阅读说明：本技术 一种确定碳酸盐岩储层热液活动年代的方法 (Method for determining hydrothermal activity age of carbonate reservoir ) 是由 刘恩涛 赵建新 冯婷婷 许家省 谷志宇 于 2019-10-16 设计创作，主要内容包括：本发明公开了一种确定碳酸盐岩储层热液活动年代的方法,包括以下步骤：步骤1、采集与筛选样品；步骤2、对样品进行储层岩石学特征分析；步骤3、对样品进行阴极发光分析；步骤4、对样品进行碳-氧同位素与微量元素分析；步骤5、对样品进行激光原位碳酸盐矿物U-Pb定年；步骤6、对样品进行热液活动年代分析。本发明具有前处理简单、测试周期短、数据精度高的有益效果。(The invention discloses a method for determining the hydrothermal activity age of a carbonate reservoir, which comprises the following steps: step 1, collecting and screening samples; step 2, performing reservoir petrophysical characteristic analysis on the sample; step 3, performing cathodoluminescence analysis on the sample; step 4, analyzing the carbon-oxygen isotope and the trace elements of the sample; step 5, carrying out laser in-situ carbonate mineral U-Pb dating on the sample; and 6, carrying out thermal liquid activity chronological analysis on the sample. The method has the advantages of simple pretreatment, short test period and high data precision.)

1. A method of determining the age of hydrothermal activity in a carbonate reservoir, comprising the steps of:

step 1, collecting and screening samples;

step 2, performing reservoir petrophysical characteristic analysis on the sample;

step 3, performing cathodoluminescence analysis on the sample;

step 4, analyzing the carbon-oxygen isotope and the trace elements of the sample;

step 5, carrying out laser in-situ carbonate mineral U-Pb dating on the sample;

and 6, carrying out thermal liquid activity chronological analysis on the sample.

2. The method of determining the age of hydrothermal activity in a carbonate reservoir of claim 1, wherein the sample collected in step 1 is a carbonate reservoir sample and the sample collected is an organic-lean sample that is fresh-cut and unaffected by late-stage alteration or metamorphism.

3. The method for determining the hydrothermal activity age of a carbonate reservoir as claimed in claim 1, wherein in step 2, the sample is divided into rock slices and cast body slices, then reservoir petrophysical characteristic analysis is performed, the type of surrounding rock and the reservoir development characteristic are determined, the distribution range of the hydrothermal cause of the carbonate is identified through the color and the interpenetration relationship, and the formation period is preliminarily determined.

4. The method for determining the age of hydrothermal activity in a carbonate reservoir as claimed in claim 1, wherein in step 3, the stage of hydrothermal activity and the distribution range of hydrothermal products at each stage are determined by performing a cathodoluminescence analysis on the development of the cement of dolomite and calcite in the sample.

5. The method for determining the age of hydrothermal activity in a carbonate reservoir as claimed in claim 1, wherein in step 4, micro-drilling is adopted to obtain cement samples of dolomite and calcite in the carbonate reservoir, complete analysis of carbon-oxygen isotopes and trace elements, determine the material source and temperature of hydrothermal solution at each stage, and further determine the activity period of hydrothermal solution.

6. The method for determining the age of hydrothermal activity in a carbonate reservoir as claimed in claim 1, wherein the samples of the hydrothermal activity products of different stages are selected in step 5, and laser target production of the samples is completed, wherein the samples are high in purity and clear in stage.

7. The method of determining the age of a hydrothermal activity in a carbonate reservoir of claim 6, wherein the laser targeting comprises cutting, cementing, targeting, polishing, and targeting.

8. The method of determining the age of hydrothermal activity in a carbonate reservoir of claim 7, wherein the target laser surface is cleaned prior to laser testing and allowed to air dry in a fume hood after cleaning.

9. The method of determining the age of hydrothermal activity in a carbonate reservoir of claim 8, wherein the determination of the U element and the Pb element is done in an ultraclean laboratory.

