Patent Publication Number: US-2015083412-A1

Title: Device and method for obtaining carbonic substances from oil sands

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2012/075687 filed Dec. 17, 2012, and claims the benefit thereof. The International Application claims the benefit of German Application No. DE 10 2012 000 092.8 filed Feb. 24, 2012. All of the applications are incorporated by reference herein in their entirety. 
    
    
     FIELD OF INVENTION 
     The invention relates to a device and also to a method for extracting carbonaceous substances, especially bitumen, from oil sands. 
     BACKGROUND OF INVENTION 
     Large portions of the worldwide oil reserves exist in the form of oil sands. A mixture of rock, clay, sand, water and bitumen or other heavy oils is understood by oil sand. Only bitumen, which typically exists with a viscosity of API 5° to 15° with respect to deposits, shall be mentioned in the following text as being representative for heavy oils, extra-heavy oils or generally long-chain hydrocarbons. By means of corresponding process steps, bitumen can be converted into synthetic crude oil. 
     Oil sand deposits are mined if they lie in strata of shallow depth, preferably by open-cast mining. Oil sand deposits, however, often lie in deeper strata which are not accessible to open-cast mining or the mining of which would be uneconomical in open-cast mining. Oil sand deposits are typically mined after depths of about 60 m by so-called in-situ processes since with these processes the removal of the surface layer, which lies above the oil sand deposit, is not necessary. 
     A common in-situ process is steam assisted gravity drainage (SAGD). With the SAGD process, the bitumen, which is present in the earth in a deposit, is heated by superheated steam. As a result of the heat effect the long-chain hydrocarbons of the highly viscous bitumen are broken down. This, and the heating of the oil sand, lead to a reduction of the viscosity of the bitumen which as a result becomes free-flowing and can be conventionally pumped out of the deposit. 
     The known device for the SAGD process comprises at least one injection pipeline for feeding the superheated steam into the deposit and a production pipeline through which the fluid bitumen can be transported out of the deposit to the local surface. The injection pipeline and the production pipeline are laid inside the deposit essentially parallel to each other and extending horizontally one above the other. The injection pipeline and the production pipeline usually have a distance of about 5 to 10 m from each other in the vertical direction. In the horizontal direction, the pipes extend inside the deposit by a length of between several hundred meters and a few kilometers. The injection pipeline is typically located above the production pipeline. As a result of the heating and the reduction of the viscosity of the bitumen, the bitumen flows downward on account of gravitational force and therefore towards the production pipeline and can be simply pumped out there and transported to the earth&#39;s surface. The transporting can be achieved either by oil lift pumps or by introduction of an overpressure in the deposit. The introduction of overpressure has the significant disadvantage, however, that earth displacements on the earth&#39;s surface (blow out) can occur in the surrounding area of the deposit, especially when the stratum above the deposit is of small thickness. For this reason, the steam pressure, before introduction into the deposit, is usually reduced by a restrictor or a throttle valve to a pressure which is lower than the rock pressure in the region of the deposit. The throttle valve is arranged between the steam generator and the injection pipeline in this case. Since the steam pressure is reduced in the throttle valve, without being utilized, the process is inefficient. A further disadvantage of the SAGD process is the enormous energy expenditure. For pumping out one barrel (159 l) of bitumen, about 20 m 3  of natural gas and about 3,000 l of water are required for steam production. 
     SUMMARY OF INVENTION 
     It is therefore an object of the present invention to develop the known SAGD process in such a way that the efficiency of the device is increased. At the same time, it is an object of the present invention to demonstrate a corresponding method for extracting carbonaceous substances. 
     The object is achieved with regard to a device and a method by the features of the independent claims. Further advantages of the invention are the subject of the dependent claims. 
