An in-situ underground curing foam flow control system and its preparation method and application

Abstract

The present invention relates to the technical field of oil and gas field development, and specifically to an in-situ solidified foam flow regulating system, its preparation method and application. The foam flow regulating system forms a foam system solution composed of a foaming agent, a foam stabilizer, a solidifying material and formation water. Among them, the solidifying material is composed of a solidifying main agent and a solidifying auxiliary agent. In the foam system solution, the mass fraction of the foaming agent is 0.1wt% - 1.2wt%, the mass fraction of the foam stabilizer is 5wt% - 20wt%, the mass fraction of the solidifying main agent is 10wt% - 40wt%, the mass fraction of the solidifying auxiliary agent is 5wt% - 20wt%, and the balance is formation water. The foam flow regulating system provided by the present invention forms a high-strength porous plugging material after being injected into the formation by adding a solidifying material to the foam system, which not only realizes the plugging of fractures and pores, but also provides shear regeneration conditions for the subsequent migration process of the foam by using the porous structure.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field development, and specifically to an in-situ solidified foam flow control system underground, a preparation method thereof, and an application thereof. Background Art

[0002] At present, foam technology can effectively solve the channeling problem in water injection and gas injection development by reducing gas-phase permeability, regulating fluidity, and cleaning action, thereby achieving the effect of improving oil recovery. However, due to the complex and harsh conditions such as the interlaced development of large-scale fractures and pores in some formations, the environment required for foam generation and migration is lacking. After the foam breaks, it is not easy to regenerate, and gas-liquid separation is extremely easy during long-distance migration, resulting in poor application effects of foam in this type of formation and limiting the effect of foam mobility control. In order to improve the effect of foam in formations with large-scale fractures or interlaced development of pores and fractures, it is urgent to realize the re-transformation of the reservoir space.

[0003] The treatment methods in the prior art include the following two:

[0004] One is to selectively solidify and block large-scale fractures and pores by injecting plugging agents to reduce the negative impact on foam migration. For example, Chinese patent document CN 112358859 A (application number 202011245320.5) discloses a gel foam type plugging agent. The gel system includes sodium alginate, tetradecyl hydroxysulfobetaine foaming agent, acrylamide monomer, N-N methylene bisacrylamide crosslinking agent, tert-butyl hydroperoxide initiator, and brine. When applied, it gels after being injected into the formation to achieve the function of temperature-resistant water plugging. Another example is that Chinese patent document CN 112358860 A (application number 202011285694.X) discloses a resin foam type channel plugging and flow control agent, which also forms resin foam after being injected into the formation to achieve the plugging effect. However, foam type plugging agents mainly focus on high temperature resistance and foam stability problems, and the main effect achieved in fracture-vug formations is to block the gas channeling channel. The foam directly blocks the fractures or pores completely, and does not consider how to solve the connectivity problem between the subsequent displacement fluid in the displacement channel - fractures and pores, resulting in a large waste of underground space.

[0005] The second is to provide strong shear conditions to create a suitable regeneration and migration environment for the foam and achieve effective action on this type of formation. For example, Chinese patent document CN 109439300 A (application number 201811223599.X) discloses a flow control agent particle, which fills the fractures and pores after being injected into the formation to form a porous medium, thereby increasing the shear effect on the foam, promoting foam regeneration, and realizing the distribution position of the particles in the fracture-vug formation by adjusting different densities. However, the sedimentation problem of the flow control agent particles during migration cannot be effectively solved, and at the same time, this type of method also has the problem of too high pressure required for particle injection.

[0006] It can be seen that the existing flow regulation methods have different problems respectively. How to take into account the advantages of the two flow regulation methods, that is, to achieve plugging without "deadlock" and provide sufficient shear force for the subsequent injected foam liquid, is the key to improving the effect of foam fluid. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above-mentioned deficiencies of the existing technology, and provide an in-situ solidified foam flow regulation system for underground, its preparation method and application. By adding a solidifying material to the foam system, a high-strength porous plugging material is formed after injection into the formation, which not only realizes the plugging of cracks and holes, but also provides shear regeneration conditions for the subsequent migration of foam by using the porous structure.

