CN112362475B - Evaluation method for trapped sealing ultimate pressure of oil reservoir type gas storage - Google Patents
Evaluation method for trapped sealing ultimate pressure of oil reservoir type gas storage Download PDFInfo
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- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0073—Fatigue
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
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- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
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Abstract
The invention discloses an evaluation method of trap sealing ultimate pressure of an oil reservoir type gas storage, and belongs to the field of gas storage evaluation. The technical scheme includes that the gas storage trap sealing limit pressure is obtained by determining the escape limit, the cover layer bearing limit and the fault bearing limit of the trap structure. The method is applied to the aspect of gas storage evaluation, solves the problem that the prior art can only judge the sealing performance of the gas storage but cannot evaluate the operation upper limit pressure of the gas storage, and has the characteristic of comprehensively analyzing the dynamic sealing pressure-bearing limit of the trap of the gas storage so as to guide scientific design of the operation upper limit pressure of the gas storage and evaluation of the pressure-raising potential.
Description
Technical Field
The invention belongs to the field of gas storage evaluation, and particularly relates to an evaluation method for the confinement sealing ultimate pressure of an oil reservoir type gas storage.
Background
Different from the research on the sealing performance of an original oil and gas reservoir, in the operation process of the gas storage, the stratum pressure changes alternately between the upper limit pressure and the lower limit pressure, the injection and production speed can reach 20-50 times of that of the oil and gas reservoir, the internal stratum pressure changes alternately and violently periodically, so that the edge of the gas storage is broken, the upper covering layer has damage risks, and the sealing performance of the gas storage is seriously challenged. In the operation process of the gas storage, the period of the formation pressure can be rapidly changed in the forced injection and forced extraction process, and further the problems of gas dissipation or cover layer damage, fault opening and the like are caused. In addition, the upper limit pressure of the operation of the existing operated gas storage is limited by the original formation pressure, so that the safety of the gas storage in the operation process is ensured. However, the design of the storage capacity space of the gas storage is severely limited by taking the original formation pressure as a boundary, if the operation upper limit pressure can be improved, the storage capacity space of the gas storage can be greatly increased, the working gas amount can be greatly increased, and further more economic benefits are created. Therefore, the method for improving the operation upper limit pressure of the gas storage as much as possible is also one of the key points and difficulties of the construction and parameter design of the current gas storage. The upper limit pressure of the gas storage is essentially controlled by the sealing performance of the trap, i.e. the maximum gas capacity that the gas storage can accommodate. In addition, the construction of an oil reservoir type gas storage is still in the starting stage in China, the sealing capacity of trap after the oil reservoir is reconstructed into the gas storage needs to be further researched, and the ultimate pressure of trap sealing is not clear, so that the design of the operation upper limit pressure of the gas storage lacks scientific basis. Therefore, the evaluation method for comprehensively analyzing the confinement sealing ultimate pressure of the oil reservoir type gas storage has important significance in guiding scientific design of the operation upper limit pressure of the gas storage and evaluating the pressure raising potential.
Chinese patent CN107975362A discloses an evaluation method of the sealing property of a lithologic gas reservoir type gas storage, which comprises the following steps that the sealing property of a cover plate and a bottom plate is evaluated, firstly, the macro sealing property of the cover plate and the bottom plate is evaluated, and secondly, the micro sealing property of the cover plate and the bottom plate is evaluated; evaluating the sealing performance of the lateral boundary, namely firstly carrying out microscopic sealing performance evaluation on the lateral boundary, secondly carrying out space form evaluation on the lateral boundary, and finally carrying out dynamic evaluation on the lateral boundary; checking the integral sealing capability of the gas storage; the method solves the problem that a system evaluation method aiming at the sealing capacity of the lithologic gas reservoir type gas storage is not available in the prior art, is scientific and reliable, has strong field operability, and can more accurately judge the sealing performance of the gas storage.
