Abstract:
Methods and apparatus for enhanced and improved viscous oil recovery are disclosed. A horizontal well is drilled through the viscous oil formation. A liner includes temperature actuated valves for delivering steam more uniformly along the heel and toe portions of the liner. The temperature actuated valves include an actuation mechanism that actuates from an open position to a closed position to control the flow of the steam therethrough. The actuation mechanism actuates to the closed position when it exceeds a predetermined temperature. Heat from the steam mobilizes and lowers the viscosity of the heavy crude wherein the crude is then produced to the surface via conventional lift arrangements.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
       [0001]    The present application for patent claims the benefit of U.S. Provisional Application bearing Ser. No. 61/286,067, filed on Dec. 14, 2009, which is incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention relates to oil field production apparatus and techniques, and more particularly, to such apparatus and techniques for use in the production of heavy oil or viscous crude oil. 
       BACKGROUND 
       [0003]    It has been known to produce viscous crude oils in reservoirs by drilling vertical wells into the producing zone and then injecting steam into the producing zone to increase the mobility and reduce the viscosity of the viscous crude. This steam injection has been done in several different ways. In one technique, wells in the reservoir can be cyclically steamed using a process called cyclic steam stimulation (CSS). In this process, steam is injected down a vertical well into the producing zone. The steam is allowed to “soak” in the reservoir for a relatively short period of time to heat the crude oils, thus reducing its viscosity and increasing its mobility. The well is then placed back in production for a relatively longer period of time to extract the heated less viscous crude oil. This cycle is typically repeated until the production becomes unprofitable. 
         [0004]    Another technique which has been used to produce viscous crude reservoirs is to drill vertical wells in a geometrical pattern into the producing zone, such as in a 5-spot or 9-spot pattern. In these geometrical patterns, the wells are placed within the reservoir field, typically in a symmetric fashion, and are designated as either an injection well or a production well based on its position in the pattern. Steam is continuously injected into the producing zone via the injection wells to heat the viscous crude oil and drive it to neighboring vertical producing wells in the geometrical array. 
         [0005]    In the initial development of a reservoir of viscous crude these described methods have worked well. Over time however, the steam tends to congregate in the upper portion of the producing zone. This, of course, may cause less heating of the viscous crude in the lower portion of the producing zone. The heavy crude saturated lower portion of the producing zone is not depleted as the high viscosity of the crude prevents its migration to the well bores of the producing wells. Thus large quantities of potentially producible crude oil can otherwise become not recoverable. 
         [0006]    It is known in the art that horizontally-oriented, or horizontal wells can be utilized to help production from the portions of the producing zone, especially the lower portion discussed above, which are typically not depleted after injecting steam with vertical wells. It is desirous in these assemblies to deliver uniformly distributed steam to the producing zone along the entire length of the horizontal section of the well. 
         [0007]    Currently available steam injection systems used for disbursement of steam in the reservoir typically include slotted liners or pipes having a series of orifices or holes. A well known problem with such assemblies is that the steam injected into the reservoir tends to be disbursed at the “toe” and “heel” portions (or the furthest and nearest portions) of the injection zone and not uniformly distributed throughout the formation. Different orifice or hole sizes have been used to control the disbursement of the steam, but such arrangements still do not provide a reliable and efficient method for optimizing the distribution of steam within the subterranean reservoir. 
       SUMMARY 
       [0008]    According to an aspect of the present invention, a valve assembly is disclosed for controlling fluid flow. The valve assembly includes a valve casing, a valve seat, and an actuation mechanism. The valve casing defines a first opening, a second opening, and a passageway extending therebetween. The valve seat is located adjacent the first opening. The actuation mechanism is carried within the valve casing, and includes an actuation chamber, an actuation member, and a sealing element such as a valve ball. The actuation chamber has a rigid chamber body defining a chamber volume therewithin. The actuation member is carried within the actuation chamber. The sealing element engages the valve seat to seal the first opening of the valve casing when in a closed position. The sealing element disengages the valve seat when in an open position. The actuation member communicates with the sealing element to actuate the sealing element to the closed position when the chamber volume exceeds a predetermined temperature, such as between about 200 to about 400 Degrees Celsius. 
