Quantitative calculation method for reservoir dissolution and permeation enhancement in carbon dioxide oil displacement and storage process

Abstract

The invention relates to a quantitative calculation method for reservoir dissolution and permeation enhancement in the carbon dioxide oil displacement and storage process. The method comprises the following steps that an initial reservoir rock model composed of grid units is established; wherein the initial type of each grid unit comprises a pore space for a carbon dioxide-fluid to flow and a solid space occupied by rock particles; taking the grid units of which the attributes are solid nodes and the surrounding grid units are not completely occupied by the solid nodes as reaction grid units, and adapting to different chemical reaction models according to the attributes of the reaction grid units; and the attributes of all the reaction grid units are updated in parallel, a final reservoir rock model is formed when the corrosion rate reaches a preset target, and the corrosion permeation increasing phenomenon is quantitatively represented through the difference between the corrosion rate and the oil-phase and gas-phase relative permeability curve of the final reservoir rock model and the initial reservoir rock model. According to the method, the corrosion permeation increasing phenomenon of the carbon dioxide-fluid in the reservoir rock under different mineral compositions and temperature and pressure environments is quantitatively represented.

Description

Technical Field

[0001] The invention relates to the technical field of carbon dioxide flooding to enhance oil reservoir recovery, and in particular to a quantitative calculation method for reservoir dissolution and permeability enhancement in a carbon dioxide flooding and sealing process. Background Art

[0002] Carbon dioxide-EOR technology helps to fully tap the potential of oil and gas resources and plays an important role in ensuring energy security and stabilizing oil and gas supply. Carbon dioxide-EOR technology effectively reduces greenhouse gas emissions, improves regional environmental quality, and has a positive impact on the surrounding ecological environment by injecting carbon dioxide into oil layers to replace traditional oil-displacing gases. This technology can increase crude oil production, bring direct economic benefits to oil and gas companies, and extend the service life of oil and gas fields.

[0003] In the study of the microscopic oil recovery mechanism of carbon dioxide immiscible phase in low permeability tight oil reservoirs, the interaction between carbon dioxide and fluid and rock has very important research value. Its research content mainly focuses on the rock mineral composition, rock physical properties, surface and interface properties, etc. in the process of carbon dioxide-fluid-rock interaction. The carbonation of formation water by carbon dioxide can improve the porosity and permeability of the reservoir, which is beneficial to the flow of fluid, so as to achieve the purpose of improving the recovery rate. And with the increase of the amount of carbon dioxide injected in crude oil, the interfacial tension of reservoir fluid / formation water and reservoir fluid / carbon dioxide continues to decrease. In the experimental study of carbon dioxide-water-rock interaction, the dissolution phenomenon of carbonate minerals and aluminosilicate minerals has been generally recognized in the industry.

[0004] There is no unified understanding and conclusion on the mechanism of dissolution and permeability enhancement of reservoir minerals caused by carbon dioxide flooding. The present invention designs a quantitative calculation method for reservoir dissolution and permeability enhancement during carbon dioxide flooding and storage. By establishing a reservoir pore model and combining the reaction kinetics data of carbon dioxide-fluid and rocks with different mineral components, the phenomenon of carbon dioxide dissolution and permeability enhancement is quantitatively characterized, providing a new solution for the study of the mechanism of dissolution and permeability enhancement caused by carbon dioxide flooding. Summary of the invention

[0005] In view of the above problems, the present invention proposes a quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage, so as to calculate the permeability increase phenomenon caused by the dissolution of the carbon dioxide-fluid-rock reaction on the rock pore structure during the implementation of the carbon dioxide flooding project, and provide a certain calculation basis for the design of carbon dioxide flooding in low permeability reservoirs.

