A temperature distribution calculation method, system, device and medium for in-situ electric heating of a reservoir

Abstract

The present invention belongs to the technical field of oil and gas field development, and discloses a temperature distribution calculation method, system, equipment and medium for in-situ electric heating of a reservoir, including: constructing a physical formation model of a formation in a near-wellbore zone; constructing mathematical physics equations of heat conduction and heat convection phenomena in the formation based on the physical formation model and combining the law of conservation of energy; calculating the oil phase flow velocity data of the oil phase in the physical formation model; calculating the internal heat source intensity distribution data generated by in-situ electric heating in the physical formation model; substituting the oil phase flow velocity data and the internal heat source intensity distribution data into the mathematical physics equation, and obtaining the temperature distribution data of the formation by integral solution. The technical solution of the present invention can improve the accuracy and reliability of temperature distribution calculation.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and in particular relates to a temperature distribution calculation method, system, equipment and medium for in-situ electric heating of a reservoir. Background Art

[0002] In-situ electrical heating of reservoirs is to place heaters underground, and the current stimulated by the instrument is passed into the formation, so that the formation rocks absorb energy and heat up. Usually, the characteristics of the heated formation are rich in organic matter but low maturity. In the process of organic matter absorbing energy and heating up, it undergoes pyrolysis reaction to generate easily exploitable oil and gas. In the current research on in-situ electrical heating, the effect of viscous skin on temperature distribution is not considered. Summary of the invention

[0003] The purpose of the present invention is to provide a temperature distribution calculation method, system, equipment and medium for in-situ electric heating of a reservoir, so as to solve the problems existing in the above-mentioned prior art.

[0004] To achieve the above object, the present invention provides a method for calculating temperature distribution of in-situ electrical heating of a reservoir, comprising:

[0005] Construct a physical stratigraphic model of the strata near the wellbore;

[0006] Based on the physical formation model, mathematical physical equations of heat conduction and heat convection phenomena in the formation are constructed in combination with the law of conservation of energy;

[0007] Calculating oil phase flow velocity data of the oil phase in the physical formation model;

[0008] Calculating the internal heat source intensity distribution data generated by in-situ electric heating in the physical formation model;

[0009] The oil phase flow velocity data and the internal heat source intensity distribution data are substituted into the mathematical physics equation, and the temperature distribution data of the formation is obtained by integral solution.

[0010] Optionally, a physical stratigraphic model of the stratigraphic formation near the wellbore is constructed, specifically including:

[0011] Determining model building parameters, wherein the model building parameters include geometric dimensions, boundary conditions and physical properties of formation materials in the near-wellbore zone;

[0012] The physical formation model is constructed based on the determined model construction parameters.

[0013] Optionally, based on the physical formation model, combined with the law of conservation of energy, a mathematical physics equation for heat conduction and heat convection in the formation is constructed, and the specific calculation formula is:

[0014]

[0015] In the formula, ρ represents the density of the formation rock, c represents the specific heat capacity of the formation rock, T represents the temperature of the formation after being heated for time t, and ρ o Indicates oil density, c o represents the specific heat capacity of oil, represents the oil phase velocity, k represents the thermal conductivity, Q represents the internal heat source intensity of the formation, and its physical meaning is the amount of heat absorbed per unit volume per unit time.

[0016] Optionally, calculating the oil phase flow velocity data of the oil phase in the physical formation model specifically includes:

[0017]

[0018] In the formula, represents the oil phase velocity, p(r) represents the radial pressure distribution, and p w represents the pressure in the wellbore, u o represents the Darcy flow rate.

[0019] Optionally, calculating the internal heat source intensity distribution data generated by in-situ electric heating in the physical formation model specifically includes:

[0020] Determining the conductivity distribution data and the potential distribution data in the radial direction, the cross section and the longitudinal section in the physical formation model;

[0021] Calculating energy distribution data generated in radial direction, cross section and longitudinal section in the physical formation model based on the conductivity distribution data and the potential distribution data;

[0022] The calculated energy distribution data is integrated by surface and volume to obtain the internal heat source intensity distribution data in the physical formation model in space.

[0023] A temperature distribution calculation system for reservoir in-situ electric heating, comprising:

[0024] A model building module is used to build a physical formation model of the formation near the wellbore; based on the physical formation model, combined with the law of conservation of energy, mathematical physics equations of heat conduction and heat convection phenomena in the formation are built;

[0025] A parameter calculation module is used to calculate the oil phase flow velocity data in the physical formation model; calculate the internal heat source intensity distribution data generated by in-situ electric heating in the physical formation model;

[0026] The temperature distribution calculation module is used to substitute the oil phase flow velocity data and the internal heat source intensity distribution data into the mathematical physics equation, and obtain the temperature distribution data of the formation by integral solution.

