CN110761763B - Horizontal well repeated fracturing method - Google Patents
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- CN110761763B CN110761763B CN201810843368.2A CN201810843368A CN110761763B CN 110761763 B CN110761763 B CN 110761763B CN 201810843368 A CN201810843368 A CN 201810843368A CN 110761763 B CN110761763 B CN 110761763B
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP 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
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
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Abstract
The invention discloses a method for horizontal well repeated fracturing. The method comprises the following steps: step (1) repeatedly evaluating and optimizing parameters before fracturing; repeatedly fracturing along old cracks or re-injecting new holes among the original old cracks; optimizing and preparing a formula of slickwater and carbon dioxide foam fracturing fluid; injecting slickwater carbon dioxide foam fracturing fluid to carry out main crack forming or extending; step (5), proppant injection construction; step (6) replacing operation; and (7) repeating the steps (4) to (6) until the construction is finished. The method greatly increases the repeated fracturing reconstruction effect of the shale gas reservoir, and the optimization result can effectively guide repeated fracturing construction, greatly increase the reconstruction volume and obviously improve the construction effect, thereby obtaining the maximum economic benefit.
Description
Technical Field
The invention relates to the technical field of oil exploitation, in particular to a horizontal well repeated fracturing method.
Background
At present, the problem of repeated fracturing of horizontal wells, whether shale, sandstone or carbonate, is becoming more and more urgent. After the first fracturing for a certain time, the flow conductivity of the fracture is continuously decreased to 0, and the volume of the original fracture structure is gradually decreased, so that the yield is reduced. After the production is below the economic limit production, repeated fracturing needs to be considered to restore or improve the production of the well and achieve economic and effective development. Especially, under the current low oil price condition, the oil and gas area which is not reached by the original cracks is continuously expanded through the repeated fracturing of the horizontal well, or the crack reaching volume can be further increased through the re-perforation among the original cracks, so that the oil and gas yield and recovery rate are improved.
Chinese patent CN106845043A discloses a shale gas horizontal well repeated fracturing process flow and a design method, which comprises repeated fracturing area selection well determination, repeated fracturing engineering design, repeated fracturing field implementation, repeated fracturing monitoring and post-fracturing evaluation. The shale gas horizontal well repeated fracturing process flow and the design method provided by the invention can ensure reasonable and accurate evaluation and analysis after construction, and can also successfully improve the shale gas reservoir fracturing yield increase transformation effect and improve the gas well productivity and recovery ratio. The fracturing fluid is slick water and glue solution, the repeated fracturing engineering design is mainly used for designing the dosage of the temporary plugging agent, and the fracturing process is not explained in detail.
The document "shale gas well repeated fracturing pore-filling optimization technology research" (energy and environmental protection, 1 month in 2017) discloses: by coupling an interpeak stress interference theory, a mass conservation law and a flowing pressure continuity principle, a shale gas reservoir repeated fracturing hole-filling optimization numerical model is established, the cluster spacing range of the maximum induced horizontal stress is predicted, perforation parameters are optimized by combining a stratum horizontal main stress reversal condition, a set of shale gas well repeated fracturing hole-filling design method is formed, and the method has certain guiding and reference effects on the design of the Fuling shale gas well repeated fracturing hole-filling. The repeated fracturing hole patching optimization technology is mainly researched from the mechanism, and a specific process method is not involved.
The research of the technical progress and inspiration of the improved recovery ratio of the shale oil-gas well through the repeated fracturing of the shale oil-gas well (the world-wide oil, 2016 year and 2 month) indicates that the repeated fracturing of the shale oil-gas well faces the challenges of technical adaptability, economy, uncertainty and the like, the current development trend is to establish a well selection standard, an expandable liner tube technology, an accurate yield prediction model, fracturing fluid and a propping agent which are suitable for an operation area, the continuous technical innovation is indicated, the repeated fracturing is taken as an important innovation direction, the development prospect is good, the related research is paid attention at any time and timely developed, and the shale oil-gas development in China can be helped. The us repeat fracturing technique is outlined here without reference to a specific process.
