Method and device for determining anisotropic horizontal principal stress of sand-mud interbed

Abstract

The invention discloses a method for determining anisotropic horizontal principal stress of a sand-mud interbed. The method comprises the steps that on the basis of logging data, under the assumption of a stratum transverse isotropic medium, longitudinal and transverse wave velocities perpendicular to and parallel to the stratum direction at the specified depth and longitudinal wave velocities in the direction forming a specified included angle with the stratum are determined; determining the rigidity modulus at the specified depth based on the first relation expression of the wave velocity and the rigidity modulus; determining the dynamic Poisson's ratio and the elastic modulus in the direction based on the second relation expression of the rigidity modulus and the dynamic Poisson's ratios and the elastic moduli in the direction parallel to and perpendicular to the stratum; converting the dynamic elastic modulus and the Poisson's ratio in the direction parallel to and perpendicular to the stratum into the static elastic modulus and the Poisson's ratio in the direction; and determining anisotropic horizontal principal stress at a specified depth by using a transverse isotropic stratum ground stress model based on the static elastic modulus and Poisson's ratio in parallel and vertical stratum directions. The calculation accuracy of the anisotropic rock mechanical parameters and the horizontal principal stress can be improved.

Description

Technical Field

[0001] This invention relates to the field of rock physics, and in particular to a method and apparatus for determining the anisotropic horizontal principal stress of interbedded sand and mud. Background Technology

[0002] Sandstone-mudstone interbedded strata are characterized by intense geological tectonic activity and the frequent development of interbedded sandstone and mudstone of varying thicknesses. Under conditions of strong tectonic compression, accurate prediction of anisotropic rock mechanical parameters can clarify the stress-blocking capacity of mudstone sections, thereby improving the calculation accuracy of anisotropic horizontal principal stresses and, further, effectively enhancing the prediction accuracy of three-pressure profiles under strong tectonic compression. Traditional rock mechanical parameter predictions are based on the assumption of stratigraphic isotropy, and rock mechanical parameters include elastic modulus and Poisson's ratio. However, sandstone-mudstone interbedded strata exhibit significant differences in mechanical properties in the horizontal and vertical directions, making them more consistent with a lateral isotropic model. Considering the differences in mechanical properties in the horizontal and vertical directions, existing methods for obtaining anisotropic rock mechanical parameters are mainly divided into special logging methods and experimental methods.

[0003] The special logging method involves first obtaining the P-wave slowness, S-wave slowness, fast S-wave slowness, slow S-wave slowness, and horizontal S-wave slowness using sonic scanning logging or cross-dipole sonic logging. This yields the elastic stiffness matrix or compliance matrix. Based on anisotropic analysis, and using a transversely isotropic medium model, the dynamic Young's modulus and Poisson's ratio in the horizontal direction and the dynamic Young's modulus and Poisson's ratio in the vertical direction are calculated. By simultaneously testing dynamic and static parameters, the relationship between the dynamic and static elastic parameters can be obtained, thus converting the dynamic Young's modulus and dynamic Poisson's ratio into static Young's modulus and static Poisson's ratio.

[0004] The experimental method was as follows: Nine parameters were determined using ultrasonic wave velocity testing, measuring the longitudinal wave velocity in six directions and the transverse wave velocity in three directions: longitudinal wave velocities Vpx, Vpy, and Vpz propagating along the x, y, and z axes; transverse wave velocities propagating along the z axis and vibrating along the x and y axes, and transverse wave velocities propagating along the x axis and vibrating along the y axis, Vsz-x, Vsz-y, and Vsy-s; and longitudinal wave velocities Vp(xy-45°), Vp(xz-45°), and Vp(yz-45°) propagating along the 45° angle between the axes in the xy, xz, and yz planes. Based on the correspondence between the nine longitudinal and transverse wave velocities and the stiffness modulus, and the correspondence between the elastic modulus and Poisson's ratio and the stiffness modulus, the elastic modulus and Poisson's ratio in the vertical and horizontal directions were calculated. Summary of the Invention

[0005] The inventors of this application have discovered that existing methods for obtaining anisotropic rock mechanical parameters, such as elastic modulus and Poisson's ratio, involve high economic and time costs when using special logging methods to obtain data on P-wave slowness, S-wave slowness, fast S-wave slowness, slow S-wave slowness, and horizontal S-wave slowness. Experimental methods are time-consuming and generally only select a specific formation depth for wave velocity data acquisition, resulting in a limited number of data points that cannot fully describe the data for the entire formation. These two methods for obtaining anisotropic rock mechanical parameters make it even more difficult to determine the anisotropic horizontal principal stress of the entire sand-mud interbedded layer, failing to provide accurate data support for practical engineering.

[0006] This invention provides a method for determining the anisotropic horizontal principal stress of interbedded sand and mud layers, comprising:

[0007] Based on well logging data, under the assumption of a transversely isotropic medium in the formation, the longitudinal and transverse wave velocities in a first specified direction and the longitudinal wave velocity in a second specified direction at a specified depth in the formation are determined. The first specified direction includes a direction perpendicular to the formation and a direction parallel to the formation, and the second specified direction includes a direction that forms a specified angle with the formation.

[0008] Based on the determined wave velocity, the stiffness modulus at a specified depth is determined using the first relationship between wave velocity and stiffness modulus.

[0009] Based on the stiffness modulus at the specified depth, the dynamic rock mechanics parameters in the first specified direction are determined using a pre-established second relationship between the stiffness modulus and the dynamic rock mechanics parameters in the first specified direction. The dynamic rock mechanics parameters include Poisson's ratio and dynamic elastic modulus. The second relationship is constructed based on the stress-strain relationship of the rock block under the assumption of a transversely isotropic medium in the formation.

[0010] Convert the dynamic rock mechanics parameters in the first specified direction into static rock mechanics parameters;

[0011] Based on the static rock mechanics parameters in the first specified direction, the anisotropic horizontal principal stress at a specified depth is determined using a transversely isotropic stratum stress model.

[0012] In some optional embodiments, determining the P-wave velocity and S-wave velocity in a first specified direction and the P-wave velocity in a second specified direction at a specified depth in the formation, based on well logging data and under the assumption of a laterally isotropic medium, includes:

[0013] Based on sonic time-of-flight logging data, determine the P-wave velocity or S-wave velocity in the vertical direction of the formation at a specified depth. Based on the determined wave velocity and a pre-determined P-wave / S-wave conversion formula, determine the S-wave velocity or P-wave velocity in the vertical direction of the formation at a specified depth.

[0014] The formation is divided into a micro-element combination of sand-mud-sand layers. Based on the logging data of each layer in the micro-element combination, the P-wave and S-wave velocities in the direction parallel to the formation at a specified depth in the mudstone section are determined. Based on the sonic transit time logging and density logging data, the P-wave and S-wave velocities in the direction parallel to the formation at a specified depth in the sandstone section are determined.

[0015] Based on the longitudinal and transverse wave velocities in the first specified direction at a specified depth, the longitudinal wave velocity in the second specified direction is determined using a transverse medium model.

[0016] In some optional embodiments, the process of determining the P-wave and S-wave conversion formula includes:

[0017] The conversion coefficients of P-wave and S-wave velocities are determined based on the rock density and a pre-established fitting relationship, and the P-wave and S-wave conversion formulas are determined based on the conversion coefficients.

[0018] In some optional embodiments, the conversion coefficients for determining P-wave and S-wave velocities based on rock density and a pre-established fitting relationship are used to determine the P-wave and S-wave conversion formulas, including...

[0019] The conversion coefficients for P-wave and S-wave velocities are determined based on the density of the rock using the following fitting relationship:

[0020]

[0021] Based on the conversion coefficients of the P and S waves, the following P and S wave conversion formulas are determined:

[0022] V s =V p A

[0023] Among them, V p V is the longitudinal wave velocity. s ρ is the transverse wave velocity; A is the conversion coefficient between the longitudinal and transverse wave velocities, determined by the rock density ρ.

[0024] In some optional embodiments, the step of dividing the formation into a micro-elemental assemblage of sand-mud-sand layers, and determining the P-wave and S-wave velocities parallel to the formation at a specified depth in the mudstone section based on well logging data of each layer in the micro-elemental assemblage, includes:

[0025] The clay content coefficient was determined based on gamma-ray logging data; the density fitting coefficient was determined based on sonic transit time logging data.

