A method for calculating formation fracture pressure of inclined wells with different completion methods

Abstract

The present invention provides a method for calculating the formation fracture pressure of an inclined well with different completion modes, comprising the following steps: S1: obtaining relevant basic data of a target oil and gas field; S2: obtaining basic parameters of formation rocks according to the basic data; S3: calculating the current ground stress field according to the basic parameters of formation rocks in step S2; S4: establishing a ground stress calculation model around the inclined well according to the completion type, calculating the ground stress field around the inclined well with the corresponding completion mode, and determining the principal stress around the well; S5: determining the minimum value of the principal stress in step S4, and calculating the formation fracture pressure P of the inclined well with different completion types in combination with the tensile strength theory. f The present invention includes open hole completion and perforation completion types, and calculates the formation fracture pressure by considering the well inclination angle and well inclination azimuth, providing a basis for the optimization design of (acid) fracturing construction parameters. The method of the present invention is simple and fast in calculation and has a wide range of applications.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field production increase, and in particular to a method for calculating formation fracture pressure of inclined wells with different well completion modes. Background Art

[0002] (Acid) fracturing technology is a production-increasing measure widely used in oil and gas field reservoir transformation. The initiation and expansion of cracks during (acid) fracturing are very important to the production-increasing effect, and the prediction results of the formation breakdown pressure directly affect the design of the (acid) fracturing program. At present, due to the complex ground conditions, inclined well types are developing rapidly at home and abroad. Different from the calculation of vertical well breakdown pressure, the inclination angle and azimuth of the inclined well will affect the calculation of formation breakdown pressure. In addition, the completion method will also affect the prediction results of the breakdown pressure. Open hole completion does not require casing and cementing. It is generally used for reservoirs with higher production capacity, mostly offshore oil and gas fields, while perforation completion requires casing and cementing. The perforator shoots through the oil and gas well pipe wall, cement ring and part of the formation, which will obviously reduce the formation breakdown pressure.

[0003] There are many methods for calculating the bursting pressure that are currently disclosed, but they are single in purpose. There are methods for calculating the bursting pressure of directional wells with open hole completion, such as patent CN201711130402.3; there are methods for calculating the bursting pressure of vertical wells with open hole completion, such as patent CN202010126768.9; there are methods for calculating the bursting pressure of deviated wells with casing perforation completion, such as patent CN201811062388.2. However, the existing patents can only be used to calculate some special completion methods and well types, and do not include all special completion methods and well types, and are not universally applicable, such as vertical wells, deviated wells, and horizontal wells with open hole completion, and vertical wells, deviated wells, and horizontal wells with casing perforation completion. Therefore, taking into account factors such as open hole completion, casing perforation completion, vertical wells, deviated wells, and horizontal wells, a method for calculating the formation bursting pressure that is universally applicable and simple to calculate is established, that is, a method for calculating the formation bursting pressure of deviated wells with different completion methods. Summary of the invention

[0004] In view of the above problems, the present invention provides a method for calculating the formation fracture pressure of inclined wells with different completion methods, which can cope with different well types and perform targeted calculations for different completion methods, has universal applicability, and has more comprehensive usage.

[0005] The present invention adopts the following technical solutions:

[0006] A method for calculating formation fracture pressure of inclined wells with different completion methods comprises the following steps:

[0007] Step S1: Obtain relevant basic information of the target oil and gas field;

[0008] Step S2: Obtaining basic parameters of formation rocks according to basic data;

[0009] Step S3: Calculate the current ground stress field according to the basic parameters of the formation rock in step S2;

[0010] Step S4: Establish a calculation model for the in-situ stress around the inclined well according to the completion type, calculate the stress field around the inclined well corresponding to the completion method, and determine the principal stress σ around the well i , σ j , σ k ;

[0011] Step S5: According to the principal stress around the well in step S4, determine the minimum value of the principal stress σ3 = min {σ i ,σ j ,σ k}, combined with the tensile strength theory, calculate the formation fracture pressure P of the inclined wells with different completion types f .

[0012] Furthermore, the basic data in step S1 includes geological data, drilling and completion data, logging data, well logging data and well testing data.

