Plugging layer three-hole three-seepage well circumference effective stress calculation method and system

Abstract

The invention relates to a plugging layer three-hole three-seepage well circumference effective stress calculation method and system, and the method comprises the steps: collecting a reservoir rock core, and obtaining rock matrix mechanical characteristic parameters through triaxial compression; the method comprises the following steps: collecting a reservoir core and on-site drilling fluid, firstly, obtaining physical and chemical parameters of interaction between a rock aperture and the drilling fluid through a pressure transfer experiment, then, testing physical and chemical parameters of interaction between a rock fracture fluid and the drilling fluid, and finally, testing physical and chemical parameters of an effective plugging layer formed by the drilling fluid and rock; establishing a three-hole three-permeability model considering a rock matrix field control equation, a rock fracture field control equation and a plugging layer field control equation; and calculating and considering the effective stress around the three-hole three-seepage well of the plugging layer. According to the method, the influence of fluid seepage and solute diffusion rules in the drilling fluid plugging layer on the well circumference stress distribution rule can be effectively analyzed, the formation collapse pressure and fracture pressure can be further calculated in combination with the strength criterion, and the drilling fluid density design is guided.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas drilling engineering, and in particular to a method and system for calculating effective stress around a well considering three-porosity and three-permeability of a plugging layer. Background Art

[0002] As shale oil and gas exploration and development continue to advance into deep and ultra-deep formations, the geological structure and lithology of the formations encountered are complex, and micro-cracks, nano-scale cracks and bedding are developed. During the drilling process, the drilling fluid and its filtrate easily pass through the formation cracks and weak structural layers, changing the pore pressure of the shale, reducing the strength of the shale, and causing the formation collapse pressure to increase, resulting in wellbore instability, which seriously affects the development process. For water-sensitive shale formations with developed cracks, ultra-low porosity and low permeability, hard and brittle (broken) and poor cementation, it is difficult to completely ensure the stability of the shale wellbore by unilaterally inhibiting hydration. Effective plugging is one of the key technologies to solve the problem of shale wellbore instability. The solid phase particles in the drilling fluid enter the rock pores to form bridge plugging, the polyol plugs the pores through the turbidity effect, and the silicates and aluminates plug the mudstone pore throats by forming precipitation to form a plugging layer, which effectively slows down the pressure transmission, reduces the increase of mudstone pore pressure, and reduces the risk of wellbore instability.

[0003] Wellbore stability research is a hot topic in the oil and gas industry. At present, the research on plugging layers is mostly focused on the development of plugging agents and mechanism interpretation at the chemical level. Common plugging agents include: polymers, polyols, asphalt, nano plugging agents, etc. The plugging mechanisms include: hydrogen bonding, surface adsorption blocking pores and throats, turbidity effect, flocculent precipitation formed at the front edge of the filtrate, blocking pores or microcracks, high temperature softening, and deformable physical plugging, which ultimately slow down the free water in the drilling fluid from entering the shale wellbore to maintain the stability of the wellbore. However, few studies have been conducted on the influence of the plugging layer on the material transport law of the double-porosity and double-permeability formation containing fracture matrix. To this end, based on the double-porosity and double-permeability theory, the influence of the plugging layer on the material transport law of the formation is introduced, and a three-porosity and three-permeability model considering the plugging layer is established, and the effective stress around the well is calculated. Clarifying the material transport law of the three-porosity and three-permeability plugging layer and the effective stress distribution around the well will help guide the development of plugging agents and mechanism interpretation, and effectively reduce the occurrence of wellbore instability accidents during drilling. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method and system for calculating effective stress around a well considering three-porosity and three-permeability of a plugging layer;

[0005] The technical solution of the present invention is:

[0006] A method for calculating effective stress around a well with three porosities and three permeabilities in a plugging layer, comprising:

[0007] Collect reservoir cores and obtain rock matrix mechanical characteristic parameters through triaxial compression, including core porosity, permeability, water content, compressive strength, Young's modulus, Poisson's ratio, internal friction angle, cohesion and pore fluid activity;

[0008] Collect reservoir cores and on-site drilling fluids. First, obtain the physicochemical parameters of the interaction between rock pores and drilling fluids through pressure transmission experiments. Then, test the physicochemical parameters of the interaction between rock fracture fluids and drilling fluids. Finally, test the physicochemical parameters of the effective plugging layer formed by drilling fluids and rocks. The physicochemical parameters of the effective plugging layer formed by drilling fluids and rocks include: membrane efficiency, hydraulic conductivity, solute diffusion coefficient, thermal conductivity, pore fluid activity and on-site drilling fluid activity.

[0009] A three-porosity and three-permeability model is established by considering the rock matrix field control equation, rock fracture field control equation and sealing layer field control equation. The shale skeleton deformation equation, stress field and physical parameter equations under the deformation field of micro-fracture porous media are established. Boundary conditions are set according to actual drilling conditions, and the stress field, pore pressure field, thermal field and chemical field are calculated using the finite element method.

[0010] Based on the Biot effective stress principle, combined with the stress and pore pressure distribution calculated by the three-porosity and three-permeability model of the plugging layer, the effective stress around the well considering the three-porosity and three-permeability of the plugging layer is calculated.

