CN113669041A - Sea hydrate reservoir exploitation method by injecting sea water to assist low-frequency electric field heating - Google Patents
Sea hydrate reservoir exploitation method by injecting sea water to assist low-frequency electric field heating Download PDFInfo
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- 230000005684 electric field Effects 0.000 title claims abstract description 64
- 238000010438 heat treatment Methods 0.000 title claims abstract description 57
- 239000013535 sea water Substances 0.000 title claims abstract description 42
- 238000000034 method Methods 0.000 title claims abstract description 30
- 238000004519 manufacturing process Methods 0.000 claims abstract description 73
- 238000002347 injection Methods 0.000 claims abstract description 31
- 239000007924 injection Substances 0.000 claims abstract description 31
- 239000004576 sand Substances 0.000 claims abstract description 14
- 230000000694 effects Effects 0.000 claims abstract description 5
- 150000003839 salts Chemical class 0.000 claims abstract description 5
- 238000000354 decomposition reaction Methods 0.000 claims description 21
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 16
- 238000009825 accumulation Methods 0.000 claims description 6
- 238000005457 optimization Methods 0.000 claims description 6
- 230000033558 biomineral tissue development Effects 0.000 claims description 5
- 238000005553 drilling Methods 0.000 claims description 5
- 238000011065 in-situ storage Methods 0.000 claims description 5
- 239000013589 supplement Substances 0.000 claims description 4
- 238000004422 calculation algorithm Methods 0.000 claims description 3
- 238000002485 combustion reaction Methods 0.000 claims description 3
- 239000012530 fluid Substances 0.000 claims description 3
- 239000008398 formation water Substances 0.000 claims description 3
- 230000008014 freezing Effects 0.000 claims description 3
- 238000007710 freezing Methods 0.000 claims description 3
- 239000011810 insulating material Substances 0.000 claims description 3
- 238000004088 simulation Methods 0.000 claims description 3
- 238000004364 calculation method Methods 0.000 claims description 2
- 229910003460 diamond Inorganic materials 0.000 claims description 2
- 239000010432 diamond Substances 0.000 claims description 2
- 238000009991 scouring Methods 0.000 claims description 2
- 239000007789 gas Substances 0.000 abstract description 26
- NMJORVOYSJLJGU-UHFFFAOYSA-N methane clathrate Chemical compound C.C.C.C.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O NMJORVOYSJLJGU-UHFFFAOYSA-N 0.000 abstract description 10
- 239000000463 material Substances 0.000 abstract description 2
- 239000008236 heating water Substances 0.000 abstract 1
- 230000002195 synergetic effect Effects 0.000 abstract 1
- 238000005065 mining Methods 0.000 description 11
- 238000005516 engineering process Methods 0.000 description 4
- 230000020169 heat generation Effects 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 238000010793 Steam injection (oil industry) Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 239000012777 electrically insulating material Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 150000004677 hydrates Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 238000005381 potential energy Methods 0.000 description 1
- 239000013049 sediment Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 238000005406 washing Methods 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
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/2401—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection by means of electricity
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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
- E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
- E21B41/0099—Equipment or details not covered by groups E21B15/00 - E21B40/00 specially adapted for drilling for or production of natural hydrate or clathrate gas reservoirs; Drilling through or monitoring of formations containing gas hydrates or clathrates
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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
- E21B43/01—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
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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
- E21B43/30—Specific pattern of wells, e.g. optimising the spacing of wells
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Abstract
The invention discloses a sea hydrate reservoir exploitation method by injecting seawater to assist low-frequency electric field heating, aiming at the problems of continuous high temperature around a shaft, poor electric field heating efficiency, poor production effect and the like existing in the low-frequency electric field heating exploitation of the hydrate reservoir, the heat around the shaft is pushed to the deep part of a hydrate layer by forced heat convection caused by injecting seawater, the heat utilization efficiency is obviously improved, the production pressure difference established in the hydrate layer provides driving force for gas production, and the salinity of the hydrate layer can be supplemented by salt in the seawater, so that the conductivity of the reservoir layer is effectively improved; when a large amount of sand is accumulated in the well shaft of the production well, the aim of removing sand in the well shaft is fulfilled by alternately rotating the production well and the injection well, and stable production of gas is ensured. The method is simple to operate and easy to realize, fully exerts the synergistic effect of depressurization, low-frequency electric field heating and seawater injection, greatly improves the production efficiency, has the natural advantage of local materials of an offshore platform, and can provide a technical means for large-scale industrial development of marine natural gas hydrate reservoirs.
