Underground intelligent separate injection anti-blocking flow adjusting structure

Abstract

The embodiment of the invention relates to an underground intelligent separate injection anti-blocking flow adjusting structure, a body of the structure is arranged in a water nozzle of an oil field intelligent separate injection system, the body comprises an overflowing part and a dredging part, and a plurality of micropores are distributed in the side wall of a blind hole in an array; acid liquor is filled between a first piston of the dredging part and the bottom of a first cavity, a second piston is slidably connected into a second cavity, and a guide rod is fixedly connected to the bottom end face of the second piston; the end, away from the second piston, of the guide rod is fixedly connected to the bottom of the second cavity, a first liquid storage area is formed between the second piston and the third piston, and a second communicating pipe is arranged between the first liquid storage area and the overflowing part. According to the embodiment of the invention, the acid liquor is injected into the structural body with the micropores, and the micropores have the effect of balancing the flow, so that the acid liquor uniformly flows into a blocked flow channel, and calcium scaling and thick oil or asphalt blockage are dissolved; the front-back pressure difference formed before and after the overflowing part is blocked enables acid liquor to flow into a channel of the overflowing part, and blocked solid particles are dissolved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of stratified water injection and oil recovery in oil and gas wells, and in particular to an underground intelligent stratified water injection and anti-blocking flow regulating structure. Background Art

[0002] As the oil layer is exploited, its energy is gradually consumed, causing the pressure to drop. In order to inject water into the oil layer to increase the energy of the oil layer, the oil layer's requirements for the amount of water injected will vary depending on the different oil layers in the oil field.

[0003] At present, a large number of small hole structures are used in oilfield downhole equipment for throttling to measure and control the injection and production flow of each layer. However, during long-term downhole work, the holes are often blocked due to particles and scaling, which requires backwashing or well maintenance, resulting in huge time waste and economic losses.

[0004] Therefore, it is necessary to improve one or more problems existing in the above-mentioned related technical solutions.

[0005] It should be noted that this section is intended to provide background or context for the technical solutions of the present invention stated in the claims. The description herein is not admitted to be prior art by inclusion in this section. Summary of the invention

[0006] The purpose of the embodiments of the present invention is to provide a downhole intelligent injection anti-blocking flow regulating structure, thereby overcoming one or more problems caused by the limitations and defects of the relevant technology at least to a certain extent.

[0007] According to an embodiment of the present disclosure, a downhole intelligent injection anti-blocking flow regulating structure is provided, the main body of which is arranged in a water nozzle of an oilfield intelligent injection system, and includes:

[0008] The main body comprises a flow-through portion and a dredging portion, wherein the flow-through portion and the dredging portion are arranged in parallel in the longitudinal direction;

[0009] The flow portion is a blind hole opened in the body along the longitudinal direction of the body, and a plurality of micropores are distributed in an array on the side wall of the blind hole;

[0010] The dredging part is used to provide acid solution to dissolve the blockage to the flow part when the flow part is blocked, so as to make the liquid in the flow part flow smoothly;

[0011] The dredging part comprises:

[0012] A first cavity, wherein the first cavity is arranged in the body along the longitudinal direction of the body, a first piston is slidably connected in the first cavity, and acid liquid is filled between the first piston and the bottom of the first cavity;

[0013] A second cavity, the second cavity is arranged in the body along the longitudinal direction of the body, adjacent to the first cavity, and a first connecting pipe is provided between the second cavity and the first cavity; a second piston is slidably connected in the second cavity, and a guide rod is fixedly connected to the bottom end surface of the second piston;

[0014] A third piston and a fourth piston are sequentially arranged on the guide rod, a first liquid storage area is formed between the second piston and the third piston, a second connecting pipe is arranged between the first liquid storage area and the flow portion, and a reset member is arranged between the fourth piston and the bottom of the second cavity.

[0015] In one embodiment of the present invention, when the flow-through portion is unobstructed, the pressure between the first piston and the bottom of the first cavity is greater than the pressure at the top of the first piston.

[0016] In one embodiment of the present invention, a second liquid storage area is formed between the third piston and the fourth piston, and when the flow portion is unobstructed, the first connecting pipe is connected to the second liquid storage area.

[0017] In one embodiment of the present invention, when the flow-through portion is blocked, the first connecting pipe is connected to the first liquid storage area.

[0018] In one embodiment of the present invention, a filter element is provided at the liquid inlet of the flow portion.

