Method for determining the evolution of diagenetic fluids after carbon dioxide injection into sandstone

Abstract

The disclosure provides a method for determining the evolution process of carbon dioxide injection into sandstone post-diagenetic fluid, comprising: obtaining the microscopic characteristics of davyne sandstone, determining the diagenetic paragenetic sequence of CO2 injection into davyne sandstone according to the microscopic characteristics; determining the fluid inclusion characteristics of davyne sandstone, determining the filling time and filling period of the fluid according to the fluid inclusion characteristics; according to the diagenetic paragenetic sequence and the filling time and filling period of the fluid, analyzing the diagenetic fluid properties corresponding to the injection of CO2 and oil and gas into davyne sandstone before and after; obtaining the characteristics of present formation water, determining the present fluid characteristics of davyne sandstone according to the characteristics of present formation water; determining the paleofluid characteristics of davyne sandstone according to the carbon and oxygen isotopic composition of davyne sandstone; determining the evolution process of diagenetic fluid after CO2 injection into davyne sandstone according to the present fluid characteristics, diagenetic fluid properties and paleofluid characteristics. The method can comprehensively analyze the evolution process of diagenetic fluid after CO2 injection into sandstone.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of sandstone fluid evolution, and particularly relates to a method for determining post-diagenetic fluid evolution process of carbon dioxide injected into sandstone. BACKGROUND

[0002] With the rapid development of modern society, the demand for fossil energy is increasing, which leads to a substantial increase in the amount of greenhouse gas emissions. The increasing CO2 in the atmosphere is generally believed to be the main cause of the greenhouse effect, and the greenhouse effect is the main cause of global climate change. Carbon capture, utilization and storage (CCUS) is an important means to cope with global climate change and reduce CO2 in the atmosphere. Among the four storage mechanisms of CO2 geological storage, the safety of CO2 stored in the form of structure, residual CO2 and dissolved CO2 gradually decreases with time, while the safety of CO2 stored in the form of mineral capture gradually dominates. CO2 mineral storage is one of the safest, permanent and environmentally friendly storage methods. After a large amount of CO2 that has been emitted or from industry is captured, it is injected into underground storage points through CO2 geological storage. CO2 entering the rock pore space will interact with minerals and fluids in the formation rock, which involves extremely complex petrology and mineralogy, kinetics and thermodynamics processes, so that CO2 is stored in the form of free CO2 phase through structural storage, and then converted into residual CO2 phase capture in the pore, and then dissolved in formation water, and finally stored in the form of mineral capture in the formation. After CO2 is injected into the formation, it can generate carbonate "carbon capture minerals" containing iron, calcium, aluminum and magnesium ions (mainly dawsonite, ankerite, etc.) through interaction with formation rock and fluid. Among them, dawsonite is considered as a "tracer mineral" that can indicate that the formation is filled and accumulated, or dispersed by CO2. It is considered that the fixation of CO2 by stable carbonate minerals such as dawsonite is an effective way.

[0003] In the current CCUS project, a long time is needed for the formation of "carbon fixation minerals" after CO2 injection into the formation, and the changes in the reservoir conditions during this period are difficult to predict. After the supercritical CO2 is artificially injected into the reservoir in large quantities, it will inevitably cause a strong change in the diagenetic environment of the reservoir. The dissolution and precipitation of davyne under the conditions of the reservoir are influenced by the formation temperature, pressure, and reservoir medium environment (pH and salinity of the formation water, mineral types and content). Therefore, systematic research on the petrology and diagenetic fluid characteristics of davyne-bearing sandstone is conducive to a reasonable understanding of the changes in the properties of the formation fluid after CO2 injection and the feasibility of CO2 geological storage. Systematic research on the evolution process of the diagenetic fluid after CO2 injection into sandstone will play an important role in the risk assessment and safety detection of the CCUS project. However, there is no comprehensive way to analyze the evolution process of the diagenetic fluid after CO2 injection into sandstone in the prior art. SUMMARY

[0004] In view of the above technical problems, the present disclosure provides a method for determining the evolution process of diagenetic fluid after carbon dioxide injection into sandstone, which at least partially solves the technical problem that the evolution process of diagenetic fluid after carbon dioxide injection into sandstone cannot be comprehensively analyzed in the prior art.

[0005] Based on this, the present disclosure provides a method for determining the evolution process of diagenetic fluid after carbon dioxide injection into sandstone, which comprises: obtaining the microscopic characteristics of davyne sandstone, determining the diagenetic paragenetic sequence after CO2 injection into davyne sandstone according to the microscopic characteristics; determining the fluid inclusion characteristics of the study area in the davyne sandstone, determining the injection time and injection period of the fluid according to the fluid inclusion characteristics; analyzing the properties of the diagenetic fluid corresponding to the injection of CO2 and oil and gas before and after the injection of davyne sandstone according to the diagenetic paragenetic sequence and the injection time and injection period of the fluid, obtaining the paleofluid characteristics I; obtaining the present formation water characteristics, determining the present fluid characteristics of the davyne sandstone according to the present formation water characteristics; determining the paleofluid characteristics II of the davyne sandstone according to the carbon and oxygen isotope composition of the davyne sandstone; determining the evolution process of the diagenetic fluid after CO2 injection into the davyne sandstone according to the present fluid characteristics, the paleofluid characteristics I and the paleofluid characteristics II.

