Method for improving recovery ratio of fractured tight sandstone gas reservoir

Abstract

The invention belongs to the technical field of oil and gas production engineering, and relates to a method for improving the recovery rate of a fractured tight sandstone gas reservoir. The method comprises the following steps: determining an unused reservoir and residual gas distribution; a perforation interval is determined according to the unused reservoir and the residual gas distribution, and perforation is carried out at the corresponding position; a new tubular column is put down, a packer is set below an original perforation section, the position of a new perforation is located below the packer, the packer separates a water production layer from a gas production layer, the purposes that water in an existing layer section returns and gas is discharged, and gas production and water drainage of an unused reservoir are achieved, and mining of residual gas is achieved; hydraulic fracturing is carried out at the new perforation position; if the new perforation section produces gas, gas is firstly produced in the oil pipe, water is discharged after water breakthrough, and if the new perforation section produces water, the oil pipe firstly discharges water. And entrapment residual gas and water seal residual gas after water breakthrough of the fractured tight sandstone gas reservoir can be effectively extracted, and the recovery efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas engineering technology and relates to a method for improving the recovery rate of fractured tight sandstone gas reservoirs. Background Technology

[0002] Fractured tight sandstone gas reservoirs are a type of gas reservoir with unique geological characteristics. Their dense matrix makes gas permeation and flow exceptionally difficult. However, fractures are prevalent in these reservoirs, formed during geological tectonic processes, providing pathways for gas storage and migration. But the presence of fractures makes the gas-water relationship within the reservoir particularly complex. Fractures are not only important spaces for gas storage but also major channels for water intrusion. During gas reservoir development, once water intrusion occurs, these fractures become the primary pathways for formation water to enter the gas reservoir.

[0003] The development of high-angle fractures complicates the geological structure of gas reservoirs. These high-angle fractures, formed under geological processes, profoundly impact the gas storage capacity and gas-water distribution of the reservoir. On the one hand, high-angle fractures provide more storage space for gas, allowing the reservoir to store more gas; on the other hand, due to the complexity of the fractures, the distribution of residual gas within the reservoir becomes discontinuous, resulting in significant amounts of water-sealed gas. (See also...) Figure 1 These water-sealed gases are surrounded by formation water, and even increasing the pressure difference makes them difficult to release effectively, resulting in the residual gas below the high-angle fracture forming a trapped state.

[0004] In summary, due to the development of high-angle fractures, fractured tight sandstone gas reservoirs form trapped residual gas and water-sealed residual gas after water exposure, resulting in a trapped state. Due to the lack of effective extraction methods in the current technology, these water-sealed residual gases are difficult to extract, which seriously affects the recovery rate of the gas reservoir. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for improving the recovery rate of fractured tight sandstone gas reservoirs. The present invention can effectively extract the residual gas in the trap and the residual gas in the water seal after the water breakthrough in fractured tight sandstone gas reservoirs, thereby improving the recovery rate.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for improving the recovery rate of fractured tight sandstone gas reservoirs, comprising the following steps:

[0008] Determine the distribution of unexploited reservoirs and remaining gas;

[0009] Determine the perforation intervals based on the distribution of unused reservoirs and residual gas, and perforate at the corresponding locations;

[0010] A new tubing string is inserted, and a packer is set below the original perforation section. The gas layer is divided into upper and lower sections by the packer's interlayer.

[0011] Hydraulic fracturing was performed at the new perforation site;

[0012] If gas is produced in the new perforation section, gas will be produced in the tubing first, and water will be drained after water is encountered; if water is produced in the new perforation section, water will be drained from the tubing first.

[0013] Furthermore, the distribution of unexploded reservoirs and remaining gas was determined as follows:

[0014] The distribution of unexploded reservoirs and remaining gas was determined based on fractured tight sandstone gas well reservoirs, actual production conditions, and logging data.

[0015] Furthermore, the perforation interval is determined based on the distribution of unexploded reservoirs and remaining gas, and perforations are made at the corresponding locations. Before perforation, the original well string needs to be pulled out.

[0016] Furthermore, when retrieving the original well casing, the original well casing should be retrieved in accordance with the single-well overhaul specifications.

