Three-dimensional borehole wall stability analysis method based on geomechanical model

Abstract

The invention relates to the technical field of oil-gas exploration, in particular to a geomechanical model-based three-dimensional borehole wall stability analysis method, which comprises the following steps of: constructing a three-dimensional structure model and an attribute model; building a multi-single-well rock mechanical parameter calculation model based on the three-dimensional structure model and the attribute model, and building a three-dimensional rock mechanical model of the oil field based on the multi-single-well rock mechanical parameter calculation model; constructing a three-dimensional pore pressure model; constructing a three-dimensional crustal stress model based on the three-dimensional rock mechanical model, the three-dimensional pore pressure model and stress boundary conditions; according to the three-dimensional crustal stress model and the three-dimensional rock mechanical model, constructing a three-dimensional collapse pressure model and a three-dimensional fracture pressure model, and obtaining a distribution rule of pressure on a region and a strata series; and predicting the safety density window curve of the development well, and evaluating the prediction precision according to the actual drilling reaction condition. The three-dimensional borehole wall stability technology is beneficial to high-precision pressure prediction and spatial distribution rule research.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration, and in particular to a three-dimensional wellbore stability analysis method based on a geomechanical model. Background Art

[0002] Wellbore stability technology is a key link in the process of oil and gas exploration and development, and it is directly related to the safety and economy of drilling operations. Since the 1980s, domestic and foreign experts and scholars have conducted a lot of research in the field of one-dimensional wellbore stability technology, achieved remarkable results, and laid a solid foundation for the in-depth understanding of wellbore stability. These research results cover geostress measurement technology, indoor and field rock mechanics parameter measurement technology, and one-dimensional longitudinal geostress along the well trajectory, rock mechanics parameters, three pressure curve calculation and wellbore stability analysis, forming a mature technical system that is widely used in field engineering practice.

[0003] However, there are still some problems to be solved in the one-dimensional wellbore stability analysis technology: conventional indoor experimental methods and field operation methods can only determine the strength of local formations and the size of in-situ stress, with few data points, and further application is limited; one-dimensional longitudinal rock mechanics parameters and pressure curve calculations can only obtain the mechanical characteristics of the formation encountered by a single well trajectory, and lack the means to accurately and continuously determine the lateral formation strength and in-situ stress state; pressure prediction using the rock mechanics parameters of multiple wells, pressure curve interpolation or modeling parameter extrapolation methods cannot truly reflect the impact of geological structure characteristics, faults, and lithology on mechanical and pressure characteristics. Summary of the invention

[0004] The purpose of the present invention is to provide a three-dimensional wellbore stability analysis method based on a geomechanical model in order to solve at least one of the above technical problems. The three-dimensional wellbore stability analysis method provided by the present invention explores the distribution laws of rock mechanics, geostress, and three pressures in regions and layers from the perspective of surface and volume, and the three-dimensional wellbore stability research is of great significance to oilfield exploration and development.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions: A three-dimensional wellbore stability analysis method based on a geomechanical model, comprising:

[0006] Construct three-dimensional structural models and property models;

[0007] Constructing a plurality of single-well rock mechanics parameter calculation models based on the three-dimensional structural model and the attribute model, and constructing a three-dimensional rock mechanics model of the oil field based on the plurality of single-well rock mechanics parameter calculation models;

[0008] Construct a three-dimensional pore pressure model;

[0009] Constructing a three-dimensional geostress model based on the three-dimensional rock mechanics model, the three-dimensional pore pressure model, and stress boundary conditions;

[0010] According to the three-dimensional geostress model and the three-dimensional rock mechanics model, a three-dimensional collapse pressure model and a three-dimensional fracture pressure model are constructed to obtain the distribution law of pressure in the region and layer system;

[0011] The safety density window curve of development wells is predicted, and the prediction accuracy is evaluated based on the actual drilling response.

[0012] Furthermore, a three-dimensional structural model and an attribute model are constructed, including:

[0013] The three-dimensional structural model and the attribute model are constructed by adopting a well, seismic and facies joint reservoir modeling method and a sequential Gaussian simulation algorithm constrained by a seismic trend body.

[0014] Further, a rock mechanics parameter calculation model of multiple single wells is constructed based on the three-dimensional structural model and the attribute model, and a three-dimensional rock mechanics model of the oil field is constructed based on the rock mechanics parameter calculation model of the multiple single wells, including:

[0015] Construct a mathematical model for calculating one-dimensional rock mechanics parameters of drilled wells in oil fields;

[0016] Performing mathematical averaging on key parameters of the one-dimensional rock mechanics parameter calculation mathematical model of a single well to obtain a three-dimensional rock mechanics parameter calculation mathematical model suitable for the oil field;

[0017] The three-dimensional rock mechanics model is constructed based on the three-dimensional acoustic wave time difference model, the three-dimensional density model and the three-dimensional porosity model according to the three-dimensional rock mechanics parameter calculation mathematical model.

[0018] Furthermore, a one-dimensional rock mechanics parameter calculation mathematical model for the drilled wells in the oil field is constructed, including:

[0019] According to the differential equation of motion, geometric equation and physical equation of elastic mechanics, the dynamic elastic rock mechanics parameters are calculated as shown in formulas (1) and (2):

[0020] E d =ρv s 2 (3v p 2 -4v s 2 ) / (v p 2 -2v s 2 ) (1)

[0021] μ d =(vp 2 -2v s 2 ) / 2(v p 2 -2v s 2 ) (2)

[0022] Among them, E d is the dynamic elastic modulus, in MPa; μ d is the dynamic Poisson's ratio, dimensionless; ρ is the rock volume density, unit is g / cm 3 ;v s 、v p are the shear wave propagation speed and longitudinal wave propagation speed respectively, in m / s;

[0023] The dynamic and static elastic parameter conversion relationship is established to calculate the static elastic modulus and static Poisson's ratio, as shown in formulas (3) and (4):

[0024] μ s =A 1 +B 1 μ d (3)

[0025] E s =A 2 +B 2 E d (4)

[0026] Among them, μ s , μ d are the static Poisson's ratio and the dynamic Poisson's ratio, dimensionless; E s 、E d They are the static elastic modulus and dynamic elastic modulus, in MPa; A 1 , B 1 , A 2 , B 2 are respectively a first conversion coefficient, a second conversion coefficient, a third conversion coefficient, and a fourth conversion coefficient;

[0027] The uniaxial compressive strength of sedimentary rock is calculated according to formula (5):

[0028] σ c =0.0045·E d1 (1-V cl )+0.008E d1 ·V cl (5)

[0029] Among them, σ c is the uniaxial compressive strength of the formation, in MPa; E d1is the dynamic Young's modulus, in MPa; V cl is the mud content, %.

[0030] Furthermore, a three-dimensional pore pressure model is constructed, including:

[0031] The calculation equation of normal velocity trend line is obtained by fitting the normal compaction layer segment;

[0032] Calculate the normal speed model according to the normal speed trend line calculation equation;

[0033] The Eaton index is obtained by back-calculating the measured pore pressure coefficient;

[0034] The three-dimensional pore pressure model is calculated based on the normal velocity model, the layer velocity model, the overburden pressure model, and the Eaton index.

[0035] Furthermore, the Eaton method shown in formula (6) is used to construct the three-dimensional pore pressure model.

[0036]

[0037] Among them, G p is the equivalent density of the formation pore pressure gradient, in g / cm 3 ; G v is the equivalent density of the pressure gradient of the overburden, in g / cm 3 ρ w is the formation water density, in g / cm 3 ; Δt is the measured sound wave time difference, unit is μs / m; Δt n It is the sound wave time difference value under normal trend, the unit is μs / m; n is the Eaton index.

[0038] Furthermore, based on the three-dimensional rock mechanics model, the three-dimensional pore pressure model, and stress boundary conditions, a three-dimensional geostress model is constructed, including: using Matlab software to compile a data interface program between geological software and finite element numerical calculation software, importing the three-dimensional model data file established by Petrel software into a finite element numerical simulator to perform finite element numerical simulation of geostress, and constructing the three-dimensional geostress model.

