Downhole conveyance line cutter

1. An apparatus comprising:

a downhole tool operable to be conveyed downhole within a wellbore along a conveyance line that conveys a tool string within the wellbore and then cut the conveyance line, wherein the downhole tool comprises:

a body;

a plurality of fluid chambers within the body;

a plurality of pistons each slidably disposed within a corresponding one of the fluid chambers;

a knife that is movable with respect to the body;

an arm operatively connecting the pistons and the knife; and

a fluid source operable to pump a fluid into the fluid chambers to cause the pistons to move the arm which moves the knife to cut the conveyance line.

2. The apparatus of claim 1 wherein the arm is or comprises a lever pivotably connected to the body, wherein the fluid source is operable to pump the fluid into the fluid chambers to cause the pistons to move a first portion of the arm in a first direction thereby causing a second portion of the arm to move in a second direction to move the knife in the second direction thereby cutting the conveyance line, and wherein the first direction and the second direction are opposite from each other.

3. The apparatus of claim 1 wherein the knife comprises a channel configured to accommodate the conveyance line therethrough.

4. The apparatus of claim 3 wherein the channel has a U-shaped profile.

5. The apparatus of claim 3 wherein:

the knife is a first knife;

the downhole tool further comprises a second knife fixedly connected to the body;

the first knife is movable with respect to the second knife;

the second knife comprises a channel configured to accommodate the conveyance line therethrough;

the channel of the first knife and the channel of the second knife are each oriented in an opposing direction; and

the first knife is movable between:

a first position in which the channel of the first knife and the channel of the second knife collectively define an axial passage configured to accommodate the conveyance line therethrough; and

a second position in which the axial passage is closed and the conveyance line is cut.

6. The apparatus of claim 5 wherein each of the channel of the first knife and the channel of the second knife has a U-shaped profile.

7. The apparatus of claim 1 wherein the downhole tool further comprises:

a fluid conduit fluidly connecting the fluid source and the fluid chambers; and

a hydraulic accumulator fluidly connected with the fluid conduit, wherein the hydraulic accumulator is configured to receive the fluid from the fluid source and/or the fluid chambers to maintain pressure of the fluid below a predetermined threshold.

8. The apparatus of claim 7 wherein the hydraulic accumulator comprises:

a fluid reservoir;

a piston slidably disposed within the fluid reservoir; and

a biasing member configured to resist movement of the piston of the hydraulic accumulator within the fluid reservoir when the fluid flows into the fluid reservoir.

9. An apparatus comprising:

a downhole tool operable to connect along a conveyance line that conveys a tool string within a wellbore, slide along the conveyance line to the tool string, and cut the conveyance line, wherein the downhole tool comprises:

a body configured to accommodate the conveyance line therethrough;

a fluid chamber;

a piston slidably disposed within the fluid chamber;

a knife;

an arm pivotably connected to the body and operatively connecting the piston and the knife; and

a fluid source operable to move a fluid into the fluid chamber to cause the piston to pivot the arm such that a first portion of the arm moves in a first direction and a second portion of the arm moves in a second direction to thereby cause the knife to move to cut the conveyance line, wherein the first direction and the second direction are opposite from each other.

10. The apparatus of claim 9 wherein:

the fluid chamber is a first fluid chamber of a plurality of fluid chambers;

the piston is a first piston of a plurality of pistons;

each piston is slidably disposed within a corresponding fluid chamber;

the arm operatively connects the pistons and the knife; and

the fluid source is operable to move the fluid into the fluid chambers.

11. The apparatus of claim 9 wherein the fluid source is operable to move the fluid into the fluid chamber to cause the piston to pivot the arm to thereby cause the knife to move in the second direction to cut the conveyance line.

12. The apparatus of claim 9 wherein the knife comprises a channel configured to accommodate the conveyance line therethrough.

13. The apparatus of claim 12 wherein the channel has a U-shaped profile.

14. The apparatus of claim 12 wherein:

the knife is a first knife and the channel is a first channel;

the downhole tool further comprises a second knife comprising a second channel configured to accommodate the conveyance line therethrough;

the first channel and the second channel are each oriented in an opposing direction; and

the first knife is movable with respect to the second knife between:

a first position in which the first channel and the second channel collectively define an axial passage configured to accommodate the conveyance line therethrough; and

a second position in which the axial passage is closed and the conveyance line is cut.

15. The apparatus of claim 14 wherein the second knife is fixedly connected to the body.

16. The apparatus of claim 14 wherein each of the first channel and the second channel has a U-shaped profile.

17. The apparatus of claim 9 wherein the downhole tool further comprises:

a fluid conduit fluidly connecting the fluid source and the fluid chamber; and

a hydraulic accumulator fluidly connected with the fluid conduit, wherein the hydraulic accumulator is operable to receive the fluid from the fluid source and/or the fluid chamber to maintain pressure of the fluid below a predetermined threshold.

18. The apparatus of claim 9 wherein the body defines a longitudinal channel configured to accommodate the conveyance line therethrough, and wherein the knife is disposed along the longitudinal channel.

19. An apparatus comprising:

a downhole tool operable to connect along a conveyance line that conveys a tool string within a wellbore, slide along the conveyance line to the tool string, and cut the conveyance line, wherein the downhole tool comprises:

a body configured to accommodate the conveyance line when the downhole tool is connected along the conveyance line;

an actuator;

a knife; and

a lever arm pivotably connected to the body and operatively connecting the actuator and the knife, wherein the actuator is operable to move a first portion of the lever arm in a first direction to cause a second portion of the lever arm to move in a second direction to thereby cause the knife to move to cut the conveyance line when the downhole tool is connected along the conveyance line, and wherein the first direction and the second direction are opposite from each other.

20. The apparatus of claim 19 wherein the actuator is operable to move the first portion of the lever arm in the first direction to cause the second portion of the lever arm to move in the second direction to thereby move the knife in the second direction to cut the conveyance line when the downhole tool is connected along the conveyance line.