阅读说明：本技术 一种恢复深层碳酸盐岩构造-流体压力的方法 (Method for recovering fluid pressure of deep carbonate rock structure ) 是由 刘嘉庆 李忠 宋一帆 梁裳恣 于 2020-12-14 设计创作，主要内容包括：本发明提供了一种恢复深层碳酸盐岩构造-流体压力的方法,该方法包括：首先通过详细的构造分析厘定不同断裂充填脉体形成的相对时间和成岩序列；然后通过测定脉体内胶结物的团簇同位素值(Δ-(47))获得脉体形成时的温度和流体的氧同位素值(δ～(18)O-w)；分析流体包裹体获得流体的盐度和烃类充注；根据流体包裹体盐度建立等容线；将团簇同位素分析的温度和流体包裹体等容线相结合限定脉体形成时的流体绝对压力,从而可以应用到盆地模拟等研究中。本发明主要通过流体包裹体和团簇同位素分析相结合获取流体压力信息,对于研究深层海相碳酸盐岩储层成因机理具有重要指导意义。(The invention provides a method for recovering fluid pressure of a deep carbonate rock structure, which comprises the following steps: firstly, determining the relative time and diagenesis sequence of different fracture filling vein bodies through detailed structural analysis; then measuring the cluster isotope value (delta) of the conglutination substance in the vein body 47 ) Obtaining the temperature at which the pulse is formed and the oxygen isotope value (delta) of the fluid 18 O w ) (ii) a Analyzing the fluid inclusions to obtain the salinity and hydrocarbon charge of the fluid; establishing an isovolumetric line according to the salinity of the fluid inclusion; the temperature of cluster isotope analysis and the isovolumetric line of the fluid inclusion are combined to limit the fluid absolute pressure when the pulse is formed, so that the method can be applied to researches such as basin simulation and the like. The fluid pressure information is obtained mainly by combining the fluid inclusion and cluster isotope analysis, and the method has important guiding significance for researching the formation mechanism of the deep sea phase carbonate reservoir.)

1. A method of restoring fluid pressure to a deep carbonate formation, the method comprising:

step (1): rock and ore observation, namely observing the intersection relation of cracks under a rock core and a polarizing microscope, then observing detailed rock and ore characteristics and the luminescent condition of a cementing material aiming at the cracks under cathode luminescence, establishing a diagenetic sequence of the cracks of different periods, combining with regional structure fracture research, and limiting the main fracture activity time and spatial distribution through three-dimensional seismic data;

step (2): a micro-drill sampling product is used for preliminarily defining the possible stages of multi-stage construction activities on the basis of the background of the regional construction, and a micro-drill sampling instrument is used for drilling powder samples on the thickened sheet aiming at calcite cement filled in different stages in the crack;

and (3): extracting, purifying and collecting cluster isotope sample, firstly dissolving the sample in super-concentration phosphoric acid, and obtaining CO₂After gas purification, freezing the gas into a transfer container for collection;

and (4): performing on-machine test and standard sample correction on the cluster isotope, and purifying the purified CO₂Introducing the gas into a mass spectrometer for on-machine test analysis to obtain the delta of the carbonate₄₇A value;

and (5): processing cluster isotope data, measuring delta of carbonate₄₇After value use of₄₇-converting the T-calibration curve into a temperature value, using the formation temperature of the carbonate and the oxygen isotope delta of the mineral¹⁸O_carbObtaining the oxygen isotope value (delta) of the fluid¹⁸O_w)；

And (6): judging the validity of the cluster isotope data, and judging whether the cluster isotope data of the sample is rearranged or not;

and (7): texture-fluid property analysis, temperature obtained from cluster isotope testing and oxygen isotope value (delta) of fluid¹⁸O_w) Analysis of formation-fluid properties and source;

and (8): observing the lithology and fluorescence characteristics of the fluid inclusion, carrying out lithology observation of the inclusion on the inclusion sheet, including occurrence positions, growth relations and the like of the inclusion, distinguishing a saline inclusion from a hydrocarbon inclusion according to a fluorescence phenomenon issued by a fluorescence microscope, and recording the fluorescence color of the hydrocarbon inclusion in detail;

and (9): testing the salinity of the fluid inclusion and establishing an isovolumetric line, wherein a fluid inclusion salinity analysis instrument can be a cold-hot table, the freezing point temperature of the inclusion in the vein is measured on the cold-hot table, the salinity is calculated and solved by a measured freezing point temperature formula, and the isovolumetric line is determined according to the salinity converted from the freezing point temperature of the fluid inclusion;

step (10): and (3) structure-fluid pressure calculation, acquiring the absolute pressure of the fluid during pulse formation according to an isovolumetric line determined by cluster isotope temperature and fluid inclusion salinity, and analyzing the fluid pressure evolution history of the major structure activity period by combining a region burial history curve, thereby providing a reliable basis for basin simulation and reservoir evaluation.

