Quantitative prediction method for expansion front of heating cavity in thick-layer heavy oil horizontal wells using steam stimulation

Abstract

The present invention discloses a quantitative prediction method for the expansion front of a heating chamber in a thick-layer heavy oil horizontal well during steam stimulation. The method comprises the following steps: dividing the horizontal well into i segments and calculating the coordinates of the nodes in each segment; calculating the steam absorption capacity of each node based on the quadratic function distribution of steam along the horizontal well; calculating the radius of the steam zone and the radius of the thermal fluid zone at each node, and correcting the steam chamber based on the difference in heat transfer capacity between the vertical and horizontal directions of the oil layer; calculating the average temperature of the two zones during the injection phase based on the thermal balance of the oil layer; calculating the average temperature and radius of the thermal fluid zone during the well soaking phase; calculating the average temperature of the thermal fluid zone during the production phase; calculating the radius and residual heat of the thermal fluid zone during the production phase; repeating the operation using the final temperature and residual heat of the previous cycle as initial conditions, and outputting the calculation results for the next cycle. The method can accurately predict the radii of the steam zone and the thermal fluid zone during the steam stimulation process of a horizontal well, has strong operability, and more accurately describes the steam chamber development characteristics during the steam stimulation process.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and in particular relates to a method for quantitatively predicting the expansion front of a steam huff-and-puff heating cavity in a thick-layer heavy oil horizontal well. Background Art

[0002] Steam injection is currently a widely used technology for enhancing the recovery of heavy oil. Unlike directional well development in onshore oilfields, offshore oilfields primarily utilize horizontal wells, based on the "few wells, high yield, high-speed, rapid recovery" strategy. Compared to vertical wells, horizontal wells have a larger drainage area and larger cyclic steam injection volumes, resulting in higher single-well productivity. Accurately predicting the development of steam chambers along horizontal wells is crucial for actual production, and quantitatively predicting the expansion front of the heating chamber during steam stimulation is essential for accurately characterizing the steam chamber development pattern. Previous research has established mathematical models to calculate the heating radius of vertical wells during steam stimulation. Researchers have considered the non-isothermal distribution of formation temperature in the heating zone and developed new mathematical models for the heating radius of vertical wells. Furthermore, other studies, based on plane potential theory, have considered the effects of steam overburden and established models for the movement of the steam front in vertical wells. While the heating radius calculation model for vertical wells cannot be directly applied to horizontal wells, researchers have developed corresponding steam injection and heating radius calculation models based on the vertical well heating radius calculation model, providing a reference for horizontal well productivity prediction and heating chamber characterization. Existing heating zone radius calculation models commonly treat the formation heating range along the horizontal well as fixed. They fail to account for steam injection losses caused by steam absorption and wellbore flow along the wellbore. They also fail to consider the differences in horizontal and vertical heat transfer velocities within the steam chamber due to differences in gasoline density across the steam chamber cross-section. Furthermore, they fail to consider the impact of the start-up pressure gradient in the formation flow model surrounding the wellbore. These three factors combined can lead to significant discrepancies between the calculated steam or thermal fluid zones and actual oilfield conditions. Consequently, there is currently no comprehensive research that comprehensively considers the effects of differences in steam absorption along the wellbore, differences in horizontal and vertical heat transfer capacity, and the start-up pressure gradient on the heating radius during horizontal well steam stimulation. Summary of the Invention

[0003] The present invention is proposed to solve the problems existing in the prior art, and its purpose is to provide a method for quantitatively predicting the expansion front of the steam stimulation heating cavity in thick-layer heavy oil horizontal wells.

[0004] The present invention is achieved through the following technical solutions:

[0005] A method for quantitatively predicting the expansion front of a steam stimulation heating chamber in a thick-layer heavy oil horizontal well comprises the following steps:

[0006] S1. Divide the horizontal well into N segments according to unit length and calculate the node coordinates of each segment;

[0007] S2. Calculate the steam absorption capacity of each node based on the quadratic function distribution of steam along the horizontal well;

[0008] S3. Calculate the steam zone radius and the hot fluid zone radius of each node, and modify the steam cavity according to the difference in heat transfer capacity between the vertical and horizontal directions of the oil layer;

[0009] S4. Considering the heat dissipation effect of the steam zone and the hot fluid zone, calculate the average temperature of the steam zone and the hot fluid zone during steam injection based on the thermal balance of the oil layer;

[0010] S5. Considering the influence of heat conduction, calculate the average temperature and radius of the hot fluid zone during the soaking stage;

[0011] S6. Calculate the average temperature of the thermal fluid zone during the production phase based on the thermal balance between oil layer injection and production;

[0012] S7. Considering the heat carrying and heat dissipation effects of the produced thermal fluid, calculate the radius of the thermal fluid zone and the residual heat during the production phase;

[0013] S8. Using the final temperature and residual heat of the previous round as initial conditions, repeat steps 2 to 7 and output the calculation results for the next round.

[0014] In the above technical solution, the method for calculating the steam absorption amount of each node in step S2 is specifically as follows: considering that the steam absorption amount along the wellbore from the injection end to the finger end is distributed as a quadratic function, the calculation equation for the absorption amount of a certain node is:

[0015] Q i =Q*(10 -5 *L 2 -0.0047*L+1.0191)ε / 100 (1)

[0016] Where: Q i is the steam absorption volume at a certain node of the horizontal well, in t / d; Q is the total daily steam injection volume, in t / d; L is the distance from the node to the injection end, in m; ε is a correction function related to the length of the horizontal well; Where L is the distance from the node to the injection end, in meters; N refers to the horizontal well being divided into N segments by length, dimensionless; i refers to the i-th node, i.e., the i-th segment, dimensionless.

[0017] In the above technical solution, the method for calculating the steam zone radius and the thermal fluid zone radius of each node in step S3 is as follows: the heating zone is divided into a thermal fluid zone and a steam zone, and each zone is divided into three stages according to whether it reaches the boundary, and the steam zone radius and the thermal fluid zone radius of each node in the three stages are calculated respectively;

[0018] S31. The calculation method of the steam zone radius and the hot fluid zone radius of each node in the first stage is:

[0019] S311. When the boundary of the thermal fluid zone does not reach the oil layer boundary, all the energy of the injected steam is used to heat the formation. The following equation is obtained from the law of energy conservation:

[0020]

[0021] Where: t is the steam injection time, unit is d; H si is the heat injection rate of the steam zone at node i, in kJ / d; Q r is the waste heat, unit is kJ; r si is the radius of the steam zone at node i, in m; M R is the reservoir heat capacity, in kJ / (m 3 ℃); T s is the injection steam temperature in °C; T r is the original formation temperature, in °C; r is the radius, used to represent the integrand in the integral, has no practical meaning, in meters;

[0022] S312. The calculation formula of the steam zone radius can be obtained from the above formula as follows:

[0023]

[0024] H si =l i ρ i L vi +E rsi (4)

[0025] Where: r si is the radius of the steam zone at node i, in m; H si is the heat injection rate of the steam zone at node i, in kJ / d; Q r is the waste heat, in kJ; in the first round of throughput, Q r =0;M R is the reservoir heat capacity, in kJ / (m 3 ·℃); dl is the microelement length, in m; T s is the injection steam temperature in °C; T r is the original formation temperature, in °C; I i is the volume outflow rate of node i, kg / d; ρ i is the steam density at node i, in kg / m 3 ;L vi is the latent heat of steam at node i, in kJ / kg; E rsiis the waste heat of the previous cycle in the steam zone of node i, in kJ; t is the steam injection time, in d;

