WO2015083113A1

WO2015083113A1 - Method and use for the tertiary mineral oil production by means of metal-organic framework materials

Info

Publication number: WO2015083113A1
Application number: PCT/IB2014/066586
Authority: WO
Inventors: Stefan Maurer; Riichiro Kimura; Andrei-Nicolae PARVULESCU; Caroline REINHARDT; Lorenz Siggel; Ulrich Müller
Original assignee: Basf Se; Basf China Company Limited
Priority date: 2013-12-05
Filing date: 2014-12-04
Publication date: 2015-06-11
Also published as: AR098619A1

Abstract

The invention relates to a method for tertiary mineral oil production, in which an aqueous suspension, comprising at least one porous metal-organic framework material,is injected through at least one injection borehole into a mineral oil deposit, and crude oil is withdrawn from the deposit through at least one production borehole. The invention further relates to the use of an aqueous suspension, comprising at least one porous metal-organic framework material. The invention further relates to the use of at least one porous metal-organic framework material or an aqueous suspension for tertiary mineral production.

Description

Method and use for the tertiary mineral oil production by means of metal-organic framework materials

Description

The invention relates to a method for tertiary mineral oil production, in which an aqueous suspension, comprising at least one porous metal-organic framework material, is injected through at least one injection borehole into a mineral oil deposit, and crude oil is withdrawn from the deposit through at least one production borehole. The invention further relates to the use of an aqueous suspension, comprising at least one porous metal-organic framework material. The invention further relates to the use of at least one porous metal-organic framework material or an aqueous suspension for tertiary mineral production.

In natural mineral oil deposits, mineral oil is present in the cavities of porous reservoir rocks which are sealed toward the surface of the earth by impervious top layers. The cavities may be very fine cavities, capillaries, pores or the like. Fine pore necks may, for example, have a diameter of only about 1 μΐτι. As well as mineral oil, including fractions of natural gas, a deposit comprises water with a greater or lesser salt content. In mineral oil production, a distinction is generally drawn between primary, secondary and tertiary production. In primary production, the mineral oil flows, after commencement of drilling of the deposit, of its own accord through the borehole to the surface owing to the autogenous pressure of the deposit. After primary production, secondary production is therefore used. In secondary production, in addition to the boreholes which serve for the production of the mineral oil, the so-called production bores, further boreholes are drilled into the mineral oil-bearing formation. Water is injected into the deposit through these so-called injection bores in order to maintain the pressure or to increase it again. As a result of the injection of the water, the mineral oil is forced slowly through the cavities into the formation, proceeding from the injection bore in the direction of the production bore. However, this only works for as long as the cavities are completely filled with oil and the more viscous oil is pushed onward by the water. As soon as the mobile water breaks through cavities, it flows on the path of least resistance from this time, i.e. through the channel formed, and no longer pushes the oil onward.

By means of primary and secondary production, generally only approx. 30 to 35% of the amount of mineral oil present in the deposit can be produced.

It is known that the mineral oil yield can be enhanced further by measures for tertiary oil produc- tion. A review of tertiary oil production can be found, for example, in "Journal of Petroleum Science of Engineering 19 (1998)", pages 265 to 280. Tertiary oil production includes, for example, thermal methods in which hot water or steam is injected into the deposit. This lowers the viscosity of the oil. The flow medium used may likewise be gases such as CO2 or nitrogen. Tertiary mineral oil production also includes methods in which suitable chemicals are used as assistants for oil production. These can be used to influence the situation toward the end of the water flow and as a result also to produce mineral oil hitherto held firmly within the rock formation.

One of the techniques of tertiary mineral oil production is called "polymer flooding". As mentioned above a mineral oil deposit is not an underground "sea of mineral oil"; instead, the mineral oil is held in tiny pores in the mineral oil-bearing rock. The diameter of the cavities in the formation is typically only a few micrometers. For polymer flooding, an aqueous solution of a thick- ening polymer is injected through injection wells into a mineral oil deposit. The injection of the polymer solution forces the mineral oil through said cavities in the formation from the injection well proceeding in the direction of the production well, and the mineral oil is produced through the production well. A further technique in mineral oil production is called "hydraulic fracturing". "Hydraulic fracturing" typically involves injecting a high-viscosity aqueous solution under high pressure into the oil- or gas-bearing formation stratum. The high pressure gives rise to cracks in the rock, which facilitate the production of oil or gas. The thickeners used here are particularly guar and the more thermally stable derivatives thereof, for example hydroxypropyl guar or carboxymethyl hydroxy- propyl guar (J. K. Fink, Oil Field Chemicals, Elsevier 2003, p. 240 ff). These biopolymers, however, like most polymers in general, have a distinct decrease in viscosity with rising temperature. Since, however, elevated temperatures prevail in the underground formations, it would be advantageous for use in "hydraulic fracturing" to use thickeners whose viscosity does not decrease or even rises with rising temperature.

