Maximum horizontal principal stress acquisition method based on well wall shear failure degree

Abstract

The invention relates to the technical field of crustal stress calculation and evaluation, in particular to a maximum horizontal principal stress acquisition method based on well wall shear failure degree, which comprises the following steps of: establishing a calculation model of a maximum horizontal principal stress profile of a drilled well according to a well wall collapse failure mechanical model; the method comprises the following steps of: acquiring comprehensive logging data, drilling formation fracture pressure test and hydraulic fracturing data and dual-caliper logging data of a drilled well in a target block, and acquiring minimum horizontal principal stress, a rock internal friction angle, rock cohesion, formation pore pressure, drilling fluid column pressure and well wall caving width; and calculating the maximum horizontal principal stress according to the calculation model of the maximum horizontal principal stress profile of the drilled well. According to the method, on the basis of the rock linear elasticity theory, a mathematical model among the maximum horizontal principal stress, the borehole caving width, the rock strength and the formation pore pressure is established, the calculation precision of the method meets the geological engineering requirement, and a scientific basis is provided for oil reservoir engineering, drilling engineering and yield increasing engineering.

Description

Technical Field

[0001] The invention relates to the technical field of ground stress calculation and evaluation, and is a method for obtaining the maximum horizontal principal stress based on the degree of well wall shear failure. Background Art

[0002] Geostress runs through the entire process of oil and gas exploration and development. The research and application of geostress are increasingly valued by the petroleum engineering community. Rapid and accurate acquisition of geostress is of great significance for drilling and completion engineering and oil and gas field development engineering. At present, the methods for obtaining geostress include: ① core differential strain test method; ② core acoustic emission Kessel effect method; ③ hydraulic fracturing test method; ④ geostress empirical formula method. The first two methods use cores to conduct indoor experimental measurements to obtain original geostress. For deep drilling, there are very few core materials and experimental data available, and the core data is discontinuous; the accuracy of the measurement results depends on the core quality and the number of samples in the experiment; the measurement process is complex and the uncertainty of the measurement results is large. Therefore, the latter two methods are currently widely used to predict horizontal geostress.

[0003] The method for obtaining the minimum horizontal principal stress is to obtain the minimum horizontal principal stress value at a specific depth point based on the hydraulic fracturing data; substitute the obtained minimum horizontal principal stress value into the minimum horizontal principal stress empirical formula and correct the coefficient in the formula; use the corrected empirical formula to calculate the continuous minimum horizontal principal stress profile.

[0004] The maximum horizontal principal stress can only be obtained through the core differential strain test method and the core acoustic emission Kessel effect method; the measurement disadvantages are as mentioned above. Through the hydraulic fracturing test method, only the minimum horizontal principal stress can be measured, and the maximum horizontal principal stress cannot be obtained. At present, all calculations of the maximum principal stress at home and abroad use empirical formulas, which have no rigorous theoretical basis, and the coefficients in the formula are difficult to accurately calibrate. Therefore, the maximum principal stress is difficult to obtain and the calculation accuracy is not high. Summary of the invention

[0005] The present invention provides a method for obtaining the maximum horizontal principal stress based on the degree of shear failure of the well wall, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problem that the existing ground breaking test (hydraulic fracturing) method and the logging empirical model method cannot accurately obtain the maximum horizontal principal ground stress.