2. The method as claimed in claim 1, wherein the apparatus used in the cathodoluminescence test in step (1) is RELIOTRON, model number RELION III, operating voltage is between 5-8kV, and current is between 300-400 μ A; in the step (2), the thickness of the thin sheet is 0.1-0.3mm, and the required sample amount is 30 mg.

3. The method according to claim 1, wherein the concentration of the phosphoric acid in the excess concentration in the step (3) is 104%, and the phosphoric acid is dissolved in a water bath at 90 ℃ for about 30 minutes; the sample is reacted more fully by moving the magnet during the reaction, the gas quantity of the exhaust gas is observed by a pressure gauge, the extracted gas is subjected to CO in a vacuum pipeline by five steps of liquid nitrogen at the temperature of-196 ℃, liquid modulated by liquid nitrogen at the temperature of-196 ℃ and alcohol at the temperature of-90 ℃, liquid nitrogen at the temperature of-196 ℃, liquid nitrogen at the temperature of-30 ℃ and liquid nitrogen at the temperature of-196 DEG C₂/H₂O separation, in which the gas is transferred through a PORAPAKTM filter to reduce organic contamination, and pure CO is finally obtained₂A gas.

4. The method according to claim 1, wherein the mass spectrometer in step (4) employs a MAT-253 mass spectrometer; said gas CO₂The standard sample comprises water balance gas prepared in a sealed container at normal temperature of 25 ℃ and CO heated to 1000 DEG C₂Gas (heated gas), the calcite standards being ETH-1, ETH-2, ETH-3, ETH-4.

5. The method according to claim 1, wherein the calibration curve in step (5) is obtained based on theoretical model calculations, and the Δ carbonate is₄₇Conversion of results toThe temperature was determined using formula (1):delta of dolomite¹⁸O_wThe values are according to equation (2):and formula (3):delta of calcite¹⁸O_wThe values are according to equation (4):and formula (5):in the formulae (2) and (4), T is a thermodynamic temperature (K) (K ═ celsius (° c) +273.15), and α is an isotopic fractionation coefficient.

6. The method of claim 1, wherein the determining whether the sample cluster isotope data has been rearranged in step (6) has two indicators: 1. whether the temperature of the sample increases with depth generally indicates that no rearrangement has occurred if the temperature of the sample does not increase with depth; 2. whether the temperature of the sample is correlated with other geological parameters (such as mineral carbon oxygen isotopes, trace elements and the like) or not, and the temperature of the rearranged sample is not correlated with other geological parameters.

7. The method of claim 6, wherein the specific method for determining whether the sample cluster isotope data is rearranged in step (6) is as follows: for calcite, cluster isotopes¹³C-¹⁸The "blocking temperature" of the solid state rearrangement of O bonds is 160 ℃ at<The initial cluster isotope value is retained at 100 ℃, partial rearrangement occurs in 1 percent of the temperature of 100-150 ℃, and rearrangement occurs in 99 percent of the temperature of 160-200 ℃,while the temperature is>Rearrangement occurs completely at 200 ℃; for dolomite, its cluster isotope¹³C-¹⁸The 'sealing temperature' of the O bond solid rearrangement is 300 ℃, and the temperature of the dolomite is>Partial rearrangement may occur at 180 ℃ and temperature>The rearrangement was complete at 300 ℃.