Viscous and capillary forces act on the mineral oil which is trapped in the pores of the deposit rock toward the end of the secondary production, the ratio of these two forces relative to one another being determined by the microscopic oil separation. By means of a dimensionless parameter, the so-called capillary number, the action of these forces is described. It is the ratio of the viscosity forces (velocity x viscosity of the forcing phase) to the capillary forces (interfacial tension between oil and water x wetting of the rock): σ cos0

In this formula, μ is the viscosity of the fluid mobilizing mineral oil, v is the Darcy velocity (flow per unit area), σ is the interfacial tension between liquid mobilizing mineral oil and mineral oil, and Θ is the contact angle between mineral oil and the rock (C. Melrose, C.F. Brandner, J. Canadian Petr. Techn. 58, Oct. - Dec, 1974). The higher the capillary number, the greater the mobilization of the oil and hence also the degree of oil removal.

It is known that the capillary number toward the end of secondary mineral oil production is in the region of about 10 ⁶ and that it is necessary to increase the capillary number to about 10 ³ to 10 ² in order to be able to mobilize additional mineral oil. A particular form of the flooding method is known as "Winsor type I II microemulsion flooding". In Winsor type II I microemulsion flooding, the injected surfactants should form a Winsor type I I I microemulsion with the water phase and oil phase present in the deposit. A Winsor type I I I microemulsion is not an emulsion with particularly small droplets, but rather a thermodynamically stable, liquid mixture of water, oil and surfactants. The three advantages thereof are that a very low interfacial tension σ between mineral oil and aqueous phase is thus achieved, it generally has a very low viscosity and as a result is not trapped in a porous matrix, it forms with even the smallest energy inputs and can remain stable over an infinitely long period (conventional emulsions, in contrast, require high shear forces which predominantly do not occur in the reservoir, and are merely kinetically stabilized). The requirements on surfactants for tertiary mineral oil production differ significantly from requirements on surfactants for other applications: suitable surfactants for tertiary oil production should reduce the interfacial tension between water and oil (typically approx. 20 mN/m) to particularly low values of less than 10² mN/m in order to enable sufficient mobilization of the mineral oil. This has to be done at the customary deposit temperatures of approx. 15°C to 130°C and in the presence of water of high salt contents, more particularly also in the presence of high proportions of calcium and/or magnesium ions; the surfactants thus also have to be soluble in deposit water with a high salt content.

To fulfill these requirements, there have already been frequent proposals of mixtures of surfac- tants, especially mixtures of anionic and nonionic surfactants.

However, the use of conventional surfactants or mixtures is not feasible in mineral oil deposits comprising water of high or very high salt contents. Such conditions can result in the insolubility of surfactants. The precipitated surfactants are no longer able to form stable emulsions and to lower the interfacial tension between mineral oil and water. The disadvantageous influence of high salt contents on the properties of thickening polymers and surfactants is for instance described in in WO 2012/068080. It is therefore a need for an improved method for the tertiary oil recovery, especially in mineral oil deposits comprising water of high salt contents.

Thus, further systems have been tested to evaluate their surface-active properties and their ability to stabilize emulsions. For example Laponite® has recently been getting attention as promising solid emulsifier in combination with surfactants.

Laponite® is a synthetic hectorite supplied by Rockwood Additives, Ltd. (United Kingdom) with the molecular formula Nao.7[(Si8Mg5.5Lio.4)04(OH)2o]. The surface of the particles is negatively charged, and Na⁺ cations are placed in the interlayer spaces. Due to the protonation of the hy- droxyl groups with the hydrogen atoms of water, a weakly positive charge appears on the rim of the disks when dispersed in water. J. Zhang et al., Langmuir, 2012, 28, 6769 to 6775 relates to the double inversion of emulsions induced by the salt concentration. Investigations were made of the effect of the salt concentration on emulsions comprising water and paraffin, which are stabilized by Laponite^® particles or by a mixture of Laponite^® particles and a surfactant. M. Reger et al., Colloids and Surfaces A: Physicochem. Eng. Aspects 413 (2012) 25 to 32 described emulsions that are stabilized by solid particles which adsorb onto the interface between the two phases (Pickering emulsion), for example by amphiphile covered clay, such as Laponite^®. It was shown that neither clay particles, which have a hydrophilic surface nor amphiphile covered clay particles lower the surface tension of water.

