WO2012107458A1

WO2012107458A1 - Multistage process for recovering petroleum using microorganisms

Info

Publication number: WO2012107458A1
Application number: PCT/EP2012/052074
Authority: WO
Inventors: Vladimir Stehle; Rajan Hollmann; Robert THUMMER
Original assignee: Wintershall Holding GmbH
Priority date: 2011-02-08
Filing date: 2012-02-08
Publication date: 2012-08-16
Also published as: CA2823752A1; EA201391042A1; EP2673332A1

Abstract

Multistage process for recovering petroleum from petroleum reservoirs by injection of aqueous flooding media into a petroleum formation through injection wells and extraction of petroleum through production wells, in which the petroleum yield is increased by use of microorganisms in combination with measures for blocking highly permeable zones of the petroleum formation.

Description

Multi-stage process for the extraction of petroleum using microorganisms

The present invention relates to a multi-stage process for extracting oil from petroleum reservoirs by injecting aqueous flooding media into a petroleum formation by injection drilling and withdrawal of petroleum through production wells, where the petroleum yield is highly permeable through the use of microorganisms in combination with blocking measures Zones of petroleum formation increase.

In natural oil deposits, petroleum is present in cavities of porous reservoirs which are closed to the earth's surface by impermeable facings. In addition to crude oil, including natural gas, a deposit will continue to contain more or less saline water. The cavities may be very fine cavities, capillaries, pores or the like, for example those having a diameter of only about 1 μΐη; However, the formation may also have areas with pores of larger diameter and / or natural fractures.

After the hole has been drilled into the oil-bearing layers, the oil initially flows to the production wells due to the natural deposit pressure and reaches the earth surface eruptively. This phase of crude oil production is called by the specialist primary production. With poor reservoir conditions, such as a high oil viscosity, rapidly decreasing reservoir pressure or large flow resistance in the oil-bearing layers, the eruption promotion comes to a halt quickly. On average, only 2 to 10% of the oil originally present in the deposit can be extracted from primary production. For higher-viscosity petroleum eruptive production is usually not possible.

In order to increase the yield, therefore, the so-called secondary production methods are used.

The most common method of secondary oil production is water flooding. In the process, water is injected into the oil-carrying layers through so-called injection bores.

This artificially increases the reservoir pressure and forces the oil from the injection wells to the production wells. By flooding, the degree of exploitation can be significantly increased under certain conditions. In the case of water flooding, ideally, a water front emanating from the injection well should press the oil evenly over the entire petroleum formation to the production well. In practice, however, a petroleum formation has regions with different high flow resistance. In addition to finely porous, oil-saturated reservoir rocks with a high flow resistance for water, there are also areas with low resistance to flow for water, such as natural or artificial fractures or very permeable areas in the reservoir rock. Such permeable areas may also be de-oiled areas. In the case of water flooding, the injected flood water naturally flows mainly through flow paths with low flow resistance from the injection well to the production well. This has to As a result, the fine-pored, oil-rich, high flow-resistant deposit areas will no longer be flooded, and more and more water and less oil will be pumped through the production well. The expert speaks in this context of a "dilution of production." The above effects are particularly pronounced in heavy or viscous petroleum.The higher the petroleum viscosity, the more likely is the rapid dilution of production.

In the prior art, therefore, measures are known to close such highly permeable zones between injection wells and production wells by means of suitable measures. This blocks highly permeable zones with low resistance to flow and forces the flood water back through the oil-saturated, low-permeability layers. Such measures are also known as "conformance control." Borling et al., "Pushing the Oil with Conformance Control," in Oilfield Review (1994), pp. 44 ff.

"Conformance Control" can be carried out using comparatively low-viscosity formulations of certain chemical substances which can be easily pressed into the formation and whose viscosity increases significantly only after being pressed into the formation under the conditions prevailing in the formation inorganic or organic or polymeric components The increase in viscosity of the pressed-in formulation may, on the one hand, simply be delayed, but formulations are also known in which the increase in viscosity is essentially triggered by the increase in temperature when the pressed-in formulation in the storage site gradually rises For example, formulations whose viscosity only increases under formation conditions are known as "thermogels" or "delayed gelling systems".

SU 1 654 554 A1 discloses mixtures of aluminum chloride or aluminum nitrate, urea and water, which are injected into the petroleum formation. At elevated temperatures in the formation, the urea hydrolyzes to carbon dioxide and ammonia. The release of the base ammonia significantly increases the pH of the water and precipitates a high viscosity aluminum hydroxide gel which clogs the highly permeable zones. US 4,889,563 discloses the use of aqueous solutions of aluminum hydroxide chloride in combination with urea or hexamethylenetetramine (urotropin) to block subterranean petroleum formations. Again, the hydrolysis of urea or hexamethylenetetramine in the formation leads to an increase in the pH and the precipitation of aluminum hydroxide.

US 4,844,168 discloses a method of blocking portions of high temperature petroleum formations comprising passing polyacrylamide and a polyvalent metal ion such as Fe (III), Al (III), Cr (III) or Zr (IV) into a petroleum formation having a reservoir temperature of min- at least 60 ° C pressed. Under the conditions in the formation, the amide groups -CONH2 partially hydrolyze to -COOH groups, the metal ions crosslinking the formed -COOH groups to form a gel with a certain time delay. Further suitable mixtures for "conformance control" are disclosed, for example, by RU 2 066 743 C1, WO 2007/135617, US Pat. No. 7,273,101 B2, US Pat. No. 6,838,417 B2 or US 2008/0035344 A1.