[0011] Preferably, according to the present invention, the Biot effective stress principle is:

[0012]

[0013] In the formula, is the effective stress tensor, p I is the matrix pore fluid pressure; p II is the fracture fluid pressure; α I is the matrix effective stress coefficient; α II is the effective stress coefficient of the crack, δ ij is the Kronecker symbol.

[0014] Preferably, according to the present invention, the rock matrix field control equations include the rock matrix fluid mass balance equation, the rock matrix solute mass balance equation, the rock matrix state equation, the rock matrix temperature control equation, the rock matrix chemical field control equation and the rock matrix pore pressure field control equation;

[0015] The rock matrix fluid mass balance equation is shown below:

[0016]

[0017] Where: φ I is the rock matrix porosity, ρ fis the fluid density, t is the time, is the rock matrix solvent flow velocity;

[0018] The rock matrix solute mass balance equation is shown below:

[0019]

[0020] Where: φ I is the rock matrix porosity, ρ f is the fluid density, t is the time, ω is the mass fraction of salt, is the rock matrix solute mass flow rate;

[0021] The rock matrix state equation is as follows:

[0022]

[0023] Where: p I is the rock matrix pore pressure, β is the compressibility coefficient of the fluid, p0 is the initial pressure, ρ0 is the fluid density at the pressure p0, and ρ0 is the rock density;

[0024] The governing equation for rock matrix temperature is shown below:

[0025]

[0026] Where: K eff is the effective thermal diffusivity;

[0027] The governing equations of the rock matrix chemical field are shown below:

[0028]

[0029] Where: D0 is the diffusion rate, I m is the membrane efficiency, c I Rock matrix solute concentration.

[0030] The governing equation of the rock matrix pore pressure field is as follows:

[0031]

[0032] Where: k I is the rock matrix permeability, μ is the fluid viscosity, v is the dissociation constant, R is the gas constant, K T Thermal conductivity.

[0033] Preferably, according to the present invention, the rock fracture field control equations include the rock fracture fluid mass balance equation, the rock fracture solute mass balance equation, the rock fracture state equation, the rock fracture temperature control equation, the rock fracture chemical field control equation, and the rock fracture pore pressure field control equation;

[0034] The mass balance equation of rock fracture fluid is shown as follows:

[0035]

[0036] Where: φ II is the rock fracture porosity, ρ f is the fluid density, t is the time, is the solvent flow velocity in rock fractures.

[0037] The mass balance equation of solute in rock fractures is shown as follows:

[0038]

[0039] Where: φ II is the rock fracture porosity, ρ f is the fluid density, t is the time, ω is the mass fraction of salt, is the solute mass flow rate in rock fractures.

[0040] The rock fracture state equation is as follows:

[0041]

[0042] Where: p II is the pore pressure of rock fractures, β is the compressibility coefficient of the fluid, p0 is the initial pressure, ρ0 is the fluid density when the pressure is p0, and ρ0 is the rock density;

[0043] The rock fracture temperature control equation is as follows:

[0044]

[0045] Where: K eff is the effective thermal diffusivity;

[0046] The governing equations of the chemical field in rock fractures are shown below:

[0047]

[0048] Where: D0 is the diffusion rate, I m is the membrane efficiency, c II Solute concentration in rock fractures;

[0049] The governing equation of the rock fracture pore pressure field is as follows:

[0050]

[0051] Where: k II is the rock fracture permeability, μ is the fluid viscosity, v is the dissociation constant, R is the gas constant, K T Thermal conductivity.

[0052] Preferably, according to the present invention, the plugging layer field control equation includes the plugging layer fluid mass balance equation, the plugging layer solute mass balance equation, the plugging layer chemical field control equation, and the plugging layer pore pressure field control equation;

[0053] The mass balance equation of the plugging layer fluid is as follows:

[0054]

[0055] Where: φ III is the porosity of the plugging layer, J v III is the solvent flow velocity of the plugging layer;

[0056] The solute mass balance equation of the plugging layer is as follows:

[0057]

[0058] Where: φ III is the porosity of the plugging layer, is the solute mass flow rate of the plugging layer;

[0059] The chemical field control equation of the plugging layer is as follows:

[0060]

[0061] Where: is the diffusion velocity of the plugging layer, I m is the membrane efficiency, c III Solute concentration in rock fractures;

[0062] The control equation of the pore pressure field of the plugging layer is as follows:

[0063]

[0064] Where: k II is the permeability of the plugging layer, μ is the fluid viscosity, v is the dissociation constant, R is the gas constant, K T Thermal conductivity;

[0065] The three-porosity and three-permeability model is a set of equations consisting of the rock matrix field control equations, the rock fracture field control equations and the sealing layer field control equations.

