A spatial sandstone acid fracturing process method of offshore oilfield platform

Abstract

The application provides a kind of offshore oilfield platform space sandstone acid fracturing process method, comprising the following steps, S1: preparing operation pump, through pipeline connection, acid fracturing process is conducted;S2: preparation of fracturing fluid, the operation pump is started, and fracturing operation is carried out, and fracturing fluid is supplemented in time according to liquid condition;S3: pump is stopped, switch to acidification process, the operation pump is started, and acid solution is pumped, while pumping liquid preparation water;S4: according to the implementation of acid fracturing process, S2, S3 alternative repetition mode is selected;S5: pump is stopped, and residual liquid is returned to row.The application reduces the land area occupied by process implementation by optimizing the process under the platform space condition, adopts integrated mixing-free fracturing fluid and concentrated single plug acid solution, effectively connects the two processes, thereby forms a sandstone acid fracturing process method suitable for offshore oilfield platform space, breaks through the operation space limitation and water source limitation, and can efficiently complete sandstone acid fracturing.

Description

Technical Field

[0001] This invention belongs to the field of offshore oilfield production enhancement and injection technology, and in particular relates to a process method for spatial sandstone acid fracturing on offshore oilfield platforms. Background Technology

[0002] Acidizing and fracturing are common techniques for enhancing oilfield production and injection. In the efficient production enhancement of low- and medium-permeability reservoirs, there is an urgent need for a production-enhancing measure that combines the effects of fracturing with the acid-induced fracture widening effect. Currently, through domestic and international research and development, acid fracturing technology used in carbonate reservoirs has been extended to sandstone reservoirs, achieving process innovations such as conventional acid fracturing, balanced acid fracturing, and closed-loop acid fracturing. Domestic and international research and applications demonstrate the feasibility of sandstone acid fracturing, with the key being that the reservoir rock surface can form a certain degree of fracture conductivity after acid etching. Currently, sandstone acid fracturing has been successively applied in oilfields such as Liaohe, Changqing, Jiangsu, Tarim, and Dagang, achieving significant production and injection enhancement effects.

[0003] In recent years, the development of low-permeability reservoirs in offshore oilfields has received increasing attention. Conventional acidizing faces problems such as high pumping pressure, low injection rate, and low acidizing efficiency. Hydraulic fracturing is the main means of developing low-permeability reservoirs. Current hydraulic fracturing adopts seawater fracturing fluid and continuous mixing, integrated non-mixing fracturing fluid, fracturing vessel and other modes to form a hydraulic fracturing implementation plan suitable for offshore oilfields.

[0004] Currently, there are relatively few patents related to acid fracturing in domestic sandstone reservoirs, mainly concerning systems and applications. For example, the invention patent number 2021106484963, entitled "A Deep Penetration Working Fluid for Acid Fracturing Stimulation of Sandstone Reservoirs and Its Application," combines fracturing and acidizing fluids. However, in offshore oilfield implementation, the following problems easily arise in order to combine fracturing and acidizing processes: First, the large construction area required is unfavorable for offshore platform space. Both operations involve a large number of equipment, requiring significant space, especially for fracturing fluid and acid. Even with the simplification of fracturing fluid tanks through integrated, non-mixing fracturing fluid, the subsequent acid consumption is expected to be in the hundreds of cubic meters, while offshore platforms cannot accommodate more than four 30-cubic-meter acid tanks. Second, the operational timeliness is relatively poor, and fractures are prone to closure, greatly limiting the process. If acidizing is performed after fracturing with re-mixed fluid, it will lead to fracture closure, and it will be impossible to use high-conductivity acid fracturing processes such as balanced acid fracturing and balanced closure acid fracturing, affecting the effectiveness of the measures.

[0005] Therefore, there is currently a lack of sandstone acid fracturing process methods suitable for offshore oilfield platform spaces, both domestically and internationally. Summary of the Invention

[0006] The problem this invention aims to solve is to provide a process flow method for sandstone acid fracturing in offshore oilfield platform space. This method effectively combines fracturing and acidizing processes. Through process optimization under platform space conditions, it greatly reduces the land area required for process implementation. It adopts integrated, non-mixing fracturing fluid and concentrated single-stage acid plugging fluid to effectively connect the two processes, thereby forming a sandstone acid fracturing process method suitable for offshore oilfield platform space. This method overcomes the limitations of operating space and water source, and can complete sandstone acid fracturing with high efficiency.

