Method, device and equipment for determining wellbore temperature field distribution under composite process

Abstract

The invention discloses a method, a device and equipment for determining wellbore temperature field distribution under a composite process, and relates to the technical field of oil and gas field exploration. Comprising the steps that a shaft is divided into N well sections, and heat transfer coefficients of the N well sections are obtained; according to two different wellbore thickened oil viscosity reduction methods, a wellbore is divided into a thin oil-doped independent working section and a thin oil-doped and insulated heating cable composite working section; and in combination with the heat transfer coefficients of the N well sections, shaft fluid temperature calculation models of the thin oil-doped independent working section and the thin oil-doped and insulated heating cable composite working section are obtained respectively, and shaft temperature field distribution is obtained based on the shaft fluid temperature calculation models. The heat transfer processes of different viscosity reduction modes under the combination of different composite technologies are considered, a wellbore fluid temperature calculation model is established in a targeted mode, the influence of a wellbore structure on heat transfer is considered, the influence of different viscosity reduction modes in a wellbore on heat transfer is also considered, and therefore more accurate wellbore temperature field distribution can be obtained.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas field exploration, and in particular to a method, device and equipment for determining the distribution of a wellbore temperature field under a composite process. Background Art

[0002] Accurately predicting the temperature field distribution of ultra-deep heavy oil wells can optimize production strategies to reduce changes in oil viscosity caused by temperature changes, thereby improving oil well recovery and preventing problems such as wax deposition and asphaltene deposition. It is an indispensable part of oil and gas field development.

[0003] In the prior art, Chinese patent CN104389589B discloses a method and system for determining the temperature field distribution of a wellbore based on a hollow rod. The method includes: obtaining data related to the hollow rod and the wellbore; setting a step length according to the height of the dynamic liquid level in the wellbore and the depth of the wellbore; dividing the wellbore and the hollow rod into multiple wellbore sections and hollow rod sections according to the step length; determining the temperature of the liquid in the multiple wellbore sections and the temperature of the fluid in the multiple hollow rod sections respectively according to the data; the temperature of the fluid in the multiple hollow rod sections and the temperature of the liquid in the multiple wellbore sections constitute the wellbore temperature field distribution. In the method, the wellbore and the hollow rod are first divided into multiple wellbore sections and hollow rod sections according to the set step length, and then the integral constant is determined according to the wellhead temperature and the bottom hole temperature; the temperature of the liquid in each wellbore section and the temperature of the fluid in each hollow rod section are determined according to the integral constant and the thermal resistance coefficient.

[0004] However, the above method segments the wellbore and hollow rod based on a preset step size, and it is difficult to ensure that the heat transfer properties in the same section of the wellbore are the same. Therefore, the accuracy of the wellbore temperature field distribution obtained based on the wellbore section and hollow rod section needs to be improved. Summary of the invention

[0005] Based on this, the present invention provides a method, device and equipment for determining the wellbore temperature field distribution under a composite process, which can solve the problem of inaccurate determination of the wellbore temperature field distribution of ultra-deep heavy oil wells under a composite process in the prior art.

[0006] The present invention adopts the following technical solutions:

[0007] The present invention provides a method for determining the temperature field distribution of a wellbore under a composite process, comprising:

[0008] The wellbore is divided into N well sections based on the wellbore structure data and the composite process data of the wellbore, and the same well section has the same wellbore structure and composite process, where N is a positive integer; and the heat transfer coefficients of the N well sections are obtained;

[0009] According to the method of reducing the viscosity of heavy oil in the wellbore, N well sections are divided into a single working section with thin oil and a composite working section with thin oil and insulated heating cable;

[0010] Combined with the heat transfer coefficient of each well section, the wellbore fluid temperature calculation models of the thin oil-added working section alone and the thin oil-added and insulated heating cable composite working section are obtained respectively; and the wellbore temperature field distribution is obtained based on the wellbore fluid temperature calculation model.

[0011] Furthermore, the wellbore is divided into N well sections based on the wellbore structure data and the composite process data, specifically including:

[0012] The wellbore is divided into 5 sections, including:

[0013] The first well section is from the ground to the deep position of the first open casing. The wellbore structure of the first well section includes the first open casing, the second open casing, the third open casing and the annulus. The composite technology of the first well section includes oil pipe, thermal insulation cement and insulated cable.

