Method for optimizing gas injection capacity of horizontal well of gas storage
By employing pre-treatment before fracturing, hydraulic pulse fracturing, and sealing of fracture perforations, the problem of low gas injection capacity in horizontal wells of gas storage facilities was solved, achieving efficient improvement in gas injection capacity and safe fracturing transformation.
Patent Information
- Application Number
- CN202411386176.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2026-03-31
AI Technical Summary
In existing technologies, the measures to improve the gas injection capacity of horizontal wells in gas storage facilities are not thorough in unblocking, have a high risk of fracturing, and cannot meet the requirements of strong injection and strong production processes.
By employing pre-fracturing treatment, hydraulic pulse fracturing, sealing of fracture orifices, and circulating hydraulic pulse fracturing, the near-wellbore blockage is relieved by high-volume instantaneous over-fracture pressure, forming shear slip fractures and improving gas injection capacity.
It effectively improves the gas injection capacity of horizontal wells in gas storage facilities, reduces fracturing costs and construction risks, and meets the requirements of strong injection and strong production processes.
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Abstract
Description
Technical Field
[0001] This invention relates to the technical field of improving the gas injection capacity of horizontal wells in gas storage facilities, and is a method for optimizing the gas injection capacity of horizontal wells in gas storage facilities. Background Technology
[0002] Underground gas storage facilities (gas well storage facilities) typically use pipelines to inject and produce standard dry gas. A single storage facility usually undergoes multiple injection and production cycles over several years. The water saturation near the well is very low. Increasing the gas injection capacity of the storage facility's gas wells can lead to an increase in water saturation near the well, resulting in a decrease in the relative permeability of the gas phase within the well. Consequently, the gas injection capacity of the storage facility's gas wells also decreases. Gas reservoirs (gas-bearing formations) usually have high permeability. The purpose of modifying gas wells to improve their injection capacity is primarily to alleviate near-well formation damage. However, improving the gas injection capacity of storage facility gas wells is influenced by multiple factors. Since the formation damage mechanism varies from well to well, it is essential to accurately identify the modification process for improving the gas injection capacity of storage facility gas wells based on the formation damage mechanism, and then design a reasonable and safe method for optimizing the gas injection capacity of storage facility gas wells.
[0003] Currently, the main method for improving the gas injection capacity of horizontal wells in gas storage facilities is to use the relatively traditional acidizing and unblocking process. However, due to the characteristics of horizontal wells, such as large perforations and numerous fluid inlet channels, the traditional acidizing and unblocking process cannot achieve balanced unblocking. On the other hand, existing measures to improve the gas injection capacity of horizontal wells in gas storage facilities do not involve fracturing, and therefore cannot meet the requirements of the strong injection and strong production process of gas storage facilities.
[0004] In the process of fracturing horizontal wells in gas storage facilities, monitoring whether the caprock and interlayer of the gas storage facility are breached is relatively difficult to solve. The spacing between horizontal wells in gas storage facilities is smaller than the spacing between wells in oil and gas reservoir development. Therefore, it is not necessary to fracture long fractures in horizontal wells of gas storage facilities. If the horizontal well fractures extend upwards and are too high, they will open the caprock of the gas storage facility, affecting the sealing of the gas well. If the horizontal well fractures extend downwards and are too deep, they will connect to the oil and water layers at the bottom of the gas storage facility, posing a great risk to the horizontal well fracturing operation and affecting the sealing of the gas storage facility. On the other hand, if sand production occurs in the formation after fracturing the horizontal well of the gas storage facility, it will damage the downhole tubing and the surface gas production and transmission equipment.
[0005] Therefore, the above-mentioned measures to improve the gas injection capacity of horizontal wells in gas storage facilities have the problems of incomplete unblocking of horizontal wells and high risk of fracturing. Moreover, even after the improvement of the gas injection capacity of horizontal wells, the gas injection capacity of horizontal wells in gas storage facilities cannot meet the process indicators of strong injection and strong production in gas storage facilities. Summary of the Invention
[0006] This invention provides a method for optimizing the gas injection capacity of horizontal wells in gas storage facilities, which overcomes the shortcomings of the existing technologies. It can effectively solve the problem that existing modification measures to improve the gas injection capacity of horizontal wells in gas storage facilities result in low gas injection capacity due to incomplete unblocking.
