CN115327665A

CN115327665A - Improved system for distinguishing dolomite cause through dolomite detritus information

Info

Publication number: CN115327665A
Application number: CN202211091159.XA
Authority: CN
Inventors: 伏美燕; 吴冬; 邓虎成; 兰浩翔; 段广慧; 凌灿
Original assignee: Chengdu Univeristy of Technology
Current assignee: Chengdu Univeristy of Technology
Priority date: 2022-09-01
Filing date: 2022-09-01
Publication date: 2022-11-11

Abstract

The invention provides an improved system for distinguishing dolomite cause through dolomite detritus information. According to the method, the dolomite formation analysis is carried out by utilizing the rock debris, so that the logging cost is greatly reduced, and the reference of the dolomite formation analysis is provided for the region with only rock debris logging information.

Description

Improved system for distinguishing dolomite cause through dolomite detritus information

Technical Field

The invention relates to the technical field of geological research, in particular to an improved system for judging dolomite cause through dolomite detritus information.

Background

From the global perspective, dolomite is an important oil and gas storage rock, wherein the discovered oil and gas resources account for more than half of the total oil and gas resources of carbonate rocks, dolomization has important significance for improving the storage performance of the carbonate rocks, and the origin characteristics of the dolomite control the development rule and the spread characteristics of the dolomite, so that the research on the dolomite origin can provide guidance for later reservoir prediction. The former research on the cause of dolomite in the picuvian group of the Sichuan basin has summarized various modes and achieved a lot of results, and the traditional research on the cause mode of the dolomite is mainly based on the research on the geochemical analysis and the under-mirror observation of a core sample.

Most of the cause mechanisms of dolomite at present are based on a core to analyze the formation environment of the dolomite so as to reestablish the cause mode type. And because the rock debris logging cost is low and the data continuity is good, the rock debris logging method is widely applied to the oil and gas exploration and development process in recent years. Therefore, the rock debris can be accurately identified and observed, the petrological parameters can be identified, and the logging cost can be greatly reduced. The foundation of reservoir research by using rock debris is to ensure the reliability of the depth of a rock sample and identify true and false rock debris. But the accuracy of the rock debris logging is affected due to geological reasons, drilling engineering and other reasons. The truth of the rock debris is mainly influenced by the following factors, and the first factor is the influence of rock debris mixing: the components of the rock debris returned to the ground by the well drilling fluid are mixed, so that the difficulty of identifying the rock debris is increased. The factors causing the rock debris mixing mainly comprise geological reasons, drilling reasons, gravity subsidence of the rock debris and the like; secondly, the effect of the drilling fluid: the properties of the drilling fluid such as viscosity, shearing force, upward return speed and the like directly determine the capability of the drilling fluid to carry rock debris, and influence the settlement of the rock debris. The poorer the performance of the drilling fluid and the slower the upward return speed, the insufficient sand carrying capacity of the drilling fluid can be caused, and rock debris is settled and then repeatedly crushed. Finally, not only are the rock debris particles fine, but also the rock debris is mixed, and the rock debris is difficult to identify; also the impact of debris contamination: the adoption of special drilling fluids such as oil-based drilling fluid can cause the pollution of crude oil to rock debris and influence the identification of an oil-gas layer. Research shows that the reservoir with better permeability is more easily polluted by crude oil, and the reservoir with poor permeability is compact in lithology and smaller in pollution degree.

Disclosure of Invention

In order to solve the problems in the background art, the invention provides an improved system for distinguishing the dolomite cause through dolomite debris information.

An improved system for distinguishing dolomite cause through dolomite detritus information comprises: the device comprises a dolomite detritus sample preparation module, a dolomite petrochemistry characteristic analysis module, a dolomite geochemistry characteristic analysis module and a dolomite cause analysis module.

1. The dolomite rock debris sample preparation module comprises: the device comprises a true and false rock debris identification unit, a dynamic and static combination verification unit and a dolomite sample preparation unit in rock debris.

1) And a real and false rock debris identification unit which is used for carrying out logging data and under-mirror observation by combining the geological background of the area and identifying the real and false rock debris.

a. And taking back the rock debris to carry out grinding. Grinding the slices into three groups according to the particle size, wherein the three groups are respectively as follows: 1. selecting larger rock debris particles (> 0.5 cm); 2. randomly obtaining; 3. selecting smaller rock debris particles (< 0.5 cm); counting and counting the dolomite in the rock debris slices if the change of the number of the dolomite particles in each group of rock debris slices is large; and if the number of the dolomite particles in the rock debris in each group is stable and has small change, performing area ratio statistics on the dolomite in the thin slices.

