Flow control method

Abstract

This flow control method in a flow passage network, which has a first flow passage having a first fluidity with respect to a non-functional fluid and a second flow passage having a second fluidity lower than the first fluidity with respect to the non-functional fluid, comprises: a first fluid introduction step for introducing a functional fluid into the flow passage network; and a second fluid introduction step for introducing the non-functional fluid into the flow passage network after the first fluid introduction step. The fluidity which is higher than the fluidity of the first flow passage is generated in the second flow passage.

Description

Flow Control Method

[0001] The present invention relates to a flow control method.

[0002] Conventionally, a method for recovering resources (e.g., oil, geothermal energy, etc.) contained in a geological formation using a fluid has been known. Specifically, in this method, an injection well for injecting the fluid from above ground and a production well for recovering the fluid containing the resource from underground to above ground are formed in the geological formation.

[0003] A fracture network (flow path network) is formed between the injection well and the production well. This fracture network includes multiple fractures (flow paths) through which fluid can flow. The fluid injected from the injection well reaches the production well via the multiple fractures (flow paths) included in the fracture network. At this time, the fluid flowing through each fracture recovers resources, etc. located around the fracture. Therefore, by recovering the fluid that has reached the production well, the resources, etc. contained in the fluid can also be recovered.

[0004] Japanese Unexamined Patent Publication No. 171501 / 1983

[0005] Among the multiple flow paths contained in a fracture network, there may be a preferred flow path with high fluidity (i.e., fluid flows easily) and a non-preferential flow path with lower fluidity (i.e., fluid flows less easily) compared to the preferred flow path. In this case, the fluid injected from the injection well mainly flows into the preferred flow path. As a result, the flow rate of the fluid flowing through the preferred flow path is larger than the flow rate of the fluid flowing through the non-preferential flow path, making it difficult to recover resources located around the non-preferential flow path.

[0006] As a method for controlling the flow rate of a fluid flowing through each of a plurality of flow paths, for example, a method has been proposed in Patent Document 1. In this method, the flow rate in each flow path is controlled by controlling the opening and closing of a valve provided in each flow path. However, since the above-mentioned fracture network exists deep underground, for example, it is difficult to provide such a valve, and therefore it is difficult to apply this method.

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide a flow control method that can cause a fluid to flow through a flow path with low fluidity in a flow path network having multiple flow paths with different fluidities.

[0008] In order to solve the above problem, a flow control method according to aspect 1 of the present invention is a flow control method in a flow path network having a first flow path having a first fluidity with respect to a non-functional fluid and a second flow path having a second fluidity with respect to the non-functional fluid that is lower than the first fluidity, the method comprising: a first fluid introduction step of introducing a functional fluid into the flow path network; and a second fluid introduction step of introducing the non-functional fluid into the flow path network after the first fluid introduction step, thereby generating a fluidity in the second flow path that is higher than the fluidity possessed by the first flow path.

[0009] A second aspect of the present invention is the flow control method according to the first aspect, wherein the functional fluid is a dilatancy fluid.

[0010] Furthermore, in aspect 3 of the present invention, in the flow control method of aspect 1 or aspect 2, the fluidity is controlled by controlling at least one of the viscosity of the functional fluid, the inflow flow rate of the non-functional fluid into the flow path network, the inflow flow rate of the functional fluid into the flow path network, the temperature of the non-functional fluid, and the temperature of the functional fluid.

[0011] Furthermore, in a fourth aspect of the present invention, in the flow control method according to any one of the first to third aspects, the flow channel network is a fracture network formed between an injection well and a production well.

[0012] According to the above aspect of the present invention, it is possible to provide a flow control method that can cause a fluid to flow through a flow path with low fluidity in a flow path network having a plurality of flow paths with different fluidities.