[0007] This invention provides a process flow method for spatial sandstone acid fracturing on offshore oilfield platforms, comprising the following steps: S1: Prepare the working pump, fracturing fluid tank, acidizing tank, ten-way valve, tee valve, and liquid filling equipment, and connect them through high-pressure pipelines and low-pressure pipelines with valves to conduct the acid fracturing process; S2: Fracturing fluid is prepared in the fracturing fluid tank using a chemical dosing pump and platform-based water for fluid preparation. The operation pump is then started to carry out fracturing operations. Fracturing fluid is replenished in a timely manner according to the fluid usage. S3: Stop the pump, switch to the acidizing process, start the working pump, pump acid from the acidizing tank, and at the same time, pump water for preparing the solution from the fracturing fluid tank; S4: Select the alternating repeating method of S2 and S3 according to the acid frosting process to be implemented; S5: Stop the pump and discharge residual liquid.

[0008] Furthermore, in S1, the operating pump is a fracturing pump and an acidizing pump. The fracturing fluid tank is connected in parallel with the fracturing pump via a low-pressure pipeline with a valve through a tee. After the fracturing pumps are connected in parallel, they are respectively connected to the wellhead via a high-pressure pipeline with a valve through a tee. The tee is connected in parallel with the fracturing fluid tank. The acidizing tank is connected in parallel with the acidizing pump via a low-pressure pipeline with a valve through a tee. After the acidizing pump and the fracturing pump are connected in parallel, they are respectively connected to the wellhead via a high-pressure pipeline with a valve through a tee.

[0009] Furthermore, the number of fracturing pumps is 1-2, and the number of acidizing pumps is at least 1.

[0010] Furthermore, in S1, the working pump is an acid fracturing pump, and the fracturing fluid tank, the acidizing tank, the fluid filler, and the acid fracturing pump are all connected in parallel through the tee via the low-pressure pipeline with valves. After the acid fracturing pumps are connected in parallel, they are respectively connected to the wellhead through the high-pressure pipeline with valves via the tee.

[0011] Furthermore, the number of acid fracturing pumps is 2.

[0012] Furthermore, the number of fracturing fluid tanks is 1-2, and the capacity of each fracturing fluid tank is at least 30m³.3 The number of acidification tanks is at least two, and the capacity of each acidification tank is at least 30m³. 3 The number of ten-way valves is at least one, and the number of three-way valves is one to three; there are multiple sets of high-pressure pipelines with valves and multiple sets of low-pressure pipelines with valves.

[0013] Furthermore, the fracturing fluid tank is a mud pit, and the mud pit has a capacity of at least 200 m³. 3 .

[0014] Furthermore, in step S2, the fracturing fluid is an integrated, non-mixing fracturing fluid with a temperature resistance greater than or equal to 150°C and a 175S... -1 Under the specified conditions, the viscosity is not less than 50 mPa•s, the liquid is in emulsion state, and it can achieve rapid dissolution within 30 seconds.

[0015] Furthermore, in S3, the acid solution is an active acid or a smart acid, and the acid solution has the functions of single-stage plug pump injection and online acidification. The acid solution can dissolve mud, dissolve calcium, and wash oil. The volume ratio of the acid solution to the water used for preparation is 1:1 to 1:2.

[0016] Furthermore, in S4, the alternating repeating mode of S2 and S3 is selected as either performing S2 and S3 or performing S2, S3, S2, S3 alternating injection mode, until all the fracturing fluid and the acid are pumped in.

[0017] The advantages and positive effects of this invention are: 1. This invention saves construction area and is beneficial for construction on offshore platforms. With 1-2 fracturing pumps, 1 acidizing pump or 2 acidizing and fracturing pumps, 1-2 fracturing fluid tanks or mud pits, 2 acidizing tanks, a ten-way valve, fluid filler, and other equipment, it can be applied to most platform spaces in offshore oilfields and acid fracturing operations in sandstone reservoirs, with a wide range of applications.