[0017] Furthermore, the formulation of the hydraulic fracturing working fluid includes fracturing fluid, fracturing fluid crosslinking fluid, fracturing fluid breaker, and proppant;

[0018] The volume ratio of fracturing fluid, fracturing fluid crosslinking fluid, and fracturing fluid breaker is 100:0.8:0.02, and 60-400 kg of proppant is added per cubic meter of fracturing fluid.

[0019] Furthermore, before hydraulic fracturing, fracturing simulation is performed based on the parameters of the single well to be fracturing and Meyer software, and hydraulic fracturing is carried out at the new perforation location based on the simulation results.

[0020] Furthermore, the drainage process is as follows:

[0021] The water seal gas displacement pressure threshold is determined, and the drainage pressure difference is changed by adjusting the oil pipe pressure to make the drainage pressure difference meet the drainage requirements while ensuring that water seal gas is not produced.

[0022] After drainage is completed, gas is generated through the annulus between the oil jacket and the casing, so that the gas generation pressure difference is greater than the water seal gas displacement pressure threshold.

[0023] Furthermore, the drainage period should be at least 6 months.

[0024] Furthermore, the water-sealed gas displacement pressure threshold represents the minimum pressure required for core displacement, and the water-sealed gas displacement pressure threshold is obtained through physical simulation experiments using formation cores.

[0025] Furthermore,

[0026] The method for obtaining the water seal gas displacement pressure threshold is as follows:

[0027] The water seal gas displacement pressure threshold is obtained by measuring the displacement pressure at the displacement end and the back pressure at the outlet end.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The method of this invention determines the distribution of unexploded reservoirs and residual gas. Based on this distribution, perforation intervals are identified, and perforations are made at corresponding locations to facilitate the extraction of trapped residual gas and water-sealed residual gas. After running a new tubing string, a packer is installed below the original perforation interval. The packer's interlayer divides the gas-bearing section into upper and lower segments. The new perforation is located below the packer, which separates the water-producing layer from the gas-producing layer. This achieves the goal of allowing gas to emerge from water in existing intervals, producing gas in unexploded reservoirs, and draining water, thus realizing the extraction of residual gas. If gas is produced in the new perforation interval, gas is produced first in the tubing, followed by drainage after water encounter. If water is produced in the new perforation interval, water is drained from the tubing. This invention can effectively extract trapped residual gas and water-sealed residual gas after water encounter in fractured tight sandstone gas reservoirs, improving the recovery rate.

[0030] 2. Hydraulic fracturing was performed at the new perforation location, which further improved the recovery efficiency of residual gas in the trap and water seal.

[0031] 3. Before hydraulic fracturing, this invention performs fracturing simulation based on the parameters of the single well to be fracturing and Meyer software, and performs hydraulic fracturing at the new perforation location based on the simulation results. This helps to ensure the fracturing effect and thus improve the recovery rate of residual gas in the trap and residual gas in the water seal. Attached Figure Description

[0032] Figure 1 A schematic diagram of the state of a fractured tight sandstone gas reservoir after water exposure;

[0033] Figure 2 This is a schematic diagram showing the downward movement of a water-submerged crack in the upper part of an air layer under the influence of gravity differentiation.

[0034] Figure 3 This diagram shows the downward movement of a flooded crack under the influence of gravity.

[0035] Figure 4 A schematic diagram of the state of a fractured tight sandstone gas reservoir after the method of the present invention has improved the recovery rate.

[0036] Figure 5 This is a flowchart of the method of the present invention.

[0037] 1. Tubing string; 2. Packer; 3. Water seal residual gas; 4. Closed loop residual gas. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0040] The present invention will now be described in further detail with reference to the accompanying drawings:

[0041] See Figure 5 This invention discloses a method for improving the recovery rate of fractured tight sandstone gas reservoirs, comprising the following steps:

[0042] S1. Determine the distribution of unused reservoirs and remaining gas, as follows:

[0043] The distribution of unexploded reservoirs and remaining gas was determined based on fractured tight sandstone gas well reservoirs, actual production conditions, and logging data.

