Method for optimizing injection parameters based on heat distribution

Abstract

The invention relates to the technical field of thickened oil recovery, and particularly provides a method for optimizing injection parameters based on heat distribution. According to the method, in the heavy oil thermal recovery process, the injected heat is divided into different parts, the heat proportion and weight of each part are calculated, and the optimal injection parameters are searched, so that invalid use of steam is reduced, the effective heat utilization rate is increased, the steam injection cost is optimized, and development benefits are improved.

Description

Technical Field

[0001] The invention relates to the technical field of heavy oil production, in particular to a method for optimizing injection parameters based on heat distribution. Background Art

[0002] With the inevitable depletion of conventional thin oil reservoirs and the further prominence of the contradiction between domestic crude oil supply and demand, heavy oil has become the main area of ​​crude oil and an important part of reducing the external dependence on oil. Heavy oil is crude oil with a viscosity greater than 50 mPa·s under reservoir conditions or a viscosity greater than 100 mPa·s of ground degassed crude oil, which has the characteristics of high viscosity and high density. Compared with conventional thin oil, heavy oil has high colloid and asphaltene content, high viscosity and poor fluidity, resulting in huge flow resistance in the formation, which is the root cause of the difficulty in heavy oil development.

[0003] Heavy oil has a strong temperature-sensitive property. It is generally believed that the viscosity of heavy oil can be reduced by half when the temperature rises by 10°C. Therefore, thermal oil recovery occupies the dominant mode of heavy oil development, including steam throughput, steam drive, SAGD and other methods. Injecting high-dryness, superheated steam into the formation reduces the viscosity of heavy oil by transferring heat. This is the underlying logic of thermal recovery of heavy oil. Rational use of steam is an indispensable part of thermal recovery of heavy oil. Chinese patent CN 117287164 A discloses a method and system for optimizing steam injection for heavy oil production in oil fields. By tracking historical development indicators, the quality and effect of steam injection are analyzed and evaluated to determine the steam injection parameters. Chinese patent CN 118673784 A discloses a method for optimizing steam throughput parameters of heavy oil, which determines the main controlling factors of steam injection parameters and geological parameters, and inputs them into a Bayesian neural network model to optimize the steam injection parameters. Chinese patent CN 117927203 A discloses super-heavy oil steam injection medium and parameter optimization method and related equipment, which determines the steam injection parameters by calculating the deficit volume, deficit rock characteristics and steam heat release. The above optimization of steam injection parameters for thermal recovery of heavy oil is based on geological parameters and historical production characteristics, and the steam injection parameters are determined, ignoring the relationship between the heat distribution after steam injection into the formation and the injection parameters, resulting in low steam heat utilization rate and ineffective heat utilization. Heat is the core of thermal recovery of heavy oil, and heat distribution is the key to the effective utilization of steam heat, and it is also an important way to reduce costs and increase efficiency of heavy oil.

[0004] Therefore, when applying thermal recovery technology for heavy oil, it is urgent to optimize the injection steam parameters according to the heat distribution characteristics of the reservoir, avoid diminishing marginal returns, maximize the steam injection heat, increase the amount of heavy oil recovered per unit steam, and improve the overall efficiency of heavy oil recovery. Summary of the invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a method for optimizing injection parameters based on heat distribution characteristics. In the heavy oil thermal recovery process, the heat distribution characteristics under different injection parameters are calculated to find the optimal injection parameters, so as to reduce the ineffective use of steam, improve the effective utilization rate of heat, optimize the steam injection cost, and improve the development efficiency.

[0006] A method for optimizing injection parameters based on heat distribution specifically comprises the following steps: S1. Establish a numerical model for heavy oil thermal recovery reservoirs; S2. Input steam injection parameters, divide the injected heat into three parts: heat loss, produced fluid carryover and reservoir absorption, and divide the reservoir absorption part into steam chamber, condensation zone, heating zone and unheated zone; S3. Calculate the comprehensive value of heat utilization according to the proportion of each injected heat to the total injected heat and its weight; S4. Set different steam injection parameters, repeat steps S2 and S3, compare the comprehensive heat utilization values ​​under various injection parameter conditions, and finally output the steam injection parameter corresponding to the maximum comprehensive heat utilization value.

