A downhole biologic enzyme pour point depressant injection device and method

Abstract

This invention relates to a bottom-hole bio-enzyme pour point depressant injection device, comprising: a wellhead device; an injection device disposed within the injection well casing and located at the bottom-hole reservoir, for receiving a booster agent from the wellhead device and injecting the booster agent into the reservoir; a booster agent supply assembly, the outlet end of a storage tank connected to the wellhead device; the storage tank comprising an outer tank and an inner tank with inner and outer sleeves, the inner tank also having a rotatable stirring shaft installed inside, a stirring device fixedly installed at the upper end of the stirring shaft and located inside the inner tank; a water jacket surrounding the outer side of the inner tank, the water jacket being located in the space between the outer tank and the inner tank; an electromagnetic induction heating coil disposed within the injection device; the stirring device comprising: a stirring disc fixedly installed at the upper end of the stirring shaft; a plurality of hoses installed on the outer side of the lower end face of the stirring disc, the plurality of hoses being arranged in a circumferential array; and a plurality of stirring bodies fixedly installed on the hoses, the plurality of stirring bodies being arranged in a vertical array.

Description

Technical Field

[0001] This invention belongs to the technical field of bio-enzyme-assisted oil recovery, specifically a device and method for injecting bio-enzyme pour point depressant at the bottom of a well. Background Technology

[0002] In the water-drive bio-enzyme depressant and viscosity reducer injection technology, the auxiliary agent is water mixed with bio-enzyme depressant and viscosity reducer. Compared with chemical flooding to enhance oil recovery, bio-enzyme flooding technology has developed rapidly in recent years. This technology has also successfully improved oil recovery in oil reservoirs of high-pour-point and heavy oil blocks around the world.

[0003] The temperature, injection rate, mixing uniformity, and pH value of the booster all affect the pour point reduction effect of the bio-enzyme booster. In engineering practice, it is always desirable to inject the bio-enzyme booster into the bottom reservoir at a specified temperature, injection rate, and pH value.

[0004] However, traditional bottom-hole bio-enzyme pour point depressant injection devices rely on surface control of the booster temperature and injection rate, lacking necessary downhole control methods. This results in excessive deviations in booster temperature and injection rate at the injection device outlet, affecting oil displacement efficiency. Furthermore, traditional injection devices use agitators within the booster tank that drive agitator rods and blades to rapidly and uniformly mix the bio-enzyme and water. However, for large tanks, the vertically dispersed agitator blades cannot adequately mix the booster throughout the entire tank.

[0005] Therefore, there is an urgent need for a bottom-hole bio-enzyme pour point depressant injection device and method that can solve the above problems. Summary of the Invention

[0006] To address the aforementioned problems, this invention proposes a bottom-hole bio-enzyme pour point depressant injection device, comprising:

[0007] Wellhead device, installed at the wellhead of the injection well, is used to inject the driving agent into the injection well;

[0008] The injection device is installed inside the injection well casing and located at the bottom reservoir. It is used to receive the booster agent from the wellhead device and inject the booster agent into the reservoir.

[0009] The auxiliary driving agent supply component has a tank containing auxiliary driving agent, the inlet end of the tank is connected to an auxiliary driving agent replenishment device, and the outlet end of the tank is connected to a wellhead device.

[0010] The storage tank includes an outer tank and an inner tank that are connected by an inner and outer shell. The driving agent is contained in the inner tank. A rotatable stirring shaft is also installed inside the inner tank. The upper end of the stirring shaft extends through the tank cover and is connected to a servo motor installed on the tank cover.

[0011] The auxiliary driving agent supply assembly also includes a stirring device, which is fixedly installed at the upper end of the stirring shaft and located inside the inner tank;

[0012] A water jacket is installed around the outside of the inner tank, and the water jacket is located in the space between the outer tank and the inner tank; an electromagnetic induction heating coil is installed inside the filling device;

[0013] Furthermore, the stirring device includes:

[0014] The mixing disc is fixedly installed at the upper end of the mixing shaft;

[0015] Several hoses are installed on the outer side of the lower end face of the mixing plate, and the hoses are arranged in a circumferential array.

[0016] Several agitators are fixedly installed on a hose, and the agitators are arranged in a vertical array.

[0017] On the other hand, the present invention proposes a method for injecting bottom-hole bio-enzyme pour point depressant using the above-mentioned bottom-hole bio-enzyme pour point depressant injection device, comprising the following steps:

[0018] S1. Connect the inlet end of the storage tank to the auxiliary driving agent supply device and the outlet end to the auxiliary driving agent inlet of the wellhead device. Start the servo motor to stir the auxiliary driving agent in the inner tank.

[0019] S2. Start the water jacket to heat the inner tank, heating the driving agent in the inner tank to a temperature higher than the ideal temperature of the driving agent, but not exceeding the inactivation temperature of the biological enzyme.

[0020] S3. At the same time, the electromagnetic induction heating coil is energized to preheat the filling device for a period of time before the power is turned off.

[0021] S4. Start the injection pump and inject the booster into the mandrel tube of the injection device. The booster flows through the first outlet, the second outlet, the flow valve in the vertical passage and the booster outlet in sequence, and enters the bottom reservoir.

[0022] S5. The temperature sensor detects the temperature of the driving agent inside the mandrel tube and determines whether the electromagnetic induction heating coil needs to be activated to heat the driving agent inside the mandrel tube based on the detected temperature value.

[0023] Compared with the prior art, the advantages of the present invention are as follows:

[0024] 1. The bottom-hole bio-enzyme pour point depressant injection device of the present invention utilizes waste heat from the surface to heat the storage tank, combined with electromagnetic induction heating within the injection device. Taking into full account temperature drop, the device heats the booster agent in the storage tank to the highest possible temperature on the surface without causing irreversible denaturation and inactivation of the bio-enzyme. The electromagnetic induction heating within the injection device preheats the device, reducing temperature drop during the booster agent's flow, and also provides supplemental heating when the booster agent temperature is too low. Therefore, it can precisely control the temperature of the bio-enzyme booster agent as it is injected into the well from the booster agent outlet of the injection device, ensuring the bio-enzyme is in its optimal active state, fully exerting its viscosity-reducing and pour point-depressing effects, and improving the tertiary recovery rate of crude oil. Simultaneously, it fully utilizes waste heat energy from the oilfield, reducing oil displacement costs.