[0006] The technical solution of the present invention is achieved by the following measures: A method for obtaining the maximum horizontal principal stress based on the degree of shear failure of the wellbore is carried out according to the following steps:

[0007] The first step is to establish a calculation model of the maximum horizontal principal stress profile of the drilled well according to the wellbore collapse failure mechanics model; the mathematical expression of the calculation model of the maximum horizontal principal stress profile of the drilled well is:

[0008]

[0009] K=ctg(45°-β / 2) Formula 2

[0010] In the formula, σ H is the maximum horizontal ground stress, MPa; σ h is the minimum horizontal ground stress, MPa; C is the rock cohesion, MPa; β is the rock internal friction angle, °; Φ b is the wellbore collapse width, deg; P m is the drilling fluid column pressure, MPa; P p is the formation pore pressure, MPa; η is the Biot coefficient, dimensionless;

[0011] The second step is to collect comprehensive logging data, drilling formation fracture pressure test and hydraulic fracturing data and dual-caliber logging data of the target block, and obtain the minimum horizontal principal stress, rock internal friction angle, rock cohesion, formation pore pressure, drilling fluid column pressure and wellbore collapse width. According to the calculation model of the maximum horizontal principal stress profile of the drilled well, the maximum horizontal principal stress is calculated.

[0012] The following are further optimizations and / or improvements to the above technical solutions:

[0013] In the second step, the formation pore pressure is calculated from the comprehensive logging data of the wells drilled in the target block according to the inversion calculation model. The mathematical expression of the inversion calculation model is:

[0014]

[0015] Where P p is the formation pore pressure, MPa; Δt is the P-wave time difference, us / ft; Δt n is the acoustic time difference reading on the normal trend line, us / ft; σ v is the vertical ground stress, MPa; P n is the hydrostatic liquid column pressure, MPa.

[0016] In the second step above, the rock internal friction angle is calculated according to the following formula:

[0017]

[0018] Where, β is the internal friction angle of rock, °; V P is the P-wave velocity, km / s, derived from well logging data.

[0019] In the second step above, the rock cohesion is calculated according to the following formula:

[0020]

[0021] UCS=1276.7*exp(-0.037*Δt) Formula 6

[0022] Where C is the cohesion of rock, MPa; UCS is the compressive strength of rock, MPa; β is the internal friction angle of rock, °; Δt is the longitudinal wave time difference, us / ft.

[0023] In the second step above, the drilling fluid column pressure is calculated according to the following formula:

[0024] P m =ρ m gh formula 7

[0025] Where P m is the drilling fluid column pressure, MPa; ρ m is the drilling fluid density, g / cm 3 ; h is the well depth, m; g is the acceleration due to gravity, m / s 2 .

[0026] In the above second step, the minimum horizontal geostress is obtained according to the following steps: collecting the formation fracture pressure test and hydraulic fracturing data of the target block, and calculating the continuous data of the minimum horizontal principal stress according to the minimum horizontal geostress calculation formula, and the minimum horizontal geostress calculation formula is:

[0027]

[0028]

[0029] In the formula, σ h is the minimum horizontal ground stress, MPa; P p is the formation pore pressure, MPa; σ v is the vertical ground stress, MPa; υ is the rock Poisson’s ratio, dimensionless; V P is the longitudinal wave velocity, km / s; Vs is the shear wave velocity, km / s.

[0030] In the second step above, the wellbore collapse width is obtained according to the following steps: the dual-wellbore diameter data in the comprehensive logging data is analyzed; if one wellbore diameter of the target well section is equivalent to the drill bit diameter and the other wellbore diameter is larger than the drill bit diameter, and the wellbore is elliptical, it is determined that shear failure occurs in the target well section, which meets the applicable conditions of Formula 1; and then the dual-wellbore diameter data is used to draw a wellbore collapse scatter plot, in which the edge point of a damage area is connected to the center of the wellbore, and the angle formed by the two line segments is the wellbore collapse width.

[0031] In the above formula 1, η ranges from 0.5 to 0.9.

