Method for identifying deepwater gravity flow cause based on directional arrangement of debris particles

Abstract

A method for identifying deepwater gravity flow causes based on directional arrangement of debris particles relates to the technical field of petroleum and natural gas exploration and development, and comprises the following steps: analyzing deepwater gravity flow deposition cause mechanisms by combining actual geological data of a to-be-detected area, selecting sandstone samples of different gravity flow cause mechanisms to obtain slice images, and preprocessing the slice images; performing quantitative statistics on the long-axis direction distribution conditions of the debris particles in the processed image of the sample slices, establishing a relationship between the long-axis direction distribution conditions of the debris particles of different sample slices and deepwater gravity flow deposition causes, and collecting the sample slices in other areas to perform statistics on the long-axis direction distribution conditions of the debris particles of the sample slices; obtaining deepwater gravity flow deposition causes of samples in other areas; according to the method, through quantitative statistical analysis of the blocky sandstone debris particles in the long axis direction, the relation between debris particle distribution and a gravity flow cause mechanism is established, the problem that the macroscopic characteristics of the blocky sandstone cannot reflect the gravity flow deposition cause is solved, and the time and cost required by related experimental analysis are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration and development, and in particular to a method for identifying the cause of deep-water gravity flow based on the directional arrangement of debris particles. Background Art

[0002] Deepwater gravity flow is the main driving mechanism for the transportation of terrestrial sediments to deepwater environments. It plays an important role in shaping deepwater sedimentary topography and sedimentary products. The deepwater sedimentary sand bodies formed by it are close to high-quality source rocks and are good oil and gas storage carriers. They have become the main targets of oil and gas exploration and development in recent years. At the same time, the formation of deepwater gravity flow requires a specific triggering mechanism and is controlled by many factors such as tectonic activities, climate evolution, volcanic action, and earthquake action. Therefore, its sedimentary products are excellent carriers for inverting paleogeographic information and event sedimentary information. The formation of deepwater gravity flow has multiple genetic mechanisms such as the collapse and re-transportation of shallow water sediments, continuous replenishment of flood hyperpycnal flow, and unloading and sedimentation of floating plumes. Deepwater gravity flow sediments with different genetic mechanisms have different sedimentary characteristics and sand body distribution laws. Therefore, clarifying the genetic mechanism of deepwater gravity flow and the distribution law of deepwater gravity flow sedimentary sand bodies under its control has become the main research content of oil and gas exploration and development. Due to the suddenness and strong destructiveness of deep-water gravity flow, it is very difficult to directly observe the formation mechanism of deep-water gravity flow. At present, the formation mechanism of deep-water gravity flow is mainly inferred based on the characteristics of deep-water gravity flow sedimentary products. Since there is no strict correspondence between sedimentary products and sedimentary processes, there are obvious multiple solutions in the research on inferring the formation mechanism based on sedimentary products. For example, in deep-water gravity flow sediments formed by different genetic mechanisms, massive sandstones with seemingly uniform internal structures are widely developed, and there are many genetic explanations such as high-density turbidity current deposits and sandy debris flow deposits. This shows that both turbulent and laminar sedimentary dynamic mechanisms can form massive sandstones. The difference is that laminar fluid forms massive sandstones in the form of overall consolidation, so the arrangement of its internal debris particles does not have obvious orientation; while turbulent fluid forms massive sandstones in the form of layer-by-layer superposition, and the arrangement orientation of its internal debris particles is more significant. In addition, the compaction effect after deposition may have a certain transformation on the orientation of debris particles, and it is not clear whether it affects the judgment of the deposition mechanism of massive sandstone. Therefore, in order to accurately distinguish the causes of deep-water gravity flow deposition, it is urgent to develop technical methods at the microscopic scale that conform to actual geological conditions, have simpler analysis schemes, lower analysis costs, and more accurate analysis results. Summary of the invention

[0003] In view of this, the present invention proposes a method for identifying the cause of deepwater gravity flow based on the oriented arrangement of debris particles. On the premise of fully considering the genetic mechanism of deepwater gravity flow, the method focuses on solving the key problem of the unknown origin of deepwater massive sandstone, and provides a basis for accurately dividing the genetic mechanism of deepwater gravity flow based on sediment characteristics.

[0004] In order to solve at least one of the above technical problems, the technical solution provided by the present invention is a method for identifying the cause of deep-water gravity flow based on the directional arrangement of debris particles, comprising the following steps:

[0005] Step S1: extracting actual geological data of the area to be tested and analyzing the deep-water gravity flow deposition mechanism of the sample;

[0006] Step S2: Select typical sandstone samples with different gravity flow genesis mechanisms to prepare sample slices, acquire images and perform preprocessing to obtain processed images;

[0007] Step S3: quantitatively counting the distribution of the long axis direction of the debris particles in the image after the sample thin slice processing, and establishing the relationship between the statistical results of the long axis direction distribution of the debris particles in different sample thin slices and the cause of deep-water gravity flow deposition;

[0008] Step S4: Collect thin sections of samples from other areas, quantitatively calculate the distribution of the long axis direction of the debris particles, and derive the deep-water gravity flow deposition causes of samples from other areas based on the relationship described in step S3.

[0009] The technical effects of the present invention are:

[0010] (1) Through quantitative statistical analysis of the long axis direction of massive sandstone debris particles under a microscope, the relationship between the distribution of debris particles and the gravity flow mechanism was established based on the angle and number of the dominant inclination of particles in thin sections, which effectively solved the problem that the macroscopic characteristics of massive sandstone cannot reflect the cause of gravity flow deposition.

