Method and equipment for analyzing wellbore stability during drilling

Abstract

The present application provides a method and device for analyzing the stability of a wellbore during drilling. The method includes: obtaining logging data of completed drillings and rock cuttings data of the current drilling; determining rock mechanical parameters based on the logging data of completed drillings and rock cuttings data of the current drilling; determining formation pressure based on the longitudinal wave velocity curve and the overlying formation pressure; determining horizontal geostress based on the rock mechanical parameters and formation pressure; based on the rock mechanical parameters and horizontal geostress, performing a wellbore stability analysis for each drilling depth, and the wellbore stability analysis includes wellbore collapse pressure analysis and wellbore rupture pressure analysis under any angle combination of the well inclination angle and azimuth angle within the corresponding angle range. The method of the present application improves the prediction accuracy of risk exploration wells and the safety of drilling operations.

Description

Technical Field

[0001] The present application relates to the field of drilling exploration, and in particular to a method and device for analyzing the stability of a wellbore during drilling. Background Art

[0002] As the exploration and development targets shift toward deep and ultra-deep layers, tight oil and gas, and unconventional oil and gas, the drilling depth continues to increase, and the well types gradually change from vertical wells to complex well types such as inclined wells, horizontal wells, and multi-branch wells. The resulting wellbore stability problems such as wellbore collapse and fracture have an increasing impact on the drilling speed, wellbore quality, and safe drilling operations.

[0003] During the drilling process, the rational and effective analysis of the wellbore stability is increasingly becoming a necessary part of safe and efficient drilling. At present, a relatively mature analysis method has been formed for wellbore stability analysis. Before drilling, the velocity curve through the well is extracted using seismic inversion data or predicted based on the logging curves of adjacent wells with similar geological conditions in the same block. After drilling, logging data and test data are used to achieve post-drilling evaluation and provide reference for subsequent drilling.

[0004] However, for exploration blocks, especially risky exploration wells, there is often a certain gap between the predicted results and the actual results, which means that the drilling process has to face "encounters" and poses a great challenge to safe drilling. Summary of the invention

[0005] The present application provides a method and device for analyzing wellbore stability during drilling, so as to solve the problem of prediction deviation in the wellbore stability analysis in the prior art when conducting risk exploration of wells.

[0006] In a first aspect, the present application provides a method for analyzing wellbore stability during drilling, comprising:

[0007] Obtain the logging data of completed drillings and the cuttings data of the current drilling;

[0008] Determine rock mechanical parameters based on logging data from completed wells and cuttings data from current wells;

[0009] Determine the formation pressure based on the P-wave velocity curve and the overlying formation pressure;

[0010] Determine horizontal ground stress based on rock mechanics parameters and formation pressure;

[0011] Based on rock mechanics parameters and horizontal geostress, wellbore stability analysis is performed at each drilling depth. The wellbore stability analysis includes wellbore collapse pressure analysis and wellbore rupture pressure analysis at any angle combination of well inclination and azimuth within the corresponding angle range.

[0012] In some embodiments, the rock mechanical parameters are determined based on the logging data of completed drillings and the cuttings data of the current drilling, including:

[0013] Perform preliminary fitting on the cuttings data of the current opening to obtain preliminary fitting data of the cuttings;

[0014] Perform secondary fitting on the preliminary cuttings fitting data according to the completed well logging data to obtain cuttings fitting data;

[0015] The rock mechanical parameters are determined based on the logging data and cuttings fitting data of the completed wells.

[0016] In some embodiments, based on rock mechanical parameters and horizontal ground stress, a wellbore stability analysis is performed for each drilling depth, including:

[0017] The minimum wellbore principal stress is calculated using the granularity reduction algorithm;

[0018] The slope halving algorithm is used to calculate the wellbore collapse pressure based on the minimum wellbore principal stress and the Mohr-Coulomb criterion.

[0019] The slope halving algorithm is used to calculate the wellbore fracture pressure based on the minimum wellbore principal stress and fracture criterion.

[0020] In some embodiments, after performing wellbore stability analysis at each drilling depth based on rock mechanics parameters and horizontal geostress, the method further includes:

[0021] Based on the wellbore collapse pressure, wellbore rupture pressure, formation pressure and leakage pressure, determine whether the corresponding well section is a risky well section.

[0022] In some embodiments, based on rock mechanical parameters and horizontal ground stress, a wellbore stability analysis is performed for each drilling depth, including:

[0023] Calculate the wellbore collapse pressure and wellbore rupture pressure according to the well inclination angle and azimuth angle of the depth to be calculated on the wellbore trajectory;

[0024] A pressure profile model of the entire well section is constructed based on the wellbore collapse pressure, wellbore rupture pressure, formation pressure and leakage pressure.

[0025] In some embodiments, after determining the formation pressure according to the P-wave velocity curve and the overlying formation pressure, the method further comprises:

[0026] The moving average algorithm is used to optimize the formation pressure and obtain the optimized formation pressure;

[0027] Accordingly, the horizontal ground stress is determined based on the rock mechanical parameters and formation pressure, including:

[0028] Determine horizontal ground stress based on rock mechanics parameters and optimized formation pressure;

[0029] The horizontal geostress is optimized by using the moving average algorithm to obtain the optimized horizontal geostress;

[0030] Accordingly, based on rock mechanical parameters and horizontal ground stress, wellbore stability analysis is performed at each drilling depth, including:

[0031] Based on rock mechanics parameters and optimized horizontal ground stress, wellbore stability analysis is performed at each drilling depth.

[0032] In a second aspect, the present application provides a device for analyzing wellbore stability during drilling, comprising:

[0033] An acquisition module is used to acquire the logging data of completed wells and the cuttings data of the current well;

[0034] A determination module is used to determine rock mechanical parameters based on the logging data of completed drillings and the cuttings data of the current drilling;

[0035] The determination module is also used to determine the formation pressure based on the P-wave velocity curve and the overlying formation pressure;

[0036] The determination module is also used to determine the horizontal ground stress based on the rock mechanical parameters and the formation pressure;

[0037] The analysis module is used to perform wellbore stability analysis at each drilling depth based on rock mechanics parameters and horizontal geostress. The wellbore stability analysis includes wellbore collapse pressure analysis and wellbore rupture pressure analysis at any angle combination of well inclination and azimuth within the corresponding angle range.

