IN-LINE MIXING MODULE FOR HIGH VISCOSITY WATER-SOLUBLE POLYMER SOLUTIONS

Abstract

Mixing module comprising - at least one pipeline including a static mixer (2), - at least one connected to the pipeline by means of at least one injection rod (4) penetrating laterally into the pipeline and extending transversely into the body thereof, the injection rod being closed at its free end and having a wall provided, in its part inserted into the body of the pipeline, with at least one orifice.

Description

Title of the invention: IN-LINE MIXING MODULE FOR HIGH VISCOSITY WATER-SOLUBLE POLYMER SOLUTIONS technical field

[0001] . The present invention relates to an inline solution mixing module of high viscosity water-soluble polymers to obtain a homogeneous aqueous solution ready to be injected into an underground formation.

[0002] It also relates to an installation implementing the mixing module as well as to enhanced oil and / or gas recovery or hydraulic fracturing processes implementing said installation. Previous art

[0003] Water-soluble polymers, and in particular polyacrylamides, are commonly used in large quantities in enhanced oil recovery (EOR) or for hydraulic fracturing operations.

[0004] Technical solutions have been developed for preparing stock solutions of water-soluble polymers with high viscosities (greater than 500 centipoise). For example, documents WO 2011 / 107683 and WO2016 / 156320 describe equipment (PSU for Polymer Slicing Unit) that both grinds and disperses the polymer in powder form in the dissolution water. This type of equipment makes it possible to limit the dissolution time to 30 minutes and to obtain very high polymer concentrations, on the order of 20 g / liter. These high concentrations allow for a significant reduction in the size of the dissolution tanks located downstream of the PSU (also called maturation tanks) and the dosing pumps, with the added advantage of a substantial reduction in the corresponding investments.Indeed, to save space and reduce costs, not only in onshore applications but also and especially in offshore applications, it is necessary to minimize the use of dissolution tanks. However, the dissolution of the powders must be as complete as possible to avoid injectivity problems in the wells.

[0005] Upstream of these systems for dissolving water-soluble polymer powders, the resulting water-soluble polymer solutions exhibit high viscosities (above 500 centipoise). To avoid preparing polymer injection solutions for storage in tanks (dilution of stock solutions), it is known to inject the stock solution inline (into the piping) into a flow of injection water. The injection water piping may include a static mixer upstream of the Injection lance. However, the water-soluble polymer solution obtained upstream of the static mixer presents homogeneity problems, particularly at low injection flow rates or with highly viscous solutions. This leads to incorrect viscosity measurements upstream and also the risk of injecting different solutions into the underground formation if the outlet line splits into multiple injection points, resulting in a loss of performance in EOR or hydraulic fracturing processes since the target viscosity will not be achieved.

[0006] Therefore, the problem that the invention proposes to solve is that of developing a device which allows the injection into an underground formation of a water-soluble polymer solution S whose viscosity is greater than 500 centipoise in a flow of injection water I, which is homogeneous.

[0007] The problem of the device's size is all the more important as the installation (PSU + maturation tanks + injection device) is intended in particular to be used for enhanced oil and / or gas recovery operations or for offshore hydraulic fracturing operations. Description of the invention

[0008] Thus, in order to guarantee homogeneity of injection solutions containing water-soluble polymer in underground formations, the Applicant has developed a mixing module of a water-soluble polymer solution with a viscosity greater than 500 centipoise, in an injection water flow circulating within a pipeline, by means of one or more polymer solution lines equipped with specific injection lances within the pipeline, the concentrated polymer stock solution lines being positioned upstream of a static mixer in the direction of the injection water flow.

[0009] More specifically, the invention relates to a mixing module comprising: - at least one pipe intended to be supplied by an aqueous injection solution I, and comprising a static mixer, - at least one line intended to be supplied with an aqueous solution S comprising at least one water-soluble polymer with a Brookfield viscosity greater than 500 centipoise (rotation speed: 60 rpm, 25°C), the line being connected to the pipeline by means of at least one injection rod penetrating laterally into the pipeline and extending transversely into the body thereof, the injection rod being closed at its free end and having a wall provided, in its part inserted into the body of the pipeline, with at least one orifice suitable for diffusing the aqueous solution S.