[0006] According to an embodiment of the present disclosure, the microscopic characteristics of the davyne sandstone are obtained, and the diagenetic paragenetic sequence after CO2 injection into the davyne sandstone is determined according to the microscopic characteristics, specifically including: obtaining the microscopic characteristics by adopting an alizarin red S staining method or a thin section microscopic observation method or a cathodoluminescence analysis method or a scanning electron microscope observation method; determining the formation sequence of different types of minerals according to the microscopic characteristics to obtain the diagenetic paragenetic sequence; wherein the diagenetic paragenetic sequence includes: autogenous minerals formed along the edges of the detrital particles are early formed; late-formed autogenous minerals are filled in the remaining pores after the growth of the early-formed autogenous minerals; the growth form of the late-formed autogenous minerals is constrained by the form of the early-formed autogenous minerals and the remaining pores; the late-formed autogenous minerals can replace the early-formed autogenous minerals; and the late-formed autogenous minerals can continue to grow along the edges of the early-formed autogenous minerals.

[0007] According to an embodiment of the present disclosure, the fluid inclusion characteristics of the research area in the davyne sandstone are determined by adopting a thin section microscopic observation method or a fluorescence observation method or a fluid inclusion microscopic temperature measurement method or a laser Raman spectroscopy method.

[0008] According to an embodiment of the present disclosure, the fluid inclusion characteristics of the research area in the davyne sandstone are determined by adopting a fluid inclusion microscopic temperature measurement method, specifically including: gradually increasing the temperature after rapidly cooling the fluid inclusions to determine the homogenization temperature when the fluid inclusions are captured, wherein the homogenization temperature is the temperature corresponding to the re-homogenization of the fluid in the fluid inclusions; calculating the salinity value of the fluid inclusion equivalent NaCl system according to the homogenization temperature as the fluid inclusion characteristics, and the calculation formula of the salinity value W is:

[0009]

[0010] wherein T m is the homogenization temperature.

[0011] According to an embodiment of the present disclosure, the filling time and filling period of the fluid are determined according to the fluid inclusion characteristics, specifically including: simulating the burial history and thermal evolution history of the research area according to the denudation thickness, paleo-heat flow value and geothermal gradient data of the research area; projecting the determined homogenization temperature of each well section to the burial history and thermal evolution history corresponding to each well section to determine the filling time and filling period of the fluid.

[0012] According to an embodiment of the present disclosure, the present formation water characteristics are obtained, specifically including: sampling to obtain a present formation water sample, and measuring the pH value and ion composition of the present formation water sample; judging the present formation water characteristics according to the Sulin formation water type division scheme based on the pH value and ion composition, comparing the present formation water characteristics with the present formation water characteristics of ordinary sandstone or typical davyne-containing sandstone in a region, and comprehensively analyzing the geochemical composition of the present formation water of the davyne-containing sandstone in the research area as the final present formation water characteristics.

[0013] According to embodiments of this disclosure, the current formation water characteristics are determined based on the Sulin formation water type classification scheme, specifically including: determining the characteristics of current formation water based on the Na+ water type in current formation water samples. + -Cl - ) / SO4 2- 、(Cl - -Na + ) / Mg 2+ The water type is determined by its content; in (Na) + -Cl - ) / SO4 2- When the value is greater than 1, the aqueous form is sodium bicarbonate; when (Cl... - -Na + ) / Mg 2+ When the value is greater than 1, the aqueous form is calcium chloride form; in (Na + -Cl - ) / SO4 2- When the value is less than 1, the aqueous form is the sodium sulfate form; in (Cl... - -Na + ) / Mg 2+ When the value is less than 1, the water form is magnesium chloride form.

[0014] According to embodiments of this disclosure, the paleofluid characteristic II of the galvanite sandstone is determined based on its carbon and oxygen isotopic composition. Specifically, this includes calculating the δ¹⁴ δ¹⁴ ​​of CO₂ in equilibrium with the formation of the galvanite using the calcite-CO₂ fractionation equation. 13 C CO2 Values, and their correlation with the δ values ​​of CO2 from different origins. 13 C CO2 The values ​​were compared to determine the carbon source; the δa of the aqueous medium during the formation of galvanic acid minerals was calculated based on the fractionation equation of galvanic acid-H2O. 18 O value, and its correlation with δ of water of different origins. 18 By comparing the O values, the source of oxygen can be determined; the paleofluid temperature can be calculated based on the carbon and oxygen isotope composition of the sodium galena sandstone; and paleofluid characteristic II can be determined based on the carbon source, oxygen source, and paleofluid temperature.

[0015] According to embodiments of this disclosure, the paleofluid temperature is calculated based on the carbon and oxygen isotope composition of galena sandstone, specifically including: determining the carbon and oxygen isotope composition of galena. Value distribution range and Value distribution range; obtain the fractionation coefficient of sodium calcite-CO2. Fractionation coefficient at equilibrium of CO2 and H2O According to δ 18 O 片钠铝石 Value distribution range Value distribution range, fractionation coefficient of sodium calcite-CO2 Fractionation coefficient at equilibrium of CO2 and H2O Calculate the CO2 content of sodium aluminum oxide. Value and CO2 and H2O equilibrium Value; based on sodium aluminum oxide - CO2 Value at equilibrium with CO2 and H2O The difference between the values ​​is used to calculate the paleofluid temperature.

[0016] According to embodiments of this disclosure, based on

[0017]

[0018] Calculate the sodium aluminum oxide-CO2 content. Value and CO2 and H2O equilibrium value.