[0026] S313. The calculation formula for the radius of the thermal fluid zone is obtained by the principle of conservation of energy as follows:

[0027]

[0028] H wi =I i ρ i (h wsi -h wri )+E rwi (6)

[0029] Where: r hi is the radius of the hot fluid zone at node i, in meters; r si is the radius of the steam zone at node i, in m; H wi are the heat injection rates of the thermal fluid zone at node i, in kJ / d; Q r is the waste heat, in kJ;

[0030] In the first round of throughput, Q r =0;M R is the reservoir heat capacity, in kJ / (m 3 ·℃); dl is the microelement length, in m; T h is the temperature of the hot fluid zone, in °C; T r is the original formation temperature, in °C; I i is the volume outflow rate of node i, kg / d; ρ i is the steam density at node i, in kg / m 3 ;h wsi and h wri are the water specific heat enthalpy of the steam temperature at node i and the water specific heat enthalpy of the formation temperature, kJ / kg; E rwi is the residual heat of the previous cycle in the thermal fluid zone of node i, in kJ;

[0031] S32. The calculation method of the steam zone radius and the hot fluid zone radius of each node in the second stage is:

[0032] S321. When the boundaries of the hot fluid zone reach the upper and lower boundaries, the heating radius of the steam zone is still calculated using the calculation method when the boundaries have not been reached;

[0033] S322. The calculation formula of the radius of the thermal fluid zone is as follows after the energy conservation equation is Laplace transformed:

[0034]

[0035] Where: r hi is the radius of the thermal fluid zone at node i, in m; d is half the formation thickness, in m; H wi are the heat injection rates of the thermal fluid zone at node i, in kJ / d; Q r is waste heat, unit is kJ; M R is the reservoir heat capacity, in kJ / (m 3 ·℃); α s is the thermal diffusivity of the boundary, in m 2 / d;λ s is the boundary heat conduction coefficient, in W / (m·℃); dl is the infinitesimal length, in m; T r is the original formation temperature, in °C; T hi is the temperature of the hot fluid zone at node i, in °C; t is the steam injection time, in d; t 1i is the time when the hot fluid zone reaches the oil layer boundary, in d;

[0036] S33. The calculation method of the steam zone radius and the hot fluid zone radius of each node in the third stage is:

[0037] S331. When the boundary of the steam zone reaches the upper and lower boundaries, the Laplace transform of the energy conservation equation is performed to obtain the calculation formula for the radius of the steam zone and the thermal fluid zone as follows:

[0038]

[0039] Where: r si is the radius of the steam zone at node i, in m; d is half the formation thickness, in m; r hi is the radius of the hot fluid zone at node i, m; T s is the injection steam temperature, °C; T r is the original formation temperature, °C; H si and H wi are the heat injection rates of the steam zone and the thermal fluid zone at node i, kJ / d; M R is the reservoir heat capacity, kJ / (m 3 ·℃); dl is the length of the microelement, m; Q r is the waste heat, kJ, I i is the volume outflow rate of node i, kg / d; ρ i is the steam density at node i, kg / m 3 ; In the first round of throughput, Q r =0;L vi is the latent heat of steam at node i, kJ / kg; E rsi is the waste heat of the previous cycle in the steam zone of node i, kJ; h wsi and h wriare the water specific heat enthalpy of the steam temperature at node i and the water specific heat enthalpy of the formation temperature, kJ / kg; E rwi is the residual heat of the previous cycle in the thermal fluid zone of node i, kJ; T h is the temperature of the hot fluid zone, °C; λ s is the boundary heat conduction coefficient, W / (m·℃); α s is the thermal diffusivity of the boundary, m 2 / d; t is the steam injection time, d; t 1i is the time when the hot fluid zone reaches the oil layer boundary, d; t 2i is the time when the steam zone reaches the oil layer boundary, d.

[0040] In the above technical solution, the step S3 of correcting the steam chamber according to the difference in heat transfer capacity between the vertical and horizontal directions of the oil layer specifically includes:

[0041] S34. Modify the shape of the steam chamber based on the difference in heat transfer velocities in the vertical and horizontal directions of the cross section caused by the difference in density between oil and steam in the expansion of the steam chamber;

[0042] When the steam chamber expands laterally, the heat transfer equation in the reservoir is:

[0043]

[0044] Based on heat conduction, the solution to the equation is:

[0045]

[0046] Where: K is the reservoir thermal conductivity, dimensionless; ρ r is the reservoir density, in kg / m 3 ; C pr is the reservoir heat capacity, in J / K; U y is the lateral diffusion rate, in m / d; ρ c is the water density in kg / m 3 ;c pc is the heat capacity of water, in J / K; V c is the convection velocity, in m / d; T is the average temperature of the steam chamber, in °C; T * is the dimensionless temperature, which means the temperature change divided by the difference between the steam temperature and the original reservoir temperature, dimensionless; T s is the injection steam temperature, °C; T r is the original formation temperature, °C; δ y is the distance the boundary moves, in meters;

[0047] S35. Assuming that the horizontal and vertical dimensions of the steam chamber maintain a certain ratio, the horizontal and vertical distance ratio is:

[0048]

[0049] The oil displacement rate of rising steam is:

[0050]

[0051] Q o =S o V (15)

[0052]

[0053] The vertical oil displacement rate is expressed by the oil phase velocity equation as follows:

[0054]

[0055] Where: α b is the ratio of the horizontal to the vertical distance of the steam chamber, dimensionless; y t is the horizontal expansion distance of the steam zone, in m; z t A is the upward expansion distance of the steam zone, in m; t The volume of the oil leakage unit in the steam zone, in m 3 ;Q o is the oil displacement volume, in kg; S o is the oil saturation, dimensionless; V is the displacement volume, unit is m 3 ;q o is the vertical oil displacement rate expressed by the oil phase velocity equation, in m 3 / d; t is the steam injection time, unit is d; z is the same as z t , is the upward expansion distance of the steam zone, in m; v o is the kinematic viscosity of the oil phase, m 2 / s;k o Oil phase permeability, unit is mD; μ o is the oil phase viscosity, unit is Pa.s; P is the steam pressure, unit is MPa; Δρ is the density difference between crude oil and steam, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ; G is the starting pressure gradient, MPa / m; η is the total available width of the chamber liquid flow, unit: m;

[0056] so:

[0057]

[0058] Where: q o is the oil displacement rate, in kg / d; v os is the viscosity of the oil phase at steam temperature, in mPa·s; k oOil phase permeability, unit is mD; Δp is the difference between steam pressure and reservoir pressure, unit is MPa; g is the acceleration of gravity, unit is m / s 2 ; α b is the ratio of the horizontal to the vertical distance of the steam chamber, dimensionless; z t is the upward extension distance of the steam zone, in meters; G is the starting pressure gradient, in MPa / m; K is the reservoir thermal conductivity, dimensionless; μ is the oil phase viscosity, in mPa·s;

[0059] The upward expansion rate in the steam chamber is obtained as:

[0060]

[0061] The distance the steam chamber expands upward is:

[0062]

[0063] The rate at which the steam chamber expands horizontally is:

[0064]

[0065] The horizontal expansion distance of the steam chamber is:

[0066]

