WO2021209148A1 - Process for making an aqueous injection fluid - Google Patents

Process for making an aqueous injection fluid Download PDF

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Publication number
WO2021209148A1
WO2021209148A1 PCT/EP2020/060839 EP2020060839W WO2021209148A1 WO 2021209148 A1 WO2021209148 A1 WO 2021209148A1 EP 2020060839 W EP2020060839 W EP 2020060839W WO 2021209148 A1 WO2021209148 A1 WO 2021209148A1
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Prior art keywords
aqueous
mixing vessel
transfer tube
process according
inlet
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Application number
PCT/EP2020/060839
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French (fr)
Inventor
Daniel Barrera-Medrano
Markus OSTERMAYR
Ines DEBEAUVAIS DE VASCONCELOS
Jack Tinsley
Brent Busby
Dennis Loesch
Anna-Corina SCHMIDT
Esther Matyka LARYEA
Marco Krueger
Faissal-Ali El-Toufaili
Original Assignee
Basf Se
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Priority to PCT/EP2020/060839 priority Critical patent/WO2021209148A1/en
Priority to ARP210101025A priority patent/AR121872A1/en
Publication of WO2021209148A1 publication Critical patent/WO2021209148A1/en

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    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
    • E21B21/06—Arrangements for treating drilling fluids outside the borehole
    • E21B21/062—Arrangements for treating drilling fluids outside the borehole by mixing components
    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
    • E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
    • E21B43/164—Injecting CO2 or carbonated water

Definitions

  • aqueous solutions of water-soluble polymers dry powders of such water-soluble polymers may be dissolved in water.
  • a large number of different processes are known in the art, for example the processes described for example in WO 2008/107492 A1, WO 2008/081048 A2, WO 2008/071808 A1 , WO 2010/020698 A2, US 2013/0292122 A1 , US 9,067,182 B2, US 2009/0095483 A1 or US 2011/0240289 A1.
  • the present invention relates to a process for producing crude oil from subterranean, oil-bearing formations, penetrated by at least one injection well and one production well, by injecting an aqueous injection fluid comprising a water-soluble, thickening polymer into the injection well by means of an injection pump, wherein the aqueous injection fluid penetrates into the subterranean formation and flows towards the production well, thereby mobilizing crude oil, and recovering crude oil form the production well, wherein the aqueous injection fluid is manufactured by a process as described above.
  • the present invention relates to a device for making an aqueous injection fluid for recovering crude oil from oil-bearing, subterranean formations, wherein the aqueous injection fluid comprises a water-soluble, thickening polymer, comprising at least
  • the water-soluble, thickening polymers comprise monoethylenically unsaturated, water- soluble monomers, such as for example acrylic acid or salts thereof or acrylamide. It is not necessary that the water-soluble monomers to be used are miscible with water without any gap. In general, the solubility of the water-soluble monomers in water at room temperature should be at least 50 g/l, preferably at least 100 g/l.
  • the specific composition of the water-soluble, thickening polymers may be selected according to the desired use of the polymers.
  • the aqueous polymer concentrates may be obtained by adiabatic gel polymerization of an aqueous solution of water-soluble, monoethylenically unsaturated monomers thereby yielding an aqueous polymer gel, preferably an aqueous polyacrylamide gel, followed by comminuting the gel and mixing it with an aqueous liquid.
  • the method of “adiabatic gel polymerization” is well known to the skilled artisan. Details are described for example in WO 2019/081318 A1 and other documents cited in the introduction.
  • the aqueous polymer gel typically has a concentration from 15 % to 50 % by weight of water-soluble polymers, preferably from 20 wt. % to 35 wt. %, relating to the total of all components of the gel.
  • aqueous base fluid comprises fresh water, brines, sea water, formation water treated water or mixtures thereof.
  • the salinity of the water may be -for example- from 500 ppm to 300,000 ppm total dissolved solids (TDS), for example from 1,000 ppm to 100,000 ppm.
  • the concentration of the water-soluble, thickening polymers in aqueous polymer concentrate is from 2 wt. % to 10 wt. %, relating to the total of all components of the aqueous polymer concentrate, preferably from 2 wt. % to 10 wt. %, and the concentration of the water-soluble, thickening polymers in the aqueous injection fluid is from 0.05 wt. % to 1 wt. %, preferably from 0.05 wt. % to 0.5 wt. %, relating to the total of all components of the aqueous injection fluid.
  • FIG. 1 One embodiment of a device according to the present invention is schematically shown in figure 1.
  • the device furthermore comprises at least a mixing vessel (3).
  • the mixing vessel may have any shape and size. Its volume may by for example be from 1 m 3 to 50 m 3 .
  • the vessel may be mounted on a mobile platform, so that it can be easily relocated, for example from one oil well to be treated to another oil well to be treated.
  • a plurality of vessels may be used. They may be used in parallel, or they may be connected as a cascade, i.e. the mixture of one vessel is transferred to another vessel for further mixing the components.
  • An embodiment of the plant comprising two mixing vessels (3) is for example shown in figures 3 and 4.
  • tube as used throughout this invention, encompasses rigid tubes such as pipes or pipelines as well as flexible tubes, such as for example hoses or flexible metal tubes.
  • a tube may of course comprise both, rigid and flexible sections.
  • the diameter of the tubes may be for example from 5 cm to 15 cm. Tubes used in oilfield applications often have a diameter of about 10.2 cm (4 inches).
  • the diameter of the inlet tubes (7) preferably should not exceed about 2.54 cm (one inch), although the invention is not restricted to this number. In embodiments of the invention, the diameter of the inlet tubes is limited to about 1.3 cm (0.5 inch) or to about 0.65 cm (0.25 inch).
  • the aqueous polymer concentrate is introduced through the at least one inlet (7) into the distributor and pressed through its perforations.
  • the distributor (13) may be arranged in the headspace of the mixing vessel (3). In such a case, the formed strings of aqueous polymer concentrate drop into the aqueous mixture.
  • the distributor (13) is submerged into the aqueous mixture in the mixing vessel (1), i.e. the aqueous mixture circulates around the distributor (13) and the formed strings of aqueous polymer concentrate are taken away with the aqueous mixture in the mixing vessel (3).
  • the device furthermore comprises at least a third transfer tube (8) connecting the mixing vessel(s) (3) with a second dilution device (9).
  • the third transfer tube (8) serves for transferring the aqueous mother solution obtained by mixing the aqueous polymer concentrate with the aqueous base fluid in the mixing vessel(s) (3) to the second dilution device (9) for further dilution.
  • the transfer through the third transfer tube (8) may be effected for example by a pump.
  • the second dilution device (9) serves for mixing the aqueous mother solution with additional base fluid, thereby obtaining an aqueous injection fluid.
