CN-121993183-A - Carbonate fracture pressure calculation method, system, equipment and medium

CN121993183ACN 121993183 ACN121993183 ACN 121993183ACN-121993183-A

Abstract

The invention provides a calculation method, a system, equipment and a medium of the cracking pressure of carbonate rock, wherein the calculation method of the cracking pressure of the carbonate rock comprises the steps of obtaining the variation of each physical parameter and mechanical parameter of a rock core compared with the variation of the rock core when the rock core is not soaked, and obtaining a relational expression of the variation of each parameter along with the change of the soaking duration through exponential fitting; according to the static Poisson's ratio and the static Young's modulus, the dynamic Poisson's ratio and the dynamic Young's modulus are linearly fitted to obtain a relation of dynamic-static conversion, for a target well, firstly converting dynamic parameters obtained by well logging calculation into static parameters, then correcting physical parameters and mechanical parameters to a state when the target well is not soaked according to soaking time, constructing a fracture pressure calculation model, introducing the corrected physical parameters and mechanical parameters, and calculating the fracture pressure of carbonate rock. According to the method, the dynamic conditions of drilling fluid invasion are considered, and the fracture pressure calculation is more accurate.

Inventors

LUO MOUBING
SHI XIN
WEI SHENG
LI LIANMIN
YANG TINGHONG
ZENG LINGQI
LI SIJIA
ZHU MENG
Wang Mengcong

Assignees

中国石油天然气集团有限公司
中国石油集团川庆钻探工程有限公司

Dates

Publication Date: 20260508
Application Date: 20241104

Claims (10)

