A molecular simulation method for dynamic evolution of rock wettability under CO2 action

Abstract

This invention discloses a molecular simulation method for the dynamic evolution of rock wettability under CO2 action, belonging to the field of petroleum engineering molecular dynamics simulation technology. It constructs a molecular dynamics system comprising a quartz or silica surface, an aqueous phase, CO2, and positive ions; and sets an O2-containing surface on the quartz surface. ‑ The surface protonation of the / OH dual-state reaction sites is achieved through topological conservation via the switching of the type and charge of the same set of Si-O-H atoms; the reaction acceptance probability of the surface sites is calculated based on local water coordination and local CO2 coordination; and the surface O2 is set according to pH or equivalent acidification degree. ‑ The remaining proportion upper limit; adjust the same amount of Na according to the reaction count. + Positive ions; and output surface O ‑ / OH state and dynamic evolution index of wettability. This invention can characterize the dynamic evolution of CO2-induced charge state of quartz surface and its influence on oil-water wetting behavior at the classical molecular dynamics scale, avoiding the problems of fixed surface charge models being unable to describe reaction fronts, hysteresis, and path dependence.

Description

Technical Field

[0001] This invention relates to the field of petroleum engineering molecular dynamics simulation technology, and in particular to a molecular simulation method for the dynamic evolution of rock wettability under the action of CO2. Background Technology

[0002] In CO2 enhanced oil recovery and CO2 geological storage, CO2, water, crude oil, and rock mineral surfaces together form a complex multiphase interface system. Quartz or silica is an important mineral component in sandstone reservoirs and related porous media. Its surface silanol groups can exhibit protonated Si-OH states or deprotonated Si-O states in aqueous environments. - State. The negative charge from the surface deprotonation sites stabilizes the near-wall water film and attracts Na. + Positive ions can affect the proximity of the oil phase to the wall, the contact state of the oil-water-solid three phases, and the overall wettability.

[0003] When CO2 dissolves into the aqueous phase, it can create an acidified environment, causing changes in the local proton chemical potential, thereby driving some Si-O atoms to react. - The sites transform into Si-OH sites. This process weakens the surface negative charge and positive ion hydration layer, thereby altering water film stability, oil-wall contact, and wetting hysteresis. For petroleum engineering processes such as CO2-EOR, the surface charge state is not a pre-fixed constant but evolves dynamically with the local spatial distribution of CO2 and water.

[0004] Existing classical molecular dynamics studies typically employ fixed hydroxylation ratios or fixed surface charge ratios to describe quartz surfaces. While these methods can compare wetting behavior under different static surface states, they struggle to characterize the gradual protonation of surface sites after CO2 reaches the interface, the advancement of the reaction front, changes in local water films, and the evolution of oil-phase contact over time. First-principles methods or fully reactive force fields, although capable of describing local reaction details, generally fail to cover the wetting evolution process at the oil-water-CO2-quartz multiphase interface in terms of system and time scales.

[0005] On the other hand, explicit statistical analysis of H3O in a nanoscale molecular dynamics box. + HCO3 - CO3 -- The reaction species in the carbonation reaction typically suffer from insufficient particle count and high statistical noise. Treating CO2, hydrated protons, and carbonate ions as explicit reactants directly would significantly increase model complexity and computational cost, and would also make it difficult to obtain stable interface evolution results suitable for dynamic analysis of wettability.

[0006] Therefore, there is an urgent need for a molecular dynamics simulation method for the CO2-oil-water-quartz interface, which can transform the local acidification effect induced by CO2 into the dynamic protonation rules of surface sites without relying on the reactive force field of the whole system, and combine it with positive ion charge compensation and wettability index output to characterize the dynamic evolution of quartz surface wettability in the context of petroleum engineering. Summary of the Invention