10. The method of determining the age of hydrothermal activity in a carbonate reservoir of claim 8, wherein the spot size is 50 to ℃100 mu m, 30-80 calcite sample test laser points in each period, and the test data comprises²³⁸U/²⁰⁶The ratio of Pb to,²⁰⁷Pb/²⁰⁶And the test data of the Pb ratio, the U content and the Pb content are processed by Iolite software, and then the Isoplot software is used for calculating to obtain age data.

Technical Field

The invention relates to the technical field of oil and gas geological exploration. More particularly, the present invention relates to a method for determining the age of hydrothermal activity in carbonate reservoirs.

Background

Carbonate is the most important hydrocarbon reservoir in the world, with about 40% of the hydrocarbons present in carbonate reservoirs. The carbonate reservoir oil gas resource is rich, and the exploration potential is huge. For example, in North America, the Michigan basin, the Tarim basin, the Sichuan basin and other carbonate rock reservoirs have the largest exploration breakthrough in recent years, and the exploration potential is huge. In contrast to clastic rock sedimentary basins, sedimentary reservoir fluids in carbonate sedimentary basins are active frequently, and hydrothermal fluids are very prevalent in sedimentary basins and have important effects on the water-rock interaction reaction of oil and gas reservoirs. Hydrothermal activity has a complex effect on carbonate reservoirs, and constructive and destructive effects are reflected in different horizons in different regions. The strong hydrothermal modification can form a high-quality reservoir, for example, a hydrothermal dolomite reservoir which can be formed by hydrothermal dolomite diagenesis is an important oil and gas reservoir type in the Tarim basin in China. Meanwhile, hydrothermal fluid can also show a strong cementing effect, and fluid products of calcite and dolomite are filled in pores of a reservoir and are unfavorable for the development of the reservoir. Therefore, the research on hydrothermal activity of carbonate reservoirs has important significance for revealing reservoir formation mechanisms and guiding the optimal exploration target area.

The hot fluid activity is an important research content of a carbonate basin, the prior researches on the microanalysis of main rocks and the isotope analysis of carbon, oxygen and strontium of fluid products (calcite and dolomite) are used for judging the fluid period, property and activity range, and the research on the fluid activity is less. Hydrothermal activity age is a challenging research direction in the field of basin fluid research, but hydrothermal age is also a problem to be solved. The determination of the fluid activity age is beneficial to accurately recovering the carbonate reservoir evolution process, revealing the development mechanism of the advantageous reservoir, finding out the relevance among basin structure evolution, fluid activity and reservoir development, and further effectively guiding oil and gas exploration and target area optimization. In hydrothermal fluid age research, fluid inclusion methods and authigenic mineral dating methods have been mainly used in the past. The fluid inclusion method is widely applied in fluid era, but the method has larger uncertainty and more influenced factors. The inclusion is usually multi-stage, and the stage and the sequence of the inclusion formation must be clarified in the inclusion temperature measurement, so that the inclusion is easily influenced by the inheritance inclusion. Particularly, in the oil-gas-containing basins in the cross-construction period, construction events are mutually overlapped, and basin burial history is difficult to recover, so that the determined fluid activity time is poor in precision. Authigenic illites are products of hydrothermal fluids, for which chronologic analysis is an important way to determine the history of hydrothermal activity. However, the method is an indirect method, and the autogenous illite formation process is also influenced by other factors such as the temperature and the properties of the fluid. In addition, the method is mainly applied to clastic rock sedimentary basins and is not suitable for carbonate reservoir hydrothermal chronology research.

