WO2015036315A1 - Method for the thermal treatment of an underground oil reservoir - Google Patents

Abstract

The invention relates to a method for thermal treatment of an underground oil reservoir (1), which has cracks (5) and into which at least one injection bore (2) has been sunk, wherein the injection bore (2) comprises perforation openings (32o) and perforation openings (32u) and two injection strands which are separate from each other, wherein the first injection strand (6) is connected via the perforation openings (32u) and the second injection strand (9) is connected via the perforation openings (32o) to the cracks (5) of the underground oil reservoir (1), wherein two formulations F1 and F2 (7, 8) are injected separately from each other through the two injection strands (6, 9) through the perforation openings (32o, 32u) into the cracks (5) of the underground oil reservoir (1) and mix in the underground oil reservoir (1) and enter into an exothermic reaction.

Description

 The present invention relates to a process for the thermal treatment of an underground oil reservoir and to a process for the production of oil from a subterranean oil reservoir.

In natural petroleum reservoirs, petroleum is generally present in the voids of porous reservoirs which are closed to the surface by impermeable facings. In addition to crude oil and natural gas, underground oil reservoirs generally contain more or less saline water. This water is also called deposit water or formation water. In the cavities in which the petroleum is present, it may be very fine cavities, capillaries, pores or the like. The cavities may, for example, have a diameter of only 1 μm.

In order to extract crude oil and / or natural gas from underground oil reservoirs, at least one well is usually first drilled (drilled) into the underground oil reservoir. After sinking the well into the subterranean oil reservoir, oil generally initially flows to the surface through the borehole due to the natural intrinsic pressure of the subsurface oil reservoir. The intrinsic pressure of the underground oil reservoir can be caused, for example, by gases present in the reservoir, such as methane, ethane or propane. This phase of oil production is also referred to as primary oil production.

In addition to primary oil production methods for secondary and tertiary mineral oil production are known. In secondary and tertiary oil production, additional drilling is being drilled (sunk) into the underground oil reservoir. A distinction is generally made between so-called production wells and so-called injection wells. The production wells are used to extract oil from the underground oil reservoir to the surface. Through the injection well, a flood agent is injected into the underground oil reservoir to maintain or increase the pressure of the underground oil reservoir. The injected flooding agent forces petroleum through the cavities of the underground oil reservoir from the injection well toward the production wells. In the secondary and tertiary processes for oil production are used as flooding agents such as water, water vapor and water to which additives are added. In addition, gases such as carbon dioxide or nitrogen are also used as flooding agents. In order to increase the flow of oil from the underground oil reservoir, at least part of the underground oil reservoir is generally hydraulically fractured. For this purpose, suitable flowable formulations, which are also referred to as fracking liquids, pressed under high pressure in the underground Erdöllagerstätte. The pressure is usually in the range of 500 to 1000 MPa. As a result, parts of the underground oil reservoir (the underground rock formation) are broken hydraulically. This process is also referred to as hydraulic fracturing. Hydraulic fracturing (hydraulic fracturing or fracturing of an underground oil deposit) is the occurrence of a fracture event in the surrounding rock of a well in an underground oil reservoir as a result of the hydraulic action of a liquid or gas pressure on the bedrock of the underground oil reservoir In the prior art, fluids containing water, gelling agents and, if necessary, proppants such as sand or proppant are described, which increase the permeability of the underground oil reservoir, thereby increasing the rate of delivery of petroleum trapped in cavities the underground oil reservoir facilitates the flow of petroleum to the production wells, and the proppants contained in the fracturing fluid serve to stabilize the fracture cracks formed during the fraying so that these cracks remain open after the completion of the fracking.

Another known method for increasing the production rates of oil from an underground oil reservoir is the thermal treatment of the underground oil reservoir. Thermal treatment processes are particularly used in underground oil reservoirs containing high viscosity petroleum. In addition, thermal treatment of oil shale deposits is used.

For this purpose, a fuel and an oxidant are generally injected into the underground oil reservoir. The fuel and the oxidizer react exothermally in the subterranean oil reservoir with evolution of heat. The heat development modifies the rheological properties of the petroleum contained in the subterranean oil reservoir, thereby increasing the production rate. Depending on the intensity of the exothermic reaction, it is also possible to effect a pyrolysis of the petroleum or the matrix of the underground Erdöllagerstätte. Pyrolysis occurs preferentially in the thermal treatment of oil shale deposits.

In the prior art, various methods for the thermal treatment of underground oil reservoirs are described. The RU 2 210 589 discloses a A method of thermal treatment of a subsurface oil reservoir wherein an aqueous solution of an oxidizer and a fuel is injected into the subterranean oil reservoir. Subsequently, an initiator solution is injected which initiates the exothermic reaction between oxidant and fuel. The aqueous solution of oxidant and fuel contains ammonium salts of organic or inorganic acids and an alkali hypochlorite and optionally salts of nitric acid.

The initiator solution is an aqueous solution of copper sulfate, aluminum chloride or acids. The initiator solution is injected separately after injection of the aqueous solution containing an oxidizer and a fuel. In the process described in RU 2 102 589, the exothermic reaction takes place mainly in the borehole interior. The underground oil reservoir is heated only slightly. The method is therefore mainly suitable for stimulating boreholes. Efficient heating of the underground oil reservoir is not achieved by the method according to RU 2 102 589.

The RU 2 401 941 also describes a method for the thermal treatment of underground oil deposits. In this procedure, two formulations are injected simultaneously into the well through two separate injection strands. The two injection strands are formed by an inner tube, which is enclosed by an outer tube. The inner tube forms the first injection strand. The annular space between the inner tube and the outer tube forms the second injection strand. At the end of the two injection strands, the formulations injected separately from each other at the same time mix in the bore.

The first formulation is a mixture containing an oxidizer and a fuel. For this purpose, for example, an aqueous solution of urea and ammonium nitrate is used, to which further additives, for example, hydrochloric acid, nitric acid or phosphoric acid and water-soluble metal salts can be added, if desired. The second formulation initiates the exothermic reaction between oxidant and fuel. As a second formulation, aqueous solutions of alkali metal nitrite, borohydride and a lye or sodium hydroxide and borohydride are used in the process of RU 2 401 941.

In the exothermic reaction in the process according to RU 2 401 941, temperatures in the range of 200 to 500 ° C are reached, depending on the concentration of the formulations. In the process according to RU 2 401 941, the two formulations mix directly in the borehole. The exothermic reaction therefore also takes place mainly in the borehole. The method according to RU 2 401 941 is therefore primarily for the stimulation of production wells and for the removal of Deposits from production wells suitable. The underground oil reservoir is only minimally heated in the process according to RU 2 401 941.