[0019] In one embodiment of the present invention, the filter element is provided with a plurality of through holes, and the plurality of through holes are used to filter the liquid entering the flow portion.

[0020] In one embodiment of the present invention, the guide rod is a sleeve with a hollow interior, and a longitudinally arranged ejector pin is fixedly connected to the interior of the sleeve, and one end of the ejector pin is connected to the second piston.

[0021] In one embodiment of the present invention, a connecting hole is provided at the bottom of the second cavity, an end of the sleeve away from the second piston is sealed with an air pipe, an inert gas is sealed inside the air pipe, and the air pipe is connected to one end of the catheter.

[0022] In one embodiment of the present invention, an annular groove is provided on the side of the main body, and expansion parts are arranged in the two annular grooves. A plurality of circulation parts are fixedly connected between the two expansion parts in a linear array so that the two expansion parts are connected. A connecting port is provided on the expansion part, and the connecting port is connected to one end of the catheter.

[0023] In one embodiment of the present invention, the acid solution is a mixed acid solution of hydrochloric acid and oxalic acid.

[0024] The technical solution provided by the embodiments of the present invention may have the following beneficial effects:

[0025] The present invention provides an underground intelligent injection anti-blocking flow regulating structure. On the one hand, after the flow passage is blocked, the pressure on the main body increases, so that the first piston and the second piston move downward, the first liquid storage area is connected to the first connecting pipe, and the acid flows into the flow passage to dissolve the blockage and make the flow passage unblocked. On the other hand, when the flow passage is blocked, the dredging part injects the acid into the structure with micropores, and the micropores have the function of balancing the flow, so that the acid flows evenly into the blocked flow passage, which can dissolve calcium scale and heavy oil or asphalt blockage. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification are used to explain the principles of the present disclosure. Obviously, the accompanying drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0027] Figure 1 A cross-sectional schematic diagram showing a downhole intelligent injection and anti-blocking flow regulating structure in an exemplary embodiment of the present invention;

[0028] Figure 2 A schematic diagram showing the combined structure of the sleeve and the second piston in an exemplary embodiment of the present invention is shown;

[0029] Figure 3 A schematic diagram showing the combined structure of the expansion member and the circulation member in an exemplary embodiment of the present invention is shown;

[0030] Figure numerals: 100, main body; 101, first piston; 102, acid liquid; 103, first connecting pipe; 200, dredging part; 201, second piston; 202, guide rod; 203, third piston; 204, fourth piston; 205, second connecting pipe; 206, reset part; 207, air pipe; 208, conduit; 209, expansion part; 210, circulation part; 211, ejector pin; 300, flow-through part; 301, filter element. DETAILED DESCRIPTION

[0031] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present invention will be more comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0032] In addition, the accompanying drawings are only schematic illustrations of embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and their repeated descriptions will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0033] This example embodiment provides a downhole intelligent injection anti-blocking flow regulating structure, the main body of which is arranged in the water nozzle of the oil field intelligent injection system, Figure 1 As shown, the underground intelligent injection and anti-blocking flow regulating structure may include: a main body 100, a dredging part 200 and a flow-through part 300.

[0034] The main body 100 includes a flow-through portion 300 and a dredging portion 200, and the flow-through portion 300 and the dredging portion 200 are arranged in parallel in the longitudinal direction;

[0035] The flow portion 300 is a blind hole opened in the body 100 along the longitudinal direction of the body 100, and a plurality of micro-holes are distributed in an array on the side wall of the blind hole;

[0036] The dredging part 200 is used to provide the blockage dissolving acid 102 to the flow part 300 when the flow part 300 is blocked, so as to make the liquid in the flow part 300 flow smoothly;

[0037] The dredging unit 200 includes:

[0038] The first cavity is arranged in the body 100 along the longitudinal direction of the body 100, a first piston 101 is slidably connected in the first cavity, and acid liquid 102 is filled between the first piston 101 and the bottom of the first cavity;

[0039] The second cavity is arranged in the body 100 along the longitudinal direction of the body 100, adjacent to the first cavity, and a first connecting pipe 103 is arranged between the second cavity and the first cavity; a second piston 201 is slidably connected in the second cavity, and a guide rod 202 is fixedly connected to the bottom end surface of the second piston 201;

[0040] A third piston 203 and a fourth piston 204 are sequentially provided on the guide rod 202, a first liquid storage area is formed between the second piston 201 and the third piston 203, a second connecting pipe 205 is provided between the first liquid storage area and the flow portion 300, and a reset member 206 is provided between the fourth piston 204 and the bottom of the second cavity.

