Method and Apparatus for Producing Thermal Vapor Stream

This invention relates generally to hot fluid generators and in particular to steam generators for the recovery of liquefiable minerals from subterranean formations.

Apparatus for the sucessful recovery of minerals using a high pressure thermal vapor stream typically involves the production of hot combustion gases for flow into a steam generating device for producing sufficient quantities of high pressure thermal vapor of steam and combustion gases which are injected into the subsurface formation for economical recovery of highly viscous petroleum therefrom. Examples of some such apparatus are described in the following U.S. Pat. Nos. to name a few: 3,980,137; 3,620,571; 2,916,877; 2,839,141; 2,793,497; 2,823,752; 2,734,578; 2,754,098; and Mexican Pat. Nos. 105,472 and 106,801. Certain very viscous hydrocarbon deposits need large amounts of heat applied thereto to reduce the viscosity to make possible recovery. Because of the very large amounts of heat that are generated and required, difficulties arise in protecting the combustion chambers of thermal vapor generators from overheating while still having the capability of providing sufficient heat of formation to effect oil recovery.

This invention is a new and improved version of generators of steam for injection into an oil well or the like and includes a pressure vessel having a combustion chamber housing mounted therein. A heating gas injector is mounted onto the combustion housing for directing heating gas produced in the combustion chamber into water to produce steam and combusted products. The pressure vessel and combustion chamber housing cooperate to provide combustion chamber cooling means for directing the steam and combusted products along the outside of the combustion chamber housing to simultaneously partly cool the combustion chamber and further heat the steam prior to injection into a subterranean formation.

FIG. 1 is an elevational view of the thermal vapor unit of the preferred embodiment of this invention;

FIGS. 2a and 2b represent a cross-sectional view of the apparatus of FIG. 1 taken along line 1--1 of FIG. 3;

FIG. 3 is a top view of the apparatus taken along line 3--3 in FIG. 1;

FIG. 4 is a cross-sectional view taken along line 4--4 in FIG. 2b;

FIG. 5 is a broken cross-sectional view illustrating the secondary air entry port;

FIG. 6 is broken cross-sectional view illustrating the igniter entry point into the combustion chamber;

FIG. 7 is a broken cross-sectional view of the view port entry means;

FIG. 8 is a cross-section of a pressure vessel with the combustion chamber removed illustrating a first set of annular baffles; and,

FIG. 9 is a view comparable to FIG. 8 illustrating a second set of annular baffles.

Referring now to the drawings, in FIG. 1 the letter U generally designates the new and improved high pressure thermal vapor unit of the preferred embodiment of this invention. The thermal vapor unit U includes an outer pressure vessel P which is made of suitable steel for withstanding the high temperature and pressure resulting from the operation of the apparatus. A combustion chamber C is mounted within the pressure vessel P; and a heating or hot gas injection means H is connected with the combustion chamber. A steam generation unit S of the vessel P surrounds the hot gas injection means H with a water supply. Heating gas produced in the combustion chamber C is directed through the hot gas injection means H and outwardly into the water in the steam generation unit S, which produces steam and combustion products gas. The steam and combustion products flows through combustion chamber cooling means M to simultaneously partly cool the combustion chamber C and receive further heat prior to flow of the additionally heated steam and combustion products gas outwardly of the pressure vessel P for use.

The pressure vessel P includes a bottom, dome shaped section 10a, a central cylindrical section 10b and a top end section 10c. A typical base support assembly 2a is provided for supporting the thermal vapor unit U on a trailer or other platform. Numerous conventional flange connections are attached to the pressure vessel P for connecting various components for the operation. Referring to FIGS. 1 and 2b, steam drum blowdown flanges, outlets 1a and 1b are shown.

Two level control flange outlets 11 and 12 are mounted in the pressure vessel section 10b. The level controller mounted on flanges 11 and 12, operate a water inlet valve to control the water level in the steam generation unit section S. An inlet supply flange connector 13 is mounted in vessel section 10b for connection with tubing which supplies the water which may be chemically treated to facilitate evaporation in the pressure vessel P. Such chemical treatment of water for pressure vessels is well-known in the art. A drum vent flange connector 14 is mounted in vessel section 10b for connection with suitable tubing and valves to allow venting of the steam generation unit.

Referring to FIG. 1, inspection port flange connectors 15, 16 and 17 are provided for connection with suitable viewing equipment and/or for physical access to the inside of the pressure vessel for repair and/or inspection.