[0026] Based on the clay content coefficient, density fitting coefficient, horizontal P-wave velocity of the upper and lower sandstone sections in the micro-element assembly, well logging data of the upper and lower sandstone sections in the micro-element assembly, and well logging data at a specified depth in the mudstone section of the micro-element assembly, the P-wave velocity parallel to the formation at a specified depth in the mudstone section of the micro-element assembly is determined using a pre-established horizontal P-wave velocity calculation model; the well logging data includes density, gamma data, and depth.

[0027] Based on the P-wave velocity in the mudstone section at a specified depth in the micro-element assembly, parallel to the strata, the P-wave and S-wave conversion formula is used to determine the S-wave velocity at the corresponding depth in the parallel to the strata.

[0028] In some optional embodiments, the process of determining the clay content coefficient includes:

[0029] The clay content coefficient is determined based on gamma logging data using the following formula:

[0030]

[0031] Where SH is the relative value of the gamma data at the current measuring point, GRmax is the maximum gamma data of the mudstone section, GRmin is the minimum gamma data of the mudstone section, and GR is the gamma data of the current measuring point.

[0032] GCUR is a dimensionless coefficient, V sh This represents the mud content coefficient.

[0033] In some optional embodiments, the step of determining the P-wave velocity parallel to the formation direction at a specified depth in the mudstone section of the micro-element assembly based on the clay content coefficient, density fitting coefficient, horizontal P-wave velocity of the upper and lower sandstone sections in the micro-element assembly, well logging data of the upper and lower sandstone sections in the micro-element assembly, and well logging data at a specified depth in the mudstone section of the micro-element assembly, using a pre-established horizontal P-wave velocity calculation model, includes:

[0034] Based on the clay content coefficient, density fitting coefficient, horizontal P-wave velocity, density, gamma data, and depth of the upper and lower sandstone sections in the micro-element assembly, and the density, gamma data, and depth of the mudstone section at a specified depth, the P-wave velocity of the measuring point corresponding to the specified depth of the mudstone section in the direction parallel to the strata is determined using the following formula:

[0035]

[0036] Among them, V ph(n) V represents the horizontal P-wave velocity at the nth measuring point in the mudstone section. ph(s1) and V ph(s2) Den represents the average longitudinal wave velocity in the horizontal direction of the upper and lower sandstone sections. n Den is the density at the nth measuring point of the mudstone segment in the micro-element.s1 and Den s2 GR represents the average density of the upper and lower sandstone sections. n GR is the gamma value at the nth measuring point in the mudstone section. s1 and GR s2 H represents the average gamma value of the upper and lower sandstone sections. n H represents the depth of the nth measuring point in the mudstone section. s1 and H s2 β1 represents the average depth of the upper and lower sandstone sections; β2 is the density fitting coefficient and β1 is the clay content fitting coefficient.

[0037] In some optional embodiments, determining the longitudinal wave velocity in the second specified direction based on the longitudinal and transverse wave velocities in the first specified direction at a specified depth using a transverse medium model includes:

[0038] Based on the P-wave velocity perpendicular to the formation and the P-wave velocity parallel to the formation at a specified depth, determine the anisotropy parameters.

[0039] Transition parameters are determined based on the transverse wave velocity perpendicular to the formation direction, the longitudinal wave velocity parallel to the formation direction, anisotropy parameters, and the longitudinal-transverse wave conversion coefficient at a specified depth; the longitudinal-transverse wave conversion coefficient is determined based on the rock density.

[0040] Based on anisotropy parameters, transition parameters, P-wave velocity perpendicular to the formation, and the angle between the specified direction and the formation, the P-wave velocity at the specified angle to the formation is determined using a transverse medium model.

[0041] In some optional embodiments, anisotropy parameters are determined based on the P-wave velocities perpendicular to and parallel to the formation at a specified depth, including:

[0042] The anisotropy parameters are determined using the following formula based on the P-wave velocities perpendicular to and parallel to the formation at a specified depth:

[0043]

[0044] Among them, V pv V represents the longitudinal wave velocity perpendicular to the strata. ph The longitudinal wave velocity is parallel to the direction of the strata.

[0045] Based on the shear wave velocity perpendicular to the formation, the P-wave velocity parallel to the formation, anisotropy parameters, and P-S / S-wave conversion coefficients at a specified depth, transition parameters are determined, including:

[0046] The transition parameters are determined using the following formula based on the shear wave velocity perpendicular to the formation, the P-wave velocity parallel to the formation, anisotropy parameters, and the P-S / S-wave conversion coefficients at a specified depth:

[0047]

[0048] Among them, V sv It is the transverse wave velocity, V, in the direction perpendicular to the strata. pv ε is the P-wave velocity parallel to the strata, ε is the anisotropy parameter, and A is the P-wave / S-wave conversion coefficient.

[0049] In some optional embodiments, determining the P-wave velocity at a specified angle to the formation using a transverse medium model based on anisotropy parameters, transition parameters, P-wave velocity perpendicular to the formation direction, and the angle between the specified direction and the formation includes:

[0050] Based on anisotropy parameters, transition parameters, P-wave velocity perpendicular to the formation, and the angle between the specified direction and the formation, the following Thmosen transverse medium formula is used to determine the P-wave velocity at the specified angle to the formation:

[0051] V p (θ)=V pv (1+δsin 2 θcos 2 θ+εsin 4 θ)

[0052] Where θ is the angle between the specified direction and the stratum, V pv ε is the longitudinal wave velocity perpendicular to the formation, ε is the anisotropy parameter, and δ is the transition parameter.

[0053] In some optional embodiments, determining the stiffness modulus at a specified depth based on the determined wave velocity using a first relationship between wave velocity and stiffness modulus includes:

[0054] Based on the determined P-wave and S-wave velocities in the first and second specified directions at a specified depth, the stiffness modulus at the first and second specified directions is determined using the following first relationship:

[0055]

[0056] C 12 =C 11 -2C 66

[0057]

[0058] Wherein, C11, C22, C33, C44, C55, C66, C12, C13, and C23 are the stiffness moduli at a specified depth in the first and second specified directions;

[0059] V sv It is the transverse wave velocity, V, in the direction perpendicular to the strata.pv It is the longitudinal wave velocity parallel to the strata, V pv V represents the longitudinal wave velocity perpendicular to the strata. ph V represents the longitudinal wave velocity parallel to the strata direction. p θ is the longitudinal wave velocity at a specified angle to the formation.

[0060] In some optional embodiments, under the assumption of a laterally isotropic medium, the process of constructing a second relational expression based on the stress-strain relationship of the rock block includes:

[0061] The stiffness and flexibility matrices of the stress-strain constitutive equations are constructed based on the stress-strain relationship of the rock block.

[0062] Based on the correspondence between the stiffness matrix and the flexibility matrix, a second relationship is determined between the stiffness modulus in the stiffness matrix and the dynamic elastic modulus and dynamic Poisson's ratio in the first specified direction in the flexibility matrix. The second relationship is expressed as follows:

[0063]

[0064]

[0065] Wherein, C11, C33, C12, and C13 are the stiffness moduli at a specified depth in the first and second specified directions;

[0066] E v E represents the dynamic elastic modulus perpendicular to the formation direction. h It represents the dynamic elastic modulus parallel to the stratum direction;

[0067] μ v μ is the dynamic Poisson's ratio perpendicular to the formation direction. h This represents the dynamic Poisson's ratio parallel to the stratum direction.

[0068] In some optional embodiments, the conversion of dynamic rock mechanical parameters in a first specified direction into static rock mechanical parameters includes:

[0069] Based on a predetermined dynamic-static rock mechanics parameter conversion relationship, the dynamic rock mechanics parameters in the first specified direction are converted into static rock mechanics parameters in the first specified direction; the dynamic-static rock mechanics parameter conversion relationship is obtained by fitting rock stress test experimental data.

[0070] In some optional embodiments, the determination of the anisotropic horizontal principal stress at a specified depth using a transversely isotropic stratigraphic stress model based on the static rock mechanics parameters in a first specified direction includes:

[0071] Based on acoustic emission Kaister test experiments, the Biot effective stress coefficient, horizontal maximum tectonic stress coefficient, and horizontal minimum tectonic stress coefficient of the transverse isotropic stratum stress model were determined.

