WO2015036317A1

WO2015036317A1 - Method for extracting petroleum from an underground formation

Info

Publication number: WO2015036317A1
Application number: PCT/EP2014/068868
Authority: WO
Inventors: Vladimir Stehle
Original assignee: Wintershall Holding GmbH
Priority date: 2013-09-10
Filing date: 2014-09-04
Publication date: 2015-03-19

Abstract

The invention relates to a method for thermally treating an underground petroleum deposit that has fracking cracks (3) and into which at least one well (1) is drilled, wherein the well (1) has perforation openings (2), by means of which the well (1) is connected to the fracking cracks (3), comprising the following steps: a) injecting a first formulation F1 through the well (1) via the perforation openings (2) into the fracking cracks (3) of the underground petroleum deposit, b) injecting a second formulation F2 through the well (1) via the perforation openings (2) into the fracking cracks (3) of the underground petroleum deposit, c) injecting a third formulation F3 through the well (1) via the perforation openings (2) into the fracking cracks (3) of the underground petroleum deposit, wherein the addition of at least one initiator (I) causes the first formulation F1 to undergo an exothermic chemical reaction and the second formulation F2 is chemically inert and the third formulation F3 contains the at least one initiator (I), which initiates the exothermic chemical reaction of the first formulation F1 in the fracking cracks (3) of the underground petroleum deposit.

Description

Description: The present invention relates to a process for the thermal treatment of a subterranean oil deposit and to a process for the production of crude oil from a subterranean mineral oil deposit.

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 the production of crude oil, flooding agents include, for example, water, water vapor and water, to which additives are added. used. 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" is the occurrence of a fracture event in the surrounding rock of a well in a subterranean oil reservoir as a result of the hydraulic action of a liquid or gas pressure on the rock of the underground oil reservoir.

The fracking liquid described in the prior art are liquids which contain water, gel formers and optionally proppants such as sand or proppant. The fraying increases the permeability of the underground oil reservoir. This increases the delivery rate of petroleum trapped in cavities. The fracture of the underground oil reservoir will facilitate the flow of oil to the production wells. The proppants contained in the fracking liquid serve to stabilize the tailing cracks formed during fraying, so that these cracks remain open after completion of the fraying.

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. RU 2 210 589 discloses a method of thermal treatment of a subsurface oil reservoir in which an aqueous solution of an oxidizer and a fuel is injected into the subterranean crude oil deposit. 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 takes place also mainly in the borehole. The method according to RU 2 401 941 is therefore primarily suitable for stimulating production wells and for removing deposits from production wells. 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 Drilling, moving in the underground Erdöllagerstätte the two flood fronts to each other.

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 thermal treatment of underground oil deposits, which does not have the disadvantages of the prior art described above, or 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 drilled into the underground Erdöllagerstätte, should be safely prevented.

This object is achieved by a method for the thermal treatment of an underground Erdöllagerstätte, the Frackrisse (3) and in which at least one bore (1) is brought down, wherein the bore (1) has perforation openings (2) through which the bore (1 in conjunction with the fracture tears (3), comprising the steps of: a) injecting a first formulation F1 through the bore (1) via the perforation openings (2) into the fracture tears (3) of the subterranean crude oil deposit, b) injecting a second formulation F2 through the bore (1) via the perforation openings (2) into the fracture cracks (3) of the underground oil reservoir; c) injecting a third formulation F3 through the bore (1) via the perforation openings (2) into the fracture cracks (3) of the subterranean Erdölagerstätte, wherein the first formulation F1 by the addition of at least one initiator (I) undergoes an exothermic chemical reaction, and

the second formulation F2 is chemically inert and

the third formulation F3 contains the at least one initiator (I) which initiates the exothermic chemical reaction of the first formulation F1 in the fracture tears (3) of the underground oil reservoir, the viscosity (V _F 2) of the second formulation _F 2 being greater than the viscosity ( V _F i) of the first formulation F1 and greater than the viscosity (V _F 3) of the third formulation F3.

The subject of the present invention is also a process for the thermal treatment of an underground oil reservoir which has tail cracks (3) and into which at least one bore (1) is drilled, wherein the bore (1) has perforation openings (2) over which the bore ( 1) in conjunction with the fracture tears (3), comprising the steps of: a) injecting a first formulation F1 through the bore (1) via the perforation openings (2) into the fracture tears (3) of the underground oil reservoir, b) injecting a second formulation F2 through the bore (1) through the perforations (2) into the fracture cracks (3) of the subterranean crude oil deposit; c) injecting a third formulation F3 through the bore (1) over the

Perforationsöffnungen (2) in the Frackrisse (3) of the underground Erdöllagerstätte, wherein the first formulation F1 by the addition of at least one initiator (I) enters into an exothermic chemical reaction, and

the second formulation F2 is chemically inert and

the third formulation F3 contains the at least one initiator (I) which initiates the exothermic chemical reaction of the first formulation F1 in the fracture tears (3) of the underground oil reservoir.

The inventive method for the thermal treatment of a subterranean oil reservoir 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. According to the invention, unconventional underground oil reservoirs are understood as meaning reservoirs which have a dense deposit matrix and / or contain crude oil having a high viscosity. Unconventional subterranean oil reservoirs include shale oil deposits, bitumen deposits, heavy oil deposits or oil shale deposits. The unconventional underground oil reservoirs generally have a permeability of less than 10 mD prior to the fracking process. 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).

In the method according to the invention at least one bore (1) is drilled into the underground oil reservoir. The term "at least one bore (1)" according to the invention comprises both exactly one bore (1) and two or more bores (1). The terms "at least one bore (1)" and "one bore (1)" become synonymous according to the invention second hand.

The hole (1) can be a vertical or a deflected hole. Methods for sinking the bore (1) are known in the art. The bore (1) is generally cased and cemented. The bore (1) according to the invention comprises perforation openings (2) via which the bore is connected to the fracking cracks (3) of the underground oil reservoir. The perforation openings (2) are produced by methods known per se. The ball perforation is preferably used here, as described for example in RU 2 358 100.