In conclusion, the hydrothermal chronology analysis is important for revealing the evolution process of the carbonate reservoir, but the fluid inclusion temperature measurement method is mainly adopted in the early research, the technology has multiple controlled factors and limited precision, and the multiple-stage hydrothermal activity chronology cannot be accurately determined. The later stages of development in carbonate reservoirs, calcite and dolomite, are direct products of the hot fluids, and their chronology studies are the most direct methods to obtain a chronological history of fluid activity. However, the U and Pb contents of calcite and dolomite are low, the average content is less than 0.2ppm, and the calcite and the dolomite are 1/1000 to 1/10000 of uranium-rich minerals such as zircon, and bring great challenges to mass spectrometry.

Disclosure of Invention

An object of the present invention is to solve at least the above problems and to provide at least the advantages described later.

The invention also aims to provide a method for determining the hydrothermal activity age of a carbonate reservoir, which takes a hydrothermal activity direct product calcite or dolomite as a research object, adopts laser test, has the advantages of short test period, high spatial resolution (up to 100 mu m) and high data precision, and can accurately determine the hydrothermal activity ages of multiple stages.

To achieve these objects and other advantages in accordance with the present invention, there is provided a method of determining the age of hydrothermal activity in a carbonate reservoir, comprising the steps of:

step 1, collecting and screening samples;

step 2, performing reservoir petrophysical characteristic analysis on the sample;

step 3, performing cathodoluminescence analysis on the sample;

step 4, analyzing the carbon-oxygen isotope and the trace elements of the sample;

step 5, carrying out laser in-situ carbonate mineral U-Pb dating on the sample;

and 6, carrying out thermal liquid activity chronological analysis on the sample.

Preferably, the sample collected in step 1 is a carbonate reservoir sample, and the collected sample is an organic-poor sample with a fresh cross section and without being affected by late alteration or metamorphism.

Preferably, in the step 2, the sample is divided into a rock slice and a cast body slice, then reservoir petrophysical characteristic analysis is carried out, the type of surrounding rock and the reservoir development characteristic are determined, the distribution range of the carbonate rock of the hydrothermal cause is identified through the color and the interpenetration relationship, and the formation period is preliminarily judged.

Preferably, in step 3, the samples are analyzed by performing cathodoluminescence on the developed dolomite and calcite cements to determine the stage of hydrothermal activity and the distribution range of hydrothermal products in each stage.

Preferably, in the step 4, micro drilling is adopted to obtain a cementing material sample of dolomite and calcite in the carbonate reservoir, so as to complete analysis of carbon-oxygen isotopes and trace elements, determine the material source and temperature of the hydrothermal solution at each stage, and further determine the activity period of the hydrothermal solution.

Preferably, in the step 5, samples of the secondary hydrothermal activity products of different stages are selected to finish the laser target production of the samples, and the samples have high purity and clear stages.

Preferably, the laser target manufacturing comprises sample cutting, glue pouring, target making, polishing and target loading.

Preferably, the laser target surface is cleaned before testing, and naturally dried in a fume hood after cleaning.

Preferably, the determination of the U element and the Pb element is performed in an ultraclean laboratory.

Preferably, in the laser test process, the size of a light spot is 50-100 μm, 30-80 calcite sample test laser points are arranged in each period, and test data comprise²³⁸U/²⁰⁶The ratio of Pb to,²⁰⁷Pb/²⁰⁶Pb ratio, U content, Pb content, testAfter being processed by Iolite software, the data are calculated by Isoplot software to obtain age data.

The invention at least comprises the following beneficial effects:

the hydrothermal activity age of the carbonate reservoir is determined by determining the age of the hydrothermal activity product authigenic carbonate rock mineral, and the method is a research method for directly determining the history of the hydrothermal activity. In addition, the dating technology belongs to a laser in-situ dating technology, has high spatial resolution (up to 100 mu m), and can simultaneously determine the age of a plurality of stages of hydrothermal activities.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

FIG. 1 is a flow chart of a method of the present invention for determining the age of hydrothermal activity in a carbonate reservoir;

FIG. 2 is a view of a dolomite vein of a lamp shadow group carbonate reservoir in the Sichuan basin according to an embodiment of the present invention;

FIG. 3 shows the result of analyzing trace elements of dolomite in a Langmuir-Bayonet carbonate reservoir in an embodiment of the present invention;

FIG. 4 is a laser in-situ U-Pb chronology analysis of a dolomite vein body of a lamp shadow group carbonate reservoir in the Sichuan basin in accordance with an embodiment of the present invention.