The purpose is to determine if the size of the rock debris particles has an effect on the amount of dolomite debris in the sheet.

b. And (d) judging the rock stratum and the drilling environment when the rock debris is logged according to the counted number of the dolomite particles in the step a. If the number of dolomite particles in the slice is less, the rock stratum is thinner and the drilling time is shorter; if the number of dolomite particles in the thin slice is more, the rock stratum is thicker and the drilling time is longer. Based on the method, the depth of the rock debris is determined by combining the well logging curve.

The reasons for the generation of the pseudo rock debris are mainly the following: the delayed time is inaccurate, the rock debris is not fished out in circulation, and the rock debris on the well wall falls off, so that the lithology of the non-lithology corresponding section is caused.

c. And the observation of the under-mirror thin slice is combined as the auxiliary identification of the true and false rock debris. By combining geological background (the characteristics of deposition and diagenesis of the same layer near a research area or in the same basin), the true rock debris under the mirror has bright color and obvious rock debris edges and corners; the color of the false rock debris is dark, and the edges and corners of the rock debris are fuzzy.

After the step of identifying the true and false rock debris, if a core well exists in the research area, the core and the rock debris of the core well in the research area are compared, the corresponding degree of the rock debris and the core is verified, and the credibility of the rock debris is judged so as to identify and observe the rock debris more accurately.

2) Dynamic and static combination verification unit

a. Static data-validation by logging parameters, geochemical parameters, and sedimentary phase sequence data

Verifying logging parameters corresponding to depths:

firstly, carrying out core homing on a well with coring, and reading logging curve values corresponding to different lithologies under the condition that the corresponding depths of the cores are determined to be not different. And then comparing the depth section with the rock debris of the corresponding depth section, and judging the reliability of the rock debris.

Verification of results of geochemical analysis

Fresh rock debris particles are selected for geochemical analysis and are longitudinally tested for continuous elemental composition changes.

Microphase mode validation of sedimentary phase sequence build

And identifying the rock debris through the established deposition phase sequence, and removing the rock debris which does not accord with the deposition rule.

For example, dolomite is found to develop between beaches, and is a fake rock fragment.

b. Dynamic data-verification of Productivity data by Single well (Single well Productivity data includes perforation display and Productivity on Single well)

I. Verification through perforation display on single well

The place where the comprehensive interpretation section is the gas layer is the dolomite reservoir, so the dolomite which is identified as the true debris in the debris at the depth section is all the true debris.

Passing capacity verification

The well with high productivity has more corresponding rock debris dolomite particles, so the place with high productivity corresponds to a dolomite reservoir.

3) Dolostone sample preparation unit in rock debris

a. Preparation of cast sheet

And selecting the rock debris particles with larger diameter and fresh lithology.

Because the cast body is treated, the debris is selected to be as large as possible, which contributes to the success of the cast body. And, it is important whether the cuttings correspond to well logging, so the cuttings should be selected to be fresh, i.e., without scratches on the surface, etc.

b. Cathodoluminescent sheet preparation

Cathodoluminescence needs to be completed under the condition of ion discharge, the cover slip treatment can make the cover slip show blue under a cathodoluminescence instrument, and the cover slip cannot be produced during the process of preparing the cover slip.

c. Geochemical sample preparation

Selecting fresh and pure rock debris

In addition to selection like casting sheets, selection methods are important in geochemical sampling, and scientific selection is achieved to ensure the characteristics of the horizon represented by the rock debris, so that artificial selection cannot be carried out.

d. Inclusion sheet milling

And in the step, after the casting body slice is finished, observation is carried out under a mirror, the lithology is determined and then carried out, the selected lithology is ensured to be dolomite as far as possible, the section of the lithology determined to be the dolomite is subjected to sample selection and sheet making, and the inclusion is easier to find under the mirror.

2. Dolomite lithology characteristic analysis module

1) Partition dolomite type unit

According to the method, the types of the dolomite are divided according to common rock debris slices, the dolomite are divided into three categories of crystalline dolomite, spot dolomite and granular dolomite according to the sizes of crystalline grains, sedimentary formations and rock structures, and the content of the clouded particles is counted.

Crystalline dolomitic rock: the color is light gray or grey white, the rock is in block shape, the grain size is 0.25-1.0mm, and the rock component is mainly compact matrix grains.

