CN109958411B - Horizontal well cluster perforation staged fracturing method - Google Patents
Horizontal well cluster perforation staged fracturing method Download PDFInfo
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- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
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- 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
- 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 horizontal well cluster perforation staged fracturing method. The method comprises the following steps: the number of the first section of perforation clusters is 2-4; the number of other perforation clusters in each section is set to be more than 6 clusters; each cluster of four perforation holes is formed, and 4 perforating charges have a 90-degree phase angle, so that the 4 perforation holes are positioned in the same plane vertical to the horizontal shaft direction; the diameter of the perforation is more than 14.5 mm. The invention improves the cluster number in a single section and forms a single crack in a single cluster by optimizing the perforation position and parameters such as the number of the perforations, the aperture, the hole density, the phase angle and the like; and then, by optimizing fracturing construction parameters and combining technologies such as medium-high viscosity acid gradual displacement increasing pretreatment and the like, multiple clusters of cracks in the sections are synchronously initiated and extended. The technology can effectively increase the number of the artificial fractures and the length of the fractures, improve the complexity of the fractures, improve the reconstruction volume of the fractures, solve the limitation of the prior art and realize the maximization of the yield increasing effect of the reservoir.
Description
Technical Field
The invention relates to the technical field of horizontal well fracturing, in particular to a horizontal well cluster perforation staged fracturing method. The invention can be used for staged fracturing of horizontal wells of reservoirs such as carbonate rock, sandstone, shale and the like.
Background
At present, the staged fracturing technology of the horizontal well is more and more commonly applied, and is widely applied to the fields of sandstone, carbonate rock, shale, coal bed gas and the like. And the completion proportion of the horizontal well casing is more than 80%. And the casing well completion horizontal well generally adopts a cluster perforation and bridge plug combined mode to perform fracturing construction operation.
Foreign cluster perforation is generally in a spiral perforation mode, single-section multi-cluster is adopted, more clusters are generally 3-8 clusters, even more clusters are more than 12 clusters, the length of the clusters is 0.3-0.6m, and the hole density is 16-20 holes/m.
As the stratum is old, the experienced structure movement is more, the stratum stress at the same depth is high, and the rock shaping characteristic is strong, the spiral perforation mode is adopted in China, the hole density and the hole diameter are also equivalent to those of the traditional method, but the number of single-section clusters is small, 2-3 clusters are common, and the length of a single-cluster perforation is large, and is 1-1.5m generally. Therefore, compared with the domestic and foreign fracturing, the domestic and foreign fracturing of each section has the same total number of perforation and the same single-section fracturing scale and displacement, the domestic and foreign effective cracks are few, the length of the crack is small, the complexity of each crack is not enough, the final crack modification volume is reduced, and the fracturing effect is greatly influenced. The reason is that the following aspects are mainly found:
(1) the large length of the single cluster of perforations can result in multiple cracks within the single cluster, at least in the initial stages of making the cracks. The foreign single cluster is small in length, although multiple cracks are possible at the beginning, due to the strong heterogeneity of the shale, one dominant crack always exists, the crack induced stress is large, the small cracks close to the dominant crack induced stress can expand the leading end of the dominant crack, the minimum principal stress is increased, and therefore the extension of the dominant crack can be rapidly restrained and stopped. When the cluster length is increased, the restraining effect of the induced stress on the adjacent small cracks is greatly reduced. Eventually there may be more than 1 main crack in the cluster, or 1 main crack coexisting with a plurality of small cracks with a certain extension, eventually resulting in a reduction of the total crack length. And a plurality of small cracks are mutually interfered, and the positive correlation between the yield and the number of the cracks in the cluster is poor. In fact, the fracturing fluid and proppant that enter the plurality of small fractures within the cluster is an inefficient construction.
(2) The small number of clusters in a single segment leads to a reduction in the induced stress effect between clusters within the segment, and therefore the complexity of the crack per cluster is correspondingly reduced. The multi-crack induced stress effect in the cluster is strong, but the induced stress in the cluster is unfavorable, even if the complexity degree of the crack in the cluster is increased, the existence of a plurality of short cracks close to the well influences the length increase of the main crack in the cluster, the seepage interference effect of the multi-crack in the cluster causes the yield not to be in direct proportion to the number of the small cracks.