The perforation openings (2) are located in a perforation section which generally has a length in the range of 1 to 20 meters (m). The hole (1) is thus perforated over a range of 1 to 20 m.

The bore (1) has a hydrodynamic connection to the fracking cracks (3) via the perforation openings (2). This allows the introduction of the formulations F1, F2 and F3 through the bore (1) via the perforation openings

(2) into the fracture cracks (3) of the underground oil reservoir.

By "hydrodynamic compound" is meant according to the invention that liquids can be introduced (exchanged) via these compounds, in particular the formulations F1, F2 and F3.The cracks (3) in the underground crude oil deposit are preferably produced by a fracking process Cracks (3) generated by this fracking process are also referred to as fracking cracks (3) Suitable fracking processes are known in principle to the person skilled in the art In conventional fracking processes for the formation of fracking cracks

(3) in the underground oil reservoir, usually a fracking liquid, which may contain a proppant, is injected at high pressure (generally 500 to 1000 MPa) into the subterranean crude oil deposit. As a result, fracture cracks (3) are formed in the underground oil reservoir.

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 (3) and the deposit matrix formed are contaminated with water, which can cause swelling of clay rocks and clay particles in the subterranean oil reservoir, especially if the deposit matrix, that is the surrounding rock, consists of clay-containing rocks.

Particularly in the development of unconventional underground oil reservoirs, this effect is very disadvantageous, since the unconventional underground oil reservoirs, as described above, in any case have a low permeability and / or contain petroleum with a high viscosity. The method by which the fracture cracks (3) are formed in the underground oil reservoir is not essential to the invention. In addition to the hydraulic fracturing described above, it is also possible to use further fracking processes which are suitable for forming fracture tears (3) in the underground oil reservoir.

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 fracture cracks (3) strongly depends on the geological conditions of the underground oil reservoir. In addition, the spatial extent of the fracture tears (3) depends on the applied pressure and the duration of the fracking process.

The Frackrisse (3) generally have a radial extent (length) in the range of 10 to 200 m, preferably in the range of 15 to 150 m, and more preferably in the range of 20 to 70 m, each measured from the center of the bore (1) in the area of the perforation openings (2).

To carry out the fracking process, an injection strand is introduced into the bore (1). The area of the bore (1) above the perforation openings is closed with a packer. Subsequently, a fracking liquid is injected at a pressure in the range of 300 to 1000 bar via the injection strand in the underground Erdöllagerstätte. Under the influence of the pressure of the fracking fluid, fracture cracks (3) are formed in the underground oil reservoir.

In the fracking liquid proppant may be included. In addition, it is possible to use a fraying liquid which contains no proppant. Suitable proppants are, for example, ceramic materials such as sand or proppant. Under the influence of the pressure of the fracking liquid, the fracture cracks (3) are produced in the underground oil reservoir. In the event that the fracking liquid contains no proppant, the fracking liquid is partly pressed out of the fracking cracks (3) after the fracking cracks (3) have been created after the pressure has been reduced. In this embodiment, the generated Frackrisse (3) close again after pressure decrease. However, this is not disadvantageous because the partially closed tailings cracks (3) are reopened by injecting the formulations F1, F2 or F3. The pressure that must be used for this is significantly lower than the pressure that had to be used to generate the fracture cracks (3).

In the case that the fracking liquids contain a proppant dispersed therein, the proppant stabilizes the generated fracking cracks (3) so that the fracking cracks (3) remain open even after the pressure has been decreased. As stated above, after the fracking process has been carried out, the fracking cracks (3) are generally heavily contaminated with the water contained in the fracking liquid. Before injecting the formulations F1, F2 and F3, the fracking liquid can be removed from the fracking cracks (3). This process is also referred to as remediation. Suitable processes for the remediation of the fracture cracks (3) are known to the person skilled in the art.

However, a remediation of the fracture cracks (3) before carrying out the process according to the invention is not absolutely necessary. In one embodiment, the inventive method is thus carried out without a prior refurbishment of Frackrisse (3).

The first formulation F1 undergoes an exothermic chemical reaction after addition of at least one initiator (I).

The second formulation F2 is chemically inert. According to the invention, the term "chemically inert" with respect to the second formulation F2 is understood to mean that the exothermic chemical reaction is not initiated when the first formulation F1 is mixed with the second formulation F. The term "chemically inert" is used in the present invention on the second formulation F2 beyond understood that even when mixing the second formulation F2 with the third formulation F3 no exothermic chemical reaction is initiated.

The third formulation F3 contains at least one initiator (I). The initiator (I) initiates the exothermic chemical reaction of the first formulation F1. This means that in contacting, for example by mixing, the first formulation F1 with the third formulation F3, the exothermic chemical reaction of the first formulation F1 is initiated. In the method according to the invention, the first formulation F1 has a viscosity (V _F i) which is lower than the viscosity (V _F 2) of the second formulation _F 2. The third formulation F3 also has a viscosity (V _F 3) which is lower than the viscosity (V _F 2) of the second formulation F2. For the viscosities of formulations F1, F2 and F3, therefore, the following condition applies:

(V _F3 ) <(V _F2 ) The present invention thus also provides a process in which the viscosity (V _F2 ) of the second formulation F2 is greater than the viscosity (V _F1 ) of the first formulation F1 and greater than the viscosity (V _F3 ) of the third formulation is F3. The second formulation F2 generally has a viscosity (V _F 2) that is 10 to 50% higher than the viscosity (V _F i) of the first formulation F1. The second formulation F2 generally has a viscosity (V _F 2) that is 10 to 50% higher than the viscosity (V _F 3) of the third formulation F3.

The subject matter of the present invention is therefore also a process in which the viscosity (V _F2 ) of the second formulation F2 is 10 to 50% higher than the viscosity (V _F1 ) of the first formulation F1, and that the viscosity (V _F2 ) the second formulation F2 is 10 to 50% higher than the viscosity (V _F3 ) of the third formulation F3.

