A method and equipment for predicting geostress based on well caliper rotation trajectory and measurement data

Abstract

This invention belongs to the field of oil and gas field development technology and discloses a method and equipment for predicting geostress based on the rotation trajectory and measurement data of a wellbore caliper. The method includes: analyzing the rotation trajectory of the wellbore caliper to find elliptical well sections and recording the major and minor axis measurements; calculating the dynamic Young's modulus and dynamic Poisson's ratio, and calculating the static Young's modulus and static Poisson's ratio using empirical formulas for dynamic-static conversion; obtaining the mud pressure based on construction data and calculating the overlying strata pressure through integration of density logging data; calculating the minimum horizontal principal stress based on the pump shutdown pressure; substituting the above parameters into the wellbore stress-strain formula, and obtaining the maximum horizontal principal stress through formula ratio, thus achieving geostress prediction for the target section. This invention can accurately calculate the biaxial stress difference and the maximum horizontal principal stress, effectively reducing the errors caused by wellbore irregularities and wellbore enlargement rate uncertainties in traditional stress relief methods, improving the accuracy of prediction results, and the testing procedure is simple and efficient.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field development technology, specifically relating to a method and equipment for predicting geostress based on the rotation trajectory of a wellbore gauge and measurement data. Background Technology

[0002] Oil and gas reservoirs have complex geological features and are difficult to develop, making the demand for rock mechanical parameters for each block particularly urgent. Mainstream methods for calculating geostress (such as the differential strain method and the Kaiser method) all require laboratory core testing, which is complex and extremely costly from core drilling and preparation to experimentation.

[0003] The stress relief method is currently a recommended in-situ method for testing geostress. This method assumes an initial circular borehole cross-section, and after drilling, the stress around the borehole redistributes, causing the circular borehole to become elliptical under geostress. The geostress is then calculated by measuring the borehole wall strain and the rock mass elastic parameters. The stress relief method is widely used in the mining industry because it involves shallow boreholes with large diameters, and the borehole profile and well wall deformation are easy to observe and obtain. However, in oil and gas field development, considering the uncertainty of the wellbore enlargement rate, the irregularity of the wellbore, and the influence of mud cake on the wellbore measuring instrument, this method can introduce significant systematic errors.

[0004] Existing patent CN108344535A discloses a horizontally effective stress testing method and device that takes drilling fluid pressure into account. This method is based on the premise that small-diameter boreholes cause minimal in-situ stress disturbance. It establishes the relationship between in-situ stress and drilling fluid pressure using a flat plate circular borehole model and a formula for a thick-walled cylinder. The principle is that after the in-situ stress caused by drilling is released, the borehole deforms, generating radial and tangential displacements around the borehole. By measuring the resulting radial and tangential displacement values, the in-situ stress is calculated in reverse. This method has low requirements for geological conditions and cored rock; no further processing of the borehole is needed after drilling, nor is it necessary to guide the drilling process. Using strain gauges bonded inside the borehole simplifies measurement operations, resulting in a higher success rate. This increased success rate reduces the need for repeated borehole measurements, thus lowering testing costs. Furthermore, the method considers drilling fluid pressure, which improves the accuracy of measurement results. However, the calculation formula of this patented method uses the initial borehole diameter, which is measured by a multi-beam phase laser rangefinder. This measurement is significantly affected by the mud cake on the well wall, leading to inaccurate final calculation results. Additionally, the testing equipment used in this method is unconventional logging tools, requiring numerous instruments and involving complex testing procedures, increasing testing costs and time.