[0039] Furthermore, the horizontal maximum principal stress and the horizontal minimum principal stress of a single well are calculated according to the Huang Rongzun model, as described in formula (7):

[0040]

[0041] Among them, σ H , σh are the maximum horizontal stress and the minimum horizontal stress respectively, μ is the Poisson's ratio of rock, ω 1 ,ω 2are the horizontal maximum geostress tectonic stress coefficient and the horizontal minimum geostress tectonic stress coefficient, σ v is the overburden pressure, α 2 is the Biot coefficient, with a range of 0.4-0.8, p p is the formation pore pressure.

[0042] Furthermore, the stress boundary conditions are set as follows: the minimum horizontal geostress gradient is 0.0180965 MPa / m, the horizontal geostress ratio is 1.1, and the minimum horizontal geostress direction is N50E°.

[0043] Furthermore, according to the three-dimensional geostress model and the three-dimensional rock mechanics model, a three-dimensional collapse pressure model and a three-dimensional fracture pressure model are constructed to obtain the distribution law of pressure in the region and layer system, including:

[0044] The calculation model of collapse pressure under vertical drilling conditions is shown in formula (8):

[0045]

[0046] Among them, p c is the collapse pressure of the first formation, in MPa; σ H , σ h are the maximum horizontal ground stress and the minimum horizontal ground stress, respectively, in MPa; σ c is the uniaxial compressive strength of the formation, in MPa; p p is the formation pore pressure, in MPa; φ is the internal friction angle, in degrees; α 1 is the effective stress coefficient, dimensionless;

[0047] The calculation model of the fracture pressure under vertical drilling conditions is shown in formula (9):

[0048] p f =3σ h -σ H -p p +σ t (9)

[0049] Among them, p f is the collapse pressure of the second formation, in MPa; σ H , σ h are the maximum horizontal ground stress and the minimum horizontal ground stress, respectively, in MPa; p p is the formation pore pressure, in MPa; σ t It is the tensile strength of the formation, in MPa.

[0050] The present invention has the following beneficial effects:

[0051] The three-dimensional wellbore stability analysis method based on the geomechanical model provided by the present invention solves the limitations of traditional one-dimensional wellbore stabilization technology under complex geological conditions. By comprehensively considering the geological structure, rock mechanical properties and ground stress distribution, this method can more accurately predict the wellbore stability and pressure distribution, especially in oil fields with few wells drilled.

[0052] The present invention constructs a three-dimensional structural model and an attribute model, and then calculates rock mechanical parameters based on these models, establishes a three-dimensional pore pressure model and a three-dimensional geostress model. Through these models, the present invention can analyze in detail the mechanical properties of the strata in the horizontal and vertical directions, as well as the influence of geological structures and faults on the stability of the wellbore. In addition, the present invention also includes the construction of a three-dimensional collapse pressure and fracture pressure model, which further reveals the distribution law of pressure in different regions and strata.

[0053] The three-dimensional wellbore stability analysis method of the present invention not only improves the accuracy of pressure prediction, but also provides a new research approach for oil field exploration and development, which helps to achieve safer and more efficient drilling operations. Through this method, wellbore stability issues can be better understood and predicted, thereby providing important decision-making support for the development of oil and gas fields, which has important theoretical and practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a flow chart of a three-dimensional wellbore stability analysis method based on a geomechanical model according to a first embodiment of the present invention;

[0055] Figure 2 This is a flow chart of a three-dimensional wellbore stability analysis method based on a geomechanical model according to a second embodiment of the present invention;

[0056] Figure 3 The three-dimensional compressive strength model of the WZL oil field is established according to the Mohr Coulomb criterion;

[0057] Figure 4 The three-dimensional horizontal maximum principal stress model of the WZL oilfield is shown as an example;

[0058] Figure 5 The three-dimensional horizontal minimum principal stress model of the WZL oilfield is shown as an example;

[0059] Figure 6 The three-dimensional collapse pressure model of the WZL oil field is shown as an example;

[0060] Figure 7 The three-dimensional fracture pressure model of the WZL oil field is shown as an example. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0062] Embodiment 1

[0063] Figure 1 FIG. 1 is a flow chart of a three-dimensional wellbore stability analysis method based on a geomechanical model according to an embodiment of the present invention. Figure 1 As shown, according to one embodiment of the present invention, a three-dimensional wellbore stability analysis method based on a geomechanical model includes:

[0064] Step S102: constructing a three-dimensional structural model and an attribute model;

[0065] Using geological data and seismic data, combined with downhole measurement data, a detailed three-dimensional geological structure model is established, which includes information such as the distribution of strata, the location of faults and the type of rocks. The attribute model describes the physical properties of rocks, such as porosity, permeability, elastic modulus and Poisson's ratio of rocks, which are crucial for understanding the mechanical behavior of rocks.

[0066] Step S104: constructing a rock mechanics parameter calculation model of multiple single wells based on the three-dimensional structural model and the attribute model, and constructing a three-dimensional rock mechanics model of the oil field based on the rock mechanics parameter calculation model of the multiple single wells;

[0067] Based on the 3D structural model and property model, combined with the rock mechanics test data of multiple wells, a single well rock mechanics parameter calculation model is established. By statistically analyzing and mathematically averaging the key parameters in these single well models, a 3D rock mechanics parameter calculation model suitable for the entire oil field is obtained.

[0068] Step S106: constructing a three-dimensional pore pressure model;

[0069] The pore pressure distribution of the formation is calculated based on the geological model and the physical properties of the rock.

[0070] Step S108: constructing a three-dimensional geostress model based on the three-dimensional rock mechanics model, the three-dimensional pore pressure model, and the stress boundary conditions;

[0071] Combining the three-dimensional rock mechanics model, pore pressure model and preset stress boundary conditions, the finite element method is used to perform numerical simulation of geostress and establish a three-dimensional geostress model. This model can reflect the principal stress distribution of the stratum at different depths and orientations, and provide key input data for wellbore stability analysis. In this embodiment, the stress boundary conditions are set as follows: the horizontal minimum geostress gradient is 0.0180965MPa / m, the horizontal geostress ratio is 1.1, and the horizontal minimum geostress direction is N50E°.

[0072] Step S110: constructing a three-dimensional collapse pressure model and a three-dimensional fracture pressure model based on the three-dimensional geostress model and the three-dimensional rock mechanics model to obtain the distribution law of pressure in the region and layer system;

[0073] The collapse pressure and fracture pressure around the wellbore are calculated using three-dimensional geostress models and rock mechanics models. These models can help predict the stability of the wellbore in different areas and layers. By analyzing the pressure distribution pattern, potential unstable areas can be identified, providing guidance for drilling design.

[0074] Step S110 includes:

[0075] The calculation model of collapse pressure under vertical drilling conditions is shown in formula (8):

[0076]

[0077] Among them, p c is the collapse pressure of the first formation, in MPa; σ H , σ h are the maximum horizontal ground stress and the minimum horizontal ground stress, respectively, in MPa; σ c is the uniaxial compressive strength of the formation, in MPa; p p is the formation pore pressure, in MPa; φ is the internal friction angle, in degrees; α 1 is the effective stress coefficient, dimensionless;

[0078] The calculation model of the fracture pressure under vertical drilling conditions is as described in formula (9):

[0079] p f =3σ h -σ H -p p +σ t (9)

[0080] Among them, p f is the collapse pressure of the second formation, in MPa; σ H , σ h are the maximum horizontal ground stress and the minimum horizontal ground stress, respectively, in MPa; pp is the formation pore pressure, in MPa; σ t It is the tensile strength of the formation, in MPa.

[0081] Step S112: predict the safety density window curve of the development well and evaluate the prediction accuracy according to the actual drilling response.

[0082] According to the established collapse pressure and fracture pressure models, the safe density window curve of drilling fluid is predicted, that is, the safe range of drilling fluid density during drilling. By comparing with actual drilling data, the prediction accuracy of the model is evaluated, and the model is adjusted and optimized as necessary.

[0083] In this implementation, a three-dimensional rock mechanics model of the oil field is established by combining the rock mechanics parameter calculation models of multiple single wells; a three-dimensional pore pressure model is established; on the basis of the three-dimensional rock mechanics model, the pore pressure model, and the stress boundary conditions, a finite element numerical solution of the geostress constrained by the one-dimensional geostress results is performed to construct a three-dimensional geostress model; on the basis of the three-dimensional geostress model and the rock mechanics model, three-dimensional collapse pressure and three-dimensional fracture pressure modeling are carried out to explore the distribution law of pressure in the region and formation; the safety density window curve of the development well is predicted, and the prediction accuracy is evaluated according to the actual drilling response.