At present, the repeated fracturing of a horizontal well mainly has the following problems in terms of technology:
1) means of repeated fracturing are limited. Generally, a method of whole well section general fracturing or temporary plugging is adopted. The number of cracks transformed by the conventional fracturing is limited, and the temporary plugging has great uncertainty. There is also a method of adopting double packer and single clamp, but the inner diameter of the pipe column is limited, so that the fracturing discharge capacity is limited.
2) The pertinence of the fracturing construction parameters is poor. Considering that the induced stress generated by the first fracture cannot completely disappear until the fracture is closed, and the double superposition effect of the induced stress caused by production is difficult to accurately calculate, the initiation direction of the repeated fracturing fracture and the influence on the construction parameters caused by large fluid loss are uncertain, so that the pertinence of the repeated fracturing parameters is greatly reduced.
Therefore, a new horizontal well re-fracturing technology needs to be developed to solve the above limitations.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a method for horizontal well repeated fracturing. The invention optimizes the combined pumping parameters of slickwater with different viscosities and proppant with different particle sizes and CO2 or N as auxiliary materials based on the repeated fracturing reservoir parameter evaluation result2And measures such as foam fracturing and the like are adopted, so that the reconstruction volume of the repeated fracturing fracture of the shale gas reservoir is fully improved. The method greatly increases the repeated fracturing reconstruction effect of the shale gas reservoir, and the optimization result can effectively guide repeated fracturing construction, greatly increase the reconstruction volume and obviously improve the construction effect, thereby obtaining the maximum economic benefit.
The general idea of the invention is as follows:
(1) repeated fracturing can be carried out at the position of the original old perforation, and new perforations can be injected between the original perforation perforations. In order to reduce the possibility that a large amount of perforating fluid enters the first cracks, the viscosity of the perforating pumping fluid can be properly improved, but the perforating pumping fluid can be completely broken and flow back after the repeated fracturing construction is finished, and the influence on the continuous production of the original cracks is avoided.
(2) And (4) adopting slickwater carbon dioxide foam fracturing fluid to make a main crack. Considering that the filtration loss of repeated fracturing is large, the fracturing fluid is beneficial to improving the crack-making efficiency and inhibiting the clay expansion (the mixture of slickwater and carbon dioxide is weakly acidic). After the main crack is finished, a small-particle-size ultralow-density proppant or a self-suspending proppant is adopted to effectively block the end part, the upper top bottom and the lower top bottom of the crack, so that the net pressure of the main crack is greatly improved. In the net pressure lifting process, the branch cracks at different positions can be opened in different degrees, so that the complexity of the cracks is greatly improved. The sand adding time of the branch cracks is properly delayed, so that liquid enters the branch cracks with different sizes, and the complexity degree of the cracks is greatly improved. The above-described frac system may be filled with smaller particle size ultra-low density proppant or self-suspending proppant. It is worth noting that high foam quality of carbon dioxide can be used initially to take advantage of its Jamin effect to block most cracks, and certainly the least stressed cracks that will eventually continue to extend. Then, the quality of the carbon dioxide foam is gradually reduced, even finally, pure slick water is used, and the viscous fingering effect is utilized, so that the carbon dioxide foam can still enter the cracks which are blocked or partially blocked at the cracks, and further, the secondary reconstruction of more cracks is realized.
(3) Because a plurality of perforation clusters exist in the shaft after the first fracturing, and the filtration loss of the fracturing fluid is larger due to the great reduction of the pore pressure during the repeated fracturing. In the case of strong formation heterogeneity, the probability that multiple fractures normally extend at the same time is not high. Only 1-2 cracks or 2-3 cracks can be simultaneously extended, end sand-removing fracturing construction can be carried out, and after the 1-2 or 2-3 main cracks are fully paved with the proppant, the remaining cracks can be continuously pressed open and extended in sequence along with the continuous increase of the bottom hole pressure.