[0072] Based on the static rock mechanics parameters, well logging data, Biot effective stress coefficient, horizontal maximum tectonic stress coefficient, and horizontal minimum tectonic stress coefficient in the first specified direction, the maximum anisotropic horizontal principal stress and minimum anisotropic horizontal principal stress of the sand-mud interbedded layer at a specified depth are determined using a transversely isotropic formation stress model; the well logging data includes overlying strata pressure and formation pore pressure.

[0073] In some optional embodiments, the static rock mechanics parameters, well logging data, Biot effective stress coefficient, maximum horizontal tectonic stress coefficient, and minimum horizontal tectonic stress coefficient in the first specified direction are used to determine the maximum and minimum anisotropic horizontal principal stresses of the sand-mud interbedded layer at a specified depth using a transversely isotropic formation stress model, including:

[0074] Based on the static elastic modulus and Poisson's ratio parallel to and perpendicular to the stratigraphic direction, overlying strata pressure, formation pore pressure, Biot effective stress coefficient, maximum horizontal tectonic stress coefficient, and minimum horizontal tectonic stress coefficient, the following Thiercelin model formula is used to determine the maximum and minimum anisotropic horizontal principal stresses of the sand-mud interbedded layer at a specified depth:

[0075]

[0076]

[0077] Where, σ H For the maximum anisotropic horizontal principal stress, σ h The minimum anisotropic horizontal principal stress;

[0078] E h E is the static elastic modulus perpendicular to the formation direction. v μ is the static elastic modulus parallel to the formation direction. h μ is the static Poisson's ratio perpendicular to the formation direction. v σ is the static Poisson's ratio parallel to the stratum direction. v For the pressure of the overlying strata, p p α represents the formation pore pressure; α is the Biot effective stress coefficient; w1 and w2 are the maximum and minimum horizontal tectonic stress coefficients, respectively.

[0079] This invention also provides an anisotropic horizontal principal stress calculation device for sand-mud interlayers, comprising:

[0080] The wave velocity determination unit is used to determine the longitudinal and transverse wave velocities in a first specified direction and the longitudinal wave velocity in a second specified direction at a specified depth of the formation based on well logging data and under the assumption of a transversely isotropic medium in the formation. The first specified direction includes a direction perpendicular to the formation and a direction parallel to the formation, and the second specified direction includes a direction that forms a specified angle with the formation.

[0081] The stiffness modulus determination unit is used to determine the stiffness modulus at a specified depth based on the determined wave velocity and using the first relationship between wave velocity and stiffness modulus.

[0082] The rock mechanics parameter determination unit is used to determine the dynamic rock mechanics parameters in the first specified direction based on the stiffness modulus at the specified depth and using a pre-established second relationship expression between the stiffness modulus and the dynamic rock mechanics parameters in the first specified direction; the dynamic rock mechanics parameters include Poisson's ratio and dynamic elastic modulus; the second relationship expression is constructed based on the stress-strain relationship of the rock block under the assumption of a transversely isotropic medium in the formation;

[0083] The elastic modulus conversion unit is used to convert dynamic rock mechanics parameters in a first specified direction into static rock mechanics parameters.

[0084] The horizontal principal stress determination unit is used to determine the anisotropic horizontal principal stress at a specified depth based on the static rock mechanics parameters in the first specified direction using a transversely isotropic stratum stress model.

[0085] This invention also provides a computer storage medium storing computer-executable instructions, which, when executed by a processor, implement the method for determining the anisotropic horizontal principal stress of sand-mud interlayers as described above.

[0086] This invention also provides a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements a method for determining the anisotropic horizontal principal stress of sand-mud interlayers as described above.

[0087] This invention also provides a computer program product, which includes a computer program that, when executed by a processor, implements a method for determining the anisotropic horizontal principal stress of sand-mud interlayers as described above.

[0088] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0089] This invention provides a method for determining the anisotropic horizontal principal stress of sand-mud interbedded layers. First, based on well logging data and under the assumption of a laterally isotropic medium, the P-wave velocities in the vertical and parallel directions to the formation, as well as the P-wave velocity at a specified depth, are determined. Based on the assumption of a laterally isotropic medium in the sand-mud interbedded layers, the method simplifies the measurement of P-wave velocities in six directions and S-wave velocities in three directions required by existing experimental methods to P-wave and S-wave velocities parallel to the formation, perpendicular to the formation, and at a specified angle. This significantly reduces the time required to determine the P-wave and S-wave velocities of the entire sand-mud interbedded layer at different depths, makes it easier to obtain data, and facilitates the formation of continuous profiles of the entire sand-mud interbedded layer based on data from different depths, enabling comparisons of mechanical properties across multiple wells.

[0090] Based on the first relationship between wave velocity and stiffness modulus in different directions at a specified depth, and the second relationship between stiffness modulus and elastic modulus, and stiffness modulus and Poisson's ratio, dynamic rock mechanical parameters at a specified depth are determined using the five wave velocities in different directions identified above. These dynamic rock mechanical parameters are then converted into static rock mechanical parameters, taking into account the influence of fluids in the pores on the dynamic rock mechanical parameters, thus more accurately reflecting the true mechanical properties of the rock. Accurate anisotropic dynamic rock mechanical parameters, such as elastic modulus and Poisson's ratio, can clarify the stress-blocking capacity of mudstone sections in sand-mud interbedded layers, thereby improving the calculation accuracy of anisotropic horizontal principal stresses in formations.

[0091] Based on static rock mechanics parameters parallel to and perpendicular to the stratigraphic direction, the horizontal principal stress at a specified depth is determined using a transversely isotropic stratigraphic stress model. Compared to the traditional horizontal principal stress calculation method under the assumption of isotropy, this invention cleverly combines the advantages of well logging and experimental methods. Through rigorous mathematical derivation and full consideration of relevant mechanical models, the calculation accuracy of the horizontal principal stress is greatly improved, and it can further effectively improve the prediction accuracy of the three-pressure profile under strong tectonic compression conditions.

[0092] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0093] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0094] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0095] Figure 1 This is a flowchart of the method for determining the anisotropic horizontal principal stress of the sand-mud interlayer in an embodiment of the present invention;

[0096] Figure 2 This is a schematic diagram illustrating the principle of the method for determining the anisotropic horizontal principal stress of the sand-mud interlayer in this invention.

[0097] Figure 3 This is a simplified analogy diagram of wave speed in an embodiment of the present invention;

[0098] Figure 4 This is a density conversion coefficient fitting diagram in an embodiment of the present invention;

[0099] Figure 5 This is a graph showing the conversion relationship between vertical strata and dynamic / static elastic modulus fitted in an embodiment of the present invention;

[0100] Figure 6 This is a graph showing the conversion relationship between parallel strata and dynamic / static elastic modulus fitted in an embodiment of the present invention.

[0101] Figure 7 This is a schematic diagram of the anisotropic horizontal principal stress determination device for sand-mud interlayer in an embodiment of the present invention. Detailed Implementation

[0102] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0103] To address the problem that existing technologies for determining anisotropic rock mechanical parameters at a specified depth in sand-mud interbedded layers are inefficient due to the high cost of special logging methods and the limited data points obtained through experimental methods, neither of which can more conveniently and accurately determine the anisotropic horizontal principal stress of the sand-mud interbedded layers, this invention provides a method for determining the anisotropic horizontal principal stress of sand-mud interbedded layers. This method determines the anisotropic rock mechanical parameters based on traditional logging data, which is easy to obtain and can easily form continuous profiles, thereby improving the calculation accuracy of the horizontal principal stress.

[0104] This invention provides a method for determining the anisotropic horizontal principal stress of interbedded sand and mud layers, the specific steps of which are as follows: Figure 1As shown, the principle block diagram of this method can be found in [reference needed]. Figure 2 As shown, it includes:

[0105] Step S101: Based on well logging data, under the assumption of a transversely isotropic medium in the formation, determine the longitudinal and transverse wave velocities in the first specified direction and the longitudinal wave velocity in the second specified direction at a specified depth in the formation. The first specified direction includes the direction perpendicular to the formation and the direction parallel to the formation, and the second specified direction includes the direction at a specified angle to the formation.

[0106] Step S102: Based on the determined wave velocity, determine the stiffness modulus at the specified depth using the first relationship between wave velocity and stiffness modulus;

[0107] Step S103: Based on the stiffness modulus at a specified depth, the dynamic rock mechanics parameters in the first specified direction are determined using a pre-established second relationship expression between the stiffness modulus and the dynamic rock mechanics parameters in the first specified direction; the dynamic rock mechanics parameters include Poisson's ratio and dynamic elastic modulus; the second relationship expression is constructed based on the stress-strain relationship of the rock block under the assumption of a transversely isotropic medium in the formation.