[0027] An electronic device comprises a memory and a processor, wherein the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the temperature distribution calculation method for in-situ electric heating of a reservoir.

[0028] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the temperature distribution calculation method for in-situ electrical heating of a reservoir.

[0029] The technical effects of the present invention are:

[0030] The temperature distribution calculation method provided by the present invention takes into account the heat conduction and heat convection phenomena of the formation during the in-situ electric heating process, so that the calculation of the temperature distribution is more comprehensive and accurate, and can more truly reflect the heat transfer process in the formation. Based on the law of conservation of energy, a convection-heat conduction equation is established. The present invention strictly follows the principles of physics to ensure the rationality and scientificity of the calculation results. At the same time, combined with the influence of the viscous skin (Visco-skin) on the temperature distribution, a formula is derived to calculate the temperature distribution and change, which improves the accuracy and reliability of the temperature distribution calculation, and also provides important reference and support for energy development and geological exploration. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0033] Figure 1 is an implementation flow chart of an embodiment of the present invention;

[0034] Figure 2 is a flow chart in an embodiment of the present invention, wherein: Figure 2 (a) is a three-dimensional physical model in an embodiment of the present invention, Figure 2 (b) is a two-dimensional longitudinal section physical model in an embodiment of the present invention;

[0035] Figure 3 Schematic diagram of longitudinal cross-section temperature distribution in an embodiment of the present invention;

[0036] Figure 4 Schematic diagram of radial temperature distribution in an embodiment of the present invention;

[0037] Figure 5 It is a time-temperature curve diagram in an embodiment of the present invention. DETAILED DESCRIPTION

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0040] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art generally understood by the present invention. Although the present invention describes only preferred methods, any method similar or equivalent to that described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0041] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0042] The words “include,” “including,” “have,” “contain,” etc. used in this article are open-ended terms, meaning including but not limited to.

[0043] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0044] Embodiment 1

[0045] like Figure 1 - Figure 5As shown, in this embodiment, a method for calculating the temperature distribution of in-situ electric heating of a reservoir is provided, including: constructing a physical formation model of the formation in the near-wellbore area; based on the physical formation model, mathematical and physical equations of heat conduction and heat convection phenomena in the formation are constructed in combination with the law of conservation of energy; calculating the oil phase flow velocity data of the oil phase in the physical formation model; calculating the internal heat source intensity distribution data generated by in-situ electric heating in the physical formation model; substituting the oil phase flow velocity data and the internal heat source intensity distribution data into the mathematical and physical equations, and obtaining the temperature distribution data of the formation by integral solution.

[0046] This embodiment provides a method for calculating temperature distribution based on in-situ electric heating under viscous skin conditions. During the in-situ electric heating process, the heat conduction and heat convection phenomena of the formation are considered, and the temperature distribution is calculated based on the law of conservation of energy and the convection-heat conduction equation. Under the influence of the viscous skin (Visco-skin) on the temperature distribution, a formula is derived to calculate the temperature distribution and change.

[0047] The specific implementation process of this embodiment includes:

[0048] (1) Setting the physical model: According to actual requirements, different dimensions and types of formation physical models can be established, such as three-dimensional cylindrical and rectangular models, two-dimensional cross-sectional and longitudinal section models. This embodiment takes a three-dimensional cylindrical longitudinal section as an example.

[0049] (2) Establishing mathematical physics equations: During the in-situ electric heating process, heat conduction and convection will occur in the formation. According to the law of conservation of energy, the convection-heat conduction equation is used to calculate the temperature distribution of the formation.

[0050]

[0051] Where T is the temperature of the formation after being heated for t time, °C; Q is the internal heat source intensity of the formation, W / m 3 , the physical meaning is the heat absorbed per unit volume per unit time; ρ represents the density of the formation rock, g / cm 3 ; c represents the specific heat capacity of formation rock, J / kg·℃; ρ o Indicates oil density, g / cm 3 ;c o It represents the specific heat capacity of oil, J / kg·℃; represents the oil phase velocity, m / s; k represents the thermal conductivity, W / m·K.

[0052] (3) Solution for oil phase velocity: The concept of viscous skin is used to describe the law of change of heavy oil viscosity with pressure. The reason for the change in viscosity is that the gaseous substances dissolved in the heavy oil escape as the pressure decreases, resulting in a decrease in the fluidity of the heavy oil and the formation of a viscous skin in the wellbore.