[0038] In a third aspect, the present application provides an electronic device, including: a memory and a processor;

[0039] The memory is used to store computer programs; the processor is used to execute the computer programs stored in the memory to implement the method for analyzing the stability of the wellbore during drilling in the first aspect and any one of the embodiments of the first aspect.

[0040] In a fourth aspect, the present application provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed by a processor, the method for analyzing the stability of the wellbore during drilling in the first aspect and any one of the embodiments of the first aspect is implemented.

[0041] In a fifth aspect, the present application provides a computer program product, which includes a computer program. When the computer program is executed by a processor, it implements the method for analyzing the stability of the wellbore during drilling in the first aspect and any one of the embodiments of the first aspect.

[0042] The method and equipment for analyzing the stability of the wellbore during drilling provided in the present application calculate rock mechanics parameters and ground stress by combining the logging data of completed drilling sessions and the cuttings data of the current session, and perform wellbore stability analysis for each drilling depth, different well inclination angles, and different azimuth angles based on the calculation results, thereby improving the accuracy of prediction of risky exploration wells and improving the safety and efficiency of drilling operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the present application or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 A flowchart of a method for analyzing wellbore stability during drilling provided in one embodiment of the present application;

[0045] Figure 2 A schematic diagram of a longitudinal wave velocity trend line provided in one embodiment of the present application;

[0046] Figure 3 A schematic diagram of the relationship between a calculated fracture pressure value and the minimum wellbore principal stress provided in one embodiment of the present application;

[0047] Figure 4 A flowchart of another method for analyzing wellbore stability during drilling provided by an embodiment of the present application;

[0048] Figure 5 A schematic diagram of the structure of a device for analyzing the stability of a wellbore during drilling provided by an embodiment of the present application;

[0049] Figure 6 A schematic diagram of the hardware structure of an electronic device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0051] With the deepening of oil and gas exploration and development, the target has gradually shifted to deep, ultra-deep, tight oil and gas and unconventional resources, and drilling operations are facing unprecedented challenges. The drilling depth has increased significantly, and the well design has become increasingly complex, evolving from traditional vertical wells to inclined wells, horizontal wells and even multi-branch wells. These changes have greatly increased the difficulty of drilling technology. Along with this, there are well wall stability problems, such as well wall collapse and fracture, which directly affect drilling efficiency, wellbore quality and operation safety.

[0052] Therefore, in the current drilling practice, it is very important to accurately model the geostress and analyze the wellbore stability of a single well, which has become an indispensable part of ensuring the safety and efficiency of drilling operations. To achieve this goal, geomechanical modeling technology has been widely used, and a relatively mature analysis system has been formed at the one-dimensional level. Before drilling operations, engineers will use seismic inversion technology to obtain the velocity curve of the underground rock formation, or refer to the logging data of wells with similar geological conditions in the adjacent area to predict the geostress state and potential wellbore stability problems of the target well section. Such prediction work provides an important scientific basis for drilling design, helps to optimize drilling plans and reduce uncertainties. After drilling is completed, by collecting detailed logging data and test results, the wellbore stability can be evaluated after drilling, the accuracy of the previous prediction can be verified, and the continuous improvement and optimization of drilling technology can be promoted.

[0053] However, when the above stability analysis method is applied to exploration blocks, especially when conducting risk exploration wells, there is often a certain deviation between the predicted results and the actual geological conditions. This deviation may lead to unforeseen geological problems during the drilling process, which poses a significant challenge to the safety and efficiency of drilling operations.

[0054] In response to the above problems, this application proposes a method and device for analyzing the stability of the wellbore during drilling. This method combines the logging data of the previous drilling and the rock cuttings data of the current drilling to perform rock mechanics modeling and geostress modeling for the well section where the current drilling is not completed and logging operations cannot be performed, and then makes a stability analysis. This method can provide wellbore stability analysis for the entire well section during drilling, and can better support the wellbore stability analysis of complex layers in risk exploration wells, ensuring that they are drilled well and quickly.

[0055] The technical solution of the present application is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0056] In the present application, the electronic device is used as the execution subject to execute the drilling wellbore stability analysis method of the following embodiment. Specifically, the execution subject can be a hardware device of the electronic device, or a software application that implements the following embodiment in the electronic device, or a computer-readable storage medium installed with the software application that implements the following embodiment, or a code that implements the software application of the following embodiment.

[0057] Figure 1 FIG. 1 is a flow chart of a method for analyzing wellbore stability during drilling provided by an embodiment of the present application. Figure 1 As shown, with the electronic device as the execution subject, the method of this embodiment may include the following steps:

[0058] S101, obtaining logging data of completed drillings and cuttings data of current drillings.

[0059] In this embodiment, after each drilling session is completed, the cuttings data and logging data of the corresponding session are collected, and the cuttings data of each session are preliminarily fitted, and the fitting results are analyzed. If the cuttings data are significantly different from the logging data, the preliminary fitting data of the cuttings are adjusted according to the logging data, including but not limited to optimizing the preliminary fitting data of the cuttings by translation, fitting or neural network algorithm to reduce the difference between the cuttings fitting data and the logging data.

[0060] If the current opening is not completed, its rock cuttings data will be used. When using it, the rock cuttings data of the current opening can be adjusted by referring to the adjustment process of the rock cuttings data of the completed opening to obtain the rock cuttings fitting data.

[0061] The multiple drilling data obtained, including logging data, cuttings data, and the test data mentioned later for verifying the calculation and analysis results, can be spliced ​​and used in time series after removing outliers and duplicate data, so that the data at each drilling depth can be processed in the same way to obtain the wellbore stability analysis results of the entire well section.