8. The method of claim 1, wherein the temperature and fluid oxygen isotope values (δ) obtained from a cluster isotope test in step (7)¹⁸O_w) Analytical configuration-fluid properties and source determination methods were: t (Delta) under normal seawater conditions₄₇) The distribution range is 0-30 ℃, and the fluid oxygen isotope delta¹⁸O_wThe distribution range is 0 ~ +2.5 ‰ SMOW; surface atmospheric water exposure, typically T (. DELTA.)₄₇)<Fluid oxygen isotope delta at 30 DEG C¹⁸O_wSMOW with a distribution range less than-2 per mill, which is a high water/rock ratio (W/R) open system; the temperature will rise with the increase of the buried depth under the normal buried condition, and the oxygen isotope delta of the buried brine water¹⁸O_wValue of>+ 2.5%, reflecting the recrystallization of the minerals during the deep burying process; in a buried environment, with a low water-rock ratio (W/R) closed system, water-rock interaction causes delta of fluid¹⁸O_wThe value is increased; the temperature of the deep-buried thermal fluid will be abnormally high, 5-10 ℃ above the maximum buried depth of the formation, and therefore the delta of the thermal fluid¹⁸O_wValue in general>+8‰。

9. The method according to any one of claims 1 to 8, wherein in the step (8), the saline inclusion shows no display under fluorescence, the liquid hydrocarbon inclusion has different luminescent colors and intensities due to the difference of organic matter evolution degree, and the change rule of the fluorescence color of the organic matter is as follows: light yellow (light yellow) → tan → brown → dark blue → blue gray → no fluorescence.

10. The method according to claim 9, wherein in step (9), the fluid inclusion salinity analyzer is a cold and hot table (model number THMS600) of Linkam Coo1ing Systems and Axiosko manufactured by Zeiss of GermanyThe microscopic temperature measuring system composed of p40 type polarizing/fluorescent microscope has calibration standard sample of pure water and CO₂The temperature rise rate of the inclusion is 2 ℃/min, and the precision is +/-0.1 ℃; the calculation formula of the salinity is as follows: salinity of 0.00+1.78T_m-0.0442T_m ²+0.000557T_m ³(ii) a Wherein, T_mIs the freezing temperature.

Technical Field

The invention relates to the technical field of petroleum geological exploration and development, in particular to a method for recovering structure-fluid pressure by combining a cluster isotope and a fluid inclusion.

Background

In sedimentary basins, the tectonic-fluid activities are always throughout the diagenetic transformation process including cementation, erosion, recrystallization and dolomite formation, and have important influence on the quality of the reservoir, so that the property of the restraint tectonic-fluid activities is important for reservoir research. However, for deep hydrocarbon reservoirs, the basin formation-fluid activity remodeling and prediction have great challenges due to the fact that the fluid activity of the deep hydrocarbon reservoirs is complicated and changeable due to the fact that the deep hydrocarbon reservoirs are subjected to a plurality of stages of superposition transformation of the burial-formation effects. Deep-ultra deep reservoirs are the key field of national oil and gas exploration, and in recent years, a plurality of sets of marine phase carbonate rock effective reservoirs are found in northwest China of the Tarim basin and Hanwu-Ordovician strata in the Tower in the West China, but the problems of deep structure-fluid activity, deep ancient pressure distribution and the like are rarely known at present.

Pressure is the most direct expression of the subsurface hydrodynamic field. Compared with the shallow layer, the deep layer of the oil-gas-containing basin is in a relatively high-temperature and high-pressure environment and undergoes superposition and evolution in a multi-stage construction process, so that the pressure distribution characteristics and the development scale of the deep layer are greatly different from those of the shallow layer. Overpressure means that the formation pressure is obviously higher than the hydrostatic pressure at the same depth, while overpressure does not mean absolute high pressure, and the magnitude of the absolute value of the formation (fluid) pressure is the key for influencing reservoir development, for example, the existence of overpressure is beneficial to reservoir preservation.

Cluster isotopes refer to naturally occurring isotopologues containing 2 or more heavy isotopes (rare isotopes). Cluster isotopologues are very low in relative abundance, but have very unique physical and chemical properties. Such as carbonate minerals¹³C¹⁸O¹⁶The abundance of O is sensitive to temperature, independent of the whole rock isotope of the mineral and the fluid properties of the mineral during its formation, and can therefore be determined by the presence of ions in the carbonate lattice ion clusters¹³C and¹⁸measuring the degree of mutual bonding of O to obtain temperature information during mineral formation, and using oxygen isotope (delta) of mineral¹⁸O_carb) According to the conventional oxygen isotope thermometer principle, the oxygen isotope (delta) of the mineral growth fluid can be further obtained¹⁸O_w). Carbonate cluster co-locationMeasurement parameter delta of elementary thermometer₄₇Defined as CO formed by acidolysis of carbonates₂The abundance of 47 molecules in a molecule relative to the abundance of that molecule in a random state. T (Delta)₄₇) Is defined by the mass number⁴⁷CO₂Derived Δ₄₇The acquired temperature is evaluated. Based on carbonate radical¹³C-¹⁸Relative abundance of O bonds versus temperature, carbonate cluster isotope (. DELTA.₄₇) The fluid has unique temperature indicating characteristics, is not influenced by the chemical and isotope composition of the fluid when carbonate precipitates, and is a good temperature index in the research of diagenetic fluid.