  • the device comprises a fourth transfer tube (10) for transferring aqueous base fluid from the source(s) (1) to the second dilution device (9) and/or the third transfer tube (8).
  • the additional aqueous base fluid may be directly entered into the second dilution device (9) or into the third transfer tube (8), i.e. mixing of the two components already starts, before the mixture enters into the second dilution device (9).
  • the second dilution device (9) basically may be any device suitable for mixing efficiently the aqueous mother solution with additional base fluid. It may be for example another mixing vessel. In one preferred embodiment, the second dilution device comprises at least one static mixer.
  • a device as described above is used.
  • the process comprises at least the process steps (I) to (VII).
  • step (VI) the aqueous mother solution is further diluted with additional aqueous base fluid provided through the fourth transfer tube (10) by means of the second dilution device (9), thereby obtaining an aqueous injection fluid.
  • the second dilution device is a static mixer.
  • At least one production well and at least one injection well are sunk into the mineral oil deposit.
  • a deposit will be provided with a plurality of injection wells and with a plurality of production wells.

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  • Engineering & Computer Science (AREA)
  • Mining & Mineral Resources (AREA)
  • Geology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Fluid Mechanics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Mechanical Engineering (AREA)
  • Processes Of Treating Macromolecular Substances (AREA)

Abstract

The present invention relates to a device and a process for making aqueous injection fluids for recovering crude oil from subterranean, oil-bearing formations, comprising water-soluble polymers, preferably polyacrylamides, by mixing an aqueous base fluid with an aqueous polymer concentrate comprising 1.0 to 10 wt. % of a water-soluble polymer, in at least one mixing vessel and further diluting the obtained aqueous solution in a second step.

Description

Process for making an aqueous injection fluid
The present invention relates to a device and a process for making aqueous injection fluids for recovering crude oil from subterranean, oil-bearing formations, comprising water-soluble polymers, preferably polyacrylamides, by mixing an aqueous base fluid with an aqueous polymer concentrate comprising 1.0 to 10 wt. % of a water-soluble polymer, in at least one mixing vessel and further diluting the obtained aqueous solution in a second step.
Enhanced oil recovery technologies (EOR) for recovering crude oil from subterranean, oil bearing formations are known in the art. In EOR, diluted solutions of water-soluble, thickening polymers, for examples of polyacrylamides, having for example a concentration from 0.05 wt. % to 0.5 wt. % are injected into the formation through an injection well and crude oil is recovered from a production well.
For making the aqueous solutions of water-soluble polymers dry powders of such water- soluble polymers may be dissolved in water. For dissolving powders of water-soluble polymers in water for oilfield applications, a large number of different processes are known in the art, for example the processes described for example in WO 2008/107492 A1, WO 2008/081048 A2, WO 2008/071808 A1 , WO 2010/020698 A2, US 2013/0292122 A1 , US 9,067,182 B2, US 2009/0095483 A1 or US 2011/0240289 A1. FR 3063230 A1 discloses a two-step process for dissolving polyacrylamide powders: In the first step, a polyacrylamide powder is dissolved yielding a concentrate having a concentration from 0.3 wt. % to 2 wt. %. In a second step, the solution is diluted with water to a final concentration from 0.025 wt. % to 0.5 wt. % by means of a static mixer.
Processes of using inverse emulsions for making aqueous polymer solutions, in particular as friction reducers are disclosed for example in US 8,841,240 B2, US 9,315,722 B1, US 2012/0214714 A1, US 2015/0240144 A1, US 2017/0121590 A1, WO 2016/109333 A1 , or WO 2017/143136 A1.
Polyacrylamides may be manufactured by adiabatic polymerization of an aqueous solution comprising acrylamide and optionally further comonomers such as acrylic acid or ATBS, thereby obtaining a solid polymer gel. Such gels may be dried after polymerization, thereby obtaining a polyacrylamide powder. For use in oilfield applications, it needs to be dissolved in aqueous fluids as described above. Because the water contents of aqueous gels typically is from around 65 to around 75 wt. % drying such gels consumes as lot of energy, and also re dissolving powders of high molecular weight polymers is laborious and expensive.
It is also known in the art, to dissolve the polymer gel in water, thereby obtaining directly an aqueous polyacrylamide solution for use for examples in US 4,605,689. Such a process can be carried out on-site, i.e. at the site where polyacrylamide solutions are needed. WO 2019/081318 A1, WO 2019/081319 A1, WO 2019/081320 A1, WO 2019/081321 A1, WO 2019/081323 A1, WO 2019/081327 A1, and WO 2019/081330 A 1 disclose different methods of manufacturing aqueous polyacrylamide solutions on-site in modular plants.
Our older application PCT/EP2019/078218 discloses a method for producing an aqueous polyacrylamide concentrate, having a concentration from 1.0 to 14.9 wt. %, preferably from 3.1 wt. % to 7 wt. % of polyacrylamides, relating to the total of all components of the aqueous polyacrylamide concentrate. The concentrate is manufactured by adiabatic gel polymerization of a monomer solution comprising 15 to 50 wt. % of acrylamide and optionally further mono-ethylenically unsaturated monomers, followed by comminuting the gel, mixing it with water, thereby obtaining the abovementioned concentrate and transporting it to the location of use. The concentrate may be used for enhanced oil recovery.
It was an object of the present invention to provide an improved process for enhanced oil recovery, in which concentrates ble,
Accordingly, the present invention relates to a process for making an aqueous injection fluid for recovering crude oil from oil-bearing, subterranean formations, wherein the aqueous injection fluid comprises a water-soluble, thickening polymer by means of a device comprising at least
• at least one source (1) for an aqueous base fluid,
• at least one source (2) for an aqueous polymer concentrate comprising 1 to 10 wt. % of a water-soluble polymer, relating to the total of all components of the polymer concentrate,
• at least one mixing vessel (3) comprising means (4) for mixing the contents of the mixing vessel,
• at least one first transfer tube (5) for transferring the aqueous base fluid from the source(s) (1) to the mixing vessel(s) (3),
• at least one second transfer tube (6) for transferring the aqueous polymer concentrate from the source(s) (2) to at least one inlet (7) for aqueous polymer concentrate, wherein the inlet(s) (7) are arranged at the mixing vessel(s) (3) and/or at the first transfer tube(s) (5), and
• a third transfer tube (8) connecting the mixing vessel(s) (3) with a second dilution device (9), and
• a fourth transfer tube (10) for transferring aqueous base fluid from the source(s) (1) to the second dilution device (9) and/or the third transfer tube (8),
• a product tube (11) for withdrawing the aqueous injection fluid from the second dilution device (9) for further processing, and wherein the process comprises at least the following steps: (I) transferring aqueous base fluid from the source(s) (1) through the first transfer tube(s) (5) into the mixing vessel(s) (3),
(II) transferring aqueous polymer concentrate from the source(s) (2) through the second transfer tube(s)(6) to the inlet(s)(7) for the aqueous polymer concentrate,
(III) adding a stream of the aqueous polymer concentrate through the inlet(s) (7) to the aqueous base fluid,
(IV) mixing the components in the mixing vessel (1) by means of the mixing means (4), thereby obtaining an aqueous mother solution,
(V) transferring the aqueous mother solution through the third transfer tube (8) from the mixing vessel(s) (3) to the second dilution device (9), and
(VI) further diluting the aqueous mother solution with additional aqueous base fluid provided through the fourth transfer tube (10) by means of the second dilution device (9), thereby obtaining an aqueous injection fluid, and
(VII) withdrawing the obtained aqueous injection fluid from the second dilution device (10) through the product tube (11) and transferring it for further processing.