It is therefore an object of the invention to provide an alternative approach to methods for tertiary mineral oil production. It is a further object to provide a method for tertiary mineral oil production applicable in mineral oil deposits which cannot be exploited satisfactory by the known methods for tertiary mineral oil production.

Accordingly, a method is provided for tertiary mineral oil production, in which an aqueous suspension, comprising an aqueous liquid and at least one porous metal-organic framework material, is injected through at least one injection borehole into a mineral oil deposit, and crude oil is withdrawn from the deposit through at least one production borehole, wherein the at least one porous metal-organic framework material comprises at least one organic compound coordinated to at least one metal ion, wherein the at least one organic compound is based on imidazole, which is unsubstituted or substituted with one or more substituents independently selected from the group consisting of C1-6 alkyl, phenyl and benzyl.

Surprisingly, it has been found that the at least one porous metal-organic framework material described herein shows exceptional good properties, such as hydrophobicity, defined structure and pore diameter distribution resulting in favorable uptake kinetics towards oil, and high stabil- ity towards temperature and salinity. It has also been found that the porous metal organic framework material as described herein is able to stabilize oil/water emulsions and to lower the interfacial tension.

Below preferred embodiments are described being preferred for both, the methods of the pre- sent invention as well as the uses of the present invention.

According to the present invention the aqueous suspension comprises at least one porous metal-organic framework material. Thus the aqueous suspension comprises one or more, like two three or four, porous metal-organic framework materials. However preferably, only one porous metal-organic framework material is comprised.

The aqueous suspension can also comprise further sorption agents and/or additives. Suitable sorption agents are activated charcoal or zeolites.

Accordingly, the suspension can comprise one, two, three or more different sorption agents. Preferably, only one sorption agent is comprised in the suspension. This sorption agent is the at least one porous metal-organic framework material as outlined above. Preferably, only one po- rous metal-organic framework material is comprised.

The at least one porous metal-organic framework material comprises at least one organic compound coordinated to at least one metal ion. The at least one porous metal-organic framework material can also comprise one or more than one metal ions, where more than one ion can dif- fer from each other by chemical nature and/or charge. Also one or more, like two, three or four, organic compounds are possible. Most preferably, the at least one porous metal-organic framework material consists of one metal ion and one organic compound. Such porous metal-organic framework material can be prepared according to methods known in the art. Examples can be found in WO 2007/131955 A1 or WO 2013/005160 A1.

The specific surface area, calculated according to the Langmuir model (DIN 66131 , 66134), of the metal organic framework in powder form is preferably more than 100 m²/g, more preferably above 300 m²/g, more preferably more than 700 m²/g, even more preferably more than 1000 m²/g, even more preferably more than 1200 m²/g and particularly preferably more than 1500 m²/g.

Shaped bodies comprising the metal-organic framework can have a lower active surface area, but preferably more than 150 m²/g, more preferably more than 300 m²/g, even more preferably more than 700 m²/g.

Preferably, the at least one metal ion is selected from the group of metals consisting of copper, iron, aluminum, zinc, magnesium, zirconium, titanium, vanadium, molybdenum, tungsten, indium, calcium, strontium, cobalt, nickel, platinum, rhodium, ruthenium, palladium, scandium, yttrium, a lanthanide, manganese and rhenium. More preferably, the at least one metal ion is an ion of Zn or Co. Particularly preferably, the at least one metal ion is Zn²⁺.

According to the present invention the at least one organic compound is based on imidazole, which is unsubstituted or substituted with one or more (preferably one or two, more preferably one) substituents independently selected from the group consisting of Ci-6 alkyl, phenyl and benzyl.

The term "Ci-6 alkyl" refers to an alkyl chain having one to six carbon atoms. The alkyl group can be straight-chained or branched. Examples are methyl, ethyl, n-propyl, i-propyl, n-butyl, sec. -butyl, tert.-butyl, n-pentyl, n-hexyl. Preferred alkyl groups are methyl and ethyl. Even more preferred is methyl.