Porphyry dolomitic rock: the rock is a transition lithology between limestone and nephrite, and is in a spot shape, the rock component consists of cloud and gray matter, and the cloud part is darker and is gray and dark gray; the gray matter part is light in color, light gray and gray white, and the plaque size of cloud matter is 3-10mm.

Granular dolomite: the residual structure of sand dust can be seen in the particles, the particle size is larger than 1.0mm, the particles have a fog-center bright-edge structure, and the sand dust can be seen under the thin sheet, such as rounding and sorting.

2) Determination of Mn during formation of Dolomite ²⁺ Content unit

Mn in the formation of dolomite by dolomite cathodoluminescence signature according to cathodoluminescence sheet analysis ²⁺ Lower contents indicate formation in the early low temperature stage. The cathode luminescence characteristics of the nepheline group dolomite in the research area are divided into three types, the cathode luminescence of the first type dolomite is dark red, and the first type dolomite is mainly fine crystalline dolomite; the cathode luminescence of the second type of dolostone is red, and the edge of the dolomite crystal emits mottled bright red light which is mainly fine-mesomorphic and mesomorphic dolostone; the third type of dolomitic cathode luminescence is orange red, and the dolomite crystal has obvious ring belt characteristics and is mainly medium-coarse crystal dolomitic.

3) Determination of dolomite order degree unit

And (4) determining the order degree of the dolomite by using the fresh dolomite detritus. The dolomite crystal characteristics are reflected by the dolomite order degree characteristics, the fine-powder crystal dolomite order degree is 0.69-0.82, and the average is 0.75. The fine-mesomorphic dolomites have a medium degree of order, with an average degree of order of 0.85. The medium-coarse crystal dolostone has high order degree reaching 0.91 and is close to ideal dolomite.

4) Determining pore throat building blocks

And (4) analyzing pores by using a casting body slice and analyzing images by using software to determine the pore throat structure. And (3) importing the rock slice photo into software, automatically analyzing parameters such as pore and pore throat relations by the software to form a result table, and identifying the pores in the red part in the software image by the software.

Through the steps, the dolomite deposition-diagenesis environment is determined, the dolomite deposition environment is judged according to the typical characteristic information of the dolomite, and then the dolomite cause type is preliminarily determined.

3. A dolomite geochemical characteristic analysis module, namely selecting corresponding geochemical parameters for analyzing aiming at the primarily determined dolomite cause type, wherein the analyzed parameters respectively comprise: elemental composition characteristic analysis, isotope composition characteristic analysis and inclusion uniformity temperature analysis.

1) Element composition characteristic analysis unit

The method comprises the steps of determining element composition by utilizing a selected fresh rock debris sample, and judging the diagenetic fluid property and diagenetic rock alteration strength of the dolomite through the analysis of the composition characteristic of the dolomite elements and the comparative analysis of the fine crystalline dolomite, the fine-medium crystalline dolomite, the medium-coarse crystalline dolomite and the trace elements of the marlite representing the seawater in the same period.

Through analyzing the trace element composition of different parts of the single-particle dolomite, 8 measuring points are selected from the inside to the outside of the annular belt for element measurement, and the trace element content of each measuring point is measured.

As a result: mgCO of single-particle dolomite at different positions ₃ And CaCO ₃ The contents are basically similar, however, the contents of trace elements at different positions are different, the Mn content at the luminous position of the dolomite annulus is higher, but the corresponding Fe content is reduced. The content of Th and U increases gradually from the inside of the crystal to the edge. The varying characteristics of these trace elements indicate differences in diagenetic fluid during dolomitic formation within the zone.

2) Isotope composition characteristic analysis unit

And (3) determining the isotope composition of carbon, oxygen and strontium by using the selected fresh rock debris sample, and analyzing by using the isotope composition characteristics of dolomite.

a. Strontium isotope

Dolomitic rock ⁸⁷ Sr/ ⁸⁶ Of Sr and contemporary seawater ⁸⁷ Sr/ ⁸⁶ Sr is used for distinguishing the source of the dolomitic petrochemical fluid, ⁸⁷ Sr/ ⁸⁶ the Sr ratio is in the Sr isotope composition range of the synchronous seawater, which indicates that the seawater is the main dolomitic petrochemical fluid, otherwise, the seawater is the exogenous allopatric fluid.

b. Carbon isotope

δ ¹³ The value of C indicates the deposition environment, the atmosphere is a fresh water environment in a negative mode, and the seawater environment is in a positive mode.

c. Oxygen isotope

δ ¹⁸ O indicates the temperature, which is biased negative by the temperature increase.

3) And (4) utilizing the inclusion pieces of the fresh rock debris to measure the uniform temperature and salinity of the saline inclusion.