[0053] Assuming that the amount of gas dissolved in heavy oil has a significant effect on oil viscosity, and assuming that the volume of free gas in the heavy oil reservoir has little effect on the pressure distribution, when the reservoir is in a steady state distribution, the pressure distribution can be obtained:

[0054]

[0055] Where p(r) represents the radial pressure distribution, MPa; p w Indicates the pressure in the wellbore, MPa; p e represents the pressure at the drainage radius, MPa; r represents the radial distance, m; r w Represents the radius of the wellbore, m; r e Indicates the drainage radius, m.

[0056] According to Darcy's radial flow formula, after separating variables and integrating from the wellbore radius to the drainage radius, the radial Darcy velocity distribution formula is obtained:

[0057]

[0058]

[0059]

[0060] In the formula, Q o represents the radial Darcy velocity distribution, m / s; K represents the permeability, mD; h represents the model height, m; μ DO Indicates the oil viscosity in the wellbore, mPa·s; μ LO Indicates the oil viscosity at the drainage radius, mPa·s; P μ Represents the viscosity parameter, dimensionless.

[0061] The above formula can be rewritten in the traditional form of Darcy's radial flow equation and viscous skin:

[0062]

[0063]

[0064] In the formula, B o Represents the oil phase volume factor, dimensionless; s vs Represents the viscous epidermal parameter, dimensionless.

[0065] The oil phase velocity can be approximately expressed by the product of oil saturation and Darcy velocity. According to the concept of viscous skin, under the condition of oil shale formation, the oil saturation at the wellbore is defined as 1, and the functional relationship between oil saturation and pressure is established:

[0066]

[0067] In the formula, u o represents the Darcy velocity, m / s.

[0068] (4) Integral calculation of internal heat source intensity: In the circular coordinate system, the energy distribution in the radial direction generated by the current excited by in-situ electric heating in the well is:

[0069]

[0070] In the formula, Q e represents the energy distribution in the radial direction, J; σ(r) represents the conductivity distribution in the radial direction, S / m; Ψ(r) represents the potential distribution in the radial direction, V.

[0071] By performing surface integration of the radial energy distribution on the cross section, we can obtain the energy distribution at any height:

[0072]

[0073] In the formula, Q A represents the energy distribution on the cross section, J; σ(r,θ) represents the conductivity distribution on the cross section, S / m; Ψ(r,θ) represents the potential distribution on the cross section, V.

[0074] Alternatively, the energy distribution generated at any angle can be obtained by performing surface integration on the longitudinal section of the radial energy distribution:

[0075]

[0076] In the formula, Q L represents the energy distribution on the longitudinal section, J; σ(r,z) represents the conductivity distribution on the longitudinal section, S / m; Ψ(r,z) represents the potential distribution on the longitudinal section, V.

[0077] Further operating the surface integral on the volume integral can give the energy distribution generated in the entire space:

[0078]

[0079] In the formula, Q V represents the energy distribution in space, J; σ(r,z,θ) represents the conductivity distribution in space, S / m; Ψ(r,z,θ) represents the potential distribution in space, V.

[0080] (5) Integral solution of mathematical physics equations: According to the requirements of the actual physical model, the initial conditions and boundary conditions are set up, and the formulas for the oil phase velocity and the internal heat source intensity are substituted into the convection-heat conduction equation. By integrating and solving, the temperature distribution formula for in-situ electric heating under the influence of the viscous skin can be obtained.

[0081] Calculation example: Choose a three-dimensional cylindrical longitudinal section as an example. The transverse length of the longitudinal section is 10m, the longitudinal length is 10m, the well radius is 0.1m, and it is assumed that the temperature of the entire wellhead is equal (such as Figure 4 shown).

[0082] Without considering the influence of the upper and lower surrounding rocks and assuming that the upper and lower boundaries are adiabatic, we can obtain the temperature distribution diagram of the longitudinal section (such as Figure 3 As shown), radial temperature distribution diagram (as shown Figure 4 As shown), and the time-temperature curve at any point (as shown Figure 5 shown). Figure 3 and Figure 4 The interception is the temperature distribution at a certain moment. Figure 5 Select the center point of the model as the typical point of the model to draw the time-temperature curve.

[0083] From the temperature distribution diagram of the longitudinal section, the radial temperature distribution diagram and the time-temperature curve diagram of the point, it can be judged that the temperature increases with time and decreases with radial depth, which is in line with the laws of physics.

