Abstract:
A downhole apparatus for oil sand exploitation, including at least a casing for housing a water conduit for receiving water, at least one steam generation chamber being in fluid communication with said water conduit and having at least one steam outlet, at least one electrical heater, being thermally connected to said steam generation chamber, at least one crude oil conduit for recovering crude oil. A method including injecting steam from at least one steam generation chamber coupled to an oil recovery conduit into a reserve; and removing oil from the reserve through the conduit, wherein the least one steam generation chamber is disposed on the oil recovery conduit, and the steam generation chamber includes a plurality of heating conduits each including a heating element and a thermally conductive material therein, and at least one reservoir surrounding the plurality of heating conduits from which the steam is produced.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The application claims the benefit of the earlier filing date of co-pending European Patent Application No. 12150055.7, filed Jan. 3, 2012, and incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates to a method and an apparatus for in situ mobilizing of heavy oil or crude oil by steam injection. 
       DESCRIPTION OF THE RELATED ART 
       [0003]    Oil sand, as well referred to as tar sand comprises sand grains coated with tar like petroleum crude oil, briefly referred to as crude oil. The crude oil in the oil sand has a high viscosity and must be heated or diluted to flow. In-situ exploitation of oil sands can be accomplished by “steam assisted gravity drainage”, abbreviated as SAGD. SAGD uses a horizontally extending steam injection well forming a steam generation chamber for mobilizing the crude oil in the oil sand. The mobilized crude oil pours downward and is recovered by a second horizontally extending well, as so called production well, as disclosed in U.S. Patent Publication No. 2001/0278001A1. 
         [0004]    The steam can be either produced by above ground facilities or downhole by an electrical heater as suggested by U.S. Pat. No. 4,805,698. The water is supplied from above ground by a water supply line. The electrical steam generator heats the water to generate steam. The steam is injected into the sand and mobilizes the crude oil, which is collected by adjacent production wells. 
       SUMMARY OF THE INVENTION 
       [0005]    The problem to be solved by the invention is to improve in-situ oil sand exploitation. 
         [0006]    Solutions of the problem are provided by a downhole apparatus and a method for exploitation of an oil sand reservoir as described by the respective independent claims. The dependent claims relate to further improvements of the invention. 
         [0007]    The downhole apparatus for oil sand exploitation, comprises a least a casing which houses a water conduit for receiving water via a water pipe and at least one steam generation chamber being in fluid communication with said water conduit and having at least one steam outlet. The steam generation chamber is thermally connected to an electrical heater. The downhole apparatus further comprises at least one crude oil conduit for recovering crude oil, which has been mobilized by said steam. Such downhole apparatus permits to inject steam for mobilization of the crude oil into the oil sand and to recover the crude oil by a single apparatus, and thus requires only a single bore. 
         [0008]    The casing may preferably house the at least one crude oil conduit. The casing may for example be or include a multiple conduit tube, wherein the at least one water conduit and the at least one crude oil conduit are each at least one of the multiple conduits. This permits a stable design of the housing. 
         [0009]    The at least one steam generation chamber is preferably supported by the peripheral surface of the casing. This position of the steam generation chamber permits a simple injection of the steam generated in said steam generation chamber into the oil sand. 
         [0010]    Preferably there are multiple, e.g. five or nine, at least two steam generation chambers arranged around the peripheral surface of the casing defining a bundle of steam generation chambers. In one embodiment, there is one bundle of steam generation chambers. In another embodiment, there are two or more bundles arranged at different positions along a distal length of the casing. The one or more bundles of steam generation chambers permit homogeneous injection of steam and thus an efficient exploitation of the oils sand. Because the one or more bundles of steam generation chambers are arranged around the casing, the one or more bundles also act to maintain or raise a temperature of the casing which aids in removal of crude oil from a reservoir (via the crude oil conduit in the casing). 
         [0011]    Each steam generation chamber preferably has a cladding compartment surrounding a heater tube. The heater tube may house at least one electrical heater cartridge. This permits on the one hand to efficiently heat the water and on the other hand a simple replacement of the electrical heater cartridge in case of failure. The heater tube preferably houses at least one spare electrical heater cartridge. This permits longer operating intervals between retracting the downhole apparatus. 
         [0012]    The heater tube may be hollow and may have an interior containing a composition of inorganic compounds and possibly pure elemental species. Examples for such a composition are described in U.S. Pat. Nos. 6,132,823; 6,911,231; 6,916,430; 6,811,720 and U.S. Patent Publication No. 2005/0056807, which are incorporated by reference as if fully disclosed herein. Such composition acts as a thermally conductive material or medium to provide at least an almost perfect homogenous distribution by the heater tube of the heat provided by the heater cartridge. The heater tube may as well be evacuated as suggested in the above references. 
