A method for constructing a kinetic model of air injection oxidation reaction in shale oil reservoirs

Abstract

The invention discloses a method for constructing a kinetic model of air injection oxidation reaction in shale oil reservoirs, comprising the following steps: step 1: obtaining shale oil fluid pseudo-component state parameters and kerogen pseudo-component state parameters, and establishing a shale oil fluid pseudo-component model and a kerogen pseudo-component model; step 2: determining a shale oil pseudo-component oxidation reaction equation and a kerogen oxidation reaction equation; step 3: determining a reaction enthalpy and an oxidation kinetic parameter value range, and assigning an initial value to the oxidation reaction equation; step 4: simulating the model, and comparing the simulation result with a physical simulation experiment result; step 5: adjusting the values ​​of the reaction enthalpy, the reaction equation stoichiometric coefficient and the kinetic parameter until the obtained simulation result and the physical simulation experiment result reach a set accuracy value; obtaining the required model; the invention defines the kerogen pseudo-component, takes the kerogen oxidation reaction into consideration, and the simulation result more accurately reflects the air injection oxidation process in shale oil reservoirs.

Description

Technical Field

[0001] The invention relates to the technical field of shale oil reservoir development, and in particular to a method for constructing a kinetic model of air injection oxidation reaction in a shale oil reservoir. Background Art

[0002] Shale oil refers to crude oil that has been generated but is still trapped in the micron-sized storage space of organic-rich mud shale formations. my country is rich in shale oil resources, with recoverable resources reaching 43.52×10 8 Tons, is one of the effective replacement energy sources for conventional oil reservoirs. Due to the poor physical properties of shale reservoirs and obvious non-Darcy seepage, water injection, chemical flooding and other development methods are difficult to apply to shale oil reservoir development. The development of air injection technology in kerogen-rich shale oil reservoirs has the following advantages. Combustion heat release can remove the "dead carbon" that is difficult to pyrolyze in the pores and change the state of crude oil occurrence; oxidation heat energy can communicate and expand the micropore structure and enhance the reservoir conductivity.

[0003] In order to study the feasibility of applying air injection technology in shale oil reservoirs, Jia et al. (Jia and Sheng. Simulation study of huff-n-puff air injection for enhanced oil recovery in shale oil reservoirs [J]. Petroleum, 2018, 4 (1): 1-7) took the lead in conducting relevant numerical simulation research. The oxidation reaction equation, activation energy, frequency factor, thermal enthalpy, etc. used in the study were directly derived from the oxidation reaction kinetic model of light oil reservoirs in the North Sea established by Tingas (Tingas J. Numerical simulation of air injection processes in high pressure light & medium oil reservoirs [D]. University of Bath, 2000), which did not conform to the oxidation characteristics of shale oil and did not consider kerogen oxidation, which seriously affected the reliability of the numerical model. In addition, the research on kerogen mainly focuses on the cracking reaction of kerogen in oil shale (Wang Q, Wang X, Pan S. Study on the structure, pyrolysis kinetics, gas release, reaction mechanism, and pathways of Fushun oil shale and kerogen in Chain [J]. Fuel Processing Technology, 2022: 107058), and there is a lack of research on the kerogen oxidation reaction equation and kinetics in shale reservoirs. At present, there is no reaction kinetic model that considers the oxidation of shale oil and kerogen at the same time, making it difficult to accurately predict the changes in temperature field, gas phase components, etc. during air injection in shale reservoirs. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for constructing a shale oil reservoir air injection oxidation reaction kinetic model capable of simulating changes in temperature field, gas phase components and the like during air injection into shale oil reservoirs.

[0005] The technical solution adopted by the present invention is:

[0006] A method for constructing a kinetic model of air injection oxidation reaction in a shale oil reservoir comprises the following steps:

[0007] Step 1: Obtain the shale oil fluid pseudo-component state parameters and kerogen pseudo-component state parameters through CMG reservoir numerical simulation software, and establish a shale oil fluid pseudo-component model and a kerogen pseudo-component model;

[0008] Step 2: Determine the oxidation reaction equation of shale oil pseudo-components and the oxidation reaction equation of kerogen;

[0009] Step 3: Determine the range of reaction enthalpy and oxidation kinetic parameters, determine the initial values ​​of reaction enthalpy and oxidation kinetic parameters, and assign the initial values ​​to the oxidation reaction equation obtained in step 2;

[0010] Step 4: Simulate the model obtained in step 3 and compare the simulation results with the physical simulation experiment results;

[0011] Step 5: According to the results of the physical simulation experiment, the values ​​of the reaction enthalpy, the stoichiometric coefficient of the reaction equation and the kinetic parameters are adjusted until the obtained simulation results and the physical simulation experiment results reach the set accuracy value; after the simulation is completed, the kinetic model of the air injection oxidation reaction in the shale oil reservoir is obtained.