[0013] 1 is a diagram showing an example of a flow channel network to which a flow control method according to an embodiment of the present invention is applied; FIG. 2 is a flowchart showing a flow control method according to an embodiment of the present invention; FIG. 3 is a diagram showing a model used in a simulation; FIG. 4 is a table showing parameters of the model shown in FIG. 3; FIG. 5 is a graph showing the change in flow velocity over time when water is introduced into a model having a pipe diameter ratio of 1.5; FIG. 6 is a graph showing the change in flow velocity over time when a dilatancy fluid is introduced into a model having a pipe diameter ratio of 1.5; FIG. 7 is a graph showing the change in flow velocity over time when a dilatancy fluid is first introduced and then water is introduced into a model having a pipe diameter ratio of 1.5; FIG. 8 is a graph showing the change in flow velocity over time when a dilatancy fluid is first introduced and then water is introduced into a plurality of models having different pipe diameter ratios; FIG. 9 is a graph plotting the relationship between pipe diameter ratio and flow velocity ratio.

[0014] A flow control method according to an embodiment of the present invention will be described below with reference to the drawings. However, the embodiment described below is merely an example, and is not intended to exclude various modifications and applications of techniques not explicitly stated in the embodiment. In other words, the present embodiment can be implemented with various modifications within the scope of its purpose.

[0015] 1 is a diagram showing an example of a flow channel network 3 to which the flow control method according to the present embodiment is applied. In the example of FIG. 1, the flow channel network 3 is a fracture network formed between an injection well 1 and a production well 2 in a stratum.

[0016] The channel network 3, which is a network of fractures, is located, for example, in the stratum (for example, several thousand meters underground). The injection well 1 and the production well 2 are each a well formed in the stratum, and connect the channel network 3 to the surface.

[0017] The injection well 1 is a well for introducing a fluid (for example, a non-functional fluid and a functional fluid, which will be described later) from the ground to the flow channel network 3. The production well 2 is a well for recovering a fluid (for example, a non-functional fluid and a functional fluid, which will be described later) from the flow channel network to the ground. An introduction means (not shown) for introducing a fluid into the injection well 1, a recovery means (not shown) for recovering a fluid from the production well 2, etc. may be provided on the ground.

[0018] The flow path network 3 includes at least a first flow path 3 a and a second flow path 3 b. Each of the flow paths 3 a and 3 b is configured to allow a fluid (e.g., a non-functional fluid and a functional fluid, etc., described below) to flow through. Each of the flow paths 3 a and 3 b is connected to both the injection well 1 and the production well 2 (details of the second flow path 3 b are omitted from the drawing).

[0019] Fluids (e.g., non-functional fluids and functional fluids, which will be described later) introduced from the ground into the injection well 1 reach the production well 2 via the respective flow paths 3a and 3b included in the flow path network 3, and are recovered to the ground from the production well 2. In the flow path network 3, which is a fracture network, the respective flow paths 3a and 3b are fractures formed in the stratum.

[0020] The fluid injected from the injection well 1 passes through the flow paths 3a and 3b included in the flow path network 3 and reaches the production well 2. At this time, the fluid flowing through each of the flow paths 3a and 3b recovers resources (e.g., oil and geothermal energy) buried in the strata from the areas 4a and 4b located around the flow paths 3a and 3b. Therefore, by recovering the fluid that has reached the production well 2, the resources contained in the fluid can also be recovered.

[0021] Here, the first flow path 3a according to this embodiment has a first fluidity with respect to the non-functional fluid described below. The second flow path 3b has a second fluidity with respect to the non-functional fluid described below that is lower than the first fluidity. That is, the second flow path 3b is a flow path through which the non-functional fluid flows less easily than the first flow path 3a. In other words, the second flow path 3b has a flow resistance (second flow resistance) higher than the flow resistance (first flow resistance) of the first flow path 3a. The first flow path 3a is also referred to as a preferential flow path. The second flow path 3b is also referred to as a non-preferential flow path.

