CN117235839B - Shaft cement sheath safe load calculation method based on self-balancing stress field analysis - Google Patents
Shaft cement sheath safe load calculation method based on self-balancing stress field analysis Download PDFInfo
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- 239000004568 cement Substances 0.000 title claims abstract description 87
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- 230000035772 mutation Effects 0.000 claims description 2
- 239000002184 metal Substances 0.000 description 4
- 238000003860 storage Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
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Abstract
The invention relates to a method for calculating the safe load of a cement sheath of a shaft based on self-balancing stress field analysis, which comprises the following steps: the method comprises the steps of obtaining the ground stress of the position of a shaft, and analyzing the distribution rule of the ground stress; rock mechanics experiments are carried out on maintenance samples under the same conditions of a shaft cement sheath; analyzing stress distribution of a certain disordered fluctuation load, and constructing a self-balancing stress field irrelevant to time; deducing a mechanical form of the structure which exists stably under the dynamic disordered load, and calculating to obtain the safety load of the cement sheath. According to the method, the safety load of the shaft structure is calculated from the theoretical analysis angle, the complex calculation process of general elastoplastic analysis is simplified, complex loading history is not needed to be considered, the shaft size, the surrounding stratum stress and the material properties of the shaft structure are considered, and the accuracy of the pre-judging result is high.
Description
Technical Field
The invention belongs to the field of underground shaft structural stability evaluation, and particularly relates to a shaft cement sheath safety load calculation method based on self-balancing stress field analysis.
Background
Basic wellbore systems are typically composed of three parts, a formation, an annular cement structure, and a metal casing, and subterranean engineering often involves the wellbore system being subjected to complex dynamic disordered loading conditions. In the field of energy development, a shaft formed by a cement ring and a sleeve is large in burial depth and high in ground stress, the pressure in the shaft is periodically reduced and increased in the fracturing process, and meanwhile, the construction procedures such as pressure test, perforation and the like also cause irregular change of the pressure in the shaft; the well bore in the field of underground salt cavern gas storage is in a layered stratum system, the ground stress is greatly changed, and the well bore system is required to not only ensure that the well bore system cannot fail under the fluctuation of gas pressure but also maintain the original tightness in a longer service life; in a shaft type underground parking garage, a plurality of vehicles take off and land simultaneously in a peak period, so that a plurality of loads frequently fluctuate in a short time in the shaft.
The well bore is in a dynamic disordered load environment for a long time, so that the structure is difficult to predict and suddenly deform, destroy and lose efficacy, various load fluctuation in the use and service process is difficult to truly determine and calculate, various stress paths of elastoplastic stress causing structural change cannot be calculated, unexpected engineering accidents are often caused, early investment is wasted when the well bore is light, underground structure collapse is caused when the well bore is heavy, and huge loss of life and property is caused. However, most of the current researches focus on the influence on the stability of the well bore under the condition of simple, single or regular change load, and cannot well reflect the effect of complex stress environment on the stability of the well bore. Thus, accurately reflecting the impact of subsurface disordered dynamic loads on wellbore structural stability is a very important issue in underground engineering.
Disclosure of Invention
The invention aims to solve the problems, and provides a method for calculating the safe load of a shaft cement sheath under complex stress conditions, which is scientific, reasonable and applicable to engineering, and is used for dynamically influencing the stability of the shaft by disordered load, and the safe load under the normal running condition of the shaft is obtained by means of elastoplastic analysis theory, so that a reference basis is provided for underground engineering construction and use.
