CN116090230A - Method and device for analyzing leakage pressure of fractured stratum - Google Patents
Method and device for analyzing leakage pressure of fractured stratum Download PDFInfo
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Abstract
The invention discloses a method and a device for analyzing the leakage pressure of a fractured stratum, which belong to the technical field of petroleum drilling, and the method comprises the following steps: obtaining geological data of crack or fault positions, and obtaining initial information of a crack stratum according to the geological data; establishing a stress parameter model around the fracture or the fault, and calculating stress parameters around the fracture or the fault according to geological data and initial information of the fractured stratum; according to initial information of the fractured stratum, converting stress parameters around the fracture or fault into stress parameters of the surface of the fractured stratum; calculating the leakage pressure of the surface of the fractured stratum according to the stress parameters around the fracture or fault and the stress parameters of the surface of the fractured stratum by using a coulomb function; and (3) a device. According to the method, the critical state of the fracture or the fault is determined by analyzing the relation between the ground stress state and the fracture or the fault structure, so that references can be provided for fracture construction transformation, and the safety of well site operation is improved.
Description
Technical Field
The invention belongs to the technical field of petroleum drilling, and particularly relates to a method and a device for analyzing leakage pressure of a fractured stratum.
Background
The leakage pressure is the highest bearing critical value when the stratum is in leakage phenomenon, is an important basis for determining the on-site drilling fluid density, and is particularly important for fractured stratum. The leakage pressure is an important basis for predicting leakage, and researchers consider the leakage pressure to be the lowest pressure value required by drilling fluid in a shaft to enter a stratum channel; in engineering practice, the leak-off pressure is generally considered to be the hydrostatic column pressure under leak-off stop conditions or the hydrostatic column pressure to which the leak-off layer is subjected under engineering allowable leak-off conditions.
Formation leak-off pressure refers to the pressure at which a formation of a certain depth will produce a loss of drilling fluid, and leak-off pressure during drilling refers to the minimum fracture pressure of the rock, typically expressed as the minimum horizontal principal stress.
In order to establish a leakage pressure calculation model which has strong applicability and is convenient to operate in the drilling process, a minimum horizontal main stress model such as a uniaxial strain model, an isotropy Kong Dan model, a Gership ground stress empirical formula, a Huang Rongzun model and the like is comprehensively analyzed, and curve data of the minimum horizontal main stress, namely the leakage pressure, along with the change of well depth can be obtained by the models. For an integral stratum, a closed pressure real-test point obtained through the method and a small fracturing experiment is calibrated, so that a relatively reliable leak-off pressure profile of the integral stratum can be obtained, but for a normal-pressure fractured stratum and a fracture zone, the actual leak-off pressure of the stratum is often much smaller than the calculated leak-off pressure of the stratum, and the drilling safety operation and the fracturing construction transformation effect of a well site are affected. Therefore, how to effectively calculate the leak-off pressure at the fractured formations and the fracture zones by using the acquired data becomes an important point of research.
The Chinese patent with the application number of CN202110753840.5 discloses a method for calculating the leakage pressure of a shaft, which comprises the following steps: firstly, collecting related logging and drilling data, and determining crack parameters to be drilled, calculated point position parameters and engineering allowable leakage rate; then calculating the initial density of the drilling fluid, so as to obtain the bottom hole pressure after the superposition update of the drilling fluid density; further establishing a drilling fluid flowing plane coordinate system in the crack so as to obtain a single crack leakage rate; and further calculating the total leakage rate of the horizontal section cracks, so as to judge whether the engineering allowable leakage rate is reached, and finally determining the leakage pressure of the well bore calculation point. The method still cannot perform effective floor drain pressure loss calculation on the range of a fractured stratum and a fault fracture zone, and the application range is limited.
Disclosure of Invention
The invention provides a method for analyzing the leakage pressure of a fractured stratum, which is used for determining the critical state of a fracture or a fault by analyzing the relation between the ground stress state and the fracture or the fault structure, can provide reference for the reconstruction of fracturing construction and improves the safety of well site operation.
A second object of the present invention is to provide a device for analyzing the leak-off pressure of a fractured formation.
In order to achieve the above object, the present invention provides a method for analyzing a leak-off pressure of a fractured formation, including:
obtaining geological data of crack or fault positions, and obtaining initial information of a crack stratum according to the geological data;
establishing a stress parameter model around a fracture or a fault, and calculating stress parameters around the fracture or the fault according to the geological data and the initial information of the fractured stratum;
according to the initial information of the fractured stratum, converting stress parameters around the fracture or fault into stress parameters of the surface of the fractured stratum;
and calculating the leakage pressure of the surface of the fractured stratum according to the stress parameters around the fracture or the fault and the stress parameters of the surface of the fractured stratum by using a coulomb function.
