INJECTION DEVICE FOR INJECTING FLUID INTO A WELL BORE

BACKGROUND OF THE INVENTION

[0001] The present invention relates to hydrocarbon recovery and, in particular, to an injection device for injecting steam into a well bore.

[0002] It is well known to inject pressurized steam into an oil reservoir to displace and recover viscous hydrocarbons deposited therein. Continuous steam injection is used to stimulate production of a plurality of wells and cyclic steam injection is used to stimulate production of an individual well. In continuous steam injection, steam is continuously injected into a reservoir through designated injection wells. The steam reduces the viscosity of heavy oil in the reservoir and hot water which condenses from the steam sweeps the oil towards producing wells. Cyclic steam injection is a three stage process. The first stage involves the injection of steam into a well bore. The second stage involves shutting in the well bore, for a specified period of time, to allow the steam to soak in and reduce the viscosity of heavy oil in the reservoir. The third phase involves putting the well into production. The cycle is then repeated as long as production remains profitable.

[0003] Steam may be generated at the surface and injected into the reservoir through a pipe which extends down a well bore as disclosed in United States Patent Number 4,398,604 to Krajicek et al. However, this method of steam injection is limited because the steam loses heat and condenses as it travels the down the pipe. To overcome this problem, devices for generating steam within a well bore have been developed. For example, United States Patent Number 4,397,356 to Retallick discloses a downhole catalytic combustor for generating a mixture of steam and combustion gas within a well bore so that the gas mixture may be injected directly into the reservoir. However, the use and efficiency of downhole combustors are limited by the dimensions of the well bore. There is also a risk that downhole combustion may light the reservoir on fire.

SUMMARY OF THE INVENTION

[0004] It is an object of the present invention to provide an improved injection device for injecting steam into a well bore.

[0005] According to a first aspect of the invention there is provided an injection device for injecting fluid into a well bore. The injection device comprises a first conduit for carrying a first fluid from above ground into the well bore. The first conduit has a release valve for allowing communication between the first conduit and the well bore. A second conduit for carrying a second fluid from above ground into the well bore is disposed within the first conduit. The first conduit and the second conduit function as heat exchanger in the well bore to heat the first fluid contained in the first conduit prior to injection of the first fluid into the well bore.

[0006] According to a second aspect of the invention there is provided an injection device for injecting fluid into a well bore. The injection device comprises a first conduit for carrying a first fluid from above ground into the well bore. The first conduit has a release valve for allowing communication between the first conduit and the well bore. A second conduit for carrying a second fluid from above ground into the well bore is disposed within the first conduit. The second conduit has a release valve for allowing communication between the second conduit and the well bore, a first exhaust valve for allowing communication between the second conduit and the first conduit, and a second exhaust valve for allowing communication between the second conduit and an environment. An inflatable bladder seals the first conduit to the well bore. The inflatable bladder is disposed about the first conduit. The first conduit and the second conduit function as heat exchanger in the well bore to heat the first fluid contained in the first conduit prior to injection of the first fluid into the well bore.

[0007] According to a third aspect of the invention there is provide a method of injecting fluid into a well bore. The method comprising the steps of discharging a first fluid from above ground into a first conduit which extends into the well bore, the first conduit having a release valve for allowing communication between the first conduit and the well bore; discharging a second fluid from above ground into a second conduit which is disposed in the first conduit; using the first conduit and the second conduit as a heat exchanger to heat the first fluid contained in the first conduit; and actuating the release valve to inject the first fluid into the well bore.

BRIEF DESCRIPTION OF THE DRAWING

[0008] Referring to the drawings:

[0009] Figure 1 is a front perspective view, partially in section, showing an injection device according to the present invention being used in continuous steam injection;

[0010] Figure 2 is a front perspective view, partially in section, showing an injection device according to the present invention being used in cyclic steam injection;

[0011] Figure 3 is a front, fragmentary, perspective view, partially in section, showing an injection device according to the present invention;

[0012] Figure 4 is a front, fragmentary, perspective view, partially in section, showing the injection device of Figure 3 being lowered into a well bore;

[0013] Figure 5 is a front, fragmentary, perspective view, partially in section, showing the injection device of Figure 3 operating in a first mode;

