Method for quantitatively predicting expansion front edge of steam huff-puff heating cavity of thick-layer heavy oil horizontal well

Abstract

The invention discloses a thick-layer heavy oil horizontal well steam huff and puff heating cavity expansion front edge quantitative prediction method which comprises the steps that a horizontal well is divided into i sections, and node coordinates of all the sections are calculated; based on steam distribution along a quadratic function of the horizontal well, the steam absorption amount of each node is calculated; the steam area radius and the hot fluid area radius of each node are calculated, and a steam cavity is corrected according to the heat transfer capacity difference in the vertical direction and the horizontal direction of an oil layer; calculating the average temperature of the two areas in the injection stage according to oil layer thermodynamic balance; calculating the average temperature and radius of a thermal fluid area in the soaking stage; calculating the average temperature of a hot fluid area in the output stage; calculating the radius and waste heat of a hot fluid area in the output stage; and taking the last-round last temperature and waste heat as initial conditions, repeating the operation, and outputting the calculation result of the next round. The method can accurately predict the radiuses of the steam area and the hot fluid area in the steam huff-puff process of the horizontal well, is high in operability, and can describe the development characteristics of the steam cavity in the steam huff-puff process more accurately.

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-huffling heating cavity in a thick-layer heavy oil horizontal well. Background Art

[0002] At present, steam injection development is a widely used heavy oil recovery technology. Different from the directional well development of onshore oil fields, offshore development mainly adopts the horizontal well development mode based on the development strategy of "few wells, high production, high speed and fast production". Compared with vertical wells, horizontal wells have a larger oil leakage area, a larger periodic steam injection volume, and a higher single well production capacity. Whether the development of steam chambers along the horizontal well can be accurately predicted plays a key role in actual production, and quantitatively predicting the expansion front of the steam heating chamber during steam injection is the basis for accurately describing the development law of the steam chamber. Past research has established a mathematical model to calculate the steam injection heating radius of vertical wells. Researchers have considered the non-isothermal distribution of formation temperature in the heating zone and established a new mathematical model for the heating radius of vertical wells. In addition, there are studies based on the plane potential theory, considering the influence of steam overprinting, and establishing a vertical well steam zone front movement model. The vertical well heating radius calculation model cannot be directly used for horizontal wells, but some researchers have established the corresponding horizontal well steam injection model and heating radius calculation model based on the vertical well heating radius calculation model, which provides a reference for horizontal well production capacity prediction and heating chamber description. The common point of the existing heating zone radius calculation models is that the formation heating range along the horizontal well is regarded as fixed, without considering the steam injection loss caused by steam absorption and wellbore flow along the way, nor the difference in horizontal and vertical heat transfer velocity of the steam chamber due to the difference in gasoline density on the cross section, and the influence of the start-up pressure gradient of the formation flow model around the well. The combined influence of the above three aspects will lead to a large difference between the calculation results of the steam zone or thermal fluid zone and the actual oil field. In summary, there is no mature research on the comprehensive consideration of the difference in steam absorption along the way, the difference in horizontal and vertical heat transfer capacity, and the start-up pressure gradient on the heating radius in the steam huff and puff of horizontal wells. 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 quantitative prediction method for the expansion front of a steam-throwing heating chamber in a thick-layer heavy oil horizontal well.

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

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

[0006] S1. Divide the horizontal well into N sections by unit length and calculate the node coordinates of each section;

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

[0008] S3, calculate the radius of the steam zone and the radius of the hot fluid zone 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;

[0009] S4. Consider the heat dissipation effect of the steam zone and the hot fluid zone, and calculate the average temperature of the steam zone and the hot fluid zone during steam injection according to 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 well 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 stage;

[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 of the next round.

