Mixing device and method for preparing a foam

Abstract

This invention provides a mixing device and a foam preparation method. The mixing device includes a first mixing chamber, in which a fluid disperser is disposed. The fluid disperser disperses a first fluid and rotates it into the first mixing chamber to mix with a second fluid. Compared with the prior art, the mixing device provided by this invention uses a rotatable fluid disperser to rotate gas into a mixture of a foaming agent and a foaming liquid, increasing the shear force of the gas on the liquid, thus making it easier to achieve thorough gas-liquid mixing and generating more and smaller diameter bubbles, forming highly stable foam. By using high-strength wear-resistant materials and a special angle design for the second and third inlets, the mixing device can be connected to a high-pressure fracturing manifold for ultra-high pressure sand-carrying foaming, achieving uniform foaming of high-viscosity foaming liquid.

Description

Technical Field

[0001] This invention relates to the field of oil and gas reservoir stimulation technology, and in particular to a mixing device and a foam preparation method. Background Technology

[0002] Currently, common foam generating devices fall into three categories: one is based on the Venturi principle, which typically incorporates a porous media or variable-diameter tubing system at the outlet to produce high-quality, stable foam; another type involves mixing gas and liquid before passing the mixture through oscillators such as variable-diameter mixing oscillators or screw mixing oscillators to generate high-quality foam; and yet another type uses ultrasonic oscillation to generate foam within the well, reducing foam loss before it enters the formation. These foaming devices or systems have several shortcomings: first, their low shear force and velocity hinder gas-liquid mixing, making it difficult to foam high-viscosity foaming liquids and preventing the formation of stable microfoam systems; second, they cannot achieve foaming after the proppant-laden liquid has carried proppant, as the proppant-laden liquid passing through porous media, variable-diameter tubing, and oscillators can cause strong scouring, damaging the foaming device, while ultrasonic oscillation may separate the proppant, affecting the foam fracturing effect; and third, existing devices or systems cannot be connected to high-pressure fracturing manifolds for ultra-high-pressure proppant-laden foaming. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the present invention aims to provide a mixing device that can effectively disperse fluid and increase the shear force of the fluid, thereby achieving full mixing of the fluid. When used to prepare foam, it can achieve full mixing of gas and liquid, which facilitates the full foaming of foaming liquid and gas to form highly stable foam.

[0004] The mixing device provided by the present invention includes a first mixing chamber, in which a fluid disperser is disposed. The fluid disperser is used to disperse a first fluid and rotate it into the first mixing chamber to mix with a second fluid.

[0005] The rotatable fluid disperser can not only effectively disperse the first fluid, but also make the first fluid rotate in the first mixing chamber, increasing the shear force of the first fluid on the second fluid and achieving full mixing of the first and second fluids. When the mixing device is used to prepare foam, the first fluid is a gas and the second fluid is a mixture of foaming agent and bubble liquid. The gas is dispersed by the fluid disperser and rotated into the mixed liquid, increasing the shear force of the gas on the mixed liquid. Therefore, it is easier to achieve full mixing of gas and liquid, which is conducive to generating more and smaller diameter bubbles and forming highly stable foam.

[0006] A fluid disperser can be driven by a motor or by the fluid flowing through it.

[0007] Preferably, the fluid disperser includes a disc-shaped body with a fluid channel formed therein. The inlet of the fluid channel is located at the center of one end face of the body, and the fluid channel has multiple outlets. The outlets of the multiple fluid channels are located on the side of the body and are evenly distributed along the circumference of the body. The outlets of the fluid channels are tangent to the circumference of the side face. The fluid disperser is rotatably embedded in the inner wall of the first mixing chamber.

[0008] A fluid disperser allows a first fluid (such as gas) to be injected tangentially into a second fluid (such as a mixture of foaming liquid and a foaming agent). The gas rotates within the chamber, increasing the shear force of the first fluid on the second fluid. In this design, the rotational speed of the fluid disperser can be adjusted by regulating the flow rate of the first fluid, thereby regulating the shear force of the first fluid on the second fluid.