The traditional technical means mainly obtains temperature information by measuring fluid inclusion captured in minerals and then combines oxygen isotopes (delta) of the minerals¹⁸O_carb) Calculating oxygen isotope (delta) of fluid¹⁸O_w). However, as the stratum reaches deep (buried depth > 4500m) -ultra-deep (buried depth > 6000m), the fluid inclusion is prone to leakage or rebalance, and the measured temperature does not truly reflect the capture temperature, thus resulting in low accuracy of the obtained fluid information.

The paleo-pressure is an important parameter for basin simulation, and an overpressure condition may exist in deep stratum, so that the reservoir distribution prediction is influenced significantly. The current method for obtaining paleo-pressure mainly utilizes the phase state calculation (PVTx) of hydrocarbon inclusion to calculate the formation pressure of paleo-fluid, wherein the temperature value is obtained by fluid inclusion test, and the uniform temperature of fluid inclusion represents the minimum capture temperature, so the software calculates the minimum capture pressure instead of the real pressure.

Disclosure of Invention

The invention aims to provide an effective method for obtaining fluid pressure based on the combination of a cluster isotope technology and a fluid inclusion, which can better solve the problem of structural fluid pressure evolution so as to improve the research on the cause mechanism and distribution prediction of a deep carbonate reservoir.

To achieve the above object, the present invention provides a method for restoring fluid pressure of a deep carbonate formation, the method comprising:

step (1): rock and ore observation, namely observing the intersection relation of cracks under a rock core and a polarizing microscope, then observing detailed rock and ore characteristics and the luminescent condition of a cementing material aiming at the cracks under cathode luminescence, establishing a diagenetic sequence of the cracks of different periods, combining with regional structure fracture research, and limiting the main fracture activity time and spatial distribution through three-dimensional seismic data;

step (2): a micro-drill sampling product is used for preliminarily defining the possible stages of multi-stage construction activities on the basis of the background of the regional construction, and a micro-drill sampling instrument is used for drilling powder samples on the thickened sheet aiming at calcite cement filled in different stages in the crack;

and (3): extracting, purifying and collecting cluster isotope samples, firstly dissolving the samples in the phosphoric acid with super concentration to obtain pure CO₂Freezing the gas into a transfer container for collection;

and (4): performing on-machine test and standard sample correction on the cluster isotope, and purifying the purified CO₂Introducing the gas into a mass spectrometer for on-machine test analysis to obtain the delta of the carbonate₄₇A value;

and (5): processing cluster isotope data, measuring delta of carbonate₄₇After value use of₄₇-converting the T-calibration curve into a temperature value, using the formation temperature of the carbonate and the oxygen isotope delta of the mineral¹⁸O_carbObtaining the oxygen isotope value (delta) of the fluid¹⁸O_w)；

And (6): judging the validity of the cluster isotope data, and judging whether the cluster isotope data of the sample is rearranged or not;

and (7): texture-fluid property analysis, temperature obtained from cluster isotope testing and oxygen isotope value (delta) of fluid¹⁸O_w) Analysis of formation-fluid properties and source;

and (8): observing the lithology and fluorescence characteristics of the fluid inclusion, carrying out lithology observation of the inclusion on the inclusion sheet, including occurrence positions, growth relations and the like of the inclusion, distinguishing a saline inclusion from a hydrocarbon inclusion according to a fluorescence phenomenon issued by a fluorescence microscope, and recording the fluorescence color of the hydrocarbon inclusion in detail;

and (9): testing the salinity of the fluid inclusion and establishing an isovolumetric line, wherein a fluid inclusion salinity analysis instrument can be a cold-hot table, the freezing point temperature of the inclusion in the fractured filling vein is measured on the cold-hot table, the salinity is calculated and calculated by a measured freezing point temperature formula, and the isovolumetric line is determined according to the salinity converted from the freezing point temperature of the fluid inclusion;

step (10): and (3) structure-fluid pressure calculation, acquiring the absolute pressure of the fluid during pulse formation according to an isovolumetric line determined by cluster isotope temperature and fluid inclusion salinity, and analyzing the fluid properties and pressure evolution history of the major structure activity period by combining a region burial history curve, thereby providing a reliable basis for basin simulation and reservoir evaluation.