[0014] Figure 6 is a front, fragmentary, perspective view, partially in section, showing the injection device of Figure 3 operating in a second mode; and

[0015] Figure 7 is a front, fragmentary, perspective view, partially in section, showing the injection device of Figure 3 operating in a third mode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0016] Referring to the drawings and first to Figure 1 , there is shown an injection device 10 for injecting heated fluid, typically in the form of steam, superheated water, or both, into a reservoir 12 through a well bore 14. The injection device 10 generally comprises a first conduit 16, a second conduit 18, and an inflatable bladder 20. The first conduit 16 is for carrying a first fluid from the ground surface 13 into the well bore 14. The second conduit 18 is disposed within the first conduit 16. The second conduit 18 is for carrying a second fluid from the ground surface 13 into the well bore 14. The inflatable bladder 20 is disposed about the first conduit 16. The inflatable bladder 20 is for sealing the well bore 14. Sealing the well bore 14 prevents the heated fluid from escaping and reduces the volume of the well bore 14 being heated.

[0017] In operation, the device 10 is connected to a first fluid supply 22 and a second fluid supply 24. The first fluid supply 22 supplies the first fluid to the first conduit 16. The second fluid supply 24 supplies the second fluid to the second conduit 18. In this example, the first fluid is water and the first fluid supply is a water reservoir. The second fluid is a combustion gas and the second fluid supply 24 is a combustion chamber.

[0018] As shown in Figure 1, the injection device 10 may be used in continuous steam injection to stimulate production of adjacent well bores 26 and 28. In continuous steam injection, steam is continuously injected into the reservoir 12 through the well bore 14. The

steam reduces the viscosity of heavy oil in the reservoir 12 and hot water which condenses from the steam sweeps the oil toward producing well bores 26 and 28 as indicated by arrows 32.1, 32.2, 32.3 and 32.4.

[0019] As shown in Figure 2, the injection device 10 may also be used in cyclic steam injection to stimulate production of the well bore 14. Cyclic steam injection is a three stage process. The first stage involves the injection of steam into the reservoir 12 through the well bore 14 as indicated by arrows 34.1 and 34.2. The second stage involves shutting in the well bore 14, for a specified period of time, to allow the steam to soak in and reduce the viscosity of heavy oil in the reservoir 12. In this example, the well bore is shut in by sealing the well bore 14 with the inflatable bladder 20. The third phase involves putting the well bore 14 into production. The cycle is repeated as long as production remains profitable.

[0020] The injection device 10 may further be used to remove contaminants in a well bore using heat and pressure. For example, the injection device 10 may be used in lieu of hot-oiling for reducing build-up from paraffin hydrocarbons. The injection device 10 may also be used in gas-lifting.

[0021] Referring now to Figure 3, the injection device 10 is shown in greater detail. In this example, the first conduit 16 is tubular and closed at a first end 36 thereof by a plug 38. The plug 38 is threadedly connected to the first end 36 of the first conduit 16. An o-ring 40 seals the first conduit 16 against the plug 38. The first conduit 16 may be filled with water from the reservoir 22, shown in Figures 1 and 2, at a second end 42 thereof to form a water plenum. There may be a valve (not shown) at the second end 42 of the first conduit 16 to restrict the flow of water into the first conduit 16. There are release valves, in the form of check valves

44 and 46, in the plug 38. The check valves 44 and 46 allow for communication between the first conduit 16 and the well bore 14, shown in Figures 1 and 2, when the injection device 10 is in use. Although in this example the first conduit 16 and the plug 38 are separate components, in other embodiments the first conduit may be unitary and closed at the first end.

[0022] The second conduit 18 is Y-shaped and is disposed within the first conduit 16. The second conduit 18 has a first end 48 which is substantially co-terminus with the first end 36 of the first conduit 16. The first end 48 of the second conduit 18 extends through an opening 50 in the plug 38 and is threadedly connected thereto. An o-ring 52 seals the second conduit

18 against the plug 38. The second conduit 18 also has second and third ends, 56 and 57 respectively, which are substantially co-terminus with the second end 42 of first conduit 16. Combustion gas from the combustion chamber 24, shown in Figures 1 and 2, may be discharged into the second conduit 18 at the second end 56 thereof. There may be a valve (not shown) at the second end 56 of the second conduit 18 to restrict the flow of combustion gas into the second conduit 18. The combustion gas may circulate through the second conduit 18 allowing the second conduit 18 and first conduit 16 to function as a heat exchanger to heat water contained in the first conduit 16. Although, in this example, the second conduit 18 is Y-shaped, in other embodiments the second conduit may be coiled to allow for increased surface area and heat exchange.