[0013] Furthermore, the basic parameters of the formation rock in step S2 include: rock density, rock static Poisson's ratio, static Young's modulus, rock tensile strength, Biot coefficient, well inclination angle, well inclination azimuth, porosity, tectonic stress coefficient, and formation pore pressure; the above basic parameters of the formation rock can be obtained through logging data and rock mechanics laboratory tests:

[0014] The average rock density ρ at each depth step is obtained through density logging data b , unit: g / cm 3 ;

[0015] The dynamic Poisson's ratio μ of the rock at each depth step is obtained by using the time difference between the longitudinal wave and the shear wave in the acoustic logging data. d ;

[0016] Through the rock mechanics indoor test, the dynamic and static rock Poisson's ratio conversion relationship is fitted to obtain the rock static Poisson's ratio μ;

[0017] The rock dynamic Young's modulus E at each depth step is obtained by using the shear wave time difference in the acoustic logging data, the rock density and the rock Poisson's ratio calculated in step S2 of claim 1. d ;

[0018] Through the rock mechanics laboratory test, the dynamic and static rock Young's modulus conversion relationship was fitted to obtain the rock static Young's modulus E;

[0019] Obtaining rock tensile strength S through rock mechanics laboratory experiments t , unit is MPa;

[0020] Calculate Biot coefficient through sonic and density logging data;

[0021] The well inclination angle α and well inclination azimuth angle β at each depth step are directly obtained through full-wave logging data;

[0022] The porosity φ at each depth step is obtained through full-wave logging data;

[0023] The structural stress coefficients ω1 and ω2 are obtained by inversion through actual formation conditions and on-site hydraulic fracturing tests;

[0024] Obtaining formation pore pressure P from well test data p .

[0025] Furthermore, the present geostress field in step S3 includes overburden stress, maximum horizontal principal stress, and minimum horizontal principal stress, which are calculated by logging data; the overburden stress σ is obtained by integrating the rock density at each depth step in the logging data. v ; The maximum horizontal principal stress σ at each depth step is calculated according to the Huang model by using the rock static Poisson's ratio, tectonic stress coefficient, Biot coefficient value obtained in step S2 and the overlying rock stress value obtained in step S3 H and the minimum horizontal principal stress σ h .

[0026] Furthermore, the drilling and completion data in step S4 is determined to be an open hole completion, and a corresponding deviated well circumferential stress calculation model is established according to the open hole completion, the open hole completion deviated well circumferential stress field is calculated, and the well circumferential principal stress is determined;

[0027]

[0028] in,

[0029] σ xx =σ H cos 2 αcos 2 β+σ h cos 2 αsin 2 β+σ v sin 2 α

[0030] σ yy =σ H sin 2 β+σ h cos 2 β

[0031] σ zz =σ H sin2 αcos 2 β+σ h sin 2 αsin 2 β+σ v cos 2 α

[0032] τ xy =(σ h -σ H )cosαcosβsinβ

[0033] τ yz =(σ h -σ H )sinαcosβsinβ

[0034] τ zx =(σ H cos 2 β+σ h sin 2 β-σ v )sinαcosα

[0035] Calculate the stress field around the open hole completion deviated well, the calculation formula is as follows:

[0036]

[0037] Furthermore, the drilling completion data in step S4 is determined to be perforation completion, and a corresponding deviated well circumferential stress calculation model is established according to the perforation completion, and the deviated well circumferential stress field of the perforation completion is calculated to determine the circumferential principal stress of the well;

[0038] Calculate the stress field around the wellbore of the perforated completion deviated well. The calculation formula is as follows:

[0039]

[0040] The calculation formula of the principal stress around the perforated completion well is as follows:

[0041]

[0042] Furthermore, the formation fracture pressure P of the inclined well in step S5 f According to the rock tensile strength theory, the calculation formula is as follows:

[0043] σ3-α p P p ≤-S t (5)

[0044] The beneficial effects of the present invention are:

[0045] The invention solves the problem of predicting the formation fracture pressure of inclined wells under open hole completion and perforation completion, provides a basis for the optimization design of (acid) fracturing construction parameters, and lays a foundation for improving the production increase and transformation effect of (acid) fracturing. The method of the invention is simple and fast in calculation and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0047] Figure 1 It is a flowchart of the present invention;

[0048] Figure 2 This is a result diagram of basic parameters of formation rock in the inclined well B2-X in the embodiment of the present invention;

[0049] Figure 3 This is a diagram showing the current ground stress field results of the inclined well B2-X in an embodiment of the present invention;

[0050] Figure 4 This is a diagram showing the fracture pressure results of the inclined well B2-X in an embodiment of the present invention; DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] like Figure 1 As shown, the present invention provides a technical solution: a method for calculating formation fracture pressure of inclined wells with different completion methods, comprising the following steps:

[0053] In step S1, geological data, drilling and completion data, well logging data, well logging data and well testing data of the target oil and gas field are obtained.