         [0009]    In one embodiment, the actuation member is a bimetallic material. In another embodiment, the actuation member is a smart memory metal. 
         [0010]    In one or more embodiments, the actuation mechanism includes a positioning member between the valve casing and the rigid chamber body of the actuation chamber to provide clearance for the passageway. 
         [0011]    In one or more embodiments, the actuation mechanism has an initial spring coefficient that actuates the sealing element to the closed position until a predetermined pressure acts on the sealing element. 
         [0012]    In one or more embodiments, the actuation member actuates the sealing element to the open position when the chamber volume is reduced below the predetermined temperature. 
         [0013]    According to another aspect of the present invention, a well assembly is disclosed for injecting steam into a subterranean reservoir. The well assembly includes a wellbore in fluid communication with a producing zone of the subterranean reservoir. The wellbore has a substantially vertical section and a substantially horizontal section extending from a lower portion of the substantially vertical section. The substantially horizontal section defines a heel portion located adjacent the vertical section and a toe portion located distally therefrom. A plurality of valve assemblies is axially located on the substantially horizontal section to disburse steam to the producing zone of the subterranean reservoir. Each valve assembly includes an actuation mechanism that actuates from an open position to a closed position to control the flow of the steam therethrough. The actuation mechanism actuates to the closed position when it exceeds a predetermined temperature, such as between about 200 to about 400 Degrees Celsius. 
         [0014]    In one or more embodiments, the valve assembly includes a valve casing defining a first opening, a second opening, and a passageway extending therebetween. The actuation mechanism is carried within the valve casing and includes an actuation chamber, an actuation member, and a sealing element such as a valve ball. The actuation chamber has a rigid chamber body defining a chamber volume therewithin. The actuation member is carried within the actuation chamber. The sealing element engages a valve seat adjacent the first opening to seal the first opening of the valve casing when in the closed position. The sealing element disengages the valve seat when in the open position. The actuation member communicates with the sealing element to actuate the sealing element to the closed position when the chamber volume exceeds the predetermined temperature. 
         [0015]    In one embodiment, the plurality of valve assemblies is located on the internal surface of the substantially horizontal section. In another embodiment, the plurality of valve assemblies is located on the external surface of the substantially horizontal section. 
         [0016]    In one or more embodiments, each valve assembly is received within a recess within the substantially horizontal section. 
         [0017]    In one embodiment, the actuation mechanism includes a bimetallic actuation member. In another embodiment, the actuation member is a smart memory metal. 
         [0018]    In one or more embodiments, the actuation mechanism has an initial spring coefficient such that the actuation mechanism is actuated to the closed position until the substantially horizontal section exceeds a predetermined pressure. 
         [0019]    In one or more embodiments, the actuation member actuates to the open position when reduced below the predetermined temperature. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a schematic, sectional view of a prior art steam delivery in a horizontal well in the field of hydrocarbon production. 
           [0021]      FIG. 2  is a schematic, sectional view of a prior art steam delivery in a horizontal well in the field of hydrocarbon production. 
           [0022]      FIG. 3  is a schematic, sectional view of a steam distribution assembly according to an embodiment of the present invention for use in the field of hydrocarbon production. 
           [0023]      FIG. 4  is a schematic, sectional view of a valve in an open position for the steam distribution assembly of  FIG. 3 . 
           [0024]      FIG. 5  is a schematic, sectional view of the valve in  FIG. 4  in a closed position. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Referring initially to prior art  FIG. 1 , a cross sectional view shows a wellbore  11  having vertical section  11 A and horizontal section  11 B. Wellbore  11  provides a flow path between the well surface and producing sand or reservoir  31 . Tubing string  13  and slotted liner  15  are also shown in  FIG. 1 . The horizontal section  11 B of tubing string  13  includes a heel portion  13 A and an opposite toe portion  13 B. Slotted liner  15  is a completion device lining horizontal section  11 B of wellbore  11  and is typically isolated by a lead seal  17  from vertical section  11 A of wellbore  11 . Live steam is supplied via tubing string  13  and exits from toe portion  13 B at end  19 . The steam flow is as indicated by arrows  21 . Direct impingement of live steam onto slotted liner  15  at the area numbered  23  can potentially cause erosion and collapse of the liner  15 , which is an undesirable condition. Also, using this technique the steams heat is concentrated near toe portion  13 B in areas  25  and  27  of reservoir  31  rather than along the length of slotted liner  15 . 
