Method for contrasting red beds by quantitative spore-pollen facies division

Abstract

The present application belongs to the technical field of oil and gas exploration, and particularly relates to a method for quantitatively dividing and contrasting red beds by spore-pollen facies. The method comprises the following steps: collecting samples; adding dyed modern lycopodium spore pieces to the collected samples respectively, and preparing slices; identifying and counting the particle numbers of each organic matter type and the numbers of modern lycopodium spores in the sample slices; calculating the amorphous organic matter abundance and total organic matter abundance of each sample, and drawing the abundance variation curves respectively; finding the maximum division point according to the variation curves of the amorphous organic matter abundance and the total organic matter abundance, and establishing the standard for dividing red beds. The present application realizes the division and isochronal correlation of red beds, effectively solves the problems existing in the division and correlation of red beds by other methods, has the advantages of strong practicability, strong generalizability and the like, and can provide the most basic and most important basis for fine exploration of red beds, and has achieved good effects in practical application.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of oil and gas exploration, and particularly relates to a method for quantitatively dividing and contrasting red beds by using sporopollen facies. BACKGROUND

[0002] Red beds generally refer to clastic rock sedimentary strata with red as the main color tone, which are mainly formed in a hot and dry geological period, and are relatively poor in paleontology. Due to the wide distribution, large lateral thickness variation, and rapid lithology change, it is difficult to establish stable division and contrast marks by using existing stratigraphic division and contrast methods. Many red beds become "dumb strata", especially the internal division and lateral isochronous correlation of red beds, which are difficult. In recent years, with the deepening of exploration, industrial oil flows have been found in red beds one after another, and red bed exploration has gradually become the focus, and the stratigraphic division restricts the deepening of exploration and the determination of reserve scale.

[0003] Due to the general lack of paleontology in red beds, the existing stratigraphic division and contrast methods have limitations, especially without isochronism, which brings great difficulty to the correlation of red beds in the region.

[0004] CN111198406A discloses a factor analysis logging lithology identification method for red bed reservoirs. The method analyzes the geological background and sedimentary facies of the study area, establishes the correspondence between lithology and logging response characteristics in combination with core analysis, analyzes logging response data by using factor analysis method, extracts public factors that can cover original logging information by constructing new variable R to perform factor analysis on red bed reservoirs, and constructs factor score equation to preliminarily divide the lithology of red bed reservoirs. Further factor analysis is performed on the core in combination with the lithology of the cored well section in the study area to obtain the factor score intersection diagram and discrimination equation after fine division, and the fine division of the lithology of red bed reservoirs is completed. The method is mainly aimed at the fine division of the lithology of red beds, and does not involve the division and correlation of red beds.

[0005] CN114428358A discloses an isochronous stratigraphic division method, which comprises the following steps: step 1, collecting and arranging the basic geological data of the study area, comparing the comprehensive data of each well, and selecting the well with complete drilled horizon, comprehensive logging curve and most developed marker layer as the standard well; step 2, collecting and arranging the thin section identification data and / or element component data of multiple wells, taking the inflection point of the content mutation of the detrital component near the standard layer interface in the standard well as the first difference feature of stratigraphic division; taking the inflection point of the content mutation of the element component analysis data as the second difference feature of stratigraphic division; marking the depth position corresponding to the first difference feature and / or the second difference feature as the reference basis for dividing the marker layer; step 3, extracting the difference features of the detrital component and / or element component analysis of the marker layer as the reference basis for dividing the horizon of other wells, and completing the stratigraphic division of a single well; step 4, building the stratigraphic framework of the study area; by combining geological stratification with seismic reflection characteristics, the isochronous stratigraphic division of the whole area is realized. This method mainly uses logging, thin section, element and other data to divide and compare the strata according to the content change inflection point, and the isochronous nature of the red layer of the multi-source continental red layer is difficult to guarantee. SUMMARY

[0006] To solve the above problems, the present application provides a method for quantitatively dividing and comparing red layers by spore phase. The method can achieve red layer division and comparison, and is simple, economical and practical to operate.

[0007] To achieve the above purpose, the present application adopts the following technical solution:

[0008] The present application provides a method for quantitatively dividing and comparing red layers by spore phase, which comprises the following steps: collecting samples; adding dyed modern lycopodium spores to each collected sample to make a slice; identifying and counting the number of each type of organic matter and the number of modern lycopodium spores in the sample slice; calculating the abundance of amorphous organic matter and total organic matter in each sample, and drawing the abundance change curve; finding the maximum distinguishing point according to the change curve of the abundance of amorphous organic matter and total organic matter, and establishing a standard for dividing red layers.