[0084] Relying on the theory of geomechanics, the present invention has successfully constructed an innovative three-dimensional wellbore stability analysis technology, which significantly improves the accuracy of pressure prediction and the in-depth understanding of spatial distribution laws. Compared with the traditional one-dimensional wellbore stabilization technology, this technology can comprehensively analyze the lateral and vertical mechanical properties of the formation, pressure distribution, and the influence of geological structures and faults through the comprehensive geological model and geomechanical model. Especially for oil fields with few wells, this technology can accurately capture the impact of the heterogeneity of geological structure and rock mechanics on ground stress and pore pressure, avoiding excessive reliance on existing drilling data, thereby significantly improving the accuracy of pressure prediction.

[0085] The present invention not only improves the accuracy of oilfield pressure prediction under complex geological conditions, but also provides a new research approach for the spatial distribution of rock mechanics, geostress and pressure. This method makes up for the limitations of one-dimensional wellbore stability technology in understanding regional geomechanical laws, and realizes an important leap from one-dimensional to three-dimensional wellbore stability analysis. Through the three-dimensional wellbore stability analysis method of the present invention, regional geomechanical characteristics can be more comprehensively understood, providing a valuable scientific basis for oilfield exploration and development.

[0086] The present invention provides an innovative three-dimensional wellbore stability analysis method based on a geomechanical model. This method significantly improves the prediction accuracy of wellbore stability by integrating geological and geomechanical information, especially in oil fields with few wells. It can comprehensively analyze the lateral and longitudinal mechanical properties of the formation, the pressure distribution law, and the influence of geological structures and faults, thus providing a more accurate and comprehensive scientific basis for oil field exploration and development.

[0087] According to an embodiment of the present invention, step S102 includes: using a well, seismic, and facies joint reservoir modeling method and a sequential Gaussian simulation algorithm constrained by a seismic trend body to construct a three-dimensional structural model and an attribute model.

[0088] In this implementation, Petrel modeling software is used, a well, seismic, and phase joint modeling method is adopted, the inversion volume is applied to geological modeling, and the sequential Gaussian (SGS) simulation algorithm under seismic trend constraints is used. After combining it with the well data, the accuracy of the attribute model can be greatly improved.

[0089] The well, seismic, and phase joint reservoir modeling method uses downhole geological data (such as drilling and logging data), seismic exploration data (such as seismic reflection waveforms, amplitudes, etc.) and geological phase analysis (interpretation and classification of rock types and sedimentary environments) to build a geological model. This fusion method of multiple data sources can provide more comprehensive geological information, thereby establishing a more accurate three-dimensional structural model and attribute model.

[0090] In the modeling process, seismic trend volume constraint refers to the use of trend information in seismic data (such as the continuity of the strata, thickness change trend, etc.) to guide and restrict the establishment of the model. This constraint ensures that the model conforms to the underground structural characteristics revealed by the seismic data, and improves the geological rationality and prediction accuracy of the model. The Sequential Gaussian (SGS) simulation algorithm can generate continuous attribute models that conform to geological trends, such as porosity, permeability, etc., under given data constraints, thereby improving the accuracy of the attribute model. Petrel modeling software is used for geological modeling. The software provides powerful data processing and modeling functions and can handle complex geological data. By applying the inversion volume (i.e., underground structural information obtained through seismic data processing) to geological modeling and combining it with well data, the accuracy and practicality of the model are further improved.

[0091] The embodiments of the present invention establish a high-precision three-dimensional structural model and attribute model by integrating multi-source geological data and advanced geostatistical algorithms. This method can more accurately reflect the mechanical properties and pore pressure distribution of underground rocks, and provide a solid foundation for wellbore stability analysis. Especially in oil fields with few wells, this method can effectively predict wellbore stability, optimize drilling design, and reduce drilling risks, which has important practical significance for improving the success rate of oil and gas exploration and development.

[0092] According to one embodiment of the present invention, step S104 includes:

[0093] Step S1042: constructing a one-dimensional rock mechanics parameter calculation mathematical model for the drilled wells in the oil field;

[0094] Step S1042 includes:

[0095] According to the differential equation of motion, geometric equation and physical equation of elastic mechanics, the dynamic elastic rock mechanics parameters are calculated as described in formulas (1) and (2):

[0096] E d =ρv s 2 (3v p 2 -4v s 2 ) / (v p 2 -2v s 2 ) (1)

[0097] μ d =(v p 2 -2v s 2 ) / 2(v p 2 -2v s 2 ) (2)

[0098] Among them, E d is the dynamic elastic modulus, in MPa; μ d is the dynamic Poisson's ratio, dimensionless; ρ is the rock volume density, unit is g / cm 3 ;v s 、v p They are the transverse wave propagation speed and longitudinal wave propagation speed respectively, and their units are m / s.

[0099] The dynamic and static elastic parameter conversion relationship is established to calculate the static elastic modulus and static Poisson's ratio, as described in formulas (3) and (4):

[0100] μs =A 1 +B 1 μ d (3)

[0101] E s =A 2 +B 2 E d (4)

[0102] Among them, μ s , μ d are the static Poisson's ratio and the dynamic Poisson's ratio, dimensionless; E s 、E d They are the static elastic modulus and dynamic elastic modulus, in MPa; A 1 , B 1 , A 2 , B 2 They are the first conversion coefficient, the second conversion coefficient, the third conversion coefficient, and the fourth conversion coefficient, which are related to the lithology and the stress on the rock;

[0103] The uniaxial compressive strength of sedimentary rock is calculated according to formula (5):

[0104] σ c =0.0045·E d1 (1-V cl )+0.008E d1 ·V cl (5)

[0105] Among them, σ c is the uniaxial compressive strength of the formation, in MPa; E d1 is the dynamic Young's modulus, in MPa; V cl is the mud content, %.

[0106] Step S1044: performing mathematical averaging on key parameters of the one-dimensional rock mechanics parameter calculation mathematical model of a single well to obtain a three-dimensional rock mechanics parameter calculation mathematical model suitable for the oil field;

[0107] Step S1046: Calculate the mathematical model according to the three-dimensional rock mechanics parameters, and construct a three-dimensional rock mechanics model based on the three-dimensional acoustic wave time difference model, the three-dimensional density model, and the three-dimensional porosity model.

[0108] In this embodiment, the key parameters of the mathematical model for calculating the rock mechanical parameters of multiple wells are mathematically averaged to obtain the mathematical model for calculating the three-dimensional rock mechanical parameters of the oil field. First, based on the rock mechanical test data of the drilled wells in the oil field, such as the elastic modulus, Poisson's ratio, compressive strength, etc. of the rock samples measured in the laboratory, a one-dimensional rock mechanical parameter calculation mathematical model for each well is established. These models provide a detailed description of the rock mechanical parameters for each well and can serve as the basis for further analysis. Next, the one-dimensional rock mechanical parameters of multiple wells are mathematically averaged to reduce the randomness and uncertainty of the single well data. In this way, a more representative three-dimensional rock mechanical parameter calculation mathematical model is obtained, which is applicable to the entire oil field and provides a basis for rock mechanical analysis at the oil field scale. After obtaining a unified three-dimensional rock mechanical parameter calculation mathematical model for the oil field, a three-dimensional rock mechanical model of the oil field is constructed in combination with geological data such as a three-dimensional acoustic time difference model, a three-dimensional density model, and a three-dimensional porosity model. This model can reflect the spatial changes in rock mechanical parameters and provide important mechanical information for the exploration and development of the oil field.

[0109] The present invention establishes a three-dimensional rock mechanics model applicable to the entire oil field by integrating the rock mechanics data of a single well and the geological model. This method not only improves the prediction accuracy of rock mechanics parameters, but also can more accurately describe the mechanical properties and spatial distribution of rocks. This has important guiding significance for engineering activities such as reservoir evaluation, drilling design, and hydraulic fracturing in oil fields. Through this method, the mechanical response of rocks under different geological conditions can be better predicted and evaluated, thereby improving the efficiency and safety of oil and gas development.