[0012] Furthermore, the oxidation reaction equation of the pseudo-component of the shale oil fluid in step 2 is as follows:

[0013] heavy fraction+1.5O 2 →0.846Oxidized oil+CO 2 +H 2 O

[0014] Oxidized oil→3.8light fraction+1.2Coke

[0015] heavy fraction+1.5O 2 →3.2148light fraction+1.0152Coke+CO 2 +H 2 O

[0016] light fraction+10.5239Oxygen→9.88078H 2 O+2.28623CO 2 +6.59455CO

[0017] Coke+1.08295Oxygen→0.5H 2 O+0.665909CO 2

[0018] In the formula: light fraction is light components, heavy fraction is heavy components, Oxidized oil is hydrocarbon oxides, and Coke is coke.

[0019] Furthermore, the kerogen oxidation reaction equation in step 2 is as follows:

[0020] Kerogen_solid 1 +17.5O 2 →101.5Coke

[0021] Kergen_solid 2 →83.8Coke+8.2light fraction+2.2heavy fraction+7.6H 2 O

[0022] Where: Kerogen_solid 1 Kerogen pseudo-component 1, Kerogen_solid 2 It is kerogen pseudo-component 2.

[0023] Furthermore, the process of obtaining the pseudo-component model of shale oil fluid in step 1 is as follows:

[0024] Crude oil is divided into light components and heavy components through CMG reservoir numerical simulation software, flash calculation and numerical optimization are performed, and the physical property parameters of crude oil measured by the experiment are fitted; the pseudo-component state parameters of shale oil fluid used for numerical simulation can be obtained; the shale oil fluid model is obtained according to the state parameters; the physical property parameters of crude oil include viscosity, density and molecular weight;

[0025] The process of obtaining the kerogen pseudo-component model is as follows:

[0026] The solid kerogen is divided into Kerogen-solid 1 and Kerogen-solid 2 Pseudo-component, obtain the state parameters of kerogen pseudo-component for numerical simulation; Kerogen-solid 1 and Kerogen-solid 2 The pseudo-components participate in oxidation and cracking reactions respectively;

[0027] A dual porosity and permeability model is set up through CMG-STARS, in which the matrix system represents the pore structure with low permeability in shale; the fracture system represents the porosity and permeability channels formed by kerogen oxidation / cracking; it is assumed that the kerogen solids are mainly filled in the shale pores, and the concentration of kerogen begins to decrease after oxidation / cracking reaction until the kerogen concentration in the pores is 0. Furthermore, the method for determining the range of reaction enthalpy and oxidation kinetic parameters in step 3 is as follows:

[0028] Shale oil and kerogen oxidation experiments were carried out at multiple heating rates using a high-pressure differential scanning calorimeter (PDSC). The enthalpy ranges of low-temperature and high-temperature oxidation reactions were preliminarily obtained based on the PDSC oxidation exothermic curves at multiple heating rates. The equal conversion rate method was used to obtain the activation energy and frequency factor ranges of low-temperature and high-temperature oxidation, that is, the oxidation kinetic parameter ranges.

[0029] The beneficial effects of the present invention are:

[0030] (1) The present invention proposes a kinetic model of air injection oxidation reaction in shale oil reservoirs that takes into account both shale oil and kerogen oxidation. It can be used to simulate the temperature field and gas phase component changes during air injection to enhance oil recovery in shale oil reservoirs, and explore the oxidation thermal front sweep mechanism and regulation method. (2) The present invention defines two kerogen pseudo-components that participate in oxidation reaction and cracking reaction respectively, making the simulation process more accurate and the simulation results more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the process of the present invention.

[0032] Figure 2 It is a schematic diagram of a porous medium thermal effect monitoring device used in the physical simulation experiment of the present invention.

[0033] Figure 3 This is a physical simulation experimental model of air injection oxidation established by simulation software in the present invention.

[0034] Figure 4 These are the temperature propagation experimental curve and numerical simulation curve.

[0035] Figure 5 These are the experimental curve and numerical simulation curve of the produced gas components in the present invention.