[0025] 2. This invention provides a cleverly designed flow valve adapted to a bottom-hole bio-enzyme pour point depressant injection device. Regardless of whether the pressure at the auxiliary agent discharge end exceeds or falls below a predetermined threshold, the space between the first surface forming the first path and the first acting surface increases or decreases, and the space between the second surface forming the second path and the second acting surface decreases or increases, ensuring a constant auxiliary agent flow rate through the flow valve. This maintains a stable injection rate of the bio-enzyme during the oil displacement process at a pre-set threshold, enhancing the positive interaction between the auxiliary agent and the reservoir rock and crude oil.

[0026] 3. The flow valve of the present invention, by changing the up and down position of the regulating ring body, adjusts the cross-section and volume of the second path formed by the regulating surface and the second working surface of the inner valve body, thereby changing the flow rate of the overall specified threshold of the flow valve, so as to adapt to more working conditions and meet the needs of different propulsion agents injected into the bottom reservoir under different conditions.

[0027] 4. The stirring device of this invention is configured inside the storage tank. The stirring shaft drives the stirring disc and the hose to rotate. Under the action of centrifugal force, the hose and the stirring body are thrown outward at a certain angle. The stirring agent in the inner tank is stirred by the hose and the stirring body. Not only can a vortex be formed to quickly and evenly mix the biological enzymes and water, but the stirring body installed on the hose is also distributed throughout the entire inner tank, which has higher mixing efficiency and is more uniform, thus improving the stirring effect.

[0028] 5. In the process of mixing the driving agent in the stirring device, the drug solution enters the driving agent from the drug solution nozzle of the stirring body. Under the action of centrifugal force, the hose and the stirring body are thrown outward, which increases the instantaneous speed of the drug solution spraying out and improves the mixing speed of the drug solution. Moreover, the stirring body is arranged in the entire inner tank, so the drug solution fills the entire inner tank when it comes out, which further shortens the time required for the drug solution to be mixed evenly.

[0029] 6. By setting up structures such as the first sealing ring, the second sealing ring, the gate, the first spring, and the second spring, the addition of acidic and alkaline solutions can be controlled by increasing the output speed of the servo motor to different degrees. Thus, during the mixing of the driving agent in the stirring device, the solution is sprayed into the driving agent from the solution nozzle of the stirring body. The increased output speed of the servo motor further improves the instantaneous speed of the solution spraying out, thereby further improving the mixing speed of the solution. Attached Figure Description

[0030] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0031] Figure 1 This is a diagram of the overall structure of the device;

[0032] Figure 2 This is a structural diagram of the filling device;

[0033] Figure 3 This is a cross-sectional view of the filling device;

[0034] Figure 4 for Figure 3 Enlarged view of a portion of point A in the middle;

[0035] Figure 5 for Figure 4 Enlarged view of a section at point B in the middle;

[0036] Figure 6 Here is a structural diagram of the flow valve;

[0037] Figure 7 Exploded view of the flow valve;

[0038] Figure 8 for Figure 5 Enlarged view of a section at point C;

[0039] Figure 9 Diagram showing the working state of the flow valve;

[0040] Figure 10 Diagram of the adjustment ring structure;

[0041] Figure 11 Component structure diagram for the drive agent supply;

[0042] Figure 12 Cross-section of components for drive agent supply Figure 1 ;

[0043] Figure 13 for Figure 13Enlarged view of a section at point D;

[0044] Figure 14 for Figure 13 Enlarged view of a section at point E in the middle;

[0045] Figure 15 Cross-section of the drive agent supply component Figure 2 And dissection Figure 2 Section and sectional view Figure 1 The included angle of the cross section is equal to the included angle between the adjacent first and second tubing sections;

[0046] Figure 16 Figure 15 Enlarged view of a section at point F in the middle;

[0047] Figure 17 Diagram of the stirring device.

[0048] In the diagram, the components are: injection device 100, electromagnetic induction heating coil 110, mandrel tube 120, first outlet 121, temperature sensor 123, intermediate cylinder 130, second outlet 131, conical platform 140, drive slip 141, rubber sleeve 150, front pusher 160, hydraulic cylinder 170, installation space 171, sealing spacer ring 172, vertical passage 173, auxiliary agent outlet 174, wellhead device 200, auxiliary agent inlet 210, injection well casing 300, auxiliary agent supply assembly 400, storage tank 500, inlet end 510, outlet end 52. 0, 530, water jacket 540, outlet 541, outer tank 550, inner tank 560, tank cover 561, hot water inlet pipe 562, first liquid inlet pipe 563, second liquid inlet pipe 564, stirring shaft 570, servo motor 571, annular mounting base 572, pH detection element 580, stirring device 600, stirring plate 610, mounting plate 611, first annular cavity 612, second annular cavity 613, first supply annular cavity 614, second supply annular cavity 615, liquid through pipe 616, first liquid Passage 617, second liquid passage 618, first inlet 619, second inlet 6110, hose mounting cavity 6111, hose 620, first hose 621, second hose 622, liquid outlet 623, flange 624, connecting structure 625, stirring body 630, liquid nozzle 631, gate 640, first spring 651, second spring 652, first sealing ring 661, second sealing ring 662, first gate 663, second gate 664, flow valve 700, auxiliary agent inlet 701, auxiliary agent outlet 702 The valve body 710 includes an inlet 711, an outlet 712, a flow channel 713 for the driving agent, a second working surface 714, an outer valve body 720, an annular flange 721, a first working surface 722, a valve core 730, an annular shoulder 731, a first surface 732, a second surface 733, an annular groove 734, a mounting cavity 735, a through groove 736, a first path 740, a second path 750, a compression spring 760, an adjusting ring 770, a guide drive disc 771, a connecting rod 772, an adjusting ring body 773, an adjusting surface 774, and a mounting part 775. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0050] like Figure 1-17As shown, this embodiment provides a bottom-hole bio-enzyme pour point depressant injection device, including an injection device 100 and a wellhead device 200. The injection device 100 is disposed within the casing 300 of the injection well and located at the bottom-hole reservoir. It receives the booster agent from the wellhead device 200 and injects the booster agent into the bottom-hole reservoir. The wellhead device 200 is disposed at the wellhead of the injection well and is used to inject the booster agent into the injection well. The wellhead device 200 includes a booster agent inlet 210 through which the booster agent is injected into the reservoir. It also includes a booster agent supply assembly 400, whose storage tank 500 contains the booster agent. The storage tank 500 has an inlet end 510 and an outlet end 520. The inlet end 510 is connected to a booster agent replenishment device, and the outlet end 520 is connected to the booster agent inlet 210 of the wellhead device 200 via a booster agent pipeline 530. The bio-enzyme pour point depressant in storage tank 500 is injected into the injection well through the auxiliary agent pipeline 530 to improve the wettability of the rock, reduce the viscosity of high pour point oil, improve and enhance the oil-water flow channel, and achieve the purpose of increasing oil injection and displacement.