[0007] The technical solution of this invention is achieved through the following measures: a method for optimizing the gas injection capacity of horizontal wells in a gas storage facility, the method being used for all horizontal wells with a conductivity coefficient greater than 1, comprising the following steps: Pre-treatment before fracturing involves first injecting pre-acid into the horizontal well to dissolve contaminants in the near-wellbore zone; then injecting low-viscosity slickwater into the horizontal well to displace the contaminants in the near-wellbore zone; finally, injecting low-viscosity slickwater into the horizontal well at a set discharge rate, pressurizing the horizontal well to P0, which promotes the formation of multiple fractures in the near-wellbore zone. When P0 decreases, hydraulic pulse fracturing is performed. Hydraulic pulse fracturing involves injecting low-viscosity slickwater into a horizontal well in a variable-displacement pulse manner until the peak pressure of the variable-displacement pulse reaches P1, causing multiple fractures to form near the wellbore and generating shear slip fractures. When sealing perforations in fractured areas and P1 suddenly decreases, first inject temporary plugging agent into the horizontal well to seal the multiple perforations formed in the near-wellbore zone; then inject low-viscosity slickwater into the horizontal well to replace the temporary plugging agent. After fracturing new fractures with circulating hydraulic pulses and sealing the perforation holes at the fracture openings, the horizontal well is pressurized to a set time, the fracturing pump discharge rate is increased to a set discharge rate, and low-viscosity slickwater is injected into the horizontal well at a set discharge rate. The horizontal well is pressurized to P2, which promotes the formation of new fractures in the near-wellbore zone. Determine if P2 is equal to P0; If yes, then stop working; if no, then perform hydraulic pulse fracturing, seal the fracture orifice, and circulate hydraulic pulse fracturing to create new fractures, updating P2.
[0008] The following are further optimizations and / or improvements to the above-mentioned technical solution: The above-mentioned injection into the horizontal well using a variable displacement pulse method continues until the peak pressure of the variable displacement pulse reaches P1, including initially injecting 5m... 3 Injecting 60m³ / min of water into a horizontal well 3 Low-viscosity slippery water, then reduce the discharge to 4m 3 Inject 30m / min into the horizontal well 3 Low viscosity slippery water, then reduce to 2m 3 Inject 10m into the horizontal well at a rate of / min 3 Low-viscosity slickwater, repeatedly pulsed 3 times at different discharge rates and volumes, with a total volume of 100m³. 3 The peak pressure of the pulse in the horizontal well with variable displacement reached P1.
[0009] The above-mentioned corrosion rates of hydrofluoric acid and hydrochloric acid on contaminants in the wellbore under different dosages, and based on the corrosion inhibitor to ensure the integrity of the rock skeleton, the pre-acid solution, by volume percentage, includes 1.5% hydrofluoric acid, 8% hydrochloric acid, and 2% corrosion inhibitor.
[0010] The aforementioned low-viscosity slickwater is based on the relationship between polymer slickwater viscosity and horizontal well fracture height, and on the reduction of water-sensitive damage to horizontal wells by clay stabilizers and potassium chloride. The low-viscosity slickwater, by volume percentage, comprises 98.7% polymer slickwater, 0.3% clay stabilizer, and 1% potassium chloride.
[0011] The total amount of temporary plugging agent used for each of the above-mentioned sealing of fracture perforations decreases sequentially. Specifically, it includes: sealing new fracture perforations formed in the near-wellbore zone, and ensuring that the temporary plugging particles can be completely degraded and hydrated after the injection of fracturing fluid into the horizontal well to create new fractures, restoring the fluid supply channel of the blocked section. The amount of temporary plugging agent required to seal each hydraulically circulated fracturing perforation decreases sequentially. The temporary plugging agents, based on particle size, include temporary plugging agents with a particle size of 1mm to 5mm, temporary plugging agents with a particle size of 5mm to 10mm, and temporary plugging agents with a particle size of 11mm to 13mm.