[0014] The second well section is from the first open casing down position to the insulated cable down position, and the wellbore structure of the second well section includes a second open casing, a third open casing and an annulus; the composite technology of the second well section includes oil pipe, thermal insulation cement and insulated cable;

[0015] The third well section is from the lower depth of the insulated cable to the lower depth of the second casing. The wellbore structure of the third well section includes the second casing, the third casing and the annulus. The composite technology of the third well section includes the oil pipe and thermal insulation cement.

[0016] The fourth well section is from the second-open casing down position to the oil pipe down position. The wellbore structure of the fourth well section includes three-open casing and annulus. The composite technology of the fourth well section includes oil pipe and thermal insulation cement.

[0017] The fifth well section is from the deep position of the oil pipe to the reservoir position, and the well body structure of the fifth well section includes three-opening casing; the composite technology of the fifth well section includes thermal insulation cement.

[0018] Further, the obtaining of the heat transfer coefficients of the N well sections specifically includes:

[0019] Calculate the heat transfer coefficient U of the i-th well section toi , i={1,2,3,4,5}:

[0020]

[0021] Among them, r tii is the inner diameter of the tubing in the i-th well section; r toi is the outer diameter of the tubing in the i-th well section; r cii is the inner diameter of the casing in the i-th well section; r coi is the outer diameter of the casing in the i-th well section; r hi h is the outer wall radius of the thermal insulation cement ring in the i-th well section; f h is the convection heat transfer coefficient of the fluid in the wellbore; ciis the convection heat transfer coefficient of the fluid in the annulus; tubi is the thermal conductivity of the tubing in the i-th well section; casi is the casing thermal conductivity of the i-th well section; cemi is the thermal conductivity of the insulation cement in the ith well section.

[0022] Furthermore, the N well sections are divided into a separate working section mixed with thin oil and a composite working section mixed with thin oil and insulated heating cable, specifically including:

[0023] The first well section to the second well section is a composite working section with diluted oil and insulated heating cables;

[0024] The third to fifth well sections are thin oil-only working sections.

[0025] Furthermore, the temperature calculation model of the thin oil blending separate working section is:

[0026]

[0027] The calculation model of the wellbore fluid temperature in the thin oil mixed single working section is solved to obtain the wellbore temperature field distribution in the thin oil mixed single working section:

[0028]

[0029] Where Q1 is the heat released from the tubing fluid to the annulus fluid; Q2 is the heat transferred from the annulus fluid to the formation; z is the formation depth; W1 is the mass flow rate in the tubing; W2 is the mass flow rate in the annulus; T f is the fluid temperature in the oil pipe; T a is the fluid temperature in the annulus; T e is the formation temperature; C p1 is the specific heat of the tubing fluid; C p2 is the specific heat of the annulus fluid; is the heat transfer coefficient between the annulus fluid and the tubing wall; U ac2 is the heat transfer coefficient between the annulus fluid and the casing wall.

[0030] Furthermore, the temperature calculation model of the composite working section of the diluted oil-added and insulated heating cable is:

[0031] qdl=WdT+U to [T-T0-ml)]dl

[0032] The calculation model of the wellbore fluid temperature in the composite working section of the thin oil mixed with the insulated heating cable is solved, and the wellbore temperature field distribution in the composite working section of the thin oil mixed with the insulated heating cable is obtained:

[0033]

[0034] Among them, U tois the total heat transfer coefficient of the wellbore; T is the fluid temperature in the wellbore; T0 is the formation temperature; m is the geothermal gradient; l is the length along the depth direction of the well; q is the unit heat source intensity; W is the heat loss of the fluid in the wellbore, and e is a natural number.

[0035] The present invention provides a device for determining the temperature field distribution of a wellbore under a composite process, comprising:

[0036] The heat transfer coefficient acquisition module is used to divide the wellbore into N well sections based on the wellbore structure data and composite process data of the wellbore, and the same well section has the same wellbore structure and composite process, where N is a positive integer; and obtain the heat transfer coefficients of the N well sections.

[0037] The viscosity reduction segmentation module is used to divide N well sections into a thin oil mixed single working section and a thin oil mixed plus insulated heating cable composite working section according to the wellbore heavy oil viscosity reduction method.

[0038] The temperature distribution calculation module is used to obtain the wellbore fluid temperature calculation model of the thin oil-mixed working section and the thin oil-mixed and insulated heating cable composite working section in combination with the heat transfer coefficient of each well section; and obtain the wellbore temperature field distribution based on the wellbore fluid temperature calculation model.

