Deep fractured formation borehole wall collapse pressure prediction method and related device

Abstract

The invention belongs to the technical field of deep fractured formation drilling. The invention discloses a deep fractured formation borehole wall collapse pressure prediction method and a related device. The method comprises the following steps: calculating a pore pressure field and a surrounding rock stress field of surrounding rock of a fractured formation under a non-uniform crustal stress condition by utilizing a control equation of a pore chemical elasticity theory; and calculating the borehole wall collapse pressure of the deep fractured formation by using a pore pressure field, a surrounding rock stress field and a three-dimensional Hook-Brownian criterion of the surrounding rock of the fractured formation under the condition of non-uniform ground stress under the flow solidification coupling effect. According to the invention, the pressure transmission process from the drilling fluid to the microcracks around the well can be simulated, the solute concentration difference between the drilling fluid and the formation water, the relationship between the rock crushing degree and the borehole wall collapse pressure are quantified, the fine dynamic design of the collapse pressure of the deep fractured layer is realized, and a theoretical support is provided for preventing the collapse accident of the fractured layer.

Description

Technical Field

[0001] This invention belongs to the field of drilling technology for deep fractured formations, specifically relating to a method and related apparatus for predicting wellbore collapse pressure in deep fractured formations. Background Technology

[0002] In deep oil and gas exploration and development, fractured formations are frequently encountered. Due to the high degree of fracture connectivity and low overall strength of fractured formations, wellbore instability and collapse are prone to occur. Therefore, the frequent occurrence of well collapse has become a major obstacle to drilling in deep fractured formations. During deep formation drilling, in terms of fluid-structure interaction (Detournay E. and Cheng A.HD, "Poroelastic response of a borehole in a non-hydrostatic stressfield"), the stress difference (normal stress and shear stress) and pressure difference (difference between fluid column pressure and original pore pressure) at the wellbore wall before and after drilling disturb the surrounding rock field variables (wellbore stability assessment focuses more on pore pressure field and stress field). Furthermore, when drilling into active formations (such as clay media in rocks with non-ideal semi-permeable membrane properties), the chemical potential (or solute-cation / anion concentration) difference between the drilling fluid and the formation pore fluid induces the entry and exit of solutes (ions) into and out of the formation, resulting in additional pore pressure and stress increases (decreases) in the wellbore field variables—a chemical-flow-stress coupling process (Heidug, WK, and Wong S.W., "Hydration swelling of water absorbing rocks: A constant model" and Ghassemi A. and Diek A., "Linear chemo-poroelasticity for swelling shales: theory and application"). This comprehensive fluid-solidification coupling process leads to a redistribution of the rock field variables around the well, determining the wellbore stability of this type of formation. Accurately describing this coupling process is crucial for understanding the wellbore collapse mechanism in this type of formation and providing corresponding engineering countermeasures. Clearly, the conventional linear elastic model (Bradley, WB, "Failure of Inclined Borehole") cannot reflect the influence of the fluid-solidification coupling process on the stress field and collapse pressure of the surrounding rock.

[0003] Currently, various methods exist for predicting the equivalent density of wellbore collapse pressure in fractured formations. For example, the invention patent No. ZL 201510077224.7 from China University of Petroleum discloses a method for predicting the equivalent density window of collapse pressure in weak-plane formations. This method includes dividing the weak-plane formation into a tight section and a fractured section based on its characteristics; testing the rock bulk strength and weak-plane strength using a triaxial compression test; determining the lower limit of the equivalent density of collapse pressure in tight formations by inverting the stress distribution and pore pressure distribution of the surrounding rocks using a fluid-structure interaction model, and combining this with the Mohr-Coulomb failure criterion; analyzing the failure state of the surrounding rocks in weak-plane formations using a weak-plane failure criterion to determine the lower and upper limits of the equivalent density window of collapse pressure in fractured formations; and comparing the equivalent density values ​​of collapse pressure in the tight section (lower limit) and the equivalent density values ​​of collapse pressure in the fractured section (lower and upper limits) to determine the equivalent density window of collapse pressure in weak-plane formations.

[0004] Southwest Petroleum University's invention patent ZL 201910705023.5 discloses an experimental system and method for pore pressure transmission under hydraulic-chemical coupling. This invention can simulate the pore pressure transmission of circulating drilling fluid under formation conditions under the combined effects of hydraulic pressure difference, chemical potential difference, and hydraulic and chemical potential differences, obtaining the degree and variation law of the influence of each factor on pore pressure. However, this method cannot predict the influence of pore pressure on the wellbore stress field, and therefore cannot accurately design the wellbore collapse pressure in (ultra)deep fractured formations.