[0012] During the aforementioned pre-fracturing process, the maximum pressure at which pre-acid fluid is injected into the horizontal well is lower than the formation fracturing pressure of the horizontal well.
[0013] During the pretreatment process before fracturing, the high-pressure pulse pressure of the low-viscosity slickwater injected into the horizontal well is lower than and approaches 2.5 times the formation fracturing pressure of the horizontal well.
[0014] The peak pressure of the aforementioned variable displacement pulse reaches the limit range of P1, which is between 1.5 and 2.5 times the formation fracture pressure in horizontal wells.
[0015] The amount of low-viscosity slickwater required to replace the pre-placed acid in the horizontal well is the volume of the horizontal wellbore; the amount of low-viscosity slickwater required to replace the excess temporary plugging agent in the horizontal well is 1.0 to 1.5 times the volume of the horizontal wellbore.
[0016] The above-mentioned methods involve using a fracturing pump truck to inject pre-acid or low-viscosity slickwater into the horizontal well; and using a sand mixing truck to mix the temporary plugging agent evenly before injecting it into the horizontal well.
[0017] This invention utilizes a working method involving pre-fracturing, hydraulic pulse fracturing, sealing of fracture orifices, and circulating hydraulic pulse fracturing of new fractures. By employing high-displacement instantaneous over-fracture pressure, the formation is opened up, the pump is stopped to release pressure, and then the displacement is rapidly increased to expand the fracture. This reciprocating oscillation causes the fracture to exhibit shear slip, thereby gaining a certain degree of conductivity, relieving blockage in the near-wellbore area, and improving the gas injection capacity of horizontal wells in gas storage facilities with strong production and injection capabilities. Attached Figure Description
[0018] Appendix Figure 1This is a schematic diagram of the method flow of the present invention.
[0019] Appendix Figure 2 This is a graph showing the coordinate relationship between the polymer slickwater viscosity and the horizontal well fracture height according to the present invention.
[0020] Appendix Figure 3 This is a graph showing the coordinate relationship between the low-viscosity slickwater discharge rate and the horizontal well fracture height according to the present invention. Detailed Implementation
[0021] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.
[0022] The present invention will be further described below with reference to embodiments: Example 1: As Figure 1 As shown, the method for optimizing the gas injection capacity of horizontal wells in a gas storage facility is applicable to all horizontal wells with a conductivity coefficient greater than 1. Its key feature is that it includes the following steps: Pre-treatment before fracturing involves first injecting pre-acid into the horizontal well to dissolve contaminants in the near-wellbore zone; then injecting low-viscosity slickwater into the horizontal well to displace the contaminants in the near-wellbore zone; finally, injecting low-viscosity slickwater into the horizontal well at a set discharge rate, pressurizing the horizontal well to P0, which promotes the formation of multiple fractures in the near-wellbore zone. When P0 decreases, hydraulic pulse fracturing is performed. Hydraulic pulse fracturing involves injecting low-viscosity slickwater into a horizontal well in a variable-displacement pulse manner until the peak pressure of the variable-displacement pulse reaches P1, causing multiple fractures to form near the wellbore and generating shear slip fractures. When sealing perforations in fractured areas and P1 suddenly decreases, first inject temporary plugging agent into the horizontal well to seal the multiple perforations formed in the near-wellbore zone; then inject low-viscosity slickwater into the horizontal well to replace the temporary plugging agent. After fracturing new fractures with circulating hydraulic pulses and sealing the perforation holes at the fracture openings, the horizontal well is pressurized to a set time, the fracturing pump discharge rate is increased to a set discharge rate, and low-viscosity slickwater is injected into the horizontal well at a set discharge rate. The horizontal well is pressurized to P2, which promotes the formation of new fractures in the near-wellbore zone. Determine if P2 is equal to P0; If yes, then stop working; if no, then perform hydraulic pulse fracturing, seal the fracture orifice, and circulate hydraulic pulse fracturing to create new fractures, updating P2.