The pressure vessel P further includes a flange connector 18 mounted in vessel section 10b for connection to suitable tubing for conducting high pressure combustion gases and steam (as explained more fully hereinafter) from the apparatus to a well being treated.

Pressure vessel top section 10c terminates with an annular flange 21 which is secured to the top section by suitable means such as by welding. Circular end closure plate 22 is mounted onto the top 10c of the vessel by connection to flange connector 21 by suitable means, such as bolts, with seal 23 preventing any leakage of the high temperature and pressure combustion gases and steam. The end closure plate 22 supports the combustion chamber C in the vessel.

Referring now to FIGS. 2a and 2b of the drawings, the high pressure combustion chamber C preferably includes a substantially cylindrical pressure housing or casing 30, which is welded to end plate 22 at the top. The lower end of the pressure casing 30 terminates in converging section 30a, cylindrical section 30b and annular flange 30c. The flange 30c is connected to a flange 30d of the injection means H by suitable means, such as by bolts with a seal 32 to prevent escape of the gases at the connection.

The inner surfaces of the combustion chamber casing 30 are lined with a refractory material which forms a plurality of combustion zones I-IV. Combustion chamber casing 30 and the inner surfaces of sections 30a and 30b are lined with a continuous inner liner 31 of refractory material which forms the combustion zones I-IV. The continuous inner liner 31 of refractory material has portions of varying cross-sectional thicknesses for forming sections of varying inner diameters. The refractory material liner 31 includes a first cylindrical section 31a having a first inner diameter; the refractory liner section 31a extends longitudinally downwardly from the end member 22 a predetermined distance to form a first combustion zone I. Continuous with the first section is a second cylindrical section 31b having a relatively smaller cross-sectional wall thickness and hence a second, larger inner diameter extending longitudinally from the first section a predetermined distance within the pressure casing 30 to form a second combustion zone II. A third section 31c is integrally formed with lower section 31b and has an even larger inner diameter and extends longitudinally from section 31b to form a third combustion zone III. Casing sections 30a and 30b are also lined with cylindrical refractory material having the same internal diameter as in zone III. A fourth zone IV having a smaller inside diameter than zone III is formed by the hot gas injection means H.

The inside diameter and the longitudinal length of the combustion zones I-IV are related in that their values determine the volume of each combustion zone which effects the controlled expansion providing the desired turbulence and mixing of the fuel and air injected into the chamber. Such a combustion chamber is more fully described in U.S. Patent application entitled "COMBUSTION CHAMBER AND THERMAL VAPOR STEAM PRODUCING APPARATUS AND METHOD", Ser. No. 771,558, filed on Feb. 24, 1977.

Referring to the upper portion of FIG. 2A, mounted with the end member 22 is a tubular member 35 communicating with an opening 22a in the end closure member 22. Flange connector 36 is secured with the tubular member 35 and is adapted to be secured by suitable bolts with a closure flange member 37. A fuel supply line 38 having a nozzle 38a is mounted with the closure flange member 37 so as to position the nozzle 38a in combustion zone I. The fuel supply line is connected with a suitable fuel supply (not shown) for supplying fuel to the combustion chamber by injecting it in a spray form through nozzle 38a.

A first air supply line 39 is connected to the tubular member 35 for connection to an air supply (not shown) for delivery of air to combustion zone I through end member opening 22a.

The combustion chamber C includes a second or secondary air stream injection means 40 which includes a plurality of passages 41 extending through a top portion 31e of the refractory material on the end closure member 22. Passages 41 are preferably eight in number and are circumferentially spaced about the nozzle 38a. Each passage 41 is vertically inclined and radially directed downwardly from an annular space 42. Annular space 42 is defined by the inside surface of the casing 30. As best shown in FIG. 5, the end closure member 22 includes an opening 22b communicating with the annular space 42. A secondary air supply line 43 is also connected with the air supply source (not shown). The plurality of passages 41 are preferably cylindrical and substantially evenly spaced circumferentially relative to each other and extend from the annular space 42 through the refractory material so that the respective longitudinal axes of these passages 41 intersect at a point on the combustion chamber longitudinal axis (which runs through the center of tube 38) a short distance downstream from the nozzle 38a.

