CN112963136A - Multi-time sand fracturing method for low-permeability coal-based gas reservoir - Google Patents
Multi-time sand fracturing method for low-permeability coal-based gas reservoir Download PDFInfo
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- CN112963136A CN112963136A CN202110259310.5A CN202110259310A CN112963136A CN 112963136 A CN112963136 A CN 112963136A CN 202110259310 A CN202110259310 A CN 202110259310A CN 112963136 A CN112963136 A CN 112963136A
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- 239000004576 sand Substances 0.000 title claims abstract description 48
- 239000003245 coal Substances 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 23
- 239000007789 gas Substances 0.000 claims abstract description 43
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 22
- 230000035699 permeability Effects 0.000 claims abstract description 14
- 239000006260 foam Substances 0.000 claims abstract description 11
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 11
- 238000010276 construction Methods 0.000 claims abstract description 7
- 238000004519 manufacturing process Methods 0.000 claims abstract description 6
- 230000008569 process Effects 0.000 claims abstract description 4
- 239000012530 fluid Substances 0.000 claims description 6
- 230000009286 beneficial effect Effects 0.000 claims description 4
- 238000009958 sewing Methods 0.000 abstract description 5
- 238000004458 analytical method Methods 0.000 abstract description 4
- 238000003795 desorption Methods 0.000 abstract description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000001131 transforming effect Effects 0.000 description 3
- 235000015076 Shorea robusta Nutrition 0.000 description 2
- 244000166071 Shorea robusta Species 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- 239000002817 coal dust Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 238000005065 mining Methods 0.000 description 2
- 239000011435 rock Substances 0.000 description 2
- 239000003034 coal gas Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- 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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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/261—Separate steps of (1) cementing, plugging or consolidating and (2) fracturing or attacking the formation
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Revetment (AREA)
Abstract
The invention belongs to the technical field of coal bed gas exploitation, and discloses a multiple sand fracturing method for a low permeability coal-based gas reservoir, which utilizes the purpose of more reserves to perform first sand adding to form a production main fracture; adding sand to the temporary plugging balls for the second time to build a reasonable layout of the proppant; the third sand adding reaches the ideal extension distance and shape of the proppant; and when the working pressure is limited safely during construction, adding temporary plugging balls and sand fracturing for the fourth time to achieve the purpose of opening the perforation section and the adjacent sandstone-mudstone stratum to the full extent. According to the invention, through multiple sand adding, temporary ball plugging, sand adding process and nitrogen foam assisted discharge, a longer, more ideal and more complex fracture network is maintained, a continuous analysis state is maintained by the fracture network in a near well zone, and the gas desorption and pressure drop funnel range is enlarged; reducing the flow pressure, improving the yield and maintaining high yield through pressure drop. The invention realizes volume net sewing and stable support.
Description
Technical Field
The invention belongs to the technical field of coal bed gas exploitation, and particularly relates to a multiple sand fracturing method for a low-permeability coal-based gas reservoir.
Background
At present, the geological structure of the coal bed gas is changeable, the coal deterioration effect is obvious due to the multi-stage evolution and multi-heat source superposition of the coal, and the physical property, the gas-containing storage condition, the mining condition and the like of the coal bed gas hidden in a coal reservoir have obvious particularity. Considerable coal bed methane reservoirs exhibit high stress and low permeability characteristics that make mining of coal bed methane reservoirs more demanding. High-stress and low-permeability gas layers are always the direction of attack in the field of energy development.
Low-permeability coal bed gas belongs to a resource difficult to develop, and a good seepage condition cannot be formed simply depending on the self condition of the stratum. Aiming at coal bed gas in coal-series strata, mudstone gas (top and bottom plates) and nearby compact sandstone gas which are low-permeability unconventional gas, developers have no specific success case for carrying out modification at present in China in order to reduce cost.
Through the above analysis, the problems and defects of the prior art are as follows: at present, no special targeted success case for reservoir reconstruction exists in China.