[0023] The above-mentioned work stoppage refers to the cessation of force pulse fracturing operations on new seams; The aforementioned update P2 refers to the process of pressurizing the horizontal well to a new pressure P3 after fracturing a new fracture using circulating hydraulic pulses, and then using this pressure to update P2. If P2 is not equal to P0 (in actual operating conditions, P2 is greater than P0), then hydraulic pulse fracturing is performed, the perforation holes at the fracture opening are sealed, and new fractures are fracturing using hydraulic pulse fracturing, as detailed below: Hydraulic pulse fracturing involves injecting low-viscosity slickwater into a horizontal well in a variable-displacement pulse manner until the peak pressure of the variable-displacement pulse reaches P1, causing multiple fractures to form near the wellbore and generating shear slip fractures. When sealing perforations in fractured areas and P1 suddenly decreases, first inject temporary plugging agent into the horizontal well to seal the multiple perforations formed in the near-wellbore zone; then inject low-viscosity slickwater into the horizontal well to replace the temporary plugging agent. After fracturing the new fracture with circulating hydraulic pulses and sealing the perforation at the fracture opening, the horizontal well is pressurized for a set time, and the pumping rate is increased to 5m³ / h. 3 / min, the low viscosity slickwater volume is 2 to 3 times the wellbore volume, the horizontal well is pressurized to a new pressure P3, and P3 is used as P2 to complete the P2 update process.
[0024] Example 2: As an optimization of the above example, injection is performed into the horizontal well using a variable displacement pulse method until the peak pressure of the variable displacement pulse reaches P1, including initially injecting 5m... 3 Injecting 60m³ / min of water into a horizontal well 3 Low-viscosity slippery water, then reduce the discharge to 4m 3 Inject 30m / min into the horizontal well 3 Low viscosity slippery water, then reduce to 2m 3 Inject 10m into the horizontal well at a rate of / min 3 Low-viscosity slickwater, repeatedly pulsed 3 times at different discharge rates and volumes, with a total volume of 100m³. 3 The peak pressure of the pulse in the horizontal well with variable displacement reached P1.
[0025] Example 3: As an optimization of the above example, as shown in the table below, based on the dissolution rate of hydrofluoric acid and hydrochloric acid on contaminants in the wellhead area under different dosages, and based on the corrosion inhibitor to ensure the integrity of the rock skeleton, the pre-acid solution includes 1.5% hydrofluoric acid, 8% hydrochloric acid, and 2% corrosion inhibitor by volume percentage.
[0026] As needed, the amount of pre-flush acid injected is half the volume of the horizontal well, which reduces costs and eliminates near-wellbore contamination.
[0027] Example 4: As an optimization of the above examples, low-viscosity slickwater is based on the relationship between polymer slickwater viscosity and horizontal well fracture height (as shown in the attached figure). Figure 2 As shown), and based on clay stabilizers and potassium chloride to reduce water-sensitive damage in horizontal wells, the low-viscosity slickwater, by volume percentage, comprises 98.7% polymer slickwater, 0.3% clay stabilizer, and 1% potassium chloride.
[0028] As needed, based on formation pressure coefficients and non-flowback process requirements, the frictional coefficients, base fluid viscosity, and residue content of slickwater and polymer slickwater were tested and compared, and a graph showing the relationship between polymer slickwater viscosity and horizontal well fracture height was plotted (e.g., Figure 1 As shown in the figure, within the same fracture height range, the drag reduction rate of polymer slickwater is >70%, and the viscosity of polymer slickwater can reach 3 MPa·s to 5 MPa·s. Polymer slickwater can meet the requirements of horizontal well hydraulic pulse fracturing without sand addition. After the gel breaks down, there is no residue left when cleaning the horizontal well, and there is no need to discharge polymer slickwater back to the horizontal well, which reduces the pollution to the gas storage formation. By volume percentage, adding 0.3% clay stabilizer and 1% potassium chloride to polymer slickwater yields low-viscosity slickwater, which also reduces water-sensitive damage (water-sensitive damage is the main form of damage to low-permeability reservoirs).