The uniform temperature of the inclusion is the instant temperature when the inclusion is converted from a two-phase fluid into a single-phase fluid when the temperature of the inclusion is raised to a certain degree through artificial heating.

The inclusion is impurities captured in the crystal growth process in the rock, and can have a certain indication effect on the formation time, the formation environment and the like of the rock.

Saline inclusions refer to entrapped components as various salts.

4. Dolomite genesis analysis module — by integrating the petrophysical characteristics of dolomite and the geochemical characteristics of dolomite, in combination with the construction background, draw conclusions:

the fine crystalline and fine-mesomorphic dolomites in the research area are mainly formed by early stage dolomization, and the modification exists in the burial period. Medium-coarse crystalline dolomite is mainly based on buried dolomite and suffers from different degrees of later hydrothermal transformation;

synthesize dolomite detritus sample preparation module, dolomite petrochemistry characteristic analysis module, the result that dolomite geochemistry characteristic analysis module obtained carries out the composition analysis and differentiates:

1) Fine-grained dolomite formation analysis unit

The exclusive indexes for identifying the fine crystalline dolomite cause are as follows: the cathode luminescence is dark red; the degree of order is low; the rare earth element distribution mode is similar to that of contemporary limestone; ⁸⁷ Sr/ ⁸⁶ the Sr value is close to the contemporaneous seawater value; the plaster is formed by carrying out quasi-syngeneic rapid clouding and recrystallization in a shallow burial period.

And (4) conclusion: the fine crystalline dolomite is mainly formed by fast clouding of stucco in the quasi-contemporaneous period, and recrystallization occurs in the shallow burial period.

2) Fine-medium crystal dolomite genesis analysis unit

Exclusive indexes for identifying the cause of the fine-medium crystal dolomite are as follows: the cathode luminescence is red, and the edge of the dolomite crystal is mottled bright red; a medium degree of order; the rare earth element distribution mode is similar to that of contemporary limestone; ⁸⁷ Sr/ ⁸⁶ sr value slightly higher than that of seawater in the same periodHigher Mn content and low Sr/Ba ratio. Dolomitic petrochemistry is formed in buried diagenetic environments.

And (4) conclusion: the fine-mesomorphic dolostone and the porphyry dolostone are pore type granular limestone which is subjected to dolostification in a quasi-synchronizing period and is formed by superposing the dolomization in a burial period in a later period.

3) Medium-coarse crystal dolomite cause analysis unit

The exclusive indexes for identifying the cause of the medium-coarse crystal dolomite are as follows: the cathode luminescence is orange red, and the dolomite crystal has obvious ring belt characteristics; medium to high degree of order; the uniform temperature of the inclusion is higher; a positive anomaly with significant europium; ⁸⁷ Sr/ ⁸⁶ the Sr value is higher than the seawater value in the same period, the Mn content is higher, and the Sr/Ba ratio is low. The dolomization is formed in a buried diagenetic environment and is generated by continuous and sufficient supply of the clouding fluid to the granular limestone in the buried period, the crystallization speed is low, and the clouding time is long.

And (4) conclusion: medium-coarse dolomites are particulate limestone which is supplied with a continuous, abundant supply of a clouding fluid during the period of burial, and is affected by the local presence of a certain degree of hydrothermal fluid.

Advantageous effects

1. In the true and false rock debris recognition unit, the dolomite particle number of different rock debris particle sizes is counted, so that the influence of the rock debris sample on the dolomite particle number can be eliminated, and the sample can not bring errors to the dolomite particle counting.

2. In the dynamic and static combination verification unit, the authenticity of the rock debris sample can be verified in an auxiliary manner, the reliability of the depth of the rock debris sample can be determined, and the fact that the rock debris is real and the depth is accurate is ensured.

3. According to the method, the dolomite formation analysis is carried out through the rock debris, so that the logging cost can be greatly reduced, and the reference of the dolomite formation analysis is provided for the region with only rock debris logging information.

Drawings

FIG. 1A is a corresponding identification chart I of a rock core and rock debris of a Mitsui 42 well;

FIG. 1B is a corresponding identification plate II of a rock core and rock debris of a Mianxi 42 well;

FIG. 2 is a composition profile of dolomite elements in a research area;

FIG. 3A is a GS001-45 well Complex bar chart I;

FIG. 3B is the GS001-45 well Complex histogram II;

FIG. 4 is a table of capacity statistics for a research area;

FIG. 5A is a photograph of a cast sheet;

FIG. 5B is a photograph of a cast sheet;

FIG. 5C is a photograph of a cast sheet;

FIG. 6A is a graph of coarser rock debris particles;

FIG. 6B is a graph of uniform debris particles;

FIG. 6C is a graph of finer rock debris particles;

fig. 7 is a flow chart of the present invention.

DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION

In order that the invention may be more clearly understood, reference will now be made in detail to the present invention as illustrated in the accompanying drawings.

According to fig. 7, an improved system for identifying the dolomite cause through dolomite debris information comprises: the device comprises a dolomite rock fragment sample preparation module, a dolomite petrochemistry characteristic analysis module, a dolomite geochemistry characteristic analysis module and a dolomite cause analysis module;

wherein the dolomite rock fragment sample preparation module comprises: the device comprises a true and false rock debris identification unit, a dynamic and static combination verification unit and a dolomite sample preparation unit in rock debris;

wherein the dolostone petrology characteristic analysis module comprises: partition of dolomite type unit, determination of Mn in formation of dolomite ²⁺ A content unit, a dolomite order degree measuring unit and a pore throat structure unit are determined;

wherein the dolomite geochemical characteristic analysis module comprises: the device comprises an element composition characteristic analysis unit, an isotope composition characteristic analysis unit and a saline water inclusion uniform temperature and salinity determination unit by utilizing inclusion pieces of fresh rock debris;

the dolomite formation analysis module is used for obtaining a conclusion that fine crystalline and fine-mesomorphic dolomite in a research area are mainly formed by early stage dolomization by combining the petrophysical characteristics and geochemical characteristics of the dolomite and combining structural backgrounds, and the improvement exists in a burying period; medium-coarse crystalline dolomite is mainly based on buried dolomite and suffers from different degrees of later hydrothermal transformation;

the dolomite genesis analysis module comprises: a fine crystalline dolomite formation analysis unit, a fine-medium crystalline dolomite formation analysis unit and a medium-coarse crystalline dolomite formation analysis unit.

Examples

Research on the cause of dolomite formation was conducted on the Cyrtymenia Sparsa group in the middle region of Sichuan.

Because the research has no coring well in the research area, the lithology identification and the identification of various parameters become very difficult, and in order to accurately identify the rock debris as much as possible, the research carries out rock debris sampling twice, and 16 single-well inhabiting-clouds group rock debris sampling is carried out totally, so that 600 rock debris slices are obtained. And the lapping, casting and geochemical analyses were performed, respectively.

1. A dolomite rock fragment sample preparation module:

1) True and false rock debris identification unit

According to the illustration of fig. 6A-6C, 600 rock debris flakes are divided into three categories according to particle size, with category 1 being larger rock debris particles (> 0.5 cm); class 2 is random sorting; category 3 is smaller debris particles (< 0.5 cm).

And (3) counting whether the sizes of the three types of rock debris particles influence the quantity of dolomite, and analyzing and considering that: the particle size of the rock debris has no direct relation with the quantity of the dolomite rock debris.

As shown in fig. 1A-1B, the corresponding analysis of the rock debris and core slice of the core well of the neighboring well indicates that the rock debris identification method is effective.

2) Dynamic and static combination verification unit

As shown in fig. 3A-4, by production dynamic data validation: the place where the comprehensive interpretation section is the gas layer is a dolomite reservoir. Therefore, the dolomite which is identified as the dolomite in the rock debris at the depth section is the real rock debris. Therefore, the rock debris identification method is effective.

3) Dolomite sample preparing unit in rock debris

Preparing a casting sheet, preparing a cathode luminescence sheet, selecting a geochemical sample and grinding an inclusion sheet.

2. Dolomite petrology characteristic analysis module

1) Partition dolomite type unit

Dividing the rock types:

Porphyry dolomitic rock: the rock is a transition lithology between limestone and nephrite, is in a spot shape, and comprises two parts of cloud and gray matter, wherein the cloud part is darker and is gray and dark gray; the gray matter part is light in color, light gray and gray white, and the plaque size of cloud matter is 3-10mm.

Granular dolomite: the grains are mainly sand chips, the size of the grains is larger than 1.0mm, the grains have no ring layer structure, and the sand chips can be seen under the thin slices for rounding, sorting and the like.

A geochemical feature analysis module:

as shown in fig. 2, fine-mesomorphic dolomites: the rare earth element distribution mode is similar to that of contemporary limestone, the Sr isotope ratio is close to that of contemporary seawater, and the high Mn content and low Sr/Ba ratio reflect the dolomitic petroleum formed in the buried diagenetic environment.