[0018] 2. The construction scale of this invention is relatively considerable. It utilizes integrated, non-mixing fracturing fluid and concentrated single-stage acid plugging fluid, combined with supporting equipment, achieving a maximum fluid supply speed of approximately 2m / s². 3 / min, two 30 cubic meter fracturing fluid tanks, providing 2.5m 3 / min Fracturing operation for 120 minutes at maximum displacement; if mud pit mixing and pumping is used, it basically meets the capacity of most mud pits, therefore, the maximum fracturing scale can reach about 300 cubic meters. Two 30 cubic meter acidizing fluid tanks are used; after fracturing, the fracturing fluid tank uses mixing water, and all construction pumps are started simultaneously; if mud pit pumping is used, based on a maximum 1m... 3 / min acidification pump injection and 2m 3 The solution injection pump at a rate of / min meets this standard, therefore, the maximum acidification scale can reach about 180 cubic meters, resulting in high production efficiency.

[0019] 3. This invention seamlessly integrates fracturing and acidizing operations, allowing for the selection of different acid fracturing processes and enhancing acid etching conductivity. The two operations are controlled by pumps and valves, enabling real-time switching to effectively prevent fracture closure. Furthermore, multi-stage injection acid fracturing modes such as fracturing-acidizing-fracturing can be employed, providing a wider range of process options. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall process flow of an embodiment of the present invention.

[0021] Figure 2 This is a schematic diagram of the process where the working pumps in an embodiment of the present invention are a fracturing pump and an acidizing pump.

[0022] Figure 3 This is a schematic diagram of the process of using an acid fracturing pump as the operating pump in an embodiment of the present invention.

[0023] in: 1. Fracturing pump; 2. Acidizing pump; 3. Acidizing fracturing pump; 4. Fracturing fluid tank; 5. Acidizing tank; 6. Ten-way valve; 7. Tee; 8. Liquid filler; 9. Low-pressure pipeline; 10. High-pressure pipeline; 11. Wellhead. Detailed Implementation

[0024] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] The embodiments of the present invention will be further described below with reference to the accompanying drawings: like Figure 1 As shown, this invention provides a process flow method for spatial sandstone acid fracturing on offshore oilfield platforms, including the following steps: S1: Prepare the following equipment: working pump, fracturing fluid tank 4, acidizing tank 5, ten-way valve 6, three-way valve 7, fluid filler 8, etc., and connect them through high-pressure pipeline 10 and low-pressure pipeline 9 with valves to conduct the acid fracturing process. The working pump is either fracturing pump 1 and acidizing pump 2, or acidizing fracturing pump 3.

[0026] Specifically, such as Figure 2As shown, when the operating pumps are fracturing pump 1 and acidizing pump 2, the fracturing fluid tank 4 is connected in parallel to fracturing pump 1 via a low-pressure pipeline 9 with a valve and a tee 6. After fracturing pump 1 is connected in parallel, it is connected to the wellhead 11 via a high-pressure pipeline 10 with a valve and a tee 7. A fluid additive 8 is connected in parallel to the tee 6 for adding fracturing fluid concentrate or breaker. The acidizing tank 5 is connected in parallel to acidizing pump 2 via a low-pressure pipeline 9 with a valve and a tee 7. After acidizing pump 2 is connected in parallel to fracturing pump 1, it is connected to the wellhead 11 via a high-pressure pipeline 10 with a valve and a tee 7. The fracturing and acidizing processes do not overlap.

[0027] like Figure 3 As shown, when the working pump is acidizing fracturing pump 3, acidizing fracturing pump 3, fracturing fluid tank 4, acidizing tank 5, fluid filler 8, and acidizing fracturing pump 3 are all connected in parallel through low-pressure pipeline 9 with valves and 6. After the acidizing fracturing pumps 3 are connected in parallel, they are connected to the wellhead 11 through high-pressure pipeline 10 with valves and 7. The acidizing fracturing pump 3 can pump fracturing fluid, acidizing fluid, or water for fluid preparation in a cross-flow manner.