[0022] In this specification, the term "fluidity" is an index indicating the ease with which a fluid flows in a flow path. In other words, high fluidity means that the fluid flows easily, and low fluidity means that the fluid does not flow easily. The fluidity may be, for example, at least one of the permeability, the permeability, the flow velocity of the fluid flowing in the flow path, and the flow rate of the fluid flowing in the flow path. Factors that cause the first fluidity and the second fluidity to differ include, for example, differences in the flow path shape (e.g., flow path diameter) between the flow paths 3a and 3b.

[0023] If a non-functional fluid is simply introduced from a production well 2 into a flow path network 3 having flow paths 3a and 3b with different fluidities, the introduced fluid will mainly flow into the first flow path 3a, as shown in FIG. 1( a). Therefore, the flow rate of the fluid flowing into the first flow path 3a will be greater than the flow rate of the fluid flowing into the second flow path 3b. This creates a problem in that even if resources and the like can be sufficiently recovered from the region 4a around the first flow path 3a, they cannot be sufficiently recovered from the region 4b around the second flow path 3b. In particular, if resources and the like in the stratum are localized in the region 4b around the second flow path 3b, the recovery of resources and the like will not be smooth.

[0024] In view of the above problems, the present inventors have conducted extensive research and found a method for generating a higher fluidity in the second flow path 3b than that in the first flow path 3a, as shown in Fig. 1(b). In other words, the present inventors have found a method for increasing the flow rate of the fluid flowing in the second flow path 3b compared to the flow rate of the fluid flowing in the first flow path 3a. This method makes it possible to recover resources from the region 4b surrounding the second flow path 3b.

[0025] Specifically, as shown in FIG. 2, the flow control method according to this embodiment includes a first fluid introducing step S1 and a second fluid introducing step S2.

[0026] In the first fluid introducing step S1, the functional fluid is introduced into the channel network 3. For example, the above-mentioned introducing means (not shown) may introduce the functional fluid into the channel network 3 through the injection well 1.

[0027] The functional fluid is, for example, a dilatancy fluid (shear thickening fluid). The dilatancy fluid is a thickening agent containing powder particles (e.g., SiO ２ Dilatancy fluids are mixtures of nanoparticles and a solvent (e.g., water), and are a type of non-Newtonian fluid. Dilatancy fluids have a thickening property, where the viscosity increases rapidly when the shear rate exceeds a certain value. Due to this thickening property, dilatancy fluids temporarily behave like solids when an external force is applied. When the external force is removed, the high viscosity achieved by the sudden increase in viscosity is lost, and the viscosity of the fluid returns to normal.

[0028] The powder particles (solute) and solvent that make up the dilatancy fluid can be changed as appropriate.

[0029] For example, the powder particles that make up the dilatancy fluid are SiO ２ The dilatancy fluid is not limited to nanoparticles. For example, a fluid that has a shear thickening effect and is used in a cornstarch solution or the like, in which particles of about 50 nm to 10 μm are dispersed in a solvent, may be used as the dilatancy fluid. The particle size of the powder particles that make up the dilatancy fluid is preferably a particle size at which Brownian motion can be ignored, that is, about 10 μm.

[0030] The solvent constituting the dilatancy fluid is not limited to water, and an organic solvent such as ethylene glycol may be used as the solvent.

[0031] Furthermore, a dilatancy fluid reinforced with a reinforcing material such as nanowires may be employed as the functional fluid.

[0032] In this way, by changing the type of powder particles and solvent that make up the dilatancy fluid, the concentration of powder particles in the solvent, or the content of reinforcing material, the thickening characteristics of the dilatancy fluid can be freely and significantly changed.

[0033] After the first fluid introducing step S1 is performed, a second fluid introducing step S2 is performed. In the second fluid introducing step S2, a non-functional fluid is introduced into the flow channel network 3. For example, the above-mentioned introducing means (not shown) may introduce the non-functional fluid into the flow channel network 3 through the injection well 1.

[0034] The non-functional fluid is, for example, water. However, the non-functional fluid is not limited to water and can be changed as appropriate as long as it does not have the thickening properties of the functional fluid (for example, a Newtonian fluid). For example, the non-functional fluid may be silicone oil or the like.