However, although the above patent also relates to dynamic evaluation in the sealing performance evaluation, it is often qualitative evaluation or parametric evaluation, and does not relate to mechanical property analysis of the cap layer and the fault, so that it can only judge the sealing performance of the gas reservoir, and cannot evaluate the gas reservoir operation upper limit pressure. In addition, few reservoir-type gas reservoirs have been investigated.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to solve the technical problem that the prior art does not relate to an oil reservoir type gas storage, the prior art can only judge the sealing performance of the gas storage and cannot evaluate the operation upper limit pressure of the gas storage, and provides the evaluation method for the oil reservoir type gas storage trap sealing limit pressure, which can comprehensively analyze the gas storage trap sealing limit pressure so as to guide scientific design of the operation upper limit pressure and the evaluation pressure-raising potential of the gas storage.
In order to solve the technical problem, the technical scheme adopted by the invention is as follows:
the invention provides an evaluation method of trap sealing ultimate pressure of an oil reservoir type gas storage, which obtains the trap sealing ultimate pressure of the oil reservoir type gas storage by determining the escape ultimate pressure of a trap structure, the cover layer sealing ultimate pressure and the fault sealing ultimate pressure.
Preferably, the trap structure escape limit pressure is obtained by detecting trap gas escape pressure; the cap layer sealing limit pressure is obtained by detecting cap layer dynamic breakthrough limit pressure, cap layer tension failure limit pressure, cap layer shear failure limit pressure and cap layer fatigue failure limit pressure, and selecting the minimum value of the cap layer dynamic breakthrough limit pressure, the cap layer tension failure limit pressure, the cap layer shear failure limit pressure and the cap layer fatigue failure limit pressure as the cap layer sealing limit pressure; the fault sealing limit pressure is obtained by detecting fault slip instability limit pressure and fault activation starting limit pressure, and selecting the minimum value of the fault slip instability limit pressure and the fault activation starting limit pressure as the fault sealing limit pressure; and the oil reservoir type gas storage trap sealing limit pressure is obtained by comparing the trap structure escape limit pressure, the cover layer sealing limit pressure and the fault sealing limit pressure and selecting the minimum value of the trap structure escape limit pressure, the cover layer sealing limit pressure and the fault sealing limit pressure as the oil reservoir type gas storage trap sealing limit pressure.
Preferably, the trapped gas dissipation pressure is calculated by the following formula:
P1＝Poil reservoir+ρwgΔH
P1Is the trapped gas dissipation pressure, MPa; pOil reservoirFor the reservoir original formation pressure, ρwIs the density of the water of the stratum in g/cm3(ii) a g is the acceleration of gravity, 9.8m/s2(ii) a Δ H is the trap closure amplitude, m.
Preferably, the dynamic breakthrough limit pressure of the cap layer is calculated by the following formula:
P2＝Pbreakthrough of+POverlying
P2Dynamically breaking through the limit pressure of the cover layer, namely MPa; pBreakthrough ofThe dynamic breakthrough pressure of the rock cover is MPa; pOverlyingThe formation pressure of the overburden stratum is MPa.
Preferably, the cap layer tensile failure limit pressure is calculated by the following formula:
P3＝σ3+T
P3the tensile failure limit pressure of the cover layer is MPa; t is tensile strength of rock, MPa; sigma3Minimum principal stress, MPa.
Preferably, the cap layer shear failure limit pressure is obtained by the following method:
selecting a sample to carry out uniaxial and different confining pressures according to the ground stress and the operating pressure of the cover layerAccording to a triaxial compression rock mechanics experiment, according to a molar-coulomb intensity criterion, fitting a cap rock shear failure envelope curve, and when the stress state of the cap rock is tangent to the shear failure envelope curve, the cap rock is subjected to shear failure, so that the cap rock shear failure limit pressure P is determined4。
Preferably, the fatigue fracture limit pressure of the cap layer is obtained by the following method:
under the condition of simulating the injection and production working conditions of the gas storage, an indoor core triaxial loading and unloading alternating stress experiment is carried out, 50 times of triaxial loading and unloading alternating stress accumulated plastic strain of the cap rock core is used as a quantitative evaluation index, 1% of accumulated plastic strain is used as a critical index of fatigue failure of the cap rock of the gas storage, and the rock strength when the accumulated plastic strain reaches 1% is obtained, namely the cap rock fatigue failure limit pressure P5。
Preferably, the fault slip instability limit pressure is calculated by the following formula:
P6＝Sn-τs/0.6
P6the fault slip instability limit pressure is MPa; snIs the normal stress of the fault plane, MPa; tau issThe shear stress at the fault plane is MPa.