Description
Technical Field
The invention belongs to the technical field of natural gas hydrate resource exploitation, and particularly relates to a sea hydrate reservoir exploitation method with seawater injection for assisting in heating of a low-frequency electric field.
Background
The natural gas hydrate is a cage-type compound formed by methane gas and water under high-pressure low-temperature environment. The hydrate has the advantages of high energy density, large reserves, cleanness, high efficiency and the like, and is considered as a potential energy source for replacing the conventional fossil energy. Hydrates are widely found in continental permafrost and deep sea sediments, wherein the marine natural gas hydrate accounts for more than 90% of the hydrate resource amount. As a new unconventional natural gas resource, the development of the high-efficiency exploitation technology of the marine natural gas hydrate reservoir is significant and draws high attention worldwide.
The depressurization method has the characteristics of convenience in implementation, good economy and the like, and is applied to two-wheel hydrate trial production in the sea area of south China sea Shen fox. However, from the trial production results, there is a large gap between the production time and the gas production rate and the requirements of commercial production. Because the hydrate decomposes a large amount of heat absorption to lead the reservoir temperature to be continuously reduced, the single depressurization production efficiency is low. Therefore, combining heat injection with depressurization can lead to better mining results. In the heat injection method, the conventional hot water or hot steam injection mode has the problem of large heat loss of a shaft and a pipeline. The low-frequency electric field heating technology has great exploitation potential by installing electrodes at the bottom of a well and taking a hydrate layer as a resistor, thereby realizing in-situ heat generation of a reservoir. However, from the current exploitation effect, the heat is mainly concentrated around the shaft in the low-frequency electric field heating process, and is difficult to diffuse to the deep part of the hydrate layer by purely depending on heat conduction, so that the hydrate decomposition range is small; in addition, the electrode facility can be damaged by the excessive temperature around the shaft, and the problems greatly restrict the application of the low-frequency electric field heating technology in the exploitation of hydrate resources.
The invention provides a novel seawater injection auxiliary low-frequency electric field heating mining method aiming at the problems in the current low-frequency electric field heating implementation process and considering the natural and rich seawater resources of an ocean natural gas hydrate mining field. The main principle is as follows: (1) the heat around the shaft is pushed to the deep part of the hydrate layer by forced heat convection caused by injecting seawater, so that the heat utilization efficiency is improved; (2) the pressure difference between the injection wells and the production wells provides driving force for gas production, and the gas production efficiency is further improved; (3) salt components in the seawater can supplement the mineralization degree of a hydrate layer, enhance the conductivity of a reservoir and facilitate the implementation of electric heating. The method is simple to operate and easy to realize, can greatly improve the recovery ratio of the marine natural gas hydrate reservoir, and is favorable for realizing large-scale industrialized exploitation of the marine natural gas hydrate reservoir.