[0066] Preferably, according to the present invention, a shale skeleton deformation equation is established, including: a rock skeleton continuity equation, a rock skeleton equilibrium equation, an effective stress equation, a geometric equation and a constitutive equation;

[0067] The rock skeleton continuity equation is shown below:

[0068]

[0069] Where: ε v is the volume strain;

[0070] The rock skeleton equilibrium equation is shown below:

[0071] σ ij,j T +f i =0 (19)

[0072] Where: ij,j T are the stress components of the formation, f i is the body load;

[0073] The geometric equation is as follows:

[0074]

[0075] Where: u i,j ,u j,i is the displacement component;

[0076] The constitutive equation is shown below:

[0077]

[0078] Where: G is the rock shear modulus, λ is the Lamellar modulus.

[0079] Preferably, according to the present invention, physical property parameter equations under the action of stress field and micro-fracture porous medium deformation field are established, including the established porosity equation, permeability equation, and pore compression coefficient equation;

[0080] The porosity equation is shown below:

[0081]

[0082] The permeability equation is shown below:

[0083]

[0084] The pore compressibility equation is as follows:

[0085]

[0086] Where: φ is the porosity after deformation, φ o The porosity under the original condition, k is the permeability after deformation, k0 is the permeability under the original condition, C φ is the pore compression coefficient, △ε is the matrix shrinkage deformation rate, and △P is the change in formation pressure.

[0087] According to the preferred embodiment of the present invention, in combination with the setting of the solution conditions, specifically including setting the initial and boundary conditions of shale skeleton deformation, the initial and boundary conditions of multi-component seepage of the three-pore and three-permeability model, and the initial conditions of reservoir temperature, the finite element method is used to calculate the formation pore pressure field and stress field, and the Biot effective stress principle is used to calculate the wellbore stress. The Biot effective stress principle is:

[0088]

[0089] In the formula, is the effective stress tensor, i.e., the effective stress around the well considering the three-porosity and three-permeability sealing layer, p I is the matrix pore fluid pressure; p II is the fracture fluid pressure; α I is the matrix effective stress coefficient; α II is the effective stress coefficient of the crack, δ ij Kronecker symbol.

[0090] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, steps of a method for calculating effective stress around a well with three porosities and three permeabilities in a plugging layer are implemented.

[0091] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for calculating effective stress around a well with three porosities and three permeabilities in a plugging layer.

[0092] A system for calculating effective stress around a well considering three porosity and three permeability of a plugging layer, comprising:

[0093] The rock matrix mechanical characteristic parameter acquisition module is configured to: collect reservoir cores and obtain rock matrix mechanical characteristic parameters through triaxial compression, including: core porosity, permeability, water content, compressive strength, Young's modulus, Poisson's ratio, internal friction angle, cohesion and pore fluid activity;

[0094] The reservoir core and on-site drilling fluid acquisition module is configured as follows: first, the physical and chemical parameters of the interaction between rock pores and drilling fluid are obtained through pressure transmission experiments, then the physical and chemical parameters of the interaction between rock fracture fluid and drilling fluid are tested, and finally, the physical and chemical parameters of the effective plugging layer formed by drilling fluid and rock are tested. The physical and chemical parameters of the effective plugging layer formed by drilling fluid and rock include: membrane efficiency, hydraulic conductivity, solute diffusion coefficient, thermal conductivity, pore fluid activity and on-site drilling fluid activity;

[0095] The three-porosity and three-permeability model establishment module is configured to: establish a three-porosity and three-permeability model that takes into account the rock matrix field control equation, the rock fracture field control equation and the sealing layer field control equation, establish the shale skeleton deformation equation, the physical property parameter equation under the stress field and the micro-fracture porous medium deformation field, set boundary conditions according to actual drilling conditions, and use the finite element method to calculate the stress field, pore pressure field, thermal field, and chemical field;

[0096] The module for calculating effective stress around a well with three pores and three seepage in a plugging layer is configured as follows: based on the Biot effective stress principle, combined with the stress and pore pressure distribution calculated by the model of three pores and three seepage in a plugging layer, the effective stress around a well with three pores and three seepage in a plugging layer is calculated.

[0097] The beneficial effects of the present invention are:

[0098] 1. A model of material transmission of three pores and three permeabilities in the plugging layer and effective stress around the well is established, which can effectively analyze the influence of fluid seepage and solute diffusion in the plugging layer of drilling fluid on the stress distribution law around the well, and can further calculate the formation collapse pressure and fracture pressure in combination with the strength criterion, so as to guide the design of drilling fluid density.

[0099] 2. It can effectively evaluate the plugging effect of drilling fluid on the formation, taking the key parameters of fluid seepage, solute diffusion, porosity and permeability as evaluation indicators, and can effectively guide the development of drilling fluid plugging agents, inhibitors and the optimization of drilling fluid formula. BRIEF DESCRIPTION OF THE DRAWINGS

[0100] Figure 1 It is the cloud diagram of pore pressure distribution of three pores and three permeabilities;

[0101] Figure 2 It is the pore pressure distribution cloud diagram of double porosity and double permeability;

[0102] Figure 3 This is the solute distribution cloud diagram of three pores and three permeabilities;

[0103] Figure 4 It is the solute distribution cloud diagram of double porosity and double permeability; DETAILED DESCRIPTION

[0104] The present invention will be further defined below in conjunction with the accompanying drawings and embodiments, but is not limited thereto.