The invention aims to provide a horizontal well repeated fracturing method.
The method comprises the following steps:
step (1) repeatedly evaluating and optimizing parameters before fracturing;
repeatedly fracturing along old cracks or re-injecting new holes among the original old cracks;
optimizing and preparing a formula of slickwater and slickwater carbon dioxide foam fracturing fluid;
injecting slickwater carbon dioxide foam fracturing fluid to carry out main crack forming or extending;
step (5), proppant injection construction;
step (6) replacing operation;
and (7) repeating the steps (4) to (6) until the construction is finished.
Among them, preferred are:
the step (1) of pre-fracturing parameter evaluation and optimization comprises the following steps: evaluating reservoir key parameters before repeated fracturing, evaluating geological engineering desserts, optimizing a repeated fracturing fracture parameter system, determining the positions of cluster holes and optimizing repeated fracturing construction parameters.
The step (2) comprises the following steps: the length of the perforation cluster is 1-1.5m, the phase angle is 60 degrees, the perforation density is 16-20 holes/m, and the aperture is more than 9.5 mm;
the aperture at the new perforation is increased by 10-20%.
If a pumping perforating gun or a hydraulic jet perforating method is adopted, the viscosity of the perforating fluid is greater than or equal to 30 mPa.s.
The step (3) comprises the following steps: the viscosity of the slickwater is 1-3mPa.s, and the foam mass in the slickwater carbon dioxide foam fracturing fluid is 70-80%. (foam quality, i.e. volume ratio of gas in carbon dioxide foam fracturing fluid)
The step (4) comprises the following steps: the liquid amount is 500-600m3Injecting 140-230-mesh ultra-low-density proppant or self-suspending proppant with the same particle size; adopting a continuous sand adding mode, wherein the sand-liquid ratio is 5-8-11-14-17-20%, and each sand-liquid ratio is liquidThe amount is 20-30% of the wellbore volume.
The density of the ultra-low density proppant is 1.05-1.25g/cm3；
During actual construction, the wellhead pressure rising speed is 1MPa/min as a standard, and if the wellhead stress rising speed is lower than the standard, the sand-liquid ratio can be further improved so that the wellhead pressure rising speed is more than or equal to 1 MPa/min.
The step (5) comprises: and (4) injecting 70-140 meshes of propping agent for construction. Optimizing the single-stage liquid quantity result in the step 1), removing the liquid used in the step 4), and carrying 70-140 meshes of conventional density (generally 1.6-1.7 g/cm) by using 40% -60% of the liquid in the residual liquid quantity3) The proppant is constructed, the sand liquid ratio is 6-8-10-12-14%, the sand can be added in a plug mode at the early stage, and the sand is continuously added at the middle and later stages;
and (5) injecting 40-70 meshes of propping agent for construction. The injection mode and parameters can refer to 70-140 meshes of proppant injection construction, and the particle size of the proppant is only required to be changed to 40-70 meshes.
The step (6) comprises: replacing 110-120% of the well bore volume at the midpoint position of the horizontal section; displacing the first 30-40% with high viscosity glue solution with viscosity of 50-60mPa.s, and collecting the rest liquid with slickwater with viscosity of 1-3 mPa.s.
The step (7) comprises: the foam quality of the slickwater carbon dioxide foam fracturing fluid for each stage of fracturing is gradually reduced by 5-20 percent until the foam quality is reduced to 0 in the last stage of fracturing.
If the pressure drop phenomenon does not occur, the slickwater carbon dioxide foam fracturing fluid is stopped, slickwater with the viscosity of 1-2mPa.s is changed, and the secondary reconstruction of more cracks is realized by utilizing the low-viscosity special effect of the slickwater and the viscous finger-feeding effect in the foam fracturing fluid;
if the pressure drop phenomenon does not occur, stopping the pump for 10-30min, opening the well and returning for 10-20min after the well mouth stress is reduced to close the crack, and controlling the flow at 2m3Below/min, go to step 6).
