CN114059987A - Cluster type multistage gap acidizing and fracturing method and application thereof - Google Patents
Cluster type multistage gap acidizing and fracturing method and application thereof Download PDFInfo
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- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
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- E21B43/26—Methods for stimulating production by forming crevices or fractures
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Abstract
The invention discloses a cluster type multistage gap acidizing and fracturing method and application thereof, wherein the method comprises the following steps: injecting and sewing the first stage, and stopping the pump intermittently; injecting and sewing the second stage, and stopping the pump intermittently; injecting and sewing the third stage, and stopping the pump intermittently; fourth-stage injection seam making; alternately injecting high-viscosity and low-viscosity acid liquid for etching; and (4) performing over-displacement. According to the method, after acid fracturing is completed, the fracture is diverted for multiple times, and the fracture-cavity body connected to the target azimuth and distance produces oil. The fracturing fluid is reasonable in design and obvious in effect, can be widely used for single-well fracturing of carbonate oil-gas reservoirs, and is particularly suitable for fracture-cavity oil reservoirs. Thereby furthest exerting the potential of the reservoir and improving the effective period of the crack and the yield of the oil well.
Description
Technical Field
The invention belongs to the field of oil and gas field development, particularly relates to a yield increasing method in the field of oil and gas field development, and particularly relates to a cluster type multistage gap acidizing and fracturing method which is mainly applied to acid fracturing of carbonate oil and gas reservoirs.
Background
Fracture acidizing is called acid fracturing for short. The fracturing without proppant is carried out by using acid liquor as fracturing fluid under the condition that the pressure is higher than the fracture pressure of the stratum. The wall surface of the crack is corroded into an uneven surface by the corrosion action of the acid liquor in the acid fracturing process, so that the wall surface of the crack cannot be completely closed after the pump is stopped to relieve pressure. Therefore, the composite material has higher flow conductivity and obvious effect on recovering and improving the production capacity of an oil well. The method is suitable for carbonate reservoirs.
At present, the discovered proportion of the ultra-deep carbonate fracture-cave type oil and gas reservoirs is more and more. For example, the newly discovered northerly oil and gas reservoir in China petrochemical industry has a common measurement vertical depth of 7000-9000m, and the oil and gas reservoir of the type has abnormal development of the fracture and holes, and large-leakage fracture and hole bodies need to be avoided during drilling, otherwise, the loss-back type leakage can be caused to greatly increase the drilling period, and even normal drilling cannot be performed. Therefore, it is often required to communicate the randomly distributed cavities by acid fracturing. However, if the fracture body can not be effectively communicated in the acid fracturing, the yield after the acid fracturing is low and the decline is fast. But the conventional acid fracturing technology has single formed crack and low probability of communicating a crack body.
In order to meet the requirements, the research on fiber temporary plugging and turning acid fracturing technology and the field test thereof propose that the temporary plugging of the fiber is adopted to realize the turning of acid corrosion cracks, so that the possibility of communicating the crack bodies in different directions is increased. However, due to the ultra-deep layer, the ground stress is large, the seam forming width is narrow, and the temporary plugging agent is difficult to move to the inside of the crack as expected by design. Therefore, even if the temporary plugging effect occurs, the diverted fracture is often close to the well bore, and the fracture forming width is narrow, the induced stress is small, and the distance for transmitting the induced stress is also small. Therefore, the target fracture-cavity body in a certain direction and distance is communicated by effective steering fracturing, and the communication is difficult to achieve and even impossible to achieve.
Meanwhile, considering that the distribution of the fracture-cavity body has great uncertainty, the single-well temporary plugging one-time acid fracturing technology is difficult to achieve the expected target of communicating the fracture-cavity body, and a new technology needs to be researched and proposed to solve the limitation.
Disclosure of Invention
In order to overcome the problems in the prior art and communicate more fracture-cavity bodies in different directions, the invention provides a cluster type multistage intermittent acid fracturing technology which utilizes the induced stress and the interference effect thereof in the fracturing or acid fracturing process to the maximum extent to realize multiple diversion of fractures. The method of the invention can exert the superposition effect of various stress interferences to the utmost extent, thereby increasing the probability of communicating the randomly distributed seam-hole bodies with different sizes by various steering seams to the utmost extent, rather than the effect of communicating a single seam-hole body in the past. Therefore, the cluster type multistage gap type fracturing and acid fracturing combined operation mode can greatly improve the reconstruction effect and the validity period of a single well.