Preferably, the fault activation opening limit pressure is calculated by the following formula:
P7＝ρwgh+ΔP
P7the fault activation opening limit pressure is MPa; rhowIs the density of the formation water in kg/m3(ii) a h is the buried depth, m; Δ P is the additional fluid pressure, MPa.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides an evaluation method of the confinement sealing ultimate pressure of an oil reservoir type gas storage, which can comprehensively analyze the confinement sealing ultimate pressure of the oil reservoir type gas storage, thereby guiding scientific design of the operation upper limit pressure of the gas storage and evaluating the pressure raising potential.
Drawings
FIG. 1 is a schematic diagram of an evaluation process of the confining sealing limit pressure of the oil reservoir type gas storage according to the invention;
FIG. 2 is a schematic illustration of additional fluid pressure calculations;
FIG. 3 is a top view of a sand section of a H-shaped broken block in a recess of a Nanbao;
FIG. 4 is a Moore circle of shear failure stress of H-broken block east three-segment mudstone.
Detailed Description
The technical solutions in the embodiments of the present invention will be fully described in detail below with reference to the accompanying drawings. It is obvious that the described embodiments are only some specific embodiments, not all embodiments, of the general technical solution of the present invention. All other embodiments, which can be derived by a person skilled in the art from the general idea of the invention, fall within the scope of protection of the invention.
The invention provides an evaluation method of trap sealing ultimate pressure of an oil reservoir type gas storage, which is characterized in that the trap sealing ultimate pressure of the oil reservoir type gas storage is obtained by determining the escape ultimate pressure of a trap structure, the cover layer sealing ultimate pressure and the fault sealing ultimate pressure. The upper limit pressure of the existing running gas storage is limited by the original formation pressure so as to ensure the safety of the gas storage in running. However, the design of the storage capacity space of the gas storage is severely limited by taking the original formation pressure as the operation upper limit pressure, if the operation upper limit pressure can be improved, the storage capacity space of the gas storage can be greatly increased, the working gas amount can be greatly increased, and further more economic benefits are created. Therefore, in order to improve the operation upper limit pressure on the premise of ensuring safety, the dynamic sealing pressure-bearing limit of the gas storage trap needs to be accurately obtained. However, in the operation process of the gas storage, the strong injection and strong mining process can cause the period of the formation pressure to change rapidly, and further causes gas dissipation or cover layer damage and fault opening. The upper limit pressure at which the reservoir operates is essentially controlled by the containment characteristics, i.e., the maximum volume of gas that can be contained by the reservoir. According to the technical scheme, by determining the trap structure loss limit pressure, the cover layer sealing limit pressure and the fault sealing limit pressure, the trap structure loss limit pressure, the cover layer sealing limit pressure and the fault sealing limit pressure are compared, the minimum value among the three is used as the oil reservoir type gas storage trap sealing limit pressure, the gas storage trap sealing limit pressure is comprehensively considered, and therefore the operation upper limit pressure and the evaluation pressure-raising potential of the scientifically designed gas storage are guided.