[0110] According to one embodiment of the present invention, step S106 includes:

[0111] Step S1062: deriving a normal velocity trend line calculation equation based on the normal compaction layer segment fitting;

[0112] Step S1064: Calculate the normal speed model according to the normal speed trend line calculation equation;

[0113] Step S1066: Obtaining the Eaton index by back-calculating according to the measured pore pressure coefficient;

[0114] Step S1068: Calculate a three-dimensional pore pressure model based on the normal velocity model, the layer velocity model, the overburden pressure model, and the Eaton index.

[0115] In this embodiment, the Eaton method as shown in formula (6) is used to construct a three-dimensional pore pressure model.

[0116]

[0117] Among them, G pis the equivalent density of the formation pore pressure gradient, in g / cm 3 ; G v is the equivalent density of the pressure gradient of the overburden, in g / cm 3 ρ w is the formation water density, in g / cm 3 ; Δt is the measured sound wave time difference, unit is μs / m; Δt n It is the sound wave time difference value under normal trend, the unit is μs / m; n is the Eaton index.

[0118] In this embodiment, according to the characteristics of the normal compaction layer segment, the normal velocity trend line calculation equation is obtained by fitting. This step is the basis for subsequent calculations. It uses the characteristics of the normal compaction layer segment to establish the velocity trend line, which provides a basis for the subsequent calculation of the normal velocity model. The normal velocity model is calculated according to the normal velocity trend line calculation equation. The normal velocity model is an important parameter for describing the formation velocity distribution. It can help us understand the physical properties of the formation and provide basic data for the subsequent pore pressure calculation. The Eaton index is obtained by back-calculating the measured pore pressure coefficient. The Eaton index is an important parameter reflecting the change of formation pore pressure. It can help us understand the change law of pore pressure and provide key parameters for the subsequent pore pressure calculation. The three-dimensional pore pressure model is calculated by combining the normal velocity model, layer velocity model, overburden pressure model and Eaton index.

[0119] The three-dimensional pore pressure model obtained by the present invention through precise calculation can more accurately reflect the changes in pore pressure in the formation, providing an important reference basis for subsequent oil and gas exploration and development; the normal velocity trend line is fitted by using the characteristics of the normal compaction layer section, thereby improving the accuracy and reliability of the calculation results; and the calculation is performed by integrating multiple models and parameters, making the calculation results more comprehensive and accurate, and better reflecting the actual situation of the formation.

[0120] According to one embodiment of the present invention, step S108 includes:

[0121] The data interface program between geological software and finite element numerical calculation software was compiled using Matlab software. The three-dimensional model data file established by Petrel software was imported into the finite element numerical simulator for finite element numerical simulation of geostress and a three-dimensional geostress model was constructed.

[0122] In this embodiment, the data interface program compiled by Matlab software is used to realize efficient data exchange between different software. This avoids the cumbersome manual data conversion and import process, improves work efficiency and reduces human errors. Petrel software is powerful in geological modeling and can establish accurate three-dimensional geological models. Through the data interface program, these models can be fully imported into the finite element numerical simulator to ensure the accuracy and integrity of the model during the simulation process. The finite element numerical simulation method is an efficient numerical calculation method that can simulate the distribution and changes of geostress under complex geological conditions. The three-dimensional geostress model constructed by this method can more accurately reflect the actual geological conditions and provide strong support for subsequent engineering design and decision-making.

[0123] The present invention uses Matlab software to compile a data interface program between geological software and finite element numerical calculation software, imports the three-dimensional model data file established by Petrel software into a finite element numerical simulator to perform finite element numerical simulation of geostress, and constructs a three-dimensional geostress model, providing an efficient, accurate and flexible method, which is of great significance for geomechanics research and engineering applications.

[0124] According to an implementation mode of the present invention, the horizontal maximum principal stress and the horizontal minimum principal stress of a single well are calculated according to the Huang Rongzun model, as described in formula (7):

[0125]

[0126] Among them, σ H , σ h are the maximum horizontal stress and the minimum horizontal stress, μ is the Poisson's ratio of rock, ω 1 ,ω 2 are the horizontal maximum geostress tectonic stress coefficient and the horizontal minimum geostress tectonic stress coefficient, σ v is the overburden pressure, α 2 is the Biot coefficient, with a range of 0.4-0.8, p p is the formation pore pressure.

[0127] In this implementation, the calculated single well geostress data is used as the calibration standard of the three-dimensional geostress model. When calculating the horizontal maximum principal stress and horizontal minimum principal stress of a single well, the Huang Rongzun model has the advantages of high prediction accuracy, wide applicability, simple operation and high reliability. These advantages make the model have broad application prospects in the field of oil and gas exploration and development.

[0128] The present invention adopts the Huang Rongzun model to calculate the horizontal maximum principal stress and the horizontal minimum principal stress of a single well, thereby improving the prediction accuracy.

[0129] The present invention provides a comprehensive and high-precision wellbore stability analysis method, which can accurately predict various parameters related to wellbore stability, provide a scientific basis for the design and implementation of drilling operations, and improve the success rate and safety of oil and gas exploration and development.

[0130] The present invention provides a three-dimensional wellbore stability analysis method based on a geomechanical model. By comprehensively utilizing downhole data, seismic data and geological interpretation, a high-precision three-dimensional structural model and attribute model are established. These models include fault models, layer models and spatial distribution parameter models of underground reservoir properties. The accuracy and reliability of the model are improved by combining the well data with the seismic trend constraint and the sequential Gaussian (SGS) simulation algorithm; by combining the rock mechanics parameters of multiple single wells, a three-dimensional rock mechanics model of the oil field is established, including key parameters such as elastic modulus, Poisson's ratio, compressive strength and cohesion. The establishment of these models takes into account the conversion relationship between dynamic and static elastic parameters, as well as the calculation of the uniaxial compressive strength of sedimentary rocks, providing important mechanical information for the exploration and development of oil fields. On the basis of the three-dimensional rock mechanics model and the pore pressure model, the present invention also establishes a three-dimensional geostress model, and through the finite element numerical solution method, the stress boundary conditions are considered to obtain the distribution model of the horizontal maximum principal stress and the minimum principal stress. These models reveal the distribution characteristics of geostress in different geological structural regions, especially the stress concentration and steering phenomenon in the fault region. The present invention also establishes a three-dimensional collapse pressure and fracture pressure model, and explores the distribution law of pressure in the horizontal and vertical directions. These models take into account the different working conditions of vertical drilling and directional drilling, and provide a theoretical basis for drilling fluid design and wellbore structure design. The present invention predicts the safe density window curve of the development well and evaluates the prediction accuracy based on the actual drilling response. This step provides an important reference for drilling fluid design and on-site construction, ensuring the safety and efficiency of drilling operations.

[0131] Embodiment 2

[0132] Figure 2 FIG. 2 is a flow chart of a three-dimensional wellbore stability analysis method based on a geomechanical model according to Embodiment 2 of the present invention. Figure 2 As shown, according to one embodiment of the present invention, a three-dimensional wellbore stability analysis method based on a geomechanical model includes the following steps:

[0133] Step S202: using the well, seismic, and facies joint reservoir modeling method and the sequential Gaussian simulation algorithm constrained by the seismic trend body to establish a three-dimensional structural model and an attribute model.

[0134] Specifically, the structural model includes a fault model and a layer model. Complex faults need to set their truncation relationships to generate stepped faults and regularize the grid. The layer model is based on the results of the division and comparison of small layers, with geological stratification and top surface structural maps as trends, and the thickness analysis of each small layer is combined to interpolate the top and bottom surfaces of each subdivided modeling unit. The layer model is established with the structural top surface and the top and bottom surfaces of the modeling unit formed by interpolation.

[0135] The attribute model is a parameter model of the spatial distribution of underground reservoir physical properties. In order to ensure the accuracy of the inter-well attribute model, the Sequential Gaussian (SGS) simulation algorithm under the constraint of seismic trend is adopted.

[0136] In this embodiment, a well, seismic, and phase joint modeling method is adopted, the inversion volume is applied to geological modeling, and a sequential Gaussian (SGS) simulation algorithm under seismic trend constraints is used to combine with well data to establish a high-precision attribute model.