Disclosure of Invention
The invention relates to a sea hydrate reservoir exploitation method by injecting sea water to assist low-frequency electric field heating, which mainly comprises the following steps:
(1) drilling a plurality of production well groups according to geological data of the marine hydrate reservoir, preferably a production block, wherein each well group at least comprises two vertical wells to form a well pattern with a certain shape, and the drilling completion position of each vertical well is positioned on a cover layer below a hydrate layer; the well patterns include, but are not limited to, five-point patterns, seven-point patterns, diamond patterns, and nine-point patterns; installing electric insulating materials at the top position of a hydrate layer and the bottom position of the hydrate layer in each vertical well shaft so as to prevent the current from being conducted through the well shaft when a low-frequency electric field is heated;
(2) all the vertical wells are used as production wells, proper bottom hole pressure is selected to control each production well to carry out depressurization and exploitation, power is provided for hydrate decomposition and gas production by utilizing the pressure and temperature of a hydrate reservoir to the maximum extent, the phenomenon that icing occurs near a well shaft due to excessive production pressure difference is avoided, and the bottom hole pressure is determined by using the following formula:
wherein: p is a radical ofwfFor the bottom hole pressure of each production well,
average pressure of hydrate layer, piceIs freezing point pressure, qgFor the rate of gas production, qgmaxAlpha is a dimensionless parameter related to the saturation of the hydrate, the thickness of the hydrate layer and the mineralization of seawater, and the expression is as follows:
wherein: shIs the hydrate saturation, XiThe mass fraction of salt in seawater is shown, h is the thickness of a hydrate layer, and a, b and c are undetermined coefficients;
(3) when the gas production rate cannot meet an economic critical value, installing a low-frequency electric field heating device at each well group, mainly comprising a cable, a low-frequency alternating current power supply and an electrode, wherein the electrode is arranged in a hydrate layer, the distance from the electrode to a cover layer is set to be 2-4m, the low-frequency alternating current power supply is started, and a constant electric field heating power or constant voltage mode is set to supplement heat for the decomposition in situ of the hydrate; one of the vertical wells is selected to be converted from a production well to an injection well, seawater is injected at a constant speed, the rest of the vertical wells are still produced at a constant bottom pressure in a depressurization mode, heat near the well shaft is convected to the deep part of a hydrate layer in the seawater injection process, and the hydrate decomposition rate and the electric field heating efficiency are greatly improved; the determination of the electric field heating power, the voltage and the seawater injection rate comprises the following steps:
calculating the initial resistivity of the hydrate layer using the modified Archie model:
wherein: rtIs the initial resistivity of the hydrate layer, Rw(T1) At a temperature of T1Resistivity of formation water in time, T1Is ambient temperature, T2Represents the temperature of the hydrate layer, phi being the effective porosity of the hydrate layer; tau is an empirical parameter;
secondly, according to the heat required by decomposition of the residual hydrate in the hydrate layer, the estimated electric field heating power and voltage are obtained through calculation according to the following formula:
wherein: pelehTo estimate the heating power of the electric field, U is the estimated voltage, ErTo effect a degree of decomposition of the hydrate layer upon heating by a low frequency electric field, VhblIs the apparent volume of the hydrate layer,ρhis the hydrate density,. DELTA.HreatChange of enthalpy of decomposition reaction of hydrate; r is the resistance of the hydrate layer, MhThe molar mass of the hydrate is shown, and eta is the heating efficiency of a low-frequency electric field; delta t is the heating duration time of the low-frequency electric field;
thirdly, on the basis of estimating the heating power and the voltage of the electric field, determining the final heating power, the final voltage and the final seawater injection rate of the electric field through a numerical simulation method and an optimization algorithm so as to fully utilize the seawater injection process and realize the purpose of low-frequency electric field balanced heating in a hydrate layer, wherein the expression of a target function in the optimization process is as follows:
wherein: mdisTo accumulate the mass of decomposed hydrate, M0Is the total hydrate mass; beta is a weighting coefficient of energy efficiency, VpgTo accumulate the volume of methane gas produced, Δ HmIs the enthalpy of combustion of the methane gas, EinThe accumulated heat generation amount for heating the low-frequency electric field;
(4) due to sand production of a hydrate layer caused by seawater scouring and gas production, when the production rate cannot meet the production requirement due to sand accumulation in a shaft of the production well, the injection well and the production well are alternated, and the flow direction of fluid in the hydrate layer is reversed, so that the sand accumulation in the shaft is reversely pushed into the hydrate layer, the aim of shaft sand removal is fulfilled, and continuous high yield of gas production is ensured.
The invention has the advantages that:
(1) in the initial stage of production, the method provided by the invention is used for selecting proper bottom hole pressure for production, so that the energy of the hydrate reservoir can be fully utilized to contribute to gas production, and the mining economy of the hydrate reservoir in the sea area is obviously improved;
(2) seawater is injected in the low-frequency electric field in-situ heat supplementing process, so that the heat utilization efficiency can be enhanced, driving pressure difference is provided for gas production, the mineralization degree is supplemented for a hydrate layer, and the hydrate decomposition is finally greatly promoted; for the marine hydrate reservoir, seawater can be directly used on an offshore mining platform, and the marine hydrate reservoir has the advantage of local material utilization;
(3) the purpose of shaft desanding can be realized by exchanging the production well and the injection well, and stable production of gas is ensured;
(4) the mining method provided by the invention is simple in structure and easy to operate, can greatly improve the gas recovery rate, and provides a feasible technology for safe and efficient mining of the marine natural gas hydrate reservoir.