In a preferred embodiment, the trap configuration dissipation limit pressure is obtained by detecting trap gas dissipation pressure; the cap layer sealing limit pressure is obtained by detecting cap layer dynamic breakthrough limit pressure, cap layer tension failure limit pressure, cap layer shear failure limit pressure and cap layer fatigue failure limit pressure, and selecting the minimum value of the cap layer dynamic breakthrough limit pressure, the cap layer tension failure limit pressure, the cap layer shear failure limit pressure and the cap layer fatigue failure limit pressure as the cap layer sealing limit pressure; the fault sealing limit pressure is obtained by detecting fault slip instability limit pressure and fault activation starting limit pressure, and selecting the minimum value of the fault slip instability limit pressure and the fault activation starting limit pressure as the fault sealing limit pressure; and the oil reservoir type gas storage trap sealing limit pressure is obtained by comparing the trap structure escape limit pressure, the cover layer sealing limit pressure and the fault sealing limit pressure and selecting the minimum value of the trap structure escape limit pressure, the cover layer sealing limit pressure and the fault sealing limit pressure as the oil reservoir type gas storage trap sealing limit pressure. As shown in fig. 1, the trap seal limit pressure PExtreme limitAnd the limit pressure P dissipated by the trap structureStructure of the deviceSealing limit pressure P of the cap layerCover layerFault sealing limit pressure PFault of a moving objectThe relationship between them is: pExtreme limit＝min{PStructure of the device，PCover layer，PFaulting}; limit pressure P for escape of trap structureStructure of the deviceAnd trapped gas escape pressure P1The relationship between them is: pStructure of the device＝P1(ii) a Ultimate sealing pressure P of cover layerCover layerDynamic breakthrough limit pressure P with cover rock2Cap layer tension failure limit pressure P3Cap layer shear failure ultimate pressure P4And cap fatigue failure ultimate pressure P5The relationship between them is: p isCover layer＝min{P2，P3，P4，P5}; ultimate pressure P of fault sealingFault of a moving objectAnd fault slip instability limit pressure P6And fault activation opening limit pressure P7The relation between is PFault of a moving object＝min{P6，P7}. The existing methods for evaluating the sealing performance of the cover layer and the fault are more, the evaluation technology is relatively mature, but the existing technology focuses on evaluating the static sealing performance of the cover layer and the fault, namely the sealing performance of the cover layer and the fault in the static state at present, but the sealing limit of the cover layer and the fault is not sufficiently researched, and the sealing performance of the cover layer and the fault in the static state is simply analyzed in the operation process of the gas storage, so that the requirement of the gas storage construction cannot be met. Different from the research on the sealing performance of an original oil and gas reservoir, in the operation process of the gas storage, the stratum pressure changes alternately between the upper limit pressure and the lower limit pressure, the injection and production speed can reach 20-50 times of that of the oil and gas reservoir, the internal stratum pressure changes alternately and violently periodically, so that the edge of the gas storage is broken, the upper covering layer has damage risks, and the sealing performance of the gas storage is seriously challenged. The existing cap layer and fault sealing performance evaluation technology is mature, is the basis of early evaluation of gas storage construction, but is not enough to support parameter design of gas storage construction. On the basis of the existing evaluation technology, the stress state of a cover layer and a fault in the operation process of the gas storage needs to be focused on, and whether the risk of sealing damage exists or not needs to be determined. However, quantitative evaluation of the bearing limit of the cover layer and the fault of the gas storage is still a difficulty established by the evaluation method, the technical scheme specifically limits the relevant evaluation indexes of the cover layer bearing limit and the fault bearing limit, realizes quantitative evaluation of the cover layer bearing limit and the fault bearing limit, and has important significance.
In a preferred embodiment, the trapped gas dissipation pressure is calculated by the following equation:
P1＝Poil reservoir+ρwgΔH
P1Is the trapped gas dissipation pressure, MPa; pOil reservoirFor the reservoir original formation pressure, ρwIs the density of the water of the stratum in g/cm3May pass through the formationAcquiring test data; g is the acceleration of gravity, 9.8m/s2(ii) a Δ H is the trap closure amplitude, m, which can be obtained by construction interpretation. When the upper limit pressure of the gas storage operation exceeds the critical pressure of the trap overflow point, the natural gas can be dissipated.
In a preferred embodiment, the dynamic breakthrough limit pressure of the cap layer is calculated by the following formula:
P2＝Pbreakthrough of+POverlying
P2Dynamically breaking through the limit pressure of the cover layer, namely MPa; pBreakthrough ofThe dynamic breakthrough pressure of the rock cover is MPa; pOverlyingThe formation pressure of the overburden stratum is MPa. The dynamic breakthrough pressure refers to the gas breakthrough pressure of the cover layer after 50 times of alternating stress action, and can be obtained through an alternating breakthrough pressure experiment.