[0006] The technical solution of the present invention is: The quantitative calculation method of reservoir dissolution and permeability increase during carbon dioxide flooding and storage is as follows: (1) Establishing an initial reservoir rock model consisting of grid cells; wherein the initial types of each grid cell include pore space for CO2-fluid flow and solid space occupied by rock particles, the pore space has the attribute of a fluid node, and the solid space has the attribute of a solid node; (2) Grid cells whose attributes are solid nodes and whose surrounding grid cells are not fully occupied by solid nodes are used as reaction grid cells, and different chemical reaction models are adapted according to their attributes; (3) Update the properties of all reaction grid cells in parallel, and form the final reservoir rock model when the dissolution rate reaches the preset target; For any reaction grid unit, combined with its adapted chemical reaction model, the initial reaction rate of the rock particles consumed in the current reaction grid unit is calculated, and the final reaction rate is corrected. The product of the final reaction rate and the unit time is taken as the rock particle consumption. The rock particle consumption is normalized by the mineral molar number of the current reaction grid unit. When the normalized result is greater than 1, it indicates that the corresponding rock particles are completely consumed, and the current reaction grid unit is dissolved, and its attributes are updated to fluid nodes; (4) Obtaining the oil phase and gas phase relative permeability curves of the final reservoir rock model, and using the difference between the oil phase and gas phase relative permeability curves of the final reservoir rock model and the initial reservoir rock model to quantitatively characterize the dissolution permeability phenomenon.

[0007] It also includes setting a cycle time step, updating the attributes of all reaction grid units in parallel in each cycle time step until the dissolution rate reaches a preset target to form a final reservoir rock model; wherein the time of each cycle time step is the unit time; the rock particle consumption of any reaction grid unit is the product of the sum of the final reaction rates of the previous and all previous cycle time steps and the unit time, and then judging whether to update the attributes of the corresponding reaction grid unit according to the rock particle consumption; The dissolution rate is the ratio of the difference between the number of solid nodes at the initial moment and the number of solid nodes in the current cycle time step to the number of solid nodes at the initial moment.

[0008] It also includes that the properties of the reaction grid unit in the current cycle time step will affect the number of solid nodes in the surrounding grid units of the reaction grid unit in the next cycle time step, and further affect the judgment of whether the reaction grid unit is dissolved in the next cycle time step.

[0009] The specific process of obtaining the final reaction rate is: judging the number of solid nodes in the grid units around the current reaction grid unit, selecting the corresponding reaction probability coefficient and multiplying it with the initial reaction rate to obtain the final reaction rate.

[0010] The reaction probability coefficients are P1-P8, which respectively represent eight probabilities corresponding to when the sum of the number of solid nodes of eight surrounding grid units with the reaction grid unit as the center is 1-8; among them, the reaction probability coefficients P1-P8 are 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4 and 0.3 respectively.

[0011] The construction process of the initial reservoir rock model is as follows: obtaining the physical and chemical properties of the reservoir rocks in the study area and the reservoir fluid property parameters; wherein the physical and chemical properties include but are not limited to the rock pore distribution structure, roar characteristics and rock mineral components; establishing the initial reservoir rock model according to the rock pore distribution structure and roar characteristics, and the properties of the solid space in the initial reservoir rock model are determined according to the rock mineral components; the reservoir fluid property parameters include but are not limited to the actual temperature, pressure and mineralization of the reservoir.

[0012] The chemical reaction model includes but is not limited to a kinetic model, a molecular reaction model and an empirical model.

[0013] When calculating the initial reaction rate, it is necessary to obtain the flow parameters and distribution parameters of the reaction grid unit through a numerical simulation algorithm that takes into account the convective mass transfer effect.

[0014] The numerical simulation algorithm considering the convective mass transfer effect includes but is not limited to the lattice Boltzmann method, the finite volume method and the finite difference method.

[0015] The rock particles include but are not limited to quartz and calcite; when the solid node is a quartz solid node, it adapts to the carbon dioxide-quartz chemical reaction model; when the solid node is a calcite solid node, it adapts to the carbon dioxide-calcite chemical reaction model.