[0007] Preferably, the heavy oil thermal recovery reservoir numerical model is optimized by historical matching based on the historical development data of the mine; When applied, the model working system is specified by referring to the production situation of the oil reservoir in the target block of the mine, and the adjustable parameters are optimized within the adjustable range based on the analysis of historical production indicators to obtain a numerical simulation model that meets the oil reservoir in the target block.

[0008] Furthermore, the steam injection parameters include steam injection rate, injection pressure, and steam quality.

[0009] Furthermore, the heat loss in step S2 refers to the heat absorbed by the reservoir caprock and the underlying strata, and the heat carried by the produced fluid refers to the heat carried by the fluid (oil, water) produced to the ground.

[0010] In the process of heavy oil development, the formed steam chamber maintains a high temperature, and the superheated high-dryness steam injected into the steam chamber makes the steam chamber have a high steam saturation characteristic; the steam exchanges heat with the cold oil at the edge of the steam chamber to form condensed water, and the condensation area has a high water saturation characteristic. In step S2, combined with the heavy oil thermal recovery reservoir numerical model in step S1, the reservoir is divided into a steam chamber, a condensation area, a heated area and an unheated area, and the division criteria are: The area with a temperature greater than T is the steam chamber; T is the saturated steam temperature corresponding to the reservoir pressure during production; The area between the limit M and the limit N is the condensation area; The limit M is the limit where the vapor saturation is zero; The limit N is the limit of the reservoir pressure corresponding to the saturated steam temperature during production.

[0011] The temperature rise area minus the steam chamber and condensation area is the heating area; The area where the temperature does not rise is the unheated area.

[0012] Furthermore, the specific process of step S3 is as follows: S3.1 Calculate the total heat injected into the reservoir based on the obtained steam injection parameters: (1); Where Q total is the total heat injected, kJ; V steam is the steam injection rate, m 3 / d; x is the steam dryness; h g is the saturated steam enthalpy, kJ / kg; h f is the saturated water enthalpy, kJ / kg; Δt is the time, d.

[0013] S3.2 The heat loss part includes: the heat dissipated by heat conduction through the cap layer and the underlying strata, the heat absorbed by the cap layer and the underlying strata, and the heat loss and its proportion to the total heat injected are: (2); (3); Where Q loss is the heat loss, kJ; ko is the number of grids corresponding to the cap layer area in the numerical model; C so is the specific heat capacity of the cap layer, kJ / (m 3 ·℃);ρ so is the density of the cap rock, kg / m 3 ; V soi is the grid volume of the i-th cover layer, m 3 ; ΔT soi is the temperature change of the cover layer grid, ℃; k so is the thermal conductivity of the cap layer, kJ / (m·d·℃); A soi is the grid area of ​​the i-th cover layer, m 2 ;d soi is the grid thickness of the cap layer, m; ku is the number of grids corresponding to the underlying stratum area in the numerical model; C su is the specific heat capacity of the underlying stratum, kJ / (m 3 ·℃);ρ su is the rock density of the underlying stratum, kg / m 3 ; V sui is the grid volume of the underlying stratum i, m 3 ; ΔTsui is the temperature change of the underlying stratum grid, ℃; k su is the underlying thermal conductivity, kJ / (m·d·℃); A sui is the grid area of ​​the underlying stratum i, m 2 ;d sui is the thickness of the underlying grid, m; M loss is the heat loss ratio, %.

[0014] S3.3 The heat carried by the produced fluid can be calculated by the produced fluid rate and the produced fluid temperature. The produced fluid temperature is the temperature of the grid where the production well is located in the numerical model. The heat carried by the produced fluid and its proportion to the total injected heat are: (4); (5); Where Q carry Carrying heat for the produced fluid, kJ; C o is the specific heat capacity of formation oil, kJ / (kg·℃); C w is the specific heat capacity of formation water, kJ / (kg·℃); Q o is the cumulative oil production, m 3 ;Q w is the cumulative water production, m 3 ρ o is the density of crude oil, kg / m 3 ρ w is the density of produced water, kg / m 3 ; ΔT is the difference between the temperature of the grid where the production well is located and the formation temperature, ℃; M carry It is the percentage of heat carried by the produced fluid.