[0009] Preferably, the fluid channel includes a flow guide cavity, which is connected to the inlet of the fluid channel and the outlet of the plurality of fluid channels respectively.

[0010] Preferably, the system further includes a second mixing chamber connected to the first mixing chamber, the second mixing chamber containing a mixer for mixing the first fluid and the second fluid. By providing the second mixing chamber and the mixer, it is beneficial to further homogenize the first fluid and the second fluid.

[0011] Preferably, the mixer includes a support, a rotating shaft, and helical blades. The helical blades are mounted on the rotating shaft, which is rotatably connected to the support. The support is fixed to the inner wall of the second mixing chamber. One end of the second mixing chamber is connected to the first mixing chamber, and the other end has an outlet. One end of the rotating shaft points to the connection between the second and first mixing chambers, and the other end points to the outlet. When the pressurized first and second fluids pass through the helical blades of the mixer, the mixer rotates. The rotation of the helical blades repeatedly shears the mixture of the first fluid / gas and the second fluid, making the mixing system more stable.

[0012] The end of the mixer near the first mixing chamber is the front end, and the end near the outlet of the second mixing chamber is the rear end. Preferably, a rear-end blade is added to the rotating shaft at the rear end of the mixer. The rear-end blade is generally disc-shaped, with raised strips on its two end faces. These raised strips are preferably annular, and their arrangement facilitates shearing of the mixture of the first fluid / gas and the second fluid. When the pressurized fluid passes through the helical blades at the front end of the mixer, it causes the mixer to rotate, which in turn drives the rear-end blades to rotate. The rotation of the helical blades and the rear-end blades repeatedly shears the fluid, resulting in a more uniform mixture.

[0013] Preferably, the spiral blade is an Archimedean spiral blade with the rotation axis as the center of rotation. By using an Archimedean spiral blade in the mixer, high-speed and multi-stage shearing can be achieved, which facilitates fluid mixing. When used to prepare foam, it facilitates the full foaming of foaming liquid and gas, and can achieve uniform foaming of high-viscosity foaming liquid.

[0014] Preferably, the first mixing chamber is provided with a first inlet, a second inlet, and a third inlet. The first inlet is connected to the inlet of the fluid disperser. The second and third inlets are in the same plane, and the included angle between them is 0° to 180°. More preferably, the included angle between the second and third inlets is 160° to 180°. Even more preferably, the included angle between the second and third inlets is 180°. The closer the included angle between the second and fourth inlets is to 180°, the less direct scouring the junction of the two inlets is caused by the fluid flowing through them. When the included angle is 180°, that is, when the second and third inlets are coaxially opposite each other, the fluid flowing through them will not cause strong direct scouring at the junction of the two inlets, thus improving the service life of the equipment. When the mixing device is used for foaming, gas is introduced through the first inlet, and foaming liquid and foaming agent are introduced through the second and third inlets, respectively. The foaming liquid and foaming agent will not cause strong direct scouring at the junction of the foaming liquid inlet and the foaming agent inlet, thus improving the service life of the equipment. Meanwhile, the foaming liquid inlet and the foaming agent inlet are set coaxially opposite each other, and when the foaming liquid and the foaming agent enter the mixing chamber, they form convection, which is conducive to the uniform mixing of the two.

[0015] Preferably, the first mixing chamber is provided with a first inlet, a second inlet, and a third inlet, the first inlet being connected to the inlet of the fluid disperser; the second inlet and the third inlet are both at an angle of 90° to the rotation axis of the mixer.

[0016] Preferably, the device also includes a heating and insulation system for controlling the temperature inside the mixing device between -30°C and 180°C. The heating and insulation system is designed on the outside of the mixing device to make the temperature controllable and to protect the mixing device from low-temperature damage caused by vaporization.

