CN112267867B - Deep coal bed gas well volume acidizing fracturing method - Google Patents
Deep coal bed gas well volume acidizing fracturing method Download PDFInfo
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Classifications
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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
-
- 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
- E21B43/006—Production of coal-bed methane
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P90/00—Enabling technologies with a potential contribution to greenhouse gas [GHG] emissions mitigation
- Y02P90/70—Combining sequestration of CO2 and exploitation of hydrocarbons by injecting CO2 or carbonated water in oil wells
Abstract
The invention discloses a deep coal bed gas well volume acidizing fracturing method, which comprises the following steps: detecting a coal seam structure, and perforating at the middle position of a coal seam of a primary structure; sequentially injecting the pad fluid, the sand carrying fluid and the displacing fluid into the coal bed through perforation; wherein, the pad fluid includes: adding quartz sand slug when injecting acid; the sand-carrying fluid comprises: the surfactant fracturing fluid carries acid and proppant when being injected; the displacement fluid comprises: the method comprises the following steps of injecting active water and acid, wherein a preset amount of active water is injected firstly, then injecting acid, and then continuing to inject the active water. The invention takes acid fracturing as a main process technology, improves pore connectivity, increases matrix permeability, realizes dual fracture channels of a supporting fracture and an acid-soluble fracture, increases the hydraulic fracture range of effective flow conductivity, weakens the influence of fracture closure after fracturing on the fracturing effect and achieves the purpose of increasing yield by optimizing the position of a perforation, optimizing a fracturing fluid system and optimizing an injection process.
Description
Technical Field
The invention relates to the technical field of coal-bed gas well exploitation, in particular to a deep coal-bed gas well volume acidizing and fracturing method.
Background
The coal bed gas fracturing well usually adopts a mode of direct perforation fracturing on a coal bed, active water fracturing fluid is used, tests of liquid systems such as guanidine gum, slick water, clean fracturing fluid and the like are also developed in a part of areas, and hydraulic fractures of high-seepage channels are formed in the coal bed in a large-scale water conservancy sand fracturing mode to realize the yield increase of the coal bed gas; or an indirect fracturing process is carried out by utilizing the top plate sandstone, and a conventional hydraulic fracturing mode is adopted to form hydraulic fractures of a high permeability channel between the top plate sandstone and the coal bed; related acidizing unblocking technology is developed aiming at old well blocking, and the flow conductivity of the cracks is improved by injecting acid liquor to erode coal dust and coal slime in the cracks.
The filtration of fracturing fluid is large due to the fact that the cleavage cracks of the coal bed are opened in the fracturing process, secondary microcracks and the opening degree of the cleavage cracks opened at the far end do not meet the condition of entering of a propping agent, active water performance is poor, the far end cracks are not easy to support, invalid cracks are formed finally after the coal bed is pressed to be closed, the condition of benefit development of a low-porosity and low-permeability deep coal bed cannot be met, and the fracturing transformation effect is influenced.
Disclosure of Invention
In view of the technical problems, the invention provides a deep coal-bed gas well volume acidizing fracturing method so as to solve or partially solve the technical problems.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a deep coal bed gas well volume acidizing and fracturing method, which comprises the following steps:
detecting a coal seam structure, and perforating at the middle position of a coal seam of a primary structure;
sequentially injecting the pad fluid, the sand carrying fluid and the displacing fluid into the coal bed through perforation; wherein the content of the first and second substances,
the pad fluid comprises: activated water and acid, wherein a quartz sand slug is added during acid injection;
the sand-carrying fluid comprises: a surfactant fracturing fluid that when injected carries acid and proppant;
the displacement fluid comprises: the method comprises the following steps of injecting active water and acid, wherein a preset amount of active water is injected firstly, then injecting acid, and then continuing to inject the active water.
Further, if it is detected that the coal seam roof develops into acid-soluble limestone, the method further comprises:
and perforating at the cementing surface of the coal bed and the top plate, and controlling the thickness of the top plate to be less than 0.5m.
Further, based on the total volume of the liquid in the pad fluid, the sand carrying fluid and the displacing fluid,
in the pad fluid, the active water accounts for 15%, the acid accounts for 10-15%, and the acid amount of the acid accounts for 15% of the total acid amount;
in the sand-carrying fluid, the surfactant fracturing fluid accounts for 64-69%, and the acid content of the acid accounts for 80% of the total acid content;
in the displacement liquid, the active water injected firstly accounts for 2%, the acid accounts for 1%, the active water injected later accounts for 3%, and the acid amount of the acid accounts for 5% of the total acid amount.