The core mechanism of the present invention is therefore how to make maximum use of the induced stresses and their disturbing effects in the fracturing or acid fracturing process. Specifically, although the rock is an ultra-deep layer and the temperature and pressure are relatively high, the lithology is mainly carbonate rock, generally limestone rock (which occupies more than 90%), and the mineral content of other clay and the like is mostly below 5%. The extremely high lithology of the brittle mineral is determined by experiments, and the brittle mineral still belongs to the linear deformation category when the temperature is below 300 ℃. In other words, once the induced stress is formed, it propagates a relatively long distance. According to current research, the distance over which the induced stress propagates is substantially comparable to the length of the seam. In addition, the magnitude of the induced stress is closely related to the net pressure within the fracture. The induced stress at a distance of 0m from the fracture face perpendicular to the fracture face is the net pressure within the fracture. Therefore, to increase the induced stress in fracturing or acid fracturing, firstly, the volumes of the injected fracturing fluid and acid liquid are relatively high; secondly, the injection discharge capacity and the viscosity of the fracturing fluid and the acid liquid are relatively high so as to obtain wider cracks; thirdly, temporary blocking in the crack is carried out, and the net pressure in the crack is promoted to be rapidly increased.
One of the objectives of the present invention is to provide a cluster type multistage gap acid fracturing method, which comprises: the single-well multistage gap type fracturing operation and the multi-well cluster type simultaneous fracturing operation are combined.
In a preferred embodiment, the single well multiple interval type fracturing operation comprises: multiple interval (intermittent) fracturing operations (thus, stopping the pump for a period of time between each fracturing stage) are performed on a single well multiple times with instantaneous pump stops and pumps.
In a further preferred embodiment, the pumping is stopped between each stage of fracturing for 1 to 60min, preferably 1 to 30min, more preferably 1 to 20min, for example 1 to 10 min.
In a further preferred embodiment, a non-reactive fracturing fluid, preferably at least one selected from the group consisting of guar fracturing fluid, polymer fracturing fluid, carboxymethylhydroxypropylguar fracturing fluid, and slickwater, is employed in performing the multi-stage interstitial fracturing operation.
Considering that an ultra-deep oil and gas reservoir is provided, the induced stress formed by primary fracturing or acid fracturing is extremely limited, even if an intra-fracture temporary plugging method is adopted, the range of temporary plugging is mostly in a fracture zone close to a well bore, the turning radius is very small, and the expected goal of communicating a fracture body which can be communicated only by a larger turning angle and turning radius is difficult to achieve.
Therefore, when single well fracturing or acid fracturing is carried out, a multi-stage clearance type (intermittent) operation mode such as multiple instantaneous pump stopping and pumping starting is adopted, the front side adopts non-reactive fracturing fluid to carry out multi-stage clearance type operation, and the fracturing fluid does not react with rocks, so that the induced stress generated in the fracturing process is larger than that of the acid fracturing (a part of rocks are consumed by the acid rock reaction, the width of a crack is larger, but the net pressure in the crack is possibly reduced on the contrary). And the size of each fracture is relatively large.
In a preferred embodiment, the viscosity of the fracturing fluid increases in stages as each stage of the fracturing operation progresses.
In a further preferred embodiment, the displacement of the fracturing fluid is optionally increased in stages as each stage of the fracturing operation progresses, preferably the displacement of the fracturing fluid is increased in stages per two stages.
In order to save the cost of the fracturing fluid and ensure that a new crack can be extended on a new crack initiation angle after each interval type fracturing, the viscosity and the discharge capacity of the fracturing fluid after each pumping start are gradually increased. Therefore, the highest viscosity and displacement of the fracturing fluid need to be simulated and determined in advance, and then the previous combination of the viscosity and displacement of the fracturing fluid is determined according to the number of stages of the gap.
Therefore, after the multistage clearance type operation mode is adopted, as long as the length of the crack of each stage of fracturing is large enough, the propagation distance of the induced stress is close to the length direction of the crack, so that the superposition effect of the induced stress formed by each stage of crack is larger and larger, and finally the turning radius of the turning crack is also greatly improved (the larger the stress turning area formed by the induced stress is, the larger the turning radius is, and once the stress turning area is broken through, the turning crack can turn to the direction of the original maximum horizontal main stress again).
In the invention, multiple times of gap injection are adopted, and the stress field is continuously changed, so that the gradual turning of the crack is realized. Thus, the crack gradually deviates from the original main force stress direction, and the target reservoir body with a certain direction and distance is effectively communicated.