[0005] Although the two patents and other existing technical solutions mentioned above have achieved certain technical effects, they cannot reasonably and accurately predict the wellbore collapse pressure of (ultra)deep fractured formations subjected to fluid-solidification coupling, thus limiting on-site operations and causing frequent stuck drill bits and stuck pipe. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention aims to provide a method and related device for predicting wellbore collapse pressure in deep fractured formations. The present invention can achieve precise design of wellbore collapse pressure in deep fractured formations, thereby solving the complex problems of frequent wellbore collapse and stuck drill in deep fractured formations.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for predicting wellbore collapse pressure in deep fractured formations includes the following steps:

[0009] The pore pressure field and surrounding rock stress field of fractured formations under non-uniform geostress conditions were calculated using the governing equations of pore chemical elasticity theory.

[0010] By utilizing the pore pressure field of the surrounding rock under fluid-solidification coupling effect in fractured formations under non-uniform geostress conditions, the stress field of the surrounding rock, and the three-dimensional Hawke-Brown criterion, the wellbore collapse pressure in deep fractured formations is calculated.

[0011] Preferably, the expression for the pore pressure field of the rock surrounding the well in the fractured formation under the non-uniform geostress condition, subjected to the fluid-solidification coupling effect, is as follows;

[0012] p = p0 + p (a) +p (d)

[0013] In the formula, p is the wellbore pore pressure, in MPa; p0 is the initial formation pore pressure, in MPa; p (a) p represents the increment of wellbore pore pressure induced by axisymmetric loading, in MPa. (d) This represents the increment of wellbore pore pressure induced by non-axisymmetric load, expressed in MPa.

[0014] Preferably, the surrounding rock stress field of the fractured formation under the non-uniform geostress condition, subjected to fluid-solidification coupling, is as follows:

[0015]

[0016] In the formula, σ r σ represents the radial stress on the rock surrounding the well, expressed in MPa. θ σ is the tangential stress on the surrounding rock of the well, in MPa; zz θ represents the axial stress on the surrounding rock of the well, expressed in MPa; r Define as an intermediate quantity for angle conversion The unit is degrees, where, The value represents the principal stress around the well in the x-direction of the xy plane in a rectangular coordinate system, in MPa. The value represents the principal stress around the well in the y direction of the xy plane in a rectangular coordinate system, in MPa. σ represents the wellbore shear stress in the xy-plane of a rectangular coordinate system, in MPa; θ is the wellbore angle, the angle between the radius vector of the studied location and the azimuth of the maximum horizontal stress, in degrees; σ r (a) σ represents the increment of radial stress around the well induced by axisymmetric loading, in MPa. r (d) σ represents the increment of radial stress around the well induced by non-axisymmetric load, in MPa. z b σ represents the axial stress around the well in the z-direction of a rectangular coordinate system, in MPa; v is Poisson's ratio, dimensionless; σ θ (a) σ represents the increment of tangential stress around the well induced by axisymmetric loading, in MPa.θ (d) α' represents the increment of tangential stress around the well induced by non-axisymmetric load, in MPa; α' is the Biot coefficient of fluidization coupling, in dimensionless units; p (a) χ represents the increment of wellbore pore pressure induced by axisymmetric loading, in MPa; χ is the chemical coupling coefficient related to the chemical stress induced by the solute mass fraction difference, in MPa; C S(a) α is the dimensionless increment of solute mass percentage induced by axisymmetric loading; α is the Biot coefficient, dimensionless; p (d) τ represents the increment of wellbore pore pressure induced by axisymmetric loading, in MPa. rθ The shear stress is the stress on the rock surrounding the well in the r-θ plane of the cylindrical coordinate system, in MPa. τ represents the additional shear stress increment induced by fluid-structure interaction in the surrounding rock of the well in the r-θ plane of cylindrical coordinates, expressed in MPa; rz The out-of-plane shear stress relative to the r-θ plane experienced by the rock surrounding the well in cylindrical coordinates, expressed in MPa. denoted as , where is the out-of-plane stress in the xy-plane rectangular coordinate system, in MPa; is the out-of-plane shear stress relative to the r-θ plane on the surrounding rock in the cylindrical coordinate system, in MPa; r is the radial distance from the wellbore center to a certain location inside the formation, in meters; a is the wellbore radius, in meters; P0 is the average formation stress; and S0 is the shear stress.