[0039] The present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, a method for determining the wellbore temperature field distribution under the above-mentioned composite process is implemented.

[0040] At least one of the above technical solutions adopted by the present invention can achieve the following beneficial effects:

[0041] In the method for determining the wellbore temperature field distribution under the composite process provided by the present invention, considering the influence of different wellbore viscosity reduction processes on the wellbore temperature field in ultra-deep heavy oil wells, the wellbore is divided into N well sections based on the composite process of the wellbore, so that the wellbore of the same well section has the same wellbore structure or composite process, and by considering the heat transfer process of different viscosity reduction methods under the combination of different composite processes, a wellbore fluid temperature calculation model is established in a targeted manner, which not only considers the influence of the wellbore structure on heat transfer, but also considers the influence of different viscosity reduction methods in the wellbore on heat transfer, so that a more accurate wellbore temperature field distribution can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0043] Figure 1 A flow chart of a method for determining the temperature field distribution of a wellbore under a composite process provided by the present invention;

[0044] Figure 2 The radial heat transfer process of the wellbore under the composite process provided by the present invention;

[0045] Figure 3 A schematic diagram of the grid division of the wellbore provided by the present invention;

[0046] Figure 4 A profile diagram of the temperature field distribution of the wellbore provided by the present invention;

[0047] Figure 5 A framework diagram of a method for determining the wellbore temperature field distribution under a composite process provided by the present invention.

[0048] Reference numerals:

[0049] 1- thin oil added into the annulus; 2- heating cable; 3- oil pipe; 4- casing; 5- insulation cement; 6- thin and thick oil mixture; I- first section; II- second section; III- third section; IV- fourth section; V- fifth section; VI- sixth section. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in combination with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the specification, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] The reservoir type of Tahe Oilfield is Ordovician carbonate rock with fracture-cave structure and good permeability. The depth of the oil reservoir is mostly around 6000m, which is an ultra-deep heavy oil reservoir. The oil layer temperature is about 140℃, and the formation temperature gradient is 0.02-0.25℃ / m. The heavy oil in Tahe Oilfield has the characteristics of high freezing point, high salt content, wax, colloid, and asphalt. At present, Tahe Oilfield mainly adopts two mining processes: thin oil blending and viscosity reduction and mineral insulated cable heating and viscosity reduction. However, due to the long section of ultra-deep wells, the heat dissipation of the wellbore increases and the temperature decreases during the lifting process of the fluid during mining. It is difficult to ensure that the temperature is maintained above the inflection point temperature of the heavy oil during mining by using these two processes alone, and the accurate prediction of the wellbore temperature field directly affects the consumption of thin oil and electricity in the mine. At present, the commonly used calculation methods of wellbore temperature field mainly focus on the calculation of ordinary wellbore heat transfer coefficient and the analysis of the direct heat transfer process between the wellbore and the formation, but ignore the influence of different wellbore viscosity reduction processes on the wellbore temperature field and the radial heat transfer process of the composite process on the wellbore. Therefore, according to the characteristics of ultra-deep heavy oil wells, it is very important to study the change law of the wellbore temperature field under the composite process and the temperature distribution of the fluid in the wellbore for the design of oil production schemes for Tahe ultra-deep heavy oil wells and other types of oil wells.