[0015] S3.4 The heat in the condensation zone and its proportion to the total heat injected are calculated using the following formula: (6); (7); Where Q con is the heat of the condensation zone, kJ; k1 is the number of grids corresponding to the condensation zone in the numerical simulation results; V ci is the grid volume of condensation region i, m 3 ; ΔT ci is the temperature change of grid i in condensation zone, ℃; is the mesh porosity of condensation zone i; S coi is the oil saturation of grid i in the condensation zone; S cwi is the water saturation of grid i in the condensation zone; ρ s is the rock density, kg / m 3 ; C sis the specific heat capacity of reservoir rock, kJ / (kg·℃); M con It is the percentage of heat carried by the produced fluid.

[0016] S3.5 For the reservoir absorption part, the heat in the heating zone and its proportion to the total heat injected are calculated using the following formula: (8); (9); Where Q heat is the heat distribution in the heating zone, kJ; k2 is the number of grids corresponding to the heating zone in the numerical simulation results; V hi is the grid volume of heating area i, m 3 ; ΔT hi is the temperature change of the grid in the heating zone i, ℃; is the mesh porosity of heating zone i; S hoi is the oil saturation of grid i in the heating area; S hwi is the water saturation of the grid in the heating zone i.

[0017] S3.6 For the reservoir absorption part, the proportion of steam chamber heat to the total injected heat is calculated using the following formula: (10); Furthermore, the calculation formula of the heat utilization integrated value (HEI) is: (11); Among them, w1 is the weight coefficient of the heat proportion of the condensation zone, w2 is the weight coefficient of the heat proportion of the heating zone, w3 is the weight coefficient of the heat proportion of the steam chamber, w4 is the weight coefficient of the heat proportion of heat loss, and w5 is the weight coefficient of the heat proportion carried by the output fluid. The method for determining the weight coefficient is: taking the internal rate of return as the target variable, establishing a multivariate linear regression model of the heat proportion of each part and the target variable, and using the least squares method to determine the specific value of each weight.

[0018] Furthermore, w1, w2, w3, w4, and w5 need to satisfy normalization conditions and positive value constraints to ensure that the contribution of each part of the heat share is proportional and to avoid unreasonable evaluation results caused by an excessive weight of one item.

[0019] Although the weight coefficient can be set through experience and theoretical analysis in the preliminary design, in actual application, the weight coefficient can be appropriately adjusted according to the geological characteristics of different reservoirs, steam injection methods and production requirements. Through numerical simulation, experimental verification and field application, the weight coefficient is optimized to improve the accuracy and practicality of the heat utilization integrated value (HEI).

[0020] Preferably, the method for optimizing injection parameters based on heat distribution is applicable to heavy oil reservoirs using steam injection for thermal recovery.

[0021] The beneficial effects of the present invention are as follows: (1) The method provided by the present invention significantly improves the rationality and accuracy of heat distribution. In the prior art, the heat distribution during steam injection often lacks systematic optimization, resulting in the failure of heat to be fully and effectively transferred to the oil layer, especially in the steam chamber area, where heat accumulation is serious, resulting in uneven heating effect. Different from the prior art, the present invention uses a scientific heat distribution optimization method to accurately control the heat share of each area, ensure that the heat is more concentrated in the effective heating area and condensation area, maximize the thermal recovery effect, and thus significantly improve the overall heat utilization efficiency.

[0022] (2) The method provided by the present invention effectively reduces heat loss and optimizes energy efficiency. In the prior art, heat loss is usually not given enough attention, resulting in a large amount of steam losing heat energy during the transmission process, affecting the economic efficiency of the thermal recovery process. The present invention can effectively identify and reduce heat loss by accurately calculating and optimizing the heat loss ratio, effectively applying more heat to oil layer heating, significantly reducing energy consumption, and improving energy efficiency.