[0009] Compared with the prior art, the present application has the following advantages:

[0010] The method of the present application can not only divide red layers, but also solve the isochronous problem of red layer comparison. Because the changes of source, climate and water body in a certain area are consistent, the abundance of organic matter in the strata is consistent, and the red layer of a well can be divided according to the change trend of total organic matter or the abundance of each type of organic matter, or the standard value of the abundance of one or more types of organic matter can be determined, and the red layers of all wells in the block are divided according to the same standard, which has isochronous nature.

[0011] The present application realizes the division and isochronous correlation of red beds, effectively solves the limitation problems of other methods in the division and correlation of red beds, has the advantages of strong practicability and strong generalization, and can provide the most basic and important basis for fine exploration of red beds, and good results are achieved in practical application. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 A quantitative sporopollen facies analysis result graph for well XX1. DETAILED DESCRIPTION

[0013] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0014] It is to be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and / or "including", when used herein, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0015] To overcome the problems described in the background art, the present application provides a method for quantitatively dividing and correlating red beds by sporopollen facies, characterized in that it comprises the following steps: collecting samples; adding dyed modern lycopodium spore tablets to the collected samples respectively, and preparing tablets; identifying and counting the number of each organic matter type and the number of modern lycopodium spores in the sample tablets; calculating the amorphous organic matter abundance and total organic matter abundance of each sample, and drawing the abundance variation curves respectively; finding the maximum division point according to the variation curves of the amorphous organic matter abundance and the total organic matter abundance, and establishing a standard for dividing red beds.

[0016] As a preferred embodiment, unpolluted mudstone samples at different depths are collected, crushed, weighed, and 1 modern lycopodium spore tablet is added.

[0017] As a preferred embodiment, the sample numbers are arranged from shallow to deep according to the depth.

[0018] As a preferred embodiment, the number of organic matter particles is counted based on 1 modern lycopodium spore when counting.

[0019] As a preferred embodiment, the diameter of the modern lycopodium spore is 30-40 μm.

[0020] As a preferred embodiment, the organic matters include water source amorphous, land source amorphous, degraded wood, non-degraded wood, chitinous, cutin, spore, pollen, chrysophytes, agamont, fresh water algae, other algae, and undefined spore type.

[0021] As a preferred embodiment, the abundance of each organic matter is calculated by the following formula:

[0022] Organic matter abundance=(statistical organic matter particle number*added modern lycopodium spore number) / (statistical modern lycopodium spore number*sample gram number);

[0023] The total organic matter is the sum of the abundance of each organic matter.

[0024] As a preferred embodiment, the maximum change point in the change curve of the abundance of each organic matter and the total organic matter is found, and the characteristics of the organic matter on both sides of the change point are established, which is the standard for dividing the red layer. The red layer of all wells in the block is divided according to the same standard.

[0025] In order for those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below with specific examples.

[0026] Example 1

[0027] A method for quantitatively dividing and contrasting red layers by spore-pollen phase, comprising the following steps:

[0028] Step 1, collecting uncontaminated mudstone samples at different depths, crushing the samples, and weighing; adding 1 dyed modern lycopodium spore piece to each sample, and the 1 modern lycopodium spore piece contains 27560 lycopodium spores; the sample numbers are arranged according to the depth from shallow to deep;

[0029] Step 2, pretreating the samples: pretreating according to the standard for analyzing and identifying fossil spores and pollen in the petroleum industry;

[0030] Step 3, slicing the pretreated samples, and using a binocular biological microscope, taking 1 modern lycopodium spore (30-40 μm in diameter) as a benchmark, respectively counting the particle numbers of water source amorphous, land source amorphous, degraded wood, non-degraded wood, chitinous, cutin, spore, pollen, chrysophytes, agamont, fresh water algae, other algae, and undefined spore type, and simultaneously counting the particle number of modern lycopodium spores.

[0031] Step 4, respectively calculating the abundance of each organic matter and the total organic matter abundance according to the formula "organic matter abundance=(statistical organic matter particle number*added modern lycopodium spore number) / (statistical modern lycopodium spore number*sample gram number)", and respectively drawing the abundance change curve according to the sample number order;

[0032] Step 5: Based on the variation curves of amorphous organic matter abundance and total organic matter abundance, find the point of maximum differentiation and establish the standard for classifying red beds. Identify the point of maximum change in the variation curves of each organic matter and total organic matter abundance, and establish the organic matter characteristics on both sides of this point of change, which are the standards for classifying red beds. Red beds in all wells within the block are classified according to the same standard.