[0052] In view of the above problems, the present invention provides a method for determining the temperature field distribution of the wellbore under a composite process. Through the study of the influence of fluid thermophysical properties such as heavy oil viscosity-temperature characteristics, oil well body structure, composite process combination, reservoir depth temperature on the wellbore temperature change, and the study of operating parameters such as heating power, heating depth, oil pipe and insulation cement depth, the influence of different wellbore viscosity reduction processes on the wellbore temperature field and the influence of composite processes on radial heat transfer between the wellbore and the formation are deeply considered, and a mathematical model and a temperature field calculation method are established. Through more refined wellbore grid division, special well conditions such as ultra-deep and ultra-thick are fully considered, and a method for determining the temperature field distribution of the wellbore under a composite process is formed. This method is aimed at the current situation of fast heat dissipation, high energy consumption, large amount of thin oil blending, and accurate prediction of the wellbore temperature field under a combination of multiple composite processes during the exploitation of ultra-deep heavy oil wells. A numerical calculation method is used to calculate the wellbore temperature change during the heavy oil exploitation process under the composite process, improve the accuracy of temperature field prediction, and achieve the purpose of reducing the amount of thin oil and reducing energy consumption in the mine. The invention comprises: obtaining the wellbore structure, reservoir basic parameters, composite process construction parameters, cable lowering parameters and heating power of the whole wellbore according to the drilling design; accurately meshing the whole wellbore according to the composite process and wellbore structure according to the wellbore structure, cable lowering depth, oil pipe depth and insulation cement depth; analyzing the heat transfer process of the wellbore under the composite process and calculating the heat transfer coefficient of different well sections of the whole wellbore based on the fluid properties, thermophysical parameters and meshing; dividing the wellbore into a single thin oil-added working section and a thin oil-added-insulated heating cable composite working section according to the cable lowering depth and the thin oil-added position, and establishing a wellbore temperature field distribution calculation model in sections according to the heat transfer theory and the law of conservation of energy through the analysis of the radial heat transfer process of the corresponding working sections; and calculating the profile of the wellbore temperature field distribution under the composite process based on the wellbore temperature field distribution calculation model. The invention takes into account the influence of the composite process on the heat transfer process of the whole wellbore, and uses a numerical calculation method to calculate the wellbore temperature change in the process of heavy oil production under the composite process and accurately predict the wellbore temperature, which has guiding significance for the production of ultra-deep heavy oil wells under the composite process.

[0053] The technical solutions provided by various embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0054] Figure 1 The present invention is a flow chart of a method for determining the temperature field distribution of a wellbore under a composite process, which specifically includes the following steps:

[0055] S1. Based on the wellbore structure data and composite process data of the wellbore, the wellbore is divided into N well sections, and the same well section has the same wellbore structure and composite process, where N is a positive integer; and the heat transfer coefficients of the N well sections are obtained. Specifically, the following steps are included:

[0056] S101. Collection of wellbore related data.

[0057] Take an oil well X in an oil field as an example, which is produced by a composite process of thin oil-insulated cable (2800m of oil pipe + 4000m of thermal insulation cement) and insulated cable + thin oil-added viscosity reduction method:

[0058] According to the drilling design, the wellbore structure of the entire wellbore is obtained, including: drilling times, casing and tubing depths, pumping parameters, and thin oil blending positions. The basic reservoir parameters are obtained, including: oil layer depth, oil layer temperature, cable running parameters, heating power, insulation cement and tubing depth. The basic production parameters include: daily oil production, daily water production, daily thin oil blending amount, thin oil blending temperature, etc. The drilling times are shown in Table 1, the basic reservoir parameters are shown in Table 2, and the basic production data are shown in Table 3.

[0059] Table 1 Drilling times data

[0060]

[0061] Table 2 Basic reservoir parameters

[0062] Parameter name unit Numeric Oil layer depth m 6100 Reservoir temperature ℃ 140 Cable insertion depth m 2000 Cable heating power kW 120 YouTube m 2800 Insulation cement m 4000

[0063] Table 3 Basic production data

[0064] Parameter name unit Numeric Daily oil production t / d 32.7 Daily water production t / d 7.8 Daily amount of thin oil t / d 44.1 Dilute oil temperature ℃ 35

[0065] S102. Grid division of the wellbore.

[0066] Then, the entire wellbore is precisely gridded according to the wellbore structure, cable running depth, oil pipe (insulated oil pipe) and insulation cement depth. The wellbore is divided into 5 sections according to the wellbore structure and the position of thin oil. The division results are as follows: Figure 2 As shown, the first composite process section: the ground to the lower deep position of the single-open casing (including oil pipes, insulated cables, annuli, single-open, double-open, triple-open casings and thermal insulation cement), the second composite process section: the lower deep position of the single-open casing to the lower deep position of the insulated cable (including oil pipes, insulated cables, annuli, double-open, triple-open casings and thermal insulation cement), the third composite process section: the lower deep position of the insulated cable to the lower deep position of the double-open casing (including oil pipes, annuli, double-open, triple-open casings and thermal insulation cement), the fourth composite process section: the lower deep position of the double-open casing to the lower deep position of the oil pipe / oil pipe (including oil pipe / oil pipes, annuli, triple-open casing and thermal insulation cement), the fifth composite process section: the lower deep position of the oil pipe / oil pipe to the reservoir position (three-open casing and thermal insulation cement). Figure 2 The sixth section is a heavy oil reservoir.

[0067] The heat exchange process between the mixed liquid in the oil pipe and the formation under the composite process is as follows: Figure 3 , the heat transfer process mainly goes through the following steps:

[0068] (1) When the cable is heated, heat is transferred to the mixture of thin and thick oil in the pipe by thermal convection. This process is limited to the composite working section of the thin oil-mixed and insulated heating cable.

