Method for determining maximum horizontal ground stress in horizontal well state

Abstract

The invention discloses a method for determining the maximum horizontal ground stress in a horizontal well state, and relates to the technical field of petroleum drilling and completion, and the method comprises the following steps: a) judging whether a radial induced crack exists on the well wall of a horizontal well or not; b) respectively calculating the components of the vertical, horizontal maximum and horizontal minimum ground stresses on the well wall of the horizontal well; c) calculating radial, circumferential and axial normal stress components on the well wall in the horizontal well state, and calculating the minimum values of the circumferential normal stress component and the axial normal stress component; d) drawing a stress polygon of the target stratum and upper and lower limit constraint lines of the horizontal maximum crustal stress; and e) determining the upper limit and the lower limit of the horizontal maximum crustal stress according to the intersection points of the horizontal minimum crustal stress and the upper limit and lower limit constraint lines of the horizontal maximum crustal stress. The horizontal maximum crustal stress in the horizontal well state can be rapidly and accurately determined, and the technical problem that in the prior art, the horizontal maximum crustal stress cannot be accurately determined in the horizontal well state is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil drilling and completion, and particularly relates to a method for determining the maximum horizontal in-situ stress under the condition of a horizontal well. BACKGROUND

[0002] Accurate in-situ stress is of great significance to oil and gas exploration and development, and is also an important basic parameter required for wellbore stability analysis, fracturing optimization design, etc. The vertical in-situ stress can be obtained by integrating the logging bulk density, the minimum horizontal in-situ stress can be determined by small-scale fracturing and geostress test, but the maximum horizontal in-situ stress cannot be directly obtained and is the most difficult component to determine in in-situ stress modeling.

[0003] In the prior art, Zoback et al. proposed a stress polygon model, and combined the imaging logging wellbore collapse and axial induced fracture to constrain and limit the maximum horizontal in-situ stress range under the condition of a vertical well. However, this method mainly uses the axial induced fracture under the condition of a vertical well, and it is usually difficult for the same depth stratum to simultaneously exist the wellbore collapse and the induced fracture, which leads to the difficulty in simultaneously constraining and limiting the upper limit and the lower limit of the maximum horizontal in-situ stress. In addition, in the stress polygon model proposed by Zoback et al., the fault friction coefficient is usually taken as 0.6-0.8, which does not consider the influence of stratum change, and will lead to the error of in-situ stress prediction and affect the accuracy of prediction.

[0004] Therefore, there is an urgent need for a method for determining the maximum horizontal in-situ stress under the condition of a horizontal well, which can quickly and accurately determine the range of the maximum horizontal in-situ stress under the condition of a horizontal well, and is also suitable for determining the maximum horizontal in-situ stress of different strata. SUMMARY

[0005] The present application aims to overcome the above-mentioned problems in the prior art, and provides a method for determining the maximum horizontal in-situ stress under the condition of a horizontal well. The present application can quickly and accurately determine the maximum horizontal in-situ stress under the condition of a horizontal well, and is also suitable for determining the maximum horizontal in-situ stress of different strata, thereby solving the technical problem that the prior art cannot accurately determine the maximum horizontal in-situ stress under the condition of a horizontal well.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] A method for determining the maximum horizontal in-situ stress under the condition of a horizontal well, comprising the following steps:

[0008] (a) collecting the imaging logging data of a target stratum, and judging whether there is a radial induced fracture on the wellbore of the horizontal well according to the imaging logging data, if there is a radial induced fracture, then turning to step (b);

[0009] (b) calculating the vertical in-situ stress σ V , the maximum horizontal in-situ stress σH and the minimum horizontal ground stress σ h The component σ on the horizontal wellbore x σ y σ z ;

[0010] (c) Calculate the radial normal stress component σ on the wellbore wall under the horizontal well condition based on the wellbore direction and the results of step (b). rr Circumferential normal stress component σ θθ and axial normal stress component σ zz And calculate the circumferential normal stress component σ θθ The minimum value σ θθmin and axial normal stress component σ zz The minimum value σ zzmin ;

[0011] (d) Draw a stress polygon of the target formation based on the stress of the target formation. Within the range of the drawn stress polygon, draw the upper and lower limit constraint lines of the maximum horizontal stress based on the radially induced fracture based on the results of step (c).