[0108] Step S104: Convert the dynamic rock mechanics parameters in the first specified direction into static rock mechanics parameters;

[0109] Step S105: Based on the static rock mechanics parameters in the first specified direction, determine the anisotropic horizontal principal stress at the specified depth using a transversely isotropic stratum stress model.

[0110] Under the assumption of a transversely isotropic medium, the mechanical properties of sand-mud interbedded rocks exhibit the same P-wave velocity and S-wave velocity in different directions within a plane parallel to the formation. Therefore, the nine wave velocities that need to be measured in existing experimental methods can be simplified to five. This can be analogized to sonic logging, where the P-wave velocity V propagating perpendicular to the formation direction can be obtained through fitting. pv The longitudinal wave velocity V propagating parallel to the strata direction ph The transverse wave velocity V propagating perpendicular to the strata sv The transverse wave velocity V propagating parallel to the strata direction sh The longitudinal wave velocity at a specified angle to the strata; such as Figure 2 In the simplified analog ultrasonic testing method section, the density fitting coefficient is determined in advance based on the density logging data, the clay content coefficient is determined based on the GR logging data, and the P-wave and S-wave velocities in the direction parallel to the formation are determined by micro-element division based on the density fitting coefficient and GR logging data; the P-wave velocity in the direction at a specified angle to the formation is determined by the Thmosen model; for the specific operation of this part, please refer to the description in step S101 below.

[0111] See Figure 2In the stress-strain constitutive equations, under the assumption of a laterally isotropic medium, there is symmetry between the stress tensor and strain tensor in the formation. Based on the stress-strain relationship of the rock block, the stiffness matrix and flexibility matrix of the stress-strain constitutive equations are constructed. The stiffness matrix is ​​represented by stiffness modulus in different directions; the flexibility matrix is ​​represented by rock mechanics parameters such as elastic modulus and Poisson's ratio in different directions. The stiffness matrix and flexibility matrix are invertible to each other. Based on the invertibility relationship between the stiffness matrix and the flexibility matrix, the relationship between the stiffness modulus and dynamic rock mechanics parameters is determined. Based on the relationship between the stiffness modulus and dynamic rock mechanics parameters, the laterally isotropic dynamic rock mechanics parameters are determined. Among them, the stiffness modulus is determined based on the wave velocity in different directions. For the specific operation of this part, please refer to the introduction of steps S102-S103 below.

[0112] The conversion relationship between dynamic and static rock mechanical parameters is determined in advance through triaxial stress testing experiments; based on the conversion relationship, the transversely isotropic dynamic rock mechanical parameters are converted into transversely isotropic static rock mechanical parameters; for the specific operation of this part, please refer to the description of step S104 below;

[0113] The coefficients of the Thiercelin geostress model are determined in advance through acoustic emission Kaister tests. Based on the pre-determined dynamic and static rock mechanics parameter conversion relationship, the coefficients of the Thiercelin geostress model, and the transversely isotropic static rock mechanics parameters, the anisotropic horizontal principal stress is determined using the Thiercelin geostress model. The anisotropic horizontal principal stress can better describe the geostress profile under transversely isotropic media. For the specific operation of this part, please refer to the description of step S105 below.

[0114] In this embodiment, the preset angle with the formation in the existing experimental method is 45°, such as... Figure 3 The diagram shown is a simplified analogy of wave velocity in an embodiment of the present invention: Existing experimental methods require measuring the longitudinal wave velocity in six directions and the transverse wave velocity in three directions, namely: the longitudinal wave velocity V propagating along the x, y, and z axes. px V py V pz The transverse wave velocity V propagating along the z-axis and vibrating along the x and y-axis; sz-x V sz-y V sx-y The longitudinal wave velocity V propagating along the 45° angle between the axes in the xy, xz, and yz planes. p(xy-45°) V p(xz-45°) V p(yz-45°) The simplified process for classifying wave velocities is as follows: 1) Using the longitudinal wave velocity (V) parallel to the stratum direction. ph(This is a substitute for the longitudinal wave velocity (V) measured along the 45° angle between the x-axis, y-axis, and xy-plane.) px (V) py (V) p(xy-45°) ); 2) Using the longitudinal wave velocity (V) perpendicular to the stratum direction. pv ) instead of the longitudinal wave velocity (V) measured along the z-axis pz ); 3) Use the transverse wave velocity (V) perpendicular to the stratum direction. sv ) instead of the transverse wave velocity (V) measured along the z-axis and vibrating along the x and y axes. sz-x (V) sz-y ); 4) Use the transverse wave velocity (V) parallel to the stratum direction. sh ) instead of the transverse wave velocity (V) measured along the y-axis and vibrating along the x-axis. sy-x 5) Using the longitudinal wave velocity (V) at a 45° angle to the formation. p45° ) instead of the longitudinal wave velocity (V) measured along the xz and yz axes at 45° angles. p(xz-45°) (V) p(yz-45°) This embodiment uses a preset included angle of 45° as an example to illustrate the process of simplifying wave velocity and the subsequent calculation process of anisotropic elastic modulus, Poisson's ratio, and anisotropic horizontal principal stress.

[0115] In some optional embodiments, step S101, based on well logging data and under the assumption of a laterally isotropic medium in the formation, determines the P-wave velocity and S-wave velocity in a first specified direction and a second specified direction at a specified depth in the formation, including:

[0116] Step 1): Determine the P-wave velocity or S-wave velocity in the vertical direction of the formation at a specified depth based on the sonic logging data. Based on the determined wave velocity and the pre-determined P-wave / S-wave conversion formula, determine the S-wave velocity or P-wave velocity in the vertical direction of the formation at the specified depth.

[0117] The conversion between P-wave velocity and S-wave velocity can be performed using appropriate formulas. The conversion relationship between P-wave velocity and S-wave velocity is related to rock density, which is usually determined by ultrasonic testing using core samples. Based on the rock density and a pre-established fitting relationship, the conversion coefficients between P-wave and S-wave velocities are determined, and the conversion formulas are then used to determine the P-wave velocity in the vertical direction at a specified depth. Similarly, based on sonic transit time logging data, the P-wave velocity in the vertical direction at a specified depth is determined, and the corresponding S-wave velocity in the vertical direction at the specified depth is obtained using the P-wave conversion formulas.

[0118] The conversion coefficients for P-wave and S-wave velocities are determined based on the density of the rock using the following fitting relationship:

[0119] Vs =V p A

[0120] Based on the conversion coefficients of the P and S waves, the following P and S wave conversion formulas are determined:

[0121]

[0122] Among them, V p V is the longitudinal wave velocity. s ρ is the transverse wave velocity; A is the conversion coefficient between the longitudinal and transverse wave velocities, determined by the rock density ρ.

[0123] In field vertical wells, only the acoustic transit time of the P-wave propagating in the direction perpendicular to the formation is usually measured. The P-wave velocity can be determined based on the P-wave acoustic transit time. The S-wave velocity in the direction perpendicular to the formation at a specified depth can be determined based on the P-wave velocity in the direction perpendicular to the formation and the P-wave to S-wave conversion formula.

[0124] Step 2): Divide the formation into a micro-element combination of sand-mud-sand layers. Based on the logging data of each layer in the micro-element combination, determine the P-wave and S-wave velocities in the direction parallel to the formation at a specified depth in the mudstone section; determine the P-wave and S-wave velocities in the direction parallel to the formation at a specified depth in the sandstone section based on sonic transit logging and density logging data.