[0069] (2) The mixture of thin and thick oil in the pipe transfers heat to the inner wall of the oil pipe / insulated oil pipe by thermal convection. The degree of convective heat transfer of the mixture in the pipe varies depending on the oil production.

[0070] (3) Heat is transferred from the inner wall of the oil pipe / insulated oil pipe to the outer wall of the oil pipe / insulated oil pipe through heat conduction. This process is affected by the composite process, such as the influence of different insulation materials on heat transfer. The better the insulation effect, the smaller the heat loss.

[0071] (4) Heat is transferred from the outer wall of the oil pipe to the inner wall of the casing through the annulus in the form of heat convection and heat radiation. This process is affected by the dilution ratio. The degree of convective heat transfer varies with the dilution ratio.

[0072] (5) The heat in the casing is transferred from the inner wall of the casing to the outer wall of the casing by heat conduction.

[0073] (6) Heat in the cement sheath / insulating cement is transferred from the outer wall of the casing to the formation through the cement sheath / insulating cement by heat conduction. This process is also affected by the composite process, such as different insulating cementing materials and different insulating cementing depths.

[0074] S103, the wellbore is meshed and the total heat transfer coefficient of the entire wellbore is calculated based on the fluid properties, thermophysical parameters and meshing.

[0075] After the heavy oil and thin oil are mixed, the viscosity and density of the mixed liquid change accordingly as the produced fluid flows in the wellbore due to temperature and a series of complex changes. Before calculating the heat transfer coefficient of the entire wellbore, it is necessary to analyze the influence of the composite process on the heat transfer process of the wellbore based on the fluid properties and thermophysical parameters, and calculate the heat transfer coefficient of the wellbore in sections based on the analysis results and grid division results. Therefore, it is necessary to accurately calculate the parameters of the wellbore mixed liquid. The specific calculation formula of the parameters is as follows:

[0076] (1) Crude oil viscosity:

[0077]

[0078] in, γ O is the relative density of crude oil, g / cm 3 ; μ is the viscosity of crude oil, in mPa·s; C o is the initial temperature of crude oil; the viscosity-temperature relationship curve calculated by the above formula shows that the inflection point temperature of heavy oil is 60℃.

[0079] (2) Viscosity of crude oil and diluted oil after mixing:

[0080]

[0081] Among them, μ m is the viscosity of the mixed oil, in mPa·s; X i is the volume ratio of various oils in the mixed oil; μ i is the viscosity of the i-th oil, in mPa·s; the viscosity-temperature relationship curve obtained by calculation is as follows Figure 3 As shown, the above formula shows that the inflection point temperature after the mixture of thin and heavy oils is 45°C.

[0082] (3) Density of mixed liquid ρ mix :

[0083] ρ mix =ρ w ×f w +ρ o ×(1-f w )

[0084] Among them, ρ w is the water density in kg / m 3 ;f w is the water content of the mixed liquid; ρ o is the density of heavy oil, in kg / m 3 .

[0085] Since the properties of liquids change after mixing, the thermal conductivity of the mixed liquid will also change. The thermal conductivity of the fluid after oil-water mixing λ is established. f Calculation formula:

[0086]

[0087] Among them, λ w is the water density thermal conductivity, λ w is the thermal conductivity of heavy oil. According to the above formula, the density of the mixed liquid is 0.97g / cm 3 The thermal conductivity of the fluid after oil and water mixing is 0.27W / (m·℃).

[0088] After the entire wellbore is precisely gridded according to the wellbore structure, cable insertion depth, and thin oil mixing position, the total heat transfer coefficient of each section is calculated according to the corresponding fluid properties at different sections and temperatures. The calculation formula is:

[0089]

[0090] Where:

[0091] U toi —Total heat transfer coefficient of the i-th well section, W / (m·℃); r tii —Inner diameter of the tubing in the i-th well section, m; r toi—Outer diameter of the tubing in the i-th well section, m; r cii —Inner diameter of casing in the i-th well section, m; r toi —Casing outer diameter of the i-th well section, m; r hi —Radius of the outer wall of cement / insulation cement ring in the i-th well section, m; h f —Convection heat transfer coefficient of fluid in wellbore, W / (m 2 ℃); h ci —Convection heat transfer coefficient of fluid in annulus, W / (m 2 ·℃);λ tubi —Thermal conductivity of the tubing in the i-th well section, W / (m·℃); λ casi —Thermal conductivity of casing in the i-th well section, W / (m·℃); λ cemi —Thermal conductivity of cement sheath in the i-th well section, W / (m·℃). The total heat transfer coefficient of each section obtained according to the above formula is shown in Table 4.