[0062] In this embodiment, the completed logging data include well diameter, gamma, sonic time difference and formation density.

[0063] The cuttings data of the current opening are adjusted to obtain the cuttings fitting data, including cuttings longitudinal wave velocity, cuttings shear wave velocity, cuttings formation density, and cuttings mud content.

[0064] S102, determining rock mechanics parameters based on the logging data of completed drillings and the cuttings data of the current drilling.

[0065] In this embodiment, the rock mechanics parameters include Poisson's ratio, Young's modulus, uniaxial compressive strength, internal friction angle and tensile strength.

[0066] Poisson's ratio is a static Poisson's ratio. The dynamic Poisson's ratio can be calculated from the well logging curve, and then converted into a static Poisson's ratio based on the correction coefficient and measured data. Among them, the well logging curve is the acoustic time difference and formation density, the measured data represents the rock mechanics test data, and the correction data can be obtained by fitting the Poisson's ratio test data. The default value is 1.

[0067] Young's modulus is the static Young's modulus. The dynamic Young's modulus can be calculated through the logging curve, and then the dynamic Young's modulus can be converted into the static Young's modulus based on the correction coefficient, empirical formula or measured data. The empirical formula is as shown in formula (1):

[0068] (1)

[0069] Among them, E s is the static Young's modulus, GPa;

[0070] E d is the dynamic Young's modulus, MPa.

[0071] To calculate the uniaxial compressive strength, it is necessary to calculate based on the mud content and dynamic Young's modulus, as shown in formula (2).

[0072] (2)

[0073] Among them, σ c is the uniaxial compressive strength, MPa;

[0074] E d is the dynamic Young's modulus, MPa;

[0075] V sh The mud content.

[0076] If the cuttings data of the current drilling are not available, only the logging data of the previous drilling are used for calculation, and the shale content is calculated according to formula (3) and formula (4). If the cuttings data are used, the shale content of the cuttings in the cuttings data can be directly called.

[0077] The gamma curve is used to calculate the mud content according to formula (3) and formula (4).

[0078] (3)

[0079] (4)

[0080] Among them, I GR is the mud content index, dimensionless;

[0081] GR, GR min , GR maxThey are the natural gamma values ​​of the target layer, pure mudstone layer and pure sandstone layer respectively;

[0082] V sh is the volume content of mud, ranging from 0 to 1, dimensionless;

[0083] GCUR is the Hilch index, which is related to the geological age. It is 3.7 for Paleogene-Neogene strata and 2 for older strata.

[0084] The internal friction angle is calculated according to formula (5).

[0085] (5)

[0086] in, is the internal friction angle, degree (°);

[0087] C is the cohesive force, MPa.

[0088] The cohesive force C is calculated according to formula (6).

[0089] (6)

[0090] K d is the dynamic bulk modulus, MPa.

[0091] The dynamic bulk modulus can be calculated based on the well logging curve.

[0092] The tensile strength is calculated according to formula (7).

[0093] (7)

[0094] S t Indicates tensile strength, MPa.

[0095] In the above rock mechanics parameter calculation process, any incomplete parts can be understood by referring to the prior art and will not be elaborated here.

[0096] S103. Determine the formation pressure according to the P-wave velocity curve and the overlying formation pressure.

[0097] In this embodiment, the longitudinal wave velocity curve can be obtained based on the logging acoustic wave time difference. By adding a trend line at the front end of the longitudinal wave velocity Vp curve, the trend line slope A and intercept B are obtained, and the compaction trend line (hereinafter referred to as the Vp trend line) is obtained. In the process of adding trend lines, mudstone filtering can be achieved based on the pre-defined gamma threshold value of each set of formations. For example, the default gamma threshold value is 75API. If the gamma curve value exceeds the threshold value, it is considered to be mudstone. The data is retained for trend establishment, and the data below the threshold value will be filtered out. Through mudstone filtering, it is ensured that the added trend line can reflect the real compaction characteristics and improve the calculation accuracy.

[0098] Figure 2 A schematic diagram of a longitudinal wave velocity trend line provided in one embodiment of the present application. Figure 2 As shown, in the formation pressure parameters, the top depth of the data segment is 1000m, the bottom depth of the data segment is 2500m, the read slope A is 14771, and the intercept B is -50000.

[0099] Based only on the longitudinal wave velocity, the following is derived:

[0100] The Vp trend line formula is Y=14771X-50000, where Y is the vertical depth and X is log(Vp trend);

[0101] X=(Y+50000) / 14771;

[0102] Vp trend = 10^((Y+50000) / 14771);

[0103] That is, the Vp trend is expressed as formula (8).

[0104] Vp trend = 10^((vertical depth - parameter B) / parameter A) (8)

[0105] After the Vp trend line is determined, the formation pressure can be calculated according to the Eaton method.

[0106] (9)

[0107] Where, Pp is the formation pressure, SG;

[0108] σ v is the overlying formation pressure, SG;

[0109] P 静水 is the hydrostatic pressure, MPa;

[0110] Vp is the longitudinal wave velocity, m / s.

[0111] In this embodiment, the overburden formation pressure includes the overburden formation pressure of the onshore drilling well and the overburden formation pressure of the offshore drilling well.

[0112] The calculation process of the overburden pressure of onshore drilling is shown in formula (10):

[0113] (10)

[0114] Among them, σ v当前 is the overlying formation pressure at the current depth, SG;

[0115] σ v上一个 is the overlying formation pressure at the previous depth, SG;

[0116] H 当前is the vertical depth of the current measuring point, m;

[0117] H 上一个 is the vertical depth of the last measuring point, m;

[0118] ρ 当前 is the formation density at the current depth, g / cm 3 .

[0119] The default overburden pressure at the first depth is 1.58 SG. It can be adjusted according to the formation pressure modeling results during use, and is generally in the range of 1.5-2.1SG.