[0067] Where: U z is the upward expansion rate of the steam zone, dimensionless; K is the reservoir thermal conductivity, dimensionless; k ro is the relative permeability of the oil phase, dimensionless; v os S is the viscosity of the oil phase at steam temperature, in mPa·s; o is the oil saturation, dimensionless; Δp is the difference between steam pressure and reservoir pressure, in MPa; z t is the upward expansion distance of the steam zone, in meters; g is the acceleration due to gravity, in meters per second 2 ; G is the starting pressure gradient, unit is MPa / m; z i is the longitudinal extension distance of node i, m; U y is the lateral expansion rate of the steam zone, dimensionless; α b is the ratio of the horizontal and vertical distances of the steam chamber, dimensionless; P is the steam pressure, in MPa; δ y is the size of the transverse steam cavity boundary, in m; T * is the dimensionless temperature, which means the temperature change divided by the difference between the steam temperature and the original reservoir temperature; m, n are the temperature coefficients, dimensionless; P st is the steam pressure, in MPa; P r is the reservoir pressure, in MPa; t is the gas injection time, in d; yi is the horizontal expansion distance of the i-node, in meters;

[0068] S36. After calculating the longitudinal and lateral expansion rates, the previously obtained cylindrical steam chamber microelement is corrected based on the volume balance:

[0069] S361. According to the law of conservation of volume, the sum of the volumes of the upper and lower parts of the steam chamber is equal to the volume of the entire chamber, and the following formula is obtained:

[0070]

[0071] y i =U y t z (26)

[0072] z i =U z t z (27)

[0073]

[0074] Where: r si is the radius of the steam zone at node i, in m; dl is the length of the infinitesimal element, in m; y i is the horizontal expansion distance of the i node, in meters; z i is the longitudinal extension distance of node i, in meters; U y is the lateral expansion rate of the steam zone, dimensionless; U z is the rate at which the steam zone expands upward, dimensionless; z 2i is the longitudinal lower extension distance, in m; t z is the steam injection time, in d;

[0075] S362, according to the above formula, calculate y i 、z i and z 2i Finally, determine the cross-sectional shape of the final steam zone;

[0076] S363, will r hi Substitute Equations 25 to 28 to determine the final cross-sectional shape of the hot fluid zone.

[0077] In the above technical solution, the average temperature calculation formula of the steam zone and the heat flow zone during steam injection in step S4 is as follows:

[0078]

[0079] Where: T asi and T ahi are the average temperatures of the steam zone and the hot fluid zone during steam injection, respectively, in °C; and are the radial heat loss influencing factors in the steam zone and hot fluid zone, respectively, dimensionless; and are the vertical heat loss influencing factors of the steam zone and the hot fluid zone, dimensionless; T r is the original formation temperature, in °C; and Denote radial and longitudinal heat losses, dimensionless; t z is the steam injection time, d; α is the thermal diffusion coefficient, m 2 / d;θ rs is the longitudinal heat loss coefficient of the steam zone, dimensionless; θ z is the transverse heat loss coefficient, dimensionless; θ rh is the longitudinal heat loss coefficient of the thermal fluid zone, dimensionless; r s is the radius of the steam zone, in m; r h is the radius of the thermal fluid zone, in m; h is the thickness of the reservoir, in m; T si is the temperature of the steam zone in section i, in °C.

[0080] In the above technical solution, the method for calculating the average temperature and radius of the hot fluid zone in the soaking stage in step S5 specifically includes:

[0081] S51. Heat conduction is the main method in the soaking stage. At the end of soaking, the average temperature of the hot fluid zone is calculated as follows:

[0082]

[0083] Where: is the average temperature of the hot fluid zone at the end of soaking, in °C; T r is the original formation temperature, in °C; T a is the temperature of the heating zone at the end of steam injection, in °C; pw is the water heat capacity, in kJ / (kg·℃); x is the steam quality, dimensionless; 1 is the horizontal well length, in m; r si is the radius of the steam zone at node i, in m; M R is the reservoir heat capacity, in kJ / (m 3 ℃); T s is the injection steam temperature, in °C; L v is the latent heat of steam, in kJ / kg; x is the steam quality, dimensionless; G is the starting pressure gradient, in MPa / m;

[0084] S52. According to the law of conservation of energy, the total energy injected into the formation is equal to the energy of heating the formation, which is the radius of the hot fluid zone after the soaking is completed. The calculation formula is as follows:

[0085]

[0086] Where r m H is the radius of the hot fluid zone after the soaking is completed, in meters; si and H wi are the heat injection rates of the steam zone and the thermal fluid zone at node i, respectively, in kJ / d; l is the length of the horizontal well, in m; M R is the reservoir heat capacity, in kJ / (m 3 ℃); T r is the original formation temperature, in °C; is the average temperature of the hot fluid zone at the end of soaking, in °C;

[0087] S53. Based on the horizontal and vertical correction ratios during the steam injection phase, the horizontal and vertical radii of the hot fluid zone during the soaking phase are calculated by volume conservation.

[0088] In the above technical solution, the calculation formula for the average temperature of the hot fluid zone in the output stage of step S6 is:

[0089]

[0090] Where: is the average temperature of the hot fluid zone during the production phase, in °C; T r is the original formation temperature, in °C; is the factor affecting the radial heat loss in the hot fluid zone and is dimensionless; is the vertical heat loss influencing factor of the hot fluid zone, dimensionless; δ is the liquid production correction coefficient, dimensionless; T si is the temperature of the steam zone in section i, in °C.

[0091] In the above technical solution, the method for calculating the radius of the hot fluid zone and the residual heat in the output stage of step S7 specifically includes:

[0092] S71. Calculate the heat carried by the hot water during the flowback phase. The calculation formula is as follows:

[0093]

[0094] Where: Q w1 is the heat carried by hot water during the flowback phase, in KJ; q w is the water production during the flowback phase, in m 3 ; is the average temperature of the hot zone during the production phase, in °C;

[0095] S72. Calculate the heat carried by the produced water during the oil production phase using the following formula:

[0096]

[0097] Where: Q w2 is the heat carried by the produced water during the oil production stage, in KJ; q w2 is the water production during the oil production phase, in m 3 ;T r is the original formation temperature, in °C; is the average temperature of the hot zone during the production phase, in °C;

[0098] S73. Calculate the heat carried by the produced oil using the following formula:

[0099]

[0100] Where: Q o It is the heat carried by the oil produced during the oil production stage, in KJ; C po is the heat capacity of oil, in KJ / (kg·℃); q o is the oil production, in m 3 ; is the average temperature of the hot zone during the production phase, in °C;

[0101] S74. According to the principle of conservation of energy, calculate the change in the radius of the thermal fluid zone during the production phase. The calculation formula is as follows:

[0102] Q r =H si +H wi -Q w1 -Q w2 -Q o (43)

[0103]

[0104] Where: Q r is the residual heat in the formation, unit is KJ; H si and H wi are the heat injection rates of the steam zone and the thermal fluid zone at node i, respectively, in kJ / d; Q w1 It is the heat carried by hot water in the backflow stage, the unit is KJ; Q w2 It is the heat carried by the produced water during the oil production stage, in KJ; Q o is the heat carried by the oil produced during the oil production phase, in KJ; r hc is the radius of the hot zone, in m; M R is the reservoir heat capacity, in kJ / (m 3 ℃); T ris the original formation temperature, in °C; 1 is the horizontal well length, in m; It is the average temperature of the hot zone during the production phase, in °C.

[0105] S75. Calculate the transverse and longitudinal radii of the hot fluid zone in the production phase using the law of volume conservation based on the transverse and longitudinal correction ratios in the steam injection phase.

[0106] S76. Calculate the waste heat of each section according to the following formula;

[0107]

[0108] Where: E rhi is the waste heat of the hot fluid zone at node i, in kJ; V hi is the volume of the hot fluid zone, in m 3 ;M R is the reservoir heat capacity, in kJ / (m 3 ℃); is the average temperature of the hot fluid zone during the production phase, °C; T r is the original formation temperature in °C.