[0035] The flow control method according to the embodiment will be described below using specific test examples. That is, it will be explained that the flow control method according to the embodiment can generate a higher fluidity in the second flow path 3b than the fluidity of the first flow path 3a. Note that the present invention is not limited to the following test examples.

[0036] A computer simulation was performed based on a model M that simulates the flow path network 3. Figure 3 is a diagram showing the model M used in this simulation. The model M includes a first pipe P1, a second pipe P2, and an injection pipe P0 that communicates with the pipes P1 and P2. The first pipe P1, the second pipe P2, and the injection pipe P0 correspond to the first flow path 3a, the second flow path 3b, and the injection well 1 in the above embodiment, respectively.

[0037] Hereinafter, the pipe diameter (inner diameter) of the first pipe P1 will be denoted as "p1", the pipe diameter (inner diameter) of the second pipe P2 will be denoted as "p2", and the pipe diameter (inner diameter) of the injection pipe P0 will be denoted as "p0". The pipe diameter ratio pr between the first pipe P1 and the second pipe P2 will be defined as pr = p1 / p2. The flow velocity of the fluid flowing through the first pipe P1 will be denoted as "v1", the flow velocity of the fluid flowing through the second pipe P2 will be denoted as "v2", and the flow velocity of the fluid flowing through the injection pipe P0 will be denoted as "v0". The flow velocity ratio vr between the first pipe P1 and the second pipe P2 will be defined as vr = v2 / v1. The flow velocity v0 is also referred to as the introduction flow velocity v0.

[0038] 4 is a table showing parameters of model M. As shown in FIG. 4, in this simulation, multiple models M were prepared, each with different parameters p1, p2, and pipe diameter ratio pr. In each model M, pipe diameter p2 is smaller than pipe diameter p1 (i.e., pipe diameter ratio pr is greater than 1). Therefore, the second pipe P2 has a lower fluidity (second fluidity) for the non-functional fluid than the fluidity (first fluidity) of the first pipe P1.

[0039] (First Simulation) In model M, where the pipe diameter ratio pr is 1.5, water, a non-functional fluid, was introduced from the injection pipe P0 to the pipes P1 and P2. The introduction flow velocity v0 was then varied between 0.05 m / s, 0.10 m / s, and 0.20 m / s, and the flow velocities v1 and v2 in each case were measured. Note that the measured flow velocities v1 and v2 are the average flow velocities in the pipes P1 and P2 (this also applies to subsequent simulations). Note that in this simulation, flow velocity is used as an example of an index of fluidity.

[0040] 5A and 5B are graphs showing the time variations of the flow velocities v1 and v2 measured in the first simulation, where Fig. 5A shows the case where the inlet flow velocity v0 is 0.05 m / s, Fig. 5B shows the case where the inlet flow velocity v0 is 0.10 m / s, and Fig. 5C shows the case where the inlet flow velocity v0 is 0.20 m / s.

[0041] 5(a) to 5(c), at any inlet flow velocity v0, flow velocity v1 is greater than flow velocity v2. In other words, the flow rate of the fluid flowing through the first pipe P1 is greater than the flow rate of the fluid flowing through the second pipe P2. This result indicates that the second pipe P2 has a lower fluidity (second fluidity) for water, a non-functional fluid, than the fluidity (first fluidity) of the first pipe P1.

[0042] (Second Simulation) In a model M with a pipe diameter ratio pr of 1.5, a dilatancy fluid, which is a functional fluid, was introduced into pipes P1 and P2 from an injection pipe P0. The introduction flow velocity v0 was changed to 0.05 m / s, 0.10 m / s, and 0.20 m / s, and the flow velocities v1 and v2 in each case were measured.

[0043] 6A and 6B are graphs showing the time variations of the flow velocities v1 and v2 measured in the second simulation, where Fig. 6A shows the case where the inlet flow velocity v0 is 0.05 m / s, Fig. 6B shows the case where the inlet flow velocity v0 is 0.10 m / s, and Fig. 6C shows the case where the inlet flow velocity v0 is 0.20 m / s.