The RU 2 349 743 also describes a method for the thermal treatment of underground oil deposits. The method is preferably used in underground oil reservoirs containing high-viscosity petroleum. For this purpose, in an initial step, an aqueous hydrogen peroxide solution is injected with a concentration of 30 wt .-% hydrogen peroxide through a hole in the underground oil reservoir. Subsequently, in a second step, an aqueous solution containing sodium hydroxide or potassium hydroxide is injected into the underground oil reservoir. Upon completion of the second process step, the hydrogen peroxide solution mixes with the aqueous alkali hydroxide solution in the underground oil reservoir. The alkali metal hydroxide catalyzes the decomposition of hydrogen peroxide. In this exothermic decomposition temperatures in the range of 500 ° C are reached. The method according to RU 2 349 743 has the advantage over the methods described above that heating of the underground oil reservoir is possible with this method.

However, a disadvantage of the process according to RU 2 349 743 is that, especially in dense subterranean oil reservoirs, the mixing of the successively injected aqueous solutions is not reliably ensured. It is difficult to predict how the aqueous solutions will disperse in the subterranean formation, so that large losses of aqueous hydrogen peroxide solution or aqueous alkali metal hydroxide solution may occur in the process according to RU 2 349 743. Another disadvantage of the method is that a decomposition of the aqueous hydrogen peroxide solution can already begin during the injection. This is because both aqueous formulations are successively injected through the same tubing.

The RU 2 278 250 also describes a process for the thermal treatment of underground oil deposits. Here, at least two holes are drilled in the underground oil reservoir. The area between the two holes is heated. In the first well, a solution containing hydrogen peroxide is injected. The second well is injected with an aqueous solution that initiates the exothermic decomposition of hydrogen peroxide. As the initiator solution, aqueous solutions containing sodium permanganate are used. The hydrogen peroxide solution has a concentration in the range of 18 to 50 wt .-%. By injecting the two solutions separately through two holes, the two flood fronts move towards each other in the underground oil reservoir. As soon as the two flood fronts meet in the underground oil reservoir, mixing of the hydrogen peroxide solution and the initiator solution occurs in the underground oil reservoir. As a result, the exothermic decomposition of hydrogen peroxide is initiated. This forms oxygen and water vapor. With the method according to RU 2 349 743 thus a thermal treatment and a significant warming of the underground oil reservoir between the two holes is possible. However, a disadvantage of this process is that the two formulations are distributed uncontrollably in the underground oil reservoir. A coincidence of the two formulations in the underground oil reservoir between the two holes is thus not guaranteed safe. This results in large losses of aqueous hydrogen peroxide solution and aqueous potassium permanganate solution since only a small portion of the two injected formulations in the subterranean crude oil deposit actually meet and thus result in the heating of the underground oil reservoir.

All the processes described above for the thermal treatment of underground oil reservoirs have the disadvantage that either the underground oil reservoir is only minimally heated or that the liquid formulations in the underground oil reservoir are distributed virtually uncontrollably. The location and volume of the area to be heated by thermal treatment can only be localized very inaccurately in an underground oil reservoir. With the methods described above, it is therefore not possible to predict exactly in which area of the underground oil reservoir the exothermic chemical reaction will take place and which area of the underground oil reservoir will be heated by the thermal treatment.

Moreover, in the processes described above, large losses of the injected formulations occur, that is, the injected formulations do not completely react but remain unreacted in the subterranean crude oil reservoir.

The present invention is therefore based on the object to provide a method for the thermal treatment of underground oil deposits that the disadvantages of the prior art described above, or not only to a reduced extent. The process according to the invention is intended to ensure reliable mixing and thus the most complete possible reaction of the formulations used. The area of underground oil reservoir, which is heated during the thermal treatment, should be as accurately predictable and controllable. Premature use of the exothermic reaction at the surface of the underground oil reservoir or in the well, which is brought down into the underground Erdöllagerstätte should be reliably prevented. This object is achieved by a method for thermal treatment of an underground oil reservoir (1), the Frackrisse (5) and in which at least one injection well (2) is drilled, said injection well (2) perforation (32o) and perforation openings (32u) and two separate injection strands (6, 9), wherein the first injection strand (6) passes through the perforation openings (32u) and the second injection strand (9) via the perforation openings (32o) in conjunction with the fracture tears (5) of the underground oil reservoir ( 1), wherein two formulations F1 and F2 (7,8) are injected separately through the two injection strands (6,9) through the perforation openings (32o, 32u) into the fracture cracks (5) of the underground oil reservoir (1) in the underground oil reservoir (1) mix together and enter an exothermic reaction. The subject of the present invention is also a process for the extraction of crude oil from an underground oil reservoir (1) which has tail cracks (5) and into which at least one injection well (2) and at least one production well (15) are drilled, the injection well (2 ) Comprises perforation openings (32o) and perforation openings (32u) and two separate injection strands (6,9),

wherein the first injection strand (6) via the perforation openings (32u) and the second injection strand (9) via the perforation openings (32o) in conjunction with the Frackrissen (5) of the underground Erdöllagerstätte (1), comprising the steps a) thermal treatment of underground oil reservoir (1), wherein two formulations F1 and F2 (7,8) are injected separately through the two injection strands (6,9) through the perforation openings (32o, 32u) into the fracture cracks (5) of the underground oil reservoir (1) and mix in the underground oil reservoir (1) with each other and enter into an exothermic reaction. b) injecting a flooding agent (1 1) through the at least one injection well (2) and removal of petroleum from at least one production well (15). The inventive method for thermal treatment of an underground oil reservoir (1) can be used in principle in all underground deposits containing petroleum. However, the process according to the invention is preferably used in unconventional underground oil reservoirs (1). According to the invention, unconventional underground oil reservoirs (1) are understood as meaning reservoirs which have a dense reservoir matrix and / or contain oil with a high viscosity. Unconventional underground oil reservoirs (1) are, for example, shale-oil deposits, bitumen deposits, Heavy oil deposits or oil-shale deposits. The unconventional underground oil reservoirs (1) generally have a permeability of less than 10 mD before the fracking process is carried out. The viscosity of the petroleum is generally in the range of 10 to 10,000 mPas. The viscosity of the bitumen can be well over 10,000 mPas. In unconventional shale-oil deposits, oil production is only possible after massive thermal treatment of the reservoir rock (pyrolysis).