[0120] When calculating the overlying stratum pressure at the second depth, the vertical depth of the first depth is taken as the core height.

[0121] According to the above calculation, the overlying stratum pressure below the seawater can also be calculated by combining the seawater density. , and then calculate the overlying formation pressure of offshore drilling at any depth based on formula (11).

[0122] (11)

[0123] Among them, σ v is the overlying formation pressure, SG;

[0124] σ v海水以下 is the overlying formation pressure below seawater, SG;

[0125] H 海水深度 is the depth from sea level to sea bottom, m;

[0126] ρ 海水 is the density of seawater, which is 1.03 g / cm 3 .

[0127] S104. Determine horizontal geostress based on rock mechanics parameters and formation pressure.

[0128] In this embodiment, a combined spring model is used to calculate the minimum horizontal geostress and the maximum horizontal geostress, and the geostress is obtained using formula (12).

[0129] (12)

[0130] in, and are the maximum horizontal ground stress and the minimum horizontal ground stress, MPa, respectively;

[0131] v is the static Poisson’s ratio, dimensionless;

[0132] E is the static Young's modulus, GPa;

[0133] is the effective stress coefficient, the default value is 1;

[0134] and are the tectonic stress coefficients in the directions of horizontal maximum geostress and horizontal minimum geostress, respectively.

[0135] Pp is the calculated formation pressure, and unit conversion is required when using it:

[0136] (13)

[0137] After the horizontal ground stress calculation is completed, unit conversion is required:

[0138] (14)

[0139] S105. Based on rock mechanics parameters and horizontal geostress, a wellbore stability analysis is performed for each drilling depth. The wellbore stability analysis includes wellbore collapse pressure analysis and wellbore rupture pressure analysis at any angle combination of well inclination angle and azimuth angle within the corresponding angle range.

[0140] The well inclination angle refers to the angle between the central axis of a point in the well and the plumb line of the earth. It is used to indicate the inclination of the wellbore trajectory, and its value range is [0, 90°].

[0141] The azimuth usually refers to the horizontal angle from the due north line of a certain point to the target direction line (such as the wellbore axis) in a clockwise direction. It is used to indicate the direction of the wellbore trajectory, and its value range is [0, 360°].

[0142] Any angle combination of the well inclination angle and the azimuth angle within the corresponding angle range refers to any angle combination of the well inclination angle in [0, 90°] and the azimuth angle in [0, 360°].

[0143] Well collapse pressure refers to the resistance of the formation to collapse due to its own weight due to formation pressure and formation mechanical properties without external forces. In simple terms, it is the minimum pressure that the formation rock can withstand while maintaining its integrity.

[0144] Wellbore fracture pressure refers to the critical pressure at which the exposed formation rock in the wellbore cracks or reopens the existing cracks when it is subjected to excessive pressure from the drilling fluid column in the wellbore. This is caused by the excessive density of the drilling fluid in the wellbore, which causes the circumferential pressure on the wellbore surrounding rock to be greater than its tensile strength.

[0145] In this embodiment, wellbore collapse pressure analysis and wellbore rupture pressure analysis are performed for each drilling depth, any well inclination angle, and any direction angle, so that a comprehensive stability analysis can be formed for each depth in order to determine the optimal drilling orientation.

[0146] The method for analyzing the stability of the wellbore wall during drilling provided in this embodiment combines the logging data of completed drillings and the cuttings data of the current drilling to perform a comprehensive stability analysis on each depth of the well during drilling. Since the cuttings data of the current drilling are combined, the final analysis result is more in line with the actual drilling situation of the current drilling, which improves the accuracy of the stability analysis for drilling risk prediction, provides a reference basis for optimizing the drilling direction, and improves the safety and efficiency of the drilling operation.

[0147] In some embodiments, the specific implementation of step S102 includes:

[0148] S1021. Perform preliminary fitting on the rock cuttings data of the current opening to obtain preliminary rock cuttings fitting data.

[0149] Among them, preliminary fitting of rock cuttings data refers to mathematical processing or statistical analysis of rock cuttings data. This processing usually involves data fitting technology, that is, connecting the discrete points of rock cuttings data into a smooth curve or function expression through mathematical methods (such as curve fitting, polynomial fitting, etc.) to better reveal the inherent laws and trends of the data.

[0150] S1022. Perform secondary fitting on the preliminary cuttings fitting data according to the completed well logging data to obtain cuttings fitting data.

[0151] Among them, the secondary fitting of the preliminary fitting data of the cuttings refers to combining the preliminary fitting data of the cuttings with the logging data to reveal the properties of underground rocks through comprehensive analysis. Through the secondary fitting, the difference between the preliminary fitting data of the cuttings and the logging data is reduced, and the subsequent cuttings data of the unlogged section can also be corrected by referring to the secondary fitting process.

[0152] S1023. Determine rock mechanics parameters based on the completed logging data and cuttings fitting data.

[0153] In this embodiment, the rock mechanical parameters are determined using the completed logging data and cuttings fitting data, which combines the advantages of the cuttings fitting data and the logging data. Through the mutual verification and supplementation of multiple data sources, the accuracy and reliability of rock property identification are improved, which helps to establish a rock physics model or empirical expression to directly describe specific geological phenomena and rock characteristics.

[0154] In some embodiments, the specific implementation of step S105 includes:

[0155] S201, using a granularity reduction algorithm to calculate the minimum wellbore principal stress;

[0156] S202, using the slope half algorithm, according to the minimum wellbore principal stress and the Mohr-Coulomb criterion, calculating the wellbore collapse pressure;

[0157] S203, using the slope half algorithm, according to the minimum wellbore principal stress and the fracture criterion, calculate the wellbore fracture pressure.

[0158] In this embodiment, the calculation process of the wellbore collapse pressure and the wellbore rupture pressure is first introduced.

[0159] The horizontal ground stress is transformed into various stress components at the wellbore wall in the polar coordinate system by performing multiple coordinate transformations and combining it with the liquid column pressure in the wellbore.