Further, the obtaining initial information of the fractured stratum includes:
acquiring the occurrence parameters through imaging logging data or a fault model in a geological model;
and acquiring the ground stress direction information through imaging logging information.
Further, the stress parameters around the fracture or fault comprise rock mechanical elasticity parameters, overburden stress, pore pressure, maximum level principal stress and minimum level principal stress, and the rock mechanical elasticity parameters comprise rock mechanical dynamic elasticity parameters and rock mechanical static elasticity parameters;
the step of establishing a stress parameter model around the fracture or the fault, calculating stress parameters around the fracture or the fault according to the geological data and the initial information of the fractured stratum, and the step of calculating the stress parameters around the fracture or the fault comprises the following steps:
according to the theoretical formula of dynamic rock mechanical parameters
Calculating the dynamic elastic parameters of the rock mechanics, wherein E d Is dynamic Young's modulus, ρ is density, V p For longitudinal wave velocity, V s For transverse wave velocity, μ d Is poisson's ratio;
obtaining the rock mechanical static elastic parameters according to rock core experimental data, fitting the rock mechanical static elastic parameters with the rock mechanical dynamic elastic parameters to obtain a dynamic-static parameter conversion formula so as to convert the rock mechanical dynamic elastic parameters into the rock mechanical static elastic parameters;
acquiring a density curve from the earth surface, integrating the depth, and acquiring the overlying stress curve
Wherein sigma z For the overburden stress, z is the vertical depth of the ground beginning, g is the gravitational acceleration;
according to Eton's method formula
To predict initial pore pressure, where P p For pore pressure, P NCT Is hydrostatic pressure, x NCT In response to normal compaction trend line for logging, x obs Is the response value of the actual measurement curve;
calculating horizontal principal stress by using an isotropic hole bullet model:
wherein mu s Is static Poisson's ratio, E s Is static Young's modulus, alpha is Biot coefficient, epsilon x 、ε y Respectively, the structural stress coefficients.
Further, according to the initial information of the fractured stratum, converting the stress parameters around the fracture or fault into stress parameters of the surface of the fractured stratum:
converting the overburden stress, pore pressure, maximum horizontal principal stress, minimum horizontal principal stress, to which each cell is subjected, into sag of each cell by mechanocynthesis decomposition according to the occurrence parametersNormal stress S being straight to the face of the fractured formation n And a shear stress τ tangential to the face of the fractured formation.
Further, according to the stress parameters around the fracture or the fault and the stress parameters of the surface of the fractured stratum, calculating the leakage pressure of the surface of the fractured stratum through a coulomb function:
cff=τ - μ (S) by coulomb function n -P p ) Wherein: s is S n Normal stress of section, tau shear stress, P p And calculating the leakage pressure of the surface of the fractured stratum by adopting a successive approximation method, wherein the pore pressure and mu are the sliding friction coefficients of the fracture surface.
To achieve the above object, an embodiment of a second aspect of the present invention provides an apparatus for analyzing leak-off pressure of a fractured formation, comprising:
the acquisition unit is used for acquiring geological data of the crack or fault position and acquiring initial information of the crack stratum according to the geological data;
the modeling unit is used for establishing a stress parameter model around the fracture or the fault, and calculating stress parameters around the fracture or the fault according to the geological data and the initial information of the fractured stratum;
the conversion unit is used for converting the stress parameters around the fracture or fault into the stress parameters of the surface of the fractured stratum according to the initial information of the fractured stratum;
and the calculating unit is used for calculating the leakage pressure of the surface of the fractured stratum through a coulomb function according to the stress parameters around the fracture or the fault and the stress parameters of the surface of the fractured stratum.