[0012] (e) Based on the minimum horizontal ground stress σ h Respectively compared with the maximum horizontal ground stress σ H The intersection of the upper and lower limit constraint lines determines the upper and lower limits of the maximum horizontal ground stress.

[0013] The stress polygon of the target formation is defined by the minimum horizontal stress σ. h and vertical ground stress σ V The ratio σ h / σ V The horizontal axis is σ, and the maximum horizontal ground stress is σ. H and vertical ground stress σ V The ratio σ H / σ V It is plotted in a coordinate system with the vertical axis as the coordinate.

[0014] The specific process for determining the upper and lower limits of the maximum horizontal ground stress is as follows: first, by using the minimum horizontal ground stress σ... h With vertical ground stress σ V The ratio σ h / σ V Find the intersection point with the upper and lower limit constraint lines of the maximum horizontal ground stress, and locate the maximum horizontal ground stress σ on the vertical axis. H With vertical ground stress σ V The range of the ratio σ H / σ V Then the vertical ground stress σ V Substitute into the determined ratio range σ H / σV , i.e. the upper and lower limits of the maximum horizontal stress.

[0015] In step (b), the vertical stress σ V , the maximum horizontal stress σ H and the minimum horizontal stress σ h on the wellbore wall of the horizontal well are calculated. x , σ y , σ z The calculation method is as follows:

[0016]

[0017] In formula (1), β b is the inclination azimuth angle, in °.

[0018] In step (c), the radial normal stress component σ rr , the circumferential normal stress component σ θθ and the axial normal stress component σ zz on the wellbore wall of the horizontal well are calculated.

[0019]

[0020] In formula (2), θ is the azimuth angle, in °; P p is the formation pore pressure, in MPa; P w is the liquid column pressure in the well, in MPa; α is the effective stress coefficient, dimensionless; v is the Poisson's ratio, dimensionless; E is the Young's modulus, in GPa; α m is the thermal expansion coefficient of the formation rock, in ℃ -1 ; T0 is the initial temperature of the formation, in ℃; T w is the circulating temperature of the drilling fluid at the bottom of the well, in ℃.

[0021] In step (c), the minimum value σ θθmin is obtained by the circumferential normal stress component σ θθ at θ = 0°, the minimum value σ zzmin is obtained by the axial normal stress component σ zz at θ = 0°, and the minimum value σ θθmin and the minimum value σ zzmin are calculated.

[0022]

[0023] In formula (3), σ θθmin and σ zzmin are the minimum values of the circumferential normal stress component σ θθ and the axial normal stress component σ zz at θ = 0° under the condition of the horizontal well, in MPa.

[0024] In step (d), the stress polygon of the target formation is plotted according to the following formula:

[0025]

[0026] In formula (4), a is the effective stress coefficient, dimensionless; P p is the formation pore pressure, in MPa; and μf represents the fault friction coefficient, dimensionless.

[0027] The calculation method of the fault friction coefficient is as follows:

[0028]

[0029] In formula (5), v is the Poisson's ratio, dimensionless.

[0030] In step (d), the upper and lower limit constraint lines of the horizontal maximum in-situ stress based on the radial induced fracture are plotted according to the radial normal stress component σ θθ , the circumferential normal stress component σ θθmin , and the axial normal stress component σ zz , under the premise that the minimum value σ zzmin of the circumferential normal stress component σ rr and the minimum value σ θθ of the axial normal stress component σ zz satisfy the constraint condition.

[0031] In step (d), the upper and lower limit constraint lines of the horizontal maximum in-situ stress based on the radial induced fracture are plotted according to the following formula:

[0032]

[0033] In formula (6), the minimum value σ θθ of the circumferential normal stress component σ θθmin n and the minimum value σ zz of the axial normal stress component σ zzmin satisfy the constraint condition σ zzmin ≤-σ t and σ zzmin ≤σ θθmin .