Preferably, the technical scheme of the invention is as follows:
(1) and evaluating key parameters of the reservoir before repeated fracturing. And determining the longitudinal and transverse distribution, lithology, physical property, rock mechanics, three-dimensional ground stress, natural fracture development condition, comprehensive fluid loss coefficient and the like of a target layer to be modified and a reservoir stratum within the range of 50m above and below the target layer to be modified by methods such as earthquake, well logging, indoor core test analysis and the like. Since the reservoir reforming process is generally a quasi-static process, the above logging dynamic parameters need to be converted into the static parameters of the core.
(2) The geologically engineered dessert is evaluated. On the basis of the step 1), calculating a continuous distribution curve of the comprehensive geological engineering double-dessert parameters along the horizontal shaft according to the mature calculation models of the geological dessert and the engineering dessert and the related parameters determined in the step 1) and an equal weight method.
(3) And (5) optimizing a fracture parameter system repeatedly. And (3) applying mature international universal software PETROL to establish a fine geological model. On the basis, mature fracturing yield prediction simulation software ECLIPSE is still adopted, and reservoir pore pressure distribution and oil-gas-water three-phase saturation distribution before repeated fracturing are fitted from the beginning after the first fracturing. Under the premise, the post-pressure yield dynamics under the conditions of extending along the old fracture or existing old fracture and new fracture are simulated respectively, and the fracture parameter combination with the maximum post-pressure yield or the lowest input-output ratio is optimized from the middle, so that the optimal value of the final fracture parameter system is obtained. In the concrete simulation, an equivalent flow conductivity method is still adopted to set the hydraulic fracture system. According to an orthogonal design method, different main crack and branch crack parameters are set, including the length of the crack, the flow conductivity, the crack extension direction (the crack direction of repeated fracturing can be changed in different directions), the gap distance and the crack distribution (the length of the crack is equal to that of the crack, the middle of the crack is short, the length of the crack is long, and the length of the crack is short, and the length of the crack is alternately distributed in a W-shaped manner, and the spindle-shaped manner. For simplicity, the seam length, flow conductivity, seam spacing and the like of the branch seams are 1/10 of the main seam length. In the above optimization, both the old fracture and the new fracture at the new perforation location are taken into account. It should be noted that the geometric size and conductivity of the first fracture can be obtained by microseism, or by inversion using fracture propagation simulation software (such as GOFHER, MEYER, etc.).
(4) And determining the positions of the shower holes. And (3) according to the result of the optimized total number of cracks in the step 3), combining the positions of the double desserts in the step (2), comprehensively considering the positions of the casing collars, and determining the final position of the shower hole.
(5) And optimizing repeated fracturing construction parameters. In order to obtain the fracture parameter system optimized in the step 3), fracture expansion simulation software (such as GOFHER, MEYER and the like) can be applied to simulate the changes of the fracture geometric size and the flow conductivity under different fracture construction parameters (including liquid amount, volume ratio of different liquid types, proppant amount, proppant ratio of different particle sizes, discharge capacity, construction sand-liquid ratio and the like). And preferably selecting the fracturing construction parameter combination capable of obtaining the result of optimizing the fracture parameters in the step 3) as the optimal fracturing construction parameter combination.
The fracturing construction parameters are optimized and can be respectively carried out aiming at the main cracks and the branch cracks. And (3) combining the final fracturing construction parameters, and taking the sum of the other parameters except the viscosity and the sand-liquid ratio.
It is worth pointing out that, when the change between the main crack direction and the first crack direction is large in the crack parameters optimized in step 3), in the determination of the displacement, the displacement needs to be increased appropriately and increased quickly in the construction so as to achieve the diversion effect of the main crack to the maximum extent, otherwise, the diversion possibility is reduced.
(6) And (5) performing perforation operation. Such as repeated fracturing along old fractures, may be used without perforating. Otherwise, new holes should be re-injected between the old cracks. If a pumping perforating gun or a hydraulic jet perforating method is adopted, the viscosity of perforating fluid is above 30mPa.s so as to reduce the filtration loss of the perforating fluid and ensure the pumping efficiency of the perforating gun. The perforating fluid can adopt a conventional glue solution formula, so that the glue can be broken thoroughly after all perforating operations are finished, and normal seam making and extension of repeated fracturing construction are not influenced.