[0137] A method of building a geological model by comprehensively utilizing different types of geological data. Among them, "well" refers to the data directly measured underground, such as core analysis, well logging data, etc.; "seismic" refers to seismic exploration data, such as seismic reflection waveforms, amplitudes, etc.; "phase" refers to geological phase analysis, that is, the interpretation and classification of rock types, sedimentary environments, etc.

[0138] Inversion refers to underground structural information obtained through seismic data processing. It inverts (i.e., infers) the physical properties and morphology of underground strata through the reflection characteristics of seismic waves. Applying this information to geological modeling can improve the model's reflection of the actual underground conditions.

[0139] In the process of geological modeling, seismic trend constraints refer to the use of trend information in seismic data (such as continuity of strata, thickness change trend, etc.) to guide and restrict the establishment of the model to ensure that the model conforms to the underground structural characteristics revealed by the seismic data.

[0140] Sequential Gaussian simulation is a geostatistical method used to simulate the spatial distribution of random variables. In geological modeling, the SGS algorithm can be used to generate continuous attribute models that conform to geostatistical laws, such as porosity and permeability.

[0141] When establishing a geological model, not only seismic data and inversion volumes are used, but also geological data on the well (i.e., surface or near-surface), such as surface geological surveys and drilling data, are combined to obtain more comprehensive geological information.

[0142] The high-precision attribute model established in this embodiment is a geological model that can accurately reflect the spatial distribution of underground rock properties (such as porosity, permeability, etc.).

[0143] In this embodiment, the modeling method of comprehensive utilization of downhole geological data (well data), seismic exploration data (seismic data) and geological interpretation (phase data) can more comprehensively understand the geological characteristics and physical property distribution of the reservoir. The three-dimensional structural model mainly focuses on the geological structure of the underground reservoir, including faults and layers. The fault model needs to set the truncation relationship of the faults in detail, that is, the mutual cutting and connection between the faults. By generating stepped faults, the subsequent grid division can be made more regular, which is convenient for numerical simulation and analysis. The layer model focuses on the different stratigraphic interfaces of the reservoir. When establishing this model, it is necessary to comprehensively analyze the thickness of each layer based on the results of the layer division and comparison, with the geological stratification and top surface structural map as the trend. Then, through the interpolation technology, the position of the top and bottom surfaces of each modeling unit is determined, so as to establish an accurate layer model. The attribute model describes the spatial distribution of reservoir physical parameters, such as porosity, permeability, etc. In order to ensure the accuracy of the inter-well attribute model, seismic trend constraints are adopted, that is, seismic data is used to guide the establishment of the attribute model. The Sequential Gaussian Simulation (SGS) algorithm is a geostatistical method used to simulate the distribution of random variables. It can generate a continuous attribute model that conforms to geological trends under given data constraints. Through accurate three-dimensional structural models and attribute models, we can better understand and predict the distribution of reservoir physical properties, providing important decision support for oil and gas exploration and development.

[0144] Step S204: Establish a three-dimensional rock mechanics model of the oil field by combining the rock mechanics parameter calculation models of multiple single wells.

[0145] Specifically, the three-dimensional rock mechanics parameter model is a three-dimensional model of rock mechanics parameters such as elastic modulus, Poisson's ratio, compressive strength, cohesion, etc. Based on the one-dimensional rock mechanics parameter calculation mathematical model, an innovative three-dimensional rock mechanics parameter modeling method is proposed:

[0146] Step S2042: Establishing a mathematical model for calculating one-dimensional rock mechanical parameters of the drilled wells in the oil field, including elastic modulus, Poisson's ratio, compressive strength, etc.;

[0147] According to the differential equation of motion, geometric equation and physical equation of elastic mechanics, the dynamic elastic rock mechanics parameters are calculated as described in formulas (1) and (2):

[0148] E d =ρv s 2 (3v p 2 -4v s 2 ) / (v p 2 -2v s 2 ) (1)

[0149] μ d =(v p 2 -2v s 2 ) / 2(v p 2 -2v s 2 ) (2)

[0150] Among them, E d is the dynamic elastic modulus, in MPa; μ d is the dynamic Poisson's ratio, dimensionless; ρ is the rock volume density, unit is g / cm 3 ;v s 、v p are the propagation speeds of transverse waves and longitudinal waves respectively, in m / s.

[0151] The dynamic and static elastic parameter conversion relationship is established to calculate the static elastic modulus and Poisson's ratio, as described in formulas (3) and (4):

[0152] μ s =A 1 +B 1 μ d (3)

[0153] E s =A 2 +B 2 E d (4)

[0154] Among them, μ s , μ d are the static Poisson's ratio and the dynamic Poisson's ratio, dimensionless; E s 、E d They are the static elastic modulus and dynamic elastic modulus, in MPa; A 1 , B 1 , A 2 , B 2 They are the first conversion coefficient, the second conversion coefficient, the third conversion coefficient and the fourth conversion coefficient, respectively, and are related to the lithology and the stress exerted on the rock.

[0155] The uniaxial compressive strength of sedimentary rock is calculated according to formula (5):

[0156] σ c =0.0045·E d1 (1-V cl )+0.008E d1 ·V cl (5)

[0157] Among them, σ cis the uniaxial compressive strength of the formation, in MPa; E d1 is the dynamic Young's modulus, in MPa; V cl is the mud content, %.

[0158] Step S2044: performing mathematical averaging on key parameters of the one-dimensional rock mechanics parameter calculation model for a single well to obtain a three-dimensional rock mechanics parameter calculation model suitable for the oil field;

[0159] The key parameters of the mathematical model for calculating rock mechanics parameters of multiple drilled wells are mathematically averaged to obtain the three-dimensional mathematical model for calculating rock mechanics parameters of the oil field, and a three-dimensional rock mechanics parameter model is established based on the geological model and attribute model.

[0160] Step S2046: Calculate the mathematical model according to the three-dimensional rock mechanics parameters, and establish a three-dimensional rock mechanics model based on the three-dimensional acoustic wave time difference model, the three-dimensional density model, and the three-dimensional porosity model.

[0161] In this embodiment, first, a one-dimensional rock mechanical parameter calculation mathematical model is established based on the geological and rock data of the wells drilled in the oil field. This model usually includes key rock mechanical parameters, such as elastic modulus, Poisson's ratio, compressive strength, etc., which describe the mechanical behavior and characteristics of rocks under stress. Next, the one-dimensional rock mechanical parameters of a single well are mathematically averaged. The purpose of this step is to reduce the randomness and uncertainty of the single well data, and to obtain more stable and representative rock mechanical parameters by averaging, so as to establish a unified three-dimensional rock mechanical parameter calculation model for the entire oil field. After obtaining a three-dimensional rock mechanical parameter calculation model suitable for the oil field, a three-dimensional rock mechanical model is established in combination with existing geological data such as three-dimensional acoustic time difference model, three-dimensional density model, and three-dimensional porosity model. This model can reflect the spatial changes of rock mechanical parameters and provide important mechanical information for the exploration and development of oil fields. This method for establishing a three-dimensional rock mechanical parameter model can more accurately describe the mechanical properties and spatial distribution of rocks, and has important guiding significance for engineering activities such as reservoir evaluation, drilling design, and hydraulic fracturing in oil fields. This approach can better predict and evaluate the mechanical response of rocks under different geological conditions, thereby improving the efficiency and safety of oil and gas development.

[0162] Figure 3 This is a three-dimensional compressive strength model of the WZL oilfield established according to the Mohr Coulomb criterion. Different colors in the model represent different numerical values.

[0163] Step S206: Establish a three-dimensional pore pressure model.

[0164] The three-dimensional pore pressure model is established using the Eaton method as described in formula (6):

[0165]

[0166] Among them, G p is the equivalent density of the formation pore pressure gradient, in g / cm 3 ; G v is the equivalent density of the pressure gradient of the overburden, in g / cm 3 ρ w is the formation water density, in g / cm 3 ; Δt is the measured sound wave time difference, the unit is μs / m; Δt n It is the sound wave time difference value under normal trend, the unit is μs / m; n is Eaton index.