[0051] To ensure the uniformity of the bio-enzyme depressant in the admixture, the admixture supply assembly 400 also includes a stirring device 600 extending into the storage tank 500. It is understood that temperature affects the depressing effect of the bio-enzyme; the bio-enzyme depressant and viscosity reducer exhibits the best activity and depressing effect at a certain ideal temperature.

[0052] Traditional waterflooding bio-enzyme pour point depressant injection systems often utilize the oilfield's waste heat recovery system to heat the surface storage tank 500, ensuring the bio-enzyme activity and thus fully utilizing waste heat energy to reduce oil displacement costs, since the bio-enzyme pour point depressant does not require or can not be heated to very high temperatures. Alternatively, an electromagnetic induction heater can be installed within the underground injection unit 100 to heat the bio-enzyme auxiliary agent within the unit, ensuring the bio-enzyme activity is at its optimal level.

[0053] However, using a waste heat recovery system to heat the above-ground equipment can lead to a temperature drop in the above-ground portion of the equipment, potentially causing the temperature of the auxiliary agent at the outlet of the refueling unit 100 to fall below the ideal value, and making it difficult to control the outlet temperature. Installing an electromagnetic induction heater within the underground refueling unit 100 requires a significant amount of additional electrical energy, resulting in higher costs.

[0054] To eliminate the aforementioned problems, in this embodiment, a water jacket 540 is installed inside the storage tank 500 to heat the booster agent inside, and an electromagnetic induction heating coil 110 is installed inside the injection device 100, connected to a frequency modulation cabinet on the ground via a cable. This heats the booster agent in the storage tank 500 to a first threshold temperature. Considering temperature drop, this first threshold temperature needs to be greater than the ideal temperature at which the booster agent is injected into the well from the booster agent outlet 174 of the injection device 100, and less than the bio-enzyme inactivation temperature. This ensures that the bio-enzyme does not undergo irreversible denaturation and inactivation due to excessively high temperatures, while also mitigating temperature drop as much as possible, keeping the booster agent temperature at the booster agent outlet 174 close to the ideal temperature. Therefore, the electromagnetic induction heating coil 110 has two functions: first, it can preheat the injection device 100 to reduce the possible temperature drop of the booster during its flow in the injection device 100, so that it can be maintained at the ideal temperature value when injected into the well from the booster outlet 174 of the injection device 100; second, when the booster temperature at the booster outlet 174 is much lower than the ideal temperature value, the electromagnetic induction heating coil 110 is restarted to raise the temperature of the booster.

[0055] Through the above configuration, the bottom-hole bio-enzyme pour point depressant injection device of this embodiment heats the storage tank 500 with waste heat from the surface, which, in conjunction with the electromagnetic induction heating within the injection device 100, fully considers the factor of temperature drop. It heats the auxiliary agent in the storage tank 500 to the highest possible temperature on the surface without causing irreversible denaturation and inactivation of the bio-enzyme. The electromagnetic induction heating within the injection device 100 preheats the device, reducing the temperature drop of the auxiliary agent during its flow within the device, and also provides supplemental heating when the auxiliary agent temperature is too low. Therefore, it can precisely control the temperature of the bio-enzyme auxiliary agent when it is injected into the well from the auxiliary agent outlet 174 of the injection device 100, ensuring that the bio-enzyme is in its optimal active state, fully exerting its viscosity-reducing and pour point-depressing effects, and improving the tertiary recovery rate of crude oil. Simultaneously, it fully utilizes waste heat energy from the oilfield, reducing oil displacement costs.

[0056] The injection device 100 in this embodiment includes a mandrel tube 120, an intermediate cylinder 130 coaxially sleeved on the outside of the mandrel tube 120, a conical platform 140 coaxially sleeved on the outside of the intermediate cylinder 130, a rubber sleeve 150, and a front pusher 160. The upper end of the mandrel tube 120 is open and communicates with the wellhead device 200, allowing the booster agent to enter the mandrel tube 120 from its upper end. The intermediate cylinder 130 is fixed relative to the mandrel tube 120, and the front pusher 160 is fixed relative to the intermediate cylinder 130. The conical platform 140 can slide vertically relative to the intermediate cylinder 130, and its upper end is provided with a drive slip 141. The rubber sleeve 150 can slide vertically relative to the intermediate cylinder 130 and is located between the conical platform 140 and the front pusher 160.

[0057] The lower end of the mandrel tube 120 is closed. The mandrel tube 120 includes a first outlet 121, and the intermediate cylinder 130 includes a second outlet 131. The first outlet 121 and the second outlet 131 are connected and located at the same height. Both the first outlet 121 and the second outlet 131 are located below the rubber sleeve 150. Thus, the injection device 100 of this embodiment can inject the booster into the reservoir through the first outlet 121 and the second outlet 131. The conical platform 140 squeezes the rubber sleeve 150 downward, causing it to expand and seal the annular space between the injection device 100 and the injection well casing 300, thereby realizing the injection of the booster into the reservoir at a specific depth.