[0017] Preferably, the C S The following relationship must be satisfied:

[0018]

[0019] In the formula, C S This represents the percentage of solute mass around the well. This represents the initial percentage of solute mass.

[0020] Preferably, the formation mean stress P0 and shear stress S0 are calculated using the following formula:

[0021]

[0022] Among them, the principal stress components of the wellbore coordinate system and shear stress components Depend on Determine, where i, j ∈ x, y, z, and the in-situ stress matrix σ ics The transformation matrix I from the in-situ stress coordinate system to the geodetic coordinate system and the transformation matrix b from the GCS to the wellbore coordinate system are defined as follows:

[0023]

[0024] Among them, Ω i γ is the angle between the azimuth of the maximum horizontal ground stress and true north, in degrees; i Ω represents the angle between the pressure of the overlying strata and the vertical direction, expressed in degrees. b γ is the wellbore azimuth angle in degrees; b σ is the well inclination angle, in degrees; H σ represents the maximum horizontal ground stress, expressed in MPa. h σ represents the minimum horizontal ground stress, expressed in MPa. v The pressure of the overlying strata is expressed in MPa; the intermediate conversion angle is θ. r Defined as The unit is degrees.

[0025] Preferably, the three-dimensional Hawke-Brown criterion is as follows:

[0026]

[0027] In the formula, τ oct It is the octahedral shear stress, with units of MPa; σ′ m Mean effective stress, measured in MPa; GSI is the geological strength index, dimensionless; m b σ and s are related to the integrity of the rock mass type and the degree of weathering, respectively, and are dimensionless; the disturbance coefficient D varies from 0 to 1 and is dimensionless; σ′1 is the maximum effective principal stress, σ′2 is the intermediate effective principal stress, and σ′3 is the minimum effective principal stress, with units of MPa;

[0028] The process of calculating wellbore collapse pressure in deep fractured formations using the pore pressure field of the surrounding rock under fluid-solidification coupling in fractured formations under non-uniform geostress conditions, the surrounding rock stress field, and the three-dimensional Hawke-Brown criterion includes:

[0029] Given the inclination angle and azimuth angle, the wellbore fluid column pressure is increased from 0 to a preset value. A judgment condition is met. At that time, the collapse pressure matrix corresponding to the well perimeter angle is obtained, where m is the dimensionless error allowable value that satisfies the judgment condition;

[0030] The maximum collapse pressure value in the collapse pressure matrix is ​​selected as the collapse pressure value corresponding to the given well inclination angle and azimuth angle.

[0031] Preferably, the upper limit of the wellbore fluid column pressure is not less than the maximum horizontal principal geostress σ. H .

[0032] This invention also provides a system for predicting wellbore collapse pressure in deep fractured formations, comprising:

[0033] Field variable calculation module: Based on the acquired geological parameters, it is used to calculate the pore pressure field and surrounding rock stress field of fractured formations under non-uniform geostress conditions by using the governing equations of pore chemical elasticity theory.

[0034] Pressure Calculation Module: Used to calculate wellbore collapse pressure in deep fractured formations by utilizing the pore pressure field, surrounding rock stress field, and three-dimensional Hawke-Brown criterion under non-uniform geostress conditions, which are influenced by the fluid-solidification coupling effect of the surrounding rock.

[0035] The present invention also provides an electronic device, comprising:

[0036] One or more processors;

[0037] A storage device on which one or more programs are stored;

[0038] When the one or more programs are executed by the one or more processors, the one or more processors implement the deep fractured formation wellbore collapse pressure prediction method of the present invention as described above.

[0039] The present invention also provides a storage medium storing a computer program thereon, wherein the computer program, when executed by a processor, implements the method for predicting wellbore collapse pressure in deep fractured formations as described above.

[0040] The present invention also provides a computer program product comprising computer instructions, characterized in that the computer instructions instruct a computer to execute the deep fractured formation wellbore collapse pressure prediction method of the present invention as described above.

[0041] The present invention has the following beneficial effects.