[0160] (15)

[0161] Among them, P i It is the liquid column pressure in the wellbore, in MPa.

[0162] θ is the wellbore angle, which represents the angle between the radial vector of the studied location and the direction of the maximum horizontal ground stress. The unit is degree (°), and the value is [0, 360°].

[0163] , , , , , They respectively represent the stress components on the surface of the inclined wellbore wall in the polar coordinate system under the combined action of the liquid column pressure in the wellbore and the horizontal ground stress, and the unit is MPa.

[0164] , , , , , They represent the stress components of the ground stress transformed to the coordinate system under specific well inclination and azimuth respectively.

[0165] On this basis, the three principal stress components of the wellbore are obtained.

[0166] (16)

[0167] in, , , They respectively represent the principal stress components of the wellbore, and the unit is MPa.

[0168] After determining the principal stress of the wellbore, the critical pressure value for wellbore collapse and wellbore rupture is determined using the criterion.

[0169] The critical pressure value of wellbore collapse pressure is calculated using the Mohr-Coulomb criterion.

[0170] (17)

[0171] (18)

[0172] Where μ is the internal friction coefficient of rock.

[0173] When calculating the collapse pressure, the fluid column pressure P in the well is i The calculation range of (SG) is 0.5-2.5SG.

[0174] Introduce the F parameter. If F is negative, the rock will not be destroyed; if F is positive, the rock will be destroyed. When F is equal to 0, the fluid column pressure P in the well is i The collapse pressure.

[0175] (19)

[0176] The critical pressure value of wellbore fracture pressure is calculated using the fracture criterion.

[0177] (20)

[0178] in, is the minimum wellbore principal stress, that is, the wellbore principal stress component , , The minimum value in MPa.

[0179] When calculating the fracture pressure, the fluid column pressure P in the well is i (SG) The calculation range is 1.5-3.0SG, and the fluid column pressure in the well that meets the fracture criteria is the fracture pressure.

[0180] After understanding how to determine the wellbore collapse pressure and the wellbore fracture pressure, the following describes how to determine the wellbore collapse pressure and the wellbore fracture pressure at any angle combination of the well inclination angle and the azimuth angle at the target depth.

[0181] The calculation amount of wellbore collapse pressure and fracture pressure in the whole well section with inclination angle of 0-90º and azimuth angle of 0-360º is very large. Taking a 7000m well as an example, assuming that the inclination angle and azimuth angle step length are 1º, the logging curve is thinned, and a set of data is taken for calculation every 1 meter, then 226,800,000 calculations are required.

[0182] In this embodiment, a granularity reduction algorithm is used to calculate the minimum wellbore principal stress.

[0183] Specifically, in the process of polar coordinate conversion of horizontal geostress and calculation of wellbore principal stress, the complete calculation needs to be performed with a step size of 0.5° and traversal of 360° of the wellbore circumference. Since the wellbore principal stress is a periodic function with a period of 180°, the granularity reduction algorithm only needs to traverse 180° of the wellbore circumference. First, traverse and calculate with a step size of 10° to find a smaller minimum wellbore principal stress. Then, with a step size of 2°, find a smaller minimum wellbore principal stress within a range of 10° around the minimum wellbore principal stress found in the previous step. Finally, with a step size of 0.5°, find the final minimum wellbore principal stress within a range of 2° around the smaller minimum wellbore principal stress found in the previous step, which is the true minimum wellbore principal stress within all wellbore circumferences. In this way, the number of calculations can be reduced from 720 to about 34 times, and the calculation time is 4% of the original algorithm. It should be understood that the step size here is only an example and does not represent a limitation on the scope of application.

[0184] This embodiment adopts a granularity decreasing algorithm, which reduces the amount of calculation and improves the calculation efficiency.

[0185] In this embodiment, the slope halving algorithm is used to calculate the wellbore fracture pressure according to the minimum wellbore principal stress and the fracture criterion.

[0186] The rupture criterion is as described above and will not be described again here. The slope halving algorithm is shown below.

[0187] Since the calculation of wellbore collapse pressure and wellbore rupture pressure requires traversing the azimuth angle from 0-360°, according to the relationship between the general calculation results and the azimuth angle change, it can be known that:

[0188] When the azimuth angle x is in [0, 180°], the calculation result is symmetric with 90° as the symmetry axis, that is, the calculation result when the azimuth angle x is 90°-180° is the same as the calculation result when the azimuth angle x is (180°-x).

[0189] When the azimuth angle x is in (180°, 360°], the calculation results are the same as when it is in [0, 180°].

[0190] Therefore, it is only necessary to calculate the wellbore collapse pressure and wellbore rupture pressure at azimuth angles of 0-90° first, and then map them to other azimuth angles according to the following relationship. The calculation time of this method is 25% of the calculation time of the original algorithm.

[0191] f(x)=f(180-x), 90° <x≤180°

[0192] f(x)=f(x-180), 180° <x≤270°

[0193] f(x)=f(360-x), 270° <x≤360°(21)

[0194] When calculating the fracture pressure corresponding to each well inclination and azimuth, the original algorithm performs traversal calculations within the set range of the trial value of the well liquid column pressure with a step size of 0.001, which usually requires thousands of calculations. When analyzing the trial value of the well liquid column pressure and the minimum wellbore principal stress, it can be found that the two present a monotonic nearly linear relationship (such as Figure 3 As shown in Figure 2, a slope-based halving algorithm is used to obtain the rupture pressure. The result can be found in about ten times, and the calculation time is about 1% of the original traversal method.

[0195] Specifically, the minimum wellbore principal stress corresponding to the lowest and highest calculated values ​​of the wellbore fluid column pressure is first calculated to obtain the interval range of the minimum wellbore principal stress. Then the fitting slope of the calculated value of the wellbore fluid column pressure and the minimum wellbore principal stress within this interval is calculated, that is, the nearly linear relationship between the calculated value of the wellbore fluid column pressure and the minimum wellbore principal stress is fitted into a completely linear relationship.