[0005] Existing patent CN110514342A discloses a measuring device and method for rapidly determining the in-situ stress in soft rock formations. It combines the characteristics of hydraulic fracturing and borehole deformation methods, consisting of a closed hydraulic fracturing pipeline system and a borehole deformation measurement system. This invention determines the in-situ stress based on the rock mass stress, applied stress, and deformation characteristics of the rock mass. The measurement employs a specific loading method to induce borehole deformation. By ellipticizing the borehole deformation, the direction of the maximum horizontal principal stress is obtained, and the elastic deformation is separated to calculate the in-situ stress value. This patent can rapidly determine the in-situ stress in soft rock formations. Rock stress can be measured in a single test, obtaining the magnitude and direction of the two-dimensional principal stress of the borehole cross-section. The measurement process does not require the removal of the borehole casing, saving more than 50% of the measurement time compared to the hydraulic fracturing method and the borehole deformation method. Three-dimensional stress results can be obtained using a three-hole or more confluence borehole system. However, the method of this patent requires additional pressure to be applied to the well wall using a telescopic capsule during the testing process. The testing process relies on a specially designed testing device, which is not a conventional logging tool. Furthermore, the numerous tools used and the complex testing procedures increase the testing cost and time.

[0006] Existing patent CN112816336A discloses a pressure-stress-relieving in-situ geostress testing method, which solves the shortcomings of traditional stress relief methods, such as complex operation of geostress measurement devices, inability of testing devices to withstand high temperatures and pressures, and the need for rock mechanics tests after the test. It also broadens the detection depth range of stress relief devices and improves the convenience of testing devices. However, the method of this patent requires additional water pressure to be applied to the well wall on-site through an inner tube pressurizer, and requires double-tube core drilling to relieve the rock stress around the test hole. It also has the problems of using many tools and complex testing procedures, which increases the testing cost and testing time. Moreover, when conducting deep well tests, the reservoir pressure is high and the working conditions are complex. Rock cuttings generated during the drilling process can easily lead to accidents such as stuck drill pipe. Summary of the Invention

[0007] This invention aims to solve at least one technical problem existing in the background art, and provides a method and equipment for predicting geostress based on the rotation trajectory of a caliper and measurement data. The method analyzes the rotation trajectory of the caliper and measurement data and introduces the pump shutdown pressure to verify the minimum horizontal principal stress, thereby accurately calculating the biaxial stress difference and the maximum horizontal principal stress. This effectively reduces the error caused by the uncertainty of wellbore irregularity and wellbore enlargement rate in traditional stress relief methods on the geostress inversion results, improves the accuracy of geostress prediction results, and uses conventional logging and drilling tools for testing, making the testing procedure simple and efficient.

[0008] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0009] A method for predicting geostress based on the rotation trajectory of a wellbore measuring instrument and measurement data, the method comprising the following steps:

[0010] Step S1: Analyze the rotation trajectory of the caliper during the lifting measurement process using the caliper measurement data, find the well section with an elliptical wellbore shape in the target layer, and record the major axis measurement value C13 and minor axis measurement value C24 of the elliptical wellbore.

[0011] Step S2: Substitute the density logging and sonic logging data of the target layer into the wave equation to obtain the dynamic Young's modulus E of the target layer. 动 With dynamic Poisson ratio μ 动 ;

[0012] Then the dynamic Young's modulus E 动 With dynamic Poisson ratio μ 动 Substituting into the empirical formula for the dynamic-static transformation of the target layer, the static Young's modulus E of the target layer is obtained. 静 Compared with static Poisson's ratio μ 静 ;

[0013] Step S3: Based on the drilling data of the target formation, obtain the mud pressure P acting on the wellbore. m The overlying stratum pressure σ is obtained by integrating the density logging data of the target formation. v ;

[0014] Step S4: Obtain fracturing operation data for the target section, and determine the pump shutdown pressure P from the fracturing operation data. t Calculate and obtain the minimum horizontal principal stress σ h ;

[0015] Step S5: Substitute the parameters from steps S1-S4 into the wellbore stress-strain formula under plane strain conditions, and calculate the biaxial stress difference Δσ and the maximum horizontal principal stress σ using the formula. H This enables the prediction of geostress in the target layer.

[0016] Further, in step S2, the density logging and sonic logging data of the target formation are substituted into the wave equation, which is:

[0017]

[0018] In the above formula, V P V is the longitudinal wave velocity; S E represents the transverse wave velocity. 动 For dynamic Young's modulus; μ 动 ρ is the dynamic Poisson's ratio; ρ is the rock density.

