A Method for Optimizing Injection Parameters Based on Heat Distribution

Abstract

The present invention relates to the technical field of heavy oil exploitation, and specifically provides a method for optimizing injection parameters based on heat distribution. During the heavy oil thermal recovery process of the present invention, by dividing the injected heat into different parts and calculating the heat proportion and weight of each part, the optimal injection parameters are found to reduce the ineffective use of steam, improve the thermal efficiency, optimize the steam injection cost, and improve the development benefit.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy oil exploitation, and specifically to a method for optimizing injection parameters based on heat distribution. Background Art

[0002] With the inevitable and increasing depletion of conventional light oil reservoirs and the further prominence of the domestic crude oil supply-demand contradiction, heavy oil has become the main field 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 for surface degassed crude oil, and has the characteristics of high viscosity and high density. Compared with conventional light oil, heavy oil has a high content of gum and asphaltene, high viscosity and poor fluidity, resulting in a huge flow resistance in the formation, which is the root cause of the development problem of heavy oil.

[0003] Heavy oil has strong thermosensitive characteristics. It is generally believed that when the temperature rises by 10°C, the viscosity of heavy oil can be reduced by half. Therefore, thermal oil recovery occupies the dominant mode of heavy oil development, including steam stimulation, steam flooding, SAGD and other methods. Injecting high-quality and superheated steam into the formation to reduce the viscosity of heavy oil by transferring heat is the underlying logic of heavy oil thermal recovery. Reasonable utilization of steam is an essential link in heavy oil thermal recovery. Chinese Patent CN 117287164 A discloses a method and system for optimizing steam injection allocation in heavy oil exploitation in oilfields. By tracking historical development indicators and analyzing and evaluating the quality and effect of steam injection, steam injection parameters are determined. Chinese Patent CN 118673784 A discloses a method for optimizing steam stimulation parameters for heavy oil, determining the main control factors of steam injection parameters and geological parameters, and inputting them into a Bayesian neural network model to optimize the steam injection parameters. Chinese Patent CN 117927203 A discloses a method and related equipment for optimizing injection media and parameters for super heavy oil steam stimulation. By calculating the deficit volume, deficit rock characteristics and steam heat release, steam injection parameters are determined. The above optimizations of steam injection parameters for heavy oil thermal recovery all determine the steam injection parameters according to geological parameters and historical production characteristics, ignoring the relationship between the heat distribution after steam injection into the formation and the injection parameters, resulting in a low steam thermal utilization rate and ineffective use of heat. Heat is the core of heavy oil thermal recovery, heat distribution is the key to the effective utilization of steam heat, and also an important way to reduce costs and increase efficiency in heavy oil exploitation.

[0004] Therefore, when applying heavy oil thermal recovery technology, it is urgent to optimize the steam injection parameters according to the heat distribution characteristics of the reservoir, avoid the diminishing marginal effect, maximize the heat injected by steam, increase the amount of heavy oil produced per unit steam, and improve the overall efficiency of heavy oil exploitation. 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. During the heavy oil thermal recovery process, by calculating the heat distribution characteristics under different injection parameters, the optimal injection parameters are found to reduce the ineffective use of steam, improve the thermal efficiency, optimize the steam injection cost, and improve the development benefit.

[0006] A method for optimizing injection parameters based on heat distribution specifically includes the following steps:

[0007] S1. Establish a numerical model of the heavy oil thermal recovery reservoir;

[0008] S2. Input the steam injection parameters. The injected heat is divided into three parts: heat loss, heat carried by the produced fluid, and heat absorbed by the reservoir. The heat absorbed by the reservoir is further divided into a steam chamber, a condensation zone, a heating zone, and an unheated zone;

[0009] S3. Calculate the comprehensive heat utilization value according to the proportion of each injected heat in the total injected heat and its weight;

[0010] S4. Set different steam injection parameters, repeat steps S2 and S3, compare the comprehensive heat utilization values under different injection parameter conditions, and finally output the steam injection parameters corresponding to the maximum value of the comprehensive heat utilization value.

[0011] Preferably, according to the historical development data of the oilfield, the numerical model of the heavy oil thermal recovery reservoir is optimized by history matching;

[0012] During application, refer to the production situation of the reservoir in the target block of the oilfield to specify the model operating system. Analyze the historical production indicators and optimize the adjustable parameters within the adjustable range to obtain a numerical simulation model that conforms to the reservoir in the target block.

[0013] Furthermore, the steam injection parameters include steam injection rate, injection pressure, and steam quality.