[0036] In the figure: 1-gas storage tank, 2-control valve, 3-flow meter, 4-ceramic heater, 5-heating controller, 6-quartz reactor, 7-gas-liquid separator, 8-liquid collecting bottle, 9-gas analyzer, 10-data acquisition box, 11-analog-digital converter, 12-optical fiber sensor. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0038] like Figure 1 As shown, a method for constructing a kinetic model of air injection oxidation reaction in a shale oil reservoir comprises the following steps:

[0039] Step 1: Obtain the shale oil fluid pseudo-component state parameters and kerogen pseudo-component state parameters through CMG reservoir numerical simulation software, and establish a shale oil fluid pseudo-component model and a kerogen component model;

[0040] The WINPROP module in CMG is used to divide crude oil into light and heavy components, and flash calculation and numerical optimization are performed to fit the experimentally measured physical properties of crude oil; the physical properties of crude oil include viscosity, density and molecular weight; thus, the pseudo-component state parameters of shale oil fluid that can be used for numerical simulation can be obtained.

[0041] Divide solid kerogen into Kerogen-solid 1 and Kerogen-solid 2 Pseudo-component, Kerogen-solid 1 and Kerogen-solid 2 The pseudo-components participate in oxidation and cracking reactions respectively. The dual porosity and permeability model is set up by CMG-STARS. The matrix system mainly represents the pore structure with low permeability in shale; the fracture system represents the porosity and permeability channels formed by kerogen oxidation / cracking. It is assumed that kerogen solids are mainly filled in shale pores, and the concentration of kerogen begins to decrease after oxidation / cracking reaction until the kerogen concentration in the pores is 0.

[0042] Step 2: Determine the oxidation reaction equation of shale oil pseudo-components and the oxidation reaction equation of kerogen;

[0043] (1) Establishing the shale oil oxidation reaction equation

[0044] The shale oil oxidation experiment was carried out in the whole temperature range (100-800℃), and the shale oil oxidation reaction equation was established by analyzing the composition of the produced gas after oxidation and the physical properties and composition of the produced oil. The low-temperature oxidation stage mainly includes the oxygenation of heavy components (Formula 1) and the cracking of hydrocarbon oxides (Formula 2), and Formulas 1 and 2 can be further synthesized into Formula 3; the high-temperature oxidation stage mainly includes the gas phase combustion of light components (Formula 4) and coke combustion (Formula 5).

[0045] heavy fraction+1.5O 2 →0.846Oxidized oil+CO 2 +H2O (1)

[0046] Oxidized oil→3.8light fraction+1.2Coke (2)

[0047] heavy fraction+1.5O 2 →3.2148light fraction+1.0152Coke+CO 2 +H 2 O(3)

[0048] light fraction+10.5239Oxygen→9.88078H 2 O+2.28623CO 2 +6.59455CO (4)

[0049] Coke+1.08295Oxygen→0.5H 2 O+0.665909CO 2 (5)

[0050] In the formula: light fraction is light components, heavy fraction is heavy components, Oxidized oil is hydrocarbon oxides, and Coke is coke.

[0051] (2) Establishing the kerogen oxidation reaction equation

[0052] Domestic and foreign scholars have conducted a lot of research on the cracking reaction of kerogen, but there is almost no research on the kerogen oxidation reaction mode. In order to establish the kerogen oxidation reaction equation, kerogen was extracted from organic-rich shale according to the international GB / T 19144-2003 "Methods for separating kerogen from sedimentary rocks", and then kerogen oxidation experiments were carried out in the full temperature range (100-800℃). By analyzing the composition of the produced gas and the physical properties and composition of the produced fluid, the kerogen pseudo-component Kerogen-solid 1 Oxidation reaction equation. The final equation includes Kerogen-solid 1 The oxygenation reaction (Equation 6) and the combustion reaction (Equation 5) of the oxidative condensation deposits (regarded as coke) generated by the oxygenation of kerogen.

[0053] Kerogen-solid 2 The cleavage reaction is Kerogen_solid 2 The cleavage generates H 2 O, light fraction, heavy fraction and Coke are as shown in Formula 7.

[0054] Kerogen_solid 1 +17.5O 2 →101.5Coke (6)

[0055] Kergen_solid 2 →83.8Coke+8.2light fraction+2.2heavg fraction+7.6H 2 O(7)

[0056] Where: Kerogen_solid 1 Kerogen pseudo-component 1, Kerogen_solid 2 It is kerogen pseudo-component 2.

[0057] Step 3: Determine the range of reaction enthalpy and oxidation kinetic parameters, determine the initial values ​​of reaction enthalpy and oxidation kinetic parameters, and assign the initial values ​​to the oxidation reaction equation obtained in step 2;

[0058] High-pressure differential scanning calorimeter (PDSC) was used to carry out shale oil and kerogen oxidation experiments at multiple heating rates (4, 8, 12 and 16 °C / min). The isoconversion rate method (such as Friedman, KAS, OFW, etc.) was used to obtain the range of activation energy and frequency factor for low-temperature and high-temperature oxidation.

