Abstract:
A direct contact heat exchanger assembly is provided. The direct contact heat exchanger includes an evaporator jacket and an inner member. The inner member is received within the evaporator jacket. A sleeve passage is formed between the evaporator jacket and the inner member. The sleeve passage is configured and arranged to pass a flow of liquid. The housing has an inner exhaust chamber that is coupled to pass hot gas. The inner member further has a plurality of exhaust passages that allow some of the hot gas passing through the inner exhaust chamber to enter the flow of liquid in the sleeve passage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This Application claims priority to U.S. Provisional Application Ser. No. 61/664,015, titled APPARATUSES AND METHODS IMPLEMENTING A DOWNHOLE COMBUSTOR, filed on Jun. 25, 2012, which is incorporated in its entirety herein by reference. 
     
    
     BACKGROUND 
       [0002]    Thermal stimulation equipment used for generating steam or a gas from a liquid such as, downhole steam generator systems, high pressure chemical processing systems, purification and cleaning process systems, pumping equipment systems, etc, are subject to failure due to creep fatigue, corrosion and erosion. The primary source of corrosion is from dissolved solids, chlorine and salts that are released from boiling water. Another source of corrosion is from fuel (e.g. sulfur). A third source of corrosion is from an oxidizing agent (i.e. dissolved oxygen that may create rust). A primary source of erosion is from high velocity water and gas and a secondary source is from particulates from the supply lines. 
         [0003]    The effectiveness of downhole steam generators is directly related to its ability to provide high quality steam. The length required for heat exchange is an essential issue related to the length of the tool and as a consequence the cost of steam generator and complexity of installation. Providing this high quality steam as close as possible to the formation being stimulated is a critical issue driving the efficiency of the downhole steam generator system. 
         [0004]    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 evaporator configuration that provides steam that is effective, efficient and robust to limit downhole stimulation equipment from fatigue, corrosion and erosion. 
       SUMMARY OF INVENTION 
       [0005]    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. 
         [0006]    In one embodiment, a direct contact heat exchanger assembly is provided. The direct contact heat exchanger includes an evaporator jacket and an inner member. The inner member is received within the evaporator jacket. A sleeve passage is formed between the evaporator jacket and the inner member. The sleeve passage is configured and arranged to pass a flow of liquid. The housing has an inner exhaust chamber that is coupled to pass hot gas. The inner member further has a plurality of exhaust passages that allow some of the hot gas passing through the inner exhaust chamber to enter the flow of liquid in the sleeve passage. 
         [0007]    In another embodiment, another direct contact heat exchanger assembly is provided. This direct contact heat exchanger assembly includes an elongated cylindrical evaporator jacket, a cylindrical inner member, and a plurality of raised fins. The cylindrical inner member is received within the evaporator jacket. The inner member has an inner surface that defines an inner exhaust chamber. The inner member is configured and arranged to pass hot gas through the inner exhaust chamber. An outer surface of the inner member and an inner surface of the evaporator jacket are spaced to form an annulus shaped sleeve passage that extends around the outer surface of the inner member. The sleeve passage is configured and arranged to pass a flow of liquid. The inner member has a plurality of exhaust passages that extend from the inner exhaust chamber into the sleeve passage. The exhaust passages allow at least some of the hot gas passing in the inner exhaust chamber to mix with the liquid passing in the sleeve passage to create a gas mix in the sleeve passage. The plurality of raised fins each extend out from the outer surface of the inner member within the sleeve passage to cause the flow of liquid to take a swirling path in the sleeve passage. 
         [0008]    In another embodiment, a method of forming a direct contact heat exchanger is provided. The method comprises passing a body of liquid through a passage and injecting hot gas into the moving body of liquid in the passage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    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: 
           [0010]      FIG. 1  is a side perspective view of direct contact heat exchanger assembly of one embodiment of the present invention; 
           [0011]      FIG. 2  is a close up side view of a portion of the direct contact heat exchanger assembly of  FIG. 1 ; and 
           [0012]      FIG. 3  is a close up view of another portion of the direct contact heat exchanger assembly of  FIG. 1 . 
       
    
    
       [0013]    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 
       [0014]    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. 