Wherein, the apparatus used in the cathodoluminescence test in the step (1) is RELIOTRON with the model number of RELION III, the working voltage is between 5 and 8kV, and the current is between 300 and 400 muA; in the step (2), the thickness of the thin sheet is 0.1-0.3mm, and the required sample amount is 30 mg.

Wherein the concentration of the over-concentration phosphoric acid in the step (3) is 104%, the phosphoric acid is dissolved in a water bath at 90 ℃ for reaction for about 30 minutes; the sample can be reacted more fully by moving the magnet during the reaction, the gas quantity of the exhaust gas can be observed by a pressure gauge, the extracted gas is passed through five steps of liquid nitrogen at-196 ℃, liquid modulated by liquid nitrogen at-196 ℃ and alcohol at-90 ℃ at-120 ℃, liquid nitrogen at-196 ℃, liquid nitrogen at-30 ℃ and liquid nitrogen at-196 ℃ to carry out CO in a vacuum pipeline₂/H₂O separation, in which the gas is transferred through a PORAPAKTM filter to reduce organic contamination, and pure CO is finally obtained₂A gas.

Wherein, the mass spectrometer in the step (4) adopts an MAT-253 mass spectrometer; said gas CO₂The standard sample comprises water balance gas prepared in a sealed container at normal temperature of 25 ℃ and CO heated to 1000 DEG C₂Gas (heated gas), the calcite standards being ETH-1, ETH-2, ETH-3, ETH-4.

Wherein the calibration curve in step (5) is obtained based on theoretical model calculation, and the carbonate Δ is₄₇Conversion to temperature using equation (1):delta of dolomite¹⁸O_wThe values are according to equation (2):and formula (3):delta of calcite¹⁸O_wThe values are according to equation (4):and formula (5):in the formulae (2) and (4), T is a thermodynamic temperature (K) (K ═ celsius (° c) +273.15), and α is an isotopic fractionation coefficient.

Wherein, there are two indexes in the step (6) for judging whether the sample cluster isotope data is rearranged: 1. whether the temperature of the sample increases with depth generally indicates that no rearrangement has occurred if the temperature of the sample does not increase with depth; 2. whether the temperature of the sample is correlated with other geological parameters (such as mineral carbon oxygen isotopes, trace elements and the like) or not, and the temperature of the rearranged sample is not correlated with other geological parameters.

The specific method for judging whether the sample cluster isotope data is rearranged in the step (6) is as follows: for calcite, cluster isotopes¹³C-¹⁸The "blocking temperature" of the solid state rearrangement of O bonds is 160 ℃ at<The initial cluster isotope value is retained at 100 ℃, the temperature is 150 ℃ and approximately 1 percent of partial rearrangement occurs, and the temperature is 200 ℃ and 160 ℃, the rearrangement occurs at about 99 percent, and the temperature>Rearrangement occurs completely at 200 ℃; for dolomite, its cluster isotope¹³C-¹⁸The 'sealing temperature' of the O bond solid rearrangement is 300 ℃, and the temperature of the dolomite is>Partial rearrangement may occur at 180 ℃ and temperature>The rearrangement was complete at 300 ℃.

Wherein the temperature and oxygen isotope value (δ) of the fluid obtained according to the cluster isotope test in step (7)¹⁸O_w) Analytical configuration-fluid properties and source determination methods were: t (Delta) under normal seawater conditions₄₇) The distribution range is 0-30 ℃, and the fluid oxygen isotope delta¹⁸O_wThe distribution range is 0 ~ +2.5 ‰ SMOW; surface atmospheric water exposure, typically T (. DELTA.)₄₇)<Fluid oxygen isotope delta at 30 DEG C¹⁸O_wSMOW with a distribution range less than-2 per mill, which is a high water/rock ratio (W/R) open system; the temperature will rise with the increase of the buried depth under the normal buried condition, and the oxygen isotope delta of the buried brine water¹⁸O_wValue of>+ 2.5%, reflecting the recrystallization of the minerals during the deep burying process; in a buried environment, with a low water-rock ratio (W/R) closed system, water-rock interaction causes delta of fluid¹⁸O_wThe value is increased; the temperature of the deep-buried thermal fluid will be abnormally high, 5-10 ℃ above the maximum buried depth of the formation, and therefore the delta of the thermal fluid¹⁸O_wValue in general>+8‰。