The significance of solving the problems and the defects is as follows: the combined transformation degree of the coal bed, the gas-containing sandstone and the gas-containing mudstone is improved, the channel is unblocked and analyzed, the gas production is stable, and the yield is improved.
Disclosure of Invention
Aiming at the problems in the existing reservoir transformation technology, the invention provides a multiple sand fracturing method for a low permeability coal gas reservoir.
The invention is realized in such a way that a low permeability coal-based gas reservoir multiple sand fracturing method is characterized by comprising the following steps:
carrying out primary sand adding to form a production main crack;
adding sand to the temporary plugging balls for the second time to build a reasonable layout of the proppant;
the third sand adding reaches the ideal extension distance and shape of the proppant;
and when the working pressure is limited safely during construction, adding temporary plugging balls and sand fracturing for the fourth time to achieve the purpose of opening the perforation section and the adjacent sandstone-mudstone stratum to the full extent.
Furthermore, the extension distance is 150-250 m longer than a single side.
Furthermore, nitrogen foam is added to enhance the drainage during the fourth operation.
Further, the preconditions of the fourth operation are: the combination of the coal bed, the shale and the sandstone is beneficial to the full adaptability of the fracturing fluid, and the shaft condition can bear the continuous high-pressure work.
Furthermore, through multiple sand adding, temporary ball plugging, sand adding process and nitrogen foam assisted discharge, a longer and more ideal and more complex fracture network is kept, the fracture network in the near wellbore zone is kept in a continuous analysis state, and the gas desorption and pressure drop funnel range is enlarged; reducing the flow pressure, improving the yield and maintaining high yield through pressure drop.
Further, the determination principle of each stop time is as follows: respectively 60min, 45min and 45 min.
Further, the number of temporary plugging balls is determined according to the principle: preparing according to 40-60% of the total hole number of the perforation section; the number of the second fracturing plus the temporary plugging balls is 40% of the number of the perforation, and the number of the fourth fracturing plus the temporary plugging balls is 60% of the number of the perforation.
By combining all the technical schemes, the invention has the advantages and positive effects that: according to the invention, the characteristics of a low-permeability coal bed, gas-containing mudstone and a gas-containing sandstone box are utilized to carry out primary sand adding to form a production main crack; at proper time intervals, carrying out secondary temporary plugging ball adding and sand adding to build reasonable layout of the proppant and increase the range of complex net sewing; adding sand for the third time at certain intervals to achieve the ideal extension distance and form of the proppant and strive to realize the relatively stable state of the volume seam net; when the construction period is under the condition of safe working pressure limiting, the fourth time of stopping for a certain time, adding a temporary plugging ball and adding sand fracturing can be carried out, so that the aim of opening a perforation section and an adjacent sandstone-mudstone stratum is fulfilled, and meanwhile, nitrogen foam is selected as fracturing fluid during the fourth time of fracturing. According to the invention, through multiple sand adding, temporary ball plugging, sand adding process and nitrogen foam assisted discharge, a longer, more ideal and more complex fracture network is maintained, a continuous analysis state is maintained by the fracture network in a near well zone, and the gas desorption and pressure drop funnel range is enlarged; reducing the flow pressure, improving the yield and maintaining high yield through pressure drop. The invention breaks through the idea of three reservoir interfaces by fully transforming the combination of the complex reservoir coal seam, the gas-containing mudstone and the gas-containing sandstone, realizes volume seam network and supports stable yield.
In the invention, nitrogen foam can be added during the fourth operation, so that the drainage is enhanced, the accumulation of coal dust and rock dust in a crack channel is reduced, and the reservoir pollution is reduced. Preconditions for the fourth operation are: the combination is beneficial to the adaptability of the fracturing fluid to coal beds, shales and sandstones, and the shaft conditions bear continuous high-pressure work. In the invention, sand is added to keep a longer and more fractured network, so that the fractured network of the near-well area is continuously analyzed, and the transformation range is expanded; reducing the flow pressure, improving the yield and maintaining high yield through pressure drop. The invention breaks through the idea of three reservoir interfaces by fully transforming complex reservoir combinations, realizes volume network-sewing and supports stable yield. The four-time fracturing of the invention has the challenges of large liquid supply, large sand amount, high discharge and high construction pressure.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained from the drawings without creative efforts.