Further, the acquisition unit includes:
the first acquisition subunit is used for acquiring the occurrence parameters through imaging logging data or a fault model in a geological model;
the second acquisition subunit is used for acquiring the ground stress direction information through imaging logging information;
further, in the modeling unit, stress parameters around the fracture or fault include a rock mechanical elasticity parameter, an overburden stress, a pore pressure, a maximum level principal stress, a minimum level principal stress, the rock mechanical elasticity parameter including a rock mechanical dynamic elasticity parameter and a rock mechanical static elasticity parameter;
the modeling unit includes:
a first computing subunit: theoretical formula for dynamic rock mechanics parameters
Calculating the dynamic elastic parameters of the rock mechanics, wherein E d Is dynamic Young's modulus, ρ is density, V p For longitudinal wave velocity, V s For transverse wave velocity, μ d Is poisson's ratio;
a second computing subunit: the rock mechanical static elastic parameter conversion method comprises the steps of obtaining rock mechanical static elastic parameters according to rock core experimental data, fitting the rock mechanical static elastic parameters with the rock mechanical dynamic elastic parameters to obtain a dynamic-static parameter conversion formula, and converting the rock mechanical dynamic elastic parameters into the rock mechanical static elastic parameters;
a third calculation subunit: for obtaining a density curve from the earth's surface, integrating the depth, and obtaining the overburden stress curve
Wherein sigma z For the overburden stress, z is the vertical depth of the ground beginning, g is the gravitational acceleration;
a fourth calculation subunit: for formula according to Eton's method
To predict initial pore pressure, where P p For pore pressure, P NCT Is hydrostatic pressure, x NCT In response to normal compaction trend line for logging, x obs Is the response value of the actual measurement curve;
a fifth calculation subunit: for calculating horizontal principal stress using an isotropic hole-bullet model:
wherein mu s Is static Poisson's ratio, E s Is static Young's modulus, alpha is Biot coefficient, epsilon x 、ε y Respectively, the structural stress coefficients.
Further, the conversion unit is specifically configured to:
according to the occurrence parameters, converting the overburden stress, pore pressure, maximum horizontal principal stress and minimum horizontal principal stress of each unit into normal stress S of each unit perpendicular to the surface of the fractured stratum through mechanocynthesis decomposition n And a shear stress τ tangential to the face of the fractured formation.
Further, in the computing unit, the computing unit is specifically configured to:
cff=τ - μ (S) by coulomb function n -P p ) Wherein: s is S n Normal stress of section, tau shear stress, P p And calculating the leakage pressure of the surface of the fractured stratum by adopting a successive approximation method, wherein the pore pressure and mu are the sliding friction coefficients of the fracture surface.
The invention provides a method and a device for analyzing the leakage pressure of a fractured stratum, which are used for acquiring initial information of the fractured stratum by analyzing geological data of the fracture or fault position, establishing a stress parameter model around the fracture or fault, and calculating stress parameters around the fracture or fault; and then converting the overlying stress, pore pressure, maximum horizontal main stress and minimum horizontal main stress received by each unit into positive stress perpendicular to the surface of the fractured stratum and shear stress tangential to the surface of the fractured stratum of each unit through mechanical synthesis and decomposition, calculating CFF values according to coulomb functions, and judging critical states of the fracture through a successive approximation method, wherein pore pressure corresponding to the critical states is the leakage pressure value corresponding to the fracture or fault in drilling and fracturing construction. For analysis of a plurality of cracks or faults, the dominant position of crack opening can be determined, and the pressure required by all opening of the cracks or faults can be determined, so that references can be provided for the permeability of the reservoir for the modification of fracturing construction, and the safety of well site operation can be improved.
Drawings
FIG. 1 is a flow chart of a method for fracture formation leak-off pressure analysis according to a first embodiment of the present invention;
FIG. 2 is a flow chart of modeling stress parameters around a fracture or fault provided in accordance with an embodiment of the present invention;
FIG. 3 is a schematic diagram showing stress decomposition when converting stress parameters around a fracture or fault into stress parameters of a face of a fractured stratum according to an embodiment of the present invention;
fig. 4 is a schematic view of a fracture moll projection of a fault C according to a second embodiment of the present invention;
fig. 5 is a schematic view of a fracture moll projection of a fault D according to a second embodiment of the present invention;
FIG. 6 is a schematic structural diagram of a device for analyzing the leak-off pressure of a fractured formation according to a third embodiment of the present invention;
fig. 7 is a structural schematic diagram of stress parameter modeling around a fracture or fault provided in accordance with a third embodiment of the present invention.
Wherein: 1. resultant force of the overburden stress and pore pressure; 2. maximum horizontal principal stress; 3. a minimum horizontal principal stress; 4. normal stress of each unit perpendicular to the face of the fractured formation; 5. shear stress of each unit tangential to the face of the fractured formation;
in the figure, the X-axis direction and the Y-axis direction are both positioned on the surface of the fractured stratum, and the Z-axis direction is perpendicular to the surface of the fractured stratum.