The technical scheme of the invention is a shaft cement sheath safe load calculation method based on self-balancing stress field analysis, S1: measuring and obtaining the ground stress of the position of the shaft, and analyzing the distribution rule of the ground stress;
s101: according to the early geological investigation condition, selecting complex stress conditions of the well section and key stratum points to drill rock blocks;
S102: machining the drilled rock block according to the test specification and the direction and size requirements;
S103: carrying out a uniaxial compression experiment on the processed rock sample, acquiring stress mutation points by matching with acoustic emission monitoring, and calculating the ground stress magnitude and distribution rule of each representative ground point;
s2: carrying out rock mechanics experiments on maintenance samples under the same conditions of a well bore cement sheath, and carrying out compression experiments under different confining pressures to obtain a stress-strain curve mode, yield stress, cohesion and internal friction angle of the samples;
s3: establishing an elastoplastic constitutive model of the well bore cement sheath to obtain the stress condition of the cement sheath;
S4: constructing a self-balancing stress field irrelevant to time;
s401: carrying out elasticity analysis under the condition of cement sheath load;
S402: carrying out plastic analysis on the cement sheath load, and solving a complete yield condition load;
s403: constructing a self-balancing stress field;
S5: deducing a mechanical form of the structure which exists stably under the dynamic disordered load, and calculating to obtain the safety load of the cement sheath.
Preferably, in step S1, a core sample is drilled on the stratum where the well section of heavy interest and the target well section are located, and samples are taken along three directions forming angles of 0 °, 45 ° and 90 ° with the reference axis, and at least one sample is taken in each direction;
carrying out a Kaisser acoustic emission experiment on the sample according to the rock mechanics experiment procedure, substituting the experimental result into the formula (1) to calculate the earth stress distribution rule of each earth particle,
（1）
Wherein σ h and σ H represent wellbore section bi-directional ground stress principal stresses;、/>、/> The compressive strength of the samples taken in three directions at 0 °, 45 ° and 90 ° angles, respectively, are shown.
Further, in step S2, the confining pressure and the compressive strength of the sample are linearly fitted, and the slope k and the intercept σ c obtained by the fitting are substituted into (2) to obtain the cohesion c and the internal friction angle of the cement sheath，
（2）。
Further, step S3 comprises the sub-steps of:
S301: establishing an elastoplastic constitutive model of the well bore cement sheath according to the stress-strain curve mode and the mechanical parameters obtained in the step S2;
S302: according to engineering dimensions and material characteristics, the stratum outside the shaft and the inner sleeve of the shaft are regarded as elastic materials, and the acting force of the stratum on the shaft is ground stress and is recorded as P out.
The acting force of the sleeve on the cement sheath is a dynamic disordered load, which is denoted as P in and is random and disordered load disturbance generated in the construction or service process.
The cement sheath deformation and strength constraints are mole-coulomb strength criteria.
In step S4, elastoplastic analysis is performed on the cement sheath, and when the cavity is in a small dynamic disturbance, the structure is in a pure elastic state, and at this time, the stress distribution is as follows:
(3)
Wherein lambda is the ratio of the inner and outer radii; sigma r、σθ respectively represents positive stress in radial and tangential directions of cement body microelements under polar coordinates; r represents the outer diameter of the cement sheath; Representing the sagittal diameter; /(I) Representing dynamic disorder disturbance born by the inside of the cement sheath, and acting force of the sleeve on the cement sheath; /(I)The external pressure of the cement sheath is the acting force of the stratum on the cement sheath.
When the size of the dynamic disturbance P in reaches the elastic critical limit P e at a certain moment, the inner diameter of the cement ring just enters the plastic stage and meets the mole-coulomb criterion first, the expression of the elastic critical limit P e is obtained,
（4）
For convenience of expression, letAnd/>Respectively is
At the moment when the dynamic disturbance exceeds P e, the structure part is subjected to plastic deformation, and the plastic region meets the plastic balance condition
（5）
Taking the internal pressure P in at the inner diameter as a boundary condition, and the stress of the plastic region meets the mole-coulomb criterion of the rock material to obtain the stress distribution of the plastic region as
（6）
Wherein sigma r p、σθ p respectively represents positive stress in the radial direction and tangential direction of the infinitesimal of the cement body plastic region under the polar coordinate; r represents the inner diameter of the well section;
the stress distribution of the elastic region is
（7）
Wherein sigma r e、σθ e is the positive stress in the radial direction and tangential direction of the microcell of the cement body elastic region under the polar coordinate respectively; η is the ratio of the boundary vector diameter ρ 0 of the elastic region to the outer diameter R,Representing the force of the plastic region against the elastic region;
The yield radius ρ 0 can be solved from σ r e=σr p at ρ=ρ 0;
when the internal pressure increases to yield throughout the structure, η=1, ρ=r, the yield internal pressure P l is derived,
（8）
Obviously, the repeated fluctuation of the carrier frequency of the cavity generates residual stress, and when a part of pressure p is unloaded in the cavity, the generated residual stress sigma r r and sigma θ r are
（9）。
Further, step S5 comprises the sub-steps of:
s501: constructing a self-balancing stress field according to the residual strain obtained in the step S4, substituting the self-balancing stress field into a yield condition to solve an unloading critical load;
For a structure which bears various fluctuating loads and can maintain stability, a self-balancing stress field is determined, and after the elastic stress generated by any load is overlapped in a load space range, the molar coulomb yield condition is not violated everywhere, so that the mechanical expression form can be expressed as:
（10）
Wherein v is a load multiplier; σ E ij is the elastic stress field under any loading path; ρ ij is the self-balancing residual stress field; f is the yield function; σ s is the yield stress; v stabilizing the structural element; s σ is a bin;
S502: and analyzing and comparing the yield condition load and the unloading critical load to obtain a load safety condition, and judging the stability of the shaft structure according to the engineering actual load.