[0196] Based on the fitting slope, the calculated value of the wellbore liquid column pressure when the minimum wellbore principal stress is equal to the tensile strength St can be estimated. Based on this calculated value of the wellbore liquid column pressure and the above-mentioned nearly linear relationship curve, the actual minimum wellbore liquid column pressure corresponding to this calculated value can be determined.

[0197] According to whether the actual minimum borehole principal stress is greater than or less than St, it can be determined that the rupture point is in the right interval or left interval of the estimated trial value of the wellbore liquid column pressure, and then the slope halving algorithm is continued to be used in this interval to find the interval where the rupture point is located. Optionally, when the step size of the interval where the rupture point is located is less than 5, the rupture point can be directly found by traversal method.

[0198] In this embodiment, the slope halving algorithm is used to calculate the wellbore collapse pressure according to the minimum wellbore principal stress and the Mohr-Coulomb criterion.

[0199] The Mohr-Coulomb criterion is as described above and will not be described here. The slope halving algorithm is similar to that used in calculating the wellbore fracture pressure. Here, the parameter greater than or less than F is used as a judgment method for the subsequent search range.

[0200] The method for analyzing the stability of the wellbore during drilling provided in this embodiment reduces the amount of calculation and improves the calculation efficiency by adopting the granularity decline algorithm and the slope half algorithm for calculation.

[0201] In some embodiments, after executing step S105, the electronic device may also determine whether the corresponding well section is a risky well section according to the well wall collapse pressure, well wall fracture pressure, formation pressure and leakage pressure.

[0202] Specifically, for each depth, the larger value between the formation pressure and the collapse pressure is recorded as M1, and the smaller value between the leakage pressure and the fracture pressure is recorded as M2.

[0203] Optionally, when M2-M1<0.5SG, it indicates that the well section corresponding to the depth is a risky well section.

[0204] Optionally, this embodiment can also use a three-dimensional view to display risk sections along the wellbore trajectory, providing a basis for drilling risk prevention and improving drilling efficiency, and also providing a reference for sidetrack point selection. In the three-dimensional view, the risk section can be displayed in purple, and the remaining sections can be displayed in different colors according to the value of M2-M1, for example, a color bar from red to blue is displayed from large to small values.

[0205] The method for analyzing wellbore stability during drilling provided in this embodiment predicts the risk of well sections, thereby identifying accident-prone layers such as wellbore instability and narrow windows, providing a basis for improving drilling safety and drilling efficiency.

[0206] In some embodiments, the specific implementation of step S105 includes:

[0207] S301, calculating the wellbore collapse pressure and the wellbore rupture pressure according to the well inclination angle and the azimuth angle of the depth to be calculated on the wellbore trajectory.

[0208] S302, constructing a pressure profile model of the entire well section according to the wellbore collapse pressure, wellbore rupture pressure, formation pressure and leakage pressure.

[0209] In this embodiment, the calculation of the wellbore collapse pressure and the wellbore rupture pressure in S301 is consistent with the process of calculating the wellbore collapse pressure and the wellbore rupture pressure in the previous embodiment, with the only difference being that the well inclination angle and azimuth angle in S301 are angles on the wellbore trajectory.

[0210] In S302, the leakage pressure may be taken as the minimum horizontal ground stress.

[0211] In this embodiment, the wellbore collapse pressure and wellbore rupture pressure of the entire well section can be calculated based on parameters such as well depth, formation pressure, overlying formation pressure, horizontal minimum geostress, horizontal maximum geostress, horizontal maximum geostress azimuth, static Poisson's ratio, internal friction coefficient, effective stress coefficient, uniaxial compressive strength, tensile strength, well inclination angle and azimuth angle.

[0212] The three-dimensional view is used to display the wellbore collapse pressure, wellbore rupture pressure, formation pressure, leakage pressure and drilling fluid density of the entire well section to obtain the pressure profile model of the entire well section. In addition, the formation, lithology, wellbore structure, wellbore diameter and accident complex information can be combined to comprehensively analyze and adjust parameters to ensure that the pressure profile modeling is reasonable and can be applied to wellbore stability research, risk section identification, etc.

[0213] In some embodiments, after executing step S103, the electronic device may also use a moving average algorithm to optimize the formation pressure and obtain an optimized formation pressure.

[0214] On this basis, the specific implementation method of step S104 is to determine the horizontal ground stress according to the rock mechanics parameters and the optimized formation pressure.

[0215] Similarly, the electronic device can also use a moving average algorithm to optimize the horizontal geostress to obtain the optimized horizontal geostress.

[0216] On this basis, the specific implementation method of step S105 is to perform a wellbore stability analysis for each drilling depth based on rock mechanics parameters and optimized horizontal geostress.

[0217] Among them, the moving average algorithm refers to the calculation based on a given window length, gradually moving according to the depth interval, and each depth value is the average value of all data within the window length. The use of the moving average algorithm can reduce the impact of logging data fluctuations on the calculation results and improve the rationality of formation pressure, horizontal ground stress and subsequent stability analysis.

[0218] Figure 4 This is a flow chart of another method for analyzing wellbore stability during drilling provided by one embodiment of the present application. Figure 4 As shown, the drilling wellbore stability analysis method of this embodiment includes the following steps:

[0219] S401, obtaining drilling data.

[0220] In this embodiment, the drilling data includes borehole trajectory, logging data, cuttings fitting data, lithology description data, geological stratification data, drilling fluid density, formation pressure test data, rock mechanics test data, ground breaking test data, mud loss density, wellbore structure data and accident complex data. Accident complex data includes accident data such as blowout, well collapse, and well leakage.

[0221] S402, using logging data and rock fitting data to perform rock mechanics modeling, formation pressure modeling, geostress modeling and wellbore stability analysis.