[0109] In the above technical solution, the specific calculation method of step S8 is: using the average temperature of the hot fluid zone in the output stage calculated in step S6 and the waste heat of the hot fluid zone in the output stage calculated in step S7 as the initial temperature and initial calorific value for the next round of calculation, and repeating the above steps multiple times to obtain the steam zone radius and the hot fluid zone radius of each round of steam throughput.

[0110] Principle of the prediction method of the present invention:

[0111] Based on the theory of thermal balance and porous media heat transfer, the radius of the steam zone and the thermal fluid zone at each node are determined. The influence of the density difference between steam and oil on the heat transfer velocity in the vertical and horizontal directions in the steam chamber is considered. According to the seepage equation considering the oil phase startup pressure gradient, a calculation model for the vertical and horizontal expansion distance of the steam chamber is established. On this basis, the axial and cross-sectional shapes of the steam zone and thermal fluid zone at each node of the horizontal well are corrected to determine the range of the steam zone and thermal fluid zone at each node of the horizontal well during the steam injection stage. The influence of heat carried by the produced thermal fluid and heat dissipation to the surrounding area on the range and residual heat of the steam zone and thermal fluid zone at each node of the horizontal well is considered. The temperature and residual heat at the end of the previous cycle are used as initial conditions, and the development of the steam zone and thermal fluid zone in each steam injection cycle is obtained through cyclic calculation.

[0112] The beneficial effects of the present invention are:

[0113] The present invention provides a method for quantitatively predicting the expansion front of the steam-huffing heating cavity in thick-layer heavy oil horizontal wells. The method takes into account factors such as the heterogeneity of the reservoir's steam absorption capacity, the anisotropy of the heat transfer capacity, and the fluid starting pressure gradient, thereby ensuring the reliability and rationality of the prediction results. The method realizes the quantitative prediction of the expansion front of the steam-huffing heating cavity in horizontal wells in thick-layer heavy oil reservoirs at sea, has strong operability, and is of great significance for the design of steam-huffing schemes and the optimization of injection and production parameters in heavy oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0114] Figure 1 is the cross-sectional diagram of the steam chamber development at node i of the horizontal well steam stimulation (vertical to the horizontal well cross-section);

[0115] Figure 2 is a flow chart of the method of the present invention;

[0116] Figure 3 1 is a cross-sectional view of the steam chamber (vertical and horizontal well cross-section) at different steam injection times in Example 1 of the present invention;

[0117] Figure 4 3D images of the steam chamber at different steam injection times in Example 1 of the present invention;

[0118] Figure 5 is a curve showing a change in the longitudinal extension length of the steam zone along the wellbore during the gas injection phase in Example 1 of the present invention;

[0119] Figure 6 is a curve showing the change in the longitudinal shape expansion rate of the steam zone over time in Example 1 of the present invention;

[0120] Figure 7 is a curve showing a change in the longitudinal extension length of the hot fluid zone along the wellbore during the gas injection phase in Example 1 of the present invention;

[0121] Figure 8 is a curve showing the change in the longitudinal shape expansion rate of the thermal fluid zone over time in Example 1 of the present invention;

[0122] Figure 9 1 is a cross-sectional view of the steam chamber (vertical and horizontal well sections) at different soaking times in Example 1 of the present invention;

[0123] Figure 10 is a curve showing the change of the steam chamber radius along the wellbore during the soaking stage in Example 1 of the present invention;

[0124] Figure 11 3D images of the steam chamber at different soaking times in Example 1 of the present invention.

[0125] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0126] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0127] Example 1

[0128] Taking a certain oil reservoir in Bohai as an example, the steam chamber development section of the horizontal well steam stimulation node i is as follows: Figure 1 As shown in Figure 1, a quantitative prediction method for the expansion front of the steam heating cavity in thick-layer heavy oil horizontal wells is presented. Figure 2 As shown, the following steps are included:

[0129] S1. Divide the horizontal well into i segments and calculate the node coordinates of each segment.

[0130] The length of the horizontal well in the target reservoir is 300m. The horizontal well is divided into 300 segments at 1m intervals, and the node coordinates of each segment are 1, 2, 3...300.

[0131] S2. Calculate the steam absorption capacity of each node based on the quadratic function distribution of steam along the horizontal well.

[0132] Calculate the steam absorption capacity of each node. Considering that the steam absorption capacity along the wellbore from the injection end to the finger end is a quadratic function distribution, the calculation equation for the absorption capacity of a node is:

[0133] Q i =Q * (3 / 10 5 *L 2 -0.0094*L+1.0191)ε / 100 (1)

[0134] Where Q i is the steam absorption volume at a node of the horizontal well, t / d; Q is the total daily steam injection volume, t / d; L is the distance from the node to the injection end, m; ε is a correction function related to the length of the horizontal well.

[0135] The daily steam injection rate Q of the target reservoir is 300t / d. When L is 10m, the air intake volume at this location is calculated by the above formula:

[0136] Q 10 =2.008t / d

[0137] S3. Calculate the steam zone radius and hot fluid zone radius of each node, and correct the steam cavity according to the difference in heat transfer capacity between the vertical and horizontal directions of the oil layer.

[0138] The heating zone is divided into a hot fluid zone and a steam zone. The zones are divided into three stages based on whether they reach the boundary. The steam zone radius and hot fluid zone radius of each node in each of the three stages are calculated as follows:

[0139] Phase 1: When the boundary of the thermal fluid zone does not reach the oil layer boundary, all the energy of the injected steam is used to heat the formation. The following equation can be obtained from the law of energy conservation:

[0140]

[0141] From the above formula, we can get the calculation expression of the steam zone radius:

[0142]

[0143] H si =I i ρ i L vi +E rsi (4)

[0144] Similarly, the calculation expression of the radius of the thermal fluid zone can be obtained by the principle of conservation of energy:

[0145]

[0146] H wi =I i ρ i (h wsi -h wri )+E rwi (6)

[0147] Phase 2: When the boundaries of the thermal fluid zone reach the upper and lower boundaries, the heating radius of the steam zone can still be calculated using the method for when the boundaries have not been reached. However, the calculation method for the thermal fluid zone radius is different. After Laplace transformation of the energy conservation equation, the calculation expression for the thermal fluid zone radius can be obtained:

[0148]

[0149] Stage 3: When the boundary of the steam zone reaches the upper and lower boundaries, the Laplace transform of the energy conservation equation is performed to obtain the following equations to calculate the radii of the steam zone and the hot fluid zone.

[0150]

[0151] Where r si is the radius of the steam zone at node i, m; r hi is the radius of the hot fluid zone at node i, m; T s is the injection steam temperature, °C; T r is the original formation temperature, °C; Hsi and H wi are the heat injection rates of the steam zone and the thermal fluid zone at node i, kJ / d; M R is the reservoir heat capacity, kJ / (m 3 ·℃); dl is the length of the microelement, m; Q r is the waste heat, kJ, I i is the volume outflow rate of node i, kg / d; ρ i is the steam density at node i, kg / m 3 ; In the first round of throughput, Q r =0;L vi is the latent heat of steam at node i, kJ / kg; E rsi is the waste heat of the previous cycle in the steam zone of node i, kJ; h wsi and h wri are the water specific heat enthalpy of the steam temperature at node i and the water specific heat enthalpy of the formation temperature, kJ / kg; E rwi is the residual heat of the previous cycle in the thermal fluid zone of node i, kJ; T h is the temperature of the hot fluid zone, °C; λ s is the boundary heat conduction coefficient, W / (m·℃); α s is the thermal diffusivity of the boundary, m 2 / d.