Horse 58H tight reservoir horizontal well segmentation multicluster perforation fracturing technology [ oil drilling and production technology ] 2015 5 months, the document provides a horizontal well segmentation multicluster perforation fracturing technology, and forms an applicable large-scale volume fracturing technology aiming at the characteristics of a typical tight reservoir with three ponds, such as a Delavan sunk horse 58H well, high porosity and low permeability, high oil saturation, small pore throat and strong heterogeneity. Aiming at the problems of difficult rapid gel breaking of low-temperature well fracturing fluid and damage to a compact oil reservoir after construction, a matched ultralow-concentration and low-damage composite fracturing fluid system is developed, and a segmented multi-cluster perforation fracturing process of a rapid drilling bridge plug is formed by optimizing the number of cracks, the length of the cracks, the flow conductivity of the cracks, the relation between the sand laying concentration and the flow conductivity, and optimizing the cluster spacing and the number of holes, so that the field implementation is successful.
The literature forms a set of volume fracturing technology mainly aiming at a three-pond lake basin Malan depressed compact reservoir, does not further research on how to increase the number of clusters in a single section, form a single crack in a cluster and enable multiple clusters of cracks in the section to synchronously initiate and extend, and has certain technical limitation.
Therefore, research is needed to propose a new fracturing technology to solve the above limitations.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a horizontal well cluster perforation staged fracturing method. Aiming at the problems of small number of effective single-stage cracks, small length of the cracks and low complexity of each crack caused by the domestic existing horizontal well cluster perforation staged fracturing technology, the cluster number in a single stage is increased through optimizing perforation positions and parameters such as perforation number, aperture, hole density, phase angle and the like, and a single crack is formed in a single cluster; and then, by optimizing fracturing construction parameters and combining technologies such as medium-high viscosity acid gradual displacement increasing pretreatment and the like, multiple clusters of cracks in the sections are synchronously initiated and extended. The technology can effectively increase the number of the artificial fractures and the length of the fractures, improve the complexity of the fractures, improve the reconstruction volume of the fractures, solve the limitation of the prior art and realize the maximization of the yield increasing effect of the reservoir.
General technical idea
(1) The large-aperture perforating bullet is adopted, the conventional spiral bullet distribution mode is changed, only 4 eyelets are shot in each cluster, but the diameter of the eyelets is increased to more than 14.5mm from the conventional commonly used 9.5mm, and the 4 perforating bullets are arranged in a way of 90-degree phase angle and are close to each other as far as possible, so that the 4 perforating bullets are finally positioned in the same plane vertical to the horizontal shaft direction. The schematic view is shown in fig. 1 and 2.
The calculation of the eyelet friction shows that the eyelet friction can be reduced by more than 50 percent after the diameter of the eyelet is increased from 9.5mm to 14.5 mm. In other words, conventionally, in order to reduce the perforation friction, the total number of perforations per section of perforation is generally set to be not less than 48. For example, by enlarging the diameter of the eyelet, the total number of the eyelets in each section can be reduced to be not less than 24 on the premise that the total eyelet friction is not increased. The number of clusters in each section of perforation can be set to be more than 6 clusters, which is improved by 100 percent compared with the current cluster number. This is suitable for well formations having a brittleness index of not less than 55%. After the brittleness index is high to a certain degree, the fracture toughness of the rock is small, and the extension speed of the crack in the length direction is far greater than that in the width direction of the crack (the height direction of the crack can be considered to be basically constant). In other words, after the brittleness index is increased to a certain degree, the relationship between the seam forming width and the number of clusters in the segment is not large. Otherwise, if the shaping characteristics are strong, the seam width is related to the number of clusters in the segment.
(2) After the thought (1), the number of clusters in the section is greatly increased, and only 1 crack in the cluster extends, so that the induced stress interference effect between clusters and the increase of the complexity of the crack are increased, the low-efficiency construction of multiple cracks in the cluster caused by the conventional spiral perforation is avoided, all fracturing fluid and propping agent extend in 1 crack in the cluster, and the extending length is increased to a certain extent.