Detailed Description
The present invention will now be described in detail with reference to the drawings and examples, wherein the examples are intended to be illustrative of only some, but not all, of the examples. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Embodiment one: as shown in fig. 1, an embodiment of the present invention provides a method for analyzing a leak-off pressure of a fractured formation, which may include:
s11, geological data of crack or fault positions are obtained, and initial information of the fractured stratum is obtained according to the geological data.
The geological data of the crack or fault position comprises imaging logging data, dip logging data, seismic interpretation, geological model and the like.
Wherein, obtaining initial information of the fractured stratum comprises:
s111, acquiring the occurrence parameters through imaging logging data or a fault model in a geological model.
The occurrence parameters comprise dip angle and inclination information of cracks or faults, and the occurrence parameters can be obtained from imaging logging data, dip angle logging data, seismic interpretation and other files. Specifically, the high-conductivity fracture can be picked up through imaging logging data to obtain the occurrence of the fracture; or using the geological model to break the layer model, and counting the fault occurrence.
S112, acquiring the ground stress direction information through imaging logging data.
The ground stress parameter represents stress data of a crack or fault, the ground stress parameter comprises ground stress magnitude information and ground stress direction information, and the ground stress parameter comprises overburden stratum pressure equivalent density, maximum horizontal main stress equivalent density, minimum horizontal main stress equivalent density, pore pressure equivalent density, maximum horizontal main stress azimuth and Biot coefficient. Specifically, when the ground stress direction information is obtained, the ground stress direction can be judged by analyzing the direction of borehole wall breakout or a drilling induced joint on an imaging graph in imaging logging data, wherein the breakout direction represents the minimum horizontal main stress direction, and the induced joint direction represents the maximum horizontal main stress direction, namely the ground stress direction.
S12, a stress parameter model around the fracture or the fault is built, and stress parameters around the fracture or the fault are calculated according to geological data and initial information of the fractured stratum.
The stress parameters around the fracture or fault comprise rock mechanical elasticity parameters, overburden stress, pore pressure, maximum horizontal main stress and minimum horizontal main stress, and the rock mechanical elasticity parameters comprise rock mechanical dynamic elasticity parameters and rock mechanical static elasticity parameters;
as shown in fig. 2, a stress parameter model around a fracture or a fault is established, and stress parameters around the fracture or the fault are calculated according to geological data and initial information of a fractured stratum, wherein the stress parameter model comprises the following components:
s121, according to a theoretical formula of dynamic rock mechanical parameters
Calculating dynamic elastic parameters of rock mechanics, wherein E d Is dynamic Young's modulus, ρ is density, V p For longitudinal wave velocity, V s For transverse wave velocity, μ d For poisson's ratio, the longitudinal wave velocity, the transverse wave velocity and the density can be obtained through the longitudinal wave velocity curve, the transverse wave velocity curve and the density curve of imaging logging data.
S122, obtaining rock mechanical static elastic parameters according to rock core experimental data, fitting the rock mechanical static elastic parameters with the rock mechanical dynamic elastic parameters to obtain a dynamic and static parameter conversion formula E of a research area s ＝0.7E d ，μ s ＝μ d Wherein E is s Is static Young's modulus, mu s The dynamic and elastic parameters of the rock mechanics are converted into static and elastic parameters of the rock mechanics based on a dynamic and static parameter conversion formula, so that the dynamic and elastic parameters of the rock mechanics are calibrated and the calculation of the horizontal main stress parameters is facilitated.
S123, obtaining a density curve from the ground surface, integrating the depth, and obtaining an overlying stress curve
Wherein sigma z For overburden stress, z is the vertical depth from the ground, g is gravity accelerationThe vertical depth at which the surface begins can be known from imaging log data.
S124, according to Eton' S method formula
To predict initial pore pressure, where P p For pore pressure, P NCT Is hydrostatic pressure, x NCT In response to normal compaction trend line for logging, x obs For the measured curve response values, the hydrostatic pressure, the log response normal compaction trend line, and the measured curve response values may be known from imaging log data.
S125, calculating horizontal principal stress by using an isotropic hole bullet model:
wherein mu s Is static Poisson's ratio, E s Is static Young's modulus, alpha is Biot coefficient, epsilon x 、ε y Respectively, the structural stress coefficients.
S13, converting stress parameters around the fracture or fault into stress parameters of the surface of the fractured stratum according to initial information of the fractured stratum.