1. A method of carbonate fracture pressure calculation, the method comprising: S1, according to petrophysical experiments of the core under different soaking time periods of drilling fluid, obtaining variation of each physical parameter and mechanical parameter of the core compared with those of the core when the core is not soaked, making an intersection graph with the invasion time period, and performing exponential fitting on the intersection graph to obtain a relation formula of variation of each parameter along with the soaking time period; s2, according to the static poisson ratio and the static Young modulus obtained by the triaxial compression experiment of the rock core, making an intersection graph with the dynamic poisson ratio and the dynamic Young modulus obtained by well logging calculation, and performing linear fitting on the intersection graph to obtain a relation of dynamic-static conversion; s3, carrying out dynamic-static conversion on the target well according to the relation in the step S2, and converting the dynamic parameters obtained by well logging calculation into static parameters; S4, constructing a fracture pressure calculation model based on a tensile fracture criterion, and introducing the corrected physical parameters and mechanical parameters in the step S3 to calculate the fracture pressure of the carbonate rock so as to calculate the fracture pressure of the carbonate rock in an un-soaked state.
2. The carbonate fracture pressure calculation method of claim 1, wherein the physical and mechanical parameters include longitudinal wave time difference, transverse wave time difference, poisson's ratio, density, young's modulus, and compressive strength.
3. The method of claim 1, wherein the obtaining the dynamic-static conversion relation comprises: S201, calculating a static Poisson ratio value by using a formula 1 in combination with a triaxial compression experimental result, wherein the formula 1 is as follows: Wherein mu s is static poisson ratio, has no dimension, d is the diameter of a plunger rock sample, mm, deltad is the diameter increment of the rock sample when the rock sample is compressed, mm, L is the length of the rock sample, mm, deltaL is the length shortening of the rock sample when the rock sample is compressed, and mm; s202, calculating a dynamic Poisson ratio value by using a formula 2, wherein the formula 2 is as follows: Wherein mu d is dynamic poisson ratio, dimensionless, delta ts is logging transverse wave time difference data, mu s/ft, delta t c is logging longitudinal wave time difference data, mu s/ft; s203, calculating the static Young' S modulus by using a formula 3 in combination with a triaxial compression experimental result, wherein the formula 3 is as follows: wherein E s is static Young's modulus, MPa, F is force applied to the rock sample in the longitudinal direction, N, A is sectional area, m 2 , L is length of the rock sample, mm, and DeltaL is length reduction when the rock sample is compressed; S204, calculating the dynamic Young' S modulus by using a formula 4, wherein the formula 4 is as follows: Wherein E d is dynamic Young modulus, MPa, ρ b is density, g/cm 3 , mu is Poisson's ratio, dimensionless, deltat c is log longitudinal wave time difference data, mu s/ft; s205, carrying out regression analysis on the dynamic and static calculation results of the Poisson ratio and the Young modulus in S201-S204, and obtaining a dynamic and static conversion relation of the Poisson ratio and the Young modulus of the rock sample in an uninhibited state.
4. The carbonate fracture pressure calculation method according to claim 1, wherein the constructing a fracture pressure calculation model includes: the fracture pressure in the inclined shaft is determined based on tensile fracture criteria as in equation 5: f T ＝σ 3 -ηP p +|σ t |type 5 Wherein f T is a tensile fracture function, when f T =0, the well wall is in a critical state of tensile fracture, sigma 3 is minimum stress of the inclined well, MPa, eta is Boit coefficient, dimensionless, P p is formation pressure, MPa, sigma t is tensile strength, and MPa.
5. The carbonate fracture pressure calculation method of claim 4, wherein solving parameters of the fracture pressure calculation model in the carbonate fracture pressure calculation process comprises: a. formation pressure is calculated using the effective stress method as in equation 6: P p ＝σ v -σ e type 6 Wherein, sigma e is effective stress, MPa, sigma v is overburden pressure, MPa, P p is stratum pressure, MPa; a101, calculating the overburden pressure by using a formula 7, wherein the formula 7 is as follows: Wherein sigma v is the overburden pressure, MPa, H is the formation sag depth of the logging without density logging, m, ρ is the average formation density of the logging without logging, ρ i is the i logging depth density value, g/cm 3 ;ΔD i is the difference between the i sag depth and the (i-1) th sag depth, m, n is the total depth number, i represents the i depth; and a102, calculating the overburden pressure, namely converting the sounding depth of the inclined shaft into the vertical depth, and converting the well inclination angle data of the upper measuring point and the lower measuring point by adopting a formula 8, wherein the formula 8 is as follows: TVD i ＝(MD i -MD i-1 )·cos(dev i-1 )+TVD i-1 type 8 Wherein TVD i is i vertical depth, m, TVD i-1 is i-1 vertical depth, m, MD i is i sounding depth, m, MD i-1 is i-1 sounding depth, m, dev i-1 is i-1 well inclination angle; a201, obtaining effective stress by subtracting measured formation pressure data according to overburden formation pressure, and obtaining a calculation formula of the effective stress by combining regression fit of related logging data; b. The Boit coefficients were calculated using equation 9, equation 9 being as follows: Wherein eta is Boit coefficients, K b is rock bulk modulus, MPa, K ma is rock skeleton bulk modulus, MPa; c. calculating minimum stress of the inclined shaft: c101, calculating the horizontal maximum principal stress and the minimum principal stress in the vertical well by using a yellow's model, as shown in formula 10: wherein, sigma H is the horizontal maximum main stress, MPa, sigma h is the horizontal minimum main stress, MPa, beta H is the maximum structural stress coefficient, beta h is the minimum structural stress coefficient, beta H and beta h are obtained by actual measurement and substitution into a yellow model for inversion, eta is Boit coefficient, sigma v is the overburden