[0084] A temperature distribution calculation system for reservoir in-situ electric heating, comprising:

[0085] A model building module is used to build a physical formation model of the formation near the wellbore; based on the physical formation model, combined with the law of conservation of energy, mathematical physics equations of heat conduction and heat convection phenomena in the formation are built;

[0086] A parameter calculation module is used to calculate the oil phase flow velocity data in the physical formation model; calculate the internal heat source intensity distribution data generated by in-situ electric heating in the physical formation model;

[0087] The temperature distribution calculation module is used to substitute the oil phase flow velocity data and the internal heat source intensity distribution data into the mathematical physics equation, and obtain the temperature distribution data of the formation by integral solution.

[0088] An electronic device comprises a memory and a processor, wherein the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute the temperature distribution calculation method for in-situ electric heating of a reservoir.

[0089] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the temperature distribution calculation method for in-situ electrical heating of a reservoir.

[0090] The above is only a preferred specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for calculating temperature distribution of in-situ electrical heating of a reservoir, characterized in that: include: Construct a physical stratigraphic model of the strata near the wellbore; Based on the physical formation model, combined with the law of conservation of energy, mathematical physics equations for heat conduction and convection in the formation are constructed: In the formula, ρ represents the density of the formation rock, c represents the specific heat capacity of the formation rock, T represents the temperature of the formation after being heated for time t, and ρ o Indicates oil density, c o represents the specific heat capacity of oil, represents the oil phase velocity, k represents the thermal conductivity, Q represents the internal heat source intensity of the formation, and its physical meaning is the amount of heat absorbed per unit volume per unit time; Calculate the oil phase flow velocity data of the oil phase in the physical formation model: In the formula, represents the oil phase velocity, p(r) represents the radial pressure distribution, and p w represents the pressure in the wellbore, u o represents the Darcy velocity; Calculating the internal heat source intensity distribution data generated by in-situ electric heating in the physical formation model; The oil phase flow velocity data and the internal heat source intensity distribution data are substituted into the mathematical physics equation, and the temperature distribution data of the formation is obtained by integral solution.

2. The temperature distribution calculation method for in-situ electrical heating of a reservoir according to claim 1, characterized in that: Construct a physical stratigraphic model of the strata near the wellbore, including: Determining model building parameters, wherein the model building parameters include geometric dimensions, boundary conditions and physical properties of formation materials in the near-wellbore zone; The physical formation model is constructed based on the determined model construction parameters.

3. The temperature distribution calculation method for in-situ electrical heating of a reservoir according to claim 1, characterized in that: Calculating the internal heat source intensity distribution data generated by in-situ electric heating in the physical formation model specifically includes: Determining the conductivity distribution data and the potential distribution data in the radial direction, the cross section and the longitudinal section in the physical formation model; Calculating energy distribution data generated in radial direction, cross section and longitudinal section in the physical formation model based on the conductivity distribution data and the potential distribution data; The calculated energy distribution data is integrated by surface and volume to obtain the internal heat source intensity distribution data in the physical formation model in space.

4. A temperature distribution calculation system for in-situ electrical heating of a reservoir, characterized in that: include: A model building module is used to build a physical stratigraphic model of the stratigraphic formation near the wellbore; Based on the physical formation model, combined with the law of conservation of energy, mathematical physics equations for heat conduction and convection in the formation are constructed: In the formula, ρ represents the density of the formation rock, c represents the specific heat capacity of the formation rock, T represents the temperature of the formation after being heated for time t, and ρ o Indicates oil density, c o represents the specific heat capacity of oil, represents the oil phase velocity, k represents the thermal conductivity, Q represents the internal heat source intensity of the formation, and its physical meaning is the amount of heat absorbed per unit volume per unit time; The parameter calculation module is used to calculate the oil phase flow velocity data in the physical formation model: In the formula, represents the oil phase velocity, p(r) represents the radial pressure distribution, and p w represents the pressure in the wellbore, u o represents the Darcy flow rate; Calculating the internal heat source intensity distribution data generated by in-situ electric heating in the physical formation model; The temperature distribution calculation module is used to substitute the oil phase flow velocity data and the internal heat source intensity distribution data into the mathematical physics equation, and obtain the temperature distribution data of the formation by integral solution.

5. An electronic device, characterized in that: It comprises a memory and a processor, wherein the memory is used to store a computer program, and the processor runs the computer program to enable the electronic device to execute a temperature distribution calculation method for in-situ electric heating of a reservoir according to any one of claims 1-3.

6. A computer-readable storage medium, characterized in that: It stores a computer program, which, when executed by a processor, implements a temperature distribution calculation method for in-situ electric heating of a reservoir as described in any one of claims 1-3.

Images