CN113803045A - Method for improving shale gas recovery ratio and simulation experiment method thereof - Google Patents
Method for improving shale gas recovery ratio and simulation experiment method thereof Download PDFInfo
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- 238000011084 recovery Methods 0.000 title claims abstract description 44
- 238000004088 simulation Methods 0.000 title claims abstract description 17
- 239000012530 fluid Substances 0.000 claims abstract description 29
- 229910021578 Iron(III) chloride Inorganic materials 0.000 claims abstract description 27
- 238000003795 desorption Methods 0.000 claims abstract description 15
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 10
- 239000000203 mixture Substances 0.000 claims abstract 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 60
- 230000008569 process Effects 0.000 claims description 7
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 4
- 229920003169 water-soluble polymer Polymers 0.000 claims description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 abstract description 17
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 abstract description 14
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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
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/72—Eroding chemicals, e.g. acids
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/80—Compositions for reinforcing fractures, e.g. compositions of proppants used to keep the fractures open
-
- 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
-
- 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
- E21B43/28—Dissolving minerals other than hydrocarbons, e.g. by an alkaline or acid leaching agent
- E21B43/283—Dissolving minerals other than hydrocarbons, e.g. by an alkaline or acid leaching agent in association with a fracturing process
Abstract
The invention provides a method for improving shale gas recovery efficiency, which comprises the following steps: FeCl is added3Mixing and dissolving the mixture in hydraulic fracturing fluid according to a preset proportion; will mix with FeCl3The hydraulic fracturing fluid is injected into a reservoir containing gas shale; shale gas is produced by hydraulic fracturing. The invention also provides a simulation experiment method. The method for improving the shale gas recovery ratio provided by the invention fully utilizes FeCl3Chemical character of easy hydrolysis: reaction of hydrolysate HCl with inorganic minerals in shale), increase porosity of shale matrix and permeability of shale reservoir, and further strengthen CH4From high-carbon sludgeDesorption, diffusion and flow in shale; hydrolysate Fe (OH)3Is easy to decompose at 95 ℃ and generate Fe2O3。Fe2O3The high hardness can be used as a propping agent to prop fresh cracks formed by hydraulic fracturing so as to promote CH4The desorption, diffusion and flow of the shale gas obviously improve the recovery ratio of the shale gas in the shale reservoir.
Description
Technical Field
The invention relates to the technical field of shale gas recovery, in particular to a method for improving the recovery ratio of shale gas and a simulation experiment method thereof.
Background
Shale gas (the main component is CH4) is an emerging unconventional natural gas resource. The shale gas is popularized and used, and the method has important significance for optimizing the existing energy consumption structure in China, relieving the supply pressure of the natural gas market, promoting energy conservation and emission reduction and preventing and controlling pollution. Therefore, the research and development of the clean and efficient shale gas exploitation technology have important strategic significance. Numerous studies have shown that the main existing forms of shale gas in shale reservoirs include: free compressed gas in pores and cracks; adsorbed gases on the surfaces of organic and inorganic minerals; asphaltenes, kerogen, liquid hydrocarbons and dissolved gases in the residual water. Generally, in conventional reservoirs, gas is stored in pores and fractures primarily as free compressed gas, while shale gas is present on organic matter particles, clay mineral particles, and pore surfaces primarily in adsorbed form (where adsorbed gas comprises 20% to 85% of the total volume).
At present, shale gas exploitation technologies mainly comprise a horizontal well technology, a multi-layer fracturing technology, a clean water fracturing technology, a shale gas exploitation repeated fracturing technology and a latest synchronous fracturing technology. Numerous studies have demonstrated that proppant selection is one of the key factors in the successful implementation of hydraulic fracturing techniques. The quality of the proppant performance and the cost directly affect the effective implementation of the hydraulic fracturing technology. Practice proves that: the proppant enters a reservoir containing gas shale along with the fracturing fluid and is filled in a fresh crack formed by hydraulic fracturing, so that the crack is prevented from being closed again due to stress release, the shale gas recovery rate is further improved, and the service life of the shale gas well is prolonged. Shale gas production from shale gas wells fractured using proppants may be improved by 30% -50%. Displaying cost accounting data: the total cost of hydraulic fracturing is about 25% of the total proppant. Therefore, the development of the low-cost proppant has important practical significance for reducing the exploitation cost of the shale gas.