Medium-coarse dolostone: the higher Mn content and the low Sr/Ba ratio reflect the formation of dolomite in the buried diagenetic environment, and the participation of hydrothermal fluid is shown by the positive abnormality of europium and the higher uniform temperature of the inclusion. Due to the sustained supply of sufficient clouding fluid and the prolonged clouding of the hydrothermal fluid during the period of burial.

Zebra dolostone: the cloud limestone is high in Mn and is a hydrothermal cause; the high Fe content of the grey dolomite is the cause of late filling and corrosion.

As shown in fig. 5A-5C, pore analysis: pore throat characteristics were studied by pore image analysis.

The final dolomite formation characteristics and the spreading rule are as follows:

cause characteristics:

the research area dolomitic formation is mainly based on quasi-syngeneic dolomitic and buried dolomite, and hydrothermal dolomitic exists locally. Wherein the fine crystalline and fine-mesomorphic dolomites are quasi-syngeneic dolomites, namely dolomites, and are superposed and buried with dolomites; medium-coarse crystalline dolomite is a buried dolomite diagenesis cause, and hydrothermal transformation exists locally; the spotted dolomite is a buried dolomite diagenesis cause, and hydrothermal transformation exists locally.

The spreading rule is as follows:

a. the perched two-section dolomite has large thickness change in the longitudinal direction and poor transverse continuity, and mainly comprises fine-grained dolomite and spot-shaped dolomite.

b. There are two layers of relatively stable dolostone on the top of the roosting section, mainly fine crystalline, fine-mesocrystalline dolostone, see saddle-shaped dolomite.

c. The spreading of the dolomite on the first perch section and the second perch section is mainly controlled by the beach facies range and is in a block shape in the north, east, south and west directions.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. The utility model provides a system that modified differentiates dolomite genesis through dolomite detritus information, its characterized in that, includes dolomite detritus sample preparation module, dolomite petrology characteristic analysis module, dolomite geochemistry characteristic analysis module, dolomite genesis analysis module:

wherein the dolostone petrology characteristic analysis module comprises: partition of dolomite type unit, determination of dolomite shapeMn in the course of time ²⁺ A content unit, a dolomite order degree measuring unit and a pore throat structure determining unit;

the dolomite genesis analysis module comprises: a fine crystalline dolomite formation analysis unit, a fine-medium crystalline dolomite formation analysis unit and a medium-coarse crystalline dolomite formation analysis unit;

the dolomite formation analysis module is used for obtaining a conclusion that fine crystalline and fine-medium crystalline dolomite in a research area are mainly formed by early stage dolomization by integrating the petrophysical characteristics and the geochemical characteristics of the dolomite and combining a structural background, the improvement exists in a burial period, and the medium-coarse crystalline dolomite is mainly formed by burial dolomite and suffers from the later stage hydrothermal improvement of different degrees.

2. The improved system for determining the cause of dolomite according to the dolomite rock debris information as claimed in claim 1, wherein:

wherein the true and false rock debris identification unit comprises: preparing rock debris grinding sheets, judging rock strata and drilling environment during rock debris logging, and observing and assisting in identification through a microscopic slice;

preparing a rock debris grinding piece: grinding the slices into three groups according to the particle size, wherein the three groups are respectively as follows:

(1) Selecting rock debris particles larger than 0.5 cm;

(2) Randomly obtaining;

(3) Selecting rock debris particles of less than 0.5 cm;

counting and counting the dolomite in the rock debris slices if the change of the number of the dolomite particles in each group of rock debris slices is large;

if the number of the dolomite particles in the rock debris in each group is stable and has small change, carrying out area ratio statistics on the dolomite in the thin slices, and aiming at determining whether the size of the rock debris particles has influence on the number of the dolomite rock debris in the thin slices;

and (3) judging rock stratum and drilling environment during rock debris logging: counting the number of dolomite particles for preparing the rock debris grinding sheet, wherein if the number of the dolomite particles in the sheet is less, the rock stratum is thinner and the drilling time is shorter;

if the number of dolomite particles in the thin slice is more, the rock stratum is thicker and the drilling time is longer, and based on the fact that the depth of the rock debris is determined by combining a logging curve, the generation reasons of the false rock debris are mainly the following types: the delay time is inaccurate, the rock debris is not fished out in circulation, and the rock debris on the well wall falls off, so that the lithology of the non-lithology corresponding section is caused;