[0014] Furthermore, in step S2, the heat loss refers to the heat absorbed by the reservoir caprock and the underlying formation, and the heat carried by the produced fluid refers to the heat carried by the fluid (oil, water) produced to the surface.

[0015] During the heavy oil development process, a high temperature is maintained in the formed steam chamber. The injected superheated high-quality steam enters the steam chamber, making 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 zone has a high water saturation characteristic. In step S2, in combination with the numerical model of the heavy oil thermal recovery reservoir in step S1, the reservoir is divided into a steam chamber, a condensation zone, a heating zone, and an unheated zone. The division criteria are as follows:

[0016] The area with a temperature higher than T is the steam chamber;

[0017] The T is the saturation vapor temperature corresponding to the reservoir pressure during production;

[0018] The area between the boundary M and the boundary N is the condensation zone;

[0019] The boundary M is the boundary with zero vapor saturation;

[0020] The boundary N is the boundary of the saturation vapor temperature corresponding to the reservoir pressure during production.

[0021] The heating area is obtained by subtracting the steam chamber and the condensation zone from the temperature rising area;

[0022] The area where the temperature does not rise is the unheated area.

[0023] Further, the specific process of the step S3 is as follows:

[0024] S3.1 Calculate the total heat injection for reservoir thermal recovery according to the obtained steam injection parameters:

[0025] (1);

[0026] In the formula, Q total is the total heat injection, kJ; V steam is the steam injection rate, m 3 / d; x is the steam quality; h g is the enthalpy value of saturated steam, kJ / kg; h f is the enthalpy value of saturated water, kJ / kg; Δt is the time, d.

[0027] S3.2 The heat loss part includes: the heat dissipated by heat conduction through the caprock and the underlying formation, the heat absorbed by the caprock and the underlying formation. The heat loss and its proportion in the total heat injection are:

[0028] (2);

[0029] (3);

[0030] In the formula, Q loss is the heat loss, kJ; ko is the number of grids corresponding to the caprock area in the numerical model; C so is the specific heat capacity of the caprock, kJ / (m 3 ·°C); ρ so is the density of the caprock rock, kg / m 3 ; V soi is the volume of the i-th caprock grid, m 3 ; ΔT soi is the temperature change value of the i-th caprock grid, °C; k sois the caprock thermal conductivity, kJ / (m·d·°C); A soi is the grid area of the i-th caprock, m 2 ; d soi is the grid thickness of the i-th caprock, m; ku is the number of grids corresponding to the underlying formation area in the numerical model; C su is the specific heat capacity of the underlying formation, kJ / (m 3 ·°C); ρ su is the rock density of the underlying formation, kg / m 3 ; V sui is the grid volume of the i-th underlying formation, m 3 ; ΔT sui is the temperature change value of the i-th underlying formation grid, °C; k su is the underlying thermal conductivity, kJ / (m·d·°C); A sui is the grid area of the i-th underlying formation, m 2 ; d sui is the thickness of the i-th underlying grid, m; M loss is the proportion of heat loss, %.

[0031] S3.3 The heat carried by the produced fluid can be calculated through 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 in the total injected heat are:

[0032] (4);

[0033] (5);

[0034] In the formula, Q carry is the heat carried by the produced fluid, kJ; C o is the specific heat capacity of formation oil, kJ / (kg·°C); C w is the specific heat capacity of formation water, kJ / (kg·°C); Q o is the cumulative oil production, m 3 ; Q w is the cumulative water production, m 3 ; ρ o is the crude oil density, kg / m 3 ; ρ w is the produced water density, kg / m 3 ; ΔT is the temperature difference between the grid where the production well is located and the formation temperature, °C; M carry is the proportion of the heat carried by the produced fluid.

[0035] S3.4 For the part absorbed by the reservoir, the heat in the condensation zone and its proportion in the total injected heat are calculated using the following formula:

[0036] (6);

[0037] (7);

[0038] Where Q con is the heat in the condensation zone, kJ; k1 is the number of grids corresponding to the condensation zone in the numerical simulation result; V ci is the volume of grid i in the condensation zone, m 3 ; ΔT ci is the temperature change value of grid i in the condensation zone, °C; is the porosity of grid i in the condensation zone; 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 the reservoir rock, kJ / (kg·°C); M con is the proportion of the heat carried by the produced fluid.