In another embodiment, the present invention relates to a process for producing crude oil from subterranean, oil-bearing formations, penetrated by at least one injection well and one production well, by injecting an aqueous injection fluid comprising a water-soluble, thickening polymer into the injection well by means of an injection pump, wherein the aqueous injection fluid penetrates into the subterranean formation and flows towards the production well, thereby mobilizing crude oil, and recovering crude oil form the production well, wherein the aqueous injection fluid is manufactured by a process as described above.
In yet another embodiment, the present invention relates to a device for making an aqueous injection fluid for recovering crude oil from oil-bearing, subterranean formations, wherein the aqueous injection fluid comprises a water-soluble, thickening polymer, comprising at least
• at least one source (1) for an aqueous base fluid,
• at least one source (2) for an aqueous polymer concentrate comprising 1 to 10 wt. % of a water-soluble polymer, relating to the total of all components of the polymer concentrate,
• at least one mixing vessel (3) comprising means (4) for mixing the contents of the mixing vessel,
• at least one first transfer tube (5) for transferring the aqueous base fluid from the source(s) (1) to the mixing vessel(s) (3),
• at least one second transfer tube (6) for transferring the aqueous polymer concentrate from the source(s) (2) to at least one inlet (7) for the aqueous polymer concentrate, wherein the inlet(s) (7) are arranged at the mixing vessel(s) (3) and/or at the first transfer tube(s) (5), and
• a third transfer tube (8) connecting the mixing vessel(s) (3) with a second dilution device (9), and · a fourth transfer tube (10) for transferring aqueous base fluid from the source(s)
(1) to the second dilution device (9) and/or the third transfer tube (8),
• a product tube (11) for withdrawing the aqueous injection fluid from the second dilution device (9) for further processing.
List of figures:
Figure imgf000006_0001
With regard to the invention, the following should be stated specifically:
In the process according to the present invention, an aqueous injection fluid for recovering crude oil from oil-bearing, subterranean formations is prepared, wherein the aqueous injection fluid comprises a water-soluble, thickening polymer, relating to the total of all components of the aqueous injection fluid. The starting material for the process is an aqueous polymer aqueous polymer concentrate comprising 1 to 10 wt. % of a water-soluble polymer, relating to the total of all components of the polymer concentrate which is mixed with at least an aqueous base fluid by means of a device as will be described below, thereby obtaining an aqueous injection fluid.
Water-soluble thickening polymers
The water-soluble, thickening polymers comprise monoethylenically unsaturated, water- soluble monomers, such as for example acrylic acid or salts thereof or acrylamide. It is not necessary that the water-soluble monomers to be used are miscible with water without any gap. In general, the solubility of the water-soluble monomers in water at room temperature should be at least 50 g/l, preferably at least 100 g/l.
Preferably, the water-soluble, thickening polymers are polyacrylamides. The term “polyacrylamide” as used herein means water-soluble polymers comprising at least 10 %, preferably at least 20 %, and more preferably at least 30 % by weight of acrylamide, wherein the amounts relate to the total amount of all monomers relating to the polymer. Polyacrylamides include homopolymers and copolymers of acrylamide and other monoethylenically unsaturated comonomers. Polyacrylamide copolymers are preferred.
Examples of water-soluble, monoethylenically unsaturated monomers comprise neutral monomers such as acrylamide, methacrylamide, N-methyl(meth)acrylamide, N,N’- dimethyl(meth)acrylamide, N-methylol(meth)acrylamide or N-vinylpyrrolidone. Further examples comprise anionic monomers, in particular monomers comprising -COOH groups and/or -SO3H groups are salts thereof such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid or fumaric acid or salts thereof. Examples of monomers comprising -SO3H groups or salts thereof include vinylsulfonic acid, allylsulfonic acid, 2- acrylamido-2-methylpropanesulfonic acid (ATBS), 2-methacrylamido-2- methylpropanesulfonic acid, 2-acrylamidobutanesulfonic acid, 3-acrylamido-3- methylbutanesulfonic acid or 2-acrylamido-2,4,4-trimethylpentanesulfonic acid. Preference is given to 2-acrylamido-2-methylpropanesulfonic acid (ATBS) or salts thereof.
Preferred monomers comprising acidic groups comprise acrylic acid and/or ATBS or salts thereof.
Further examples of monomers comprise water-soluble, monoethylenically unsaturated monomers comprising cationic groups. Suitable cationic monomers include especially monomers having ammonium groups, especially ammonium derivatives of N-(w- aminoalkyl)(meth)acrylamides or w-aminoalkyl (meth)acrylates such as 2-trimethylammoniooethyl acrylate chloride H C=CH-CO-CH CH N+(CH ) CI (DMA3Q).
Furthermore, associative monomers may be used. Examples of associative monomers have been described for example in WO 2010/133527, WO 2012/069478, WO 2015/086468 or WO 2015/158517.
Besides water-soluble monoethylenically unsaturated monomers, also water-soluble, ethylenically unsaturated monomers having more than one ethylenic group may be used. Monomers of this kind can be used in special cases in order to achieve easy crosslinking of the polymers. The amount thereof should generally not exceed 2% by weight, preferably 1% by weight and especially 0.5% by weight, based on the sum total of all the monomers. More preferably, the monomers to be used in the present invention are only monoethylenically unsaturated monomers.
The specific composition of the water-soluble, thickening polymers may be selected according to the desired use of the polymers.
Preferred polymers are polyacrylamides and comprise, besides at least 10 % by weight, preferably at least 20 % by weight and for example at least 30 % by weight of acrylamide, one further water-soluble, monoethylenically unsaturated monomer, preferably at least one further monomer selected from the group of acrylic acid or salts thereof, ATBS or salts thereof, or associative monomers. In certain embodiments, the polyacrylamides comprise from 50 to 95 wt. % of acrylamide and from 5 to 50 wt. % of ATBS and/or acrylic acid or salts thereof. In another preferred embodiment, the polyacrylamides comprise additionally at least one associative monomer are described above. The amounts of associative monomers typically are low and may be, for example, from 0.5 % by weight to 2 % by wt., relating to the total of all components of the polyacrylamides.