Moreover, the liquid inlet amount of a single crack in the cluster and 4 holes is far higher than that of a single hole crack inlet mode of the spiral perforation, and the three-dimensional crack geometric dimension of the crack is favorably improved. This is more important for shale gas fracturing where the minimum principal stress gradient is close to the vertical stress gradient, otherwise, the insufficient displacement may result in insufficient height of the vertical principal fracture, and the increased extension probability of the horizontal bedding fracture may result in reduced fracture reformation volume.
(3) And a pretreatment mode of gradually increasing the discharge amount of the acid liquid with medium and high viscosity is adopted, so that synchronous initiation and extension of multiple clusters of cracks in the section are ensured. Because the number of clusters in the segment is as high as more than 6 clusters, the synchronous initiation and extension of a plurality of clusters of fractures are difficult to ensure by the conventional acid pretreatment calculation. Therefore, the acid liquor with medium and high viscosity should be adopted to prevent the acid rock reaction from occurring too fast, and the method of gradually increasing the discharge amount is adopted to transport the acid liquor to each cluster of cracks as uniformly as possible.
The invention aims to provide a horizontal well cluster perforation staged fracturing method.
The number of each section of perforation clusters is more than 6; the first section can be slightly less, such as 2-4 clusters;
each cluster of the four perforation holes is provided with 4 perforating charges with a phase angle of 90 degrees, so that the 4 perforation holes are positioned in the same plane vertical to the horizontal shaft direction;
the diameter of the perforation is more than 14.5 mm;
and a pretreatment mode of gradually increasing the discharge amount of the acid liquid with medium and high viscosity is adopted, so that synchronous initiation and extension of multiple clusters of cracks in the section are ensured.
The method comprises the following steps:
(1) evaluating key reservoir parameters;
(2) determining a geological engineering comprehensive dessert and determining the positions of cluster perforation;
(3) optimizing crack parameters;
(4) optimizing fracturing construction parameters;
(5) performing combined operation of the perforation and the bridge plug;
(6) the medium and high viscosity acid gradually increases the discharge capacity for pretreatment operation;
(7) synchronous joint making construction of fast lifting discharge capacity of the slick water;
(8) carrying out proppant conveying construction;
(9) and (5) replacing operation.
Wherein the content of the first and second substances,
and (5) performing bridge plug perforation combination of staged fracturing based on the position of the stage cluster in the step (2).
Step (6), three acid solutions with the viscosity of 10-15mPa.s, 20-25mPa.s and 30-35mPa.s respectively are obtained;
using a 1-1.5m3And (2) replacing the acid discharge amount per min, firstly injecting acid liquid with the viscosity of 10-15mPa.s, wherein the injection amount is 30-35% of the designed acid amount, then injecting acid liquid with the viscosity of 20-25mPa.s, wherein the injection amount is 30-35% of the designed acid amount, and then injecting acid liquid with the viscosity of 30-35 mPa.s.
After all the acid with three viscosities enters a shaft, the displacement of the acid is 3-4m3Injecting in min, and reducing the displacement of the acid to the original displacement of the acid when the acid reaches the first cluster of perforations close to the heel; after 30-35% of acid enters the stratum, the other 30-35% of acid is used for 5-6m3Injecting acid at a displacement of/min, and using 7-8m of residual acid3And/min is used for replacing the discharge amount of acid.
Closing the well for 5-10min after acid replacement is finished.
Step (7), adopting the amount and the discharge capacity of the slickwater optimized in the step (4), and quickly increasing the designed maximum discharge capacity within 1-2min, wherein the viscosity of the slickwater is 1-3 mPa.s;
the amount of the slickwater injected accounts for 20-30% of the total amount of the fracturing fluid injected into the section.
And (8) the rising rate of the wellhead pressure is not higher than 1 MPa/min.
Step (9) is to design the displacement liquid amount according to 105-110% of the current section well bore volume.