In a preferred embodiment, during single well fracturing, a low-viscosity high-displacement fracturing fluid is injected after the multi-stage gap type fracturing operation, and cooling and crack expanding operations are performed.
In a further preferred embodiment, after the slot expanding operation, high-viscosity acid liquid and low-viscosity acid liquid are alternately injected for etching.
In a preferred embodiment, the multi-well cluster simultaneous fracturing operation comprises: within a well group or a plurality of well groups, each operation step of all wells is synchronously carried out, including simultaneously starting the pump, simultaneously stopping the pump, and simultaneously replacing fracturing fluid or acid liquor.
In other words, the mode of action of the multi-well cluster is the multi-well synchronous replication of the single-well multi-stage gap type operation. The purpose is to utilize the induced stress superposition effect caused by single-well multi-stage gap type operation and temporary blocking in the seam, and also to perform the same induced stress interference effect on a plurality of adjacent wells, and finally to exert the superposition effect of various stress interferences to the utmost extent in an oil and gas reservoir unit covered by one well group or a plurality of well groups, thereby increasing the probability of communicating the randomly distributed seam-hole bodies with different sizes by various steering seams to the utmost extent, and being not the conventional assumption of communicating only a single seam-hole body. Therefore, the cluster type multistage gap type fracturing and acid fracturing combined operation mode can greatly improve the reconstruction effect and the validity period of a single well.
In a preferred embodiment, the clustered multilevel interstitial acid fracturing method comprises the following steps:
(1) injecting low-viscosity medium-displacement fracturing fluid to perform first-stage seam formation, and intermittently stopping the pump;
(2) injecting medium-viscosity medium-displacement fracturing fluid to perform second-stage seam formation, and intermittently stopping the pump;
(3) injecting high-viscosity high-displacement fracturing fluid to perform third-stage seam formation, and intermittently stopping the pump;
(4) injecting high-viscosity high-displacement acid liquor to finish the last stage of seam making;
(5) injecting low-viscosity high-displacement fracturing fluid to perform cooling and joint expansion operation;
(6) injecting high-viscosity high-displacement acid liquid to perform high-viscosity acid injection operation;
(7) injecting low-viscosity high-displacement acid liquid to perform high-viscosity acid injection operation;
(8) repeating the steps (6) to (7);
(9) performing replacement operation;
(10) and (4) if one well group or a plurality of well groups exist, adopting a cluster type simultaneous operation mode, and repeating the steps (1) to (9) until all wells are constructed.
Wherein the non-reactive common fracturing fluid adopted in the steps (1) to (4) is at least one selected from guar gum fracturing fluid, polymer fracturing fluid, carboxymethyl hydroxypropyl guar gum fracturing fluid and slick water. And (4) adopting acid liquor selected from at least one of gelling acid, ground cross-linking acid, viscidic acid and diverting acid in the steps (5) to (8).
In a preferred embodiment, in step (1), the first stage fracture length is 40% to 80%, preferably 60%, of the projected length of the line connecting the wellbore and the fracture body in the original direction of maximum principal stress.
In a preferred embodiment, in step (1), the fracturing fluid displacement is 2-3m3Min, the viscosity of the fracturing fluid is 2-3mPa.s, and the liquid amount of the fracturing fluid is 150-3。
In the step (1), commercial optimization design software for both fracturing and acid fracturing, such as STIMPLAN, Frac PROPT and the like, is applied to simulate the three-dimensional geometrical sizes and the flow conductivity of the fractures under different liquidity (fracturing fluid and acid fluid), fluid quantity, discharge capacity and viscosity. And determining fracturing or acid fracturing construction parameters under the target fracture length, and performing fracturing construction according to the parameters.
After the construction in the step (1), the pump is stopped for 1-60min, preferably 1-30 min, more preferably 1-20 min, for example 1-10 min.
In a preferred embodiment, in the step (2), the discharge capacity of the fracturing fluid is 2-3m3Min, the viscosity of the fracturing fluid is 15-20mPa.s, and the amount of the fracturing fluid is 130-3。
In a preferred embodiment, in step (2), the second stage fracture length is 10% to 50%, preferably 20%, of the projected length of the wellbore-to-cavity junction in the direction of the original maximum principal stress.
In the step (2), commercial optimization design software for fracturing or acid fracturing, such as stimlan, Frac prop and the like, is used to simulate the three-dimensional geometrical size and the flow conductivity of the fracture under different properties (fracturing fluid and acid fluid), fluid quantity, discharge capacity and viscosity.