[0032] The present invention is based on the theory of rock linear elasticity and the law of wellbore collapse that conforms to the Mohr-Coulomb criterion. A mathematical model between the maximum horizontal principal stress and the borehole collapse width, rock strength and formation pore pressure is established. The relevant parameters are obtained by using logging, ground breaking tests, drilling data, etc. of the target formation section, and the maximum horizontal principal stress is inversely calculated. The present invention fully considers factors such as tectonic stress, drilling conditions, and formation fluids, and obtains the wellbore collapse width through logging data; there is no need for indoor core testing, which overcomes the shortcomings of experimental testing. Since logging data is continuous, the present invention is suitable for the continuous calculation of the geostress profile of the drilled well, and the calculation accuracy fully meets the requirements of geological engineering, providing a scientific basis for reservoir engineering, drilling engineering, and production increase engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Attached Figure 1 This is a flowchart of the method for obtaining the maximum horizontal principal stress in Example 1 of the present invention.

[0034] Attached Figure 2 It is a schematic diagram of the mechanical model of well wall collapse failure in the present invention.

[0035] Attached Figure 3 This is a double wellbore curve diagram of Well Huo 001 in Example 9 of the present invention.

[0036] Attached Figure 4 This is a wellbore collapse diagram of the 1600m-1700m section of the Huo 001 well in Example 9 of the present invention. DETAILED DESCRIPTION

[0037] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0038] The present invention will be further described below in conjunction with embodiments:

[0039] Embodiment 1: The method for obtaining the maximum horizontal principal stress based on the degree of wellbore shear failure is carried out according to the following steps:

[0040] The first step is to establish a calculation model of the maximum horizontal principal stress profile of the drilled well according to the wellbore collapse failure mechanics model; the mathematical expression of the calculation model of the maximum horizontal principal stress profile of the drilled well is:

[0041]

[0042] K=ctg(45°-β / 2) Formula 2

[0043] In the formula, σ H is the maximum horizontal ground stress, MPa; σ h is the minimum horizontal ground stress, MPa; C is the rock cohesion, MPa; β is the rock internal friction angle, °; Φb is the wellbore collapse width, deg; P m is the drilling fluid column pressure, MPa; P p is the formation pore pressure, MPa; η is the Biot coefficient, dimensionless;

[0044] The second step is to collect comprehensive logging data, drilling formation fracture pressure test and hydraulic fracturing data and dual-caliber logging data of the target block, and obtain the minimum horizontal principal stress, rock internal friction angle, rock cohesion, formation pore pressure, drilling fluid column pressure and wellbore collapse width. According to the calculation model of the maximum horizontal principal stress profile of the drilled well, the maximum horizontal principal stress is calculated.

[0045] When the drilling fluid column pressure is less than the equivalent density of the formation collapse pressure, the Mohr-Coulomb yield condition is first reached at the direction of the minimum principal stress on the wellbore surface. The rock around the wellbore gradually enters the strain softening stage due to damage, so that a damaged area appears around the wellbore. The area that is still in the elastic stage is called the elastic domain. When the surrounding rock stress in the damage domain exceeds the elastic limit, the original damage will expand and cause damage, and the wellbore wall will experience initial shear failure and collapse, such as Figure 2 The extent of wellbore collapse damage can be expressed as the wellbore collapse width Φ b (i.e. the angle of the wellbore collapse edge, extracted from the four (six) arm caliper logging data). Based on the basic assumption, the stress state of the wellbore surrounding rock can be solved by the wellbore collapse failure mechanics model. On an infinite plane, a circular hole is subjected to a uniform internal pressure P m At the same time, the maximum horizontal principal stress σ is received on this plane which is far from the circular hole. H , minimum horizontal principal stress σ h The vertical direction is subject to the overlying stratum pressure. According to the linear poroelasticity theory, through theoretical derivation, the calculation model of the maximum horizontal principal stress profile of the drilled well can be obtained as follows:

[0046]

[0047] The present invention is based on the rock linear elasticity theory and the wellbore collapse law that conforms to the Mohr-Coulomb criterion. A mathematical model between the maximum horizontal principal stress and the wellbore collapse width, rock strength and formation pore pressure is established. The relevant parameters are obtained by using the well logging, ground breaking test, drilling data, etc. of the target formation section to reversely calculate the maximum horizontal principal stress. Since the well logging data has continuity, the present invention can be applied to the continuous calculation of the maximum horizontal principal stress profile of the drilled well.