[0028] Specifically, the number of fracturing pump 1 is 1-2 units, the number of acidizing pump 2 is at least 1 unit, and when acidizing fracturing pump 3 is used, the number is 2 units. The horsepower, pressure, and displacement of fracturing pump 1 or acidizing fracturing pump 3 meet the design parameters of the fracturing reservoir; the number of fracturing fluid tanks 4 is 1-2 units, and the capacity of fracturing fluid tank 4 is at least 30m³. 3 The number of acidification tanks 5 shall be at least 2, and the capacity of acidification tanks 5 shall be at least 30m³. 3 The number of 6-way valves must be at least one, and the number of 7-way valves must be 1-3; there must be multiple sets of high-pressure pipelines 10 and multiple sets of low-pressure pipelines 9 with valves. Alternatively, the fracturing fluid tank 4 can be replaced with a mud pit, with a mud pit capacity of at least 200m³. 3 .

[0029] S2: Fracturing fluid is prepared in fracturing fluid tank 4 using a chemical dosing pump and platform-based mixing water. The operation pump is started to carry out fracturing operations. Fracturing fluid is replenished in a timely manner according to the fluid usage. The fracturing fluid used is an integrated, non-mixing fracturing fluid with a temperature resistance of ≥150℃ and a 175S rating. -1 Under the specified conditions, the viscosity is not less than 50 mPa•s, the liquid is in emulsion state, and it can achieve rapid dissolution within 30 seconds.

[0030] S3: Stop the pump, switch to the acidizing process, start the working pump, and pump acid from acidizing tank 5. Simultaneously, pump water for mixing from fracturing fluid tank 4. The acid is an active acid or a smart acid; preferably, it is an active acid from the Engineering and Technology Branch of CNOOC Energy Development Co., Ltd. or a smart acid from Southwest Petroleum University. The acid has the function of single-stage plug pump injection and online acidizing. The acid achieves mud dissolution, calcium dissolution, and oil washing. The volume ratio of acid to water for mixing is 1:1-1:2.

[0031] S4: Depending on the acid fracturing process being implemented, select the alternating repeating method of S2 and S3; specifically, it can be S2 and S3, or S2, S3, S2, S3 alternating injection method, until all fracturing fluid and acid are pumped in.

[0032] S5: Stop the pump and discharge residual liquid.

[0033] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0034] Example 1:

[0035] S1: Prepare two fracturing pumps. Fracturing pump 1 is a 2300 model, not acid-resistant, with a maximum pressure of 105 MPa and a maximum displacement of 2.46 m³ / s. 3 / min; Prepare one acidification pump 2, which is a type 1000, acid-resistant, with a maximum pressure of 73.2MPa and a maximum displacement of 2.16m³ / min. 3 / min; Prepare two fracturing fluid tanks, each with a capacity of at least 30m³. 3 Prepare two acidification tanks, each with a capacity of at least 30m³. 3 ; 6 is one ten-way valve; 7 is three three-way valves; 8 is one liquid filler valve; connected through high and low pressure pipelines 9 with valves to conduct the acid pressure process.

[0036] The fracturing process involves fracturing fluid tank 4 connected to fracturing pump 1 via a low-pressure pipeline 9 with a valve and a tee 6. After fracturing pump 1 is connected in parallel, it is connected to wellhead 11 via a high-pressure pipeline 10 with a valve and a tee 7. Fluid filler 8 is connected in parallel with tee 6 to add fracturing fluid concentrate or breaker. The acidizing process involves acidizing tank 5 connected to acidizing pump 2 via a low-pressure pipeline 9 with a valve and a tee 7. After acidizing pump 2 is connected to fracturing pump 1 in parallel, it is connected to wellhead 11 via a high-pressure pipeline 10 with a valve and a tee 7. The fracturing and acidizing processes do not overlap.

[0037] S2: Using a chemical dosing pump and platform-based mixing water, 200m³ of integrated, non-mixing fracturing fluid was prepared in fracturing fluid tank 4. 3 Its performance meets the requirements of withstanding temperatures up to 150℃ and 175S-1, with a viscosity of 65mPa•s. The liquid is in emulsion state and can dissolve rapidly within 30s. Start fracturing pump 1 to carry out fracturing operations, and replenish fracturing fluid in a timely manner according to the fluid usage.