[0029] Example 5: As an optimization of the above embodiment, the total amount of temporary plugging agent used decreases sequentially each time the perforation hole at the crack is sealed. The temporary plugging agent used each time includes: Based on the sealing of newly formed fracture perforations in the near-wellbore zone, and based on the fact that after the injection of fracturing fluid into the horizontal well to create new fractures, the temporary plugging particles can be completely degraded and hydrated, restoring the fluid supply channel of the blocked section, and the amount of temporary plugging agent required to seal the perforations of new fractures created by each hydraulic cycle of fracturing decreases sequentially, the temporary plugging agents, based on particle size, include temporary plugging agents with particle sizes of 1mm to 5mm, 5mm to 10mm, and 11mm to 13mm.
[0030] Depending on the requirements, the temporary plugging agent may be biodegradable fiber particles.
[0031] Example 6: As an optimization of the above example, during the pretreatment process before fracturing, the maximum pressure of injecting pre-acid fluid into the horizontal well is lower than the formation fracturing pressure of the horizontal well.
[0032] Example 7: As an optimization of the above example, during the pretreatment process before fracturing, the high-pressure pulse pressure of the low-viscosity slickwater injected into the horizontal well is lower than and approaches 2.5 times the formation fracturing pressure of the horizontal well.
[0033] Example 8: As an optimization of the above example, the peak pressure of the variable displacement pulse reaches the limited range of P1, which is between 1.5 and 2.5 times the formation fracture pressure of the horizontal well.
[0034] Example 9: As an optimization of the above example, the amount of low-viscosity slickwater required to replace the pre-placed acid in the horizontal well is the volume of the horizontal wellbore; the amount of low-viscosity slickwater required to replace the excess temporary plugging agent in the horizontal well is 1.0 to 1.5 times the volume of the horizontal wellbore.
[0035] Example 10: As an optimization of the above example, a fracturing pump truck is used to inject pre-acid or low-viscosity slickwater into the horizontal well; a sand mixing truck is used to mix the temporary plugging agent evenly and then inject it into the horizontal well.
[0036] The known technical parameters of a horizontal well in a gas storage facility are as follows: (1) The horizontal section is 619.7m long, the maximum well inclination is 91.7°, the modified section is 243m long, and the perforation operation of the whole well section is carried out by using 89 guns strong pulse perforation method. The total thickness of the perforation is 560.2m, the perforation density is 16 holes / m, the number of perforation clusters is 11, and the total number of perforation holes is 8963. (2) Select well sections with good reservoir properties and perform hydraulic pulse fracturing without sand addition. The horizontal section of the target formation is 243m long, with a perforation density of 16 holes / m, 2 perforation clusters, a total of 3772 perforations, a porosity of 11.55%, a formation permeability of 11.17mD, and an oil saturation of 55.83%. (3) A single-seal sheath tubing string is adopted. The main structure of the tubing string includes φ89mm tubing, φ73mm tubing, and Y241-114 packer.
[0037] The coordinate relationship curve between low-viscosity slickwater discharge rate and horizontal well fracture height is shown in the attached figure. Figure 3 As shown in the figure, without damaging the horizontal well cover and interlayer of the gas storage, the pumping discharge rate in this invention ensures that the peak pulse pressure of the fracturing fluid (low viscosity slickwater) on the horizontal well is 1.5 to 2.5 times the formation fracturing pressure.
[0038] Example 11: The method for optimizing the gas injection capacity of the horizontal well in this gas storage facility is carried out according to the following steps: Based on the pressure gradient extending from adjacent wells in the block, the fracture pressure of this well is estimated to be around 42 MPa. Without damaging the caprock or interlayer, the optimal pump injection rate is 2.0 m³ / s. 3 / min to 5.0m 3 The pumping pressure is expected to be between 44.97 MPa and 67.7 MPa per minute.