The existing hydraulic fracturing propping agent mainly comprises quartz sand and ceramic particles. The ceramic particle proppant is prepared by taking raw bauxite or light-burned bauxite as a main raw material and adding part of rare earth concentrate. The Chinese patent with the patent number of CN101691486A discloses an ultrahigh-strength ceramsite proppant and a manufacturing method thereof, but the density of the ceramsite proppant reaches 3.50g/cm3, fracturing fluid is required to be used for pressure injection and export, the used fracturing fluid causes serious environmental pollution, the requirements on the process and equipment are high, and the construction difficulty is high. The Chinese patent with the patent number of CN107151554A provides an ultra-light ceramsite proppant applied to clean water fracturing and a preparation method thereof. Although the method can reduce the pollution of the fracturing fluid to the ecological environment, the preparation temperature condition of the proppant is as high as 1500 ℃, and the preparation energy consumption of the proppant is increased. In addition, the raw materials for preparing the two proppants are expensive, the reserves are exhausted, the proppants are not easy to purchase, and the mass production cannot be realized. The Russian Federal patent with the patent number RU2235703C1 discloses a production method of a magnesium silicate ceramsite proppant. Although the raw materials for preparing the proppant are cheap and readily available, some of the magnesium silicates undergo hydration reactions under shale reservoir conditions and reduce the mechanical durability of the proppant particles.
For China, although the shale gas reserves are abundant, the shale gas exploitation cost is far higher than that of the United states and Canada in China due to the fact that the shale gas is deep in buried depth and low in permeability. Therefore, for sustainable development of the shale gas industry, the development of a hydraulic fracturing propping agent which has low density and high strength and is environment-friendly is urgently needed in China to make up for the defects of the existing shale gas exploitation technology.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for improving shale gas recovery ratio and a simulation experiment method thereof, which fully combine the condition characteristics of gas-bearing shale reservoirs in China and FeCl3(ferric chloride) very easily hydrolyzed chemical property, and utilizes FeCl3Mineral corrosion capacity of hydrolysate HCl, dissolving inorganic minerals in shale, improving porosity of shale matrix and permeability of shale reservoir, and using FeCl3Hydrolysate Fe (OH)3Further decomposition of the resulting Fe2O3The proppant is used as a proppant to support fresh cracks formed by hydraulic fracturing, and finally the shale gas recovery rate is improved through the above functions.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
a method for improving the recovery ratio of shale gas specifically comprises the following steps: s01 FeCl3Mixed and dissolved in hydraulic fracturing fluid according to a preset proportion. S02 FeCl is doped3The hydraulic fracturing fluid is injected into a reservoir containing gas shale. And S03, exploiting the shale gas through hydraulic fracturing.
The shale gas burial depth in China is generally deep and reaches 3000-4000m, and the shale reservoir temperature range corresponding to the burial depth range reaches 70-95 ℃. Thus, the above temperature conditions will promote FeCl3Fully hydrolyzed and finally generates HCl and Fe (OH)3. On one hand, the hydrolysate HCl reacts with inorganic minerals in the shale (namely mineral corrosion), so that the porosity of a shale matrix and the permeability of a shale reservoir are improved, and CH is further enhanced4Desorption, diffusion and flow of (methane). In another aspect, the hydrolyzate is Fe (OH)3Is easy to decompose at 70-95 ℃ and generate Fe2O3。Fe2O3The high hardness can be used as a propping agent to prop fresh cracks formed by hydraulic fracturing so as to promote CH4Desorption, diffusion and flow of (methane). The two aspects can obviously improve the shale gas recovery rate. The invention not only providesAn efficient shale gas exploitation method is provided, and a FeCl is also provided3The utilization route of (1).
With respect to the above technical solution, further improvements as described below can be made.
Specifically, in a preferred embodiment, in step S01, FeCl3The mass percentage of the water-soluble polymer in the hydraulic fracturing fluid is 10-35%.
