CN110700807A - Dry-hot rock heat energy development cooling fracturing method - Google Patents
Dry-hot rock heat energy development cooling fracturing method Download PDFInfo
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- CN110700807A CN110700807A CN201910834685.2A CN201910834685A CN110700807A CN 110700807 A CN110700807 A CN 110700807A CN 201910834685 A CN201910834685 A CN 201910834685A CN 110700807 A CN110700807 A CN 110700807A
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- fracturing
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- 239000011435 rock Substances 0.000 title claims abstract description 19
- 238000001816 cooling Methods 0.000 title claims abstract description 17
- 238000000034 method Methods 0.000 title claims abstract description 16
- 239000012530 fluid Substances 0.000 claims abstract description 50
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 16
- 230000000694 effects Effects 0.000 claims abstract description 9
- 239000004576 sand Substances 0.000 claims description 13
- 230000008569 process Effects 0.000 claims description 6
- 238000010276 construction Methods 0.000 claims description 4
- 230000000373 effect on fracture Effects 0.000 claims description 2
- 230000009467 reduction Effects 0.000 claims description 2
- 230000008719 thickening Effects 0.000 claims description 2
- 238000009826 distribution Methods 0.000 abstract description 11
- 230000015572 biosynthetic process Effects 0.000 abstract description 8
- 230000008859 change Effects 0.000 abstract description 7
- 238000010248 power generation Methods 0.000 abstract description 5
- 238000002347 injection Methods 0.000 abstract description 4
- 239000007924 injection Substances 0.000 abstract description 4
- 238000005516 engineering process Methods 0.000 abstract description 3
- 239000002699 waste material Substances 0.000 abstract 1
- 238000004458 analytical method Methods 0.000 description 2
- 238000004132 cross linking Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
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Classifications
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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
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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
- E21B36/00—Heating, cooling or insulating arrangements for boreholes or wells, e.g. for use in permafrost zones
- E21B36/001—Cooling arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24T—GEOTHERMAL COLLECTORS; GEOTHERMAL SYSTEMS
- F24T10/00—Geothermal collectors
- F24T10/20—Geothermal collectors using underground water as working fluid; using working fluid injected directly into the ground, e.g. using injection wells and recovery wells
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- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/10—Geothermal energy
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- Geochemistry & Mineralogy (AREA)
- Fluid Mechanics (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- Hydrology & Water Resources (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
Abstract
The invention discloses a dry hot rock heat energy development cooling fracturing method of a dry hot rock heat energy utilization technology in an enhanced geothermal power generation system (EGS). The method aims to cool a target stratum by injecting the low-sand-ratio thickened water fracturing fluid into a dry hot rock stratum, and due to the injection of the low-sand-ratio thickened water fracturing fluid, the temperature of a shaft and the temperature of the fracturing fluid in a crack are gradually reduced, so that a good cooling effect is guaranteed, the aim of avoiding waste is achieved, and the injection amount of the low-sand-ratio thickened water fracturing fluid needs to be accurately calculated. Because the temperature distribution condition of the formation around the shaft is different from the temperature distribution of the rock around the fracture, the temperature of the formation around the shaft is increased along with the change of the well depth according to the temperature gradient of the ground, and the temperature of the reservoir around the fracture is an average value, the temperature change of the position of the downhole perforation and the temperature distribution condition of the fracturing fluid in the fracture need to be calculated, so that the better dry-hot rock layer cooling effect is realized.
Description
Technical Field
The invention relates to a hot dry rock heat energy utilization technology in an enhanced geothermal power generation system (EGS), in particular to a hot dry rock heat energy development, cooling and fracturing method.
Background
The geothermal energy is used as renewable new energy, has great resource potential and CO2The advantages of low emission and wide distribution are achieved, and the renewable clean energy is mainly researched and developed in all countries of the world. Geothermal energy is divided into a hydrothermal type and a dry-hot rock type, geothermal resources are mined and utilized mainly in the world at present and are hydrothermal geothermal, but the potential of the future resources is the exploitation of the dry-hot rock type geothermal energy, namely an enhanced geothermal power generation system (EGS), and the enhanced geothermal power generation system (EGS) faces a series of engineering technical difficulties at present, so that no commercially successful example exists in the world at present.
Hydraulic fracturing is a key technology for achieving commercial success of an enhanced geothermal power generation system (EGS), and a water injection well and a water production well are communicated through artificial cracks, so that efficient development of geothermal energy is realized. However, due to the ultra-high formation temperature of the geothermal reservoir, great challenge is provided for the high temperature resistance of the fracturing fluid during fracturing, the temperature resistance of the conventional crosslinking fracturing fluid is below 160 ℃, but the temperature of the commercially-used dry hot rock formation is more than 250 ℃ and even reaches more than 300 ℃. The conventional crosslinking fracturing fluid cannot meet the temperature resistance requirement required by construction, and if the temperature resistance of the fracturing fluid is improved, the development cost is greatly increased, and a series of technical challenges are faced.