[0125] Based on the lithology of the formation, sand-mud transitional strata consist of numerous combinations of sand-mud-sand layers. Therefore, sand-mud transitional strata can be divided into numerous sand-mud-sand layer combinations, with the average scale of these combinations being much smaller than the formation depth. They can be considered as small micro-elements with identical mechanical properties. Among them, the sandstone section conforms to an isotropic model, with no significant difference in wave velocity perpendicular to and parallel to the formation direction, and can be calculated based on conventional sonic transit time logging and density logging data. The mudstone section conforms to a lateral isotropic model, with differences in wave velocity perpendicular to and parallel to the formation direction. The anisotropy of the mudstone section can be calibrated using the upper and lower sandstone layers within the micro-elements, and the wave velocity propagating parallel to the formation direction in the mudstone section can be fitted. The thickness of the sand-mud-sand combination layer is less than 0.3% of the well depth, ensuring the accuracy of the fitting formula. The specific operation is as follows:

[0126] ① Determine the clay content coefficient based on gamma logging data; determine the density fitting coefficient based on sonic transit time logging data;

[0127] The density fitting coefficient essentially reflects the degree to which density variations in a formation affect the mechanical properties of rocks. Under the traditional isotropic assumption, there is a linear relationship between the elastic modulus and density, determined by the square of the sonic transit time Δt. Therefore, a fitting relationship between the elastic modulus and density is established, and their correlation coefficient is taken as the density conversion coefficient. Here, the elastic modulus E, density ρ, and shear wave sonic transit time Δt are represented. s and the longitudinal wave acoustic time difference Δt p The relationship is expressed as follows:

[0128]

[0129] Therefore, density conversion coefficient The transverse wave acoustic time difference Δt can be measured. s and the longitudinal wave acoustic time difference Δt p The density conversion factor can also be determined by fitting the relationship between density and elastic modulus, such as... Figure 4 The figure shows the fitting relationship between elastic modulus and rock density. The density conversion coefficient is determined based on the fitting relationship.

[0130] The clay content coefficient is determined based on gamma logging data using the following formula:

[0131]

[0132] Where SH is the relative value of the gamma data at the current measuring point, GRmax is the maximum gamma value of the mudstone section, GRmin is the minimum gamma value of the mudstone section, and GR is the gamma value at the current measuring point.

[0133] GCUR is a dimensionless coefficient, V sh This represents the mud content coefficient.

[0134] ② Based on the clay content coefficient, density fitting coefficient, horizontal P-wave velocity of the upper and lower sandstone sections in the micro-element assembly, well logging data of the upper and lower sandstone sections in the micro-element assembly, and well logging data at a specified depth in the mudstone section of the micro-element assembly, the P-wave velocity parallel to the formation direction at a specified depth in the mudstone section of the micro-element assembly is determined using a pre-established horizontal P-wave velocity calculation model; the well logging data includes density, gamma data, and depth.

[0135] Based on the clay content coefficient, density fitting coefficient, horizontal P-wave velocity, density, gamma data, and depth of the upper and lower sandstone sections in the micro-element assembly, and the density, gamma data, and depth of the mudstone section at a specified depth, the P-wave velocity of the measuring point corresponding to the specified depth of the mudstone section in the direction parallel to the strata is determined using the following formula; different strata depths correspond to different measuring points:

[0136]

[0137] Among them, V ph(n) V represents the horizontal P-wave velocity at the nth measuring point in the mudstone section. ph(s1) and V ph(s2) Den represents the average longitudinal wave velocity in the horizontal direction of the upper and lower sandstone sections. n Den is the density at the nth measuring point of the mudstone segment in the micro-element. s1 and Den s2 GR represents the average density of the upper and lower sandstone sections.n GR is the gamma value at the nth measuring point in the mudstone section. s1 and GR s2 H represents the average gamma value of the upper and lower sandstone sections. n H represents the depth of the nth measuring point in the mudstone section. s1 and H s2 β1 represents the average depth of the upper and lower sandstone sections; β2 is the density fitting coefficient and β1 is the clay content fitting coefficient.

[0138] ③ Based on the P-wave velocity parallel to the formation at a specified depth in the mudstone section of the micro-element assembly, the S-wave velocity parallel to the formation at the corresponding depth is determined using the P-wave to S-wave conversion formula. The method for determining the P-wave to S-wave conversion formula has been described in detail in step 1) determining the P-wave and S-wave velocities perpendicular to the formation at the specified depth.

[0139] There is no order requirement for determining the P-wave and S-wave velocities in the direction perpendicular to the strata in step 1) and in step 2) parallel to the strata in step 2). You can first perform step 2) to determine the P-wave and S-wave velocities in the direction parallel to the strata, and then perform step 1) to determine the P-wave and S-wave velocities in the direction perpendicular to the strata.

[0140] Step 3): Based on the longitudinal and transverse wave velocities in the first specified direction at a specified depth, determine the longitudinal wave velocity in the second specified direction using a transverse medium model.

[0141] In some optional embodiments, the anisotropy parameters are determined using the following formula based on the P-wave velocity perpendicular to the formation and the P-wave velocity parallel to the formation at a specified depth.

[0142]

[0143] Among them, V pv V is the longitudinal wave velocity propagating perpendicular to the strata. ph The longitudinal wave velocity is the wave velocity that propagates parallel to the direction of the strata.

[0144] Based on the transverse wave velocity perpendicular to the formation, the longitudinal wave velocity parallel to the formation, the anisotropy parameters, and the longitudinal-transverse wave conversion coefficient at a specified depth, the transition parameters are determined using the following formula;

[0145]

[0146] Among them, V sv It is the transverse wave velocity, V, in the direction perpendicular to the strata. pv ε is the P-wave velocity propagating parallel to the strata, ε is the anisotropy parameter, and A is the P-wave / S-wave conversion coefficient, which has been determined in step 1).

[0147] Based on anisotropy parameters, transition parameters, P-wave velocity perpendicular to the formation, and the angle between the specified direction and the formation, the P-wave velocity at the specified angle to the formation is determined using a transverse medium model.

[0148] In this embodiment, the preset angle with the formation is 45°. Based on the P-wave velocities, anisotropy parameters, and transition parameters determined in steps 1) and 2) above, respectively, the P-wave velocity in the direction at a 45° angle with the formation is determined using the following Thmosen transverse medium formula:

[0149] V p (θ)=V pv (1+δsin 2 θcos 2 θ+εsin 4 θ)

[0150] Where θ is the angle perpendicular to the stratum direction, V pv ε is the longitudinal wave velocity propagating perpendicular to the stratum, ε is the anisotropy parameter, and δ is the transition parameter.

[0151] In some optional embodiments, step S102, based on the determined wave velocity, uses a first relationship between wave velocity and stiffness modulus to determine the stiffness modulus at a specified depth, including:

[0152] Under the assumption of a transversely isotropic medium in sand-mud interbedded strata, the stiffness matrix and flexibility matrix of the stress-strain constitutive equation are constructed based on the stress-strain relationship of the rock block. The stiffness matrix describes the ability of the rock block to generate normal strain when subjected to normal stress; the flexibility matrix describes the stress required for the rock block to be subjected to unit strain. As shown below, c represents the stiffness matrix, and C11, C22, C33, C44, C55, C66, C12, and C13 represent the stiffness modulus at a specified depth in the direction parallel to the strata, perpendicular to the strata, and at a specified angle to the strata. The relationship between the stiffness matrix and the flexibility matrix is ​​described in detail in step S103 below.

[0153]

[0154] There is a relationship between the stiffness modulus of rock and the wave velocities of longitudinal and transverse waves propagating at different angles. In step S101, five wave velocities have been determined: longitudinal and transverse wave velocities perpendicular to the strata, parallel to the strata, and longitudinal wave velocities at a 45° angle perpendicular to the strata.

[0155] Based on the five wave velocities at a specified depth determined in step S101, the stiffness modulus at the corresponding depth is determined using the following first relationship:

[0156]

[0157] C 12 =C 11 -2C 66

[0158]

[0159] Wherein, C11, C22, C33, C44, C55, C66, C12, and C13 are the stiffness moduli at a specified depth in the directions parallel to the formation, perpendicular to the formation, and at a specified angle to the formation; V sv It is the transverse wave velocity, V, in the direction perpendicular to the strata. pv It is the longitudinal wave velocity parallel to the strata, V pv V represents the longitudinal wave velocity perpendicular to the strata. ph V represents the longitudinal wave velocity parallel to the strata direction. p 45° is the longitudinal wave velocity at a 45° angle perpendicular to the stratum.

[0160] In some optional embodiments, step S103, based on the stiffness modulus at a specified depth, uses a pre-established second relationship between the stiffness modulus and the dynamic rock mechanics parameters in the first specified direction to determine the dynamic rock mechanics parameters in the first specified direction, including:

[0161] In this embodiment, based on the stiffness modulus at the specified depth determined in step S102, the dynamic elastic modulus and dynamic Poisson's ratio in the first specified direction are determined using a pre-established second relationship expression between the stiffness modulus and the dynamic elastic modulus in the first specified direction, and between the stiffness modulus and the dynamic Poisson's ratio in the first specified direction. The process of establishing the second relationship expression between the stiffness modulus and the dynamic elastic modulus in the first specified direction includes:

[0162] The stiffness and flexibility matrices of the stress-strain constitutive equations are constructed based on the stress-strain relationship of the rock block.