FeCl is added3The mass percentage of the FeCl in the hydraulic fracturing fluid is controlled within the range, and the FeCl can be well ensured3The shale gas is fully hydrolyzed in the hydraulic fracturing fluid, and unnecessary waste is avoided as far as possible on the premise of ensuring the improvement of the exploitation efficiency of the shale gas.
Specifically, in a preferred embodiment, the hydraulic fracturing operation temperature is 70 to 95 ℃ in step S03.
The above temperature conditions will promote FeCl3Fully hydrolyzed and finally generates HCl and Fe (OH)3。
Specifically, in a preferred embodiment, in step S03, the hydraulic fracturing operation pressure is 25 to 50 MPa.
The fracturing operation pressure range can ensure the stability of the hydraulic fracturing operation process and can ensure the effective improvement of the shale gas recovery ratio.
Specifically, in a preferred embodiment, in step S02, a booster pump is used to inject the hydraulic fracturing fluid into the gas-containing shale reservoir.
The adoption of the booster pump can effectively ensure that the FeCl is added and matched3The hydraulic pressure liquid is injected into the gas-containing shale reservoir at high pressure.
Compared with the prior art, the method for improving the shale gas recovery ratio has the advantages that:
(1) the invention makes full use of FeCl3The characteristic that the hydrolysis reaction is easy to occur under the condition of a gas-containing shale reservoir is utilized, HCl which is one of hydrolysis products reacts with a part of inorganic mineral substances in the shale, so that the part of the inorganic mineral substances are corroded, the porosity and the reservoir permeability of the shale are improved, and the desorption, diffusion and flowing capacity of the shale gas is further improved.
(2) The invention utilizes another hydrolysate Fe (OH)3Decomposition product of (4) Fe2O3As a proppant to replace the expensive ceramsite proppant commonly adopted by the existing hydraulic fracturing shale gas exploitation technology. Fe2O3As the proppant, on one hand, the defect that the existing commercial proppant is easy to hydrate so as to reduce the mechanical durability of the proppant can be overcome; on the other hand, the use cost of the commercial proppant is reduced, and the total cost of exploiting the shale gas by hydraulic fracturing is favorably and remarkably reduced.
(3) The method for improving the shale gas recovery ratio provided by the invention has important practical significance for cleanly, efficiently and cheaply exploiting the shale gas and reducing the consumption of raw materials (such as bauxite) for preparing commercial ceramsite proppant.
The simulation experiment method of the second aspect of the invention, which aims at the method for improving the shale gas recovery efficiency, comprises the following steps: s01: a shale sample is taken from the gas-bearing shale reservoir. S02: the shale sample is placed in a pressure-resistant container placed in a thermostatic device. S03: high-pressure methane gas is filled into the pressure-resistant container to promote the shale to fully adsorb methane and achieve an adsorption equilibrium state. S04: injecting a shale sample in a pressure-resistant container into a container dissolved with FeCl3And performing hydraulic fracturing. S05: and (3) measuring the total desorption amount of methane in the hydraulic fracturing process by using a drainage and gas collection method.
According to the simulation experiment method, the method for improving the shale gas recovery ratio can be truly and completely simulated in a laboratory, so that the deep research on the subsequent shale gas recovery technology is facilitated.
With respect to the above technical solution, further improvements as described below can be made.
Further, in a preferred embodiment, in step S03, the pressure-resistant vessel is vacuumized before the pressure-resistant vessel is filled with the high-pressure methane gas.
After the vacuum pumping treatment, the pressure-resistant container can be ensured to be filled with more methane as much as possible, so that the shale is promoted to fully adsorb methane, and an adsorption balance state is achieved.
Further, in a preferred embodiment, the method further comprises the following steps: s06 comparing the amount of shale gas desorbed obtained by hydraulic fracturing with commercial proppants.
By comparing the data obtained by the shale gas recovery method in the prior art, the recovery efficiency of the method for improving the shale gas recovery efficiency provided by the invention can be well verified.
Specifically, in a preferred embodiment, in step S01, the shale sample is a columnar high-carbon shale sample.
By adopting the columnar high-carbon shale sample, the hydraulic fracturing operation on the shale sample in a pressure-resistant container is facilitated, and a real shale gas reservoir can be truly simulated.