In view of the above problems, there is a need to design an effective solution.
Disclosure of Invention
Based on the analysis, the invention designs a dry hot rock heat energy development cooling fracturing method, which aims to cool a target stratum by injecting low-sand ratio thickened water fracturing fluid into a dry hot rock stratum. Because the temperature distribution condition of the formation around the shaft is different from the temperature distribution of the rock around the fracture, the temperature of the formation around the shaft is increased along with the change of the well depth according to the temperature gradient of the ground, and the temperature of the reservoir around the fracture is an average value, the temperature change of the position of the downhole perforation and the temperature distribution condition of the fracturing fluid in the fracture need to be calculated, so that the better dry-hot rock layer cooling effect is realized.
A method of reducing temperature and fracturing for thermal energy development of hot dry rock, in one embodiment, comprising the steps of:
1) injecting 27m of fracturing pad fluid (clear water) before injecting the sand-carrying fluid and the conventional fracturing fluid3The part of water is injected to the front end 55m of the crack;
2) injecting low sand ratio (sand carrying concentration is less than 10%) thickening water fracturing fluid, and cooling the stratum;
3) injecting conventional cross-linked fracturing fluid to carry out normal fracturing according to a normal sand carrying ratio;
4) the continuous fracturing construction process must be ensured, and the pump stop phenomenon must not occur. If the pump is stopped before the cross-linked fracturing fluid is pumped, the amount of the low sand ratio fracturing fluid is increased to ensure the effect of cooling the stratum.
The flow conductivity of the tail end of the crack formed by the temperature-reducing fracturing process is slightly lower than that of the conventional fracturing because the sand ratio is lower. However, because geothermal reservoirs are inherently strong, the reduction in proppant volume does not have a significant effect on fracture closure.
Compared with the prior art, the invention has the advantages that: (1) in the fracturing process, the problem of development cost increase caused by selecting high-temperature-resistant fracturing fluid due to ultrahigh formation temperature under a geothermal reservoir can be effectively solved, and the development cost of the whole reservoir can be greatly saved; (2) the temperature at the perforation location decreases more slowly as the injection time increases. When the temperature gradient of the fracturing fluid in the fracture is large, the temperature of the fracturing fluid in the range of 55m at the front end of the fracture is reduced by more than 80 ℃ for a high-temperature reservoir at 300 ℃, and the temperature resistance of the used fracturing fluid can meet the requirement of EGS ultrahigh-temperature stratum fracturing.
Drawings
The invention will be described in more detail hereinafter on the basis of embodiments and with reference to the accompanying drawings. Wherein:
FIG. 1 is a schematic representation of the steps of a method embodying the present invention;
FIG. 2 is a graph of temperature changes at the location of perforations in a wellbore during fracturing;
FIG. 3 is a temperature distribution image of liquid in a fracture 1-20 min before fracture termination;
FIG. 4 is a graph of the temperature change at the perforations under different geothermal gradients;
FIG. 5 is an image of the temperature distribution of the fluid in the fracture before fracture termination at different geothermal gradients;
Detailed Description
The invention will be further explained with reference to the drawings.
In one embodiment of the present invention, the geothermal gradient is 7 ℃/100 m. The temperature difference between the fluid in the fracture and the stratum reaches more than 80 ℃ within 55m of the front end of the fracture, and the volume of the fracturing fluid is 100m at the moment3。
As shown in figure 1, the dry hot rock thermal energy development cooling fracturing method comprises the following steps:
step 1: in one embodiment of the invention, the formation temperature at 4000m downhole is 300 ℃. The clear water injected into the pad fluid in the fracturing process has a good cooling effect on a shaft, and the cooling effect of the fracturing pad fluid on the stratum can be obtained by calculating the temperature distribution of the fracturing fluid in the fracture as shown in figure 3. Therefore, before injecting the sand-carrying fluid and the conventional fracturing fluid, 27m of fracturing pad fluid (clear water) is injected3This portion of water is injected at the front 55m of the fracture.
Step 2: in one embodiment of the invention, the heat transfer properties between the fracturing fluid and the reservoir are obtained by a temperature solution model of the perforation locations and a model of the heat transfer within the fracture during fracturing.
In one embodiment of the invention, COMSOL Multiphysics 5 is applied. 1, calculating by a software heat transfer Module (HeatTransfer Module) to obtain the temperature change of the perforation position as shown in figure 2, wherein the analysis result shows that the temperature of a shaft is rapidly reduced in a short time in the initial stage of fracturing construction, and the fracturing fluid has an obvious effect of reducing the temperature of the stratum. At t-20 min, i.e. at the end of the fracture, the temperature at the perforations is about 105 ℃, which is the initial temperature of the fracturing fluid in the fracture.