Further, when the acid in the pad fluid is injected, 2-3 sections of quartz sand slugs with 70-140 meshes are added;
when the surfactant fracturing fluid in the sand-carrying fluid is injected, 70-140 meshes of quartz sand and acid are injected into the multistage slug, then 40-70 meshes of quartz sand are injected into the multistage slug, and then 30-50 meshes of quartz sand or ceramsite is continuously injected into the multistage slug.
Further, the total volume of the quartz sand or the ceramsite is not less than 70 cubic meters based on the total volume of the quartz sand and the ceramsite used by the pad fluid and the sand-carrying fluid;
when the acid in the pad fluid is injected, the added quartz sand with 70-140 meshes accounts for 8 percent;
when the surfactant fracturing fluid in the sand-carrying fluid is injected, 12% of the added quartz sand of 70-140 meshes, 50% of the added quartz sand of 40-70 meshes and 30% of the added quartz sand or ceramsite of 30-50 meshes are added.
Further, the active water is 1% -2% of KCl, and the surfactant fracturing fluid is a low-molecular clean fracturing fluid.
Further, the acid in the pad fluid is hydrochloric acid or sulfamic acid, and the acid is carried by active water.
Further, the acid in the sand-carrying fluid is hydrochloric acid or sulfamic acid, and the acid is carried by the surfactant fracturing fluid.
Further, the acid in the displacement fluid is hydrochloric acid or sulfamic acid, and the acid is carried by active water.
Further, when the pad fluid is injected, the discharge capacity of the active water is 8-12m 3 The acid is injected in a form carried by active water, and the discharge capacity is 8-12m 3 /min；
When the sand-carrying fluid is injected, the discharge capacity of the surfactant fracturing fluid is 12-16m 3 /min；
When the displacement liquid is injected, the discharge volume of the active water injected firstly is 10-14m 3 The acid is injected in a form carried by the surfactant fracturing fluid, and the discharge capacity is 1-2m 3 Min, the discharge capacity of the active water injected later is 2-4m 3 /min。
In conclusion, the beneficial effects of the invention are as follows:
according to the deep gas well acidizing and fracturing method, firstly, perforation is carried out at the middle position of a primary structure coal bed with high gas content and stable coal body structure, so that the generation of coal dust is reduced, and the extension of a crack in a high gas-containing layer section of a reservoir is realized; and then sequentially injecting the pad fluid, the sand-carrying fluid and the displacing fluid into the coal bed through perforation, performing program injection in a mode of combining various liquid systems and proppants according to the modes of the pad fluid, the sand-carrying fluid and the displacing fluid, and realizing efficient acidification and volume fracturing of the coal reservoir by utilizing different functions of different liquid systems and proppants during different program periods. In a deep coal seam (the buried depth is more than 1500 m), the acidizing and fracturing method can improve the permeability of a coal seam matrix, uneven etching is performed on cleavages opened at the far end of a fracture and fracture acid-soluble fillers, the pore connectivity is improved, the problem that a propping agent cannot enter and is closed again so that the propping agent cannot be effectively utilized is solved, and the yield of a deep coal seam gas well is increased by improving artificial fractures and the permeability of the matrix.
Drawings
FIG. 1 is a diagram illustrating the steps performed in a deep coal-bed gas well volumetric acidizing fracturing method in accordance with one embodiment of the present invention;
FIG. 2 is a schematic representation of a perforation location in accordance with an embodiment of the present invention;
figure 3 is a schematic representation of the location of perforations in another embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in this application will be understood to be a specific case for those of ordinary skill in the art.
In one embodiment of the present invention, a deep coal bed gas well volume acidizing and fracturing method is provided, which includes the following steps, as shown in fig. 1:
step 1, detecting a coal seam structure, as shown in fig. 2, perforating at the middle position of a primary structure coal seam with high gas content and stable coal body structure, effectively reducing coal dust generation, and in the fracturing process, extending a crack in a high gas-bearing stratum section of a reservoir stratum to obtain a better fracturing effect.
And 2, injecting the pad fluid, the sand carrying fluid and the displacing fluid into the coal bed in sequence through perforation.