[0092] Table 4 Segmented calculation results of the total heat transfer coefficient of the wellbore

[0093] Segmentation Starting position End position Overall heat transfer coefficient Paragraph 1 0 800 2.92 Paragraph 2 800 2800 3.07 Paragraph 3 2800 4000 3.16 Paragraph 4 4000 5000 3.87 Paragraph 5 5000 6000 4.29 Paragraph 6 6000 6100 4.76

[0094] S2. According to the method of reducing the viscosity of heavy oil in the wellbore, N well sections are divided into a single working section mixed with thin oil and a composite working section mixed with thin oil and insulated heating cable.

[0095] According to the cable lowering depth and the position of the diluted oil, the wellbore is divided into two sections: the diluted oil-only working section and the diluted oil-plus-insulated heating cable composite working section. The wellbore temperature field distribution models are established based on the heat transfer theory and the law of conservation of energy. The first section to the second section is the diluted oil-plus-insulated heating cable composite working section; the third section to the fifth section is the diluted oil-only working section.

[0096] S3. Combined with the heat transfer coefficient of each well section, the wellbore fluid temperature calculation models of the thin oil-mixed working section and the thin oil-mixed and insulated heating cable composite working section are obtained respectively; and the wellbore temperature field distribution is obtained based on the wellbore fluid temperature calculation model.

[0097] According to the cable running depth and the position of diluted oil, the wellbore is divided into two sections: diluted oil alone and diluted oil-insulated cable heating. The wellbore temperature field distribution models are established by heat transfer theory and energy conservation law. The temperature field calculation models of different sections are established by deeply studying the heat exchange mechanism between the wellbore and the reservoir, the influence of heat source and diluted oil on the wellbore temperature field distribution.

[0098] Among them, the energy balance analysis on the separate thin oil blending working section needs to consider the impact of the composite process on the heat transfer of the oil pipe and the annulus at the same time, and the energy balance equation relationship is established as follows:

[0099]

[0100] According to the assumption of steady-state heat transfer in the wellbore, the solution is:

[0101]

[0102] Where Q1 is the heat released from the tubing fluid to the annulus fluid; Q2 is the heat transferred from the annulus fluid to the formation; z is the formation depth; W1 is the mass flow rate in the tubing; W2 is the mass flow rate in the annulus; T f is the fluid temperature in the oil pipe; T a is the fluid temperature in the annulus; T e is the formation temperature; C p1 is the specific heat of the tubing fluid; C p2 is the specific heat of the annular fluid; U ta1 is the heat transfer coefficient between the annulus fluid and the tubing wall; U ac2 is the heat transfer coefficient between the annulus fluid and the casing wall.

[0103] Energy balance analysis is performed on the thin oil-insulated cable heating composite working section. It is necessary to consider the temperature of the oil pipe, annulus and cable heating at the same time, and the energy balance equation relationship is established as follows:

[0104] qdl=WdT+U to [T-(T0-ml)]dl

[0105] By solving the above energy balance equation, the wellbore fluid temperature distribution model is obtained as follows:

[0106]

[0107] Among them, U to is the total heat transfer coefficient of the wellbore; T is the fluid temperature in the wellbore; T0 is the formation temperature; m is the geothermal gradient; l is the length along the depth direction of the well; q is the unit heat source intensity; W is the heat loss of the fluid in the wellbore, and e is a natural number.

[0108] Based on the wellbore temperature field distribution model, the wellbore temperature field distribution diagram is calculated. The calculated fluid temperature in the tubing and its change process with well depth are shown in the following figure. Figure 4 shown.