         [0013]    The heater tube may extend over the steam generation chamber, e.g. extend axially. Thus, at least one section of the heater tube extends out of the steam generation chamber into the bore. The heater tube thus reheats steam or water that cooled in a reservoir after its injection and enhances the efficiency of the exploitation. 
         [0014]    The method for exploitation of an oil sand reservoir comprises at least the steps of producing steam in a steam generation chamber of a downhole apparatus, injecting said steam via steam outlets into the oil sand reservoir for mobilizing crude oil of the oil sand reservoir. At least part of the mobilized crude oils is recovered by said downhole apparatus. This method reduces the minimum number of bores for in situ oil sand exploitation compared to SAGD, and thus the costs. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0015]    In the following, the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiment with reference to the drawings. 
           [0016]      FIG. 1  shows a schematic depiction of an oil sand exploitation system, 
           [0017]      FIG. 2  shows a perspective view of a section of downhole apparatus, 
           [0018]      FIG. 3  shows section of steam generation chamber. 
           [0019]      FIG. 4  shows a schematic depiction of a second embodiment of an oil sand exploitation system. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    The oil sand exploitation system  100  in  FIG. 1  has a ground station  110  for housing the above ground facilities, like for example a controlling station  115  for monitoring and controlling the oil sand exploitation. Ground station  110  also includes a power source to, for example, provide power to an extraction well. Finally, ground station  110  includes a water source, such as a reservoir, to provide water (e.g., fresh water) to an extraction well. The ground station  110  is depicted as an onshore station, but can as well be a swimming station for exploitation of water covered oil sands. 
         [0021]    The oil sand exploitation system  100  includes an extraction well  120  with a downhole apparatus inserted into bore  105 . The downhole apparatus includes a multi conduit tube like casing  130 , e.g. for a power cable  230  (see  FIG. 2 ) for supplying power to downhole equipment, for example a protector  165 , and/or a motor  153  for driving a well head and a well monitor device  140 , as schematically depicted in  FIG. 1 . The extraction well  120  includes a steam generator  200  which may be mounted to the peripheral surface of the casing  130 . The steam generator  200  is explained below in more detail with respect to  FIGS. 2 and 3 . The steam generator  200  is positioned in this embodiment around casing  130  at a bottom or distal portion of casing  130  a first preferably vertical section of the extraction bore  105 . The steam generator  200  injects steam generally laterally into oil sand as shown in  FIG. 1 . The steam mobilizes crude oil in the oil sand. 
         [0022]    Extraction well  120  is configured to collect oil (including mobilized oil in the oil sand). To this end casing  130  of the extraction well  120  includes one or more oil inlets  135  along its length that allow oil to infiltrate the casing. Disposed within casing  130  is oil conduit  125 . The oil conduit  125  extends from the bottom or distal portion of casing  130  to the above ground station  110 . Oil that infiltrates casing  130  enters oil conduit  125  at the conduit&#39;s distal end and is pumped to the surface and fed to a production line  109  for example by a centrifugal pump  180  being arranged in the bottom or distal portion of casing  130 . Before pumping the crude oil to the above ground station  110 , water may be separated from the crude oil by separator  176 . Also, in the bottom or distal portion of casing  130  are an Electric Cable Clip  195 , a Venting Valve  172 , Single Flow Valve  185 , a Power Cable  175 , the Rotary Separator  176 , a Protector  165 , a Cable Head  162 , a Motor  152  and Well Monitor Device  140 . In between are a couple of water spray holes  145  to eject water or steam (e.g., when connected to steam generation unit  200  described below) and oil inlets  135 . 
         [0023]      FIG. 2  shows a section of an isometric view of casing  130  including the steam generator  200  of extraction well  120 . The casing  130  is tube like and constructed of a metal material such as steel. Casing  130  and has multiple compartments or conduits around an inner periphery which may serve as water conduit  250  (for water from ground station  110  to steam generator  200 ), oil conduit  125  (for oil infiltrating oil inlets  135  in casing  130 ) or as cable conduit (for providing power to components in the casing (e.g., centrifugal pump  180 , motor  152 ) and to heat cartridges associated with the steam generator  200 ). 
         [0024]    The steam generator  200  comprises a bundle of heating members  300  (cf.  FIG. 3 ). The heating members  300  are arranged around the peripheral surface of the casing  130  and are each connected to the casing  130  by, for example, one or more weld connections. Where it is desired to have more than one bundle associated with a well like extraction well  120 , the bundles may be stacked one above the other along the casing  130 . Referring to  FIG. 3 , each heating member  300  includes a heater conduit, illustrated as heater tube  310 , and steam generation chamber  375  respectively made of and defined by a metal material such as steel. 