Injection of the formulations F1, F2 and F3 according to process steps a), b) and c) is carried out directly one after the other in a preferred embodiment of the present invention. The term "directly after one another" is understood according to the invention to mean that no other fluids are injected through the bore (1) between the injection of the first formulation F1 according to method step a) and the injection of the second formulation F2 according to method step b) Method steps b) and c), that is to say also between the injection of the second formulation F2 according to method step b) and the injection of the third formulation F3 according to method step c), in a preferred embodiment, no other fluids are injected through the bore (1).

The subject matter of the present invention is therefore also a process in which steps a), b) and c) are carried out directly one after the other.

Due to the difference in viscosity between the first formulation F1 and the second formulation F2, the second formulation F2 in method step b) displaces the first formulation F1. The second formulation F2 thus displaces the first formulation F1 "flask-like" away from the bore (1) along the fracture tears 3. This phenomenon is also referred to as the "piston effect". Due to the viscosity difference between the third formulation F3 and the second formulation F2, the formulation F2 is only partially replaced by the formulation F3. Due to the lower viscosity of the third formulation F3, the formulations F2 and F3 mix when injecting the formulation F3 according to process step c). As a result, the third formulation F3 can penetrate the second formulation F2. This effect is also called "tunneling" or "fingering". As a result, the third formulation F3 comes into contact with the first formulation F1 in the fracture tears (3). That in the third formulation F3 contained initiator (I) subsequently initiates the exothermic chemical reaction of the first formulation F1.

The present invention thus also provides a process in which, during or after process step c), the third formulation F3 permeates the second formulation F 2 and comes into contact with the first formulation F1 and initiates the exothermic chemical reaction, resulting in a subsurface oil reservoir heated zone (10) is formed. The viscosity of the second formulation F2 can be adjusted by the addition of at least one thickener. Suitable thickening agents are known to the person skilled in the art. Suitable thickeners are, for example, synthetic polymers such as polyacrylamide or copolymers of acrylamide and other monomers, especially monomers containing sulfonic acid groups, and polymers of natural origin such as glucosyl, glucans, xanthan, diuthane or glucan. Glucan is preferred.

The second formulation F2 generally contains 0.1 to 5 wt .-% of at least one thickener, based on the total weight of the second formulation F2.

The first formulation F1 and / or the third formulation F3 may also contain thickening agents. However, the content of thickening agents in the formulations F1 and F3 is lower than the content of thickening agent in the second formulation F2, in general, to meet the conditions described above, the viscosity (V _F i), (V _F2) and (V _F3) ,

The viscosity (V _F 2) of the second formulation F2 is generally in the range from 50 to 500 mPas, preferably in the range from 55 to 400 mPas.

The viscosity (V _F1 ) of the first formulation F1 is generally in the range from 1 to <50 mPas, preferably in the range from 1 to 40 mPas.

The viscosity (V _F3 ) of the third formulation F3 is generally in the range of 1 to <50, preferably in the range of 1 to 40 mPas.

The present invention thus also provides a process in which the viscosity (V _F1 ) of the first formulation F1 in the range of 1 to <50 mPas and the viscosity (V _F2 ) of the second formulation F2 in the range of 50 to 500 mPas and the Viscosity (V _F3 ) of the third formulation F3 in the range of 1 to <50 mPas.

The viscosity of the second formulation F2 depends mainly on the type and concentration of the thickener used. The viscosity (V _F2 ) of the second formulation F2 is adjusted to the viscosity (V _F1 ) of the first formulation F1. The viscosity can be calculated by means of the ratio (R1) according to the following formula:

R1 = M2 M1 = (k _r2 / ₂ ) / (kn / μι)

M-1 describes in it the mobility of the first formulation F1 in the Frackrissen (3) of the underground oil reservoir.

M ₂ describes the mobility of the second formulation F2 in the Frackrissen (3) of the underground oil reservoir.

k _r1 describes the relative permeability of the first formulation F1 in the fracking cracks (3) in the underground oil reservoir.

k _r2 describes the relative permeability of the second formulation F2 in Frackrissen (3) in the underground Erdöllagerstätte.

μι describes the viscosity of the first formulation F1 under the conditions in Frackrissen (3) in the underground Erdöllagerstätte.

μ ₂ describes the viscosity of the second formulation F2 under the conditions in Frackrissen (3) in the underground Erdöllagerstätte.

The relative permeability (k _r) is a dimensionless quantity. It defines the ratio of the permeability at a certain fluid saturation of the fracture cracks (3) in relation to the permeability without fluid saturation.

In order to ensure the displacement of the first formulation F1 by the second formulation F2 along the Frackrisse (3), the value R1 <1 must be. The necessary viscosity differences between the first formulation F1 and the second formulation F2 can be calculated from the above formula.

In order to ensure a safe mixing of the third formulation F3 with the second formulation F2 in Frackrissen (3), so that the third formulation F3 penetrates to the first formulation F1 and initiates the exothermic chemical reaction, the viscosity (V _F 3) of the third Formulation as described above, lower than the viscosity (V _F2 ) of the second formulation F2. The viscosities necessary for this can be calculated analogously to the formula described above via the ratio R2. R2 is determined by the following formula:

R2 = M ₃ / M ₂ = (WM I (k _r2 / ₂ )

M ₂ describes in it the mobility of the second formulation F2 in the Frackrissen (3) of the underground oil reservoir.

M ₃ describes the mobility of the third formulation F3 in the Frackrissen (3) of the underground oil reservoir. k _r2 describes the relative permeability of the second formulation F2 in Frackrissen (3) in the underground Erdöllagerstätte.

k _r3 describes the relative permeability of the third formulation F3 in Frackrissen (3) in the underground Erdöllagerstätte.

μ ₃ describes the viscosity of the third formulation F3 under the conditions in Frackrissen (3) in the underground Erdöllagerstätte. In order to ensure the penetration of the third formulation F3 by the second formulation F2 safely, values> 1 are selected for R2. The necessary viscosity (V _F 3) of the third formulation F3 can be determined by the above formula. The volume ratio of the first formulation F1 to the second formulation F2 may range between 9: 1 and 7: 3. The volume of the third formulation F3 injected in process step c) is generally from 5 to 30% by volume of the total volume of the formulations F1 and F2 injected in process steps a) and b).