[0044] S2. Determine the perforation interval based on the distribution of unused reservoirs and residual gas, and perforate at the corresponding locations;

[0045] Preferably, the original well string needs to be removed before perforation.

[0046] When retrieving the original well casing, the original well casing should be retrieved in accordance with the single-well overhaul specifications.

[0047] S3. Run in a new tubing string and set the packer below the original perforation section. Use the packer's interlayer to divide the gas layer into upper and lower sections.

[0048] S4. Perform hydraulic fracturing at the new perforation location;

[0049] Preferably, the formulation of the hydraulic fracturing working fluid includes fracturing fluid, fracturing fluid crosslinking fluid, fracturing fluid breaker, and proppant;

[0050] The volume ratio of fracturing fluid, fracturing fluid crosslinking fluid, and fracturing fluid breaker is 100:0.8:0.02, and 60-400 kg of proppant is added per cubic meter of fracturing fluid.

[0051] Preferably, hydraulic fracturing is performed. Before hydraulic fracturing, fracturing simulation is conducted based on the parameters of the single well to be fracturing and Meyer software. Based on the simulation results, hydraulic fracturing is performed at the new perforation location.

[0052] S5. If gas is produced in the new perforation section, gas will be produced in the tubing first, and water will be drained after water is encountered. If water is produced in the new perforation section, water will be drained from the tubing first.

[0053] Preferably, the drainage process is as follows:

[0054] The water seal gas displacement pressure threshold was determined, and the drainage pressure difference was changed by adjusting the oil pipe pressure to ensure that the drainage pressure difference met the drainage requirements without causing water seal gas to be produced.

[0055] After drainage is completed, gas is generated through the annulus between the oil jacket and the casing, so that the gas generation pressure difference is greater than the water seal gas displacement pressure threshold.

[0056] Preferably, the drainage period is at least 6 months.

[0057] Preferably, the water-sealed gas displacement pressure threshold represents the minimum pressure required for core displacement.

[0058] Preferably, the water-sealed gas displacement pressure threshold is obtained through physical simulation experiments using formation cores, as follows:

[0059] Step 1: Immerse the core in formation water and vacuum saturate it to obtain a core saturated with formation water;

[0060] Step 2: Place the core saturated with formation water into the core holder;

[0061] Step 3: Apply confining pressure to the core holder, where the magnitude of the confining pressure is the pressure of the overlying strata of the formation;

[0062] Step 4: Apply back pressure to the outlet end of the core holder, where the initial value of the back pressure is the formation pressure;

[0063] Step 5: Apply displacement pressure to the displacement end of the core holder. The magnitude of the displacement pressure is the formation pressure.

[0064] Step 6: Gradually reduce the back pressure value until a stable airflow is seen at the outlet;

[0065] Step 7: Calculate the water seal gas displacement pressure threshold. The water seal gas displacement pressure threshold is: displacement pressure at the displacement end - back pressure at the outlet end.

[0066] The water seal gas displacement pressure threshold is equal to the displacement pressure at the displacement end minus the back pressure at the outlet end. The formula for calculating the water seal gas displacement pressure threshold is as follows:

[0067] p = p1 - P2

[0068] Where p is the water seal gas displacement pressure threshold, p1 is the displacement pressure at the displacement end, and p2 is the back pressure value at the outlet end.

[0069] See Figure 5 In another feasible embodiment of the present invention, the following modifications are made as appropriate. Determine the distribution of unexploded reservoirs and residual gas. Based on the distribution of unexploded reservoirs and residual gas, determine the perforation zone and perforate at the corresponding location. Run a new tubing string and set a packer below the original perforation zone, using the packer's interlayer to divide the gas zone into upper and lower sections. The packer separates the water-producing zone from the gas-producing zone, achieving the goal of water retreat and gas release in the existing zone, gas production and drainage of the unexploded reservoir, and realizing the exploitation of residual gas. Perform hydraulic fracturing at the new perforation location. If the new perforation zone produces gas, gas is produced in the tubing first, followed by drainage after water is encountered; if the new perforation zone produces water, drainage is performed in the tubing first. See [link to relevant documentation]. Figure 4 This diagram illustrates the state of a fractured tight sandstone gas reservoir after the method of the present invention has been used to enhance oil recovery. The present invention can effectively extract the residual gas in the trap and the residual gas in the water seal after water exposure in fractured tight sandstone gas reservoirs, thereby improving the oil recovery rate.