[0034] In step (a), the basis for identifying whether there is a radial induced fracture on the well wall of the horizontal well is that there is a group of approximately parallel and intermittent dark short straight lines on the imaging logging data.

[0035] In step (b), the vertical in-situ stress σ V can be calculated by density logging integration, and the horizontal minimum in-situ stress σ h can be obtained by hydraulic fracturing or formation leakage test.

[0036] The advantage of the present application is that:

[0037] 1、The method for determining the horizontal maximum stress in the horizontal well state of the present application mainly comprises five steps, wherein the advantage of step (a) is that the radial induced fracture of the horizontal well can be directly and simply obtained through the imaging logging data; the advantage of step (b) is that the component of the ground stress on the well wall in the horizontal well state can be obtained; the advantage of step (c) is that the constraint condition of the horizontal maximum stress can be determined; the advantage of step (d) is that the limited range of the horizontal maximum stress can be conveniently determined; and the advantage of step (e) is that the horizontal maximum stress in the horizontal well state can be quickly and accurately determined in combination with the foregoing results.

[0038] In summary, the present application only needs to utilize the radial induced fracture of the horizontal well, establish the stress polygon and the upper and lower limit constraint lines of the horizontal maximum stress, and then combine the horizontal minimum stress to quickly, accurately and conveniently determine the range of the horizontal maximum stress in the horizontal well state, which is not only simple in process and high in accuracy, but also suitable for determining the horizontal maximum stress of different strata lithology.

[0039] 2、The present application can quickly limit the range of the horizontal maximum stress without using a complex ground stress calculation model in actual application. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The flow chart of the present application;

[0041] Figure 2 The example diagram of identifying the radial induced fracture of a certain horizontal well according to the imaging logging data;

[0042] Figure 3 The schematic diagram of determining the upper and lower limits of the horizontal maximum stress of a certain horizontal well. DETAILED DESCRIPTION

[0043] Example 1

[0044] The present application provides a method for determining the horizontal maximum stress in the horizontal well state, as shown in the figure, which comprises the following steps: Figure 1

[0045] (a) Collect the imaging logging data of the target stratum, and identify whether there is a radial induced fracture on the well wall of the horizontal well according to the imaging logging data, if there is a radial induced fracture, then turn to step (b); if there is no radial induced fracture, then the method cannot be used to determine the horizontal maximum stress in the horizontal well state.

[0046] ​The basis for determining whether radial induced fractures exist on the wellbore of a horizontal well is that there is a set of approximately parallel and discontinuous dark short lines on the imaging logging data. If there is a set of approximately parallel and discontinuous dark short lines, it indicates that radial induced fractures exist; otherwise, there are no radial induced fractures.

[0047] (b) Collect target formation physical properties and rock mechanics parameters. These target formation physical properties and rock mechanics parameters can be obtained through the interpretation of conventional sonic logging data and empirical relationships of dynamic and static conversion, or through laboratory rock mechanics parameter testing. The collected target formation physical properties and rock mechanics parameters specifically include vertical geostress, horizontal minimum geostress, formation pore pressure, Young's modulus, Poisson's ratio, formation tensile strength, initial formation temperature, formation rock thermal expansion coefficient, in-well fluid column pressure, effective stress coefficient, and drilling fluid bottom hole circulation temperature.

[0048] Then, based on the collected target stratum physical properties and rock mechanical parameters, the vertical stress σ is calculated respectively. V Horizontal maximum ground stress σ H and the minimum horizontal ground stress σ h The component σ on the horizontal wellbore x σ y σ z .

[0049] Specifically, the vertical ground stress σ V Horizontal maximum ground stress σ H and the minimum horizontal ground stress σ h The component σ on the horizontal wellbore x σ y σ z The calculation method is as follows:

[0050]

[0051] In equation (1), β b The azimuth angle is the well inclination angle, in degrees.

