CN110543745B - Method for evaluating sealing integrity of cement sheath of thermal production well - Google Patents
Method for evaluating sealing integrity of cement sheath of thermal production well Download PDFInfo
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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
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices or the like
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/10—Geothermal energy
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- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
- Earth Drilling (AREA)
Abstract
The invention provides a method for evaluating the sealing integrity of a cement sheath of a thermal production well. The evaluation method comprises the following steps: determining thermal recovery construction parameters of the steam injection thermal recovery well; analyzing the change of the environment in the shaft; the influence of temperature on the performance parameters of the set cement is determined through experiments; establishing a heat conduction model by using ABAQUS; generating an ODB file through an ABAQUS numerical interface program; establishing a fluid-solid coupling model of the casing-cement sheath-stratum assembly; importing the ODB file of the heat conduction model into the fluid-solid coupling model; the model is solved and the numerical results are analyzed. The evaluation method combines the strength degradation of the set cement with the damage of the set cement caused by the severe environment with high temperature and high pressure, and has very important significance for evaluating the sealing integrity of the cement sheath of the thermal production well.
Description
Technical Field
The invention relates to a method for evaluating the cementing and sealing integrity of a cement sheath of a thermal production well, belonging to the field of petroleum and natural gas exploration and development.
Background
When cementing, it is a construction operation of setting a casing into the well and injecting cement into the annular space between the well and the casing. After well cementation, the sleeve-cement sheath-ground layer combination can be cemented together, and good cementation plays a role in protecting the sleeve, supporting the ground layer and sealing the oil-gas layer, and has important influence on safe and efficient production. However, the cementing failure occurs due to misoperation during cementing or the harsh environment during oil and gas production and development. The problem of long-term attention of the well cementation engineering when how to improve the sealing quality of the cement sheath between the casing and the well wall and improve the strength of the cement sheath is solved. The mechanical property of the well cementation cement sheath influences the well cementation quality and the service life of the oil and gas well. In the remaining petroleum resources around the world today, the heavy oil resource far exceeds the conventional crude oil, and the heavy oil will be one of the important energy sources in the 21 st century. At present, the main modes of thick oil recovery at home and abroad are steam huff and puff and steam flooding, and the steam temperature is as high as 380 ℃ during thermal oil recovery. Under the condition of thermal recovery, the cement stones inevitably have compressive strength recession, permeability increase and other phenomena at high temperature, the stability of the cement stones is damaged, the interlayer packing efficiency of a shaft is invalid, and the wellhead is seriously bubbled by steam, so that interlayer gas channeling and annulus pressure are caused, the casing damage is serious, the production life of a heavy oil well is greatly shortened, the recovery efficiency of the heavy oil thermal recovery well is influenced, serious economic loss is caused, and meanwhile, the acid gas field can cause pollution to the environment and bring harm to the public. According to field data statistics of domestic thick oil production blocks such as Liaohe oil field, clamayi and the like, the casing loss rate of a thick oil well is as high as 50%, the production stop well is increased year by year in a proportion of 10% due to the problem of interlayer packing failure of a cement ring, and the well mouth pressure, steam bubbling around the well site and interlayer channeling are serious. At present, the analysis of the well cementation and sealing integrity of a conventional stratum oil and gas well is more, the analysis and evaluation of the sealing integrity of a cement ring of a gas injection well is less, the obstruction is caused to the identification and control of risks in the construction and production processes of the gas injection development well, and the limitation exists on the safety of the well cementation operation of the gas injection development well, the long-term efficient exploitation of the oil and gas well and the long-term sealing stability of the cement ring of the well cementation of the gas injection development well.
Disclosure of Invention
The invention aims to provide a method for evaluating the sealing integrity of a cement sheath in a high-temperature and high-pressure environment of a thermal production well, which is used for analyzing the performance reduction of a cement sheath caused by temperature and analyzing and evaluating the failure of a cement sheath body and the failure of an interface under the action of external force (temperature, pressure, injected fluid and the like), so that a set of complete mechanical system is established.
In order to realize the purpose, the invention adopts the following technical scheme:
a method for evaluating the sealing integrity of a cement sheath of a thermal production well comprises the following steps:
1) Acquiring construction parameters of a thermal production well;
2) Curing the set cement under different temperature conditions and testing the performance of the set cement, including compressive strength, tensile strength, elastic modulus and Poisson ratio;
3) Establishing a heat conduction model of the casing-cement sheath-stratum combination based on the data in 1) and 2);
4) Calculating the heat conduction model to obtain an ODB file;
5) Establishing a thermo-fluid-solid coupling model of the casing-cement sheath-stratum combination based on the data of 1) and 2);
6) And solving the heat fluid-structure interaction model imported with the ODB file and analyzing a numerical result, wherein the analysis content comprises the temperature distribution of the set cement, the circumferential stress and the shear stress of the set cement and whether micro-annular gaps appear on a first interface and a second interface.