The cracks (5) in the underground oil reservoir (1) are preferably produced by a fracking process. The cracks (5) generated by this fracking process are also referred to as fracking cracks (5). Suitable fracking processes are known in principle to the person skilled in the art. In conventional fracking process to form fracking cracks (5) in the underground oil reservoir (1), usually a fracking liquid, which may contain a proppant, at high pressure in the underground Erdöllagerstätte (1) is pressed. As a result, fracture cracks (5) are formed in the underground oil reservoir (1).

Frequently, water is used as the fracking fluid, to which other additives such as thickening agents are optionally added. This process is also referred to as "hydraulic fracturing." In this process, the fracture cracks (5) formed and the deposit matrix are contaminated with water, leading to swelling of clay rocks and clay particles in the underground oil reservoir (1) Case, if the deposit matrix, that is the surrounding rock, consists of clay-containing rocks.

In particular, in the development of unconventional underground oil deposits (1), this effect is very disadvantageous, since the unconventional underground oil deposits (1), as described above, in any case have low permeability and / or high-viscosity petroleum.

The method by which the fracture cracks (5) are formed in the underground oil reservoir (1) is not essential to the invention. In addition to the hydraulic fracturing described above, it is also possible to use further fracking methods which are suitable for forming fracking cracks (5) in the underground oil reservoir (1).

FIG. 1 shows, by way of example, the condition of an underground oil reservoir (1) in which a fracking zone (50) has been produced by a fracking process and has fracking cracks (5). Figure 1 shows a vertical section through the underground Erdöllagerstätte (1). A vertical injection well (2) was drilled into the subterranean crude oil deposit (1). A borehole section was perforated, to create the perforation openings (3). The perforation openings (3) were produced by methods known per se. The ball perforation is preferably used here, as described, for example, in RU 2 358 100.

Subsequently, an injection string (not shown) was drilled in the injection well (2), which was sealed to the surface with a packer (4). Subsequently, a high pressure fracking liquid was introduced into the underground oil reservoir (1) to produce the fraying zone (50) containing the fracture tears (5).

Suitable fracking liquids and fracking processes are described, for example, in WO 2008/106695 and US Pat. No. 7,213,651. The spatial extent of the fracking zone (50) depends strongly on the geological conditions of the underground oil reservoir (1). In addition, the spatial extent of the fracking zone (50) depends on the applied pressure and the duration of the fracking process. The fracking zone (50) generally has a radial extent in the range of 10 to 200 m, preferably in the range of 15 to 150 m and particularly preferably in the range of 20 to 70 m, in each case measured from the injection bore (2) in the region of the perforation openings (3).

Figure 1 a) shows the state of the underground Erdöllagerstätte (1) after the implementation of a single-stage fracking process. Figure 1 b) shows the state of the underground Erdöllagerstätte (1) after carrying out a two-stage fracking process. For this purpose, initially the perforation openings (3) were produced in the lower region of the injection bore (2) and subsequently the part of the underground oil reservoir (1) adjoining the perforation openings (3) in the lower area was scrapped. Subsequently, in the overlying part of the injection well (2) further perforation openings (3) were generated and the adjoining region of the underground Erdöllagerstätte (1) was cracked.

In the process according to the invention, at least one injection well (2) is drilled into the subterranean crude oil deposit (1). The term "at least one injection well (2)" according to the invention comprises both exactly one injection well (2) and two or more injection wells (2). The terms "at least one injection well (2)" and "one injection well (2)" are synonymous according to the invention According to the invention, the injection bore (2) comprises perforation openings (32o) and perforation openings (32u) and two injection strands (6, 9) separated from one another. The injection strands (6, 9) are separated from one another in the injection bore (2), that is to say that the first injection strand (6) and the second injection strand (9) have no hydrodynamic connection to one another within the injection bore (2). This reliably prevents mixing of the formulations F1 and F2 (7, 8) in the injection well (IB) and thus the occurrence of the exothermic reaction between the formulations F1 and F2 (7, 8) within the injection well (2). The term "no hydrodynamic compound" is understood according to the invention to mean that no liquids, in particular no formulations F1 and F2 (7, 8), can be exchanged between the two injection strands (6, 9) within the injection well (2) Injection strands (6, 9) within the injection bore (2) are sealed off from one another for this purpose In general, at least one packer (4) is used as the subject of the present invention. 9) within the injection bore (2) have no hydrodynamic connection to one another.

The first injection strand (6) has a hydrodynamic connection to the perforation openings (32u). The second injection strand (9) has a hydrodynamic connection to the perforation openings (32o). This allows the introduction of the formulations F1 and F2 (7, 8) via the injection strands (6, 9) in the Frackrisse (5) of the fracking zone (50). The term "hydrodynamic compound" is understood according to the invention to mean that liquids can be exchanged via these compounds, in particular the formulations F1 and F2 (7, 8) ) is also referred to as the second injection strand (9) according to the invention.

The formulation F1 (7) may be injected through the first injection string (6) or through the second injection string (9). The same applies to the formulation F2 (8), which can also be injected through the first injection strand (6) or through the second injection strand (9). According to the invention, it is essential that the formulations F1 and F2 (7, 8) are injected separately into the tailings cracks (5) of the fraying zone (50). In one embodiment, the formulation F1 (7) is injected through the first injection string (6) and the formulation F2 (8) is injected through the second injection string (9) into the dressing cracks (5) of the fraying zone (50). In another embodiment, the formulation F1 (7) is injected through the second injection strand (9) and the formulation F2 (8) through the first injection strand (6) into the fracking cracks (5) of the fraying zone (50). The perforation openings (32o) and the perforation openings (32u) are in a hydrodynamic connection via the fracking cracks (5) of the fraying zone (50). This makes it possible that the formulations F1 and F2 (7, 8) via the Frackrisse (5) in the fracking zone (50) mix together and enter into an exothermic reaction. Despite the hydrodynamic connection between the perforation openings (32o) and (32u) via the fracking cracks (5), mixing of the formulations F1 and F2 (7, 8) in the injection well (2) is reliably prevented. This is achieved by injecting the formulations F1 and F2 (7, 8) under pressure via the injection strands (6, 9). The pressure within the injection strands (6, 9) thus prevents the formulations F1 and F2 (7, 8) from the fracking cracks (5) of the fraying zone (50) from entering the injection strands (6, 9) of the injection well (2).

