A geological storage target area optimization method based on CO2-water-rock reaction mineralization effect and reservoir engineering adaptability

Abstract

The application discloses a geological storage target area optimization method based on CO2-water-rock reaction mineralization effect and reservoir engineering adaptability. The method divides the target area into several evaluation areas, collects the mineral composition, formation water chemical composition, temperature and pressure conditions, reservoir area, porosity and permeability parameters of each evaluation area, constructs a CO2-water-rock reaction model and carries out batch simulation of multiple evaluation areas, according to the change of mineral content before and after the reaction, sums the increase of the mineral with increased content as the mineralization capacity index, and then dimensionless weights the reservoir area, porosity and permeability, calculates the comprehensive optimization index, and sorts and grades the evaluation areas for output. The application couples the mineralization effect with the reservoir engineering parameters for evaluation, can quantitatively characterize the long-term CO2 mineralization storage potential of different evaluation areas, and is suitable for CO2 geological storage target area screening and CCUS engineering injection area selection.

Description

Technical Field

[0001] This invention relates to a method for selecting geological storage target areas based on the CO2-water-rock reaction mineralization effect and reservoir engineering adaptability, belonging to the technical fields of CO2 geological storage, reservoir geochemical simulation, CCUS engineering and oil and gas reservoir evaluation. Background Technology

[0002] The optimal selection of CO2 geological storage target areas typically requires comprehensive consideration of factors such as reservoir size, porosity, permeability, caprock sealing, burial depth, and structural stability. These parameters can reflect the injection and accumulation basis of the reservoir, but they are insufficient to reflect the long-term mineralization and fixation capacity formed by the reaction of CO2 with minerals and formation water after entering the water-bearing reservoir.

[0003] When CO2 dissolves in formation water, it forms a weakly acidic fluid that can promote the dissolution, precipitation, or transformation of feldspar, carbonate minerals, clay minerals, and iron-magnesium minerals. Among these, Ca²⁺… + Mg² + Fe² + Plasma combines with carbonate ions to form carbonate minerals such as calcite, dolomite, magnesite, and siderite, which is an important form of long-term stable CO2 sequestration.

[0004] Existing methods for selecting target areas for sequestration are mostly based on static geological conditions, and the results of water-rock reaction simulations are mostly limited to the interpretation of mechanisms in single samples or single blocks. There is a lack of technical processes that couple the changes in mineral increase or decrease after reaction, the total increase in minerals, and reservoir engineering parameters in a unified manner and use them for ranking multiple evaluation areas. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing methods for selecting CO2 geological storage target areas, which focus on static geological parameters, are difficult to quantitatively evaluate long-term mineralization and storage potential, have inconsistent simulation conditions in different evaluation intervals, are difficult to make comparable rankings, and have insufficient integration of simulation results with reservoir engineering adaptability. This invention provides a method for selecting geological storage target areas based on the CO2 water-rock reaction mineralization effect and reservoir engineering adaptability.

[0006] This invention constructs a unified CO2-water-rock reaction model to conduct batch simulations of multiple evaluation areas. It standardizes and couples the chemical mineralization capacity characterized by the increase in mineral content with engineering indicators such as reservoir area, porosity, and permeability, thereby providing a quantitative decision-making basis for the scientific ranking of CO2 geological storage target areas, the selection of experimental target areas, and the deployment of in-situ injection.

[0007] This invention focuses on buried hill reservoirs in basins. First, it divides the region according to differences in tectonic units, reservoir types, and mineral composition. Second, it collects basic parameters such as mineral composition, formation water ion concentration, temperature and pressure conditions, reservoir size, porosity, and permeability for each region. Then, it constructs a CO2-water-rock reaction numerical model based on PHREEQC to simulate the mineral dissolution, precipitation, and CO2 mineralization processes in different regions under target reservoir conditions. Finally, it performs a standardized comprehensive evaluation of the degree of mineralization and reservoir physical parameters to determine favorable areas for CO2 geological sequestration.