Wherein various parameters in the step 1) can be obtained by a construction site and substituted into the steps 3) and 5). The cement paste in the step 2) can be obtained by laboratory tests on cement paste and is substituted into the steps 3) and 5).
Preferably, the thermal recovery well construction parameters in the step 1) comprise well mouth steam injection parameters, well trajectory parameters, casing property parameters, stratum property parameters, cement stone property parameters and target horizon load; the wellhead steam injection parameters comprise steam injection pressure, temperature, speed and steam injection time; the well trajectory parameters comprise casing size, casing wall thickness, annulus size, drilled borehole size and target horizon depth; the property parameters of the sleeve comprise density, elastic modulus, poisson's ratio, thermal expansion coefficient and thermal conductivity; the attribute parameters of the stratum comprise density, elastic modulus, poisson's ratio, thermal conductivity, thermal expansion coefficient, porosity and permeability; the attribute parameters of the set cement comprise density, thermal conductivity, thermal expansion coefficient, porosity and permeability; the target horizon load comprises temperature and pressure;
preferably, the target horizon load calculating method in step 1) is as follows:
1) Temperature change in the wellbore: the steam temperature in the oil pipe is regarded as corresponding to the ground temperature, i.e.
T＝T sur (t)(0＜t≤t end ) (1)
Wherein t is time; t is the steam temperature, DEG C; t is sur (t) is the ground temperature, DEG C;
the surface temperature refers to the temperature at which steam is injected at the surface.
2) The pressure drop in the well bore is calculated by the formula:
wherein, p-mean pressure, p a (ii) a z-well depth, m; d-the internal diameter of the gas transmission pipeline, m; a. The p Is the cross-sectional area of the oil pipe, m 2 ；i s -steam mass flow, kg/h; q. q.s g Steam volume flow, m 3 /h。p、i s 、q g All are determined by site construction.
ρ m Is density, kg/m 3 The calculation formula is as follows:
in the formula, M is gas molecular weight and has no dimension; r is a general gas constant, and is generally R = 8.314J/(mol) -1 ·℃ -1 ) (ii) a Gamma is gas specific gravity, and has no dimension; t is a unit of f Is the gas temperature, DEG C.
v m Is the velocity, m/s, calculated as:
wherein q is the steam injection flow rate, m 3 And/d, determining on-site construction.
The calculation of the gas compression factor Z is:
A 1 、A 2 、A 3 、A 4 、A 5 、A 6 、A 7 、A 8 respectively take values of
A 1 ＝0.31506237、A 2 ＝-1.0467099、A 3 ＝-0.57832729、A 4 ＝0.53530771、A 5 ＝-0.61232932、A 6 ＝-0.1048813、A 7 ＝0.68157001、A 8 ＝0.68446549
In the formula, A 1 -A 8 The value of the compound is determined by an empirical formula by adopting a method commonly recognized at present, such as Dranchuk, purris and Robinson; t is pr Is the temperature at a location downhole, DEG C, from T f Iteratively solved, or simplified to be equal to T f Are equal.
f m The coefficient of friction resistance of the wet vapor fluid is calculated as:
wherein e is the absolute roughness of the inner wall of the pipe column, and the average oil pipe is 4.57 multiplied by 10 -5 ；
R e Is gas phase Reynolds number, no factor, and the calculation formula is
μ m ＝μ s 1-H ·μ w H (8)
V m ＝XV s +(1-X)V w (10)
In the formula, V T Is the cannula volume; mu.s s And mu w Viscosity of gaseous and liquid water, respectively; v w And V s The volumes of injected liquid water and gaseous water, respectively; v m And H is the intermediate transition amount;
x is dryness and the calculation formula is:
in the formula (I), the compound is shown in the specification,
C 1 ＝i s (h s -h w ) (12)
wherein Q is the heat loss of the shaft, W; h is s For latent enthalpy of vaporization, h w Is the sensible enthalpy of water; adopting a calculation method of W.S.Tortlike and S.M.Farouq Ail; h is m The calculation method is that for the total enthalpy, KJ/kg:
h m ＝Xh s +(1-X)h w (15)
preferably, in the step 2), firstly, curing for two days by using a normal temperature curing box (50 ℃), transferring to a high temperature curing kettle for curing for two days, wherein the curing temperature interval is 50-380 ℃, a tensile strength test is performed by using a press machine, and the method for calculating the tensile strength by using the breaking load of the Brazilian splitting experiment comprises the following steps:
wherein σ t Is tensile strength; d is the diameter of the test piece; l is the thickness of the test piece; p is the breaking load.