[0059] The enthalpy of shale oil and kerogen in the low-temperature oxidation stage is assigned to equation 3 and equation 6 respectively. Taking the enthalpy of shale oil and kerogen in the high-temperature oxidation stage as the range, one of the numbers is preliminarily selected and assigned to equation 5. According to the range of activation energy and frequency factor obtained by Friedman method. Preliminary selection of a number is performed for assignment. Among them, the kinetic parameters (activation energy and frequency factor) of shale oil and kerogen in the low-temperature oxidation stage are assigned to equation 3 and equation 6 respectively; taking the kinetic parameters of shale oil and kerogen in the high-temperature oxidation stage as the range, one of the numbers is preliminarily selected and assigned to equation 5. The initial assignment of the enthalpy and kinetic parameters of the gas phase combustion of light components (Equation 4) refers to the prior art. The initial assignment of the kinetic parameters of the kerogen cracking reaction (Equation 7) refers to the prior art.

[0060] Step 4: Simulate the model obtained in step 3 and compare the simulation results with the physical simulation experiment results;

[0061] A porous media thermal effect monitoring device (CN109030558A) was used to carry out a physical simulation experiment of air injection oxidation of natural shale (containing oil and kerogen). Figure 2 shown.

[0062] The experimental steps are:

[0063] 1) Fill quartz sand from the injection end (the length of the slug accounts for 1 / 4 of the length of the quartz reactor);

[0064] 2) Loading the natural core (containing oil and kerogen) into the reactor;

[0065] 3) Fill the remaining space of the reactor with quartz sand;

[0066] 4) placing the measuring end of the optical fiber thermal sensor close to the outer wall of the reactor, and connecting the sensor output end to the analog signal input end;

[0067] 5) The reactor is heated by a ceramic heater and air is injected into the reactor injection end.

[0068] Heating procedure: from room temperature to 50°C at 10°C / min, then keep constant at this temperature for 10 minutes, then heat to 350°C at 30°C / min, and start injecting air for ignition. The air flow rate is set to 0.25L / min. Record the reaction temperature and gas phase composition changes during the air injection oxidation physical simulation experiment.

[0069] The physical simulation experimental model of air injection oxidation of natural shale (containing oil and kerogen) was established using the CMG-STARS reservoir simulator. Figure 3 As shown, the physical simulation experiment is simulated by a three-dimensional Cartesian coordinate system (8×1×1 grid), the grid size is 1.25cm×2.5cm×2.5cm, and the leftmost and rightmost grids represent the injection well and the production well, respectively. Other conditions are set consistent with the physical simulation experiment conditions.

[0070] Step 5: According to the results of the physical simulation experiment, the reaction enthalpy, the stoichiometric coefficient of the oxidation reaction equation and the kinetic parameters are adjusted until the obtained simulation results and the physical simulation experiment results reach the set accuracy value; at the end of the simulation, the kinetic model of the air injection oxidation reaction in the shale oil reservoir is obtained.

[0071] By continuously adjusting the stoichiometric coefficients, oxidation kinetic parameters and reaction enthalpy of the oxidation reaction equations of shale oil and kerogen pseudo-components, step-by-step fitting is completed, making the fitting results close to the experimental results.

[0072] Figure 4 The experimental curves and numerical simulation curves of temperature propagation, the experimental curves and numerical simulation curves of produced gas components are shown in Figure 5 As shown in the figure, it can be seen that the simulation curve is close to the experimental curve, indicating that the shale oil reservoir air injection oxidation reaction kinetic model considering kerogen oxidation established in the present invention can successfully simulate the temperature and produced gas component changes in natural shale during the dynamic air injection process.

[0073] Figure 4 The solid line in the middle is the experimental curve (curve 1), and the dotted line is the numerical simulation curve (curve 2); A1 and A2 are 1 / 6 away from the core injection end, B1 and B2 are 2 / 6 away from the core injection end, C1 and C2 are 3 / 6 away from the core injection end, D1 and D2 are 4 / 6 away from the core injection end, and E1 and E2 are 5 / 6 away from the core injection end.

[0074] Figure 5 The A curve is O 2Volume fraction experimental curve and numerical model curve (the solid line is the experimental curve, the dotted line is the numerical model curve, the two lines are too close to be distinguished). Curve B is CO 2 Volume fraction experimental curve and numerical model curve (the solid line is the experimental curve, the dotted line is the numerical model curve, and the two lines are too close to be distinguished).