[0039] (1) Pretreatment before fracturing The fracturing pump operates at a speed of 1.0m. 3 / min to 1.5m 3 Inject 25m³ of pre-fed acid fluid into the horizontal well at a flow rate of / min. 3 Dissolve contaminants in the near-well zone, then at 3m3 Injecting 15m³ of low-viscosity slickwater into a horizontal well at a flow rate of / min 3 It is replacing pollutants in the vicinity of the well.
[0040] (2) Hydraulic pulse fracturing fracturing pump at 5m 3 / min inject low-viscosity slickwater into the horizontal well, and increase the pumping rate as much as possible within the range of the horizontal well pulse peak. By eroding through the near-well rock skeleton collapse and damage zone, the low-viscosity slickwater volume is 2 to 3 times the well volume. The horizontal well is pressurized to P0. This is to use the hydraulic pressure transmission principle to make the low-viscosity liquid form artificial multiple fractures in the near-well zone. When P0 decreases, the fracturing pump initially operates at 5m... 3 Injecting 60m³ / min of water into a horizontal well 3 Then reduce the displacement to 4m 3 Inject 30m / min into the horizontal well 3 Low viscosity slippery water, then reduce to 2m 3 Inject 10m into the horizontal well at a rate of / min 3 Low-viscosity slickwater, repeatedly pulsed 3 times at different discharge rates and volumes, with a total volume of 100m³. 3 When the peak pressure of the variable displacement pulse in the horizontal well reaches P1, the repeated oscillation of the variable displacement causes shear slip fractures to form.
[0041] (3) Seal the crack opening and perforation hole When the peak pressure P1 of the variable displacement pulse in the horizontal well suddenly decreases, the sand mixing truck moves at a speed of 1.0m. 3 / min to 1.5m 3 At a flow rate of / min, 200 kg of temporary plugging agent with a particle size of 1 mm to 5 mm, 100 kg of temporary plugging agent with a particle size of 5 mm to 10 mm, and 50 kg of temporary plugging agent with a particle size of 11 mm to 13 mm are injected into the horizontal well to effectively seal the perforations at the fracture openings in the near-wellbore area. Then, at a flow rate of 4.0 m... 3 / min displacement to inject 15m of low-viscosity slippery water 3 It replaces excess temporary plugging agent in horizontal wells.
[0042] (4) New fractures formed by circulating hydraulic pulse fracturing First, maintain pressure in the horizontal well for 10 to 15 minutes. After the perforations at multiple fracture sites near the wellbore close, begin injecting fracturing fluid to create new fractures, increasing the pumping rate to 5 m³ / min. 3 / min, the low viscosity slickwater volume is 2 to 3 times the wellbore volume, and the horizontal well is pressurized to P2, which promotes the formation of new fractures in the near-wellbore zone; At this point, P2 is higher than P0, and when P2 suddenly decreases, the fracturing pump first accelerates at 5m... 3 Injecting 60m³ / min of water into a horizontal well 3Then reduce the displacement to 4m 3 Inject 30m / min into the horizontal well 3 Low viscosity slippery water, then reduce to 2m 3 Inject 10m into the horizontal well at a rate of / min 3 Low-viscosity slickwater, repeatedly pulsed 3 times at different discharge rates and volumes, with a total volume of 100m³. 3 In a horizontal well, the peak pressure of the variable displacement pulse reaches P3. Through repeated oscillations of the variable displacement, shear slip fractures are generated in the new fractures. Then, when P3 suddenly decreased, the sand mixing truck moved at 1.0m. 3 / min to 1.5m 3 At a flow rate of / min, 100kg of temporary plugging agent with a particle size of 1mm to 5mm, 100kg of temporary plugging agent with a particle size of 5mm to 10mm, and 25kg of temporary plugging agent with a particle size of 11mm to 13mm are injected into the horizontal well to effectively seal the perforations at new fracture openings in the near-wellbore area. Then, at a flow rate of 4.0m... 3 / min displacement to inject 15m of low-viscosity slippery water 3 It replaces excess temporary plugging agent in horizontal wells.