Wherein, the pad fluid includes: adding active water and acid, and adding a quartz sand slug when injecting the acid; the active water has the effect of generating hydraulic fractures, and the low-viscosity active water is easy to open micro-cutting fractures, so that the effective modification volume of the coal bed is increased, the temperature of a reservoir is reduced, the reaction speed of acid rocks is reduced, the effect efficiency of acid liquid at the far ends of the fractures is improved, the acid liquid reacts and erodes fillers in the fractures, cutting fractures and fractures opened by the active water, the matrix permeability is improved, the coal bed gas migration is facilitated, and carbon dioxide generated by the reaction of an acid liquid system and the fillers can be replaced with methane in the coal bed, so that the methane desorption efficiency is improved.
The sand-carrying fluid comprises: the surfactant fracturing fluid carries acid and a propping agent when being injected, so that the reaction speed of acid rock is further slowed down, the acid acts on the tail end of the fracture, the flow conductivity of the fracture which is not supported by the tail end after the fracture is pressed is improved, and the effectiveness of hydraulic fracturing is improved; the surfactant fracturing fluid can improve the viscosity of the fracturing fluid, reduce the filtration loss of the fracturing fluid and enlarge the scale of a main fracturing crack. The surfactant fracturing fluid carries solid quartz sand when being injected; the surfactant fracturing fluid has the effects of improving the sand carrying performance of the fracturing fluid, filling secondary cracks around the main cracks, further promoting the expansion of the main cracks, reducing the adding difficulty of the propping agent and improving the length of the propping cracks.
The displacement fluid comprises: the method comprises the following steps of injecting active water and acid, wherein a preset amount of active water is injected firstly, then injecting acid, and then continuing to inject the active water. The active water injected firstly has the function of completely displacing the proppant into the coal bed gas reservoir, so that the smoothness of the shaft of the coal bed gas well is ensured. The acid is used for dissolving soluble substances generated in the fracturing and proppant adding processes, so that the main fracture is further cleaned, and the main fracture is ensured to have higher flow conductivity. And active water continuously injected later plays a role of deep pushing, acid liquid is deeply pushed to the deep part of the coal bed gas reservoir, the whole crack system is cleaned, and meanwhile, the safety of the shaft of the coal bed gas well is ensured.
The surfactant fracturing fluid in the embodiment is a fracturing fluid, has certain viscosity, has better sand carrying property than active water, and can improve the length of a support fracture; the surfactant fracturing fluid is a cationic surfactant mainly composed of tetradecyl trimethyl ammonium chloride and octadecyl trimethyl ammonium chloride, has low molecular weight, small damage to a coal bed, good drag reduction performance, and can reduce the friction resistance by more than 60%, and is beneficial to improving the construction discharge capacity.
The coal bed is a plastic reservoir, the permeability is reduced due to the fact that deformation is prone to occurring under the influence of external force, particularly, deep coal bed gas is large in buried depth, high in three-dimensional stress and extremely low in permeability of the reservoir, most deep coal rocks are primary structure coal, mechanical strength is high, shearing and sliding damage are prone to forming after the compressive strength is exceeded, a geological foundation of scale fracturing is provided, the cleat fracture development is suitable for adopting a volume fracturing mode, the cleat fracture and the fracture are filled with substances such as acid liquor soluble calcite and the like, the permeability of a matrix and an ineffective supporting fracture can be effectively improved through acidification, the effective flow conductivity after fracturing dynamic fracture is increased, and the transformation area is increased. Meanwhile, the acidification also improves the pore connectivity, avoids the problem that the proppant cannot enter to cause reclosure and cannot be effectively utilized, and realizes the yield increase of the deep coal bed gas well through the improvement of artificial cracks and the matrix permeability. The acid fracturing method in the embodiment is suitable for deep wells with the buried depth of more than 1500m, experimental analysis shows that the deep coal seam has high porosity and poor permeability, the cleat fractures in the coal seam are mostly filled with calcite and minerals soluble in acid liquor, the acid fracturing is used as a main process technology, and through optimization of perforation positions, optimization of a fracturing fluid system and optimization of an injection process, pore connectivity is improved, matrix permeability is increased, double fracture channels of supporting fractures and acid-soluble fractures are realized, the hydraulic fracture range of effective flow conductivity is increased, the influence of fracture closure after fracturing on the fracturing effect is weakened, and the purpose of increasing the yield is achieved. Firstly, perforating at the middle position of a primary structure coal bed with high gas content and stable coal body structure, so that the generation of coal powder is reduced, and the extension of cracks in a high gas-containing layer section of a reservoir is realized; and then sequentially injecting the pad fluid, the sand-carrying fluid and the displacing fluid into the coal bed through perforation, performing program injection in a mode of combining various liquid systems and proppants according to the modes of the pad fluid, the sand-carrying fluid and the displacing fluid, and realizing efficient acidification and volume fracturing of the coal reservoir by utilizing different functions of different liquid systems and proppants during different program periods.
