier is preferably formed as a separate component from the tool body. One advantage of this is that the barrier may be connectable to the body by bearings, thereby permitting relative rotation between the tool body and the barrier. Accordingly the barrier need not rotate against the well bore tubular, enabling improved longevity through less wear. Additionally, the barrier may be replaced, if necessary, without the requirement of replacing the entire tool body.
It may be appreciated that these advantages are most applicable where the barrier contacts the well bore tubular. Preferably, the barrier is a resilient member which is radially compressed by the well bore tubular in use and which is adapted to wipe the well bore tubular as the tool moves up or down the well bore.
There may be more than one barrier, and in a preferred embodiment, a barrier in the form of a resilient wiping member may be provided toward each end of the tool.
Where the tool is adapted for connection to a pipe string or coiled tubing, the tool body is preferably provided with an internal bore adapted to communicate with a circulation path in the work string.
The filtration means may be a wire screen sized to prevent particles of a predetermined size from passing therethrough. It will be appreciated however that many different types of filtration apparatus may be used, including permeable textiles, holed tubes or cages, and so on. The filtration means need not be limited to any one particular type of screen or filter, but may rather comprise of a plurality of filters in series; the filters being potentially of varying type and permeability.
The tool may also act as a collector or trap for debris and the like. For example, a trap may be provided on the up-stream side of the filter means for storing the filtered debris.
Optionally, a separate filter may be provided for each filtered flow path, and the flow paths on the up-stream side of the filter means may act as the traps for collecting the debris particles.
Preferably the tool comprises an emergency by-pass means, whereby well fluid is enabled to by-pass the filter means, for example when the filter becomes blocked or clogged. The emergency by-pass means may comprise of means for displacing the barrier relative to the tool body to a position where it no longer diverts substantially all of the fluid passing the tool through the tool body. Alternatively, the tool body may include radial outlets communicating with the one or more flow paths, the outlets being maintained in a closed state by an obturating member in normal use, but being openable by movement of the obturating member to create the emergency bypass flow path. Typically, the obturating member may be held in an obturating position by one or more shear pins, wherein said shear pins are adapted to shear or otherwise fai
Carmichael Mark
Howlett Paul
Browning Clifford W.
Novosad Christopher J.
SPS-AFOS Group Limited
Woodard Emhardt Naughton Moriarty & McNett
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