[0105] Example 1

[0106] A method for calculating effective stress around a well with three porosities and three permeabilities in a plugging layer, comprising:

[0107] Collect reservoir cores and obtain rock matrix mechanical characteristic parameters through triaxial compression, including core porosity, permeability, water content, compressive strength, Young's modulus, Poisson's ratio, internal friction angle, cohesion and pore fluid activity;

[0108] In addition to the above parameters, other parameters can also be tested, such as rock weak surface strength parameters, rock particle size distribution, etc.; core porosity, permeability, water content, compressive strength, Young's modulus, Poisson's ratio, internal friction angle, cohesion and pore fluid activity are all parameters that have ready-made testing instruments, such as porosity using a porosity test instrument (PoroPDP-200 overburden porosity and permeability measuring instrument); permeability using a permeability tester (PoroPDP-200 overburden porosity and permeability measuring instrument), water content by drying weighing method (first weigh the core rock mass as m1, then dry the core and measure its mass as m 0 , water content is (m1-m0) / m0*100%); compressive strength, Young's modulus, Poisson's ratio, internal friction angle, and cohesion are directly measured using rock mechanics measuring instruments (RTR-2000 high temperature and high pressure rock comprehensive testing system); pore fluid activity is measured using activity testing instruments (HD-6 water activity measuring instrument).

[0109] Collect reservoir cores and on-site drilling fluids. First, obtain the physicochemical parameters of the interaction between rock pores and drilling fluids through pressure transmission experiments. Then, test the physicochemical parameters of the interaction between rock fracture fluids and drilling fluids. Finally, test the physicochemical parameters of the effective plugging layer formed by drilling fluids and rocks. The physicochemical parameters of the effective plugging layer formed by drilling fluids and rocks include: membrane efficiency, hydraulic conductivity, solute diffusion coefficient, thermal conductivity, pore fluid activity and on-site drilling fluid activity.

[0110] Parameters such as membrane efficiency, hydraulic conductivity, solute diffusion coefficient, and thermal conductivity can be obtained through pressure transmission experimental instruments (SHM-3 high-temperature and high-pressure well wall stability simulation experimental device); pore fluid activity and on-site drilling fluid activity can be obtained through activity testers (HD-6 water activity measuring instrument).

[0111] A three-porosity and three-permeability model is established by considering the rock matrix field control equation, rock fracture field control equation and sealing layer field control equation. The shale skeleton deformation equation, stress field and physical parameter equations under the deformation field of micro-fracture porous media are established. Boundary conditions are set according to actual drilling conditions, and the stress field, pore pressure field, thermal field and chemical field are calculated using the finite element method.

[0112] Based on the Biot effective stress principle, combined with the stress and pore pressure distribution calculated by the three-porosity and three-permeability model of the plugging layer, the effective stress around the well considering the three-porosity and three-permeability of the plugging layer is calculated.

[0113] Example 2

[0114] The difference between the method for calculating effective stress around a well considering three porosity and three permeability of the plugging layer described in Example 1 is that:

[0115] Biot's effective stress principle is:

[0116]

[0117] In the formula, is the effective stress tensor, p I is the matrix pore fluid pressure; p II is the fracture fluid pressure; α I is the matrix effective stress coefficient; α II is the effective stress coefficient of the crack, δ ij is the Kronecker symbol.

[0118] The rock matrix field control equations include the rock matrix fluid mass balance equation, the rock matrix solute mass balance equation, the rock matrix state equation, the rock matrix temperature control equation, the rock matrix chemical field control equation and the rock matrix pore pressure field control equation;

[0119] The rock matrix fluid mass balance equation is shown below:

[0120]

[0121] Where: φ I is the rock matrix porosity, ρ f is the fluid density, t is the time, is the rock matrix solvent flow velocity;

[0122] The rock matrix solute mass balance equation is shown below:

[0123]

[0124] Where: φ I is the rock matrix porosity, ρ f is the fluid density, t is the time, ω is the mass fraction of salt, is the rock matrix solute mass flow rate;

[0125] The rock matrix state equation is as follows:

[0126] Assuming that the density of the solute fluid in the rock matrix is ​​a function of pressure and is only related to pressure, ignoring the effects of temperature and mass fraction on liquid density, the state equation is given by the following formula:

[0127]

[0128] Where: p I is the rock matrix pore pressure, β is the compressibility coefficient of the fluid, p0 is the initial pressure, ρ0 is the fluid density when the pressure is p0, and ρ0 is the rock density;

[0129] The governing equation for rock matrix temperature is shown below:

[0130] Since the shale permeability is very low, the fluid convection heat transfer can be ignored, and its temperature control equation can be expressed as:

[0131]

[0132] Where: K eff is the effective thermal diffusivity;

[0133] The governing equations for the rock matrix chemical field are shown below:

[0134] During the drilling process, there is a chemical potential difference between the drilling fluid and the shale pore fluid, which generates chemical potential energy and drives the fluid in and out of the formation. The chemical field control equation is as follows:

[0135]

[0136] Where: D0 is the diffusion rate, I m is the membrane efficiency, c I Rock matrix solute concentration.

