Nozzle for steam injection

1. A steam injection nozzle for a pipe, the nozzle having:

an inlet and an outlet and a passage extending from the inlet to the outlet, the inlet having a circular shape, the passage comprising:

a pressure dissipation section downstream of the inlet, the pressure dissipation section comprising:

a convergence zone downstream of the inlet, the convergence zone comprising a region of reducing cross-sectional area;

a first divergence zone adjacent to and immediately downstream of the convergence zone, the first divergence zone comprising a region of increasing cross-sectional area; and,

a first region, adjacent to and immediately downstream of the first divergence zone, comprising a region of generally constant cross-sectional area; and,

a pressure recovery section adjacent to and immediately downstream of the pressure dissipation section and upstream of the outlet, the pressure recovery section comprising:

a second divergence zone, comprising a region of increasing cross-sectional area.

2. The steam injection nozzle of claim 1 , wherein the convergence zone comprises a curved and narrowing passage wall.

3. The steam injection nozzle of claim 1 , wherein the first divergence zone comprises a curved and expanding passage wall.

4. Steam injection nozzle of claim 1 , wherein the second divergence zone comprises an expanding conical passage wall.

5. The steam injection nozzle of claim 1 , wherein the second divergence zone comprises a curved and expanding passage wall.

6. The steam injection nozzle of claim 1 , wherein the passage has a generally circular cross-section.

7. An apparatus for injection of steam into a subterranean reservoir, the apparatus comprising:

a base pipe for communicating fluids from the surface to the subterranean reservoir, the base pipe having at least one port extending through the wall thereof, the port being adapted to permit passage of steam from the base pipe into the reservoir;

a nozzle provided on or adjacent to the port and being retained against the base pipe;

the nozzle comprising:

an inlet and an outlet and a passage extending from the inlet to the outlet, the passage having:

a pressure dissipation section downstream of the inlet, the pressure dissipation section comprising:

a first convergence zone downstream of the inlet, the first convergence zone comprising a region of reducing cross-sectional area;

a first divergence zone downstream of the first convergence zone, the first divergence zone comprising a region of increasing cross-sectional area; and,

a first region, downstream of the first divergence zone, comprising a region of generally constant cross-sectional area; and,

a pressure recovery section downstream of the pressure dissipation section and upstream of the outlet, the pressure recovery section comprising:

a second divergence zone, comprising a region of increasing cross-sectional area.

8. The apparatus of claim 7 , wherein the pressure recovery section further comprises:

a second convergence zone downstream of the pressure dissipation zone and upstream of the second divergence zone, the second convergence zone comprising a region of reducing cross-sectional area.

9. The apparatus of claim 8 , wherein the pressure recovery section further comprises:

a second region, downstream of the second convergence zone and upstream of the second divergence zone, comprising a region of generally constant cross-sectional area.

10. The apparatus of claim 7 , wherein the first convergence zone comprises a curved and narrowing passage wall.

11. The apparatus of claim 7 , wherein the first divergence zone comprises a curved and expanding passage wall.

12. The apparatus of claim 7 , wherein the second convergence zone comprises a narrowing conical passage wall.

13. The apparatus of claim 7 , wherein the second divergence zone comprises an expanding conical passage wall.

14. The apparatus of claim 7 , wherein the second divergence zone comprises a curved and expanding passage wall.

15. The apparatus of claim 7 , wherein the passageway passage has a generally circular cross-section.

16. A method of injecting steam into a subterranean reservoir, the method comprising:

injecting steam from the surface into the reservoir through a base pipe, the base pipe having at least one port extending through the wall thereof and a nozzle associated with the port, wherein the steam is passed from the port through an inlet of the nozzle and through an outlet of the nozzle and into the reservoir;

wherein, during passage through the nozzle the injected steam is:

(a) subjected to a pressure dissipation downstream of the inlet, the pressure dissipation involving:

passing the steam through a first convergence zone downstream of the inlet, the first convergence zone comprising a region of reducing cross-sectional area;

passing the steam through a first divergence zone downstream of the first convergence zone, the first divergence zone comprising a region of increasing cross-sectional area; and,

passing the steam through a first region, downstream of the first divergence zone, comprising a region of generally constant cross-sectional area; and,

(b) subjected to a pressure recovery after the pressure dissipation, the pressure recovery comprising:

passing the steam through a second divergence zone, comprising a region of increasing cross-sectional area.

17. The method of claim 16 , wherein step (b) further comprises:

passing the steam through a second convergence zone downstream of the first region and upstream of the second divergence zone, the second convergence zone comprising a region of reducing cross-sectional area.

18. The method of claim 17 , wherein step (b) further comprises:

passing the steam through a second region, downstream of the second convergence zone and upstream of the second divergence zone, comprising a region of generally constant cross-sectional area.