A method for predicting the production capacity of in-situ oil shale production using steam injection

Abstract

The present invention provides a method for predicting the production capacity of in-situ steam injection mining of oil shale, which belongs to the technical field of oil and gas field development. The method for predicting the production capacity of in-situ steam injection mining of oil shale uses the steam front evolution theory, combined with the basic characteristics of the pyrolysis reaction of kerogen in oil shale, to divide the entire oil shale reservoir during the steam injection in-situ mining process into different areas, establish a mathematical model for the in-situ steam injection mining of oil shale, and use it to predict its production capacity, while reflecting the different development stages of the oil shale reservoir; the production capacity prediction method belongs to the field of oil and gas field development, and can solve the problems of existing production capacity prediction methods such as numerous calculation parameters and poor calculation ability, which greatly increase the difficulty of solving the model and the model is prone to non-convergence, so that the production capacity settlement result cannot be given; at the same time, it can also solve the problems of existing methods such as difficulty in correcting the reaction model according to actual conditions, involving multiple experimental tests and theoretical calculations, and complex actual operations resulting in poor practicality.

Description

Technical Field

[0001] The present invention belongs to the technical field of oil and gas field development, and in particular relates to a method for predicting the production capacity of in-situ oil shale steam injection mining. Background Art

[0002] Oil shale is an unconventional oil and gas resource with vast reserves. my country's proven oil shale reserves rank second in the world. Its efficient development can greatly alleviate the problem of tight oil and gas supply in my country and provide great protection for my country's energy security. At present, the main method for developing oil shale is ground distillation technology, but ground distillation technology has problems such as low utilization rate and environmental pollution. Steam injection, as a green and efficient in-situ oil shale mining technology, has received increasing attention in recent years. Its main working principle is to inject high-temperature steam directly into the underground oil shale reservoir through injection wells, and use steam convection to heat the oil shale. The oil and gas generated by the pyrolysis of kerogen in the oil shale are extracted from the surface through production wells.

[0003] Productivity prediction is a crucial component of in-situ steam injection recovery of oil shale. This technology provides the basis for increasing individual well production, optimizing well placement, controlling the production and construction pace, and mitigating production and construction risks. It plays a crucial role in ensuring the economic benefits of oil and gas field development. However, limited research has been conducted on production capacity prediction methods for in-situ steam injection recovery of oil shale. Numerical simulation software primarily calculates the production capacity of in-situ oil shale development using chemical reaction models. These software inputs describe the pyrolysis and oil and gas generation process of kerogen in oil shale, involving a series of chemical reaction equations and reaction parameters. The numerous parameters involved in the pyrolysis reaction and the limited computational power significantly increase the difficulty of solving the model, making it prone to non-convergence and the inability to produce production capacity calculation results. The two most widely used models are the Braun-Burnham and Wellington models. Different types of oil shales pyrolyze under different heating conditions, resulting in different chemical reaction models. Typically, one of these models is modified based on the specific situation. However, the modification process is complex, involving multiple experimental tests and theoretical calculations. This complexity leads to limited practical application. Summary of the Invention

[0004] In view of this, the present invention provides a method for predicting the production capacity of in-situ production of oil shale by steam injection, which can solve the problems of existing production capacity prediction methods, such as the large number of calculation parameters and poor computing power, which greatly increases the difficulty of solving the model and the model is prone to non-convergence, making it impossible to provide production capacity settlement results; at the same time, it can also solve the problem that existing methods are difficult to correct the reaction model according to actual conditions, involve multiple experimental tests and theoretical calculations, and the actual operation is complicated, resulting in poor practicality.

[0005] The present invention is achieved in that:

[0006] The present invention provides a method for predicting the production capacity of in-situ oil shale steam injection mining, comprising the following specific steps:

[0007] S10: Identify different zones of oil shale reservoirs during in-situ recovery with steam injection;

[0008] S20: Determine the structural parameters of the steam zone for in-situ production of oil shale by steam injection;

[0009] S30: Determine the structural parameters of the transition zone for in-situ production of oil shale with steam injection;

[0010] S40: Determine the structural parameters of the oil-rich zone for in-situ production of oil shale by steam injection;

[0011] S50: Establishing a productivity prediction model for in-situ steam injection mining of oil shale based on the structural parameters of the steam zone, transition zone, and oil-rich zone of the in-situ steam injection mining of oil shale, and predicting the productivity of in-situ steam injection mining of oil shale.