[0167] The specific modeling steps include:

[0168] Step S2062: deriving a normal velocity trend line calculation equation based on the normal compaction layer segment fitting;

[0169] Step S2064: Calculate the normal speed model according to the normal speed trend line calculation equation;

[0170] Step S2066: Obtaining the Eaton index by back-calculating according to the measured pore pressure coefficient;

[0171] Step S2068: Calculate the pore pressure coefficient model according to the normal velocity model, the layer velocity model, the overburden pressure model, and the Eaton index.

[0172] Specifically, undercompaction caused by fluid discharge obstruction is the most common cause of abnormal pressure. Therefore, the basic principle of three-dimensional pore pressure modeling is compaction theory, that is, based on the established geological model, the acoustic time difference attribute body is used to identify the normal compaction and undercompaction layers, and the normal velocity trend line calculation equation is obtained according to the normal compaction layer fitting. The normal velocity model is calculated and then the pore pressure model is established. It should be noted that the specific method of three-dimensional pore pressure modeling is similar to the one-dimensional single well pore pressure calculation, the difference is that the basic data is a three-dimensional attribute body. The key parameters of three-dimensional modeling come from the wells involved in the modeling, and the modeling results need to be returned to the one-dimensional single well for verification.

[0173] Undercompaction caused by fluid drainage obstruction is the most common cause of abnormal underground pressure. During the geological sedimentation process, if the fluid in the rock layer cannot be effectively discharged, the pore pressure will increase and form an undercompacted state. The establishment of the three-dimensional pore pressure model is based on the compaction theory, that is, the pore pressure is predicted by analyzing the compaction degree of the rock. This theory assumes that the compaction of the rock during the sedimentation process is related to its burial depth, geological age and sedimentary environment. Based on the established geological model, the normal compaction and undercompacted layers are identified by analyzing the acoustic time difference attribute body. Acoustic time difference is a commonly used parameter in seismic exploration, which can reflect the porosity and compaction degree of the rock. By fitting the acoustic time difference data of the normally compacted layer section, the normal velocity trend line is obtained and the calculation equation is established. This trend line represents the relationship between the acoustic time difference and the burial depth under normal compaction conditions. According to the normal velocity model, the actual acoustic time difference of each layer section can be calculated and compared with the normal velocity trend line to identify the undercompacted layer section. These data are used to establish the pore pressure model and predict the pore pressure at different depths. Although 3D pore pressure modeling is based on 3D attribute volumes, its method is similar to 1D single well pore pressure calculation. The key parameters of 3D modeling come from the wells involved in the modeling, and the modeling results need to be verified and tested back to the single well to ensure the accuracy and reliability of the model.

[0174] The establishment of the three-dimensional pore pressure model of this embodiment is a process of integrating geological, seismic and pore pressure data, which is of great significance for reservoir evaluation, drilling risk assessment and production decision-making in oil and gas exploration and development. Through this method, the underground pore pressure distribution can be predicted more accurately, providing a scientific basis for the rational development of oil fields.

[0175] Step S208: Based on the three-dimensional rock mechanics model, pore pressure model, and stress boundary conditions, a finite element numerical solution of the in-situ stress is performed with the one-dimensional in-situ stress result as a constraint.

[0176] Specifically, in this embodiment, the stress boundary conditions are set as follows: the horizontal minimum geostress gradient is 0.0180965 MPa / m, the horizontal geostress ratio is 1.1, and the horizontal minimum geostress direction is N50E°.

[0177] It should be noted that the three-dimensional effective stress directions obtained by numerical simulation of geostress are not completely horizontal and vertical. The effective stress is converted into horizontal and vertical normal stress and tangential stress through coordinate transformation. The normal stress perpendicular to each other in three directions is considered to be the horizontal and vertical effective stress. Since the vector results are not convenient for viewing the results, the stress vector results are converted into 6 stress component scalar results, and further converted into horizontal and vertical three-dimensional effective stress scalar results. The three-dimensional geostress model of three-dimensional principal stress is obtained by adding the effective stress to the pore pressure. Figure 4The three-dimensional horizontal maximum principal stress model of the WZL oilfield is shown as an example; Figure 5 The three-dimensional horizontal minimum principal stress model of WZL oilfield is shown as an example. Figure 4 and Figure 5 As shown in the figure, in the area without faults, the ground stress transition is smooth, and the magnitude and direction gradually change with the structural undulation and mechanical properties. There is stress concentration and steering in the ground stress passing through the fault and the area near the fault. The stress magnitude is significantly greater than that in the non-fault area, and the stress direction obviously deviates from the non-fault area.

[0178] It should be noted that before conducting numerical simulation of geostress, high-precision one-dimensional geostress longitudinal profile calculation of a single well that has been drilled should be carried out, and the obtained one-dimensional geostress curve should be used as the calibration standard of the three-dimensional geostress model.

[0179] As a preferred implementation of this embodiment, the maximum horizontal principal stress and the minimum horizontal principal stress of the drilled well can be calculated according to the Huang Rongzun model, as shown in formula (7):

[0180]

[0181] Among them, σ H , σ h are the maximum horizontal stress and the minimum horizontal stress, μ is the Poisson's ratio of rock, ω 1 ,ω 2 are the tectonic stress coefficients of the maximum horizontal stress and the minimum horizontal stress, σ v is the overburden pressure, α 2 is the Biot coefficient, with a range of 0.4-0.8, p p is the formation pore pressure.

[0182] Matlab software was used to compile a data interface program between geological software and finite element numerical calculation software to generate an input file type that can be recognized by the finite element numerical simulator. The three-dimensional model data file established by Petrel software was imported into the finite element numerical simulator. The finite element numerical solution of geostress was performed based on the three-dimensional rock mechanics model, pore pressure model and certain stress boundary conditions. The calculated single well geostress data was used as the calibration standard for the three-dimensional geostress model.

[0183] In this embodiment, the finite element method is used to numerically solve the geostress, in which the one-dimensional geostress result is used as a constraint condition. The three-dimensional effective stress direction obtained by simulation may not be completely horizontal or vertical. Through coordinate transformation, the effective stress is converted into horizontal and vertical normal stress and tangential stress. This step is to simplify the representation and understanding of the results. The stress vector result is converted into a scalar result of six stress components, and further converted into a scalar result of horizontal and vertical three-dimensional effective stress. This conversion process helps to analyze and understand the geostress state more intuitively. By adding the effective stress to the pore pressure, a three-dimensional geostress model of the three-dimensional principal stress is obtained. This model can intuitively show the distribution of geostress in space. Before performing numerical simulation of geostress, a high-precision one-dimensional geostress longitudinal profile calculation of a single well that has been drilled should be carried out. The obtained one-dimensional geostress curve will be used as a calibration standard for the three-dimensional geostress model to ensure the accuracy of the model.

[0184] As an optional implementation, horizontal geostress can be calculated according to the Huang Rongzun model formula. This formula takes into account factors such as the Poisson's ratio, Biot coefficient, formation pore pressure, and tectonic stress coefficient of the rock, and can provide an estimate of the horizontal geostress. By analyzing the three-dimensional horizontal maximum principal stress and horizontal minimum principal stress models, it can be observed that the geostress transition is smooth in areas without faults, while there is stress concentration and steering in the fault area. This analysis is of great significance for understanding the impact of geological structure on geostress distribution and guiding drilling and mining activities.

[0185] Step S210: Based on the three-dimensional geostress model and rock mechanics model, a three-dimensional collapse pressure model and a three-dimensional fracture pressure model are established to explore the pressure distribution law;

[0186] The calculation model of collapse pressure under vertical drilling conditions is shown in formula (8):

[0187]

[0188] Among them, p c is the collapse pressure of the first formation, in MPa; σ H , σ h are the maximum horizontal ground stress and the minimum horizontal ground stress, respectively, in MPa; σ c is the uniaxial compressive strength of the formation, in MPa; p p is the formation pore pressure, in MPa; φ is the internal friction angle, in degrees; α 1 is the effective stress coefficient, dimensionless.

[0189] The calculation model of the fracture pressure under vertical drilling conditions is as described in formula (9):

[0190] p f =3σh -σ H -p p +σ t (9)

[0191] Among them, p f is the collapse pressure of the second formation, in MPa; σ H , σ h are the maximum horizontal ground stress and the minimum horizontal ground stress, respectively, in MPa; p p is the formation pore pressure, in MPa; σ t It is the tensile strength of the formation, in MPa.