[0016] The technical effects of the present invention are: The present invention proposes a quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage. The flow parameters and distribution parameters are solved by a numerical simulation algorithm that considers the convective mass transfer effect. According to the chemical reaction model of carbon dioxide with different types of mineral components under different reaction conditions, a reservoir rock dissolution model that considers the solid space position effect is designed. By calculating the oil phase and gas phase relative permeability curves of the reservoir rock during the dissolution calculation process in the reservoir space, the dissolution and permeability increase phenomenon of carbon dioxide-fluid in the reservoir rock under different mineral compositions and temperature and pressure environments can be quantitatively characterized. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a curve change diagram of the relative permeability curves of the oil phase and gas phase. DETAILED DESCRIPTION

[0018] Example 1 The quantitative calculation method of reservoir dissolution and permeability increase during carbon dioxide flooding and storage is as follows: (1) Establishing an initial reservoir rock model consisting of grid cells; wherein the initial types of each grid cell include pore space for CO2-fluid flow and solid space occupied by rock particles, the pore space has the attribute of a fluid node, and the solid space has the attribute of a solid node; (2) Grid cells whose attributes are solid nodes and whose surrounding grid cells are not fully occupied by solid nodes are used as reaction grid cells, and different chemical reaction models are adapted according to their attributes; (3) Update the properties of all reaction grid cells in parallel, and form the final reservoir rock model when the dissolution rate reaches the preset target; For any reaction grid unit, combined with its adapted chemical reaction model, the initial reaction rate of the rock particles consumed in the current reaction grid unit is calculated, and the final reaction rate is corrected. The product of the final reaction rate and the unit time is taken as the rock particle consumption. The rock particle consumption is normalized by the mineral molar number of the current reaction grid unit. When the normalized result is greater than 1, it indicates that the corresponding rock particles are completely consumed, and the current reaction grid unit is dissolved, and its attributes are updated to fluid nodes; (4) Obtaining the oil phase and gas phase relative permeability curves of the final reservoir rock model, and using the difference between the oil phase and gas phase relative permeability curves of the final reservoir rock model and the initial reservoir rock model to quantitatively characterize the dissolution permeability phenomenon.

[0019] Example 2 On the basis of Example 1, the method further includes: if the dissolution rate does not reach the preset target after executing step (4), a cycle time step is added, and the attributes of all reaction grid units are updated in parallel in each cycle time step until the dissolution rate reaches the preset target to form a final reservoir rock model; wherein the time of each cycle time step is the unit time; the rock particle consumption of any reaction grid unit is the product of the sum of the final reaction rates of the previous and all previous cycle time steps and the unit time, and then whether to update the attributes of the corresponding reaction grid unit is determined according to the rock particle consumption; The dissolution rate is the ratio of the difference between the number of solid nodes at the initial moment and the number of solid nodes in the current cycle time step to the number of solid nodes at the initial moment.

[0020] Example 3 On the basis of Example 2, it also includes: the properties of the reaction grid unit in the current cycle time step will affect the number of solid nodes in the surrounding grid units of the reaction grid unit in the next cycle time step, thereby affecting the judgment of whether the reaction grid unit is dissolved in the next cycle time step.

[0021] Example 4 On the basis of Example 3, the invention further includes: The specific process of obtaining the final reaction rate is as follows: determine the number of solid nodes in the grid units surrounding the current reaction grid unit, select the corresponding reaction probability coefficient and multiply it by the initial reaction rate to obtain the final reaction rate.

[0022] The reaction probability coefficients are P1-P8, which respectively represent eight probabilities corresponding to when the sum of the number of solid nodes of eight surrounding grid units with the reaction grid unit as the center is 1-8; among them, the reaction probability coefficients P1-P8 are 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4 and 0.3 respectively.