The present invention thus also provides a process in which the volume ratio of the first formulation F1 to the second formulation F2 is in the range from 9: 1 to 7: 3. The present invention thus also provides a process in which the volume of the third formulation F3 is 5 to 30% by volume of the total volume of the formulations F1 and F2 injected in step a) and b).

In the case where a fracturing fluid containing proppant was used in generating the fracture cracks (3), the fracture cracks (3) in the subterranean crude oil reservoir are stabilized by the proppants. In this case, formulations F1, F2 and F3 in a preferred embodiment do not contain proppants. In the event that fracking fluids containing no proppant were used to create the fracture cracks (3) in the underground oil reservoir, the fracture cracks (3) do not contain proppants. When pressure is reduced by the fracking process, the fracking cracks (3) therefore partially close again. However, this is not a problem since the partially closed tailings cracks (3) are reopened by injecting the formulations F1, F2 and / or F3. In addition, by injecting the formulations F1, F2 and / or F3 in the underground oil reservoir further tail cracks may form. To form further fracture cracks, the formulations F1, F2 and / or F3 are injected into the subterranean crude oil deposit at a pressure in the range of 300 to 1000 bar.

The present invention thus also provides a process in which the formulations F1, F2 and / or F3 are injected at a pressure in the range from 300 to 1000 bar, whereby further fracture cracks are formed in the subterranean crude oil deposit.

In a further embodiment, it is possible to use the first formulation F1 and optionally the formulations F2 and / or F3 itself as fracking liquids. In this embodiment, initially no fracture cracks (3) are contained in the underground oil reservoir. The first formulation F1 is in this case injected at a pressure in the range of 300 to 1000 bar, whereby the Frackrisse (3) form in the underground Erdöllagerstätte. The formulations F2 and / or F3 can also be injected at a pressure in the range from 300 to 1000 bar.

In this embodiment, the thermal treatment process of the invention is combined with a fracking process. The fracking process and the thermal treatment are realized simultaneously by the process steps a) to c).

The subject matter of the present invention is therefore also a method in which the fracture cracks (3) of the underground oil reservoir are produced by injecting the first formulations F1 and optionally by injecting the formulations F2 and / or F3.

In this embodiment, the formulations F1, F2 and / or F3 may contain proppants. The proppants are in this case in the process steps a), b) and / or c) registered in the Frackrisse (3). After expiration of the exothermic chemical reaction, the proppants remain in the fracking gaps (3) and stabilize them, so that even after pressure decrease the Frackrisse (3) remain open. However, the use of proppants in the formulations F1, F2 and / or F3 is not absolutely necessary. In one embodiment, formulations F1, F2 and F3 do not contain proppants.

In another embodiment, formulations F1 and F2 contain no proppant and formulation F3 contains a proppant. In a further embodiment, the formulation F1 contains no proppant and the formulations F2 and F3 contain a proppant. In a further embodiment, all formulations F1, F2 and F3 contain a proppant.

By means of the method according to the invention, the area in the underground oil reservoir in which the exothermic chemical reaction starts can be determined in advance. A premature reaction in the bore (1) can be reliably prevented by the method according to the invention. By injecting the second formulation F2, the first formulation F1 can be deeply introduced into the fracture cracks (3) of the underground oil reservoir. By separating the first formulation F1 and the third formulation F3 during injection, premature onset of the exothermic chemical reaction is reliably prevented, whereby damage to the bore (1) can be excluded. By the exothermic chemical reaction of the first formulation F1, the region of the Frackrisse (3), in which the exothermic chemical reaction takes place, heated, whereby a heated zone (10) is formed.

As a result, any water contained in the fracking cracks (3) is heated or evaporated. The tailoring cracks (3) can thus be remediated by the method according to the invention for thermal treatment. Due to the sudden increase in temperature during the exothermic chemical reaction, further cracks can be formed in the surrounding rock of the fracture cracks (3). These cracks are also referred to as micro-cracks (5).

FIG. 1 shows the state at the beginning of method step c). FIG. 1 shows a vertical section of the underground oil reservoir. Through the bore (1), the first formulation F1 was first injected into the fracking cracks (3) via the perforation openings (2). Subsequently, the second formulation F2 was injected. The second formulation F2 has displaced the first formulation F1 piston-like along the Frackrisse (3). By injecting the third formulation F3, the second formulation F2 was partially displaced further along the tailings cracks (3). The second formulation F2 has in turn displaced the first formulation F1 along the tailings cracks (3). Due to the low viscosity (V _F 3) and the higher mobility of the third formulation F3 this in the implementation of the process step c) partially mixed with the second formulation F2.

FIG. 5, like FIG. 1, shows by way of example the state at the beginning of method step c). FIG. 5 shows a horizontal section of the underground oil reservoir. Through the perforation (2) as described in FIG. 1, the formulations F1, F2 and F3 were injected into the fracture cracks (3) through the bore (1). As a result, there are three quasi-centric areas in the underground oil reservoir educated. The outermost region is filled with the first formulation F1. The middle area is filled with the second formulation F2 and the inner area is filled with the third formulation F3. Due to the low viscosity (V _F 3) and the higher mobility of the third formulation F3 this in the implementation of the process step c) partially mixed with the second formulation F2.

Figure 2 shows the state after the injection of the third formulation F3 has been carried out for a long time (toward the end of the process step c)). FIG. 2 shows a vertical section of the underground oil reservoir. Due to the low viscosity (V _F 3) and the higher mobility of the third formulation F3, the third formulation F3 has penetrated the second formulation F2 and comes into contact with the first formulation F1 in the fracture tears (3). The initiator (I) contained in the third formulation F3 initiates the exothermic chemical reaction of the first formulation F1.