[0042] The method for calculating wellbore collapse in deep fractured formations provided by this invention utilizes the governing equations of pore chemical elasticity theory to calculate the field variables of the surrounding rock under fluid-solidification coupling under non-uniform geostress conditions. These field variables include the pore pressure field and the surrounding rock stress field. The calculation of the surrounding rock stress field considers the solute mass fraction field. This invention can simulate the pressure transmission process of drilling fluid to the microfractures around the well, quantify the solute concentration difference (activity difference) between drilling fluid and formation water, and the relationship between the degree of rock fracturing and wellbore collapse pressure. This enables precise dynamic (time-dependent) design of collapse pressure in deep fractured formations, providing theoretical support for preventing fractured formation collapse accidents. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a technical roadmap of the method for predicting wellbore collapse pressure in deep fractured formations, as described in this invention.

[0045] Figure 2 The graph shows the variation of the equivalent density of collapse pressure with time and drilling fluid type (solute concentration difference) obtained in the embodiments of the present invention (basic data source: QSH group 7972m of well X1);

[0046] Figure 3(a) shows the variation of the equivalent density of collapse pressure with time, formation fracturing degree, and drilling fluid type (solute concentration difference) obtained in the embodiment of the present invention (wherein, GSI = 50, basic data source: QSH group 7972m of well X1); Figure 3(b) shows the variation of the equivalent density of collapse pressure with time, formation fracturing degree, and drilling fluid type (solute concentration difference) obtained in the embodiment of the present invention (wherein, GSI = 40, basic data source: QSH group 7972m of well X1); Figure 3(c) shows the variation of the equivalent density of collapse pressure with time, formation fracturing degree, and drilling fluid type (solute concentration difference) obtained in the embodiment of the present invention (wherein, GSI = 30, basic data source: QSH group 7972m of well X1). Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0048] This invention addresses the complex and frequent problems of wellbore collapse and stuck pipe in deep fractured formations. Based on the pore chemical elasticity control equation, it derives the pore pressure and stress fields formed by the non-uniform geostress and fluid-solidification coupling effects on the surrounding rock in deep fractured formations. Combined with the generalized three-dimensional Hoek-Brown shear failure criterion reflecting the degree of rock fracturing, it establishes a method for predicting collapse pressure in deep fractured formations. This invention achieves precise design of collapse pressure in deep fractured formations by quantifying the relationship between the solute concentration difference (activity difference) between drilling fluid and formation water, the degree of rock fracturing, and wellbore collapse pressure, thereby solving the complex problems of frequent wellbore collapse and stuck pipe in deep fractured formations.

[0049] Specifically, refer to Figure 1 The method for predicting wellbore collapse pressure in deep fractured formations in this embodiment includes the following steps:

[0050] Step 1: Use a gas permeameter to test the porosity and permeability of the rock core;

[0051] Step 2: Use triaxial compression tests on the rock core to test the pore medium mechanical parameters and strength parameters;

[0052] Step 3: Use the SCMS-E high-temperature and high-pressure core multi-parameter tester to test the membrane efficiency of the core.

[0053] Step 4: Use a high-temperature and high-pressure core dilatometer to test the chemical expansion coefficient of the core.

[0054] Step 5: Use a pressure transmission experimental device to test the solute diffusion coefficient of the core.

[0055] Step 6: Utilize acoustic emission tests to measure in-situ stress and combine this with well logging data to obtain the in-situ stress distribution;

[0056] Step 7: Use logging parameters to invert and obtain the original formation pore pressure distribution;

[0057] Step 8: Based on the data obtained in Steps 1 to 7, the field variables of the well-surrounding rock under the fluid-solidification coupling effect of fractured formations under non-uniform geostress conditions are analyzed using the governing equations of the pore chemical elasticity theory.

[0058] The governing equations of the porosity chemoelasticity theory include:

[0059] Constitutive equation:

[0060] σ ij =2Gε ij +(K-2G / 3)ε kk δ ij +α′pδ ij -χC s δ ij

[0061] ζ=-αε kk +βp+χ′C s

[0062] Stress balance equation:

[0063]

[0064] mass conservation equation:

[0065]

[0066] And chemical equilibrium equation:

[0067]

[0068] The pore fluidization coupling parameters in the above equations are defined as follows:

[0069]