[0152] Target reservoir steam temperature T s is 340℃, the original formation temperature T r is 50℃, the reservoir heat capacity M R The specific heat enthalpy of water at steam temperature is 2575 kJ / (kg·℃), h wsi is 2624.3 kJ / kg, and the specific heat enthalpy of water at reservoir temperature is h wri is 1603.3kJ / kg, and the boundary heat conduction coefficient λ s is 1.73W / (m·℃), and the thermal diffusivity α of the boundary s 0.089m 2 / d, steam injection time is 20d, and reservoir thickness is 40m.

[0153] According to the above steps,

[0154] H si =I i ρ i L vi +E rsi =4.51×10 6 kJ / d

[0155] H wi =I i ρ i (h wsi -hwri )+E rwi =2.04×10 6 kJ / d

[0156] in,

[0157] I i ρ i =Q 10 =1.8161×10 3 kg / d

[0158] E rsi =0

[0159] E rwi =0

[0160] Time when the boundary of the thermal fluid zone reaches the boundary of the oil layer:

[0161]

[0162] Time when the steam zone boundary reaches the oil layer boundary:

[0163]

[0164] The steam zone and the hot fluid zone have not reached the boundary, so

[0165]

[0166] The cross-section of the steam chamber calculated by the above method is circular, but due to the existence of steam overburden phenomenon, the above method needs to be corrected to a certain extent.

[0167] Indoor physical research results show that the cross-section of the steam chamber is an ellipse with a vertical axial length greater than the horizontal axis length. Statistical results show that the ratio of the vertical to horizontal axis lengths of the physically simulated steam chamber is always greater than 1, indicating that the vertical expansion rate of the steam chamber is higher than the horizontal expansion rate during steam stimulation in horizontal wells. The main reason for this is the density difference between steam and crude oil. The steam chamber shape is modified based on the difference in heat transfer velocities in the vertical and horizontal directions of the cross section caused by the density difference between oil and steam during steam chamber expansion.

[0168] When the steam chamber expands laterally, the heat transfer equation in the reservoir is:

[0169]

[0170] Based on heat conduction, the solution to the equation is:

[0171]

[0172] Where: K is the reservoir thermal conductivity; ρ r is the reservoir density, kg / m3 ; C pr is the reservoir heat capacity, J / K; U x is the lateral diffusion rate m / d; ρ c is the water density, kg / m 3 ;c pc is the heat capacity of water, J / K; V c is the convection velocity, m / d; T is the average temperature of the steam chamber, °C. * It is the dimensionless temperature, which means the temperature change divided by the difference between the steam temperature and the original reservoir temperature.

[0173] Assuming that the steam chamber maintains a ratio between the horizontal and vertical directions, the ratio of the horizontal and vertical distances is:

[0174]

[0175] The oil displacement rate of rising steam is:

[0176]

[0177] Q o =S o V (15)

[0178]

[0179] The vertical oil displacement rate can be expressed by the oil phase velocity equation as follows:

[0180]

[0181] Where K is the reservoir thermal conductivity; ρ r is the reservoir density, kg / m 3 ; C pr is the reservoir heat capacity, J / K; U y is the lateral diffusion rate, m / d; ρ c is the water density, kg / m 3 ;c pc is the heat capacity of water J / K; V c is the convection velocity, m / d; Δρ is the density difference between crude oil and steam, kg / m 3 ; At is the volume of the oil leakage unit in the steam zone; y t is the horizontal expansion distance of the steam zone; zt is the upward expansion distance of the steam zone, Q o is the oil displacement, kg; S o is the oil saturation; V is the displacement volume, m 3 ;q o is the oil displacement rate, kg / d; δ y is the normal distance to the strong steam front, m; v o is the kinematic viscosity of the oil phase, m2 / s;k o Oil phase permeability, mD; μ o is the oil phase viscosity, Pa.s; ρ o is the oil density, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ; G is the starting pressure gradient, MPa / m; η b is the effective oil drainage width of the chamber liquid flow, m.

[0182] so:

[0183]

[0184] The upward expansion rate in the steam chamber is obtained as:

[0185]

[0186]

[0187] Where, v os is the viscosity of the oil phase at steam temperature, mPa·s; Δp is the difference between steam pressure and reservoir pressure, MPa; z i is the vertical extension distance of node i, m; y i is the horizontal expansion distance of node i, m; m, n are temperature coefficients; P st is the steam pressure, MPa; P r is the reservoir pressure, MPa.

[0188] After calculating the longitudinal and lateral expansion rates, the previously obtained cylindrical steam chamber element is corrected according to the volume balance.

[0189] According to the law of conservation of volume, the sum of the volumes of the upper and lower parts of the steam chamber is equal to the volume of the entire chamber:

[0190]

[0191] y i =U x t z (26)

[0192] z i =U z t z (27)

[0193]

[0194] According to the above formula, calculate y i 、z i and z 2i Finally, determine the cross-sectional shape of the final steam zone. Similarly, hiSubstituting Equations 25 to 28, the final cross-sectional shape of the thermal fluid zone can be determined.

[0195] Substituting the target reservoir parameters, the horizontal and vertical distance ratios of the steam zone are calculated according to the above formula:

[0196]

[0197] Where, K = 3000mD, μ = 28854mPa·s, m = 2.35, n = 2

[0198] Substitute into formula (25) to obtain:

[0199] z 2i =1.5290m

[0200] Specifically, if Figure 3 、 Figure 4 、 Figure 5 、 Figure 6 According to the relevant formulas in the second and third steps, the radius change data of the steam zone and the hot fluid zone along the way are calculated and drawn into a graph.

[0201] S4. Considering the heat dissipation effect of the steam zone and the hot fluid zone, calculate the average temperature of the two zones during the injection stage based on the thermal balance of the oil layer.

[0202] Specific operation: The average temperature of the steam zone and the heat flow zone during steam injection can be expressed as:

[0203]

[0204] Among them, T asi and T ahi are the average temperatures of the steam zone and the hot fluid zone during steam injection, respectively; and are the radial heat loss influencing factors in the steam zone and hot fluid zone, respectively, dimensionless; and are the vertical heat loss influencing factors in the steam zone and the hot fluid zone, respectively, and are dimensionless; and Denote radial and longitudinal heat losses, dimensionless; t z is the steam injection time, d; α is the thermal diffusion coefficient, m 2 / d;θ rs is the longitudinal heat loss coefficient of the steam zone, dimensionless; θ z is the transverse heat loss coefficient, dimensionless; θ rh is the longitudinal heat loss coefficient of the hot fluid zone, dimensionless.

[0205] The thermal diffusion coefficient α of the target reservoir is 0.089m 2 / d, steam injection time t zFor 20 days, calculated according to the above formula:

[0206] Average temperature of steam zone:

[0207]

[0208] Average temperature of thermal fluid area:

[0209]

[0210] S5. Considering the influence of heat conduction, calculate the average temperature and radius of the hot fluid zone during the soaking stage.

[0211] The soaking stage is mainly heat conduction. At the end of soaking, the average temperature of the hot fluid zone is:

[0212]

[0213] Where, is the average temperature of the hot fluid zone at the end of soaking, ℃; pw is the water heat capacity; KJ / (kg·℃); x is the steam quality, dimensionless; 1 is the horizontal well length, m; T a is the heating zone temperature at the end of steam injection, °C.