FIG. 6, like FIG. 3, shows the state after the injection of the third formulation has been carried out for a long time. Figure 6 shows a horizontal section through the underground Erdöllagerstätte. The third formulation F3 has penetrated the quasi-centered region filled with the second formulation F2 and comes into contact with the first formulation F1 initiating the exothermic chemical reaction.

The mixing of formulations F1 and F3 takes place in the fracture tears (3) of the underground oil reservoir. After mixing formulations F1 and F3, an exothermic chemical reaction begins in the fracture tears (3).

The inventive method, the mixing of the formulations F1 and F3 in Frackrissen (3) is guaranteed safe. The losses of the formulations F1 and F3 are minimized by the method according to the invention. The areas in which the exothermic chemical reaction takes place and which are consequently heated can thus be accurately predicted.

The state after onset of the exothermic reaction is shown by way of example in FIG. The Frackrisse (3) were hereby generated by a Frackflüssigkeit in which a proppant was suspended. The Frackrisse (3) are therefore stabilized by a proppant. Subsequently, the formulations F1, F2 and F3 were injected into the fracture tears (3).

After the third formulation F3 has penetrated the second formulation F2, the exothermic chemical reaction of the first formulations F1 was initiated in the tailings tears (3) of the underground oil reservoir. In the exothermic reaction of formulations F1, a heated zone (10) was produced. About that In addition, further micro-cracks (5) have formed due to the exothermic chemical reaction. The temperature of the heated zones (10) is generally in the range between 80 ° C and 1200 ° C. 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 thus also a method in which the temperature of the heated zone (10) is 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. having. Due to the thermal treatment and the temperature increase due to the exothermic reaction, the fracture cracks (3) present in the underground oil reservoir are being remediated.

After conducting a fracking process, the subterranean crude oil deposit and especially the fracture cracks (3) produced in the fracking process are heavily contaminated with water. By the thermal treatment (the temperature rise) in the heated zone (10), the water in the Frackrissen (3) is heated or even evaporated. This increases the mobility of the water contained in the Frackrissen (3), in the case of evaporation, the water from Frackrissen (3) even removed. Additives added to the tailing liquids used to form the fracture tears (3), such as thickeners, 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 (3), 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.

FIG. 4 shows by way of example the state after the onset of the exothermic reaction. The Frackrisse (3) were hereby generated by a Frackflüssigkeit in which no proppant was suspended. After completion of the fracking process and pressure decrease, the Frackrisse (3) have therefore partially closed again. The process steps a), b) and c) according to the invention were subsequently carried out. Due to the pressure when injecting the formulations F1, F2 and F3, the fracking cracks (3) have opened again. Formulations F1 and F2 have no proppant. In the formulation third F3, a proppant was suspended.

After the formulation F3 has penetrated the formulation F2, the exothermic chemical reaction of the formulations F1 in the fracture tears (3) of the underground oil reservoir was initiated. In the exothermic chemical reaction of formulations F1, a heated zone (10) was also produced.

The geometric extension of the heated zone (10) corresponds at least to the region of the fracture cracks (3) which was filled with the first formulation F1 prior to the onset of the exothermic chemical reaction. In one embodiment, injecting the third formulation F3 is continued even after initiating the exothermic reaction of the first formulation F1. This ensures that the exothermic reaction of the first formulation F1 is completely complete. In another embodiment of the present invention, after formation of the heated zone (10) in the subterranean oil deposit, injection of the formulations F1, F2 and F3 is discontinued and subsequently a flood medium (11) is injected through the well (1) into the subterranean crude oil deposit , 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 which has tail cracks (3) and into which at least one bore (1) and at least one production well are drilled, comprising the steps i) thermal treatment of the underground oil reservoir by the inventive method described above, ii) injecting a flooding agent (1 1) through the at least one bore (1) and extraction of petroleum from at least one production well.

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 (1 1) mobilizes the existing in the underground oil reservoir oil and displaces this in the direction of the production well. The oil is taken from the production wells. 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.

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 underground Erdöllagerstätte and at any Teufe.

By injecting the aqueous flooding agent (11) through the well (1) into the heated zone (10) of the underground oil reservoir, the heated zone (10) is cooled. In a particular embodiment of the inventive 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 100 ° C, preferably below 80 ° C, cooled is. Subsequently, the inventive method for thermal treatment of the underground Erdöllagerstätte is performed again to form again a heated zone (10). Subsequently, the injection of an aqueous flooding agent (1 1) can be made again. The bore (1) can be a vertical, a quasi-horizontal or a horizontal bore. Preferably, the bore (1) is designed as a vertical bore. The production holes can also be designed as vertical, quasi-horizontal or horizontal bores. The production bores are preferably configured as quasi-horizontal or horizontal bores, particularly preferably as horizontal bores.

When an aqueous flooding agent (11) is injected through the bores (1), it is heated or evaporated in the heated zones (10). The flooding agent (1 1) subsequently displaces the oil in the direction of the production wells and is funded from these.

In another embodiment of the inventive method of producing oil, the well (1) which has thermally treated the subterranean oil deposit is used as a production well in the process of producing oil.

A further subject of the present invention is also a process for the in situ combustion of petroleum in a subterranean well deposit having tail cracks (3) and into which at least one well (1) is drilled, comprising the steps of i1) thermally treating the subsurface oil well the method according to the invention, ii1) injecting an oxygen-containing mixture through the at least one bore (1).

The oxygenated mixture is injected through the bore (1) into the heated zone (10) of the underground oil reservoir. 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 may also burn. This process is also referred to as in situ petroleum burning. Prior to 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.

Continuous injection of the oxygen-containing mixture maintains petroleum burning in the underground oil reservoir. As a result, a combustion front is formed in the underground oil reservoir.

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.

In situ petroleum burning, initiated by injecting an oxygen-containing mixture in accordance with step ii1), can further increase the temperature in the combustion zone. As a result, the Frackrisse (3) are further heated. In accordance with method step ii1), a thermal treatment of the underground oil reservoir is thus possible without having to inject further formulations F1, F2 and F3. In other words, in step ii1), a thermal treatment of the underground oil reservoir is carried out using, as means for heating the underground oil reservoir, the oil contained in the underground oil reservoir / burned.