[0019] The method for determining the evolution process of diagenetic fluids after carbon dioxide injection into sandstone, as provided in the embodiments of this disclosure, has at least the following beneficial effects:

[0020] Since fluid inclusions are the only original samples of paleogeological fluid activity, this method, based on the characteristics of fluid inclusions in the sodalite sandstone of the study area, analyzes the charging time and periods, combined with the diagenetic co-occurrence sequence determined by microscopic features. This allows for a true reflection of the fluid chemical properties during diagenesis and mineralization, and thus an accurate and comprehensive assessment of the fluid evolution characteristics during CO2 charging. Furthermore, by determining the paleofluid characteristics of the sodalite sandstone based on its carbon and oxygen isotope composition, the method fully demonstrates the fluid evolution characteristics during CO2 injection. Combined with current fluid characteristics, this method comprehensively determines the diagenetic fluid evolution process after CO2 injection into the sandstone. Overall, this method combines multiple perspectives to determine the diagenetic fluid evolution process after CO2 injection into the sandstone, resulting in a more comprehensive and effective determination. Attached Figure Description

[0021] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0022] Figure 1 The flowchart illustrates a method for determining the evolution of diagenetic fluids after carbon dioxide injection into sandstone, as provided in an embodiment of this disclosure.

[0023] Figure 2 A flowchart illustrating the paleofluid temperature calculation method provided according to an embodiment of this disclosure is shown schematically.

[0024] Figure 3 The schematic diagram illustrates the carbon and oxygen isotope characteristics of diatomite in the study area and other areas provided according to embodiments of this disclosure.

[0025] Figure 4 A diagram showing a model of evolution of diagenetic fluid of a sandstone containing jeromite in a study area is schematically shown. DETAILED DESCRIPTION

[0026] For the purposes of the present disclosure, the technical solutions and advantages are more clearly apparent, the following will be combined with specific embodiments, and referring to the drawings, the present disclosure is further described in detail. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without making creative labor are within the scope of protection of the present disclosure.

[0027] The terms used herein are merely used to describe specific embodiments, and are not intended to limit the present disclosure. The terms "include", "contain" and the like used herein indicate the existence of the described features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0028] In the present disclosure, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting", "fixing" and the like should be understood broadly, for example, can be fixed connection, or detachable connection, or integral; can be mechanical connection, or electrical connection or can communicate with each other; can be direct connection, or indirect connection through intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present disclosure can be understood according to the specific circumstances.

[0029] In the description of the present disclosure, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "length", "circumferential", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present disclosure and simplifying the description, and does not indicate or imply that the subsystems or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present disclosure.

[0030] Throughout the drawings, the same elements are denoted by the same or similar reference numerals. When it may cause confusion in understanding the present disclosure, the conventional structure or configuration will be omitted. And the shape, size, positional relationship of each component in the drawing does not reflect the true size, proportion and actual positional relationship. In addition, in the claims, any reference symbol located between parentheses should not be constructed as a limitation on the claims.

[0031] Similarly, to simplify the present disclosure and help understand one or more of the various disclosed aspects, in the above description of exemplary embodiments of the present disclosure, various features of the present disclosure are sometimes grouped together in a single embodiment, figure, or description thereof. Reference to a term "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that a particular feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. Illustrative descriptions of such terms in the specification should not be interpreted to mean that all embodiments or examples have to include the particular feature, structure, material or characteristic. Moreover, descriptions of a particular feature, structure, material or characteristic in relation to one or more embodiments or examples should not be interpreted to mean that each and every embodiment or example has to include the particular feature, structure, material or characteristic.

[0032] Further, the terms "first", "second", etc. are used only for descriptive purposes and do not necessarily connote an absolute importance or implicitly indicate the number of technical features indicated. Thus, a feature defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present disclosure, the meaning of "a plurality" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0033] Figure 1 A flowchart of a method for determining a diagenetic fluid evolution process after carbon dioxide injection into sandstone provided by an embodiment of the present disclosure is schematically shown.

[0034] As shown in Figure 1 The method for determining a diagenetic fluid evolution process after carbon dioxide injection into sandstone may, for example, include operations S101-S106.

[0035] In operation S101, the microscopic features of a dawsonite sandstone are acquired, and the diagenetic paragenetic sequence after CO2 injection into the dawsonite sandstone is determined according to the microscopic features.

[0036] In an embodiment of the present disclosure, first, the microscopic features can be acquired by using an alizarin red S staining method or a thin section microscopic observation method or a cathodoluminescence analysis method or a scanning electron microscope observation method. Then, the order of formation of different types of minerals is determined according to the microscopic features, and a diagenetic paragenetic sequence is obtained.

[0037] The determined diagenetic paragenetic sequence includes: autogenous minerals formed along the edges of detrital particles are early in time; late-formed autogenous minerals fill the remaining pores after the growth of early-formed autogenous minerals; the growth form of late-formed autogenous minerals is constrained by the form of early-formed autogenous minerals and the remaining pores; late-formed autogenous minerals can replace early-formed autogenous minerals; and late-formed autogenous minerals can continue to grow along the edges of early-formed autogenous minerals.

[0038] At operation S102, the fluid inclusion characteristics of the research area in the davyne sandstone are determined, and the fluid charging time and charging period are determined according to the fluid inclusion characteristics.

[0039] In the embodiments of the present disclosure, the fluid inclusion characteristics of the research area in the davyne sandstone can be determined by using thin section microscopic observation or fluorescence observation method or fluid inclusion micro-temperature measurement method or laser Raman spectroscopy, so as to further determine the fluid charging period and charging time.

[0040] The fluid inclusion characteristics of the research area in the davyne sandstone determined by using the fluid inclusion micro-temperature measurement method can specifically include: the fluid inclusions are rapidly cooled and then gradually heated, the homogenization temperature when the fluid inclusions are captured is determined, the homogenization temperature is the temperature corresponding to the fact that the fluid in the fluid inclusion is re-homogenized when the fluid inclusion fluid is heated to be captured, that is, the minimum temperature when the fluid inclusion is captured, that is, the temperature when the last piece of ice crystal disappears after the fluid inclusion is rapidly cooled and then slowly reheated. The salinity value of the fluid inclusion equivalent NaCl system is calculated according to the homogenization temperature, as the fluid inclusion characteristics.