[0017] Preferably, any one of the first mixing chamber, the second mixing chamber, or the mixer can be made of 5CrNiMo steel, Q125 steel, or Hastelloy. 5CrNiMo steel or Q125 steel has high strength, resulting in a chamber with strong resistance to internal pressure. Hastelloy is corrosion-resistant and wear-resistant, providing excellent corrosion and wear resistance as the inner wall of the chamber. The mixing device can be connected to a high-pressure fracturing manifold for ultra-high pressure sand-carrying foaming.

[0018] This invention also provides a foam preparation method. This method uses the mixing device described above to prepare foam. Gas is dispersed by a fluid disperser and rotated into a first mixing chamber to mix with the foaming liquid and foaming agent to form foam. The gas is the first fluid, and the mixture of the foaming agent and the foaming liquid is the second fluid. Compared with the prior art, the mixing device provided by this invention can not only effectively disperse the first fluid through the rotatable fluid disperser, but also cause the first fluid to rotate in the first mixing chamber, increasing the shear force of the first fluid on the second fluid and achieving thorough mixing between the fluids. This mixing device can be used to prepare foam, where the first fluid is a gas and the second fluid is a mixture of the foaming agent and the foaming liquid. By dispersing the gas through the fluid disperser and causing the gas to rotate into the mixed liquid, the shear force of the gas on the liquid is increased, thus making it easier to achieve thorough mixing of the gas and liquid, which is beneficial for generating more and smaller diameter bubbles, forming highly stable foam. By using high-strength wear-resistant materials and setting the second and third inlets on the same plane with an included angle of 180°, the mixing device can be connected to the high-pressure fracturing manifold for ultra-high pressure sand-carrying foaming. It has high shear force (rate), can achieve uniform foaming of high-viscosity foaming liquid, and can perform micro-foaming, producing foam with a particle size of less than 100 micrometers.

[0019] This invention is applicable to foam fracturing in tight sandstone oil and gas reservoirs, carbonate oil and gas reservoirs, shale oil and gas reservoirs, and coalbed methane reservoirs, with a wide range of applications.

[0020] The above-mentioned technical features can be combined in various suitable ways or replaced by equivalent technical features, as long as the purpose of the present invention can be achieved. Attached Figure Description

[0021] The invention will now be described in more detail based on embodiments that are merely non-limiting and with reference to the accompanying drawings. Wherein:

[0022] Figure 1 This is a schematic diagram of the structure of a mixing device provided in an embodiment of the present invention;

[0023] Figure 2 This is a top view of a pipeline connector provided in an embodiment of the present invention;

[0024] Figure 3 This is a three-dimensional structural schematic diagram of a fluid disperser provided in an embodiment of the present invention;

[0025] Figure 4 This is a top view of a fluid disperser provided in an embodiment of the present invention;

[0026] Figure 5 for Figure 3 Cross-sectional view at point A in the middle;

[0027] Figure 6 for Figure 3 Cross-sectional view at point B in the middle;

[0028] Figure 7 This is a side view of a second mixing cavity provided in an embodiment of the present invention;

[0029] Figure 8 This is a schematic diagram of the structure of the second mixing chamber and mixer provided in an embodiment of the present invention;

[0030] Figure 9 A left view of a rear-end blade provided in an embodiment of the present invention;

[0031] Figure 10 This is a right view of a rear-end blade provided in an embodiment of the present invention.

[0032] Explanation of reference numerals in the attached figures:

[0033] 1. First mixing chamber; 2. Second mixing chamber; 3. First inlet; 4. Second inlet; 5. Third inlet; 6. Fluid disperser; 7. Mixer; 8. Heating and insulation system; 9. Foam outlet; a, b, c, d. Pipeline joints; 11. First mixing chamber; 21. Second mixing chamber; 71. Support; 72. Rotating shaft; 73. Helical blade; 74. Rear end blade; 741, 742. Annular convex strips; 61. Body; 62. Fluid channel; 621. Inlet of fluid channel; 622. Outlet of fluid channel; 623. Guide chamber. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Based on the specific embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0035] The terms "first," "second," and similar words used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. Words such as "including" or "contains" mean that the element preceding the word encompasses the element listed after it, and do not exclude the possibility of encompassing other elements as well. Terms such as "above," "below," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, this relative positional relationship may also change accordingly.