The invention can adopt the following specific implementation steps
(1) Evaluation of key reservoir parameters
The method comprises the characteristics of structure and deposition, longitudinal and transverse spreading characteristics of a reservoir, lithology, physical properties, oil (gas) containing performance, five-sensitive characteristics, rock mechanics and three-dimensional ground stress characteristics, natural fracture characteristics and filling or not, horizontal bedding and fissure characteristics, fluid properties and temperature and pressure characteristics and the like.
The method can be comprehensively applied to measures such as earthquake, well logging, indoor core testing, stratum testing and the like, and dynamic and static analysis, macroscopic analysis, microscopic analysis, near well and far well analysis and the like can be carried out from multiple aspects.
Especially, it is necessary to convert the dynamic data into corresponding static parameters and establish the corresponding conversion relationship.
The static parameter distribution of the horizontal shaft can be comprehensively evaluated and determined by referring to the comparison between logging and logging of the horizontal shaft and the vertical pilot hole well and the dynamic and static conversion relation of relevant parameters on the pilot hole well.
(2) Geological engineering integrated dessert determination and cluster perforation position determination
On the basis of the step (1), a geological modeling software PETROL is used for establishing a fine geological model of the target well layer in the expected crack extension range along the horizontal shaft direction and the vertical horizontal shaft direction. On the basis, calculating a geological dessert and an engineering dessert according to a conventional method, determining a final comprehensive dessert in the full-seam-length distribution range of the comprehensive dessert along the directions of the horizontal shaft and the vertical shaft according to an equal weight method, and determining the division of the sections and the positions of the cluster holes according to a method that the comprehensive dessert is equal or close (the difference is not more than 10%) to the positions of the cluster holes in the sections by combining the optimized fracture parameters in the step (3) and the cementing quality of the horizontal shaft and other information.
(3) Optimization of fracture parameters
On the basis of the fine geological modeling in the step (2), introducing the fracture well yield prediction common commercial simulation software ECLIPSE into the fracture well, setting a hydraulic fracture system according to an equivalent diversion capability method (for reducing simulation workload, after the width of a fracture is amplified by a certain multiple, the width is generally not more than 0.1m, the permeability of a propping agent in the fracture is proportionally reduced, and the product of the permeability and the diversion capability of the fracture is kept unchanged), and applying an orthogonal design method to simulate different fracture lengths, diversion capabilities, fracture intervals and fracture arrangement modes (equal-fracture-length distribution, U-shaped distribution with two ends long and a short middle, W-shaped distribution with long and short cross distribution, spindle-shaped distribution and the like). And optimizing a fracture parameter system corresponding to the maximum yield (the critical point of the gradual slope on the yield-seam length relation curve) or the maximum economic net present value after the pressure is optimized, wherein the result is the optimization result.
(4) Optimization of fracturing construction parameters
In order to obtain the fracture parameter system optimized in the step (3), common fracture propagation simulation commercial software for fracturing, such as Frac ProPT, stimlan, GOFHER, MEYER and the like, is used for simulating the dynamic change rule of the fracture geometric dimensions under different fracturing construction parameters (discharge capacity, fracturing fluid amount, different types of fracturing fluid ratios, different fracturing fluid viscosities, propping agent amounts, different particle size propping agent ratios, sand-liquid ratios, injection programs and the like), and finding out the fracturing construction parameter combination corresponding to the optimized fracture parameters in the step 3) to be a final optimized value.
(5) Perforation and bridge plug combined operation
And (3) performing bridge plug perforation combination of staged fracturing based on the position of the stage cluster in the step (2). The first section is sent into the perforating string by a continuous oil pipe without using a bridge plug. The perforating gun is provided with a large-aperture perforating bullet according to the requirement of the thought (1), and the diameter of the perforation can reach more than 14.5 mm.
Each section is perforated for 6 clusters, and the first section can be slightly fewer, such as 2-4 clusters. And at the beginning of the second section, a lower bridge plug perforation combination tool pushes the tool string in a pumping mode. After the bridge plug seat is sealed, the bridge plug is released, the perforating guns are lifted to the preset positions, and after all perforating is finished, the perforating pipe string is lifted. Then, the fracture injection procedure is reversed.