[0012] The structural parameters of the steam zone for in-situ production of oil shale by steam injection in S20 specifically include: a description formula for the steam front of oil shale, the top and bottom radii of the steam zone, and the volume of oil displaced by expansion of the steam zone;

[0013] The oil shale steam front description formula is:

[0014]

[0015] Where: r se is the top radius of the steam zone, in m; r sb is the bottom radius of the steam zone, in m; ω 2 is the ratio of the radial mass flow rate of steam in the oil shale reservoir to the steam injection velocity, which is set to 0.75; M′ is the pseudo-mobility ratio, which is set to 0.5; A′ RD To correct the shape factor, calculate as follows:

[0016]

[0017] Where: c is the correction coefficient; μ s is the steam viscosity, in mPa·s; i s is the steam injection rate, in kg / s; g is the acceleration due to gravity, in m / s 2 ; h is the thickness of the oil shale reservoir, in m; ρ o is the oil density, in kg / m 3 ρ s is the steam density, in kg / m 3 ;k s is the average effective steam permeability, in units of 10 -3 μm2 ;

[0018] The bottom radius of the steam zone is:

[0019]

[0020] Where A sb is the bottom area of the steam zone, in m 2 ;

[0021] The radius of the top of the steam zone is:

[0022]

[0023] Where: α=1 / [A′ RD ω(1-M′) 1 / 2 ];

[0024] Volume of oil displaced by steam zone expansion:

[0025]

[0026] Where: V s is the volume of the steam zone, in m 3 ; V so The volume of oil displaced by expansion in the steam zone, in m 3 ρ o is the oil density, in kg / m 3 ρ os is the density of oil shale, in kg / m 3 ; ψ is the oil content of oil shale.

[0027] The structural parameters of the transition zone for in-situ production of oil shale by steam injection in S30 specifically include the front description formula of the transition zone of oil shale, the bottom radius of the transition zone, and the volume of oil displaced by expansion of the transition zone;

[0028] The formula for describing the front edge of the oil shale transition zone is as follows:

[0029]

[0030] Where: h t is the thickness of the transition zone, in m; r tb is the bottom radius of the transition zone, in m; r is the radial distance in the oil shale reservoir, in m;

[0031] Transition zone bottom radius:

[0032]

[0033] The volume of oil displaced by expansion in the transition zone:

[0034]

[0035] Where: V to The volume of oil displaced from the transition zone, in m 3 .

[0036] The formula for describing the front of the oil-rich area of oil shale is as follows:

[0037]

[0038] Where: h f is the thickness of the oil-rich zone, in m; r fb is the bottom radius of the oil-rich area, in m;

[0039] Oil-rich zone top radius:

[0040] r fe =r se +(r fb -r sb )

[0041] Where: r fe is the radius of the top of the oil-rich zone, in m;

[0042] Volume of oil-rich area:

[0043]

[0044] Where: S fo is the oil saturation of the oil-rich area; V f is the volume of the oil-rich area, in m 3 .

[0045] The specific process of establishing the productivity prediction model for in-situ production of oil shale by steam injection in S50 includes:

[0046] Phase 1: Oil-free production phase, cumulative oil production is 0;

[0047] The second stage: rapid oil production stage, the cumulative oil production is:

[0048]

[0049] Where: V o is the cumulative oil production, in m 3 ; V fp is the volume of the oil-rich area discharged from the production well, in m 3 ; The third stage: slow oil production stage, the cumulative oil production is:

[0050]

[0051] Where: V tpis the volume of the transition zone discharged from the production well, in m 3 ;S to is the oil saturation in the transition zone;

[0052] The fourth stage: the final oil production stage, until the oil production stops, the cumulative oil production is:

[0053]

[0054] Where: V sp The volume of the steam zone discharged from the production well, in m 3 ;S so is the oil saturation in the steam zone.

[0055] Among them, the process of in-situ extraction of oil shale by steam injection is divided into:

[0056] The first stage is the oil-free production stage, from the start of steam injection into the oil shale reservoir to the initial migration of the oil-rich front to the production well.

[0057] The second stage is from the initial migration of the oil-rich zone front to the production well to the initial migration of the transition zone front to the production well. This stage is the rapid oil production stage.

[0058] The third stage: after the transition zone front initially migrates to the production well and before the steam zone front initially migrates to the production well, this stage is the slow oil production stage;

[0059] Stage 4: After the steam front initially migrates to the production well, this stage belongs to the final oil production stage.