[0010] In practice, the viscous polymer solution S is distributed in a pipeline in the direction of the flow of injection solution I by means of at least 1 line equipped with at least one injection rod whose cylindrical part immersed in the flow of injection solution I diffuses the polymer through at least 1, advantageously 2 transverse orifices, the injection rod(s) being located upstream of a static agitator through which the flow of the resulting solution (S+I) passes.

[0011] Advantageously, the orifice(s) through which the polymer solution flows are positioned at least partially opposite the mixer. In other words, the orifices are distributed along the wall of the injection tube so as to deliver the polymer solution in the direction of the injection water flow. That is to say, the injection tube has no orifice positioned opposite the static mixer. No turbulence is thus generated.

[0012] The mixing module according to the invention further advantageously has at least one of the following characteristics: - the injection lance is cylindrical in shape and has an internal diameter between 15 and 200 millimeters, preferably between 15 and 50 millimeters. - the part of the rod inserted into the pipe has between 1 and 10, advantageously between 3 and 6 circular orifices, - The circular orifices have an identical internal diameter between 1 and 50 millimeters, preferably between 4 and 15 millimeters, - the orifices are vertically aligned, - the walls of the injection tube(s) have a thickness of between 1 and 10 millimeters, preferably between 2 and 5 millimeters.

[0013] In a preferred embodiment, the mixing module line of the invention comprises at least 2 injection rods.

[0014] The Applicant noted that the homogeneity of the mixture was improved when the distance between the axes of at least two injection rods was between 1 and 10 times the outside diameter of these rods, advantageously between 1 and 3 times the outside diameter of these rods.

[0015] Similarly and still according to the invention, the distance between the injection lance closest to the static mixer and said static mixer is equal to 0.5 to 5 times the diameter of the lance, preferably equal to 0.5 to 2 times the diameter of the lance.

[0016] In practice, the axis of at least one injection rod is positioned perpendicular to the wall of the pipeline.

[0017] In a first embodiment, the at least 2 injection rods are aligned along the pipeline.

[0018] In a second embodiment, the at least 2 injection rods are offset along the pipeline and are inclined relative to each other.

[0019] In a third embodiment, the line comprises at least 2 first injection rods aligned along the pipeline and at least 2 second injection rods aligned, offset and inclined along the pipeline relative to the first injection rods.

[0020] The injection lances are in practice connected to the line directly or via an intermediate component in the form of a flexible or rigid tube. To allow adjustment of the flow rate of the aqueous polymer solution S, at least one injection lance is equipped with a valve capable of shutting it off.

[0021] Polymer solutions prepared using the device of the invention can be directly injected into an underground formation for enhanced oil recovery or hydraulic fracturing operations, thus eliminating the need for storage tanks for said solutions. The footprint of the installation for preparing injection solutions from powdered polymers (PSU + maturation tanks + device of the invention) is therefore reduced.

[0022] The invention also relates to an installation implementing the mixing module described above.

[0023] More specifically, the installation includes a so-called "main" pipeline intended to be supplied with an aqueous injection solution I, and in which the mixing module according to the invention is inserted so that at least one injection lance is positioned upstream of the static mixer in the direction of flow of the aqueous injection solution I.

[0024] In addition, the main pipeline and the mixer pipeline preferably have identical internal and external diameters, at least at the point where the mixer pipeline is inserted into the main pipeline.

[0025] In a particular embodiment, the installation further includes a silo containing a propping agent, the silo being positioned downstream of the mixer in the direction of flow of the aqueous injection solution I.

[0026] Finally, two other aspects of the invention relate to a process for enhanced oil and / or gas recovery and a process for hydraulic fracturing of an oil or gas reservoir, implementing the installation described above, these two processes including a step of preparing a water-soluble polymer injection solution with the mixing module of the invention.