In one embodiment, as shown in fig. 3, if it is detected that the coal seam roof has developed into acid-soluble limestone, the method further includes:
and perforating at the cementing surface of the coal bed and the top plate, and controlling the thickness of the top plate to be less than 0.5m. When the coal seam roof is developed into mudstone, perforating only in the middle of the primary structure coal seam with high gas content and stable coal body structure; when the coal seam roof develops into the limestone, perforation is carried out on the cementing surface of the coal seam and the roof while perforation is carried out on the middle position of the original structure coal seam. The limestone can react with the acid liquor system to generate gaps, so that acid fracturing double seepage channels are formed on the cementing surfaces of the reservoir and the roof, the fracturing fluid can enter conveniently, when entering the stratum from the top of the coal bed, the fracturing on the upper half part of the coal bed can be realized, and the fracturing effect is better.
In a preferred embodiment, the pad fluid has 15% active water, 10-15% acid, and 15% acid by total acid, based on the total fluid volume of the pad fluid, the sand-carrying fluid, and the displacement fluid.
In the sand carrying liquid, the surfactant fracturing liquid accounts for 64-69%, wherein the surfactant fracturing liquid with acid accounts for 15% of the total surfactant fracturing liquid in the sand carrying liquid, and the acid accounts for 80% of the total acid.
In the displacement liquid, active water injected firstly accounts for 2%, acid accounts for 1%, active water injected later accounts for 3%, and acid amount of the acid accounts for 5% of the total acid amount.
In one embodiment, when acid is injected into the pad fluid, a 2-3 section 70-140 mesh quartz sand slug is added, and when active water carries acid to be injected, a 2 section 70-140 mesh quartz sand slug is added to fill and block micro cracks and fissures, so that the filtration loss of the fracturing fluid is reduced, the expansion of a main crack is promoted, and good conditions are provided for the subsequent addition of quartz sand.
When the sand-carrying fluid surfactant fracturing fluid is injected, 70-140 meshes of quartz sand and acid are injected into the multistage slug, then 40-70 meshes of quartz sand are injected into the multistage slug, and then 30-50 meshes of quartz sand or ceramsite are continuously injected into the multistage slug.
In a preferred embodiment, the total volume of the quartz sand or the ceramsite is not less than 70 cubic meters based on the total volume of the quartz sand and the ceramsite by using the pre-solution and the sand-carrying solution.
When acid is injected into the pad liquor, the added quartz sand with 70-140 meshes accounts for 8 percent.
When the surfactant fracturing fluid in the sand-carrying fluid is injected, the added quartz sand with 70-140 meshes accounts for 12%, the added quartz sand with 40-70 meshes accounts for 50%, and the added quartz sand or ceramsite with 30-50 meshes accounts for 30%.
In one embodiment, the active water is 1% to 2% KCl.1% -2%, the KCl solution has low viscosity, can be fully communicated with small cleavage cracks, and is beneficial to increasing the pressure relief area; meanwhile, the specific surface temperature of reservoir fractures can be reduced, and the effects of maintaining the viscosity of the surfactant fracturing fluid and reducing the acid rock reaction speed are better promoted.
In one embodiment, the surfactant fracturing fluid is a low molecular weight clean fracturing fluid. The surfactant fracturing fluid not only has the advantages of the conventional surfactant fracturing fluid, but also can form slippery acid after being mixed with acid liquor, still has good viscosity and drag reduction performance, can reduce the stress speed of low-acid rock by more than 3 times, and is beneficial to improving the action distance of the acid liquor to the far end of a crack.