(6) Pretreatment operation for gradually increasing discharge of medium and high viscosity acid
And (2) applying the rock core of the pilot hole well in the step (1), carrying out compatibility and acid dissolution rate experiments under different acid types and formulas, preferably selecting three acid solutions with viscosities of 15, 20 and 30mPas, and preparing by using three acid tanks respectively. The acid amount used in each stage is generally 20-30m 3.
Firstly using 1-1.5m3And (3) replacing the acid discharge amount at/min, opening an acid tank with the pressure of 15mPa.s, injecting acid solution with the viscosity of 20mPa.s of 1/3 after injecting 1/3 of the designed acid amount, and replacing the acid solution with the viscosity of 30 Pa.s. In order to keep the acid pouring construction stable, the closing of the gate of the first acid tank and the opening of the gate of the second acid tank can be synchronously carried out, and the opening change speeds of the gates are the same or equivalent as much as possible. The third acid tank gate operation process refers to the second gate method。
After all three types of acid enter the shaft, the displacement of the acid is 3-4m3And injecting in min, and when the acid reaches the first cluster of perforations close to the heel, reducing the displacement of the acid to the original displacement of the acid injection so as to increase the reaction time of the acid rock and the effect of acid pressure reduction. After 1/3 acid enters the stratum, another 1/3 acid amount is 5-6m3The acid is injected in a displacement manner of/min, and finally the acid amount of 1/3 is 7-8m3And/min is used for replacing the discharge amount of acid.
In order to fully utilize the reaction effect of the acid rock, the well can be properly closed for 5-10min after the acid replacement is finished.
(7) Synchronous joint construction of fast lifting and discharging capacity of slick water
And (3) applying the optimized slickwater liquid quantity and discharge capacity in the step (4), quickly increasing the designed highest discharge capacity within 1-2min, wherein the viscosity is generally 1-3mPa.s, and the combination of the low viscosity and the high discharge capacity can quickly establish enough high pressure in the horizontal well barrel, and because the slickwater is low in viscosity and low in pressure gradient in the horizontal well barrel, the nearly same or similar horizontal well barrel pressure can be conveniently generated at all perforation clusters in the section, so that all perforation clusters can be synchronously cracked and extended.
The liquid level in this stage is generally from 20 to 30% of the total liquid level in this stage.
(8) Proppant transport construction
And (4) applying the proppant type, the particle size and the sand-liquid ratio optimized in the step (4) to perform continuous or slug injection, and in order to improve the support efficiency, according to the condition that the wellhead pressure rising rate is not higher than 1MPa/min, and the sand-liquid ratio of the stage can be improved when the wellhead pressure rising rate is lower than the value until all the proppants are added.
(9) Replacement work
The displacement fluid volume is designed to be 110% of the current wellbore volume (including surface line, straight wellbore and horizontal wellbore). And (3) using high-viscosity glue solution with the viscosity of 50-60mPa.s at 30-40% of the displacement liquid amount to reduce the sand setting effect of the horizontal shaft and facilitate the subsequent bridge plug setting operation. Then, low-viscosity slickwater with the viscosity of 1-3mPa.s is used for replacing until the displacement is finished.
(10) And (5) performing fracturing construction on other sections, and repeating the steps (5) to (9) until all sections are constructed.
(11) Other drilling, plugging, flowback, testing, and production, etc., are performed according to conventional procedures, and are not redundant.
ADVANTAGEOUS EFFECTS OF INVENTION
Compared with the conventional staged fracturing technology of a horizontal well, the invention provides a brand-new fracturing technology, aims at the problems of small number of effective single-stage fractures, small fracture length and low complexity of each fracture caused by the domestic prior art, determines a geological engineering comprehensive dessert on the basis of reservoir parameter evaluation, further determines the positions of cluster perforation holes, improves the cluster number in a single stage by optimizing perforation parameters such as the perforation number, the aperture, the hole density, the phase angle and the like, forms a single fracture in the single cluster, and synchronously starts and extends a plurality of clusters of fractures in the stage by technologies such as optimizing the construction parameters of fracturing and gradually increasing the displacement of medium-high viscosity acid and the like.