The stress parameter of the surface of the fractured stratum is the stress parameter taking the surface of the fractured stratum as a reference surface.
Specifically, as shown in fig. 3, according to initial information of the fractured formation, the stress parameters around the fracture or fault are converted into stress parameters of the surface of the fractured formation: according to the yield parameters, each unit is subjected to the overlying stress sigma z Pore pressure P p Maximum horizontal principal stress 2S hmax Minimum horizontal principal stress 3S hmin Is converted into positive stress 4S of each unit perpendicular to the surface of the fractured stratum through mechanocynthesis decomposition n And withShear stress 5τ tangential to the face of the fractured formation.
S14, calculating the leakage pressure of the surface of the fractured stratum through a coulomb function according to the stress parameters around the fracture or the fault and the stress parameters of the surface of the fractured stratum.
By analyzing the relation between the stress state of the destination block and the fracture or fault, the critical state of the fracture or fault is determined, and the critical point pressure corresponding to the critical state can be identified as the leakage pressure according to the calculation standard in drilling and fracturing construction by referring to reservoir geomechanics (Mark D. Zobai, oil industry Press, 2012).
Specifically, according to stress parameters around the fracture or fault and stress parameters of the surface of the fractured stratum, the leakage pressure of the surface of the fractured stratum is calculated through a coulomb function:
cff=τ - μ (S) by coulomb function n -P p ) Wherein: s is S n Normal stress of section, tau shear stress, P p And calculating the leakage pressure of the surface of the fractured stratum by adopting a successive approximation method, wherein the pore pressure and mu are the sliding friction coefficients of the fracture surface.
Specifically, the slurry density increase is equivalent to the pore pressure increase in the crack, the gas injection or water injection process is simulated by a successive approximation method, the pore pressure is increased step by step, when the pressure is increased to a certain value, cff=0, at the moment, the crack is opened, and the corresponding pore pressure value is the leakage pressure corresponding to the crack.
In this embodiment, the geological data of the fracture or fault position is analyzed to obtain initial information of the fractured stratum, a stress parameter model around the fracture or fault is established, and stress parameters around the fracture or fault are calculated. And converting stress parameters around the fracture or the fault into stress parameters of the surface of the fractured stratum, judging the critical state of the fracture by a successive approximation method according to a coulomb function, wherein the pore pressure corresponding to the critical state is the leakage pressure value corresponding to the fracture or the fault in drilling and fracturing construction. When a plurality of cracks or faults are analyzed, the dominant crack opening direction can be determined, and the pressure required by all the cracks or faults to be opened can be determined, so that references can be provided for the permeability of the reservoir for the fracturing construction reconstruction, and the safety of well site operation can be improved.
Embodiment two: according to the analysis method for the leakage pressure of the fractured stratum, when the leakage pressure of the faults C and D in the oil field B block A is calculated, the method can comprise the following steps:
(1) Geological data of the fracture or the fault position is obtained, and initial information of fracture stratum of the fault C and the fault D is obtained according to the geological data.
By utilizing geological data such as imaging logging data and the like, preprocessing, dynamic and static image generation and the like are carried out on the geological data, a clear imaging diagram can be obtained, various geological events including natural cracks, well wall breakout, well drilling induced joints and the like are picked up on the imaging diagram, and initial information of fractured strata such as occurrence parameters, ground stress direction information and the like of faults C and D can be obtained. Among them, in order to describe the data of fracture or fault occurrence including inclination angle, tendency, a fracture or fault occurrence data table may be prepared as shown in table 1.
TABLE 1 section yield data sheet
(2) And respectively utilizing geological data of the crack or fault positions to establish stress parameter models around the crack or fault for the fault C and the fault D, calculating stress parameters around the crack or fault according to initial information of a fractured stratum, calibrating rock mechanical elastic parameters, calibrating pore pressure by stratum test data, and calibrating minimum horizontal main stress by leakage pressure obtained by floor drain experiments to obtain a high-precision single-well rock mechanical model.
Fracture and perifracture stress profile data for faults C and D, respectively, are collated and include overburden pressure equivalent density, maximum horizontal principal stress equivalent density, minimum horizontal principal stress equivalent density, pore pressure equivalent density, maximum horizontal principal stress azimuth, biot coefficient.
(3) According to the cross section shown in Table 1The production data table converts the overburden stress, pore pressure, maximum horizontal principal stress and minimum horizontal principal stress of each unit into the normal stress S of each unit perpendicular to the surface of the fractured stratum through mechanocynthesis decomposition n And a shear stress τ tangential to the face of the fractured formation.