[0019] Furthermore, in step S2, the dynamic Young's modulus E of the target layer is obtained. 动 With dynamic Poisson ratio μ 动 They are respectively:

[0020] μ 动 =[(V P / V S ) 2 -2] / [(V P / V S ) 2 -1]

[0021] E 动 =[ρV S 2 (3V P 2 -4V S 2 )] / [V P 2 -V S 2 ]

[0022] In the above formula, V P V is the longitudinal wave velocity; S E represents the transverse wave velocity. 动 For dynamic Young's modulus; μ 动 ρ is the dynamic Poisson's ratio; ρ is the rock density.

[0023] Furthermore, in step S2, the empirical formula for the dynamic-static transformation of the target layer segment is obtained as follows:

[0024] The dynamic Young's modulus E of the target formation was obtained from well logging data. 动 With dynamic Poisson ratio μ 动 The static Young's modulus E of the target layer was obtained through indoor core experiments. 静 Compared with static Poisson's ratio μ 静 Then, empirical formulas for the dynamic-static transformation of the target layer are obtained through mathematical fitting.

[0025] Further, in step S4, the minimum horizontal principal stress σ h The calculation formula is:

[0026] σ h =P t +ρgH 静

[0027] In the above formula, σ h The minimum horizontal principal stress; P t The pump stop pressure is ρ; the rock density is g; the acceleration due to gravity is H. 静 This represents the height of the hydrostatic column in the wellbore.

[0028] Further, in step S5, the wellbore stress-strain formula is:

[0029]

[0030] In the above formula, C13 is the measured value of the major axis; C24 is the measured value of the minor axis; r is the initial hole radius; E 静 μ is the static Young's modulus. 静 σ is the static Poisson's ratio; Δσ is the biaxial stress difference; σ v The pressure of the overlying strata; P m σ is the mud pressure; h This represents the minimum horizontal principal stress.

[0031] Further, in step S5, the wellbore stress-strain formula is simplified, and the biaxial stress difference Δσ is calculated using the following formula:

[0032]

[0033] In the above formula, C13 is the measured value of the major axis; C24 is the measured value of the minor axis; r is the initial hole radius; E 静 μ is the static Young's modulus. 静 σ is the static Poisson's ratio; Δσ is the biaxial stress difference; σ v The pressure of the overlying strata; P m σ is the mud pressure; h This represents the minimum horizontal principal stress.

[0034] Furthermore, in step S5, the maximum horizontal principal stress σ H The calculation formula is as follows:

[0035] σ H =σ h +Δσ

[0036] In the above formula, σ H The maximum horizontal principal stress; σ h Δσ represents the minimum horizontal principal stress; Δσ represents the biaxial stress difference.

[0037] In addition, the present invention also provides a computer-readable storage medium storing a computer program, the computer program including program instructions, which, when executed by a computer, cause the computer to perform the method described in any of the preceding claims.

[0038] In addition, the present invention provides an electronic device comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, it implements the method described in any of the preceding claims.

[0039] Compared with the prior art, the beneficial effects of the present invention are:

[0040] (1) The geostress prediction method provided by the present invention analyzes the rotation trajectory and measurement data of the caliper to find well sections with an approximately elliptical wellbore shape. The measured values ​​of the major and minor axes of the corresponding elliptical wellbore are substituted into the stress-strain relationship of the well wall under plane strain conditions (stress relief method formula). The minimum horizontal principal stress is checked by the pump shutdown pressure during the hydraulic fracturing construction of the corresponding well section, thereby accurately calculating the biaxial stress difference and the maximum horizontal principal stress. This method can greatly reduce the error caused by the irregularity of the wellbore and the uncertainty of the wellbore enlargement rate when applying the traditional stress relief method to the geostress inversion results, and improve the accuracy of the geostress prediction results.

[0041] (2) The geostress prediction method provided by the present invention theoretically only requires conventional logging data (including caliper measurement data), fracturing construction data and empirical formulas for the conversion of dynamic and static elastic parameters of the target layer to obtain the minimum horizontal principal stress, maximum horizontal principal stress and biaxial stress difference of the target layer. Compared with the laboratory test of geostress, the geostress prediction method of the present invention requires field construction data that is easier to obtain during the development of oil and gas fields, and does not require additional experimental testing. The testing method of the present invention is more economical and efficient.