The method can effectively increase the number of the artificial fractures and the length of the fractures, improve the complexity of the fractures, improve the reconstruction volume of the fractures, enhance the supply capacity of the fractures to oil-gas seepage channels and furthest excavate the yield-increasing capacity of the reservoir.
The site operation also has operability, acid liquor, slippery water and the like are prepared in advance, and different construction discharge capacities can generally meet requirements.
Drawings
FIG. 1 is a schematic representation of the location of perforations in accordance with the present invention;
fig. 2 is a left side view of fig. 1.
Detailed Description
The present invention will be further described with reference to the following examples.
Examples
The lithology of the target interval of the well A is gray fluorescent gravel-containing fine sandstone, and natural fractures are relatively developed. The fracturing well section of the target stratum is 3128.2-3589.7m, the average Young modulus of the reservoir is 23.2GPa, and the average Poisson ratio is 0.22; the stress difference between the target layer and the upper interlayer is about 8MPa, and the stress difference between the target layer and the lower interlayer is about 4 MPa; the temperature of the target layer was 112 ℃. In order to know the gas content and the productivity of the target layer and carry out the next exploration and evaluation work on the block, the fracturing scheme design and the field pilot test of the well are carried out by taking the process method provided by the patent as reference and combining the actual situation of the well, and the specific implementation method and the effect are as follows:
(1) evaluating reservoir parameters: according to earthquake, geology, well logging and core test data, the lithology of the target interval is gray fluorescent gravel-containing fine sandstone, the oil-gas-containing property is gas-containing, and natural fractures are relatively developed; the distribution condition is obtained by combining simulation calculation, the formation pressure is 29.6-31.4MPa, the Young modulus is averagely 44.8GPa, the Poisson ratio is averagely 0.22, the stress difference between the target layer and the upper interlayer is about 4.2MPa, the stress difference between the target layer and the lower interlayer is about 7.1MPa, and the temperature of the target layer is 112 ℃.
(2) Determining a perforation position: determining the division of sections and the positions of cluster perforating holes by combining a geological dessert and an engineering dessert, dividing into 4 sections for fracturing, wherein the 1 st section is a cluster with 3 clusters, the 2 nd to 4 th sections are each a cluster with 6 clusters, each cluster is provided with four perforating holes, and 4 perforating charges present a 90-degree phase angle, so that the 4 perforating holes are positioned in the same plane vertical to the horizontal shaft direction; the diameter of the perforation is 14.5 mm; the perforation positions are distributed as follows: paragraph 1, tuft 2, tuft 3497m, tuft 3, 3475 m; paragraph 2, cluster 1, cluster 3450m, cluster 2, cluster 3429m, cluster 3, cluster 3410m, cluster 4, cluster 3392m, cluster 5, cluster 3372m, cluster 6, cluster 3354 m; paragraph 3, cluster 1, cluster 3331m, cluster 2, cluster 3312m, cluster 3, cluster 3296m, cluster 4, cluster 3280m, cluster 5, cluster 3265m, cluster 6, cluster 3250 m; paragraph 4, cluster 1, 3230m, cluster 2, 3212m, cluster 3, 3197m, cluster 4, 3171m, cluster 5, 3156m, cluster 6, 3140 m.
(3) Optimizing crack parameters: through the simulation calculation of an orthogonal method, the equal slit length distribution is determined, the half slit length is 200-220m, and the flow conductivity is 3-6 dc.cm.
(4) Optimizing construction parameters: determining the crack parameters according to the step (3), and determining the construction parameters of each section based on Gohfer software orthogonal simulation calculation optimization: the total liquid amount in the 1 st stage was 850.0m3The construction discharge capacity is 4.0-10.0m3Min, total sand amount of proppant 69.0m3(ii) a The total liquid amount of the 2 nd stage was 1135.0m3The construction discharge capacity is 4.0-10.0m3Min, total sand amount of proppant 78.0m3(ii) a The total liquid amount of the 3 rd stage is 1190.0m3The construction discharge capacity is 4.0-10.0m3Min, total sand amount of proppant 81.0m3(ii) a The total liquid amount of the 4 th stage was 1225.0m3Construction displacement of 4.0-10.0m3Min, total sand amount of proppant 82.0m3。
(5) And (3) perforation and bridge plug combined operation: the aperture is 14.5mm, the first section does not need a bridge plug, a coiled tubing is used for feeding the coiled tubing into a perforating string, the second section starts to put a bridge plug perforating combination tool, and the tool string is pushed in a pumping mode. After the bridge plug seat is sealed, releasing the bridge plug seat, lifting the perforating gun to the preset position, and after all perforating is completed, lifting the perforating pipe string to prepare for entering a fracturing injection process.