[0023] (3) The method provided by the present invention breaks through the shackles of traditional steam injection parameters that are only optimized through production. The existing technology adjusts the injection parameters by simply increasing production, ignoring the rationality of heat distribution, resulting in diminishing marginal benefits. In contrast, the present invention proposes a more accurate steam injection parameter optimization scheme by comprehensively evaluating the heat share of each region, achieving the maximum utilization of steam heat, thereby improving the oil reservoir recovery rate and improving the overall economic benefits of the oil field. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A flow chart of a method for optimizing injection parameters based on heat distribution; Figure 2 This is a three-dimensional numerical model diagram of the heavy oil SAGD thermal recovery reservoir in Example 1; Figure 3 This is the temperature field of heavy oil SAGD thermal recovery in Example 1; Figure 4 The water saturation field of heavy oil SAGD thermal recovery in Example 1; Figure 5 This is the steam saturation field of heavy oil SAGD thermal recovery in Example 1. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments: Example 1 Reference Figure 1, provides a method for optimizing injection parameters based on heat distribution. This embodiment takes a block in Xinjiang Oilfield as an example. The oilfield block is a heavy oil reservoir with an average porosity of 32%. The crude oil viscosity at 50°C is about 20000 mPa·s. The development is difficult. The SAGD development method is adopted. Limited by the on-site process measures, the steam dryness is fixed at 0.8, the temperature is 250°C, and the injection pressure is 0.7MPa. The steam injection rate needs to be optimized.

[0026] A method for optimizing injection parameters based on heat distribution specifically comprises the following steps: S1. Establishment of numerical model of heavy oil thermal recovery reservoir: Furthermore, when applied, the geological characteristics, crude oil properties and other reservoir information of the target block are finely analyzed, the grid step size is set, and a series of parameters such as permeability, reservoir porosity and oil saturation are set according to the actual data of the mine to establish a heavy oil thermal recovery reservoir numerical model. The specific parameters of the reservoir are shown in Table 1: Table 1 Reservoir parameters parameter Parameter Value Model size 51m×400m×45m Model top depth 180m Permeability 2000mD Porosity 0.32 Oil saturation 0.72 Formation temperature 20℃ Formation pressure 2.3MPa The heavy oil SAGD thermal recovery three-dimensional numerical model is established based on reservoir parameter information. Further, according to the historical development data of the mine, the heavy oil thermal recovery reservoir numerical model is optimized by historical fitting. The optimized heavy oil thermal recovery reservoir SAGD thermal recovery reservoir three-dimensional numerical model is as follows: Figure 2 As shown in the figure, the colors represent the top depth of each grid reservoir, and the top depth of the grid reservoir increases from top to bottom.

[0027] S2. Set the steam injection rate to 75m 3 / d, according to the destination of steam injection heat, the total injected heat is divided into heat loss, heat carried by produced fluid and reservoir absorption, and the reservoir grid is divided into regions according to the division criteria.

[0028] like Figure 3-5 They are respectively the temperature field, water saturation field, and steam saturation field diagrams of heavy oil SAGD thermal recovery obtained after running the heavy oil SAGD thermal recovery three-dimensional numerical model. In the figure, the color bars represent temperature, water saturation, and steam saturation, respectively. It can be seen from the figure that the high temperature area maintains a high steam saturation, and the water saturation increases after the temperature is reduced to the saturated steam temperature. The division criteria for each area in this embodiment are determined as follows: The area where the temperature is greater than the saturated steam temperature corresponding to the reservoir pressure during production is the steam chamber; The area between the zero limit of steam saturation and the limit of saturated steam temperature corresponding to reservoir pressure during production is the condensation zone; The temperature rise area minus the steam chamber and condensation area is the heating area; The area where the temperature does not rise is the unheated area.

[0029] Furthermore, the total number of grids is 2295, the number of grids for dividing the steam chamber area is 1026, the number of grids for the condensation area is 519, the number of grids for the heating area is 426, and the number of grids for the unheated area is 324.

[0030] S3. Calculate the comprehensive value of heat utilization based on the heat loss, produced fluid carryover, and heat absorption ratio of each area in the reservoir and their weights.