It is also known to increase the oil yield by using suitable chemicals as auxiliaries for oil extraction. These measures are designed to increase the mobility of the oil in the formation so that it can be more easily pushed out of the formation as it floods. This phase of oil production is often referred to as "tertiary oil recovery" or "enhanced oil recovery" (EOR). For example, one can lower for this purpose the interfacial tension σ between the petroleum and the aqueous phase by the addition of suitable surfactants and thereby increase the mobility of the oil phase. This technique is also known as "surfactant flooding." For an overview of tertiary oil production techniques, see, for example, Journal of Petroleum Science and Engineering 19 (1998) 265-280.

As a technique of tertiary oil production is known to use microorganisms, in particular bacteria to increase the oil yield. This technique is known as "Microbial Enhanced Oil Recovery" (MEOR), which either injects suitable microorganisms, nutrients for the microorganisms and possibly oxygen into the petroleum formation, or promotes the growth of microorganisms already contained in the petroleum formation by injecting nutrients and possibly oxygen ,

Various mechanisms are known by which bacteria can increase the mobility of petroleum, such as by the formation of surfactants, the formation of polymeric substances and the resulting increase in viscosity of the aqueous phase, the formation of biofilms and concomitant cross-sectional constriction of pores for complete blockage (change of the flow paths), reducing the viscosity of oil by degradation of high molecular weight hydrocarbons, the formation of gases (eg CO 2 or CH _4), formation of organic acids which can attack the rock formation and thus create new flow paths, or by the Replacement of petroleum from the rock surface. Processes for MEOR and microorganisms suitable for this purpose are disclosed, for example, in US Pat. Nos. 4,475,590, 4,905,761 or 6,758,270 B1.

RU 2 060 371 C1 discloses a method of conveying petroleum using microorganisms from an inhomogeneous permeability deposit having at least one injection well and at least one production well. In the described method, the reservoir pressure is periodically increased and decreased. In phases of pressure increase, a nutrient solution is injected into the petroleum formation to activate microorganisms contained in the petroleum formation. Subsequently, the injection well is closed. By the removal Oil or water mixtures through the production well reduce the pressure again.

RU 2 194 849 C1 discloses a process for extracting petroleum using microorganisms from an inhomogeneous permeability deposit having at least one injection and at least one production well. In the described method, the reservoir pressure is periodically increased and decreased. In phases of increasing the pressure, microorganisms and nutrient solution are injected into the formation through the injection and production wells, and in phases of pressure reduction, the injection well is closed off and liquid is withdrawn through the production well of the formation. Preferably, mesophilic bacteria are injected into the injection well and thermophilic bacteria are introduced into the production well. A disadvantage of this method is the low efficiency, since the production well does not produce continuous oil, but is switched off regularly. Ru 2 204 014 C1 discloses a method for pumping petroleum, in which a nutrient solution and carbon-oxidizing bacteria are injected into a petroleum formation and subsequently a biotechnologically produced polyacrylamide together with a crosslinker.

Petroleum formations often do not have a homogeneous temperature distribution, but have more or less severe temperature gradients. Such temperature gradients can be of natural origin, but they can be caused in particular by measures of secondary and / or tertiary mineral oil production. During flooding, cold water is often injected into the formation for months or even years. As a result, the formation temperature in the area around the injection well generally decreases more or less strongly. As a typical example, Table 1 shows the temperature drop of the formation temperature for some deposits in northern Siberia after prolonged flooding:

Table 1: Site temperatures of various Siberian deposits S1 to S6 after prolonged flooding. The object of the invention was to provide a method for MEOR, which is particularly suitable for the extraction of oil from deposits with a heterogeneous temperature distribution. Accordingly, a process has been found for extracting oil from underground oil reservoirs having reservoir temperatures (T 1) ranging from 25 ° C to 120 ° C, with at least one injection well and at least one production well drilled into the formation and petroleum from the reservoir being mined by: Aqueous flood media are injected into the at least one injection well and petroleum is conveyed through the at least one production well, wherein in a process step (0) flood water of a temperature <25 ° C is injected so that-as a consequence of the continued injection of the flood water- the temperature the deposit is lowered at the location of the injection well (Ti) from the originally prevailing deposit temperature TL and a temperature gradient builds up between the injection well and the production well with the temperature TP <Ti_, and the process additionally in the said order the following steps are included, in which the following, in each case, aqueous flooding media are injected through the said (at least one) injection well into the formation:

(I) Mobilization of petroleum in the formation by means of microorganisms

(la) injecting at least one aqueous formulation of oil-mobilizing microorganisms, an aqueous nutrient solution and optionally an oxygen source, and / or

Activating micro-mobilizing microorganisms already present in the formation by injecting an aqueous nutrient solution and optionally an oxygen source,

Injecting floodwater,

Blockage of highly permeable areas of the formation,

Injecting floodwater,

Mobilization of petroleum in the formation by means of microorganisms by repeating process step (I), and

Inject floodwater.

In a preferred embodiment of the invention, process step (III) is carried out by injecting at least one aqueous, gel-forming formulation (F), wherein the formulations (F) comprise water and one or more water-soluble or water-dispersible components which, after being pressed into the deposit under the influence of Deposit temperature form highly viscous gels and thus completely or partially close the highly permeable areas.