Preferably, in the step 3) and the step 5), the model is established without using Tie constraint, namely, the assembly is allowed to be disengaged.
Preferably, in the step 3), the establishing step of the heat conduction model is (1) establishing a component; (2) applying the attribute; (3) assembling the components; (4) an application analysis step; (5) adding an interaction; (6) applying a load; (7) dividing grids; (8) and submitting the operation.
Wherein, step (1) establishes the part: three different parts, namely a casing, a cement sheath and a stratum, are established, and the thickness of the stratum is 10 times of that of the casing-cement sheath combination. The casing size, casing wall thickness, annulus size, and borehole size required to build the components are determined by in situ borehole trajectory parameters.
Step (2) applying attributes: the properties of the casing including casing density, casing modulus of elasticity, casing poisson's ratio, casing coefficient of thermal expansion, casing thermal conductivity are given by the job site. The attributes of the stratum comprise rock density, rock elastic modulus, rock Poisson ratio, rock thermal conductivity, rock thermal expansion coefficient, rock porosity and rock permeability, the density of the set cement, the thermal conductivity of the set cement, the thermal expansion coefficient of the set cement, the porosity of the set cement and the permeability of the set cement are all determined by construction site stratum reports, and the data of the currently common 1000-meter stratum model parameters are shown in the table 1. The relation between the elastic modulus and the Poisson ratio of the cement sheath and the temperature change is large, so that the step 2) provides that when the elastic parameters are set, the temperature-related data options are selected and used, and the cement stone elastic modulus and the Poisson ratio data obtained in the step 2) are input to form a maintenance temperature value.
Assembling parts in step (3): and selecting a creation component option to create dependent examples of the casing, the cement sheath and the stratum.
Step (4) applying an analysis step: a transient heat transfer analysis step is applied.
Step (5) adding interaction: and adding heat conduction properties between the casing and the cement sheath and between the cement sheath and the stratum.
Step (6) applying a load: temperature boundary conditions are added to the inner wall of the casing and predefined temperature conditions are added.
Step (7) grid division: the object is selected to be a part and the mesh type is DC3D8.
(8) And submitting the operation.
The heat conduction model referred to herein is defined as: the method is characterized in that components made of different materials are built by software, the temperature is applied to the inner wall of the sleeve, and the characteristic that heat energy is transferred from high temperature to low temperature is utilized, so that the temperature is transferred among the different materials.
Preferably, in the step 5), the establishing step of the thermo-fluid-solid coupling model is (1) establishing a component; (2) applying the attribute; (3) assembling the components; (4) an analysis step is applied; (5) adding an interaction; (6) applying a load; (7) dividing grids; (8) and submitting the operation.
Step (1) establishing a component: three different components, casing, cement sheath and formation, were created, the formation thickness being 10 times the casing-cement sheath combination. The casing size, casing wall thickness, annulus size, and borehole size required to build the components are determined by in situ borehole trajectory parameters.
Step (2) applying attributes: the properties of the casing including casing density, casing modulus of elasticity, casing poisson's ratio, casing coefficient of thermal expansion, casing thermal conductivity are given by the job site. The attributes of the stratum comprise rock density, rock elastic modulus, rock Poisson ratio, rock thermal conductivity, rock thermal expansion coefficient, rock porosity and rock permeability, the density of the set cement, the thermal conductivity of the set cement, the thermal expansion coefficient of the set cement, the porosity of the set cement and the permeability of the set cement are all determined by construction site stratum reports, and the data of the currently common 1000-meter stratum model parameters are shown in the table 1. The relation between the elastic modulus and the Poisson ratio of the cement sheath and the temperature change is large, so that the step 2) provides the elastic parameters, and when the elastic parameters are set, the temperature-related data options are selected and used, and the cement stone elastic modulus and the Poisson ratio data obtained in the step 2) and the maintenance temperature value are input.
Assembling parts in step (3): and selecting a creation component option to create non-independent examples of the casing, the cement sheath and the stratum.
Step (4) applying an analysis step: 2 analysis steps are applied, wherein one step is a ground stress balance analysis step, and the other step is a transient soil analysis step; the load is applied to the inner wall of the casing, the calculation method is shown in the formulas 1-16, the size is shown in figures 8, 10 and 12, and the calculation method is determined by actual construction data.