(6) The medium and high viscosity acid gradually increases the discharge capacity pretreatment operation: according to the type of the core and the acid liquor, the compatibility of a formula and an acid dissolution rate experiment, the soil acid with the viscosity of 15/20/30mPa.s is selected, and the formula is as follows: 12% HCL + 3% HF + 0.5% acidizing corrosion inhibitor + 0.2% iron ion stabilizer, 12% HCL + 3% HF + 1% acidizing corrosion inhibitor + 0.4% iron ion stabilizer, 12% HCL + 3% HF + 1.5% acidizing corrosion inhibitor + 0.6% iron ion stabilizer;
the total amount of acid liquor injected in the first stage is 21m3First, 1m is adopted3Injecting 7m acid solution with viscosity of 15mPa.s into the container at a discharge rate of min3And then 1m3Injecting 7m acid solution with viscosity of 20mPa.s into the container at a discharge rate of/min3Finally, 1.5m3Injecting 7m acid solution with viscosity of 30mPa.s into the container at a discharge rate of/min3(ii) a The total amount of acid liquor injected in the second stage is 24m3First, 1m is adopted3Injecting acid solution with viscosity of 15mPa.s into the container at a rate of 8 m/min3And then 1m3Injecting acid solution with viscosity of 20mPa.s into the container at a rate of 8 m/min3Finally, 1.5m3Injecting acid solution with viscosity of 30mPa.s into the container at a rate of 8 m/min3(ii) a The total amount of acid liquor injected into the third stage is 24m3First, 1m is adopted3Injecting acid solution with viscosity of 15mPa.s into the container at a rate of 8 m/min3And then 1m3Injecting acid solution with viscosity of 20mPa.s into the container at a rate of 8 m/min3Finally, 1.5m3Injecting acid solution with viscosity of 30mPa.s into the container at a rate of 8 m/min3(ii) a The total amount of acid liquor injected into the fourth section is 27m3First, 1m is adopted3Injecting 9m acid solution with viscosity of 15mPa.s into the container at a discharge rate of/min3And then 1m3Injecting 9m acid solution with viscosity of 20mPa.s into the container at a discharge rate of/min3Finally, 1.5m3Viscosity at/min deliveryAcid solution of 30mPa.s 9m3。
After all three types of acid of each section enter a shaft, the discharge capacity of the substituted acid is 3m3Injecting at min, and reducing the displacement of the acid to 1.5m when the acid reaches the first cluster of perforation close to the heel3Min; wait 1/3 acid to enter the formation, another 1/3 acid amount was 5m3The acid is injected in a displacement of/min, and the final residual acid amount is 7m3And/min is used for replacing the discharge amount of acid.
Closing the well for 10min after acid replacement.
(7) The slippery water is carried fast and the discharge capacity is built and constructed synchronously: the formula of the low-viscosity slick water comprises: 0.03 percent of SRFR-1 drag reducer, 0.3 percent of SRCS-1 clay stabilizer and 0.1 percent of SRCU-1 cleanup additive, wherein the dosage of each section is respectively as follows: first segment 200m3Second segment 280m3Third segment 300m3Fourth stage 310m3The process flow is shown in the implementation step (7).
(8) Carrying and replacing the proppant: see Steps (8) - (9) for implementation.
The well is subjected to fracturing construction according to the steps, and the site construction process is successful. And combining the well temperature logging interpretation result after the well is fractured and the fracture secondary simulation result after the well is fractured, verifying that a single fracture in a cluster is formed after the well is fractured, the fracture initiation and extension time is equivalent, and the fracture length is greater than the fracture length formed by the fracture of the adjacent well in the same-specification fracturing mode. The well has good effect after being pressed, and the daily gas production rate at the initial stage after being pressed is 6 x 104m3A half-year later daily production stabilized at 3.0 x 104m3And/d is about.