[0039] For the absorption part of the S3.5 reservoir, the heat in the heating zone and its proportion in the total injected heat are calculated using the following formulas:

[0040] (8);

[0041] (9);

[0042] Where Q heat is the distributed heat in the heating zone, kJ; k2 is the number of grids corresponding to the heating zone in the numerical simulation result; V hi is the volume of grid i in the heating zone, m 3 ; ΔT hi is the temperature change value of grid i in the heating zone, °C; is the porosity of grid i in the heating zone; S hoi is the oil saturation of grid i in the heating zone; S hwi is the water saturation of grid i in the heating zone.

[0043] For the absorption part of the S3.6 reservoir, the proportion of the heat in the steam chamber in the total injected heat is calculated using the following formula:

[0044] (10);

[0045] Furthermore, the calculation formula for the comprehensive heat utilization value (HEI) is:

[0046] (11);

[0047] Where, w 1 is the weight coefficient of the proportion of the heat in the condensation zone, w 2 is the weight coefficient of the proportion of the heat in the heating zone, w3 is the weight coefficient of the heat proportion in the steam chamber, w 4 is the weight coefficient of the heat loss proportion, w 5 is the weight coefficient of the heat carried by the produced 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 the specific values of each weight.

[0048] Further, the w 1 、w 2 、w 3 、w 4 、w 5 need to meet the normalization condition and positive value constraint to ensure that the contributions of the heat proportions of each part are proportional and avoid unreasonable evaluation results caused by one item being too heavy.

[0049] Although the weight coefficient can be set through experience and theoretical analysis in the preliminary design, in actual applications, according to the geological characteristics of different reservoirs, steam injection methods and production requirements, the weight coefficient can be appropriately adjusted. Through numerical simulation, experimental verification and field application, the weight coefficient is optimized to improve the accuracy and practicability of the comprehensive heat utilization value (HEI).

[0050] Preferably, the reservoir applicable to the method for optimizing injection parameters based on heat distribution is a heavy oil reservoir for steam injection thermal recovery.

[0051] The beneficial effects of the present invention are as follows:

[0052] (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 the steam injection process often lacks systematic optimization, resulting in the heat not being fully and effectively transferred to the oil layer. Especially in the steam chamber area, heat accumulation is serious, causing uneven heating effects. Different from the prior art, the present invention precisely controls the heat proportion of each area through a scientific heat distribution optimization method, ensuring that the heat is more concentrated in the effective heating area and the condensation area, maximizing the thermal recovery effect, and thus significantly improving the overall heat utilization efficiency.

[0053] (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 economy of the thermal recovery process. The present invention can effectively identify and reduce heat loss by precisely calculating and optimizing the heat loss proportion, apply more heat effectively to oil layer heating, significantly reduce energy consumption, and improve energy efficiency.

[0054] (3) The method provided by the present invention breaks through the shackles of traditional steam injection parameters optimized only by production. The prior art adjusts injection parameters solely by increasing production, ignoring the rationality of heat distribution, resulting in diminishing marginal benefits. In contrast, the present invention proposes a more precise steam injection parameter optimization scheme by comprehensively evaluating the heat proportion in each region, achieving the maximum utilization of steam heat, thereby improving the oil reservoir recovery factor and enhancing the overall economic efficiency of the oilfield. Description of the Drawings

[0055] Figure 1 It is a flow chart of the method for optimizing injection parameters based on heat distribution;

[0056] Figure 2 It is a three-dimensional numerical model diagram of a heavy oil SAGD thermal recovery reservoir in Example 1;

[0057] Figure 3 It is the heavy oil SAGD thermal recovery temperature field in Example 1;

[0058] Figure 4 It is the heavy oil SAGD thermal recovery water saturation field in Example 1;

[0059] Figure 5 It is the heavy oil SAGD thermal recovery steam saturation field in Example 1. Detailed Embodiment

[0060] The following further elaborates on the present invention in conjunction with the drawings and specific embodiments:

[0061] Example 1

[0062] Referring to Figure 1 , a method for optimizing injection parameters based on heat distribution is provided. In this example, a certain block in the Xinjiang Oilfield is taken as an example. This oilfield block is a heavy oil reservoir with an average porosity of 32%, and the viscosity of crude oil at 50 °C is about 20,000 mPa·s. The development is difficult. The SAGD development method is adopted. Limited by on-site process measures, the fixed steam dryness is 0.8, the temperature is 250 °C, and the injection pressure is 0.7 MPa. It is necessary to optimize the steam injection rate.