[0023] Example 5 On the basis of Example 4, it also includes: The construction process of the initial reservoir rock model is as follows: obtaining the physical and chemical properties of the reservoir rocks in the study area and the reservoir fluid property parameters; wherein the physical and chemical properties include but are not limited to the rock pore distribution structure, roar characteristics and rock mineral components; establishing the initial reservoir rock model according to the rock pore distribution structure and roar characteristics, and the properties of the solid space in the initial reservoir rock model are determined according to the rock mineral components; the reservoir fluid property parameters include but are not limited to the actual temperature, pressure and mineralization of the reservoir.

[0024] Example 6 On the basis of Example 5, the present invention further comprises: The chemical reaction model includes but is not limited to a kinetic model, a molecular reaction model and an empirical model; When calculating the initial reaction rate, it is necessary to calculate the flow parameters and distribution parameters of the reaction grid unit through a numerical simulation algorithm that takes into account the convective mass transfer effect; The numerical simulation algorithm considering the convective mass transfer effect includes but is not limited to the lattice Boltzmann method, the finite volume method and the finite difference method; The rock particles include but are not limited to quartz and calcite; when the solid node is a quartz solid node, it adapts to the carbon dioxide-quartz chemical reaction model; when the solid node is a calcite solid node, it adapts to the carbon dioxide-calcite chemical reaction model.

[0025] Specific experimental cases Taking a study area in the Ordos Basin as an example, the main mineral components in the study area are quartz and calcite, and the specific parameters of the reservoir fluid properties include: reservoir temperature 35°C, formation pressure 5.7MPa, and mineralization 7500mg / L.

[0026] A quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage is as follows: (1) An initial reservoir rock model was established with reference to the reservoir pores in the study area. The initial reservoir rock model included pore space for the flow of CO2-fluid and solid space occupied by rock particles. The solid space included quartz solid space and calcite solid space.

[0027] (2) The initial reservoir rock model is divided into 1000*1000 grid cells, and the cycle time step is set to 100,000 steps and the dissolution rate is set to 0.8, which is used as the cycle termination condition; each grid cell is represented by the coordinates (i, j) Positioning, adoption V ( i, j ) mark the properties of the grid cell; when V(i, j) =0, the coordinates are (i, j) The grid cells are fluid nodes; when V(i, j) ≠0, the coordinates are (i, j) The mesh elements of are solid nodes; V(i, j) =1, the coordinates are (i, j) The mesh unit is a quartz solid node. V(i, j) =2, the coordinates are (i, j) The mesh elements are calcite solid nodes.

[0028] (3) According to the initial reservoir rock model and reservoir fluid property parameters, the SHAN-CHEN two-phase flow model of LBM was used, the inlet flow velocity of 1000*1000 grid cells was set to 1, and the rebound format was used for the solid wall. The CO2 flow rate and concentration of all fluid nodes in the initial reservoir rock model were calculated, and the CO2 flow rate and concentration were used as the basic parameters for each cycle time step.

[0029] (4) Solid nodes with attributes ( V(i, j) ≠0) and the grid cells around them are not completely occupied by solid nodes as reactive grid cells; Right now: V ( i, j) =0 fluid node, no reaction conditions are met; V(i, j) =1 for a quartz solid node and its surrounding grid cells are not all occupied by solid nodes, the corresponding grid cell has the reaction conditions as a reaction grid cell, and the corresponding reaction grid cell adapts to the carbon dioxide-quartz reaction kinetic model; V(i, j) =2 and the surrounding grid cells are not completely occupied by solid nodes, the corresponding grid cell has the reaction conditions as a reaction grid cell, and the corresponding reaction grid cell adapts to the carbon dioxide-calcite reaction kinetic model.

[0030] (5) For any reaction grid unit, its position needs to be judged to characterize the contact degree between the reaction grid unit and the fluid. For the reaction grid unit with high contact degree, a higher probability reaction probability coefficient is used. The contact degree is related to the number of solid nodes of the grid unit around the reaction grid unit; In this specific experimental case, the reaction probability coefficients of the reaction grid unit are set to P1~P8, which represent the eight probabilities corresponding to the sum of the number of solid nodes of the eight surrounding grid units with the reaction grid unit as the center to 1~8. The reaction probability coefficients P1~P8 are 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4 and 0.3 respectively.