     The device according to aspects of the invention for extracting carbonaceous substances, especially bitumen, from oil sands, has at least one steam generator, at least one injection pipeline and at least one production pipeline—wherein via the injection pipeline steam can be introduced into the oil sand and via the production pipeline the carbonaceous substance can be removed from the oil sand—is distinguished by at least one steam turbine being arranged between the steam generator and the injection pipeline. As a result of the arrangement of the steam turbine between the steam generator and the injection pipeline the pressure reduction, which is usually carried out via the throttle valve without being utilized, can be used for energy recovery. To this end, the steam turbine is preferably connected to a generator for current generation. The generated current can then be utilized directly at site for crude oil production or be fed into an electricity network. The steam, which is directed from the steam generator to the steam turbine, is expanded in this case inside the steam turbine to a pressure which is equal to, or lower than, the rock pressure in the region of the deposit. This steam is then directed into the deposit via the injection pipelines. 
     An advantageous embodiment of the invention provides that the steam production carried out by a heat exchanger, wherein hot exhaust gas of a heat engine, especially a gas turbine, is used for steam production. By using a heat engine, especially a gas turbine, the heating of the water and the subsequent evaporation can be carried out in a particularly efficient manner. The gas turbine in this case is connected to a second generator for current generation. The exhaust gas of the gas turbine is used for the heating and evaporating of the water. The heat energy of the exhaust gas is preferably realized by a heat exchanger in which the gas flow is conducted in counterflow to the water/steam. The current which is generated in the generator can in turn be used directly at site for processing the bitumen to form crude oil, or can be fed into an electricity network. The steam production can also be carried out by direct firing of the boiler. 
     The method according to aspects of the invention for extracting carbonaceous substances, especially bitumen, from oil sands by a device as claimed, includes the following method steps: -Producing steam in the steam generator; -Feeding the steam to the steam turbine; -Expanding the steam in the steam turbine to a steam pressure which is lower than, or equal to, that of the rock pressure in the region of the deposit of bitumen; -Introducing the steam via the injection pipeline into the oil sand; -Heating the oil sand by the steam and breaking down the long-chain hydrocarbons of the carbonaceous substances; -Removing the carbonaceous substances (bitumen) via the production pipeline. 
     The bitumen which is removed can then be processed at the earth&#39;s surface by suitable measures to form crude oil. 
     By expanding the steam in the steam turbine to a steam pressure which is lower than, or equal to, the rock pressure in the region of the deposit, the energy of the steam, which previously was discharged by the throttle valve into the environment without being utilized, can be utilized for energy recovery, especially for generating electric current by connecting the steam turbine to a generator. By utilizing the steam pressure for generating electric current the efficiency of the method is improved. 
     Further advantages of the invention, which can be applied individually or in combination with each other, are explained below based on an exemplary embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows in this case a device according to the invention for extracting carbonaceous substances, especially bitumen, from oil sands. The representation is a simplified and schematic representation in which only the components which are essential for the invention are shown. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
       FIG. 1  shows an exemplary embodiment of a device according to aspects of the invention for extracting carbonaceous substances, especially bitumen, from oil sands. The oil sands are located in a deposit  7  in the earth  8 . If the rock layer above the deposit  7  is not excessively large, the mining of the oil sand is carried out by open-cast mining. After a depth of about 60 m, open-cast mining is uneconomical, however, as already described, so that the in-situ process which is described in the description introduction is then used. 
     The device according to aspects of the invention for such a method has at least one steam generator  1  and at least one injection pipeline  2  and at least one production pipeline  3 . The injection pipeline  2  and the production pipeline  3  usually extend horizontally inside the deposit  7 . The injection pipeline  2  and the production pipeline  3  in this case extend parallel to each other and typically at a distance of about 5 to 10 m from each other. In the horizontal direction, the pipes extend inside the deposit  7  over a length of between several hundred meters and a few kilometers. 