Following process step U1), in a further preferred embodiment of the present invention according to process step iii1), a flooding agent (11) can be injected through the bore (1) into the underground oil reservoir. 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 ii1) in method step iii1), a flood medium (11) is injected through the at least one bore (1) into the underground oil reservoir.

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

Suitable formulations F1, F2 and F3 which fulfill the requirements described above are known in principle to the person skilled in the art. 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 F3 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 F3 can be safely excluded.

The second formulation F2 used is preferably a formulation which is at least 70% by weight, preferably at least 80% by weight, particularly preferably at least 90% by weight and particularly preferably at least 95% by weight of water and 0.1 to 5 Wt .-% of at least one of the thickening agents described above.

Suitable formulations F1 and F3 are disclosed, for example, in the patents described in the introductory part of the present invention.

In one embodiment of the present invention, the first formulation F1 contains at least one oxidant and at least one fuel and the third formulation F3 contains an initiator (I) which initiates the exothermic chemical reaction between oxidant and fuel. The subject of the present invention is also a process in which the first formulation F1 contains at least one oxidizing agent (O) and at least one fuel (B).

In a further embodiment, the first formulation F1 contains a peroxide and the third formulation F3 contains an initiator which initiates the decomposition of the peroxide.

In a preferred embodiment, the first formulation F1 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 , The third formulation F3 used here is an aqueous initiator solution which initiates the exothermic decomposition of the hydrogen peroxide. Preferred aqueous solutions which contain at least one initiator (I) selected from the group consisting of alkali metal hydroxides, alkaline earth metal hydroxides and an alkali permanganate are preferred as suitable initiator solutions (third formulation F3.) Sodium permanganate and / or potassium permanganate are particularly preferred as alkali permanganate F3) 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 (I) described above, each based on the total weight the third formulation F3. The present invention thus also provides a process in which the first formulation F1 contains from 10 to 50% by weight of hydrogen peroxide and from 50 to 90% by weight of water and the third formulation F3 contains from 90 to 99.9% by weight of water and 0.1 to 10% by weight of at least one initiator (I) 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. Particularly preferred as the oxidizing agent is ammonium nitrate.

As fuel, for example, hydrocarbons such as kerosene or petroleum, urea, polyethylene glycol, glycerol or metal powder can be used. As metal powder, aluminum powder and / or magnesium powder is particularly preferred. In a particularly preferred embodiment, the first formulation F1 employed is a composition comprising 10 to 70% 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% by weight of ammonia, 0 to 5% by weight of a metal powder and 0 to 1% by weight of one of the thickening agents described above. The third formulation F3 used here is a solution which contains 40 to 90% by weight of water and 10 to 60% by weight of alkali nitrite and / or 10 to 40% by weight of hydrochloric acid. As the alkali nitrite, sodium nitrite is particularly preferable.

The present invention thus also provides a process in which the first formulation F1 contains 10 to 70% 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, 0 to 2 wt .-% ammonia, 0 to 5 wt .-% of a metal powder and 0 to 1 wt .-% of a thickener

and the third formulation F3 40 to 90 wt .-% water and up to 10 to 60 wt .-% Alkalinalitrit and / or 10 to 40 wt.% Hydrochloric acid.

LIST OF REFERENCE NUMBERS

1 hole

2 perforations

3 tail cracks

4 proppants

5 micro cracks

10 heated zone

1 1 flooding agent

F1 first formulation

F2 second formulation

F3 third formulation

Brief Description:

Figure 1 shows a vertical section through the underground Erdöllagerstätte at the beginning of the process step c). FIG. 2 shows a vertical section through the underground oil reservoir after process step c) has been carried out for some time.

Figure 3 shows a vertical section through the underground Erdöllagerstätte after the exothermic chemical reaction, the Frackrisse (3) are filled with a proppant.

Figure 4 shows a vertical section through the underground Erdöllagerstätte after the exothermic chemical reaction, the Frackrisse (3) are partially filled by the third formulation F3 a proppant.

Figure 5 shows a horizontal section through the underground Erdöllagerstätte at the beginning of the process step c).

FIG. 6 shows a horizontal section through the underground oil reservoir after process step c) has been carried out for some time.

The present invention is further illustrated by the following embodiments, without, however, limiting it thereto. Embodiment 1 In a deep-lying dense oil deposit a vertical hole (1) is brought down. The oil present in the underground oil reservoir has a viscosity in the range of 200 to 220 mPas. The temperature of the underground oil reservoir is 85 ° C. The hole (1) is scanned in one step, with quasi-vertical fracture cracks (3) forming. For fraying, a fracking liquid is used, in which ceramic proppant is dispersed. 600 m ^{3 of} the fracking liquid are injected into the subterranean crude oil deposit at a pressure of 700 bar. Subsequently, the hole (1) and the Frackrisse (3) are rehabilitated. After the remediation 500 m ^{3 of} the first formulation F1 are injected at a pressure in the range of 300 to 400 bar.

The first formulation F1 has the following composition:

69% by weight of ammonium nitrate (NH ₄ ) (NO ₃ ),

16.8% by weight of urea,

0.5% by weight of aluminum powder,

0.5% by weight of magnesium powder,

13% by weight of water and

0.2% by weight of polyacrylamide.

The viscosity (V _F i) of the first formulation F1 is 30 mPas. This prevents premature settling of the aluminum and magnesium powder suspended in the first formulation F1. Immediately after injecting the first formulation F1, the second formulation F2 is injected into the tailings cracks (3) of the subterranean crude oil deposit.

The second formulation F2 contains water whose viscosity has been adjusted to 150 mPas with polyacrylamide. 30 m ^{3 of} the second formulation F2 are injected. As a result, the first formulation F1 along the Frackrisse (3) is displaced deeper into the underground Erdöllagerstätte. Around the bore (1) this forms a quasi-concentric zone with a radius of 5 to 7 m, which is filled with the second formulation F2.