[0137] The governing equation of the rock matrix pore pressure field is as follows:

[0138]

[0139] Where: k I is the rock matrix permeability, μ is the fluid viscosity, v is the dissociation constant, R is the gas constant, K T Thermal conductivity.

[0140] The rock fracture field control equations include the rock fracture fluid mass balance equation, the rock fracture solute mass balance equation, the rock fracture state equation, the rock fracture temperature control equation, the rock fracture chemical field control equation, and the rock fracture pore pressure field control equation;

[0141] The mass balance equation of rock fracture fluid is shown as follows:

[0142]

[0143] Where: φ II is the rock fracture porosity, ρ f is the fluid density, t is the time, is the solvent flow velocity in rock fractures.

[0144] The mass balance equation of solute in rock fractures is shown as follows:

[0145]

[0146] Where: φ IIis the rock fracture porosity, ρ f is the fluid density, t is the time, ω is the mass fraction of salt, is the solute mass flow rate in rock fractures.

[0147] The rock fracture state equation is as follows:

[0148] Assuming that the density of the solute fluid in the rock fracture is a function of pressure and is only related to pressure, ignoring the influence of temperature and mass fraction on the liquid density, the state equation is given by the following formula:

[0149]

[0150] Where: p II is the pore pressure of rock fractures, β is the compressibility coefficient of the fluid, p0 is the initial pressure, ρ0 is the fluid density when the pressure is p0, and ρ0 is the rock density;

[0151] The rock fracture temperature control equation is as follows:

[0152] Since the shale permeability is very low, the fluid convection heat transfer can be ignored, and its temperature control equation can be expressed as:

[0153]

[0154] Where: K eff is the effective thermal diffusivity;

[0155] The governing equations of the chemical field in rock fractures are shown below:

[0156] During the drilling process, there is a chemical potential difference between the drilling fluid and the shale pore fluid, which generates chemical potential energy and drives the fluid in and out of the formation. The chemical field control equation is as follows:

[0157]

[0158] Where: D0 is the diffusion rate, I m is the membrane efficiency, c II Solute concentration in rock fractures;

[0159] The governing equation of the rock fracture pore pressure field is as follows:

[0160]

[0161] Where: k II is the rock fracture permeability, μ is the fluid viscosity, v is the dissociation constant, R is the gas constant, K T Thermal conductivity.

[0162] The plugging layer field control equations include the plugging layer fluid mass balance equation, the plugging layer solute mass balance equation, the plugging layer chemical field control equation, and the plugging layer pore pressure field control equation;

[0163] The mass balance equation of the plugging layer fluid is as follows:

[0164]

[0165] Where: φ III is the porosity of the plugging layer, is the solvent flow velocity of the plugging layer;

[0166] The solute mass balance equation of the plugging layer is as follows:

[0167]

[0168] Where: φ III is the porosity of the plugging layer, is the solute mass flow rate of the plugging layer;

[0169] The chemical field control equation of the plugging layer is as follows:

[0170]

[0171] Where: is the diffusion velocity of the plugging layer, I m is the membrane efficiency, c III Solute concentration in rock fractures;

[0172] The control equation of the pore pressure field of the plugging layer is as follows:

[0173]

[0174] Where: k II is the permeability of the plugging layer, μ is the fluid viscosity, v is the dissociation constant, R is the gas constant, K T Thermal conductivity;

[0175] The three porosities and three permeabilities represent the porosity and permeability of the rock matrix, the porosity and permeability of the rock fractures, and the porosity and permeability of the sealing layer respectively. The three porosities and three permeabilities model is a set of equations consisting of the rock matrix field control equations, the rock fracture field control equations, and the sealing layer field control equations.

[0176] Establish shale skeleton deformation equations, including: rock skeleton continuity equation, rock skeleton equilibrium equation, effective stress equation, geometric equation and constitutive equation;

[0177] The rock skeleton continuity equation is shown below:

[0178]

[0179] Where: ε v is the volume strain;

[0180] The rock skeleton equilibrium equation is shown below:

[0181] The surrounding rock of the shale formation well is subjected to external forces. When the surrounding rock stress is balanced, the microelement is taken to analyze the stress state. The tensor form is expressed as follows:

[0182] σ ij,j T +f i =0 (19)

[0183] Where: ij,j T are the stress components of the formation, f i is the body load;

[0184] The geometric equation is as follows:

[0185] The degree of formation deformation is characterized by strain. According to the basic principle of small deformation in solid mechanics, strain is related to displacement, and the differential relationship between the strain component and the displacement component satisfies the deformation geometry equation:

[0186]

[0187] Where: u i,j ,u j,i is the displacement component;

[0188] The constitutive equation is shown below:

[0189] For linear elastic deformation problems, there is a linear correspondence between stress and strain. The strain component and the stress component conform to the generalized Hooke's law, and the constitutive equation is expressed as follows:

[0190]

[0191] Where: G is the rock shear modulus, λ is the Lamellar modulus.