[0060] Among them, the regional classification of oil shale reservoirs in the in-situ steam injection mining process in S10 includes: steam zone, transition zone, oil-rich zone and original oil shale zone; the steam zone is due to the low density and low viscosity of steam. Under the action of gravity differentiation, steam rises and advances in the oil shale reservoir, resulting in steam overburden phenomenon in the steam zone; the transition zone is an area formed in front of the steam zone by condensed water and oil produced by pyrolysis of oil shale under the action of thermal convection, heat conduction and driving of steam; the oil-rich zone is an area formed in front of the heated zone by the pyrolysis oil of oil shale driven out when the steam zone and the transition zone serve as heated zones.

[0061] Among them, the pyrolysis process of oil shale can be summarized into three stages: the mass loss in the first stage is mainly caused by water evaporation, especially the adsorbed water and interlayer water of clay minerals; the mass loss in the second stage is mainly due to the pyrolysis of kerogen in oil shale, which is regarded as the oil production stage. In this patent, the mass loss in this stage is considered to be a linear change from the initial temperature to the final temperature of kerogen pyrolysis; the mass loss in the third stage is mainly determined by the pyrolysis of carbonate and clay minerals.

[0062] The front edges of the steam zone, the transition zone, the oil-rich zone and the original oil shale zone are parallel to each other.

[0063] Among them, with the continuous injection of steam, different areas formed under the action of steam heating and driving continue to expand forward in the original oil shale area, and pyrolysis oil is continuously produced after reaching the production well.

[0064] Compared with the prior art, the method for predicting the productivity of in-situ steam injection production of oil shale provided by the present invention has the following beneficial effects: it reduces the complexity of the kerogen pyrolysis reaction model in numerical simulation software, eliminates the need to expend excessive time and effort on correcting and solving the pyrolysis reaction model with numerous parameters, and greatly improves the efficiency of its productivity prediction while ensuring the accuracy of the prediction of the productivity of in-situ steam injection production of oil shale; introduces the steam front prediction theory, provides a convenient way to explore the impact of steam front development on the productivity of in-situ steam injection production of oil shale, fills some theoretical gaps in the prediction of the productivity of in-situ steam injection production of oil shale, and can solve the problem that the existing productivity prediction methods have many calculation parameters and poor computing power, which greatly increases the difficulty of solving the model and makes it easy for the model to fail to converge and thus cannot provide a productivity settlement result; the entire oil shale reservoir during the steam injection in-situ production process is simplified and partitioned, and the different production stages of in-situ steam injection production of oil shale can be intuitively reflected based on its productivity calculation data, thereby improving its applicability to oilfield development projects and solving the problem that the existing methods are difficult to correct the reaction model according to actual conditions, involve multiple experimental tests and theoretical calculations, and are complex in actual operation, resulting in poor practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0066] Figure 1 A specific flow chart of a method for predicting the production capacity of in-situ oil shale production through steam injection;

[0067] Figure 2 Schematic diagram of different areas of oil shale reservoirs for in-situ steam injection recovery of oil shale;

[0068] Figure 3 TG curve and simplified diagram of oil shale pyrolysis;

[0069] Figure 4 Schematic diagram of the first stage of in-situ steam injection recovery of oil shale - oil-free production stage;

[0070] Figure 5 Schematic diagram of the second stage of in-situ steam injection recovery of oil shale - rapid oil production stage;

[0071] Figure 6 Schematic diagram of the third stage of in-situ steam injection recovery of oil shale - the slow oil production stage;

[0072] Figure 7 Schematic diagram of the fourth stage - the final oil production stage - of in-situ steam injection recovery of oil shale;

[0073] Figure 8 This is a diagram showing the front changes in the four production stages of in-situ steam injection production of oil shale;

[0074] Figure 9 This is a comparison chart of the cumulative oil production predicted by this method of in-situ steam injection recovery of oil shale and CMG numerical simulation. DETAILED DESCRIPTION

[0075] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0076] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0077] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0078] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0079] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0080] like Figure 1 FIG. 1 is a flow chart of a method for predicting the production capacity of in-situ oil shale production by steam injection provided by the present invention. The method includes the following specific steps:

[0081] S10: Identify different zones of oil shale reservoirs during in-situ recovery with steam injection;

[0082] S20: Determine the structural parameters of the steam zone for in-situ production of oil shale by steam injection;

[0083] S30: Determine the structural parameters of the transition zone for in-situ production of oil shale with steam injection;

[0084] S40: Determine the structural parameters of the oil-rich zone for in-situ production of oil shale by steam injection;

[0085] S50: Establishing a productivity prediction model for in-situ steam injection mining of oil shale based on the structural parameters of the steam zone, transition zone, and oil-rich zone of the in-situ steam injection mining of oil shale, and predicting the productivity of in-situ steam injection mining of oil shale.

