Abstract:
An injector insert apparatus is provided. The injector insert apparatus includes a body that has an inner oil passage that is configured and arranged to allow oil to pass there through. The body further has an annular chamber formed around the inner oil passage. The annular chamber has a chamber opening that is configured to be coupled to receive a flow of thermal gas medium. The body also has at least one injector orifice that provides a passage between the annular chamber and the inner oil passage. The at least one injector orifice is configured to inject the thermal gas medium into oil passing through the inner oil passage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This Application claims priority to U.S. Provisional Application Ser. No. 61/761,629 titled Utilizing A Downhole Steam Generator System For Thermal Gas Lift, filed on Feb. 6, 2013, which is incorporated in its entirety herein by reference. 
     
    
     BACKGROUND  
       [0002]    Artificial lift techniques are used to increase the flow rate of oil out of a production well. One commercially available type of artificial lift is a gas lift. With a gas lift, compressed gas is injected into a well to increase the flow rate of the produced fluid by decreasing head losses associated with the weight of the column of fluids being produced. In particular, the injected gas reduces pressure on the bottom of the well by decreasing the bulk density of the fluid in the well. The decreased density allows the fluid to flow more easily out of the well. Gas lifts, however, do not work in all situations. For example, gas lifts do not work well with a reserve of high viscosity oil (heavy oil). Typically, thermal methods are used to recover heavy oil from a reservoir. In a typical thermal method, steam generated at the surface is pumped down a drive side well into a reservoir. As a result of the heat exchange between the steam pumped into the well and the downhole fluids, the viscosity of the oil is reduced by an order of magnitude that allows it to be pumped out of a separate producing bore. A gas lift would not be used with a thermal system because the relatively cool temperature of the gas would counter the benefits of the heat exchange between the steam and the heavy oil therein increasing the viscosity of the oil negating the desired effect of the thermal system. The delivery of steam or other stimulation typically requires a major intervention or workover. During a workover the completion is reconfigured to produce oil instead of injecting steam or vice versa reducing the time and in turn amount of oil produced. 
         [0003]    For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an effective and efficient apparatus for delivering downhole steam or another supply of stimulation and/or fluid without a major intervention or workover. 
       SUMMARY OF INVENTION  
       [0004]    The above-mentioned problems of current systems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification. The following summary is made by way of example and not by way of limitation. It is merely provided to aid the reader in understanding some of the aspects of the invention. 
         [0005]    In one embodiment, an injector insert apparatus is provided. The injector apparatus includes a body having an inner oil passage configured and arranged to allow oil to pass there through, the body further having an annular chamber formed around the inner oil passage. The annular chamber has a chamber opening that is configured to be coupled to receive a flow of thermal gas medium. The body also has at least one injector orifice that provides a passage between the annular chamber and the inner oil passage. The at least one injector orifice is configured to inject the stimulation thermal gas lift medium into oil passing though the inner oil passage. 
         [0006]    In another embodiment a downhole system is provided. The system includes a Y-tool and an injector insert. The Y-tool is positioned to provide a path between a first well bore and a second well bore. The injector insert apparatus is positioned within the Y-tool. The injector insert has a body and an inner oil passage that is configured and arranged to allow oil to pass there through. The body further has an annular chamber formed around the inner oil passage. The annular chamber has a chamber opening that is configured to be coupled to receive a flow of thermal gas medium from a second well bore. The body also has at least one injector orifice that provides a passage between the annular chamber and the inner oil passage. The at least one injector orifice is configured to inject the thermal gas medium into the inner oil passage. 
         [0007]    In still another embodiment, a method of stimulating oil production for an oil reserve is provided. The method includes: Delivering a high velocity thermal gas medium to an annular chamber that surrounds an oil passage in a first well; and injecting the thermal gas medium through at least one injector orifice into an oil flow passing through the oil passage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0008]    The present invention can be more easily understood and further advantages and uses thereof will be more readily apparent, when considered in view of the detailed description and the following figures in which: 
           [0009]      FIG. 1  is a side view of a downhole system of one embodiment of the present invention; 
           [0010]      FIG. 2  is a close up side view of a nozzle assembly insert of one embodiment of the present invention; 
           [0011]      FIG. 3  is a close up side view of the nozzle assembly insert of  FIG. 2  and the positioning of a plug in one embodiment of the present invention; 
           [0012]      FIG. 4  is a close up side view of the nozzle assembly insert of  FIG. 2  and the positioning of a plug in another location in another embodiment of the present invention; and 
           [0013]      FIG. 5  is a close up side view of another embodiment of a nozzle assembly insert. 