The weight average molecular weight Mw of the water-soluble, thickening polymers, in particular the water-soluble, thickening polyacrylamides is selected by the skilled artisan according to the intended use of the polymer. For enhanced oil recovery applications high molecular weights are desirable. A high molecular weight corresponds to a high intrinsic viscosity (IV) of the polyacrylamides. In one embodiment of the invention, the intrinsic viscosity may be at least 15 deciliter/gram (dL/g). In one embodiment of the invention, the intrinsic viscosity is from 30 to 45 dl/g. The numbers mentioned relate to the measurement with an automatic Lauda iVisc® LMV830 equipped with an Ubbelohde capillary tube and automatic injection. For the measurements an aqueous solution of the polymers to be analyzed was prepared having a concentration of 250 ppm. The pH was adjusted at 7 by means of a buffer and the solution comprised additionally 1 mol /I of NaCI. Further four dilutions were done automatically. The viscosity at five different concentrations was measured at 25 °C. The IV value [dL/g] was determined in usual manner by extrapolating the viscosities to infinite dilution. The error range is about +/- 2 dL/g. Aqueous polvmer concentrates
The aqueous polymer concentrates to be used in the process according to the present invention comprises at least a water-soluble, thickening polymer, preferably a polyacrylamide, more preferably a polyacrylamide copolymer as described above and an aqueous liquid.
The aqueous liquid comprises water. The term “water” includes any kind of water such as desalinated water, fresh water or water comprising salts, such as brines, sea water, formation water, produced water or mixtures thereof. Besides water, the aqueous liquid may comprise organic solvents miscible with water, however the amount of water relating to the total of all solvent should be at least 70 % by weight, preferably at least 90 % by weight, more preferably at least 95 % by weight. In one preferred embodiment, the aqueous liquid comprises only water as solvent.
The aqueous polymer concentrates to be used for making aqueous treatment fluids according to the present invention are homogeneous. The term should be understood as “substantially homogeneous”, so minor variations of polymer density or polymer concentration within a concentrate may be possible. However, polyacrylamide dispersions in oil or water-in-oil emulsions of polyacrylamides are heterogeneous products (which comprise at least to different phases), which are not subject of the process according to the present invention.
The concentration of the water-soluble, thickening polymers, preferably of the polyacrylamides in the aqueous polymer concentrate is from 1 to 10 wt. % relating to the total of all components of the polymer concentrate, in particular from 2 to 10 wt. %, preferably from 2.5 to 10 wt. % or from 2.5 to 8 wt. % and for example from 3.1 to 7 wt. %.
Keeping the concentration and the molecular weights of the water-soluble, thickening polymers, preferably the polyacrylamides to be used in mind, the aqueous polymer concentrates typically may be identified as (soft) solids or viscos solutions. The aqueous polymer concentrates are pumpable.
The aqueous polymer concentrate preferably has a viscosity of at least 1 ,000 mPas*s, measured at 10 s 1, for example at least 1,000 mPas*s, preferably at least 5,000 mPas*s, more preferably at least 10,000 mPas*s. As a rule, its viscosity should not exceed 500,000 mPa*s, preferably not 300,000 mPa*s. In one embodiment, the viscosity of the aqueous polymer concentrate is from 1,000 mPa*s to 500,000 mPa*s, preferably from 5,000 mPa*s to 300,000 mPa*s, for example from 10,000 mPa*s to 100,000 mPa*s. Said viscosities relate to a measurement by means of a rotational rheometer having a plate-plate geometry (DHR-1 of TA Instruments, plate diameter 040 mm, h = 1mm, deformation 10 %) and a measuring temperature of 23°C.
The aqueous polymer concentrates, preferably the aqueous polyacrylamide concentrates to be used for the method according to the present invention basically may be manufactured by any technology.
In one embodiment of the invention, the aqueous polymer concentrates may be obtained by mixing water-soluble polymers as described above with an aqueous liquid. The term “aqueous liquid” has already been defined above. Basically, any kind of mixing unit capable of mixing solids with liquids may be used. For example, extruder or kneaders may be used.
In one embodiment of the invention, a kneader may be used for mixing. Examples of suitable kneaders are disclosed in WO 2006/034853 A1 and the literature cited therein. Suitable kneaders are also commercially available.
In a preferred embodiment of the invention, the aqueous polymer concentrates may be obtained by adiabatic gel polymerization of an aqueous solution of water-soluble, monoethylenically unsaturated monomers thereby yielding an aqueous polymer gel, preferably an aqueous polyacrylamide gel, followed by comminuting the gel and mixing it with an aqueous liquid. The method of “adiabatic gel polymerization” is well known to the skilled artisan. Details are described for example in WO 2019/081318 A1 and other documents cited in the introduction. The aqueous polymer gel typically has a concentration from 15 % to 50 % by weight of water-soluble polymers, preferably from 20 wt. % to 35 wt. %, relating to the total of all components of the gel.
The aqueous polymer gel obtained by adiabatic gel polymerization is comminuted and mixed with an aqueous liquid in a second step thereby obtaining an aqueous polymer concentrate as described above. Comminution and mixing may be followed by a step of homogenization. Basically, any kind of comminution means may be used for disintegrating the aqueous polymer gel into smaller particles. Examples of suitable means for comminuting aqueous polymer gels include cutting devices such as knives or perforated plates, crushers, kneaders, static mixers or water-jets. Homogenization may be effected by simply allowing to stand a mixture of small gel pieces and aqueous liquid in a suitable vessel. It may be supported for example by pumping the mixture through a loop using circulation pumps. Optionally, the loop may comprise one or more static mixers. Further examples include tumbling, shaking or any mixing method known to skilled in the art for highly viscous liquids, for example using progressive cavity pumps.
Components of the aqueous injection fluid
The aqueous injection fluid to be manufactured according to the process according to the present invention comprises a water-soluble, thickening polymer, preferably a polyacrylamide as described above which is introduced into the process as aqueous polymer concentrate as also described above.
It furthermore comprises at least an aqueous base fluid. Examples of aqueous base fluids comprise fresh water, brines, sea water, formation water treated water or mixtures thereof. The salinity of the water may be -for example- from 500 ppm to 300,000 ppm total dissolved solids (TDS), for example from 1,000 ppm to 100,000 ppm.