In one aspect the imidazole is unsubstituted. In another aspect the imidazole is substituted. Pre- ferred substituents are methyl, ethyl, phenyl, and benzyl. More preferred the substituent is methyl, ethyl, or benzyl. Even more preferred is methyl. A preferred substitution is in 2-position of the imidazole.

Even more preferred is the at least one organic compound 2-methylimidazole, 2-ethylimidazole, 2-benzylimidazole or a deprotonated form thereof (i.e. the imidazolate).

In a most preferred embodiment the at least one porous metal-organic framework material is Zn-2-methylimidazolate. The term "based on" means that imidazole, which can also be partly or fully deprotonated (anion), is used. Thus the at least one porous metal-organic framework material may have all imid- azolates in deprotonated form or only part of them.

In one embodiment, the at least one porous metal-organic framework material is in form of shaped bodies. The preparation of shaped bodies is described for example in WO-A 03/102000 or WO-A 2006/050898. Further methods are known in the art. A shaped body can contain further additives or consists of the at least one porous metal-organic framework material.

The conversion step of molding, shaping or forming and the like may be achieved by any meth- od known to an expert to achieve agglomeration of a powder, a suspension or a paste-like mass.

In general, the following main pathways can be discerned: (i) briquetting, i.e. mechanical pressing of the powdery material, with or without binders and/or other additives, (ii) granulating (pelletizing), i.e. compacting of moistened powdery materials by subjecting it to rotating movements, and (iii) sintering, i.e. subjecting the material to be compacted to a thermal treatment.

Specifically, the molding step is preferably performed by using at least one method selected from the following group: briquetting by piston presses, briquetting by roller pressing, binderless briquetting, briquetting with binders, pelletizing, compounding, melting, extruding, co-extruding, spinning, deposition, foaming, spray drying, coating, granulating, in particular spray granulating or granulating according to any process known within the processing of plastics or any combination of at least two of the aforementioned methods. The molding may be affected by extrusion in conventional extruders, for example such that result in extrudates having a diameter of, usually, from about 1 to about 10 mm, in particular from about 1 ,5 to about 5 mm. Such extrusion apparatuses are described, for example, in Ullmann's Enzyclopadie der Technischen Chemie, 4th Edition, Vol. 2, p. 295 et seq., 1972. In addition to the use of an extruder, an extrusion press is preferably also used for molding.

The preferred process of molding is performed at elevated pressure, i.e. by pressing of the MOF containing powder. The pressure may range from atmospheric pressure to several 100 bar. Also elevated temperatures (ranging from room temperature to 300 °C) or in a protective atmosphere (noble gases, nitrogen or mixtures thereof) are suitable. Any combination of these conditions is possible as well. The conditions under which the pressing may be accomplished depend on, e.g. the press, the filling height, the press capacity, and the form of the shaped body.

Preferred shaped bodies are granulates and extrudates. Method of mineral oil production

In the method for mineral oil production according to the invention, an aqueous suspension comprises an aqueous liquid and at least one porous metal-organic framework material, the suspension is injected through at least one injection borehole into the mineral oil deposit, and crude oil is withdrawn from the deposit through at least one production borehole. In general, a deposit is provided with several injection boreholes and with several production boreholes.

The term "aqueous liquid" for the purpose of the invention means that the liquid is water or a solution of one or more solids and/or liquids in water. Suitable aqueous liquids for the purpose of the invention are for example fresh water, brackish water, saline water, sea water, production water or formation water, preferably brackish water, saline water, formation water or production water.

In a preferred embodiment of the invention the aqueous liquid has a salinity of at least 10 000 mg/l, preferably at least 30 000 mg/l Total Dissolved Solids.

The term "suspension" means that the aqueous liquid as defined above contains particles, which are at least partly insoluble in the aqueous liquid. Solid particles according to the invention are particles comprising, preferably consisting of, the at least one porous metal-organic framework material.

The term "crude oil" in this context of course means not only single-phase oil; instead, the term also comprises the usual crude oil-water emulsions. In one preferred embodiment the average particle size of the at least one porous metal-organic framework material in the aqueous suspension is less than 15 μιτι, preferably less than 10 μιτι, particularly preferably less than 1 μιτι. Also preferred is an aqueous suspension, in which all particles comprised in the suspension have the above preferred particle sizes. The term„average particle size" for the purpose of the invention relates to the average particle sizes D50. , i.e. 50% of the particles have a particle size of more than the given value, and 50% of the particles have a particle size of less than the given value. The average particle size may be determined by laser diffraction according to ISO 13320.