[0031] (6) With coordinates (50 ， 50) as an example, V (50 ， 50)=2, which is a calcite solid node, and the carbon dioxide-calcite reaction kinetic model is applicable. In this specific experimental case, the carbon dioxide-calcite reaction kinetic model is specifically the PWP mechanism model.

[0032] (7) According to the calculation results of the SHAN-CHEN two-phase flow model, the temperature, pressure, salinity and carbon dioxide concentration of the current reaction grid unit are substituted into the carbon dioxide-calcite reaction kinetic model. Taking the 1600th cycle time step as an example, the coordinates are calculated to be (50 ， 50), the initial reaction rate of calcite consumption in the reaction grid unit is 0.00172; the surrounding grid units have 6 solid nodes in the current cycle time step, that is, the reaction probability coefficient P6=0.5 is used for correction, that is, the reaction probability coefficient P6 is multiplied by the initial reaction rate to obtain the final reaction rate of 0.00086.

[0033] (8) Accumulate the final reaction rate of the current reaction grid unit in each cycle time step, multiply it by the unit time to get the calcite consumption, and use the mineral mole number of the current reaction grid unit to normalize the calcite consumption; if the normalized result is greater than 1, it means that the calcite in the reaction grid unit with coordinates (50, 50) has been completely consumed and dissolution has occurred, then update the coordinates to (50 ， 50) is a fluid node; that is, modify its V’ (50, 50) = 0; Table 1 shows the update process of the (50, 50) reaction grid unit: Table 1 (50, 50) reaction grid unit update process .

[0034] Each cycle time step needs to perform the following operations on 1000*1000 grid cells: ① Obtain the carbon dioxide flow rate and concentration of the grid unit according to the lattice Boltzmann method, as in step (3); ② Determine the properties of any grid cell and the conditions of the surrounding grid cells, and then determine the reaction grid cell and its adapted carbon dioxide-rock reaction kinetic model and corresponding reaction probability coefficient, and update or not update the properties of the corresponding reaction grid cell, such as steps (4) to (8); ③ When the attributes of all reaction grid cells are changed, the new reservoir rock model is obtained; After solving the dissolution rate of the new reservoir rock model, if the dissolution rate does not reach the preset target, the new reservoir rock model is substituted into the next cycle time step to solve the carbon dioxide flow rate and concentration.

[0035] The calculation formula of dissolution rate is as follows: η =( n 0 - n i ) / n 0 ; in, η is the dissolution rate, n 0 is the number of solid nodes of the initial reservoir rock model, n i For the i The number of solid nodes of the new reservoir rock model under the cyclic time step; when the dissolution rate η When it is greater than 0.8 or the loop step is greater than 100000, the loop stops; In this specific experimental case, when the 78223 cycle time step is reached, the dissolution rate η If it is greater than 0.8, the loop stops.

[0036] (9) Calculation of relative permeability curve The initial reservoir rock model of the initial cycle time step (T0), the reservoir rock model of 20,000 time steps (T1), and the reservoir rock model of 40,000 time steps (T2) were selected, and their oil phase and gas phase relative permeability curves were drawn respectively to characterize the dissolution permeability phenomenon at T0, T1, and T2. The results are shown in Figure 2. Figure 1 shown.