(4) According to the stress parameter around the fracture or fault and the stress parameter of the surface of the fractured stratum, the fracture or fault is formed by the coulomb function CFF=tau-mu (S n -P p ) Calculating the leak-off pressure of the surface of the fractured stratum, wherein S n Normal stress of section, tau shear stress, P p And calculating the leakage pressure of the surface of the fractured stratum by adopting a successive approximation method, wherein the pore pressure and mu are the sliding friction coefficients of the fracture surface. The difference between the positive stress and the pore pressure in the formula is effective positive stress, the sliding friction coefficient is multiplied by the effective positive stress to be friction force, and the CFF value can be obtained by comparing the friction force and the shearing force of the section, when the CFF is smaller than 0, the crack or the fault is stable, when the CFF is equal to 0, the crack or the fault is in a critical state, and at the moment, the pore pressure density equivalent, namely the leakage pressure corresponds to the density equivalent.
As shown in FIG. 4, the loss pressure density equivalent of the fault C is 1.35g/cm 3 While the actual drilling fluid density of the drilled well is 1.37Sg/cm 3 The pressure is lost, and the leakage occurs; as shown in FIG. 5, the leak-off pressure density of fault D is 1.49S g/cm 3 While the actual drilling fluid density of the drilled well is 1.36Sg/cm 3 The method has the advantages that the leakage pressure is not reached, no leakage occurs, the application result of the method is better matched with the actual leakage condition of the well drilling, and the method is applicable to the leakage stratum which is fractured and developed.
Embodiment III: as shown in fig. 6, an embodiment of the present invention provides a leak-off pressure analysis apparatus for a fractured formation, which may include:
an acquisition unit 21 for acquiring geological data of the fracture or fault position, and acquiring initial information of the fractured stratum according to the geological data.
And a modeling unit 22 for establishing a stress parameter model around the fracture or fault, and calculating stress parameters around the fracture or fault according to the geological data and the initial information of the fractured stratum.
And the conversion unit 23 is used for converting the stress parameter around the fracture or fault into the stress parameter of the surface of the fractured stratum according to the initial information of the fractured stratum.
And the calculating unit 24 is used for calculating the leakage pressure of the surface of the fractured stratum according to the stress parameter around the fracture or the fault and the stress parameter of the surface of the fractured stratum through a coulomb function.
The acquisition unit 21 includes:
a first obtaining subunit 211, configured to obtain a yield parameter through imaging logging data or a fault model in the geological model;
a second obtaining subunit 212, configured to obtain the direction information of the ground stress through imaging logging data;
in the modeling unit 22, stress parameters around the fracture or fault include rock mechanical elasticity parameters including rock mechanical dynamic elasticity parameters and rock mechanical static elasticity parameters, overburden stress, pore pressure, maximum level principal stress, minimum level principal stress;
as shown in fig. 7, the modeling unit 22 includes:
the first calculation subunit 221: theoretical formula for dynamic rock mechanics parameters
Calculating dynamic elastic parameters of rock mechanics, wherein E d Is dynamic Young's modulus, ρ is density, V p For longitudinal wave velocity, V s For transverse wave velocity, μ d Is poisson's ratio;
the second calculation subunit 222: the rock mechanical static elastic parameter conversion method comprises the steps of obtaining rock mechanical static elastic parameters according to rock core experimental data, fitting the rock mechanical static elastic parameters with rock mechanical dynamic elastic parameters to obtain a dynamic-static parameter conversion formula, and converting the rock mechanical dynamic elastic parameters into rock mechanical static elastic parameters;
the third calculation subunit 223: for obtaining a density curve from the surface and integrating depthDividing to obtain an overlying stress curve
Wherein sigma z For overburden stress, z is the vertical depth from the ground, g is the gravitational acceleration,
a fourth calculation subunit 224 for calculating according to the Eton's formula
To predict initial pore pressure, where P p For pore pressure, P NCT Is hydrostatic pressure, x NCT In response to normal compaction trend line for logging, x obs Is the response value of the actual measurement curve;
a fifth calculation subunit 225: for calculating horizontal principal stress using an isotropic hole-bullet model:
wherein mu s Is static Poisson's ratio, E s Is static Young's modulus, alpha is Biot coefficient, epsilon x 、ε y Respectively, the structural stress coefficients.