       
    
    
       [0014]    In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the present invention. Reference characters denote like elements throughout Figures and text. 
       DETAILED DESCRIPTION  
       [0015]    In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the inventions may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the claims and equivalents thereof. 
         [0016]    In an embodiment, an annual diverging converging nozzle is installed into a Y-tool at the exit of a steam generator or other hot fluid generator. The annual nozzle redirects the flow of gas to be parallel to the oil production and will act as a downhole ejector pump by transferring momentum to the oil being produced. In another embodiment, the nozzle exit of the pump will be injected into the flow at a slight angle. This injection will be upstream of a diverging contour. The injected flow of the motivating medium will self-choke to a Mach number less than 1. 
         [0017]    Moreover, embodiments of the present invention provide an injector insert apparatus that forms a downhole jet pump with a gas source. The invention increases production of a well as an artificial lift device and enables the production of oil around a downhole steam generator such as a heat exchanger. In an embodiment, a downhole generator is a combination of a combustor and a direct contact heat exchanger. An example of a combustor is found in the commonly assigned patent application Ser. No. 13/782,865 entitled “HIGH PRESSURE IGNITION OF GASOUS HYDROCARBONS WITH HOT SURFACE IGNITION,” filed on Mar. 1, 2013 which is incorporated herein. An example of a heat exchanger is found in commonly assigned patent application Ser. No. 13/793,891 entitled “HIGH EFFICIENCY DIRECT CONTACT HEAT EXCHANGER,” filed on Mar. 11, 2003 which is herein incorporated by reference. The heat exchanger, in embodiments, may be cooled with either a liquid, e.g, water (steam mode), propane, or various hydrocarbons or another fluid such a CO, CO2, N2, etc. In an embodiment, the direct contact heat exchanger takes high temperature, high pressure exhaust from a downhole combustor and injects the gaseous effluent into water to create steam which is a stimulation medium generally described as a thermal gas medium. In other embodiments, as discussed above, the cooling matter can be used such as propane, or various hydrocarbons or another gasses such a CO, CO2, N2, etc., that mix with the exhaust gasses of the combustor to form the thermal gas medium. Hence, the matter supplied by the heat exchanger will generally be referred to as the thermal gas medium. Embodiments of an injector insert apparatus with a nozzle is installed in a Y-tool that redirects flow of the thermal gas medium from the heat exchanger going into the well to going out of the well. Thus the nozzle functions as an ejector as discussed below. In an embodiment an annular nozzle is used, performing work on the oil being pumped by transferring momentum and lowering the static pressure at the exit of the nozzle. The bulk flow will then be increased by the lift properties of the gaseous mixture to further increase production. The injection insert apparatus allows the ability to stimulate a well and produce from the same well without a major workover, which presents a significant cost savings and increases efficiency. 
         [0018]    Referring to  FIG. 1 , a downhole system  50  of one embodiment is illustrated. In an embodiment, the downhole system  50  includes a combustor and heat exchanger  100  as discussed above which are positioned along side of the production string  120  in the same well. The combustor and heat exchange system  100  can generally be called a hot fluid supply system  100  that supplies the thermal gas medium. The hot fluid supply system  100  is illustrated as having an outer housing  103  that protects the inner components  102 . The downhole system  50  further includes a Y-tool  200  which provides a path to the production string  120 . Oil is to be extracted from the production string  120 . Within the Y-tool is installed an injector insert apparatus  400  of an embodiment. 
         [0019]      FIG. 2  illustrates a close up view of the Y-tool  200  with an injector insert apparatus  300  of an embodiment. The injector insert apparatus  300  includes an elongated annular body  300   a  that includes an inner passage  302  that provides a pathway between an upper portion  120   a  of the production string  120  that leads to the surface and a lower portion  120   b  that leads to an oil reservoir. The annular body  300   a  has a first end  320   a  that would be positioned towards an oil reservoir and an opposed second end  320   b  that would be positioned towards the well head. The annular body  300   a  further includes an annular chamber  304  (annular plenum) that is formed in a body  300   a  of the injector insert apparatus  300 . The annular chamber  304  extends around the inner oil passage  302 . The annular chamber  304  has an opening  322  that is in fluid communication with the Y-tool to receive the thermal gas lift medium  101  from the hot fluid supply system  100 . A narrow ejector orifice  306  (annular injector) between the annular chamber  304  and the inner oil passage  302  provides a path for the thermal gas lift medium into the oil in the inner oil passage  302 . As illustrated, the ejector orifice  306  (an annular injector orifice in this embodiment) is configured to direct the thermal gas lift medium up towards the surface in this embodiment. The ejector orifice  306  is also positioned proximate the second end  320   b  of the injector insert assembly  300  in this embodiment. The thermal gas lift medium entering the oil  115  will perform work on the oil  115  being pumped out the well by transferring momentum and lowering the static pressure at the exit of the nozzle. The bulk flow will then be increased by the lift properties of the gaseous mixture to further increase production. 