The purpose of the geostress equilibrium analysis step described here is to automatically balance the geostress and the purpose of the transient soil analysis step is to see the set cement-formation as permeable rock.
Step (5) adding interaction: and adding heat conduction properties between the casing and the cement sheath and between the cement sheath and the stratum.
Step (6) applying a load: a target horizon load is applied at the casing inner boundary, an outer boundary with a pore pressure of 0 is applied at the formation outer boundary, and a predefined pore ratio and a predefined temperature are applied.
Step (7) grid division: the object is selected as a component, the casing mesh type is C3D8R, and the set cement and formation mesh type is C3D8P.
And (8) submitting the operation.
The definition of the thermo-fluid-solid coupling model is as follows: establishing a new fluid-solid coupling model, wherein the model has the interaction between fluid and solid, and introducing the result in the heat conduction model, namely the temperature at each node of the part into the newly established model so that the temperature exerts an effect on the fluid-solid coupling model.
TABLE 1 common casing-cement sheath-formation parameter table
Preferably, in the step 6), the shear failure factor and the radial cracking failure factor are defined as eta respectively c And η t The formulas are respectively as follows:
when eta c And η t When the stress exceeds 1, the cement sheath respectively generates shear failure and radial cracking failure;
for the micro-annular gap discrimination method, use
An interface r o ＝r if -r oc ＞0
Two interfaces r i ＝r ic -r ot ＞0 (19)
In the formula, σ i (i =1,2, 3) is the maximum, intermediate and minimum principal stress in the cement ring, MPa, calculated in step 6;
is the internal friction angle, rad, of set cement; sigma H For tensile strength, the results are calculated in step 6; sigma max For the experimental results, as shown in fig. 4, it is related to the cement curing temperature; r is if The distance from the center of the casing to an interface of the cement sheath; r is a radical of hydrogen oc The distance from the center of the sleeve to the outer wall of the sleeve; r is ic The distance from the center of the casing to the inner boundary of the stratum; r is a radical of hydrogen ot Is the distance, r, from the center of the casing to the outer boundary of the cement sheath if 、r oc 、r ic 、r ot The results are calculated in step 6).
Compared with the prior art, the invention has the following advantages:
1) Combining the strength decline of the set cement with the damage of the set cement under high temperature and high pressure by a Mogi-Coulomb damage criterion;
2) A thermal-fluid-solid coupling model is established, and the calculation can be correctly carried out to obtain a corresponding research result; 3) The invention relates to a set of complete method for researching the well cementation and sealing integrity of a thermal production well, and realizes the method for obtaining the failure evaluation of a cement sheath only by utilizing the parameters of on-site steam injection.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a schematic diagram of the technical scheme of the present invention.
Fig. 2 is a schematic technical route of the thermo-fluid-solid coupling model.
FIG. 3 shows the compressive strength of cement at different temperatures in the examples.
FIG. 4 shows the tensile strength of cement at different temperatures in the examples.
FIG. 5 shows the modulus of elasticity of cement at different temperatures in the examples.
FIG. 6 shows the Poisson's ratio of the cement at different temperatures in the examples.
FIG. 7 is a graph of steam injection rate versus wellbore quality for the examples.
FIG. 8 is a graph of steam injection rate versus wellbore pressure for the examples.
FIG. 9 is a graph of steam injection pressure versus wellbore dryness for the examples.
FIG. 10 is a graph of steam injection pressure versus wellbore pressure for an example embodiment.
FIG. 11 is a graph of steam injection temperature versus wellbore quality for the examples.
FIG. 12 is a graph of steam injection temperature versus wellbore pressure for the examples.
Detailed Description
The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention should not be construed as limiting the implementable scope of the present invention.
The embodiment obtains thermal production well construction parameters from a construction site, including wellhead steam injection parameters (steam injection pressure, temperature, rate, steam injection time), well trajectory parameters (casing size, casing wall thickness, annulus size, drilled borehole size, target horizon depth), casing property parameters (density, elastic modulus, poisson's ratio, thermal expansion coefficient, thermal conductivity), formation property parameters (density, elastic modulus, poisson's ratio, thermal conductivity, thermal expansion coefficient, porosity, permeability), and set cement property parameters (density, thermal conductivity, thermal expansion coefficient, porosity, permeability). And (3) introducing the acquired parameters (or given data, such as table 1) into the components or attributes, calculating target horizon loads (including temperature and pressure) by using formulas 1-6, and acquiring cement elastic modulus and Poisson's ratio parameters by using the step 2).