[0008] To achieve the above technical effects, the present invention adopts the following technical solutions:

[0009] An in-situ solidified foam flow regulation system for underground is composed of a foaming agent, a foam stabilizer, a solidifying material and formation water to form a foam system solution. Among them, the solidifying material is composed of a solidifying main agent and a solidifying auxiliary agent;

[0010] In the foam system solution, the mass fraction of the foaming agent is 0.1wt%-1.2wt%, the mass fraction of the foam stabilizer is 5wt%-20wt%, the mass fraction of the solidifying main agent is 10wt%-40wt%, the mass fraction of the solidifying auxiliary agent is 5wt%-20wt%, and the balance is formation water;

[0011] The foam stabilizer is selected as particles with a particle size less than 200 mesh;

[0012] The solidifying main agent is industrial slag or modified clay, and the solidifying auxiliary agent is inorganic sodium salt,

[0013] In the components of the solidifying main agent, the proportion of SiO 2 is 19.26wt%-53.12wt%, the proportion of Al 2 O 3 is 6.23wt%-15.15wt%, the proportion of Fe 2 O 3 is 0.5wt%-1.63wt%, the proportion of CaO is 35.65wt%-60.12wt%, and the proportion of MgO is 8.85wt%-9.12wt%;

[0014] The salinity of the formation water is 15×10 4 mg / L - 25×10 4 mg / L.

[0015] The foam flow control system provided by the present invention can solidify into an inorganic hydrated gel material with a porous structure under high-temperature and high-mineral conditions after being injected into the formation by adding a solidifying material composed of a solidifying main agent and a solidifying assistant to the foam system. While realizing the in-situ solidification and plugging of underground fractures and cavities, the porous structure also provides shear regeneration conditions for the subsequent injection of foam to migrate in the fractures and cavities, ensuring the effect of the foam.

[0016] Preferably, the foaming agent is selected from at least one of high-carbon fatty alcohol polyoxyethylene ether, dodecylphenol polyoxyethylene ether, sodium bis(2-ethylhexyl) sulfosuccinate, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzenesulfonate, α-olefin sulfonate, hydroxysulfobetaine, lauric acid diethanolamide, fatty alcohol polyoxyethylene ether sulfate, or sodium carboxymethyl cellulose.

[0017] Preferably, the foam stabilizer is selected from at least one of fly ash particles, silica particles, montmorillonite, kaolin, montmorillonite, illite, attapulgite, kaolinite, sepiolite, or chlorite.

[0018] Preferably, the solidifying assistant is selected from at least one of sodium silicate, sodium aluminate, or sodium phosphate.

[0019] Preferably, the liquid separation half-life of the foam flow control system for in-situ underground solidification is 6h - 24h.

[0020] The present invention also provides a preparation method of the above-mentioned foam flow control system for in-situ underground solidification, which includes the following steps:

[0021] S1. Add a foaming agent and a foam stabilizer to formation water, and stir and mix evenly to obtain a mixed solution;

[0022] S2. Add the solidifying main agent to the mixed solution under stirring to obtain an intermediate solution;

[0023] S3. Add the solidifying assistant to the intermediate solution and stir, then use the Waring Blender method to stir and foam at high speed to obtain the foam flow control system.

[0024] The foam flow control system provided by the present invention first constructs a strongly stable foam system. Through the modification of the foam stabilizer by the foaming agent, the modification form here is that the foaming agent adsorbs on the clay particles to form a synergistic stabilizer, so as to increase the foaming volume and stability of the foam; and the synergistic adsorption of the foaming agent and the foam stabilizer at the gas-liquid interface effectively prevents the coalescence and coarsening of bubbles, improving the stability of the foam. Then, using this foam system as a template, a curing material composed of a curing main agent and a curing assistant is added. After the foam is formed and injected into the formation, it is wrapped by the hydrated gel generated by the curing material under high temperature and high salinity conditions to form gel foam, significantly enhancing the strength of the foam interface film. The foam stabilizer and the hydrated gel work synergistically to reduce the interfacial tension and increase the viscoelastic modulus. Among them, the foam stabilizer improves the viscosity of the foam base liquid, thereby enhancing the ability of the foam to resist deformation, and the hydrated gel adsorbs at the gas-liquid interface to form a high-strength foam interface film, thus enhancing the self-healing ability of the foam.

[0025] In a high-temperature and high-salinity environment, due to the synergistic effect of the foaming agent and the foam stabilizer, it helps to stabilize the bubbles, and the bubbles are not easily broken and remain; at the same time, the curing main agent and the curing assistant form a hydrated gel, which covers the surface of the foam and the voids between the foams with the foam as a template, generating a three-dimensional network structure, and the "foam stabilizer" particles serve as the filling skeleton. These network structures form a supporting effect inside the material. At the same time, due to the nucleation and growth of the gel, the voids gradually expand to form an open pore network. At the same time, the bubbles fuse with each other through pressure and expansion to form larger and more stable pores. The fusion of adjacent bubbles promotes the formation of connected pores, that is, porous foam materials are formed.