In one embodiment, the acid in the pad is hydrochloric acid or sulfamic acid, which is injected in a form carried by the active water. The hydrochloric acid can react with soluble fillers in the cleat and the crack, the pore connectivity is improved through uneven corrosion, and for a reservoir stratum with a limestone top plate, acid liquor can form uneven corrosion on the top plate, and a dual-seepage channel of acid fracturing is formed on the cemented surface of the reservoir stratum and the top plate. If sulfamic acid is used, active water is directly used to carry solid sulfamic acid, the reaction time is prolonged by 3 times compared with hydrochloric acid, the action distance of the acid liquor can be effectively extended to the far end of a crack, and meanwhile, the reaction of the acid liquor and a roof can be effectively weakened when the roof is a limestone reservoir, so that the action of the acid liquor on a coal bed is improved.
In one embodiment, the acid in the carrier fluid is hydrochloric acid or sulfamic acid, which is carried in the form of a surfactant fracturing fluid.
In one embodiment, the acid in the displacement fluid is hydrochloric acid or sulfamic acid, which is in the form carried by the activated water.
In one embodiment, the displacement of the active water is 8-12m when the pad fluid is injected 3 Min, acid is injected in the form of active water with the discharge capacity of 8-12m 3 /min。
When the sand-carrying fluid is injected, the discharge capacity of the surfactant fracturing fluid is 12-16m 3 /min。
When the displacing liquid is injected, the discharge volume of the active water injected firstly is 10-14m 3 In the method, acid is injected in a form carried by surfactant fracturing fluid, and the discharge capacity is 1-2m 3 Min, the discharge capacity of active water injected later is 2-4m 3 /min。
According to the deep coal bed gas acidizing fracturing method, perforation is conducted on the middle position of a primary structure coal bed with high gas content and stable coal body structure, fracturing fluid can conveniently enter the coal bed structure to fracture the coal bed, through the perforation, pad fluid, sand carrying fluid and displacing fluid are injected into the coal bed in sequence, wherein the pad fluid can achieve pad fracturing on the coal bed, then the sand carrying fluid fills and blocks the fracture, and finally the displacing fluid is used for ensuring smoothness of a shaft of a coal bed gas well. The fracturing method adopts a mode of combining a plurality of liquid systems and proppants, performs program injection according to modes of a pad fluid, a sand carrying fluid and a displacement fluid, and realizes efficient acidification and volume fracturing of a coal reservoir by utilizing different functions of different liquid systems and the proppants during different programs. The invention takes acid fracturing as a main process technology, and improves the pore connectivity, increases the matrix permeability and achieves the purpose of increasing the yield by optimizing the position of a perforation, optimizing a fracturing fluid system and optimizing an injection process.
The coal bed is fractured by the fracturing method, and then test analysis is carried out, and the rock core analysis result shows that the acid liquor can effectively improve the matrix permeability of the coal bed by more than 10 times, the influence on the coal rock strength is within 15 percent, and the coal rock strength after the fracturing is effectively ensured. The underground microseism monitoring result shows that the volume seam network formed by fracturing modification is obvious, 5 wells are applied to the coal seam with the east edge burial depth of Ordos basin being more than 2100m, and the effective modification volume of the coal reservoir reaches 110000m 3 Carbon dioxide generated by acid rock reaction replaces methane gas to be mixed with surfactant fracturing fluid to form foam, the self-draining rate after the fracturing fluid is pressed is more than 20%, the foam is combustible at the initial stage of flowback of the fracturing fluid, the pressure is quickly increased to more than 5MPa within 1 month of production, the flowing pressure is kept to more than 15MPa, and the production can be stably improved to 3500m within 2 months of production 3 And d. The current production time of the longest well is kept at 16MPa of flowing pressure for 300 days, the casing pressure is 2.5MPa, and the yield is 3500m 3 Stable production of/d.
While the foregoing is directed to embodiments of the present invention, other modifications and variations of the present invention may be devised by those skilled in the art in light of the foregoing teachings. It should be understood by those skilled in the art that the foregoing detailed description is for the purpose of better explaining the present invention, and the scope of the present invention should be determined by the scope of the appended claims.