         [0025]    In one embodiment, heater tube  310  has a circular cross-section and a diameter on the order of 57 millimeters and a length on the order of 3800 millimeters. The front facing (upper) side of the heater tube  310  is closed by conical cap  330 , which may be weld connected to the heater tube  310 . The rear facing side of the heater tube  310  is closed by an end cap  340 , which may preferably be a water tight but releasable connection, e.g. a threaded connection. 
         [0026]    Heater tube  310 , conical cap  330  and end cap  340  define a volume or chamber  335 . In one embodiment, the components, heater tube  310 , conical cap  330  and end cap  340  may be pressure tested to withstand, for example, a 1.5 millipascal (mPa) pressure test. Further, an inside surface of heater tube  310  defining a volume of chamber  335 , in one embodiment, is free of burrs or other debris or oil to provide a smooth, unvaried and clean surface. 
         [0027]    As shown in  FIG. 3 , chamber  335  of heating member  300  is divided into a first portion and a second portion by cap  360  of a thermally conductive material such as a metal material (e.g., steel). In one embodiment, a heating element such as electrical heater cartridge  350  with positive and negative terminals located at a single end (a proximal end as viewed) is positioned in a first portion of chamber  335  (proximal to cap  360 ). Heater cartridge  350  may have a length on the order of 300 millimeters or less, such as a length on the order of 150 millimeters. In one embodiment, cap  360  divides chamber  335  at a distance from a first end to be sufficient to allow heater cartridge  350  to be disposed in a first portion of chamber  335  but minimizes any additional volume for the first portion. As shown in  FIG. 3 , when heater cartridge  350  is disposed in a first portion of chamber  335  terminals  355  extend into a volume of end cap  340 . In one embodiment, end cap  340  includes lateral opening  365  that is, for example, a threaded opening for power connection to terminals  355 . A conductor is fed through a peripheral conduit of casing  130  into lateral opening  365 . Current is supplied to the conductor from an above ground power source in ground station  110 . 
         [0028]    Each steam generation chamber  375  is defined by, for example, cylindrical shell  320  a front wall  380  and a rear wall  370  connected by, for example, weld connections. The front wall  380  and the rear wall  370  each have an opening through which a heater tube  310  is disposed. The heater tube  310  extends axially through the steam generation chamber  375 . The connection of the heater tube  310  and the front wall  380  and/or the rear wall  370  may be a weld connection. 
         [0029]    In one embodiment, shell  320  has a length dimension on the order of 3,000 millimeters. Front wall  380  and rear wall  370  each have a diameter on the order of 110 millimeters. Rear wall  370  of shell  320  includes inlet  395  for a water source to be connected thereto to provide water to steam generation chamber  375 . Water is provided from a water source at, for example, ground station  110  to steam generation chamber  375  by a peripheral conduit of casing  130  that is in fluid communication with inlet  395 . 
         [0030]    The electrical heater cartridge  350  is thermally connected to the heater tube  310  and electrically connected with a power line e.g. by power cable  230 . The power (e.g., electrical current) line is preferably controlled by the controlling station  115  and may be ducted via a lateral opening like lateral opening  365 . A gasket may be used for sealing the cable feedthrough. Inside heater tube  310  is a thermally conductive material like it is described in the U.S. Pat. Nos. 6,132,823; 6,911,231; 6,916,430; 7,220,365 and U.S. Patent Publication No. 2005/0056807. 
         [0031]    Water inserted into the steam generation chamber  375  via a water inlet  395  may be heated by a heat generated in heater tube  310 . A current supplied to electrical heater cartridge  350  generates heat in the heater tube  310 . This heat is transferred to the steam generation chamber  375 . Steam develops inside the steam generation chamber  375  and escapes through steam outlet  390  into the oil sand. A single flow pressure valve may be provided in the steam outlet  390 . Thereby it can be avoided that foreign matter, like sand grains and the like enter the steam generation chamber  375 . Further, the steam can be pressurized. As the heater tube  310  extends over the steam generation chamber part of the heat provided by the electrical heater cartridge  350  is as well transferred directly to the oil sand. This heat reduces the condensation of the steam close to the extraction well  120  and thus permits the steam to heat a bigger area around the extraction well and thus to better mobilize the crude oil. The mobilized crude oil can be collected via oil inlets  135  (see  FIGS. 1 and 2 ), separated from water by rotary separator  176  and pumped by centrifugal pump  180  into the production line  109  a schematically represented in  FIG. 1 . 
         [0032]    As described above and shown in  FIGS. 2 and 3 , heater tube  310  of heating member  300  includes a heat source (heater cartridge  350 ) and a thermally conductive material or media  355 . Thermally conductive material  355  is present in the second portion of heater tube  310  an amount sufficient to transfer heat from heater cartridge  350  to the surface of heater tube  310 . Suitable representative thermally conductive material is described in U.S. Pat. Nos. 6,132,823; 6,911,231; 6,916,430; 7,220,365 and U.S. Patent Publication No. 2005/0056807, which are incorporated by reference herein. In another embodiment, thermally conductive material  355  is an inorganic material that is a combination of oxides and one or more pure elemental species, particularly titanium and silicon. One such combination is provided in Table 1. 
         [0000]    
       