In step S5, according to the stable condition of the structure, when the structure reaches the critical condition of reverse yield, the critical internal pressure P v satisfies P v=Pin =p, and the critical internal pressure is obtained as
（11）
The cement sheath structure does not yield as long as the loading process and the unloading process are met at the same time, and the whole shaft structure cannot fail due to overlarge deformation;
the conditions for safe loading of the shaft structure are as follows
（12）
In the middle ofRepresentation/>Is smaller of (a);
The internal pressure P in can maintain stability of the well bore structure as long as the formula (12) is satisfied,
The critical value of the safety load of the well bore cement sheath is equal toWhen P in is less than the critical value of the safety load of the well bore cement sheath, the well bore cement sheath is environment-friendly and stable.
Compared with the prior art, the invention has the beneficial effects that:
1) According to the method, the safety load of the shaft structure bearing the disordered dynamic load is innovatively calculated from the theoretical analysis angle, the complex calculation process of general elastoplastic analysis is simplified, the shaft size, the surrounding stratum stress and the material property of the shaft structure are considered, and the accuracy of the prejudgment result is high.
2) The method for safely loading the cement sheath of the shaft is accurate and scientifically attached to the characteristics of rock materials. The full plastic analysis process is added to the cement sheath, so that the stress state performance during the service period of the cement sheath is met to a greater extent, and the exertion of the material performance is considered as much as possible.
3) The cement sheath safe load of the shaft does not need to calculate the historic disordered load path while considering various stress fluctuation, greatly simplifies the calculation process, is suitable for providing direct reference for construction site engineers, and has higher application value.
Drawings
The invention is further described below with reference to the drawings and examples.
Fig. 1 is a schematic flow chart of a method for calculating a safe load of a cement sheath of a well bore according to an embodiment of the invention.
FIG. 2 is a horizontal cross-sectional view of a wellbore structure according to an embodiment of the invention.
FIG. 3 is a longitudinal cross-sectional view of a wellbore structure according to an embodiment of the invention.
FIG. 4 is a schematic diagram of a cement sheath and a micro-element stress analysis according to an embodiment of the invention.
Reference numerals illustrate: a formation 1; a cement sheath 2; a metal sleeve 3.
Detailed Description
As shown in fig. 1, the method for calculating the safe load of the cement sheath of the shaft based on the self-balancing stress field analysis comprises the following steps:
Step 1: core samples are drilled from the stratum where the well section or the target well section is focused, and the core samples are sampled along a certain reference axis in three directions of 0 DEG, 45 DEG and 90 DEG, wherein at least one direction exists. And (3) carrying out a Kernel acoustic emission experiment on the sample according to the related rock mechanics experiment rules, and substituting an experimental result into the formula (1) to obtain the earth stress distribution rule of each place particle.
（1）
Wherein σ h and σ H represent wellbore section bi-directional ground stress principal stresses;、/>、/> The compressive strength of the samples taken in three directions at 0 °, 45 ° and 90 ° angles, respectively, are shown.