[0041] The calculation formula of the salinity value W is:

[0042]

[0043] Wherein, T m is the homogenization temperature, and the unit of the salinity value is wt.%.

[0044] In the embodiments of the present disclosure, the fluid charging time and charging period are determined according to the fluid inclusion characteristics, specifically including: the burial history and thermal evolution history of the research area are simulated according to the denudation thickness, paleo-heat flow value and geothermal gradient data of the research area; the homogenization temperature of each well section determined is projected to the burial history and thermal evolution history corresponding to each well section, so as to determine the fluid charging time and charging period. The burial history and thermal evolution history of the research area can be simulated by using the PetroMod software.

[0045] At operation S103, according to the diagenetic paragenetic sequence and the fluid charging time and charging period, the properties of the diagenetic fluid corresponding to the injection of CO2 and oil and gas before and after the injection into the davyne sandstone are analyzed, to obtain the paleo-fluid characteristics I.

[0046] In the embodiments of the present disclosure, based on the fluid inclusion characteristics of the research area in the davyne sandstone, by analyzing the charging time and charging period, the diagenetic paragenetic sequence analysis determined by combining the microscopic features can truly reflect the fluid chemical properties at the diagenetic and ore-forming time.

[0047] At operation S104, the present-day formation water characteristics are obtained, and the present-day fluid characteristics of the davyne sandstone are determined according to the present-day formation water characteristics.

[0048] In the embodiments of the present disclosure, the obtaining of the present formation water characteristics specifically comprises: sampling to obtain a present formation water sample, and determining the pH value and ion composition of the present formation water sample. Based on the pH value and ion composition, the present formation water characteristics are determined according to the Sulin formation water type classification scheme, and the present formation water characteristics are compared with the present formation water characteristics of common sandstone or typical region sandstone containing jerarasite, and the geochemical composition of the present formation water of the sandstone containing jerarasite in the research region is comprehensively analyzed to serve as the final present formation water characteristics.

[0049] In the embodiments of the present disclosure, the determining of the present formation water characteristics according to the Sulin formation water type classification scheme specifically comprises: determining the water type according to the content of Na + / Cl - , (Na + -Cl - ) / SO4 2- , (Cl - -Na + ) / Mg 2+ and SO4 2- / Cl - in the present formation water sample. In the case that (Na + -Cl - ) / SO4 2- is greater than 1, the water type is sodium bicarbonate type. In the case that (Cl - -Na + ) / Mg 2+ is greater than 1, the water type is calcium chloride type. In the case that (Na + -Cl - ) / SO4 2- is less than 1, the water type is sodium sulfate type. In the case that (Cl - -Na + ) / Mg 2+ is less than 1, the water type is magnesium chloride type.

[0050] In operation S105, the paleofluid characteristics II of the jerarasite sandstone are determined according to the carbon and oxygen isotope composition of the jerarasite sandstone.

[0051] In the embodiments of the present disclosure, the process of determining the paleofluid characteristics II can be: calculating the δ 13 C CO2 value of CO2 in equilibrium with the jerarasite when the jerarasite is formed according to the calcite-CO2 fractionation equation, and comparing the δ 13 C CO2 value with the δ 13 C CO2 values of different genetic CO2 to determine the carbon source. The δ 18 O value of the water medium when the jerarasite mineral is formed is calculated according to the jerarasite-H2O fractionation equation, and the δ 18O values are compared to determine the oxygen source. The paleofluid temperature is calculated according to the carbon and oxygen isotope compositions of the dawsonite sandstone. The paleofluid characteristics II are determined according to the carbon source, the oxygen source and the paleofluid temperature.

[0052] The paleofluid temperature is calculated according to the carbon and oxygen isotope compositions of the dawsonite sandstone. The paleofluid characteristics II are determined according to the carbon source, the oxygen source and the paleofluid temperature. The δ value distribution range and the δ value distribution range are determined. The fractionation coefficient of dawsonite-CO2 and the fractionation coefficient of CO2 and H2O in equilibrium are obtained. 18 O 片钠铝石 values, the δ value distribution range, the fractionation coefficient of dawsonite-CO2 and the fractionation coefficient of CO2 and H2O in equilibrium are used to calculate the δ value of dawsonite-CO2 and the δ value of CO2 and H2O in equilibrium. The paleofluid temperature is calculated according to the difference between the δ value of dawsonite-CO2 and the δ value of CO2 and H2O in equilibrium.

[0053] Further, the δ

[0054]

[0055] The δ value of dawsonite-CO2 and the δ value of CO2 and H2O in equilibrium are calculated.

[0056] The paleofluid temperature is calculated according to T P = 16.9-4.2δ+0.13δ 2 and T P = 16.9-4.38δ+0.10δ 2 , using the oxygen isotope composition of the dawsonite mineral to estimate the paleofluid temperature when the dawsonite mineral is formed, wherein δ represents the difference between the δ 18 O value of the dawsonite mineral releasing CO2 and the δ 18 O value of CO2 in equilibrium. The paleofluid temperature distribution range when the dawsonite mineral is precipitated is finally calculated.

[0057] In operation S106, the diagenetic fluid evolution process after CO2 is injected into the dawsonite sandstone is determined according to the present fluid characteristics, the paleofluid characteristics I and the paleofluid characteristics II.