[0054] In step S2, the basic parameters of the formation rock are obtained through logging data and rock mechanics laboratory tests, and the average rock density ρ at each depth step is obtained through density logging data. b ; Obtain the dynamic Poisson's ratio μ of the rock at each depth step through the time difference values ​​of the longitudinal and shear waves in the acoustic logging data d , the formula for calculating the dynamic Poisson's ratio of rock is:

[0055]

[0056] In the formula, Δt c , Δt s are the time differences of the formation longitudinal wave and transverse wave, respectively, in μs / ft; μ d is the dynamic Poisson's ratio of rock, dimensionless;

[0057] The rock dynamic and static Poisson's ratio conversion relationship is fitted by rock mechanics indoor test to obtain the rock static Poisson's ratio μ; the rock dynamic Young's modulus E at each depth step is obtained by the shear wave time difference in the acoustic logging data, the rock density and the rock Poisson's ratio value calculated in step S2 of claim 1 d , the calculation formula of rock dynamic Young's modulus is:

[0058]

[0059] In the formula, E d is the dynamic Young's modulus of rock, in GPa; a is the conversion coefficient, with a value of 1.34×10 10 ;

[0060] The conversion relationship between dynamic and static rock Young's modulus is fitted through rock mechanics indoor experiments to obtain the static rock Young's modulus E; the rock tensile strength S is obtained through rock mechanics indoor experiments t ; The Biot coefficient is calculated using the acoustic wave and density logging data. The calculation formula is:

[0061]

[0062] In the formula, α p is the Biot coefficient, dimensionless; ρ b , m are the volume density of stratum and rock skeleton, respectively, in g / cm 3 ; Δt mc , Δt ms are the longitudinal and transverse wave time differences of the rock skeleton, respectively, in μs / ft;

[0063] The well inclination angle α and well inclination azimuth β at each depth step are directly obtained through full-wave logging data; the porosity φ at each depth step is obtained through full-wave logging data; the structural stress coefficients ω1 and ω2 are obtained through inversion of actual formation conditions and on-site hydraulic fracturing tests; the formation pore pressure P is obtained through well test data p .

[0064] In step S3, the current geostress field is calculated according to the basic parameters of the formation rock in step S2, and the current geostress field includes the overlying rock stress, the maximum horizontal principal stress, and the minimum horizontal principal stress, which are calculated by well logging data;

[0065] The overburden stress σ is obtained by integrating the rock density at each depth step in the logging data.v , the calculation formula is:

[0066]

[0067] In the formula, σ v is the stress of the overlying rock formation, in MPa; H1 is the turntable altitude; H2 is the depth from sea level to the mud surface on the seabed, in m; H3 is the depth of the formation below the mud surface, in m; ρ w is the density of seawater, in g / cm 3 ; g is the acceleration due to gravity, in m / s 2 .

[0068] The maximum horizontal principal stress σ at each depth step is calculated according to the Huang model by using the rock static Poisson's ratio, tectonic stress coefficient, Biot coefficient value obtained in step S2 and the overlying rock stress value obtained in step S3. H and the minimum horizontal principal stress σ h , the calculation formula is:

[0069]

[0070] In the formula, σ H is the maximum horizontal principal stress, in MPa; σ h is the minimum horizontal principal stress, in MPa.