[0052] It should be noted that the aforementioned vertical ground stress σ V The minimum horizontal geostress σ can be calculated through density logging integration. h It can be obtained through hydraulic fracturing or formation leakage tests.

[0053] (c) Determine the horizontal wellbore direction through drilling design or actual drilling, and based on the horizontal wellbore direction and the vertical in-situ stress σ obtained in step (b). V Horizontal maximum ground stress σ H and the minimum horizontal ground stress σ h The component σ on the horizontal wellbore x σ y σz , respectively, the radial normal stress component σ rr , the circumferential normal stress component σ θθ , and the axial normal stress component σ zz on the well wall under the horizontal well condition, and the minimum value σ θθ of the circumferential normal stress component σ θθmin and the minimum value σ zz of the axial normal stress component σ zzmin .

[0054] Specifically, the calculation method of the radial normal stress component σ rr , the circumferential normal stress component σ θθ , and the axial normal stress component σ zz on the well wall under the horizontal well condition is as follows:

[0055]

[0056] In formula (2), θ is the well circumference angle, unit °; P p is the formation pore pressure, unit MPa; P w is the liquid column pressure in the well, unit MPa; α is the effective stress coefficient, dimensionless; v is the Poisson's ratio, dimensionless; E is the Young's modulus, unit GPa; α m is the thermal expansion coefficient of the formation rock, unit ℃ -1 ; T0is the initial temperature of the formation, unit ℃; T w is the circulating temperature of the drilling fluid at the well bottom, unit ℃.

[0057] Further, the minimum value σ θθ of the circumferential normal stress component σ θθmin is obtained by the circumferential normal stress component σ θθ at θ = 0°, and the minimum value σ zzmin of the axial normal stress component σ zz is obtained by the axial normal stress component σ θθ at θ = 0°. The calculation method of the minimum value σ θθmin of the circumferential normal stress component σ zz and the minimum value σ zzmin of the axial normal stress component σ θθmin is as follows:

[0058]

[0059] In formula (3), σ zzmin and σ θθ are the minimum values of the circumferential normal stress component σ zz and the axial normal stress component σ h at θ = 0° under the horizontal well condition, unit MPa.

[0060] (d) Draw a stress polygon of the target stratum based on the target stratum stress. The stress polygon of the target stratum is based on the minimum horizontal stress σ. h and vertical ground stress σ V The ratio σ h / σ V The horizontal axis is σ, and the maximum horizontal ground stress is σ. H and vertical ground stress σ V The ratio σ H / σ V The stress polygon, plotted in a coordinate system with the vertical axis as the coordinate system, serves to define the entire range of geostress.

[0061] Within the drawn stress polygon, draw upper and lower limit constraint lines for the maximum horizontal geostress based on the results of step (c).

[0062] Specifically, in the circumferential normal stress component σ θθ The minimum value σ θθmin and axial normal stress component σ zz The minimum value σ zzmin Under the premise of satisfying the constraints, according to the radial normal stress component σ rr Circumferential normal stress component σ θθ and axial normal stress component σ zz Draw the upper and lower limit constraint lines for the maximum horizontal geostress based on radially induced fractures.

[0063] Furthermore, the stress polygon of the target stratum is drawn using the following formula:

[0064]

[0065] In equation (4), α is the effective stress coefficient, which is dimensionless; P p It represents the formation pore pressure, in MPa; μf represents the fault friction coefficient, which is dimensionless.

[0066] The method for calculating the fault friction coefficient is as follows:

[0067]

[0068] In equation (5), ν is Poisson's ratio, which is dimensionless.

[0069] Furthermore, the upper and lower limit constraint lines for the maximum horizontal in-situ stress based on radially induced cracks are derived using the following formulas:

[0070]

[0071] In equation (6), the circumferential normal stress component σ θθ The minimum value σ θθminn and the axial normal stress component σ zz the minimum value σ zzmin The constraint condition satisfied is σ zzmin ≤-σ t and σ zzmin ≤σ θθmin .