[0014] In the above technical solution, the calculation method of 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 of 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 at a certain node of the horizontal well, in t / d; Q is the total daily steam injection, 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 means the distance from the node to the injection end, in meters; N means dividing the horizontal well 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 calculation method of 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 hot fluid zone does not reach the boundary of the oil layer, 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, in 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 m;

[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 of 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 of 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 energy conservation principle 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 m; r si is the radius of the steam zone at node i, in m; H wi are the heat injection rate of the hot 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 of 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 hot 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 boundary of the hot fluid zone reaches the upper and lower boundaries, the heating radius of the steam zone is still calculated by the calculation method when the boundary is not reached;

[0033] S322. The calculation formula of the radius of the thermal fluid zone is obtained by Laplace transformation of the energy conservation equation, and the calculation formula of the radius of the thermal fluid zone is as follows:

[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 rate of the hot fluid zone at node i, in kJ / d; Q r is the waste heat, in 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 microelement 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 energy conservation equation is Laplace transformed to obtain the calculation formula for the radius of the steam zone and the hot 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 hot fluid zone at node i, kJ / d; M R is the reservoir heat capacity, kJ / (m 3 ·℃); dl is the microelement length, m; Q r is the residual 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 hot fluid zone of node i, kJ; T h is the temperature of the hot fluid zone, °C; λ s is the boundary heat conductivity, 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, modifying the shape of the steam chamber according to 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 m;

[0047] S35. Assuming that the steam chamber maintains a ratio between the horizontal and vertical directions, the ratio of the horizontal and vertical distances is:

[0048]

[0049] The oil displacement 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:

[0054]

[0055] Where: α b is the ratio of the horizontal and vertical distances of the steam chamber, dimensionless; y t is the lateral expansion distance of the steam zone, in meters; z t A is the upward expansion distance of the steam zone, in meters; t is the volume of the oil leakage unit in the steam zone, in m 3 ;Q o is the oil displacement, 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 meters; 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, in Pa.s; P is the steam pressure, in MPa; Δρ is the density difference between crude oil and steam, in 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 the 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 gravity acceleration, unit is m / s 2 ; α b is the ratio of the horizontal and vertical distances 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 distance that the steam chamber expands horizontally is:

[0066]

[0067] Where: U z is the rate at which the steam zone expands upward, dimensionless; K is the thermal conductivity of the reservoir, dimensionless; k ro is the relative permeability of the oil phase, dimensionless; v os is the viscosity of the oil phase at the steam temperature, in mPa·s; 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 gravitational acceleration, in meters per second 2 ; G is the starting pressure gradient, unit is MPa / m; z i is the vertical 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 according to the volume balance:

[0069] S361. According to the law of volume conservation, 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 microelement length, in m; y i is the horizontal expansion distance of the i node, in meters; z i is the vertical extension distance of the i node, 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 meters; 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, r hi Substitute into Formula 25 to Formula 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 the 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 Represents 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; 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 i-th steam zone, in °C.

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

[0081] S51, the soaking stage is mainly based on heat conduction. At the end of soaking, the calculation formula of the average temperature of the hot fluid zone is 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 energy conservation, the total energy injected into the formation is equal to the energy of heating the formation, that is, the radius of the hot fluid zone after the well is soaked is obtained, and the calculation formula is as follows:

[0085]

[0086] In the formula, r m is the radius of the hot fluid zone after the well is soaked, in meters; H si and H wi are the heat injection rates of the steam zone and the hot 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 in the steam injection stage, the horizontal and vertical radii of the hot fluid zone in the well soaking stage 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 radial heat loss influencing factor of the hot fluid zone, 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 i-th steam zone, in °C.

[0091] In the above technical solution, the calculation method of 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 the hot water in the return 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 stage. The calculation formula is as follows:

[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. The calculation formula is as follows:

[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 energy conservation, the change in the radius of the thermal fluid zone during the production phase is calculated using the following formula:

[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 hot fluid zone at node i, respectively, in kJ / d; Q w1 It is the heat carried by the hot water in the return phase, in 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, according to the transverse and longitudinal correction ratios in the steam injection stage, the transverse and longitudinal radii of the hot fluid zone in the production stage are calculated by volume conservation;

[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 scheme, the specific calculation method of step S8 is: use 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 repeat 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 thermal balance and porous media heat transfer theory, the radius of the steam zone and the radius of 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. Considering 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, the temperature and residual heat at the end of the previous round are taken as the initial conditions, and the development of the steam zone and thermal fluid zone in each steam intake and discharge round is obtained by 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 a thick-layer heavy oil horizontal well. 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 result and realizing the quantitative prediction of the expansion front of the steam-huffing heating cavity in a horizontal well in an offshore thick-layer heavy oil reservoir. The method has strong operability and is of great significance to 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 It is the cross-sectional diagram of steam chamber development at node i of horizontal well steam stimulation (vertical to horizontal well cross section);