[0058] The filling device 100 also includes a hydraulic cylinder 170 coaxially sleeved on the outside of the front pusher 160, and the hydraulic cylinder 170 is fixed relative to the spindle tube 120; an installation space 171 is formed between the inner wall of the hydraulic cylinder 170 and the outer wall of the intermediate cylinder 130, and a sealing ring 172 is fixedly installed in the installation space 171. The lower end of the sealing ring 172 is flush with the upper opening of the second water outlet 131, and the electromagnetic induction heating coil 110 is installed at the upper end of the sealing ring 172. Thus, the installation space 171 where the electromagnetic induction heating coil 110 is installed is completely isolated from the water passage by the sealing ring 172, thus protecting the electromagnetic induction heating coil 110. The hydraulic cylinder 170 is also provided with a plurality of vertical passages 173 arranged in a circumferential array, which are connected to the second outlet 131, and the upper end of the vertical passages 173 is flush with the lower end of the second outlet 131; the side wall of the hydraulic cylinder 170 is also provided with a booster outlet 174 connected to the vertical passages 173. Thus, the booster in the mandrel tube 120 flows sequentially through the first outlet 121, the second outlet 131, the vertical passages 173 and the booster outlet 174.

[0059] The vertical passage 173 is equipped with a flow valve 700. The second outlet 131 is connected to the auxiliary agent inlet 701 of the flow valve 700. The flow valve 700 also includes an auxiliary agent outlet 702, which is connected to the auxiliary agent outlet 174. The inner wall of the mandrel tube 120 is also equipped with a temperature sensor 123, which is located at the upper edge of the electromagnetic induction heating coil 110. This sensor is used to detect the temperature of the auxiliary agent in the mandrel tube 120 and determine whether to heat the auxiliary agent in the mandrel tube 120 through the electromagnetic induction heating coil 110 based on the detected temperature value.

[0060] Understandably, the injection rate of the booster during the injection into the bottom hole core affects the interaction between the booster and the reservoir rock and crude oil to a certain extent. Therefore, it is necessary to maintain the injection rate of the bio-enzyme during the oil displacement process at a pre-set threshold. However, traditional bottom hole bio-enzyme pour point depressant injection devices only focus on controlling the flow rate above the well and lack necessary downhole control measures.

[0061] To overcome the aforementioned defects, in this embodiment, the flow valve 700 includes a tubular inner valve body 710, which is provided with an inlet 711 and an outlet 712. A flow channel 713 for the driving agent extends between the inlet 711 and the outlet 712. A tubular outer valve body 720 is fixedly sleeved on the outside of the inner valve body 710, and an annular flange 721 extends inward from the outer valve body 720. The upper end face of the inner valve body 710 abuts against the lower end face of the annular flange 721. A valve core 730 is slidably disposed inside the inner valve body 710, and the valve core 730 is coaxial with the inner valve body 710. The valve core 730 engages with the annular flange 721.

[0062] In other words, the valve core 730 includes an annular shoulder 731, and the annular shoulder 731 is configured with a first surface 732 that matches the first working surface 722 of the annular flange 721 and a second surface 733 that matches the second working surface 714 of the inner valve body 710.

[0063] A first path 740 with a first variable volume and a first variable cross-sectional area is formed between the first surface 732 and the first working surface 722, and a second path 750 with a second variable volume and a second variable cross-sectional area is formed between the second surface 733 and the second working surface 714, wherein the first variable volume and the second variable volume are equal under a predetermined threshold inlet pressure.

[0064] Specifically, the flow valve 700 also includes a compression spring 760 disposed in the inner valve body 710, and the compression spring 760 is coaxial with the inner valve body 710. The compression spring 760 is sleeved on the outside of the valve core 730, and the lower end of the compression spring 760 is connected to the inner valve body 710, and the upper end is connected to the lower end face of the annular shoulder 731, so that the valve core 730 moves up and down in the inner valve body 710 in response to changes in inlet pressure.

[0065] The inner valve body 710 also includes a horizontally arranged auxiliary agent discharge end 702, which is connected to the outlet 712. The upper end of the outer valve body 720 is provided with an auxiliary agent discharge end 702, which is connected to the inlet 711.

[0066] When the pressure at the auxiliary displacement outlet 702 exceeds a predetermined threshold, the compression spring 760 is compressed, increasing the first variable volume and decreasing the second variable volume, thereby maintaining a fixed auxiliary displacement flow rate from the flow valve 700. Conversely, when the pressure at the auxiliary displacement outlet 702 drops below the predetermined threshold, the first variable volume decreases and the second variable volume increases, again maintaining a fixed auxiliary displacement flow rate from the flow valve 700.

[0067] In other words, under the pressure of the auxiliary driving agent discharge end 702 at the specified threshold, the space between the first surface 732 of the annular shoulder 731 and the first working surface 722 of the annular flange 721 is equal to the space between the second surface 733 of the annular shoulder 731 and the second working surface 714 of the inner valve body 710.

[0068] When the pressure at the discharge end 702 of the auxiliary driving agent exceeds the specified threshold pressure, the space between the first surface 732 and the first working surface 722 forming the first path 740 increases, and the space between the second surface 733 and the second working surface 714 forming the second path 750 decreases, but the flow rate of the auxiliary driving agent through the flow valve 700 remains constant.

[0069] When the pressure at the discharge end 702 of the auxiliary agent drops below a specified threshold, the space between the first surface 732 and the first working surface 722 forming the first path 740 decreases, and the space between the second surface 733 and the second working surface 714 forming the second path 750 increases, but the flow rate of the auxiliary agent through the flow valve 700 remains constant again.

[0070] Preferably, the first surface 732 and the second surface 733 of the annular shoulder 731 are both inclined, and the first working surface 722 of the annular flange 721 and the second working surface 714 of the inner valve body 710 are also inclined, with the inclination angles being the same as those of the first surface 732 and the second surface 733, respectively.

[0071] Through the above configuration, a cleverly designed flow valve 700 is provided, adapted to a bottom-hole bio-enzyme pour point depressant injection device. Regardless of whether the pressure at the auxiliary agent discharge end 702 exceeds or falls below a predetermined threshold, the space between the first surface 732 and the first action surface 722 forming the first path 740 increases or decreases, and the space between the second surface 733 and the second action surface 714 forming the second path 750 decreases or increases, ensuring that the auxiliary agent flow rate through the flow valve 700 remains constant. This maintains the injection rate of the bio-enzyme during the oil displacement process at a pre-set predetermined threshold, enhancing the positive interaction between the auxiliary agent and the reservoir rock and crude oil.

