Consumable downhole packer or plug

1. A packer or plug for use in a wellbore, comprising: a tubular mandrel made from a composite material comprising a pyrotechnic composition; an expandable seal disposed on an outer surface of the mandrel; and an igniter operable to initiate combustion of the mandrel, wherein the igniter includes a charge and a trigger, the trigger operable to expose the charge to wellbore fluid.

2. The packer or plug of claim 1 , wherein the composite material further comprises a polymer matrix and fiber.

3. The packer or plug of claim 2 , wherein the polymer matrix is infused with the pyrotechnic composition.

4. The packer or plug of claim 2 , wherein the fiber is a continuous bundle.

5. The packer or plug of claim 4 , wherein a fiber of the bundle is made from the pyrotechnic composition.

6. The packer or plug of claim 2 , wherein at least a portion of the fiber is made from the pyrotechnic composition.

7. The packer or plug of claim 1 , wherein the pyrotechnic composition is thermite or thermate.

8. The packer or plug of claim 1 , further comprising a set of slips and a slip cone disposed on an outer surface of the mandrel.

9. The packer or plug of claim 1 , wherein the charge is a pyrogen charge; and the trigger is operable to arm in response to a downhole event and expose the pyrogen charge to wellbore fluid after a predetermined time delay.

10. The packer or plug of claim 9 , wherein the pyrogen charge is water-reactive.

11. The packer or plug of claim 9 , wherein the trigger comprises:

a pressure port;

a pressure relief device closing the pressure port;

a plunger disposed in the pressure port;

a solvent vial disposed in the pressure port; and

a solute plug or disk located adjacent the solvent vial.

12. A bottomhole assembly (BHA), comprising:

the packer or plug of claim 9 ;

a setting tool releasably fastened to the packer or plug; and

a perforation gun connected to the setting tool.

13. The packer or plug of claim 9 , wherein the trigger comprises:

a timer power supply;

a first switch;

a second switch;

an ignition power supply; and

an ignition valve.

14. The packer or plug of claim 13 , wherein the first switch is operable to close in response to the downhole event.

15. The packer or plug of claim 14 , wherein the first switch is operable to supply electricity from the timer power supply to the second switch.

16. The packer or plug of claim 14 , wherein the downhole event is a ball landing in a ball seat.

17. The packer or plug of claim 13 , wherein the ignition valve is operable to open and expose the igniter to wellbore fluid.

18. The packer or plug of claim 17 , wherein the second switch is operable to supply electricity from the ignition power supply to open the ignition valve.

19. The packer or plug of claim 13 , wherein the ignition valve is configured to fail to a closed position, isolating the igniter from wellbore fluid.

20. A method for fracturing a production zone in a formation, comprising:

deploying the BHA of claim 12 into the wellbore to a depth below the production zone, wherein the packer or plug is a frac plug;

operating the setting tool to set the frac plug;

releasing the set frac plug from the BHA;

raising the remaining BHA to a depth adjacent the production zone;

firing the perforation gun;

closing a bore of the mandrel;

retrieving the remaining BHA to surface; and

fracturing the perforated production zone,

wherein the downhole event is one of: releasing the set frac plug, closing the mandrel bore, and commencement of fracturing the perforated production zone.