[0007] To address the limitations of existing molecular dynamics models with fixed surface charge in describing the dynamic evolution of quartz surface states induced by CO2-rich brine, and the statistical insufficiency of explicit carbonation reaction species in nanoboxes, this invention discloses a molecular simulation method for the dynamic evolution of rock wettability under CO2 influence. This method utilizes topologically conserved O... - The system dynamically couples the local CO2-water environment with the charge state of the quartz surface using methods such as / OH surface site switching, CO2 / water local controlled reaction probability, acidification equilibrium upper limit, and positive ion charge compensation, and outputs dynamic indicators of oil-water wettability as the surface state changes.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a molecular simulation method for the dynamic evolution of rock wettability under CO2 action, specifically including the following steps: S1, constructing a CO2-quartz interface simulation system; constructing a molecular dynamics model containing a quartz or silica surface, an aqueous phase, CO2, and positive ions; S2, setting two-state reaction sites on the surface; setting O2-containing sites on the quartz or silica surface. - Surface reaction sites in the OH and O states; surface reaction sites achieve O through switching of atomic types and partial charges. - Dynamic protonation from the OH state; S3, calculate the local gated reaction probability of CO2 / water; determine the reaction acceptance probability of the surface reaction site based on the local water coordination and local CO2 coordination, where local water coordination is a necessary gated condition for the reaction to occur, and the reaction acceptance probability increases with local CO2 coordination; S4, set the upper limit of acidification equilibrium; set the O2 equilibrium upper limit based on the target pH, equivalent acidification degree, or surface ionization reference relationship. - The remaining percentage of sites or the maximum number of reactions ensures that the dynamic evolution of the surface state does not unconditionally transform into a fully OH state; S5, perform dynamic protonation and charge compensation; during molecular dynamics, perform O on the surface reaction sites according to the stated reaction acceptance probability. - The dynamic protonation events from the OH state are recorded, and a corresponding number of monovalent cations are removed based on the number of protonation events to maintain the system's electroneutrality; S6 outputs the dynamic evolution index of wettability; outputs the surface O - Indicators of the dynamic evolution of / OH state and wettability.

[0009] Furthermore, the system in step S1 also includes an oil phase, which forms an oil-water-solid interface with the water phase and the quartz or silica surface; the molecular dynamics model is selected from a plate-like layered system, a slit-pore system, and a droplet system with water droplets placed on the surface for contact angle measurement; when CO2 is located on the oil phase side and the corresponding surface site lacks water coordination, the surface site does not experience dynamic protonation events.

[0010] Preferably, the surface hydroxyl density is set according to the experimental reference aperture of the target mineral, such as the surface of crystalline silica at approximately 2.4-4.7 OH / nm²; the system temperature and CO2 pressure can be set according to the reservoir or storage conditions, such as supercritical CO2 conditions on the order of 333 K and approximately 10 MPa.

[0011] Furthermore, in step S2, each surface reaction site contains the same set of Si-OH atoms, and the Si-OH atom ID is in O - The state and the OH state remain unchanged; O - In the OH state, the H atom is a vacant hydrogen with zero charge, while in the OH state, the H atom is a real silanol hydrogen, and no H atom is created or deleted from the surface site during the reaction.

[0012] Furthermore, in step S3, the probability of response acceptance is expressed as follows: ;in, Let be the probability of acceptance of the reaction at the i-th surface site; As a probability factor; For water gate functions; Coordination number of CO2 The CO2 half-saturation coordination number; when water molecules are present within the water-gated radius at the surface sites. Choose 1, otherwise Take 0; when At this time, the reaction acceptance probability of the surface site is 0; thus, CO2 and water together constitute localized controlled conditions to prevent isolated CO2 on the oil side or dry surface from erroneously triggering surface protonation.

[0013] Furthermore, in step S4, the surface O is set according to the target pH or equivalent acidification degree. - The remaining percentage of sites or the maximum number of reactions ensures that the dynamic protonation process reaches the preset O. - It stops or tends to stop after the remaining percentage.

[0014] Furthermore, in step S5, each protonation event updates the atom types and partial charges of O, H, and edge Si, and each O... - The conversion to OH increases the total surface charge by one unit positive charge. The number of newly added protonation events is counted after a reaction window ends, and the result is obtained from Na… +The same number of positive ions are removed from the monovalent cation pool to restore the electroneutrality of the system.

[0015] Furthermore, in step S6, during and after the dynamic protonation simulation, the surface O... - / OH ratio, reaction event location, near-wall water film thickness, Na + Statistical analysis was conducted on near-wall distribution, CO2-water-wall coordination, oil-wall contact, near-wall oil phase density, and dynamic contact angle or adhesion trend to analyze how changes in surface charge state induced by CO2-rich brine affect the wettability of the oil-water-quartz interface.