[0031] Furthermore, the total heat injected into the reservoir for thermal recovery is calculated based on the obtained steam injection parameters: (1); Where Q total is the total heat injected, kJ; V steam is the steam injection rate, m 3 / d; x is the steam dryness; h g is the saturated steam enthalpy, kJ / kg; h f is the saturated water enthalpy, kJ / kg; Δt is the time, d.

[0032] Furthermore, the ratio of heat loss to total heat input is calculated using the following formula: (2); (3); Where Q loss is the heat loss, kJ; ko is the number of grids corresponding to the cap layer area in the numerical model; C so is the specific heat capacity of the cap layer, kJ / (m 3 ·℃);ρ so is the density of the cap rock, kg / m 3 ; V soi is the grid volume of the i-th cover layer, m 3 ; ΔT soi is the temperature change of the grid in the i-th cover layer, ℃; k so is the thermal conductivity of the cap layer, kJ / (m·d·℃); A soi is the grid area of ​​the i-th cover layer, m 2 ;d soi is the grid thickness of the cap layer, m; ku is the number of grids corresponding to the underlying stratum area in the numerical model; C su is the specific heat capacity of the underlying stratum, kJ / (m 3 ·℃);ρ su is the rock density of the underlying stratum, kg / m 3 ; V sui is the grid volume of the underlying stratum i, m 3 ; ΔT suiis the temperature change of the underlying stratum grid, ℃; k su is the underlying thermal conductivity, kJ / (m·d·℃); A sui is the grid area of ​​the underlying stratum i, m 2 ;d sui is the thickness of the underlying grid, m; M loss is the heat loss ratio, %.

[0033] Furthermore, the heat carried by the fluid production can be calculated by the fluid production rate and the temperature of the produced fluid. The temperature of the produced fluid is the temperature of the production well grid in the numerical model. The heat carried by the fluid and its proportion of the total injected heat are calculated using the following formula: (4); (5); Where Q carry Carrying heat for the produced fluid, kJ; C o is the specific heat capacity of formation oil, kJ / (kg·℃); C w is the specific heat capacity of formation water, kJ / (kg·℃); Q o is the cumulative oil production, m 3 ;Q w is the cumulative water production, m 3 ρ o is the density of crude oil, kg / m 3 ρ w is the density of produced water, kg / m 3 ; ΔT is the difference between the temperature of the grid where the production well is located and the formation temperature, ℃; M carry It is the percentage of heat carried by the produced fluid.

[0034] Furthermore, the heat of the condensation zone in the reservoir heating and its proportion to the total injected heat are calculated using the following formula: (6); (7); Where Q con is the heat of the condensation zone, kJ; k1 is the number of grids corresponding to the condensation zone in the numerical simulation results; V ci is the grid volume of condensation region i, m 3 ; ΔT ci is the temperature change of grid i in condensation zone, ℃; is the mesh porosity of condensation zone i; S coi is the oil saturation of grid i in the condensation zone; S cwi is the water saturation of grid i in the condensation zone; ρ s is the rock density, kg / m 3 ; C sis the specific heat capacity of reservoir rock, kJ / (kg·℃); M con It is the percentage of heat carried by the produced fluid.

[0035] Furthermore, the heat of the heated area in the heated reservoir and its proportion of the total injected heat are calculated using the following formula: (8); (9); Where Q heat is the heat distribution in the heating zone, kJ; k2 is the number of grids corresponding to the heating zone in the numerical simulation results; V hi is the grid volume of heating area i, m 3 ; ΔT hi is the temperature change of the grid in the heating zone i, ℃; is the mesh porosity of heating zone i; S hoi is the oil saturation of grid i in the heating area; S hwi is the water saturation of the grid in the heating zone i.

[0036] Furthermore, the proportion of the heat distributed in the steam chamber to the total heat injected in the heated reservoir is calculated using the following formula: (10).

[0037] The comprehensive value of heat utilization is calculated using the following formula.

[0038] (11); Among them, w1, w2, w3, w4, and w5 are the weight coefficients of the heat share of each area. Taking the internal rate of return as the target variable, a multivariate linear regression model is established, and the weight coefficients are determined by the least squares method to be 0.4, 0.3, 0.1, 0.1, and 0.1, respectively.