Detailed Description

The present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.

It is to be noted that the experimental methods described in the following embodiments are all conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified.

The invention provides a method for determining the hydrothermal activity age of a carbonate reservoir, which comprises the following steps as shown in figure 1:

step 1, collecting and screening samples: the system collects carbonate reservoir samples in a research area, and guarantees that the collected samples are poor organic matter samples with fresh sections and without influence of later-stage alteration or deterioration in the sample collection process. The samples containing the vein-like or hole-filling calcite and the dolomite are intensively researched.

Step 2, performing reservoir petrophysical characteristic analysis on the sample: and cutting the sample into rock slices and casting body slices for analysis, determining the type of surrounding rocks and the development characteristics of a reservoir, identifying the distribution range of dolomite or calcite of a hydrothermal cause through color and interpenetration, and preliminarily judging the formation period.

And 3, performing cathodoluminescence analysis on the sample: and (3) performing cathodoluminescence analysis on the cement of dolomite and calcite in the carbonate reservoir to determine the stage of hydrothermal activity and the distribution range of hydrothermal products in each stage. The authigenic carbonate minerals in different periods have little difference in color, transparency and impurity content, and the hydrothermal activity period can be found out through the rock slices. Furthermore, the cathodoluminescence of carbonate minerals is mainly dominated by Fe in the crystal lattice²⁺、Mn²⁺Based on the Mn in the autogenous carbonate mineral²⁺/Fe²⁺The pulse body shows cathode lights with different intensities under the mirror due to different ratios. Early formed authigenic carbonate mineral Mn²⁺/Fe²⁺The ratio is lower, and the cathode luminescence is red to dark red; and the late formed authigenic carbonate mineral Mn^{2 +}/Fe²⁺The ratio is relatively large, the cathode luminescence is bright red to orange red, and accordingly division of hydrothermal activity period and fracture activity period can be completed.

And 4, analyzing the carbon-oxygen isotope and the trace elements of the sample: adopting a micro drill to obtain a cementing material sample of dolomite and calcite in a carbonate reservoir, completing analysis of carbon-oxygen isotope isotopes and trace elements, determining material sources and temperatures of hydrothermal solutions at various stages, and further determining the activity period of the hydrothermal solution. Hydrothermal products (authigenic carbonate minerals) of different stages have large differences in C-O isotopes and trace element compositions. For example, early diagenesis stage dolomite has a higher Sr element content but very low Fe, Mn element content than later diagenesis stage precipitated dolomite. The reducibility of the hydrothermal solution is enhanced along with the increase of the burying depth, so that the authigenic carbonate mineral formed in the deep burying stage has higher contents of Fe and Mn elements. As another example, the temperature of the secondary hydrothermal solution at different stages is different, and thus the C-O isotopic composition must be different.