[0041] Through the underground intelligent injection anti-blocking flow regulating structure, on the one hand, after the flow portion 300 is blocked, the pressure on the main body 100 increases, so that the first piston 101 and the second piston 201 move downward, the first liquid storage area is connected with the first connecting pipe 103, and the acid 102 flows into the flow portion 300 to dissolve the blockage and make the flow channel unblocked. On the other hand, when the flow portion 300 is blocked, the dredging part 200 injects the acid 102 into the structure with micropores. The micropores have the function of balancing the flow, so that the acid 102 can flow evenly into the blocked flow channel, which can dissolve calcium scale and heavy oil or asphalt blockage.

[0042] Next, we will refer to Figures 1 to 3 The various parts of the above-mentioned downhole intelligent injection anti-blocking flow regulating structure in this example embodiment are described in more detail.

[0043] In one embodiment, when the flow portion 300 is unobstructed, the pressure between the first piston 101 and the bottom of the first cavity is greater than the pressure at the top of the first piston 101. It should be understood that when the flow portion is unobstructed, the circulation of the fluid is in a normal state, and there is a certain pressure at the top of the dredging portion 200. In order to prevent the first piston 101 from moving downward by the pressure, the acid 102 contained between the first piston 101 in the first cavity and the bottom of the first cavity is squeezed, and the pressure between the first piston 101 and the bottom of the first cavity is greater than the pressure at the top of the first piston 101. When the flow portion is blocked, the fluid at the top of the body 100 cannot circulate through the flow portion 300, and the pressure at the top of the body 100 increases. When the pressure at the top of the body 100 increases to a preset value, the pressure pushes the first piston 101 and the second piston 201 to move downward. The first piston 101 moves downward to squeeze the acid liquid 102 contained between the first piston 101 in the first cavity and the bottom of the first cavity into the first connecting pipe 103. The second piston 201 moves downward, and the guide rod 202 connected to the second piston 201 also moves downward. The fourth piston 204 on the guide rod 202 compresses the reset member 206 arranged between the fourth piston 204 and the bottom of the second cavity. At this time, the first liquid storage area formed between the second piston 201 and the third piston 203 moves downward, and the first liquid storage area is connected to the first connecting pipe 103. The acid liquid 102 squeezed in the first connecting pipe 103 by the first piston 101 flows into the first liquid storage area. A second connecting pipe 205 is provided between the first liquid storage area and the flow portion 300. The acid liquid 102 flowing into the first liquid storage area flows into the flow portion 300 through the second connecting pipe 205. The acid liquid 102 dissolves the blocked solid particles to make the flow channel unblocked. It should also be understood that the reset member 206 is a spring, one end of which is sleeved on the guide rod 202, a stopper is provided at the bottom of the second cavity, and the other end of the spring is sleeved on the stopper, so that the spring is arranged between the fourth piston 204 and the bottom of the second cavity. The acid solution 102 is a mixed acid solution 102 of hydrochloric acid and oxalic acid, which can dissolve calcium scale and heavy oil or asphalt blockage.

[0044] In one embodiment, a second liquid storage area is formed between the third piston 203 and the fourth piston 204, and when the flow portion 300 is unobstructed, the first connecting pipe 103 is connected to the second liquid storage area. When the flow portion 300 is blocked, the first connecting pipe 103 is connected to the first liquid storage area. It should be understood that when the flow portion 300 is unobstructed, the circulation of the fluid is in a normal state, the pressure on the upper part of the body 100 cannot push the first piston 101 and the second piston 201 to move, and the reset member 206 between the fourth piston 204 and the bottom of the second cavity is in a normal state without being compressed. At this time, a second liquid storage area is formed between the third piston 203 and the fourth piston 204 and is connected to the first connecting pipe 103. The second liquid storage area is not connected to the second connecting pipe 205, and the acid liquid 102 cannot be input into the flow portion 300, resulting in the loss of the acid liquid 102. When the acid solution 102 dissolves the blocked solid particles and makes the flow channel unblocked, the pressure on the upper part of the second piston 201 decreases, and the compressed reset member 206 recovers its elastic deformation, pushing the fourth piston 204 to move the guide rod 202 upward. At this time, the first liquid storage area is formed between the second piston 201 and the third piston 203 and moves upward, and the second liquid storage area is formed between the third piston 203 and the fourth piston 204 and moves upward, and the first connecting pipe 103 is connected to the second liquid storage area.