[0048] Embodiment 2: As an optimization of the above embodiment, in the second step, the formation pore pressure is calculated by the comprehensive logging data of the wells drilled in the target block according to the inversion calculation model, and the mathematical expression of the inversion calculation model is:

[0049]

[0050] Where P p is the formation pore pressure, MPa; Δt is the P-wave time difference, us / ft; Δt n is the acoustic time difference reading on the normal trend line, us / ft; σ v is the vertical ground stress, MPa; P n is the hydrostatic column pressure, MPa. Where, the vertical geostress σ v It can be converted from the density logging data and obtained by using relevant professional software (GMI ModelBuilder).

[0051] Embodiment 3: As an optimization of the above embodiment, in the second step, the rock internal friction angle is calculated according to the following formula:

[0052]

[0053] Where, β is the internal friction angle of rock, °; V P is the P-wave velocity, km / s, derived from well logging data.

[0054] Embodiment 4: As an optimization of the above embodiment, in the second step, the rock cohesion is calculated according to the following formula:

[0055]

[0056] UCS=1276.7*exp(-0.037*Δt) Formula 6

[0057] Where C is the rock cohesion, MPa; UCS is the rock compressive strength, MPa; β is the rock internal friction angle, °; Δt is the P-wave time difference, us / ft, which comes from well logging data.

[0058] Embodiment 5: As an optimization of the above embodiment, in the second step, the drilling fluid column pressure is calculated according to the following formula:

[0059] P m =ρ m gh formula 7

[0060] Where P m is the drilling fluid column pressure, MPa; ρ m is the drilling fluid density, g / cm 3 ; h is the well depth, m; g is the acceleration due to gravity, m / s 2 , take 0.0098.

[0061] Embodiment 6: As an optimization of the above embodiment, in the second step, the minimum horizontal geostress is obtained according to the following steps: collecting the formation fracture pressure test and hydraulic fracturing data of the target block, and calculating the continuous data of the minimum horizontal principal stress according to the minimum horizontal geostress calculation formula, the minimum horizontal geostress calculation formula is:

[0062]

[0063]

[0064] In the formula, σ h is the minimum horizontal ground stress, MPa; P p is the formation pore pressure, MPa; σ v is the vertical ground stress, MPa; υ is the rock Poisson’s ratio, dimensionless; V P is the longitudinal wave velocity, km / s; Vs is the shear wave velocity, km / s.

[0065] Embodiment 7: As an optimization of the above embodiment, in the second step, the wellbore collapse width is obtained according to the following steps: the dual wellbore data in the comprehensive logging data is analyzed. If one wellbore of the target well section is equivalent to the drill bit diameter and the other wellbore is larger than the drill bit diameter, and the wellbore is elliptical, it is determined that shear failure has occurred in the target well section, which meets the applicable conditions of Formula 1; then the dual wellbore data is used to draw a wellbore collapse scatter plot. After shear failure occurs in the wellbore, basically equal damage areas will appear symmetrically on both sides. In the wellbore collapse scatter plot, the edge point of a damage area is connected to the center of the wellbore, and the angle formed by the two line segments is the wellbore collapse width.

[0066] Embodiment 8: As an optimization of the above embodiment, in Formula 1, the value range of η is 0.5 to 0.9.

