Method of abandoning a well
A method of abandoning a well, said well comprising at least two concentric conduits (28,30) defining a main bore and at least one annular chamber (40) there between, comprising the steps of providing a perforation in one or more of the conduits, pumping out the fluiti from the annular chamber and/or main bore to create a fluiti-free void, inserting sealing material in the annular chamber and/or main bore to seal it/them. There is also provided an apparatus for abandoning a well having at least two concentric conduits defining at least one annular chamber there between, the apparatus including a pump (50) and a perforation forming device (42).
Over the past 20 years or so a large number of offshore structures have been constructed which are now or will soon be exhausted and will need to be abandoned. These offshore structures may comprise production platforms which are either steel or concrete structures resting on the sea bed or floating platforms. Numerous conduits are connected to these offshore structures to carry the various fluids being gas, oil or water etc., which are necessary for the production of oil and/or gas from the well.
In abandoning a well, consideration has to be given to the potential environmental threat from the abandoned well for many years in the future.
In the case of offshore structure there is usually no rig derrick in place which can be used to perform the required well abandonment procedure. Therefore it is typically necessary to install a new derrick or alternatively a mobile derrick can be positioned above the well. This requirement adds considerable expense to the to the task of abandoning the offshore well, compared to a land based well.
A typical production well will comprise a number of tubular conduits arranged concentrically with respect to each. The method of abandoning the well which is presently known in the art involves the separate sealing of each of the concentric conduits which requires a large number of sequential steps.
In the abandonment method known in the art the first step is to seal the first central conduit usually by means of cement or other suitable sealant. The first annular channel between the first and second conduits is then sealed and the first central conduit is then cut above the seal and the cut section is removed from the well.
The second annular channel between the second and third conduits is then sealed and the second conduit cut above the seal and the cut section is removed from the well.
This process is repeated until all the conduits are removed. The number of separate steps required is typically very large indeed and the number of separate operations is five times the number of conduits to be removed. This adds considerably to the cost of the well abandonment due to the time taken and the resources required at the well head.
It is the purpose of the present invention to provide a method of abandoning a well which avoids the disadvantageous and numerous operations which are required by the existing known methods. This will greatly reduce the costs of safely abandoning a well. It is a further objective of the invention to provide a method of abandoning a well without the requirement of a rig which involves significant expense particularly in sea based wells.
It is a further advantage of the invention to isolate all the conduits and annuli with no return of the well bore or annular fluids to the surface. Additionally if required all tubing and casing can remain in the well. Further more the method of abandonment of the well will comply with all the regulatory guidelines for the isolation of a well.
According to the present invention there is provided a method of abandoning a well, said well comprising at least two concentric conduits defining a main bore and at least one annular chamber there between, comprising the steps of:
-
- providing a perforation in one or more of the conduits,
- pumping out the fluid from the annular chamber and/or main bore to create a fluid-free void,
- inserting sealing material in the annular chamber and/or main bore to seal it/them.
According to another aspect of the present invention there is provided an apparatus for abandoning a well having at least two concentric conduits defining at least one annular chamber there between, the apparatus including a pump and a perforation forming device.
Thus by means of the method according to the invention the number of operations required is greatly reduced thus resulting in a considerable reduction in the cost of carrying out the well abandonment.
The following is a more detailed description of an embodiment according to invention by reference to the following drawings in which:
FIGS. 13 to 16 shows the stages of another embodiment of the method.
Referring to the figures in more detail,
As shown in
Referring now to
Holes are made in the production tubing 30, by the holing means. This could be any suitable holing means such as by using perforating charges 61. This is shown in
Whilst in this embodiment the plug, sealing, holing and pumping actions are carried out in that particular sequence using a single pump assembly tool, it is also possible to use separate tools for the separate steps and variations to the sequence.
For example, the sealing material could be provided after the holing of the production tubing. The fluids could then be pumped downwards into the reservoir section also instead of out wards to surface, before a sealing material is placed behind them. This would avoid the need to make separate arrangements for the disposal of the fluids pumped out.
Referring back to the embodiment shown in the drawings, and in particular
Referring to
If the drained fluid rises above the pump 53, then the excess fluid can be pumped out the well via the umbilical. Finally, Referring to
Referring to
Referring to
Referring to
Once this cement has set, a pressure test or a tag test may be carried out to confirm the cement's location and pressure holding capability. If such testing is not required, then the space out tube 103 and pump 53 may be pulled free of the tailpipe assembly and can be moved up the hole, as shown in
Claims
1. A method of abandoning a well, said well comprising at least two concentric conduits defining a main bore and at least one annular chamber there between, comprising the steps of:
- providing a perforation in one or more of the conduits,
- pumping out the fluid from the annular chamber and/or main bore to create a fluid-free void,
- inserting sealing material in the annular chamber and/or main bore to seal it/them.
2. A method according to claim 1 wherein sealing material is inserted into the bore of the innermost conduit to seal it.
3. A method according to claim 1 wherein a tube is introduced and the fluid pumped to the surface through the tube.
4. A method according to claim 1 wherein the fluid is pumped downwards into the well.
5. A method according to claim 1 wherein the sealing material is inserted in the annular chamber before the fluid from the annular chamber is pumped out.
6. A method according to claim 1 wherein perforations are formed in at least one conduit and the annular chamber or chambers are sealed at one level in the well, and then further perforations are formed in a greater number of conduits at a second higher level in the well.
7. A method according to claim 6 wherein after forming the further perforations in the greater number of conduits at the second higher level, the annular chambers between these conduits are sealed.
8. An apparatus for abandoning a well having at least two concentric conduits defining at least one annular chamber there between, the apparatus including a pump and a perforation forming device.
9. An apparatus according to claim 8 wherein there is also provided a valve unit capable of securing itself in an innermost conduit and including a check valve to permit the one-way flow of fluids.
10. An apparatus according to claim 8 wherein the pump and the valve unit are separable.
11. An apparatus according to claim 8 wherein there is provided a cable on which the pump may be lowered into the well.
12. An apparatus according to claim 8 wherein the perforation forming device is incorporated into the pump.
13. An apparatus according to claim 8 wherein the perforation forming device is incorporated into the valve unit.
14. An apparatus according to claim 8 wherein the cable includes a through bore.
15. (canceled)
Type: Application
Filed: Oct 22, 2004
Publication Date: Jul 19, 2007
Inventor: Philip Head (West Drayton)
Application Number: 10/576,799
International Classification: E21B 33/035 (20060101);