[0008] Specifically, the geological sequestration target area selection method based on CO2 water-rock reaction mineralization effect and reservoir engineering adaptability provided by the present invention includes the following steps: S1. Obtain geological data of the target area and divide the target area into several CO2 geological storage evaluation areas; S2. For each evaluation area, collect parameters such as mineral composition, formation water ion concentration, temperature, pressure, reservoir area, reservoir thickness, porosity, and permeability, and convert the mineral composition into mineral molar amounts or relative contents that the model can recognize. S3. Based on the formation water composition, mineral composition and temperature and pressure conditions of each evaluation area, establish a CO2-formation water-reservoir mineral reaction model, and set reaction boundary conditions and output control conditions. S4. Under uniform or comparable boundary conditions, conduct water-rock reaction simulations for each evaluation area and output the relative amounts of each mineral before and after the reaction. S5. Based on the mineral content before and after the reaction in each evaluation area, calculate the change in the content of each mineral, sum up the increases in the content of the minerals that have increased, and obtain the total increase in minerals in each evaluation area, which is used as an evaluation index of mineralization capacity. S6. Based on the reservoir area, porosity, and permeability of each evaluation zone, establish reservoir engineering parameter evaluation indicators; S7. The mineralization capacity evaluation index and reservoir engineering parameter evaluation index are dimensionless and weighted, the comprehensive optimization index of each evaluation zone is calculated, and the evaluation zones are sorted and graded according to the comprehensive optimization index.

[0009] In step S3, the reaction model is the PHREEQC reaction model, which includes at least the following settings: (1) Mineral reaction kinetics settings: Set the reaction rate constant, activation energy, specific surface area and reaction order for quartz, feldspar, calcite, dolomite, clay minerals and iron-magnesium minerals; (2) Groundwater and temperature and pressure settings: Input the formation water ion concentration, pH, temperature, pressure and CO2 partial pressure conditions; (3) Initial mineral content setting: Convert mineral content fractions into mineral molar amounts or relative contents that the model can recognize; (4) Reaction and output control: Set the reaction time, step size and output mineral quantity and solution composition.

[0010] In step S5, for each evaluation zone, if the content of a certain mineral after the reaction is greater than its content before the reaction, the change in the mineral content is included in the increase in mineral content; if the content of a certain mineral after the reaction is less than or equal to its content before the reaction, it is not included in the increase in mineral content; the formula for calculating the total increase in mineral content is:

[0011] In the formula, For the first Total mineral increase in each evaluation area; This represents the amount of minerals after the reaction. This represents the amount of minerals present before the reaction.

[0012] In step S7, the comprehensive optimization index is the mineralization and storage favorable index. The formula for its calculation is:

[0013] In the formula, The index represents the favorable conditions for mineralization and storage. A standardized indicator for the increase in mineral content; Standardized index for reservoir area; A standardized index for porosity; A standardized indicator for penetration rate; , , , The values ​​represent the weights of each component, with a+b+c+d=1. The larger the value, the more favorable the geological conditions for CO2 sequestration in the region. Among them, the increase in mineral content characterizes the degree of increase in precipitated minerals after CO2 water-rock reaction, the reservoir area characterizes the basic scale of sequestration, porosity characterizes the storage space for CO2 and formation fluids, and permeability characterizes the fluid migration and water-rock reaction contact capacity.

[0014] Preferably, the standardized indices for total mineral increase, reservoir area, porosity, and permeability are all processed using an extreme value standardization method, and calculated based on the maximum value in each evaluation zone:

[0015]

[0016]

[0017]

[0018] In the formula, For the first Mineral increase in each evaluation area This represents the maximum increase in mineral content in each evaluation area. For the first Reservoir area in each evaluation region The maximum reservoir area in each evaluation region; For the first Porosity of each evaluation region The maximum porosity in each evaluation region; For the first Penetration rate in each evaluation area The maximum penetration rate in each evaluation region, after standardization, , , , All are dimensionless indices, ranging from 0 to 1. Calculations were performed for different regions. The comprehensive index can be used to rank favorable areas for CO2 geological storage. The higher the comprehensive index, the more suitable the area is as a target area for CO2 geological storage.