         
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
             
             
               
                   
                 sodium peroxide 
                 2.705% 
                   
               
               
                   
                 disodium oxide 
                 2.505% 
               
               
                   
                 silicon 
                 1.6% 
               
               
                   
                 diboron trioxide 
                 0.505% 
               
               
                   
                 titanium 
                 0.405% 
               
               
                   
                 copper oxide 
                 0.405% 
               
               
                   
                 cobalt oxide 
                 0.255% 
               
               
                   
                 beryllium oxide 
                 0.255% 
               
               
                   
                 water, distilled, conductivity or of similar purity 
                 89.256% 
               
               
                   
                 dirhodium trioxide 
                 1.6% 
               
               
                   
                 trimanganese tetraoxide 
                 0.255% 
               
               
                   
                 strontium carbonate 
                 0.255% 
               
               
                   
                   
               
             
          
         
       
     
         [0033]    In an embodiment using the thermally conductive material described in Table 1, the material is introduced into each heater tube  310  of bundle  200  (see  FIG. 1 ) in a representative range amount minus the water component, equivalent to 1/400,000 of the volume of a heating tube. In other words, a 2400 mm heating tube with a 20 mm inside diameter would have a volume of 3,215,360 mm and the thermally conductive material would be present in an amount of 8 mm3 by volume. Other amounts may also be suitable such as an amount ranging from 1/400,000 to 1/200,000 by volume. For those thermally conductive materials described in the referenced incorporated patent documents, other amounts of thermally conductive material may also be used. For example, U.S. Pat. No. 7,220,365 describes an inorganic thermally conductive material of cobalt oxide, boron oxide, calcium dichromate, magnesium dichromate, potassium dichromate, beryllium oxide, titanium diboride and potassium peroxide in amounts of 0.001 to 0.025 by volume. 
         [0034]    In one embodiment, the thermally conductive material is introduced into a second portion of each heater tube  310  of tube bundle  200  (the second portion of heater tube  310  is defined by cap  360 ). Each tube is heated to evaporate the water component. The presence of cap  360  allows a proximal portion of chamber  335  to be accessed (to, for example, remove or replace heater cartridge  350 ) without disrupting the seal or the contents of the second portion of chamber  335 . Without wishing to be bound by theory, it is believed that the thermally conductive material in the second portion of each heater tube  310  operates by mechanically conducting heat generated by a heating cartridge to the steam generation chamber  375  (e.g., solid particles of the thermally conductive material colliding with one another and with a wall of the heater tube). The thermally conductive material in heater tube  310  permits heat distribution through the tube and conducts the heat to steam generation chamber  375  (e.g., axially conducts heat). That heat, in turn, evaporates water added to chamber  375  and produces steam. 
         [0035]    With 1 kW power provided by a heat source (e.g., an electrical heating rod), heater tube  310  including 1/400,000 by volume of the thermally conductive material described in Table 1 can generate on the order of 2000 kcal of heat or more on the surface (on an outer surface of outer cylinder  310 ). 