[0016] The beneficial effects of this invention are: (1) This invention transforms the acidification of the quartz surface by CO2-rich brine into a dynamic protonation rule with local CO2 / water co-gated, enabling classical molecular dynamics to describe the dynamic evolution of surface states that cannot be given by the fixed surface charge model; (2) This invention utilizes the O of the same group of Si-OH atoms. - / OH two-state switching realizes topological conservation reaction, without the need to dynamically create or delete H atoms in the surface site, reducing the instability risk of reaction template switching and long-range electrostatic calculation; (3) This invention clearly divides water and CO2 into two gating factors: water determines whether the site is in a reactive environment, and CO2 determines the local acidification triggering intensity in the form of concentration-dependent probability, thereby avoiding false triggering of CO2 in the oil phase or dry surface; (4) This invention achieves charge compensation by deleting positive ions after the reaction window, so that the system after dynamic protonation remains electrically neutral, which is suitable for using long-range electrostatic algorithm to simulate oil-water-CO2-quartz interface; (5) This invention is aimed at CO2-EOR and CO2 sequestration scenarios in petroleum engineering, and can output dynamic contact angle, oil-wall contact, water film thickness, surface O - Indicators such as the dynamic ratio of / OH and wetting hysteresis provide a molecular-scale method for analyzing the dynamic evolution of rock surface wettability under CO2 action, and can be extended to the analysis of displacement-related processes under CO2 injection conditions. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the method flow of an embodiment of the present invention.

[0018] Figure 2 For the surface site O of the present invention - A molecular rendering diagram illustrating the topological conservation switching between the OH and OH states.

[0019] Figure 3 This invention provides a schematic diagram of the CO2 / water local gated reaction rules and minimum verification results; wherein, (a) represents water as a geometric gate, CO2 as a concentration-dependent probability gate, and acidification upper limit limiting the final O2. -The process relationship of the remaining proportions, (b) is a schematic diagram of the minimum verification result.

[0020] Figure 4 This is a schematic diagram illustrating the application of the dynamic evolution of the water droplet contact angle in this invention; wherein, (a) represents a quartz substrate, a water droplet, and Na. + The spatial relationship between positive ions, CO2, and the oil phase environment, (b) shows the dynamic contact angle and surface O - A schematic curve showing how the number of loci changes over simulation time. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] This invention discloses a molecular simulation method for the dynamic evolution of rock wettability under CO2 action, such as... Figure 1 This illustrates the CO2-water-rock interface system and O - The relationship between the two-state reaction sites of / OH, the local control rules of CO2 / water, the acidification upper limit, charge compensation, and the dynamic output of wettability is as follows: 1. Construct a CO2-quartz interface simulation system and build a quartz or silica interface model in a computer system. The model can be a slit-pore or plate-layered system with upper and lower walls, or a contact angle system with quasi-two-dimensional columnar water droplets on the substrate surface; the system includes an aqueous phase and Na+. + The study includes positive ion and CO2 phases, with an oil phase that can be configured depending on the research object. The oil phase can be characterized using n-decane, a mixture of alkanes, or a representative component of crude oil; the aqueous phase can be a Na-containing... + The salt water; CO2 can be CO2 molecules dissolved near the aqueous phase, CO2 phase surrounding the water droplets, or CO2-rich regions near the water film. The surface hydroxyl density is controlled according to the experimental reference aperture, for example, approximately 2.4 OH / nm² for a crystalline silica surface, to ensure that changes in surface charge state can be distinguished in the wettability index.

[0023] Preferably, the quartz phase uses an INTERFACE force field, the water phase uses SPC / E, the CO2 phase uses EPM2, and the oil phase uses GAFF2. ​​The above components employ AMBER-family compatible 12-6 Lennard-Jones nonbonded interaction forms and mixing rules, and the default mixing rules can be overridden with calibrated SPC / E-EPM2 CO2-water cross-parameters, thereby reducing errors caused by inconsistencies in multi-component cross-interactions.

[0024] 2. Set up surface two-state reaction sites: Set up dynamically protonable surface reaction sites on some silanol sites on the quartz surface, such as... Figure 2 As shown. Each reaction site contains the same group of Si-OH atoms, and the same group of Si-OH atoms are in O - The Si, O, and H atoms contain occupying hydrogen in the OH state and real silanol hydrogen in the OH state. The atomic IDs of Si, O, and H atoms remain unchanged before and after the switching.

[0025] In O - In the OH state, surface O atoms are deprotonated oxygen, and H atoms are occupying hydrogen atoms with zero charge; in the OH state, surface O atoms and H atoms are in the true silanol state, and the charge of edge Si atoms connected to the surface O is updated synchronously. Preferably, a reaction template switching method is used to achieve O. - The state transition to OH requires O as the reaction template. - OH state template, OH state template, and map file.