Specifically, in a preferred embodiment, in step S03, a pressure-resistant vessel is filled with 30MPa of methane gas.
The high-pressure methane gas in the pressure range can effectively ensure that the shale fully adsorbs methane, and the adsorption balance state is achieved, so that the accuracy and reliability of the experimental result are ensured.
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 schematically illustrates the principles of the enhanced shale gas recovery method of example 1 of the present invention;
fig. 2 schematically shows a simulation experiment flow of the method for enhancing shale gas recovery according to example 2 of the present invention.
In the drawings, like parts are provided with like reference numerals. The figures are not drawn to scale.
Detailed Description
The invention will be further explained in detail with reference to the figures and the embodiments without thereby limiting the scope of protection of the invention.
Fig. 1 schematically illustrates the principle of the method for enhanced shale gas recovery of example 1 of the present invention. Fig. 2 schematically shows a simulation experiment flow of the method for enhancing shale gas recovery according to example 2 of the present invention.
Example 1
The method for improving the shale gas recovery ratio comprises the following steps: s01 FeCl3Mixed and dissolved in hydraulic fracturing fluid according to a preset proportion. S02 FeCl is doped3The hydraulic fracturing fluid is injected into a reservoir containing gas shale. And S03, exploiting the shale gas through hydraulic fracturing. The shale gas burial depth in China is generally deep and reaches 3000-4000m, and the shale reservoir temperature range corresponding to the burial depth range reaches 70-95 ℃. Thus, the above temperature conditions will cause FeCl3 to hydrolyze sufficiently and eventually produce HCl and Fe (OH)3. On one hand, the hydrolysate HCl reacts with inorganic minerals in the shale (namely mineral corrosion), so that the porosity of a shale matrix and the permeability of a shale reservoir are improved, and CH is further enhanced4Desorption, diffusion and flow of (methane). In another aspect, the hydrolyzate is Fe (OH)3Is easy to decompose at 70-95 ℃ and generate Fe2O3。Fe2O3The high hardness can be used as a propping agent to prop fresh cracks formed by hydraulic fracturing so as to promote CH4Desorption, diffusion and flow of (methane). The two aspects can obviously improve the shale gas recovery rate. The invention provides a high-efficiency shale gas exploitation method and also provides FeCl3The utilization route of (1).
Specifically, in the present embodiment, in step S01, FeCl3The mass percentage of the water-soluble polymer in the hydraulic fracturing fluid is 10-35%. FeCl is added3The mass percentage of the FeCl in the hydraulic fracturing fluid is controlled within the range, and the FeCl can be well ensured3The shale gas is fully hydrolyzed in the hydraulic fracturing fluid, and unnecessary waste is avoided as far as possible on the premise of ensuring the improvement of the exploitation efficiency of the shale gas. Also, in this embodiment, the shale gas-containing reservoir is a dark shale reservoir, a black shale reservoir, and a high carbon shale reservoir. Specifically, in this embodiment, in step S02, a booster pump is used to inject the hydraulic fracturing fluid into the gas-containing shale reservoir. The adoption of the booster pump can effectively ensure that the FeCl is added and matched3Hydraulic pressure liquid high pressure injection gasInside the shale reservoir.
Specifically, in the present embodiment, the hydraulic fracturing operation temperature is 70 to 95 ℃ in step S03. The above temperature conditions will promote FeCl3Fully hydrolyzed and finally generates HCl and Fe (OH)3. Specifically, in the present embodiment, in step S03, the hydraulic fracturing operation pressure is 25 to 50 MPa. The fracturing operation pressure range can ensure the stability of the hydraulic fracturing operation process and can ensure the effective improvement of the shale gas recovery ratio.