[0214] After calculating the average temperature of the thermal fluid zone, according to the law of conservation of energy, the total energy injected into the formation is equal to the energy heated up the formation. The radius of the thermal fluid zone after soaking is calculated:

[0215]

[0216] Where r m is the radius of the hot fluid zone after the soaking is completed, m.

[0217] Target reservoir water heat capacity C pw is 4.18 kJ / (kg·℃), x is 0.6, and the latent heat of steam L v It is 2260kJ / kg, calculated according to the above formula:

[0218]

[0219] G=4.016×10 4 kg

[0220]

[0221]

[0222] r m =8.865m

[0223] Specifically, if Figure 7 、 Figure 8 、 Figure 9 After calculating the radius of the hot fluid zone after well shut-in according to the formula in the fifth step, the horizontal and vertical radii of the hot fluid zone in the well shut-in stage are calculated by volume conservation based on the horizontal and vertical correction ratios of the steam injection stage.

[0224] S6. Calculate the average temperature of the thermal fluid zone during the production phase based on the thermal balance between oil layer injection and production.

[0225] The average temperature of the hot fluid zone during the production phase can be expressed as:

[0226]

[0227] in, is the average temperature of the hot fluid zone during the production phase, °C; δ is the liquid production correction coefficient, dimensionless.

[0228] According to the target reservoir conditions, T si 340℃, T r At 50℃, the number of days of soaking is t m 7 days, based on production days s Taking 20 days as an example, calculate according to the above steps:

[0229]

[0230] The heat carried out is calculated based on the actual production output of the target oil field for 20 days:

[0231]

[0232] Similarly,

[0233]

[0234] S7. Considering the heat carrying and heat dissipation effects of the produced thermal fluid, calculate the radius of the thermal fluid zone and the residual heat during the production stage.

[0235] During the flowback stage, the heat carried by hot water is:

[0236]

[0237] During the oil production stage, the heat carried by the produced water is:

[0238]

[0239] Heat carried by produced oil:

[0240]

[0241] According to the principle of conservation of energy, the change in the radius of the thermal fluid zone during the production stage is calculated:

[0242] Q r =H si +H wi -Q w1 -Q w2 -Q o (43)

[0243]

[0244] Where Q w1 is the heat carried by hot water during the flowback phase, KJ; Q w2 is the heat carried by the produced water during the oil production stage, KJ; Q o is the heat carried by the oil produced during the oil production phase, KJ; C po is the heat capacity of oil, KJ / (kg·℃); q w is the water production, kg; q o is the oil production, kg; Q r is the residual heat in the formation, KJ; r hc is the radius of the thermal fluid zone, m.

[0245] The residual heat expression of each section:

[0246]

[0247] Among them, E rhi is the waste heat of the hot fluid zone at node i, kJ; V hi is the volume of the hot fluid zone, m 3 .

[0248] According to the target reservoir conditions, taking the actual production for 20 days as an example, the water production q w is 91.91 kg, q w2 is 5533.63 kg, q o is 3993.83kg, C po It is 2kJ / (kg·℃), calculated according to the above formula:

[0249]

[0250] Q r =H si +H wi -Q w1 -Q w2 -Q o =6.2×10 6 kJ

[0251] r hc =16.7433m

[0252]

[0253] S8. Using the final temperature and residual heat of the previous round as initial conditions, repeat steps S2 to S7 and output the calculation results of the next round.

[0254] The temperature and residual heat calculated in step S6 and step S7 are used as the initial temperature and initial calorific value for the next round of calculation. By repeating the above steps multiple times, the steam zone radius and the hot fluid zone radius of each round of steam throughput can be obtained.

[0255] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A quantitative prediction method for the expansion front of the steam heating chamber in a thick-layer heavy oil horizontal well, characterized by: The following steps are involved: S1. Divide the horizontal well into N segments according to unit length and calculate the node coordinates of each segment; S2. Calculate the steam absorption capacity of each node based on the quadratic function distribution of steam along the horizontal well; S3. Calculate the steam zone radius and the hot fluid zone radius of each node, and modify the steam cavity according to the difference in heat transfer capacity between the vertical and horizontal directions of the oil layer; S4. Considering the heat dissipation effect of the steam zone and the hot fluid zone, calculate the average temperature of the steam zone and the hot fluid zone during steam injection based on the thermal balance of the oil layer; S5. Considering the influence of heat conduction, calculate the average temperature and radius of the hot fluid zone during the soaking stage; S6. Calculate the average temperature of the thermal fluid zone during the production phase based on the thermal balance between oil layer injection and production; S7. Considering the heat carrying and heat dissipation effects of the produced thermal fluid, calculate the radius of the thermal fluid zone and the residual heat during the production phase; S8, using the final temperature and residual heat of the previous round as initial conditions, repeat S2 to S7 and output the calculation results of the next round; The specific calculation method of step S8 is: using the average temperature of the hot fluid zone in the output stage calculated in step S6 and the residual heat of the hot fluid zone in the output stage calculated in step S7 as the initial temperature and initial calorific value for the next round of calculation, and repeating the above steps multiple times to obtain the steam zone radius and the hot fluid zone radius of each round of steam throughput.

2. The method for quantitatively predicting the expansion front of the steam stimulation heating chamber in thick-layer heavy oil horizontal wells according to claim 1 is characterized in that: The method for calculating the steam absorption amount of each node in step S2 is specifically as follows: considering that the steam absorption amount from the injection end to the finger end along the wellbore is distributed as a quadratic function, the calculation equation for the absorption amount of a certain node is: Q i =Q*(10 -5 *L 2 -0.0047*L+1.0191)ε / 100 (1) Where: Q i is the steam absorption volume at a certain node of the horizontal well, in t / d; Q is the total daily steam injection volume, in t / d; L is the distance from the node to the injection end, in m; ε is a correction function related to the horizontal well length; Where L is the distance from the node to the injection end, in meters; N refers to the horizontal well being divided into N segments by length, dimensionless; i refers to the i-th node, i.e., the i-th segment, dimensionless.