Immediately after injecting the second formulation F2, the third formulation F3 is injected. Of the third formulation F3 30 m ^{3 are} injected. The third formulation F3 contains water and hydrochloric acid in a weight ratio of 8: 2. The viscosity (V _F 3) of the third formulation F3 is 2mPas. Due to the low viscosity (V _F 3) and the high mobility of the third formulation F3, the third formulation F3 penetrates the quasi-concentric zone, which is filled with the second formulation F2. As a result, the third formulation F3 comes into contact with the first formulation F1. The third formulation F3 initiates the exothermic chemical reaction of the first formulation F1, wherein the hydrochloric acid serves as initiator (I). Between the metal powder and the hydrochloric acid initiates an exothermic chemical reaction, which in turn initiates the exothermic chemical reaction between the ammonium nitrate and the urea. The exothermic chemical reaction is complete within a few minutes. One kg of the first formulation F1 generates about 900 L of water vapor at a temperature of over 1000 ° C. In addition, carbon dioxide and nitrogen are formed. The released amount of heat is about 800 kcal. Thus, about 1000 L gases per kg of the first formulation F1 are generated. Urea and ammonium nitrate react according to the following equation: 3 NH4NO3 + CO (NH ₂ ) ₂ -> 8 H ₂ 0 (vapor) + 4 N ₂ + C0 ₂

In the exothermic chemical reaction thus only toxicologically harmless substances. The sudden pressure and temperature increase in the underground oil reservoir further numerous micro-crack cracks (5) are generated.

Subsequently, a rest period of 1 week is inserted. Thereafter, the bore (1) is converted to a production well and the production of petroleum through the bore (1) resumed after conventional measures. Due to the thermal treatment of the underground oil reservoir and the formation of large-scale further micro-cracks (5), the degree of deoiling of the underground oil reservoir is significantly increased.

Embodiment 2

A deep-seated oil shale deposit is being developed that is weakly saturated with petroleum and has a dense deposit matrix. The thickness of the oil-bearing layer of the underground oil reservoir is in the range of 30 to 40 m 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. The underground oil reservoir is being developed by the so-called in situ petroleum burning.

For this purpose, three vertical holes (1) are drilled in the underground oil reservoir, the vertical holes (1) are drilled in series. The row of boreholes is located on the line corresponding to the direction of the maximum horizontal geomechanical stress of the deposits matrix. The distance between the vertical holes (1) is about 300 m. The near area of the hole (1) is scratched, forming the quasi-vertical tailings cracks (3). For fraying, a conventional fracking liquid containing a ceramic proppant is used. After the formation of the Frackrisse (3) the Frackrisse (3) are rehabilitated. The bore (1) is provided with a packer (4). The first 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 volume of the first formulation F1 is 70% of the volume of the tailing liquid used. The first formulation F1 has a viscosity (V _F i) in the range of 2 to 5 mPas. As the second formulation F2, 20 m ^{3 of} water are injected, which was adjusted to a viscosity of 60 cP with polyacrylamide. Immediately thereafter, the third formulation F3 is injected into the fracture tears (3). The volume of the third formulation F3 is 100 m ³ and has the following composition: 45% by weight of alkali metal nitrite,

55% by weight of water.

The alkali metal nitrite used is potassium nitrite. The viscosity (V _F3 ) of the third formulation F3 is in the range of 2 to 5 mPas.

In Frackrissen (3), the formulations F1 and F3 meet, whereby the exothermic chemical reaction is initiated. After the start of the exothermic chemical reaction, the injection of the third formulation F3 is not stopped, that is, the third formulation F3 is further injected even after the onset of the exothermic chemical reaction to guarantee complete reaction of the first formulation F1. As a result, areas are formed in the underground oil reservoir, which are heated to a temperature of 200 to 300 ° C.

Subsequently, in the holes (1) 10 000 m ^{3 of} compressed air per day are pressed. In the heated zone, the oxidation of the petroleum spontaneously begins. By the in-situ combustion of the petroleum evolve in the underground Erdölagerstätte a combustion zone, which has a temperature in the range of 200 to 600 ° C.

Subsequently, through the bore (1) a mixture of water and air is injected, 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 mainly in the horizontal direction starting from the perforation openings of the bore (1). Example 3

It is developed a low-lying dense Erdöllagerstätte in which a vertical bore (1) is brought down. The petroleum has a viscosity in the range of 200 to 250 mPas. The hole (1) is being scrapped, whereby quasi vertical tailings cracks (3) are formed. The Frackrisse (3) are stabilized with ceramic proppant. Prior to initiating injection of the first formulation F1, the vertical bore (1) is packaged. The first formulation F1 is a 40 wt .-% tiger hydrogen peroxide solution is used. 400 m ^{3 of} the first formulation F1 are injected. The viscosity (V _F i) of the first formulation F1 is 1 mPas.

Immediately following, 40 m ^{3 of} the second formulation F2 are injected. The viscosity (V _F 2) of the second formulation F2 is 120 mPas. The second formulation F2 contains water and polyacrylamide. Subsequently, a 5% by weight aqueous sodium permanganate is initiated as the third formulation F3. The viscosity (V _F 3) of the third formulation F3 is 1 to 2 mPas.

The potassium permanganate serves as an initiator for the decomposition of the hydrogen peroxide. This forms water vapor and oxygen and the range of the exothermic chemical reaction, we heated to temperatures of about 500 ° C. Due to the sudden increase in temperature and the resulting gas pressure further micro cracks (5) are formed. Subsequently, a rest period of 6 days is inserted. Subsequently, the hole (1) is converted as a production well and extracted oil. This increases the degree of de-oiling of the underground oil reservoir. After 6 to 12 months of oil production, the operation described above is repeated.

Embodiment 4

It is a hole (1), which serves as a production well stimulated. In the course of oil production, oil production rates have fallen. The permeability of the underground oil reservoir is in the range of 0.05 to 0.1 μηη ^second The viscosity of the Petroleum is at 190 mPas. The reservoir pressure is mPa. The deposit is 2300 m.