[0109] Figure 5 The framework diagram of the method for determining the wellbore temperature field distribution under the composite process is shown in Figure 5As shown in the figure, firstly, an oil well under the conditions of composite process exploitation, Well X in a certain oil field, is selected as an example: according to the drilling design, the wellbore structure of the entire wellbore is obtained, including: drilling opening, casing and tubing depth, and thin oil mixing position. The basic parameters of the reservoir are obtained, including: oil layer depth and oil layer temperature. The construction parameters of the composite process are obtained, including: insulation oil pipe and insulation cement depth. The cable running parameters and heating power are obtained. Next, the entire wellbore is accurately gridded according to the wellbore structure, cable running depth, insulation oil pipe and insulation cement depth. Secondly, based on the fluid properties, thermophysical parameters and grid division, the heat transfer process of the wellbore under the composite process is analyzed and the total heat transfer coefficient of the entire wellbore is calculated. Then, according to the cable running depth and the thin oil mixing position, the wellbore is divided into two sections: thin oil mixing alone and thin oil mixing-insulated cable heating. The wellbore temperature field distribution model is established by heat transfer theory and the law of conservation of energy. Finally, based on the wellbore temperature field distribution model, the wellbore temperature field distribution plan view under the composite process is calculated. The present invention takes into account the influence of the composite process on the entire wellbore heat transfer process, adopts a numerical calculation method to calculate the wellbore temperature change during the heavy oil production process under the composite process and accurately predicts the wellbore temperature, which has guiding significance for the production of ultra-deep heavy oil wells under the composite process and achieves the purpose of reducing the use of thin oil and reducing energy consumption in the mine.

[0110] The above is a method for determining the temperature field distribution of a wellbore under a composite process provided by one or more embodiments of the present invention. Based on the same idea, the present invention also provides a corresponding device for determining the temperature field distribution of a wellbore under a composite process, including:

[0111] The heat transfer coefficient acquisition module is used to divide the wellbore into N well sections based on the wellbore structure data and composite process data of the wellbore so that the wellbore in the same well section has the same wellbore structure or composite process, where N is a positive integer; and obtain the heat transfer coefficients of the N well sections.

[0112] The viscosity reduction segmentation module is used to divide the wellbore into a single working section with thin oil blending and a composite working section with thin oil blending and insulating heating cables according to two different methods of viscosity reduction of heavy oil in the wellbore: single viscosity reduction with thin oil blending and composite viscosity reduction with thin oil blending and insulating heating cables.

[0113] The temperature distribution calculation module is used to obtain the wellbore fluid temperature calculation model of the thin oil-mixed working section and the thin oil-mixed and insulated heating cable composite working section in combination with the heat transfer coefficient of each well section, and obtain the wellbore temperature field distribution based on the wellbore fluid temperature calculation model.

[0114] The specific definition of the device for determining the temperature field distribution of the wellbore under the composite process can be found in the above definition of the method for determining the temperature field distribution of the wellbore under the composite process, which will not be repeated here. Each module in the above-mentioned device for determining the temperature field distribution of the wellbore under the composite process can be implemented in whole or in part by software, hardware and a combination thereof. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0115] The present invention also provides a computer device. At the hardware level, the computer device includes a processor, an internal bus, a network interface, a memory, and a non-volatile memory, and may also include other hardware required for the business. The processor reads the corresponding computer program from the non-volatile memory into the memory and then runs it to achieve the above Figure 1 A method for determining the wellbore temperature field distribution under a composite process is provided.

[0116] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0117] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the present invention.

Claims

1. A method for determining the temperature field distribution of a wellbore under a composite process, characterized in that: include: The wellbore is divided into N well sections based on the wellbore structure data and the composite process data of the wellbore, and the same well section has the same wellbore structure and composite process, where N is a positive integer; and the heat transfer coefficients of the N well sections are obtained; According to the method of reducing the viscosity of heavy oil in the wellbore, N well sections are divided into a single working section with thin oil and a composite working section with thin oil and insulated heating cable; Combined with the heat transfer coefficient of each well section, the wellbore fluid temperature calculation models of the thin oil-added working section alone and the thin oil-added and insulated heating cable composite working section are obtained respectively; and the wellbore temperature field distribution is obtained based on the wellbore fluid temperature calculation model.

2. The method for determining the temperature field distribution of a wellbore under a composite process according to claim 1, characterized in that: The wellbore is divided into N well sections based on the wellbore structure data and the composite process data, specifically including: The wellbore is divided into 5 sections, including: The first well section is from the ground to the deep position of the first open casing. The wellbore structure of the first well section includes the first open casing, the second open casing, the third open casing and the annulus. The composite technology of the first well section includes oil pipe, thermal insulation cement and insulated cable. The second well section is from the first open casing down position to the insulated cable down position, and the wellbore structure of the second well section includes a second open casing, a third open casing and an annulus; the composite technology of the second well section includes oil pipe, thermal insulation cement and insulated cable; The third well section is from the lower depth of the insulated cable to the lower depth of the second casing. The wellbore structure of the third well section includes the second casing, the third casing and the annulus. The composite technology of the third well section includes the oil pipe and thermal insulation cement. The fourth well section is from the second-open casing down position to the oil pipe down position. The wellbore structure of the fourth well section includes three-open casing and annulus. The composite technology of the fourth well section includes oil pipe and thermal insulation cement. The fifth well section is from the deep position of the oil pipe to the reservoir position, and the well body structure of the fifth well section includes three-opening casing; the composite technology of the fifth well section includes thermal insulation cement.