In the step (8), the saline water inclusion does not display under fluorescence, the liquid hydrocarbon inclusion has different luminescent colors and intensities due to the difference of organic matter evolution degrees, and the change rule of the fluorescence color of the organic matter is as follows: light yellow (light yellow) → tan → brown → dark blue → blue gray → no fluorescence.

In the step (9), the fluid inclusion salinity analyzer is a microscopic temperature measuring system consisting of a cold and hot table (model number THMS600) of Linkam Coo1ing Systems and an Axioskop40 type polarizing/fluorescent microscope produced by Zeiss of Germany, and the calibration standard samples are pure water and CO₂The temperature rise rate of the inclusion is 2 ℃/min, and the precision is +/-0.1 ℃; the calculation formula of the salinity is as follows: salinity of 0.00+1.78T_m-0.0442T_m ²+0.000557T_m ³(ii) a Wherein Tm is the freezing temperature.

Compared with the ambiguity of the traditional isotope in the analysis of the properties of the diagenetic fluid and the uncertainty of the temperature analysis of the fluid inclusion test. The temperature and fluid information of the past environment can be provided when the cluster isotope is used for carrying out ancient carbonate reservoir research, and the absolute pressure can be obtained by further combining the cluster isotope temperature and the isovolumetric line of the inclusion, so that more accurate parameters are provided for basin simulation, and the method has important guiding significance for researching reservoir distribution prediction.

Drawings

FIG. 1 is a graph of the fluid oxygen isotope value (δ)¹⁸O_w) Is calculated by

FIG. 2 is a graph of oxygen isotope values (δ) for different fluids¹⁸O_w) Distribution range

FIG. 3 is a contour recovery paleo-pressure map established based on cluster isotope temperature and fluid inclusion salinity

FIG. 4 is a flow chart of fluid pressure versus deep carbonate formation

Detailed Description

The following takes the underground Otaotystem eagle mountain reservoir in oil field in a Tarim basin tower as an example, and the specific implementation method of the present invention is further described in detail with reference to the accompanying drawings.

In the technical implementation process, an instrument model adopted for cluster isotope analysis is an MAT-253 mass spectrometer, an instrument adopted for fluid inclusion salinity test analysis is Linkam Coo1ing Systems, and a microscopic temperature measurement system consists of a cold and hot table (model is THMS600) and an Axioskop40 type polarization/fluorescence microscope produced by Zeiss company in Germany.

Referring to the accompanying fig. 4, fig. 4 is a method for restoring fluid pressure to a deep carbonate formation according to the present invention, as shown in fig. 4, the method includes:

the first step is as follows: rock and ore observation

Observing the intersection relation of the cracks under a rock core and a polarizing microscope, then observing detailed rock and mineral characteristics and cement light-emitting conditions aiming at the cracks under cathode light-emitting, and establishing diagenetic sequences of the cracks of different periods. The cathodoluminescence test instrument is RELIOTRON, model number is RELION III, working voltage is between 5-8kV, and current is between 300-400 muA. And (3) combining the regional structure fracture research, and defining the time and spatial distribution of main fracture activity through three-dimensional seismic data.

The second step is that: micro-drill sampling product

Preliminarily defining the possible stages of the multi-stage construction activities on the basis of the regional construction background; then, powder samples are drilled on the thickened thin sheet (the thickness of the thin sheet is 0.1-0.3mm) by using a micro-drilling sampling instrument aiming at the calcite cement filled in different periods in the crack, and the required sample amount is 30 mg.