Step 2: triaxial compression experiments under different confining pressure conditions are carried out on standard samples of cement sheath for maintaining cement sheath under the same conditions of a target well section, the number of sample groups in each well section is not less than 3, the confining pressure and the compressive ultimate strength of the samples are subjected to linear fitting once, the slope k and the intercept sigma c of a fitting curve are substituted into (2), and the internal friction angle of cohesive force c of the cement sheath is obtained，
（2）
Step 3: the basic structure of the well system is shown in fig. 2 and 3, the outermost layer is a stratum, the middle is a metal sleeve, and the cementing quality is good before the well is stressed. The stratum acts on the cement sheath to form a ground stress P out, the magnitude of the ground stress P out is sigma h, the acting force of the metal sleeve on the cement sheath caused by internal pressure change is P in., and the shaft system can be simplified into an annular cement structure which is subjected to internal and external pressure.
Fig. 4 shows the stress analysis of the cement sheath and its infinitesimal, σ r and σ θ are respectively the radial and tangential normal stresses of a infinitesimal at the polar coordinates on the cement body, and τ rθ is the tangential stress.
Step 4: analyzing stress distribution of a certain disordered fluctuation load, and constructing a self-balancing stress field irrelevant to time;
when the cavity disturbance is small, the structure is in a pure elastic state, and the stress distribution is as follows:
(3)
Where λ is the ratio of the inner and outer radii. Sigma r、σθ respectively represents positive stress in radial and tangential directions of cement body microelements under polar coordinates; r represents the outer diameter of the cement sheath; The sagittal diameter is indicated.
When the dynamic disturbance P in reaches a certain value P e at a certain moment, the inner diameter of the cement ring just enters a plastic stage and meets the yield criterion first, the expression of the elastic critical limit P e is calculated,
（4）
For convenience of expression, letAnd/>The two kinds of the materials are respectively that,
At a certain moment, the dynamic disturbance exceeds P e, the structure part is subjected to plastic deformation, and the plastic region meets the plastic balance condition（5）
The internal pressure P in at the internal diameter is used as a boundary condition, and the stress of the plastic region meets the general yield criterion of rock materials, namely the molar coulomb criterion, so that the stress distribution of the plastic region is obtained
（6）
Wherein sigma r p、σθ p is the positive stress of a certain infinitesimal radial and tangential directions of the plastic region of the cement body under the polar coordinate respectively.
The stress distribution of the elastic region is
（7）
Wherein eta is the ratio of the sagittal diameter rho 0 at the juncture of the elastic region to the outer diameter R, and P' represents the acting force of the plastic region on the elastic region, and can be calculated by substituting rho 0 into formula (6). σ r e、σθ e represents the positive stress in the radial and tangential directions of a certain infinitesimal of the cement body elastic region at the polar coordinates, respectively.
For the above solution of the yield radius ρ 0, it can be solved from the succession of radial stresses at ρ=ρ 0, i.e. σ r e and σ r p are equal.
When the internal pressure increases to yield the whole structure, η=1 and ρ=r in the formula (6) can derive the yield internal pressure P l,
（8）
It is apparent that the cavity is subject to residual stress when repeatedly fluctuating, so that when a portion of the pressure p is relieved in the cavity, the residual stresses σ r r and σ θ r are
（9）
Step 5: deducing a mechanical form of the structure which exists stably under a fluctuation state disordered load, calculating the safety load of the cement sheath, and judging the stability of the shaft according to the safety load;
For bearing various fluctuation loads and maintaining structural stability, a self-balancing stress field is determined, and the elastic stress generated by any load is overlapped in a certain load space range and does not violate the molar coulomb condition everywhere, so that the mechanical expression form can be written as follows:
（10）
Wherein v is a load multiplier; σ E ij is the elastic stress field under any loading path; ρ ij is the self-balancing residual stress field; f is the yield function; σ s is the yield stress; v stabilizing the structural element; s σ is a bin.