[0072] (e) The intersection point of the upper limit and lower limit constraint lines of the horizontal maximum in-situ stress σ h respectively with the horizontal minimum in-situ stress σ H is used to determine the upper limit and lower limit of the horizontal maximum in-situ stress.

[0073] Specifically, the specific process of determining the upper limit and lower limit of the horizontal maximum in-situ stress is as follows: first, the intersection point of the ratio σ h / σ V of the horizontal minimum in-situ stress σ h to the vertical in-situ stress σ V and the upper limit and lower limit constraint lines of the horizontal maximum in-situ stress is found, to find the range σ H / σ V of the ratio of the horizontal maximum in-situ stress σ H to the vertical in-situ stress σ V on the ordinate axis, and then the vertical in-situ stress σ V is brought into the determined ratio range σ H / σ V , that is, the upper limit and lower limit of the horizontal maximum in-situ stress are obtained.

[0074] The present application adopts the above specific process, and in implementation, only the radial induced fracture of the horizontal well is used to establish the stress polygon and the upper limit and lower limit constraint lines of the horizontal maximum in-situ stress, and then the horizontal minimum in-situ stress is combined to quickly, accurately and conveniently determine the range of the horizontal maximum in-situ stress under the horizontal well state, which is not only simple in process and high in accuracy, but also suitable for determining the horizontal maximum in-situ stress of different formation lithology.

[0075] Example 2

[0076] This example further illustrates example 1 in combination with a certain horizontal well, and the specific process is as follows,

[0077] (a) Collect the imaging logging data of the target formation, and identify whether the radial induced fracture exists on the well wall of the horizontal well.

[0078] Figure 2 A radial induced fracture example diagram of the imaging logging image of a certain horizontal well is shown, and the radial induced fracture is a group of approximately parallel and intermittent dark short straight lines, which are circled by a blue dashed line box. In the figure, T represents the high side of the horizontal wellbore, S represents the side of the horizontal wellbore, and B represents the bottom side of the horizontal wellbore.

[0079] (b) Collect target formation physical properties and rock mechanics parameters. These parameters can be obtained through the interpretation of conventional sonic logging data and empirical relationships of dynamic-static conversion, or through laboratory rock mechanics parameter testing. The collected target formation physical properties and rock mechanics parameters specifically include vertical geostress, horizontal minimum geostress, formation pore pressure, Young's modulus, Poisson's ratio, formation tensile strength, initial formation temperature, formation rock thermal expansion coefficient, well fluid column pressure, effective stress coefficient, and drilling fluid bottom hole circulation temperature.

[0080] In this embodiment, the relevant parameters mentioned above are shown in the table below:

[0081]

[0082]

[0083] (c) First calculate the vertical stress σ based on the wellbore direction of the horizontal well. V Horizontal maximum ground stress σ H and the minimum horizontal ground stress σ h The component σ on the horizontal wellbore x σ y σ z Then, calculate the radial normal stress component σ on the well wall under the horizontal well condition. rr Circumferential normal stress component σ θθ and axial normal stress component σ zz And calculate the circumferential normal stress component σ θθ The minimum value σ θθmin and axial normal stress component σ zz The minimum value σ zzmin The specific calculation method is as follows:

[0084]

[0085] In equation (1), σ x σ y and σ z These are the components of vertical geostress, maximum horizontal geostress, and minimum horizontal geostress on the horizontal wellbore wall, respectively, in MPa; θ is the wellbore angle, in °; P p P is the formation pore pressure, measured in MPa. w α is the pressure of the fluid column in the well, in MPa; α is the effective stress coefficient, dimensionless; ν is Poisson's ratio, dimensionless; E is Young's modulus, in GPa; α m It is the coefficient of thermal expansion of the geological strata, in °C. -1 T0 is the initial formation temperature, in °C; T w It is the bottom-hole circulation temperature of the drilling fluid, in °C.