[0058] In order to further clearly describe Figure 1 ​The method for determining the evolution of post-injection sandstone diagenetic fluid of CO2 is shown below. The specific process is as follows:

[0059] The detected davyne-containing sandstone is taken as a natural analogue, and sampling is conducted for research:

[0060] According to the microscopic characteristics, the diagenetic paragenetic sequence of the davyne-containing sandstone is determined as follows: quartz secondary enlargement, authigenic kaolinite, first-stage calcite, davyne, second-stage calcite, ferric calcite, dolomite, and ferric dolomite. The authigenic mineral assemblage after CO2 injection is: davyne + calcite + ferric calcite + dolomite + ferric dolomite.

[0061] According to the characteristics of fluid inclusions, the fluid injection period and injection time are determined:

[0062] The oil and gas injection period in the Fangwang area is from the late deposition of the Minghuazhen Formation to the present (2.6-0 Ma), and the two fluid injection periods in the Shangdian area are the deposition of the Guantao Formation (9.81-5.56 Ma) and the deposition of the Minghuazhen Formation to the present (3.38-0 Ma). The main evidence is as follows: The brine inclusion homogenization temperature of the Bin 16 well is 90-100℃, and the corresponding oil and gas injection period is 2.57-0.25 Ma, i.e., from the late deposition of the Minghuazhen Formation to the end of the Quaternary. The brine inclusion homogenization temperature of the Bin 52 well is 90-110℃, and the corresponding fluid injection period is 2.69-0 Ma, i.e., from the late deposition of the Minghuazhen Formation to the present. The homogenization temperatures of the two-stage brine inclusions of the Shanggu 1 well are 95-105℃ and 120-135℃, respectively, and the corresponding fluid injection periods are 9.81-5.56 Ma and 3.38-0 Ma, respectively, i.e., the deposition of the Guantao Formation and the deposition of the Minghuazhen Formation to the present.

[0063] According to the characteristics of present formation water, the present fluid characteristics of the sandstone are determined:

[0064] The present formation water characteristics are determined, as shown in Table 1. The present formation water of the sandstone containing jerarasite in Shangdian-Pingfangwang area, the present formation water of the sandstone containing jerarasite in typical area, and the present formation water of the ordinary sandstone are studied. The present formation water of the sandstone containing jerarasite in Shangdian-Pingfangwang area is of NaHCO3 type, which is the same as the present formation water of the sandstone containing jerarasite in typical area. The present formation water of the ordinary sandstone is mainly of CaCl2 type, and contains a small amount of NaHCO3 type, Na2SO4 type and MgCl2 type. The pH value of the present formation water of the sandstone containing jerarasite in Shangdian-Pingfangwang area is 6.1-9.3, and the average is 7.2, which shows weak alkalinity. The pH value of the present formation water of the ordinary sandstone is about 6.4, which shows weak acidity. The present formation water of the sandstone containing jerarasite in typical area shows weak alkalinity, and the present formation water of the sandstone containing jerarasite in Wuerxun sag shows the strongest alkalinity (pH value is 8.4). The alkalinity characteristics of the present formation water of the sandstone containing jerarasite are consistent with the alkaline fluid environment for forming jerarasite.

[0065] Table 1 Formation water characteristics of the sandstone containing jerarasite in the study area, the ordinary sandstone and the sandstone containing jerarasite in typical area

[0066]

[0067] Compared with the sandstone containing jerarasite in typical area, the present formation water of the sandstone containing jerarasite in Shangdian-Pingfangwang area shows similar Ca 2+ and Mg 2+ geological characteristics, but also shows some differences. Although the present formation water of the sandstone containing jerarasite in Shangdian-Pingfangwang area also has a high value of HCO 3- content, the content is lower than the Cl - content, while the present formation water of the sandstone containing jerarasite in typical area not only shows a high value of HCO 3- content, but also the content is significantly higher than the Cl - content. The difference in Cl - content between the present formation water of the sandstone containing jerarasite in Shangdian-Pingfangwang area and the present formation water of the sandstone containing jerarasite in typical area is determined by the geochemical characteristics of the regional formation water. In the area of the sandstone containing jerarasite in Shangdian-Pingfangwang area, the water type of the formation water is changed from CaCl2 type to NaHCO3 type, and the acidity is changed from weak acid to weak alkalinity due to CO2 charging. In the area of the sandstone containing jerarasite in typical area, the formation water is weakly alkaline before CO2 charging, and the water type is NaHCO3 type. CO2 charging causes the increase of HCO 3- content, but does not cause the change of acidity and water type.

[0068] Figure 2 A flowchart of a method for calculating paleofluid temperature is schematically shown.

[0069] As Figure 2As shown, the carbon and oxygen isotope composition was used to calculate the paleofluid temperature and determine the paleofluid characteristics that formed the diatomite:

[0070] δ-type of sodium aluminum minerals in Shangdian-Pingfangwang area 13 The C value ranges from -2.49‰ to +3.50‰, with an average of -1.17‰. δ 18 O PDB The values ​​ranged from -14.73‰ to -10.82‰, with an average of -12.63‰ (Table 2). Based on δ... 18 O SMOW With δ 18 O PDB The conversion formula is shown in equation: δ 18 O SMOW =1.03091δ 18 O PDB +30.91, calculate δ 18 O SMOW The values ​​range from 16.64‰ to 19.76‰, with an average value of 17.55‰.

[0071] Table 2. Carbon and oxygen isotopic composition characteristics of argillace in the study area

[0072]

[0073] Where, δ 13 C DAW The δ of galvanite 13 C value, δ 18 O PDB The δ of diatomite 18 The PDB value of O, δ 18 O SMOW The δ of diatomite 18 The SMOW value of O, The δ value of CO2 in equilibrium with the formation of galvanite. 13 C value, The δ value of the aqueous medium during the formation of diatomite indicates the molecular weight of the diatomite. 18 O value; Z = 2.048 × [δ( 13 C PDB )+50]+0.498×[δ( 18 O PDB )+50].