Solving and calculating the formulas 1 to 6 to obtain the changes of the pressure and the dryness in the shaft under the conditions of different steam injection temperatures, different steam injection pressures and different steam injection rates, as shown in figures 7 to 12.
In the embodiment, a commonly used formulation (Jiahua grade G cement and silica sand) of the thermal production well cementing cement slurry is adopted, the calcium-silicon ratio is 1. The cement paste was cured at room temperature (50 ℃) using a standard mold of 50mm × 50mm × 50mm for 2d in order to simulate the case where the formation temperature is not high during cementing.
And after the set cement is completely hydrated, performing high-temperature curing on the set cement for 2d by using a high-temperature curing kettle, and simulating the construction condition of the thermal production well. The curing temperature is 50 deg.C, 75 deg.C, 90 deg.C, 120 deg.C, 150 deg.C, 190 deg.C, 230 deg.C, 265 deg.C, 300 deg.C, 340 deg.C, 380 deg.C, respectively.
And after the maintenance is finished, coring the cement blocks by using a coring machine, wherein the coring diameter is 25mm, and the coring length is 50mm.
And testing the compressive strength of the cured cement block by using a press, and calculating the tensile strength by using a Brazilian splitting experiment after coring, wherein the calculation formula is shown as a formula 7. The elastic modulus and poisson ratio under different curing temperature conditions were tested by using a three-axis testing machine, and the results are shown in fig. 3-6.
In FIG. 3, the compressive strengths of the cement at different temperatures are fitted in a segmented manner to obtain the compressive strength σ c The relationship with temperature T is:
in FIG. 4, the tensile strength of cement under different temperature conditions is fitted in a segmented manner to obtain the tensile strength σ H The relationship with temperature T is:
establishing a heat conduction model: establishing three different parts which are respectively a casing, a cement sheath and a stratum, wherein the sizes of the parts are determined by well structure parameters obtained on site, the parameters comprise the casing size, the casing wall thickness, the annular size and the size of a drilled hole, the stratum thickness is 10 times of that of a casing-cement sheath combination body, importing the obtained relational values of the elastic modulus and the Poisson ratio of the set cement and the parameters (or given data, such as table 1) of the stratum, the casing and other cement sheaths obtained on site into ABAQUS software to be set as cement parameters, selecting and using data options related to temperature when setting the cement elasticity parameters, and inputting the elastic modulus and the Poisson ratio data obtained in the step 2) and maintenance temperature values. Simulating the strength degradation condition of the high-temperature set cement, establishing a heat conduction analysis step, establishing boundary conditions, and applying temperature boundary conditions, wherein the size of the boundary conditions is the steam injection temperature data given by the construction site in the step 1). The analysis step time is determined according to the steam injection time, the steam injection temperature and pressure applying part is the inner wall of the casing, and the size is determined according to the model calculation result. The predefined temperature is set to the actual temperature of the formation. The units of casing-cement sheath-stratum are all DC3D8.
After the operation is submitted and the operation is finished, an ODB file of the heat conduction model is found under the working path, and the ODB file records the temperature distribution of different units and nodes at different times in the casing-cement sheath-stratum assembly and provides conditions for establishing a subsequent heat-fluid-solid coupling model.
Establishing a heat-fluid-solid coupling model: similarly, three different parts are established, namely a casing, a cement sheath and a stratum, the sizes of the parts are determined by structural parameters of a well body obtained on site, the structural parameters comprise the casing size, the casing wall thickness, the annular size and the drilled hole size, the stratum thickness is 10 times of that of a casing-cement sheath combination, the relation values of the elastic modulus and the poisson ratio of the obtained set cement and the parameters of the stratum, the casing and other cement sheaths obtained on site (or given data, such as table 1) are led into ABUS software to be set as cement parameters, when the cement elastic parameters are set, data options related to temperature are selected, and the elastic modulus and the poisson ratio data obtained in the step 2) and maintenance temperature values (formula 11, formula 12 or figures 5 and 6) are input. Simulating the strength degradation condition of the high-temperature set cement, and establishing two different analysis steps, wherein the first analysis step is used for automatically balancing the ground stress. The second analysis step is a soil body analysis step for applying a fluid-solid coupling model, and selecting values needing to be considered such as NT (node temperature), TEMP (unit temperature), COORD (node coordinate) and the like in field output. And establishing a pressure load in the second analysis step, wherein the load is the target horizon pressure data calculated in the step 1), and the outer boundary of the stratum is defined as a pore pressure boundary, and the pore pressure is 0. In the predefined field, a predefined temperature field is applied in the second analysis step, the area of the temperature field is selected as the whole component, and the ODB file is imported, which is the most critical step of the thermo-fluid-structure coupling model. And finally, setting initial ground stress according to actual stratum parameters and balancing the stress by adopting an automatic ground stress balancing mode. And the casing unit is C3D8R, and the units of the cement sheath and the stratum are all C3D8P, and solving calculation is carried out.
