An embodiment of the present invention will now be described by way of example, and with reference to the accompanying drawings, in which:
Referring now to the drawings, a debris collecting device 1 comprises an inner body 5 having box and pin connections at respective ends in order to facilitate connection of the inner body 5 into a conventional drill string or cleaning string. The inner body 5 has, on its outer surface, a pair of helical vanes 8a and 8b, which start at diagonally opposite positions on the inner body 5. The radially outermost edges of the helical vanes 8 are grooved to receive resilient seal 9 (e.g. a Viton® seal) (Viton is a register trademark of the DuPont Company.) The helical vanes 8 typically extend for at least two or three turns around the outer surface of the inner body 5, creating an auger having two separate helical pathways along the outer surface of the inner body 5. The lower ends of the helical vanes 8 (nearest to the pin end on the left hand side of the figures) are both at this stage open to the lower end of the inner body 5. The upper ends of the helical plates 8 are welded to upper helical baffles 12a and 12b respectively. The pitch of upper helical baffles 12 is less than the pitch of the helical vanes 8, and typically, the helical baffles 12 each extend only 180° around the circumference of the inner body 5. The upper baffles 12 terminate below a deflector plate 15 that is welded to the inner body 5, and has a generally inverted cup-shaped arrangement, so that the end of each upper plate 12 terminates within a cup formed by the deflector plate 15. The end termination of each upper plate 12 is spaced from the apex of the cup formed by the deflector plate 15, so there is a space between the end of the upper plate 12 and the deflector plate 15.
The helical vanes 8 and 12 and the deflector plate 15 are all encased within an outer sleeve 20 forming an outer housing. The sleeve 20 compresses the seal 9 to form a water-tight seal, thereby isolating the two helical channels 10a and 10b extending along the outer surface of the inner body 5. The lower end of the sleeve 20 has an end plug 22 shown in
At the upper end of the annulus 20a, a filter ring 30 (shown in more detail in
In operation, the device 1 is typically rotated along with the inner body 5 as part of the string. Typically, this rotation can be initiated from the kelly on the rig, or by any other means desirable. The helical vanes 8 and baffles 12 are set in a clockwise helix when the string is to be rotated in a clockwise direction. If the string is to be rotated in an anticlockwise direction, the helical vanes 8 and baffles 12 can be set in the opposite configuration. The central bore 5b of the inner body 5 carries clean circulation fluid from the surface, and expels it from the string in a region of the well bore below the device 1 that is to be washed. The circulating fluid is expelled from the bore 5b and passes up the annulus between the string and the formation, washing suspended solids comprising junk to be recovered upwards in the annulus between the string and the formation (or the casing). When the debris-saturated circulation fluid reaches the lower end of the device 1, the optional scoop 25 diverts the fluid through the aperture 22a into the mouth of the open channel, and into the first helical pathway 10a (the collection pathway), which is axially aligned with the aperture 22a. The blanked portion 22b of the end plug 22 isolates the other helical channel 10b from the lower end of the device 1, and prevents the ingress of the fluid directly into the channel 10b from the lower end of the device 1. Optionally, the end plug 22 can be welded to the inner body 5 and the helical vanes 8 in order to effect the seal, and can optionally be sealed on its outer surface by means similar to the seal 9, so as to close off the collection chamber 10b entirely, thereby ensuring that the recovered circulation fluid that is saturated with debris only travels up the collection pathway 10a.
The clockwise rotation of the device 1 thereby moves the suspended debris and circulation fluid in the direction of the arrows shown in
The particulate debris from the baffles 12 and the diverter plate 15 continues to fall in a helical path down the helical collection chamber 10b and collects at the lower end adjacent to the end plug 22. Since the end plug 22 seals off the lower end of the collection chamber 10b in a blind ending, the particulate debris settles and is retained within the collection chamber. The clockwise rotation of the helical vanes 8 throughout serves to compress the particulate matter within the collection chamber 10b so as to drive it down to the lower end, and this helps to maximise the capacity of the device 1.
When the collection chamber 10b is full the string can be recovered to surface, and the end plug 22 removed (or the sleeve 20 removed by releasing the locking bolts) and the collection chamber emptied ready for a return trip. Similar devices 1 can be arranged in the same string in series, with finer filters to remove different sizes of particulate matter in the upper states of the well.
Modifications and improvements can be incorporated without departing from the scope of the invention. For example, magnets and other devices to retain junk within the collection chamber can be employed at the blanked portion 22b of the end plug 22 and can help to retain any metallic particles within the collection chamber 10b. The outer diameter of the sleeve 20 can be substantially the same as the drift size of the casing, so as to restrict the size of particulate matter that can pass outside the sleeve 20 without passing through the device, or the outer sleeve 20 can have a seal to close off the annulus and force debris into the collection pathway.
While the present invention has been described with respect to various preferred embodiments, it should be readily apparent to those skilled in the art that a variety of modifications are possible in light of the teachings provided herein.
Number | Date | Country | Kind |
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0614990.0 | Jul 2006 | GB | national |