The concentration of the water-soluble, thickening polymer, preferably the water-soluble polyacrylamides in the aqueous injection fluid may be selected by the skilled artisan according to his/her needs. The concentration may be for example from 0.05 wt. % to 2 wt. %, or from 0.05 wt. % to 1 wt. %, or from 0.05 wt. % to 0.5 wt. %, in each case relating to the total of all components of the aqueous injection fluid. It goes without saying, that the concentration of the aqueous polymer concentrate used as starting material for the process is higher than the concentration of the aqueous injection fluid and is selected by the skilled artisan. In one embodiment, the concentration of the water-soluble, thickening polymers in aqueous polymer concentrate is from 2 wt. % to 10 wt. %, relating to the total of all components of the aqueous polymer concentrate, preferably from 2 wt. % to 10 wt. %, and the concentration of the water-soluble, thickening polymers in the aqueous injection fluid is from 0.05 wt. % to 1 wt. %, preferably from 0.05 wt. % to 0.5 wt. %, relating to the total of all components of the aqueous injection fluid.
The aqueous treatment fluid may of course comprise further components. The nature and the amount of such further components depend on the intended use of the aqueous treatment fluid. Examples of such additional components comprise biocides, stabilizers, free- radical scavengers, initiators, surfactants, cosolvents, bases and complexing agents.
Device to be used for the process
For making aqueous injection fluids comprising water-soluble polymers according to the process according to the present invention a device as will be described in the following is used.
One embodiment of a device according to the present invention is schematically shown in figure 1.
The device comprises at least one source (1) for the aqueous base fluid. The term “source” is intended to cover any kind of source. For example, a river, a lake or another water reservoir may serve as source (1) for the aqueous base fluid. In one embodiment, the aqueous base fluid may be provided in a pipeline to the site of use. In one embodiment, the source (1) is a tank. Of course, a plurality of sources (1) may be used, for example a plurality of tanks. Preferably, such tanks are mobile, so that they can be easily relocated, for example from one oil well to another oil well. In certain embodiments of the present invention, the tanks may be tank containers, tank trailers or tank trucks. Basically, the tanks may have any shape and size. In one embodiment, tanks may be cylindrical. The volume of the tanks is not limited. Mobile tanks as mentioned, may have a volume from 10 m3 to 100 m3, for example from 50 m3 to 100 m3. The tanks may also serve a buffer tanks to ensure an uninterrupted supply with the aqueous base fluid, that is to say they are simultaneously filled from a water source such as a river, a lake or another water reservoir and aqueous base fluid is withdrawn from the tank(s) for use in the process.
The device furthermore comprises at least one source (2) for the aqueous polymer concentrate comprising 1 to 10 wt. % of a water-soluble polymer, relating to the total of all components of the polymer concentrate. The source (2) may be for example a container, vessel or tank comprising the aqueous polymer concentrate. In one embodiment, the source (2) may be one or more than one intermediate bulk containers (IBC), for example having a volume from 0.5 to 5 m3.
The device furthermore comprises at least a mixing vessel (3). Basically, the mixing vessel may have any shape and size. Its volume may by for example be from 1 m3 to 50 m3. The vessel may be mounted on a mobile platform, so that it can be easily relocated, for example from one oil well to be treated to another oil well to be treated. Also, a plurality of vessels may be used. They may be used in parallel, or they may be connected as a cascade, i.e. the mixture of one vessel is transferred to another vessel for further mixing the components. An embodiment of the plant comprising two mixing vessels (3) is for example shown in figures 3 and 4.
In the mixing vessel(s) (3), the aqueous polymer concentrate is mixed with a part of the aqueous base fluid, thereby obtaining an aqueous mother solution. The aqueous mother solution obtained is diluted in a second dilution step as will be described below, thereby obtaining the aqueous injection fluid.
The mixing vessel (3) comprises at least an inlet for the aqueous base fluid and an outlet for the aqueous mother solution. It may comprise inlets for further components of the fluid. It furthermore, comprises means (4) for mixing the contents of the mixing vessel.
Mixing means (4) may be any kind of means suitable for mixing the contents of the mixing vessel. In one embodiment, the inlet(s) for the aqueous base fluid itself may function as mixing means (2). In this embodiment, the mixing vessel (3) preferably comprises a plurality of inlets for the aqueous base fluid. The stream aqueous base fluid is introduced into the mixing vessel (4) through the inlet(s) at a velocity capable of creating turbulences in the mixing vessel (1) which serve to mix the contents of the mixing vessel (1). In order to increase the velocity of the streaming aqueous base fluid, in one embodiment, the inlet(s) may be connected with orifices. In other embodiments, the mixing vessel (1) may be equipped with a stirrer as indicated in figure 1. Other mixing means comprise a loop through which the contents of the mixing vessel is circulated by means of a pump.
The device furthermore comprises furthermore at least one first transfer tube (5) for transferring the aqueous base fluid from the source(s) (1) to the mixing vessel(s) (3). It may comprise a plurality of first transfer tubes, if the device comprises a plurality of sources (1) of aqueous base fluid. The transfer of the aqueous base fluid through the first transfer tube (5) may preferably effected by means of a pump.
The term “tube” as used throughout this invention, encompasses rigid tubes such as pipes or pipelines as well as flexible tubes, such as for example hoses or flexible metal tubes. A tube may of course comprise both, rigid and flexible sections. The diameter of the tubes may be for example from 5 cm to 15 cm. Tubes used in oilfield applications often have a diameter of about 10.2 cm (4 inches).
The device furthermore comprises at least one second transfer tube (6) for transferring the aqueous polymer concentrate from the source(s) (2) to at least one inlet (7) for the aqueous polymer concentrate. The transfer of the aqueous polymer concentrates through the second transfer tube (6) may preferably be effected by means of a pump, for example a gear pump. The inlet(s) (7) for the aqueous polymer concentrate may be arranged at the first transfer tube(s) (5), i.e. the aqueous polymer concentrate is already mixed with the aqueous base fluid before it enters into the mixing vessel. If the first transfer tube (5) comprises a pump, in one embodiment the inlet (7) is be arranged before the pump, so that the mixture of aqueous base fluid and aqueous polymer concentrate passes through the pump which supports the dissolution of the polymer. In another embodiment, the inlet(s) (7) are arranged at the mixing vessel(s) (3), i.e. the aqueous polymer concentrate is added into the mixing vessel(s) (3). Of course, both possibilities may be combined with each other. If the device comprises a cascade of mixing vessel(s)(3), the aqueous polymer concentrate preferably is added into the second transfer tube (6) and/or the first of the mixing vessel(s).
In one embodiment of the invention, the aqueous polymer concentrate is added into the first transfer tube(s) (5).