[0063] A method for optimizing injection parameters based on heat distribution specifically includes the following steps:

[0064] S1. Establish a numerical model of a heavy oil thermal recovery reservoir:

[0065] Further, in application, the geological characteristics, crude oil physical 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 field data to establish a numerical model of a heavy oil thermal recovery reservoir. The specific reservoir parameters are shown in Table 1:

[0066] Table 1 Reservoir Parameters

[0067] Parameter Parameter value Model size 51m × 400m × 45m Top depth of the model 180m Permeability 2000mD Porosity 0.32 Oil saturation 0.72 Formation temperature 20℃ Formation pressure 2.3MPa

[0068] A three-dimensional numerical model for heavy oil SAGD thermal recovery is established based on reservoir parameter information. Further, according to the historical production data of the field, historical fitting optimization is carried out on the numerical model of the heavy oil thermal recovery reservoir. The optimized three-dimensional numerical model of the heavy oil thermal recovery reservoir for SAGD thermal recovery is as shown in Figure 2 . In the figure, the color represents the top depth of the reservoir in each grid, and the top depth of the reservoir in the grid increases successively from top to bottom.

[0069] S2. Set the steam injection rate to 75 m 3 / d. According to the heat destination of the injected steam, the total injected heat is divided into heat loss, heat carried by the produced fluid, and heat absorbed by the reservoir, and the reservoir grid is divided into regions according to the division criteria.

[0070] As shown in Figures 3 - 5 are the diagrams of the temperature field, water saturation field, and steam saturation field of heavy oil SAGD thermal recovery obtained after running the three-dimensional numerical model of heavy oil SAGD thermal recovery. 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 region maintains a high steam saturation, and the water saturation increases after the temperature drops to the saturated steam temperature. The division criteria for each region in this embodiment are determined as follows:

[0071] The region where the temperature is greater than the saturated steam temperature corresponding to the reservoir pressure during production is the steam chamber;

[0072] The region between the zero limit of steam saturation and the saturated steam temperature limit corresponding to the reservoir pressure during production is the condensation zone;

[0073] The heating zone is the temperature-rising region minus the steam chamber and the condensation zone;

[0074] The region where the temperature has not risen is the unheated zone.

[0075] Further, the total number of grids is 2295, the number of grids in the steam chamber region is 1026, the number of grids in the condensation zone is 519, the number of grids in the heating zone is 426, and the number of grids in the unheated zone is 324.

[0076] S3. Calculate the comprehensive heat utilization value according to the heat proportion and its weight of each region of heat loss, heat carried by the produced fluid, and heat absorbed by the reservoir.

[0077] Further, calculate the total injected heat for reservoir thermal recovery according to the obtained steam injection parameters:

[0078] (1);

[0079] In the formula, Qtotal is the total injected heat, kJ; V steam is the steam injection rate, m 3 / d; x is the steam quality; h g is the enthalpy of saturated steam, kJ / kg; h f is the enthalpy of saturated water, kJ / kg; Δt is the time, d.

[0080] Furthermore, the proportion of heat loss in the total injected heat is calculated by the following formula:

[0081] (2);

[0082] (3);

[0083] where Q loss is the heat loss, kJ; ko is the number of grids corresponding to the caprock area in the numerical model; C so is the specific heat capacity of the caprock, kJ / (m 3 ·°C); ρ so is the density of the caprock rock, kg / m 3 ; V soi is the volume of the i-th caprock grid, m 3 ; ΔT soi is the temperature change value of the i-th caprock grid, °C; k so is the thermal conductivity of the caprock, kJ / (m·d·°C); A soi is the area of the i-th caprock grid, m 2 ; d soi is the thickness of the i-th caprock grid, m; ku is the number of grids corresponding to the underlying formation area in the numerical model; C su is the specific heat capacity of the underlying formation, kJ / (m 3 ·°C); ρ su is the density of the underlying formation rock, kg / m 3 ; V sui is the volume of the i-th underlying formation grid, m 3 ; ΔT sui is the temperature change value of the i-th underlying formation grid, °C; k su is the underlying thermal conductivity, kJ / (m·d·°C); A sui is the area of the i-th underlying formation grid, m 2 ; d sui is the thickness of the i-th underlying grid, m; M loss is the proportion of heat loss, %.