Fig. 1 is a flow chart of a multiple sand fracturing method for a low permeability coal-based gas reservoir according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Aiming at the problems in the prior art, the invention provides a multiple sand fracturing method for a low-permeability coal-based gas reservoir, and the invention is described in detail below with reference to the accompanying drawings.
Aiming at coal bed gas in a coal-series stratum, mudstone gas (a top plate and a bottom plate) and nearby compact sandstone gas, the low-permeability unconventional gas is adopted; at present, no specific success case for the improvement is existed in China. The invention breaks through the idea of three reservoir interfaces by fully transforming complex reservoir combinations, realizes volume network-sewing and supports stable yield.
Determination principle of each stopping time: respectively 60min, 45min and 45 min.
The number of temporary plugging balls is determined according to the principle: prepared according to 40-60% of the total number of holes of the perforation section. The number of the second fracturing plus the temporary plugging balls is 40% of the number of the perforation, and the number of the fourth fracturing plus the temporary plugging balls is 60% of the number of the perforation.
Nitrogen foam dosage principle: the fourth sand adding amount is needed.
As shown in fig. 1, the multiple sand fracturing method for the low permeability coal-based gas reservoir provided by the embodiment of the invention includes:
s101: the method comprises the following steps of (1) carrying out primary sand adding to form a production main crack by utilizing the characteristics of a low-permeability coal bed, gas-containing mudstone and a gas-containing sandstone box;
s102: at proper time intervals, carrying out secondary temporary plugging ball adding and sand adding to build reasonable layout of the proppant and increase the range of complex net sewing;
s103: adding sand for the third time at certain intervals to achieve the ideal extension distance and form of the proppant and strive to realize the relatively stable state of the volume seam net;
s104: when the construction period is under the condition of safe working pressure limiting, the fourth time of stopping for a certain time, adding a temporary plugging ball and adding sand fracturing can be carried out, so that the aim of opening a perforation section and an adjacent sandstone-mudstone stratum is fulfilled, and meanwhile, nitrogen foam is selected as fracturing fluid during the fourth time of fracturing.
A person skilled in the art can also perform other steps in the low permeability coal-based gas reservoir multiple sand fracturing method provided by the present invention, and the low permeability coal-based gas reservoir multiple sand fracturing method provided by the present invention shown in fig. 1 is only one specific example.
In S103 provided by the embodiment of the invention, the extension distance is 150-250 m longer than a single side.
In the step S104 provided by the embodiment of the invention, nitrogen foam can be added during the fourth operation, so that the drainage is enhanced, the accumulation of coal dust and rock dust in a fracture channel is reduced, and the reservoir pollution is reduced.
In S104 provided in the embodiment of the present invention, the preconditions of the fourth operation are as follows: the combination is beneficial to the adaptability of the fracturing fluid to coal beds, shales and sandstones, and the shaft conditions bear continuous high-pressure work.
In S104 provided by the embodiment of the invention, sand is added to keep a longer and more fractured network, so that the fractured network of the near-well zone can be continuously analyzed, and the transformation range is expanded; reducing the flowing pressure, improving the yield and maintaining high yield through pressure drop,
based on data of indoor tests, after construction is carried out in the first step and the second step of the technology, the sand amount before and after the temporary plugging ball is added accounts for 40% and 60% respectively, the crushing is very obvious, the sand addition is smooth, the crack detection range reaches the unilateral crack length of 137m +185m, the crack height is 9.3m +3.9m, and the purpose of enlarging the modification range is achieved.