     Before the bitumen can be extracted from the deposit, this first of all has to be heated in order to reduce the viscosity of the bitumen which is present in the oil sand or in the oil rock. As a result of the heating, a break down of the long-chain hydrocarbons of the highly viscous bitumen occurs, as a result of which the viscosity reduces and the bitumen becomes free-flowing. The heating of the deposit  7  is carried out by introduction of the steam, which is produced in the steam generator  1 , via the injection pipeline  2 . The free-flowing bitumen sinks downward on account of gravitational force and can then be transported to the surface as bitumen-water emulsion. For the transporting, simple oil lift pumps are suitable. The bitumen-water emulsion can then be processed in a corresponding processing plant to form crude oil. The water of the water-oil emulsion is preferably recovered in the process and fed again to the steam generator  1  via a corresponding return line  10 . The steam which is introduced into the deposit  7  via the injection pipeline  2  has to have a pressure which lies below the rock pressure since otherwise earth displacements on the surface (blow out) can occur. This occurs especially when the earth above the deposit  7  is of small thickness. Since the pressure of the steam downstream of the steam generator  1  is excessively high, the steam first of all has to be reduced to the corresponding rock pressure. To this end, a steam turbine  5  is arranged between the steam generator  1  and the injection pipeline  2 . The steam turbine  5  is connected to a generator G 2  which serves for current generation. The generated current can be used directly for the plant or be fed into an electricity network. The steam turbine  5  is designed and/or controlled in such a way that the steam, which is directed from the steam generator  1  into the turbine  5 , is only expanded to such a degree that in the main it corresponds to the rock pressure inside the deposit. By using the steam turbine  5  for pressure reduction of the steam, energy recovery and therefore a considerably more efficient operation are made possible compared with the previously used throttle valves or restrictors. 
     The heat energy for the steam generator  1  is provided by the exhaust gas of a gas turbine  6 . The gas turbine  6  is connected to a further generator  1  for current generation. The generated current can in turn be used directly for the electric consumers of the plant or be fed into an electricity network. Since the production sites for oil sand frequently lie in regions which are not accessible to a current supply, the current is usually used directly for the plant, however. The heat energy of the exhaust gas is yielded to the water or to the steam in the steam generator  1  by a heat exchanger. In this case, the hot exhaust gas preferably flows in counterflow to the water/steam. Alternatively, the steam production can also be carried out by direct firing of the boiler. 
     The method for extracting bitumen from oil sands by the described device is briefly explained in the following text. In the method, steam is first of all produced in the steam generator  1 . To this end, the heat energy of the exhaust gas of the steam turbine  6  is fed via a heat exchanger to the steam generator  1 . In the steam generator  1 , the water is evaporated and the hot steam is first of all fed to the steam turbine  5 . A cyclone separator or the like is advantageously incorporated upstream of the steam turbine, as a result of which the water and impurities are separated from the steam. As a result of this, the steam is dry saturated and superheated. In the steam turbine  5 , the steam pressure is expanded, wherein the steam turbine  5  generates electric current via a generator G 2 . The expanded steam, which has a steam pressure which for example has the rock pressure in the deposit  7 , is introduced into the deposit  7  via the injection pipeline  2 . The hot steam in this case brings about a breakdown of the long-chain hydrocarbons of the highly viscous bitumen in the oil sand. A bitumen-water emulsion, which trickles downward on account of gravitational force, is created in the process. The bitumen-water emulsion can then be transported via the production pipeline  3  to the earth&#39;s surface. To this end, an oil lift pump, which is not shown in  FIG. 1 , is used. The bitumen-water emulsion from there makes its way to a processing plant  9 . In this, the bitumen is separated from the water on the one hand and then the bitumen is further processed to form crude oil. The water is fed back to the evaporator  1  via a corresponding line  10  and can be evaporated again there. 
     The device according to aspects of the invention and the method according to aspects of the invention for extracting carbonaceous substances, especially bitumen, from oil sand are distinguished by surplus pressure energy of the steam being expanded in a steam turbine downstream of the steam generator and by the steam turbine generating additional electric energy via a generator which can especially be utilized for the device. As a result of this, an efficiency increase and therefore a more economical operation of the device are made possible.