[0038] S3: Stop the pump, switch to the acidification process, start acidification pump 2, and pump a total of 60m³ of acid solution from acidification tank 5. 3The acid solution is an active acid from the Engineering and Technology Branch of CNOOC Energy Development Co., Ltd., capable of dissolving mud, dissolving calcium, and washing oil. Simultaneously, water for mixing the solution is pumped from fracturing fluid tank 4. The volume ratio of acid solution to water for mixing is 1:2, and the total acid volume after dilution is 180 m³. 3 .

[0039] S4: Use injection methods S2 and S3 until all fracturing fluid and acid are pumped in.

[0040] S5: Stop the pump and discharge residual liquid.

[0041] Example 2:

[0042] S1: Prepare two fracturing pumps. Fracturing pump 1 is a 2300 model, not acid-resistant, with a maximum pressure of 105 MPa and a maximum displacement of 2.46 m³ / s. 3 / min; Prepare one acidification pump 2, which is a type 1000, acid-resistant, with a maximum pressure of 73.2MPa and a maximum displacement of 2.16m³ / min. 3 / min; Prepare 300m 3 Prepare a mud pit; prepare two acidification tanks, each with a capacity of at least 30m³. 3 ; 6 is one ten-way valve; 7 is three three-way valves; 8 is one liquid filler valve; connected through high and low pressure pipelines 9 with valves to conduct the acid pressure process.

[0043] The fracturing process involves a mud pit connected to fracturing pump 1 via a low-pressure pipeline 9 with valves and a tee 6. After fracturing pump 1 is connected in parallel, it is connected to wellhead 11 via a high-pressure pipeline 10 with valves and a tee 7. Fluid additive 8 is connected in parallel with tee 6 to add fracturing fluid breaker. The acidizing process involves an acidizing tank 5 connected to acidizing pump 2 via a low-pressure pipeline 9 with valves and a tee 7. After acidizing pump 2 is connected in parallel with fracturing pump 1, it is connected to wellhead 11 via a high-pressure pipeline 10 with valves and a tee 7. The fracturing and acidizing processes do not overlap.

[0044] S2: Prepare 300m³ of solution in the mud pit using a dosing pump and platform-based mixing water. 3 The integrated, non-mixing fracturing fluid meets the requirements of a temperature resistance of up to 150℃ and a viscosity of 65 mPa•s under 175 s-1 conditions. The liquid is in emulsion state and can dissolve rapidly within 30 seconds. Start fracturing pump 1 to carry out fracturing operations.

[0045] S3: Stop the pump, switch to the acidification process, start acidification pump 2, and pump a total of 60m³ of acid solution from acidification tank 5. 3 The acid solution is a smart acid developed by Southwest Petroleum University, capable of dissolving mud, dissolving calcium, and washing oil. Simultaneously, water for mixing the solution is pumped from mud tank 4. The volume ratio of acid solution to water for mixing is 1:2, resulting in a total acid volume of 180 m³ after dilution. 3 .

[0046] S4: Use the alternating S2 and S3 method until all fracturing fluid and acid are pumped in.

[0047] S5: Stop the pump and discharge residual liquid.

[0048] Example 3:

[0049] S1: Prepare two acid fracturing pumps (model 2300), which are acid-resistant, with a maximum pressure of 105 MPa and a maximum displacement of 2.46 m³ / h. 3 / min; Prepare two fracturing fluid tanks, each with a capacity of at least 30m³. 3 Prepare two acidification tanks, each with a capacity of at least 30m³. 3 The 6-way valve is one unit; the 7-way valve is three units; the 8-way valve is one unit, which are connected to the high and low pressure pipelines 9 with valves to conduct the acid pressure process.

[0050] The fracturing fluid tank 4, acidizing tank 5, fluid filler 8, and acidizing fracturing pump 3 are all connected in parallel via a low-pressure pipeline 9 with a valve and a tee 6. After the acidizing fracturing pump 3 is connected in parallel, it is connected to the wellhead 11 via a high-pressure pipeline 10 with a valve and a tee 7. The acidizing fracturing pump 3 can pump fracturing fluid, acidizing fluid, or water for fluid preparation in a cross-flow manner.