[0071] In step S4, the completion type is determined by obtaining the drilling completion data, and the completion types include open hole completion and perforation completion. According to different completion types, a corresponding deviated well circumferential stress calculation model is established to calculate the deviated well circumferential stress field of different completion methods, and determine the principal stress around the well;

[0072] The stress field of open hole completion deviated well is calculated by the wellbore stress calculation model of open hole completion deviated well. The calculation formula is as follows:

[0073]

[0074] in,

[0075] σ xx =σ H cos 2 αcos 2 β+σ h cos 2 αsin 2 β+σ v sin 2 α

[0076] σ yy =σ H sin 2 β+σh cos 2 β

[0077] σ zz =σ H sin 2 αcos 2 β+σ h sin 2 αsin 2 β+σ v cos 2 α

[0078] τ xy =(σ h -σ H )cosαcosβsinβ

[0079] τ yz =(σ h -σ H )sinαcosβsinβ

[0080] τ zx =(σ H cos 2 β+σ h sin 2 β-σ v )sinαcosα

[0081] The total stress calculation formula of the rock at the borehole wall is:

[0082]

[0083] The stress field around the wellbore of the perforated completion deviated well is calculated by the calculation model of the wellbore stress around the wellbore of the perforated completion deviated well. The calculation formula is as follows:

[0084]

[0085] The total stress calculation formula of the rock at the perforation hole is:

[0086]

[0087] In step S5, the minimum principal stress value σ3=min{σ i ,σ j ,σ k}, combined with the tensile strength theory, calculate the formation fracture pressure P of the inclined wells with different completion types f , the calculation formula is as follows:

[0088] σ3-α p P p ≤-S t (5)

[0089] The present invention realizes a method for predicting formation fracture pressure of inclined wells under open hole completion and perforation completion modes, so that different completion modes and well types can realize formation fracture pressure prediction and increase oil production.

[0090] Embodiment 1:

[0091] like Figures 1 to 4 As shown, the method of the present invention is applied to the open hole completion deviated well B2-X well, specifically comprising the following steps:

[0092] Step S1: Obtaining geological data, drilling and completion data, logging data, well logging data and well testing data of the target oil and gas field;

[0093] Step S2: Obtain the basic parameters of the formation rock based on the basic data, and obtain the rock density ρ based on the well logging data and rock mechanics laboratory test b , rock static Poisson's ratio μ, static Young's modulus E, Biot coefficient, well inclination angle α, well inclination azimuth β, and formation pore pressure P are calculated through well test data p ; The rock tensile strength obtained through rock mechanics indoor tests is 3MPa; the porosity φ is calculated to be 4.4%; the tectonic stress coefficient is calculated based on the inversion of the field hydraulic fracturing test, and the tectonic stress coefficient ω1 is 0.441, and ω2 is 0.096.

[0094] Step S3: Calculate the current ground stress field according to the basic parameters of the formation rock at each depth step in step S2, and calculate the overburden pressure σ at each depth step v , maximum horizontal principal stress σ H and the horizontal minimum principal stress σ h , the calculated average overburden pressure σ v is 123.5MPa, and the average value of the maximum horizontal principal stress σ H is 110.3MPa and the average value of the minimum horizontal principal stress σ h It is 73.1MPa.

[0095] Step S4: According to the drilling and completion data, it is determined that the B2-X well is an open hole completion, and the open hole completion deviated well circumferential stress field is calculated by the open hole completion deviated well circumferential stress calculation model, and then the total stress calculation formula of the rock at the open hole well wall is solved.

[0096] Step S5: By obtaining the minimum principal stress σ3 at each depth step, combined with the tensile strength theory, the bottom hole fluid pressure P is solved i That is, the formation fracture pressure P of the inclined well at this time f , calculated at each depth step the deviated well fracture pressure P fThe average value is 98.6MPa, and the error of the playback data before and after the on-site acid fracturing construction is 1.21%. The method of the present invention can obtain significantly higher calculation accuracy.