[0072] In this embodiment, a vertical annular groove 734 is formed on one side of the second surface 733 of the annular shoulder 731, and a slidable adjusting ring 770 is provided in the annular groove 734. Specifically, the upper end of the valve core 730 is also provided with a mounting cavity 735, and the side wall of the mounting cavity 735 is provided with a plurality of arrayed through grooves 736 communicating with the annular groove 734; the adjusting ring 770 includes a guide drive disk 771 and a plurality of connecting rods 772 arranged in an array and mounted on the side wall of the guide drive disk 771. The adjusting ring 770 also includes an adjusting ring body 773 disposed on the outer periphery of the guide drive disk 771, and the end of the connecting rod 772 away from the guide drive disk 771 is mounted on the inner side wall of the adjusting ring body 773.

[0073] The adjusting ring body 773 is slidably mounted in the annular groove 734, and the guide drive disk 771 is slidably mounted in the mounting cavity 735. The connecting rod 772 passes through the through groove 736 to connect with the adjusting ring body 773 and the guide drive disk 771 respectively. The adjusting ring body 773 is provided with an adjusting surface 774 that matches the second surface 733 of the annular shoulder 731, and the adjusting surface 774 and the second acting surface 714 of the inner valve body 710 form a second path 750. An actuator (not shown) that can drive the guide drive disk 771 to rise and fall is also provided in the mounting cavity 735, and a cover 780 is provided at the upper end of the mounting cavity 735 to seal the mounting cavity 735.

[0074] By changing the upper and lower positions of the regulating ring body 773, the cross-section and volume of the second path 750 formed by the regulating surface 774 and the second working surface 714 of the inner valve body 710 are adjusted, thereby changing the overall flow rate of the flow valve 700 at the specified threshold, thus adapting to more working conditions and meeting the needs of different propulsion agents injected into bottom well reservoirs under different conditions.

[0075] Preferably, the upper end of the guide drive disk 771 is also provided with a mounting part 775 to facilitate connection with the actuation end of the actuator.

[0076] In this embodiment, the storage tank 500 includes an outer tank 550 and an inner tank 560 connected by an inner and outer shell, with the driving agent contained within the inner tank 560. A water jacket 540 is arranged around the outside of the inner tank 560 and is located in the space between the outer tank 550 and the inner tank 560. A tank cover 561 is provided at the upper end of the inner tank 560 to close the inner tank 560. A hot water inlet pipe 562 is provided on the tank cover 561, and the outlet of the hot water inlet pipe 562 extends to the outside of the inner tank 560 and communicates with the water jacket 540. A cold water outlet pipe (not shown) is also provided at the lower end of the outer tank 550, and the cold water outlet pipe communicates with the outlet 541 of the water jacket 540. Thus, the waste heat utilization system of the oilfield adds hot water into the water jacket 540 through the hot water inlet pipe 562 to heat the driving agent in the inner tank 560. After the hot water and the driving agent exchange heat, the cooled water is discharged into the waste heat utilization system through the outlet 541 of the water jacket 540, thus completing one heating cycle.

[0077] A rotatable stirring shaft 570 is installed inside the inner tank 560, and the stirring shaft 570 is coaxial with the inner tank 560. The upper end of the stirring shaft 570 extends through the tank cover 561 and is connected to a servo motor 571 mounted on the tank cover 561. The stirring device 600 is fixedly installed at the upper end of the stirring shaft 570 and located inside the inner tank 560. Thus, the servo motor 571 drives the stirring shaft 570 and the stirring device 600 to rotate at a predetermined speed threshold, mixing the admixture in the inner tank 560 evenly and improving the admixture effect.

[0078] Understandably, the traditional stirring device 600 uses the stirring shaft 570 to drive the stirring rod and stirring blades to rotate. The stirring rod and stirring blades cause the auxiliary agent to form a vortex, so as to quickly and evenly mix the biological enzymes and water. However, for large storage tanks 500, the vertically discrete stirring blades cannot fully mix the auxiliary agent in the entire tank. If a lifting mechanism is configured to drive the entire stirring device and its connected drive components to move up and down together so that the stirring blades cover the space inside the tank, it will significantly increase the structural complexity of the entire auxiliary agent supply component 400 and increase the operating cost of the device.

[0079] To overcome the aforementioned defects, the stirring device 600 of this embodiment includes a stirring disc 610 fixedly installed on the upper end of a stirring shaft 570 and a plurality of flexible hoses 620 installed on the outer side of the lower end face of the stirring disc 610. The plurality of flexible hoses 620 are arranged in a circumferential array, and a plurality of vertically arranged stirring elements 630 are installed on the flexible hoses 620. Thus, the stirring shaft 570 drives the stirring disc 610 and the flexible hoses 620 to rotate. Under the action of centrifugal force, the flexible hoses 620 and the stirring elements 630 are thrown outward at a certain angle. The stirring agent in the inner tank 560 is stirred through the flexible hoses 620 and the stirring elements 630. This not only forms a vortex to quickly and evenly mix the biological enzymes and water, but also, since the stirring elements 630 installed on the flexible hoses 620 are distributed throughout the entire inner tank 560, the mixing efficiency is higher and more uniform, thus improving the stirring effect.

[0080] Preferably, a mounting plate 611 is provided at the center of the lower end face of the mixing plate 610, and an annular mounting seat 572 is fixedly installed at the upper end of the mixing shaft 570. The mixing plate 610 is fixedly installed on the annular mounting seat 572 through the mounting plate 611. Thus, the mixing device 600 is fixedly installed on the mixing shaft 570 through the cooperation of the mounting plate 611 and the annular mounting seat 572.

[0081] It is understandable that each enzyme has an optimal pH value, at which the catalytic reaction rate is at its maximum. A pH value that is too low will alter the ionization of groups at the enzyme's active site, thus reducing enzyme activity. A pH value that is too high will disrupt many non-covalent bonds maintaining the enzyme's three-dimensional structure, leading to denaturation of the enzyme protein itself.