[0026] 3. Calculate the probability of local gated reactions of CO2 / water. For each surface reaction site, statistically analyze the local coordination of surrounding water and CO2 molecules. The gated reaction rules are as follows: Figure 3 As shown in Figure (a), the water-gated radius can be determined by the first minimum of the radial distribution function of surface oxygen and water oxygen in the fixed surface system; the CO2-gated radius can be determined as the capture radius in the CO2 loading scan of the fixed surface, used to characterize CO2 close to the outer side of the hydration shell that is sufficient to participate in the local acidification channel. The water-gated radius is 3.2 Å, and the CO2-gated radius is 5.0 Å. Choose 1. The probability of acceptance is: ;in, For water gate functions, Coordination number of CO2 This represents the half-saturation coordination number of CO2. This form makes CO2 one of the gating factors: when... When the CO2 coordination increases, the probability is 0; when the CO2 coordination increases, the probability increases with the Langmuir saturation term but does not increase indefinitely.

[0027] 4. Set the upper limit of acidification equilibrium. Based on the target pH, the degree of CO2 acidification, or the reference relationship of quartz surface ionization, set the O2 limit. - The final remaining percentage of sites or the maximum allowable number of reactions. This step is used to prevent the model from including all O sites. - Sites are unconditionally protonated, thereby maintaining the range of surface charge states corresponding to acidification equilibrium. This step is preferred; in embodiments without an upper limit, the degree of surface conversion is controlled by the gating probability and the simulation duration.

[0028] 5. Perform dynamic protonation and charge compensation, periodically calling the reaction template switching module during molecular dynamics operation. For candidate sites that meet water gating, CO2 probability gating, and acidification upper limits, execute O... - Switching to the OH state.

[0029] Preferably, under the IFF force field, each occurrence of O - Upon conversion to OH, the total surface charge increases by one unit positive charge. This charge change is composed of partial charge changes from O, H, and edge Si. Subsequently, after the reaction window ends, the number of newly added reactions is counted, and the change is calculated from Na... + The same amount of Na was removed from the positive ion cell. + This allows the system to regain its electrical neutrality.

[0030] 6. Output dynamic evolution indices of wettability, post-process the trajectory and reaction log, and output the following indices: surface O - / OH ratio over time, spatial distribution of reaction events, reaction front, near-wall water film thickness, water density distribution, Na + Density distribution, CO2-water-wall coordination, oil-wall contact, near-wall oil phase density, dynamic contact angle, or oil phase adhesion tendency. These indicators are used to determine how the evolution of surface charge induced by CO2-rich brine affects the wettability of the oil-water-quartz interface.

[0031] This invention also provides a terminal equipped with a memory and a processor. The memory stores a computer program that can run on the processor. When the processor runs the computer program, it executes the steps of the methods described in the above embodiments. The terminal includes, but is not limited to, terminal devices such as servers, mobile phones, computers, and tablet computers.

[0032] Specifically, in this embodiment of the invention, the processor can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor. It should also be understood that the memory in this embodiment can be volatile memory or non-volatile memory, or it can include both. Non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. Volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of random access memory (RAM) are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate synchronous DRAM (DDR SDRAM), enhanced synchronous DRAM (ESDRAM), synchronous linked DRAM (SLDRAM), and direct rambus RAM (DRRAM).

[0033] Application Example 1: Verification of CO2 / water gated dynamic protonation module

[0034] This application example is used to verify the dynamic protonation gating, charge compensation, and acidification upper limit modules of the present invention. The verification results are as follows. Figure 3 ,in, Figure 3Figure (a) illustrates water as a geometric gate, CO2 as a concentration-dependent probability gate, and the acidification upper limit restricting the final O2. - The process relationship of the remaining proportion; Figure 3 Figure (b) shows the CO2-deficient sites maintaining O - CO2 enrichment sites undergo protonation and acidification, with the upper limit of O retained. - Sites and deletion of Na by reaction number + The verification results.

[0035] Using a quartz-water-Na + -CO2 minimal system, the top surface contains 16 silanol sites, of which 5 sites are initialized to O - This corresponds to 31.25% of the top surface O. - The system contains 80 water molecules and 5 Na+ molecules. + A positive ion and 3 EPM2 CO2 molecules, of which 3 O - A CO2 enrichment environment was set up near the site, and two other O2 enrichment environments were also established. - The site served as a control for insufficient CO2 coordination.