In one embodiment, the aqueous polymer concentrate is added into the first transfer tube(s) (5) through one single inlet (7) per input tube (5). Such a single inlet (7) may have a diameter of about 5.1 cm (2 inches), if the first transfer tube (5) has a diameter of about 10.2 cm (4 inches).
In another embodiment of the invention, the aqueous polymer concentrate is added into the first transfer tube(s) (5) through a plurality of inlets (7) per input tube. Such an embodiment is schematically shown in figure 2. Such an embodiment has the advantage, that the total amount to be added is distributed over a larger number of inlets, so that the diameter of the inlets (7) can be reduced. Strings of aqueous polymer concentrates having a lower diameter are easier to dissolve in the aqueous base fluid than strings having a larger diameter. The number of inlets may be selected by the skilled artisan according to his/her needs. In this embodiment, for example the number of inlets (7) may be from 5 to 50 or from 5 to 15 per tube. Staying with the example above, for adding an aqueous polymer concentrate to a stream of aqueous base fluid in the first transfer tube (5) having a diameter of about 10.2 cm (4 inches), instead of a single inlet having a diameter of about 5.1 cm (2 inches), 5 to 10 inlets (5) having a diameter of about 1.3 cm (0.5 inch) or from 10 to 20 having a diameter of about 0.65 cm (0.25 inch) may be used.
In another embodiment of the invention, the inlet (7) for the aqueous polymer concentrate is connected with a distributor (12) which is a hollow body comprising a plurality of perforations, which is arranged in the first transfer tube (5) and the stream of the aqueous base fluid circulates around the distributor. The hollow body may be for example a hollow cylinder comprises perforations in the lateral area. The perforations preferably may be circular, but of course also other shapes are possible. The diameter and the number of perforations may be selected by the skilled artisan according to his/her needs. The diameter of the perforations may for example be from 1 mm to 10 mm, preferably from 1 mm to 5 mm and for example from 1.5 mm to 3 mm. For non-circular perforations, the term “diameter” refers to the longest dimension. The number of perforations may be for example from 100 to 2000. In operation, aqueous polymer concentrate is introduced through the inlet (7) into the distributor and pressed through its perforations. The formed strings of aqueous polymer concentrate are carried away by the aqueous base fluid. One example of this embodiment is schematically shown in figures 6 and 7. The drawing show a cylindrical distributor (12) which is fixed at its lower and upper end to the first transfer tube (5). The lateral area of the cylinder comprises perforations. Its diameter is less than the diameter of the input tube (7), so that aqueous base fluid flows around the distributor. It is the advantage that the distributor comprises a large number of perforations, however, only one tube which provides aqueous polymer concentrate needs to be connected to the inlet (7).
Another example of this embodiment is schematically shown in figure 8. In this embodiment, the distributor (12) is a hollow cuboid, which is arranged in such a manner, that the narrow sides of the cuboid point in flow direction. The two broader sides of the cuboid point perpendicular to the flow direction and comprise perforations. Details of the perforations have already mentioned above and we refer to the respective passage. In operation, the aqueous polymer concentrate is introduced through the inlet (7) into the cuboid distributor and pressed through its perforations. The formed strings of aqueous polymer concentrate are carried away by the aqueous base fluid.
In another embodiment of the invention, the aqueous polymer concentrate is added into the mixing vessel (3). In one embodiment of the invention, the aqueous polymer concentrate is added into the mixing vessel (3) through one inlet tube (7) or a plurality of inlet tubes (7). Using more than one inlet (7) has the advantage, that the total amount to be added is distributed over a larger number of inlets, so that the diameter of the inlets (7) can be reduced. Strings of aqueous polymer concentrates having a lower diameter are easier to dissolve in the aqueous base fluid than strings having a larger diameter. The number of inlets may be selected by the skilled artisan according to his/her needs. The number of inlets (7) may be for example from 2 to 20 or from 4 to 8 per tube. The diameter of the inlet tubes (7) preferably should not exceed about 2.54 cm (one inch), although the invention is not restricted to this number. In embodiments of the invention, the diameter of the inlet tubes is limited to about 1.3 cm (0.5 inch) or to about 0.65 cm (0.25 inch).
In a further embodiment, the mixing vessel (1) comprises at least one inlet tube (7) for the aqueous polymer concentrate comprising at least one distributor (13) which is a hollow body comprising a plurality of perforations. Of course, the mixing vessel may comprise two or more inlet tubes (7) each of them comprising at least one distributor. Such an embodiment schematically is shown in figure 5.
The hollow body may be for example a hollow cylinder comprising perforations in the lateral area. In another embodiment, the hollow body is a flat body and the perforations preferably are located at its lower surface (similar like a shower head). The perforations preferably may be circular, but of course also other shapes are possible. The diameter and the number of perforations may be selected by the skilled artisan according to his/her needs. The diameter of the perforations may for example be from 1 mm to 10 mm, preferably from 1 mm to 5 mm and for example from 1.5 mm to 3 mm. For non-circular perforations, the term “diameter” refers to the longest dimension. The number of perforations may be for example from 10 to 2000.
In operation, the aqueous polymer concentrate is introduced through the at least one inlet (7) into the distributor and pressed through its perforations. The distributor (13) may be arranged in the headspace of the mixing vessel (3). In such a case, the formed strings of aqueous polymer concentrate drop into the aqueous mixture. In another embodiment, the distributor (13) is submerged into the aqueous mixture in the mixing vessel (1), i.e. the aqueous mixture circulates around the distributor (13) and the formed strings of aqueous polymer concentrate are taken away with the aqueous mixture in the mixing vessel (3).
The device furthermore comprises at least a third transfer tube (8) connecting the mixing vessel(s) (3) with a second dilution device (9). The third transfer tube (8) serves for transferring the aqueous mother solution obtained by mixing the aqueous polymer concentrate with the aqueous base fluid in the mixing vessel(s) (3) to the second dilution device (9) for further dilution. The transfer through the third transfer tube (8) may be effected for example by a pump. The second dilution device (9) serves for mixing the aqueous mother solution with additional base fluid, thereby obtaining an aqueous injection fluid.
For providing additional aqueous base fluid, the device comprises a fourth transfer tube (10) for transferring aqueous base fluid from the source(s) (1) to the second dilution device (9) and/or the third transfer tube (8). So, the additional aqueous base fluid may be directly entered into the second dilution device (9) or into the third transfer tube (8), i.e. mixing of the two components already starts, before the mixture enters into the second dilution device (9).
The second dilution device (9) basically may be any device suitable for mixing efficiently the aqueous mother solution with additional base fluid. It may be for example another mixing vessel. In one preferred embodiment, the second dilution device comprises at least one static mixer.