[0026] The excellent carrying capacity of the foam improves the migration ability of the system. The foam stabilizer particles are filled in the three-dimensional skeleton formed by the hydrated gel to construct a crosslinked interpenetrating network, enhancing the skeleton structure of the porous foam material, thereby forming a porous medium material with high porosity, good permeability, high strength and good toughness. Since the hydrated gel material needs to be cured under high temperature and high salinity conditions, the foam flow control system provided by this application can be transported to the fracture or hole area for in-situ underground curing and plugging, and provide shear regeneration conditions for the subsequent injection of foam by virtue of the porous structure. At the same time, the continuous phase skeleton characteristics of the porous structure contribute to long-range compression, allowing oil and water to seep through it, thereby effectively controlling the differential seepage of oil and water.

[0027] Preferably, in step S1, the stirring speed is 1000 rpm and the stirring duration is 0.5 h - 2 h; in step S2, the stirring speed is 600 rpm and the stirring duration is 1 h - 4 h; in step S3, the stirring speed is 500 rpm and the stirring duration is 5 min - 15 min; the high-speed stirring speed is 8000 rpm and the high-speed stirring duration is 2 min - 7 min.

[0028] Preferably, in step S3, the gas condition for high-speed stirring and foaming is one of nitrogen, carbon dioxide, natural gas or air.

[0029] The present invention also provides an application of the above-mentioned foam flow control system for in-situ curing underground or the foam flow control system prepared by the above-mentioned preparation method in profile control and channel plugging operations in high-temperature formations. Specifically, the temperature of the high-temperature formation is greater than 100°C.

[0030] Preferably, the application method is to inject 1 - 1.5 PV of the foam flow control system into the formation along the injection well, soak the well for 3 - 7 days, and then open the well for production after the foam flow control system solidifies to form a porous foam material.

[0031] Preferably, the applicable temperature range of the high-temperature formation is between 100°C and 300°C.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The present invention provides a foam flow control system for in-situ curing underground. Combining the good filling and fluidity of water-based foam and the high plugging strength and good permeability of the cured porous foam material, and utilizing the high temperature of the reservoir and the high salinity condition of formation water, a plugging structure with adjustable density can be formed in-situ at fractures or pores after injection into the formation; specifically, the density is regulated by the concentration of foam stabilizer particles and the gas-liquid ratio of the foam.

[0034] 2. The foam flow control system provided by the present invention has a rich pore structure after curing, and can "transform fractures or pores into low-permeability porous media" in fractured-vuggy formations. On the one hand, it can solve the differential seepage caused by the viscosity difference between gas and water, and on the other hand, it can solve the problem that the foam lacks mechanical shear in fractures and vugs and is difficult to regenerate after defoaming. The shear regeneration of the foam is realized through the constructed porous structure, and the migration depth of the foam is increased.

[0035] 3. The foam flow control system in the present invention has good temperature resistance, salt resistance and dilution resistance, has a good liquid separation half-life, and can be applied to the harsh environment of high temperature, high salinity and high dilution underground.

[0036] 4. The foam flow control system in the present invention constructs a double-crosslinked interpenetrating network through the curing of the curing material and the inorganic filling components of the foam stabilizer, enhancing the skeleton structure of the porous foam material; at the same time, the porous foam material swells by absorbing water, enhancing the adhesion between the cured porous foam material and the fracture-vug wall surface, and improving the filling property of the porous foam material.

[0037] 5. The solid plugging agents provided by the prior art are relatively hard and have a low permeability. For example, the thermosetting foam profile control and plugging agent provided by Chinese patent document CN111826143 A (application number 201910322573.9) only has a remaining permeability of 1.25 mD after plugging a sand-filled tube with an original permeability of 1842 mD during specific use, severely restricting the pore distribution and thus the mass transfer. In contrast, the porous continuous-phase framework of the present invention contributes to long-range compression, which allows water to seep through it, resulting in a high-quality diffusion rate.