[0036] In this disclosure, when a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other devices without an intermediary device, or it may be not directly connected to the other devices but have an intermediary device.

[0037] All terms used in this disclosure (including technical or scientific terms) have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in a general dictionary, such as a dictionary, should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and not as having an idealized or highly formalized meaning, unless expressly defined herein.

[0038] Example 1

[0039] like Figures 1 to 8 The structure of the mixing device is schematically shown. The mixing device includes a first mixing chamber 1 and a second mixing chamber 2. A first mixing chamber 11 is formed inside the first mixing chamber 1, and a second mixing chamber 21 is formed inside the second mixing chamber 2. The first mixing chamber 1 and the second mixing chamber 2 are connected by a flange, thereby connecting the second mixing chamber 21 and the second mixing chamber 11.

[0040] like Figure 1 As shown, the first mixing chamber 1 is provided with a first inlet 3, a second inlet 4, and a third inlet 5, which are connected to the first mixing chamber 11. The first inlet 3, the second inlet 4, and the third inlet 5 are respectively connected to corresponding pipeline joints a, b, and c via flanges. In this embodiment, it is preferable that the second inlet 4 and the third inlet 5 are arranged on the same plane with an included angle of 180°. In this case, the fluids (such as foaming fluid (fracturing fluid or fracturing fluid containing proppant) and foaming agents) introduced into the second and third inlets will not cause strong direct scouring at the junction of the second inlet 4 and the third inlet 5, thus improving the service life of the equipment. At the same time, the second inlet 4 and the third inlet 5 are arranged coaxially opposite each other, so that when the fluid enters the first mixing chamber 1 from the second inlet 4 and the third inlet 5, convection is formed, which is conducive to uniform mixing.

[0041] A rotatable fluid disperser 6 is installed inside the first mixing chamber 1. Figures 2 to 6As shown, the fluid disperser 6 includes a disc-shaped body 61, inside which a fluid channel 62 is formed. The fluid channel 62 includes a fluid channel inlet 621, a guide cavity 623, and a fluid channel outlet 622 connected in sequence. The fluid channel inlet 621 is located at the center of one end face of the body 61 and is connected to a first inlet 3. The fluid channel outlet 622 is located on the side of the body 61. At least two fluid channel outlets 622 are provided; in this embodiment, three fluid channel outlets 622 are provided, evenly distributed along the circumference of the body 61, and tangent to the circumference of the side face. The fluid disperser 6 is installed in a sealed, embedded manner on the wall of the mixing chamber 1, so that the first fluid in the first inlet 3 can only enter the first mixing chamber 11 through the fluid channel 62 of the fluid disperser 6. Since the fluid channel outlet 622 is tangent to the circumference of the side, when the first fluid in the first inlet 3 flows through the fluid disperser 6, it can drive the fluid disperser 6 to rotate. Through the fluid disperser 6, the first fluid can be injected tangentially into the second fluid in the first mixing chamber 11. The first fluid rotates in the chamber, increasing the shear force of the first fluid on the second fluid, thus making it easier to achieve full mixing of the fluid.

[0042] like Figure 1 , Figure 7 and Figure 8 As shown, a foam outlet 9 is provided on the side of the second mixing chamber 2 away from the first mixing chamber 1. The foam outlet 9 is connected to the interior of the second mixing chamber 2 and is connected to a pipeline connector d via a flange. A mixer 7 is provided inside the second mixing chamber 2 to fully mix the first fluid and the second fluid.