[0086] Among them, in the above technical solution, the process of confirming the structural parameters of the steam zone for in-situ production of oil shale by steam injection in S20 is specifically as follows:

[0087] Based on the existing steam front prediction theory, the description formula of the oil shale steam front is as follows:

[0088]

[0089] Where: h s is the thickness of the steam zone, in m; h is the thickness of the oil shale reservoir, in m; r se is the radius of the top of the steam zone, in m; r is the radial distance in the oil shale reservoir, in m; ω 2 is the ratio of the radial mass flow rate of steam in the oil shale reservoir to the steam injection velocity, which is set to 0.75; M′ is the pseudo-mobility ratio, which is set to 0.5; A′ RD To correct the shape factor, calculate as follows:

[0090]

[0091] Where: c is the correction coefficient; μ sis the steam viscosity, in mPa·s; i s is the steam injection rate, in kg / s; g is the acceleration due to gravity, in m / s 2 ρ o is the oil density, in kg / m 3 ρ s is the steam density, in kg / m 3 ;k s is the average effective steam permeability, in units of 10 -3 μm 2 ;

[0092] When the steam zone thickness is equal to the reservoir thickness, the formula describing the oil shale steam front can be changed to:

[0093]

[0094] Where: r sb is the bottom radius of the steam zone, in m;

[0095] According to the circular area formula, the area relationship between the top of the steam zone and the bottom of the steam zone can be obtained by the above formula:

[0096]

[0097] Where: a=1 / [A′ RD ω(1-M′) 1 / 2 ], A se is the top area of the steam zone, in m 2 ; A sb is the bottom area of the steam zone, in m 2 ;

[0098] Using integral transformation, according to the area relationship between the top and bottom of the steam zone and the description formula of the oil shale steam front, the volume of the steam zone can be expressed as:

[0099]

[0100] Where: F = 1-A' RD ω(1-M′) 1 / 2 e 2α2 {α / e 2α2 +(2π) 1 / 2 / 4[erfc(2 1 / 2 α)-1]}; V s is the volume of the steam zone, in m 3 ;

[0101] As the temperature rises, the oil shale will undergo pyrolysis. During the steam injection process, the heat absorbed in the steam zone is divided into two parts: one part is used to heat the oil shale, and the other part is used for the endothermic reaction of the oil shale pyrolysis. Therefore, considering the main endothermic reaction of the second stage of kerogen pyrolysis, the thermal growth rate of the steam zone can be written as:

[0102]

[0103] Where: Q sv is the thermal growth rate of the steam zone, in J / s, M is the heat capacity of the oil shale reservoir, in J / (m 3 ℃), defined as Among them, M w is the heat capacity of water, in J / (m 3 ℃), M s is the heat capacity of oil shale, in J / (m 3 ℃), is the average porosity of the oil shale reservoir; ΔT is the temperature difference between the injected steam and the initial temperature of the oil shale reservoir, in °C, defined as ΔT = T s -T i , where T s is the injection steam temperature, in °C, T i The initial temperature of the oil shale reservoir is in °C; t is the steam injection time in seconds; β is the thermal decomposition conversion rate of kerogen in the steam zone, defined as β = (T s -T st ) / (T sp -T st ), T st ≤T s ≤T sp , where T st is the initial temperature of kerogen pyrolysis, in °C, T sp is the kerogen pyrolysis termination temperature, in °C; C is the initial kerogen concentration in oil shale, in mol / m 3 ; H is the enthalpy of thermal decomposition reaction, unit is J / mol;

[0104] Heat loss rate per unit area:

[0105]

[0106] Where: q is the heat loss rate per unit area, unit is J / (m 2 ·s); K ob is the thermal conductivity of the top and bottom layers of the oil shale reservoir, in W / (m·℃); D is the thermal diffusivity of the top and bottom layers of the oil shale reservoir, in m 2 / s;

[0107] The sum of the heat loss rates from the steam zone to the top and bottom layers of the oil shale reservoir is:

[0108]

[0109] Where: Q s1 is the sum of the heat loss rates of the steam zone to the top and bottom layers of the oil shale reservoir, in J / s; A is the unit area, in m 2 ;τ is the unit time, the unit is s;