[0038] 6. The foam flow control system in the present invention solidifies under the formation high temperature and high salinity water curing conditions. By virtue of the characteristics of defoaming when encountering oil, being stable when encountering water, plugging water but not oil, and selectively plugging high-permeability layers, it can accurately reach the target holes and large fractures, thereby realizing in-situ curing of the cracks and holes. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is the image of the solidified foam system prepared in Example 1;

[0040] Figure 2 is the microscopic image of the solidified foam system prepared in Example 1;

[0041] Figure 3 is the image of the solidified foam system prepared in Example 2;

[0042] Figure 4 is the microscopic image of the solidified foam system prepared in Example 2;

[0043] Figure 5 is the CT scan image of different parts from top to bottom of the porous foam material prepared in Example 3, where the labels a - f are the scan images at the first 1.5 cm to the sixth 1.5 cm from the top of the porous foam material in sequence;

[0044] Figure 6 is the experimental device diagram for foam displacement in Experimental Example 1;

[0045] Figure 7 is the pressure distribution in the long and thin tube during foam flooding in Experimental Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0046] The reagents and experimental equipment used in the examples, comparative examples and experimental examples of the present invention are all commercially available conventional reagents and experimental equipment. For example, the fly ash is sourced from the industrial waste generated during the combustion power generation process in a thermal power plant, and the modified clay is prepared by the preparation method of "salt-modified soil" (Wang Lianjun, Huang Zhonghua, Liu Xiaodong, etc. Modification research of bentonite. Industrial Water Treatment, 1999, (01): 11 - 13 + 47.). The sources and selections of other reagents and experimental equipment will not be elaborated further.

[0047] Example 1

[0048] An in-situ underground solidifying foam flow control system, which consists of a foaming agent, a foam stabilizer, a solidifying material and formation water to form a foam system solution. Among them, the solidifying material consists of a solidifying main agent and a solidifying auxiliary agent;

[0049] In this example, in the foam system solution, sodium carboxymethylcellulose is selected as the foaming agent, and the mass fraction of the foaming agent is 0.5wt%. Sepiolite is selected as the foam stabilizer, the mesh number of sepiolite is 400 meshes, and the mass fraction of the foam stabilizer is 10wt%. The solidifying main agent is selected as industrial slag, and the mass fraction of the solidifying main agent is 20wt%. Sodium silicate is selected as the solidifying auxiliary agent, and the mass fraction of the solidifying auxiliary agent is 10wt%. The balance is formation water with a salinity of 21×10 4 mg / L;

[0050] In this example, the component content of industrial slag is as follows:

[0051] SiO 2 accounts for 32.12wt%, Al 2 O 3 accounts for 15.13wt%, Fe 2 O 3 accounts for 1.61wt%, CaO accounts for 36.65wt%, and MgO accounts for 8.94wt%;

[0052] The preparation method of the above foam flow control system is as follows:

[0053] S1. Add 0.5g of sodium carboxymethylcellulose and 10g of sepiolite to 100ml of formation water with a salinity of 210000mg / L, and stir at 1000rpm for 1h to obtain a mixed solution;

[0054] S2. Slowly add 20g of slag to the above-prepared mixed solution while stirring, and continue to stir at 600rpm for 2h to obtain an intermediate solution;

[0055] S3. After adding 10g of sodium silicate to the intermediate solution, immediately stir at 8000rpm for 3min under a nitrogen atmosphere to foam to obtain the foam flow control system.

[0056] Place the prepared foam flow control system in an oven at 130°C and seal it for 6h to simulate the in-situ solidification process, and a porous foam material is obtained. As Figure 1 shown, the black line in the figure is the liquid level of the foam flow control system before solidification. It can be seen that the solidified porous foam material is extremely stable at high temperatures and can maintain its original volume with almost no change; as Figure 2 shown, it can be seen from the microscopic image that its pore distribution is uniform and it has good pore connectivity.

[0057] Example 2

[0058] An in-situ underground solidifying foam flow regulating system is composed of a foaming agent, a foam stabilizer, a solidifying material and formation water to form a foam system solution. Among them, the solidifying material is composed of a solidifying main agent and a solidifying assistant;

[0059] In this example, in the foam system solution, the foaming agent is selected as hydroxysulfobetaine, and the mass fraction of the foaming agent is 0.3 wt%. The foam stabilizer is selected as fly ash, the mesh number of the fly ash is 400 mesh, and the mass fraction of the foam stabilizer is 15 wt%. The solidifying main agent is selected as industrial slag, and the mass fraction of the solidifying main agent is 20 wt%. The solidifying assistant is selected as sodium aluminate, and the mass fraction of the solidifying assistant is 10 wt%. The balance is formation water with a salinity of 15×10 4 mg / L;