[0019] In step S7, the graded output includes: dividing the evaluation area into a preferred target area, a candidate area, and a temporarily non-preferred area according to the comprehensive optimization index; wherein, the mineralization contribution index is used as the main indicator, the reservoir condition index is used as the basic constraint index, and the engineering adaptation index is used as the correction index.

[0020] The present invention further provides a geological sequestration target area selection system based on CO2 water-rock reaction mineralization effect and reservoir engineering adaptability, comprising: The evaluation area division module is used to obtain geological data of the target area and divide the target area into several CO2 geological storage evaluation areas. The parameter acquisition and conversion module is used to acquire parameters such as mineral composition, formation water ion concentration, temperature, pressure, reservoir area, reservoir thickness, porosity and permeability of each evaluation area, and convert the mineral composition into mineral molar amounts or relative contents that the model can recognize. The reaction model construction module is used to establish CO2-formation water-reservoir mineral reaction models based on the formation water composition, mineral composition and temperature and pressure conditions of each evaluation area; The batch simulation module is used to conduct water-rock reaction simulations for each evaluation area under uniform or comparable boundary conditions, and output the relative amounts of each mineral before and after the reaction. The mineralization capacity calculation module is used to calculate the total increase in minerals based on the mineral content before and after the reaction in each evaluation zone. The comprehensive evaluation module is used to perform dimensionless processing and weighting of mineralization capacity evaluation indicators and reservoir engineering parameter evaluation indicators, calculate the comprehensive optimization index of each evaluation area, and sort and classify the evaluation areas according to the comprehensive optimization index.

[0021] Advantages compared to existing technologies: (1) Incorporate CO2 water-rock reaction and carbonaceous mineral formation capabilities into the target area selection process, expanding the evaluation from "can inject and can store" to "can react, can mineralize, and can be stably fixed for a long time".

[0022] (2) By using a unified model framework and comparable boundary conditions, multiple evaluation areas are simulated in batches to improve the comparability between areas and reduce the subjectivity of empirical judgment.

[0023] (3) The positive increment of mineralization-related carbonaceous minerals is used as an indicator of mineralization capacity to avoid miscounting the increment of minerals that do not directly fix CO2 as mineralization contribution, thereby improving the physical meaning and evaluation accuracy of the indicator.

[0024] (4) By coupling mineralization capacity with reservoir area, porosity, permeability and engineering constraints, geochemical simulation results can be converted into target area sorting and classification results.

[0025] (5) It can provide a pre-screening basis for high temperature and high pressure water-rock reaction experiments, sample selection and on-site injection engineering deployment, reducing the workload of blind experiments and on-site evaluation. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the CO2 geological storage target area selection process of the present invention, which shows the technical process of evaluation area division, parameter acquisition and model conversion, reaction model construction, batch simulation of multiple evaluation areas, mineralization capacity index calculation, reservoir engineering parameter evaluation, and comprehensive evaluation and graded output.

[0027] Figure 2 This is a schematic diagram of the input-calculation-output structure of the reaction simulation model of the present invention, which shows the relationship between mineral reaction kinetics, groundwater composition, temperature and pressure conditions, initial mineral content, reaction control and simulation results.

[0028] Figure 3 This is a table showing the comprehensive evaluation index system for CO2 geological storage target areas in this invention. It illustrates the relationship between four evaluation indicators—total mineral increase, reservoir area, porosity, and permeability—and the mineralization storage favorable index.