pressure, MPa, P p is the formation pressure, MPa, mu is the Poisson's ratio, and dimensionless; c201, a shaft stress distribution model in the inclined shaft sequentially utilizes a transformation matrix L and a transformation matrix B to carry out coordinate transformation on an original principal stress coordinate (sigma H σ h σ v ) to obtain an inclined shaft stress distribution calculation type of a rectangular coordinate system and a cylindrical coordinate system; 1) The matrix L is as in equation 11: Wherein alpha is azimuth angle, beta is well inclination angle; 2) Matrix B is as in equation 12: Wherein θ is the well circumference angle; 3) The calculation formula of the stress distribution of the inclined shaft in the rectangular coordinate system is shown as formula 13: Wherein, sigma H is the horizontal maximum principal stress, MPa, sigma h is the horizontal minimum principal stress, MPa, alpha is azimuth angle, beta is well inclination angle, sigma v is overburden pressure, MPa, sigma xx is earth stress component in x-axis direction under rectangular coordinate system, MPa, sigma yy is earth stress component in y-axis direction under rectangular coordinate system, MPa, sigma zz is earth stress component in z-axis direction under rectangular coordinate system, MPa, tau xy is earth stress component in xy plane under rectangular coordinate system, MPa, tau xz is earth stress component in xz plane under rectangular coordinate system, MPa, tau yz is earth stress component in yz plane under rectangular coordinate system, MPa; 4) The calculation formula of the stress distribution of the inclined shaft in the cylindrical coordinate system is shown as formula 14: Wherein θ is the well circumference angle in degrees, P wf is the slurry liquid column pressure, MPa, μ is poisson's ratio, no dimension, σ r is the radial normal stress in the column coordinate system, MPa, σ θ is the circumferential normal stress in the column coordinate system, MPa, σ z is the axial normal stress in the column coordinate system, MPa, τ rθ is the rθ plane tangential stress in the column coordinate system, MPa, τ zθ is the zθ plane tangential stress in the column coordinate system, MPa, σ rz is the rz plane tangential stress in the column coordinate system, MPa; c301, solving eigenvalues of a borehole wall stress tensor matrix to obtain borehole wall main stresses corresponding to any well inclination angle and azimuth angle of the borehole, wherein the principal stresses are as shown in formula 15: Wherein sigma i 、σ j 、σ k is the three-dimensional main stress at the well wall and MPa; sequencing the magnitude of the three-dimensional main stress sigma i 、σ j 、σ k to obtain a main stress of a certain point of the well wall from large to small sigma 1 、σ 2 、σ 3 , and obtaining a minimum stress sigma 3 of the inclined well; d. The tensile strength was calculated by a regression fit formula of tensile strength and compressive strength in triaxial compression test, as shown in formula 16: Sigma t ＝a+bσ c type 16 Wherein, sigma t is tensile strength, MPa, sigma c is compressive strength, MPa, a and b are constants; The compressive strength is calculated by combining the compressive strength and Young's modulus of the triaxial compression test with the argillaceous content regression fit formula as shown in formula 17: Sigma c ＝cE s (1-V sh )+dE s V sh type 17 Wherein sigma c is compression strength, MPa, V sh is clay content,%, E s is static Young's modulus, and c and d are constants.
6. The method of claim 5, wherein the regression fit in a201 comprises performing a linear fit by plotting the ratio of the shear wave time difference to the longitudinal wave time difference against the measured formation pressure.
7. The carbonate fracture pressure calculation method according to claim 1, wherein the carbonate fracture pressure calculation method is a calculation method based on a drilling fluid invasion dynamic condition, and the error of the calculation result of the fracture pressure calculation method is reduced by 5-10% compared with that of the fracture pressure calculation method under a static condition.
8. A carbonate fracture pressure calculation system is characterized in that the system comprises a first calculation unit, a second calculation unit, a correction unit and a fracture pressure calculation unit which are connected in sequence, wherein, The first calculation unit is configured to obtain the variation of each physical parameter and mechanical parameter of the rock core compared with the variation when the rock core is not soaked according to rock physical experiments of the rock core under different soaking time lengths of the drilling fluid, and makes an intersection graph with the invasion time length, and makes an exponential fit on the intersection graph to obtain a relational expression of the variation of each parameter along with the change of the soaking time length; the second calculation unit is configured to perform an intersection graph with the dynamic poisson ratio and the dynamic Young modulus obtained by well logging calculation according to the static poisson ratio and the static Young modulus obtained by the triaxial compression experiment of the core, and perform linear fitting on the intersection graph to obtain a relation of dynamic-static conversion; The correction unit is configured to perform dynamic-static conversion on the target well according to the relation of the second calculation unit, and convert the dynamic parameters obtained by logging calculation into static parameters; The fracture pressure calculation unit is configured to construct a fracture pressure calculation model based on a tensile fracture criterion, and to calculate the fracture pressure of the carbonate rock by introducing the corrected physical and mechanical parameters of the correction unit, thereby realizing the calculation of the fracture pressure of the carbonate rock in an unwoaked state.
9. A computer device, the computer device comprising: At least one processor, and A memory storing program instructions, wherein the program instructions are configured to be executed by the at least one processor, the program instructions comprising instructions for performing the carbonate fracture pressure calculation method according to any one of claims 1-7.
10. A computer readable storage medium having stored thereon computer program instructions, which when executed by a processor, implement the carbonate fracture pressure calculation method of any one of claims 1 to 7.