After the construction in the step (2), the pump is stopped for 1-60min, preferably 1-30 min, more preferably 1-20 min, for example 1-10 min.
In a preferred embodiment, in the step (3), the discharge amount of the fracturing fluid is 5-6m3The viscosity of the fracturing fluid is 50-60mPa.s, and the liquid volume of the fracturing fluid is 100-3。
In a preferred embodiment, in step (3), the third stage fracture length is 10% to 40%, preferably 20%, of the projected length of the connecting line of the wellbore and the fracture body in the original direction of the maximum principal stress.
In the step (3), commercial optimization design software for both fracturing and acid fracturing, such as stimlan, Frac prop and the like, is applied to simulate the three-dimensional geometrical sizes and the flow conductivity of the fractures under different liquidities (fracturing fluid and acid fluid), fluid amounts, discharge amounts and viscosities.
After the construction in the step (3), the pump is stopped for 1-60min, preferably 1-30 min, more preferably 1-20 min, for example 1-10 min.
In a preferred embodiment, in the step (4), the acid liquor displacement is 5-6m3The viscosity of the acid solution is 70-80mPa.s, and the liquid volume of the acid solution is 40-50m3。
In a preferred embodiment, in step (4), the fourth stage fracture length is equal to 10% to 30%, preferably 20%, of the length of the line connecting the wellbore and the fracture body.
In the step (4), commercial optimization design software for both fracturing and acid fracturing, such as stimlan, Frac prop and the like, is applied to simulate the three-dimensional geometrical sizes and the flow conductivity of the fractures under different liquidities (fracturing fluid and acid fluid), fluid amounts, discharge amounts and viscosities. And determining the fracturing or acid fracturing construction parameters under the target fracture length.
In a preferred embodiment, in the step (5), the discharge capacity of the fracturing fluid is 5-6m3Min, the viscosity of the fracturing fluid is 1-10mPa.s, and the amount of the fracturing fluid is 200-3。
In a preferred embodiment, in the step (6), the acid liquor displacement is 5-6m3Min, the viscosity of the acid solution is 40-100mPa.s, the liquid volume of the acid solution is 100-3。
In a preferred embodiment, in the step (7), the acid liquor displacement is 5-6m3The viscosity of the acid solution is 4-10mPa.s, the liquid volume of the acid solution is 100-3。
Wherein, the step (6) and the step (7) realize viscosity finger advance, which is beneficial to etching effect.
In a preferred embodiment, in step (9), the displacement is performed at 110-300% of the wellbore volume.
In a further preferred embodiment, in step (9), displacement is carried out with a low viscosity slickwater of 2-3 mpa.s.
According to the method, after acid fracturing is completed, the fracture is diverted for multiple times, and the fracture-cavity body connected to the target azimuth and distance produces oil.
The second purpose of the invention is to provide the application of the cluster type multistage gap acid fracturing method in acid fracturing of carbonate oil and gas reservoirs.
The method is mainly applied to acid fracturing of carbonate oil-gas reservoirs, and has wide application prospects in Tahe oil fields, northward oil-gas fields and Tarim oil-gas fields.
The endpoints of the ranges and any values disclosed in the present application are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein. In the following, various technical solutions can in principle be combined with each other to obtain new technical solutions, which should also be regarded as specifically disclosed herein.
Compared with the prior art, the invention has the following beneficial effects: the fracturing fluid is reasonable in design and obvious in effect, can be widely used for single-well fracturing of carbonate oil-gas reservoirs, and is particularly suitable for fracture-cavity oil reservoirs. Thereby furthest exerting the potential of the reservoir and improving the effective period of the crack and the yield of the oil well.
Drawings
FIG. 1 is a schematic diagram of a trench-hole body for a fracturing method according to the present invention;
1-a wellbore; 2-a hole sewing body; 3-direction of maximum principal stress; 4-diversion crack.
Detailed Description
While the present invention will be described in detail with reference to the following examples, it should be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the present invention.
It is to be further understood that the various features described in the following detailed description may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention can be made, as long as the technical solution formed by the combination does not depart from the idea of the present invention, and the technical solution formed by the combination is part of the original disclosure of the present specification, and also falls into the protection scope of the present invention.
The raw materials used in the examples and comparative examples are disclosed in the prior art if not particularly limited, and may be, for example, directly purchased or prepared according to the preparation methods disclosed in the prior art.