[0163] Based on the correspondence between the stiffness matrix and the flexibility matrix, a second relationship expression is determined between the stiffness modulus in the stiffness matrix and the dynamic elastic modulus and dynamic Poisson's ratio in the first specified direction in the flexibility matrix.

[0164] Specifically, under the assumption of a transversely isotropic medium in sand-mud interbedded strata, the stiffness matrix and flexibility matrix of the stress-strain constitutive equation are constructed based on the stress-strain relationship of the rock block. The stiffness matrix describes the ability of the rock block to generate normal strain when subjected to normal stress; the flexibility matrix describes the stress required for the rock block to be subjected to unit strain. As shown below, c represents the stiffness matrix and s represents the flexibility matrix.

[0165]

[0166] There is a symmetry between the stress tensor in the compliance matrix and the strain tensor in the stiffness matrix, and the stiffness and compliance matrices are invertible. By inverting the stiffness matrix and comparing it with the compliance matrix, we can obtain the second relationship between the stiffness modulus and the elastic modulus and Poisson's ratio, as shown below:

[0167] Relationship between dynamic elastic modulus and stiffness modulus in the vertical direction of the formation:

[0168] Relationship between dynamic elastic modulus and stiffness modulus parallel to the formation direction:

[0169] The relationship between dynamic Poisson's ratio and stiffness modulus in the vertical direction of the formation:

[0170] Relationship between dynamic Poisson's ratio and stiffness modulus parallel to the formation direction:

[0171] Where C11, C33, C12, and C13 are the stiffness moduli at a specified depth in the directions parallel to the formation, perpendicular to the formation, and at a specified angle to the formation; E v E represents the dynamic elastic modulus perpendicular to the formation direction. h μ is the dynamic elastic modulus parallel to the formation direction. v μ is the dynamic Poisson's ratio perpendicular to the formation direction. h This represents the dynamic Poisson's ratio parallel to the stratum direction.

[0172] In some optional embodiments, step S104, converting the dynamic rock mechanics parameters in the first specified direction into static rock mechanics parameters, includes:

[0173] The dynamic rock mechanics parameters calculated based on well logging data in step S103 are affected by fluid in the pores and cannot accurately reflect the true mechanical properties of the rock. Therefore, it is necessary to determine the conversion relationship between dynamic and static rock mechanics parameters by fitting data from rock stress testing experiments, such as triaxial rock stress testing experiments.

[0174] Dynamic rock mechanics parameters include dynamic elastic modulus and dynamic Poisson's ratio. In this embodiment, a fitting relationship between dynamic calculation results and static experimental results is established based on experimental data of rock mechanics parameters. Experimental data shows that the dynamic Poisson's ratio and the static Poisson's ratio are similar in magnitude, while the fitting relationship between the dynamic elastic modulus and the static elastic modulus is linear. Figure 5 The figure shows the dynamic and static elastic modulus conversion model in the vertical direction of the strata, as follows: Figure 6 The figure shows the dynamic and static elastic modulus conversion model parallel to the stratum direction.

[0175] Based on the dynamic-static elastic modulus conversion model, the dynamic elastic modulus in the direction parallel to the strata and perpendicular to the strata is converted into the static elastic modulus in the same direction. The static Poisson's ratio in the direction parallel to the strata and perpendicular to the strata remains consistent with the dynamic Poisson's ratio.

[0176] In some optional embodiments, step S105, which involves determining the anisotropic horizontal principal stress at a specified depth using a transversely isotropic stratigraphic stress model based on static rock mechanics parameters in a first specified direction, includes:

[0177] The Biot effective stress coefficient, horizontal maximum tectonic stress coefficient, and horizontal minimum tectonic stress coefficient of the transversely isotropic strata stress model are determined based on acoustic emission Kaister test experiments; these can be selected either by choice or by empirical values.

[0178] Based on the static rock mechanics parameters, well logging data, Biot effective stress coefficient, horizontal maximum tectonic stress coefficient, and horizontal minimum tectonic stress coefficient in the first specified direction, the maximum anisotropic horizontal principal stress and minimum anisotropic horizontal principal stress of the sand-mud interbedded layer at a specified depth are determined using a transversely isotropic formation stress model; the well logging data includes overlying strata pressure and formation pore pressure.

[0179] In this embodiment, based on the static elastic modulus and Poisson's ratio parallel to and perpendicular to the formation direction, overlying strata pressure, formation pore pressure, Biot effective stress coefficient, maximum horizontal tectonic stress coefficient, and minimum horizontal tectonic stress coefficient, the following Thiercelin model formula is used to determine the maximum and minimum anisotropic horizontal principal stresses of the sand-mud interbedded layer at a specified depth:

[0180]

[0181] Where, σ H For the maximum anisotropic horizontal principal stress, σ h The minimum anisotropic horizontal principal stress;

[0182] E h E is the static elastic modulus perpendicular to the formation direction. v μ is the static elastic modulus parallel to the formation direction. h μ is the static Poisson's ratio perpendicular to the formation direction. v σ is the static Poisson's ratio parallel to the stratum direction. v For the pressure of the overlying strata, p p α represents the formation pore pressure; α is the Biot effective stress coefficient, which is set to 1; w1 and w2 are the maximum and minimum horizontal tectonic stress coefficients, respectively; the maximum and minimum horizontal tectonic stress coefficients are determined by acoustic emission Kaister test experiments.

[0183] In this embodiment, the nine wave velocities that need to be measured in the experimental method are simplified to five, which greatly reduces the time required to determine the P-wave and S-wave velocities of strata at different depths. This makes it easier to obtain data and facilitates the formation of continuous profiles based on data from strata at different depths. At the same time, when determining the P-wave and S-wave velocities in the direction parallel to the strata, the sand-mud interbedded strata are divided into micro-elements, which can be used to evaluate the anisotropy of strata at different depths. Subsequently, special points in the strata with significant changes in mechanical properties can be analyzed in detail. In addition, the Thierselin model is used to calculate the horizontal principal stress. Compared with the Georg model and Huang model, it adds directionality on the basis of considering the elastic modulus, making the calculation results closer to the actual strata mechanics and the calculation accuracy higher.

[0184] Based on the same inventive concept, this invention also provides an anisotropic horizontal principal stress calculation device for sand-mud interlayers, as shown in the schematic diagram of the device. Figure 7 As shown, it includes: wave velocity determination unit 10, stiffness modulus determination unit 20, rock mechanics parameter determination unit 30, elastic modulus conversion unit 40 and horizontal principal stress determination unit 50;

[0185] The wave velocity determination unit 10 is used to determine the longitudinal and transverse wave velocities in a first specified direction and the longitudinal wave velocity in a second specified direction at a specified depth of the formation based on well logging data and under the assumption of a transversely isotropic medium in the formation. The first specified direction includes a direction perpendicular to the formation and a direction parallel to the formation, and the second specified direction includes a direction that forms a specified angle with the formation.

[0186] The stiffness modulus determination unit 20 is used to determine the stiffness modulus at a specified depth based on the determined wave velocity and using the first relationship between wave velocity and stiffness modulus.

[0187] The rock mechanics parameter determination unit 30 is used to determine the dynamic rock mechanics parameters in the first specified direction based on the stiffness modulus at the specified depth and using a pre-established second relationship expression between the stiffness modulus and the dynamic rock mechanics parameters in the first specified direction; the dynamic rock mechanics parameters include Poisson's ratio and dynamic elastic modulus; the second relationship expression is constructed based on the stress-strain relationship of the rock block under the assumption of a transversely isotropic medium in the formation.

[0188] The elastic modulus conversion unit 40 is used to convert dynamic rock mechanics parameters in a first specified direction into static rock mechanics parameters.

[0189] The horizontal principal stress determination unit 50 is used to determine the anisotropic horizontal principal stress at a specified depth based on the static rock mechanics parameters in the first specified direction using a transversely isotropic stratum stress model.

[0190] This invention also provides a computer storage medium storing computer-executable instructions, which, when executed by a processor, implement the method for determining the anisotropic horizontal principal stress of sand-mud interlayers as described above.