[0043] like Figure 8 As shown, the mixer 7 includes a support 71, a rotating shaft 72, a helical blade 73, and a rear end blade 74. The support 71 is fixed to the inner wall of the second mixing chamber 2, and the rotating shaft 72 is rotatably connected to the support 71, allowing the rotating shaft 72 to be rotatably mounted within the second mixing chamber 21. One end of the rotating shaft 72 points to the connection between the second mixing chamber 2 and the first mixing chamber 1, and the other end points to the foam outlet 9. The end of the mixer 7 closest to the first mixing chamber 1 is the front end of the mixer 7, and the end of the mixer 7 closest to the foam outlet 9 is the rear end of the mixer 7. The helical blade 73 and the rear end blade 74 are respectively mounted on the front and rear ends of the mixer 7. The helical blade 73 is arranged around the rotating shaft 72 and fixed to the outer wall surface of the rotating shaft 72, and the rear end blade 74 is mounted at the rear end of the rotating shaft 72.

[0044] like Figures 8 to 10As shown, the rear blade 74 is generally disc-shaped, with annular protrusions 741 and 742 protruding from its two end faces, respectively. Preferably, the annular protrusion 741 on the end face closer to the front end has a larger diameter, while the annular protrusion 742 on the end face closer to the rear end has a smaller diameter. The annular protrusions facilitate shearing of the mixture of the first and second fluids. When the pressurized fluid passes through the helical blade 73 at the front end of the mixer 7, it causes the mixer 7 to rotate, which in turn drives the rear blade 74 of the mixer 7 to rotate. The rotation of the helical blade 73 and the rear blade 74 repeatedly shears the mixture of the first and second fluids, making the fluid mixing system more stable.

[0045] Preferably, the helical blade 73 is an Archimedean curve helical blade with the rotation axis 72 as the center of rotation, and the outer contour of the helical blade 73 is an Archimedean curve. By adopting the Archimedean curve helical blade, the mixer 7 can achieve high speed and multi-stage shearing, which facilitates the thorough mixing of fluids.

[0046] More preferably, the angles between the second inlet 4 and the third inlet 5 and the rotation axis 72 of the mixer 7 are both 90°, which further reduces the scouring of the inner wall of the mixing chamber 1 during the introduction of fluid into the second inlet 4 and the third inlet 5. When this mixing device is used to prepare foam, safe mixing (carrying) of sand and foaming can be achieved.

[0047] To control the temperature inside the mixing unit, a heating and insulation system 8 can be added, such as... Figure 1 As shown, the heating and insulation system 8 is wrapped around the outer wall of the mixing chamber 1 and the second mixing chamber 2. The heating and insulation system 8 can control the temperature inside the mixing device between -30°C and 180°C. This temperature control protects the mixing device from low-temperature damage caused by vaporization.

[0048] Any one of the first mixing chamber 1, the second mixing chamber 2, or the mixer 7 can be made of 5CrNiMo steel, Q125 steel, or Hastelloy. 5CrNiMo steel or Q125 steel has high strength, resulting in chambers with strong resistance to internal pressure. Hastelloy is corrosion-resistant and wear-resistant, providing excellent corrosion and wear resistance as the inner wall of the chamber.

[0049] When preparing foam using the mixing apparatus provided in this application, the first fluid is a gas, and the second fluid is a mixture of a foaming agent and a bubble liquid. The gas enters through the first inlet 3, is dispersed by the fluid disperser 6, and rotates into the first mixing chamber 11, where it mixes with the bubble liquid entering through the second inlet 4 and the foaming agent (or other additives) entering through the third inlet 5. Then, the gas and liquid are mixed and stirred through the mixer 7 to form foam. Preferably, the mixer 7 operates at a pressure of 0–140 MPa, a temperature of -30–180°C, and a rotational speed of 0–10000 r / min.

[0050] Example 2

[0051] Based on Example 1, with other structures remaining unchanged, only the included angle between the second and third inlets is changed to 0°.

[0052] Example 3

[0053] Based on Example 1, with other structures remaining unchanged, only the included angle between the second and third inlets is changed to 90°.