[0060] In this example, the component content of the industrial slag is as follows:

[0061] SiO 2 accounts for 32.12 wt%, Al 2 O 3 accounts for 15.13 wt%, Fe 2 O 3 accounts for 1.61 wt%, CaO accounts for 36.65 wt%, and MgO accounts for 8.94 wt%;

[0062] The preparation method of the above foam flow regulating system is as follows:

[0063] S1. Add 0.3 g of hydroxysulfobetaine and 15 g of fly ash to 100 ml of formation water with a salinity of 150,000 mg / L and stir at 1000 rpm for 1.5 h to obtain a mixed solution;

[0064] S2. Slowly add 20 g of slag to the above-prepared mixed solution while stirring, and continue to stir at 600 rpm for 2 h;

[0065] S3. After adding 10 g of sodium aluminate to the above solution, immediately stir at 8000 rpm for 3 min in a carbon dioxide atmosphere to foam to obtain the foam flow regulating system.

[0066] Place the prepared foam flow regulating system in an oven at 130 °C and seal it for 6 h to simulate the formation solidification process, and a porous foam material is obtained. As Figure 3 shown, the black line in the figure is the liquid level of the foam flow regulating system before solidification. It can be seen that the cured porous foam material is extremely stable at high temperatures and can maintain its original volume with almost no change; as Figure 4 shown, it can be seen from the microscopic image that its pore distribution is uniform and it has good pore connectivity.

[0067] From Figure 2 andFigure 4 It can be seen that in Example 2, due to the decrease in salinity, the hydrated gel formed by the solidifying main agent and the solidifying aid decreases, the stability of the foam at high temperature decreases, the foam coarsens and merges, the pore size of the formed solidified foam is relatively large, and there are cracks, thereby reducing the overall strength. Compared with Example 1, the overall strength of Example 2 is smaller.

[0068] Example 3

[0069] A foam flow control system for in-situ solidification underground consists of a foaming agent, a foam stabilizer, a solidifying material and formation water to form a foam system solution. Among them, the solidifying material consists of a solidifying main agent and a solidifying aid;

[0070] In this example, in the foam system solution, sodium carboxymethylcellulose is selected as the foaming agent, and the mass fraction of the foaming agent is 0.5 wt%, attapulgite is selected as the foam stabilizer, the mesh number of attapulgite is 400 mesh, the mass fraction of the foam stabilizer is 10 wt%, the modified clay is selected as the solidifying main agent, the mass fraction of the solidifying main agent is 15 wt%, sodium phosphate is selected as the solidifying aid, the mass fraction of the solidifying aid is 8 wt%, and the balance is formation water with a salinity of 25×10 4 mg / L;

[0071] In this example, the component content of the modified clay is as follows:

[0072] SiO 2 accounts for 32.29 wt%, Al 2 O 3 accounts for 12.13 wt%, Fe 2 O 3 accounts for 0.948 wt%, CaO accounts for 36.36 wt%, and MgO accounts for 8.03 wt%;

[0073] The preparation method of the above foam flow control system is as follows:

[0074] S1. Add 0.5 g of sodium carboxymethylcellulose and 10 g of attapulgite to 100 ml of formation water with a salinity of 250000 mg / L and stir at 1000 rpm for 2 h to obtain a mixed solution;

[0075] S2. Slowly add 15 g of modified clay to the above-prepared mixed solution while stirring and continue to stir at 600 rpm for 2 h;

[0076] S3. After adding 8 g of sodium phosphate to the above solution, immediately stir at 8000 rpm for 3 min in an air atmosphere to foam to obtain the foam flow control system.

[0077] The prepared foam flow control system was placed in an oven at 130 °C and sealed for 6 h to simulate the formation curing process, thus obtaining a porous foam material. The porous foam material was scanned by CT from top to bottom, and scanning images were selected at intervals of 1.5 cm, as Figure 5 shown, Figure 5 in which, a - f are the scanning images from the first 1.5 cm to the sixth 1.5 cm from the top of the porous foam material downwards in sequence. It can be seen from the CT scanning images that the foam is evenly distributed from top to bottom, and the pores of the porous foam material have good connectivity.

[0078] Example 4

[0079] A foam flow control system for in - situ underground curing. The difference between this example and Example 3 lies in that in the preparation method of the foam flow control system, the gas condition in step S3 is a natural gas atmosphere, and other components and steps are the same.