[0029] Figure 4 This is a schematic diagram of the parameter settings and output control of the PHREEQC reaction model of the present invention. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to specific embodiments. The embodiments given are merely illustrative of the invention and are not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0031] Example 1: Identification of Favorable CO2 Sequestration Zones in Buried Hill Reservoirs in Bohai Bay Taking the buried hill reservoirs in the Bohai Bay as the evaluation object, the CO2 water-rock reaction simulation and multi-parameter comprehensive evaluation method of this invention is used to identify the favorable conditions for CO2 geological storage in different buried hill tectonic units. The specific implementation process is as follows: Step 1: Evaluation Area Division First, based on the structural unit distribution, reservoir type, and existing oil and gas reservoir distribution characteristics of the Bohai Bay buried hill reservoirs, the study area was divided into multiple evaluation regions, including the Shaleitian Uplift, Shijiutuo Uplift, Liaozhong Uplift, Bozhong Depression, Liaoxi Depression, Miaoxinan Uplift, Chengbei Low Uplift, Miaoxibei Uplift, Liaoxi Uplift, Laizhou Bay Uplift, Qinnan Uplift, Liaodong Uplift, and Bohai South Low Uplift. Each evaluation region was used as an independent calculation unit, and CO2 water-rock reaction simulation and storage favorableness evaluation were carried out separately.

[0032] Step 2: Basic Parameter Acquisition For each evaluation area, mineral composition, formation water type, temperature and pressure conditions, and reservoir physical property parameters were obtained. The mineral composition mainly includes quartz, potassium feldspar, plagioclase, clay minerals, and a small amount of carbonate minerals; the formation water type is mainly Sorrento water type; the temperature and pressure conditions include reservoir temperature and reservoir pressure; and the reservoir physical property parameters include reservoir area, porosity, and permeability.

[0033] In this embodiment, mineral composition and formation water composition are used to establish the PHREEQC reaction model, while reservoir area, porosity, and permeability are used for subsequent comprehensive evaluation calculations.

[0034] Table 1. Reservoir granite gneiss composition in various regions

[0035] Step 3: Establishment of the PHREEQC reaction model In the PHREEQC software, CO2-water-rock reaction models were established for each evaluation area. The model input parameters included the kinetic parameters of the reacting minerals, groundwater composition, temperature and pressure conditions, and initial mineral content.

[0036] Among them, the reaction mineral kinetic parameters are used to describe the dissolution or precipitation behavior of quartz, feldspar, clay minerals and carbonate minerals; groundwater components are used to characterize the hydrochemical environment of different regions; temperature and pressure conditions are used to simulate the actual reservoir reaction environment; and initial mineral content is used to characterize the basic mineral composition of rocks in each evaluation area.

[0037] The mineral content fractions of each evaluation zone were converted into initial mineral molar amounts recognizable by the model. Using a 500g rock sample as the calculation baseline, the first... The first evaluation zone The initial content of the mineral in the model is:

[0038] In the formula, For the first The first evaluation zone The initial content of the model for the mineral; The percentage of the mineral in the sample is expressed as a decimal; 500 is the reference mass of the rock sample, in grams. This represents the relative molecular mass of the mineral, expressed in g / mol.

[0039] The model uniformly sets the reaction time step and output control conditions, and outputs results such as the changes in the content of each mineral and the composition of the solution after the reaction.

[0040] Step 4: Statistics on the Increase in Mineral Content After the simulation, the changes in mineral content before and after the reaction in each evaluation area were statistically analyzed. The increase in mineral content is used to characterize the degree of increase in precipitated minerals after the CO2 water-rock reaction, and its calculation formula is as follows:

[0041] In the formula, For the first Mineral increase in each evaluation area; This represents the amount of precipitated minerals after the reaction. This represents the amount of minerals present before the reaction.

[0042] In this embodiment, the statistical results of the increase in mineral content in each region are as follows: Table 2. Statistics on the increase in total minerals after the reaction.