The operation method for automatically balancing the ground stress comprises the following steps: when the analysis step module is applied, a ground stress analysis step is selected, the type of the increment step is selected to be automatic, the matrix storage is selected to be an asymmetric and direct iteration method, and the geometric non-linear option is closed.
Changing construction conditions, such as different steam injection pressures, different steam injection times, different steam injection temperatures and different steam injection rates; changing formation parameters, such as different formation elastic moduli, different formation poisson ratios, and different formation permeability coefficients; and (4) considering complex working conditions at the bottom of the well, such as different cement sheath thicknesses and different casing eccentricity. And performing submission operation again to achieve the analysis and evaluation of the sealing integrity of the cement sheath of the thermal production well under different working conditions, wherein the submitted JOB names are different so as to facilitate the operation of post-processing.
And (3) deriving the temperature distribution from the first interface to the second interface of the cement sheath, and deriving the temperature distribution condition of the first interface and the second interface along with the change of time. The maximum principal stress, the intermediate principal stress and the minimum principal stress are respectively led out to be sigma through ABAQUS post-treatment 1 、σ 2 、σ 3 ，σ c For compressive strength at different temperatures, the shear failure factor η is shown in FIG. 3 c The calculation formula is formula (8), wherein sigma c Determined according to equation 11 and the temperature profile. Deriving the circumferential stress S22 toσH，σ max Tensile strength at different temperatures, as shown in fig. 4. Radial crack failure factor eta t The calculation formula is formula 9, wherein σ H According to the formula 12 and the temperature distribution. The distances of the casing-cement sheath interface and the cement sheath-stratum interface are led out to be r respectively o And r i The formula for calculating the interface failure is equation 10. When eta c And η t When the stress exceeds 1, the cement sheath respectively generates shear failure and radial cracking failure; when r is o And r i Above 0, interfacial failure of the cement sheath occurs.
Further, it should be noted that various modifications, additions and substitutions for the specific embodiments described are possible to those skilled in the art. It should be understood that other embodiments and equivalent substitutions for parts of technical features can be made by those skilled in the art without inventive step without departing from the spirit of the technical solution of the present invention, and the technical solution of the present invention is covered by the protection scope of the present invention.
Claims (7)
1. A method for evaluating the sealing integrity of a cement sheath of a thermal production well is characterized by comprising the following steps: the method comprises the following steps:
1) Acquiring construction parameters of a thermal production well;
2) Curing the set cement under different temperature conditions and testing the performance of the set cement, including compressive strength, tensile strength, elastic modulus and Poisson ratio;
3) Establishing a heat conduction model of the casing-cement sheath-stratum combination based on the data in 1) and 2);
4) Calculating the heat conduction model to obtain an ODB file;
5) Establishing a thermo-fluid-solid coupling model of the casing-cement sheath-stratum combination based on the data of 1) and 2);
6) Solving the heat fluid-solid coupling model imported into the ODB file and analyzing a numerical result, wherein the analysis content comprises the temperature distribution of set cement, the circumferential stress and the shearing stress of the set cement and whether a micro annular gap appears on a first interface and a second interface;
in the step 3), the heat conduction model is established by the following steps:
step (1) establishing a component: establishing three different parts which are respectively a casing, a cement sheath and a stratum, wherein the thickness of the stratum is 10 times of that of the casing-cement sheath combination;
step (2) applying attributes: the properties of the sleeve, including the sleeve density, the sleeve elastic modulus, the sleeve Poisson ratio, the sleeve thermal expansion coefficient and the sleeve thermal conductivity, are given by a construction site; the attributes of the stratum comprise rock density, rock elastic modulus, rock Poisson ratio, rock thermal conductivity, rock thermal expansion coefficient, rock porosity and rock permeability, and the cement density, the cement thermal conductivity, the cement thermal expansion coefficient, the cement porosity and the cement permeability are determined by parameters reported by the stratum of the construction site; the relation between the elastic modulus and the Poisson ratio of the cement sheath and the temperature change is large, the relation is given by the step 2), when the elastic parameters are set, data options related to the temperature are selected and used, and the cement stone elastic modulus and the Poisson ratio data obtained in the step 2) are input to form a maintenance temperature value;
assembling parts in step (3): selecting a creation component option, and creating non-independent examples of a casing, a cement sheath and a stratum;
step (4) applying an analysis step: applying a transient heat transfer analysis step;
step (5) adding interaction: adding heat conduction properties between the casing and the cement sheath and between the cement sheath and the stratum;
step (6) applying a load: adding a temperature boundary condition on the inner wall of the sleeve, and adding a predefined temperature condition;
step (7) grid division: selecting an object as a component and a grid type as DC3D8;
and (8) submitting the operation.