List of pictures:

Figure 1 Schematic representation of water flooding.

Figure 2 Schematic representation of the formation after injecting microorganisms.

Figure 3 Schematic representation of the closure of highly permeable regions of the formation by gels.

Figure 4 Schematic representation of the formation of a new flood zone.

Figure 5 Schematic representation of the formation after injecting microorganisms into the new flood zone.

Figure 6 Schematic representation of the application of the method to a

Deposit with several funding horizons.

More specifically, the following is to be accomplished for the invention:

The process according to the invention is used after the primary oil production has come to a standstill due to the inherent pressure of the deposit and the pressure in the deposit is maintained by injecting aqueous flooding media. It can be used particularly advantageously, even if the injection of water leads to only insufficient results. deposits

The oil reservoirs may be deposits for all grades of oil, for example those for light or heavy oil, provided that the reservoir temperatures (T _L ) are in the range of 25 ° C to 120 ° C, preferably 30 ° C to 1 10 ° C, more preferably 35 ° C to 105 ° C and, for example, at 40 ° C to 105 ° C. By reservoir temperature is meant the naturally prevailing temperature in the reservoir. It can be changed by the method steps described below.

The deposits have a heterogeneous permeability. By this is meant that the permeability is not the same in all areas of the deposit, but that the deposit has zones of higher and lower permeability. method

To carry out the process at least one

Drilled production well and at least one injection well. As a rule, a deposit is provided with several injection wells and possibly multiple production wells. The injection wells allow aqueous flooding media to be injected into the oil reservoir, and production wells (also called production wells) are used to extract oil from the reservoir. The aqueous flooding media used in each of the individual process steps are described below. According to the invention, the same injection wells are always used for injecting the aqueous flooding media in the process steps described below; so it will not be drilled new injection wells. In the following, it will not be important whether the terms "injection well" or "production well" are used below in the singular or plural, but in each case "at least one injection well" or "at least one production well" should be meant.

By the term "petroleum" is meant, of course, not phase-pure petroleum, but meant the usual emulsions comprising oil and formation water, which are extracted from petroleum reservoirs.The oil and the water phase are separated after conveying in a manner known in the art.

Process step (0)

The method according to the invention is applied to a deposit in which the pressure is already maintained by injecting flooding water. Flood water is injected into the injection well (s) and oil is extracted from the production wells. This procedure is also known as "water flooding." The flood water used can be all types of water, such as fresh water, salt water, or brine, which may also contain other additives, and may flood for months or even years This process step (I) upstream process step, is referred to below as process step (0).

The process step (0) changes the original conditions in the deposit.

As pressure builds up through the flood water injected into the injection well, the petroleum in the formation is forced toward the production well, naturally by least resistance. The oil or the flood water so flow first through zones of higher permeability.

Accordingly, a zone is formed in the area between the injection and the production well, in which oil is displaced by water, while no oil is displaced from other regions of the formation. This is shown schematically in Figure 1. Into the Water is injected from the drilling hole (1) and flows from there in the direction of the production well (2), pushing oil out of the pores in the direction of the production well. The flow direction is indicated by the arrows (3). Within the (gray-shaded) zone (4) oil is at least partially displaced by the water front.

The direction of the water front (3) and the size and location of the zone (4) are determined by the conditions in the deposit, such as the spatial dynamics of the permeability index, the fracture or local geological disturbances. The zone (4) may have a complicated branched shape, especially if there are multiple injection wells for water and multiple production wells on that section.

In the flow zone (4), the flood water usually does not press the crude oil in front of it in a uniform manner. The reason for this is that even in the flow zone the permeability is generally not uniform. If more porous areas are present, for example fine gaps, fractures or cracks, the water preferably flows through these zones of lower flow resistance. In addition, the oil may be only partially removed from pores. For example, an oil droplet, which is no longer taken away by the water flowing through this pore, remain in a pore. With increasing duration of flooding, more and more preferential flood paths can form for the water. As a result, more and more water reaches the production well and accordingly increases the proportion of water in the extracted oil-water mixture with increasing duration of water flooding. The dilution of the production is therefore an indication that the aqueous flood medium no longer flows evenly from the injection well to the production well through the formation, but has found preferential flooding paths through above-average permeable zones of the formation. The flood water flowing through the preferred flood path no longer mobilizes or at least insufficiently mobilizes oil, and substantial amounts of oil may still remain in the zone (4) which has been flown through, and further oil remains in the crude oil formation outside the zone (4) be used to advantage if production dilution has already started, and can be used in particular if production dilution has reached 70 to 80%.

By injecting flood water, the temperature distribution in the crude oil formation continues to change. The flood water used for injecting is in fact generally comparatively cold. It may, for example, be seawater. It therefore generally has a temperature of less than 25 ° C, preferably less than 20 ° C and often even significantly lower. As a result of the continued injection of cold flood water, the temperature of the reservoir at the location of the injection well initially decreases in relation to the originally prevailing reservoir temperature T _L. The temperature of the deposit at the location of the injection well is hereinafter referred to as Ti. By pouring the flood water in the direction of Production wells (ie the zone (4)) can also cool down other areas of the flowed through zone. Naturally, the cooling effect at the injection well is strongest and decreases with increasing distance from the production well. In the flow-through zone (4) between the injection hole (1) and the production bore (2) thus forms a temperature gradient, wherein the temperature tends to increase in the direction of the production well, but depending on the Strömungsverhältnissen- not uniform. Accordingly, the temperature of the deposit at the injection well (Ti) is lower than the temperature at the production well deposit (TP). Depending on the conditions, TP may be equal to the reservoir temperature TL, or else the production well may already have cooled down somewhat due to the inflow of colder floodwater, so TP <TL. The temperature difference T _p _ Ti is generally at least 5 ° C, preferably at least 10 ° C and more preferably at least 20 ° C, and especially at least 30 ° C, for example 5 ° C to 60 ° C, preferably 10 ° C to 55 ° C, more preferably 15 ° C to 50 ° C.