[0192] Establish physical property parameter equations under the action of stress field and micro-fracture porous medium deformation field, including the established porosity equation, permeability equation, and pore compression coefficient equation;

[0193] The porosity equation is shown below:

[0194]

[0195] The permeability equation is shown below:

[0196]

[0197] The pore compressibility equation is as follows:

[0198]

[0199] Where: φ is the porosity after deformation, φ o The porosity under the original condition, k is the permeability after deformation, k0 is the permeability under the original condition, C φ is the pore compression coefficient, △ε is the matrix shrinkage deformation rate, and △P is the change in formation pressure.

[0200] The boundary conditions are set according to the actual drilling conditions, and the stress field, pore pressure field, thermal field and chemical field are calculated using the finite element method.

[0201] The stress field, pore pressure field, thermal field, and chemical field can be solved by COMSOL finite element software. The specific solution steps are as follows:

[0202] 1) Establish a physical model. Simply put, it is to establish a geometric model that needs to be solved, such as a square research area, a circular research area, etc.;

[0203] 2) Use COMSOL finite element software. There are many interfaces in this software, such as the stress field interface for solid mechanics, the pore pressure field interface for Darcy's law, the thermal field interface for solid heat transfer, and the chemical field interface for dilute material transfer. After selecting these interfaces, fill in the parameters required by the control equation into the corresponding interfaces in turn;

[0204] 3) Setting boundary conditions, such as setting roller support, stress boundary conditions, and displacement boundary conditions for stress field; setting pressure boundary conditions for pore pressure field; setting temperature boundary conditions for thermal field; and setting solute concentration boundary conditions for chemical field;

[0205] 4) Set the initial conditions. There is an initial condition node in each physical field interface. You can directly enter the parameters.

[0206] 5) Grid division;

[0207] 6) Click Calculate to get the calculation result.

[0208] Combined with the setting of the solution conditions, including the initial and boundary conditions of shale skeleton deformation, the initial and boundary conditions of multi-component seepage in the three-porosity and three-permeability model, and the initial conditions of reservoir temperature, the finite element method is used to calculate the formation pore pressure field and stress field, and the Biot effective stress principle is used to calculate the wellbore stress. The Biot effective stress principle is:

[0209]

[0210] In the formula, is the effective stress tensor, i.e., the effective stress around the well considering the three-porosity and three-permeability sealing layer, pI is the matrix pore fluid pressure; p II is the fracture fluid pressure; α I is the matrix effective stress coefficient; α II is the effective stress coefficient of the crack, δ ij Kronecker symbol.

[0211] The values ​​and units of various parameters are shown in Table 1:

[0212] Table 1

[0213]

[0214] Figure 1 It is the cloud diagram of pore pressure distribution of three pores and three permeabilities; Figure 2 This is the pore pressure distribution cloud diagram of double porosity and double permeability; Figure 1 and Figure 2 , the results show that: Figure 1 The pressure around the wellbore is significantly lower than Figure 2 The presence of the plugging layer slows down the pressure transmission around the wellbore, increases the effective stress of the formation, and effectively improves the stability of the wellbore.

[0215] Figure 3 This is the solute distribution cloud diagram of three pores and three permeabilities; Figure 4 This is the solute distribution cloud diagram of double porosity and double permeability; Figure 3 and Figure 4 The results show that the existence of the plugging layer slows down the diffusion of drilling fluid solutes into the formation. On the one hand, it reduces the pollution of drilling fluid filtrate to the formation. On the other hand, the concentration gradient between the plugging layer and the drilling fluid solute is small, which reduces the potential energy transferred from the drilling fluid solute to the formation.

[0216] Example 3

[0217] A computer device includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of a method for calculating effective stress around a well considering three porosity and three permeability of a plugging layer described in Example 1 or 2 are implemented.

[0218] Example 4

[0219] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the steps of a method for calculating effective stress around a well considering three porosity and three permeability of a plugging layer as described in Example 1 or 2.

[0220] Example 5

[0221] A system for calculating effective stress around a well considering three porosity and three permeability of a plugging layer, comprising:

[0222] The rock matrix mechanical characteristic parameter acquisition module is configured to: collect reservoir cores and obtain rock matrix mechanical characteristic parameters through triaxial compression, including: core porosity, permeability, water content, compressive strength, Young's modulus, Poisson's ratio, internal friction angle, cohesion and pore fluid activity;

[0223] The reservoir core and on-site drilling fluid acquisition module is configured as follows: first, the physical and chemical parameters of the interaction between rock pores and drilling fluid are obtained through pressure transmission experiments, then the physical and chemical parameters of the interaction between rock fracture fluid and drilling fluid are tested, and finally, the physical and chemical parameters of the effective plugging layer formed by drilling fluid and rock are tested. The physical and chemical parameters of the effective plugging layer formed by drilling fluid and rock include: membrane efficiency, hydraulic conductivity, solute diffusion coefficient, thermal conductivity, pore fluid activity and on-site drilling fluid activity;

[0224] The three-porosity and three-permeability model establishment module is configured to: establish a three-porosity and three-permeability model that takes into account the rock matrix field control equation, the rock fracture field control equation and the sealing layer field control equation, establish the shale skeleton deformation equation, the physical property parameter equation under the stress field and the micro-fracture porous medium deformation field, set boundary conditions according to actual drilling conditions, and use the finite element method to calculate the stress field, pore pressure field, thermal field, and chemical field;

[0225] The module for calculating effective stress around a well with three pores and three seepage in a plugging layer is configured as follows: based on the Biot effective stress principle, combined with the stress and pore pressure distribution calculated by the model of three pores and three seepage in a plugging layer, the effective stress around a well with three pores and three seepage in a plugging layer is calculated.