The specific perforation parameters can be consistent with the perforation parameters of the first fracturing, such as the cluster length is 1-1.5m, the phase angle is 60 degrees, the perforation density is 16-20 holes/m, and the aperture is more than 9.5 mm. The aperture can also be increased by 10-20% at the new perforation to increase the probability of the fracture at the new perforation fully initiating and extending.
(7) Optimizing and preparing a formula of slickwater and slickwater carbon dioxide foam fracturing fluid. Detecting the rheological property and sand carrying performance of slickwater foam fracturing fluid with different carbon dioxide foam qualities (20% -40% -60% -80%) indoors, and determining the formula of the foam fracturing fluid according to the related rheological and sand suspension standards of the foam fracturing fluid by combining the data such as the reservoir temperature and the like obtained in the step 1) according to the change of the optimized construction sand-fluid ratio in the step 5). The quantity and the injection discharge capacity of the carbon dioxide tank cars are determined on site according to the indoor optimized quality of the carbon dioxide foam, and the continuity and the high efficiency of the whole construction process are ensured.
(8) And injecting slickwater carbon dioxide foam fracturing fluid to perform main crack making or extending.
And (5) injecting the foam fracturing fluid according to the optimized fluid amount and discharge capacity in the step 5). According to the liquid production or gas production profile data, the total repeated fracturing segment number is determined (generally, 2-3 clusters or 3-4 clusters per segment are used for determining the total partial pressure segment number) on the principle that the pressing force and the yield are equivalent, synchronous pressing is easy to open, and the gas production after pressing is not interfered mutually. The liquid amount is 500-600m370-80% of the mass of carbon dioxide foam is adopted. Because of the large repeated fracturing fluid loss and the narrow width of the fracture, 140-230 mesh ultra-low density proppant or self-suspending proppant with the same particle size is injected. The continuous sand adding mode is adopted, the sand-liquid ratio is 5% -8% -11% -14% -17% -20%, and the liquid ratio of each sand-liquid can be 20-30% of the volume of a well bore. In actual construction, the pressure rise rate at the well head is 1MPa/min as a standard, and if the stress rise rate at the well head is lower than the standard, the sand-liquid ratio can be further improved. If the pressure rising speed is maintained within 10 percent of 1MPa/min and the duration is more than 2-3min, the next stage of construction can be carried out.
(9) And (4) injecting 70-140 meshes of propping agent for construction. And (3) optimizing the result of the single-stage liquid amount in the step 5), removing the liquid used in the step 8), and carrying 70-140-mesh conventional density proppant with liquid of which the residual liquid amount is about 50% for construction, wherein the sand-liquid ratio is 6-8-10-12-14%, the sand can be added in a plug mode at the early stage, and the sand can be continuously added in the middle and later stages.
(10) And (5) injecting 40-70 meshes of propping agent for construction. The injection mode and parameters can be referred to as step 9), and the particle size of the proppant is only required to be changed to 40-70 meshes.
(11) And (5) replacing operation. Considering that the sequence of the partial pressure sections is different and difficult to determine, the partial pressure sections can be replaced by 120% of 110-fold of the well bore volume at the midpoint position of the horizontal section. In order to prevent the sand setting effect of the horizontal well bore, the first 30-40% of the displacement amount is made of high-viscosity glue solution with the viscosity of 50-60mPa.s, and the rest liquid is made of slickwater with the viscosity of 1-3 mPa.s.
(12) And (5) repeating the steps 8) to 11) for the construction of other sections until the construction is finished. However, it should be noted that the foam mass of each stage is gradually reduced by 5-20% until the foam mass of the last stage is reduced to 0. By utilizing the viscous fingering effect, the subsequently injected slick water can enter the cracks which are blocked or partially blocked by the carbon dioxide foam, thereby realizing the secondary reconstruction of more cracks.