[0042] (3) The geostress prediction method provided by the present invention uses conventional logging and drilling tools. It does not require additional pressure or measurement on the well wall through special tools, nor does it require stress relief of the rock around the test hole through casing drilling. It requires fewer testing tools, has a simple testing procedure, and high testing efficiency. It can be used not only for geostress prediction of conventional wells, but also for geostress prediction of deep wells. Attached Figure Description

[0043] Figure 1 This is a flowchart of the geostress prediction method based on the rotation trajectory of the wellbore measuring instrument and measurement data in Embodiment 1 of the present invention;

[0044] Figure 2 This refers to the wellbore measurement data for the 3739.6-3742.0m section of Well X in Embodiment 2 of the present invention;

[0045] Figure 3 This is a schematic diagram of the rotation trajectory of the well caliper measuring instrument in the 3740.8-3741.3m section of Well X in Embodiment 2 of the present invention. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Example 1

[0048] This invention provides a method for predicting geostress based on the rotation trajectory of a caliper and measurement data, combined with... Figure 1 As shown, the method includes the following steps:

[0049] Step S1: Analyze the rotation trajectory of the caliper during the lifting measurement process using the caliper measurement data, find the well section with an elliptical wellbore shape in the target layer, and record the major axis measurement value C13 and minor axis measurement value C24 of the elliptical wellbore.

[0050] Step S2: Substitute the density logging and sonic logging data of the target layer into the wave equation to obtain the dynamic Young's modulus E of the target layer. 动 With dynamic Poisson ratio μ 动 ;

[0051] Then the dynamic Young's modulus E 动 With dynamic Poisson ratio μ 动 Substituting into the empirical formula for the dynamic-static transformation of the target layer, the static Young's modulus E of the target layer is obtained. 静 Compared with static Poisson's ratio μ 静 .

[0052] The wave equation is as follows:

[0053]

[0054] The dynamic Young's modulus E of the target layer can be obtained by solving the above formula (1). 动 With dynamic Poisson ratio μ 动 They are respectively:

[0055] μ 动 =[(V P / V S ) 2 -2] / [(V P / V S ) 2 -1] (2)

[0056] E 动 =[ρV S 2 (3V P 2 -4V S 2 )] / [V P 2 -V S 2 (3)

[0057] In equations (1)-(2) above, VP V is the longitudinal wave velocity; S E represents the transverse wave velocity. 动 For dynamic Young's modulus; μ 动 ρ is the dynamic Poisson's ratio; ρ is the rock density.

[0058] The empirical formula for the dynamic-static transformation of the target layer is obtained as follows:

[0059] The dynamic Young's modulus and dynamic Poisson's ratio of the target layer are obtained by well logging data, and the static Young's modulus and static Poisson's ratio of the target layer are obtained by indoor core experiments. Then, the empirical formula for the dynamic-static conversion of the target layer is obtained by mathematical fitting.

[0060] Step S3: Based on the well drilling data of the target formation, obtain the mud pressure P acting on the wellbore. m The overlying stratum pressure σ is obtained by integrating the density logging data of the target formation. v .

[0061] Step S4: Obtain fracturing operation data for the target section, and determine the pump shutdown pressure P from the fracturing operation data. t Calculate and obtain the minimum horizontal principal stress σ h :

[0062] σ h =P t +ρgH 静 (4)

[0063] In equation (4) above, σ h The minimum horizontal principal stress; P t The pump stop pressure is ρ; the rock density is g; the acceleration due to gravity is H. 静 This represents the height of the hydrostatic column in the wellbore.

[0064] Step S5: Substitute the parameters from steps S1-S4 into the wellbore stress-strain formula under plane strain conditions, and calculate the biaxial stress difference Δσ and the maximum horizontal principal stress σ using the formula. H This enables the prediction of geostress in the target layer.