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

[0116] Figure 3 It 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 is a three-dimensional image of the steam chamber at different steam injection times in Example 1 of the present invention;

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

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

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

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

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

[0123] Fig.10 is a curve showing the change of the steam chamber radius along the wellbore during the well-sucking stage in Example 1 of the present invention; Fig.11 It is a three-dimensional image of the steam chamber at different soaking times in Example 1 of the present invention. For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0124] 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 is further described below with reference to the accompanying drawings and through specific implementation methods.

[0125] Example 1

[0126] 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 chamber in a thick-layer heavy oil horizontal well is shown in Figure 2. Figure 2 As shown, the following steps are included:

[0127] S1. Divide the horizontal well into i segments and calculate the node coordinates of each segment.

[0128] The length of the horizontal well in the target reservoir is 300m. The horizontal well is divided into 300 sections at 1m each, and the coordinates of the nodes in each section are 1, 2, 3...300.

[0129] S2. Calculate the steam absorption at each node based on the quadratic function distribution of steam along the horizontal well.

[0130] Calculate the steam absorption at each node. Considering that the steam absorption along the wellbore from the injection end to the finger end is a quadratic function distribution, the calculation equation for the steam absorption at a certain node is:

[0131] Q i =Q * (3 / 10 5 *L 2 -0.0094*L+1.0191)ε / 100 (1)

[0132] In the formula, Q i is the steam absorption at a certain node of the horizontal well, t / d; Q is the total daily steam injection, 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.

[0133] The daily steam injection rate Q of the target reservoir is 300t / d. When L is 10m, the air intake at this point is calculated by the above formula:

[0134] Q 10 =2.008t / d

[0135] S3. Calculate the radius of the steam zone and the radius of the hot fluid zone at 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.

[0136] The heating area is divided into a hot fluid area and a steam area. It is divided into three stages according to whether each area reaches the boundary. The steam area radius and hot fluid area radius of each node in the three stages are calculated respectively. The specific operations are as follows:

[0137] Stage 1: When the boundary of the hot fluid zone does not reach the boundary of the oil layer, 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:

[0138]

[0139] From the above formula, we can get the calculation expression of the steam zone radius:

[0140]

[0141] H si =I i ρ i L vi +E rsi (4)

[0142] Similarly, the calculation expression of the radius of the hot fluid zone can be obtained through the principle of energy conservation:

[0143]

[0144] H wi =I i ρ i (h wsi -h wri )+E rwi (6)

[0145] Stage 2: When the boundaries of the hot fluid zone reach the upper and lower boundaries, the heating radius of the steam zone can still be calculated by the calculation method when the boundaries are not reached. However, the calculation method of the hot fluid zone radius is different. After Laplace transformation of the energy conservation equation, the calculation expression of the hot fluid zone radius can be obtained:

[0146]

[0147] Stage 3: When the boundary of the steam zone reaches the upper and lower boundaries, the Laplace transform of the energy conservation equation gives the following equations to calculate the radii of the steam zone and the hot fluid zone.

[0148]

[0149] In the formula, 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; H si and H wi are the heat injection rates of the steam zone and the hot fluid zone at node i, kJ / d; M Ris the reservoir heat capacity, kJ / (m 3 ·℃); dl is the microelement length, m; Q r is the residual 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 hot fluid zone of node i, kJ; T h is the temperature of the hot fluid zone, °C; λ s is the boundary heat conductivity, W / (m·℃); α s is the thermal diffusivity of the boundary, m 2 / d.

[0150] Target reservoir steam temperature T s is 340℃, the original formation temperature T r is 50℃, the reservoir heat capacity M R is 2575 kJ / (kg·℃), the specific heat enthalpy of water at steam temperature is h wsi is 2624.3 kJ / kg, and the specific heat enthalpy of water at reservoir temperature is h wri is 1603.3 kJ / kg, and the boundary heat conductivity coefficient λ s is 1.73W / (m·℃), and the thermal diffusivity of the boundary is α s 0.089m 2 / d, the steam injection time is 20d, and the reservoir thickness is 40m.