[0222] Among them, lithology description data, geological stratification data, drilling fluid data, wellbore structure and accident complexity data are used to conduct a comprehensive analysis of the modeling results and guide parameter adjustments to reduce the uncertainty of the wellbore stability analysis results.

[0223] Rock mechanics modeling includes the calculation of Poisson's ratio, Young's modulus, uniaxial compressive strength, internal friction angle, and tensile strength. After calculation, calibration can be performed using rock mechanics test data.

[0224] Formation pressure modeling includes the calculation of formation pressure. After calculation, the formation pressure can be calibrated using formation pressure test data and accident complex data.

[0225] The geostress modeling includes the calculation of the horizontal maximum geostress and the horizontal minimum geostress. After the calculation, the calculation results can be calibrated in combination with the ground failure test data and / or the mud loss density.

[0226] The wellbore stability analysis of this embodiment includes wellbore collapse pressure analysis and wellbore rupture pressure analysis at each depth under the well trajectory parameters, that is, full well section pressure profile modeling analysis. Wellbore stability analysis also includes wellbore collapse pressure analysis and wellbore rupture pressure analysis under any angle combination of well inclination and azimuth within the corresponding angle range. Wellbore stability analysis results can also be corrected according to accident complexity data and drilling fluid density.

[0227] The above calculation process is similar to the above embodiment, and will not be described in detail in this embodiment. Compared with the above embodiment, this embodiment also calibrates the modeling result in combination with other data, thereby improving the reliability of the modeling result.

[0228] The wellbore stability analysis results of this embodiment can be used to predict unstable well sections, abnormal pressure well section warnings, provide drilling fluid safety density windows, optimal drilling directions, assist in adjusting casing depth, and select side drilling well sections.

[0229] Figure 5 FIG. 1 is a schematic diagram showing the structure of a device for analyzing the stability of a wellbore during drilling provided by an embodiment of the present application. Figure 5 As shown, the drilling well wall stability analysis device 10 of this embodiment is used to implement the operation corresponding to the electronic device in any of the above method embodiments. The drilling well wall stability analysis device 10 of this embodiment includes:

[0230] The acquisition module 11 is used to acquire the logging data of completed wells and the cuttings data of the current well;

[0231] A determination module 12 is used to determine rock mechanical parameters based on the logging data of completed drillings and the cuttings data of the current drilling;

[0232] The determination module 12 is further used to determine the formation pressure according to the P-wave velocity curve and the overlying formation pressure;

[0233] The determination module 12 is also used to determine the horizontal ground stress according to the rock mechanical parameters and the formation pressure;

[0234] The analysis module 13 is used to perform wellbore stability analysis at each drilling depth based on rock mechanics parameters and horizontal geostress. The wellbore stability analysis includes wellbore collapse pressure analysis and wellbore rupture pressure analysis at any angle combination of well inclination angle and azimuth angle within the corresponding angle range.

[0235] The drilling well wall stability analysis device 10 provided in the embodiment of the present application can execute the above method embodiment. Its specific implementation principle and technical effects can be found in the above method embodiment, and this embodiment will not be repeated here.

[0236] Figure 6 FIG. 1 shows a hardware structure diagram of an electronic device provided in an embodiment of the present application. Figure 6 As shown, the electronic device 20 is used to implement the operations corresponding to the electronic device in any of the above method embodiments. The electronic device 20 of this embodiment may include: a memory 21, a processor 22 and a communication interface 24.

[0237] The memory 21 is used to store computer programs. The memory 21 may include a high-speed random access memory (RAM), and may also include a non-volatile memory (NVM), such as at least one disk memory, and may also be a USB flash drive, a mobile hard disk, a read-only memory, a disk or an optical disk.

[0238] The processor 22 is used to execute the computer program stored in the memory to implement the method in the above embodiment. For details, please refer to the relevant description in the above method embodiment. The processor 22 can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc. The steps of the method disclosed in the invention can be directly embodied as being executed by a hardware processor, or can be executed by a combination of hardware and software modules in the processor.

[0239] Optionally, the memory 21 may be independent or integrated with the processor 22 .

[0240] When the memory 21 is a device independent of the processor 22, the electronic device 20 may further include a bus 23. The bus 23 is used to connect the memory 21 and the processor 22. The bus 23 may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus. The bus may be divided into an address bus, a data bus, a control bus, and the like. For ease of representation, the bus in the drawings of the present application is not limited to only one bus or one type of bus.

[0241] The communication interface 24 may be connected to the processor 22 via the bus 23. The processor 22 may control the communication interface 24 to implement the functions of receiving and sending signals.

[0242] The electronic device 20 provided in this embodiment can be used to execute the above-mentioned method for analyzing the stability of the wellbore during drilling. Its implementation method and technical effect are similar, and this embodiment will not be repeated here.

[0243] The present application also provides a computer-readable storage medium, in which a computer program / instruction is stored. When the computer program / instruction is executed by a processor, it is used to implement the methods provided in the various embodiments described above.

[0244] Among them, the computer-readable storage medium can be a computer storage medium or a communication medium. The communication medium includes any medium that is convenient for transmitting a computer program from one place to another. The computer storage medium can be any available medium that can be accessed by a general-purpose or special-purpose computer. For example, a computer-readable storage medium is coupled to a processor so that the processor can read information from the computer-readable storage medium and write information to the computer-readable storage medium. Of course, the computer-readable storage medium can also be a component of the processor. The processor and the computer-readable storage medium can be located in an application-specific integrated circuit (ASIC). In addition, the ASIC can be located in a user device. Of course, the processor and the computer-readable storage medium can also exist in a communication device as discrete components.

[0245] Specifically, the computer-readable storage medium may be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk. The storage medium may be any available medium that can be accessed by a general or special-purpose computer.

[0246] The present application also provides a computer program product, which includes a computer program / instruction, and the computer program / instruction is stored in a computer-readable storage medium. At least one processor of the device can read the computer program / instruction from the computer-readable storage medium, and at least one processor executes the computer program / instruction so that the device implements the methods provided in the various embodiments described above.