[0110] The steam quality of superheated steam is 1, and the heat injection rate of the steam zone is:

[0111] Qs i =i s (H s -H wh )

[0112] Where: Q si is the heat injection rate of the steam zone, in J / s; H s is the enthalpy of injected steam, in J / kg; H wh is the enthalpy of water at saturated steam temperature, in J / kg;

[0113] Based on the principle of conservation of energy, the heat balance of the steam zone is as follows:

[0114]

[0115] The heat balance formula of the steam zone belongs to the second type of Voltera integral formula and can be solved using Laplace transform as follows:

[0116]

[0117] Where: S is the variable in the Latent space; L(·) is the Latent transformation function;

[0118] The solution of the above formula in Laszlo space is as follows:

[0119]

[0120] Where: b = K ob △T(1+e 2α2 ) / [D 1 / 2 Fh(MΔT+βCH)].

[0121] By La inverse transformation, the bottom area of the steam zone is:

[0122]

[0123] Where: t D is the dimensionless time, defined as t D =Kob 2 ΔT 2 t / [(MΔT+βCH) 2 h 2 D];λ=(1+e 2α2 ) 2 / F 2 ;

[0124] According to the steam zone bottom area formula and the circle area formula, the steam zone bottom radius is:

[0125]

[0126] Combining the area relationship formula between the top and bottom of the steam zone, the area formula of the bottom of the steam zone, and the area formula of a circle, the radius of the top of the steam zone is:

[0127]

[0128] Volume of oil displaced by steam zone expansion:

[0129]

[0130] Where: V so The volume of oil displaced by expansion in the steam zone, in m 3 ρ os is the density of oil shale, in kg / m 3 ; ψ is the oil content of oil shale.

[0131] Kerogen is dispersed organic matter in sedimentary rocks that is insoluble in alkalis, non-oxidizing acids, and organic solvents. Steam dryness refers to the mass percentage of dry saturated steam per kilogram of wet steam. Steam dryness is a crucial parameter for the safe operation of oilfield steam injection boilers and a key indicator of thermal recovery effectiveness.

[0132] Among them, in the above technical solution, the confirmation process of the structural parameters of the transition zone of the in-situ mining of oil shale by steam injection in S30 is specifically as follows:

[0133] The heat absorbed by the transition zone is divided into two parts: one part is used to heat up the oil shale, and the other part is used to decompose the oil shale into an endothermic reaction. The thermal growth rate of the transition zone can be written as:

[0134]

[0135] Where: Q tv is the thermal growth rate of the transition zone, in J / s; ΔT′ is the temperature difference between the transition zone and the initial temperature of the oil shale reservoir, in °C, defined as ΔT′=ΔT / 2; β′ is the pyrolysis conversion rate of kerogen in the transition zone, defined as β′=β / 2;

[0136] The sum of the heat loss rates of the transition zone to the top and bottom layers of the oil shale reservoir is:

[0137]

[0138] Where: Q tl is the sum of the heat loss rates of the transition zone to the top and bottom layers of the oil shale reservoir, in J / s; r te is the top radius of the transition zone, in m; r tb is the bottom radius of the transition zone, in m;

[0139] Let ζ1 = rr se and ζ2=rr sb ζ1 is the radial distance from the top of the transition zone, m; ζ2 is the radial distance from the bottom of the transition zone, m; using the substitution integral method, the integral variable in the sum of the heat loss rates of the transition zone to the top and bottom layers of the oil shale reservoir is changed to time. The formula for the sum of the heat loss rates of the transition zone to the top and bottom layers of the oil shale reservoir can be changed to:

[0140]

[0141] The thermal growth rate formula in the transition zone can be changed to:

[0142]

[0143] Based on the principle of energy conservation, the thermal balance in the transition zone is as follows:

[0144]

[0145] Where: H wi is the enthalpy of water at the initial temperature of the oil shale reservoir, in J / kg; dA′=π(2r+e α2 r sb -r sb )dr, where A′ is the pseudo bottom area of the transition zone, in m 2 ;

[0146] Using Laplace transform and inverse Laplace transform, the heat balance formula of the transition zone can be changed to:

[0147]

[0148] At the same time, the pseudo bottom area of the transition zone can be written as

[0149]

[0150] Therefore, the bottom radius of the transition zone is:

[0151]

[0152] because:

[0153] r te =r se +(r tb -r sb )

[0154] At the same time, according to the description formula of the oil shale steam front, the description formula of the oil shale transition zone front can be obtained as follows:

[0155]

[0156] Where: h t is the thickness of the transition zone, in m;

[0157] Given the transition zone radius and the transition zone leading edge description formula, the total volume of the steam zone and the transition zone can be obtained by integration. The volume of the transition zone can be expressed as:

[0158] V t =V s+t -V s

[0159] Where: V s+t is the total volume of the steam zone and transition zone, in m 3 ; V t is the volume of the transition zone, in m 3 .