[0067] Example 9: The Horgos anticline is located at the southern edge of the Junggar Basin. It belongs to the middle section of the second row of structural belts at the southern edge in terms of structural zoning. It is a long-axis anticline extending nearly east-west. The 1600m-1700m section of the Huo 001 well (Anjihaihe Formation) is taken as the research object, and the maximum horizontal principal stress acquisition method based on the degree of wellbore shear failure is applied. Figure 1 As shown, the specific process is as follows:

[0068] ① Collect and organize comprehensive logging data and drilling fluid density data, as shown in columns 1 to 6 of Tables 1-1 to 1-4;

[0069] ② According to formulas 2 to 7, calculate the rock internal friction angle, compressive strength, rock cohesion, drilling fluid column pressure, Poisson's ratio, and vertical geostress (see columns 7 to 12 in Tables 1-1 to 1-4);

[0070] ③ Use relevant professional software (GMI ModelBuilder) to draw the normal trend line of P-wave time difference, read the P-wave time difference value on the normal trend line, and further calculate the formation pore pressure (column 13 in Table 1-1 to Table 1-4);

[0071] ④ According to equations 8 and 9, calculate the minimum horizontal principal stress (column 14 in Tables 1-1 to 1-4)

[0072] ⑤ Use relevant professional software (GMI Caliper) to analyze the dual-caliber data (such as Figure 3 ), in the 1600m-1700m section of Well Huo001, one well diameter is basically equivalent to the drill bit diameter, and the other well diameter is significantly larger than the drill bit diameter. Therefore, it can be considered that shear failure occurred in this well section, which meets the applicable conditions of formula (1); then the double well diameter data is used to draw a scatter plot of well wall collapse (such as Figure 4 ). After the wellbore wall is sheared, basically equal damage areas will appear symmetrically on both sides. In the wellbore collapse scatter diagram, the edge point of a damage area is connected to the center of the wellbore, and the angle formed by the two line segments is the wellbore collapse width. In the 1600m-1700m section of the Huo 001 well, the double wellbore curve is stable and has little change. The wellbore collapse width difference in this section is small, and the average value Φ b ≈100° (column 15 in Tables 1-1 to 1-4).

[0073] ⑥ According to formula 1, calculate the minimum horizontal principal stress of the 1600m-1700m section of Well Huo 001 (see column 16 in Table 1-1 to Table 1-4).

[0074] ⑦ Experimental verification of calculation results: Through indoor core mechanics test and acoustic emission Kessel experiment, relevant rock mechanics parameters and ground stress values ​​are obtained, as shown in Table 2. As can be seen from Table 2, the maximum horizontal principal stress calculated by the invention is very close to the result of indoor acoustic emission Kessel experiment.

[0075] The maximum horizontal principal stress acquisition method based on the degree of wellbore shear failure of the present invention provides a calculation model obtained through careful derivation based on the porous medium elastic mechanics theory, which is a theoretical formula with high accuracy and certainty, and the calculation model is simple and practical, and the acquisition of relevant parameters is also relatively easy. It has been verified that the method has high reliability, small result error, and simple and convenient operation.

[0076] In summary, the present invention provides a method for obtaining the maximum horizontal principal stress based on the degree of shear failure of the well wall, which solves the problem that the ground breaking test (hydraulic fracturing) method and the logging empirical model method cannot accurately obtain the maximum horizontal principal ground stress. At the same time, it solves the problem that there are few experimental samples in the core chamber, the data is discontinuous and the cost is high. The calculation results meet the technical requirements of petroleum engineering, the method is simple and practical, and has good operability.

[0077] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

[0078] Table 1-1

[0079]

[0080] Table 1-2

[0081]

[0082] Table 1-3

[0083]

[0084] Table 1-4

[0085]

[0086] Table 2

[0087]

Claims

1. A method for obtaining the maximum horizontal principal stress based on the degree of wellbore shear failure, characterized in that Follow these steps: The first step is to establish a calculation model of the maximum horizontal principal stress profile of the drilled well according to the wellbore collapse failure mechanics model. The mathematical expression of the calculation model of the maximum horizontal principal stress profile of the drilled well is: K=ctg(45°-β / 2) Formula 2 In the formula, σ H is the maximum horizontal ground stress, MPa; σ h is the minimum horizontal ground stress, MPa; C is the rock cohesion, MPa; β is the rock internal friction angle, °; Φ b is the wellbore collapse width, deg; P m is the drilling fluid column pressure, MPa; P p is the formation pore pressure, MPa; η is the Biot coefficient, dimensionless; The second step is to collect comprehensive logging data, drilling formation fracture pressure test and hydraulic fracturing data and dual-caliber logging data of the target block, and obtain the minimum horizontal principal stress, rock internal friction angle, rock cohesion, formation pore pressure, drilling fluid column pressure and wellbore collapse width. According to the calculation model of the maximum horizontal principal stress profile of the drilled well, the maximum horizontal principal stress is calculated.