         [0026]    Referring now to prior art  FIG. 2 , wellbore  29  has vertical section  29 A, which goes to the surface, and horizontal section  29 B that penetrates a long horizontal section of producing sand or reservoir  31 . Slotted liner  37  lines horizontal section  29 B of wellbore  29 . Tubing string  33  is run in from the surface and, on the lower end thereof is plugged off by plug  35 . The horizontal section  298  of tubing string  33  includes a heel portion  33 A and an opposite toe portion  33 B. The length of tubing string  33 , prior to the plug  35 , is provided with spaced apart drilled holes  39  along its entire horizontal section between heel portion  33 A and toe portion  33 B. Each drilled hole  39  is covered with a sacrificial impingement strap  41 . Sacrificial impingement straps  41  are constructed of a carbon steel material and may be ceramic coated if desired. Sacrificial impingement straps  41  are welded to tubing string  33  with an offset above each drilled hole  39 . 
         [0027]    A steam generator source (not shown) is located at the surface and provides an input of steam into tubing string  33 . The steam travels down tubing string  33  to its lower horizontal section  29 B where it exits via drilled holes  39 . 
         [0028]    Referring to  FIG. 3 , wellbore  110  is in fluid communication with a producing zone of subterranean reservoir  31 . Wellbore  110  includes substantially vertical section  113  and substantially horizontal section  115  extending from a lower portion of substantially vertical section  113 . According to an embodiment of the present invention, horizontal section  115  includes liner  111 , which extends from vertical section  113  and through which steam is delivered into reservoir  31 . Horizontal section  115  includes heel portion  117 , adjacent seals  119 , and toe portion  121  distally located away from seals  119  and vertical section  113 . Liner  111  receives steam from string of tubing  123  for delivery into reservoir  31 . A plurality of valves  125  are positioned intermittently between heel and toe portions  117 ,  121 . The axial distance between valves  125  can be adjusted for optimum, uniform or targeted delivery of steam into reservoir  31 . 
         [0029]    Referring to  FIGS. 4 and 5 , valve  125  is shown in the open position ( FIG. 4 ) and the closed position ( FIG. 5 ). Valve  125  is positioned to communicate steam from within liner  111  through orifice  127  to the producing zone of reservoir  31 . Valve  125  can be positioned on either the internal or external surface of liner  111 . While valve  125  is attached to liner  111  in  FIG. 3 , one skilled in the art will appreciate that tubing  123  can extend throughout horizontal section  115  and valve  125  could alternatively be attached thereto. 
         [0030]    Valve  125  includes a valve casing  129  defining the outer portion of valve  125  through which steam flows. Valve casing  129  initially extends radially outward from the axis of orifice  127  a predetermined distance to define the diameter of valve  125 . Valve casing  129  then extends parallel with the axis of orifice  127  and back radially inward to define the boundaries of valve  125 . Valve casing  129  extends radially inward a lesser distance than extending radially outward to define an opening  130  through which steam communicates. 
         [0031]    Valve  125  includes actuation assembly  131  carried within valve casing  129 . Actuation assembly  131  comprises valve base  133  and valve housing  135 , which define valve actuation chamber  137 . Guide member  139 , which is connected to valve base  133 , guides valve ball  141  between open and closed positions when actuation assembly  131  actuates. Valve ball  141  engages and disengages from valve seat  143  formed in the portion of orifice  127  adjacent valve  125 . 
         [0032]    Liner  111  can include recess  145  for receiving valve casing  129 . Recess  145  is preferably formed radially outward of orifice  127  a predetermined distance to thereby form valve connector  147 . Valve connector  147  extends along the axis of orifice  127  for engagement with valve  125 . Those skilled in the art will readily appreciated there are several ways for valve  125  to connect with valve connector  147 . For example, valve connector  147  can be threaded for threadedly engaging valve casing  129 . Alternatively, valve casing  129  can have a predetermined clearance over valve connector  147  to form an interference fit, or such that when liner  111  is heated an interference fit is formed. 