[0082] Therefore, the stirring device 600 of this embodiment also integrates supporting supply equipment for acidic and alkaline medicinal solutions. Specifically, the stirring plate 610 is provided with a first annular receiving cavity 612 and a second annular receiving cavity 613 to respectively contain the acidic and alkaline medicinal solutions. For ease of description, the first annular receiving cavity 612 contains the acidic medicinal solution, and the second annular receiving cavity 613 contains the alkaline medicinal solution. The mixing plate 610 is also provided with a first supply ring cavity 614 and a second supply ring cavity 615, which are respectively connected to the first annular receiving cavity 612 and the second annular receiving cavity 613. The positions of the first supply ring cavity 614 and the second supply ring cavity 615 correspond to the positions of the hose 620. The hose 620 includes a first hose 621 and a second hose 622, which are respectively connected to the first supply ring cavity 614 and the second supply ring cavity 615. The first hose 621 and the second hose 622 are arranged at intervals. The outside of the mixing body 630 is provided with a liquid spray nozzle 631, and the outside of the hose 620 is provided with a liquid outlet 623 in the same number as the mixing body 630. The liquid outlet 623 is connected to the liquid spray nozzle 631.

[0083] Therefore, when the pH value of the driving agent is too high, the acidic solution in the first annular cavity 612 enters the driving agent sequentially through the first supply annular cavity 614, the first hose 621, and the solution nozzle 631 of the stirrer 630 to lower the pH value of the driving agent. Conversely, when the pH value of the driving agent is too low, the alkaline solution in the second annular cavity 613 enters the driving agent sequentially through the second supply annular cavity 615, the second hose 622, and the solution nozzle 631 of the stirrer 630 to raise the pH value of the driving agent.

[0084] With the above settings, during the mixing process of the driving agent in the stirring device 600, the liquid enters the driving agent from the liquid spray nozzle 631 of the stirring body 630. Under the action of centrifugal force, the hose 620 and the stirring body 630 are thrown outward, which increases the instantaneous speed of the liquid spray and improves the mixing speed of the liquid. Moreover, the stirring body 630 is arranged in the entire inner tank 560, so the liquid fills the entire inner tank 560 when it comes out, which further shortens the time required for the liquid to be mixed evenly.

[0085] Understandably, in order to facilitate the determination of the pH value of the driving agent inside the inner tank 560, a pH value detection element 580 is also installed on the side of the outer tank 550, and the detection head of the pH value detection element 580 extends into the interior of the inner tank 560.

[0086] Specifically, the lower end of the first supply ring cavity 614 is also provided with a number of liquid medicine passage pipes 616 equal to the number of first hoses 621, and the liquid medicine passage pipes 616 pass through the lower opening of the second supply ring cavity 615 and are connected to the inlet of the first hose 621. The position of the liquid medicine passage pipes 616 corresponds to the position of the first hose 621. Thus, the first supply ring cavity 614 is connected to the first hose 621 through the liquid medicine passage pipes 616, while the second supply ring cavity 615 is directly connected to the second hose 622. The outer periphery of the first annular cavity 612 is provided with a first liquid passage 617, the same number as the first tubing 621, and the first liquid passage 617 is connected to the first supply annular cavity 614. The outer periphery of the second annular cavity 613 is provided with a second liquid passage 618, the same number as the second tubing 622, and the second liquid passage 618 is connected to the second supply annular cavity 615. Thus, the liquid enters the first supply annular cavity 614 and the second supply annular cavity 615 from the first annular cavity 612 and the second annular cavity 613, respectively. The canister cover 561 is also provided with a first liquid inlet pipe 563 and a second liquid inlet pipe 564, and the outlets of the first liquid inlet pipe 563 and the second liquid inlet pipe 564 extend to the inner side of the inner canister 560, and are respectively connected to the first inlet 619 of the first annular cavity 612 and the second inlet 6110 of the second annular cavity 613. Thus, when the liquid in the first annular cavity 612 and the second annular cavity 613 is used up, it can be replenished from the outside to the first annular cavity 612 and the second annular cavity 613.

[0087] In this embodiment, the outer side of the lower end face of the stirring plate 610 is provided with the same number of hose mounting cavities 6111 as the hoses 620. The hoses 620 are installed in the hose mounting cavities 6111. The hose mounting cavities 6111 are connected to the liquid medicine pipe 616 and the second supply ring cavity 615 respectively, so that the liquid medicine enters the hoses 620 through the hose mounting cavities 6111. The upper end face of the hose 620 is disposed within the hose mounting cavity 6111, and a flange 624 is installed on the upper end face of the hose 620. A spring element is sleeved on the outer side of the hose 620, and the upper end of the spring element abuts against the lower end face of the flange 624, while the lower end of the spring element abuts against the bottom end face of the hose mounting cavity 6111. This allows the hose 620, thrown outward under centrifugal force, to overcome the elastic force of the spring element, causing the flange 624 to move downward and compress the spring. A gate 640 is also installed on the upper end of the flange 624, so that the flange 624 can drive the gate 640 to move, thereby closing or opening the hose mounting cavity 6111.

[0088] Specifically, a first spring 651 is sleeved on the outer side of the first hose 621, and a second spring 652 is sleeved on the outer side of the second hose 622. The elastic coefficient of the first spring 651 is smaller than that of the second spring 652. A first sealing ring 661 and a second sealing ring 662 are fixedly installed in the hose mounting cavity 6111 and above the flange 624, respectively. The first sealing ring 661 is located above the second sealing ring 662. A first gate 663 and a second gate 664 are respectively opened at the center of the first sealing ring 661 and the second sealing ring 662. A gate plate 640 is installed above the flange 624 through a connecting structure 625 provided on the upper end face of the flange 624, and the gate plate 640 is located inside the first gate 663.

[0089] Therefore, the servo motor 571 outputs its working speed to drive the stirring device 600 to rotate at a specified speed, stirring the auxiliary agent in the inner tank 560; when the pH value detection element 580 detects that the pH value of the auxiliary agent in the inner tank 560 exceeds the specified value, the servo motor 571 outputs a first speed, which is greater than the working speed, increasing the rotational speed of the stirring device 600. The centrifugal force on the hose 620 increases, causing the flange 624 and the gate 640 to move downwards. The first spring 651 and the second spring 652 are both compressed. Due to the elasticity of the first spring 651... The coefficient of the second spring 652 is smaller than that of the second spring 652. The first hose 621 moves downward a greater distance than the second hose 622. At this time, the gate 640 connected to the first hose 621 is disengaged from the first sealing ring 661 and located between the first sealing ring 661 and the second sealing ring 662. The first supply ring cavity 614 is no longer sealed. The gate 640 connected to the second hose 622 has not yet disengaged from the first sealing ring 661. The second supply ring cavity 615 is still sealed. The acidic liquid in the first supply ring cavity 614 can enter the first hose 621 and then be thrown out through the liquid nozzle 631.