Pilot experiments through this well demonstrated: by using the process method provided by the patent for reference, the daily gas production rate at the initial stage after the fracturing reaches about 2-3 times of that of an adjacent well, the gas production rate after the fracturing is reduced obviously slower than that of the adjacent well or an adjacent block, the stable yield after the fracturing and the effective period are obviously prolonged, the obvious yield increasing effect is obtained, and the fracturing transformation effect of the reservoir is improved.
Claims (9)
1. A horizontal well cluster perforation staged fracturing method is characterized by comprising the following steps:
the number of the first section of perforation clusters is 2-4; the number of other perforation clusters in each section is set to be more than 6 clusters;
each cluster of four perforation holes is formed, and 4 perforating charges have a 90-degree phase angle, so that the 4 perforation holes are positioned in the same plane vertical to the horizontal shaft direction;
the diameter of the perforation is more than 14.5 mm;
and a pretreatment mode of gradually increasing the discharge amount of the acid liquid with medium and high viscosity is adopted, so that synchronous initiation and extension of multiple clusters of cracks in the section are ensured.
2. The horizontal well cluster perforation staged fracturing method of claim 1, wherein the method comprises:
(1) evaluating key reservoir parameters;
(2) determining a geological engineering comprehensive dessert and determining the positions of cluster perforation;
(3) optimizing crack parameters;
(4) optimizing fracturing construction parameters;
(5) performing combined operation of the perforation and the bridge plug;
(6) the medium and high viscosity acid gradually increases the discharge capacity for pretreatment operation;
(7) synchronous joint making construction of fast lifting discharge capacity of the slick water;
(8) carrying out proppant conveying construction;
(9) and (5) replacing operation.
3. The horizontal well cluster perforation staged fracturing method of claim 2, characterized in that:
and (5) performing bridge plug perforation combination of staged fracturing based on the position of the stage cluster in the step (2).
4. The horizontal well cluster perforation staged fracturing method of claim 2, characterized in that:
step (6), three acid solutions with the viscosity of 10-15mPa.s, 20-25mPa.s and 30-35mPa.s respectively are obtained;
using a 1-1.5m3And (2) replacing the acid discharge amount per min, firstly injecting acid liquid with the viscosity of 10-15mPa.s, wherein the injection amount is 30-35% of the designed acid amount, then injecting acid liquid with the viscosity of 20-25mPa.s, wherein the injection amount is 30-35% of the designed acid amount, and then injecting acid liquid with the viscosity of 30-35 mPa.s.
5. The horizontal well cluster perforation staged fracturing method of claim 4, wherein:
after all the acid with three viscosities enters a shaft, the displacement of the acid is 3-4m3Injecting in min, and reducing the displacement of the acid to the original displacement of the acid when the acid reaches the first cluster of perforations close to the heel; after 30-35% of acid enters the stratum, the other 30-35% of acid is used for 5-6m3Injecting acid at a displacement of/min, and using 7-8m of residual acid3And/min is used for replacing the discharge amount of acid.
6. The horizontal well cluster perforation staged fracturing method of claim 5, characterized in that:
closing the well for 5-10min after acid replacement is finished.
7. The horizontal well cluster perforation staged fracturing method of claim 2, characterized in that:
step (7), adopting the amount and the discharge capacity of the slickwater optimized in the step (4), and quickly increasing the designed maximum discharge capacity within 1-2min, wherein the viscosity of the slickwater is 1-3 mPa.s;
the amount of the slickwater injected accounts for 20-30% of the total amount of the fracturing fluid injected into the section.
8. The horizontal well cluster perforation staged fracturing method of claim 2, characterized in that:
and (8) the rising rate of the wellhead pressure is not higher than 1 MPa/min.
9. The horizontal well cluster perforation staged fracturing method of claim 2, characterized in that:
step (9) is to design the displacement liquid amount according to 105-110% of the current section well bore volume.
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