The at least one porous metal-organic framework material is typically activated by heating it to from about 100°C to 200°C. This can be accompanied by application of reduced pressure or use of protective gas such as nitrogen. Here, guest molecules, for example carbon dioxide or water can be removed and the oil uptake capacity can be increased as a result.

Preferably the aqueous suspension has a pH value of from 4 to 1 1 , preferably from 6 to 10.

Without being bound by theory, an effect of the metal-organic framework may lie in the adsorption of oil in the pores of the at least one porous metal-organic framework material. A further effect of the at least one porous metal-organic framework material may be found in the stabilization of emulsions and the lowering of the interfacial tension between water and oil. It was found that the at least one porous metal-organic framework material accumulates at the surface of the oil droplets and surrounds them. For the method according to the invention, an aqueous suspension comprising an aqueous liquid and at least one porous metal-organic framework material is used.

The aqueous suspension of the invention can be prepared by adding the at least one porous metal-organic framework material to the aqueous liquid or to add the aqueous liquid to the at least one porous metal-organic framework material.

In a preferred embodiment the at least one porous metal-organic framework material is provided as powder or in crystalline form. The at least one porous metal-organic framework material can also be provided in the form of shaped bodies to increase the stability or to decrease dust formation of the material while the transport. However, in this case the shaped bodies advantageously are disintegrated before the preparation of the aqueous suspension. Disintegration can be carried out by all conventional methods known in the art. Typically, shaped bodies according to the invention are disintegrated by milling them, for example in a ball mill.

If desired, the at least one porous metal-organic framework material provided as powder or in crystalline form can also be subjected to such disintegration step to modify the average particle size as described above.

In a preferred embodiment the aqueous suspension is homogenized before the injection in the mineral oil deposit. The term "homogenized" means that the insoluble particles (especially the at least one porous metal-organic framework material) are, preferably finely, dispersed in the aqueous liquid. The term also means that the average particle size of the at least one porous metal-organic framework material can be further decreased during the homogenization. Preferably, the insoluble particles are finely dispersed and simultaneously their average particle size is decreased.

The homogenization can be carried out by mixing or stirring the aqueous suspension. Suitable methods for mixing or stirring the aqueous suspension are for example stirring with at least 60 rpm (revolutions per minute), preferably at least 500 rpm, preferably at least 5 000 rpm, prefer- ably at least 10 000 rpm, and particularly preferably at least 15 000 rpm. Suitable mixers or stirrers are well-known to the person skilled in the art, including portable mixers or stirres. Typically the stirring is carried out by Ultra-Turrax^®. Also typically the homogenization is carried out by treating the suspension with ultra sound. The homogenization of the suspension typically is carried out less than 48 h, preferably less than 24 h, preferably 10 h and more preferably less than 5 h before the injection. In a particularly preferred embodiment the homogenization of the aqueous suspension is carried out immediately before the injection of the suspension in the deposit. In another embodiment the suspension is prepared up to one week before the injection and stored under continuous stirring or mixing, preferably stirring, until the injection.

To increase the mineral oil yield, the method according to the invention can be, if appropriate, combined with other, preferably tertiary, mineral oil production techniques, for example "polymer flooding" or "Winsor type III microemulsion flooding". The person skilled in the art is aware of details of the industrial performance of "polymer flooding" and "Winsor type III microemulsion flooding", and employs an appropriate technique according to the type of deposit.

In one embodiment the pressure after the injection of the aqueous suspension can be main- tained by injecting water into the formation ("water flooding") or preferably a higher-viscosity aqueous solution of a polymer with strong thickening action ("polymer flooding"). Also known, however, are techniques by which the at least one porous metal-organic framework material is first of all allowed to act on the formation. The aqueous suspension can also be injected together with a polymer with strong thickening action. Suitable thickening polymers are known to the skilled person.