[0070] Example 1:

[0071] This embodiment discloses a method for improving the recovery rate of fractured tight sandstone gas reservoirs, including the following steps:

[0072] S1. Determine the distribution of unexploded reservoirs and remaining gas based on fractured tight sandstone gas well reservoirs, actual production conditions, and logging data.

[0073] S2. Remove the original well casing according to the single-well overhaul specifications.

[0074] S3. Determine the perforation interval based on the unused reservoir conditions and perforate at the corresponding locations.

[0075] S4. Run a new tubing string according to well control specifications and construction requirements. Based on the untouched reservoir conditions, set the packer below the original perforation section. Use the interlayer to divide the gas layer into two sections, named Upper Section A and Lower Section B respectively.

[0076] S5. Perform hydraulic fracturing at the new perforation location to improve the permeability of the unused reservoir and enhance its production capacity.

[0077] S6. If gas is generated in section B of the new perforation section, gas will be generated in the tubing first, followed by drainage after water is encountered. Then, the water in the upper fracture will move downwards under the action of gravity differentiation. See [link to relevant documentation]. Figure 2If water is produced in section B of the new perforation, the tubing is drained, causing the water in the fracture to move downwards under the influence of gravity, achieving "water retreat and gas release." (See [link to relevant documentation]). Figure 3 .

[0078] S7. The water seal gas displacement pressure threshold is determined by experiment. The drainage pressure difference is changed by adjusting the oil pipe pressure to meet the drainage requirements without causing the water seal gas to be produced.

[0079] S8. After a certain period of drainage, the drainage time is at least 6 months. Gas is generated through the annulus between the oil jacket and the casing, so that the gas generation pressure difference is greater than the water seal gas displacement pressure threshold.

[0080] The hydraulic fracturing process requires determining the formulation and dosage based on the characteristics of the unexploded reservoir.

[0081] The water-sealed gas displacement pressure threshold was obtained through physical simulation experiments using formation cores, representing the minimum pressure required for core displacement.

[0082] The packer separates the water-producing layer from the gas-producing layer, achieving the goal of allowing gas to emerge from the existing water layer without utilizing the reservoir for gas production and drainage, thus enabling the exploitation of the remaining gas and having extremely important economic and social benefits.

[0083] This invention can effectively extract untapped reservoir gas and residual gas 3 from water-sealed fractured tight sandstone gas reservoirs after water exposure, and has extremely important economic and social benefits.

[0084] Example 2:

[0085] This embodiment discloses a method for improving the recovery rate of fractured tight sandstone gas reservoirs, as detailed below;

[0086] Gas well F-6 has a reservoir section of 6401-6572m and a perforated section of 6401-6450m. The reservoir is a fractured tight sandstone gas reservoir. Initially, the daily production of liquid was 2t and the daily production of gas was 260,000 cubic meters. Due to the continuous production and development, water has invaded high-angle fractures in the single well, resulting in a daily production of 100t of liquid and 10,000 cubic meters of gas. Moreover, the production capacity is showing a downward trend. See Table 1 for the parameters of gas well F-6.

[0087] S1. Based on the fractured tight sandstone gas well reservoir of gas well F-6, logging data and actual production situation, the distribution of unexploited reservoir and residual gas was determined. The reservoir properties in the perforated section of the well are well developed, with high-angle fractures of 45m, which cause formation water to flow along the high-permeability strip to the wellbore and be produced. There is also a large section of reservoir below the perforated section with great potential.

[0088] S2. Remove the original well casing according to the single-well overhaul specifications.

[0089] S3. Determine the perforation zone based on the unexploded reservoir condition and perforate at the corresponding location: For gas well F-6, the lower 100m to 150m of the perforation zone is the gas / poor gas layer, specifically from 6501m to 6500m. This is designated as a new production zone for perforation and production. Run a new tubing string according to well control specifications and construction requirements. Based on the unexploded reservoir condition, set packer 2 below the original perforation zone. Utilize the interlayer to divide the gas layer into two sections, named the upper section and the lower section respectively. See [link to relevant documentation]. Figure 1 The location of packer 2 contains a large amount of residual water seal gas 3 and residual closed loop gas 4.