The above description is only for the purpose of illustrating the present invention and the appended claims are not to be construed as limiting the scope of the invention, which is intended to cover all modifications, equivalents and improvements that are within the spirit and scope of the invention as defined by the appended claims.
Claims (7)
1. A multiple sand fracturing method for a low-permeability coal-based gas reservoir is characterized by comprising the following steps:
carrying out primary sand adding to form a production main crack;
adding sand to the temporary plugging balls for the second time to build a reasonable layout of the proppant;
the third sand adding reaches the ideal extension distance and shape of the proppant;
and when the working pressure is limited safely during construction, adding temporary plugging balls and sand fracturing for the fourth time to achieve the purpose of opening the perforation section and the adjacent sandstone-mudstone stratum to the full extent.
2. The multiple sand fracturing method of a low permeability coal-based gas reservoir of claim 1, wherein the extension distance is 150 to 250 meters long on one side.
3. The multi-sanding fracturing method of low permeability coal-based gas reservoir of claim 1, wherein nitrogen foam is added to enhance drainage during the fourth operation.
4. The multiple sand fracturing method of a low permeability coal-based gas reservoir of claim 1, wherein the precondition for the fourth operation is: the combination of the coal bed, the shale and the sandstone is beneficial to the full adaptability of the fracturing fluid, and the shaft condition can bear the continuous high-pressure work.
5. The low permeability coal-based gas reservoir multiple-sanding fracturing method of claim 1, wherein multiple sanding, temporary plugging, sanding process and nitrogen foam assisted drainage are performed.
6. The low permeability coal-based gas reservoir multiple sand fracturing method of claim 1, wherein the determination principle of each stop time is as follows: respectively 60min, 45min and 45 min.
7. The low permeability coal-based gas reservoir multiple sand fracturing method of claim 1, wherein the number of temporary plugging balls is determined according to the principle: preparing according to 40-60% of the total hole number of the perforation section; the number of the second fracturing plus the temporary plugging balls is 40% of the number of the perforation, and the number of the fourth fracturing plus the temporary plugging balls is 60% of the number of the perforation.
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| CN202110259310.5A CN112963136A (en) | 2021-03-10 | 2021-03-10 | Multi-time sand fracturing method for low-permeability coal-based gas reservoir |
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| CN202110259310.5A CN112963136A (en) | 2021-03-10 | 2021-03-10 | Multi-time sand fracturing method for low-permeability coal-based gas reservoir |
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|---|---|---|---|---|
| US4442897A (en) * | 1980-05-23 | 1984-04-17 | Standard Oil Company | Formation fracturing method |
| US20070227732A1 (en) * | 2006-03-28 | 2007-10-04 | Schlumberger Technology Corporation | Method of fracturing a coalbed gas reservoir |
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| CN107387053A (en) * | 2017-06-13 | 2017-11-24 | 北京大学 | A kind of method that big passage major fracture cooperates with pressure break with complicated seam net |
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| CN111271040A (en) * | 2020-03-30 | 2020-06-12 | 重庆地质矿产研究院 | Hydraulic fracturing method suitable for multiple and thin coal seams |
| CN111648755A (en) * | 2020-05-20 | 2020-09-11 | 中国石油化工股份有限公司 | Method for promoting balanced expansion of multiple clusters of cracks through ball throwing and temporary plugging |
-
2021
- 2021-03-10 CN CN202110259310.5A patent/CN112963136A/en active Pending
Patent Citations (10)
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|---|---|---|---|---|
| US4442897A (en) * | 1980-05-23 | 1984-04-17 | Standard Oil Company | Formation fracturing method |
| US20070227732A1 (en) * | 2006-03-28 | 2007-10-04 | Schlumberger Technology Corporation | Method of fracturing a coalbed gas reservoir |
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| CN111648755A (en) * | 2020-05-20 | 2020-09-11 | 中国石油化工股份有限公司 | Method for promoting balanced expansion of multiple clusters of cracks through ball throwing and temporary plugging |
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