[0044] As shown in Figures 6(b) and 6(c), when the inlet flow velocity v0 was 0.10 m / s or greater, the flow velocity v1 was greater than the flow velocity v2. On the other hand, as shown in Figure 6(a), when the inlet flow velocity v0 was 0.05 m / s, the difference between the flow velocities v1 and v2 was smaller. In other words, the difference between the flow rate of the fluid flowing through the first pipe P1 and the flow rate of the fluid flowing through the second pipe P2 was smaller.

[0045] (Third Simulation) In a model M having a pipe diameter ratio pr of 1.5, a dilatancy fluid, which is a functional fluid, and water, which is a non-functional fluid, were introduced into pipes P1 and P2 from an injection pipe P0. Specifically, the dilatancy fluid was first introduced into pipes P1 and P2, and then water was introduced into pipes P1 and P2. In other words, this simulation corresponds to the flow control method according to the above embodiment.

[0046] In the third simulation, a dilatancy fluid was placed in pipes P1 and P2 in advance, and water was introduced into the pipes P1 and P2 with the dilatancy fluid placed therein. This was done to facilitate the simulation (to prevent divergence of the calculation results). The inlet flow velocity v0 was also varied between 0.05 m / s, 0.10 m / s, and 0.20 m / s, and the flow velocities v1 and v2 were measured for each case. However, when the inlet flow velocity v0 was 0.20 m / s, the simulation calculations diverged, so this is not shown in the figure.

[0047] 7A and 7B are graphs showing the time variations of the flow velocities v1 and v2 measured in the third simulation, where Fig. 7A shows the case where the introduction flow velocity v0 is 0.05 m / s, and Fig. 7B shows the case where the introduction flow velocity v0 is 0.10 m / s.

[0048] As shown in Figure 7(b), when the introduction flow velocity v0 was 0.10 m / s, the flow velocity v1 was greater than the flow velocity v2. On the other hand, as shown in Figure 7(a), when the introduction flow velocity v0 was 0.05 m / s, the flow velocity v2 was greater than the flow velocity v1. In other words, the flow rate of the fluid flowing through the second pipe P2 was greater than the flow rate of the fluid flowing through the first pipe P1.

[0049] That is, at least under the conditions of the third simulation, it was found that the fluidity of the pipes P1 and P2 (flow paths 3a and 3b) can be reversed by a flow control method in which a dilatancy fluid, which is a functional fluid, is introduced (first fluid introduction step S1) and then water, which is a non-functional fluid, is introduced (second fluid introduction step S2). In other words, it was found that the flow control method according to the above embodiment can make the flow rate of the fluid flowing in the second pipe P2 (second flow path 3b) greater than the flow rate of the fluid flowing in the first pipe P1 (first flow path 3a).

[0050] (Fourth Simulation) In multiple models M (four models shown in FIG. 4 ) with different pipe diameter ratios pr, a dilatancy fluid, which is a functional fluid, and water, which is a non-functional fluid, were introduced from the injection pipe P0 into pipes P1 and P2. Specifically, the dilatancy fluid was first introduced into the pipes P1 and P2, and then water was introduced into the pipes P1 and P2. That is, like the third simulation, this simulation also corresponds to the flow control method according to the above embodiment.

[0051] In the fourth simulation, a dilatancy fluid was placed in the pipes P1 and P2 in advance, and water was introduced into the pipes P1 and P2 with the dilatancy fluid placed in them. The introduction flow velocity v0 was set to 0.05 m / s for all pipe diameter ratios p.