[0086] Among them, the vertical ground stress σ V Horizontal maximum ground stress σ H and the minimum horizontal ground stress σ h The component σ on the horizontal wellbore x σ y σ z The specific calculation method is as follows:

[0087]

[0088] In equation (2), σ V σ H and σ h These are the vertical ground stress, the maximum horizontal ground stress, and the minimum horizontal ground stress, respectively, in MPa; β b β is the well inclination azimuth. b The azimuth angle is the well inclination angle, in degrees.

[0089] In this embodiment, the wellbore direction of the horizontal well is along the direction of minimum horizontal stress, where the direction of minimum horizontal stress is 0°, i.e., β in equation (2) b =0°, thus obtaining the component of the geostress on the horizontal wellbore wall σ x σ y and σ z :

[0090]

[0091] (d) Under the minimum horizontal ground stress σ h and vertical ground stress σ V The ratio σ h / σ V The horizontal axis is σ, and the maximum horizontal ground stress is σ. H and vertical ground stress σ V The ratio σ H / σ V To plot the stress polygon of the target formation in the coordinate system of the vertical axis, the stress polygon of the target formation is obtained by the following formula:

[0092]

[0093] In equation (4), α is the effective stress coefficient, which is dimensionless; P p It represents the formation pore pressure, in MPa; μf represents the fault friction coefficient, which is dimensionless.

[0094] The method for calculating the fault friction coefficient is as follows:

[0095]

[0096] In equation (5), ν is Poisson's ratio, which is dimensionless.

[0097] Furthermore, the upper and lower limit constraint lines for the maximum horizontal in-situ stress based on radially induced cracks are derived using the following formulas:

[0098]

[0099] In equation (6), ν is Poisson's ratio, dimensionless; α is the effective stress coefficient, dimensionless; E is Young's modulus, in GPa; α m It is the coefficient of thermal expansion of rock, in °C. -1 ;P w P is the pressure of the fluid column inside the well, in MPa. p T0 is the initial pore pressure of the formation, in MPa; T0 is the initial temperature of the formation, in °C; T w σ is the bottom hole circulation temperature of the drilling fluid, in °C. t It is the tensile strength of the formation, measured in MPa.

[0100] The upper and lower limit constraint lines of the maximum horizontal stress in radially induced fractures mentioned above pass through the wellbore stress component σ under horizontal well conditions according to equation (1). θθ and σ zz The minimum value σ is obtained when θ = 0°. θθmin and σ zzmin And satisfy σ zzmin ≤-σ t and σ zzmin ≤σ θθmin We obtain the circumferential normal stress component σ. θθ The minimum value σ θθmin and axial normal stress component σ zz The minimum value σ zzmin The calculation method is as follows:

[0101]

[0102] In equation (7), σ θθmin and σ zzmin σ is the circumferential normal stress component under horizontal well conditions. θθ and axial normal stress component σ zz The minimum value at θ = 0°, in MPa.

[0103] Equation (7) above satisfies two constraint conditions σ zzmin ≤-σ t and σ zzmin ≤σ θθmin Equation (6) is obtained based on the upper and lower limit constraint lines of the maximum horizontal stress in radially induced cracks.

[0104] In this embodiment, the wellbore direction of the horizontal well is along the direction of minimum horizontal stress, where the direction of minimum horizontal stress is 0°. Substituting equation (3) into equation (6) yields the upper and lower limit constraint lines of the maximum horizontal stress of radially induced fractures when the wellbore of the horizontal well in this embodiment is along the direction of minimum horizontal stress:

[0105]

[0106] Equation (8) above can be further expressed as the following equation:

[0107]

[0108] In the formula: ν is Poisson's ratio, dimensionless; α is the effective stress coefficient, dimensionless; E is Young's modulus, GPa; α m It is the coefficient of thermal expansion of rock, in °C. -1 ;P w P is the pressure of the fluid column inside the well, in MPa; p T is the initial pore pressure of the formation, in MPa; T0 is the initial temperature of the formation, in °C; T w It is the bottom hole circulation temperature of the drilling fluid, in °C; σ t It is the tensile strength of the formation, in MPa; These are the lower and upper limits of the maximum horizontal ground stress, respectively, in MPa.