Claims

1. A method for calculating effective stress around a well with three porosities and three permeabilities in a plugging layer, characterized in that: include: Collect reservoir cores and obtain rock matrix mechanical characteristic parameters through triaxial compression, including core porosity, permeability, water content, compressive strength, Young's modulus, Poisson's ratio, internal friction angle, cohesion and pore fluid activity; Collect reservoir cores and on-site drilling fluids. First, obtain the physicochemical parameters of the interaction between rock pores and drilling fluids through pressure transmission experiments. Then, test the physicochemical parameters of the interaction between rock fracture fluids and drilling fluids. Finally, test the physicochemical parameters of the effective plugging layer formed by drilling fluids and rocks. The physicochemical parameters of the effective plugging layer formed by drilling fluids and rocks include: membrane efficiency, hydraulic conductivity, solute diffusion coefficient, thermal conductivity, pore fluid activity and on-site drilling fluid activity. A three-porosity and three-permeability model is established by considering the rock matrix field control equation, rock fracture field control equation and sealing layer field control equation. The shale skeleton deformation equation, stress field and physical parameter equations under the deformation field of micro-fracture porous media are established. Boundary conditions are set according to actual drilling conditions, and the stress field, pore pressure field, thermal field and chemical field are calculated using the finite element method. Based on the Biot effective stress principle, combined with the stress and pore pressure distribution calculated by the three-porosity and three-permeability model of the plugging layer, the effective stress around the well considering the three-porosity and three-permeability of the plugging layer is calculated.

2. The method for calculating effective stress around a well considering three porosity and three permeability of the plugging layer according to claim 1 is characterized in that: Biot's effective stress principle is: In the formula, is the effective stress tensor, p I is the matrix pore fluid pressure; p II is the fracture fluid pressure; α I is the matrix effective stress coefficient; α II is the effective stress coefficient of the crack, δ ij is the Kronecker symbol.

3. The method for calculating effective stress around a well considering three porosity and three permeability of the plugging layer according to claim 1 is characterized in that: The rock matrix field control equations include the rock matrix fluid mass balance equation, the rock matrix solute mass balance equation, the rock matrix state equation, the rock matrix temperature control equation, the rock matrix chemical field control equation and the rock matrix pore pressure field control equation; The rock matrix fluid mass balance equation is shown below: Where: φ I is the rock matrix porosity, ρ f is the fluid density, t is the time, is the rock matrix solvent flow velocity; The rock matrix solute mass balance equation is shown below: Where: φ I is the rock matrix porosity, ρ f is the fluid density, t is the time, ω is the mass fraction of salt, is the rock matrix solute mass flow rate; The rock matrix state equation is as follows: Where: p I is the rock matrix pore pressure, β is the compressibility coefficient of the fluid, p0 is the initial pressure, ρ0 is the fluid density when the pressure is p0, and ρ0 is the rock density; The governing equation for rock matrix temperature is shown below: Where: K eff is the effective thermal diffusivity; The governing equations for the rock matrix chemical field are shown below: Where: D0 is the diffusion rate, I m is the membrane efficiency, c I rock matrix solute concentration; The governing equation of the rock matrix pore pressure field is as follows: Where: k I is the rock matrix permeability, μ is the fluid viscosity, v is the dissociation constant, R is the gas constant, K T Thermal conductivity.

4. The method for calculating effective stress around a well considering three porosity and three permeability of the plugging layer according to claim 1, characterized in that: The rock fracture field control equations include the rock fracture fluid mass balance equation, the rock fracture solute mass balance equation, the rock fracture state equation, the rock fracture temperature control equation, the rock fracture chemical field control equation, and the rock fracture pore pressure field control equation; The mass balance equation of rock fracture fluid is shown as follows: Where: φ II is the rock fracture porosity, ρ f is the fluid density, t is the time, is the solvent flow velocity in rock fractures; The mass balance equation of solute in rock fractures is shown as follows: Where: φ II is the rock fracture porosity, ρ f is the fluid density, t is the time, ω is the mass fraction of salt, is the solute mass flow rate in rock fractures; The rock fracture state equation is as follows: Where: p II is the pore pressure of rock fractures, β is the compressibility coefficient of the fluid, p0 is the initial pressure, ρ0 is the fluid density when the pressure is p0, and ρ0 is the rock density; The rock fracture temperature control equation is as follows: Where: K eff is the effective thermal diffusivity; The governing equations of the chemical field in rock fractures are shown below: Where: D0 is the diffusion rate, I m is the membrane efficiency, c II Solute concentration in rock fractures; The governing equation of the rock fracture pore pressure field is as follows: Where: k II is the rock fracture permeability, μ is the fluid viscosity, v is the dissociation constant, R is the gas constant, K T Thermal conductivity.