Process step (I) In process step (I), the petroleum formation is treated with suitable microorganisms.

The treatment can be carried out in a first embodiment (1a) by injecting suitable microorganisms into the deposit. In a second embodiment (Ib), microorganisms already present in the petroleum formation are activated. By means of both methods, further crude oil is mobilized in the formation and the oil yield is increased again. The mobilization takes place essentially in the area between the injection and the production well, which has already been partially deoiled by method step (0) (zone (4) in FIG. 1), but in addition, in principle, further regions of the formation can also be detected , For the preparation of process step (I) expediently first geophysical and biochemical investigations of petroleum formation should be carried out. On the one hand, the temperature distribution of the petroleum formation is determined, at least in the area between the injection well and the production well, and in particular in the area of the water flow zone ((4) in Figure 1). Methods for determining the temperature distribution of a crude oil deposit are known in principle to the person skilled in the art. It is usually carried out from temperature measurements at specific points of the formation in combination with simulation calculations, which is taken into account in the simulation calculations, inter alia, in the formation of introduced amounts of heat and the amount of heat dissipated from the formation. By means of biochemical analyzes, the presence and amount of aerobic and anaerobic microorganisms in the drillhole close to the injection well (1) and the production well (2) can be determined. For this purpose, samples of the formation can be taken. Furthermore, the production water or backwashed injection water can be examined for the presence of microorganisms. Process step (la)

In embodiment (la), at least one aqueous formulation of oil-mobilizing microorganisms, in particular bacteria, is injected into the formation. It can be both aerobic and anaerobic, preferably anaerobic microorganisms. Furthermore, a nutrient solution and optionally an oxygen source are injected into the petroleum formation. The microorganisms enter through the injection wells at a location of formation with temperature (Ti). Like the water flood in the previous process step (0), the aqueous formulation preferably flows into the already partially de-oiled zone in the area between the injection and the production well (ie the zone (4) in Figure 1), but it is not excluded that the Microorganism-containing flood medium also flows along new flood paths. The three components, microorganisms, nutrient solution and optionally an oxygen source can be injected together, or also successively in individual portions, so that microorganisms, nutrient solution and, optionally, the oxygen source mix together only in the formation. The oxygen source may be an oxygen-forming substance such as hydrogen peroxide or, preferably, an oxygen-containing gel. An oxygen-containing gas may be injected as such or it may preferably be an oxygen-containing flood medium, in particular oxygen-containing water or sols injected. The concentration of dissolved oxygen in the aqueous flooding medium, in particular water, may for example be 0.05 to 0.5 m ³ oxygen / m ³ flooding medium. Injection of an oxygen-containing gas takes place when aerobic microorganisms are used, and it remains intact when anaerobic microorganisms are used.

Suitable microorganisms for mobilizing crude oil in a petroleum formation are known in principle to the person skilled in the art, for example from the literature cited at the outset. The mobilization of petroleum may be due to one or more of the following mechanisms: formation of surfactants, reduction of petroleum viscosity by degradation of high molecular weight hydrocarbons, formation of CO2 and / or methane, formation of organic acids capable of attacking the rock formation and thus new ones Creating flow paths or by the separation of the petroleum from the rock surface. Examples of suitable microorganisms are described, for example, in "The Phylogenetic Diversity of Aerobic Organotropic Bacteria from the Dangang High-Temperature OH Field".

T. N. Nazina, D. Sh. Sokolova, N.M. Shestakova, A.A. Grigoryan, E. M. Mikhailova, T.L. Barbich, A.M. Lysenko, T.P. Tourova, A.B. Poltaraus, Qingxian Feng, Fangtian Ni, and S.S. Belyaev Microbiology, Vol. 3, 2005, pp. 343-351. Translated from Mikrobiologiya, Vol. 3, 2005, pp. 401-409 or "Use of Microorganisms in Biotechnology

for the Enhancement of OH Recovery. SS Belyaev, IA Borzenkov, TN Nazina, EP Rozanova, IF Glumov, RR Ibatullin, and MV Ivanov, Microbiology, Vol. 73, no. 5, 2004, pp. 590-598 ". Examples of suitable microorganisms include anaerobic members of various genera such as Clostridium sp., Bacillus sp., Desulfovibrio sp., Arthrobacter sp., Mycobacterium sp., Micrococcus sp., Brevibacillus sp., Actinomyces sp. or Pseudomonas sp.

Suitable nutrient solutions for microorganisms are known in principle to the person skilled in the art. They contain, for example, phosphate or ammonium salts. They may contain as main components, for example NaN0 ₃ , KN0 ₃ , NH ₄ N0 ₃ , Na ₂ HPO ₄ , NH ₄ Cl, trace elements such as B, Zn, Cu, Co, Mg, Mn, Fe, Mo, W, Ni, Se, vitamins such as Folic acid, ascorbic acid, riboflavin, electron acceptors such as S0 ₄ ^2_ , N0 ₃ ² , Fe ⁺³ , humic acids, mineral oxides, quinone compounds or combinations thereof.