The third step: cluster isotope sample extraction, purification and collection

The samples (10-15mg) were first dissolved in 104% super concentrated phosphoric acid, which was dissolved in a water bath at 90 ℃ for about 30 minutes. During the reaction, the sample can be more fully reacted by moving the magnet, and the gas quantity of the exhaust gas can be seen by the pressure gauge to obtain CO₂After the gas is treated, in order to obtain pure CO₂For cluster isotope analysis, the extracted gas is subjected to CO in a vacuum pipeline through five steps of liquid nitrogen at-196 ℃, liquid at-120 ℃ modulated by liquid nitrogen at-196 ℃ and alcohol at-90 ℃, liquid nitrogen at-196 ℃, liquid nitrogen at-30 ℃ and liquid nitrogen at-196 DEG₂/H₂O separation, in which the gas is transferred through a PORAPAKTM filter to reduce organic contamination, and pure CO will be obtained₂The gas was frozen into a transfer vessel for collection and the gas was introduced into a MAT-253 mass spectrometer. Wherein the liquid prepared from-196 deg.C liquid nitrogen and-90 deg.C alcohol at-120 deg.C is a mixed liquid prepared from-196 deg.C liquid nitrogen and-90 deg.C alcohol at-120 deg.C, and the preparation ratio is not specifically limited.

The fourth step: cluster isotope on-machine test and standard sample correction

Purifying the above CO₂Introducing the gas into an MAT-253 mass spectrometer for on-machine test analysis to obtain the delta of the carbonate₄₇The value is obtained. Standards required in the cluster isotope testing process include calcite and gaseous CO₂. Gaseous CO₂The standard sample comprises water balance gas prepared in a sealed container at normal temperature of 25 ℃ and CO heated to 1000 DEG C₂Gas (heated gas). Calcite standards are ETH-1, ETH-2, ETH-3, ETH-4. The standard samples were used mainly for the construction of Delta₄₇Absolute frame of reference (ARF) of data, making nonlinear corrections for the MAT253 mass spectrometer.

The fifth step: cluster isotope data processing

Measurement of Delta of carbonate₄₇After value use of₄₇-converting the T-calibration curve into a temperature value. The calibration curve can be calculated based on theoretical models, or can be obtained by synthesizing carbonate at a known temperature in a laboratory. Delta of the invention₄₇Conversion of results to temperature using equation (1); delta of dolomite¹⁸O_wThe value is according to the formula (2) and the formula (3), delta of calcite¹⁸O_wThe values are according to equation (4) and equation (5). Then using the formation temperature of carbonate and the oxygen isotope delta of the mineral¹⁸O_carbObtaining the oxygen isotope value (delta) of the fluid¹⁸O_w) (see FIG. 1).

In the formulae (2) and (4), T is a thermodynamic temperature (K) (K ═ celsius (° c)) +273.15, and α is an isotopic fractionation coefficient.

And a sixth step: cluster isotope data validity determination

High temperature can change in carbonate minerals¹³C-¹⁸Abundance of O bond, generation of carbonate¹³C-¹⁸Solid-state rearrangement of O-bonds, thereby changing the initial delta of carbonate₄₇Value, T (Δ) of the test₄₇) No longer represents diagenetic temperature but reflects rearranged temperature, so we need to analyze whether cluster data is rearranged when applying data interpretation. Typically, calcite cluster isotopes¹³C-¹⁸The "blocking temperature" of the solid state rearrangement of O bonds is 160 ℃ at<The initial cluster isotope value is retained at 100 ℃, the temperature is 150 ℃ and approximately 1 percent of partial rearrangement occurs, and the temperature is 200 ℃ and 160 ℃, the rearrangement occurs at about 99 percent, and the temperature>Rearrangement occurred in all cases at 200 ℃. For dolomite, its cluster isotope¹³C-¹⁸The 'sealing temperature' of the O bond solid rearrangement is 300 ℃, and the temperature of the dolomite is>Partial rearrangement may occur at 180 ℃ and temperature>The rearrangement was complete at 300 ℃.

Two indexes are provided for judging whether the sample cluster isotope data is rearranged: 1. whether the temperature of the sample increases with depth. If the temperature of the sample does not increase with depth, it is generally indicated that it is not rearranged; 2. whether the temperature of the sample is correlated with other geological parameters (such as mineral carbon oxygen isotopes, trace elements and the like) or not, and the temperature of the rearranged sample is not correlated with other geological parameters.

In the oil field research area in the tower, the cluster temperature of the test analysis sample does not increase along with the increase of the depth, and the good correlation between the carbon-oxygen isotope of the mineral and the cluster temperature excludes the influence of rearrangement on the sample, so that the cluster temperature can represent the temperature of the structure-fluid movement.