In a further embodiment the aqueous suspension optionally further comprises one or more surfactants. Surfactants suitable for the mineral oil production are known in the art. Examples of suitable surfactants for surfactant flooding comprise surfactants having sulfate groups, sulfonate groups, polyoxyalkylene groups, anionically modified polyoxyalkylene groups, betaine groups, glucoside groups or amine oxide groups, for example alkylbenzenesulfonates, olefinsulfonates or amidopropyl betaines. In addition to the surfactants, the aqueous suspension may also comprise further components, for example C4-8 alcohols and/or basic salts (called "alkali surfactant flooding"). Such additives can be used, for example, to reduce retention in the formation. Examples of useful basic salts include NaOH and Na2CC>3. Optionally, the basic salts are used together with complexing agents such as EDTA or with polycarboxylates. The ratio of the alcohols based on the total amount of surfactant used is generally at least 1 :1 - however, it is also possible to use a significant excess of alcohol. The amount of basic salts may typically range from 0.1 % by weight to 5% by weight. The aqueous suspension may also comprise biocides, stabilizer and/or inhibitors, for example corrosion inhibitors.

In a preferred embodiment of the invention, the at least one porous metal-organic framework material should make up the main component among all components in the aqueous suspen- sion which is ultimately injected into the deposit.

The deposits in which the method is employed generally have a temperature of at least 10°C, for example 10 to 150°C, preferably a temperature of at least 15°C to 120°C. The total concentration of the at least one porous metal-organic framework material is from 0.01 to 50% by weight, based on the total weight of the aqueous suspension, preferably from 1.0 to 40% by weight, further preferably from 5.0 to 30% by weight. It is apparent to the person skilled in the art that the total concentration of the at least one porous metal-organic framework material depends on the conditions in the mineral oil deposit, and the optional further components in the aqueous suspension, such as surfactants or polymers with thickening action.

The person skilled in the art makes a suitable selection of optional further components according to the desired properties, especially according to the conditions in the mineral oil deposit. It is clear here to the person skilled in the art that the concentration of the metal organic- framework material and optional further components can change after injection into the for- mation because the formulation can mix with formation water.

It is the great advantage of the suspension used in accordance with the invention that the at least one porous metal-organic framework material shows good adsorption properties over oil and a high ability to stabilize oil/water emulsions. A further advantage is that the at least one porous metal-organic framework material according to the invention is capable to pass through the fine pores of reservoir rocks.

It is also an advantage that the at least one porous metal-organic framework material shows high stability in water of high salt content, especially high contents of magnesium and calcium ions present in customary oil deposits. It is a further advantage that the adsorption properties of the at least one porous metal-organic framework material are even improved in mineral oil deposits, comprising high saline water. A further advantage of the invention is that the at least one porous metal-organic framework material can be formulated with brackish water or saline water. The aqueous suspension therefore can also be prepared with production water; i. e the production water can be re-used without a step of recycling, desalinating or purification. This results additionally in ecological and economical advantages of the present suspension.

Present method in general is suitable for all mineral oil deposits. The method according to the invention is particularly suitable for mineral oil deposits comprising high saline water, wherein the known chemical substances, applied for tertiary mineral oil production, e. g. surfactants or polymeric thickeners, do not produce satisfactory results and thus are not appropriate.

The salinity of water according to the invention can be defined as "Total Dissolved Solids" (TDS) which is a measure of the total ionic concentration of dissolved minerals in water. The TDS is recorded in milligrams of dissolved solid in one liter of water (mg/L= Parts per million - ppm). Water can therefore be classified by the amount of TDS per liter. Fresh water for example contains less than 1 000 mg/L TDS, brackish water comprises from 1 000 to 10 000 mg/L TDS, saline water from 10 000 to 30 000 mg/L TDS and brine for example more than 30 000 mg/L TDS. Water in mineral oil deposits can also comprise up to 200 000 mg/L TDS. The deposits in which the method is employed generally have a salinity of at least 250 mg/l, preferably at least 1000 mg/l, preferably at least 10 000 mg/l, preferably at least 30 000 mg/l and for example at least 200 000 mg/l.

In a particularly preferred embodiment the invention relates to a method for the tertiary mineral oil production from mineral oil deposits, wherein the formation water has a salinity of at least 250 mg/l TDS, preferably at least 1000 mg/l TDS, preferably at least 10 000 mg/l TDS, particularly preferably at least 30 000 mg/l TDS and also particularly preferably at least 200 000 mg/l TDS. In a preferred embodiment the aqueous suspension is used without adding further components.

In mineral oil deposits having a high salinity of more than 30 000 mg/l TDS the aqueous suspension is particularly preferably used without adding further components. The withdrawn crude oil is present in a mixture, comprising water and crude oil and the at least one porous metal-organic framework material. The phase, comprising the crude oil and the at least one porous metal-organic framework material can be separated from the aqueous phase by breaking the emulsion. Methods for breaking emulsions are known to the person skilled in the art, for example changing the pH value, preferably lowering the pH value, of the withdrawn mixture. The emulsion can also be broken when it is allowed to rest for a certain time, for example more than 24 h. Crude oil comprised in the pores of the at least one porous metal-organic framework material can be removed by methods known in the art, for example by temperature swing adsorption, inert or solvent driven displacement purge and elution/desorption cycles, among other methods known from adsorption processes prior art.