(13) If the pressure drop phenomenon does not occur, the carbon dioxide foam can be immediately stopped, the slickwater with the viscosity of only 1-2mPa.s is changed, and the secondary reconstruction of more cracks is realized by utilizing the low-viscosity special effect of the slickwater and the viscous finger-feeding effect in the foam fracturing fluid. If the effect is still not achieved, the pump can be stopped for 10-30min, after the wellhead stress is reduced to close the crack, the well is opened again for 10-20min, the flow is controlled to be below 2m3/min, and at the moment, carbon dioxide foam can be damaged to lose the prior Jamin effect. At this point, go to step 11).
13) Other flowbacks, tests, and normal production, are performed with reference to conventional flow, and are not cumbersome here.
The invention has the following technical characteristics and excellent effects:
the method has the advantages of reasonable design, clear method, simplicity, convenience, high efficiency and capability of obtaining the shale oil reservoir repeated fracturing construction parameters and the process flow design at one time. The optimization result can effectively guide repeated fracturing construction of the shale gas reservoir, greatly increase the reconstruction volume and obviously improve the construction effect, thereby obtaining the maximum economic benefit.
Detailed Description
The present invention will be further described with reference to the following examples.
Example 1
The vertical depth of a well A of a certain shale gas well is 2320m, the horizontal section is 1500m long, the length of the first fracturing section is totally 18, and the repeated fracturing step comprises the following steps:
step 1, evaluating a reservoir stratum before repeated fracturing of a well A. Accurately evaluating the formation pressure, the magnitude and direction of the ground stress, the effective permeability, the comprehensive formation fluid loss coefficient and the change of rock mechanical parameters based on the construction parameters and pressure curve of the first fracturing, the production dynamic characteristic analysis after the fracturing and various test data (pressure recovery well testing, gas production profile testing and the like) for designing a construction scheme; and (3) researching the reservoir utilization condition around the first fracturing fracture and the reserve distribution condition between two adjacent perforation clusters by adopting geological modeling software PETROL, ECLIPSE and the like.
And 2, taking a high-strength chemical temporary plugging agent to temporarily plug old cracks, wherein 30kg of temporary plugging agent is needed for a single-cluster crack.
And 3, performing perforating bridge plug combined staged fracturing. And according to the stratum evaluation result, the position with large gas outlet potential is preferably considered for hole patching.
The cluster length is 1.5m, the phase angle is 60 degrees, the perforation density is 20 holes/m, and the aperture is 9.5 mm;
and 4, taking the level 1 as an example, carrying out repeated fracturing construction sand adding program design of the well A.
The viscosity of the used slickwater is 2mPa.s, the foam mass in the carbon dioxide foam fracturing fluid is 70 percent, and the fluid amount is 550m3Injecting 140 meshes of ultra-low density proppant; adopting a continuous sand adding mode, wherein the sand-liquid ratio is 5-8-11-14-17-20%, and the liquid volume of each sand-liquid ratio slug is 20m3. The density of the ultra-low density proppant is 1.05g/cm3。
Step 5, carrying 70-140 mesh conventional density proppant (density is 1.65 g/cm)3) Constructing, namely adding 6 percent and 8 percent of sand by a slug type sand adding mode, and adopting a continuous sand adding mode in the later period, wherein the sand-liquid ratio is 10-12-14 percent; the specific slug amount of each sand liquid is 30m3(ii) a The same injection pattern was used to add 40-70 mesh proppant.
And 6, replacing the operation. Firstly injecting high-viscosity glue solution of 65mPa.s of 28m3Then injecting slick water with viscosity of 2mPa.s of 42m3Performing displacement;
and 7, constructing other sections, and gradually reducing the foam quality of each section from the 2 nd section to the 8 th section by 10 percent until the foam quality is reduced to 0 in the 8 th section. By utilizing the viscous finger advance effect, the slick water injected in the subsequent section can enter the cracks which are blocked or partially blocked by the carbon dioxide foam, thereby realizing the secondary reconstruction of more cracks.