[0027] More specifically, the invention relates to a mixing module for mixing an aqueous solution S comprising at least one water-soluble polymer with a Brookfield viscosity greater than 500 centipoise (rotation speed: 60 rpm, 25°C) in a pipe through which a flow of an aqueous injection solution I passes, in particular for enhanced oil and / or gas recovery operations or for hydraulic fracturing operations, said device comprising:

[0028] - a pipeline through which a flow of solution I passes, said pipeline comprising a static mixer;

[0029] - at least one line through which a flow of solution S flows, connected to the pipeline transversely by means of a cylindrical injection rod perforated transversely, in its part immersed in the fluid I, by at least 1 circular orifice to diffuse the solution S in the direction of the flow of solution I, the injection rod being located upstream of the static mixer.

[0030] Preferably, solution S has a Brookfield viscosity between 500 and 10,000 centipoise (rotation speed: 60 rpm*, 25°C), more preferably between 1,000 and 3,000 centipoise. The viscosity of solution S is determined using a Brookfield viscometer. Those skilled in the art know how to select the viscometer module to measure the target viscosity range (advantageously modules LV1 or LV2).

[0031] Solution S is an aqueous solution; advantageously, solution S comprises at least one water-soluble polymer dissolved in water or dissolved in a brine containing alkali and / or alkaline earth salts. The alkali salts are preferably monovalent and / or divalent.

[0032] The water-soluble polymer has a molecular weight greater than or equal to 1 million daltons, preferably between 1 and 40 million daltons, more preferably between 3 and 30 million daltons. Molecular weight is understood to be the average molecular weight by weight.

[0033] The molecular weight is determined by the intrinsic viscosity of the polymer. The intrinsic viscosity can be measured by methods known to those skilled in the art and can be calculated from the reduced viscosity values ​​for different polymer concentrations by a graphical method consisting of plotting the reduced viscosity values ​​(ordinate axis) against the concentration (abscissa axis) and extrapolating the curve down to zero concentration. The intrinsic viscosity value is plotted on the ordinate axis or using the least squares method. The molecular weight can then be determined by the Mark-Houwink equation: [q] = KM [q] represents the intrinsic viscosity of the polymer determined by the solution viscosity measurement method. K represents an empirical constant. M represents the molecular weight of the polymer, a represents the Mark-Houwink coefficient. K and a depend on the particular polymer-solvent system.

[0034] By "water-soluble polymer" is meant a polymer which gives an aqueous solution without insoluble particles when dissolved under stirring at 25°C and with a concentration of 10 gL 1 in deionized water.

[0035] Advantageously, solution S is prepared from at least one water-soluble polymer in powder form using a device such as the PSU (Polymer Slicing Unit) described in documents WO 2011 / 107683 and WO2016 / 156320. This device both grinds and disperses the polymer in powder form in the aqueous dissolution solution. The resulting solution S is then successively transferred from this device to one or more maturation tanks (tanks equipped with stirring paddles to ensure complete dissolution of the polymer).

[0036] The injection fluid I circulating in the pipeline is an aqueous solution such as water or brine containing alkali and / or alkaline earth metal salts. This aqueous solution may be seawater drawn directly from the underground formation's production field, particularly when the field is an offshore field.

[0037] A person skilled in the art knows how to adapt the materials constituting the mixing module's piping according to the injection fluid I. For example, the material may be chosen to prevent corrosion. The mixing module's piping is preferably cylindrical and rigid.

[0038] The invention also relates to a method for enhanced oil and / or gas recovery and a method for hydraulic fracturing of an oil or gas reservoir, implementing the installation described above.

[0039] These processes have the following steps in common: - preparation of a polymer solution S comprising at least one water-soluble polymer, solution S having a Brookfield viscosity greater than 500 centipoise, - feeding the line with polymer solution S, - supplying the main pipeline with solution I composed of water or brine, - adjustment of the flow rate of polymer solution S with the flow rate of solution I circulating in the mixer pipe, the solution thus obtained constituting an injection fluid.