[0074] The δa of the formation fluid in equilibrium with calcite was calculated based on O'Neil's (1969) CaCO3-H2O equilibrium fractionation equation. 18 O value:

[0075]

[0076] The aqueous medium during the formation of sodium aluminum oxide in the Shangdian-Pingfangwang area The values ​​range from -3.76‰ to +1.84‰, with an average of -1.16‰. (Atmospheric freshwater) Values ​​less than -2‰ indicate the presence of sealed underground brine and geothermal fluids. The values ​​are located in the ranges of -2‰ to +6‰ and +6‰ to +10‰, respectively (Li and Li, 2016). δa of the aqueous medium during the formation of diaspore in the Shangdian-Pingfangwang area. 18 The O value basically matches the oxygen isotope composition characteristics of sealed underground brine, indicating that the water medium during its formation was sealed underground brine.

[0077] To further analyze the fluid properties, the paleofluid temperature at the time of formation was estimated using the oxygen isotopic composition of the sorbate mineral, based on the formula proposed by Fonts et al. (1993). See the equation: TP = 16.9 - 4.2δ + 0.13δ 2 TP = 16.9 - 4.38δ + 0.10δ 2 .

[0078] In the formula, δ represents the δ value of CO2 released by diatomaceous earth. 18 O value and δ of CO2 in water balance 18 The difference in O values ​​( ),

[0079] and The calculation formula is as follows:

[0080]

[0081] In the formula, The fractionation coefficient of sodium aluminum oxide-CO2 at 25℃ is represented by δ. 18 O 片钠铝石 The δ of the soda ash mineral 18 O SMOW value, This represents the fractionation coefficient at which H2O and CO2 are in equilibrium at 25℃. δ represents the formation fluid 18 O SMOW value.

[0082] Fractionation coefficient of calcite for CO2 release via phosphoric acid at 25°C The fractionation coefficient of 1.01025 for sodium aluminate-CO2 was also adopted in this study. The fractionation coefficient at CO2 and H2O equilibrium was... It is 1.04120, while the formation fluid is The value is based on the aqueous medium during the formation of diatomite calculated above. The average value is -1.16‰. The paleofluid temperature during the precipitation of sialic acid in the Shangdian-Pingfangwang area ranges from 69.30 to 96.82℃, with an average paleofluid temperature of 81.72℃, which is basically consistent with the paleotemperature range (78.64 to 111.07℃) of the sialic acid sandstone strata in the study area.

[0083] Figure 3 The schematic diagram illustrates the carbon and oxygen isotope characteristics of diatomite in the study area and other areas provided according to embodiments of this disclosure.

[0084] like Figure 3 As shown, compared with the formation temperature range of diatomite in various regions, the oxygen isotope temperature is mostly lower than the fluid inclusion temperature. This difference may be due to the diatomite-water distillation equation being equated with the calcite-water distillation equation.

[0085] Based on the CO2 charging sequence and the formation time of different types of minerals, the diagenetic symbiotic sequence is determined. Based on the formation and dissolution processes of different types of minerals, authigenic mineral assemblages are classified. Combined with the characteristics of fluid inclusions, the properties of diagenetic fluids before and after CO2 and hydrocarbon charging are comprehensively analyzed.

[0086] Figure 4 The diagram illustrates the diagenetic fluid evolution model of the sodium aluminum shale sandstone in the study area provided in the embodiments of this disclosure.

[0087] like Figure 4 As shown, a diagenetic fluid evolution model diagram after CO2 injection into sandstone is obtained by comparing the current fluid characteristics and ancient fluid characteristics of sandstone. The diagenetic fluid evolution process after CO2 injection into sandstone is deduced based on the model diagram.

[0088] Based on the tectonic evolution characteristics of the Shangdian-Pingfangwang area and the fluid environment during the precipitation of authigenic minerals, the diagenetic symbiotic sequence is divided into three sets of authigenic mineral assemblages: secondary enlarged quartz + kaolinite, first-stage calcite + galena + second-stage calcite, and ferrocalcite + dolomite + ferrodolithite. These represent the stratigraphic fluid characteristics of different stages.

[0089] The first authigenic mineral assemblage is a secondary enlarged quartz + kaolinite combination, representing an acidic fluid environment in the early stages of CO2 charging. The Dongying Movement led to uplift and erosion in the Shangdian-Pingfangwang area, causing a decrease in the temperature of the Sha-4 Member strata. Magmatic activity occurred in the Pingfangwang area; during intrusion, the magma released large amounts of CO2 due to the decrease in temperature and pressure. This CO2 charged along the Pingfangwang fault into the Pingfangwang Uplift and accumulated in the upper part of the Sha-4 Member. In the gas reservoir, CO2 dissolved in formation water to form unstable carbonic acid, which decomposed into HCO3. - and CO3 2- and releases a large amount of H +, the formation fluid properties turn to be acidic. A large amount of unstable minerals are dissolved, and a large amount of secondary pores are generated. The dissolution of carbonate minerals releases a large amount of Ca 2+ and Mg 2+ , and the dissolution of feldspar releases a large amount of Na + and Al 3+ . Feldspar [(Na, K) AlSi3O8] or other aluminum-rich minerals reacts with CO2 fluid in an acidic fluid environment to form kaolinite [Al4(Si4O 10 )(OH)8] precipitation, and as feldspar continues to dissolve, SiO2 is supersaturated and precipitates from the geological fluid, generally in the form of quartz secondary enlargement (SiO2) (Peltonen et al., 2009; Hyodo et al., 2014), and the chemical reaction equation is:

[0090]

[0091] The second set of authigenic mineral assemblage is the first calcite + davyne + second calcite assemblage, which represents the late stage of CO2 filling in an alkaline fluid environment. The dissolution of unstable minerals consumes a large amount of H + in the formation fluid, the formation fluid salinity increases, and the fluid properties gradually change from acidic to alkaline. Since the main reservoir lithology of CO2 gas reservoir is the upper reef limestone of the fourth member of Shahejie Formation, CO2 filling will lead to a large amount of dissolution of carbonate minerals, and the Ca 2+ content in the formation fluid increases. When the fluid properties change to alkaline, these Ca 2+ will first precipitate in the form of calcite (first calcite). After magmatic activity stops, magma cools and crystallizes, and continuously degasses CO2, so CO2 filling is a continuous process. With the continuous filling of CO2, the partial pressure of CO2 in the gas reservoir increases, and when the formation fluid meets the high CO2 partial pressure, high Na + concentration and high Al 3+ concentration of alkaline fluid environment required for davyne precipitation, Na + and Al 3+ in the formation fluid will combine with HCO3 - to form davyne [NaAl(OH)2CO3]:

[0092]

[0093] With the continuous precipitation of davyne, Al 3+ and HCO3 -The CO2 generated by magma degassing was consumed in large quantities, and as time evolved, the CO2 produced gradually decreased, resulting in a decrease in the partial pressure of CO2 in the strata. This made it impossible to meet the fluid conditions required for the precipitation of calcite, and calcite was precipitated again in the study area (second-stage calcite).

[0094] The third authigenic mineral assemblage is a combination of ferrocalcite, dolomite, and ferrodolithite, representing a weakly alkaline fluid environment following hydrocarbon charging. The presence of numerous primary hydrocarbon inclusions in the carbonate minerals indicates a high hydrocarbon content in the formation fluids during this period. Hydrocarbon charging brought abundant organic acids and hydrocarbons; these organic acids neutralized the alkaline fluid environment, lowering the pH, while some Fe in the fluid was also neutralized. 3+ Under the reducing action of hydrocarbons, metal ions are activated (Wigley et al., 2012), transforming into Fe. 2+ In the study area, ferrocalcite begins to precipitate, and some calcite (CaCO3) undergoes ion substitution to transform into ferrocalcite (CaCO3). 1-n Fe n CO3). As ferrocalcite continues to precipitate, the Ca in the formation fluids... 2+ and Fe 2+ Large amounts of Mg are consumed. 2+ and Ca 2+ As the ratio increases, dolomite [CaMg(CO3)2] begins to precipitate. With deeper burial and increased formation temperature, the organic matter in the Sha-4 Member source rocks matures and begins to generate hydrocarbons. These hydrocarbons, acting as reducing agents, further reduce the Fe content in the formation fluids. 3+ Reduced to Fe 2+ Iron dolomite [CaMg 1-n Fe n [CO3)2] begins to precipitate, and some dolomite undergoes ferrodolomitization. The chemical reaction equation for the formation of ferrocalcite and ferrodolomitization is as follows:

[0095]

[0096] The current formation water characteristics in the Shangdian-Pingfangwang area indicate that the formation water in ordinary sandstone is weakly acidic, mainly of the CaCl2 type, while the formation water in sodic sandstone is alkaline, mainly of the NaHCO3 type, and Ca... 2+ and Mg 2+ The content is significantly lower than that of ordinary sandstone. Within the distribution area of ​​sodium aluminum phosphate sandstone, abundant carbonate minerals such as calcite, dolomite, ferrocalcite, and ferrodolithite are developed. The precipitation of these carbonate minerals consumes a large amount of Ca from the formation fluids. 2+ and Mg 2+ This led to the formation water containing sodium aluminum ore sandstone having Ca2+ in the current formation. 2+ and Mg 2+The content of the significant low value, with ordinary sandstone, significant difference. Therefore, the diagenetic fluid evolution model with the sandstone containing daphnite formation water characteristics have good consistency.

[0097] In summary, the formation fluid evolution of the study area can be divided into five stages: the first stage is the alkaline fluid environment of the original depositional water; the second stage is the weakly alkaline fluid environment of organic acid generation; the third stage is the early CO2 filling of the acidic fluid environment, which stage a large number of feldspar and carbonate minerals are dissolved, forming quartz secondary enlargement and authigenic kaolinite; the fourth stage is the late CO2 filling of the alkaline fluid environment, which stage the first stage of calcite is precipitated in the early stage, the daphnite is precipitated in the middle stage due to the increase of CO2 partial pressure, and the second stage of calcite is precipitated in the late stage due to the decrease of CO2 partial pressure; the fifth stage is the weakly alkaline fluid environment of the oil and gas filling period, which stage the pH of the formation fluid is reduced due to the large amount of organic acid and hydrocarbon brought by the oil and gas filling in the early stage, and a part of Fe 3+ is reduced to Fe 2+ by hydrocarbons, and iron calcite is precipitated, the dolomite is precipitated in the middle stage due to the increase of Mg 2+ and Ca 2+ ratio, and the iron dolomite is precipitated in the late stage due to the hydrocarbon generation of the hydrocarbon source rock of the fourth member of Shahejie Formation. 2+ 3+ 2+

[0098] The above-described specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above-described specific embodiments are merely specific embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.​​​