In a preferred embodiment, the cap layer tensile failure limit pressure is calculated by the following formula:
P3＝σ3+T
P3the tensile failure limit pressure of the cover layer is MPa; t is tensile strength of rock, MPa, and can be obtained through a tensile strength test of the rock of the cover layer; sigma3The minimum principal stress, MPa, can be obtained through ground stress test data or an empirical formula. When the formation pressure is greater than the minimum principal stress, the cap layer may experience tensile failure. In particular, in the case of a gas reservoir type gas storage reservoir buried shallowly, the risk of tension failure of the cover layer is much higher than the risk of shear failure. Hydraulic fracturing occurs when the pore fluid pressure is greater than the sum of the minimum principal stress and the rock tensile strength, i.e., when the minimum effective principal stress is expressed as a tensile force and greater than the rock tensile strength. The critical pressure of tensile failure of the cap layer is the sum of the minimum principal stress to which the cap layer is subjected and the tensile strength of the rock.
In a preferred embodiment, the cap layer shear failure limit pressure is obtained by:
selecting samples to carry out uniaxial and different confining pressure triaxial compression rock mechanical experiments according to the ground stress and the operating pressure of the cap rock, fitting the cap shear failure envelope curve according to the molar-coulomb intensity criterion, and performing the test on the cap rockWhen the force state is tangential to the shearing failure envelope curve, the overlay rock is subjected to shearing failure, so that the overlay shearing failure limit pressure P is determined4。
In a preferred embodiment, the cap layer fatigue failure limit pressure is obtained by:
under the condition of simulating the injection and production working conditions of the gas storage, an indoor core triaxial loading and unloading alternating stress experiment is carried out, 50 times of triaxial loading and unloading alternating stress accumulated plastic strain of the cap rock core is used as a quantitative evaluation index, 1% of accumulated plastic strain is used as a critical index of fatigue failure of the cap rock of the gas storage, and the rock strength when the accumulated plastic strain reaches 1% is obtained, namely the cap rock fatigue failure limit pressure P5。
In a preferred embodiment, the fault slip instability limit pressure is calculated by the following formula:
P6＝Sn-τs/0.6
P6the fault slip instability limit pressure is MPa; snIs the normal stress of the fault plane, MPa; tau issThe shear stress of the fault surface, MPa, can be directly calculated by using the ground stress data, the fault dip angle and the like.
In a preferred embodiment, the fault activation cracking limit pressure is calculated by the following formula:
P7＝ρwgh+ΔP
P7the fault activation opening limit pressure is MPa; rhowIs the density of the formation water in kg/m3(ii) a h is the buried depth, m; Δ P is the additional fluid pressure, MPa. The additional fluid pressure may be calculated using the stress Mohr circle of the fault rock, as shown in FIG. 2.
In order to more clearly and specifically describe the method for evaluating the dynamic seal pressure-bearing limit of the gas storage trap provided by the embodiment of the invention, the following description is given with reference to specific embodiments.
Example 1
And selecting H broken blocks of the Nanbao pit for example analysis. The broken block is of a broken nose structure, the proposed reservoir layer position is a sand section, the sand section is covered with an east three-section mudstone cover layer, and the broken block is controlled by a side fault, as shown in figure 3.
1. Gas escape pressure P of trapped overflow point1
The trap closing height of the fault block is 220m, the original formation pressure of the oil reservoir is 40.17MPa, and the density of the formation water is 1.05g/cm3Then, the gas escape pressure of the H-shaped broken block is 61.84MPa by using a calculation formula of the gas escape pressure.
2. Dynamic breakthrough limit pressure P of cover layer2
After 50 times of fatigue loading, the average value of the breakthrough pressure of the H broken block east three-section cover layer mudstone sample is 8.21MPa, the average buried depth of the middle part of the east three-section stratum is 3913m, and the pressure of the overlying stratum is 38.5MPa, so that the dynamic breakthrough limit pressure is equal to the sum of the pressure of the overlying stratum and the dynamic breakthrough pressure and is 46.71 MPa.