Claims (8)
1. A deep coal bed gas well volume acidizing fracturing method is characterized by comprising the following steps:
detecting a coal seam structure, and perforating at the middle position of a coal seam of a primary structure;
sequentially injecting the pad fluid, the sand carrying fluid and the displacing fluid into the coal bed through perforation; wherein, the first and the second end of the pipe are connected with each other,
the pad fluid comprises: activated water and acid, wherein a quartz sand slug is added during acid injection;
the sand-carrying fluid comprises: a surfactant fracturing fluid that when injected carries acid and proppant;
the displacement fluid comprises: injecting active water and acid, namely injecting a preset amount of active water, then injecting acid, and continuing to inject the active water;
based on the total volume of the liquid in the pad fluid, the sand-carrying fluid and the displacing fluid,
in the pad fluid, the active water accounts for 15%, the acid accounts for 10-15%, and the acid content of the acid accounts for 15% of the total acid content;
in the sand-carrying fluid, the surfactant fracturing fluid accounts for 64-69%, and the acid content of the acid accounts for 80% of the total acid content;
in the displacement liquid, the active water injected firstly accounts for 2 percent, the acid accounts for 1 percent, the active water injected later accounts for 3 percent, and the acid amount of the acid accounts for 5 percent of the total acid amount;
when the pad fluid is injected, the discharge capacity of the active water is 8-12m 3 The acid is injected in a form carried by active water, and the discharge capacity is 8-12m 3 /min；
When the sand-carrying fluid is injected, the discharge capacity of the surfactant fracturing fluid is 12-16m 3 /min；
When the displacement liquid is injected, the discharge volume of the active water injected firstly is 10-14m 3 The acid is injected in a form carried by the surfactant fracturing fluid, and the discharge capacity is 1-2m 3 Min, the discharge capacity of the active water injected later is 2-4m 3 /min。
2. The deep coal-bed gas well volumetric acid fracturing method of claim 1, wherein if it is detected that the coal-bed roof has developed into acid-soluble limestone, the method further comprises:
and perforating at the cementing surface of the coal bed and the top plate, and controlling the thickness of the top plate to be less than 0.5m.
3. The deep coal-bed gas well volumetric acid fracturing method of claim 1,
when the acid in the pad fluid is injected, 2-3 sections of quartz sand slugs with 70-140 meshes are added;
when the surfactant fracturing fluid in the sand-carrying fluid is injected, 70-140 meshes of quartz sand and acid are injected into the multistage slug, then 40-70 meshes of quartz sand are injected into the multistage slug, and then 30-50 meshes of quartz sand or ceramsite is continuously injected into the multistage slug.
4. The deep coal-bed gas well volumetric acid fracturing method of claim 3, wherein the total volume of the quartz sand or the ceramsite is not less than 70 cubic meters based on the total volume of the pad fluid and the sand-carrying fluid using the quartz sand and the ceramsite;
when the acid in the pad fluid is injected, the added quartz sand with 70-140 meshes accounts for 8 percent;
when the surfactant fracturing fluid in the sand-carrying fluid is injected, 12% of the added quartz sand of 70-140 meshes, 50% of the added quartz sand of 40-70 meshes and 30% of the added quartz sand or ceramsite of 30-50 meshes are added.
5. The deep coal-bed gas well volumetric acid fracturing method of claim 1, wherein the active water is 1-2% KCl and the surfactant fracturing fluid is a low molecular weight clean fracturing fluid.
6. The deep coal-bed gas well volumetric acid fracturing method of claim 1, wherein the acid in the pad fluid is hydrochloric acid or sulfamic acid, the acid being in a form carried by the activated water.
7. The deep coal-bed gas well volumetric acid fracturing method of claim 1, wherein the acid in the sand-carrying fluid is hydrochloric acid or sulfamic acid, the acid being in a form carried by a surfactant fracturing fluid.
8. The deep coal-bed gas well volumetric acid fracturing method of claim 1 wherein the acid in the displacement fluid is hydrochloric acid or sulfamic acid, the acid being in a form carried by the activated water.
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Effective date of registration: 20231218 Address after: 100007 No. 9 North Main Street, Dongcheng District, Beijing, Dongzhimen Patentee after: PETROCHINA Co.,Ltd. Patentee after: PETROCHINA COALBED METHANE Co.,Ltd. Patentee after: CHINA UNITED COALBED METHANE NATIONAL ENGINEERING RESEARCH CENTER Co.,Ltd. Address before: 100028 room 417, building 1, No.6 liupukang street, Xicheng District, Beijing Patentee before: PETROCHINA COALBED METHANE Co.,Ltd. Patentee before: CHINA UNITED COALBED METHANE NATIONAL ENGINEERING RESEARCH CENTER Co.,Ltd. |