Claims

1. A method for determining the evolution process of diagenetic fluids after carbon dioxide injection into sandstone, characterized in that, include: Obtaining microscopic features of sodalite sandstone and determining the diagenetic sequence following CO2 injection based on these features includes: acquiring the microscopic features using Alizarin Red S staining, thin section microscopy, cathodoluminescence analysis, or scanning electron microscopy; determining the chronological order of formation of different types of minerals based on these microscopic features to obtain the diagenetic sequence; wherein the diagenetic sequence includes: authigenic minerals growing along the edges of clastic grains forming earlier; later-formed authigenic minerals filling the remaining pores after the growth of earlier-formed authigenic minerals; the growth morphology of later-formed authigenic minerals being constrained by the morphology of earlier-formed authigenic minerals and the remaining pores; later-formed authigenic minerals replacing earlier-formed authigenic minerals; and later-formed authigenic minerals being able to continue growing along the edges of earlier-formed authigenic minerals. The fluid inclusion characteristics in the study area of ​​the soda ash sandstone were determined using thin-section microscopy, fluorescence observation, inclusion microthermometry, or laser Raman spectroscopy. The fluid influencing time and influencing periods were determined based on these characteristics. The fluid inclusion microthermometry method for determining the fluid inclusion characteristics in the study area of ​​the soda ash sandstone included: rapidly cooling the inclusions and then gradually heating them to determine the homogenization temperature at which the inclusions were captured, where the homogenization temperature is the temperature at which the fluid within the inclusions regained homogenization; and calculating the salinity value of the equivalent NaCl system of the fluid inclusions based on the homogenization temperature, which was used as a fluid inclusion characteristic. The formula for calculating the salinity value W is as follows: Among them, T m To achieve a uniform temperature; Based on the diagenetic co-existence sequence and the charging time and charging period of the fluids, the properties of the diagenetic fluids before and after CO2 and oil and gas injection into the soda ash sandstone were analyzed to obtain paleofluid characteristic I, which reflects the fluid chemical properties during diagenesis and mineralization. The process involves obtaining current formation water characteristics and determining the current fluid characteristics of the argillaceous sandstone based on these characteristics. Specifically, obtaining current formation water characteristics includes: sampling current formation water samples and determining their pH value and ionic composition; based on the pH value and ionic composition, determining the current formation water characteristics according to the Sulin formation water type classification scheme; comparing the current formation water characteristics with those of ordinary sandstone or typical regional argillaceous sandstone; and comprehensively analyzing the geochemical composition of the current formation water in the argillaceous sandstone of the study area as the final current formation water characteristics. The paleofluid characteristics II of the soda ash sandstone were determined based on its carbon and oxygen isotopic composition, including: calculating the δ¹⁴ of CO₂ in equilibrium with the soda ash sandstone during its formation based on the calcite-CO₂ fractionation equation. 13 C CO2 Values, and their correlation with the δ values ​​of CO2 from different origins. 13 C CO2 The values ​​were compared to determine the carbon source; the δa of the aqueous medium during the formation of the soda ash mineral was calculated based on the soda ash-H2O fractionation equation. 18 O value, and its correlation with δ of water of different origins. 18 The oxygen source is determined by comparing the O values; the paleofluid temperature is calculated based on the carbon and oxygen isotope composition of the sodium aluminum sandstone; and the paleofluid characteristic II is determined based on the carbon source, the oxygen source, and the paleofluid temperature. The evolution of diagenetic fluids after CO2 injection into the soda ash sandstone was determined based on the present fluid characteristics, paleofluid characteristics I, and paleofluid characteristics II.

2. The method for determining the evolution process of diagenetic fluids after carbon dioxide injection into sandstone according to claim 1, characterized in that, The step of determining the fluid filling time and filling stages based on the characteristics of the fluid inclusions specifically includes: The burial history and thermal evolution history of the study area were simulated based on the erosion thickness, paleothermal flow value and geothermal gradient data of the study area. The uniform temperature of each well section is projected onto the corresponding burial history and thermal evolution history of each well section to determine the fluid injection time and injection period.

3. The method for determining the evolution process of diagenetic fluids after carbon dioxide injection into sandstone according to claim 1, characterized in that, The determination of current formation water characteristics based on the Sulin formation water type classification scheme specifically includes: Through current formation water samples (Na) + -Cl - ) / SO4 2- 、(Cl - -Na + ) / Mg 2+ To determine the water type, use the content of the substance. in (Na + -Cl - ) / SO4 2- When the value is greater than 1, the aqueous form is sodium bicarbonate type; In (Cl - -Na + ) / Mg 2+ When the value is greater than 1, the water type is calcium chloride type; in (Na + -Cl - ) / SO4 2- When the value is less than 1, the aqueous form is the sodium sulfate form; In (Cl - -Na + ) / Mg 2+ When the value is less than 1, the water type is magnesium chloride type.

4. The method for determining the evolution process of diagenetic fluids after carbon dioxide injection into sandstone according to claim 1, characterized in that, The calculation of paleofluid temperature based on the carbon and oxygen isotope composition of the sodium aluminum sandstone specifically includes: Determine the sodium aluminum oxide Value distribution range and Value distribution range; Obtain the fractionation coefficient of sodium aluminum oxide-CO2 Fractionation coefficient at equilibrium of CO2 and H2O ; According to the δ 18 O 片钠铝石 Value distribution range, the Value distribution range, fractionation coefficient of the sodium aluminum oxide-CO2 and the fractionation coefficient at equilibrium of CO2 and H2O Calculate the sodium aluminum oxide-CO2 Value and CO2 and H2O equilibrium value; According to the sodium aluminum oxide-CO2 Value at equilibrium with CO2 and H2O The difference between the values ​​is used to calculate the ancient fluid temperature.

5. The method for determining the evolution process of diagenetic fluids after carbon dioxide injection into sandstone according to claim 4, characterized in that, according to Calculate the sodium aluminum oxide-CO2 Value and CO2 and H2O equilibrium value.

Images