The present invention thus also relates to a method in which the first injection strand (6) and the second injection strand (9) have a hydrodynamic connection to one another via the tailings cracks (5) of a fraying zone (50).

As injection strands (6, 9) usually two separate pipe strands are used. In a preferred embodiment, the injection well (2) comprises an inner tube that acts as a first injection string (6) and an outboard tube that encloses the inner tube. The annular space between the outer wall of the inner tube and the inner wall of the outer tube preferably forms the second injection strand (9).

The subject of the present invention is therefore also a method in which the injection bore (2) comprises an inner tube and an outer tube enclosing the inner tube, wherein the inner tube acts as the first injection strand (6) and the annular space between the outer wall of the inner tube and the inner wall of the outer tube functions as a second injection string (9).

A preferred embodiment of the injection bore (2) is shown by way of example in FIG.

FIG. 2a) shows the section of a vertical section through the underground oil reservoir (1) in the region of the fracking zone (50). In this case, the injection bore (2) comprises an inner tube which acts as the first injection strand (6) and an outer tube which encloses the inner tube. The second injection strand (9) is in this case formed by the annular space between the outer wall of the inner tube and the inner wall of the outer tube.

The injection bore (2) has perforation openings (31), (32o) and (32u). These perforation openings correspond to the perforation openings (3) as in FIG. 1 a). shown. In FIG. 2a) there are two packers (4) in the injection bore (2) which seal the first injection strand (6) with respect to the second injection strand (9). The two packers (4) interrupt the hydrodynamic connection between the two injection strands (6, 9) within the injection bore (2). Through the first injection strand (6), the formulation F1 (7) is injected through the perforation opening (32u) into the fracking cracks (5) of the fraying zone (50). The flow direction of formulation F1 (7) is indicated by arrows in FIG. 2a).

The formulation F2 (8) is injected through the perforation opening (32o) into the fracking cracks (5) of the fracking zone (50) through the annular space serving as the second injection strand (9) in FIG. 2a). The flow direction of formulation F2 (8) is indicated by arrows in FIG. 2 a). The two packers (4) encapsulate the perforation opening (31) from the first and second injection strand (6, 9). Thus, no liquids can escape from the injection bore (2) into the fracking cracks (5) through the encapsulated perforation opening (31).

FIG. 2b) shows a further embodiment of the method according to the invention. In this embodiment, only one packer (4) is present in the injection bore (2) to interrupt the hydrodynamic connection between the injection strands (6, 9).

FIG. 3 shows a further embodiment of the process according to the invention, in which the fracture cracks (5) of the fraying zone (50) were produced by a two-stage fracking process. FIG. 3 shows the section of a vertical section of the underground oil reservoir (1) in the region of the fracking zone (50). The fracking process was carried out in two stages, as described for FIG. 1 b). Accordingly, the injection bore (2) has two spaced-apart perforation openings (32o), (32u). In this embodiment, a packer (4) is placed in the non-perforated area between the perforations (32o) and (32u) to interrupt the hydrodynamic communication between the first injection string (6) and the second injection string (9).

The distance between the perforation openings (32o) and (32u) is generally in the range of 5 to 100 m, preferably in the range of 5 to 50 m and particularly preferably in the range of 10 to 30 m.

The subject matter of the present invention is thus also a method in which the perforation openings (32o) and the perforation openings (32u) are at a distance from each other which is in the range of 5 to 100 m.

The mixing of the formulations F1 and F2 (7, 8) takes place in the fracking cracks (5) of the fracking zone (50). After mixing the formulations F1 and F2 (7, 8) begins a chemical exothermic reaction between the two formulations F1 and F2 (7, 8) in Frackrissen (5) of the fracking zone (50).

The inventive method ensures the mixing of the formulations F1 and F2 (7, 8) in the fracking zone (50). The losses of the formulations F1 and F2 (7, 8) are minimized by the method according to the invention. The location and spacing of the perforations (32o, 32u) accurately predicts the area where the exothermic reaction takes place, which is consequently heated.

The state after onset of the exothermic reaction is shown by way of example in FIG. 4a). After mixing the formulations F1 and F2 (7, 8) in the fracking cracks (5) in the fracking zone (50), the exothermic reaction between the two formulations F1 and F2 (7, 8) begins. The flow direction of the formulations F1 and F2 (7, 8) is indicated by arrows in FIG. 4a). In the exothermic reaction between formulations F1 and F2 (Figs. 7, 8) heated zones (10) are generally produced. The temperature of the heated zones (10) is generally in the range between 80 ° C and 1200 ° C. The present invention thus also provides a process in which the formulations F1 and F2 (7, 8) in the fracking cracks (5) of the fraying zone (50) mix and undergo an exothermic reaction, whereby in the underground oil reservoir (1) heated zone (10) is formed. Preferably, the thermal treatment process is carried out so that the heated zone (10) after carrying out the thermal treatment has a temperature of at least 150 ° C, preferably at least 200 ° C and particularly preferably at least 300 ° C. The subject matter of the present invention is therefore also a method in which the temperature of the heated zone (10) has a temperature in the range from 80 to 1200 ° C., preferably in the range from 100 to 1000 ° C. and more preferably in the range from 150 to 800 ° C has. Due to the thermal treatment and the temperature increase due to the exothermic reaction, the fracture cracks (5) present in the underground oil reservoir (1) are remediated.

After conducting a fracking process, the subterranean crude oil deposit (1) and especially the tailings cracks (5) produced in the fraying process are heavily contaminated with water. By the thermal treatment (the temperature rise) in the heated zone (10), the water in the Frackrissen (5) heated or even evaporated. This increases the mobility of the water contained in the Frackrissen (5), in the case of evaporation, the water from Frackrissen (5) even removed. Additives which have been added to the fracking liquids used to form the fracking cracks (5), such as thickening agents, are destroyed during the thermal treatment.

In the event that an aqueous fracking liquid containing thickening agents (gel-forming additives) was used to produce the fracking cracks (5), the viscosity of the fracking liquor decreases by the thermal treatment process according to the invention. This phenomenon is also referred to as "yellow rake." In the event that the heated zone (10) after carrying out the thermal treatment temperatures> 100 ° C, for example temperatures in the range of 150 to 1200 ° C, the Frackflüssigkeit is evaporated. The thickening agents contained in the fracking liquid are thermally decomposed.

The formulations F1 and F2 (7, 8) can be simultaneously or temporally offset, that is, injected one after the other into the fracture tears (5) of the fraying zone (50). In a preferred embodiment, the formulations F1 and F2 (7, 8) are injected simultaneously into the fracking cracks (5) of the fraying zone (50).