The maximum growth rate of microorganisms depends on the temperature. The temperature at which the growth of microorganisms is greatest will be referred to as Tw. The person skilled in the art distinguishes between different classes of microorganisms, namely psychrophilic, mesophilic, thermophilic and hyperthermophilic bacteria, wherein the temperature ranges of maximum growth rate may be slightly differently defined depending on the literature citation. Table 3 below shows a common classification to be used for the present invention.

Minimum temperature optimum maximum temperature

Psychrophile - 5 ° C 12 to 15 ° C 25 ° C

Mesophiles 15 ° C 30 to 40 ° C 47 ° C

Thermophiles 40 ° C 55 to 75 ° C 90 ° C

Hyperthermophilic 70 ° C 80 to 90 ° C 1 10 ° C

Table 2: Minimum, maximum and optimal growth temperature for different classes of microorganisms. For optimum results, the type of microorganisms used should be adjusted to the temperature in the already partially deoiled zone in the area between the injection well and the production well. Depending on the temperature of the zone mentioned, psychrophilic, mesophilic, thermophilic or hyperthermophilic microorganisms are selected, and as far as possible within this class as far as possible microorganisms which have as high a growth rate as possible at the temperature of the deposit in the partially de-oiled zone. As a rule, Tw should be in the range of Ti to TP.

Table 3 below shows some microorganisms, each having an optimum growth temperature: Psychrophilic Mesophilic Thermophilic Hyperthermophiles

Flavobacterium antarc- Escherichia coli Streptococcus Aquifex pyrophilus ticum 37 ° C thermophilus 85 ° C

15 ° C 45 ° C

Photobacterium pro Streptomyces Geobacillus stea- Pyrodictium brockii fundum coelicolor rothermophilus 85-105 ° C

10 ° C 28 ° C 55 ° C

Shewanella benthica Bacillus subtilis Thermus aquaticus Pyrobaculum islan-4 ° C 30 ° C 70 ° C dicum

95 - 100 ° C

Chlamydomonas nivalis Corynebacterium Streptomyces Methanopyrus

glutamicum thermogriseus kandier!

30 ° C 55 - 60 ° C 98 ° C

Flavobacterium frigida- Pseudomonas clostridium sterco-Ignisphaera aggre- rium putida rarium goose

15 ° C 26 ° C 60 ° C 92 ° C

Leptothrix mobilis Salmonella ente- Thermovorax sub- archaeoglobus ve- 25 ° C rica terraneus neficus

30 - 37 ° C 70 ° C 75 ° C

Bacillus marinus Micrococcus lu- Geothermobacter Geoglobus acetivo- 20 ° C teus ehrlichii rans

30 ° C 50 - 55 ° C 80 ° C

Table 3: Optimum growth temperature of various microorganisms

It is of course also possible to use several different microorganisms for process step (Ia), for example gas-evolving microorganisms and surfactant-developing microorganisms. The microorganisms can be injected together or in succession. Optionally, an aqueous formulation, in particular water, can also be injected between formulations containing individual microorganisms. The use of various microorganisms is particularly recommended for petroleum formations with larger temperature differences T _p -Ti, for example, formations with a temperature difference Tp-Ti of at least 20 ° C, in particular of at least 30 ° C, for example those with a difference of 30 to 50 ° C. In a preferred embodiment of the invention Therefore, n formulations having different optimal growth temperatures Twn are injected, where n> 2, and the optimum growth temperature of each portion of the injected microorganisms decreases. Flooding water can optionally be injected in each case between formulations containing individual microorganisms.

By means of the described preferred embodiment of the invention, microorganisms in the entire partially oiled area between the at least one injection well and the at least one production well can mobilize additional crude oil and not only in a partial area thereof. Figure 2 shows schematically the formation already shown after injecting 3 different portions of microorganisms (5).

Process step (Ib)

In the embodiment (Ib), no microorganisms are injected into the formation, but already existing, oil-mobilizing microorganisms, in particular bacteria are activated in the formation.

The activation of the existing microorganisms takes place by injecting an aqueous nutrient solution and optionally an oxygen source, in particular an oxygen-containing gas, wherein the gas may also be present in the nutrient solution. Details of the nutrient solutions and the possibilities to introduce oxygen into the formation have already been described at the beginning.

In one embodiment of method step (Ib), alternating aerobic and anaerobic microorganisms can be activated. In this case, alternating oxygen-containing nutrient solution and no or little oxygen-containing nutrient solutions are injected.

Of course, the two process steps (la) and (lb) can be combined with one another. For example, in a first step, it is possible first of all to activate microorganisms present in the formation and, in a second step, to inject additional microganisms, nutrient solution and optionally oxygen into the formation.

In process step (I), the production well or production wells should not be closed, but the above-mentioned flooding media are consistently injected into the formation, and accordingly, petroleum can be consistently withdrawn through the production well (s). This does not exclude a temporary closure. As a rule, however, the production wells should be open for at least 80% of the total time for process step (I). By means of process step (I), hitherto immobile crude oil is mobilized in the formation and accordingly the production of crude oil can be increased again and the dilution of production decreases. Process step (II)

Subsequent to mobilizing petroleum in the formation by process step (I), oil recovery is continued by injecting flood water into the injection well and withdrawing petroleum through the production well.