The underground oil reservoir is being scrapped using conventional fracking fluids in which ceramic proppant is suspended. For fraying, 200 m ^{3 of} a fracking liquid containing 50 t of proppant is used. The fracture cracks are in a radius of 20 to 40 m, starting from the hole (1). To redevelop the fracture tears (3), 120 m ^{3 of} an aqueous solution having the following composition are injected as the first formulation F1:

55% by weight of ammonium nitrate,

15% by weight of urea,

5 wt .-% of water-soluble copper salt and

100% by weight of water.

The viscosity (V _F i) is 2 to 5 mPas. Subsequently, the second formulation F2 is injected with polyacrylamide thickened water. The second formulation F2 has a viscosity (V _F 2) of 150 mPas. 15 m ^{3 of} this formulation are injected.

As a third formulation, 80 m ^{3 of} an aqueous suspension of aluminum powder are injected. The third formulation F3 has a viscosity (V _F 3) of 30 mPas. The third formulation F3 contains 20 t of aluminum powder and about 1, 5 wt .-% surfactant. When mixing the formulations F1 and F3, a reaction pressure of 300 to 500 bar is produced in the fracture cracks (3) and the temperature rises to 400 ° C.

After completion of the exothermic chemical reaction, a rest period of 3 days is inserted. Subsequently, the oil production through the hole (1) is resumed after conventional measures.

Claims

Patent claims

1 . Method for the thermal treatment of an underground petroleum deposit which has frac cracks (3) and into which at least one bore (1) is drilled, the bore (1) having perforation openings (2) through which the bore (1) is connected to the frac cracks (3), comprising the steps: a) injecting a first formulation F1 through the bore (1) via the perforation openings (2) into the frac cracks (3) of the underground petroleum deposit, b) injecting a second formulation F2 through the bore (1 ) via the perforation openings (2) into the frac cracks (3) of the underground petroleum deposit, c) injecting a third formulation F3 through the bore (1) via the perforation openings (2) into the frac cracks (3) of the underground petroleum deposit, the first formulation F1 enters into an exothermic chemical reaction by adding at least one initiator (I) and

the second formulation F2 is chemically inert and

the third formulation F3 contains the at least one initiator (I), which initiates the exothermic chemical reaction of the first formulation F1 in the frac cracks (3) of the underground petroleum deposit, the viscosity

(V _F 2) of the second formulation F2 greater than the viscosity (V _F i ) of the first formulation F1 and greater than the viscosity

(V _F 3) of the third formulation F3 is.

Method according to claim 1, characterized in that the viscosity (V _F 2) of the second formulation F2 is 10 to 50% higher than the viscosity (V _F i) of the first formulation F1, and that the viscosity (V _F 2) the second formulation F2 is 10 to 50% higher than the viscosity (V _F3 ) of the third formulation F3.

Method according to one of claims 1 or 2, characterized in that steps a), b) and c) are carried out directly one after the other.

EB13-5509PC

4. The method according to any one of claims 1 to 3, characterized in that during or after process step c) the third formulation F3 penetrates the second formulation F2 and comes into contact with the first formulation F1 and initiates the exothermic chemical reaction, whereby in the underground petroleum deposit forms a heated zone (10).

5. The method according to any one of claims 1 to 4, characterized in that the viscosity (V _F i) of the first formulation F1 is in the range of 1 to <50 mPas and the viscosity (V _F 2) of the second formulation F2 is in the range of 50 to 500 mPas and the viscosity (V _F 3) of the third formulation F3 is in the range from 1 to <50 mPas.

6. The method according to any one of claims 1 to 5, characterized in that the volume ratio of the first formulation F1 to the second

Formulation F2 is in the range from 9:1 to 7:3.

7. The method according to any one of claims 1 to 6, characterized in that the volume of the third formulation F3 is 5 to 30% by volume of the total volume of the formulations F1 and injected in step a) and b).

F2 is.

8. The method according to any one of claims 1 to 7, characterized in that the formulations F1, F2 and / or F3 are injected at a pressure in the range of 300 to 1000 bar, whereby in the underground

Further frack cracks form in the oil deposit.

9. Method according to one of claims 4 to 8, characterized in that the heated zone (10) has a temperature in the range from 80 to 1200 °C.

10. A method for extracting petroleum from an underground petroleum deposit which has frack cracks (3) and into which at least one borehole (1) and at least one production borehole are drilled, comprising the steps i) thermal treatment of the underground petroleum deposit by the method according to one of Claims 1 to 9, ii) injecting a flooding agent (1 1) through the at least one bore (1) and withdrawing petroleum from at least one production bore.

EB13-5509PC

1 1 . Method for the in situ combustion of petroleum in an underground petroleum deposit which has frac cracks (3) and into which at least one borehole (1) is drilled, comprising the steps i1) thermal treatment of the underground petroleum deposit by the method according to one of claims 1 to 9 , ii1) Injecting an oxygen-containing mixture through the at least one bore (1).

Method according to one of claims 1 to 1 1, characterized in that the second formulation F2 contains at least 70% by weight of water and 0.1 to 5% by weight of at least one thickener.

Method according to one of claims 1 to 12, characterized in that the first formulation F1 contains 10 to 50% by weight of hydrogen peroxide and 50 to 90% by weight of water and the third formulation F3 contains 90 to 99.9% by weight of water and contains 0.1 to 10% by weight of an initiator (I) selected from the group consisting of alkali metal hydroxides and alkali metal permanganate.

Method according to one of claims 1 to 12, characterized in that the first formulation F1 contains 10 to 70% 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, 0 to 2% by weight of ammonia, 0 to 5% by weight of a metal powder and 0 to 1% by weight of a thickener and the third formulation F3 contains 40 to 90% by weight of water and up to 10 to Contains 60% by weight of alkali nitrite and/or 10 to 40% by weight of hydrochloric acid.

Method according to one of claims 1 to 14, characterized in that the fracture cracks (3) of the underground petroleum deposit are generated by injecting the first formulations F1 and optionally by injecting the formulations F2 and/or F3

EB13-5509PC