3. Ultimate stress of cap layer shear failure P3
The shear failure stress Mohr circle of the mudstone sample can be obtained by triaxial compression of the rock under different confining pressure conditions, and as shown in FIG. 4, when the stress state of the cap rock is tangent to the shear failure envelope curve, the cap rock will be subjected to shear failure.
Under the condition of an original stratum, the average buried depth of the middle part of the east three sections of cover layers is 3913m, the minimum principal stress is 65MPa, and the corresponding maximum principal stress is 224.4MPa, so that the shear failure limit pressure of the cover layers can be calculated to be 95.9 MPa.
4. Ultimate tension failure pressure P of cover layer4
The average buried depth of the H-shaped Cengdong three-stage cover layer is 3913m, the original minimum horizontal principal stress is 64.29MPa according to the relation between the minimum horizontal principal stress and the depth established by Xuke and the like (2019), the tensile strength average value of the rock is 1.47MPa through a uniaxial compression test, and the tensile failure limit pressure of the cover layer is 65.76 MPa.
5. Ultimate stress P of fatigue failure of cap layer5
After 50 times of fatigue tests, the minimum value of the compressive strength of the rock sample of the overlay is 218.88MPa, and the rock sample can be used as the fatigue failure limit pressure of the overlay.
6. Fault activation opening limit pressure P6
The average buried depth of the constructed library section is 3913m, the maximum principal stress is 224.4MPa, the minimum principal stress is 65MPa, the original formation pressure is 38.53MPa, the additional fluid pressure required by fault activation opening is 31.17MPa according to the fault activation opening limit pressure calculation method and the calculation formula, and the fault activation opening limit pressure is 69.7 MPa.
7. Fault sliding instability limit pressure P7
As can be seen from fig. 3, the H fault block is controlled by three fault layers F1, F2, and F3, and the minimum value of the critical pressure of the slip instability in the three fault layers is the critical pressure of the slip instability of the fault block. According to the calculation formula of the normal stress and shear stress of the cross section of each fault, the slip instability critical pressure of each fault can be calculated, and as can be seen from table 1, the slip instability critical pressures of three faults of F1, F2 and F3 are 57.22MPa, 61.21MPa and 60.33MPa respectively, so that the fault slip instability limiting pressure of the H fault block is the minimum value of the three, namely 57.22 MPa.
TABLE 1 Limit pressure of slip instability of depressed H-fault block boundary in Nanbao
8. Gas storage trap sealing limit pressure
And (3) integrating the trap, the cover layer and the fault dynamic damage risk, wherein the trap structure ultimate pressure is 61.84MPa, the cover layer sealing ultimate pressure is 46.74MPa, and the fault sealing ultimate pressure is 57.22MPa, so that the gas storage trap sealing ultimate pressure is the minimum value of the three, and is 46.74MPa (table 2).
TABLE 2 confined dynamic seal pressure limit of H-shaped broken block trap in Nanbao
In order to ensure the tightness of the gas storage, the upper limit pressure of the gas storage is designed to be generally not more than the original formation pressure (Sun army Chang et al, 2018), the original formation pressure of the block is 40.17MPa, and the confining sealing limit pressure determined by the technical scheme of the application can reach 46.74MPa, which indicates that the gas storage has a large pressure-raising space.