[0040] In the case of the enhanced oil and / or gas recovery process, said process further comprises the following steps: - injection of the injection fluid into an underground formation, - scanning of the underground formation using the injected fluid, - recovery of the aqueous and hydrocarbon mixture.

[0041] In the case of the hydraulic fracturing process, said process further comprises the following steps: - Injection of the injection fluid into a silo containing a propping agent to obtain a fracturing fluid, - Injection of fracturing fluid under pressure to create fractures distributed perpendicularly to the production well, - recovery of an aqueous and hydrocarbon mixture.

[0042] As is known, the proppant is preferably sand. The fracturing fluid is an aqueous suspension containing at least the proppant and the polymer.

[0043] In particular embodiments, the 2 processes also have at least one of the following characteristics: - the cumulative flow rate of solution S within the injection tubes is between 0.5 and 2.5 ms-1, - the flow rate of solution I in the mixing module pipeline is between 5 and 10 times higher than the cumulative flow rate of solution S in the injection lances.

[0044] Example of implementation

[0045] The invention and the advantages arising therefrom are clearly shown in the following description with support of the attached figures.

[0046] Fig. 1 is a schematic representation of the mixing module according to a first embodiment of the invention.

[0047] Fig. 2 is a schematic representation of the installation according to the invention incorporating a mixing module according to a second embodiment.

[0048] As shown in [Fig. 1], the mixing module according to the invention comprises a pipe (1) itself comprising a static mixer (2). Those skilled in the art know how to choose the geometry of the elements of the static mixer. This static mixer is advantageously composed of intersecting spacers (Sulzer SMX type). Depending on the embodiment, either the elements of the static mixer are integrated directly into the pipe (1) as shown in [Fig. 1], or the static mixer incorporating the elements is attached directly to the end of the pipe (1) as shown in [Fig. 2].

[0049] The module further comprises a line (3) intended to carry a polymeric solution S, the line being made of materials that those skilled in the art can select according to, in particular, the nature of the solution S. This line is advantageously a cylindrical pipe. In practice, the line 3 is intended to be connected to a reservoir of solution S, not shown in the figures, located upstream of said line. By way of example, this reservoir could be a maturation tank.

[0050] According to [Fig. 1], the line (3) is connected to the pipeline (1) through which the injection solution I flows by means of 3 injection lances (4) aligned longitudinally with respect to the axis of the pipeline (1). Those skilled in the art know Select the material for the injection lances (4). In practice, the injection lances (4) are connected to the line (3) either permanently (e.g., crimped, welded) or temporarily (screw / threaded). The connection can be made directly to the line (3) as shown in [Fig. 1] or via an intermediate pipe (8) as shown in [Fig. 2].

[0051] The injection lances (4) are connected to the pipeline (1) transversely, that is to say, they are positioned perpendicular to the wall of the pipeline (1). The lances are fixed to the pipeline (1) permanently (example: crimping, welding) or temporarily (example: screw / thread).

[0052] The injection rods (4) penetrate the pipe (1) to within close proximity of its opposite wall. In practice, the injection rods penetrate the pipe (1) perpendicularly to its wall and penetrate the pipe body to a distance equivalent to 50 to 90% of its diameter.

[0053] As shown in [Fig.1], the injection rods (4), in this specific embodiment, penetrate the pipeline (1) to a distance equivalent to 60% of its diameter.

[0054] According to the embodiment of [Fig. 1], the injection lances (4) are cylindrical and perforated, in their portion immersed in fluid I, by three circular orifices (5) distributed along a vertical axis. The orifices thus diffuse the solution S in the direction of the flow of solution I. The injection lances are positioned longitudinally, upstream of the static mixer (2). In an embodiment not shown, the lances may comprise several series of orifices distributed along a vertical axis, each series being distributed over half the circumference of the injection lance opposite the static mixer.