Further, the temperature change with time at the perforation position according to the geothermal gradient of 5 deg.C/100 m, 6 deg.C/100 m, and 7 deg.C/100 m, respectively, is shown in FIG. 4. As can be seen from fig. 4, the temperatures at the perforation locations before fracture termination were 80 deg.f each. 0,92. 4,105 ℃, the fracturing fluid has obvious effect of reducing the temperature of the shaft. The temperature distribution of the fracture internal fracturing fluid in the fracture is shown in figure 5 when the ground temperature gradient is respectively 5 ℃/100m, 6 ℃/100m and 7 ℃/100 m. When the reservoir temperature is 220 ℃, before fracturing is terminated, the temperature difference between the fracturing fluid at the position 50m from the front end of the fracture and the stratum reaches more than 70 ℃, and the temperature is reduced to 150 ℃ (figure 5 (a)); when the reservoir temperature is 260 ℃, before fracturing is terminated, the temperature difference between the fracturing fluid at the front end of the fracture 60m and the stratum reaches more than 80 ℃, the temperature is reduced to 180 ℃, and the performance requirement of the conventional fracturing fluid is met [ fig. 5(b) ]; when the reservoir temperature is 300 ℃, the temperature difference between the fracturing fluid at the front end of the fracture 55m and the stratum before fracturing is terminated reaches more than 80 ℃, the temperature is reduced to 220 ℃, and the performance requirement of the high-temperature-resistant fracturing fluid is met [ figure 5(c) ]. And injecting the low sand ratio (the sand carrying concentration is less than 10%) thickened water fracturing fluid according to the calculation result, and cooling the stratum.
And step 3: in one embodiment of the invention, a conventional cross-linked fracturing fluid is injected to perform normal fracturing at normal sand-carrying ratio.
And 4, step 4: in one embodiment of the invention, after the design displacement is reached, pumping is stopped and fracturing is completed.
Claims (1)
1. A dry hot rock heat energy development cooling fracturing method is characterized by comprising the following steps and conditions:
1) injecting 27m of fracturing pad fluid (clear water) before injecting the sand-carrying fluid and the conventional fracturing fluid3The part of water is injected to the front end 55m of the crack;
2) injecting low sand ratio (sand carrying concentration is less than 10%) thickening water fracturing fluid, and cooling the stratum;
3) injecting conventional cross-linked fracturing fluid to carry out normal fracturing according to a normal sand carrying ratio;
4) the continuous fracturing construction process must be ensured, and the pump stop phenomenon must not occur. If the pump is stopped before the cross-linked fracturing fluid is pumped, the amount of the low sand ratio fracturing fluid is increased to ensure the effect of cooling the stratum.
The flow conductivity of the tail end of the crack formed by the temperature-reducing fracturing process is slightly lower than that of the conventional fracturing because the sand ratio is lower. However, because geothermal reservoirs are inherently strong, the reduction in proppant volume does not have a significant effect on fracture closure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910834685.2A CN110700807A (en) | 2019-09-04 | 2019-09-04 | Dry-hot rock heat energy development cooling fracturing method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910834685.2A CN110700807A (en) | 2019-09-04 | 2019-09-04 | Dry-hot rock heat energy development cooling fracturing method |
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| Publication Number | Publication Date |
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| CN110700807A true CN110700807A (en) | 2020-01-17 |
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| CN201910834685.2A Pending CN110700807A (en) | 2019-09-04 | 2019-09-04 | Dry-hot rock heat energy development cooling fracturing method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114112564A (en) * | 2020-08-28 | 2022-03-01 | 中国石油化工股份有限公司 | Method for manufacturing core sample for dry-hot rock fracturing, mining and injecting integrated experiment |
| CN114263451A (en) * | 2021-12-02 | 2022-04-01 | 河北省煤田地质局第二地质队 | Hot dry rock hydraulic fracturing method |
-
2019
- 2019-09-04 CN CN201910834685.2A patent/CN110700807A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114112564A (en) * | 2020-08-28 | 2022-03-01 | 中国石油化工股份有限公司 | Method for manufacturing core sample for dry-hot rock fracturing, mining and injecting integrated experiment |
| CN114112564B (en) * | 2020-08-28 | 2024-04-12 | 中国石油化工股份有限公司 | Manufacturing method of core sample for dry-hot rock fracturing, mining and injection integrated experiment |
| CN114263451A (en) * | 2021-12-02 | 2022-04-01 | 河北省煤田地质局第二地质队 | Hot dry rock hydraulic fracturing method |
| CN114263451B (en) * | 2021-12-02 | 2024-08-09 | 河北省煤田地质局第二地质队 | Hydraulic fracturing method for dry-hot rock |
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Application publication date: 20200117 |