[0065] The wellbore stress-strain formula is as follows:

[0066]

[0067] The above formula (5) can be simplified to:

[0068]

[0069] Then, the maximum horizontal principal stress σ is calculated using the following formula. H :

[0070] σ H =σ h +Δσ (7)

[0071] In equations (5)-(7) above, C13 is the measured value of the major axis; C24 is the measured value of the minor axis; r is the initial hole radius; E 静 μ is the static Young's modulus. 静 σ is the static Poisson's ratio; Δσ is the biaxial stress difference, i.e., the difference between the maximum and minimum horizontal principal stresses; σ v The pressure of the overlying strata; P m σ is the mud pressure; h σ is the minimum horizontal principal stress; H This represents the maximum horizontal principal stress.

[0072] The parameters in steps S1-S4 (major axis measurement value C13, minor axis measurement value C24, static Young's modulus E) 静 Static Poisson's ratio μ 静 Mud pressure P m Overlying strata pressure σ v Minimum horizontal principal stress σ h Substituting into formula (6) above, the biaxial stress difference Δσ can be obtained, and then the maximum horizontal principal stress σ can be obtained according to formula (7). H This enables the prediction of geostress in the target layer.

[0073] As can be seen from formulas (6) and (7), the initial borehole radius r is not involved in the calculation process. This calculation method can avoid the influence of the error in obtaining the initial borehole diameter on the calculation results, thereby avoiding the error caused by the uncertainty of borehole irregularity and borehole enlargement rate on the geostress inversion results when applying the traditional stress relief method.

[0074] Example 2

[0075] This embodiment of the invention applies the method from Example 1 to well X in a certain oil reservoir. The initial testing interval is 3734.0-3774.0m. The specific implementation process of this embodiment is as follows:

[0076] Step S1: Analyze the rotation trajectory during the lifting measurement process using the caliper measurement data obtained from the conventional logging data of the 3739.6-3742.0m section of Well X through a four-arm caliper measuring instrument. Figure 2 As shown, the well section in the target formation with an approximate elliptical wellbore shape is 3740.8-3741.3m. The major axis measurement C13 of the elliptical wellbore is recorded as 8.485 ft (ft), and the minor axis measurement C24 is recorded as 8.449 ft (ft).

[0077] Step S2: Using conventional logging data from the 3740.8-3741.3m section of well X, the longitudinal wave velocity V... p (3976.2 m / s, mean) and shear wave velocity V s Substituting the value of (2354.3 m / s, mean) into the wave equation formula (1), the dynamic Young's modulus E is obtained. 动 With dynamic Poisson ratio μ 动 ;

[0078] Then the dynamic Young's modulus E 动 With dynamic Poisson ratio μ 动 Substitute the following empirical formula (8) for the dynamic-static transformation of the target layer:

[0079]

[0080] The static Young's modulus E can be calculated. 静 =18.14 GPa; static Poisson's ratio μ 静 =0.243.

[0081] Step S3: Based on the drilling data of the target formation, obtain the mud pressure P acting on the wellbore. m The pressure is 51.3 MPa; σ is obtained by integrating the density logging curve. v It is 85.39 MPa.

[0082] Step S4: Pump shutdown pressure P in the target layer t The value is 24.0 MPa. Substituting this value into formula (4), the minimum horizontal principal stress σ is calculated. h It is 61.4 MPa.

[0083] Step S5: Calculate the parameters from steps S1-S4 (major axis measurement C13, minor axis measurement C24, static Young's modulus E). 静 Static Poisson's ratio μ 静 Mud pressure P m Overlying strata pressure σ v Minimum horizontal principal stress σ h Substituting into formula (6), the biaxial stress difference Δσ is found to be 20.4 MPa. Then, the maximum horizontal principal stress σ is obtained according to formula (7). H The pressure is 81.8 MPa.

[0084] The comparison data between the prediction results of the present invention embodiment and the core experimental results of the Kaiser method are shown in Table 1 below.

[0085] Table 1 Comparison of Calculation Results and Kaiser Method Core Experiment Results

[0086]

[0087]

[0088] As can be seen from Table 1, the calculation results of the embodiments of the present invention are similar to the core test results of the corresponding well sections using the Kaiser method. Therefore, the prediction results of the embodiments of the present invention have high credibility and the prediction method is reliable.

[0089] Example 3

[0090] This invention provides a computer-readable storage medium storing a computer program, the computer program including program instructions, which, when executed by a computer, cause the computer to perform the method described in Embodiment 1.