[0090] S4. The fracturing string for this well is the same as the completion string; under KCk weighting conditions, the density is 1.15 g / cm³. 3 The construction displacement is 4.0-4.5m³. 3 / min, control the pump pressure to within 110MPa; during construction, maximize the discharge rate while considering the safety of the tubing.

[0091] Table 1: Parameters of Gas Well F-6

[0092] Target segment, m 6501-6500m Penetration rate, md 0.057 Porosity, % 6.2 Extended pressure gradient, MPa / m 0.0192 Formation temperature, °C 145 Minimum horizontal principal stress, MPa 139.1 pressure coefficient 1.7 Young's modulus, MPa 30000 <![CDATA[Consistency coefficient of fracturing fluid, Pa·s n > 0.4851 Poisson's ratio 0.25 Fracturing fluid flow index 0.9256 <![CDATA[Pumping rate, m 3 / min]]> 4.0

[0093] Using Meyer software for simulation, when the scale of the first-stage artificial crack with added sand reaches 25m... 3 At that time, the crack propagation tended to be gradual, therefore the sand addition scale for this stage was determined to be 25m. 3 When the scale of the second-level artificial crack with added sand reaches 15m 3 At this point, the crack propagation tends to slow down, therefore the sand addition scale for this stage is determined to be 15m³, and the total sand addition scale for both stages is 40m³. 3 Hydraulic fracturing was performed at the new perforation location, with a fracturing scale of 860m. 3 To improve the permeability of unused reservoirs and enhance their production capacity, see Table 2, which shows the fracturing working fluid formula and preparation volume.

[0094] Table 2: Fracturing Working Fluid Formulation and Preparation Quantity Table

[0095]

[0096] S5. Water is produced in the new perforation section. Water is drained from tubing string 1, causing the water-flooded fractures to move downwards under gravity, achieving "water retreat and gas release." (See [link]). Figure 3 .

[0097] S6. The water seal gas displacement pressure threshold was determined to be 7.6 MPa through experiments. The drainage pressure difference at the bottom of the packer 2 was changed to 7 MPa by adjusting the oil pressure, and the daily drainage was 50 cubic meters.

[0098] S7. After 7 months of drainage, gas is generated through the annulus between the oil jacket and the casing. Based on the water seal gas displacement pressure threshold of 7.6 MPa, the water seal gas production pressure difference is determined to be 9 MPa, with a daily liquid production of 3 tons and a daily gas production of 200,000 cubic meters.

[0099] The hydraulic fracturing process requires determining the formulation and dosage of the fracturing working fluid by combining the characteristics of the unexploded reservoir, porosity, and section information.

[0100] The water-sealed gas displacement pressure threshold was obtained through physical simulation experiments using formation cores, representing the minimum pressure required for core displacement.

[0101] The packer separates the water-producing layer from the gas-producing layer, achieving the goal of allowing gas to emerge from the existing water layer without utilizing the reservoir for gas production and drainage, thus enabling the exploitation of the remaining gas and having extremely important economic and social benefits.

[0102] In summary, this invention determines the distribution of unexploded reservoirs and residual gas. Based on this distribution, perforation intervals are identified, and perforations are made at corresponding locations to facilitate the extraction of trapped residual gas and water-sealed residual gas. After running a new tubing string, a packer is installed below the original perforation interval. The packer's interlayer divides the gas-bearing section into upper and lower segments, with the new perforation located below the packer. The packer separates the water-producing and gas-producing layers, achieving the goal of allowing gas to emerge from existing water in the existing intervals, producing gas from unexploded reservoirs, and draining water, thus realizing the extraction of residual gas. If gas is produced in the new perforation interval, gas is produced first in the tubing, followed by drainage after water encounter; if water is produced in the new perforation interval, drainage is performed first in the tubing. This invention can effectively extract trapped residual gas and water-sealed residual gas from fractured tight sandstone gas reservoirs after water encounter, improving recovery rates.