[0051] S2: Prepare 200m³ of fracturing fluid in fracturing fluid tank 4 using a chemical dosing pump and platform-based water mixing. 3 Integrated, no-mixing fracturing fluid with performance meeting temperature resistance requirements up to 150℃ and 175S. -1 Under the conditions of 65 mPa•s, the liquid is in emulsion state and can dissolve rapidly within 30 seconds. Start acid fracturing pump 3 to carry out fracturing operations and replenish fracturing fluid in a timely manner according to the fluid usage.

[0052] S3: Stop the pump, switch to the acidizing process, start the acidizing fracturing pump 3, and pump a total of 60m³ of acid from the acidizing tank 5. 3 The acid solution is an active acid from the Engineering and Technology Branch of CNOOC Energy Development Co., Ltd., capable of dissolving mud, dissolving calcium, and washing oil. Simultaneously, water for mixing the solution is pumped from fracturing fluid tank 4. The volume ratio of acid solution to water for mixing is 1:2, and the total acid volume after dilution is 180 m³. 3 .

[0053] S4: Use injection methods S2 and S3 until all fracturing fluid and acid are pumped in.

[0054] S5: Stop the pump and discharge residual liquid.

[0055] Example 4:

[0056] S1: Prepare two acid fracturing pumps (model 2300), which are acid-resistant, with a maximum pressure of 105 MPa and a maximum displacement of 2.46 m³ / h.3 / min; Prepare 300m 3 Mud pit; prepare two acidizing tanks, each with a capacity of at least 30m³. 3 The 6-way valve is one unit; the 7-way valve is three units; the 8-way valve is one unit, which are connected to the high and low pressure pipelines 9 with valves to conduct the acid pressure process.

[0057] The mud pit 4, acidizing tank 5, fluid filler 8, and acidizing fracturing pump 3 are all connected in parallel via a low-pressure pipeline 9 with a valve and a tee 6. After the acidizing fracturing pump 3 is connected in parallel, it is connected to the wellhead 11 via a high-pressure pipeline 10 with a valve and a tee 7. The acidizing fracturing pump 3 can pump fracturing fluid, acidizing fluid, or water for fluid preparation in a cross-flow manner.

[0058] S2: Prepare 300m³ of solution in mud tank 4 using a dosing pump and platform-based mixing water. 3 Integrated, no-mixing fracturing fluid with performance meeting temperature resistance requirements up to 150℃ and 175S. -1 Under the conditions of 65 mPa•s, the liquid is in emulsion state and can dissolve rapidly within 30 seconds. Start acid fracturing pump 3 to carry out fracturing operations and replenish fracturing fluid in a timely manner according to the fluid usage.

[0059] S3: Stop the pump, switch to the acidizing process, start the acidizing fracturing pump 3, and pump a total of 60m³ of acid from the acidizing tank 5. 3 The acid solution is a smart acid developed by Southwest Petroleum University, capable of dissolving mud, dissolving calcium, and washing oil. Simultaneously, water for mixing the solution is pumped from mud tank 4. The volume ratio of acid solution to water for mixing is 1:2, resulting in a total acid volume of 180 m³ after dilution. 3 .

[0060] S4: Use the alternating S2 and S3 method until all fracturing fluid and acid are pumped in.

[0061] S5: Stop the pump and discharge residual liquid.

[0062] In summary, this invention significantly reduces the footprint of the process by optimizing the process under platform space conditions. It adopts an integrated, non-mixing fracturing fluid and a concentrated single-stage acid plugging fluid to effectively connect the two processes, thereby forming a sandstone acid fracturing process suitable for offshore oilfield platform space. This method overcomes the limitations of operating space and water source, and can complete sandstone acid fracturing with high efficiency.