From equation (10), it can be seen that the residual stress field of equation (9) is the self-balancing stress field constructed, and the critical equation can be obtained by substituting σ r r and σ θ r of equation (9) into the structural yield criterion
（11）
Based on the stable condition of the structure, i.e., the formula (11), when the structure reaches the critical condition of reverse yield, the critical internal pressure pv=p in =p is obtained to obtain the critical internal pressure as
（12）
Therefore, as long as the whole cement structure meets the loading process and the unloading process simultaneously, the whole shaft structure does not fail due to excessive deformation, so that the inner pressure P in fluctuates anyway, the shaft structure does not fail only by meeting the formula (13),
（13）
In the key monitoring well section with depth 953.3m above the underground cavity in the embodiment, the stratum rock where the key monitoring well section is located is measured by a Kernel acoustic emission experiment to obtain the section P out =42.12 MPa, and the cohesive force is 7.0MPa and the internal friction angle is 27.8 degrees by a cement well triaxial compression experiment used in the well section. The inner diameter r= 127.36mm and the outer diameter r=139.7 mm of the well section. And substituting the related data into the formula (8) and the formula (12), taking the minimum values of the formula and the formula, and finally obtaining the highest value of the fluctuation of the internal pressure of the shaft by conversion, wherein the highest value is 17.42MPa. In various construction processes in the future, the internal pressure fluctuates within a range smaller than the value, and the whole section of the shaft is stable and can be normally used.
The method is suitable for wellbore stability analysis of underground engineering such as underground chambers, salt cavern gas storages, geological storage of carbon dioxide and the like.
Claims (7)
1. The method for calculating the safe load of the cement sheath of the shaft based on the self-balancing stress field analysis is characterized by comprising the following steps of:
S1: measuring and obtaining the ground stress of the position of the shaft, and analyzing the distribution rule of the ground stress;
s101: according to the early geological investigation condition, selecting complex stress conditions of the well section and key stratum points to drill rock blocks;
S102: machining the drilled rock block according to the test specification and the direction and size requirements;
S103: carrying out a uniaxial compression experiment on the processed rock sample, acquiring stress mutation points by matching with acoustic emission monitoring, and calculating the ground stress magnitude and distribution rule of each representative ground point;
s2: carrying out rock mechanics experiments on maintenance samples under the same conditions of a well bore cement sheath, and carrying out compression experiments under different confining pressures to obtain a stress-strain curve mode, yield stress, cohesion and internal friction angle of the samples;
s3: establishing an elastoplastic constitutive model of the well bore cement sheath to obtain the stress condition of the cement sheath;
S4: constructing a self-balancing stress field irrelevant to time;
s401: carrying out elasticity analysis under the condition of cement sheath load;
S402: carrying out plastic analysis on the cement sheath load, and solving a complete yield condition load;
s403: constructing a self-balancing stress field;
S5: deducing a mechanical form of the structure which exists stably under the dynamic disordered load, and calculating to obtain the safety load of the cement sheath.
2. The method for calculating the safe load of the cement sheath of the shaft according to claim 1, wherein in the step S1, core samples are drilled on the stratum where the well section of heavy attention and the target well section are located, and the core samples are sampled along three directions forming angles of 0 degree, 45 degrees and 90 degrees with the reference axis, and at least one sample is taken in each direction;
carrying out a Kaisser acoustic emission experiment on the sample according to the rock mechanics experiment procedure, substituting the experimental result into the formula (1) to calculate the earth stress distribution rule of each earth particle,
（1）
Wherein σ h and σ H represent wellbore section bi-directional ground stress principal stresses;、/>、/> The compressive strength of the samples taken in three directions at 0 °, 45 ° and 90 ° angles, respectively, are shown.
3. The method for calculating the safe load of the cement sheath of the well bore according to claim 2, wherein in the step S2, the confining pressure and the compressive strength of the sample are linearly fitted, and the slope k and the intercept sigma c obtained by the fitting are substituted into the formula (2) to obtain the cohesion c and the internal friction angle of the cement sheath，
（2）。
4. A method of wellbore cement sheath safety load calculation according to claim 3, wherein step S3 comprises the sub-steps of:
S301: establishing an elastoplastic constitutive model of the well bore cement sheath according to the stress-strain curve mode and the mechanical parameters obtained in the step S2;
S302: according to engineering dimensions and material characteristics, the stratum outside the shaft and the inner sleeve of the shaft are regarded as elastic materials, and the acting force of the stratum on the shaft is ground stress and is recorded as P out;
The acting force of the sleeve on the cement sheath is a dynamic disordered load, which is marked as P in and is random and disordered load disturbance generated in the construction or service process;
the cement sheath deformation and strength constraints are mole-coulomb strength criteria.