Drawings
FIG. 1 is a schematic diagram of the initial depressurization production of a marine natural gas hydrate reservoir.
FIG. 2 is a schematic diagram of the sea hydrate reservoir water injection assisted low frequency electric field heating exploitation.
FIG. 3 is a schematic illustration of alternating desanding of a marine hydrate reservoir injection well and a production well.
In the figure: 1. covering layer I; 2. a hydrate layer; 3. covering layer II; 4. a first vertical well; 5. a wellhead assembly; 6. a vertical well II; 7. an electrically insulating material; 8. perforating; 9. a low frequency alternating current power supply; 10. a cable; 11. and an electrode.
Detailed Description
The invention is further described with reference to the accompanying drawings, but the invention is not limited to the scope of the invention.
(1) According to geological data of a marine hydrate reservoir, preferably selecting a mining block, drilling a plurality of mining well groups, taking one mining well group as an example, wherein the mining well group comprises two straight wells, as shown in figure 1, a cover layer II is arranged below hydrate layers of a first straight well and a second straight well, and electric insulating materials 7 are arranged at the top position of the hydrate layer 2 and the bottom position of the hydrate layer 2 in a first straight well and the second straight well so as to prevent current from being conducted through the wellbores when a low-frequency electric field is heated;
(2) the first vertical well and the second vertical well are both used as production wells, proper bottom hole pressure is selected to control each production well to reduce pressure for exploitation, the pressure and temperature of a hydrate reservoir are utilized to the maximum extent to provide power for hydrate decomposition and gas production, the phenomenon that icing occurs near a shaft due to excessive production pressure difference is avoided, and the bottom hole pressure is determined by using the following formula:
wherein: p is a radical ofwfThe bottom hole pressure of a straight well I and a straight well II,
average pressure of hydrate layer 2, piceIs freezing point pressure, qgFor the rate of gas production, qgmaxAlpha is a dimensionless parameter related to the saturation of the hydrate, the thickness of the hydrate layer 2 and the mineralization of the seawater, and the expression is as follows:
wherein: shIs the hydrate saturation, XiThe mass fraction of salt in the seawater, h is the thickness of the hydrate layer 2, and a, b and c are undetermined coefficients;
(3) as shown in fig. 2, the gas production rate is continuously reduced due to heat absorption caused by hydrate decomposition, when the gas production rate cannot meet an economic critical value, a low-frequency electric field heating device is installed in a well group, the low-frequency electric field heating device mainly comprises a cable 10, a low-frequency alternating current power supply 9 and an electrode 11, the electrode 11 is arranged in a hydrate layer 2, the distances from the upper part of the electrode 11 to a cover layer (i) and the lower part of the electrode 11 to the cover layer (ii) are both set to be 3m, the low-frequency alternating current power supply 9 is started, and a constant electric field heating power or constant voltage mode is set to supplement heat for the hydrate decomposition in situ; a vertical well II is selected to be converted from a production well into an injection well, seawater is injected at a constant speed, the vertical well I is still exploited at a constant bottom pressure, heat near a shaft is convected to the deep part of a hydrate layer 2 in the seawater injection process, and the hydrate decomposition rate and the electric field heating efficiency are greatly improved; determining the electric field heating power, voltage and seawater injection rate by:
first, the initial resistivity of the hydrate layer 2 was calculated using the modified Archie model:
wherein: rtIs the initial resistivity of the hydrate layer 2, Rw(T1) At a temperature of T1Resistivity of formation water in time, T1Is ambient temperature, T2Represents the temperature of the hydrate layer 2, phi being the effective porosity of the hydrate layer 2; tau is an empirical parameter;
secondly, according to the heat required by decomposition of the residual hydrate in the hydrate layer 2, the estimated electric field heating power and voltage are calculated by the following formula:
wherein: pelehTo estimate the heating power of the electric field, U is the estimated voltage, ErTo effect the decomposition of the hydrate layer 2 upon heating by a low frequency electric field, VhblApparent volume of hydrate layer 2, ρhIs the hydrate density,. DELTA.HreatChange of enthalpy of decomposition reaction of hydrate; r is the electrical resistance of the hydrate layer 2, MhThe molar mass of the hydrate is shown, and eta is the heating efficiency of a low-frequency electric field; delta t is the heating duration time of the low-frequency electric field;
thirdly, on the basis of estimating the heating power and voltage of the electric field, determining the final heating power, voltage and seawater injection rate of the electric field through a numerical simulation method and an optimization algorithm so as to fully utilize the seawater injection process and realize the aim of balanced heating of the low-frequency electric field in the hydrate layer 2, wherein the expression of an objective function in the optimization process is as follows:
wherein: mdisFor tirednessScore resolving mass of hydrate, M0Is the total hydrate mass; beta is a weighting coefficient of energy efficiency, VpgTo accumulate the volume of methane gas produced, Δ HmIs the enthalpy of combustion of the methane gas, EinThe accumulated heat generation amount for heating the low-frequency electric field;
(4) due to sand production of the hydrate layer 2 caused by seawater washing and gas production, when the gas production rate cannot meet the production requirement due to sand accumulation of a shaft of the production well (vertical well), as shown in fig. 3, the injection well (vertical well) and the production well (vertical well) are alternated, and the flow direction of fluid in the hydrate layer 2 is reversed, so that the sand accumulation in the shaft of the vertical well (vertical well) is reversely pushed into the hydrate layer 2, the purpose of removing sand from the shaft is realized, and continuous high yield of gas production is ensured. The above embodiments are only used for illustrating the present invention, and the structure, connection mode, etc. of the components may be changed, and all equivalent changes and modifications based on the technical solution of the present invention should not be excluded from the protection scope of the present invention.
Claims (4)
1. A method for exploiting a marine hydrate reservoir by injecting seawater to assist heating of a low-frequency electric field is characterized by comprising the following steps:
(1) drilling a plurality of production well groups according to geological data of the marine hydrate reservoir, preferably a production block, wherein each well group at least comprises two vertical wells to form a well pattern with a certain shape, and the drilling completion position of each vertical well is positioned on a cover layer below a hydrate layer; the well patterns include, but are not limited to, five-point patterns, seven-point patterns, diamond patterns, and nine-point patterns; installing electric insulating materials at the top position of a hydrate layer and the bottom position of the hydrate layer in each vertical well shaft so as to prevent the current from being conducted through the well shaft when a low-frequency electric field is heated;
(2) all the vertical wells are used as production wells, proper bottom pressure is selected to control each production well to reduce pressure for exploitation, power is provided for hydrate decomposition and gas production by utilizing the pressure and temperature of a hydrate reservoir to the maximum extent, and the phenomenon that icing occurs near a shaft due to excessive production pressure difference is avoided;
(3) when the gas production rate cannot meet the economic critical value, a low-frequency electric field heating device is installed on each well group, a low-frequency alternating current power supply is started, and constant electric field heating power or a constant voltage mode is set to supplement heat for the decomposition in situ of the hydrate; one of the vertical wells is selected to be converted from a production well to an injection well, seawater is injected at a constant speed, the rest of the vertical wells are still produced at a constant bottom pressure in a depressurization mode, heat near the well shaft is convected to the deep part of a hydrate layer in the seawater injection process, and the hydrate decomposition rate and the electric field heating efficiency are greatly improved;
(4) due to sand production of a hydrate layer caused by seawater scouring and gas production, when the production rate cannot meet the production requirement due to sand accumulation in a shaft of the production well, the injection well and the production well are alternated, and the flow direction of fluid in the hydrate layer is reversed, so that the sand accumulation in the shaft is reversely pushed into the hydrate layer, the aim of shaft sand removal is fulfilled, and continuous high yield of gas production is ensured.