[0052] Figure 8 is a graph showing the time changes in flow velocities v1 and v2 measured in the fourth simulation. Figure 8(a) shows the case where the pipe diameter ratio pr is 1.5, Figure 8(b) shows the case where the pipe diameter ratio pr is 1.75, Figure 8(c) shows the case where the pipe diameter ratio pr is 2.0, and Figure 8(d) shows the case where the pipe diameter ratio pr is 2.25. Figure 9 is a graph plotting the relationship between the pipe diameter ratio pr and the flow velocity ratio vr.

[0053] As shown in Figures 8(c), 8(d), and 9, when the pipe diameter ratio pr was 2.0 or more, the flow velocity v1 was greater than the flow velocity v2, and the flow velocity ratio vr was less than 1. On the other hand, as shown in Figures 8(c), 8(d), and 9, when the pipe diameter ratio pr was 1.75 or less, the flow velocity v2 was greater than the flow velocity v1, and the flow velocity ratio vr exceeded 1. In other words, the flow rate of the fluid flowing through the second pipe P2 was greater than the flow rate of the fluid flowing through the first pipe P1.

[0054] That is, it was found that, at least when the pipe diameter ratio pr is 1.75 or less, by setting the introduction flow velocity v0 to 0.05 m / s, the flow control method in which a dilatancy fluid, which is a functional fluid, is introduced (first fluid introduction step S1) and then water, which is a non-functional fluid, is introduced (second fluid introduction step S2) can reverse the fluidity of the pipes P1 and P2 (flow paths 3a and 3b). In other words, it was found that the flow control method according to the above embodiment can make the flow rate of the fluid flowing in the second pipe P2 (second flow path 3b) greater than the flow rate of the fluid flowing in the first pipe P1 (first flow path 3a).

[0055] In the third and fourth simulations, the pipe diameter ratio pr and the introduction flow velocity v0 (i.e., the inflow flow rate of the non-functional fluid into the flow path network 3) were considered as parameters that can vary the fluidity occurring in the pipes P1 and P2 (flow paths 3a and 3b). However, the parameters that can vary the fluidity occurring in the pipes P1 and P2 (flow paths 3a and 3b) are not limited to these.

[0056] For example, parameters such as the viscosity (thickening characteristics) of the functional fluid, the inflow rate (inflow flow velocity) of the functional fluid into the flow path network 3, the temperature of the non-functional fluid, and the temperature of the functional fluid may also affect the fluidity occurring in the pipes P1 and P2 (flow paths 3a and 3b). Therefore, in the flow control method according to the above embodiment, the fluidity occurring in the flow paths 3a and 3b may be controlled by controlling at least one of these parameters (the viscosity of the functional fluid, the inflow rate of the non-functional fluid into the flow path network 3, the inflow rate of the functional fluid into the flow path network 3, the temperature of the non-functional fluid, and the temperature of the functional fluid). By appropriately controlling these parameters, it is expected that the fluidity in the pipes P1 and P2 (flow paths 3a and 3b) can be reversed, for example, even when the pipe diameter ratio pr is 2.0 or greater.

[0057] In the above explanation, the flow path network 3 is described as a fracture network formed between the injection well 1 and the production well 2, but the flow path network 3 to which the flow control method according to the above embodiment is applied is not limited to this. If the flow path network 3 includes flow paths 3a, 3b having different fluidities with respect to the non-functional fluid, it is expected that the same effects as those of the above-mentioned actual form can be obtained even if the flow path network 3 is not a fracture network.

[0058] As described above, the flow control method according to this embodiment is a flow control method in a flow path network 3 having a first flow path 3a having a first fluidity with respect to a non-functional fluid and a second flow path 3b having a second fluidity with respect to the non-functional fluid that is lower than the first fluidity, and includes a first fluid introduction step S1 of introducing the functional fluid into the flow path network 3, and a second fluid introduction step S2 of introducing the non-functional fluid into the flow path network 3 after the first fluid introduction step S1, thereby generating a fluidity in the second flow path 3b that is higher than the fluidity possessed by the first flow path 3a.

[0059] With this configuration, in the channel network 3 having a plurality of channels 3a, 3b with different fluidities, it is possible to make the fluid flow through the channel with lower fluidity (second channel 3b).