The mobilized by the microorganisms oil is now so promoted by further water flooding. Due to the continuous removal of oil from the already partially de-oiled zone, the permeability of the water-permeated zone continues to increase and finally new, preferred flood paths are formed again. This again causes a significant dilution of production.

Process step (III) In process step (III), highly permeable regions of the formation are blocked. The highly permeable regions are essentially the previously described zone through which water flows in the region between the at least one injection well and the at least one production well, ie essentially that zone in which in step (I) the mobility of oil is initiated by injecting or activating Microorganisms was improved. However, it is also possible to block further highly permeable regions, for example those which have only formed by process step (II).

Techniques for blocking highly permeable regions of petroleum formations are known in principle to those skilled in the art, for example from the literature cited above. In this case, suitable aqueous formulations are injected through the injection well into the formation, which can cause closure of the highly permeable regions.

In a preferred embodiment of the invention, process step (III) is carried out by injecting at least one aqueous, gel-forming formulation (F), wherein the formulations (F) comprise water and one or more water-soluble or water-dispersible components which after injection into the deposit will form highly viscous gels under the influence of the reservoir temperature. After being injected into the formation, the formulations (F) naturally flow essentially through the highly permeable regions and close them after the gel has formed. This is shown schematically in Figure 3. A gel plug (6) seals the high permeability areas between the injection and production wells.

Aqueous, gel-forming formulations for blocking permeable regions of a petroleum formation are known in principle to the person skilled in the art. The aqueous gel-forming formulations (F) comprise, in addition to water, one or more different water-soluble or water-dispersible chemical components which are responsible for gelation. It is preferably at least two different components. This can be both to deal with inorganic components as well as organic components and of course also combinations of inorganic and organic components.

For example, they can be formulations based on water-soluble polymers, as disclosed, for example, in US Pat. No. 4,844,168, US Pat. No. 6,838,417 B2 or US Pat. No. 2008/0035344 A1, or formulations based essentially on inorganic components, for example SU 1 654 554 A1, US Pat. No. 4,889,563 , RU 2 066 743 C1, WO 2007/135617, US Pat. No. 7,273,101 B2 or RU 2 339 803 C2. Suitable formulations are also commercially available.

The temperature starting from gelation (hereinafter referred to as TGei) and the time at which this happens (hereinafter called tGei) can be influenced, for example, by the nature and concentration of the components. They can be adjusted so that gels are formed between 20 and 120.degree. C., preferably 30 to 120.degree. C. and particularly preferably 40 to 120.degree. The cited citations contain information. The formulations can thus be adjusted so that the formulations form gels at the desired location of the highly permeable areas and block the high-permeability areas.

In a preferred embodiment, formulation (F) is an acidic aqueous formulation, preferably having a pH <5, which is at least

• Water,

• a metal compound dissolved in it, which can form gels when mixed with bases, as well as

A water-soluble activator which, at a temperature T> TG, comprises an increase in the pH of the aqueous solution.

In addition to water, the formulation may optionally include other water-miscible organic solvents. Examples of such solvents include alcohols. As a rule, however, the formulations (F) should comprise at least 80% by weight of water with respect to the sum of all solvents of the formulation, preferably at least 90% by weight and more preferably at least 95% by weight. Most preferably, only water should be present.

The dissolved metal compound is preferably aluminum compounds, in particular dissolved aluminum (III) salts, such as, for example, aluminum (III) chloride, aluminum (III) nitrate, aluminum (III) sulfate, aluminum (III) acetate or aluminum (III) acetylacetonate. However, it may also be partially hydrolyzed aluminum (III) salts, such as aluminum hydroxychloride. Of course, mixtures of several different aluminum compounds can be used. The pH of the formulation is generally <5, preferably <4.5. Preference is given to aluminum (III) chloride, aluminum (III) nitrate or aluminum (III) sulfate, very particularly preferably aluminum (III) chloride. Suitable water-soluble activators are all compounds which, on heating to a temperature T> TGei, release bases in an aqueous medium or bind acids and thus ensure an increase in the pH of the solution. By increasing the pH value, highly viscous, water-insoluble gels are formed, which comprise metal ions, hydroxide ions and optionally further components. In the case of the use of aluminum compounds, an aluminum hydroxide or oxide hydrate gel can form, in which, of course, further components, such as for example the anions of the aluminum salt used, may comprise. As water-soluble activators, for example, urea, substituted ureas such as Ν, Ν'-alkylureas, in particular Ν, Ν'-dimethylurea, hexamethylenetetramine (urotropin) or cyanates, in particular urea, substituted ureas or hexamethylenetetramine may be used. For example, urea hydrolyzes in aqueous medium to ammonia and CO2. Of course, mixtures of several different activators can be used. Preference is given to urea and / or hexamethylene tetramine.

The formulations may further comprise other components which can accelerate or retard gelation. Examples include other salts or naphthenic acids. The concentrations of the metal compounds used are selected by the skilled person so that a gel forms with the desired viscosity. He will therefore use the activator in such a concentration that a sufficient amount of base can be formed to lower the pH so much that a gel can actually precipitate. Furthermore, it is also possible to determine the gel formation time tcei via the amounts or the proportions. The higher the concentration of the activator, the greater the rate of gelation at a given metal compound concentration. The expert can use this connection to specifically accelerate or slow down the gelation time TG 1. The rate of gel formation is naturally also determined by the temperature prevailing in the formation after exceeding TG. In the case of aluminum, an amount of from 0.2 to 3% by weight of aluminum (III) based on the aqueous formulation has been proven. The amount of activator should be at least such that 3 moles of base per mole of Al (III) are released.