[0055] As represented, the injection rods (4) have an internal diameter between 15 and 200 millimeters.

[0056] The circular orifices (5) of the same injection lance (4) have an identical internal diameter and are between 1 and 50 millimeters.

[0057] The walls of the injection lance(s) have a thickness of between 1 and 10 millimeters.

[0058] According to this embodiment, the injection rods (4) are identical.

[0059] Advantageously, the distance between the axes of the three injection rods (4) is between 1 and 10 times the outside diameter of these rods.

[0060] Still in this embodiment, the distance between the rod (4) closest to the static mixer and the static mixer (2) is equal to 0.5 to 5 times the diameter of the rod (4).

[0061] The flow rate of polymer solution P in each injection lance is controlled by means of a valve (9).

[0062] Fig. 2 is a representation of an installation according to the invention incorporating a mixing module according to a second embodiment.

[0063] The installation thus comprises a main pipeline (6) intended to be supplied with aqueous injection solution I in the direction of arrow (7). The mixing module according to the invention is inserted into the main pipeline (6) via pipeline (1). The diameter of pipeline (1) is identical to that of the main pipeline. Pipe (1) further comprises a static mixer (2) positioned downstream of pipeline (1) in the direction of the injection solution flow represented by arrow (7). As shown in [Fig. 2], the static mixer (2) is attached to pipeline (1). The elements of the static mixer are not visible in [Fig. 2] but correspond to those shown in [Fig. 1].

[0064] In this embodiment, the module has two sets of two injection rods: a first set of aligned injection rods (4.1, 4.2) and a second set of injection rods (4.3, 4.4) offset longitudinally and transversely with respect to the first set. The distance between the axes of the four injection rods (4) is identical, practically equal to twice the outside diameter of these rods.

[0065] The 4 injection rods are connected to a single line (3) which is supplied with polymer solution S.

[0066] The invention also relates to a method for enhanced oil and / or gas recovery and a method for hydraulic fracturing of an oil or gas reservoir, implementing the installation described above.

[0067] The installation as shown in [Fig.2] can be used in both types of process and implements the following common steps for preparing the injection fluid: - preparation of a polymer solution S comprising at least one water-soluble polymer, solution S having a Brookfield viscosity greater than 500 centipoise, - feeding the line with polymer solution S, - supplying the main pipeline with solution I composed of water or brine, - adjustment of the flow rate of polymer solution S with the flow rate of solution I circulating in the mixer pipe, the solution thus obtained constituting an injection fluid.

[0068] In the case of the enhanced oil and / or gas recovery process, said process further comprises the following steps: - injection of the injection fluid into an underground formation, - scanning of the underground formation using the injected fluid, - recovery of the aqueous and hydrocarbon mixture.

[0069] In the case of the hydraulic fracturing process, said process further comprises the following steps: - Injection of the injection fluid into a silo not shown in [Fig.2], containing a propping agent to obtain a fracturing fluid, - Injection of fracturing fluid under pressure to create fractures distributed perpendicularly to the production well, - recovery of an aqueous and hydrocarbon mixture.

[0070] In both cases, the cumulative flow rate of solution S within the injection tubes (4) is preferably between 0.5 and 2.5 ms', even more preferably between 1.5 and 2 ms'. This flow rate is controlled by means of the valves (9).

[0071] The flow rate of solution I in the pipeline (1) is between 2 and 20 times higher than the cumulative flow rate of solution S in the injection lances (4), more advantageously between 5 and 10 times higher.

[0072] The invention and its advantages are clearly apparent from the preceding description. In particular, the mixing module's ability to produce a homogeneous injection fluid that can be used directly and in-line in an enhanced oil / gas recovery or hydraulic fracturing process with limited ground impact is noteworthy.