[0109] Figure 3 The equations (4), (5), and (9) are shown with σ on the horizontal axis. h / σ V The vertical axis is σ. H / σ V The stress polygon and upper and lower limit constraint lines of the maximum horizontal geostress in this embodiment are drawn in the coordinate system under the horizontal well state.

[0110] (e) Based on the minimum horizontal ground stress σ h Respectively compared with the maximum horizontal ground stress σ H The intersection of the upper and lower limit constraint lines determines the upper and lower limits of the maximum horizontal ground stress.

[0111] from Figure 3 Minimum horizontal stress σ h With vertical ground stress σ V The ratio σ h / σ V σ h / σ V Find the intersection of σ = 0.68 with the upper and lower limit constraint lines, and locate σ on the vertical axis. H / σ V Ratio range σ H / σ V=0.71~0.87, indicated by two blue lines and two black lines with arrows in the figure. Further, the ratio σ is introduced from the vertical ground stress of 93.6 MPa. H / σ V The maximum horizontal stress range of the horizontal well in this embodiment is 66.5 to 81.4 MPa.

[0112] The beneficial effect of this invention is that by simply using radially induced fractures in a horizontal well to establish a stress polygon and upper and lower limit constraint lines for the maximum horizontal stress, and combining this with the minimum horizontal stress, the range of the maximum horizontal stress can be easily predicted. At the same time, this invention is applicable to the prediction and analysis of the maximum horizontal stress in different lithological strata.

[0113] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All features or steps in the disclosed methods or processes may be combined in any way, except for mutually exclusive features and / or steps.

Claims

1. A method of determining the horizontal maximum stress in the state of a horizontal well, characterized in that The method comprises the following steps: (a) collecting imaging logging data of a target formation, identifying whether there is a radial induced fracture on the well wall of a horizontal well according to the imaging logging data, and if there is a radial induced fracture, then going to step (b); (b) calculating components σx, σy and σz of vertical stress σV, horizontal maximum stress σH and horizontal minimum stress σh on the well wall of the horizontal well respectively; (c) calculating radial normal stress component σrr, circumferential normal stress component σθθ and axial normal stress component σzz on the well wall of the horizontal well under the horizontal well condition respectively according to the well hole direction of the horizontal well and the result of step (b), and calculating minimum value σθθmin of the circumferential normal stress component σθθ and minimum value σzzmin of the axial normal stress component σzz; (d) drawing a stress polygon of the target formation according to the stress of the target formation, and drawing upper limit and lower limit constraint lines of the horizontal maximum stress based on the radial induced fracture according to the result of step (c) within the range of the drawn stress polygon; (e) determining the upper limit and the lower limit of the horizontal maximum stress according to the intersection of the horizontal minimum stress σh and the upper limit and the lower limit constraint lines of the horizontal maximum stress σH respectively.

2. The method of determining the maximum horizontal stress in the horizontal well condition according to claim 1, characterized in that: The stress polygon of the target stratum is defined by the minimum horizontal stress σh and the minimum vertical stress σh. V The ratio σh / σ V The horizontal axis is σ, and the maximum horizontal ground stress is σ. H and vertical ground stress σ V The ratio σ H / σ V It is plotted in a coordinate system with the vertical axis as the coordinate.

3. The method of determining the maximum horizontal stress in the horizontal well condition according to claim 2, characterized in that: The specific process of determining the upper limit and lower limit of the horizontal maximum stress value is: first, the intersection of the ratio σh / σ V of the horizontal minimum stress σh and the vertical ground stress σ V and the upper limit and lower limit constraint line of the horizontal maximum stress is found, the range σ H / σ V of the ratio of the horizontal maximum stress σ H and the vertical ground stress σ V on the longitudinal coordinate axis is found, and then the vertical ground stress σ V is brought into the determined ratio range σ H / σ V , that is, the upper limit and lower limit of the horizontal maximum stress is obtained.