[0091] Example 4

[0092] This invention provides an electronic device, which includes a processor, a memory, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the method described in Embodiment 1.

[0093] The above description is merely an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for predicting geostress based on the rotation trajectory and measurement data of a wellbore caliper, characterized in that, The method includes the following steps: Step S1: Analyze the rotation trajectory of the caliper during the lifting measurement process using the measurement data from the caliper, locate the elliptical well section in the target formation, and record the major axis measurement value of the elliptical well section. With minor axis measurement ; Step S2: Substitute the density logging and sonic logging data of the target layer into the wave equation to obtain the dynamic Young's modulus of the target layer. Compared with dynamic Poisson ratio ; Then the dynamic Young's modulus Compared with dynamic Poisson ratio Substituting into the empirical formula for the dynamic-static transformation of the target layer, the static Young's modulus of the target layer is obtained. Compared with static Poisson's ratio ; Step S3: Based on the drilling data of the target formation, obtain the mud pressure acting on the wellbore. P m The pressure of the overlying strata is calculated by integrating the density logging data of the target formation. v ; Step S4: Obtain fracturing operation data for the target section, and determine the pump shutdown pressure from the fracturing operation data. P t Calculate and obtain the minimum horizontal principal stress h ; Step S5: Substitute the parameters from steps S1-S4 into the wellbore stress-strain formula under plane strain conditions, and calculate the biaxial stress difference using the formula. and maximum horizontal principal stress H To achieve in-situ stress prediction for the target layer; In step S2, the dynamic Young's modulus of the target layer is obtained. E 动 Compared with dynamic Poisson ratio They are respectively: In the above formula, For longitudinal wave velocity; The transverse wave velocity; For dynamic Young's modulus; For dynamic Poisson's ratio; Density of the rock; In step S2, the empirical formula for the dynamic-static transformation of the target layer segment is obtained as follows: The dynamic Young's modulus of the target formation was obtained using well logging data. Compared with dynamic Poisson ratio The static Young's modulus of the target layer was obtained through indoor core experiments. Compared with static Poisson's ratio Then, empirical formulas for the dynamic-static transformation of the target layer are obtained through mathematical fitting.

2. The method according to claim 1, characterized in that, In step S2, the density logging and sonic logging data of the target formation are substituted into the wave equation, which is: In the above formula, For longitudinal wave velocity; The transverse wave velocity; For dynamic Young's modulus; For dynamic Poisson's ratio; This represents the density of the rock.

3. The method according to claim 1, characterized in that, In step S4, the minimum horizontal principal stress h The calculation formula is: In the above formula, h The minimum horizontal principal stress; P t This is the pump stop pressure; Density of the rock; It is the acceleration due to gravity; This represents the height of the hydrostatic column in the wellbore.

4. The method according to claim 1, characterized in that, In step S5, the wellbore stress-strain formula is: In the above formula, This is the measurement of the major axis; This is the measurement value for the minor axis; r The initial aperture radius; It is the static Young's modulus; The static Poisson's ratio; It represents the biaxial stress difference; v This refers to the pressure of the overlying strata. P m For mud pressure; h This represents the minimum horizontal principal stress.

5. The method according to claim 1, characterized in that, In step S5, the wellbore stress-strain formula is simplified, and the biaxial stress difference is calculated using the following formula. : In the above formula, This is the measurement of the major axis; This is the measurement value for the minor axis; r The initial aperture radius; It is the static Young's modulus; The static Poisson's ratio; It represents the biaxial stress difference; v This refers to the pressure of the overlying strata. P m For mud pressure; h This represents the minimum horizontal principal stress.

6. The method according to claim 5, characterized in that, In step S5, the maximum horizontal principal stress The calculation formula is as follows: In the above formula, This represents the maximum horizontal principal stress. h The minimum horizontal principal stress; It represents the biaxial stress difference.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, the computer program including program instructions that, when executed by a computer, cause the computer to perform the method as described in any one of claims 1-6.

8. An electronic device comprising a processor, a memory, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the method as described in any one of claims 1-6.

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