[0160] Since the pyrolysis conversion rate of kerogen in the transition zone is β / 2, we can get:

[0161]

[0162] Where: V to The volume of oil displaced from the transition zone, in m 3 .

[0163] Among them, Laplace transform is an integral transform commonly used in engineering mathematics.

[0164] Among them, in the above technical solution, the specific process of confirming the structural parameters of the oil-rich area of S40 oil shale in-situ steam injection mining is as follows:

[0165] The volume of oil driven out through the heated zone can be obtained as V f is the volume of the oil-rich area, in m 3 :

[0166]

[0167] Where: S fo is the oil saturation of the oil-rich zone;

[0168] According to the description formula of the oil shale steam front, the description formula of the oil shale oil-rich area front can be obtained as follows:

[0169]

[0170] Where: h f is the thickness of the oil-rich zone, in m; r fb is the bottom radius of the oil-rich area, in m;

[0171] By integrating the front edge description formula of the oil-rich area, the volume of the oil-rich area can also be obtained, and the bottom radius of the oil-rich area can be solved by using the bisection method;

[0172] because:

[0173] r fe =r se +(r fb -r sb )

[0174] Where: r fe is the top radius of the oil-rich area, in meters.

[0175] Among them, in the above technical solution, the specific process of establishing the production capacity prediction model for in-situ production of oil shale by steam injection in S50 includes:

[0176] Phase 1: Oil-free production phase, cumulative oil production is 0;

[0177] The second stage: rapid oil production stage, the cumulative oil production is:

[0178]

[0179] Where: V o is the cumulative oil production, m 3 ; V fp is the volume of the oil-rich area discharged from the production well, in m 3 ;

[0180] The third stage: slow oil production stage, the cumulative oil production is:

[0181]

[0182] Where: V tp is the volume of the transition zone discharged from the production well, in m 3 ;S to is the oil saturation in the transition zone;

[0183] The fourth stage: the final oil production stage, until the oil production stops, the cumulative oil production is:

[0184]

[0185] Where: V sp The volume of the steam zone discharged from the production well, in m 3 ;S so is the oil saturation in the steam zone.

[0186] Among them, in the above technical solution, the process of in-situ extraction of oil shale by steam injection is divided into:

[0187] The first stage is from the beginning of steam injection into the oil shale reservoir to the initial migration of the oil-rich front to the production well. This stage is the oil-free production stage.

[0188] The second stage is from the initial migration of the oil-rich zone front to the production well to the initial migration of the transition zone front to the production well. This stage is the rapid oil production stage.

[0189] The third stage: after the transition zone front initially migrates to the production well and before the steam zone front initially migrates to the production well, this stage is the slow oil production stage;

[0190] Stage 4: After the steam front initially migrates to the production well, this stage belongs to the final oil production stage.

[0191] Among them, in the above technical scheme, the regional classification of oil shale reservoirs in the steam injection in-situ mining process in S10 includes: steam zone, transition zone, oil-rich zone and original oil shale zone; the steam zone is due to the low density and low viscosity of steam. Under the action of gravity differentiation, steam rises and advances in the oil shale reservoir, resulting in steam overburden phenomenon in the steam zone; the transition zone is an area formed in front of the steam zone by condensed water and oil produced by pyrolysis of oil shale under the action of thermal convection, heat conduction and driving of steam; the oil-rich zone is an area formed in front of the heated zone by the expelled oil shale pyrolysis oil when the steam zone and the transition zone are used as heated zones.

[0192] Among them, gravity differentiation is also called density differentiation. During the mixing effect of the reservoir, driven by gravity and buoyancy, the fluid inside the reservoir gradually forms a differentiated distribution of gas cap, oil column and bottom water (or edge water) from top to bottom according to the density difference. The oil column also shows a differentiated distribution phenomenon with the crude oil density gradually increasing from top to bottom. Both are called gravity differentiation, or density differentiation. Steam overburden phenomenon refers to the dissipation of heat carried by the injected steam to the upper and lower covering layers when heating the oil layer during steam flooding. The heat dissipation at the top and bottom layers reduces the heat utilization rate.