4. The method of determining the horizontal maximum stress in the horizontal well condition according to any one of claims 1-3, characterized in that: In step (b), the calculation method of the components σx, σy and σz of the vertical stress σV, the horizontal maximum stress σH and the horizontal minimum stress σh on the well wall of the horizontal well is as follows: In formula (1), βb is the inclination azimuth angle, and the unit is °.

5. The method of determining the maximum horizontal stress in the horizontal well condition according to claim 4, characterized in that: In step (c), the calculation method of the radial normal stress component σrr, the circumferential normal stress component σθθ and the axial normal stress component σzz on the well wall of the horizontal well is as follows: In formula (2), θ is the hole angle, and the unit is °; Pp is the formation pore pressure, and the unit is MPa; Pw is the liquid column pressure in the well, and the unit is MPa; α is the effective stress coefficient, and the unit is dimensionless; ν is the Poisson's ratio, and the unit is dimensionless; E is the Young's modulus, and the unit is GPa; am is the thermal expansion coefficient of the formation rock, in °C-1 1 ; T0 is the initial temperature of the formation, and the unit is ℃; and Tw is the bottom hole circulating temperature of the drilling fluid, and the unit is ℃.

6. The method of determining the maximum horizontal stress in the horizontal well condition according to claim 5, wherein: In step (c), the minimum value σθθmin is obtained by the circumferential normal stress component σθθ at θ=0°, and the minimum value σzzmin is obtained by the axial normal stress component σzz at θ=0°, and the calculation method of the minimum value σθθmin and the minimum value σzzmin is as follows: In formula (3), σθθmin and σzzmin are the minimum values of the circumferential normal stress component σθθ and the axial normal stress component σzz at θ=0° under the horizontal well condition, and the unit is MPa.

7. The method of determining the maximum horizontal stress in the horizontal well condition according to claim 6, wherein: In step (d), the stress polygon of the target formation is drawn by the following formula: In formula (4), α is the effective stress coefficient, and the unit is dimensionless; Pp is the formation pore pressure, and the unit is MPa; and μf represents the fault friction coefficient, and the unit is dimensionless.

8. The method of determining the maximum horizontal stress in the horizontal well condition according to claim 7, wherein: The calculation method of the fault friction coefficient is as follows: In formula (5), ν is the Poisson's ratio, and the unit is dimensionless.

9. The method of determining the maximum horizontal stress in the horizontal well condition according to claim 6, wherein: In step (d), upper and lower constraint lines of the horizontal maximum principal stress based on the radial induced crack are plotted from the radial normal stress component σrr, the circumferential normal stress component σθθ, and the axial normal stress component σzz under the premise that the minimum value σθθmin of the circumferential normal stress component σθθ and the minimum value σzzmin of the axial normal stress component σzz satisfy the constraint condition. θθ In step (d), upper and lower constraint lines of the horizontal maximum principal stress based on the radial induced crack are plotted from the radial normal stress component σrr, the circumferential normal stress component σθθ, and the axial normal stress component σzz under the premise that the minimum value σθθmin of the circumferential normal stress component σθθ and the minimum value σzzmin of the axial normal stress component σzz satisfy the constraint condition.

10. The method of determining the maximum horizontal stress in the horizontal well condition according to claim 9, wherein: In step (d), the upper limit and the lower limit constraint lines of the horizontal maximum stress based on the radial induced fracture are drawn by the following formula: In formula (6), the minimum value σθθmin of the circumferential normal stress component σθθ and the minimum value σzzmin of the axial normal stress component σzz satisfy the constraint conditions σzzmin ≤ -σt and σzzmin ≤ σθθmin.

11. The method of determining the maximum horizontal stress in the horizontal well condition according to claim 1, wherein: In step (a), the basis for identifying whether the radial induced fractures exist on the well wall of the horizontal well is a set of approximately parallel and intermittent dark short straight lines on the imaging logging data.

12. The method of determining the maximum horizontal stress in the horizontal well condition according to claim 1, wherein: In step (b), the vertical stress σV can be calculated by density logging integration, and the horizontal minimum stress σh can be obtained by hydraulic fracturing or formation leakage test.

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