The device according to the present invention furthermore comprises a product tube (11) for withdrawing the aqueous injection fluid from the second dilution device (9) for further processing. Through the product tube (11), the aqueous injection fluid may be for example transferred to high pressure pumps which inject the aqueous injection fluid into a subterranean, oil bearing formation. In another embodiment, the aqueous injection fluid may be transferred to a buffer tank or a plurality of buffer tanks for storing before injection.
Process for making aqueous injection fluids
In the process for making an aqueous injections fluid comprising water-soluble polymers for treating subterranean formations a device as described above is used. The process comprises at least the process steps (I) to (VII).
In course of step (I), aqueous base fluid is transferred from the source(s) (1) through the first transfer tube(s) (5) into the mixing vessel(s) (3).
In course step (II), an aqueous polymer concentrate is transferred from the source(s) (2) through the second transfer tube(s)(6) to the inlet(s)(7) for the aqueous polymer concentrate.
In course of step (III), a stream of the aqueous polymer concentrate, preferably an aqueous polyacrylamide concentrate is added through the inlet(s) (7) to the aqueous base fluid. As already described above, the aqueous polymer concentrate is added either into the first transfer tube(s) (5) or directly into the mixing vessel(s) (3). Further components for the aqueous injection fluid may optionally be added into the mixing vessel(s)(3). In course of step (IV), at least the aqueous polymer concentrate, the aqueous base fluid and optionally further components are mixed in the mixing vessel (3) by means of the mixing means (4), thereby obtaining an aqueous mother solution. The aqueous mother solution may for example have a concentration of water-soluble, thickening polymers, preferably polyacrylamides from 0.51 to 1.0 wt %, relating to the total of all components of the aqueous mother solution.
In course of step (V), the aqueous mother solution is transferred through the third transfer tube (8) from the mixing vessel(s) (3) to the second dilution device (9).
In course of step (VI), the aqueous mother solution is further diluted with additional aqueous base fluid provided through the fourth transfer tube (10) by means of the second dilution device (9), thereby obtaining an aqueous injection fluid. As already outlined above, in a preferred embodiment, the second dilution device is a static mixer.
In course of step (VII), the obtained aqueous injection fluid is withdrawn from the second dilution device (10) through the product tube (11) and transferring for further processing. The aqueous injection fluid may be for example transferred to high pressure pumps which inject the aqueous injection fluid into a subterranean, oil bearing formation. In another embodiment, the aqueous injection fluid may be transferred to a buffer tank or a plurality of buffer tanks for storing before injection.
Process for producing crude oil from subterranean oil-bearina formations
In another embodiment, the present invention relates process for producing crude oil from subterranean, oil-bearing formations, penetrated by at least one injection well and one production well, by injecting an aqueous injection fluid comprising a water-soluble, thickening polymer, preferably a polyacrylamide into the injection well(s) by means of an injection pump, wherein the aqueous injection fluid penetrates into the subterranean formation and flows towards the production well, thereby mobilizing crude oil, and recovering crude oil form the production well(s), wherein the aqueous injection fluid is manufactured by a process as described above.
For the method of producing crude oil, at least one production well and at least one injection well are sunk into the mineral oil deposit. In general, a deposit will be provided with a plurality of injection wells and with a plurality of production wells.
The aqueous injection fluid manufactured according to the process as outlined above is injected by means of an injection pump into the subterranean, oil-bearing formation through the at least one injection well, and crude oil is withdrawn from the formation through at least one production well. By virtue of the pressure generated by the aqueous injection fluid injected, also called the “polymer flood”, the crude oil in the formation flows in the direction of the production well and is produced through the production well. In this context, the term “crude oil” does not of course just mean a single-phase oil; instead, the term also encompasses the customary crude oil-water emulsions.
Typical compositions of the aqueous injection fluid, and typical compositions of the water- soluble polymers, preferably the polyacrylamides, as well as typical concentrations of the water-soluble polymers, preferably the polyacrylamides in the aqueous injection fluid have already been described above and we refer to the passages above. In one embodiment, the concentration of the water-soluble polymer, preferably the polyacrylamide in the aqueous injection fluid is from 0.05 wt. % to 0.5 wt. %, relating to the total of all components of the aqueous injection fluid.

Claims

Claims
1. Process for making an aqueous injection fluid for recovering crude oil from oil-bearing, subterranean formations, wherein the aqueous injection fluid comprises a water-soluble, thickening polymer by means of a device comprising at least
• at least one source (1) for an aqueous base fluid,
• at least one source (2) for an aqueous polymer concentrate comprising 1 to 10 wt. % of a water-soluble polymer, relating to the total of all components of the polymer concentrate,
• at least one mixing vessel (3) comprising means (4) for mixing the contents of the mixing vessel,
• at least one first transfer tube (5) for transferring the aqueous base fluid from the source(s) (1) to the mixing vessel(s) (3),
• at least one second transfer tube (6) for transferring the aqueous polymer concentrate from the source(s) (2) to at least one inlet (7) for aqueous polymer concentrate, wherein the inlet(s) (7) are arranged at the mixing vessel(s) (3) and/or at the first transfer tube(s) (5), and
• a third transfer tube (8) connecting the mixing vessel(s) (3) with a second dilution device (9), and
• a fourth transfer tube (10) for transferring aqueous base fluid from the source(s) (1) to the second dilution device (9) and/or the third transfer tube (8),
• a product tube (11) for withdrawing the aqueous injection fluid from the second dilution device (9) for further processing, and wherein the process comprises at least the following steps:
(I) transferring aqueous base fluid from the source(s) (1) through the first transfer tube(s) (5) into the mixing vessel(s) (3),
(II) transferring aqueous polymer concentrate from the source(s) (2) through the second transfer tube(s)(6) to the inlet(s)(7) for the aqueous polymer concentrate,
(III) adding a stream of the aqueous polymer concentrate through the inlet(s) (7) to the aqueous base fluid,
(IV) mixing the components in the mixing vessel (1) by means of the mixing means (4), thereby obtaining an aqueous mother solution,
(V) transferring the aqueous mother solution through the third transfer tube (8) from the mixing vessel(s) (3) to the second dilution device (9), and (VI) further diluting the aqueous mother solution with additional aqueous base fluid provided through the fourth transfer tube (10) by means of the second dilution device (9), thereby obtaining an aqueous injection fluid, and
(VII) withdrawing the obtained aqueous injection fluid from the second dilution device (10) through the product tube (11) and transferring it for further processing.
2. Process according to claim 1, wherein the aqueous polymer concentrate is an aqueous polyacrylamide concentrate.
3. Process according to claims 1 or 2, wherein the aqueous polymer concentrate has a viscosity of at least 1,000 mPas*s, measured at 10 s 1.
4. Process according to any of claims 1 to 3, wherein the aqueous polymer concentrate comprises 2.5 to 10 wt. % of the water-soluble, thickening polymer, relating to the total of all components of the polymer concentrate.