[ example 1 ]
The well depth is 5548 m, the target fracture body containing oil is 102 m away from the well bore, and the angle of the direction of the maximum principal stress is 35 degrees. Three-stage intermittent acid pressing is adopted.
The first stage injection displacement is 2.5m3The viscosity is 3mPa.s, the liquid quantity is 150m3. After the construction at this stage, the pump is stopped for 2min instantaneously.
The second stage injection displacement is 3m3Min, viscosity of 15mPa.s, liquid amount of 130m3. After the construction at this stage, the pump is stopped for 4min instantaneously.
The third stage injection displacement is 5m3The viscosity is 50mPa.s, the liquid quantity is 120m3. After the construction at this stage, the pump is stopped for 1min instantaneously.
The fourth stage injection displacement is 6m3The viscosity is 75mPa.s, the liquid quantity is 40m3。
After the intermittent construction is finished, the discharge capacity is injected into the pipe again for 6m3350m of fracturing fluid with viscosity of 2-3 mPa.s/min3And cooling and expanding the seam.
Discharge capacity of 6m3150m of high-viscosity crosslinked acid with viscosity of 50 mPa.s/min3+ discharge capacity 6m3Low-viscosity adhesive with viscosity of 5 mPa.s/minCoagulated acid 100m3Performing viscosity-finger etching.
Discharge capacity of 6m3150m of high-viscosity crosslinked acid with viscosity of 50 mPa.s/min3+ discharge capacity 6m3Low viscosity gelling acid 100m with viscosity of 5 mPa.s/min3Performing viscosity-finger etching.
Slick water 100m3And (4) displacing.
And after the well is closed and the reaction is carried out for 60 minutes, opening the well and carrying out open flow to solve the yield. During oil production, the initial yield of the oil well is 147 tons/day, and after production for one year, the yield is still maintained at 102 tons/day every day, and the pressure of the well head is 18 MPa. The production pressure is always kept at a high level, and the acid fracturing fractures effectively communicate with the fracture-cavity body. Therefore, the yield of the oil well constructed by the acid fracturing method is obviously improved.
[ example 2 ]
The well depth is 7980 m, the target oil-containing fracture body is 85 m away from the well shaft, and the angle between the direction of the maximum principal stress is 22 degrees. Two-stage intermittent acid pressing is adopted.
The first stage injection displacement is 4m3The viscosity is 3mPa.s, the liquid quantity is 200m3. After the construction at this stage, the pump is stopped for 5min instantaneously.
The second stage injection displacement is 5m3Min, viscosity of 20mPa.s, liquid amount of 120m3. After the construction at this stage, the pump is stopped for 5min instantaneously.
The third stage injection displacement is 6m3The viscosity is 50mPa.s, the liquid quantity is 120m3. After the construction at this stage, the pump is stopped instantaneously for 3 min.
After the intermittent construction is finished, the discharge capacity is injected to 8m3500m of slickwater with viscosity of 2-3 mPa.s/min3And cooling and expanding the seam.
Discharge capacity of 7m3200m of high-viscosity crosslinked acid with viscosity of 50 mPa.s/min3+ discharge capacity 9m3120m of cross-linked acid base solution with viscosity of 10 mPa.s/min3Performing viscosity-finger etching.
Slippery water 200m3And (4) displacing.
And after the well is closed and the reaction is carried out for 60 minutes, opening the well and carrying out open flow to solve the yield. During oil production, the initial yield of the oil well is 208 tons/day, and the pressure of the well head is 35 MPa. The production pressure is always kept at a high level, and the acid fracturing fractures effectively communicate with the fracture-cavity body. Therefore, the yield of the oil well constructed by the acid fracturing method is obviously improved.
The invention has been described in detail with reference to specific embodiments and illustrative examples, but the description is not intended to be construed in a limiting sense. Those skilled in the art will appreciate that various equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its embodiments without departing from the spirit and scope of the present invention, which fall within the scope of the present invention. The scope of the invention is defined by the appended claims.
Claims (14)
1. A clustered multi-stage gap acidizing fracturing method, comprising: the single-well multistage gap type fracturing operation and the multi-well cluster type simultaneous fracturing operation are combined.
2. The fracturing method of claim 1, wherein the single well multi-stage interstitial-type fracturing operation comprises: and performing multi-stage gap type fracturing operation of instantly stopping and restarting the pump for multiple times on a single well, preferably stopping the pump for 1-60min, and preferably 1-30 min between every two stages of fracturing.
