Wellbore cleanout tool

Abstract

A downhole tool string forming a free end portion for performing an operation in a well having a well fluid, the string comprising towards the free end portion; a motor for delivering a rotational speed, a pump connected the motor for circulating the well fluid through a first port and a second port, a gear housing comprising a gear being driven by the pump and delivering a reduced rotational speed, a tool shaft rotatable by the gear at the reduced rotational speed; a reservoir around a section of the tool shaft for collecting dislodged material, and a material dislodging means connected to the tool shaft, wherein the gear housing further comprises a first fluid channel for providing fluid communication between the pump and the first port via the tool shaft being hollow, and a second fluid channel for providing fluid communication between the pump and second port via the reservoir.

Claims

1. A wireline based downhole tool string forming a free end portion for performing an operation in a well having a well fluid, the downhole tool string comprising towards the free end portion: a motor for delivering a rotational speed; a pump for circulating the well fluid through a first port at the free end portion of the downhole tool string, and through a second port at the free end portion of the downhole tool string, the pump being connected to the motor; a gear housing comprising a gear, the gear being driven by the pump and delivering a reduced rotational speed, the reduced rotational speed being lower than the rotational speed of the motor; a hollow tool shaft rotatable by the gear at the reduced rotational speed, the tool shaft being continuous hollow from the gear housing to the free end portion; a reservoir for collecting dislodged material, the reservoir being around a section of the hollow tool shaft, and a material dislodging means connected to the hollow tool shaft, wherein the gear housing further comprises a first fluid channel for providing fluid communication between the pump and the first port via the hollow tool shaft, and a second fluid channel for providing fluid communication between the pump and the second port via the reservoir.

2. The wireline based downhole tool string according to claim 1, comprising a second gear arranged between the motor and pump for altering the rotational speed from the motor to the pump.

3. The wireline based downhole tool string according to claim 1, wherein the second port is arranged in proximity to the material dislodging means.

4. The wireline based downhole tool string according to claim 1, wherein the material dislodging means is derived from a group of tools consisting of a drilling tool, a milling tool or a jetting tool.

5. The wireline based downhole tool string according to claim 1, comprising a rotatable screw for distributing and retaining dislodged material in the reservoir.

6. The wireline based downhole tool string according to claim 5, wherein the rotatable screw is arranged on a section of the tool shaft within the reservoir.

7. The wireline based downhole tool string according to claim 1, comprising a filter for retaining dislodged material within the reservoir.

8. A wireline based downhole tool string assembly comprising the downhole tool string according to claim 1 and a wireline for connection to the downhole tool string.

9. The wireline based downhole tool string assembly according to claim 8, comprising a wireline tractor for displacing the tool string in a well.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) In the following is described examples of a preferred embodiments illustrated in the accompanying drawings, wherein:

(2) FIG. 1 shows a cross section of a downhole tool string according to one embodiment of the invention. The downhole tool string is split into three sections for illustration purposes;

(3) FIG. 2 shows a cross section, in a larger scale than FIG. 1, of a bottom section of the downhole tool string comprising a drilling bit and a lower portion of a reservoir;

(4) FIG. 3 shows a cross section, in the same scale as FIG. 2, of a section of the downhole tool string comprising an upper portion of the reservoir;

(5) FIG. 4 shows a cross section, in the same scale as FIG. 2, of a section of the downhole tool string comprising an upper portion of a tool shaft and a lower portion of a gear;

(6) FIG. 5 shows a cross section, in the same scale as FIG. 2, of a section of the downhole tool string comprising an upper portion of a gear and the pump;

(7) FIG. 6a shows the downhole tool string assembly according to one embodiment of the invention, where the downhole tool string being connected to a wireline; and

(8) FIG. 6b shows the downhole tool string assembly according to one embodiment of the invention, where the downhole tool string being connected to a wireline tractor, the wireline tractor further being connected to a wireline.

DETAILED DESCRIPTION OF THE INVENTION

(9) The figures are depicted in a simplified manner, and details that are not relevant to illustrate what is new with the invention may have been excluded from the figures. The different elements in the figures may necessarily not be shown in the correct scale in relation to each other. Equal reference numbers refer to equal or similar elements. In what follows, the reference numeral 1 indicates a downhole tool string according to the invention. The downhole tool string 1 comprises a material dislodging means 2, in the figures depicted as a drill bit, connected to a first end portion 31 of a tool shaft 3. A second end portion 32 of the tool shaft 3 is connected to a gear 4. A pump 5 is connected to the gear 4 for driving the gear 4, the pump 5 being driven by a motor 6, in the figures depicted as an electric motor.