         [0015]    Embodiments of the present invention provide an evaporator assembly that works with a downhole combustor. The evaporator assembly utilizes swirling water to provide a robust evaporator assembly that generates steam or other high vapor fraction fluid. The steam would then be injected into a reservoir for the production of hydrocarbons or utilized to provide energy into a downstream mechanism. Referring to  FIG. 1 , an evaporator assembly  100  of one embodiment is illustrated. The evaporator assembly  100  includes a jacket  102  that encases the evaporator. The evaporator assembly  100  is positioned between a combustor  200  positioned at an intake end  100   a  of the evaporator assembly  100  and an optional radial support portion  300  that is positioned at an exit end  100   b  of the evaporator assembly  100 . The hot gas generator  200 , in an embodiment, provides a fuel rich combustion. An example of a combustor  200  is illustrated in commonly owned patent application, U.S. patent application Ser. No. 13/745,196 filed on Jan. 18, 2013 entitled DOWNHOLE COMBUSTOR which is herein incorporated in its entirety by reference and the combustor described in U.S. Provisional Application Ser. No. 61/664,015, titled “APPARATUSES AND METHODS IMPLEMENTING A DOWNHOLE COMBUSTOR,” filed on Jun. 25, 2012. The combustor  200 , in an embodiment, includes an initial ignition chamber (secondary chamber) and a main combustion chamber. The combustor  200  takes separate air and fuel flows and mixes them into a single premix air/fuel stream. The momentum from a premix injection stirs the ignition chamber at extremely low velocities relative to the total flow of air and fuel through the combustor  200 . Diffusion and mixing caused by the stirring effect changes the initial mixture of the air/oxidant (air/fuel) to a premixed combustible flow. This premixed combustible flow is then ignited by one or more glow plugs. Insulated walls limit heat loss therein helping to raise the temperature of the premixed gases. Once the gases reach the auto-ignition temperature, an ignition occurs. This ignition acts as a pulse sending a deflagration wave into the main combustor chamber of the combustor  200  therein igniting the main flow field. Once this is accomplished, the one or more glow plugs are turned off and the initial ignition chamber no longer sustains combustion. One benefit to this system is that only a relatively small amount of power (around 300 Watts) is needed to heat up the glow plugs at a steady state. The combustion product of the combustor  200  is used by the evaporator assembly  100  to heat water to generate steam as described below. 
         [0016]    In  FIG. 1 , the jacket  102  of the evaporator assembly  100  is shown as transparent so the inner assembly is illustrated. The jacket  102  provides protection for the inner assemblies. The inner assemblies of the evaporator assembly include a cylindrical inner member  111  with includes a turning vane  114  and a stator  116 . The turning vane  114  and the stator  116  are positioned between the combustor  200  and a radial support  300 . The stator  116 , in this embodiment, includes a first stator portion  116   a,  a second stator portion  116   b  and a third stator portion  116   c.  The first stator  116   a  is cylindrical in shape and has a first diameter. The second stator  116   b  is also cylindrical in shape and has a second diameter. The third stator  116   c  is also cylindrical in shape and has a third diameter. The third diameter of the third stator  116   c  is less than the second diameter of the second stator  116   c  and the second diameter of the second stator  116   b  is less than the first diameter of the first stator  116   a.  The stator portions  116   a,    116   b  and  116   c  are separated from each other by reducers  104   a  and  104   b  that provide a reduction passage between the respective first, second and third stators  116   a,    116   b  and  116   c.  The reduction of the diameter of the stators  116   a,    116   b  and  116   c,  in this embodiment, corresponds to an increase in distance from the combustor which reduces the pressure required to drive the flow through the evaporator as discussed further below. 
         [0017]    Close up views  108  and  110  of  FIGS. 2 and 3  further illustrate portions of the evaporator assembly  100 . In particular, portion  108  of  FIG. 2 , illustrates a portion of the evaporator assembly  100  next to the combustor  200 . As illustrated in the close up view  108 , the evaporator assembly  100  includes the outer evaporator jacket  102  that protects the system. The assembly  100  includes an inner exhaust chamber  118  in which the combustor exhausts combustion product  130 . Defining the inner chamber  118  includes a cylindrical turning vane portion  114  and the cylindrical stator  116 . Also illustrated is an outer sleeve passage  115  that is annular in shape that is formed between the evaporator jacket  102  and the turning vane  114  and stator portions  116   a,    116   b  and  116   c.    
         [0018]    Further leading from the combustor  200  in a collar  112 . Water  120  pumped into the assembly  100  passes out under the collar  112  and into the sleeve passage  115 . As discussed above, the turning vane  114  is cylindrical in shape. The turning vane  114  has a plurality of elongated outer extending raised directional turning fins  119 . The raised directional turning fins  119  are shaped and positioned to direct the flow of water  120  passing under the collar  112 . In particular, the raised directional turning fins  119  of the turning vane  114  direct the flow of water  120  into a helical path in the sleeve passage  115 . In one embodiment, the directional turning fins  119  include a curved surface  119   a  that extends along its length to direct the helical flow of water  120  in the sleeve passage  115 . This helical flow path (swirl flow) in the sleeve passage  115  is maintained with the stator portion  116  as described below. The swirl flow causes a centrifugal force such that the water to act as a single body forced against the outer wall, .e.i, no individual droplets of water are able to form. The swirl flow further prevents the water from pooling in areas due to gravitational effects which can cause an uneven thermal distribution throughout the evaporator assembly  100  potentially reducing its useful life. The swirl angle is set such that the centrifugal force generated is able to overcome gravity based on the total throughput in the tool. 