[0039] S4. Set different injection parameters and repeat the above steps.

[0040] Furthermore, the calculation results of the steam injection parameters in steps S3 and S4 are shown in Table 2.

[0041] Table 2 Optimization results of different steam injection rates

[0042] It can be seen from the above table that the comprehensive value of heat utilization is positively correlated with the corresponding output per unit steam, proving that the comprehensive value of heat utilization calculated in this embodiment has a certain degree of accuracy. Through data comparison, it can be seen that increasing the steam injection rate increases the degree of recovery, but after increasing to a certain value, the steam injected into the formation is recovered without effectively conducting heat, and more heat goes to the produced fluid, and more heat accumulates in the steam chamber range, and the formation fluid is not effectively heated, so that after the steam injection rate increases to a certain value, the degree of recovery is basically the same, but the corresponding output per unit steam is reduced. According to the traditional parameter optimization method, parameters with a higher degree of recovery are usually adopted, resulting in low effective heat utilization and diminishing marginal benefits. The method provided by the present invention accurately controls the heat share of each region, ensures that the heat is more concentrated in the effective heating area and the condensation area, maximizes the thermal recovery effect, and gives full play to the efficient utilization of steam heat.

[0043] Finally, it should be noted that the above-described embodiments are intended to help readers understand the implementation methods of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and implementation examples. A person skilled in the art can make various other specific variations and combinations based on the technical inspirations disclosed by the present invention without departing from the essence of the present invention, and these variations and combinations are still within the protection scope of the present invention.

[0044] The above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for optimizing injection parameters based on heat distribution, characterized in that: The specific steps include: S1. Establish a numerical model for heavy oil thermal recovery reservoirs; S2. Input steam injection parameters, divide the injected heat into three parts: heat loss, produced fluid carryover and reservoir absorption, and divide the reservoir absorption part into steam chamber, condensation zone, heating zone and unheated zone; S3. Calculate the comprehensive value of heat utilization according to the proportion of each injected heat to the total injected heat and its weight; S4. Set different steam injection parameters, repeat steps S2 and S3, compare the comprehensive heat utilization values ​​under various injection parameter conditions, and finally output the steam injection parameter corresponding to the maximum value of the comprehensive heat utilization value; The steam injection parameters include steam injection rate, injection pressure, and steam quality.

2. The method for optimizing injection parameters based on heat distribution according to claim 1, characterized in that: In step S2, the absorption part of the reservoir is divided into a steam chamber, a condensation zone, a heating zone and an unheated zone in combination with the heavy oil thermal recovery reservoir numerical model in step S1. The division criteria are: The area with a temperature greater than temperature T is the steam chamber; The area between the limit M and the limit N is the condensation area; The temperature rise area minus the steam chamber and condensation area is the heating area; The area where the temperature does not rise is the unheated area; The temperature T is the saturated steam temperature corresponding to the reservoir pressure during production; The limit M is the limit where the vapor saturation is zero; The limit N is the limit of the reservoir pressure corresponding to the saturated gas temperature during production.

3. The method for optimizing injection parameters based on heat distribution according to claim 1, characterized in that: In step S3, the calculation formula of the comprehensive value of heat utilization is: （11）； Among them, HEI is the comprehensive value of heat utilization, w1 is the weight coefficient of the heat share of the condensation zone, w2 is the weight coefficient of the heat share of the heating zone, w3 is the weight coefficient of the heat share of the steam chamber, w4 is the weight coefficient of the heat share of heat loss, and w5 is the weight coefficient of the heat share carried by the output fluid; The method for determining the weight coefficient is as follows: taking the internal rate of return as the target variable, establishing a multiple linear regression model of the heat proportion of each part and the target variable, and using the least squares method to determine each weight coefficient.

4. The method for optimizing injection parameters based on heat distribution according to claim 3, characterized in that: Calculate the total heat injected into the reservoir based on the obtained steam injection parameters: （1）； Where Q total is the total heat injected, kJ; V steam is the steam injection rate, m 3 / d; x is the steam dryness; h g is the saturated steam enthalpy, kJ / kg; h f is the saturated water enthalpy, kJ / kg; Δt is the time, d.