Preferably, the conversion unit 23 may be specifically configured to: according to the yield parameters, the overburden stress, pore pressure, maximum horizontal principal stress and minimum horizontal principal stress of each unit are converted into the normal stress S of each unit perpendicular to the surface of the fractured stratum through mechanocynthesis decomposition n And a shear stress τ tangential to the face of the fractured formation.
Preferably, the calculating unit 24 may specifically be configured to: cff=τ - μ (S) by coulomb function n -P p ) Wherein: s is S n The fracture surface normal stress, tau shear stress, pp pore pressure and mu fracture surface sliding friction coefficient are calculated by adopting a successive approximation methodThe pressure is lost at the face.
In this embodiment, the geological data of the fracture or fault position is analyzed to obtain initial information of the fractured stratum, a stress parameter model around the fracture or fault is established, and stress parameters around the fracture or fault are calculated. And converting stress parameters around the fracture or the fault into stress parameters of the surface of the fractured stratum, judging the critical state of the fracture by a successive approximation method according to a coulomb function, wherein the pore pressure corresponding to the critical state is the leakage pressure value corresponding to the fracture or the fault in drilling and fracturing construction. When a plurality of cracks or faults are analyzed, the dominant crack opening direction can be determined, and the pressure required by all the cracks or faults to be opened can be determined, so that references can be provided for the permeability of the reservoir for the fracturing construction reconstruction, and the safety of well site operation can be improved.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (10)
1. A method for fracture formation leak-off pressure analysis, comprising:
obtaining geological data of crack or fault positions, and obtaining initial information of a crack stratum according to the geological data;
establishing a stress parameter model around a fracture or a fault, and calculating stress parameters around the fracture or the fault according to the geological data and the initial information of the fractured stratum;
according to the initial information of the fractured stratum, converting stress parameters around the fracture or fault into stress parameters of the surface of the fractured stratum;
and calculating the leakage pressure of the surface of the fractured stratum according to the stress parameters around the fracture or the fault and the stress parameters of the surface of the fractured stratum by using a coulomb function.
2. The method for analysis of the leak-off pressure of a fractured formation of claim 1, wherein obtaining initial information of the fractured formation comprises:
acquiring the occurrence parameters through imaging logging data or a fault model in a geological model;
and acquiring the ground stress direction information through imaging logging information.
3. The method for fracture formation leak-off pressure analysis according to claim 1, wherein the stress parameters surrounding the fracture or fault include rock mechanical elasticity parameters including rock mechanical dynamic elasticity parameters and rock mechanical static elasticity parameters, overburden stress, pore pressure, maximum level principal stress, minimum level principal stress;
the step of establishing a stress parameter model around the fracture or the fault, calculating stress parameters around the fracture or the fault according to the geological data and the initial information of the fractured stratum, and the step of calculating the stress parameters around the fracture or the fault comprises the following steps:
according to the theoretical formula of dynamic rock mechanical parameters
Calculating the dynamic elastic parameters of the rock mechanics, wherein E d Is dynamic Young's modulus, ρ is density, V p For longitudinal wave velocity, V s For transverse wave velocity, μ d Is poisson's ratio;
obtaining the rock mechanical static elastic parameters according to rock core experimental data, fitting the rock mechanical static elastic parameters with the rock mechanical dynamic elastic parameters to obtain a dynamic-static parameter conversion formula so as to convert the rock mechanical dynamic elastic parameters into the rock mechanical static elastic parameters;
acquiring a density curve from the earth surface, integrating the depth, and acquiring the overlying stress curve
Wherein sigma z For the overburden stress, z is the vertical depth of the ground beginning, g is the gravitational acceleration;
according to Eton's method formula
To predict initial pore pressure, where P p For pore pressure, P NCT Is hydrostatic pressure, x NCT In response to normal compaction trend line for logging, x obs Is the response value of the actual measurement curve;
calculating horizontal principal stress by using an isotropic hole bullet model:
wherein mu s Is static Poisson's ratio, E s Is static Young's modulus, alpha is Biot coefficient, epsilon x 、ε y Respectively, the structural stress coefficients.
4. The method for analysis of fracture formation leak-off pressure of claim 3, wherein the stress parameters around the fracture or fault are converted into stress parameters of the face of the fractured formation based on the initial information of the fractured formation:
converting the overburden stress, pore pressure, maximum horizontal principal stress, minimum horizontal principal stress, which each unit is subjected to, into the normal stress of each unit perpendicular to the face of the fractured formation by mechanocynthesis according to the occurrence parametersForce S n And a shear stress τ tangential to the face of the fractured formation.