5. The method of claim 4, wherein in step S4, the cement sheath is subjected to elastoplastic analysis, and when the cavity is subjected to small dynamic disturbance, the structure is in a pure elastic state, and the stress distribution is as follows:
(3)
Wherein lambda is the ratio of the inner and outer radii; sigma r、σθ respectively represents positive stress in radial and tangential directions of cement body microelements under polar coordinates; r represents the outer diameter of the cement sheath; Representing the sagittal diameter; /(I) Representing dynamic disorder disturbance born by the inside of the cement sheath, and acting force of the sleeve on the cement sheath; /(I)The external pressure of the cement sheath is shown as the acting force of the stratum on the cement sheath;
When the size of the dynamic disturbance P in reaches the elastic critical limit P e at a certain moment, the inner diameter of the cement ring just enters the plastic stage and meets the mole-coulomb criterion first, the expression of the elastic critical limit P e is obtained,
（4）
For convenience of expression, letAnd/>Respectively is
At the moment when the dynamic disturbance exceeds P e, the structure part is subjected to plastic deformation, and the plastic region meets the plastic balance condition
（5）
Taking the internal pressure P in at the inner diameter as a boundary condition, and the stress of the plastic region meets the mole-coulomb criterion of the rock material to obtain the stress distribution of the plastic region as
（6）
Wherein sigma r p、σθ p respectively represents positive stress in the radial direction and tangential direction of the infinitesimal of the cement body plastic region under the polar coordinate; r represents the inner diameter of the well section;
the stress distribution of the elastic region is
（7）
Wherein sigma r e、σθ e is the positive stress in the radial direction and tangential direction of the microcell of the cement body elastic region under the polar coordinate respectively; η is the ratio of the boundary vector diameter ρ 0 of the elastic region to the outer diameter R,Representing the force of the plastic region against the elastic region;
The yield radius ρ 0 can be solved from σ r e=σr p at ρ=ρ 0;
when the internal pressure increases to yield throughout the structure, η=1, ρ=r, the yield internal pressure P l is derived,
（8）
Obviously, the repeated fluctuation of the carrier frequency of the cavity generates residual stress, and when a part of pressure p is unloaded in the cavity, the generated residual stress sigma r r and sigma θ r are
（9）。
6. The wellbore cement sheath safety load calculation method of claim 5, wherein step S5 comprises the sub-steps of:
s501: constructing a self-balancing stress field according to the residual strain obtained in the step S4, substituting the self-balancing stress field into a yield condition to solve an unloading critical load;
For a structure which bears various fluctuating loads and can maintain stability, a self-balancing stress field is determined, and after the elastic stress generated by any load is overlapped in a load space range, the molar coulomb yield condition is not violated everywhere, so that the mechanical expression form can be expressed as:
（10）
Wherein v is a load multiplier; σ E ij is the elastic stress field under any loading path; ρ ij is the self-balancing residual stress field; f is the yield function; σ s is the yield stress; v stabilizing the structural element; s σ is a bin;
S502: and analyzing and comparing the yield condition load and the unloading critical load to obtain a load safety condition, and judging the stability of the shaft structure according to the engineering actual load.