[0080] Comparative Example 1

[0081] The foam plugging agent provided in this comparative example is the system provided in Example 8 of Chinese Patent Document CN 111526143 A.

[0082] Comparative Example 2

[0083] The plugging agent provided in this comparative example is the system provided in Example 2 of Chinese Patent Document CN 112358859 A.

[0084] Comparative Example 3

[0085] The difference between the foam flow control system provided in this comparative example and Example 1 is that sodium citrate of equal mass is selected as the curing aid instead of sodium silicate, and other preparation methods and parameters are the same as those in Example 1.

[0086] Comparative Example 4

[0087] The difference between the foam flow control system provided in this comparative example and Example 1 is that the mass fraction of the main curing agent is 15 wt%, and the mass fraction of the curing aid is 10 wt%, and other preparation methods and parameters are the same as those in Example 1.

[0088] Comparative Example 5

[0089] The difference between the foam flow control system provided in this comparative example and Example 1 is that the mass fraction of the main curing agent is 15 wt%, and the mass fraction of the curing aid is 15 wt%, and other preparation methods and parameters are the same as those in Example 1.

[0090] Comparative Example 6

[0091] The difference between the foam flow regulating system provided in this comparative example and that in Example 1 is that the mass fraction of the curing main agent is 10 wt%, and the mass fraction of the curing auxiliary agent is 15 wt%. Other preparation methods and parameters are the same as those in Example 1.

[0092] Comparative Example 7

[0093] The difference between the foam flow regulating system provided in this comparative example and that in Example 1 is that the mass fraction of the curing main agent is 10 wt%, and the mass fraction of the curing auxiliary agent is 20 wt%. Other preparation methods and parameters are the same as those in Example 1.

[0094] Table 1 Curing time and compressive strength of curing agents with different ratios

[0095]

[0096] It can be seen from Table 1 that the curing time of Example 1 is 4.5 h and the compressive strength is 1.5 MPa, meeting the design requirements. The system of Comparative Example 3 did not cure, indicating that the acid radical ions of inorganic acid salts are required for curing, and sodium organic salts cannot help with curing. At the same time, as the ratio of the curing main agent decreases, the compressive strength decreases accordingly. It can be seen that the curing main agent mainly affects the compressive strength of the cured foam system; while as the ratio of the curing auxiliary agent increases, the curing time decreases, indicating that the curing auxiliary agent affects the curing time of the cured foam system.

[0097] Experimental Example 1

[0098] As Figure 6 shown, using a long and thin tube displacement device, the pressures at different positions during the foam flooding process were monitored, and the pressure propagation during the foam flooding process was compared; nine pressure measurement points were evenly arranged along the seepage direction, and the long and thin tube was evenly divided into eight sections, each section being 37.5 m long. The pressure was collected in real time through a pressure sensor and a pressure automatic acquisition device. The inlet pressure (P1) of the system was controlled by an injection pump, and the outlet pressure (P9) was controlled by a back pressure valve. The experimental gas was nitrogen; the length of the thin tube was 3 m, the diameter was 12 mm, and the gas and solution were injected at a constant speed simultaneously.

[0099] a. Experimental Group 1: The specific steps are as follows:

[0100] 1. Prepare a 0.5 wt% YF-1 foam system and the foam flow regulating system described in Example 1 for use;

[0101] 2. Fill the long and thin tube model with quartz sand of 80 - 120 mesh, and then saturate the sand-filled long and thin tube with water;

[0102] 3. Calculate the porosity of the sand-filled core tube and measure its permeability with water. The measured permeability is 2500×10 -3 -4000×10-3 Proceed to the next experiment when it reaches [[μm²]], otherwise repeat steps 2 and 3;

[0103] 4. Constant temperature heating: Turn on the power switch of the constant temperature oven and heat up to the formation temperature (130 °C);

[0104] 5. After the preheating of the long thin tube is completed, first inject a foam flow control system with a gas-liquid ratio of 2:1 at a rate of 3 mL / min for 1.5 PV. After the foam system solidifies for 6 h, secondly, perform a pre-water drive at a rate of 3 mL / min for 1.5 PV, then inject nitrogen and YF-1 foam with a gas-liquid ratio of 2:1 at a rate of 3 mL / min for 9 PV for foam flooding, and finally perform a subsequent water drive at a rate of 3 mL / min for 2 - 3 PV. The experimental back pressure is set to 1 MPa;

[0105] 6. During the experiment, use a pressure acquisition device to record the pressures P1 - P9 at different positions of the model in real time.