As shown in fig. 1, the principle of embodiment 1 of the present invention is: (1) FeCl3High solubility in water (FeCl in water at 20 ℃)3The solubility reached 91.80 g). Thus, FeCl3Dissolved in the fracturing fluid and carried with the fracturing fluid into the target shale reservoir. FeCl3Exists in a dissolved state in the fracturing fluid and enters the interior of the shale reservoir along with the fracturing fluid. Thus, the above FeCl3The injection mode of (2) will significantly reduce the shaft power of the injection pump and improve the delivery efficiency of the injection pump. (2) The shale gas burial depth in China is generally deep (3000-. The above temperature conditions will intensify FeCl3Hydrolysis reaction process, and final generation of HCl and Fe (OH)3. (3) The hydrolysate HCl has strong mineral corrosion capacity. Thus, HCl reacts with some of the inorganic minerals in shale (e.g., potassium feldspar, plagioclase feldspar, calcite, and dolomite, etc.). The results of pore structure characterization and permeability characterization show that: the porosity and reservoir permeability of the shale matrix after partial mineral corrosion are obviously increased, so that desorption, diffusion and flow of shale gas are facilitated, and the shale gas recovery rate is improved. (4) Hydrolysis product Fe (OH) at 70-95 deg.C3Further decomposition takes place and Fe is finally formed2O3。Fe2O3The self-hardness is high (Mohs hardness range: 5.5-6.5), and the composite material can be used as a propping agent to effectively prop fresh cracks formed by high-pressure hydraulic fracturing, so that the diffusion and flow of shale gas in a shale reservoir are facilitated, and the shale gas recovery rate is further improved.
According to the above embodiments, it can be seen that the present invention relates to the improvement of shale gas recoveryMethod of making full use of FeCl3The characteristic that hydrolysis reaction is easy to occur under the condition of a gas-containing shale reservoir is utilized, HCl which is one of hydrolysis products reacts with a part of inorganic mineral substances in the shale, so that the part of inorganic mineral substances are corroded, the porosity and the reservoir permeability of the shale are improved, and the desorption, diffusion and flowing capacity of the shale gas is further improved; by means of a further hydrolyzate Fe (OH)3Decomposition product of (4) Fe2O3As a proppant to replace the expensive ceramsite proppant commonly adopted by the existing hydraulic fracturing shale gas exploitation technology. Fe2O3As the proppant, on one hand, the defect that the existing commercial proppant is easy to hydrate so as to reduce the mechanical durability of the proppant can be overcome; on the other hand, the use cost of the commercial proppant is reduced, and the total cost of exploiting shale gas by hydraulic fracturing is remarkably reduced; the method has important practical significance for mining shale gas cleanly, efficiently and cheaply and reducing the consumption of raw materials (such as bauxite) for preparing commercial ceramsite proppant.
Example 2
As shown in fig. 2, the simulation experiment method for the method for improving shale gas recovery according to the embodiment of the present invention includes the following steps: s01: a shale sample is taken from the gas-bearing shale reservoir. S02: the shale sample was placed in a pressure-resistant container placed in a thermostat set at a temperature of 95 ℃. S03: charging high-pressure CH into a pressure-resistant container4Methane gas promotes the shale to fully adsorb methane and reach an adsorption equilibrium state. S04: injecting a shale sample in a pressure-resistant container into a container dissolved with FeCl3The hydraulic fracturing fluid is used for hydraulic fracturing, and FeCl in the hydraulic fracturing fluid3Is 35 percent, and the hydraulic fracturing operation pressure is 50 MPa. S05: and (3) measuring the total desorption amount of methane in the hydraulic fracturing process by using a drainage and gas collection method. According to the simulation experiment method provided by the embodiment of the invention, the method for improving the shale gas recovery ratio provided by the invention can be truly and completely simulated in a laboratory, so that the deep research on the subsequent shale gas recovery technology is facilitated.
Further, in this embodiment, the method further includes the following steps: s06 comparing the amount of shale gas desorbed obtained by hydraulic fracturing with commercial proppants. Specifically, the feasibility of the technical scheme provided by the invention is further clarified by comparing the desorption amount of shale gas obtained by hydraulic fracturing (the granularity of the proppant is 20-60 meshes, the hydraulic fracturing pressure is 50MPa, and the sand carrying ratio is 40%) by using commercial ceramsite as a proppant. By comparing the data obtained by the shale gas recovery method in the prior art, the recovery efficiency of the method for improving the shale gas recovery efficiency provided by the invention can be well verified.