[0036] In this system, all water gate conditions are met: CO2-enriched sites have non-zero CO2 coordination, while CO2-deficient sites have zero CO2 coordination. A maximum reaction number of 2 is set to represent the upper limit of acidification equilibrium. O is used as the reaction template. - O state template, OH state template, and map file; custom constraints in the map file are also checked. - / Occupied hydrogen state, water gating and CO2 probability gating.

[0037] The results showed that the two CO2-deficient sites remained O due to the CO2 coordination being 0. - Two of the three CO2 enrichment sites showed O2 accumulation. - Dynamic protonation of OH occurs, and another CO2 enrichment site remains at the upper limit of acidification due to O. - Two Na+ molecules were removed after the reaction. + The final system retains 3 Na atoms. + And 3 O - The site remains electrically neutral.

[0038] The verification result of this application example is: Top surface O - Sites = 5 / 16 (31.25%, target 30%), water molecules = 80, CO2 = 3, Na + =5; CO2 enrichment candidate sites =3; maximum number of reactions at the upper limit of acidification =2; CO2 enrichment sites have been protonated =2; CO2 enriched but limited by the upper limit =1; CO2 insufficient coordination and retaining O -=2; reaction site number = [2, 4], total number of reactions = 2, final Na + =3, final O - Site = 3; Total Si charge changes from 68.525 to 69.275. The maximum net charge deviation is negligible after removing positive ions; Si-O = 1.6800-1.6800 A; OH = 0.9055-0.9849 A; Average Si-OH = 111.07 deg.

[0039] This application example illustrates that CO2 is an effective gating factor; water gating and CO2 gating together determine whether surface protonation occurs, and the acidification upper limit restricts the final conversion degree. Na + Deleting the ledger ensures electrical neutrality after dynamic evolution.

[0040] Application Example 2: Dynamic Evolution of Water Droplet Contact Angle in a CO2 Environment

[0041] This application example illustrates how the present invention is applied in the dynamic characterization of wettability, such as... Figure 4 As shown, Figure 4 Figure (a) shows a quartz substrate, water droplet, and Na+ obtained from static calibration configuration rendering. + Spatial relationship between positive ions, CO2, and the oil phase environment; Figure 4 Figure (b) shows the dynamic contact angle and surface O. - A schematic curve showing the change in the number of sites over simulation time. Quasi-two-dimensional columnar water droplets containing Na were constructed on a quartz or silica substrate. + Positive ions are generated, and a CO2 phase or CO2-containing oil phase environment is set around the water droplet. The substrate surface is initialized with a certain proportion of silanol sites as O according to the target ionization degree. - For example, 10%-50%. A columnar water droplet penetrates the simulation chamber along a periodic direction, and its contact angle can be obtained by fitting an arc to the water density contour lines, independent of line tension correction. Preferably, the hydroxyl density on the substrate surface is controlled according to an experimental reference aperture, for example, approximately 2.4 OH / nm², to avoid excessive hydroxylation that would make the contact angle insensitive to changes in surface charge state.

[0042] First, static calibration is performed on a frozen surface: without enabling the dynamic protonation module, a series of fixed O2 atoms are calibrated. - The equilibrium contact angles of the surfaces with / OH ratios were measured to obtain a static calibration curve of "protonation degree - contact angle", which serves as a reference scale for dynamic simulation.

[0043] The dynamic protonation module of this invention is then activated. The O2 gating conditions simultaneously satisfy water gating and CO2 gating in the water droplet coverage area and near the three-phase contact line. - O occurs at the site according to the gating probability - Dynamic protonation of OH, and removal of an equal amount of Na by reaction counting.+ Surface sites located outside the water droplet coverage area and only in contact with CO2 or the oil phase remain O2 due to water gating not being met. - The simulation process synchronously outputs surface O. - The changes in the / OH ratio, spatial distribution of reaction events, and dynamic contact angle over time were compared with static calibration curves to reveal the dynamic migration process of wettability driven by CO2-induced surface charge evolution and its hysteresis characteristics.

[0044] This application example features a simple system configuration and direct observations, sufficient to fully demonstrate steps S1 to S6 of the present invention. This application example does not require CO2 to be used as a consumed explicit chemical reactant, but rather as a gating factor for the localized acidification environment, suitable for situations where explicit carbonate species are statistically insufficient in nanoscale molecular dynamics boxes. The same method can be directly extended to layered or porous systems containing oil phases to characterize the wettability evolution and even displacement-related processes at the oil-water-rock interface under CO2 injection conditions; the present invention does not impose any limitations on this.