It is believed that the air passages 41 should be oriented so that they direct the secondary air at or near the point of initial combustion. The burning or initial ignition of the fuel air mixture is believed to cause a swirling out effect with some unburned fuel at the exterior of the swirl. Accordingly, the secondary air is for mixing with any such unburned fuel to further facilitate combustion. The above description of the results of the preferred orientation of the secondary air supply passages is not based on known scientific theory. Whatever may be the reasons behind the obtaining of the substantially complete combustion which is obtained from the apparatus, it nevertheless occurs; there is no intent to limit the results and benefits obtained as based solely on the above description of operation or theory.

An electrical ignition assembly (not shown) is mountable in entry flange assembly generally designated as 45 illustrated in FIG. 6. A flange 46 is connected with a passage 47 which extends through the end closure member 22 and refractory material. A conventional ignition assembly (not shown) may be mounted with the flange 46 for extending through the passageway 47 into the first zone I of the combustion chamber for providing ignition to the hydrocarbon fuel. The ignition assembly may be a reciprocal longitudinally sliding ram which has a conventional electrical spark producing means positioned at one end. In operation, such a ram is longitudinally moved through the passage 47 to position the spark means adjacent the fuel injection nozzle 38a. The hydrocarbon fuel and pressurized air streams from a suitable compressor (not shown) are then supplied to the combustion zone I and an electrical spark is generated to ignite the fuel. After ignition, the longitudinal ram is pulled back into the passage for protection from the heat generated in the combustion zone I.

Returning to FIG. 7, a view port entry assembly 50 is connected with the end closure member 22 to communicate with passage 51 to provide a view port into the combustion chamber. A suitable sight glass (not shown) may be attached to the flange assembly 50 for viewing into the combustion chamber as is known in the art.

As best shown in FIGS. 1 and 3, a flange assembly 52 is mounted on closure 22 over a passageway extending through an opening in the closure member 22, connecting to the annular space between the pressure casing 30, and the pressure vessel top section 10 to allow mounting of a relief valve upon the flange connector 52. Accordingly, should excess pressure build up inside the combustion chamber, the relief valve would activate to protect the apparatus from excess pressure.

The hot gas injection means H shown in FIG. 2b passes hot gases from the combustion chamber C to the steam generating portion S of the pressure vessel P for injecting the gases into a water bath or supply in the vessel 10. The longitudinal axis of the hot gas injection means H coincides with the longitudinal axes of the generally concentric vessel cylindrical section 10b and chamber casing 30. The hot gas injection means H includes a tubular housing member or section 60 which is lined with refractory material 61 so that the inside diameter of the refractory material is defined by cylindrical surface 61a. The refractory material 61 terminates at its upper end in an enlarged portion 61b which fits over and is supported on flange 30d. The internal surface of enlarged refractory material portion 61b forms zone IV of the combustion chamber C. A plurality of rows of radial openings 62 extends through the tubular member 60 and refractory material 61. There are preferably seven vertical rows of openings extending around the tubular member 60, which lies upon the same longitudinal axis as the pressure vessel section 10b and chamber casing 30. The lower end 63 of the tubular member 60 is open to allow for flow of combustion gases therethrough so as to strike impingement plate 64. The impingement plate 64 is spaced below opening 63 and is mounted on the inside of vessel bottom 10a by suitable supports 64a. The distance between adjacent rows of openings 62 increases from bottom to top of tubular member 60. The heating gases flowing through the injection tubular member 60 are caused to pass through the openings 62 into steam generator S which includes water therein for generating steam. A large portion of the gases will be directed through the opening 63 at the lower end of the injection tube member 60.

The steam generator unit S is formed in the lower part of the main cylindrical vessel section 10b and in the dome-shaped bottom 10a. The steam generator unit S includes a chamber which is formed by the lower portion of the main pressure vessel cylindrical housing 10b and the dome-shaped bottom 10a to hold water. The level of the water is typically slightly above or below the top row of radial openings 62 of the heating gas injection means H. A baffle assembly generally designated by the number 70 is mounted onto the interior wall of the main vessel section 10b in order to substantially consume the annular space formed between the main vessel section wall 10b and the tubular member 60 of the heating gas injection means H. The baffle assembly 70 includes two vertically spaced baffle units 71 and 72, which are identical except for vertical positioning. Each baffle unit 71 and 72 includes a mounting ring such as 71a which is welded onto the interior wall of the main vessel section 10b and further includes an annular baffle plate 71b which is bolted to the mounting ring 71a. The baffle plate 71b includes an inner set of openings 71c and an outer set of openings 71d, each set of openings being circumferentially spaced about the annular baffle plate 71b. Such a heating gas injection means H, steam generating unit S and baffle assembly 70 is discussed in some detail in U.S. Patent application Ser. No. 771,557, entitled "THERMAL VAPOR STREAM TEMPERATURE CONTROL APPARATUS AND METHOD", filed Feb. 24, 1977. The circumferentially positioned baffle openings or apertures 71c and 71d cause the break-up of the heating gases passing therethrough into smaller bubbles as the gas is passed through the opening so that the surface area of the combustion gas bubbles is greater, thereby increasing the efficiency of vaporization. Also, the baffles 71 and 72 act to retain the combustion gases in water longer than without the use of baffles.