[0033] Example 2

[0034] Taking the southern slope of the Dongying Depression in the Jiyang Depression as an example, the method for quantitative pollen facies classification and contrasting red beds is explained.

[0035] This area is located in the lower section of the fourth segment of the Shixin Tongshahe Street Group (referred to as Sha Si Xia, Es4). 下 Red beds are widely developed in the Kongdian Formation (Ek1), and the boundary between the lower part of Sha-4 and Kong1 has been controversial.

[0036] First, we selected a well with a relatively large number of core samples taken from the red layer section—Well ××1. A total of 41 mudstone core samples were collected and analyzed, and the sample numbers were arranged from shallow to deep.

[0037] The samples were crushed, weighed, and one modern lycophyte spore tablet was added. The samples were then pretreated according to the petroleum industry standards for fossil pollen analysis and identification.

[0038] Prepare slides of the processed samples and use a binocular biological microscope to count the number of amorphous spores from aquatic sources, terrestrial sources, degraded lignin, undegraded lignin, chitin, cutin, spores, pollen, dinoflagellates, dinoflagellates, freshwater algae, other algae, and amorphous spore types, using one modern lycophyte spore (30μm-40μm in diameter) as a baseline. Also count the number of modern lycophyte spores that were added.

[0039] The abundance of each organic matter and the total organic matter abundance are calculated according to the formula: "Organic matter abundance = (number of counted organic grains * number of added modern lycophyte spores) / (number of counted modern lycophyte spores * sample weight)".

[0040] The abundance variation curves of total organic matter and amorphous organic matter (water source + terrestrial source) are shown in the figure below (due to the uneven core sampling depth, the horizontal axis of the figure below represents the sample number to better reflect the variation trend):

[0041] Depend on Figure 1 It can be seen that the total organic matter abundance changes from high to low and then back to high, which is consistent with the climate change from semi-arid to arid and then to semi-arid-semi-humid during the deposition period. The depth of sample 21 is the turning point. The climate at this depth was the driest during the deposition period, which can be used as the dividing line between Es4 and Ek1.

[0042] Ek1 amorphous organic matter is generally less than 1000 particles / g, Es4 下The amorphous organic matter is generally greater than 1000 particles / g. Other wells in the area can be divided into red beds according to this method. Within a certain area, the climate changes are consistent, and the boundaries of each well divided according to this method have isochronous properties, and can be isochronously compared.

[0043] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are all included in the protection scope of the present application.

Claims

1. A method for quantitatively contrasting red beds by spore-pollen facies division, characterized in that, The method comprises the following steps: Collecting samples; Adding dyed modern lycopodium spore tablets to the collected samples respectively to make tablets; Identifying and counting the number of each type of organic matter and the number of modern lycopodium spores in the sample tablets; Calculating the abundance of each sample amorphous organic matter and total organic matter, and drawing the abundance change curve in the order of sample number respectively, and calculating the abundance of each organic matter by using the following formula: Organic matter abundance = (the number of counted organic matter particles * the number of added modern lycopodium spores) / (the number of counted modern lycopodium spores * the sampling weight); Finding the maximum division point according to the change curve of the amorphous organic matter abundance and the total organic matter abundance, and establishing the standard for dividing the red layer.

2. The method for quantifying spore load phase division contrast red layer according to claim 1, characterized in that, Collecting uncontaminated mudstone samples at different depths, crushing the samples, weighing, and adding 1 modern lycopodium spore tablet.

3. The method for quantifying spore load phase division contrast red layers according to claim 1 or 2, characterized in that, The sample numbers are arranged from shallow to deep according to the depth.

4. The method for quantifying spore load phase division contrast red layer according to claim 1, characterized in that, The number of each type of organic matter particle is counted based on the size of 1 modern lycopodium spore.

5. The method for quantifying spore load phase division contrast red layer according to claim 4, characterized in that, The diameter of the modern lycopodium spore is 30-40 μm.

6. The method for quantifying spore load phase division contrast red layer according to claim 1, characterized in that, The organic matter includes amorphous organic matter, degraded wood, undegraded wood, chitin, cutin, spores, pollen, chrysophytes, acritarchs, freshwater algae, other algae, and undefined spore types.

7. The method for quantifying spore load phase division contrast red layer according to claim 1, characterized in that, The total organic matter abundance is the sum of the abundance of each organic matter.

8. The method for quantifying spore load phase division contrast red layer according to claim 1, characterized in that, The maximum change point in the change curve of the amorphous organic matter abundance and the total organic matter abundance is found, and the characteristics of the organic matter on both sides of the change point are established respectively, which is the standard for dividing the red layer.

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