Claims

Demands

1. Mixing module comprising - at least one pipeline intended to be supplied with an aqueous injection solution I, and comprising a static mixer (2), - at least one line intended to be supplied with an aqueous solution S comprising at least one water-soluble polymer of Brookfield viscosity greater than 500 centipoise (rotational speed: 60 rpm, 25°C), the line being connected to the pipeline by means of at least one injection lance (4) penetrating laterally into the pipeline and extending transversely into the body thereof, the injection lance being closed at its free end and having a wall provided, in its part inserted into the body of the pipeline, with at least one orifice suitable for diffusing the aqueous solution S.

2. Mixing module according to claim 1, characterized in that the injection wand is cylindrical in shape and has an internal diameter between 15 and 200 millimeters.

3. Mixing module according to any one of claims 1 or 2, characterized in that the part of the rod inserted in the pipeline has 3 to 6 circular orifices (5).

4. Mixing module according to claim 3, characterized in that the circular orifices (5) have an identical internal diameter and are between 1 and 50 millimeters.

5. Mixing module according to any one of the preceding claims, characterized in that the orifices are vertically aligned.

6. Mixing module according to any one of the preceding claims, characterized in that at least one orifice is positioned at least partially facing the static mixer.

7. Mixing module according to any one of the preceding claims, characterized in that the line comprises at least 2 rods.

8. Mixing module according to claim 7, characterized in that the distance between the axes of at least two injection rods (4) is between 1 and 10 times the outside diameter of these rods.

9. Mixing module according to any one of claims 7 or 8, characterized in that at least 2 injection rods are aligned along the pipeline.

10. Mixing module according to any one of claims 7 or 8 characterized in that at least 2 injection rods are offset along the pipeline and are inclined relative to each other.

11. Mixing module according to any one of the preceding claims characterized in that at least one injection lance (4) is provided with a valve.

12. Installation comprising a so-called "main" pipeline intended to be supplied with an aqueous injection solution I, characterized in that it further comprises a mixing module according to any one of claims 1 to 11, inserted into the main pipeline so that at least one injection lance is positioned upstream of the static mixer in the direction of flow of the aqueous injection solution I.

13. Installation according to claim 12, characterized in that it further comprises a silo containing a propping agent, the silo being positioned downstream of the mixing module in the direction of flow of the aqueous injection solution I.

14. An enhanced oil and / or gas recovery process employing the installation of claim 12, comprising the following steps: - preparation of a polymer solution S comprising at least one water-soluble polymer, the solution S having a Brookfield viscosity greater than 500 centipoise, - supplying the line (3) with polymer solution S, - supplying the main pipeline with solution I composed of water or brine, - adjusting the flow rate of polymer solution S with the flow of solution I circulating in the mixer pipeline, the solution thus obtained constituting an injection fluid, - injection of the injection fluid into an underground formation, - sweeping of the underground formation with the injected fluid, - recovery of the aqueous and hydrocarbon mixture.

15. A method for hydraulically fracturing an oil or gas production well employing the installation of claim 13, comprising the following steps: - preparation of a polymer solution S comprising at least one water-soluble polymer, solution S having a Brookfield viscosity greater than 500 centipoise, - supplying line (3) with polymer solution S, - supplying the main pipeline with solution I composed of water or brine, - adjusting the flow rate of polymer solution S with the flow of solution I circulating in the mixer pipeline, the resulting solution constituting an injection fluid, - injecting the injection fluid into a silo containing a proppant to obtain a fracturing fluid, - injecting the fracturing fluid under pressure to create fractures distributed perpendicular to the production well, - recovering an aqueous and hydrocarbon mixture.

16. A method for enhanced oil and / or gas recovery or hydraulic fracturing according to claim 14 or 15, characterized in that the cumulative flow rate of solution S within the injection pipes (4) is between 0.5 and 2.5 ms

17. Enhanced oil and / or gas recovery or hydraulic fracturing method according to any one of claims 14 to 16, characterized in that the flow rate of solution I in the pipeline (1) is between 5 and 10 times higher than the cumulative flow rate of solution S in the injection pipes (4).

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