Well intervention method using a chemical barrier
A well treatment fluid containing borated galactomannan may be used to isolate a pre-determined productive zone in an oil or gas well. The fluid is pumped into the well in a substantially non-hydrated form and forms a temporary seal. The fluid may be used as a chemical packer in place of a mechanical packer. After the pre-determined productive zone is isolated, a well intervention operation may be performed within the isolated pre-determined zone.
1. A method for performing an intervention operation in a defined zone within an oil or gas well with a temporary chemical packer and in the absence of a mechanical packer, the method comprising:
(a) isolating a pre-determined productive zone within the well by introducing into an annulus of the well a fluid comprising an unhydrated borated galactomannan gum and a crosslinking agent and then hardening the fluid to form the temporary chemical packer; and
(b) performing the intervention operation within the isolated pre-determined zone.
2. The method of claim 1 , further comprising:
(c) reducing the viscosity of the temporary chemical packer; and
(d) removing the temporary chemical packer from the wellbore.
3. The method of claim 2 , further comprising repeating steps (a) and (b) in a second pre-determined productive zone.
4. The method of claim 1 , wherein the fluid is introduced into the annulus between casing and a tubing or screen and further wherein the gelled temporary seal is formed between the casing and the tubing or screen.
5. The method of claim 1 , wherein the well is open hole and further wherein the gelled temporary seal is formed between a tubing or screen within the well and the wellbore.
6. The method of claim 1 , wherein the intervention operation comprises a pumping operation, a milling operation, a jarring operation, a mechanical vibration operation, a drilling operation and/or a perforating operation.
7. The method of claim 1 wherein the intervention operation is one or more of the following:
(a) a well cleanout operation;
(b) a well testing operation;
(c) a formation testing operation;
(d) a stimulation operation;
(e) a fluid shutoff operation;
(f) a fluid control device adjustment; or
(g) a sensor repair or replacement operation.
8. The method of claim 7 , wherein the stimulation operation is one or more of the following:
(a) a perforating operation;
(b) a fracturing operation;
(c) an acidizing operation; or
(d) a wellbore cleanout operation.
9. The method of claim 1 , wherein the annulus contains tubing having disposed therein a zonal isolation assembly and further wherein the intervention operation is performed in the isolated pre-determined zone within the zonal isolation assembly.
10. A method for performing an intervention operation within an oil or gas well without a mechanical packer, the method comprising:
(a) introducing into an annulus of the well a fluid comprising unhydrated borated galactomannan gum and a crosslinking agent, wherein the unhydrated galactomannan gum, prior to being crosslinked, contains borate ions;
(b) forming a gelled temporary seal within the annulus by reacting the borated galactomannan gum and the crosslinking agent;
(c) isolating a zone in the annulus with the gelled temporary seal; and
(d) performing the intervention operation within the isolated zone.
11. The method of claim 10 , wherein the well is a horizontal well.
12. The method of claim 10 , wherein the annulus is encased within a cement sheath and further wherein the gelled temporary seal is formed between the cement sheath and a tubing or screen within the annulus.
13. The method of claim 10 , wherein the well is open hole and further wherein the gelled temporary seal is formed between a tubing or screen within the annulus and the wellbore.
14. The method of claim 10 , wherein the intervention operation is one or more of the following:
(a) a well cleanout operation;
(b) a well testing operation;
(c) a formation testing operation;
(d) a stimulation operation;
(e) a fluid shutoff operation;
(f) a fluid control device adjustment; or
(g) a sensor repair or replacement operation.
15. A method of treating an oil or gas well which comprises:
(a) introducing into an annulus within the well a fluid comprising an unhydrated borated galactomannan gum and a crosslinking agent;
(b) reacting the borated galactomannan gum and the crosslinking agent; and
(c) forming a gelled temporary seal in the annulus wherein the annulus is void of a mechanical packer.
16. The method of claim 15 , wherein the fluid is introduced into the annulus between casing and a tubing or screen within the annulus and further wherein the gelled temporary seal is formed between the casing and the tubing or screen.
17. The method of claim 15 , wherein the well is open hole and further wherein the gelled temporary seal is formed between a tubing or screen within the annulus and the wellbore.
18. The method of claim 15 , wherein the well is a horizontal well.
19. The method of claim 15 , wherein the well is a vertical well.
20. The method of claim 15 , wherein the subterranean formation is sandstone, carbonate or shale.