[0090] When the pH detection element 580 detects that the pH value of the driving agent in the inner tank 560 is lower than the specified value, the servo motor 571 outputs a second speed, which is greater than the first speed, further increasing the rotation speed of the stirring device 600. The centrifugal force on the hose 620 further increases, and it continues to move downward with the flange 624 and the gate 640. At this time, the gate 640 connected to the first hose 621 disengages from the second sealing ring 662 and is located below the second sealing ring 662. The first supply ring cavity 614 is still closed. The gate 640 connected to the second hose 622 disengages from the first sealing ring 661 and is located between the first sealing ring 661 and the second sealing ring 662. The second supply ring cavity 615 is no longer closed, and the alkaline solution in the second supply ring cavity 615 can enter the second hose 622 and then be thrown out through the solution nozzle 631.

[0091] By configuring the first sealing ring 661, the second sealing ring 662, the gate 640, the first spring 651, and the second spring 652, the addition of acidic and alkaline solutions can be controlled by increasing the output speed of the servo motor 571 to different degrees. Thus, during the mixing of the driving agent in the stirring device 600, the solution is sprayed into the driving agent from the solution nozzle 631 of the stirring body 630. The increased output speed of the servo motor 571 further improves the instantaneous speed of the solution spraying out, thereby further improving the mixing speed of the solution.

[0092] As another specific embodiment, a method for injecting bottom-hole bio-enzyme pour point depressant is also provided, comprising the following steps:

[0093] S1. Connect the inlet end 510 of the storage tank 500 to the auxiliary driving agent supply device, and connect the outlet end 520 to the auxiliary driving agent inlet 210 of the wellhead device 200. Start the servo motor 571 to stir the auxiliary driving agent in the inner tank 560.

[0094] S2. Start the water jacket 540 to heat the inner tank 560, heating the driving agent in the inner tank 560 to a temperature higher than the ideal temperature of the driving agent, but not exceeding the inactivation temperature of the biological enzyme.

[0095] S3. At the same time, the electromagnetic induction heating coil 110 is energized to preheat the filling device 100 for a period of time before the power is turned off.

[0096] S4. Start the injection pump and inject the booster into the mandrel tube 120 of the injection device 100. The booster flows through the first outlet 121, the second outlet 131, the flow valve 700 in the vertical passage 173 and the booster outlet 174 in sequence, and enters the bottom reservoir.

[0097] S5. Temperature sensor 123 detects the temperature of the driving agent in mandrel tube 120 and determines whether electromagnetic induction heating coil 110 needs to be activated to heat the driving agent in mandrel tube 120 based on the detected temperature value.

[0098] In this embodiment, in step S1, the servo motor 571 initially operates at its working speed;

[0099] When the pH value detection element 580 detects that the pH value of the driving agent in the inner tank 560 exceeds the specified value, the servo motor 571 outputs the first speed, and the first speed is greater than the working speed, and the acidic liquid in the first supply ring cavity 614 is thrown out through the liquid spray nozzle 631.

[0100] When the pH detection element 580 detects that the pH value of the driving agent in the inner tank 560 is lower than the specified value, the servo motor 571 outputs a second speed, and the second speed is greater than the first speed. The alkaline liquid in the second supply ring cavity 615 is thrown out through the liquid nozzle 631.

[0101] In this embodiment, in step S4, before starting the injection pump, the actuator in the mounting cavity 735 drives the adjustment ring 770 to rise and fall, adjusting the cross-section and volume of the second path 750 formed by the adjustment surface 774 and the second working surface 714 of the inner valve body 710, thereby changing the specified threshold of the output flow of the flow valve 700.

[0102] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A bottom-hole bio-enzyme pour point depressant injection device, comprising: Wellhead device, installed at the wellhead of the injection well, is used to inject the driving agent into the injection well; The injection device is installed inside the injection well casing and located at the bottom reservoir. It is used to receive the booster agent from the wellhead device and inject the booster agent into the reservoir. The auxiliary driving agent supply component has a tank containing auxiliary driving agent, the inlet end of the tank is connected to an auxiliary driving agent replenishment device, and the outlet end of the tank is connected to a wellhead device. The storage tank includes an outer tank and an inner tank that are connected by an inner and outer shell. The driving agent is contained in the inner tank. A rotatable stirring shaft is also installed inside the inner tank. The upper end of the stirring shaft extends through the tank cover and is connected to a servo motor installed on the tank cover. The auxiliary driving agent supply assembly also includes a stirring device, which is fixedly installed at the upper end of the stirring shaft and located inside the inner tank; The feature is that a water jacket is arranged around the outside of the inner tank, and the water jacket is located in the space between the outer tank and the inner tank; an electromagnetic induction heating coil is provided inside the filling device; Furthermore, the stirring device includes: The mixing disc is fixedly installed at the upper end of the mixing shaft; Several hoses are installed on the outer side of the lower end face of the mixing plate, and the hoses are arranged in a circumferential array. Several stirring elements are fixedly installed on a hose, and the stirring elements are arranged in a vertical array; The refueling device includes: The mandrel tube is open at the top and closed at the bottom; the top end is connected to the wellhead device, the mandrel tube has a first water outlet, and a temperature sensor is installed on the inner wall of the mandrel tube, with the temperature sensor located at the upper edge of the electromagnetic induction heating coil. The intermediate cylinder is coaxially fixedly sleeved on the outside of the mandrel tube, and is provided with a second water outlet. The first water outlet and the second water outlet are connected and located at the same height. A hydraulic cylinder is coaxially fixedly sleeved on the outside of the intermediate cylinder. An installation space is formed between the inner wall of the hydraulic cylinder and the outer wall of the intermediate cylinder. A closed spacer is fixedly installed in the installation space. The lower end of the closed spacer is flush with the upper opening of the second water outlet. The electromagnetic induction heating coil is installed on the upper end of the closed spacer. The hydraulic cylinder is also provided with several vertical passages in a circumferential array that are connected to the second water outlet, and the upper end of the vertical passages is flush with the lower end of the second water outlet; the side wall of the hydraulic cylinder is also provided with a booster outlet that is connected to the vertical passages. A flow valve is installed in the vertical passage. The second outlet is connected to the inlet end of the flow valve. The flow valve also includes an outlet end for the driving agent, and the outlet end is connected to the outlet end of the driving agent. The mixing plate is provided with a first annular receiving cavity and a second annular receiving cavity to respectively contain acidic and alkaline drug solutions; The mixing plate is also provided with a first supply ring cavity and a second supply ring cavity, and the first supply ring cavity and the second supply ring cavity are respectively connected to the first annular receiving cavity and the second annular receiving cavity. The position of the supply ring cavity corresponds to the position of the hose. The hose includes a first hose and a second hose, and the first hose and the second hose are respectively connected to the first supply ring cavity and the second supply ring cavity, and the first hose and the second hose are arranged at intervals. The outside of the agitator is provided with a liquid spray nozzle, and the outside of the hose is provided with the same number of liquid outlets as the agitator, and the liquid outlets are connected to the liquid spray nozzles. A pH value detection element is also installed on the side of the outer tank, and the detection head of the pH value detection element extends into the interior of the inner tank.