In the following Table 4 is the time to gelation for a mixture of 8 wt.% AICI3 (calculated as anhydrous product, corresponds to 1, 6 wt.% Al (III)), 25 wt.% Urea and 67 wt. Water shown.

Table 4: Time to gelation at different temperatures In Table 5 below, the time to gelation for various mixtures of AlC (calculated as anhydrous product), urea and water at 100 ° C and 100 ° C is shown.

Table 5: Time to gelation ("-" no measurement)

It can be seen that as the amount of activator urea decreases, the time to form the gel for both the 8 wt.% AICI ₃ series and the 4 wt.% AICI ₃ series becomes increasingly longer as the amount of urea decreases. The gelation time can thus be changed in a targeted manner via the ratio aluminum salt / urea.

Gel-forming formulations, which are particularly suitable for low storage temperatures, can be obtained by replacing urea as an activator in whole or in part by urotropin (hexamethylenetetramine) as an activator. Urotropin also releases ammonia under reservoir conditions. Such gel-forming formulations also lead

Temperatures below 50 ° C for gelation. Typical aqueous formulations may comprise 4 to 16% by weight of urea, 2 to 8% by weight of urotropin and 2 to 4% by weight of aluminum chloride or nitrate (calculated as the anhydrous salt) and water or salt water. Such formulations are disclosed, for example, in RU 2 066 743 C1. Table 6 below presents some of the formulations disclosed in RU 2,066,743 C1, pages 5 to 7 and their gelation at different temperatures.

The described preferred formulations based on dissolved metal compounds, in particular aluminum salts and activators have the advantage that inorganic gels are formed. Furthermore, the inorganic gels can also be easily removed from the formation if necessary by injecting acid into the formation and dissolving the gels.

Further examples of gel-forming aqueous formulations include formulations based on polyacrylamides and trivalent or tetravalent cations, such as, for example, Cr (III), Fe (III) or Zr (IV) as crosslinker. When using this system, acrylamide groups at least partially hydrolyze to carboxylate groups which can crosslink with the cations, polyacrylamides having different degrees of hydrolysis can be used in the application, whereby different recovery times and penetration depths can be achieved.

As a further alternative silicate gels can be used, for example colloidal silicate gels or combined polymer / silicate gels. Sodium silicate forms a sol or gel-like mass with various chemicals that can reduce permeability. The gel can be widely varied in terms of density, viscosity, solids and other properties. The advantages of the system are the low operating costs and the stability at higher temperatures. It is also known to use silicate solutions in combination with polymers, e.g. Polyacrylamide, use. As a result, improved long-term stability (aging) and better temperature stability can be achieved.

Process Step (IV) After the closure of the high permeability regions of the petroleum formation in the area between the injection and production wells, the production of oil is continued by injecting flood water and withdrawing oil through the at least one production well.

Since the previous flood paths were closed with a gel in the course of process step (III), and consequently can no longer be flowed through, oil from hitherto not detected by flooding, lower permeable areas of petroleum formation is now detected, and thus can further crude oil be promoted from the formation. This is shown schematically in Figure 4. The original flood path (4) is closed by means of a gel drop and it forms a new flood path (7) from the petroleum from the formation to the production hole is pushed out. Details of the displacement of the petroleum and optionally the formation of preferred flood paths has already been mentioned in the description of process step (I). Process step (V)

To further increase the petroleum yield, after carrying out process step (IV), process step (V) is carried out. Unless otherwise stated, this is a repetition of process step (I).

The process step (V) should be carried out at the latest, when in step (IV) again an unacceptable production dilution has occurred. However, it can also be carried out earlier, for example if the formation has a very low permeability in the region of the new flood path, so that the oil production is unsatisfactory. Depending on the duration of the water flooding in process step (IV), the temperature in the region of the new flood paths can be only slightly lowered or greatly reduced compared with the formation temperature. Furthermore, the temperature difference between injection and production well T _P - T _{I can be} very different. With only a short duration of water flooding, it can be very low, for example, only 1 to 5 ° C, and at long duration, it can be very pronounced as already described above, for example 5 ° C to 60 ° C, preferably 10 ° C to 55 ° C and more preferably 15 ° C to 50 ° C.

Also in process step (V) two variants are to be distinguished, namely the injection of microorganisms into the formation (step (Va)) or the activation of existing in the formation, oil mobilizing microorganisms (step (Vb)). By injecting or activating microorganisms, additional petroleum can be mobilized in the new flood zone. This is shown schematically in Figure 5. In preferred embodiments of the invention, the microorganisms injected in method step (la) and method step (Va) are specially matched to one another.

In one embodiment, mesophilic microorganisms are injected in process step (la) and thermophilic and / or hyperthermophilic microorganisms in process step (V).

