Well abandonment and slot recovery
Method and apparatus for single-trip cementing and casing cutting for well abandonment and slot recovery. Using a tool string including a casing cutter and a stinger, where the casing cutter has a central through bore including a wall to isolate the cutting assembly from the cement, cement can be passed through the cutter and deposited using the stinger to form a plug. Embodiments of casing cutters are provided for parting an upper length of casing from a lower length of casing.
1. A method comprising, in a single trip in a well bore, the steps:
(a) running a tool string downhole in the well bore, the tool string including a casing cutter and a stinger;
(b) passing a fluidised plugging material through the casing cutter and the stinger to deposit a quantity of the fluidised plugging material into the well bore to form a plug;
(c) drawing the stinger out of at least a portion of the deposited fluidised plugging material; and
(d) using the casing cutter to part an upper length of casing from a lower length of casing.
2. A method according to claim 1 wherein the method includes the step of pulling the upper length of casing on the same trip into the well bore.
3. A method according to claim 1 wherein the method includes the step of continuing to pull the tool string after step (c) to position the casing cutter at a desired location for step (d).
4. A method according to claim 1 wherein the method includes the additional steps of including a bridge plug on the tool string and setting the bridge plug in the well bore before step (b).
5. A method according to claim 1 wherein the method includes the step of conducting an inflow test before step (b).
6. A method according to claim 1 wherein step (b) includes pumping the fluidised plugging material from surface.
7. A method according to claim 1 wherein the tool string includes a receptacle for holding a plugging material and step (c) includes releasing the plugging material from the receptacle to pass as fluidised plugging material through the casing cutter.
8. A method according to claim 1 wherein the method includes the step of pumping a separation member behind the quantity of the fluidised plugging material.
9. A method according to claim 1 wherein the method includes pumping a wash fluid through the tool string and casing cutter.
10. A method according to claim 9 wherein the method includes directing at least a portion of the wash fluid through at least one port in the casing cutter.
11. A method according to claim 1 wherein the method includes the step of pulling the casing between steps (c) and (d).
12. A method according to claim 1 wherein in step (d) the casing is severed by making a circumferential cut through the casing.
13. A method according to claim 1 wherein in step (d) the casing is milled over a length of the casing.
14. A method according to claim 1 wherein the method includes the further steps of pulling the tool string to a second location, at a shallower depth, in the well and repeating step (d).