[0151] According to the above steps,

[0152] H si =I i ρ i L vi +E rsi =4.51×10 6 kJ / d

[0153] H wi =I i ρ i (h wsi -h wri )+E rwi =2.04×10 6 kJ / d

[0154] in,

[0155] I i ρ i =Q 10 =1.8161×10 3 kg / d

[0156] E rsi =0

[0157] E rwi =0

[0158] Time when the thermal fluid zone boundary reaches the oil layer boundary:

[0159]

[0160] Time when the steam zone boundary reaches the oil layer boundary:

[0161]

[0162] The steam zone and the hot fluid zone have not reached the boundary, so

[0163]

[0164] The cross-section of the steam chamber calculated by the above method is circular, but due to the existence of steam overlay, the above method needs to be corrected to a certain extent.

[0165] The results of indoor physical research 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 speed of the steam chamber is higher than the horizontal expansion speed during the steam huff and puff of horizontal wells. The main reason is the density difference between steam and crude oil. Based on the difference in heat transfer speed in the vertical and horizontal directions of the cross section caused by the density difference between oil and steam in the expansion of the steam chamber, the shape of the steam chamber is corrected.

[0166] When the steam chamber expands laterally, the heat transfer equation in the reservoir is:

[0167]

[0168] Based on heat conduction, the solution to the equation is:

[0169]

[0170] Where: K is the thermal conductivity of the reservoir; ρ r is the reservoir density, kg / m 3 ; C pr is the reservoir heat capacity, J / K; U x is the lateral diffusion rate m / d; ρc 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.

[0171] Assuming that the steam chamber maintains a certain ratio in the horizontal and vertical directions, the ratio of the horizontal and vertical distances is:

[0172]

[0173] The oil displacement of rising steam is:

[0174]

[0175] Q o =S o V (15)

[0176]

[0177] The vertical oil displacement rate can be expressed by the oil phase velocity equation as follows:

[0178]

[0179] Where K is the thermal conductivity of the reservoir; 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 of the strong steam front, m; v o is the kinematic viscosity of the oil phase, m 2 / s;k o Oil phase permeability, mD; μ o is the oil phase viscosity, Pa.s; ρo 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.

[0180] so:

[0181]

[0182] The upward expansion rate in the steam chamber is obtained as:

[0183]

[0184]

[0185] In the formula, v os is the viscosity of the oil phase at the steam temperature, mPa·s; Δp is the difference between the steam pressure and the reservoir pressure, MPa; z i is the vertical expansion distance of the i node, 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.

[0186] After calculating the longitudinal and lateral expansion rates, the previously obtained cylindrical steam chamber microelement is corrected according to the volume balance.

[0187] According to the law of volume conservation, the sum of the volumes of the upper and lower parts of the steam chamber is equal to the volume of the entire chamber:

[0188]

[0189] y i =U x t z (26)

[0190] z i =U z t z (27)

[0191]

[0192] According to the above formula, calculate y i 、z i and z 2i Finally, determine the final cross-sectional shape of the steam zone. hi By substituting into Formula 25 to Formula 28, the cross-sectional shape of the final hot fluid zone can be determined.

[0193] Substituting the target reservoir parameters, the horizontal and vertical distance ratio of the steam zone is calculated according to the above formula:

[0194]

[0195] Where, K = 3000mD, μ = 28854mPa·s, m = 2.35, n = 2

[0196] Substituting into formula (25) we obtain:

[0197] z 2i =1.5290m

[0198] Specifically, Figure 3 , Figure 4 , Figure 5 , Figure 6 According to the relevant formulas in the second and third steps, the radius change data along the steam zone and the hot fluid zone are calculated and plotted.

[0199] S4. Considering the heat dissipation effect of the steam zone and the hot fluid zone, the average temperature of the two zones during the injection stage is calculated based on the thermal balance of the oil layer.

[0200] Specific operation: The average temperature of the steam zone and the heat flow zone during steam injection can be expressed as:

[0201]

[0202] Among them, T asi and T ahi are the average temperatures of the steam zone and the hot fluid zone during steam injection, ℃; 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, dimensionless; and Represents 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.