2. The wellbore bottom biological enzyme pour point depressant injection device according to claim 1, characterized in that, Flow valves include: The inner valve body is tubular and has an inlet and an outlet. A flow channel for the driving agent extends between the inlet and the outlet. The inner valve body has a driving agent discharge end arranged laterally, and the driving agent discharge end is connected to the outlet. The outer valve body is tubular and is fixedly sleeved on the outside of the inner valve body. It has an annular flange extending inward, and the upper end face of the inner valve body abuts against the lower end face of the annular flange. The upper end of the outer valve body has a drive agent discharge end, which is connected to the inlet. The valve core is slidably disposed inside the inner valve body and is provided with an annular shoulder. The annular shoulder is provided with a first surface that matches the first working surface of the annular flange and a second surface that matches the second working surface of the inner valve body. A compression spring is located inside the inner valve body and sleeved on the outside of the valve core. The lower end of the compression spring is connected to the inner valve body, and the upper end is connected to the lower end face of the annular shoulder. Wherein, a first path with a first variable volume is formed between the first surface and the first working surface, and a second path with a second variable volume is formed between the second surface and the second working surface, and the first variable volume and the second variable volume are equal under a specified threshold inlet pressure.

3. The wellbore bottom biological enzyme pour point depressant injection device according to claim 2, characterized in that, The first and second surfaces of the annular shoulder are both inclined, and the first working surface of the annular flange and the second working surface of the inner valve body are also inclined, with the inclination angles being the same as those of the first and second surfaces, respectively.

4. The wellbore bottom biological enzyme pour point depressant injection device according to claim 2, characterized in that, A vertical annular groove is provided on one side of the second surface of the annular shoulder, and an adjustable ring is provided in the annular groove; The valve core has an installation cavity at its upper end, and the side wall of the installation cavity has a through groove with several arrayed annular grooves. The adjusting ring includes a guide drive disk and a number of connecting rods arranged in an array on the side wall of the guide drive disk. The adjusting ring also includes an adjusting ring body disposed on the outer periphery of the guide drive disk, and the end of the connecting rod away from the guide drive disk is installed on the inner side wall of the adjusting ring body. The adjusting ring body is slidably mounted in the annular groove, the guide drive disk is slidably mounted in the mounting cavity, and the connecting rod passes through the through groove to connect with the adjusting ring body and the guide drive disk respectively. The regulating ring body is provided with an regulating surface that matches the second surface of the annular shoulder, and the regulating surface forms a second path with the second working surface of the inner valve body; The mounting cavity is also equipped with an actuator that can drive the guide drive disc to rise and fall.

5. The wellbore bottom biological enzyme pour point depressant injection device according to claim 1, characterized in that, The lower end of the first supply ring cavity is also provided with a number of liquid medicine passage tubes equal to the number of first hoses, and the liquid medicine passage tubes pass through the lower opening of the second supply ring cavity and are connected to the inlet of the first hoses. The position of the liquid medicine passage tubes corresponds to the position of the first hoses. The outer periphery of the first annular cavity is provided with a first liquid passage, the same number as the number of the first tubing, and the first liquid passage is connected to the first supply annular cavity. The outer periphery of the second annular cavity is provided with a second liquid passage, the same number as the number of second tubing, and the second liquid passage is connected to the second supply annular cavity.

6. The wellbore bottom biological enzyme pour point depressant injection device according to claim 1, characterized in that, The lower end face of the mixing plate has a hose mounting cavity with the same number of hoses as the outer side. The hoses are installed in the hose mounting cavity, and the hose mounting cavity is connected to the liquid medicine pipe and the second supply ring cavity respectively. The upper end face of the hose is positioned inside the hose mounting cavity, and a flange is mounted on the upper end face of the hose. The first flexible tube is fitted with a first spring on its outer side, and the second flexible tube is fitted with a second spring on its outer side, wherein the elastic coefficient of the first spring is smaller than that of the second spring. A first sealing ring and a second sealing ring are fixedly installed inside the hose installation cavity and above the flange, respectively, with the first sealing ring located above the second sealing ring. A first gate and a second gate are respectively opened at the center of the first sealing ring and the second sealing ring. A gate is also installed at the upper end of the flange via a connecting structure, and the gate is located inside the first gate.

7. A method for injecting bottom-hole bio-enzyme pour point depressant, using the bottom-hole bio-enzyme pour point depressant injection device as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Connect the inlet end of the storage tank to the auxiliary driving agent supply device and the outlet end to the auxiliary driving agent inlet of the wellhead device. Start the servo motor to stir the auxiliary driving agent in the inner tank. S2. Start the water jacket to heat the inner tank, heating the driving agent in the inner tank to a temperature higher than the ideal temperature of the driving agent, but not exceeding the inactivation temperature of the biological enzyme. S3. At the same time, the electromagnetic induction heating coil is energized to preheat the filling device for a period of time before the power is turned off. S4. Start the injection pump and inject the booster into the mandrel tube of the injection device. The booster flows through the first outlet, the second outlet, the flow valve in the vertical passage and the booster outlet in sequence, and enters the bottom reservoir. S5. The temperature sensor detects the temperature of the driving agent inside the mandrel tube and determines whether the electromagnetic induction heating coil needs to be activated to heat the driving agent inside the mandrel tube based on the detected temperature value.

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