[0043] Finally, the horizontal well is pressure maintained for 10 to 15 minutes. After the fracture closes, the next cycle of hydraulic pulse fracturing is started to create a new fracture. The hydraulic pulse fracturing of the new fracture is stopped when P0 in the last hydraulic pulse remains constant. The horizontal well pressure is 6 MPa when the pump is stopped.
[0044] In summary, the pre-flush acid used in this invention has a low dosage and a high dissolution rate for near-wellbore contaminants, ensuring the integrity of the gas storage rock skeleton. The low viscosity of the slickwater meets the requirements of horizontal well hydraulic pulse fracturing without sand addition. After breaking the gel, there is no residue left when cleaning the horizontal well, and it does not need to be returned to the outside of the horizontal well, reducing the pollution of the gas storage formation. The addition of clay stabilizer and potassium chloride reduces water-sensitive damage (water-sensitive damage is the main form of damage to low-permeability reservoirs). By fracturing the formation fractures in the horizontal well through a variable displacement circulating pulse method, the horizontal well fractures exhibit shear slip and obtain a certain conductivity, improving the permeability of the gas storage layer and further improving the gas injection capacity of the horizontal well in the gas storage. It also has the advantages of low fracturing cost and low fracturing construction risk.
[0045] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.
Claims
1. A method for optimizing gas injection capacity of a gas storage horizontal well, characterized in that, The method is used for all horizontal wells with a flow capacity coefficient greater than 1, and comprises the following steps: Pre-treatment before fracturing, first, preflush is injected into the horizontal well to dissolve the near-wellbore zone contaminants; then, low-viscosity slickwater is injected into the horizontal well to replace the near-wellbore zone contaminants; finally, low-viscosity slickwater is injected into the horizontal well at a set rate, the horizontal well is pressured to P0, and the near-wellbore zone is caused to form multiple fractures, when P0 is reduced, hydraulic pulse fracturing is performed; Hydraulic pulse fracturing, low-viscosity slickwater is injected into the horizontal well in a variable-rate pulse mode until the variable-rate pulse peak pressure reaches P1, so that the near-wellbore zone forms multiple fractures to generate shear-slip fractures; Blocking the fracture perforation, when P1 is suddenly reduced, first, temporary plugging agent is injected into the horizontal well to block the multiple fractures formed in the near-wellbore zone; then, low-viscosity slickwater is injected into the horizontal well to replace the temporary plugging agent; Circulating hydraulic pulse fracturing of new fractures, after blocking the fracture perforation, the horizontal well is pressured to a set time, the fracturing pump rate is increased to a set rate, and low-viscosity slickwater is injected into the horizontal well at the set rate, the horizontal well is pressured to P2, and the near-wellbore zone is caused to form new fractures; Judging whether P2 is equal to P0; If yes, the work is stopped, and if no, hydraulic pulse fracturing, blocking the fracture perforation, and circulating hydraulic pulse fracturing of new fractures are performed, and P2 is updated.
2. The method for optimizing gas injection capacity of a gas storage horizontal well according to claim 1, characterized in that Inject into horizontal well in variable displacement pulse mode until variable displacement pulse peak pressure reaches P1, including first injecting 60 m 3 low viscosity slick water into horizontal well at 5 m 3 / min displacement, then reducing displacement to 4 m 3 / min to inject 30 m 3 low viscosity slick water into horizontal well, then reducing to 2 m 3 / min to inject 10 m 3 low viscosity slick water into horizontal well, repeatedly pulsing 3 times at different displacement and liquid volume, total liquid volume 100 m 3 , horizontal well variable displacement pulse peak pressure reaches P1.