[0070] The symbols in the above formulas have the following meanings: principal stress and shear stress components around the well σ ij or τ ij (i, j∈(r, θ, z)), in MPa; p is the wellbore pore pressure, in MPa; C S Percentage of solute mass around the well; Lagrange porosity ν pore , dimensionless; ζ, the increase (decrease) in pore fluid content, dimensionless; Poisson's ratio υ measured under drained and non-drained conditions. u υ, dimensionless; Biot modulus M, unit: MPa; Skempton pore pressure coefficient B, dimensionless; Bulk modulus K under undrained conditions, unit: GPa; Shear modulus G, unit: GPa; Chemical expansion coefficient ω0, unit: MPa; Molar mass of solute M s The unit is kg / mol; R is the gas constant, with units of J / (mol·K); the average temperature of the system under study. The unit is K; This represents the average mass percentage of the solute. Solvent average mass percentage; Biot effective stress coefficient α, dimensionless; solid particle bulk modulus K. s The unit is GPa; the bulk modulus of pore fluid K f The unit is GPa; the initial intrinsic mass density of the fluid. The unit is kg / m 3 r is the radial distance from the wellbore center to a certain location inside the formation, in meters (m); a is the wellbore radius, in meters (m); t is time, in seconds (s). D is the Laplace operator for the r-θ plane. S Solute diffusion coefficient, in m 2 / s; displacement vector u, unit is m; permeability coefficient κ is defined as permeability k(m 2 The ratio of the viscosity of the fluid to its viscosity μ (mPa·s), expressed in m³ / s. 2 / (mPa·s); δ ij δ is the Kronecker content. ij =1 (i=j), δ ij =0, (i≠j).

[0071] The field variables of the surrounding rock of the fractured formation under non-uniform geostress conditions under fluid-solidification coupling include the pore pressure field, the surrounding rock stress field, and the solute mass fraction field. The expressions for the pore pressure field, the surrounding rock stress field, and the solute mass fraction field are as follows:

[0072] The expression for the pore pressure field is as follows;

[0073] p = p0 + p (a) +p (d)

[0074] The expression for the stress field of the surrounding rock is as follows;

[0075]

[0076] The expression for the solute mass fraction field is as follows;

[0077]

[0078] In the formula, σ ij and τ ij (i, j∈(r, θ, z)) represent the principal stress and shear stress components around the well, in MPa; (or )and (or ) represents the stress components related to axisymmetric and non-axisymmetric aspects, in MPa; p represents the wellbore pore pressure, in MPa; C S ρ is the percentage of solute mass around the well; r is the radial distance from the well center to a certain location inside the formation, in meters; a is the well radius, in meters; p0 is the initial formation pore pressure, in MPa; p m This refers to the wellbore fluid column pressure, expressed in MPa. The initial solute mass percentage is given; the formation mean stress P0 and shear stress S0 are as follows:

[0079]

[0080] Among them, the principal stress components of the wellbore coordinate system and shear stress components Depend on Determined. Among them, the in-situ stress matrix σ ics In-situ stress coordinate system ICS(X) i Y i Z i ) to the geodetic coordinate system GCS(X) g Y g Z g The transformation matrix (I) from GCS to the wellbore coordinate system BCS (X) b Y b Z b The transformation matrix (b) of ) is defined as follows:

[0081]

[0082] Among them, Ωi γ is the angle between the azimuth of the maximum horizontal ground stress and true north, in degrees; i Ω represents the angle between the pressure of the overlying strata and the vertical direction, expressed in degrees. b γ is the wellbore azimuth angle in degrees; b σ represents the wellbore inclination angle, measured in degrees. H σ represents the maximum horizontal ground stress, expressed in MPa. h σ represents the minimum horizontal ground stress, expressed in MPa. v The pressure of the overlying strata is expressed in MPa; the intermediate conversion angle is θ. r Defined as The unit is degrees.

[0083]

[0084]

[0085]

[0086] Step 9: Using the pore pressure field and surrounding rock stress field of fractured formations under non-uniform geostress conditions, which are subjected to fluid-solidification coupling, and the three-dimensional Hawke-Brown criterion, the collapse pressure is determined, and a quantitative control method for wellbore collapse prevention is proposed.

[0087] The three-dimensional Hawke-Brown criterion can be applied to the evaluation of wellbore collapse failure in fractured formations. It uses octahedral shear stress τ... oct and average effective stress σ′ m for:

[0088]

[0089]

[0090] In the formula, τ oct It is the octahedral shear stress, with units of MPa; σ′ m Mean effective stress, measured in MPa; GSI is the geological strength index, dimensionless; m b σ and s are related to factors such as rock mass type, integrity, and weathering degree, respectively, and are dimensionless; the perturbation coefficient D varies from 0 to 1 and is dimensionless. The maximum effective principal stress σ′1, the intermediate effective principal stress σ′2, and the minimum effective principal stress σ′3 mentioned above correspond to the matrix tensor σ of the wellbore stress field. ccs [σ ij The eigenvalues ​​σ of [i, j ∈ (r, θ, z)] n It is determined by the following determinant.