Step 5, in recent years, along with the enhancement of laser energy and the improvement of the precision of a mass spectrometer, the laser in-situ carbonate rock U-Pb dating technology is successfully researched and developed, has the advantages of short test period, high spatial resolution (up to 100 mu m) and high test precision, and provides a new idea for the thermal liquid chronology analysis of the basin; the laser in-situ carbonate mineral U-Pb dating technology comprises the following steps: and (3) selecting samples of secondary hydrothermal activity products (calcite, dolomite and the like) at different stages to finish the manufacture of the sample laser target. The sample is representative, and the sample is high in purity and clear in period. The laser target manufacturing comprises the processes of sample cutting, glue pouring, target manufacturing, polishing, target installation and the like. The contents of U and Pb elements in the authigenic carbonate minerals are low, the authigenic carbonate minerals need to be kept clean by attention in the early-stage treatment, the target surface needs to be cleaned systematically before testing, the target surface is naturally dried in a fume hood of an ultra-clean laboratory after the cleaning is finished, and the later-stage testing needs to be finished in the ultra-clean laboratory. According to the analysis results of previous hydrothermal stages, the research on the autogenous carbonate minerals of each stage in the era is carried out, and hydrothermal products of different stages cannot be mixed. In the laser test process, the spot size is usually 50-100 μm, 30-80 calcite sample test laser spots are obtained in each period, and the test data comprises²³⁸U/²⁰⁶The ratio of Pb to,²⁰⁷Pb/²⁰⁶Pb ratio, U content, Pb content, etc. After the test data are processed by Iolite software, the age data can be obtained by calculation by using Isoplot software. The age of the multi-stage authigenic carbonate minerals can be obtained by the chronology analysis of the multi-stage authigenic carbonate minerals in the same sample. The laser in-situ carbonate mineral U-Pb dating technology has high spatial resolution (up to 100 mu m), and can be used for the chronology analysis of a development system of multiple stages of secondary hydrothermal products in the same reservoir sample to determine the age of each stage of secondary hydrothermal product.

Step 6, hydrothermal activity age analysis: the carbon-oxygen isotope of carbonate mineral, trace elements and laser in-situ carbonate mineral U-Pb dating results are analyzed systematically, the period and the next age of each period of autogenous carbonate mineral are determined, and the source, the temperature and the characteristics of hydrothermal solution in each period are determined.

< example >

A dolomite vein sample collected from a carbonate reservoir of a lamp shadow group in a Sichuan basin is shown in figure 2, and is considered to be a first-stage hydrothermal activity product through microscopic construction and cathodoluminescence analysis, and lithology is medium-coarse crystal saddle-shaped dolomite. The dolomite vein components are uniform, and the cathodoluminescence result shows no multi-stage activity phenomenon. Microscopic slice analysis shows that the dolomite pulse body at the period is pure and is suitable for carrying out the chronology analysis. The dolomite sample at this stage is obtained by using a micro drill, and then the analysis of carbon-oxygen isotopes and trace elements is completed. The carbon-oxygen isotope analysis results are as follows: delta¹³C＝-0.9‰，δ¹⁸C ═ 9.3 ‰, and other phase of hydrothermal products (delta) in the study area¹³C and delta¹⁸C values around-0.4% and-8.8%) are considered to be the sole hot liquid activity product. The trace element analysis result further verifies the difference of the dolomite pulse and other dolomite pulse bodies in the research area in the components. After the north american shale is standardized, the content of heavy rare earth elements in the sample to be tested is obviously higher than that of light rare earth elements, while other dolomite samples in the region show opposite characteristics, and the content of light rare earth elements is slightly higher than that of heavy rare earth elements, as shown in fig. 3. In conclusion, through reservoir petrophysical characteristics, cathodoluminescence, carbon-oxygen isotope and trace element analysis, the crude crystal saddle-shaped dolomite pulse body and other dolomite pulse bodies in the period are found to have larger difference in composition and are single hydrothermal activity products in the period, and the hydrothermal activity age in the period can be determined through laser in-situ dolomite U-Pb chronology research. The laser in-situ laser calcite U-Pb fixed-year test is completed in a radioactive isotope ultra-clean laboratory of Australian Queensland university, a laser-induced multi-receiving cup inductively coupled plasma mass spectrometer is selected as a test instrument, a RESOlution laser ablation system is arranged, and the laser energy is 3J.cm^-2The single laser spot test time was 48s, with a laser ablation time of 25 s. The data are processed by Iolite software and then are usedThe soplot software calculated the hydrothermal activity age at this stage to be 520.5 ± 9.2Ma (MSWD ═ 1.6), and the test results are shown in fig. 4.

While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.