[0191] This invention also provides a computer device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements a method for determining the anisotropic horizontal principal stress of sand-mud interlayers as described above.

[0192] This invention also provides a computer program product, which includes a computer program that, when executed by a processor, implements a method for determining the anisotropic horizontal principal stress of sand-mud interlayers as described above.

[0193] In the above-described apparatus of the present invention, the specific manner in which each module performs its operation has been described in detail in the embodiments of the method, and will not be elaborated upon here.

[0194] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0195] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features in a single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of the invention.

[0196] Those skilled in the art will also understand that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments herein can be implemented as electronic hardware, computer software, or a combination thereof. To clearly illustrate the interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps described above are generally described in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in alternative ways for each specific application; however, such implementation decisions should not be construed as departing from the scope of this disclosure.

[0197] The steps of the methods or algorithms described in conjunction with the embodiments herein can be directly embodied in hardware, software modules executed by a processor, or a combination thereof. The software modules can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium well known in the art. An exemplary storage medium is connected to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user terminal. Alternatively, the processor and storage medium can exist as discrete components in the user terminal.

[0198] For software implementation, the techniques described in this application can be implemented using modules (e.g., procedures, functions, etc.) that perform the functions described in this application. This software code can be stored in memory units and executed by a processor. The memory units can be implemented within the processor or outside the processor; in the latter case, they are communicatively coupled to the processor via various means, as is well known in the art.

[0199] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as interpreted when used as a conjunction in the claims. Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

Claims

1. A method for determining the anisotropic horizontal principal stress of interbedded sand and mud, characterized in that, include: Based on well logging data, under the assumption of a transversely isotropic medium in the formation, the longitudinal and transverse wave velocities in a first specified direction and the longitudinal wave velocity in a second specified direction at a specified depth in the formation are determined. The first specified direction includes a direction perpendicular to the formation and a direction parallel to the formation, and the second specified direction includes a direction that forms a specified angle with the formation. Based on the determined wave velocity, the stiffness modulus at a specified depth is determined using the first relationship between wave velocity and stiffness modulus. Based on the stiffness modulus at the specified depth, the dynamic rock mechanics parameters in the first specified direction are determined using a pre-established second relationship between the stiffness modulus and the dynamic rock mechanics parameters in the first specified direction. The dynamic rock mechanics parameters include Poisson's ratio and dynamic elastic modulus. The second relationship is constructed based on the stress-strain relationship of the rock block under the assumption of a transversely isotropic medium in the formation. Convert the dynamic rock mechanics parameters in the first specified direction into static rock mechanics parameters; Based on the static rock mechanics parameters in the first specified direction, the anisotropic horizontal principal stress at a specified depth is determined using a transversely isotropic stratum stress model.

2. The method as described in claim 1, characterized in that, The determination of the P-wave and S-wave velocities in a first specified direction and the P-wave velocity in a second specified direction at a specified depth in the formation, based on well logging data and under the assumption of a laterally isotropic medium, includes: Based on sonic time-of-flight logging data, determine the P-wave velocity or S-wave velocity in the vertical direction of the formation at a specified depth. Based on the determined wave velocity and a pre-determined P-wave / S-wave conversion formula, determine the S-wave velocity or P-wave velocity in the vertical direction of the formation at a specified depth. The formation is divided into a micro-element combination of sand-mud-sand layers. Based on the logging data of each layer in the micro-element combination, the P-wave and S-wave velocities in the direction parallel to the formation at a specified depth in the mudstone section are determined. Based on the sonic transit time logging and density logging data, the P-wave and S-wave velocities in the direction parallel to the formation at a specified depth in the sandstone section are determined. Based on the longitudinal and transverse wave velocities in the first specified direction at a specified depth, the longitudinal wave velocity in the second specified direction is determined using a transverse medium model.

3. The method as described in claim 2, characterized in that, The process of determining the P-wave and S-wave conversion formula includes: The conversion coefficients of P-wave and S-wave velocities are determined based on the rock density and a pre-established fitting relationship, and the P-wave and S-wave conversion formulas are determined based on the conversion coefficients.

4. The method as described in claim 3, characterized in that, The conversion coefficients for P-wave and S-wave velocities are determined based on the rock density and a pre-established fitting relationship. Based on these conversion coefficients, the P-wave and S-wave conversion formulas are determined, including... The conversion coefficients for P-wave and S-wave velocities are determined based on the density of the rock using the following fitting relationship: Based on the conversion coefficients of the P and S waves, the following P and S wave conversion formulas are determined: In s =V p And Among them, V p V is the longitudinal wave velocity. s ρ is the transverse wave velocity; A is the conversion coefficient between the longitudinal and transverse wave velocities, determined by the rock density ρ.

5. The method as described in claim 2, characterized in that, The process of dividing the formation into a micro-elemental system of sand-mud-sand layers, and determining the P-wave and S-wave velocities parallel to the formation at a specified depth in the mudstone section based on well logging data of each layer in the micro-elemental system, includes: The clay content coefficient was determined based on gamma-ray logging data; the density fitting coefficient was determined based on sonic transit time logging data. Based on the clay content coefficient, density fitting coefficient, horizontal P-wave velocity of the upper and lower sandstone sections in the micro-element assembly, well logging data of the upper and lower sandstone sections in the micro-element assembly, and well logging data at a specified depth in the mudstone section of the micro-element assembly, the P-wave velocity parallel to the formation at a specified depth in the mudstone section of the micro-element assembly is determined using a pre-established horizontal P-wave velocity calculation model; the well logging data includes density, gamma data, and depth. Based on the P-wave velocity in the mudstone section at a specified depth in the micro-element assembly, parallel to the strata, the P-wave and S-wave conversion formula is used to determine the S-wave velocity at the corresponding depth in the parallel to the strata.

6. The method as described in claim 5, characterized in that, The process of determining the clay content coefficient includes: The clay content coefficient is determined based on gamma logging data using the following formula: Where SH is the relative value of the gamma data at the current measuring point, GRmax is the maximum gamma data of the mudstone section, GRmin is the minimum gamma data of the mudstone section, and GR is the gamma data of the current measuring point. GCUR is a dimensionless coefficient, V sh This is the mud content coefficient.

7. The method as described in claim 5, characterized in that, The method, based on the clay content coefficient, density fitting coefficient, horizontal P-wave velocity of the upper and lower sandstone sections in the micro-element assembly, well logging data of the upper and lower sandstone sections in the micro-element assembly, and well logging data at a specified depth in the mudstone section of the micro-element assembly, uses a pre-established horizontal P-wave velocity calculation model to determine the P-wave velocity parallel to the formation at a specified depth in the mudstone section of the micro-element assembly, including: Based on the clay content coefficient, density fitting coefficient, horizontal P-wave velocity, density, gamma data, and depth of the upper and lower sandstone sections in the micro-element assembly, and the density, gamma data, and depth of the mudstone section at a specified depth, the P-wave velocity of the measuring point corresponding to the specified depth of the mudstone section in the direction parallel to the strata is determined using the following formula: Among them, V ph(n) V represents the horizontal P-wave velocity at the nth measuring point in the mudstone section. ph(s1) and V ph(s2) Den represents the average longitudinal wave velocity in the horizontal direction of the upper and lower sandstone sections. n Den is the density at the nth measuring point of the mudstone segment in the micro-element. s1 and Den s2 GR represents the average density of the upper and lower sandstone sections. n GR is the gamma value at the nth measuring point in the mudstone section. s1 and GR s2 H represents the average gamma value of the upper and lower sandstone sections. n H represents the depth of the nth measuring point in the mudstone section. s1 and H s2 β1 represents the average depth of the upper and lower sandstone sections; β2 is the density fitting coefficient and β1 is the clay content fitting coefficient.

8. The method as described in claim 2, characterized in that, The determination of the longitudinal wave velocity in the second specified direction based on the longitudinal and transverse wave velocities in the first specified direction at a specified depth using a transverse medium model includes: Based on the P-wave velocity perpendicular to the formation and the P-wave velocity parallel to the formation at a specified depth, determine the anisotropy parameters. Transition parameters are determined based on the transverse wave velocity perpendicular to the formation direction, the longitudinal wave velocity parallel to the formation direction, anisotropy parameters, and the longitudinal-transverse wave conversion coefficient at a specified depth; the longitudinal-transverse wave conversion coefficient is determined based on the rock density. Based on anisotropy parameters, transition parameters, P-wave velocity perpendicular to the formation, and the angle between the specified direction and the formation, the P-wave velocity at the specified angle to the formation is determined using a transverse medium model.