[0106] b. The specific steps of experimental group 2 are different from those of experimental group 1 in that in step 5, 1.5 PV of the foam flow control system is not injected, and other steps and parameters are the same.

[0107] As Figure 7 shown, the pressure change at different positions during the foam flooding process, and the pressure distribution in the horizontal coordinate direction reflects the pressure propagation during the foam flooding. It can be seen from the figure that as the foam injection volume increases, the pressure at each pressure measurement point increases accordingly and gradually propagates towards the outlet end. However, the pressure increase at different position points is different, and the pressure increase gradually decreases from the inlet section to the outlet end of the long thin tube, and the pressure distribution almost decreases linearly. Among them, in experimental group 1, a certain pressure has built up even before the nitrogen foam is injected, indicating that the solidified foam reduces the permeability of the long thin tube and plays a certain plugging role. At the same time, the pressure of experimental group 1 under the condition of the same foam injection volume is higher than that of experimental group 2, which reflects the shear regeneration of the solidified foam system for nitrogen foam, improves the migration ability of the foam, and thus increases the pressure at different positions of the long thin tube.

[0108] Experimental Example 2

[0109] Take the systems provided in Examples 1 - 3 and Comparative Examples 1 - 2, and conduct a performance evaluation test on the plugging sand-filled tube. Refer to the experimental equipment and experimental methods in Test Example of Comparative Example 2 to design the performance evaluation test of the plugging sand-filled tube for Examples 1 - 3. Since the systems in Comparative Example 2 and Comparative Example 3 are mainly for medium and low permeability formations, and this application is mainly for large holes and fractures, a higher permeability is set, and only the plugging rates in Comparative Example 2 and Comparative Example 3 are compared. The difference between the experimental equipment and Experimental Example 1 is only that the long thin tube is replaced with a sand-filled tube with a diameter of 25 mm and a length of 60 cm.

[0110] 1. Prepare the foam flow control system described in Examples 1 - 3 for use;

[0111] 2. Fill the sand-packed tube with quartz sand of 80 - 120 mesh, and then saturate the sand-packed tube with water;

[0112] 3. Calculate the porosity of the sandstone core tube and measure its permeability with water. When the measured permeability is 3500×10 -3 μm², proceed to the next experiment; otherwise, repeat steps 2 and 3;

[0113] 4. Constant temperature heating: Turn on the power switch of the constant temperature oven and heat up to the formation temperature (130°C);

[0114] 5. After the preheating of the sand-packed tube is completed, inject 1.5 PV of the foam flow control system with a gas-liquid ratio of 2:1 at a speed of 3 mL / min. After the foam system solidifies for 6 hours, measure the permeability of the sand-packed tube, and set the experimental back pressure to 1 MPa;

[0115] Table 2 Statistical data of plugging

[0116]

[0117] As can be seen from Table 2, the plugging rates of Experimental Examples 1 - 3 are in the range of 61% - 89%, while the plugging rates of Comparative Examples 1 - 2 are in the range of 98.53% - 99.93%; this shows that Comparative Examples 1 - 2 are completely blocked, and it is impossible to ensure the subsequent migration of foam between fractures and cavities; at the same time, the plugging rate of Example 2 is relatively poor but still within an acceptable range, indicating that a lower salinity will reduce the plugging effect of the foam system.

[0118] Comparative Example 7

[0119] The difference between the foam flow control system provided in this comparative example and Example 1 is that the proportion of sepiolite is 2.5 wt%, and other preparation methods and parameters are the same as those in Example 1.

[0120] Comparative Example 8

[0121] The difference between the foam flow control system provided in this comparative example and Example 1 is that the proportion of sepiolite is 5 wt%, and other preparation methods and parameters are the same as those in Example 1.

[0122] Comparative Example 9

[0123] The difference between the foam flow control system provided in this comparative example and Example 1 is that the proportion of sepiolite is 7.5 wt%, and other preparation methods and parameters are the same as those in Example 1.