[0043] Step 5: Calculation of Comprehensive Indicators To comprehensively evaluate the favorable conditions for CO2 geological sequestration in different regions, this embodiment selects mineral enrichment, reservoir area, porosity, and permeability as the main evaluation indicators to construct a mineralization sequestration favorableness index. The calculation formula is:

[0044] In this embodiment, weight , , , The selection of target areas for CO2 geological sequestration was based on a comprehensive consideration of the key controlling factors and the importance of the indicators. Among these, the total mineral increase directly reflects the ability to form new minerals after CO2-water-rock reaction and is a core indicator for evaluating mineralization effects; therefore, it was given a high weight and selected as the primary indicator. =0.40; Reservoir area reflects the basic scale of storage and has a significant impact on target area selection. =0.25; Porosity characterizes the storage space for CO2 and formation fluids, taking... =0.20; Permeability reflects fluid transport capacity and water-rock reaction contact conditions, taken as... =0.15. The sum of the above weights is 1, which can highlight the mineralization effect while taking into account reservoir size, reservoir space and seepage conditions. Therefore, the mineralization preservation favorableness index in this embodiment can be expressed as:

[0045] In the formula, The index represents the favorable conditions for mineralization and storage. A standardized indicator for the increase in mineral content; Standardized index for reservoir area; A standardized index for porosity; This is a standardized indicator for penetration rate.

[0046] Step Six: Prioritizing Favorable Areas and Determining Target Areas By substituting the standardized indicators of each evaluation area into the comprehensive evaluation formula, the mineralization sequestration favorable index of each area is obtained. The higher the comprehensive index, the more suitable the area is as a target area for CO2 geological sequestration.

[0047] In this embodiment, the mineral abundance in the Shaleitian Uplift is at a high level, and the reservoir area is large, providing a good foundation for CO2 storage capacity. Compared with areas such as the Shijiutuo Uplift, Liaozhong Uplift, and Bozhong Depression, the Shaleitian Uplift has comprehensive advantages in terms of mineralization reaction potential and reservoir size. Therefore, the Shaleitian Uplift is identified as a favorable area for CO2 geological storage and serves as the target area for subsequent high-temperature and high-pressure CO2 water-rock reaction experiments and storage suitability evaluation.

[0048] Table 3. Comprehensive evaluation results of CO2 geological sequestration in each evaluation area

[0049] As shown in Table 3, the Liaozhong Uplift has the highest increase in total minerals, indicating that it has a strong ability to form new minerals after CO2 water-rock reaction. Although the Shaleitian Uplift does not have the highest increase in total minerals, it is among the top in the evaluation area. At the same time, it has significant advantages in reservoir area, porosity and permeability. Therefore, after comprehensively considering the mineralization effect and reservoir engineering conditions, the Shaleitian Uplift has the highest comprehensive selection index and has been identified as the preferred target area for CO2 geological sequestration.

Claims

1. A method for selecting geological storage target areas based on CO2 water-rock reaction mineralization effect and reservoir engineering adaptability, comprising the following steps: S1. Obtain geological data of the target area and divide the target area into several CO2 geological storage evaluation areas; S2. For each evaluation area, collect parameters such as mineral composition, formation water ion concentration, temperature, pressure, reservoir area, reservoir thickness, porosity, and permeability, and convert the mineral composition into mineral molar amounts or relative contents that the model can recognize. S3. Based on the formation water composition, mineral composition and temperature and pressure conditions of each evaluation area, establish a CO2-formation water-reservoir mineral reaction model, and set reaction boundary conditions and output control conditions. S4. Under uniform or comparable boundary conditions, conduct water-rock reaction simulations for each evaluation area and output the relative amounts of each mineral before and after the reaction. S5. Based on the mineral content before and after the reaction in each evaluation area, calculate the change in the content of each mineral, sum up the increases in the content of the minerals that have increased, and obtain the total increase in minerals in each evaluation area, which is used as an evaluation index of mineralization capacity. S6. Based on the reservoir area, porosity, and permeability of each evaluation zone, establish reservoir engineering parameter evaluation indicators; S7. The mineralization capacity evaluation index and reservoir engineering parameter evaluation index are dimensionless and weighted, the comprehensive optimization index of each evaluation zone is calculated, and the evaluation zones are sorted and graded according to the comprehensive optimization index.