[0203] The thermal diffusion coefficient α of the target reservoir is 0.089m 2 / d, steam injection time t z For 20 days, calculated according to the above formula:

[0204] Average temperature of steam zone:

[0205]

[0206] Average temperature of thermal fluid area:

[0207]

[0208] S5. Considering the influence of heat conduction, calculate the average temperature and radius of the hot fluid zone during the soaking stage.

[0209] The soaking stage is mainly heat conduction. At the end of soaking, the average temperature of the hot fluid zone is:

[0210]

[0211] In the formula, is the average temperature of the hot fluid zone at the end of soaking, ℃; C 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.

[0212] After finding the average temperature of the hot fluid zone, according to the law of energy conservation, the total energy injected into the formation is equal to the energy of heating the formation, and the radius of the hot fluid zone after the soaking is completed can be found:

[0213]

[0214] In the formula, r m is the radius of the hot fluid zone after the soaking is completed, m.

[0215] 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:

[0216]

[0217] G = 4.016 × 10 4 kg

[0218]

[0219]

[0220] r m =8.865m

[0221] Specifically, Figure 7 , Figure 8 , Fig. 9After 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.

[0222] 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.

[0223] The average temperature of the hot fluid zone during the production phase can be expressed as:

[0224]

[0225] in, is the average temperature of the hot fluid zone during the production stage, °C; δ is the liquid production correction factor, dimensionless.

[0226] According to the target reservoir conditions, T si 340℃, T r 50℃, number of days of well soaking t m 7 days, based on production days s Take 20 days as an example and calculate according to the above steps:

[0227]

[0228] The heat carried is calculated based on the actual production of the target oil field for 20 days:

[0229]

[0230] Similarly,

[0231]

[0232] 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.

[0233] In the flowback stage, the heat carried by hot water is:

[0234]

[0235] During the oil production stage, the heat carried by the produced water is:

[0236]

[0237] Heat carried by produced oil:

[0238]

[0239] According to the principle of energy conservation, the change in the radius of the thermal fluid zone during the production stage is calculated:

[0240] Q r =Hsi +H wi -Q w1 -Q w2 -Q o (43)

[0241]

[0242] In the formula, Q w1 is the heat carried by hot water during the return 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.

[0243] The residual heat expression for each section is:

[0244]

[0245] Among them, E rhi is the residual heat of the hot fluid zone at node i, kJ; V hi is the volume of the hot fluid zone, m 3 .

[0246] According to the target reservoir conditions, taking the actual production for 20 days as an example, the water production q w is 91.91kg, q w2 is 5533.63kg, q o is 3993.83kg, C po It is 2kJ / (kg·℃), calculated according to the above formula:

[0247]

[0248] Q r =H si +H wi -Q w1 -Q w2 -Q o =6.2×10 6 kJ

[0249] r hc =16.7433m

[0250]

[0251] 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.

[0252] 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 calculations. The above steps are repeated multiple times to obtain the steam zone radius and the hot fluid zone radius for each round of steam throughput.

[0253] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope 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 shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A quantitative prediction method for the expansion front of a 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 sections by unit length and calculate the node coordinates of each section; S2, based on the quadratic function distribution of steam along the horizontal well, calculate the steam absorption capacity of each node; S3, calculate the radius of the steam zone and the radius of the hot fluid zone 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; S4. Consider the heat dissipation effect of the steam zone and the hot fluid zone, and calculate the average temperature of the steam zone and the hot fluid zone during steam injection according to 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 well 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 stage; 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 of the next round.