[0091]

[0092] For wellbore collapse (blowout) caused by shear failure of the rock mass, the calculation process for determining the collapse pressure for safe drilling, based on the above-mentioned strength failure criteria and wellbore stress, is as follows:

[0093] First, the well inclination angle γ is defined. bi =i°(i=0:i:90), azimuth angle Ω bj =j° (j = 0:j:360), well perimeter angle θ k =k° (k=0:k:360) and pressure array Used to determine the final required collapse pressure value; where, Set as the maximum horizontal principal stress σ H Or a stress value greater than the maximum principal stress at horizontal levels;

[0094] Then, given the matrix (γ) bi Ω bj ), will pressure p ml The interval l increases from 0 to When the judgment condition is met The well perimeter angle θ can be obtained. k Corresponding collapse pressure matrix Finally, the matrix was selected. The maximum value in the given well inclination and azimuth (γ) is used as the value of the well inclination. bi Ω bj The corresponding collapse pressure value.

[0095] Where m is the allowable error value for satisfying the judgment condition, which is dimensionless and can be set according to actual needs. This invention does not impose specific limitations.

[0096] Once the collapse pressure value is calculated, if it is necessary to calculate the equivalent density of the collapse pressure, then the collapse pressure is further divided by the corresponding vertical depth and gravitational acceleration to obtain the equivalent density of the collapse pressure.

[0097] Note that the effective stress value mentioned in this invention is defined as σ′. ij =σ ij -α(p0+p (d) )δ ij -α′p (a) δ ij Furthermore, the smaller the values ​​of the positive real numbers i, j, k, and l, the higher the accuracy of the collapse pressure value determined by the above method.

[0098] This invention determines the pore medium mechanical-chemical coupling parameters and physical property parameters required for model calculation through indoor experiments and well logging data. Combining pore chemical elasticity theory and rock failure (shear and tension) models, it proposes a method for determining the pre-drilling collapse pressure equivalent density in deep fractured formations. It also plots a time-dependent collapse pressure equivalent density chart showing the effects of different solute concentration differences (activity differences) and rock fracturing degrees. This provides a scientific basis for field construction personnel to determine reasonable drilling fluid density, effectively preventing wellbore collapse problems and complex downhole accidents.

[0099] Example 1

[0100] In this embodiment, the geological parameters involved in the method for predicting wellbore collapse pressure in deep fractured formations (the relevant parameters are from the QSH group 7972m of well X1) are shown in Table 1:

[0101] Table 1

[0102]

[0103]

[0104] The solute mass fraction difference ΔC used to calculate the difference is defined as follows: Oil-based drilling fluid: Solute mass percentage C in the drilling fluid. m Solute mass fraction of formation pore fluid The fractional difference between them is defined as Water-based drilling fluid: ΔC = -0.1.

[0105] In this embodiment, Set as the maximum horizontal principal stress σ H m is set to 1e-5.

[0106] Based on the above parameters, combined with Figures 2-3(c) The collapse pressure values ​​and collapse pressure equivalents calculated in this embodiment are shown in Table 2 (GSI=30), Table 3 (GSI=40), and Table 4 (GSI=50):

[0107] Table 2

[0108]

[0109]

[0110] Table 3

[0111]

[0112] Table 4

[0113]

[0114] The results above show that the collapse pressure value is equal to the collapse pressure equivalent density multiplied by the vertical depth of 7972 multiplied by 0.00981. The collapse pressure equivalent density can be directly read from the graph. The horizontal axis time is 1e-8 days, 1e-6 days, 1e-4 days, 1e-2 days, 1 day, 2 days, and 5 days. Figure 2 The data is consistent with that in Figure 3(a).

[0115] This invention also provides a deep fractured formation wellbore collapse pressure prediction system to implement the deep fractured formation wellbore collapse pressure prediction method described above, comprising:

[0116] Field variable calculation module: Based on the acquired geological parameters, it is used to calculate the pore pressure field and surrounding rock stress field of fractured formations under non-uniform geostress conditions by using the governing equations of pore chemical elasticity theory.

[0117] Pressure Calculation Module: Used to calculate wellbore collapse pressure in deep fractured formations by utilizing the pore pressure field, surrounding rock stress field, and three-dimensional Hawke-Brown criterion under non-uniform geostress conditions, which are influenced by the fluid-solidification coupling effect of the surrounding rock.