and (3) auxiliary identification of under-mirror sheet observation: observing by combining the geological background, namely the deposition and diagenesis characteristics of the same layer near a research area or in the same basin, wherein the true rock debris has bright color and obvious rock debris edge angle under a mirror, the false rock debris has dark color and fuzzy rock debris edge angle under the mirror;

wherein the dynamic and static combination verification unit comprises: verifying logging parameters of corresponding depths, verifying geochemical analysis results, verifying microphase modes established by sedimentary phase sequences, verifying through perforation display on a single well and verifying through productivity;

and (3) verifying logging parameters of corresponding depths: firstly, performing core homing on a well with coring, reading logging curve values corresponding to different lithologies under the condition that the corresponding depths of the cores are not different, and then comparing the logging curve values with rock debris at corresponding depth sections to judge the reliability of the rock debris;

and (3) verifying the geochemical analysis result: selecting fresh rock debris particles to carry out geochemical analysis, and detecting whether continuous element composition changes or not in the longitudinal direction;

microphase mode verification of sedimentary phase sequence establishment: identifying the rock debris through the established deposition phase sequence, and removing the rock debris which does not accord with the deposition rule;

and (3) displaying and verifying through the perforation on a single well: the place where the comprehensive interpretation section is the gas layer is a dolomite reservoir, so the dolomite which is identified as true debris in the debris at the depth section is all the true debris;

and (4) passing capacity verification: the number of corresponding rock debris dolomite particles of a well with high productivity is large, so that a place with high productivity corresponds to a dolomite reservoir;

wherein the dolomitic sample preparation unit in the rock debris comprises: preparing a casting sheet, preparing a cathode luminescence sheet, preparing a geochemical sample and grinding an inclusion sheet;

preparing a casting body sheet: selecting rock debris particles with larger diameter and fresh lithology, wherein the rock debris is selected from large particles because of cast body treatment, and whether the rock debris corresponds to well logging is important, so that the rock debris is selected to be fresh, namely the surface of the rock debris has no scratch;

preparation of a cathodoluminescent sheet: cathodoluminescence needs to be finished under the condition of ion discharge, the cover sheet treatment can lead the cover sheet to be blue under a cathodoluminescence instrument, and the cover sheet can not be produced;

preparation of geochemical samples: selecting fresh and pure rock debris;

grinding an inclusion sheet: and after the casting body thin slice is finished, observing under a mirror, and determining the lithology, wherein the lithology is dolomite.

3. The improved system for determining the cause of dolomite according to the dolomite rock debris information as claimed in claim 1, wherein:

wherein the partition dolomite type unit:

according to the common rock debris slice, the types of the dolomites are divided, according to the grain size, the sedimentary structure and the rock structure, the types of the dolomites are divided into three categories of the crystalline dolomites, the speckled dolomites and the granular dolomites, the content of the clouded particles is counted,

crystalline dolomitic rock: the color is light gray or grey white, the block shape is formed, the size of the crystal grain is 0.25-1.0mm, and the rock component is mainly compact matrix crystal grain;

porphyry dolomitic rock: the rock is in a transition lithology between limestone and nephrite and is in a spot shape, the rock component consists of cloud and gray matter, the cloud part is darker and is gray and dark gray, the gray matter part is lighter and is light gray and gray white, and the size of the cloud plaque is 3-10mm;

granular dolomite: residual structures of sand scraps can be seen in the particles, the particle size is larger than 1.0mm, the particles have a haze center bright edge structure, the sand scraps can be seen under the thin sheets, and the abrasive rounding and sorting are moderate;

wherein the determination of Mn at dolomite formation is described ²⁺ Content unit:

mn in the formation of dolomite by dolomite cathodoluminescence signature according to cathodoluminescence sheet analysis ²⁺ The content is lower, which indicates that the early low-temperature stage is formed;

wherein the unit for determining the dolomite order degree:

fresh dolomite detritus is used for determining the dolomite order degree, the dolomite crystal characteristics are reflected through the dolomite order degree characteristics, the fine-powder crystal dolomite order degree is 0.69-0.82, the average is 0.75, the fine-medium crystal dolomite has medium order degree, the average order degree is 0.85, the medium-coarse crystal dolomite has high order degree, reaches 0.91, and is close to ideal dolomite;

wherein said defined pore throat building block:

and analyzing pores by using a cast body slice, analyzing a software image to determine a pore throat structure, importing a rock slice photo into the software, and automatically analyzing the pore and pore throat relation parameters by the software to form a result table.