A combustion cooling means generally designated by the number 80 is mounted about the combustion chamber housing 30 for passing the steam and combustion products rising upwardly from the water about the outside of the combustion chamber housing 30 for removing possibly damaging heat therefrom and simultaneously adding heat to the produced steam and combustion products prior to exit through vessel outlet 18. The combustion cooling means 80 includes an annular space or chamber 81 which is formed between the wall of the main vessel section 10b and the outside wall of the combustion chamber housing 30. The annular chamber 81 is in fluid communication with the steam and combustion products which rise upwardly out of the water of steam generating unit S. A plurality of vertically spaced baffles 82 are mounted by suitable means such as welding onto the inside wall of the pressure vessel section 10b. One set of baffles 82a is illustrated in FIG. 8 and a second set of baffles 82b is illustrated in FIG. 9. The baffles 82a and the baffles 82b are alternately spaced vertically within annular chamber 81 of the combustion cooling means 80. The baffles 82a include a slot 84 to allow for the flow of steam and combustion products upwardly therethrough. The baffles 82b include slot 85, which is positioned opposite from slot 84 on the outside of the housing 30 of the combustion chamber C for passing steam and combustion products upwardly therethrough. The slots 84 and 85 in the baffles 82a and 82b, respectively, are oriented 180 degrees apart from each other in order to uniformly circulate the steam and combustion products circumferentially about the exterior of the combustion chamber housing 30. In this manner, the entire outer combustion chamber housing surface or skin is contacted by the flow of steam and combustion products so as to transfer heat from the combustion chamber to the steam and hot gases to avoid hot spots in the combustion chamber that could otherwise result in failure. The flow of hot gases and steam over the surface of the combustion chamber cylindrical housing 30 also adds some heat to maintain the steam and hot gases in the super heat range which may be desirable for effectively treating of the well. An uppermost, inclined baffle 86 is positioned above the uppermost horizontally directed baffle 82a in order to assist in flowing the additionally heated gases outwardly through vessel outlet 18.

In the operation of the thermal vapor generating unit U of the present invention, a high pressure air (or other oxidizer, stream is combined with fuel exiting nozzle 38a such that initial combustion takes place in chamber I of the compression chamber C.

Prior to such fuel ignition, a flowing stream of water, which may be chemically treated as is well known in the boiler art, is passed through entry flange connector 13 so as to provide a desired water level in the steam generator unit S. The amount of water which is maintained in the steam generator unit S is empirically determined upon operations to provide the desired amount of steam necessary to treat a well or other subterranean formation. The depth of water in the steam generator unit S can be regulated to further help control the temperature of the hot gas and steam exiting pressure vessel outlet 18.

The combusted gases flow from combustion chamber zone I sucessively through zones II and III into zone IV and radially outwardly through openings 62 in the hot gas injection means H or outwardly through bottom opening 63 thereof. The heating gases percolate and bubble through the baffles 71 and 72 located below the water line within the steam generator unit S. The passing of the heating gases through the baffles 71 and 72 generate steam or water vapor. The steam and combustion products rise upwardly into the annular space 81 of the combustion cooling means M and flow countercurrently upwardly in almost a helical flow pattern about the outside of the combustion chamber housing 30, such helical flow pattern being caused by the oppositely positioned slots 84 and 85 in adjacently vertically positioned baffles 82a and 82b, respectively. As the steam and combustion products flow upwardly through the annular space 81, heat from the combustion chamber C is transferred into the steam and heating gases thereby relieving some of the heat which might otherwise be damaging to the combustion chamber C and adding such heat to the steam and combustion products.

The foregoing disclosure and description of the invention are illustrative and explanatory thereof, and various changes in the size, shape, and materials as well as in the details of the illustrated construction may be made without departing from the spirit and scope of the invention.