         [0019]    The stator  116  extends from the turning vane  114  and is also cylindrical in shape with reducer sections  104   a  and  104   b  as discussed above. The stator portions  116   a,    116   b  and  116   c  each include a plurality of elongated outer extending directional maintaining fins  117  that are designed to preserve the swirl flow of water and vapor started by the directional turning fins  119  of the turning vane  114  in the sleeve passage  115 . At least one of the stator portions  116   a,    116   b  and  116   c  includes a plurality of exhaust passages  132  that extend from the inner chamber  118  to the sleeve passage  115 . The exhaust passages  132  provide an effluent path for the combustion product  130  from the inner chamber  118  to the sleeve passage  115 . The exhaust passages  132  are angled to enhance and maintain the helical flow path in the sleeve passage  115 . Some of the combustion product  130  (exhaust from the combustor  200 ) passes through the exhaust passages  132  and heats up the water  120  flowing in the sleeve passage  115 . The water  120 , in response to the hot combustion product  130 , turns into a steam mix  125  in the sleeve passage  115  that continues in the swirl pattern. As stated above, the exhaust passages  132  are angled to aid and maintain the helical flow path of the water  120 /steam mix  125 . In one embodiment, at least some of the exhaust passages  132  pass out an end of a respective directional maintaining fin  117  of the stator portion  116 . As illustrated in  FIG. 2 , a directional maintaining fin  117  has a length defined between a first end  117   a  and an opposed second end  117   b.  The first end  117   a  in this embodiment is rounded to minimize friction encountered by the steam mix  125  as the steam mix  125  flows in the spiral pattern in the sleeve passage  115 . Moreover, in this embodiment, the first end  117   a  of the directional maintaining fin  117  is wider than the second end  117   b  of the directional maintaining fin  117  to enhance flow. An exhaust passage  132 , in an embodiment, is positioned to extend out of the second end  117   b  of the directional maintaining portion  117 . 
         [0020]    Referring to  FIG. 3 , a close up view of section  110  of the evaporator assembly  100  of  FIG. 1  is illustrated. This exit end  100   b  of the evaporator assembly  100  illustrates where the combustion product  130  and steam mix  125  exit the evaporator assembly  100 . As illustrated, an end portion  150  extends from the stator  116 . The end portion  150  is generally cylindrical in shape to maintain the inner chamber  118  and the sleeve passage  115 . The end portion  150  includes an inner surface  151  that is as wide as an inner surface of the stator  116  but narrows as it extends to an orifice end cap  162 . Hence, the inner chamber  118  narrows as it reaches the end cap  160 . The end cap  160  includes a central opening  162  in which the combustion product  130  leaves the evaporator assembly  100 . Within the orifice end cap  160  is housed a orifice member  190  that includes an orifice passage  191  that leads from the inner chamber  118  to the central opening  162  of the end cap  160 . The orifice member  190  creates a back pressure. This backpressure is used to increase the flow rate to the upstream portions of the tool at low flow rates. At high flow rates this orifice member relieves backpressure so that the structural integrity of the evaporator meets its life requirements for operation. The end portion  150  further includes an outer surface that includes a first portion  152   a  and a second portion  152   b.  The first portion  152   a  of the outer surface  152  of the end portion  150  is positioned next to the stator portion  116 . The second portion  152   b  has a smaller diameter than the first portion  152   a  of the outer surface  152  of the end portion  150  such that a shoulder  153  is formed between the first portion  152   a  and the second portion  152   b  of the outer surface  152  of the end portion  150 . A thermal growth spring  170  is positioned over the second portion  152   b  of the outer surface  152  of the end portion  150 . The thermal growth spring  170  has a first end  170   a  that engages the shoulder  153  in the outer surface  152  of the end portion  150 . A second end  170   b  of the thermal growth spring  170  engages a portion of the radial support  300 . The thermal growth spring  170  allows the stator assembly to transmit structural loads of transportation and handling while providing the flexibility to relieve thermal growth once downhole and in operation which reduces the propensity for creep fatigue failures. Also illustrated in the embodiment of  FIG. 3 , is a first centering spring  180 . The first centering spring  180  is received in an inner groove  181  in the radial support  300 . The first centering spring  180  further engages the second portion  152   b  of the outer surface  152  of the end portion  150  to help position the end portion  150  in relation to the radial support  300  in order to effectively transfer loads from  150  to  300  while allowing relative motion along the longitudinal axis. Also illustrated is a second centering spring  182 . The second centering spring  182  is received in a groove  183  in the end cap  162 . The second centering spring  182  is engaged with an outer surface of the orifice portion  190 . The second centering spring  182  helps position the orifice portion  190  in relation to the end cap  160  and relieve thermal growth of the orifice. As illustrated in  FIG. 3 , the steam mixture  125  exits the evaporator assembly  100  via the sleeve passage  115  which extends to an exit end  100   b  of the evaporator assembly  100 . 
         [0021]    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. 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.