3. The method for determining the temperature field distribution of a wellbore under a composite process according to claim 2, characterized in that: The obtaining of the heat transfer coefficients of N well sections specifically includes: Calculate the heat transfer coefficient U of the i-th well section toi , i={1,2,3,4,5}: Among them, r tii is the inner diameter of the tubing in the i-th well section; r toi is the outer diameter of the tubing in the i-th well section; r cii is the inner diameter of the casing in the i-th well section; r coi is the outer diameter of the casing in the i-th well section; r hi h is the outer wall radius of the thermal insulation cement ring in the i-th well section; f h is the convection heat transfer coefficient of the fluid in the wellbore; ci is the convection heat transfer coefficient of the fluid in the annulus; tubi is the thermal conductivity of the tubing in the i-th well section; casi is the casing thermal conductivity of the i-th well section; cemi is the thermal conductivity of the insulation cement in the ith well section.

4. The method for determining the temperature field distribution of a wellbore under a composite process according to claim 2, characterized in that: The method of dividing the N well sections into a separate working section mixed with thin oil and a composite working section mixed with thin oil and insulated heating cable specifically includes: The first well section to the second well section is a composite working section with diluted oil and insulated heating cables; The third to fifth well sections are thin oil-only working sections.

5. The method for determining the temperature field distribution of a wellbore under a composite process according to claim 4, characterized in that: The temperature calculation model of the thin oil blending separate working section is: The calculation model of the wellbore fluid temperature in the thin oil mixed single working section is solved to obtain the wellbore temperature field distribution in the thin oil mixed single working section: Where Q1 is the heat released from the tubing fluid to the annulus fluid; Q2 is the heat transferred from the annulus fluid to the formation; z is the formation depth; W1 is the mass flow rate in the tubing; W2 is the mass flow rate in the annulus; T f is the fluid temperature in the oil pipe; T a T is the fluid temperature in the annulus; e is the formation temperature; C p1 is the specific heat of the tubing fluid; C p2 is the specific heat of the annulus fluid; is the heat transfer coefficient between the annulus fluid and the tubing wall; U ac2 is the heat transfer coefficient between the annulus fluid and the casing wall.

6. The method for determining the temperature field distribution of a wellbore under a composite process according to claim 4, characterized in that: The temperature calculation model of the composite working section of the diluted oil-added and insulated heating cable is: qdl=WdT+U to [T-(T0-ml)]dl The calculation model of the wellbore fluid temperature in the composite working section of the thin oil mixed with the insulated heating cable is solved, and the wellbore temperature field distribution in the composite working section of the thin oil mixed with the insulated heating cable is obtained: Among them, U to is the total heat transfer coefficient of the wellbore; T is the fluid temperature in the wellbore; T0 is the formation temperature; m is the geothermal gradient; l is the length along the depth direction of the well; q is the unit heat source intensity; W is the heat loss of the fluid in the wellbore, and e is a natural number.

7. A device for determining the temperature field distribution of a wellbore under a composite process, characterized in that: include: A heat transfer coefficient acquisition module is used to divide the wellbore into N well sections based on the wellbore structure data and composite process data of the wellbore, and the same well section has the same wellbore structure and composite process, where N is a positive integer; and obtain the heat transfer coefficients of the N well sections; The viscosity reduction segmentation module is used to divide N well sections into a thin oil mixed single working section and a thin oil mixed plus insulated heating cable composite working section according to the wellbore heavy oil viscosity reduction method; The temperature distribution calculation module is used to obtain the wellbore fluid temperature calculation model of the thin oil-mixed working section and the thin oil-mixed and insulated heating cable composite working section in combination with the heat transfer coefficient of each well section; and obtain the wellbore temperature field distribution based on the wellbore fluid temperature calculation model.

8. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method described in any one of claims 1 to 6 is implemented.

Images