[0063] The foregoing has described several embodiments of the present invention in detail, but these are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent variations and improvements made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A process flow method for spatial sandstone acid fracturing on offshore oilfield platforms, characterized in that: Includes the following steps, S1: Prepare the working pump, fracturing fluid tank, acidizing tank, ten-way valve, tee valve, and liquid filling equipment, and connect them through high-pressure pipelines and low-pressure pipelines with valves to conduct the acid fracturing process; S2: Fracturing fluid is prepared in the fracturing fluid tank using a chemical dosing pump and platform-based water for fluid preparation. The operation pump is then started to carry out fracturing operations. Fracturing fluid is replenished in a timely manner according to the fluid usage. S3: Stop the pump, switch to the acidizing process, start the working pump, pump acid from the acidizing tank, and at the same time, pump water for preparing the solution from the fracturing fluid tank; S4: Select the alternating repeating method of S2 and S3 according to the acid frosting process to be implemented; S5: Stop the pump and discharge residual liquid.

2. The method for a spatial sandstone acid fracturing process on an offshore oilfield platform according to claim 1, characterized in that: In S1, the working pumps are a fracturing pump and an acidizing pump. The fracturing fluid tank is connected in parallel with the fracturing pump via a low-pressure pipeline with a valve through a tee. After the fracturing pumps are connected in parallel, they are connected to the wellhead via high-pressure pipelines with valves through a tee. The tee is connected in parallel with the fracturing fluid tank. The acidizing tank is connected in parallel with the acidizing pump via a low-pressure pipeline with a valve through a tee. After the acidizing pump and the fracturing pump are connected in parallel, they are connected to the wellhead via high-pressure pipelines with valves through a tee.

3. The method for a spatial sandstone acid fracturing process on an offshore oilfield platform according to claim 2, characterized in that: The number of fracturing pumps is 1-2, and the number of acidizing pumps is at least 1.

4. The method for a spatial sandstone acid fracturing process on an offshore oilfield platform according to claim 1, characterized in that: In S1, the working pump is an acid fracturing pump. The fracturing fluid tank, the acidizing tank, the fluid filler, and the acid fracturing pump are all connected in parallel through the tee via the low-pressure pipeline with valves. After the acid fracturing pumps are connected in parallel, they are respectively connected to the wellhead through the high-pressure pipeline with valves via the tee.

5. The method for a spatial sandstone acid fracturing process on an offshore oilfield platform according to claim 4, characterized in that: The number of acid fracturing pumps is 2.

6. A method for spatial sandstone acid fracturing process on an offshore oilfield platform according to any one of claims 2 to 5, characterized in that: The number of fracturing fluid tanks is 1-2, and the capacity of each fracturing fluid tank is at least 30m³. 3 The number of acidification tanks is at least two, and the capacity of each acidification tank is at least 30m³. 3 The number of ten-way valves is at least one, and the number of three-way valves is one to three; there are multiple sets of high-pressure pipelines with valves and multiple sets of low-pressure pipelines with valves.

7. A method for spatial sandstone acid fracturing process on an offshore oilfield platform according to any one of claims 1 to 5, characterized in that: The fracturing fluid tank is a mud pit, and the mud pit has a capacity of at least 200 m³. 3 .

8. A method for spatial sandstone acid fracturing process on an offshore oilfield platform according to any one of claims 1 to 5, characterized in that: In step S2, the fracturing fluid is an integrated, non-mixing fracturing fluid with a temperature resistance of ≥150℃ and a 175S rating. -1 Under the specified conditions, the viscosity is not less than 50 mPa•s, the liquid is in emulsion state, and it can achieve rapid dissolution within 30 seconds.

9. A method for spatial sandstone acid fracturing process on an offshore oilfield platform according to any one of claims 1 to 5, characterized in that: In S3, the acid solution is an active acid or a smart acid, and the acid solution has the functions of single-stage plug pump injection and online acidification. The acid solution can dissolve mud, dissolve calcium, and wash oil. The volume ratio of the acid solution to the water used for preparation is 1:1 to 1:

2.

10. A method for spatial sandstone acid fracturing process on an offshore oilfield platform according to any one of claims 1 to 5, characterized in that: In S4, the alternating repeating mode of S2 and S3 is selected as either performing S2 and S3 or performing S2, S3, S2, S3 alternating injection mode, until all the fracturing fluid and the acid are pumped in.

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