2. The method according to claim 1, characterized in that: In step S3, the reaction model is the PHREEQC reaction model, which includes at least the following settings: (1) Mineral reaction kinetics settings: Set the reaction rate constant, activation energy, specific surface area and reaction order for quartz, feldspar, calcite, dolomite, clay minerals and iron-magnesium minerals; (2) Groundwater and temperature and pressure settings: Input the formation water ion concentration, pH, temperature, pressure and CO2 partial pressure conditions; (3) Initial mineral content setting: Convert mineral content fractions into mineral molar amounts or relative contents that the model can recognize; (4) Reaction and output control: Set the reaction time, step size and output mineral quantity and solution composition.

3. The method according to claim 1 or 2, characterized in that: In step S5, for each evaluation zone, if the content of a certain mineral after the reaction is greater than its content before the reaction, the change in the mineral content is included in the increase in mineral content; if the content of a certain mineral after the reaction is less than or equal to its content before the reaction, it is not included in the increase in mineral content; the formula for calculating the total increase in mineral content is: ； In the formula, For the first Total mineral increase in each evaluation area; This represents the amount of minerals after the reaction. This represents the amount of minerals present before the reaction.

4. The method according to any one of claims 1-3, characterized in that: In step S7, the comprehensive optimization index is the mineralization and storage favorable index. The formula for its calculation is: ； In the formula, The index represents the favorable conditions for mineralization and storage. A standardized indicator for the increase in mineral content; Standardized index for reservoir area; A standardized index for porosity; A standardized indicator for penetration rate; , , , Let a be the weight of each part, and a+b+c+d=1.

5. The method according to claim 4, characterized in that: The standardized indices for total mineral increase, reservoir area, porosity, and permeability were all processed using the extreme value standardization method, and calculated based on the maximum value in each evaluation zone. ； ； ； ； In the formula, For the first Mineral increase in each evaluation area The maximum increase in mineral content in each evaluation area; For the first Reservoir area in each evaluation region The maximum reservoir area in each evaluation region; For the first Porosity of each evaluation region The maximum porosity in each evaluation region; For the first Penetration rate in each evaluation area The maximum penetration rate in each evaluation region, after standardization, , , , All are dimensionless indices, with values ​​ranging from 0 to 1.

6. The method according to any one of claims 1-5, characterized in that: In step S7, the graded output includes: dividing the evaluation area into a preferred target area, a candidate area, and a temporarily non-preferred area according to the comprehensive optimization index; wherein, the mineralization contribution index is used as the main indicator, the reservoir condition index is used as the basic constraint index, and the engineering adaptation index is used as the correction index.

7. A geological target area selection system based on CO2 water-rock reaction mineralization effect and reservoir engineering adaptability, comprising: The evaluation area division module is used to obtain geological data of the target area and divide the target area into several CO2 geological storage evaluation areas. The parameter acquisition and conversion module is used to acquire parameters such as mineral composition, formation water ion concentration, temperature, pressure, reservoir area, reservoir thickness, porosity and permeability of each evaluation area, and convert the mineral composition into mineral molar amounts or relative contents that the model can recognize. The reaction model construction module is used to establish CO2-formation water-reservoir mineral reaction models based on the formation water composition, mineral composition and temperature and pressure conditions of each evaluation area; The batch simulation module is used to conduct water-rock reaction simulations for each evaluation area under uniform or comparable boundary conditions, and output the relative amounts of each mineral before and after the reaction. The mineralization capacity calculation module is used to calculate the total increase in minerals based on the mineral content before and after the reaction in each evaluation zone. The comprehensive evaluation module is used to perform dimensionless processing and weighting of mineralization capacity evaluation indicators and reservoir engineering parameter evaluation indicators, calculate the comprehensive optimization index of each evaluation area, and sort and classify the evaluation areas according to the comprehensive optimization index.

8. The application of the system described in claim 7 in the selection of CO2 geological storage target areas, the screening of high-temperature and high-pressure CO2-water-rock reaction experimental target areas, or the selection of CCUS engineering injection areas.

Images