The at least one porous metal-organic framework material can be recycled if desired. Suitable methods for the recycling are known in the art.

Another aspect of the present invention is the use of an aqueous suspension comprising an aqueous liquid and at least one porous metal-organic framework material, for tertiary mineral oil production, wherein the aqueous suspension is injected into a mineral oil deposit through at least one injection borehole and crude oil is withdrawn from the deposit through at least one production borehole, wherein the at least one metal-organic framework material comprises at least one organic compound coordinated to at least one metal ion, wherein the at least one organic compound is based on imidazole, which is unsubstituted or substituted with one or more substituents independently selected from the group consisting of C1-6 alkyl, phenyl and benzyl.

Another aspect of the invention is the use of at least one porous metal-organic framework material as described herein or an aqueous suspension as described herein, for tertiary mineral oil production. The preferred embodiments described above in view of the method according to the invention are preferred for both, the use of the aqueous suspension and the use of the at least one porous metal-organic framework material.

The examples which follow are intended to illustrate the invention in detail:

1 .1 Synthesis of Basolite Z1200 (Zinc-2-methylimidazolate, ZIF-8)

A solution of zink sulfate hepta-hydrate (800 g) in deionized water (2666 g) was prepared. In a separate vessel a second solution was prepared by adding 2-methylimidazole (456 g) to water (2666 g). To the second solution methanol (2222 g) was added within one hour. After allowing the second solution to stir for 1.25 h solution 1 was added to solution 2 over a period of 1 hour and 10 minutes. During the addition of zinc sulfate solution to the imidazole solution, a white suspension was formed. The resulting suspension was stirred for 1 hour and 15 minutes at 27°C with a stirring speed of 90 mirr¹. To that suspension NaOH solution (50 wt%, 444 g) was added slowly keeping the temperature below 30°C. After stirring the suspension for another 1 hour and 15 minutes the content of the vessel was released on a filter and washed ten times with deionized water until the conductivity of the filtrate was below 100 (+/- 50) μθ. For each washing step 1 I of deionized water were used. The water was layered over the material for one hour and afterwards sucked trough the filter cake. The wet filter cake was dried in a circulating air oven for 24h at 120 °C. 600 g of Basolite Z1200 were obtained exhibiting a Langmuir surface area of 1804 m²/g.

Synthesis of Basolite A520 (Aluminum Fumarate)

Fumaric acid (333 g) was added to a solution of 688 g 50% aqueous sodium hydroxide in 4578 g of water. In a second vessel aluminum sulfate * 14 H2O (907 g) was dissolved in 4095 g water. Solution 1 (fumaric acid/NaOH/h O) was added to solution 2 (Al-sulfate/h O) under stirring at room temperature during 40 min. The resulting suspension was heated up to 60 °C within 30- 40 min. and kept at this temperature for 1 .5 h. The white precipitate was filtered and washed with distilled water until the conductivity of the water was lower than 150 με. After drying at 120 °C for 16 h 378 g Basolite A520 was obtained with a Langmuir surface area of 1314 m²/g. The water uptake (water isotherm at 25 °C up to 85 % relative humidity) of that material is up to 46 weight-%.

2 Oil recovery by sandpacked column experiments Oil recovery properties of Basolite Z1200, Basolite A520 and Laponite^® are examined by sand- packed column experiments. The following experiments allow examination of the amount of oil recovered by a suspension comprising a sorption agent.

A cylinder with height of 200 mm and diameter of 15 mm was used for a vessel. 150 ml of sand provided by Wintershall (Well: Bockstedt-83) and 10 ml of crude oil (Wintershall Holding GmbH, 226 mPa^»s at 20°C) was mixed prior to the experiment. The mixture was put into the column until its height be 100 mm. From the top of the column, first deionized water was passed through the column for 1 .5 minutes and then a suspension of the sorption material was passed through for 5 minutes with a flow rate of 20 ml/min. The carbon content of passed through liquid phases was calculated based on elemental analysis.