Step 8, through the design of the invention, the A well completes 8-grade fracturing altogether, and the total injected stratum liquid amount is 21000m3Cumulative sand addition 500m3After numerical simulation pressure, the unimpeded flow reaches 10 multiplied by 104m3And d, the yield is increased by 20 percent before heavy fracturing, and remarkable economic benefit is obtained.
Example 2
The vertical depth of a certain shale gas well B well is 2100m, the horizontal section length is 1380m, the first fracturing totally 15 sections, and the repeated fracturing step comprises the following steps:
step 1, evaluating a reservoir stratum before repeated fracturing of a well B. Accurately evaluating the formation pressure, the magnitude and direction of the ground stress, the effective permeability, the comprehensive formation fluid loss coefficient and the change of rock mechanical parameters based on the construction parameters and pressure curve of the first fracturing, the production dynamic characteristic analysis after the fracturing and various test data (pressure recovery well testing, gas production profile testing and the like) for designing a construction scheme; and (3) researching the reservoir utilization condition around the first fracturing fracture and the reserve distribution condition between two adjacent perforation clusters by adopting geological modeling software PETROL, ECLIPSE and the like.
And 2, taking a high-strength chemical temporary plugging agent to temporarily plug old cracks, wherein 25kg of temporary plugging agent is needed for a single-cluster crack.
And 3, performing perforating bridge plug combined staged fracturing. And according to the stratum evaluation result, the position with large gas outlet potential is preferably considered for hole patching.
The cluster length is 1m, the phase angle is 60 degrees, the perforation density is 16 holes/m, and the aperture is 12.7 mm;
and 4, taking the level 1 as an example, carrying out repeated fracturing construction sand adding program design of the well B.
The viscosity of the used slickwater is 3 mPas, the foam mass in the carbon dioxide foam fracturing fluid is 50 percent, and the fluid amount is 650m3Injecting 140 meshes of ultra-low density proppant; adopting a continuous sand adding mode, wherein the sand-liquid ratio is 5-8-11-14-17-20%, and the liquid volume of each sand-liquid ratio slug is25m3. The density of the ultra-low density proppant is 1.25g/cm3。
Step 5, carrying 70-140 mesh conventional density proppant (density is 1.65 g/cm)3) Constructing, namely adding 6 percent and 8 percent of sand by a slug type sand adding mode, and adopting a continuous sand adding mode in the later period, wherein the sand-liquid ratio is 10-12-14 percent; the specific slug amount of each sand liquid is 25m3(ii) a The same injection pattern was used to add 40-70 mesh proppant.
And 6, replacing the operation. Firstly injecting 70 mPas of high-viscosity glue solution with the thickness of 25m3Then injecting slick water with viscosity of 3mPa.s for 45m3Performing displacement;
and 7, constructing other sections, and gradually reducing the foam quality of each section from the 2 nd section to the 6 th section by 10 percent until the foam quality is reduced to 0 in the 6 th section. By utilizing the viscous finger advance effect, the slick water injected in the subsequent section can enter the cracks which are blocked or partially blocked by the carbon dioxide foam, thereby realizing the secondary reconstruction of more cracks.
Step 8, completing 8-grade fracturing in the well B by the design of the invention, and accumulating the total injected stratum liquid amount to 18500m3Cumulative sand addition of 430m3After numerical simulation pressure, the unimpeded flow reaches 8.3 multiplied by 104m3And d, the yield is increased by 15 percent compared with the yield before repeated fracturing, and remarkable economic benefit is obtained.