[0045] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A molecular simulation method for the dynamic evolution of rock wettability under CO2 action, characterized in that, Specifically, the following steps are included: S1, Constructing a CO2 quartz interface simulation system; Construct a molecular dynamics model containing a quartz or silica surface, an aqueous phase, CO2, and positive ions; S2, setting two-state reaction sites on the surface; An O-shaped surface is formed on the quartz or silica surface. - Surface reaction sites in the OH and O states; surface reaction sites achieve O through switching of atomic types and partial charges. - Dynamic protonation from the OH state; S3, calculate the local controlled reaction probability of CO2 / water; The reaction acceptance probability of a surface reaction site is determined based on the local water coordination and local CO2 coordination. Local water coordination is a necessary gating condition for the reaction to occur, and the reaction acceptance probability increases with local CO2 coordination. S4 sets the upper limit of acidification balance; Based on the target pH, equivalent acidification degree, or surface ionization degree reference relationship, set O - The remaining percentage of sites or the maximum number of reactions ensures that the dynamic evolution of the surface state will not unconditionally transform into the all-OH state. S5 performs dynamic protonation and charge compensation; During molecular dynamics, O is performed on surface reaction sites according to the stated reaction acceptance probability. - The dynamic protonation events from the OH state are observed, and a corresponding number of monovalent cations are removed based on the number of protonation events to maintain the electroneutrality of the system. S6 outputs dynamic evolution indicators of wettability; Output characterization surface O - Indicators of the dynamic evolution of / OH state and wettability.

2. The molecular simulation method for the dynamic evolution of rock wettability under CO2 action as described in claim 1, characterized in that, The system in step S1 also includes an oil phase, which forms an oil-water-solid interface with the water phase and the quartz or silica surface; the molecular dynamics model is selected from a plate-like layered system, a slit-pore system, and a droplet system with water droplets placed on the surface for contact angle measurement. When CO2 is located on the oil phase side and the corresponding surface site lacks water coordination, dynamic protonation events do not occur at that surface site.

3. The molecular simulation method for the dynamic evolution of rock wettability under CO2 action as described in claim 2, characterized in that, In step S2, each surface reaction site contains the same set of Si-OH atoms, and the Si-OH atom ID is in O - The state and the OH state remain unchanged; O - In the OH state, the H atom is a vacant hydrogen with zero charge, while in the OH state, the H atom is a real silanol hydrogen, and no H atom is created or deleted from the surface site during the reaction.

4. The molecular simulation method for the dynamic evolution of rock wettability under CO2 action as described in claim 3, characterized in that, In step S3, the probability of acceptance of the response is expressed as follows: ； in, Let be the probability of acceptance of the reaction at the i-th surface site; As a probability factor; For water gate functions; Coordination number of CO2 The half-saturation coordination number of CO2; When water molecules are present at the surface sites within the water-gated radius Choose 1, otherwise Take 0; when At that time, the probability of acceptance of the reaction at the surface site is 0.

5. The molecular simulation method for the dynamic evolution of rock wettability under CO2 action as described in claim 4, characterized in that, In step S4, the surface O is set according to the target pH or equivalent acidification degree. - The remaining percentage of sites or the maximum number of reactions ensures that the dynamic protonation process reaches the preset O. - The remaining percentage will stop or tend to stop.

6. The molecular simulation method for the dynamic evolution of rock wettability under CO2 action as described in claim 5, characterized in that, In step S5, each protonation event updates the atom types and partial charges of O, H, and edge Si, and O... - The conversion to OH increases the total surface charge by one unit positive charge. The number of newly added protonation events is counted after a reaction window ends, and the result is obtained from Na… + The same number of positive ions are removed from the monovalent cation pool to restore the electroneutrality of the system.

7. The molecular simulation method for the dynamic evolution of rock wettability under CO2 action as described in claim 6, characterized in that, In step S6, during and after the dynamic protonation simulation, the surface O... - / OH ratio, reaction event location, near-wall water film thickness, Na + Statistical analysis was conducted on near-wall distribution, CO2-water-wall coordination, oil-wall contact, near-wall oil phase density, and dynamic contact angle or adhesion trend.

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