         [0033]    Positioning member  149  is preferably positioned between valve casing  129  and valve base  133  of actuation assembly  131  so that there is clearance for communicating steam when valve ball  141  is in the open position ( FIG. 4 ). Valve ball  141  engages valve seat  143  when in the closed position ( FIG. 5 ) such that steam communication is ceased or impinged. 
         [0034]    Actuation assembly  131  also includes actuation member  151  that engages valve ball  141 , and actuates valve ball  141  between open and closed positions. Actuation assembly  131  actuates between the open and closed positions of  FIGS. 4 and 5 , respectively, when the temperature exceeds or drops below a predetermined value. Such can be achieved with such technologies as bimetallic materials, smart memory metals/alloys, or a combination thereof. U.S. patent application Ser. No. 12/262,750 provides examples of such technologies and is hereby incorporated by reference. 
         [0035]    In one embodiment, the actuation mechanism actuates to the closed position when it exceeds 200 Degrees Celsius, and opens when it drops below 200 Degrees Celsius. In another embodiment, the actuation mechanism actuates to the closed position when it exceeds 400 Degrees Celsius, and opens when it drops below 400 Degrees Celsius. In another embodiment, the actuation mechanism is designed to actuate between about 200 to about 400 Degrees Celsius. Typically the actuation point is determined based on the well characteristics, reservoir characteristics, and the amount of heat needed to mobilize the viscous crude within the reservoir. 
         [0036]    Actuation assembly  131  can be set with an initial spring coefficient such that valve ball  141  is actuated to the closed position until liner  111  is pressurized by the steam being injected. Then actuation assembly  131  and valve ball  141  remain open until actuation assembly  131  exceeds the predetermined temperature necessary to actuate valve ball  141  to the closed position. Alternatively, a spring (not shown) could be positioned between valve ball  141  and valve housing  135  for biasing valve ball  141  to the closed position prior to pressurizing liner  111  with steam. 
         [0037]    In operation, string of tubing  123  delivers steam to liner  111 . Steam travels from heel  117  to toe portion  121 . Portions of steam are communicated through open valves  125  and orifices  127  into reservoir  31  while traveling from heel portion  117  to toe portion  121 . In the preferred embodiment, valves  125  are biased to the closed position prior to liner  111  being pressurized by the delivery of steam from string of tubing  123 . Once steam is delivered to liner  111  and the pressure within liner  111  is increased above a predetermined amount, valves  125  open such that steam is delivered to reservoir  31 . 
         [0038]    Depending upon whether valves  125  are positioned on the internal or external surface of liner  111 , steam communicates into valve through either opening  130  (internal positioning) or between valve seat  143  of orifice  127  and valve ball  141  (external positioning). Steam flows between the interior of valve casing  129  and the exterior of actuation assembly  131  while communicating between opening  130  and the clearance between valve seat  143  and valve ball  141  for delivery into reservoir  31 . Steam also communicates between valve ball  141  and valve actuation base  133  such that steam collects within chamber  137 . Actuation member  151  is exposed to the steam within chamber  137 . As steam collects within chamber  137 , the temperature of actuation member  151  increases. 
         [0039]    When the temperature of chamber  137  and actuation member  151  exceed the predetermined value, actuation member  151  actuates valve ball  141  from the open position shown in  FIG. 4  to the closed position shown in  FIG. 5 . Valve ball  141  sealingly engages valve seat  143  so that steam no longer communicates from liner  111  to reservoir  31 . While valve ball  141  is closed, steam also does not communicate into chamber  137 , thereby allowing actuation member  151  to cool. When actuation member  151  cools below the predetermined temperature, actuation member  151  actuates valve ball  141  back to the open position shown in  FIG. 4 . This opening and closing cycle continues to help ensure uniform delivery of steam from liner  111  into reservoir  31 . 
         [0040]    While the invention has been shown in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but susceptible to various changes without departing from the scope of the invention.