5. The method for optimizing injection parameters based on heat distribution according to claim 4, characterized in that: In step S3, the heat loss part includes: the heat dissipated by the cover layer and the underlying strata in the form of heat conduction, and the heat absorbed by the cover layer and the underlying strata. The heat loss heat and its proportion to the total heat injected are: （2）； （3）； Where Q loss is the heat loss, kJ; ko is the number of grids corresponding to the cap layer area in the numerical model; C so is the specific heat capacity of the cap layer, kJ / (m 3 ·℃);ρ so is the density of the cap rock, kg / m 3 ; V soi is the grid volume of the i-th cover layer, m 3 ; ΔT soi is the temperature change of the cover layer grid, ℃; k so is the thermal conductivity of the cap layer, kJ / (m·d·℃); A soi is the grid area of ​​the i-th cover layer, m 2 ;d soi is the grid thickness of the cap layer, m; ku is the number of grids corresponding to the underlying stratum area in the numerical model; C su is the specific heat capacity of the underlying stratum, kJ / (m 3 ·℃);ρ su is the rock density of the underlying stratum, kg / m 3 ; V sui is the grid volume of the underlying stratum i, m 3 ; ΔT sui is the temperature change of the underlying stratum grid, ℃; k su is the underlying thermal conductivity, kJ / (m·d·℃); A sui is the grid area of ​​the underlying stratum i, m 2 ;d sui is the thickness of the underlying grid, m; M loss is the heat loss ratio, %.

6. The method for optimizing injection parameters based on heat distribution according to claim 4, characterized in that: In step S3, the heat carried by the output fluid and its proportion to the total heat injected are: （4）； （5）； Where Q carry Carrying heat for the produced fluid, kJ; C o is the specific heat capacity of formation oil, kJ / (kg·℃); C w is the specific heat capacity of formation water, kJ / (kg·℃); Q o is the cumulative oil production, m 3 ;Q w is the cumulative water production, m 3 ; ρ o is the density of crude oil, kg / m 3 ; ρ w is the density of produced water, kg / m 3 ; ΔT is the difference between the temperature of the grid where the production well is located and the formation temperature, ℃; M carry It is the percentage of heat carried by the produced fluid.

7. The method for optimizing injection parameters based on heat distribution according to claim 4, characterized in that: In the reservoir absorption part, the heat of the condensation zone and its proportion of the total injected heat are calculated using the following formula: （6）； （7）； Where Q con is the heat of the condensation zone, kJ; k1 is the number of grids corresponding to the condensation zone in the numerical simulation results; V ci is the grid volume of condensation region i, m 3 ; ΔT ci is the temperature change of grid i in condensation zone, ℃; is the mesh porosity of condensation zone i; S coi is the oil saturation of grid i in the condensation zone; S cwi is the water saturation of grid i in the condensation zone; ρ s is the rock density, kg / m 3 ; C s is the specific heat capacity of reservoir rock, kJ / (kg·℃); M con It is the percentage of heat carried by the produced fluid.

8. The method for optimizing injection parameters based on heat distribution according to claim 4, characterized in that: The absorption part of the reservoir, the heat in the heating zone and its proportion to the total injected heat are calculated using the following formula: （8）； （9）； Where Q heat is the heat distribution in the heating zone, kJ; k2 is the number of grids corresponding to the heating zone in the numerical simulation results; V hi is the grid volume of heating area i, m 3 ; ΔT hi is the temperature change of the grid in the heating zone i, ℃; is the mesh porosity of heating zone i; S hoi is the oil saturation of grid i in the heating area; S hwi is the water saturation of the grid in the heating zone i.

9. The method for optimizing injection parameters based on heat distribution according to claim 4, characterized in that: In the reservoir absorption part, the proportion of steam chamber heat to the total injected heat is calculated using the following formula: （10）。 10. The method for optimizing injection parameters based on heat distribution according to any one of claims 1 to 9, characterized in that: The method for optimizing injection parameters based on heat distribution is applicable to heavy oil reservoirs for steam injection thermal recovery.

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