[0192] Due to the inclination of the wellbore, the analysis method of wellbore stability of directional wells is significantly different from that of vertical wells. The basic idea of ​​modeling the three-dimensional collapse pressure and fracture pressure along a specific wellbore inclination azimuth is: based on the rock mechanics, geostress and other models obtained in the previous study, the wellbore stress field in cylindrical coordinates is obtained by coordinate transformation of any grid according to a certain wellbore inclination angle and azimuth; the three-dimensional principal stress expression of any point on the wellbore in the cylindrical coordinate system of the wellbore trajectory is obtained; the mechanical equilibrium equation of any point is obtained by combining the corresponding failure model, and the mechanical equilibrium equation of each point on the wellbore is solved to obtain the collapse pressure and fracture pressure to maintain the stability of the wellbore. The maximum collapse pressure and the minimum fracture pressure in the 360-degree circumference of the well are determined as the collapse pressure and fracture pressure values ​​of the grid; the calculation process is repeated for all grids to obtain the three-dimensional collapse pressure and fracture pressure model.

[0193] Specifically, under vertical drilling conditions, a specific calculation model is used to model the three-dimensional collapse pressure and fracture pressure. Under directional drilling conditions, the ground stress in the rectangular coordinate system is converted into the wellbore stress field in the cylindrical coordinate system through coordinates, and the three-dimensional principal stress expression is obtained. The mechanical equilibrium equation is combined with the corresponding failure model, and the mechanical equilibrium equation is solved for each point on the wellbore to obtain the collapse pressure and fracture pressure that maintain the stability of the wellbore. The maximum collapse pressure and the minimum fracture pressure in the 360-degree circumference of the well are determined as the collapse pressure and fracture pressure values. The calculation process is repeated for all grids to obtain the three-dimensional collapse pressure and fracture pressure model of the directional well. Figure 6 The three-dimensional collapse pressure model of the WZL oil field is shown as an example; Figure 7 The three-dimensional fracture pressure model of WZL oilfield is shown in Figure 2. Figure 6 and Figure 7 As shown in the figure, the collapse pressure in the area around the development well is higher than that in the far well area, and the fracture pressure is significantly lower than that in the far well area. The far well area mainly develops mudstone, which has higher strength and mechanical properties than the sandstone section. At the same time, in areas with similar mechanical properties, the collapse pressure of the structural interface convex and concave areas is greater than that of the gentle formation, and the fracture pressure is smaller than that of the gentle formation.

[0194] According to a preferred implementation of this embodiment, the spatial distribution characteristics of the collapse pressure and the fracture pressure in the horizontal and vertical directions are analyzed by stratum and slice.

[0195] In this embodiment, in the case of vertical drilling, a specific calculation model is used to establish a three-dimensional collapse pressure and fracture pressure model. These models are usually based on the distribution of ground stress and the mechanical properties of rocks to predict the stability of the wellbore. For directional drilling, the ground stress in the rectangular coordinate system needs to be converted into the wellbore stress field in the cylindrical coordinate system. This conversion is to adapt to the specific geometry and stress conditions of directional drilling. Through the coordinate conversion, the three-way principal stress expression of the wellbore stress field is obtained. These expressions are the basis for understanding and calculating the stability of the wellbore. Combined with the failure model of the rock, such as the Mohr-Coulomb failure criterion or other applicable failure criteria, a mechanical equilibrium equation is established. These equations are used to evaluate the stability of the wellbore under different stress states. The mechanical equilibrium equations at each point of the wellbore are solved to determine the collapse pressure and fracture pressure that keep the wellbore stable. The maximum collapse pressure and the minimum fracture pressure in the 360-degree circumference of the well are selected as key values. Repeat the above calculation process for all grid points to obtain the three-dimensional collapse pressure and fracture pressure model of the entire directional well. By analyzing the WZL oilfield model, it can be observed that the collapse pressure in the area around the development well is higher than that in the far well area, while the fracture pressure is significantly lower than that in the far well area. This distribution feature is affected by the lithology of the formation, the structural interface and the ground stress state. As an optional implementation method, a stratum-by-stratum and slice-by-slice method can be used to analyze the spatial distribution characteristics of collapse pressure and fracture pressure in the horizontal and vertical directions. This method can provide more detailed pressure distribution information, which is helpful for targeted drilling design and risk assessment.

[0196] Step S212: predict the safety density window curve of the development well and evaluate the prediction accuracy according to the actual drilling response.

[0197] In this embodiment, the safe density window curve under the specific trajectory of the development well is predicted, and its prediction accuracy is evaluated according to the actual drilling response. Specifically, based on the three-dimensional pore pressure, collapse pressure, and fracture pressure model, the safe density window is predicted along the specific wellbore trajectory to provide a theoretical basis for drilling fluid design, wellbore structure design, and on-site drilling and completion operations. Table 1 shows the predicted collapse pressure and fracture pressure data for each drilling time of the example WZL oilfield.

[0198] Table 1 Predicted pressure curves for wells A5, A6, A7 and A8 Unit: g / cm3

[0199]

[0200] In this embodiment, before predicting the safe density window, it is necessary to establish a three-dimensional pore pressure, collapse pressure and fracture pressure model. These models are based on geological data, geostress analysis and rock mechanics parameters, and can provide information on the pressure state and rock stability of the formation around the wellbore. The above three-dimensional model is used to predict the safe density window along a specific wellbore trajectory. The safe density window refers to a range of drilling fluid density within which the drilling fluid can stabilize the wellbore wall, prevent collapse and fracture, and avoid excessive intrusion and damage to the formation. The predicted safe density window provides an important theoretical basis for drilling fluid design. The density of the drilling fluid needs to be adjusted according to the safe density window to ensure the stability of the wellbore wall. At the same time, the wellbore structure design also needs to consider these pressure data to ensure the integrity and safety of the wellbore. The prediction of the safe density window is equally important for on-site drilling and completion operations. Construction personnel can adjust the drilling fluid density according to the prediction results, optimize drilling parameters, and reduce construction risks. According to the actual drilling response, the accuracy of the predicted safe density window is evaluated. This step is the key to verifying the effectiveness of the model. By comparing the predicted values ​​with the observed data during the actual drilling process, the model can be adjusted and optimized to improve the prediction accuracy. Table 1 provides the predicted collapse pressure and fracture pressure data of the WZL oilfield. These data can help understand the formation conditions and wellbore stability under different drilling times and provide specific references for drilling operations.

[0201] The present invention provides a comprehensive and high-precision wellbore stability analysis method, which can accurately predict various parameters related to wellbore stability, provide a scientific basis for the design and implementation of drilling operations, and improve the success rate and safety of oil and gas exploration and development.

[0202] The present invention innovatively establishes a three-dimensional wellbore stabilization technology based on geological models and geomechanical models. According to the geological distribution law, that is, the distribution, arrangement characteristics and occurrence and development process of structural features, the stress field conditions, rock mechanical properties and pressure distribution laws are analyzed, which can intuitively reflect the lateral and longitudinal mechanical characteristics of the stratum and the pressure distribution law, the influence of geological structural characteristics and faults. The three-dimensional wellbore stabilization technology has an incomparable advantage over the one-dimensional wellbore stabilization technology in the understanding of regional geomechanical laws. For oil fields with a small number of wells, the three-dimensional research can truly consider the influence of geological structure and rock mechanical heterogeneity on ground stress and three pressures, avoiding the simple use or high reference to the data of wells that have been drilled in the past, thereby improving the pressure prediction accuracy. The three-dimensional wellbore stability analysis method based on geological models and geomechanical models provided by the present invention explores the distribution laws of rock mechanics, ground stress and three pressures in regions and strata from the perspective of surface and volume. The three-dimensional wellbore stability research is of great significance to oil field exploration and development, and is conducive to high-precision pressure prediction and spatial distribution law research.