The duration of injection of formulations F1 and F2 (7, 8) may be carried out for a period of time ranging from 1 day to 1 year. In general, the duration of injection of formulations F1 and F2 (7, 8) is 1 week to 9 months, preferably 1 week to 6 months. Due to the continuous inflow of the formulations F1 and F2 (7, 8) through the perforation openings (32o, 32u), the exothermic reaction in the fracking cracks (5) in the fracking zone (50) is maintained. The formation of the heated zone (10) changes the rheological properties of the fluids contained in the fracture cracks (5). By continuously injecting the formulations F1 and F2 (7, 8), the liquids contained in the fracking cracks (5) can also be displaced by the formulations F1 and F2 (7, 8). Continuously injecting the formulations F1 and F2 (Figs. 7, 8), the heated zone (10) expands continuously. As a result, gaseous products of the reaction between the formulations F1 and F2 are pressed into the deposit. In this case, a combined effect on the deposit occurs due to gas flooding and heat input.

In a preferred embodiment, the injection of the formulations F1 and F2 (7, 8) is carried out until the heated zone (10) corresponds to the expansion of the fracking zone (50).

In a further embodiment, it is also possible to carry out the injection of the formulations F1 and F2 (7, 8) until the heated zone (10) exceeds the extent of the fracking zone (50). As a result of the increase in temperature, as described above, the rheological properties of the liquids which are contained outside the fracking zone (50) in the underground crude oil deposit (1) change. These fluids may be formation water, as well as water that has passed from upstream petroleum recovery operations into the underground oil reservoir (1). In addition, these fluids may be petroleum. With the expansion of the heated zone (10), these liquids are also heated and displaced by injecting the formulations F1 and F2 (7, 8).

In a further embodiment of the present invention, after formation of the heated zone (10) in the subterranean crude oil deposit (1), injection of the formulations F1 and F2 (7, 8) is discontinued, and subsequently a flood means (11) is inserted through the injection well (2) ) injected into the underground oil reservoir (1). Alternately, water is injected into the heated fracture cracks (5), which is completely or partially evaporated. After the fracking cracks (5) have been cooled by water, the formulations F1 and F2 can continue to be pressed in. It is known that the use of conventional steam flooding is limited by the depth of the deposit. For deposits> 1000 m, steam flooding is normally not used. The inventive method allows the steam generation directly in the deposit and in any Teufe.

This embodiment is shown by way of example in FIG. 4b). The injection of a flooding agent (11) can take place here through the first injection strand (6) and / or the second injection strand (9). In a preferred embodiment, however, before the injection of the flooding agent (1 1), the packer (4) and optionally the inner tube, which has served as the first injection strand (6) removed. As a result, the encapsulated perforation (31) are free again and the flooding agent (1 1) can enter through all perforation, which were generated in the fracking process to form the Frackrisse (5), in the underground Erdöllagerstätte (1).

Figure 4b) shows an example of an embodiment in which the flooding agent (1 1) without removal of the packer (4) in the underground Erdöllagerstätte (1) is injected. The flooding agent (11) only flows through the perforation openings (32o and 32u) into the underground oil reservoir (1).

Figure 5 shows an example of an embodiment in which the flooding agent (1 1) after removal of the packer (4) in the underground oil reservoir (1) is injected. In this case, the flooding agent (11) flows through all the perforation openings into the underground oil reservoir (1). Suitable flooding agents (11) are known to the person skilled in the art. Preferred flours (1 1) are flours which contain at least 50% by weight, preferably at least 70% by weight, particularly preferably at least 80% by weight and especially preferably at least 90% by weight of water. It is also possible to use as flooding agent (1 1) only water. Pure water, partially desalinated seawater, seawater or formation water can be used here as water. The flooding agent (1 1) may contain 0 to 50 wt .-%, preferably 0 to 30 wt .-%, particularly preferably 0 to 20 wt .-% and particularly preferably 0 to 10 wt .-% further conventional additives. The wt .-% - information with regard to the flooding agent (1 1) each relate to the total weight of the flooding agent used (1 1). Thickeners, surfactants, urea or glycerol, for example, can be used as further customary additives.

The subject matter of the present invention is therefore also a process for the extraction of crude oil from an underground oil reservoir (1) which has tail cracks (5) and into which at least one injection well (2) and at least one production well (15) are drilled, comprising the steps a ) thermal treatment of the underground Erdöllagerstätte (1) by the inventive method, b) injecting a flood medium (1 1) through the at least one injection well (2) and removal of petroleum from at least one production well (15).

As soon as the preferred aqueous flooding agent (11) hits the heated zone (10), the water contained in the aqueous flooding agent (11) is heated or evaporated.

The heated aqueous flooding agent (11) mobilizes the oil present in the underground oil reservoir (1) and displaces it in the direction of the production wells (15). The oil is taken from the production wells (15). Depending on the temperature of the heated zone (10), the aqueous flooding agent (1 1) can also be evaporated to water vapor.

By the method according to the invention for crude oil production in the heated zone (10) in situ, the aqueous flooding agent (1 1) is heated or evaporated. This has over conventional methods in which water vapor is used as a flood, the advantage that the heat loss is minimal and that costly and technically complex generators for steam generation on the surface of the underground oil reservoir (1) can be omitted. By injecting the aqueous flooding agent (11) through the injection well (2) into the heated zone (10) of the underground oil reservoir (1), the heated zone (10) is cooled. In a particular embodiment of the invention A method for the production of petroleum, the injection of the aqueous flooding agent (1 1) is carried out until the temperature of the heated zone (10) to temperatures below 80 ° C, preferably below 100 ° C, cooled. Subsequently, the inventive method for thermal treatment of the underground Erdöllagerstätte (1) is performed again to again form a heated zone (10). Subsequently, the injection of an aqueous flooding agent (1 1) can be made again.

In the injection hole (2) may be a vertical, a quasi-horizontal or a horizontal hole. Preferably, the injection bore (2) is designed as a vertical bore.

Also, the production holes (15) can be configured as vertical, quasi-horizontal or horizontal holes. The production bores (15) are preferably configured as quasi-horizontal or horizontal bores, particularly preferably as horizontal bores.