(10) FIG. 1 shows the downhole tool string 1 split into three sections for illustration purposes. In use, the three sections would be arranged in series with the ends A-A and B-B adjoining each other. The drill bit 2 is rotatable for dislodging material in a well (not shown). The drill bit 2 is rotated by the tool shaft 3. In another embodiment, the material dislodging means may be a milling bit or a jetting tool. A jetting tool may comprise one or several nozzles for ejecting well fluid, thereby dislodging material in the well. The nozzle(s) may be rotated by the tool shaft 3. The tool shaft 3 extends through a housing 7, a portion of the internal volume of the housing 7 being configured as a reservoir 71 for collecting debris from the well. The tool shaft 3 is arranged with a screw 72, in the figure shown as an auger. The screw 72 rotates with the tool shaft 3 to distribute the debris in the reservoir 71. A filter 73 retains material in the reservoir 71, but allows well fluid to escape the reservoir 71.

(11) The second end portion 32 of the tool shaft 3 is connected to the gear 4. The gear 4 is connected to the pump 5 configured to drive the gear 4. The pump 5 is connected to the motor 6 by means of a shaft 51 for driving the pump 5. The pump 5 is driven with a rotational speed delivered from the motor 6. The rotational speed is continued by the pump 5 to the gear 4. The gear 4 reduces the rotational speed to drive the tool shaft 3 at a lower rotational speed than the pump 5. In this particular embodiment, a second gear 41 is arranged between the motor 6 and pump 5. The second gear 41 being configured to alter the rotational speed from the motor 6 to the pump 5. The motor 6 receives energy through a wireline (see FIG. 5a) from an energy source at the surface.

(12) FIG. 2 shows the free end portion of the downhole tool string 1. Well fluid 10, illustrated with arrows, may be circulated out through an outlet 21 on the drill bit 2 and in through an inlet 8. Circulating the well fluid 10 while drilling will suspend the dislodged material in the well fluid 10 and the material may be transported with the flow of well fluid 10. The inlet 8 is arranged on a lower end 70 of the housing 7 to reduce the distance the dislodged material has to be transported with the well fluid 10 before entering the downhole tool string 1. In one embodiment, the inlet 8 may be arranged further from the drill bit 2. A check-valve 9 allows flow of well fluid 10 into the reservoir 71, but restricts return flow.

(13) FIG. 3 shows an upper portion of the reservoir 71. A filter 11 is arranged concentrically around the tool shaft 3 to filtrate particles from the well fluid 10. The filter 11 retains particles of a certain size, dependent on the filter mesh, but allows fluid to pass through.

(14) FIG. 4 shows a cross-section of a connection area 110 between the tool shaft 3 and the gear 4. In use, the motor 6 drives the pump 5 to push well fluid 10 from the pump 5 around the gear 4 in a first annular fluid channel 410 inside the gear housing 400. The well fluid 10 enters the tool shaft 3 through a perforated section 420 on the tool shaft 3. The tool shaft 3 is hollow and acts as a conduit for the well fluid 10, guiding the well fluid 10 to the outlet 21 on the drill bit 2. The pump will suck well fluid 10 through the second port and around the tool shaft 3 in an annulus 430. The well fluid 10 enters a second annular fluid channel 440 through a perforated section 33 concentrically arranged around the tool shaft 3. The second annular fluid channel 440 in the gear housing 400 guides the well fluid 10 past the gear 4 and to the pump 5.

(15) FIG. 5 shows the well fluid 10 being pumped into the first annular fluid channel 410 in the gear housing 400 from the pump 5, and further past the gear 4. Well fluid 10 flowing towards the pump 5 passes the pump 5 in the second annular fluid channel 440 and enters the pump 5 through a top portion 50 of the pump 5. The well fluid 10 is recycled by the pump 5, and pumped back into the first annular fluid channel 410. It should be understood that the well fluid 10 may flow the opposite direction to what is described above if circulation is reversed.

(16) FIG. 6a shows a downhole tool string assembly 200. The downhole tool string 1 is connected to a wireline 160. The wireline 160 extends to the surface and can transmit power to and control signals to and from the tool string 1. The wireline 160 can lower and hoist the tool string 1 in the well.

(17) FIG. 6b shows another embodiment of the downhole tool string assembly 200. The downhole tool string 1 being connected to a wireline tractor 150. The wireline tractor 150 can displace the downhole tool string 1 in the well.

(18) It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb “comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.

(19) The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.