3. The fracturing method according to claim 2,
along with the progress of each stage of fracturing operation, the viscosity of the fracturing fluid is gradually increased; and/or
The displacement of the fracturing fluid is optionally increased in stages as each stage of the fracturing operation progresses, preferably the displacement of the fracturing fluid is increased in stages per two stages.
4. The fracturing method of claim 2, wherein in single well fracturing, a low viscosity high displacement fracturing fluid is injected after the multi-stage interval type fracturing operation to perform cooling and crack expanding operation.
5. The fracturing method according to claim 4, wherein the slot expanding operation is followed by alternately injecting a high viscosity liquid and a low viscosity liquid for etching.
6. The fracturing method of claim 1, wherein the multi-well clustered simultaneous fracturing operation comprises: within a well group or a plurality of well groups, each operation step of all wells is synchronously carried out, including simultaneously starting the pump, simultaneously stopping the pump, and simultaneously replacing fracturing fluid or acid liquor.
7. The fracturing method according to any one of claims 1 to 6, wherein the clustered multi-stage gap acidizing fracturing method comprises the following steps:
(1) injecting low-viscosity medium-displacement fracturing fluid to perform first-stage seam formation, and intermittently stopping the pump;
(2) injecting medium-viscosity medium-displacement fracturing fluid to perform second-stage seam formation, and intermittently stopping the pump;
(3) injecting high-viscosity high-displacement fracturing fluid to perform third-stage seam formation, and intermittently stopping the pump;
(4) injecting high-viscosity high-displacement acid liquor to finish the last stage of seam making;
(5) injecting low-viscosity high-displacement fracturing fluid to perform cooling and joint expansion operation;
(6) injecting high-viscosity high-displacement acid liquid to perform high-viscosity acid injection operation;
(7) injecting low-viscosity high-displacement acid liquid to perform high-viscosity acid injection operation;
(8) repeating the steps (6) to (7);
(9) performing replacement operation;
(10) and (4) if one well group or a plurality of well groups exist, adopting a cluster type simultaneous operation mode, and repeating the steps (1) to (9) until all wells are constructed.
8. The fracturing method according to claim 7, wherein in step (1):
the length of the first-stage crack is 40-80% of the projection length of the connecting line of the shaft and the crack body in the original maximum principal stress direction; and/or
Fracturing fluidThe discharge capacity is 2-3m3Min, the viscosity of the fracturing fluid is 2-3mPa.s, and the liquid amount of the fracturing fluid is 150-3。
9. The fracturing method according to claim 7, wherein in step (2):
the length of the second-stage crack is 10-50% of the projection length of the connecting line of the shaft and the crack body in the original maximum main stress direction; and/or
The discharge capacity of the fracturing fluid is 2-3m3Min, the viscosity of the fracturing fluid is 15-20mPa.s, and the amount of the fracturing fluid is 130-3。
10. The fracturing method according to claim 7, wherein in step (3):
the third-stage crack length is 10% -40% of the projection length of the connecting line of the shaft and the crack body in the original maximum main stress direction; and/or
The discharge capacity of the fracturing fluid is 5-6m3The viscosity of the fracturing fluid is 50-60mPa.s, and the liquid volume of the fracturing fluid is 100-3。
11. The fracturing method according to claim 7, wherein in step (4):
the fourth-stage fracture length is equal to 10% -30% of the connecting line length of the shaft and the fracture-cavity body; and/or
The acid liquor discharge capacity is 5-6m3The viscosity of the acid solution is 70-80mPa.s, and the liquid volume of the acid solution is 40-50m3。
12. The fracturing method according to claim 7,
in the step (5), the discharge capacity of the fracturing fluid is 5-6m3Min, the viscosity of the fracturing fluid is 1-10mPa.s, and the amount of the fracturing fluid is 200-3(ii) a And/or
In the step (6), the acid liquor discharge capacity is 5-6m3Min, the viscosity of the acid solution is 40-100mPa.s, the liquid volume of the acid solution is 100-3(ii) a And/or
In the step (7), the acid liquor discharge amount is 5-6m3/min，The viscosity of the acid solution is 4-10mPa.s, the liquid volume of the acid solution is 100-3。
13. Fracturing method according to claim 7, characterized in that in step (9) a displacement of 110-300% of the wellbore volume is performed, preferably with a low viscosity slickwater of 2-3 mPa.s.
14. Use of the clustered multi-stage gap acidizing fracturing method of any one of claims 1 to 13 in acid fracturing of carbonate oil and gas reservoirs.
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