5. Process according to any of claims 1 to 4, wherein the concentration of the water- soluble, thickening polymer in the aqueous injection fluid is from 0.05 to 0.5 wt %, relating to the total of all components of the aqueous mother solution.
6. Process according to claim 4, wherein the concentration of the water-soluble, thickening polymer in the aqueous mother solution is from 0.51 to 1.0 wt %, relating to the total of all components of the aqueous mother solution.
7. Process according to any of claims 1 to 6, wherein the means (4) for mixing the contents of the mixing vessel comprise at least one stirrer.
8. Process according to any of claims 1 to 7, wherein inlet(s) (7) are arranged at the first transfer tube(s) (5).
9. Process according to claim 8, wherein the aqueous polymer concentrate is added into at least one first transfer tube(s) (5) through one single inlet (7).
10. Process according to claim 8, wherein the aqueous polymer concentrate is added into at least one first transfer tube(s) (5) through a plurality of inlets (7).
11. Process according to claim 10, wherein the number of inlets (7) is from 5 to 100.
12. Process according to claim 8, wherein the inlet (7) is connected with a distributor (12) which is a hollow body comprising a plurality of perforations, which is arranged in the first transfer tube (5) and the stream of the aqueous base fluid circulates around the distributor, wherein the aqueous polymer concentrate is introduced through the inlet (7) into the distributor and pressed through its perforations.
13. Process according to any of claims 1 to 7, wherein inlet(s) (7) are arranged at the mixing vessel (3).
14. Process according to claim 13, wherein the mixing vessel (3) comprises a plurality of inlets (7) for the aqueous polymer concentrate.
15. Process according to claim 13, wherein the mixing vessel (3) comprises at least one inlet (7) for the aqueous polymer concentrate, which is connected with at least one distributor (13) which is a hollow body comprising a plurality of perforations.
16. Process according to claim 15, wherein the hollow body is cylindrical.
17. Process according to claim 15, wherein the hollow body is a flat body and the perforations are located at its lower surface.
18. Process according to any of claims 15 to 17, wherein the perforations in the distributor have a diameter from 1 to 10 mm.
19. Process according to any of claims 15 to 18, wherein the number of perforations in the distributor is from 10 to 2000.
20. Process according to any of claims 15 to 19, wherein the distributor (13) is arranged is arranged in the headspace of the mixing vessel (3).
21. Process according to any of claims 15 to 19, wherein the distributor (13) is submerged into the aqueous mixture in the mixing vessel (3).
22. Process according to any of claims 1 to 21, wherein the second dilution device (9) comprises at least one static mixer.
23. Process for producing crude oil from subterranean, oil-bearing formations, penetrated by at least one injection well and one production well, by injecting an aqueous injection fluid comprising a water-soluble, thickening polymer into the injection well(s) by means of an injection pump, wherein the aqueous injection fluid penetrates into the subterranean formation and flows towards the production well, thereby mobilizing crude oil, and recovering crude oil form the production well(s), wherein the aqueous injection fluid is manufactured by a process according to any of claims 1 to 22.
24. Process according to claim 23, wherein the water-soluble polymer is a polyacrylamide.
25. Process according to claim 23, wherein the concentration of the water-soluble polymer in the aqueous injection fluid is from 0.05 wt. % to 0.5 wt. %, relating to the total of all components of the aqueous injection fluid.
26. Device for making an aqueous injection fluid for recovering crude oil from oil-bearing, subterranean formations, wherein the aqueous injection fluid comprises a water-soluble, thickening polymer, comprising at least
• at least one source (1) for an aqueous base fluid,
• at least one source (2) for an aqueous polymer concentrate comprising 1 to 10 wt. % of a water-soluble polymer, relating to the total of all components of the polymer concentrate,
• at least one mixing vessel (3) comprising means (4) for mixing the contents of the mixing vessel,
• at least one first transfer tube (5) for transferring the aqueous base fluid from the source(s) (1) to the mixing vessel(s) (3),
• at least one second transfer tube (6) for transferring the aqueous polymer concentrate from the source(s) (2) to at least one inlet (7) for the aqueous polymer concentrate, wherein the inlet(s) (7) are arranged at the mixing vessel(s) (3) and/or at the first transfer tube(s) (5), and
• a third transfer tube (8) connecting the mixing vessel(s) (3) with a second dilution device (9), and
• a fourth transfer tube (10) for transferring aqueous base fluid from the source(s) (1) to the second dilution device (9) and/or the third transfer tube (8),
• a product tube (11) for withdrawing the aqueous injection fluid from the second dilution device (9) for further processing.
27. Device according to claim 26, wherein the means (4) for mixing the contents of the mixing vessel comprise at least one stirrer.
28. Device according to claims 26 or 27, wherein inlet(s) (7) are arranged at the first transfer tube(s) (5).
29. Device according to claim 28, wherein the aqueous polymer concentrate is added into at least one first transfer tube(s) (5) through one single inlet (7).
30. Device according to claim 28, wherein the aqueous polymer concentrate is added into at least one first transfer tube(s) (5) through a plurality of inlets (7).
31. Device according to claim 30, wherein the number of inlets (7) is from 5 to 100.
32. Device according to claim 28, wherein the inlet (7) is connected with a distributor (12) which is a hollow body comprising a plurality of perforations, which is arranged in the first transfer tube (5) and the stream of the aqueous base fluid circulates around the distributor, wherein the aqueous polymer concentrate is introduced through the inlet (7) into the distributor and pressed through its perforations.
33. Device according to claims 26 or 27, wherein inlet(s) (7) are arranged at the mixing vessel (3).
34. Device according to claim 33, wherein the mixing vessel (3) comprises a plurality of inlets (7) for the aqueous polymer concentrate.
35. Device according to claim 33, wherein the mixing vessel (3) comprises at least one inlet (7) for the aqueous polymer concentrate, which is connected with at least one distributor (13) which is a hollow body comprising a plurality of perforations.
36. Device according to claim 35, wherein the hollow body is cylindrical.
37. Device according to claim 35, wherein the hollow body is a flat body and the perforations are located at its lower surface.
38. Device according to any of claims 35 to 37, wherein the perforations in the distributor have a diameter from 1 to 10 mm.
39. Device according to any of claims 35 to 38, wherein the number of perforations in the distributor is from 10 to 2000.
40. Device according to any of claims 35 to 39, wherein the distributor (13) is arranged is arranged in the headspace of the mixing vessel (3).
41. Device according to any of claims 35 to 39, wherein the distributor (13) is submerged into the aqueous mixture in the mixing vessel (3).
42. Device according to any of claims 26 to 41, wherein the second dilution device (9) comprises at least one static mixer.
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