The seventh step: texture-fluid property analysis

Temperature and oxygen isotope value (delta) of fluid obtained from cluster isotope test¹⁸O_w) The formation was analyzed-fluid properties and source (see figure 2). T (Delta) under normal seawater conditions₄₇) The distribution range is 0-30 ℃, and the fluid oxygen isotope delta¹⁸O_wThe distribution range is 0 ~ +2.5 ‰ SMOW; surface atmospheric water exposure, typically T (. DELTA.)₄₇)<Fluid oxygen isotope delta at 30 DEG C¹⁸O_wSMOW with a distribution range less than-2 per mill, which is a high water/rock ratio (W/R) open system; under normal burying conditions, the temperature will rise with the increase of the buried depthOxygen isotope delta of brine¹⁸O_wValue of>+ 2.5%, reflecting the recrystallization of the mineral during the deep burying process. In a buried environment, with a low water-rock ratio (W/R) closed system, water-rock interaction causes delta of fluid¹⁸O_wThe value is increased; the temperature of the deep-buried thermal fluid will be abnormally high, 5-10 ℃ above the maximum buried depth of the formation, and therefore the delta of the thermal fluid¹⁸O_wValue in general>+8‰。

Eighth step: fluid inclusion petrographic and fluorescence feature observation

And performing lithology observation on the inclusion sheet, wherein the lithology observation comprises occurrence positions, growth relations and the like of inclusions. Then distinguishing the saline bag body from the hydrocarbon bag body according to the fluorescence phenomenon emitted by a fluorescence microscope, and recording the fluorescence color of the hydrocarbon bag body in detail. The saline water inclusion body does not display under fluorescence, and the light-emitting color and the intensity of the liquid hydrocarbon inclusion body are different due to the difference of the evolution degree of organic matters. From low maturity to high maturity, the change rule of the fluorescence color of the organic matter is as follows: light yellow (light yellow) → tan → brown → dark blue → blue gray → no fluorescence. The fluorescence color feature can be used as an auxiliary index for identifying different phases of secondary hydrocarbon charging. The research area mainly has two stages of oil gas filling, the hydrocarbon inclusion for oil gas filling in the early ages fluoresces yellow, and the hydrocarbon inclusion for oil gas filling in the late ages fluoresces blue.

The ninth step: fluid inclusion salinity test and establishment of isochoric line

The fluid inclusion salinity analyzer was the THMS600 chill-heat stage of Linkam Coo1ing Systems. The calibration standard sample is pure water and CO₂The temperature rise rate of the inclusion is 2 ℃/min, and the precision is +/-0.1 ℃. Measuring the freezing point temperature of the inclusion in the vein on a cold-hot table, and calculating the salinity which is 0.00+1.78T according to the measured freezing point temperature formula_m-0.0442T_m ²+0.000557T_m ³(ii) a Wherein Tm is the freezing temperature. When analyzing data, attention needs to be paid to eliminating stretching to form the inclusion data, because deformation leakage can occur. And determining an isovolumetric line according to the salinity of the fluid inclusion freezing point temperature conversion.

The tenth step: structure-fluid pressure determination

The absolute pressure of the fluid when the pulse is formed is obtained according to the isovolumetric line determined by the cluster isotope temperature and the fluid inclusion salinity (see figure 3), and the result can be applied to basin simulation analysis, so that a geological model is more accurately established. Calculation shows that the reservoir of the eagle mountain group in the tower is mainly normal pressure. The local overpressure is caused by oil and gas generation, the overpressure drives oil and gas migration, and the reservoir is distributed near normal pressure.

The conventional determination of the formation pressure of an inclusion by using the equation of state of the fluid has a considerable problem, and firstly, the fluid in the inclusion is not a single-component system but a multi-component system. Due to their interaction, the use of the equation of state of the one-component system as an approximation introduces considerable errors. When considered as a multicomponent system, the composition is difficult to determine accurately, and thus, also causes a large error. Compared with the traditional method, the technical method provided by the invention has better accuracy and is closer to the actual geological condition. The technical method adopts the cluster isotope temperature to replace the temperature of the inclusion, and establishes an isovolumetric line by using the salinity of the inclusion, thereby providing a more accurate means for testing the ancient fluid pressure of the deep reservoir and providing a reliable basis for basin simulation and reservoir evaluation.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.