[0103] In addition, the present invention performs hydraulic fracturing at the new perforation location, which further improves the recovery efficiency of residual gas in the trap and residual gas in the water seal.

[0104] This invention simulates hydraulic fracturing using the parameters of the single well to be fracturing and Meyer software before the actual fracturing. Based on the simulation results, hydraulic fracturing is then performed at the new perforation location. This approach helps ensure effective fracturing and facilitates the recovery of residual gas from trapped areas and water seals, thereby improving the recovery rate of these gases. This invention can effectively recover untapped reservoir gas, residual gas from water seals 3, and residual gas from trapped areas 4 after water breakthrough in fractured tight sandstone gas reservoirs, resulting in significant economic and social benefits.

[0105] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for improving the recovery rate of fractured tight sandstone gas reservoirs, characterized in that, Includes the following steps: Determine the distribution of unexploited reservoirs and remaining gas; Determine the perforation intervals based on the distribution of unused reservoirs and residual gas, and perforate at the corresponding locations; Run a new tubing string and set the packer below the original perforation section. The new perforation position is located below the packer. Hydraulic fracturing was performed at the new perforation site; If gas is produced in the new perforation section, gas will be produced in the tubing first, and water will be drained after water is encountered. If water is produced in the new perforation section, the oil pipe should be drained.

2. The method for improving the recovery rate of fractured tight sandstone gas reservoirs according to claim 1, characterized in that, The specific steps for determining the distribution of unused reservoirs and remaining gas are as follows: The distribution of unexploded reservoirs and remaining gas was determined based on fractured tight sandstone gas well reservoirs, actual production conditions, and logging data.

3. The method for improving the recovery rate of fractured tight sandstone gas reservoirs according to claim 1, characterized in that, The perforation section is determined based on the distribution of unused reservoirs and remaining gas, and perforations are made at the corresponding locations. Before perforation, the original well string needs to be removed.

4. The method for improving the recovery rate of fractured tight sandstone gas reservoirs according to claim 3, characterized in that, When retrieving the original well casing, the original well casing shall be retrieved in accordance with the single-well overhaul specifications.

5. The method for improving the recovery rate of fractured tight sandstone gas reservoirs according to claim 1, characterized in that, The formulation of the hydraulic fracturing working fluid includes fracturing fluid, fracturing fluid crosslinking fluid, fracturing fluid breaker, and proppant. The volume ratio of fracturing fluid, fracturing fluid crosslinking fluid, and fracturing fluid breaker is 100:0.8:0.02, and 60-400 kg of proppant is added per cubic meter of fracturing fluid.

6. The method for improving the recovery rate of fractured tight sandstone gas reservoirs according to claim 5, characterized in that, Before hydraulic fracturing, fracturing simulation is performed based on the parameters of the single well to be fracturing and Meyer software. Based on the simulation results, hydraulic fracturing is then performed at the new perforation location.

7. The method for improving the recovery rate of fractured tight sandstone gas reservoirs according to claim 1, characterized in that, The drainage process is as follows: The water seal gas displacement pressure threshold is determined, and the drainage pressure difference is changed by adjusting the oil pipe pressure to make the drainage pressure difference meet the drainage requirements while ensuring that water seal gas is not produced. After drainage is completed, gas is generated through the annulus between the oil jacket and the casing, so that the gas generation pressure difference is greater than the water seal gas displacement pressure threshold.

8. The method for improving the recovery rate of fractured tight sandstone gas reservoirs according to claim 7, characterized in that, The drainage period is at least 6 months.

9. A method for improving the recovery rate of fractured tight sandstone gas reservoirs according to claim 7, characterized in that, The water-sealed gas displacement pressure threshold represents the minimum pressure required for core displacement, and the water-sealed gas displacement pressure threshold is obtained through physical simulation experiments using formation cores.

10. A method for improving the recovery rate of fractured tight sandstone gas reservoirs according to claim 9, characterized in that, The method for obtaining the water seal gas displacement pressure threshold is as follows: The water seal gas displacement pressure threshold is obtained by measuring the displacement pressure at the displacement end and the back pressure at the outlet end.

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