Claims (7)
1. A method of horizontal well re-fracturing, characterized in that the method comprises:
step (1) repeatedly evaluating and optimizing parameters before fracturing;
repeatedly fracturing along old cracks or re-injecting new holes among the original old cracks;
optimizing and preparing a formula of slickwater and slickwater carbon dioxide foam fracturing fluid;
the viscosity of the slickwater is 1-3mPa & s, and the foam mass in the slickwater carbon dioxide foam fracturing fluid is 70-80%;
injecting slickwater carbon dioxide foam fracturing fluid to carry out main crack forming or extending;
liquid amount is 500-m3Injecting 140-230-mesh ultra-low-density proppant or self-suspending proppant with the same particle size; adopting a continuous sand adding mode, wherein the sand-liquid ratio is 5-8-11-14-17-20%, and the liquid ratio of each sand-liquid is 20-30% of the volume of a shaft;
step (5), proppant injection construction;
injecting 70-140 meshes of propping agent for construction; removing the liquid used in the step 4) according to the result of optimizing the single-stage liquid amount in the step 1), carrying 70-140 meshes of propping agent by using liquid which is 40% -60% of the residual liquid amount for construction, wherein the sand-liquid ratio is 6% -8% -10% -12% -14%, carrying out slug type sand feeding in the early stage, and continuously feeding sand in the middle and later stages;
then injecting 40-70 mesh proppant for construction; the same liquid amount as that of 70-140 meshes of propping agent injection construction, and the same sand-liquid ratio;
step (6) replacing operation;
step (7) repeating the steps (4) to (6) until the construction is finished;
the foam quality of the slickwater carbon dioxide foam fracturing fluid for each stage of fracturing is gradually reduced by 5-20 percent until the foam quality is reduced to 0 in the last stage of fracturing.
2. The method of horizontal well re-fracturing of claim 1, wherein:
the step (1) of pre-fracturing parameter evaluation and optimization comprises the following steps: evaluating reservoir key parameters before repeated fracturing, evaluating geological engineering desserts, optimizing a repeated fracturing fracture parameter system, determining the positions of cluster holes and optimizing repeated fracturing construction parameters.
3. The method of horizontal well re-fracturing of claim 2, wherein:
the step (2) comprises the following steps: the length of the perforation cluster is 1-1.5m, the phase angle is 60 degrees, the perforation density is 16-20 holes/m, and the aperture is more than 9.5 mm;
the aperture at the new perforation is increased by 10 to 20 percent;
if a pumping perforating gun or a hydraulic jet perforating method is adopted, the viscosity of the perforating fluid is greater than or equal to 30 mPa.s.
4. The method of horizontal well re-fracturing of claim 1, wherein:
in the step (4),
if only 1-2 cracks or 2-3 cracks extend simultaneously, the end sand-removing fracturing construction is carried out, and after the 1-2 or 2-3 main cracks are fully paved with the proppant, the remaining cracks are continuously pressed open and extended in sequence along with the continuous increase of the bottom hole pressure.
5. The method of horizontal well re-fracturing of claim 1, wherein:
in the step (4), the density of the ultra-low density proppant is 1.05-1.25g/cm3；
If the stress rising speed of the wellhead is lower than 1MPa/min, the sand-liquid ratio is further increased to ensure that the pressure rising speed of the wellhead is more than or equal to 1 MPa/min.
6. The method of horizontal well re-fracturing of claim 1, wherein:
the step (6) comprises: replacing 110-120% of the well bore volume at the midpoint position of the horizontal section; displacing the first 30-40% with high viscosity glue solution with viscosity of 50-60mPa.s, and collecting the rest liquid with slickwater with viscosity of 1-3 mPa.s.
7. The method of horizontal well re-fracturing of claim 1, wherein:
step (7), if the pressure drop phenomenon does not occur, stopping using the slickwater carbon dioxide foam fracturing fluid, changing the slickwater into slickwater with the viscosity of 1-2mPa.s, and realizing secondary reconstruction of more cracks by utilizing the low-viscosity special effect of the slickwater and the viscous fingering effect in the foam fracturing fluid;
if the pressure drop phenomenon does not occur, stopping the pump for 10-30min, opening the well and returning for 10-20min after the well mouth stress is reduced to close the crack, and controlling the flow at 2m3Below/min, go to step 6).
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