[0075] The present invention proposes a kinetic model of air injection oxidation reaction in shale oil reservoirs that simultaneously considers the oxidation of shale oil and kerogen. The model can be used to simulate the temperature field and gas phase component changes during air injection to enhance oil recovery in shale oil reservoirs, and explore the oxidation thermal front propagation mechanism and regulation method. Two kerogen pseudo-components are defined, which participate in oxidation reaction and cracking reaction respectively, so that the simulation process is more accurate and the simulation results are more credible.

Claims

1. A method for constructing a kinetic model of air injection oxidation reaction in shale oil reservoirs, characterized in that: The following steps are involved: Step 1: Obtain the shale oil fluid pseudo-component state parameters and kerogen pseudo-component state parameters through CMG reservoir numerical simulation software, and establish the shale oil fluid pseudo-component model and kerogen pseudo-component model; Step 2: Determine the oxidation reaction equation of shale oil pseudo-components and the oxidation reaction equation of kerogen; The oxidation reaction equation of the pseudo-component of shale oil fluid in step 2 is as follows: heavy fraction+1.5O2→0.846Oxidized oil+CO2+H2O Oxidized oil→3.8light fraction+1.2Coke heavy fraction+1.5O2→3.2148light fraction+1.0152Coke+CO2+H2O light fraction+10.5239Oxygen→9.88078H2O+2.28623CO2+6.59455CO Coke+1.08295Oxygen→0.5H2O+0.665909CO2 In the formula: light fraction is light components, heavy fraction is heavy components, Oxidized oil is hydrocarbon oxides, Coke is coke; The kerogen oxidation reaction equation is as follows: Kerogen_solid1+17.5O2→101.5Coke Kergen_solid2→83.8Coke+8.2light fraction+2.2heavy fraction+7.6H2O Where: Kerogen_solid1 is kerogen pseudo-component 1, Kerogen_solid2 is kerogen pseudo-component 2; Step 3: Determine the range of reaction enthalpy and oxidation kinetic parameters, determine the initial values ​​of reaction enthalpy and oxidation kinetic parameters, and assign the initial values ​​to the oxidation reaction equation obtained in step 2; Step 4: Simulate the model obtained in step 3 and compare the simulation results with the physical simulation experiment results; Step 5: According to the results of the physical simulation experiment, the reaction enthalpy, the stoichiometric coefficient of the reaction equation and the values ​​of the kinetic parameters are adjusted until the obtained simulation results and the physical simulation experiment results reach the set accuracy value; at the end of the simulation, the kinetic model of the air injection oxidation reaction in the shale oil reservoir is obtained.

2. The method for constructing a kinetic model of air injection oxidation reaction in shale oil reservoirs according to claim 1, characterized in that: The process of obtaining the pseudo-component model of shale oil fluid in step 1 is as follows: Crude oil is divided into light components and heavy components through CMG reservoir numerical simulation software, flash calculation and numerical optimization are performed, and the physical property parameters of crude oil measured by the experiment are fitted; the pseudo-component state parameters of shale oil fluid used for numerical simulation can be obtained; the shale oil fluid model is obtained according to the state parameters; the physical property parameters of crude oil include viscosity, density and molecular weight; The process of obtaining the kerogen pseudo-component model is as follows: The solid kerogen is divided into Kerogen-solid1 and Kerogen-solid2 pseudo-components by CMG reservoir numerical simulation software, and the state parameters of the kerogen pseudo-components used for numerical simulation are obtained; Kerogen-solid1 and Kerogen-solid2 pseudo-components participate in oxidation reaction and cracking reaction respectively; A dual porosity and permeability model was set up using CMG-STARS, in which the matrix system represents the pore structure with low permeability in shale; the fracture system represents the porosity and permeability channels formed by kerogen oxidation / cracking. It was assumed that kerogen solids were mainly filled in the shale pores, and the concentration of kerogen began to decrease after oxidation / cracking reactions until the kerogen concentration in the pores was 0.

3. The method for constructing a kinetic model of air injection oxidation reaction in shale oil reservoirs according to claim 1, characterized in that: The method for determining the range of reaction enthalpy and oxidation kinetic parameter values ​​in step 3 is as follows: Shale oil and kerogen oxidation experiments were carried out at multiple heating rates using a high pressure differential scanning calorimeter (PDSC). The enthalpy ranges of low-temperature and high-temperature oxidation reactions were preliminarily obtained based on the PDSC oxidation exothermic curves at multiple heating rates. The equal conversion rate method was used to obtain the activation energy and frequency factor ranges of low-temperature and high-temperature oxidation, that is, the oxidation kinetic parameter ranges.

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