In a further embodiment, in method step (Ia), psychrophilic microorganisms are injected and in method step (V) mesophilic and / or thermophilic and / or hyperthermophilic microorganisms are injected. Both variants are particularly suitable for formations in which the zone through which flow is already clearly cooled in process step (I), and already has a temperature well below the reservoir temperature T _L. In this case, it is advantageous to use for mobilizing petroleum microorganisms, which can grow even at relatively low temperatures. The newly formed in step (IV) flow zone is located in less permeable areas of the formation and can accordingly less cool well. Therefore, the use of microorganisms which have a higher optimal growth temperature than those used in step (I) is recommended here. Process step (VI)

Following the mobilization of petroleum in the formation by process step (IV), the production of petroleum is continued by injecting flood water into the injection well and withdrawing petroleum through the production well. The mobilized by the microorganisms oil is now so promoted by further water flooding.

Further Process Variants The process according to the invention may also comprise further variants.

For example, it is possible to repeat the process steps (III), (IV), (V) and (VI) a second time. In this case, the new cladding zone formed during the process is closed by means of a gel and a further cladding zone is formed between the injection and the production well.

The method according to the invention can also be used if crude oil from a group of horizons (layers at different depths) with different permeability is to be conveyed simultaneously. This is shown schematically in Figure (6). Figure 6 shows schematically an injection well (1) and a production well (2), which are designed for oil production from two different horizons. In this embodiment, first method step (I) is applied to the already cooled horizon with high permeability (9) (Figure (6a)). Finally, the horizon (9) is closed by using a gel-forming formulation (step (3)). After sealing, it is conveyed from the second horizon (10), which has the original deposit temperature, using microorganisms to mobilize petroleum. In the cooled horizon (9), portions (5) of microorganisms (psychrophilic or mesophilic) are injected. Portions (8) of microorganisms (thermophilic or hyperthermophilic) are injected into the horizon (10) at elevated temperature.

The inventive method with a combination of the use of microbiological methods (Microbiological Enhanced Oil Recovery (MEOR)) to increase Ölausbeu- te as well as the bucking highly permeable region of petroleum formation (Conformance Control) leads to an improved oil yield and thus the degree of de-oiling of the formation. Compared to other methods / methods of improving the oil yield, the MEOR method is cost-effective. The combination with Conformance Control is therefore also a very economical process.

Claims

claims

Method for extracting oil from underground oil reservoirs with reservoir temperatures (Tij in the range of 25 ° C to 120 ° C) into which at least one injection well and at least one production well have been drained and the oil is extracted from the reservoir by pouring water into the at least one injection well Injected flood media and through the at least one production well oil promotes

wherein, in step (0), flood water at a temperature <25 ° C is injected so that, as a result of continued flooding of the flood water, the temperature of the reservoir at the injection well (Ti) location is lowered from the originally prevailing reservoir temperature TL between the injection well and the production well having the temperature TP <Ti.a temperature gradient, characterized in that the process-in the order mentioned-additionally comprises at least the following steps, in which each of the following, aqueous flooding media by said ( n) injected at least one injection well into the formation:

(I) Mobilization of petroleum in the formation by means of microorganisms

(Ib) activating oil-mobilizing microorganisms already present in the formation by injecting an aqueous nutrient solution and optionally an oxygen source,

(II) injecting floodwater,

(III) blocking highly permeable regions of the formation,

(IV) injecting floodwater,

(V) mobilization of petroleum in the formation by means of microorganisms by repeating step (I), and

(VI) Inject floodwater.

A method according to claim 1, characterized in that as a result of the continued Injizierens of flood water in step (0) has already used production dilution. A method according to claim 1, characterized in that in a step (I) upstream step, the temperature distribution in the region between the injection well and the production well analyzed.

Method according to one of claims 1 to 3, characterized in that it is process step (la) in process step (I).

A method according to claim 4, characterized in that the optimal Wachtstums- temperature Tw of the microorganisms used in step (la) is in the range of Ti to T _L.

A method according to claim 4 or 5, characterized in that in step (la) successively injected n portions of different microorganisms having different optimal growth temperatures T _w , starting with the microorganisms having the highest T _w and T _{w of} the microorganisms from portion to portion decreases.

A method according to claim 4, characterized in that in step (la) mesophilic microorganisms and in step (V) thermophilic and / or hyperthermophilic microorganisms injected.

A method according to claim 4, characterized in that in step (la) psychrophilic microorganisms and in step (V) mesophilic and / or thermophilic and / or hyperthermophilic microorganisms injected.

Process according to any one of Claims 1 to 8, characterized in that the blocking of highly permeable regions of the formation is carried out by injecting at least one aqueous gel-forming formulation (F), the formulations (F) comprising water and one or more water-soluble or water-dispersible components which, after being pressed into the deposit under the influence of the reservoir temperature, form highly viscous gels.

A process according to claim 9, characterized in that the aqueous gel-forming formulation (F) is an acidic aqueous formulation which comprises at least

• Water,

• Aluminum (III) compounds dissolved in it, which can form gels when mixed with bases, as well as

A water-soluble activator which, above a temperature T _Ge i, causes an increase in the pH of the aqueous solution selected from Group of urea, substituted ureas, hexamethylenetetramine or cyanates.

A process according to claim 10, characterized in that the aluminum (III) compound is at least one selected from the group consisting of aluminum (III) chloride, aluminum (III) nitrate, aluminum (III) sulfate, aluminum ( III) acetate or aluminum (III) acetylacetonate.

Method according to one of claims 1 to 11, characterized in that it is the oxygen source in step (la) or (Ib) is an oxygen-containing gas.