2. 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 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 means the distance from the node to the injection end, in meters; N means dividing the horizontal well 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 hot fluid zone radius of each node in step S3, the heating zone is divided into a hot fluid zone and a steam zone, and is divided into three stages according to whether each zone reaches the boundary. The steam zone radius and the hot 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 hot fluid zone does not reach the boundary of the oil layer, 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, in 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 m; 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 of 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 of 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 energy conservation principle 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 m; r si is the radius of the steam zone at node i, in m; H wi are the heat injection rate of the hot fluid zone at the i node, in kJ / d; Qr 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 of 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 hot 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 boundary of the hot fluid zone reaches the upper and lower boundaries, the heating radius of the steam zone is still calculated by the calculation method when the boundary is not reached; S322. The calculation formula of the radius of the thermal fluid zone is obtained by Laplace transformation of the energy conservation equation, and the calculation formula of the radius of the thermal fluid zone is as follows: Where: r hi is the radius of the hot fluid zone at node i, in m; d is half of the formation thickness, in m; H wi are the heat injection rate of the hot fluid zone at node i, in kJ / d; Q r is the waste heat, in 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 microelement 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 energy conservation equation is Laplace transformed to obtain the calculation formula for the radius of the steam zone and the hot 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 hot fluid zone at node i, kJ / d; M R is the reservoir heat capacity, kJ / (m 3 ·℃); dl is the microelement length, m; Q r is the residual 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 hot fluid zone of node i, kJ; T h is the temperature of the hot fluid zone, °C; λ s is the boundary heat conductivity, 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 reservoir 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 a thick-layer heavy oil horizontal well 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, modifying the shape of the steam chamber according to 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 m; S35. Assuming that the steam chamber maintains a ratio between the horizontal and vertical directions, the ratio of the horizontal and vertical distances is: The oil displacement of rising steam is: Q o =S o V (15) The vertical oil displacement rate is expressed by the oil phase velocity equation: Where: α b is the ratio of the horizontal and vertical distances of the steam chamber, dimensionless; y t is the lateral expansion distance of the steam zone, in meters; z t A is the upward expansion distance of the steam zone, in meters; t is the volume of the oil leakage unit in the steam zone, in m 3 ;Q o is the oil displacement, 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 meters; 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, in Pa.s; P is the steam pressure, in MPa; Δρ is the density difference between crude oil and steam, in 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 the 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; 9 is gravity acceleration, unit is m / s 2 ; α b is the ratio of the horizontal and vertical distances of the steam chamber, dimensionless; z t is the upward expansion 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 rate at which the steam zone expands upward, dimensionless; K is the thermal conductivity of the reservoir, dimensionless; k ro is the relative permeability of the oil phase, dimensionless; v os is the viscosity of the oil phase at the steam temperature, in mPa·s; 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 gravitational acceleration, in meters per second 2 ; G is the starting pressure gradient, unit is MPa / m; z i is the vertical 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 according to the volume balance: S361. According to the law of volume conservation, 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 microelement length, in m; y i is the horizontal expansion distance of the i node, in meters; z i is the vertical extension distance of the i node, 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 meters; 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, 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 average temperature calculation formula of the steam zone and the heat flow zone during the 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, 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 lateral heat loss coefficient, dimensionless; θ rh is the longitudinal heat loss coefficient of the hot 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 i-th steam zone, 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 in the soaking stage in step S5 specifically includes: S51, the soaking stage is mainly based on heat conduction. At the end of soaking, the calculation formula of the average temperature of the hot fluid zone is 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 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; S52. According to the law of energy conservation, the total energy injected into the formation is equal to the energy of heating the formation, that is, the radius of the hot fluid zone after the well is soaked is obtained, and the calculation formula is as follows: In the formula, r m H is the radius of the hot fluid zone after the well is soaked, in meters; si and H wi are the heat injection rates of the steam zone and the hot 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 in the steam injection stage, the horizontal and vertical radii of the hot fluid zone in the well soaking stage 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 of 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 radial heat loss influencing factor of the hot fluid zone, dimensionless; is the factor affecting the vertical heat loss in the hot fluid zone, dimensionless; δ is the liquid production correction coefficient, dimensionless; T si is the temperature of the i-th steam zone, 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 calculation method of the radius of the hot fluid zone and the residual heat in the output stage of 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 the hot water in the return 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 stage. The calculation formula is as follows: 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. The calculation formula is as follows: 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 energy conservation, the change in the radius of the thermal fluid zone during the production phase is calculated using the following formula: Q r =H si +H wi -Q w1 -Q w2 -Q o (43) 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 hot fluid zone at node i, respectively, in kJ / d; Q w1 It is the heat carried by the hot water in the return phase, in 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; 1 is the horizontal well length, in m; It is the average temperature of the hot zone during the production phase, in °C. S75, according to the transverse and longitudinal correction ratios in the steam injection stage, the transverse and longitudinal radii of the hot fluid zone in the production stage are calculated by volume conservation; 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.

9. 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, characterized in that: 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.

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