3. The method for quantitatively predicting the expansion front of the steam stimulation heating chamber in a thick-layer heavy oil horizontal well according to claim 1 is characterized in that: In the calculation of the steam zone radius and the thermal fluid zone radius of each node in step S3, the heating zone is divided into the thermal fluid zone and the steam zone. The zones are divided into three stages according to whether each zone reaches the boundary. The steam zone radius and the thermal fluid zone radius of each node in the three stages are calculated respectively. Specifically, S31. The calculation method of the steam zone radius and the hot fluid zone radius of each node in the first stage is: S311. When the boundary of the thermal fluid zone does not reach the oil layer boundary, all the energy of the injected steam is used to heat the formation. The following equation is obtained from the law of energy conservation: Where: t is the steam injection time, unit is d; H si is the heat injection rate of the steam zone at node i, in kJ / d; Q r is the waste heat, unit is kJ; r si is the radius of the steam zone at node i, in m; M R is the reservoir heat capacity, in kJ / (m 3 ℃); T s is the injection steam temperature in °C; T r is the original formation temperature, in °C; r is the radius, used to represent the integrand in the integral, has no practical meaning, in meters; S312. The calculation formula of the steam zone radius can be obtained from the above formula as follows: H si =I i r i L vi +E rsi (4) Where: r si is the radius of the steam zone at node i, in m; H si is the heat injection rate of the steam zone at node i, in kJ / d; Q r is the waste heat, in kJ; in the first round of throughput, Q r =0;M R is the reservoir heat capacity, in kJ / (m 3 ·℃); dl is the microelement length, in m; T s is the injection steam temperature in °C; T r is the original formation temperature, in °C; I i is the volume outflow rate of node i, kg / d; ρ i is the steam density at node i, in kg / m 3 ;L vi is the latent heat of steam at node i, in kJ / kg; E rsi is the waste heat of the previous cycle in the steam zone of node i, in kJ; t is the steam injection time, in d; S313. The calculation formula for the radius of the thermal fluid zone is obtained by the principle of conservation of energy as follows: H wi =I i ρ i (h wsi -h wri )+E rwi (6) Where: r hi is the radius of the hot fluid zone at node i, in meters; r si is the radius of the steam zone at node i, in m; H wi are the heat injection rates of the thermal fluid zone at node i, in kJ / d; Q r is the waste heat, in kJ; In the first round of throughput, Q r =0;M R is the reservoir heat capacity, in kJ / (m 3 ·℃); dl is the microelement length, in m; T h is the temperature of the hot fluid zone, in °C; T r is the original formation temperature, in °C; I i is the volume outflow rate of node i, kg / d; ρ i is the steam density at node i, in kg / m 3 ;h wsi and h wri are the water specific heat enthalpy of the steam temperature at node i and the water specific heat enthalpy of the formation temperature, kJ / kg; E rwi is the residual heat of the previous cycle in the thermal fluid zone of node i, in kJ; S32. The calculation method of the steam zone radius and the hot fluid zone radius of each node in the second stage is: S321. When the boundaries of the hot fluid zone reach the upper and lower boundaries, the heating radius of the steam zone is still calculated using the calculation method when the boundaries have not been reached; S322. The calculation formula of the radius of the thermal fluid zone is as follows after the energy conservation equation is Laplace transformed: Where: r hi is the radius of the hot fluid zone at node i, in meters; d is half of the formation thickness, in m; H wi are the heat injection rates of the thermal fluid zone at node i, in kJ / d; Q r is waste heat, unit is kJ; M R is the reservoir heat capacity, in kJ / (m 3 ·℃); α s is the thermal diffusivity of the boundary, in m 2 / d;λ s is the boundary heat transfer coefficient, in W / (m·℃); dl is the infinitesimal length, in m; T r is the original formation temperature, in °C; T hi is the temperature of the hot fluid zone at node i, in °C; t is the steam injection time, in d; t 1i is the time when the hot fluid zone reaches the oil layer boundary, in d; S33. The calculation method of the steam zone radius and the hot fluid zone radius of each node in the third stage is: S331. When the boundary of the steam zone reaches the upper and lower boundaries, the Laplace transform of the energy conservation equation is performed to obtain the calculation formula for the radius of the steam zone and the thermal fluid zone as follows: Where: r si is the radius of the steam zone at node i, in m; d is half the formation thickness, in m; r hi is the radius of the hot fluid zone at node i, m; T s is the injection steam temperature, °C; T r is the original formation temperature, °C; H si and H wi are the heat injection rates of the steam zone and the thermal fluid zone at node i, KJ / d; M R is the reservoir heat capacity, kJ / (m 3 ·℃); dl is the length of the microelement, m; Q r is the waste heat, kJ, I i is the volume outflow rate of node i, kg / d; ρ i is the steam density at node i, kg / m 3 ; In the first round of throughput, Q r =0;L vi is the latent heat of steam at node i, kJ / kg; E rsi is the waste heat of the previous cycle in the steam zone of node i, kJ; h wsi and h wri are the water specific heat enthalpy of the steam temperature at node i and the water specific heat enthalpy of the formation temperature, kJ / kg; E rwi is the residual heat of the previous cycle in the thermal fluid zone of node i, kJ; T h is the temperature of the hot fluid zone, °C; λ s is the boundary heat conduction coefficient, W / (m·℃); α s is the thermal diffusivity of the boundary, m 2 / d; t is the steam injection time, d; t 1i is the time when the hot fluid zone reaches the oil layer boundary, d; t 2i is the time when the steam zone reaches the oil layer boundary, d.

4. The method for quantitatively predicting the expansion front of the steam stimulation heating chamber in thick-layer heavy oil horizontal wells according to claim 1 is characterized in that: The step S3 of correcting the steam chamber according to the difference in heat transfer capacity between the vertical and horizontal directions of the oil layer specifically includes: S34. Modify the shape of the steam chamber based on the difference in heat transfer velocities in the vertical and horizontal directions of the cross section caused by the difference in density between oil and steam in the expansion of the steam chamber; When the steam chamber expands laterally, the heat transfer equation in the reservoir is: Based on heat conduction, the solution to the equation is: Where: K is the reservoir thermal conductivity, dimensionless; ρ r is the reservoir density, in kg / m 3 ; C pr is the reservoir heat capacity, in J / K; U y is the lateral diffusion rate, in m / d; ρ c is the water density in kg / m 3 ;c pc is the heat capacity of water, in J / K; V c is the convection velocity, in m / d; T is the average temperature of the steam chamber, in °C; T * is the dimensionless temperature, which means the temperature change divided by the difference between the steam temperature and the original reservoir temperature, dimensionless; T s is the injection steam temperature, °C; T r is the original formation temperature, °C; δ y is the distance the boundary moves, in meters; S35. Assuming that the horizontal and vertical dimensions of the steam chamber maintain a certain ratio, the horizontal and vertical distance ratio is: The oil displacement rate of rising steam is: Q o =S o V (15) The vertical oil displacement rate is expressed by the oil phase velocity equation as follows: Where: α b is the ratio of the horizontal to the vertical distance of the steam chamber, dimensionless; y t is the horizontal expansion distance of the steam zone, in m; z t A is the upward expansion distance of the steam zone, in m; t The volume of the oil leakage unit in the steam zone, in m 3 ;Q o is the oil displacement volume, in kg; S o is the oil saturation, dimensionless; V is the displacement volume, unit is m 3 ;q o is the vertical oil displacement rate expressed by the oil phase velocity equation, in m 3 / d; t is the steam injection time, unit is d; z is the same as z t , is the upward expansion distance of the steam zone, in m; v o is the kinematic viscosity of the oil phase, m 2 / s;k o Oil phase permeability, unit is mD; μ o is the oil phase viscosity, unit is Pa.s; P is the steam pressure, unit is MPa; Δρ is the density difference between crude oil and steam, kg / m 3 ; g is the acceleration due to gravity, m / s 2 ; G is the starting pressure gradient, MPa / m; η is the total available width of the chamber liquid flow, unit: m; so: Where: q o is the oil displacement rate, in kg / d; v os is the viscosity of the oil phase at steam temperature, in mPa·s; k o Oil phase permeability, unit is mD; Δp is the difference between steam pressure and reservoir pressure, unit is MPa; g is the acceleration of gravity, unit is m / s 2 ; α b is the ratio of the horizontal to the vertical distance of the steam chamber, dimensionless; z t is the upward extension distance of the steam zone, in meters; G is the starting pressure gradient, in MPa / m; K is the reservoir thermal conductivity, dimensionless; μ is the oil phase viscosity, in mPa·s; The upward expansion rate in the steam chamber is obtained as: The distance the steam chamber expands upward is: The rate at which the steam chamber expands horizontally is: The horizontal expansion distance of the steam chamber is: Where: U z is the upward expansion rate of the steam zone, dimensionless; K is the reservoir thermal conductivity, dimensionless; k ro is the relative permeability of the oil phase, dimensionless; v os S is the viscosity of the oil phase at steam temperature, in mPa·s; o is the oil saturation, dimensionless; Δp is the difference between steam pressure and reservoir pressure, in MPa; z t is the upward expansion distance of the steam zone, in meters; g is the acceleration due to gravity, in meters per second 2 ; G is the starting pressure gradient, unit is MPa / m; z i is the longitudinal extension distance of node i, m; U y is the lateral expansion rate of the steam zone, dimensionless; α b is the ratio of the horizontal and vertical distances of the steam chamber, dimensionless; P is the steam pressure, in MPa; δ y is the size of the transverse steam cavity boundary, in m; T * is the dimensionless temperature, which means the temperature change divided by the difference between the steam temperature and the original reservoir temperature; m, n are the temperature coefficients, dimensionless; P st is the steam pressure, in MPa; P r is the reservoir pressure, in MPa; t is the gas injection time, in d; y i is the horizontal expansion distance of the i-node, in meters; S36. After calculating the longitudinal and lateral expansion rates, the previously obtained cylindrical steam chamber microelement is corrected based on the volume balance: S361. According to the law of conservation of volume, the sum of the volumes of the upper and lower parts of the steam chamber is equal to the volume of the entire chamber, and the following formula is obtained: y i =U y t z (26) z i =U z t z (27) Where: r si is the radius of the steam zone at node i, in m; dl is the length of the infinitesimal element, in m; y i is the horizontal expansion distance of the i node, in meters; z i is the longitudinal extension distance of node i, in meters; U y is the lateral expansion rate of the steam zone, dimensionless; U z is the rate at which the steam zone expands upward, dimensionless; z 2i is the longitudinal lower extension distance, in m; t z is the steam injection time, in d; S362, according to the above formula, calculate y i 、z i and z 2i Finally, determine the cross-sectional shape of the final steam zone; S363, will r hi Substitute into formula (25) to formula (28) to determine the final cross-sectional shape of the hot fluid zone.