2. The method for evaluating the sealing integrity of a cement sheath for a thermal production well according to claim 1, wherein: the hot production well construction parameters in the step 1) comprise well mouth steam injection parameters, well bore track parameters, casing pipe attribute parameters, stratum attribute parameters, cement stone attribute parameters and target horizon load; the wellhead steam injection parameters comprise steam injection pressure, temperature, speed and steam injection time; the well trajectory parameters comprise casing size, casing wall thickness, annulus size, drilled wellbore size and target horizon depth; the property parameters of the sleeve comprise density, elastic modulus, poisson's ratio, thermal expansion coefficient and thermal conductivity; the attribute parameters of the stratum comprise density, elastic modulus, poisson's ratio, thermal conductivity, thermal expansion coefficient, porosity and permeability; the attribute parameters of the set cement comprise density, thermal conductivity, thermal expansion coefficient, porosity and permeability; the target horizon load comprises temperature and pressure.
3. The method for evaluating the sealing integrity of the cement sheath of a thermal production well according to claim 2, wherein: the target horizon load calculation method in the step 1) is as follows:
1) Temperature change in the wellbore: the steam temperature in the oil pipe is regarded as corresponding to the ground temperature, i.e.
T＝T sur (t)(0＜t≤t end ) (1)
Wherein t is time; t is the steam temperature, DEG C; t is sur (t) is the ground temperature, DEG C;
2) The pressure drop in the well bore is calculated by the formula:
wherein, p-mean pressure, p a (ii) a z-well depth, m; d-the internal diameter of the gas transmission pipeline, m; a. The p Is the cross-sectional area of the oil pipe, m 2 ；i s -steam mass flow, kg/h; q. q.s g Steam volume flow, m 3 /h；p、i s 、q g All the steps are determined by site construction;
ρ m is density, kg/m 3 The calculation formula is as follows:
in the formula, M is the molecular weight of gas and has no dimension; r is a general gas constant, and is generally R = 8.314J/(mol) -1 ·℃ -1 ) (ii) a Gamma is gas specific gravity, and has no dimension; t is f Gas temperature, deg.C;
v m is the velocity, m/s, calculated as:
wherein q is the steam injection flow rate, m 3 Determining site construction;
the calculation of the gas compression factor Z is:
A 1 、A 2 、A 3 、A 4 、A 5 、A 6 、A 7 、A 8 respectively take values of
A 1 ＝0.31506237、A 2 ＝-1.0467099、A 3 ＝-0.57832729、A 4 ＝0.53530771、A 5 ＝-0.61232932、A 6 ＝-0.1048813、A 7 ＝0.68157001、A 8 ＝0.68446549
In the formula, A 1 -A 8 The value of (A) is determined by an empirical formula by adopting a method generally accepted at present, such as Dranchuk, purris and Robinson; t is pr Is the temperature at a location downhole, DEG C, from T f Iterative solution, or simplification to sum with T f Equal; rho pr Is the pseudo-contrast density;
f m the coefficient of friction resistance of the wet vapor fluid is calculated as:
wherein e is the absolute roughness of the inner wall of the column,the common oil pipe is generally 4.57 multiplied by 10 -5 ；
R e Is gas phase Reynolds number, no factor, and the calculation formula is
μ m ＝μ s 1-H ·μ w H (8)
V m ＝XV s +(1-X)V w (10)
In the formula, V T Is the cannula volume; mu.s s And mu w Viscosity of gaseous and liquid water, respectively; v w And V s The volumes of injected liquid water and gaseous water, respectively; v m And H is the intermediate transition amount;
x is dryness and the calculation formula is as follows:
in the formula (I), the compound is shown in the specification,
C 1 ＝i s (h s -h w ) (12)
wherein Q is the heat loss of the shaft, W; h is s For latent enthalpy of vaporization, h w Is the sensible enthalpy of water; adopting a calculation method of W.S.Tortlike and S.M.FarouqAil; h is m Is a total ofEnthalpy, KJ/kg, is calculated by:
h m ＝xh s +(1-x)h w (15)。
4. the method for evaluating the sealing integrity of a cement sheath for a thermal production well according to claim 1, wherein: in the step 2), firstly, a normal-temperature curing box is used for curing for two days at 50 ℃, the normal-temperature curing box is transferred into a high-temperature curing kettle for curing for two days, the curing temperature interval is 50-380 ℃, a press machine is used for testing the tensile strength, and the method for calculating the tensile strength by using the breaking load of the Brazilian splitting experiment comprises the following steps:
wherein σ t Is tensile strength; d is the diameter of the test piece; l is the thickness of the test piece; p is the breaking load.