2. The method for exploiting the marine hydrate reservoir heated by the seawater injection assisted low-frequency electric field as claimed in claim 1, wherein in the step (2), the bottom hole pressure during the depressurization exploitation is determined by using the following formula:
wherein: p is a radical ofwfFor the bottom hole pressure of each production well,
average pressure of hydrate layer, piceIs freezing point pressure, qgFor the rate of gas production, qgmaxAlpha is a dimensionless parameter related to the saturation of the hydrate, the thickness of the hydrate layer and the mineralization of seawater, and the expression is as follows:
wherein: shIs the hydrate saturation, XiIs the mass fraction of salt in seawater, h is the thickness of the hydrate layer, and a, b and c are undetermined coefficients.
3. The method for exploiting the marine hydrate reservoir heated by the seawater injection auxiliary low-frequency electric field according to claim 1, wherein in the step (3), the low-frequency electric field heating device mainly comprises a cable, a low-frequency alternating current power supply and electrodes, the electrodes are arranged in the hydrate layer, and the distance from the cover layer is set to be 2-4 m.
4. The method for exploiting the marine hydrate reservoir heated by the seawater injection assisted low-frequency electric field as claimed in claim 1, wherein the step (3) of determining the electric field heating power, voltage and seawater injection rate during the low-frequency electric field heating comprises the following steps:
calculating the initial resistivity of the hydrate layer using the modified Archie model:
wherein: rtIs the initial resistivity of the hydrate layer, Rw(T1) At a temperature of T1Resistivity of formation water in time, T1Is ambient temperature, T2Represents the temperature of the hydrate layer, phi being the effective porosity of the hydrate layer; tau is an empirical parameter;
secondly, according to the heat required by decomposition of the residual hydrate in the hydrate layer, the estimated electric field heating power and voltage are obtained through calculation according to the following formula:
wherein: pelehTo estimate the heating power of the electric field, U is the estimated voltage, ErTo effect a degree of decomposition of the hydrate layer upon heating by a low frequency electric field, VhblApparent volume of hydrate layer, phIs the hydrate density,. DELTA.HreatChange of enthalpy of decomposition reaction of hydrate; r is the resistance of the hydrate layer, MhThe molar mass of the hydrate is shown, and eta is the heating efficiency of a low-frequency electric field; delta t is the heating duration time of the low-frequency electric field;
thirdly, on the basis of estimating the heating power and the voltage of the electric field, determining the final heating power, the final voltage and the final seawater injection rate of the electric field through a numerical simulation method and an optimization algorithm so as to fully utilize the seawater injection process and realize the purpose of low-frequency electric field balanced heating in a hydrate layer, wherein the expression of a target function in the optimization process is as follows:
wherein: mdisTo accumulate the mass of decomposed hydrate, M0Is the total hydrate mass; beta is a weighting coefficient of energy efficiency, VpgTo accumulate the volume of methane gas produced, Δ HmIs the enthalpy of combustion of the methane gas, EinThe accumulated heat generated by the heating of the low-frequency electric field.
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| US20070265782A1 (en) * | 2006-05-11 | 2007-11-15 | Schlumberger Technology Corporation | Method and apparatus for locating gas hydrate |
| CN107575193A (en) * | 2017-10-23 | 2018-01-12 | 大庆东油睿佳石油科技有限公司 | A kind of method of offshore natural gas hydrate row formula horizontal wells |
| CN107676061A (en) * | 2017-10-23 | 2018-02-09 | 大庆东油睿佳石油科技有限公司 | A kind of method of parallel water horizontal well exploitation offshore natural gas hydrate |
| WO2019114226A1 (en) * | 2017-12-12 | 2019-06-20 | 大连理工大学 | Method for exploiting marine natural gas hydrates using water erosion method |
| WO2019134220A1 (en) * | 2018-01-08 | 2019-07-11 | 中国科学院广州能源研究所 | Gas production method and system for natural gas hydrate exploitation |
| CN112084695A (en) * | 2020-09-21 | 2020-12-15 | 中国石油大学(华东) | Numerical simulation method for exploiting natural gas hydrate reservoir by heating in low-frequency electric field |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN115306366A (en) * | 2022-09-13 | 2022-11-08 | 中国石油大学(华东) | Efficient yield-increasing exploitation method for natural gas hydrate |
| US11952869B1 (en) | 2022-09-13 | 2024-04-09 | China University Of Petroleum (East China) | High-efficiency yield-increasing exploitation method for natural gas hydrates |
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