[0097] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for calculating formation fracture pressure of inclined wells with different completion methods, characterized in that: The following steps are involved: Step S1: Obtain relevant basic information of the target oil and gas field; Step S2: Obtaining basic parameters of formation rocks according to basic data; Step S3: Calculate the current ground stress field according to the basic parameters of the formation rock in step S2; Step S4: Establish a calculation model for the in-situ stress around the inclined well according to the completion type, calculate the stress field around the inclined well corresponding to the completion method, and determine the principal stress σ around the well i , σ j , σ k ; Step S5: According to the principal stress around the well in step S4, determine the minimum value of the principal stress σ3 = min{σ i , σ j , σ k }, combined with the tensile strength theory, the formation fracture pressure of inclined wells with different completion types is calculated. The calculation formula is as follows: σ3-a p P p ≤-S t Where, σ3 is the minimum principal stress, in MPa; α p is the Biot coefficient, dimensionless; S t is the tensile strength of rock, in MPa; P p is the formation pore pressure, in MPa; The drilling and completion data in step S4 determine that the completion type is an open hole completion, establish a corresponding deviated well circumferential stress calculation model based on the open hole completion, calculate the open hole completion deviated well circumferential stress field, and determine the well circumferential principal stress; Calculate the stress field around the open hole completion deviated well, the calculation formula is as follows: in, s xx =s H cos 2 acos 2 b+s h cos 2 asin 2 b+s v sin 2 a s yy =s H sin 2 b+s h cos 2 b s zz =s H sin 2 acos 2 b+s h sin 2 asin 2 b+s v cos 2 a t xy =(s h -s H )cosαcosβsinβ t yz =(s h -s H )sinαcosβsinβ t zx =(s H cos 2 b+s h sin 2 b-s v )sinacosα In the formula, σ r is the radial stress in the borehole cylindrical coordinates, in MPa; σ θ is the circumferential stress in the borehole cylindrical coordinates, in MPa; σ z is the vertical stress in the borehole cylindrical coordinates, in MPa; τ θz , τ rθ , τ rz are the shear stress in the borehole cylindrical coordinates, in MPa; xx , σ yy , σ zz , τ xy , τ yz , τ zx are the wellbore stress in rectangular coordinates, in MPa; H is the maximum horizontal principal stress, in MPa; σ h is the minimum horizontal principal stress, in MPa; σ v is the overlying rock stress, in MPa; P i is the bottom hole fluid pressure, in MPa; θ is the wellbore angle, in degrees; α is the well inclination angle, in degrees; β is the angle between the well inclination azimuth and the horizontal maximum ground stress azimuth, in degrees; η is the permeability coefficient, which is 1 when the formation is permeable and 0 when the formation is impermeable, and is dimensionless; φ is the formation porosity, which is dimensionless; μ is the static Poisson's ratio of rock; The calculation formula of the principal stress around the open hole completion deviated well is as follows: In the formula, σ il , σ jl , σ kl are the principal stress of open hole completion wellbore, in MPa; σ r is the radial stress in the borehole cylindrical coordinates, in MPa; σ θ is the circumferential stress in the borehole cylindrical coordinates, in MPa; σ z is the vertical stress in the borehole cylindrical coordinates, in MPa; τ θz is the shear stress in the borehole cylindrical coordinates, in MPa; The drilling and completion data in step S4 determine that the completion type is perforation completion, establish a corresponding deviated well circumferential stress calculation model based on the perforation completion, calculate the deviated well circumferential stress field of the perforation completion, and determine the principal stress around the well; Calculate the stress field around the wellbore of the perforated completion deviated well. The calculation formula is as follows: In the formula, σ s is the radial stress in cylindrical coordinates of the perforation hole, in MPa; is the circumferential stress of the perforation hole in cylindrical coordinates, in MPa; zz’ is the axial stress in cylindrical coordinates of the perforation hole, in MPa; τ szz’ are the shear stress in cylindrical coordinates of the perforation hole, in MPa; The calculation formula of the principal stress around the perforated completion well is as follows: In the formula, σ is , σ js , σ ks are the principal stresses at the perforation holes, in MPa; s is the radial stress in cylindrical coordinates of the perforation hole, in MPa; is the circumferential stress of the perforation hole in cylindrical coordinates, in MPa; zz’ is the axial stress in cylindrical coordinates of the perforation hole, in MPa; is the shear stress in cylindrical coordinates of the perforation hole, in MPa.

2. The method for calculating formation fracture pressure of inclined wells with different completion modes according to claim 1, characterized in that: The basic data in step S1 include geological data, drilling and completion data, logging data, well logging data and well testing data.

3. The method for calculating formation fracture pressure of inclined wells with different completion modes according to claim 1, characterized in that: The basic parameters of the formation rock in step S2 include: rock density, rock static Poisson's ratio, static Young's modulus, rock tensile strength, Biot coefficient, well inclination angle, well inclination azimuth, porosity, tectonic stress coefficient, and formation pore pressure.

4. The method for calculating formation fracture pressure of inclined wells with different completion modes according to claim 1, characterized in that: The current geostress field in step S3 includes overlying rock stress, horizontal maximum principal stress, and horizontal minimum principal stress, which are calculated through well logging data.

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