[0118] The embodiments of the present invention also provide corresponding electronic devices and computer-readable storage media for implementing the solutions provided in the embodiments of the present invention.

[0119] The electronic device includes a storage device and a processor. The storage device is used to store instructions or code, and the processor is used to execute the instructions or code to enable the electronic device to perform the deep fractured formation wellbore collapse pressure prediction method according to any embodiment of this application.

[0120] In practical applications, the computer-readable storage medium can be any combination of one or more computer-readable media. The computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium.

[0121] This invention also provides a computer program product, which includes computer instructions that instruct a computer to execute the deep fractured formation wellbore collapse pressure prediction method described in any embodiment of this application.

[0122] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0123] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0124] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0125] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for predicting wellbore collapse pressure in deep fractured formations, characterized in that, The process includes the following: Based on the obtained geological parameters, the pore pressure field and surrounding rock stress field of the well-surrounding rock under the fluid-solidification coupling effect of fractured formations under non-uniform geostress conditions are calculated using the governing equations of the pore chemical elasticity theory. By utilizing the pore pressure field of the surrounding rock under fluid-solidification coupling effect in fractured formations under non-uniform geostress conditions, the stress field of the surrounding rock, and the three-dimensional Hawke-Brown criterion, the wellbore collapse pressure in deep fractured formations is calculated.

2. The method for predicting wellbore collapse pressure in deep fractured formations according to claim 1, characterized in that, The expression for the pore pressure field of the surrounding rock of the fractured formation under non-uniform geostress conditions under the fluid-solidification coupling effect is as follows; p=p0+p (a) +p (d) In the formula, p is the wellbore pore pressure, in MPa; p0 is the initial formation pore pressure, in MPa; p (a) p represents the increment of wellbore pore pressure induced by axisymmetric loading, in MPa. (d) This represents the increment of wellbore pore pressure induced by non-axisymmetric load, expressed in MPa.

3. The method for predicting wellbore collapse pressure in deep fractured formations according to claim 1, characterized in that, The stress field of the surrounding rock of the fractured formation under non-uniform geostress conditions, subjected to fluid-solidification coupling, is as follows: In the formula, σ r σ represents the radial stress on the rock surrounding the well, expressed in MPa. θ σ is the tangential stress on the surrounding rock of the well, in MPa; zz θ represents the axial stress on the surrounding rock of the well, expressed in MPa; r Define as an intermediate quantity for angle conversion The unit is degrees, where, The value represents the principal stress around the well in the x-direction of the xy plane in a rectangular coordinate system, in MPa. The value represents the principal stress around the well in the y direction of the xy plane in a rectangular coordinate system, in MPa. σ represents the wellbore shear stress in the xy-plane of a rectangular coordinate system, in MPa; θ is the wellbore angle, the angle between the radius vector of the studied location and the azimuth of the maximum horizontal stress, in degrees; σ r (a) σ represents the increment of radial stress around the well induced by axisymmetric loading, in MPa. r (d) σ represents the increment of radial stress around the well induced by non-axisymmetric load, in MPa. z b σ represents the axial stress around the well in the z-direction of a rectangular coordinate system, in MPa; v is Poisson's ratio, dimensionless; σ θ (a) σ represents the increment of tangential stress around the well induced by axisymmetric loading, in MPa. θ (d) α represents the increment of tangential stress around the well induced by non-axisymmetric load, in MPa. ＇ p represents the Biot coefficient for fluidization coupling, in dimensionless units. (a) χ represents the increment of wellbore pore pressure induced by axisymmetric loading, in MPa; χ is the chemical coupling coefficient related to the chemical stress induced by the solute mass fraction difference, in MPa; C S(a) α is the dimensionless increment of solute mass percentage induced by axisymmetric loading; α is the Biot coefficient, dimensionless; p (d) τ represents the increment of wellbore pore pressure induced by axisymmetric loading, in MPa. rθ The shear stress is the stress on the rock surrounding the well in the r-θ plane of the cylindrical coordinate system, in MPa. τ represents the additional shear stress increment induced by fluid-structure interaction in the surrounding rock of the well in the r-θ plane of cylindrical coordinates, expressed in MPa; rz The out-of-plane shear stress relative to the r-θ plane experienced by the rock surrounding the well in cylindrical coordinates, expressed in MPa. is the out-of-plane stress in the xy plane rectangular coordinate system, in MPa; is the out-of-plane shear stress relative to the r-θ plane on the rock surrounding the well in the cylindrical coordinate system, in MPa. r denoted as , where is the radial distance from the wellbore center to a location within the formation, in meters; 'a' is the wellbore radius, in meters; 'P0' is the average formation stress; and 'S0' is the shear stress.