Preferably, in this embodiment, in step S03, before filling the pressure-resistant vessel with the high-pressure methane gas, the pressure-resistant vessel is vacuumized by using a zheng' S eye pump so that the absolute pressure in the pressure-resistant vessel becomes 6Pa or less. After the vacuum pumping treatment, the pressure-resistant container can be ensured to be filled with more methane as much as possible, so that the shale is promoted to fully adsorb methane, and an adsorption balance state is achieved. Specifically, in this embodiment, in step S03, 30MPa of methane gas was charged in the pressure resistant vessel. The high-pressure methane gas in the pressure range can effectively ensure that the shale fully adsorbs methane, and the adsorption balance state is achieved, so that the accuracy and reliability of the experimental result are ensured.
Specifically, in the present embodiment, in step S01, the shale sample is a columnar high-carbon shale sample. By adopting the columnar high-carbon shale sample, the hydraulic fracturing operation on the shale sample in a pressure-resistant container is facilitated, and a real shale gas reservoir can be truly simulated.
The experimental results obtained according to the simulation experiment method of this example show that: compared with the methane desorption amount corresponding to hydraulic fracturing adopting commercial ceramsite as a propping agent, the methane desorption amount corresponding to the implementation of the method in the embodiment 1 of the invention is improved by 24%.
According to the embodiments, it can be seen that the method for improving shale gas recovery efficiency provided by the invention fully utilizes FeCl by taking high-carbon shale as a sample3Chemical character of easy hydrolysis: on one hand, the hydrolysate HCl reacts with inorganic minerals in the shale (namely mineral corrosion), so that the porosity of a shale matrix and the permeability of a shale reservoir are improved, and CH is further enhanced4Desorb, diffuse, and flow from high carbon shale. In another aspect, the hydrolyzate is Fe (OH)3Is easy to decompose at 95 ℃ and generate Fe2O3。Fe2O3The high hardness can be used as a propping agent to prop fresh cracks formed by hydraulic fracturing so as to promote CH4Desorption, diffusion and flow. The two aspects can obviously improve the recovery rate of the shale gas in the high-carbon shale reservoir.
While the invention has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (10)
1. The method for improving the recovery rate of the shale gas is characterized by comprising the following steps of:
s01 FeCl3Mixing and dissolving the mixture in hydraulic fracturing fluid according to a preset proportion;
s02 FeCl is doped3The hydraulic fracturing fluid is injected into a reservoir containing gas shale;
and S03, exploiting the shale gas through hydraulic fracturing.
2. The method for enhanced shale gas recovery of claim 1, wherein in step S01 FeCl3The mass percentage of the water-soluble polymer in the hydraulic fracturing fluid is 10-35%.
3. The method for enhanced shale gas recovery of claim 1 or 2, wherein in step S03, the hydraulic fracturing operation temperature is 70-95 ℃.
4. The method for enhanced shale gas recovery of claim 1 or 2, wherein in step S03, the hydraulic fracturing operation pressure is 25-50 MPa.
5. The method for enhanced shale gas recovery of claim 1 or 2, wherein in step S02, a booster pump is used to inject the hydraulic fracturing fluid into the gas-bearing shale reservoir.
6. A simulation experiment method for the method for enhanced shale gas recovery of any one of claims 1 to 5, comprising the steps of:
s01: taking a shale sample from a gas-bearing shale reservoir;
s02: placing a shale sample into a pressure-resistant container in a constant temperature device;
s03: filling high-pressure methane gas into the pressure-resistant container;
s04: injecting a shale sample in the pressure-resistant container into a hydraulic fracturing fluid dissolved with FeCl3 and performing hydraulic fracturing;
s05: and (3) measuring the total desorption amount of methane in the hydraulic fracturing process by using a drainage and gas collection method.
7. The simulation experiment method of claim 6, wherein in step S03, the pressure vessel is vacuumized before the pressure vessel is filled with the high-pressure methane gas.
8. A simulation experiment method according to claim 6, further comprising the steps of:
s06 comparing the amount of shale gas desorbed obtained by hydraulic fracturing with commercial proppants.
9. The simulation experiment method of claim 6, wherein in step S01, the shale sample is a columnar high-carbon shale sample.
10. The simulation experiment method according to claim 6, wherein in step S03, the pressure-resistant vessel is filled with 30MPa of methane gas.
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