Claims (8)
1. The evaluation method of the confinement seal ultimate pressure of the oil reservoir type gas storage is characterized in that the confinement seal ultimate pressure of the oil reservoir type gas storage is obtained by determining the escape ultimate pressure of a confinement structure, the cover layer seal ultimate pressure and the fault seal ultimate pressure;
the trap structure escape limit pressure is obtained by detecting the trap gas escape pressure;
the cap layer sealing limit pressure is obtained by detecting cap layer dynamic breakthrough limit pressure, cap layer tension failure limit pressure, cap layer shear failure limit pressure and cap layer fatigue failure limit pressure, and selecting the minimum value of the cap layer dynamic breakthrough limit pressure, the cap layer tension failure limit pressure, the cap layer shear failure limit pressure and the cap layer fatigue failure limit pressure as the cap layer sealing limit pressure;
the fault sealing limit pressure is obtained by detecting fault slip instability limit pressure and fault activation starting limit pressure, and selecting the minimum value of the fault slip instability limit pressure and the fault activation starting limit pressure as the fault sealing limit pressure;
and the oil reservoir type gas storage trap sealing limit pressure is obtained by comparing the trap structure escape limit pressure, the cover layer sealing limit pressure and the fault sealing limit pressure and selecting the minimum value of the trap structure escape limit pressure, the cover layer sealing limit pressure and the fault sealing limit pressure as the oil reservoir type gas storage trap sealing limit pressure.
2. The method for evaluating the confinement seal limit pressure of a reservoir-type gas reservoir according to claim 1, wherein the confinement gas escape pressure is calculated by the following formula:
P1＝Poil reservoir+ρwgΔH
P1Is the trapped gas dissipation pressure, MPa; pOil reservoirFor the reservoir original formation pressure, ρwIs the density of the water of the stratum in g/cm3(ii) a g is the acceleration of gravity, 9.8m/s2(ii) a Δ H is the trap closure amplitude, m.
3. The method for evaluating the confining sealing ultimate pressure of the reservoir type gas storage according to claim 1, wherein the dynamic breakthrough ultimate pressure of the cover layer is calculated by the following formula:
P2＝Pbreak through+POverlying
P2Dynamically breaking through the limit pressure, MPa, for the cover layer; pBreakthrough ofThe dynamic breakthrough pressure of the rock cover is MPa; pOverlyingThe formation pressure of the overburden stratum is MPa.
4. The method for evaluating the confining sealing ultimate pressure of the reservoir type gas storage according to claim 1, wherein the cap layer tension failure ultimate pressure is calculated by the following formula:
P3＝σ3+T
P3the tensile failure limit pressure of the cover layer is MPa; t is tensile strength of rock, MPa; sigma3Minimum principal stress, MPa.
5. The method for evaluating the trapping sealing ultimate pressure of a reservoir-type gas storage reservoir according to claim 1, wherein the cap layer shear failure ultimate pressure is obtained by the following method:
selecting a sample to carry out a uniaxial and different confining pressure triaxial compression rock mechanical experiment according to the ground stress and the operating pressure of the cap rock, fitting a cap shear failure envelope line according to a molar-coulomb intensity criterion, and when the stress state of the cap rock is tangent to the shear failure envelope line, the cap rock is subjected to shear failure, so that the cap shear failure limit pressure P is determined4。
6. The method for evaluating the confinement seal ultimate pressure of a reservoir-type gas reservoir according to claim 1, wherein the cap layer fatigue failure ultimate pressure is obtained by the following method:
under the condition of simulating the injection and production working conditions of the gas storage, an indoor core triaxial loading and unloading alternating stress experiment is carried out, 50 times of triaxial loading and unloading alternating stress accumulated plastic strain of the cap rock core is used as a quantitative evaluation index, 1% of accumulated plastic strain is used as a critical index of fatigue failure of the cap rock of the gas storage, and the rock strength when the accumulated plastic strain reaches 1% is obtained, namely the cap rock fatigue failure limit pressure P5。
7. The method for evaluating the trapping sealing limit pressure of the reservoir type gas storage according to claim 1, wherein the fault slip instability limit pressure is calculated by the following formula:
P6＝Sn-τs/0.6
P6the fault slip instability limit pressure is MPa; snIs the normal stress of the fault plane, MPa; tau issThe shear stress at the fault plane is MPa.
8. The method for evaluating the trapping sealing limit pressure of the reservoir type gas storage according to claim 1, wherein the fault activation opening limit pressure is calculated by the following formula:
P7＝ρwgh+ΔP
P7the fault activation opening limit pressure is MPa; rhowIs the density of formation water in kg/m3(ii) a h is the buried depth, m; Δ P is the additional fluid pressure, MPa.
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