[0060] In addition, the fluidity occurring in the flow paths 3a and 3b may be controlled by controlling at least one of the viscosity of the functional fluid, the inflow flow rate of the non-functional fluid into the flow path network 3, the inflow flow rate of the functional fluid into the flow path network, the temperature of the non-functional fluid, and the temperature of the functional fluid.

[0061] According to this configuration, it becomes easier to realize the reversal of the fluidity occurring in the flow paths 3a, 3b for various flow paths 3a, 3b having different conditions such as shapes (for example, pipe diameter ratio pr).

[0062] The flow path network 3 may also be a fracture network formed between the injection well 1 and the production well 2. The flow control method according to this embodiment does not require valves or the like to be installed in the flow paths 3a and 3b, and therefore can be suitably applied to fracture networks located deep underground. By increasing the fluidity of the second flow path 3b (increasing the flow rate of the fluid flowing into the second flow path 3b), resources and the like can be efficiently recovered from the region 4b surrounding the second flow path 3b.

[0063] The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0064] For example, the flow channel network 3 may include three or more flow channels. That is, the flow channel network 3 may include a plurality of flow channels having a fluidity with respect to the non-functional fluid that is lower than the first fluidity.

[0065] Furthermore, although the flow path network 3 in the above embodiment is a flow path network used for extracting resources buried in a geological layer, the flow path network 3 to which the present invention can be applied is not limited to this. The present invention is applicable to any flow path network 3 having flow paths with a fluidity lower than the first fluidity for a non-functional fluid. For example, the present invention is also applicable to flow paths located in shallow ground through which groundwater or the like flows, or to flow path networks 3 having microfluidics or the like, which are minute flow paths. By using the present invention, the flow rate of a fluid can be controlled for each flow path without providing a valve or the like.

[0066] 2, the first fluid introduction step S1 and the second fluid introduction step S2 are each performed once, but the number of times steps S1 and S2 are performed can be changed as appropriate. For example, one cycle including the first fluid introduction step S1 and the second fluid introduction step S2 may be repeated multiple times. It is believed that if the above-described reversal of the fluidity in the flow paths 3a and 3b occurs once by performing this cycle once, the reversed state of the fluidity will be maintained to some extent due to the inertia of the fluid. However, it is expected that performing this cycle multiple times will make it even easier to maintain the reversed state of the fluidity.

[0067] In addition, although a dilatancy fluid is used as the functional fluid in the above embodiment, the functional fluid can be changed as appropriate as long as the same effects as those in the above embodiment can be obtained. Similarly, the non-functional fluid is not limited to water and can be changed as appropriate as long as the same effects as those in the above embodiment can be obtained.

[0068] In addition, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, and the above-described embodiments and variations may be combined as appropriate, without departing from the spirit of the present invention.

[0069] 1... injection well 2... production well 3... flow path network 3a... first flow path 3b... second flow path S1... first fluid introduction step S2... second fluid introduction step

Claims

1. A method for controlling flow in a flow path network having a first flow path having a first fluidity with respect to a non-functional fluid, and a second flow path having a second fluidity with respect to the non-functional fluid that is lower than the first fluidity, the method comprising: a first fluid introduction step of introducing a functional fluid into the flow path network; and a second fluid introduction step of introducing the non-functional fluid into the flow path network after the first fluid introduction step, wherein the second flow path is caused to have a fluidity higher than the fluidity possessed by the first flow path.

2. The flow control method according to claim 1, wherein the functional fluid is a dilatancy fluid.

3. The flow control method according to claim 1 or 2, wherein the fluidity is controlled by controlling at least one of the viscosity of the functional fluid, the inflow flow rate of the non-functional fluid to the flow path network, the inflow flow rate of the functional fluid to the flow path network, the temperature of the non-functional fluid, and the temperature of the functional fluid.

4. The flow control method according to claim 1 or 2, wherein the flow path network is a fracture network formed between an injection well and a production well.

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