[0247] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of modules is only a logical function division. There may be other division methods in actual implementation. For example, multiple modules can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, which can be electrical, mechanical or other forms.

[0248] Among them, each module can be physically separated, for example, installed in different locations of a device, or installed on different devices, or distributed on multiple network units, or distributed on multiple processors. Each module can also be integrated together, for example, installed in the same device, or integrated in a set of codes. Each module can exist in the form of hardware, or can also exist in the form of software, or can also be implemented in the form of software plus hardware. The present application can select some or all of the modules according to actual needs to achieve the purpose of the present embodiment.

[0249] It should be understood that, although the various steps in the flowcharts in the above-described embodiments are sequentially displayed according to the indications of the arrows, these steps are not necessarily executed sequentially in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps is not strictly limited in order, and they can be executed in other orders. Moreover, at least a portion of the steps in the figure may include a plurality of sub-steps or a plurality of stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily to be carried out sequentially, but can be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0250] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with the relevant laws, regulations and standards of relevant countries and regions, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0251] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for analyzing wellbore stability during drilling, characterized in that: The method comprises: Obtain the logging data of completed drillings and the cuttings data of the current drilling; Determine rock mechanical parameters based on logging data from completed wells and cuttings data from current wells; Determine the formation pressure based on the P-wave velocity curve and the overlying formation pressure; determining horizontal geostress according to the rock mechanics parameters and the formation pressure; Based on the rock mechanics parameters and the horizontal geostress, a wellbore stability analysis is performed for each drilling depth, wherein the wellbore stability analysis includes wellbore collapse pressure analysis and wellbore rupture pressure analysis under any angle combination of well inclination angle and azimuth angle within the corresponding angle range; Based on the logging data of completed drillings and the cuttings data of the current drilling, the rock mechanical parameters are determined, including: Performing preliminary fitting on the rock cuttings data of the current opening to obtain preliminary rock cuttings fitting data; The preliminary cuttings fitting data are adjusted according to the completed logging data, and the preliminary cuttings fitting data are optimized by translation, fitting or neural network algorithm to reduce the difference between the cuttings fitting data and the logging data, thereby obtaining the cuttings fitting data; The rock mechanics parameters are determined based on the logging data of the completed wells and the cuttings fitting data.

2. The method according to claim 1, characterized in that Based on the rock mechanics parameters and the horizontal geostress, a wellbore stability analysis is performed for each drilling depth, including: The minimum wellbore principal stress is calculated using the granularity reduction algorithm; The wellbore collapse pressure is calculated by using a slope halving algorithm according to the minimum wellbore principal stress and the Mohr-Coulomb criterion; The wellbore fracture pressure is calculated by adopting the slope halving algorithm according to the minimum wellbore principal stress and the fracture criterion.

3. The method according to claim 2, characterized in that After the wellbore stability analysis is performed at each drilling depth based on the rock mechanics parameters and the horizontal geostress, the method further includes: According to the wellbore collapse pressure, the wellbore fracture pressure, the formation pressure and the leakage pressure, it is determined whether the corresponding well section is a risky well section.

4. The method according to claim 1, characterized in that Based on the rock mechanics parameters and the horizontal geostress, a wellbore stability analysis is performed for each drilling depth, including: Calculate the wellbore collapse pressure and wellbore rupture pressure according to the well inclination angle and azimuth angle of the depth to be calculated on the wellbore trajectory; A full-well section pressure profile model is constructed according to the wellbore collapse pressure, the wellbore fracture pressure, the formation pressure and the leakage pressure.

5. The method according to any one of claims 1 to 4, characterized in that: After determining the formation pressure based on the P-wave velocity curve and the overlying formation pressure, it also includes: Using a moving average algorithm to optimize the formation pressure, and obtain an optimized formation pressure; Accordingly, determining the horizontal geostress according to the rock mechanical parameters and the formation pressure includes: Determining horizontal geostress according to the rock mechanics parameters and the optimized formation pressure; Using a moving average algorithm to optimize the horizontal geostress to obtain optimized horizontal geostress; Accordingly, based on the rock mechanical parameters and the horizontal geostress, a wellbore stability analysis is performed for each drilling depth, including: Based on the rock mechanics parameters and the optimized horizontal geostress, a wellbore stability analysis is performed at each drilling depth.

6. A device for analyzing the stability of a wellbore during drilling, characterized in that: include: An acquisition module is used to acquire the logging data of completed wells and the cuttings data of the current well; A determination module is used to determine rock mechanical parameters based on the logging data of completed drillings and the cuttings data of the current drilling; The determination module is further used to determine the formation pressure according to the P-wave velocity curve and the overlying formation pressure; The determination module is further used to determine horizontal ground stress according to the rock mechanical parameters and the formation pressure; An analysis module, for performing a wellbore stability analysis for each drilling depth based on the rock mechanics parameters and the horizontal geostress, wherein the wellbore stability analysis includes a wellbore collapse pressure analysis and a wellbore rupture pressure analysis under any angle combination of the well inclination angle and the azimuth angle within the corresponding angle range; The determination module is specifically used to perform preliminary fitting on the rock cuttings data of the current opening to obtain preliminary rock cuttings fitting data; adjust the preliminary rock cuttings fitting data according to the logging data of the completed opening, optimize the preliminary rock cuttings fitting data through translation, fitting or neural network algorithm to reduce the difference between the rock cuttings fitting data and the logging data, and obtain the rock cuttings fitting data; determine the rock mechanical parameters according to the logging data of the completed opening and the rock cuttings fitting data.

7. An electronic device, characterized in that: include: Memory and processor; The memory is used to store computer programs; The processor is used to execute the computer program stored in the memory to implement the method for analyzing wellbore stability during drilling as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, it is used to implement the method for analyzing the stability of a wellbore during drilling as claimed in any one of claims 1 to 5.

9. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor, the method for analyzing the stability of a wellbore during drilling according to any one of claims 1 to 5 is implemented.

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