2. The method for obtaining the maximum horizontal principal stress based on the degree of wellbore shear failure according to claim 1 is characterized in that In the second step, the formation pore pressure is calculated from the comprehensive logging data of the wells drilled in the target block according to the inversion calculation model. The mathematical expression of the inversion calculation model is: Where P p is the formation pore pressure, MPa; Δt is the P-wave time difference, us / ft; Δt n is the acoustic time difference reading on the normal trend line, us / ft; σ v is the vertical ground stress, MPa; P n is the hydrostatic liquid column pressure, MPa.

3. The method for obtaining the maximum horizontal principal stress based on the degree of wellbore shear failure according to claim 1 or 2, characterized in that In the second step, the rock internal friction angle is calculated according to the following formula: Where, β is the internal friction angle of rock, °; V P is the longitudinal wave velocity, km / s.

4. The method for obtaining the maximum horizontal principal stress based on the degree of wellbore shear failure according to any one of claims 1 to 3, characterized in that In the second step, the rock cohesion is calculated according to the following formula: UCS=1276.7*exp(-0.037*Δt) Formula 6 Where C is the cohesion of rock, MPa; UCS is the compressive strength of rock, MPa; β is the internal friction angle of rock, °; Δt is the longitudinal wave time difference, us / ft.

5. The method for obtaining the maximum horizontal principal stress based on the degree of wellbore shear failure according to any one of claims 1 to 4, characterized in that In the second step, the drilling fluid column pressure is calculated according to the following formula: P m =ρ m gh formula 7 Where P m is the drilling fluid column pressure, MPa; ρ m is the drilling fluid density, g / cm 3 ; h is the well depth, m; g is the acceleration due to gravity, m / s 2 .

6. The method for obtaining the maximum horizontal principal stress based on the degree of wellbore shear failure according to any one of claims 1 to 5, characterized in that In the second step, the minimum horizontal geostress is obtained according to the following steps: collecting the formation fracture pressure test and hydraulic fracturing data of the target block, and calculating the continuous data of the minimum horizontal principal stress according to the minimum horizontal geostress calculation formula, and the minimum horizontal geostress calculation formula is: In the formula, σ h is the minimum horizontal ground stress, MPa; P p is the formation pore pressure, MPa; σ v is the vertical ground stress, MPa; υ is the rock Poisson’s ratio, dimensionless; V P is the longitudinal wave velocity, km / s; Vs is the shear wave velocity, km / s.

7. The method for obtaining the maximum horizontal principal stress based on the degree of wellbore shear failure according to any one of claims 1 to 6, characterized in that In the second step, the wellbore collapse width is obtained according to the following steps: the dual-wellbore data in the comprehensive logging data are analyzed. If one wellbore diameter of the target well section is equivalent to the drill bit diameter and the other wellbore diameter is larger than the drill bit diameter, and the wellbore is elliptical, it is determined that shear failure occurs in the target well section, which meets the applicable conditions of Formula 1; then the dual-wellbore data is used to draw a wellbore collapse scatter plot. In the wellbore collapse scatter plot, the edge point of a damage area is connected to the wellbore center, and the angle formed by the two line segments is the wellbore collapse width.

8. The method for obtaining the maximum horizontal principal stress based on the degree of wellbore shear failure according to any one of claims 1 to 7, characterized in that In formula 1, η ranges from 0.5 to 0.9.

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