         [0036]    Representatively, as described above with reference to  FIG. 1 , one or more tube bundles  200  of extraction well  120  may be used to generate and discharge steam into a petroleum reserve to, in the case of oil sands, provide sufficient liquidity to the crude oil in oil sands to allow its extraction through casing  130  and pumping conduit  125 , and secondarily to provide thermal insulation to casing  130 . In one embodiment, maintenance of an appropriate temperature is desired. In one embodiment, ideal performance attempts to maintain an appropriate target temperature of the steam discharge temperature despite possible changing condition (e.g., heating of the reserve). In such embodiment, the temperature of the steam produced in tubes of a tube bundle may be monitored and/or controlled by controller  115 . For example, a processing protocol delivered to control computer  115  includes instructions for receiving temperature measurements from temperature sensors. Based on these measurements, instructions are provided in a machine-readable form to be executed by controller  115 . Accordingly, controller  115  executes the instructions to increase or decrease the power output to one or more heating rods  350  to achieve a target temperature in a range f (e.g., 250° C. to 280° C.). It is appreciated that controller  115  may be increasing power to some heating cartridges  350  while at the same time decreasing power to other heating cartridges  350 . Still further, controller  115  may be connected to pump  180  and other components in pumping conduit  125  and control the pump and/or other components based on program instructions to achieve a desired throughput from the well. 
         [0037]      FIG. 4  shows an another embodiment of an oil sand exploitation system. In this embodiment, oil sand exploitation system  400  includes ground station  410  for housing the above ground facilities, like for example, a controller  415 , a power source and a water source. Similar to  FIG. 1 , the above ground station  410  is depicted as onshore station, but can as well be a swimming station for exploitation of water covered oil sands. The system  400  includes a bore  405  into which an extraction well  420  with a downhole apparatus is inserted. In  FIG. 1 , the extraction well was inserted vertically or approximately vertically the entire length of the well. In  FIG. 4 , the extraction well  420  extends vertically through bore  405  at a ground surface of the well, but then extends laterally into the well. Otherwise, the construction and operation of extraction well  420  and system  400  is similar to the construction and operation of extraction well  120  and system  100  described with reference to  FIGS. 1-3 . The downhole apparatus includes casing  430  which is, for example a multi-conduit casing configured similar to casing  130  in  FIG. 1 , and one or more bundles of steam generators  500  configured similar to steam generators  200 .  FIG. 4  shows a single bundle disposed about and connected to a distal portion of casing  430 . Water provided to each steam generation chamber of steam generator  500  is converted to steam by heat provided to the chamber by a heater tube containing a heater cartridge and a thermally conductive material as described above with reference to  FIGS. 1-3 . The steam is dispensed from steam outlets  490  of a steam generation chamber into the oil sands reservoir to mobilize oil in the oil sand. Mobilized oil infiltrates casing  430  through oil inlets  435  and is pumped to the surface of the well. 
         [0038]    In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiments. It will be apparent however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. The particular embodiments described are not provided to limit the invention but to illustrate it. The scope of the invention is not to be determined by the specific examples provided above but only by the claims below. In other instances, well-known structures, devices, and operations have been shown in block diagram form or without detail in order to avoid obscuring the understanding of the description. Where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics. 
         [0039]    It should also be appreciated that reference throughout this specification to “one embodiment”, “an embodiment”, “one or more embodiments”, or “different embodiments”, for example, means that a particular feature may be included in the practice of the invention. Similarly, it should be appreciated that in the description various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects may lie in less than all features of a single disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the invention.