[0054] Comparative Example 1

[0055] Based on Example 1, the fluid disperser is removed, allowing the gas to directly enter the first mixing chamber.

[0056] The foaming effects were compared using the mixing apparatus provided in Examples 1-3 and Comparative Example 1. The foaming effects (with the same foaming liquid and additives) are shown in Table 1.

[0057]

[0058] As shown in Table 1, the mixing device of the present invention can achieve thorough gas-liquid mixing by setting a fluid disperser and a mixer. When using the device to prepare foam, bubbles are easily formed, and the obtained foam particle size is less than 400 micrometers (a foam system with a foam particle size of less than 150 micrometers can be obtained under the best embodiment conditions). The gas is fully foamed, which is conducive to the formation of highly stable foam. Furthermore, when the included angle between the second inlet and the third inlet is designed to be 180°, the wear on the equipment can be effectively reduced.

[0059] Finally, it should be noted that the above embodiments and examples are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments and examples, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments or examples, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments or examples of the present invention.

Claims

1. A mixing device, characterized by It includes a first mixing chamber, in which a fluid disperser is disposed, the fluid disperser being used to disperse a first fluid and rotate it into the first mixing chamber to mix with a second fluid; The system also includes a second mixing chamber connected to the first mixing chamber. A mixer is disposed within the second mixing chamber to mix the first fluid and the second fluid. A disperser injects the first fluid tangentially into the second fluid within the first mixing chamber, causing the first fluid to rotate within the chamber and increasing the shear force exerted by the first fluid on the second fluid. The first mixing chamber is provided with a first inlet, a second inlet, and a third inlet. The first inlet is connected to the inlet of the fluid disperser. The angles between the second inlet and the third inlet and the rotation axis of the mixer are both 90°. The angle between the second inlet and the third inlet is 180°, meaning the second inlet and the third inlet are coaxially opposite each other. The fluid disperser is rotatably mounted on the inner wall of the first mixing chamber. The mixer includes a support, a rotating shaft, and helical blades. The helical blades are mounted on the rotating shaft, which is rotatably connected to the support. The support is fixed to the inner wall of the second mixing chamber. The helical blades are arranged around the rotating shaft and fixed to the outer wall of the rotating shaft. The rear end blade is mounted at the rear end of the rotating shaft. The rear end blade is generally disc-shaped, with annular protrusions on its two end faces. The diameter of the annular protrusions on the end face closer to the front end is larger than the diameter of the annular protrusions on the end face closer to the rear end. The annular protrusions are used to shear the mixture of the first fluid and the second fluid.

2. The mixing device of claim 1, wherein, The fluid disperser includes a disc-shaped body with a fluid channel formed within it. The inlet of the fluid channel is located at the center of one end face of the body, and the fluid channel has multiple outlets. The outlets of the multiple fluid channels are located on the side of the body and are evenly distributed along the circumference of the body. The outlets of the fluid channels are tangent to the circumference of the side face.

3. The mixing device of claim 2, wherein, The fluid channel includes a flow guide cavity, which is connected to the inlet of the fluid channel and the outlets of the plurality of fluid channels.

4. The mixing apparatus according to claim 3, characterized in that, The aforementioned helical blade is an Archimedean curve helical blade with the rotation axis as the center of rotation.

5. The mixing apparatus according to claim 1, characterized in that, It also includes a heating and insulation system, which is used to control the temperature inside the mixing device between -30 and 180°C.

6. The mixing apparatus according to claim 4, characterized in that, The first mixing chamber, the second mixing chamber, or the mixer are all made of 5CrNiMo steel, Q125 steel, or Hastelloy.

7. A method for preparing foam, characterized in that, Foam is prepared using the mixing apparatus according to any one of claims 1-6, wherein gas is dispersed by a fluid disperser and rotated into a first mixing chamber to mix with the foaming liquid and foaming agent to form foam.

Images