7. The method according to claim 6, wherein in step S5, when the structure reaches a critical condition of reverse yield according to the stable condition of the structure, the critical internal pressure P v satisfies P v=Pin =p, and the critical internal pressure is obtained as
（11）
The cement sheath structure does not yield as long as the loading process and the unloading process are met at the same time, and the whole shaft structure cannot fail due to overlarge deformation;
the conditions for safe loading of the shaft structure are as follows
（12）
In the middle ofRepresentation/>Is smaller of (a);
The internal pressure P in can maintain stability of the well bore structure as long as the formula (12) is satisfied,
The critical value of the safety load of the well bore cement sheath is equal toWhen P in is less than the critical value of the safety load of the well bore cement sheath, the well bore cement sheath is environment-friendly and stable.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311033336.3A CN117235839B (en) | 2022-09-16 | 2022-09-16 | Shaft cement sheath safe load calculation method based on self-balancing stress field analysis |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211128796.XA CN115470635B (en) | 2022-09-16 | 2022-09-16 | Shaft stability prediction method under dynamic disordered load condition |
| CN202311033336.3A CN117235839B (en) | 2022-09-16 | 2022-09-16 | Shaft cement sheath safe load calculation method based on self-balancing stress field analysis |
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| CN202211128796.XA Division CN115470635B (en) | 2022-09-16 | 2022-09-16 | Shaft stability prediction method under dynamic disordered load condition |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2545401A1 (en) * | 2003-12-10 | 2005-06-23 | Jfe Steel Corporation | A method for constructing a portion of a pipeline |
| CN106991235A (en) * | 2017-04-01 | 2017-07-28 | 中国石油天然气集团公司 | Cementing concrete ring integrity analysis Forecasting Methodology and device |
| CN112257230A (en) * | 2020-09-21 | 2021-01-22 | 中国石油天然气股份有限公司 | Casing mechanical analysis and calculation method under action of alternating pressure of horizontal well casing |
| CN114896775A (en) * | 2022-04-28 | 2022-08-12 | 西南石油大学 | Method for evaluating interlayer packing of well cementation cement sheath under fracturing working condition |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2351350B (en) * | 1999-06-23 | 2001-09-12 | Sofitech Nv | Cavity stability prediction method for wellbores |
| US6834233B2 (en) * | 2002-02-08 | 2004-12-21 | University Of Houston | System and method for stress and stability related measurements in boreholes |
| US10101498B2 (en) * | 2014-09-05 | 2018-10-16 | Schlumberger Technology Corporation | Well survivability in multidimensional geomechanical space |
| EP3341562B1 (en) * | 2015-08-25 | 2022-03-16 | ConocoPhillips Company | Method for estimating stress magnitude |
| CN107575210A (en) * | 2016-11-30 | 2018-01-12 | 中国石油天然气股份有限公司 | A kind of evaluation method of oil gas well cementing operation Behavior of Hardened Cement Paste elasticity |
| CN109356567B (en) * | 2018-05-04 | 2022-04-08 | 中国石油集团海洋工程有限公司 | Method for predicting stability of deep water shallow stratum well wall |
| CN109538185B (en) * | 2018-10-30 | 2022-04-22 | 中国海洋石油集团有限公司 | Multilayer cased well shaft integrity analysis model under coupled temperature field condition |
| US11326447B2 (en) * | 2019-07-15 | 2022-05-10 | Saudi Arabian Oil Company | Wellbore stability prediction |
| CN110543745B (en) * | 2019-09-29 | 2023-04-07 | 中国石油大学(华东) | Method for evaluating sealing integrity of cement sheath of thermal production well |
| CN113820750B (en) * | 2021-08-12 | 2024-04-16 | 中海石油（中国）有限公司天津分公司 | Method for quantitatively predicting mudstone structural cracks based on elastoplastic mechanics |
-
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2545401A1 (en) * | 2003-12-10 | 2005-06-23 | Jfe Steel Corporation | A method for constructing a portion of a pipeline |
| CN106991235A (en) * | 2017-04-01 | 2017-07-28 | 中国石油天然气集团公司 | Cementing concrete ring integrity analysis Forecasting Methodology and device |
| CN112257230A (en) * | 2020-09-21 | 2021-01-22 | 中国石油天然气股份有限公司 | Casing mechanical analysis and calculation method under action of alternating pressure of horizontal well casing |
| CN114896775A (en) * | 2022-04-28 | 2022-08-12 | 西南石油大学 | Method for evaluating interlayer packing of well cementation cement sheath under fracturing working condition |
Non-Patent Citations (1)
| Title |
|---|
| 水泥环缺损时套管损坏有限元分析;崔明月;张颖;杨军征;练章华;屈超豫;;石油矿场机械;20160825(第08期);全文 * |
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