Claims

1. A quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage, characterized by: Here’s how: (1) Establishing an initial reservoir rock model consisting of grid cells; wherein the initial types of each grid cell include pore space for CO2-fluid flow and solid space occupied by rock particles, the pore space has the attribute of a fluid node, and the solid space has the attribute of a solid node; (2) Grid cells whose attributes are solid nodes and whose surrounding grid cells are not fully occupied by solid nodes are used as reaction grid cells, and different chemical reaction models are adapted according to their attributes; (3) Update the properties of all reaction grid cells in parallel, and form the final reservoir rock model when the dissolution rate reaches the preset target; For any reaction grid unit, combined with its adapted chemical reaction model, the initial reaction rate of the rock particles consumed in the current reaction grid unit is calculated, and the final reaction rate is corrected. The product of the final reaction rate and the unit time is taken as the rock particle consumption. The rock particle consumption is normalized by the mineral molar number of the current reaction grid unit. When the normalized result is greater than 1, it indicates that the corresponding rock particles are completely consumed, and the current reaction grid unit is dissolved, and its attributes are updated to fluid nodes; (4) Obtaining the oil phase and gas phase relative permeability curves of the final reservoir rock model, and using the difference between the oil phase and gas phase relative permeability curves of the final reservoir rock model and the initial reservoir rock model to quantitatively characterize the dissolution permeability phenomenon.

2. The quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage according to claim 1 is characterized by: It also includes setting a cycle time step, updating the attributes of all reaction grid units in parallel in each cycle time step until the dissolution rate reaches a preset target to form a final reservoir rock model; wherein the time of each cycle time step is the unit time; the rock particle consumption of any reaction grid unit is the product of the sum of the final reaction rates of the previous and all previous cycle time steps and the unit time, and then judging whether to update the attributes of the corresponding reaction grid unit according to the rock particle consumption; The dissolution rate is the ratio of the difference between the number of solid nodes at the initial moment and the number of solid nodes in the current cycle time step to the number of solid nodes at the initial moment.

3. The quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage according to claim 2 is characterized by: It also includes that the properties of the reaction grid unit in the current cycle time step will affect the number of solid nodes in the surrounding grid units of the reaction grid unit in the next cycle time step, and further affect the judgment of whether the reaction grid unit is dissolved in the next cycle time step.

4. The quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage according to claim 3 is characterized by: The specific process of obtaining the final reaction rate is: judging the number of solid nodes in the grid units around the current reaction grid unit, selecting the corresponding reaction probability coefficient and multiplying it with the initial reaction rate to obtain the final reaction rate.

5. The quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage according to claim 4 is characterized by: The reaction probability coefficients are P1-P8, which respectively represent eight probabilities corresponding to when the sum of the number of solid nodes of eight surrounding grid units with the reaction grid unit as the center is 1-8; among them, the reaction probability coefficients P1-P8 are 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4 and 0.3 respectively.

6. The quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage according to claim 1 is characterized by: The construction process of the initial reservoir rock model is as follows: obtaining the physical and chemical properties of the reservoir rocks in the study area and the reservoir fluid property parameters; wherein the physical and chemical properties include but are not limited to the rock pore distribution structure, roar characteristics and rock mineral components; establishing the initial reservoir rock model according to the rock pore distribution structure and roar characteristics, and the properties of the solid space in the initial reservoir rock model are determined according to the rock mineral components; the reservoir fluid property parameters include but are not limited to the actual temperature, pressure and mineralization of the reservoir.

7. The quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage according to claim 1, characterized in that: The chemical reaction model includes but is not limited to a kinetic model, a molecular reaction model and an empirical model.

8. The quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage according to claim 1, characterized in that: When calculating the initial reaction rate, it is necessary to obtain the flow parameters and distribution parameters of the reaction grid unit through a numerical simulation algorithm that takes into account the convective mass transfer effect.

9. The quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage according to claim 8, characterized in that: The numerical simulation algorithm considering the convective mass transfer effect includes but is not limited to the lattice Boltzmann method, the finite volume method and the finite difference method.

10. The quantitative calculation method for reservoir dissolution and permeability increase during carbon dioxide flooding and storage according to claim 1, characterized in that: The rock particles include but are not limited to quartz and calcite; when the solid node is a quartz solid node, it adapts to the carbon dioxide-quartz chemical reaction model; when the solid node is a calcite solid node, it adapts to the carbon dioxide-calcite chemical reaction model.

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