FIG. 6 shows by way of example an embodiment of the method according to the invention for the extraction of crude oil. FIG. 6 shows a horizontal section through the underground oil reservoir (1). In the underground oil reservoir (1) two injection wells (2) are drilled. By means of a fracking process, fracking zones (50) having tailoring cracks (5) were formed starting from the injection bores (2). In addition, two horizontal production wells (15) were drilled in the underground oil reservoir. Subsequently, the fracking zones (50) were thermally treated by the method according to the invention, whereby the heated zones (10) were formed. Subsequently, an aqueous flooding agent (11) is injected through the injection bores (2). This is heated or evaporated in the heated zones (10). The flooding agent (1 1) subsequently displaces the crude oil in the direction of the horizontal production wells (15) and is conveyed from these.

In a further embodiment of the method according to the invention for the production of crude oil, the injection well (2), by which the underground crude oil deposit (1) has been thermally treated, is used as a production well (15) in the process for the production of crude oil.

A further subject of the present invention is therefore also a process for the in situ combustion of petroleum in an underground oil reservoir (1) having tail cracks (5) and in which at least one injection well (2) is drilled, comprising the steps a1) thermal treatment of the underground oil reservoir (1) by the method according to the invention, b1) injection of an oxygen-containing mixture through the at least one injection well (2).

The subject matter of the present invention is also a process for the production of crude oil, wherein after step a) and before step b) the following step is carried out: b1) injecting an oxygen-containing mixture through the at least one injection well (2).

 The oxygen-containing mixture is injected through the injection well (2) into the heated zone (10) of the underground oil reservoir (1). As an oxygen-containing mixture, for example, pure oxygen, air or oxygen-enriched air can be used. Preferably, air is used as the oxygen-containing mixture. Optionally, the oxygen-containing gases described above may be used in admixture with water.

By injecting the oxygen-containing mixture, the oil contained in the heated zone (10) is oxidized. Depending on the temperature of the heated zone (10), the oil contained in the underground oil reservoir (1) may also burn. This process is also referred to as in situ petroleum burning.

Before injecting the oxygen-containing mixture, the heated zone (10) in this embodiment preferably has a temperature in the range of 200 to 1200 ° C, preferably in the range of 300 to 1000 ° C and more preferably in the range of 400 to 1000 ° C.

By continuously injecting the oxygen-containing mixture, the petroleum burning in the underground oil reservoir (1) is maintained. As a result, a combustion front whose dimension corresponds to the extent of the fracking zone (50) is formed in the subterranean crude oil deposit (1).

The method according to the invention has the advantage that large volumetric combustion fronts can be formed. In conventional in-situ oil burning processes, combustion fronts of this size can only be achieved by very long term injection of an oxidizer.

By in-situ petroleum combustion, which is initiated by injecting an oxygen-containing mixture according to process step b1), the temperature in the combustion zone can be increased even further. As a result, the fracking zone (50) is further heated. According to process step b1) is thus a thermal treatment of Underground oil reservoir (1) possible without further formulations F1 and F2 (7, 8) must be injected. In other words, in process step b1), a thermal treatment of the underground oil reservoir (1) is carried out using as the means for heating the underground oil reservoir (1) the oil contained in the underground oil reservoir (1) / burned.

Subsequent to method step b1), in a further preferred embodiment of the present invention, according to method step c1), a flood agent (11) can be injected through the injection bore (2) into the underground oil reservoir (1). The preferably aqueous flooding agent (11) is hereby heated or evaporated as described above.

The subject matter of the present invention is thus also a method in which, after method step b1) in method step c1), a flooding agent (11) is injected through the at least one injection bore (2) into the underground oil reservoir (1).

According to the invention, a process for the extraction of crude oil from the subterranean crude oil deposit (1) can thus also follow the method according to the invention for in-situ petroleum combustion. For this method, the above statements and preferences apply accordingly.

Suitable formulations F1 and F2 (7, 8) which, after mixing in the fracking cracks (5) of the fracking zone (50) in the subterranean crude oil deposit (1), undergo an exothermic reaction and thus form the heated zone (10) are in principle familiar to the person skilled in the art known. According to the invention, it is possible to use all known formulations which are suitable for undergoing an exothermic reaction after mixing. Preference is given to formulations F1 and F2 (7, 8) which are chemically stable separately from one another and thus do not undergo an exothermic reaction in separate form, that is to say as individual formulations. As a result, the occupational safety is increased, since an onset of the exothermic reaction before mixing the formulations F1 and F2 (7, 8) can be safely excluded.

Suitable formulations F1 and F2 (7, 8) are disclosed, for example, in the patents described in the introductory part of the present invention.

In one embodiment of the present invention, formulation F1 (7) contains an oxidizing agent and formulation F2 (8) contains a fuel. In a further embodiment, the formulation F1 (7) contains a peroxide and the formulation F2 (8) contains an initiator which initiates the decomposition of the peroxide.

In another embodiment, formulation F1 (7) includes an oxidizer and a fuel and formulation F2 (8) contains an initiator that initiates the exothermic reaction between the oxidant and the fuel of formulation F1 (7).

In a preferred embodiment, the formulation F1 (7) used is an aqueous hydrogen peroxide solution which contains 10 to 50% by weight, preferably 10 to 30% by weight and particularly preferably 20 to 30% by weight of hydrogen peroxide, based on the total weight of the Formulation F1 (7). Formulation F2 (8) uses an aqueous initiator solution which initiates the exothermic decomposition of the hydrogen peroxide. Preferred suitable initiator solutions (formulation F2 (8)) are aqueous solutions which contain at least one initiator selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides and an alkali permanganate. As the alkali permanganate, sodium permanganate and / or potassium permanganate are particularly preferred. The initiator solution (formulation F2 (8)) generally contains 0.1 to 10 wt .-%, preferably 1 to 10 wt .-% and particularly preferably 4 to 10 wt .-% of at least one of the initiators described above, respectively based on the total weight of formulation F2 (8).

The present invention thus also provides a process in which the formulation F1 (7) contains 10 to 50% by weight of hydrogen peroxide and 50 to 90% by weight of water and the formulation F2 (8) contains 90 to 99.9% by weight. % Water and 0.1 to 10% by weight of at least one initiator selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides and alkali permanganates. As the oxidizing agent, for example, dinitrogen tetroxide (N ₂ O ₄ ), hydrogen peroxide, ammonium nitrate, nitric acid, alkali chlorates and alkali metal perchlorates are suitable.

As fuel, for example, hydrocarbons such as kerosene or petroleum, urea or glycerol can be used. Particularly preferred as the oxidizing agent is ammonium nitrate.