[0023] The second conduit 18 comprises a release valve, in the form of a first check valve 54, at the first end 48 thereof. The first check valve 54 allows for communication between the first conduit 16 and the well bore 14, shown in Figures 1 and 2, when the injection device 10 is in use. The second conduit 18 also comprises exhaust valves, in the form of second and third check valves 58 and 60 respectively. The second and third check valves 58 and 60 restrict release of combustion gas from the second conduit 18 to the ground surface 13. The second check valve 58 allows for communication between the second conduit 18 and the first conduit 16. The third check valve 60 restricts the flow of combustion gas to the third end 57 of the second conduit 18.

[0024] Referring now to Figure 4, in operation the injection device 10 is lowered into the well bore 14 with inflatable bladder 20 deflated. The inflatable bladder 20 is controlled by a fluid source (not shown) located at the surface. Fluid used to inflate the bladder 20 is pumped

from the surface to the bladder 20 via a conduit 21. When the injection device 10 is in a desired position, the bladder 20 is inflated and the first conduit 16 is sealed against a casing 62 in the well bore 14. The well bore 14 is thereby sealed to prevent fluids discharged from injection device 10 from escaping. When the well bore 14 is sealed the injection device 10 is actuated to injection fluid into the well bore 14.

[0025] In a first mode of operation, shown in Figure 5, combustion gas is circulated through the second conduit 18 as indicated by arrows 64.1 , 64.2 and 64.3. The combustion gas enters the second conduit 18 at the second end 56 thereof. The combustion gas then flows through the second conduit 18, though the third check valve 60, and to the third end 57 of the second conduit 18 where the combustion gas may be collected or released into the environment. The circulating combustion gas heats the water contained in the first conduit 16. When sufficient pressure is built up in the first conduit 16, the checks valves 44 and 46 in the plug 38 are actuated and steam, superheated water, or both are discharged into the well bore 14 as indicated by arrows 66.1 and 66.2.

[0026] In a second mode of operation, shown in Figure 6, combustion gas is circulated through the second conduit 18 as indicated by arrows 64.1 and 64.2. The combustion gas enters the second conduit 18 at the second end 56 thereof. The combustion gas then flows through the second conduit 18 but is prevented from flowing out the third end 57 thereof by the third check valve 60. Instead combustion gas is released into the first conduit 16 through the second check valve 58 as indicated by arrow 63. The combustion gas heats the water in the first conduit 16. When sufficient pressure is built up in the first conduit 16, the check valves 44 and 46 in the plug 38 are actuated and steam, superheated water, or both are discharged into the well bore as indicated by arrows 66.1 and 66.2.

[0027] In a third mode of operation, shown in Figure 7, combustion gas is circulated through the second conduit 18 as indicated by arrows 64.1 and 64.2. The combustion gas enters the second conduit 18 at the second end 56 thereof. The combustion gas then flows

through the second conduit 18 but is prevented from flowing out the third end 57 thereof by the third check valve 60. The circulating combustion gas heats the water in the first conduit 16. When sufficient pressure is built up in the first conduit 16, the check valves 44 and 46 in the plug 38 are actuated and steam, superheated water, or both are discharged into the well bore as indicated by arrows 66.1 and 66.2. Combustion gas may also be discharged into the well bore 14 through the second check valve 54 of the second conduit 18 as indicated by arrow 65.

[0028] It will be understood by a person skilled in the art that the mode in which the injection device operates is dependent on the release pressures of the individual check valves and the pressures in the first and second conduits. It will further be understood by a person skilled in the art that the above-described modes may also operate in concert. For example, combustion gas may be simultaneously by any combination the first, second and third check valves of the second conduit.

[0029] It will be understood by someone skilled in the art that many of the details provided above are by way of example only and are not intended to limit the scope of the invention which is to be determined with reference to the following claims.