[0193] Among them, in the above technical scheme, the pyrolysis process of oil shale can be summarized into three stages: the mass loss in the first stage is mainly caused by water evaporation, especially the adsorbed water and interlayer water of clay minerals; the mass loss in the second stage is mainly due to the pyrolysis of kerogen in oil shale, which is regarded as the oil production stage. In this patent, the mass loss in this stage is considered to be a linear change from the initial temperature to the final temperature of kerogen pyrolysis; the mass loss in the third stage is mainly determined by the pyrolysis of carbonate and clay minerals.

[0194] Wherein, in the above technical solution, the front edges among the steam zone, the transition zone, the oil-rich zone and the original oil shale zone are parallel to each other.

[0195] Among them, in the above technical solution, with the continuous injection of steam, different areas formed under the action of steam heating and driving continue to expand forward in the original oil shale area, and pyrolysis oil is continuously produced after reaching the production well.

[0196] Table 1 shows the basic parameters required for the CMG numerical simulation of the method for in-situ steam injection production of oil shale in one embodiment of the present invention. The front changes of the four production stages of in-situ steam injection production of oil shale obtained by using the productivity prediction method in one embodiment of the present invention are shown in FIG. Figure 8 As shown in the figure, it can be seen that with the continuous injection of steam, the front edges of each area overlap and keep moving toward the production wells. Every time a front edge reaches the production well, the production stage will change accordingly.

[0197] Table 2 shows the kerogen pyrolysis chemical reaction model used in the CMG numerical simulation in one embodiment of the present invention, which is modified from the Braun-Burnham model. It includes seven reaction components, namely kerogen, water (H2O), heavy oil component (IC 37 ), light oil components (IC 13 ), hydrocarbon gases (IC2), carbon dioxide (CO2) and solid residue (Prechar). Figure 9 The present invention compares the cumulative oil production predicted by the in-situ steam injection method for oil shale in one embodiment of the present invention with that predicted by CMG numerical simulation. It can be seen that the prediction results of the patented method are basically consistent with those of the CMG numerical simulation, and the error meets industrial requirements.

[0198] Table 1 Parameters of in-situ steam injection mining of oil shale

[0199]

[0200] Table 2 Chemical reaction model of kerogen pyrolysis

[0201]

[0202]