5. The method for calculating effective stress around a well considering three porosity and three permeability of the plugging layer according to claim 1 is characterized in that: The plugging layer field control equations include the plugging layer fluid mass balance equation, the plugging layer solute mass balance equation, the plugging layer chemical field control equation, and the plugging layer pore pressure field control equation; The mass balance equation of the plugging layer fluid is as follows: Where: φ III is the porosity of the plugging layer, is the solvent flow velocity of the plugging layer; The solute mass balance equation of the plugging layer is as follows: Where: φ III is the porosity of the plugging layer, is the solute mass flow rate of the plugging layer; The chemical field control equation of the plugging layer is as follows: Where: is the diffusion velocity of the plugging layer, I m is the membrane efficiency, c III Solute concentration in rock fractures; The control equation of the pore pressure field of the plugging layer is as follows: Where: k II is the permeability of the plugging layer, μ is the fluid viscosity, v is the dissociation constant, R is the gas constant, K T Thermal conductivity; The three-porosity and three-permeability model is a set of equations consisting of the rock matrix field control equations, the rock fracture field control equations and the sealing layer field control equations.

6. The method for calculating effective stress around a well considering three porosity and three permeability of the plugging layer according to claim 1, characterized in that: Establish shale skeleton deformation equations, including: rock skeleton continuity equation, rock skeleton equilibrium equation, effective stress equation, geometric equation and constitutive equation; The rock skeleton continuity equation is shown below: Where: ε v is the volume strain; The rock skeleton equilibrium equation is shown below: s ij,j T +f i =0 (19) Where: ij,j T are the stress components of the formation, f i is the body load; The geometric equation is as follows: Where: u i,j ,u j,i is the displacement component; The constitutive equation is shown below: Where: G is the rock shear modulus, λ is the Lamellar modulus.

7. The method for calculating effective stress around a well considering three porosity and three permeability of the plugging layer according to claim 1, characterized in that: Establish physical property parameter equations under the action of stress field and micro-fracture porous medium deformation field, including the established porosity equation, permeability equation, and pore compression coefficient equation; The porosity equation is shown below: The permeability equation is shown below: The pore compressibility equation is as follows: Where: φ is the porosity after deformation, φ o The porosity under the original condition, k is the permeability after deformation, k0 is the permeability under the original condition, C φ is the pore compression coefficient, △ε is the matrix shrinkage deformation rate, and △P is the formation pressure change; Further preferably, in combination with the setting of the solution conditions, specifically including setting the initial and boundary conditions of shale skeleton deformation, the initial and boundary conditions of multi-component seepage of the three-pore and three-permeability model, and the initial conditions of reservoir temperature, the finite element method is used to calculate the formation pore pressure field and stress field, and the Biot effective stress principle is used to calculate the wellbore stress. The Biot effective stress principle is: In the formula, is the effective stress tensor, i.e., the effective stress around the well considering the three-porosity and three-permeability plugging layer, p I is the matrix pore fluid pressure; p II is the fracture fluid pressure; α I is the matrix effective stress coefficient; α II is the effective stress coefficient of the crack, δ ij Kronecker symbol.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of a method for calculating effective stress around a well considering three porosities and three permeabilities of a plugging layer as described in any one of claims 1 to 7 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of a method for calculating effective stress around a well considering three porosities and three permeabilities of a plugging layer as described in any one of claims 1 to 7 are implemented.

10. A system for calculating effective stress around a well considering three porosity and three permeability of the plugging layer, characterized in that: include: The rock matrix mechanical characteristic parameter acquisition module is configured to: collect reservoir cores and obtain rock matrix mechanical characteristic parameters through triaxial compression, including: core porosity, permeability, water content, compressive strength, Young's modulus, Poisson's ratio, internal friction angle, cohesion and pore fluid activity; The reservoir core and on-site drilling fluid acquisition module is configured as follows: first, the physical and chemical parameters of the interaction between rock pores and drilling fluid are obtained through pressure transmission experiments, then the physical and chemical parameters of the interaction between rock fracture fluid and drilling fluid are tested, and finally, the physical and chemical parameters of the effective plugging layer formed by drilling fluid and rock are tested. The physical and chemical parameters of the effective plugging layer formed by drilling fluid and rock include: membrane efficiency, hydraulic conductivity, solute diffusion coefficient, thermal conductivity, pore fluid activity and on-site drilling fluid activity; The three-porosity and three-permeability model establishment module is configured to: establish a three-porosity and three-permeability model that takes into account the rock matrix field control equation, the rock fracture field control equation and the sealing layer field control equation, establish the shale skeleton deformation equation, the physical property parameter equation under the stress field and the micro-fracture porous medium deformation field, set boundary conditions according to actual drilling conditions, and use the finite element method to calculate the stress field, pore pressure field, thermal field, and chemical field; The module for calculating effective stress around a well with three pores and three seepage in a plugging layer is configured as follows: based on the Biot effective stress principle, combined with the stress and pore pressure distribution calculated by the model of three pores and three seepage in a plugging layer, the effective stress around a well with three pores and three seepage in a plugging layer is calculated.

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