3. The method for optimizing gas injection capacity of a gas storage horizontal well according to claim 1 or 2, characterized in that, Based on the dissolution rate of hydrogen fluoride and hydrochloric acid on the contaminants in the wellbore zone under different dosages, and based on the corrosion inhibitor ensuring the integrity of the rock skeleton, the preflush comprises, by volume percentage, 1.5% hydrogen fluoride, 8% hydrochloric acid, and 2% corrosion inhibitor; Or / and, based on the relationship between the viscosity of polymer slickwater and the fracture height of the horizontal well, and based on the clay stabilizer and potassium chloride to reduce the water sensitivity damage of the horizontal well, the low-viscosity slickwater comprises, by volume percentage, 98.7% polymer slickwater, 0.3% clay stabilizer, and 1% potassium chloride.
4. The method for optimizing gas injection capacity of a gas storage horizontal well according to claim 1 or 2, characterized in that, The total amount of temporary plugging agent used in blocking the fracture perforation decreases successively each time, and specifically comprises: based on blocking the new fracture perforation formed in the near-wellbore zone, and based on the temporary plugging particles being completely degraded and hydrated after the end of injecting the fracturing fluid into the horizontal well to form new fractures, the liquid supply channel of the blocked section is restored, and the amount of temporary plugging agent required for blocking the perforation of each hydraulic fracturing of new fractures decreases successively, the temporary plugging agent comprises, by particle size, 1mm to 5mm temporary plugging agent, 5mm to 10mm temporary plugging agent, and 11mm to 13mm temporary plugging agent.
5. The method for optimizing gas injection capacity of a horizontal well of a gas storage according to claim 3, characterized in that, The total amount of temporary plugging agent used in blocking the fracture perforation decreases successively each time, and specifically comprises: based on blocking the new fracture perforation formed in the near-wellbore zone, and based on the temporary plugging particles being completely degraded and hydrated after the end of injecting the fracturing fluid into the horizontal well to form new fractures, the liquid supply channel of the blocked section is restored, and the amount of temporary plugging agent required for blocking the perforation of each hydraulic fracturing of new fractures decreases successively, the temporary plugging agent comprises, by particle size, 1mm to 5mm temporary plugging agent, 5mm to 10mm temporary plugging agent, and 11mm to 13mm temporary plugging agent.
6. The method for optimizing gas injection capacity of a gas storage horizontal well according to claim 1 or 2 or 5, characterized in that The maximum pressure of the preflush injected into the horizontal well during the pre-treatment process before fracturing is lower than the formation fracture pressure of the horizontal well, or / and the peak pressure of the variable displacement pulse reaches P1, which is limited to 1.5 to 2.5 times the formation fracture pressure of the horizontal well.
7. The method for optimizing gas injection capacity of a horizontal well of a gas storage according to claim 3, characterized in that The maximum pressure of the preflush injected into the horizontal well during the pre-treatment process before fracturing is lower than the formation fracture pressure of the horizontal well, or / and the peak pressure of the variable displacement pulse reaches P1, which is limited to 1.5 to 2.5 times the formation fracture pressure of the horizontal well.
8. The method of claim 4, wherein The maximum pressure of the preflush injected into the horizontal well during the pre-treatment process before fracturing is lower than the formation fracture pressure of the horizontal well, or / and the peak pressure of the variable displacement pulse reaches P1, which is limited to 1.5 to 2.5 times the formation fracture pressure of the horizontal well.
9. The method according to any one of claims 1 to 8, c h a r a c t e r i z e d b y When injecting low viscosity slick water into a horizontal well at a set displacement, the set displacement of the fracturing pump is 5 m 3 / min, the low viscosity slick water is 2 to 3 times the volume of the wellbore, and the low viscosity slick water is injected into the horizontal well such that the high pressure pulse pressure is less than and approaches 2.5 times the formation fracture pressure of the horizontal well.
10. The method of optimizing gas injection capacity of a gas storage horizontal well according to any one of claims 1 to 8, characterized in that The low-viscosity slick water required for the positive squeeze to replace the preflush in the horizontal well is the volume of the horizontal wellbore; the low-viscosity slick water required to replace the excess temporary plugging agent in the horizontal well is 1.0 to 1.5 times the volume of the horizontal wellbore.