         [0020]    In particular, the thermal gas medium  101 , such as hot gas from the hot gas supply system  100  is delivered to the annular chamber  304  (annular plenum) at a pressure sufficient to allow the thermal gas medium  101  to reach high velocity. In some configurations the velocity will be sonic and in others it will be subsonic velocity. The thermal gas lift medium  101  is accelerated through the injector orifice  306  such that the static pressure downstream of the injection point is reduced thus increasing the driving potential of the reservoir fluid. The final velocity of the stimulation thermal gas lift medium  101  and in turn the maximum momentum that can be imparted to the hydrocarbon stream is dictated by the geometry of the annular injection as well as the effective annulus created between the contour of the wall making up the internal surface  300   b  of the insert  300  and the hydrocarbon fluid being pumped. In this instance the outer boundary is fixed and defined by the geometry of the insert  300 , while the inner boundary is defined by the discontinuity of densities between the hydrocarbon stream and the hot fluid. 
         [0021]    The injector insert apparatus  300 , with an inner oil passage  302 , of embodiments allows for plugs to be inserted either above the injector insert apparatus  300  or below the nozzle injector insert apparatus  300 . For example, referring to  FIG. 3 , a plug  350  has been passed through the inner oil passage  302  and positioned below the narrow ejector orifice  306 . The plug  350 , in this position, isolates the oil reservoir from the surface and the nozzle assembly insert  300  can be removed prior to stimulation of the reservoir and serviced prior to the next production period. This allows for faster and less expensive maintenance as well as longer and more robust performance between major overhauls. The plug  350  in this position also prevents the oil from entering the hot gas supply system  100  when it is not in operation during the soak period of cyclic steam stimulation or CSS.  FIG. 4  illustrates a plug  360  positioned above the narrow ejector orifice  306 . In this configuration, the output of the hot gas supply system  100  is allowed to flow downhole into the oil in the reservoir. This allows the hot gas to stimulate the oil in the reserve. As demonstrated with other Cyclic Steam Production methods, dramatic increase of oil is exhibited with thermal stimualtion. Certain operational metrics would dictate when the insert  300  was left in the Y-tool  200  during CSS as shown in  FIG. 4  and when it would be best to remove the insert  300  before stimulating the reservoir as shown in  FIG. 3 . 
         [0022]    A different embodiment of an injector insert apparatus  400  is illustrated in  FIG. 5 . In this embodiment, an annular chamber  502  (an outer hot gas passage) is designed to accelerate the thermal gas medium before the thermal gas medium is expelled through narrowed orifice  504  into the flow of oil in the upper well portion  120   a.  In this embodiment, the acceleration of the thermal gas medium  101  occurs within the annular chamber  502 . Injector insert apparatus  400  includes an elongated annular body  400   a  that includes an outer wall  402   a  and an inner wall  402   b.  The annular chamber  502  is formed between the outer wall  402   a  and the inner wall  402   b.  Further in this embodiment, spaced protrusions  404  extend from the inner wall  402   b  into the annular space  502 . The protrusions  404 , act as structural supports for the inner wall and can enhance heat transfer from the hot fluid to the hydrocarbon stream. The body  400   a  has a first end  420   a  that is positioned towards an oil reserve and an opposed second end  420   b  positioned towards a surface. The narrow orifice  504  is positioned proximate the second end  420   b  of the body  400   a.  Also illustrated in  FIG. 5 , is a chamber opening  422  which allows the thermal gas lift medium  101  to enter the annular chamber  502 . 
         [0023]    Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. For example, although the above embodiments show a fixed geometry, variations of this injector apparatus insert can incorporate a variable minimum area which would allow for substantial ratios of “steaming flow” to “motivating flow”. Other variations include delivering a motivating fluid and pressure below which a sonic velocity is created in the annular injection mechanism, and discrete injection holes spaced circumferentially around the inner cylinder of the insert  300 . Hence, this application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.