[0203] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for predicting the production capacity of in-situ oil shale steam injection mining, characterized in that: The specific steps include: S10: Identify different zones of oil shale reservoirs during in-situ recovery with steam injection; S20: Determine the structural parameters of the steam zone for in-situ production of oil shale by steam injection; S30: Determine the structural parameters of the transition zone for in-situ production of oil shale with steam injection; S40: Determine the structural parameters of the oil-rich zone for in-situ production of oil shale by steam injection; S50: establishing a productivity prediction model for in-situ steam injection production of oil shale based on the structural parameters of the steam zone, transition zone, and oil-rich zone determined above, and predicting the productivity of in-situ steam injection production of oil shale; The structural parameters of the steam zone for in-situ production of oil shale by steam injection in S20 specifically include: a description formula of the oil shale steam front, the top and bottom radii of the steam zone, and the volume of oil displaced by expansion of the steam zone; The oil shale steam front description formula is: ； Where: r se is the top radius of the steam zone, in m; r sb is the bottom radius of the steam zone, in m; ω 2 is the ratio of the radial mass flow rate of steam in the oil shale reservoir to the steam injection velocity, which is 0.75; M' is the pseudo-mobility ratio, which is 0.5; A' RD To correct the shape factor, calculate as follows: ； Where: c is the correction coefficient; μ s is the steam viscosity, in mPa·s; i s is the steam injection rate, in kg / s; g is the acceleration due to gravity, in m / s 2 ; h is the thickness of the oil shale reservoir, in m; ρ o is the oil density, in kg / m 3 ρ s is the steam density, in kg / m 3 ;k s is the average effective steam permeability, in units of 10 -3 μm 2 ; The bottom radius of the steam zone is: Where: A sb is the bottom area of the steam zone, in m 2 ; The radius of the top of the steam zone is: ； where: α = 1 / [A' RD ω(1 - M') 1 / 2 ; Volume of oil displaced by steam zone expansion: ； Where: V s is the volume of the steam zone, in m 3 ; V so The volume of oil displaced by expansion in the steam zone, in m 3 ρ o is the oil density, in kg / m 3 ρ os is the density of oil shale, in kg / m 3 ; is the oil content of oil shale; The structural parameters of the transition zone for in-situ production of oil shale by steam injection in S30 specifically include the front description formula of the oil shale transition zone, the bottom radius of the transition zone, and the volume of oil displaced by expansion of the transition zone; The formula for describing the front edge of the oil shale transition zone is as follows: ； Where: h t is the thickness of the transition zone, in m; r tb is the bottom radius of the transition zone, in m; r is the radial distance in the oil shale reservoir, in m; Transition zone bottom radius: ； The volume of oil displaced by expansion in the transition zone: ； Where: V to The volume of oil displaced from the transition zone, in m 3 ; The structural parameters of the oil-rich zone in the in-situ production of oil shale by steam injection in S40 specifically include: a front description formula for the oil-rich zone, a bottom radius of the oil-rich zone, and a volume of the oil-rich zone; The formula for describing the front of the oil-rich area of oil shale is as follows: ； Where: h f is the thickness of the oil-rich zone, in m; r fb is the bottom radius of the oil-rich area, in m; Oil-rich zone top radius: ； Where: r fe is the radius of the top of the oil-rich area, in m; Volume of oil-rich area: ； Where: S fo is the oil saturation of the oil-rich area; V f is the volume of the oil-rich area, in m 3 The specific process of establishing the productivity prediction model for in-situ production of oil shale by steam injection in S50 includes: Phase 1: Oil-free production phase, cumulative oil production is 0; The second stage: rapid oil production stage, the cumulative oil production is: ； Where: V o is the cumulative oil production, in m 3 ; V fp is the volume of the oil-rich area discharged from the production well, in m 3 ; The third stage: slow oil production stage, the cumulative oil production is: ； Where: V tp is the volume of the transition zone discharged from the production well, in m 3 ;S to is the oil saturation in the transition zone; The fourth stage: the final oil production stage, until the oil production stops, the cumulative oil production is: ； Where: V sp is the volume of the steam zone discharged from the production well, in m 3 ;S so is the oil saturation in the steam zone The process of in-situ oil shale steam injection mining is divided into: The first stage is from the beginning of steam injection into the oil shale reservoir to the initial migration of the oil-rich front to the production well. This stage is the oil-free production stage. The second stage: after the oil-rich zone front initially migrates to the production well, and before the transition zone front initially migrates to the production well, this stage is the rapid oil production stage; The third stage: after the transition zone front initially migrates to the production well, and before the steam zone front initially migrates to the production well, this stage is the slow oil production stage; Stage 4: After the steam front initially migrates to the production well, this stage belongs to the final oil production stage.

2. The method for predicting the production capacity of in-situ oil shale steam injection according to claim 1, characterized in that: The regional classification of oil shale reservoirs in the in-situ steam injection mining process in S10 includes: steam zone, transition zone, oil-rich zone and original oil shale zone; the steam zone is due to the low density and low viscosity of steam. Under the action of gravity differentiation, steam rises and advances in the oil shale reservoir, resulting in steam overburden phenomenon in the steam zone; the transition zone is the area formed in front of the steam zone by the condensed water and the oil produced by the pyrolysis of oil shale under the action of thermal convection, heat conduction and driving of steam; the oil-rich zone is the area formed in front of the heated zone by the pyrolysis oil of oil shale driven out when the steam zone and the transition zone serve as heated zones.

3. The method for predicting the production capacity of in-situ oil shale steam injection according to claim 2, characterized in that: The pyrolysis process of oil shale can be summarized into three stages: the mass loss in the first stage is mainly caused by water evaporation, which is the adsorbed water and interlayer water of clay minerals; the mass loss in the second stage is mainly due to the pyrolysis of kerogen in oil shale, which is regarded as the oil production stage. The mass loss in this stage is considered to be a linear change from the initial temperature to the final temperature of kerogen pyrolysis; the mass loss in the third stage is mainly determined by the pyrolysis of carbonate and clay minerals.

4. The method for predicting the production capacity of in-situ oil shale steam injection according to claim 3, characterized in that: The fronts among the steam zone, the transition zone, the oil-rich zone and the original oil shale zone are parallel to each other.

5. The method for predicting the production capacity of in-situ oil shale steam injection according to claim 4, characterized in that: With the continuous injection of steam, different areas formed under the action of steam heating and driving continue to expand forward in the original oil shale area, and pyrolysis oil is continuously produced after reaching the production well.

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