5. The method for evaluating the sealing integrity of a cement sheath for a thermal production well according to claim 1, wherein: in the step 3) and the step 5), the model building does not use Tie constraint, namely the assembly is allowed to be separated.
6. The method for evaluating the sealing integrity of a cement sheath for a thermal production well according to claim 1, wherein: in the step 5), the establishing step of the thermo-fluid-solid coupling model is as follows:
step (1) establishing a component: establishing three different parts which are respectively a casing, a cement sheath and a stratum, wherein the thickness of the stratum is 10 times of that of the casing-cement sheath combination;
step (2) applying attributes: the properties of the sleeve, including sleeve density, sleeve elastic modulus, sleeve Poisson ratio, sleeve thermal expansion coefficient and sleeve thermal conductivity, are given by a construction site; the attributes of the stratum comprise rock density, rock elastic modulus, rock Poisson ratio, rock thermal conductivity, rock thermal expansion coefficient, rock porosity and rock permeability, and the cement density, the cement thermal conductivity, the cement thermal expansion coefficient, the cement porosity and the cement permeability are determined by parameters reported by the stratum of the construction site; the relation between the elastic modulus and the Poisson ratio of the cement sheath and the temperature change is large, the relation is given by the step 2), when the elastic parameters are set, data options related to the temperature are selected and used, and the cement stone elastic modulus and the Poisson ratio data obtained in the step 2) are input to form a maintenance temperature value;
assembling parts in step (3): selecting a creation component option, and creating non-independent examples of a casing, a cement sheath and a stratum;
step (4) applying an analysis step: 2 analysis steps are applied, one is a geostress balance analysis step, and the other is a transient soil analysis step; applying a load to the inner wall of the casing;
step (5) adding interaction: adding heat conduction properties between the casing and the cement sheath and between the cement sheath and the stratum;
step (6) applying a load: applying a target horizon load at the inner boundary of the casing, applying an outer boundary with pore pressure of 0 at the outer boundary of the stratum, and applying a predefined pore ratio and a predefined temperature;
step (7) grid division: selecting an object as a component, wherein the type of a casing grid is C3D8R, and the type of a cement stone and stratum grid is C3D8P;
and (8) submitting the operation.
7. The method for evaluating the sealing integrity of a cement sheath for a thermal production well according to claim 1, wherein: in the step 6), defining the shear failure factor and the radial cracking failure factor as eta respectively c And η t The formulas are respectively as follows:
when eta c And η t When the cement sheath diameter exceeds 1, the cement sheath respectively generates shearing failure and diameterFailure towards cracking;
for the micro-annular space discrimination method, use
An interface r o ＝r if -r oc ＞0
Two interfaces r i ＝r ic -r ot ＞0 (19)
In the formula, σ i (i =1,2,3) are the maximum, intermediate and minimum principal stresses in the cement annulus, MPa, calculated in step 6;
is the internal friction angle, rad, of set cement; sigma H For tensile strength, the results are calculated in step 6; sigma max The experimental result is related to the cement curing temperature; r is if The distance from the center of the casing to an interface of the cement sheath; r is oc The distance from the center of the sleeve to the outer wall of the sleeve; r is ic The distance from the center of the casing to the inner boundary of the stratum; r is ot Is the distance from the center of the casing to the outer boundary of the cement sheath, r if 、r oc 、r ic 、r ot The results are calculated in step 6. />
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| CN113688533B (en) * | 2021-09-01 | 2022-08-26 | 西南石油大学 | Calculation method for predicting annular equivalent circulating density of well cementation cement injection |
| CN115992669A (en) * | 2021-10-20 | 2023-04-21 | 中国石油天然气股份有限公司 | Formula development method of cement slurry for thermal production well |
| CN117235839B (en) * | 2022-09-16 | 2024-04-19 | 中国葛洲坝集团三峡建设工程有限公司 | Shaft cement sheath safe load calculation method based on self-balancing stress field analysis |
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