[0203] The present invention improves the pressure prediction accuracy of complex oil fields with long-distance wells, and provides a research method for rock mechanics, ground stress, and pressure spatial distribution laws, which makes up for the shortcomings of one-dimensional wellbore stability technology in understanding regional geomechanical laws, and promotes the "quality" improvement of wellbore stability analysis from one dimension to three dimensions. Three-dimensional wellbore stability technology has incomparable advantages over one-dimensional wellbore stability technology in understanding regional geomechanical laws. For oil fields with a small number of wells, three-dimensional research can truly consider the impact of geological structure and rock mechanics heterogeneity on ground stress and three pressures, avoiding the simple use or high reference to the data of drilled wells in the past, thereby improving the pressure prediction accuracy. The three-dimensional wellbore stability analysis method based on geological model and geomechanical model provided by the present invention explores the distribution laws of rock mechanics, ground stress, and three pressures in regions and formations from the perspective of surface and volume, and the research on three-dimensional wellbore stability is of great significance to oilfield exploration and development.

[0204] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0205] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A three-dimensional wellbore stability analysis method based on a geomechanical model, characterized in that: include: Construct three-dimensional structural models and property models; Constructing a plurality of single-well rock mechanics parameter calculation models based on the three-dimensional structural model and the attribute model, and constructing a three-dimensional rock mechanics model of the oil field based on the plurality of single-well rock mechanics parameter calculation models; Construct a three-dimensional pore pressure model; Constructing a three-dimensional geostress model based on the three-dimensional rock mechanics model, the three-dimensional pore pressure model, and stress boundary conditions; According to the three-dimensional geostress model and the three-dimensional rock mechanics model, a three-dimensional collapse pressure model and a three-dimensional fracture pressure model are constructed to obtain the distribution law of pressure in the region and layer system; The safety density window curve of development wells is predicted, and the prediction accuracy is evaluated based on the actual drilling response.

2. The three-dimensional wellbore stability analysis method based on geomechanical model according to claim 1 is characterized in that: Construct 3D structural and property models, including: The three-dimensional structural model and the attribute model are constructed by adopting a well, seismic and facies joint reservoir modeling method and a sequential Gaussian simulation algorithm constrained by a seismic trend body.

3. The three-dimensional wellbore stability analysis method based on geomechanical model according to claim 1 is characterized in that: Constructing a plurality of single-well rock mechanics parameter calculation models based on the three-dimensional structural model and the attribute model, and constructing a three-dimensional rock mechanics model of the oil field based on the plurality of single-well rock mechanics parameter calculation models, including: Construct a mathematical model for calculating one-dimensional rock mechanics parameters of drilled wells in oil fields; Performing mathematical averaging on key parameters of the one-dimensional rock mechanics parameter calculation mathematical model of a single well to obtain a three-dimensional rock mechanics parameter calculation mathematical model suitable for the oil field; The three-dimensional rock mechanics model is constructed based on the three-dimensional acoustic wave time difference model, the three-dimensional density model and the three-dimensional porosity model according to the three-dimensional rock mechanics parameter calculation mathematical model.

4. The three-dimensional wellbore stability analysis method based on geomechanical model according to claim 3 is characterized in that: Construct a mathematical model for calculating the one-dimensional rock mechanics parameters of the drilled wells in the oil field, including: According to the differential equation of motion, geometric equation and physical equation of elastic mechanics, the dynamic elastic rock mechanics parameters are calculated as shown in formulas (1) and (2): E d =ρv s 2 (3v p 2 -4v s 2 ) / (v p 2 -2v s 2 ) (1) μ d =(in p 2 -2v s 2 ) / 2(in p 2 -2v s 2 ) (2) Among them, E d is the dynamic elastic modulus, in MPa; μ d is the dynamic Poisson's ratio, dimensionless; ρ is the rock volume density, unit is g / cm 3 ;v s 、v p are the shear wave propagation speed and longitudinal wave propagation speed respectively, in m / s; The dynamic and static elastic parameter conversion relationship is established to calculate the static elastic modulus and static Poisson's ratio, as shown in formulas (3) and (4): m s =A1+B1μ d (3) <h2 style=";text-align:left;direction:ltr">E<h2 style=";text-align:left;direction:ltr"> s <h2 style=";text-align:left;direction:ltr"> =A2+B2E<h2 style=";text-align:left;direction:ltr"> d <h2 style=";text-align:left;direction:ltr"> (4) Among them, μ s , μ d are the static Poisson's ratio and the dynamic Poisson's ratio, dimensionless; E s 、E d are the static elastic modulus and dynamic elastic modulus, in MPa; A1, B1, A2, B2 are the first conversion coefficient, the second conversion coefficient, the third conversion coefficient, and the fourth conversion coefficient, respectively; The uniaxial compressive strength of sedimentary rock is calculated according to formula (5): s c =0.0045·E d1 (1-V cl )+0.008E d1 ·V cl (5) Among them, σ c is the uniaxial compressive strength of the formation, in MPa; E d1 is the dynamic Young's modulus, in MPa; V cl is the mud content, %.

5. The three-dimensional wellbore stability analysis method based on geomechanical model according to claim 1, characterized in that: Construct a 3D pore pressure model, including: The calculation equation of normal velocity trend line is obtained by fitting the normal compaction layer segment; Calculate the normal speed model according to the normal speed trend line calculation equation; The Eaton index is obtained by back-calculating the measured pore pressure coefficient; The three-dimensional pore pressure model is calculated based on the normal velocity model, the layer velocity model, the overburden pressure model, and the Eaton index.

6. The three-dimensional wellbore stability analysis method based on the geomechanical model according to claim 5 is characterized in that: The three-dimensional pore pressure model is constructed using the Eaton method shown in formula (6): Among them, G p is the equivalent density of the formation pore pressure gradient, in g / cm 3 ; G v is the equivalent density of the pressure gradient of the overburden, in g / cm 3 ρ w is the formation water density, in g / cm 3 ; Δt is the measured sound wave time difference, the unit is μs / m; Δt n It is the sound wave time difference value under normal trend, the unit is μs / m; n is the Eaton index.

7. The three-dimensional wellbore stability analysis method based on geomechanical model according to claim 1 is characterized in that: Based on the three-dimensional rock mechanics model, the three-dimensional pore pressure model, and the stress boundary conditions, a three-dimensional geostress model is constructed, including: using Matlab software to compile a data interface program between geological software and finite element numerical calculation software, importing the three-dimensional model data file established by Petrel software into a finite element numerical simulator to perform finite element numerical simulation of geostress, and constructing the three-dimensional geostress model.

8. The three-dimensional wellbore stability analysis method based on geomechanical model according to claim 7 is characterized in that: The maximum horizontal principal stress and the minimum horizontal principal stress of a single well are calculated according to the Huang Rongzun model, as described in formula (7): Among them, σ H , σ h are the maximum horizontal stress and the minimum horizontal stress, μ is the Poisson's ratio of rock, ω1 and ω2 are the tectonic stress coefficients of the maximum horizontal stress and the minimum horizontal stress, σ v is the overburden pressure, α2 is the Biot coefficient, ranging from 0.4 to 0.8, and p p is the formation pore pressure.

9. The three-dimensional wellbore stability analysis method based on geomechanical model according to claim 8, characterized in that: The stress boundary conditions are set as follows: the minimum horizontal geostress gradient is 0.0180965 MPa / m, the horizontal geostress ratio is 1.1, and the minimum horizontal geostress direction is N50E°.

10. The three-dimensional wellbore stability analysis method based on geomechanical model according to claim 1, characterized in that: According to the three-dimensional geostress model and the three-dimensional rock mechanics model, a three-dimensional collapse pressure model and a three-dimensional fracture pressure model are constructed to obtain the distribution law of pressure in the region and layer system, including: The calculation model of collapse pressure under vertical drilling conditions is shown in formula (8): Among them, p c is the collapse pressure of the first formation, in MPa; σ H , σ h are the maximum horizontal ground stress and the minimum horizontal ground stress, respectively, in MPa; σ c is the uniaxial compressive strength of the formation, in MPa; p p is the formation pore pressure, in MPa; φ is the internal friction angle, in degrees; α1 is the effective stress coefficient, dimensionless; The calculation model of the fracture pressure under vertical drilling conditions is shown in formula (9): p f =3σ h -s H -p p +s t (9) Among them, p f is the collapse pressure of the second formation, in MPa; σ H , σ h are the maximum horizontal ground stress and the minimum horizontal ground stress, respectively, in MPa; p p is the formation pore pressure, in MPa; σ t It is the tensile strength of the formation, in MPa.

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