Description

Carbonate fracture pressure calculation method, system, equipment and medium Technical Field The invention relates to the technical field of oil and gas field exploration and development, in particular to a carbonate fracture pressure calculation method, a system, equipment and a medium. Background In petroleum drilling engineering, accurate calculation of fracture pressure of carbonate formations is critical to ensure drilling safety and improve drilling efficiency. The mechanical properties of the carbonate rock are changed due to the invasion of the drilling fluid, so that the accuracy of fracture pressure calculation is affected, and the influence of dynamic conditions of the invasion of the drilling fluid on the mechanical properties of the rock is often ignored by the traditional fracture pressure calculation method, so that a larger deviation exists between a calculation result and an actual situation. The currently widely used fracture pressure calculation model focuses on analysis under static conditions, and lacks comprehensive consideration of the hydraulic invasion process of the drilling fluid. When the drilling fluid invades, the rock is contacted with the fluid to cause the formation and expansion of cracks in the rock, the pore structure and mineral composition of a carbonate reservoir are changed, the physical properties and mechanical properties of the reservoir are also changed, and if the influence of the invasion of the drilling fluid is not considered, the fracture pressure calculation result can be larger in and out than the actual situation. In order to ensure the safety in the drilling process and improve the exploitation efficiency of the oil and gas reservoir, a carbonate fracture pressure calculation method based on the dynamic condition of drilling fluid invasion is needed to be researched. Therefore, it is of great significance to provide a carbonate fracture pressure calculation method, system, apparatus and medium. The Chinese patent with the application number of CN201010534630.9 and the name of method for predicting reservoir fracture pressure after acid damage discloses a method for predicting reservoir fracture pressure after acid damage, which mainly comprises the following steps of preparing standard cylinder rock samples meeting experimental conditions, identifying mineral components of the rock cylinders, determining single mineral content, calculating initial radius of the single mineral cylinder, performing acid damage treatment on the rock samples, testing Young modulus, poisson ratio and compressive strength of the standard rock samples and the rock samples after acid damage under confining pressure conditions, calculating damage variables of the rock under different acid types, acid consumption and acid action time, preparing rock mechanical parameters for predicting the reservoir fracture pressure after acid damage, and predicting the reservoir fracture pressure after acid damage. The method can effectively solve the problem of prediction accuracy of reservoir fracture pressure after acid damage, thereby providing reasonable basic data for fracturing optimization design of the reservoir and improving the success rate of reservoir transformation. But this method is different from the present application. Disclosure of Invention The present invention aims to address at least one of the above-mentioned deficiencies of the prior art. For example, one of the purposes of the invention is to solve the problem that the analysis under static conditions is focused on and the consideration of the dynamic invasion condition of the drilling fluid is lacking in the traditional fracture pressure calculation, and the other purpose is to solve the problem that the fracture pressure of a complex reservoir and/or a variable drilling fluid system under the invasion environment of the drilling fluid cannot be calculated dynamically and accurately. In order to achieve the above purpose, the invention provides a carbonate fracture pressure calculation method which comprises the steps of S1, obtaining variation of physical parameters and mechanical parameters of a rock core compared with those of the rock core when the rock core is not soaked according to rock physical experiments of the rock core under different soaking time periods of the drilling fluid, performing intersection graphs with the soaking time periods, performing exponential fitting on the intersection graphs to obtain relational expression of variation of the parameters with the soaking time periods, S2, performing intersection graphs with dynamic Poisson ratio and dynamic Young modulus obtained according to triaxial compression experiments of the rock core, performing linear fitting on the intersection graphs to obtain relational expression of dynamic Poisson ratio and dynamic Young modulus obtained through well logging, S3, firstly performing dynamic-static conversion on a target well according to the relational expre