[0045] In one embodiment, a filter 301 is provided at the liquid inlet of the flow section 300. The filter 301 is provided with a plurality of through holes, and the plurality of through holes are used to filter the liquid entering the flow section 300. It should be understood that the plurality of through holes provided on the filter 301 can be used for liquid infiltration, and the plurality of through holes are used to filter the liquid entering the flow section 300. At the same time, the micropores have a throttling effect, which avoids uneven discharge of the acid solution 102, and allows the acid solution 102 to reach the flow channel of the flow section 300 evenly. With the injection and flow of the acid solution 102, the scale and blockage in the flow channel are dissolved, thereby achieving the purpose of clearing the blockage.

[0046] In one embodiment, the guide rod 202 is a hollow sleeve, and a longitudinally arranged ejector pin 211 is fixedly connected inside the sleeve, and one end of the ejector pin 211 is connected to the second piston 201. An annular groove is provided on the side of the body 100, and expansion members 209 are arranged inside the two annular grooves. A plurality of circulation members 210 are fixedly connected between the two expansion members 209 in a linear array, so that the two expansion members 209 are connected. A connecting hole is provided at the bottom of the second cavity, and one end of the air pipe 207 is sealed and connected to the sleeve through the connecting hole. The interior of the air pipe 207 is sealed with inert gas, and the other end of the air pipe 207 is fixedly connected to the conduit 208. A connecting port is provided on the expansion member 209, and the connecting port is connected to the conduit 208. It should be understood that the air pipe 207 is inserted into the inner position of the sleeve, the interior of the air pipe 207 is sealed with inert gas, the bottom end of the air pipe 207 is fixedly connected with a flexible structure of the conduit 208, and the end of the conduit 208 away from the air pipe 207 is connected to the expansion member 209. By providing the air pipe 207, when the sleeve moves downward, the ejector pin 211 fixedly connected to the inside of the sleeve can be inserted into the air pipe 207, so that the inert gas in the air pipe 207 can be supplied to the inside of the expansion member 209 arranged on the outer peripheral surface of the body 100 by using the conduit 208 fixedly connected to the bottom end surface of the air pipe 207, and reverse support and clamping operations are performed, thereby achieving the purpose of rapid limiting. The faucet channel is sealed to ensure the upper pressure of the body 100 when blocked. Compared with the traditional fixed structure, which is easy to be displaced and fall off when subjected to impact due to the lack of an effective limiting structure, this design improves the stability and reliability of the device during installation.

[0047] Working principle:

[0048] The main body 100 is arranged in the water nozzle structure of the intelligent injection system of the oil field.

[0049] When the flow passage 300 is unobstructed, the flow of the fluid is in a normal state, and a certain pressure already exists on the upper part of the body 100, that is, a certain pressure already exists on the upper part of the first piston 101 and the upper part of the second piston 201, and the pressure between the first piston 101 and the bottom of the first cavity is greater than the pressure on the upper part of the first piston 101. The pressure on the upper part of the first piston 101 cannot push the first piston 101 to move, the reset member 206 between the fourth piston 204 and the bottom of the second cavity is in a normal state without being compressed, and the second liquid storage area is connected to the first connecting pipe 103, and the acid liquid 102 cannot be input into the flow passage 300 at this time.

[0050] When the flow portion 300 is blocked, the fluid in the upper part of the main body 100 cannot flow through the flow portion 300, and the pressure in the upper part of the main body 100 increases. When the pressure in the upper part of the main body 100 increases to a preset value, that is, the pressure in the upper part of the first piston 101 and the upper part of the second piston 201 increases, the pressure pushes the first piston 101 and the second piston 201 to move downward. The first piston 101 moves downward to squeeze the acid liquid 102 contained between the first piston 101 in the first cavity and the bottom of the first cavity into the first connecting pipe 103. The second piston 201 moves downward, and the guide rod 202 connected to the second piston 201 also moves downward. The fourth piston 204 on the guide rod 202 compresses the reset member 206 provided between the fourth piston 204 and the bottom of the second cavity. At this time, the first liquid storage area moves downward, and the first liquid storage area is connected to the first connecting pipe 103. The acid liquid 102 squeezed in the first connecting pipe 103 by the first piston 101 flows into the first liquid storage area. A second connecting pipe 205 is provided between the first liquid storage area and the flow portion 300. The acid liquid 102 flowing into the first liquid storage area flows into the flow portion 300 through the second connecting pipe 205. The acid liquid 102 dissolves the blocked solid particles to make the flow channel unblocked.