2.1 Oil Recovery Properties in Brine

Table 1 : Composition of the used suspensions

¹ Comparative Example

² Commercial Laponite® provided by Rockwood Additives Ltd.

³ Total Dissolved Solids" Suspension 1 was stirred with Ultra-Turrax^® with 15 ^χ 10³ rpm for 1 minute prior to the experiment. The results given in Table 1 indicate that Z1200 MOF adsorbed and recovered crude oil. In the case of A520 MOF adsorption and recovery of crude oil was not observed. In the case of Laponite^® as sorption agent, significant amounts of the particles were stacked in and on the sands and didn^'t pass through the glass column.

Oil Recovery Properties in water of high salt content Table 2: Composition of the used suspension

¹ Obtained by dissolving 56 429.0 mg of CaCI₂'2H₂0, 22 420.2 mg of MgCl2^«6H₂0, 132 000.0 mg of NaCI, 270.0 mg of Na2S04, and 380.0 mg of NaB02*4H20 in 1 I of deionized water, adjusting pH to 5.5 - 6.0 with HCI afterwards.

The suspension was stirred with Ultra-Turrax^® with 15 ^χ 10³ rpm for 1 minute prior to the experiment.

The result given in Table 2 indicates that the adsorption property of Z1200 MOF is improved in water with a high salinity of more than 200 000 TDS.

Claims

A method for tertiary mineral oil production, in which an aqueous suspension, comprising an aqueous liquid and at least one porous metal-organic framework material, is injected through at least one injection borehole into a mineral oil deposit, and crude oil is withdrawn from the deposit through at least one production borehole, wherein the at least one metal-organic framework material comprises at least one organic compound coordinated to at least one metal ion, wherein the at least one organic compound is based on imidazole, which is unsubstituted or substituted with one or more substituents independently selected from the group consisting of Ci-6 alkyl, phenyl and benzyl.

The method of claim 1 , wherein the aqueous suspension comprises only one porous metal-organic framework material.

The method of claim 1 or 2, wherein the at least one metal ion is selected from the group of metals consisting of copper, iron, aluminum, zinc, magnesium, zirconium, titanium, vanadium, molybdenum, tungsten, indium, calcium, strontium, cobalt, nickel, platinum, rhodium, ruthenium, palladium, scandium, yttrium, a lanthanide, manganese and rhenium.

The method of any one of claims 1 to 3, wherein the at least one metal ion is Zn²⁺.

The method of any one of claims 1 to 4, wherein the at least one organic compound is 2- methylimidazole, 2-ethylimidazole, 2-benzylimidazole or a deprotonated form thereof.

The method of any one of claims 1 to 5, wherein the at least one metal-organic framework material is Zn-2-methylimidazolate.

The method of any one of claims 1 to 6, wherein the total concentration of the at least one metal-organic framework material is from 0.01 to 50% by weight, based on the total weight of the aqueous suspension.

The method of any one of claims 1 to 7, wherein the aqueous suspension is homogenized before the injection in the mineral oil deposit.

The method of any one of claims 1 to 8, wherein the aqueous liquid has a salinity of at least 10 000 mg/l Total Dissolved Solids. 10. The method of any one of claims 1 to 9, wherein the aqueous suspension is used in a mineral oil deposit, wherein the formation water has a salinity of at least than 30 000 mg/l Total Dissolved Solids.

1 1 . The method of any one of claims 1 to 10, wherein the aqueous suspension has a pH value of from 4 to 1 1 .

The method of any one of claims 1 to 1 1 wherein the average particle size of the at least one metal-organic framework material is less than 15 μιτι.

The method of any one of claims 1 to 12 wherein the crude oil is removed from the metal- organic framework material by temperature swing adsorption, inert or solvent driven displacement purge or elution/desorption cycles.

Use of an aqueous suspension comprising an aqueous liquid and at least one porous metal-organic framework material, for tertiary mineral oil production, wherein the aqueous suspension is injected into a mineral oil deposit through at least one injection borehole and crude oil is withdrawn from the deposit through at least one production borehole, wherein the at least one metal-organic framework material comprises at least one organic compound coordinated to at least one metal ion, wherein the at least one organic compound is based on imidazole, which is unsubstituted or substituted with one or more substituents independently selected from the group consisting of Ci-6 alkyl, phenyl and benzyl

15. Use of at least one porous metal-organic framework material as defined in any one of claims 1 to 13 or an aqueous suspension as defined in any one of claims 1 to 13, for tertiary mineral oil production.