9. The method as described in claim 8, characterized in that, The determination of anisotropy parameters based on the P-wave velocity perpendicular to the formation and the P-wave velocity parallel to the formation at a specified depth includes: The anisotropy parameters are determined using the following formula based on the P-wave velocities perpendicular to and parallel to the formation at a specified depth: Among them, V pv V represents the longitudinal wave velocity perpendicular to the strata. ph The longitudinal wave velocity is parallel to the direction of the strata. The determination of transition parameters based on the shear wave velocity perpendicular to the formation direction, the P-wave velocity parallel to the formation direction, anisotropy parameters, and P-wave / S-wave conversion coefficients at a specified depth includes: The transition parameters are determined using the following formula based on the shear wave velocity perpendicular to the formation, the P-wave velocity parallel to the formation, anisotropy parameters, and the P-S / S-wave conversion coefficients at a specified depth: Among them, V sv It is the transverse wave velocity in the direction perpendicular to the strata, V pv ε is the P-wave velocity parallel to the strata, ε is the anisotropy parameter, and A is the P-wave / S-wave conversion coefficient.

10. The method as described in claim 8, characterized in that, The determination of the P-wave velocity at a specified angle to the formation using a transverse medium model, based on anisotropy parameters, transition parameters, P-wave velocity perpendicular to the formation direction, and the angle between the specified direction and the formation, includes: Based on anisotropy parameters, transition parameters, P-wave velocity perpendicular to the formation, and the angle between the specified direction and the formation, the following Thmosen transverse medium formula is used to determine the P-wave velocity at the specified angle to the formation: V p (θ)=V pv (1+δsin 2 θcos 2 θ+εsin 4 i) Where θ is the angle between the specified direction and the stratum, V pv ε is the longitudinal wave velocity perpendicular to the formation, ε is the anisotropy parameter, and δ is the transition parameter.

11. The method as described in claim 1, characterized in that, The step of determining the stiffness modulus at a specified depth based on the determined wave velocity and using the first relationship between wave velocity and stiffness modulus includes: Based on the determined P-wave and S-wave velocities in the first and second specified directions at a specified depth, the stiffness modulus at the first and second specified directions is determined using the following first relationship: C 12 *C 11 -2C 66 Wherein, C11, C22, C33, C44, C55, C66, C12, C13, and C23 are the stiffness moduli at a specified depth in the first and second specified directions; V sv It is the transverse wave velocity in the direction perpendicular to the strata, V pv It is the longitudinal wave velocity parallel to the strata, V pv V represents the longitudinal wave velocity perpendicular to the strata. ph V represents the longitudinal wave velocity parallel to the strata direction. p θ is the longitudinal wave velocity at a specified angle to the formation.

12. The method as described in claim 1, characterized in that, Under the assumption of a laterally isotropic medium, the process of constructing a second relational expression based on the stress-strain relationship of rock blocks includes: The stiffness and flexibility matrices of the stress-strain constitutive equations are constructed based on the stress-strain relationship of the rock block. Based on the correspondence between the stiffness matrix and the flexibility matrix, a second relationship is determined between the stiffness modulus in the stiffness matrix and the dynamic elastic modulus and dynamic Poisson's ratio in the first specified direction in the flexibility matrix. The second relationship is expressed as follows: Wherein, C11, C33, C12, and C13 are the stiffness moduli at a specified depth in the first and second specified directions; E v E represents the dynamic elastic modulus perpendicular to the formation direction. h It represents the dynamic elastic modulus parallel to the stratum direction; μ v μ is the dynamic Poisson's ratio perpendicular to the formation direction. h This represents the dynamic Poisson's ratio parallel to the stratum direction.

13. The method as described in claim 1, characterized in that, The conversion of dynamic rock mechanics parameters in the first specified direction into static rock mechanics parameters includes: Based on a predetermined dynamic-static rock mechanics parameter conversion relationship, the dynamic rock mechanics parameters in the first specified direction are converted into static rock mechanics parameters in the first specified direction; the dynamic-static rock mechanics parameter conversion relationship is obtained by fitting rock stress test experimental data.

14. The method as described in claim 1, characterized in that, The static rock mechanics parameters based on the first specified direction are used to determine the anisotropic horizontal principal stress at a specified depth using a transversely isotropic stratum stress model, including: Based on acoustic emission Kaister test experiments, the Biot effective stress coefficient, horizontal maximum tectonic stress coefficient, and horizontal minimum tectonic stress coefficient of the transversely isotropic stratum stress model were determined. Based on the static rock mechanics parameters, well logging data, Biot effective stress coefficient, horizontal maximum tectonic stress coefficient, and horizontal minimum tectonic stress coefficient in the first specified direction, the maximum anisotropic horizontal principal stress and minimum anisotropic horizontal principal stress of the sand-mud interbedded layer at a specified depth are determined using a transversely isotropic formation stress model; the well logging data includes overlying strata pressure and formation pore pressure.

15. The method as described in claim 1, characterized in that, The static rock mechanics parameters, well logging data, Biot effective stress coefficient, maximum horizontal tectonic stress coefficient, and minimum horizontal tectonic stress coefficient in the first specified direction are used to determine the maximum and minimum anisotropic horizontal principal stresses of the sand-mud interbedded layers at a specified depth using a transversely isotropic formation stress model, including: Based on the static elastic modulus and Poisson's ratio parallel to and perpendicular to the stratigraphic direction, overlying strata pressure, formation pore pressure, Biot effective stress coefficient, maximum horizontal tectonic stress coefficient, and minimum horizontal tectonic stress coefficient, the following Thiercelin model formula is used to determine the maximum and minimum anisotropic horizontal principal stresses of the sand-mud interbedded layer at a specified depth: Where, σ H For the maximum anisotropic horizontal principal stress, σ h The minimum anisotropic horizontal principal stress; E h E is the static elastic modulus perpendicular to the formation direction. v μ is the static elastic modulus parallel to the formation direction. h μ is the static Poisson's ratio perpendicular to the formation direction. v σ is the static Poisson's ratio parallel to the stratum direction. v For the pressure of the overlying strata, p p α represents the formation pore pressure; α is the Biot effective stress coefficient; w1 and w2 are the maximum and minimum horizontal tectonic stress coefficients, respectively.

16. A device for calculating the anisotropic horizontal principal stress of interbedded sand and mud layers, characterized in that, include: The wave velocity determination unit is used to determine the longitudinal and transverse wave velocities in a first specified direction and the longitudinal wave velocity in a second specified direction at a specified depth of the formation based on well logging data and under the assumption of a transversely isotropic medium in the formation. The first specified direction includes a direction perpendicular to the formation and a direction parallel to the formation, and the second specified direction includes a direction that forms a specified angle with the formation. The stiffness modulus determination unit is used to determine the stiffness modulus at a specified depth based on the determined wave velocity and using the first relationship between wave velocity and stiffness modulus. The rock mechanics parameter determination unit is used to determine the dynamic rock mechanics parameters in the first specified direction based on the stiffness modulus at the specified depth and using a pre-established second relationship expression between the stiffness modulus and the dynamic rock mechanics parameters in the first specified direction; the dynamic rock mechanics parameters include Poisson's ratio and dynamic elastic modulus; the second relationship expression is constructed based on the stress-strain relationship of the rock block under the assumption of a transversely isotropic medium in the formation; The elastic modulus conversion unit is used to convert dynamic rock mechanics parameters in a first specified direction into static rock mechanics parameters. The horizontal principal stress determination unit is used to determine the anisotropic horizontal principal stress at a specified depth based on the static rock mechanics parameters in the first specified direction using a transversely isotropic stratum stress model.

17. A computer storage medium, characterized in that, The computer storage medium stores computer-executable instructions, which, when executed by a processor, implement the method for determining the anisotropic horizontal principal stress of sand-mud interlayers as described in any one of claims 1-15.

18. A computer device, characterized in that, include: The memory, the processor, and the computer program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements the method for determining the anisotropic horizontal principal stress of sand-mud interlayers as described in any one of claims 1-15.

19. A computer program product, characterized in that, The computer program product includes a computer program that, when executed by a processor, implements a method for determining the anisotropic horizontal principal stress of sand-mud interlayers as described in any one of claims 1-15.

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