4. The improved system for determining the cause of dolomite according to the dolomite rock debris information as claimed in claim 1, wherein:

wherein the element composition feature analysis unit:

determining element composition by using a selected fresh rock debris sample, and judging the diagenetic fluid property and diagenetic rock alteration strength of the dolomite through the analysis of the composition characteristics of the dolomite elements and the comparative analysis of the fine crystalline dolomite, the fine-medium crystalline dolomite, the medium-coarse crystalline dolomite and the trace elements of the marlite representing the seawater in the same period;

analyzing the composition of trace elements at different positions of single-particle dolomite, selecting 8 measuring points from the inside to the outside of the girdle band for element measurement, and measuring the content of the trace elements at each measuring point;

wherein the isotope composition characteristic analysis unit: determining the isotope composition of carbon, oxygen and strontium by using the selected fresh rock debris sample, and analyzing by using the isotope composition characteristics of dolomite;

isotope analysis of strontium: dolomitic rock ⁸⁷ Sr/ ⁸⁶ Of Sr and contemporaneous sea water ⁸⁷ Sr/ ⁸⁶ Sr is used for distinguishing the source of the dolomitic petrochemical fluid, ⁸⁷ Sr/ ⁸⁶ the Sr ratio is in the same-phase seawater Sr isotope composition range, which indicates that the seawater is a main dolomitic petrochemical fluid, otherwise, the seawater is an exogenous allopatric fluid;

carbon isotope analysis: delta. For the preparation of a coating ¹³ The C value indicates a deposition environment, the negative is an atmospheric fresh water environment, and the positive is a seawater environment;

oxygen isotope analysis: delta ¹⁸ O indicates the temperature, which is biased negative by the temperature increase;

wherein the brine inclusion homogeneous temperature and salinity determination is carried out by using the inclusion sheet of the fresh rock debris:

the uniform temperature of the inclusion is the instant temperature when the inclusion is heated artificially and is converted into a single-phase fluid from two phases when the temperature is raised to a certain degree;

the inclusion is impurities captured in the crystal growth process in the rock and can indicate the formation time and the formation environment of the rock;

saline inclusions refer to entrapped components as various salts.

5. The improved system for determining the cause of dolomite according to the dolomite rock debris information as claimed in claim 1, wherein:

the composition analysis and judgment are carried out by integrating the results obtained by the dolostone rock debris sample preparation module, the dolostone petrochemistry characteristic analysis module and the dolostone geochemistry characteristic analysis module;

wherein the fine crystalline dolomite formation analysis unit:

the exclusive indexes for identifying the fine crystalline dolomite formation are as follows: the cathode luminescence is dark red, the degree of order is low, the rare earth element distribution mode is similar to that of the limestone in the same period, ⁸⁷ Sr/ ⁸⁶ The Sr value is close to the seawater value of the same period, and the lime is formed by the quick clouding of the quasi-syngeneic mortar and the recrystallization in the shallow burial periodThe conclusion is that the fine crystalline dolomite is mainly formed by fast clouding of plaster in the quasi-syngenesis period, and recrystallization occurs in the shallow burial period;

wherein the fine-mesomorphic dolostone cause analysis unit comprises:

exclusive indexes for identifying the cause of the fine-medium crystal dolomite are as follows: the cathodoluminescence is red, the edge of the dolomite crystal is mottled bright red, the medium order degree and the rare earth element distribution mode are similar to those of contemporary limestone, ⁸⁷ Sr/ ⁸⁶ the Sr value is slightly higher than the seawater value in the same period, the Mn content is higher, the Sr/Ba ratio is low, and dolomite is formed in a buried diagenetic environment;

wherein the medium-coarse crystal dolomite formation analysis unit:

the exclusive indexes for identifying the cause of the medium-coarse crystal dolomite are as follows: the cathode luminescence is orange red, the dolomite crystal has obvious ring belt characteristics, medium to high order degree, high temperature uniformity of the inclusion, obvious positive abnormality of europium, ⁸⁷ Sr/ ⁸⁶ The Sr value is higher than the seawater value in the same period, the Mn content is higher, the Sr/Ba ratio is low, the dolomization is formed in a buried diagenetic environment, the dolomization is generated when the particle limestone is supplied by continuous and sufficient clouding fluid in the buried period, the crystallization speed is lower, and the clouding time is longer.

6. The improved system for judging the dolomite formation according to the dolomite debris information as recited in any one of claims 1 to 5, further comprising a core-taking well, if the research area has a core-taking well, comparing the core and the debris of the core-taking well in the research area, verifying the corresponding degree of the debris and the core, and judging the reliability of the debris so as to identify and observe the debris more accurately.