[0051] After the blockage in the flow section 300 is cleared, the pressure on the upper part of the second piston 201 decreases, and the compressed reset member 206 recovers its elastic deformation, pushing the fourth piston 204 to move the guide rod 202 upward. At this time, a first liquid storage area is formed between the second piston 201 and the third piston 203 and moves upward, and a second liquid storage area is formed between the third piston 203 and the fourth piston 204 and moves upward, and the first connecting pipe 103 is connected to the second liquid storage area.

[0052] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like in the above description indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present invention.

[0053] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0054] In the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] In the embodiments of the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes the first feature being directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0056] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0057] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present invention are indicated by the appended claims.

Claims

1. A downhole intelligent injection anti-blocking flow regulating structure, the main body of which is arranged in the water nozzle of the oilfield intelligent injection system, characterized in that: include: The main body comprises a flow-through portion and a dredging portion, wherein the flow-through portion and the dredging portion are arranged in parallel in the longitudinal direction; The flow portion is a blind hole opened in the body along the longitudinal direction of the body, and a plurality of micropores are distributed in an array on the side wall of the blind hole; The dredging part is used to provide acid solution to dissolve the blockage to the flow part when the flow part is blocked, so as to make the liquid in the flow part flow smoothly; The dredging part comprises: A first cavity, wherein the first cavity is arranged in the body along the longitudinal direction of the body, a first piston is slidably connected in the first cavity, and acid liquid is filled between the first piston and the bottom of the first cavity; A second cavity, the second cavity is arranged in the body along the longitudinal direction of the body, adjacent to the first cavity, and a first connecting pipe is provided between the second cavity and the first cavity; a second piston is slidably connected in the second cavity, and a guide rod is fixedly connected to the bottom end surface of the second piston; A third piston and a fourth piston are sequentially arranged on the guide rod, a first liquid storage area is formed between the second piston and the third piston, a second connecting pipe is arranged between the first liquid storage area and the flow portion, and a reset member is arranged between the fourth piston and the bottom of the second cavity.

2. The underground intelligent injection and anti-blocking flow regulating structure according to claim 1 is characterized in that: When the flow passage is unobstructed, the pressure between the first piston and the bottom of the first cavity is greater than the pressure at the top of the first piston.

3. The underground intelligent injection and anti-blocking flow regulating structure according to claim 1 is characterized in that: A second liquid storage area is formed between the third piston and the fourth piston. When the flow portion is unobstructed, the first communicating pipe is communicated with the second liquid storage area.

4. The underground intelligent injection and anti-blocking flow regulating structure according to claim 1 is characterized in that: When the flow portion is blocked, the first communicating pipe is communicated with the first liquid storage area.

5. The underground intelligent injection and anti-blocking flow regulating structure according to claim 1 is characterized in that: A filter is provided at the liquid inlet of the flow portion.

6. The underground intelligent injection and anti-blocking flow regulating structure according to claim 5 is characterized in that: The filter element is provided with a plurality of through holes, and the plurality of through holes are used for filtering the liquid inlet of the flow portion.

7. The underground intelligent injection and anti-blocking flow regulating structure according to claim 1 is characterized in that: The guide rod is a sleeve with a hollow interior, and a longitudinally arranged ejector pin is fixedly connected to the interior of the sleeve, and one end of the ejector pin is connected to the second piston.

8. The underground intelligent injection and anti-blocking flow regulating structure according to claim 7 is characterized in that: A connecting hole is provided at the bottom of the second cavity, and an end of the sleeve away from the second piston is sealed with an air pipe, the interior of the air pipe is sealed with inert gas, and the air pipe is connected to one end of the catheter.

9. The underground intelligent injection and anti-blocking flow regulating structure according to claim 8 is characterized in that: An annular groove is provided on the side of the body, and expansion parts are arranged in the two annular grooves. A plurality of circulation parts are fixedly connected between the two expansion parts in a linear array so that the two expansion parts are connected. A connection port is provided on the expansion part, and the connection port is connected to one end of the catheter.

10. The underground intelligent injection and anti-blocking flow regulating structure according to claim 1, characterized in that: The acid solution is a mixed acid solution of hydrochloric acid and oxalic acid.

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