In a particularly preferred embodiment, formulation F1 (7) used is a solution comprising 10 to 60% by weight of ammonium nitrate, 10 to 30% by weight of water, 10 to 40% by weight of urea and 0 to 10% by weight. Iron nitrate and 0 to 2 wt .-% ammonia. The formulation F2 (8) used here is a solution which contains 10 to 60% by weight of sodium nitrite and 40 to 90% by weight of water. The present invention thus also provides a process in which the formulation F1 (7) comprises 10 to 60% by weight of ammonium nitrate, 10 to 30% by weight of water, 10 to 40% by weight of urea and 0 to 10% by weight. Contains% iron nitrate and 0 to 2 wt .-% ammonia and the formulation contains F2 (8) 10 to 60 wt .-% sodium nitrite and 40 to 90 wt .-% water.

A further subject of the present invention is an injection well (2) which is drilled into an underground oil reservoir (1) with fracking cracks (5) comprising perforations (32o) and perforations (32u) and two separate injection strands (6,9) the first injection strand (6) via the perforation openings (32u) and the second injection strand (9) via the perforation openings (32o) in conjunction with the Frackrissen (5) of the underground Erdöllagerstätte (1), and the first injection strand (6) and second injection strand (9) within the injection bore (2) have no hydrodynamic connection to one another.

For the injection well (2), the above statements and preferences apply to the method accordingly.

Another object of the present invention is an injection well (2), in which the first injection strand (6) and the second injection strand (9) via the Frackrisse (5) of a fracking zone (50) have a hydrodynamic connection to each other.

Another object of the present invention is an injection well (2) comprising an inner tube and an outer tube enclosing the inner tube, the inner tube acting as a first injection string (6) and the annulus between the outer wall of the inner tube and the inner wall of the outer tube functions as the second injection string (9).

LIST OF REFERENCE NUMBERS

1 underground oil reservoir

 2 injection wells

 3 perforations

 4 packers

 5 tail cracks (cracks)

 6 injection line (first injection line)

 7 Formulation F1

 8 Formulation F2

9 injection line (second injection line; 10 heated zone

 1 1 flooding agent

 13 perforated borehole section

 14 perforated borehole section

 15 production well (horizontal production well)

 31 encapsulated perforation opening

 32o perforation openings

 32u perforation openings

 50 fracking zone

Brief Description:

Figure 1 a) shows the state of an underground Erdöllagerstätte (1) after performing a single-stage fracking process.

Figure 1 b) shows the state of an underground oil reservoir (1) after carrying out a two-stage fracking process. Figures 2a), 2b) and 3 show the section of a vertical section through the underground Erdöllagerstätte (1) in the region of the fracking zone (50).

Figures 4a) and 4b) show a vertical section through the underground Erdöllagerstätte (1) in the region of the fracking zone (50), after formation of the heated zone (10).

Figure 5 shows a vertical section through the underground Erdöllagerstätte (1) area of the fracking zone (50), wherein through the injection hole (2) a flood medium (1 1) the underground Erdöllagerstätte (1) is injected.

Figure 6 shows a horizontal section through the underground Erdöllagerstätte (1) in which through the injection hole (2) a flood medium (1 1) is injected and from the horizontal production wells (15) oil is promoted. The present invention is further illustrated by the following embodiments, without, however, limiting it thereto.

Embodiment 1 A deep-lying oil shale deposit is developed which is only weakly saturated with petroleum and has a dense deposit matrix. The thickness of the oil-bearing layer of the underground oil reservoir (1) is in the range of 30 to 40 meters and has a deposit temperature of 95 ° C. The conventional extraction methods allow only a maximum of 5% of the oil contained in the underground oil reservoir (1). The underground oil reservoir (1) is developed by the so-called in-situ petroleum burning.

For this purpose, three vertical holes are drilled into the underground oil reservoir (1), with the vertical holes, which serve as injection holes (2), drilled in series. The row of boreholes is on the line corresponding to the direction of maximum horizontal geomechanical stress of the deposit matrix. The distance between the vertical injection bores (2) is approx. 300 m. The near area of the injection well (2) is scanned in one or two stages, wherein the fracking zones (50) form, which have the Frackrisse (5). For fraying, a conventional fracking liquid containing a ceramic proppant is used. After formation of the fracture tears (5) in the fracking zone (50), formulations F1 and F2 are injected through the injection wells (2). The injection bores (2) are provided with packers (4), as shown by way of example in FIG. The formulations F1 and F2 are subsequently injected simultaneously through different perforation openings (32o, 32u) into the fracking cracks (5) of the fraying zone (50).

The formulation F1 has the following composition:

5% by weight of ammonium nitrate (NH ₄ ) (NO ₃ ),

5% by weight iron nitrate (Fe) (NO ₃ ),

90% by weight of the aqueous solution A.

The composition of solution A corresponds to a commercial nitrogen fertilizer: 35% by weight of urea,

 45% by weight of ammonium nitrate,

 19.5% by weight of water,

0.5% by weight of ammonia (NH ₃ ). The formulation F2 has the following composition:

45% by weight of sodium nitrite,

55% by weight of water. The injection rate when injecting the formulation F2 is two times smaller than the injection rate when injecting the formulation F1. The total injection rates of formulations F1 and F2 are in the range of 3 to 10 L / sec. After through the Injection bore (2) 100 m ³ of Formulation F1 and 50 m ³ of Formulation F2 were injected, injection of Formulation F2 is discontinued because the injection of Formulas F1 and F2 made hitherto in the subterranean crude oil deposit (1) is heated Zone (10) has formed, which has a temperature of 200 ° C. Therefore, the exothermic reaction of Formulation F1 proceeds without further injection of Formulation F2. Subsequently, another 500 m ^{3 of} the formulation F1 through the injection hole (2) are pressed into the underground Erdöllagerstätte (1). As a result, formed in the underground Erdöllagerstätte (1) from a large volumetric heated zone (10) whose temperature is in the range of 200 to 300 ° C. Subsequently, the injection of formulation F1 is discontinued.

Subsequently, 10 000 m ^{3 of} compressed air per day are injected into the injection wells (2). In the heated zone (10), the oxidation of the petroleum begins spontaneously. Due to the in-situ combustion of the petroleum, a combustion zone, which has a temperature in the range of 200 to 600 ° C, develops in the subterranean crude oil deposit (1).

Subsequently, a mixture of water and air is injected through the injection bore (2), wherein the ratio of water to air in the range of 0.001 to 0.005. As a result, the combustion front spreads in the underground oil reservoir (1) mainly in the horizontal direction starting from the perforation openings of the injection well (2) in the direction of the production wells (15). As a result, a significant increase in the degree of deoiling is achieved.