[0084] Furthermore, the heat carried by the fluid production can be calculated from the fluid production rate and the temperature of the produced fluid. The temperature of the produced fluid is the temperature at the grid of the production well in the numerical model. The heat carried by the fluid and its proportion of the total injected heat are calculated using the following formulas:

[0085] (4);

[0086] (5);

[0087] In the formula, Q carry is the heat carried by the produced fluid, kJ; C o is the specific heat capacity of formation oil, kJ / (kg·°C); C w is the specific heat capacity of formation water, kJ / (kg·°C); Q o is the cumulative oil production, m 3 ; Q w is the cumulative water production, m 3 ; ρ o is the crude oil density, kg / m 3 ; ρ w is the produced water density, kg / m 3 ; ΔT is the temperature difference between the grid where the production well is located and the formation temperature, °C; M carry is the proportion of the heat carried by the produced fluid.

[0088] Furthermore, the heat in the condensation zone in the heat for heating the reservoir and its proportion of the total injected heat are calculated using the following formulas:

[0089] (6);

[0090] (7);

[0091] In the formula, Q con is the heat in the condensation zone, kJ; k1 is the number of grids corresponding to the condensation zone in the numerical simulation result; V ci is the volume of grid i in the condensation zone, m 3 ; ΔT ci is the temperature change value of grid i in the condensation zone, °C; is the porosity of grid i in the condensation zone; 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 the reservoir rock, kJ / (kg·°C); M con is the proportion of the heat carried by the produced fluid.

[0092] Furthermore, the heat in the heated zone of the reservoir and its proportion of the total injected heat are calculated using the following formulas:

[0093] (8);

[0094] (9);

[0095] Where Q heat is the distributed heat in the heated zone, kJ; k2 is the number of grids corresponding to the heated zone in the numerical simulation results; V hi is the grid volume of the heated area i, m 3 ; ΔT hi is the temperature change value of the grid in the heated zone i, °C; is the porosity of the grid in the heated zone i; S hoi is the oil saturation of the grid in the heated zone i; S hwi is the water saturation of the grid in the heated zone i.

[0096] Furthermore, the proportion of the distributed heat in the steam chamber in the heated reservoir to the total injected heat is calculated using the following formula:

[0097] (10).

[0098] The comprehensive heat utilization value is calculated using the following formula.

[0099] (11);

[0100] Where w 1 , w 2 , w 3 , w 4 , w 5 are the weight coefficients of the heat proportions in each region. Taking the internal rate of return as the target variable, a multiple linear regression model is established, and the weight coefficients are determined to be 0.4, 0.3, 0.1, 0.1, 0.1 by solving using the least squares method.

[0101] S4. Set different injection parameters and repeat the above steps.

[0102] Furthermore, the calculation results of the steam injection parameters in steps S3 and S4 are shown in Table 2.

[0103] Table 2 Optimization results of different steam injection rates

[0104]

[0105] As can be seen from the above table, the comprehensive heat utilization value is positively correlated with the corresponding output of unit steam, which proves that the comprehensive heat utilization value 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 recovery degree. However, after increasing to a certain value, the steam injected into the formation is produced without effectively conducting heat, more heat goes to the produced fluid, and more heat accumulates in the steam chamber range, without effectively heating the formation fluid. As a result, after the steam injection rate increases to a certain value, the recovery degree is basically the same, but the corresponding output of unit steam decreases. According to the traditional method of optimizing parameters, parameters with a higher recovery degree are usually adopted, resulting in a low effective heat utilization rate and a decreasing marginal benefit. The method provided by the present invention precisely controls the heat proportion in 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.

[0106] Finally, it should be noted that the above embodiments are intended to help readers understand the implementation method 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 embodiments. Those of ordinary skill in the art can make various specific deformations and combinations that do not depart from the essence of the present invention based on the technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

[0107] 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 those skilled in the art within the essence 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; 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, and 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; In step S3, the calculation formula of the comprehensive value of heat utilization is: （11）； 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, w5 is the weight coefficient of the heat share of the output fluid, M con is the heat ratio of the produced fluid, M heat is the ratio of the heat in the heating zone to the total heat input, M steam is the ratio of steam chamber heat to total heat input, M loss is the heat loss ratio, M carry The percentage of heat carried by the produced fluid; The method for determining the weight coefficient is as follows: 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 each weight coefficient; 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; 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, %.

2. The method for optimizing injection parameters based on heat distribution according to claim 1, 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.

3. The method for optimizing injection parameters based on heat distribution according to claim 1, 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.

4. The method for optimizing injection parameters based on heat distribution according to claim 1, 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.

5. The method for optimizing injection parameters based on heat distribution according to claim 1, 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）。 6. The method for optimizing injection parameters based on heat distribution according to any one of claims 1 to 5, 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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