5. The method for analysis of the leak-off pressure of a fractured formation according to claim 4, wherein the leak-off pressure of the face of the fractured formation is calculated by a coulomb function based on the stress parameter around the fracture or fault and the stress parameter of the face of the fractured formation:
cff=τ - μ (S) by coulomb function n -P p ) Wherein: s is S n Normal stress of section, tau shear stress, P p And calculating the leakage pressure of the surface of the fractured stratum by adopting a successive approximation method, wherein the pore pressure and mu are the sliding friction coefficients of the fracture surface.
6. A leak-off pressure analysis apparatus for a fractured formation, comprising:
the acquisition unit is used for acquiring geological data of the crack or fault position and acquiring initial information of the crack stratum according to the geological data;
the modeling unit is used for establishing a stress parameter model around the fracture or the fault, and calculating stress parameters around the fracture or the fault according to the geological data and the initial information of the fractured stratum;
the conversion unit is used for converting the stress parameters around the fracture or fault into the stress parameters of the surface of the fractured stratum according to the initial information of the fractured stratum;
and the calculating unit is used for calculating the leakage pressure of the surface of the fractured stratum through a coulomb function according to the stress parameters around the fracture or the fault and the stress parameters of the surface of the fractured stratum.
7. The apparatus for fracture formation leak-off pressure analysis as defined in claim 6, wherein the acquisition unit comprises:
the first acquisition subunit is used for acquiring the occurrence parameters through imaging logging data or a fault model in a geological model;
and the second acquisition subunit is used for acquiring the ground stress direction information through imaging logging data.
8. The apparatus for analysis of fracture formation leak-off pressure according to claim 6, wherein in the modeling unit, the stress parameters around the fracture or fault include a rock mechanical elasticity parameter, an overburden stress, a pore pressure, a maximum level principal stress, a minimum level principal stress, the rock mechanical elasticity parameter including a rock mechanical dynamic elasticity parameter and a rock mechanical static elasticity parameter;
the modeling unit includes:
a first computing subunit: theoretical formula for dynamic rock mechanics parameters
Calculating the dynamic elastic parameters of the rock mechanics, wherein E d Is dynamic Young's modulus, ρ is density, V p For longitudinal wave velocity, V s For transverse wave velocity, μ d Is poisson's ratio;
a second computing subunit: the rock mechanical static elastic parameter conversion method comprises the steps of obtaining rock mechanical static elastic parameters according to rock core experimental data, fitting the rock mechanical static elastic parameters with the rock mechanical dynamic elastic parameters to obtain a dynamic-static parameter conversion formula, and converting the rock mechanical dynamic elastic parameters into the rock mechanical static elastic parameters;
a third calculation subunit: for obtaining a density curve from the earth's surface, integrating the depth, and obtaining the overburden stress curve
Wherein sigma z For the overburden stress, z is the vertical depth of the ground beginning, g is the gravitational acceleration; />
A fourth calculation subunit: for formula according to Eton's method
To predict initial pore pressure, where P p For pore pressure, P NCT Is hydrostatic pressure, x NCT In response to normal compaction trend line for logging, x obs Is the response value of the actual measurement curve;
a fifth calculation subunit: for calculating horizontal principal stress using an isotropic hole-bullet model:
wherein mu s Is static Poisson's ratio, E s Is static Young's modulus, alpha is Biot coefficient, epsilon x 、ε y Respectively, the structural stress coefficients.
9. The apparatus for fracture formation leak-off pressure analysis as defined in claim 8, wherein the switching unit is specifically configured to:
according to the occurrence parameters, converting the overburden stress, pore pressure, maximum horizontal principal stress and minimum horizontal principal stress of each unit into normal stress S of each unit perpendicular to the surface of the fractured stratum through mechanocynthesis decomposition n And a shear stress τ tangential to the face of the fractured formation.
10. The apparatus for analysis of the leak-off pressure of a fractured formation according to claim 9, wherein the computing unit is configured to:
cff=τ - μ (S) by coulomb function n -P p ) Wherein: s is S n Normal stress of section, tau shear stress, P p And calculating the leakage pressure of the surface of the fractured stratum by adopting a successive approximation method, wherein the pore pressure and mu are the sliding friction coefficients of the fracture surface.
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| CN116956754B (en) * | 2023-09-21 | 2023-12-15 | 中石化经纬有限公司 | Crack type leakage pressure calculation method combined with deep learning |
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