4. The method for predicting wellbore collapse pressure in deep fractured formations according to claim 3, characterized in that, The C S The following relationship must be satisfied: In the formula, C S This represents the percentage of solute mass around the well. This represents the initial percentage of solute mass.

5. The method for predicting wellbore collapse pressure in deep fractured formations according to claim 3, characterized in that, The mean stress P0 and shear stress S0 of the formation are calculated using the following formula: Among them, the principal stress components of the wellbore coordinate system and shear stress components Depend on Determine, where i, j ∈ x, y, z, and the in-situ stress matrix σ ics The transformation matrix I from the in-situ stress coordinate system to the geodetic coordinate system and the transformation matrix b from the GCS to the wellbore coordinate system are defined as follows: Among them, Ω i γ is the angle between the azimuth of the maximum horizontal ground stress and true north, in degrees; i Ω represents the angle between the pressure of the overlying strata and the vertical direction, expressed in degrees. b γ is the wellbore azimuth angle in degrees; b σ is the well inclination angle, in degrees; H σ represents the maximum horizontal ground stress, expressed in MPa. h σ represents the minimum horizontal ground stress, expressed in MPa. v The pressure of the overlying strata is expressed in MPa; the intermediate conversion angle is θ. r Defined as The unit is degrees.

6. The method for predicting wellbore collapse pressure in deep fractured formations according to claim 5, characterized in that: The three-dimensional Hawke-Brown criterion is as follows: In the formula, τ oct It is the octahedral shear stress, with units of MPa; σ′ m Mean effective stress, measured in MPa; GSI is the geological strength index, dimensionless; m b σ and s are related to the integrity of the rock mass type and the degree of weathering, respectively, and are dimensionless; the disturbance coefficient D varies from 0 to 1 and is dimensionless; σ′1 is the maximum effective principal stress, σ′2 is the intermediate effective principal stress, and σ′3 is the minimum effective principal stress, with units of MPa; The process of calculating wellbore collapse pressure in deep fractured formations using the pore pressure field of the surrounding rock under fluid-solidification coupling in fractured formations under non-uniform geostress conditions, the surrounding rock stress field, and the three-dimensional Hawke-Brown criterion includes: Given the inclination angle and azimuth angle, the wellbore fluid column pressure is increased from 0 to a preset value. A judgment condition is met. At that time, the collapse pressure matrix corresponding to the well perimeter angle is obtained, where m is the dimensionless error allowable value that satisfies the judgment condition; The maximum collapse pressure value in the collapse pressure matrix is ​​selected as the collapse pressure value corresponding to the given well inclination angle and azimuth angle.

7. The method for predicting wellbore collapse pressure in deep fractured formations according to claim 6, characterized in that, The upper limit of the wellbore fluid column pressure shall not be less than the maximum horizontal principal geostress σ. H .

8. A wellbore collapse pressure prediction system for deep fractured formations, characterized in that, include: Field variable calculation module: Based on the acquired geological parameters, it is used to calculate the pore pressure field and surrounding rock stress field of fractured formations under non-uniform geostress conditions by using the governing equations of pore chemical elasticity theory. Pressure Calculation Module: Used to calculate wellbore collapse pressure in deep fractured formations by utilizing the pore pressure field, surrounding rock stress field, and three-dimensional Hawke-Brown criterion under non-uniform geostress conditions, which are influenced by the fluid-solidification coupling effect of the surrounding rock.

9. An electronic device, characterized in that, include: One or more processors; A storage device on which one or more programs are stored; When the one or more programs are executed by the one or more processors, the one or more processors implement the deep fractured formation wellbore collapse pressure prediction method as described in any one of claims 1 to 7.

10. A storage medium, characterized in that, It stores a computer program, wherein the computer program, when executed by a processor, implements the method for predicting wellbore collapse pressure in deep fractured formations as described in any one of claims 1 to 7.

11. A computer program product, said computer program product comprising computer instructions, characterized in that, The computer instructions instruct the computer to execute the method for predicting wellbore collapse pressure in deep fractured formations as described in any one of claims 1-7.

Images