[0124] Take the systems provided in Examples 1 - 3 and Comparative Examples 7 - 9, and measure the half-life of liquid separation after foaming,

[0125] Table 3 Bleeding half-life

[0126]

[0127] Since the addition of the curing agent has an impact on the bleeding half-life at high temperatures, only the impact of different concentrations of foam stabilizer content that affect the foam stability time on the bleeding half-life was measured. According to Table 2, Examples 1-3 have a bleeding half-life of 8-16 h, indicating good foam stability; while the bleeding half-life of Comparative Example 7 in Comparative Examples 7-9 is poor, indicating that the proportion of the foam stabilizer affects the foam stability. As the content of the foam stabilizer increases, the bleeding half-life increases; among them, for the foam stabilizer with a concentration of 10 wt% as well, the foam stability time of fly ash in Example 2 is less than that of sepiolite and attapulgite in Examples 1 and 3.

[0128] At the same time, different contents of the foam stabilizer can change the density of the foam system, thereby increasing the migration distance of the foam carrying the curing agent in the formation.

Claims

1. An underground in-situ solidified foam flow regulating system, characterized in that: The foam system solution is composed of a foaming agent, a foam stabilizer, a solidifying material and formation water, wherein the solidifying material is composed of a solidifying main agent and a solidifying auxiliary agent; In the foam system solution, the mass fraction of the foaming agent is 0.1wt%-1.2wt%, the mass fraction of the foam stabilizer is 5wt%-20wt%, the mass fraction of the curing main agent is 10wt%-40wt%, the mass fraction of the curing auxiliary agent is 5wt%-20wt%, and the balance is formation water; The foam stabilizer should be particles with a particle size less than 200 mesh; The main curing agent is industrial slag or modified clay, and the curing auxiliary agent is inorganic acid sodium salt. Among the components of the curing agent, SiO2 accounts for 19.26wt%-53.12wt%, Al2O3 accounts for 6.23wt%-15.15wt%, Fe2O3 accounts for 0.5wt%-1.63wt%, CaO accounts for 35.65wt%-60.12wt%, and MgO accounts for 8.85wt%-9.12wt%; The mineralization of formation water is 15×10 4 mg / L-25×10 4 mg / L; The foaming agent is selected from at least one of high-carbon fatty alcohol polyoxyethylene ether, dodecylphenol polyoxyethylene ether, sodium di(2-ethylhexyl) sulfosuccinate, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium α-olefin sulfonate, hydroxysulfobetaine, lauric acid diethanolamide, fatty alcohol polyoxyethylene ether sulfate or sodium carboxymethyl cellulose; The foam stabilizer is selected from at least one of fly ash particles, silica particles, montmorillonite, kaolin, montmorillonite, illite, attapulgite, kaolinite, sepiolite or chlorite; The curing aid is selected from at least one of sodium silicate, sodium aluminate or sodium phosphate; The foam flow regulating system foams and solidifies under high temperature and high mineral content to form a porous foam material with uniform pore distribution and interconnection.

2. The underground in-situ solidified foam flow regulating system according to claim 1, characterized in that: The liquid separation half-life of the underground in-situ solidified foam flow regulation system is 6h-24h.

3. A method for preparing an underground in-situ solidified foam flow regulating system as claimed in any one of claims 1 to 2, characterized in that: The steps include: S1. Add a foaming agent and a foam stabilizer to the formation water, and stir to obtain a mixed solution; S2. Under stirring, adding the curing agent to the mixed solution to obtain an intermediate solution; S3. After adding the curing aid to the intermediate solution and stirring, the foam flow regulating system is obtained by high-speed stirring and foaming using the Waring Blender method.

4. The preparation method according to claim 3, characterized in that: In step S1, the stirring speed is 1000 rpm and the stirring time is 0.5 h-2 h; In step S2, the stirring speed is 600 rpm and the stirring time is 1 h-4 h; In step S3, the stirring speed is 500 rpm, and the stirring time is 5 min-15 min; the high-speed stirring speed is 8000 rpm, and the high-speed stirring time is 2 min-7 min.

5. The preparation method according to claim 3, characterized in that: In step S3, the gas condition for high-speed stirring and foaming is one of nitrogen, carbon dioxide, natural gas or air.

6. An application of an underground in-situ solidified foam flow control system in profile control and channel sealing operations in high-temperature formations, characterized in that: The underground in-situ solidified foam flow regulating system is provided by any one of claims 1-2, or the underground in-situ solidified foam flow regulating system is prepared by the preparation method described in any one of claims 3-5, The temperature of the high-temperature formation is greater than 100°C.

7. The use according to claim 6, characterized in that The application method is to inject 1-1.5PV of foam flow regulation system into the formation along the injection well, then keep the well in a coolant for 3-7 days, and then start production after the foam flow regulation system solidifies to form a porous foam material.

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