Embodiment 2

A deep underground oil deposit (1) is being developed containing high viscosity petroleum with a viscosity in the range of 300 to 500 cP. The underground oil reservoir (1) has a dense storage rock. A vertical hole is drilled into the underground oil reservoir (1) which is used as the injection well (2). Subsequently, the underground Erdöllagerstätte (1) is one or two-stage cracked, with quasi vertical Frackrisse (5) form, as shown by way of example in Figure 6. For the fracking process, conventional fracking fluids containing ceramic proppant are used. Before injecting the formulations F1 and F2, the vertical injection well (2) is provided with a packer (4), as shown by way of example in FIG. Thereafter, as the formulation F1, a 30% by weight hydrogen peroxide solution is injected into the subterranean crude oil deposit (1) through the first injection strand (6). The formulation F1 also contains a thickening agent and others Additives that prevent the premature reaction of hydrogen peroxide and a dilution of the formulation F1 underground. The thickener used is polyacrylamide. 400 m ^{3 of} the formulation F1 are injected through the first perforation opening (32o). The total volume of the injected formulation F1 is 10 to 30% smaller than the volume of the fracking liquid used. Subsequently, 40 m ^{3 of} water, which is thickened with polyacrylamide, are injected through the first injection strand (6). Thereafter, by the second injection strand (9) as Formulation F2, a solution containing 95 wt .-% water and 5 wt .-% sodium permanganate (NaMn0 ₄ 3H ₂ 0) injected. The two formulations F1 and F2 mix in Frackrissen (5) of the fracking zone (50) whereby the exothermic decomposition of hydrogen peroxide is initiated. The hydrogen peroxide decomposes under the formation of water vapor and oxygen, whereby temperatures of about 500 C are reached. Due to the explosive decomposition of the formulations F1 and F2 after mixing, a heated zone (10) is formed in the subterranean crude oil deposit. In addition, the formation of additional fracture cracks may occur, increasing the permeability of the underground oil reservoir (1). Subsequently, a rest period of 4 to 8 days is inserted. The original injection well (2) is subsequently used as the production well (15). Subsequently, for 3 to 6 months, oil is extracted from the production well (15) (former injection well (2)). The process for thermal treatment is repeated below. This achieves an effective increase in the degree of de-oiling of the underground oil reservoir.

Claims

claims 1 . A method for extracting oil from an underground oil reservoir (1) having tail cracks (5) and into which are drilled at least one injection well (2) and at least one production well (15), said injection well (2) having perforation openings (32o) and perforations (32u) and comprises two separate injection strands (6,9),  wherein the first injection strand (6) via the perforation openings (32u) and the second injection strand (9) via the perforation openings (32o) in conjunction with the Frackrissen (5) of the underground Erdöllagerstätte (1), comprising the steps a) thermal treatment of underground oil reservoir (1), where two formulations F1 and F2 (7,8) separated by the two Injection strands (6,9) are injected through the perforation openings (32o, 32u) into the fracture tears (5) of the underground oil reservoir (1) and mix in the underground oil reservoir (1) and undergo an exothermic reaction. b) injecting a flooding agent (1 1) through the at least one injection well (2) and removal of petroleum from at least one production well (15). 2. The method according to claim 1, characterized in that the first injection strand (6) and the second injection strand (9) within the injection bore (2) have no hydrodynamic connection to each other. 3. The method according to claim 1 or 2, characterized in that the first injection strand (6) and the second injection strand (9) via the Frackrisse (5) of a fracking zone (50) have a hydrodynamic connection to each other. 4. The method according to any one of claims 1 to 3, characterized in that the injection bore (2) comprises an inner tube and an outer tube which surrounds the inner tube, wherein the inner tube acts as the first injection strand (6) and the annulus between the outer wall of the inner tube and the inner wall of the outer tube acts as a second injection strand (9). 5. The method according to any one of claims 1 to 4, characterized in that the perforation openings (32o) and the perforation openings (32u) have a distance from each other, which is in the range of 5 to 100 m. 6. The method according to any one of claims 1 to 5, characterized in that the formulations F1 and F2 (7, 8) in the fracking cracks (5) of the fraying zone (50) mix and enter into an exothermic reaction, whereby in the underground Erdöllagerstätte ( 1) forms a heated zone (10). 7. The method according to claim 1 to 6, characterized in that the temperature of the heated zone (10) has a temperature in the range of 80 to 1200 ° C, preferably in the range of 100 to 1000 ° C and more preferably in the range of 150 to 800 ° C. 8. A method for producing oil according to any one of claims 1 to 7, wherein after step a) and before step b), the following step is carried out: b1) injecting an oxygen-containing mixture through the at least one injection well (2). 9. The method according to any one of claims 1 to 8, characterized in that the formulation F1 (7)  Contains from 10 to 50% by weight of hydrogen peroxide and from 50 to 90% by weight of water and the formulation F2 (8)  From 90 to 99.9% by weight of water and from 0.1 to 10% by weight of at least one initiator selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides and alkali permanganates. 10. The method according to any one of claims 1 to 8, characterized in that the formulation F1 (7)  10 to 60 wt .-% ammonium nitrate, 10 to 30 wt .-% water, 10 to 40 wt .-% urea and 0 to 10 wt .-% iron nitrate and 0 to 2 wt .-% ammonia and contains  the formulation F2 (8) 10 to 60 wt.% Of sodium nitrite and 40 to 90 wt .-% water. 1 1. Injection well (2) drilled in a subsurface oil reservoir (1) with fracture cracks (5), comprising perforations (32o) and perforations (32u) and two separate injection strands (6,9),  5 wherein the first injection strand (6) via the perforation openings (32u) and the second injection strand (9) via the perforation openings (32o) in conjunction with the Frackrissen (5) of the underground Erdöllagerstätte (1), and the first injection strand (6) and the second injection strand (9) within the injection bore (2) have no hydrodynamic connection to one another. 10  12. Injection bore (2) according to claim 1 1, characterized in that the first injection strand (6) and the second injection strand (9) via the Frackrisse (5) of a fracking zone (50) have a hydrodynamic connection to each other. 13. Injection well (2) according to claim 11 or 12, characterized in that the injection well (2) comprises an inner tube and an outer tube enclosing the inner tube, the inner tube acting as the first injection strand (6) and the annulus between the outer wall of the inner tube and the inner wall of the outer tube functions as a second injection string (9)