5. The method for quantitatively predicting the expansion front of the steam stimulation heating chamber in a thick-layer heavy oil horizontal well according to claim 1 is characterized in that: The calculation formula for the average temperature of the steam zone and the heat flow zone during steam injection in step S4 is as follows: Where: T asi and T ahi are the average temperatures of the steam zone and the hot fluid zone during steam injection, respectively, in °C; and are the radial heat loss influencing factors in the steam zone and hot fluid zone, respectively, dimensionless; and are the vertical heat loss influencing factors in the steam zone and the hot fluid zone, respectively, and are dimensionless; T r is the original formation temperature, in °C; and denote radial and longitudinal heat losses, respectively, and are dimensionless; t z is the steam injection time, d; α is the thermal diffusion coefficient, m 2 / d;θ rs is the longitudinal heat loss coefficient of the steam zone, dimensionless; θ z is the transverse heat loss coefficient, dimensionless; θ rh is the longitudinal heat loss coefficient of the thermal fluid zone, dimensionless; r s is the radius of the steam zone, in m; r h is the radius of the thermal fluid zone, in m; h is the thickness of the reservoir, in m; T si is the temperature of the steam zone in section i, in °C.

6. The method for quantitatively predicting the expansion front of the steam stimulation heating chamber in a thick-layer heavy oil horizontal well according to claim 1 is characterized in that: The method for calculating the average temperature and radius of the hot fluid zone during the soaking stage in step S5 specifically includes: S51. Heat conduction is the main method in the soaking stage. At the end of soaking, the average temperature of the hot fluid zone is calculated as follows: Where: is the average temperature of the hot fluid zone at the end of soaking, in °C; T r is the original formation temperature, in °C; T a is the temperature of the heating zone at the end of steam injection, in °C; pw is the water heat capacity, in kJ / (kg·℃); x is the steam quality, dimensionless; l is the horizontal well length, in meters; r si is the radius of the steam zone at node i, in m; M R is the reservoir heat capacity, in kJ / (m 3 ℃); T s is the injection steam temperature, in °C; L v is the latent heat of steam, in kJ / kg; x is the steam quality, dimensionless; G is the starting pressure gradient, in MPa / m; S52. According to the law of conservation of energy, the total energy injected into the formation is equal to the energy of heating the formation, which is the radius of the hot fluid zone after the soaking is completed. The calculation formula is as follows: Where r m H is the radius of the hot fluid zone after the soaking is completed, in meters; si and H wi are the heat injection rates of the steam zone and the thermal fluid zone at node i, respectively, in kJ / d; l is the length of the horizontal well, in m; M R is the reservoir heat capacity, in kJ / (m 3 ℃); T r is the original formation temperature, in °C; is the average temperature of the hot fluid zone at the end of soaking, in °C; S53. Based on the horizontal and vertical correction ratios during the steam injection phase, the horizontal and vertical radii of the hot fluid zone during the soaking phase are calculated by volume conservation.

7. The method for quantitatively predicting the expansion front of the steam stimulation heating chamber in a thick-layer heavy oil horizontal well according to claim 1 is characterized in that: The calculation formula for the average temperature of the hot fluid zone in the output stage in step S6 is: Where: is the average temperature of the hot fluid zone during the production phase, in °C; T r is the original formation temperature, in °C; is the factor affecting the radial heat loss in the hot fluid zone and is dimensionless; is the factor affecting the vertical heat loss in the thermal fluid zone and is dimensionless; δ is the liquid production correction coefficient, dimensionless; T si is the temperature of the steam zone in section i, in °C.

8. The method for quantitatively predicting the expansion front of the steam stimulation heating chamber in a thick-layer heavy oil horizontal well according to claim 1 is characterized in that: The method for calculating the radius of the hot fluid zone and the residual heat in the production stage in step S7 specifically includes: S71. Calculate the heat carried by the hot water during the flowback phase. The calculation formula is as follows: Where: Q w1 is the heat carried by hot water during the flowback phase, in KJ; q w is the water production during the flowback phase, in m 3 ; is the average temperature of the hot zone during the production phase, in °C; S72. Calculate the heat carried by the produced water during the oil production phase using the following formula: Where: Q w2 is the heat carried by the produced water during the oil production stage, in KJ; q w2 is the water production during the oil production phase, in m 3 ;T r is the original formation temperature, in °C; is the average temperature of the hot zone during the production phase, in °C; S73. Calculate the heat carried by the produced oil using the following formula: Where: Q o It is the heat carried by the oil produced during the oil production stage, in KJ; C po is the heat capacity of oil, in KJ / (kg·℃); q o is the oil production, in m 3 ; is the average temperature of the hot zone during the production phase, in °C; S74. According to the principle of conservation of energy, calculate the change in the radius of the thermal fluid zone during the production phase. The calculation formula is as follows: Where: Q r is the residual heat in the formation, unit is KJ; H si and H wi are the heat injection rates of the steam zone and the thermal fluid zone at node i, respectively, in kJ / d; Q w1 It is the heat carried by hot water in the backflow stage, the unit is KJ; Q w2 It is the heat carried by the produced water during the oil production stage, in KJ; Q o is the heat carried by the oil produced during the oil production phase, in KJ; r hc is the radius of the hot zone, in m; M R is the reservoir heat capacity, in kJ / (m 3 ℃); T r is the original formation temperature, in °C; l is the horizontal well length, in m; is the average temperature of the hot zone during the production phase, in °C; S75. Calculate the transverse and longitudinal radii of the hot fluid zone in the production phase using the law of volume conservation based on the transverse and longitudinal correction ratios in the steam injection phase. S76. Calculate the waste heat of each section according to the following formula; Where: E rhi is the waste heat of the hot fluid zone at node i, in KJ; V hi is the volume of the hot fluid zone, in m 3 ;M R is the reservoir heat capacity, in kJ / (m 3 ℃); is the average temperature of the hot fluid zone during the production phase, °C; T r is the original formation temperature in °C.

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