[0011] (2) The fluid genesis mechanism is identified by microscopic statistics of the debris particles in blocky sandstone thin sections. This method is simple and efficient, has strong universality and operability, and can effectively reduce the time and cost required for experimental analysis related to the classification of deep-water gravity flow sedimentation dynamic mechanisms. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0013] Figure 1 It is a specific flow chart of the present invention;

[0014] Figure 2 This is a diagram depicting the spatial distribution characteristics of deepwater gravity flow sediments in a certain area of ​​Shengli Oilfield in the present invention;

[0015] Figure 3This is a diagram of the classification of deepwater gravity flow sedimentary facies types in a certain area of ​​Shengli Oilfield in the present invention;

[0016] Figure 4 This is a deepwater gravity flow sedimentary lithofacies combination sequence and sedimentary environment interpretation diagram of a certain area of ​​Shengli Oilfield in the present invention;

[0017] Figure 5 A is a schematic diagram of the observation area of ​​an actual sample slice under a microscope in the present invention;

[0018] Figure 5 B is a distribution diagram of the divided images in the microscopic observation area of ​​the actual sample slice in the present invention;

[0019] Figure 5 C is a mosaic of the divided pictures in the microscopic observation area of ​​the actual sample slice in the present invention;

[0020] Figure 6 This is an example diagram of the identification of debris particles and the statistics of the major axis direction in the actual sample slice of the present invention;

[0021] Figure 7 This is an example diagram of quantitative statistics of the major axis orientation of debris particles in the actual sample slices of the present invention;

[0022] Figure 8 This is the overall quantitative statistical rose diagram of the overall long axis direction of the sandy block sandstone of the actual sample of Niu 110 well in the present invention;

[0023] Fig. 9 This is the overall quantitative statistical rose diagram of the overall long axis direction of the blocky sandstone of the actual sample of Well Shi 110 in the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below in conjunction with the embodiments and drawings.

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention.

[0026] A method for identifying the cause of deep-water gravity flow based on the directional arrangement of debris particles comprises the following steps:

[0027] Step S1: extract the actual geological data of the area to be tested, and analyze the deep-water gravity flow deposition mechanism of the sample, wherein the deep-water gravity flow deposition mechanism mainly includes flood hyperpycnal flow deposition cause and sediment collapse and re-transport cause.

[0028] Among them, the steps for analyzing the deep-water gravity flow deposition mechanism of samples mainly include:

[0029] 1) Using actual geological data and combining basic core observation and analysis, summarize the location, stratigraphic structure, and distribution characteristics of deepwater gravity flow deposits. The actual geological data include core, well logging, and 3D seismic data;

[0030] 2) Conduct analysis on the composition, grain size, and sedimentary structural characteristics of the cores, and further analyze the lithofacies, lithofacies combination types, and lithofacies combination sequences. Based on the distribution characteristics and lithofacies analysis, clarify the genetic mechanism of deep-water gravity flow deposition.

[0031] Step S2: Select typical sandstone samples of different gravity flow genesis mechanisms to prepare sample slices, acquire images and perform preprocessing to obtain processed images.

[0032] Among them, the steps of preprocessing the image are:

[0033] 1) Obtaining a magnified image of the sample slice, the magnification is 5 to 40 times, and the specific magnification is determined according to the actual distribution of particles in the sample slice, selecting 9 pictures distributed in a nine-square grid in the center of the image, and performing inverted splicing on the pictures, wherein the inverted splicing method is to use the center picture of the nine-square grid as the axis, and respectively exchange the positions of the two pictures located at the axis position;

[0034] 2) Identify no less than 60 debris particles in each grid area of ​​the inverted spliced ​​nine-grid image.

[0035] Step S3: quantitatively counting the distribution of the long axis direction of the debris particles in the image after the sample thin section processing, and establishing the relationship between the statistical results of the long axis direction distribution of the debris particles in different sample thin sections and the cause of deep-water gravity flow deposition.

[0036] Wherein, the step of quantitatively counting the distribution of the long axis direction of the debris particles in the image after the sample slice is processed in step S3 is:

[0037] 1) Observe the longest straight line that can exist on the plane of the debris particles identified in each grid area of ​​the nine-grid image, and use it as the long axis of the debris particles;

[0038] 2) Then draw a semicircular base map in the drawing software, overlap and intersect the center of the long axis of all debris particles with the center of the semicircular base map, take the 10° sector surface in the semicircular base map as one grid, and count the number of long axes of debris particles contained in each grid within the range of 0 to 180°.

[0039] Step S4: Collect thin sections of samples from other areas, quantitatively calculate the distribution of the long axis direction of the debris particles, and derive the deep-water gravity flow deposition causes of samples from other areas based on the relationship described in step S3.

[0040] Example:

[0041] The specific technical scheme of the invention is illustrated by taking the quantitative statistical method of the long axis direction of massive sandstone debris particles deposited by deep-water gravity flow of different origins in a certain area of ​​Shengli Oilfield as an example.

[0042] 1. First, based on the actual geological conditions and sample test and analysis data, determine the mechanism of deep-water gravity flow deposition. The specific steps are as follows:

[0043] (1) Using core data, well logging, 3D seismic data, and basic core observation and analysis, the location, stratigraphic structure, and distribution characteristics of deepwater gravity flow deposits were summarized.

[0044] See Figure 2 According to the characteristics of large sets of thick stable mudstone intercalated with local sandstone development shown in the logging data, the well locations where gravity flow deposits developed were determined. Geoframe software was used to make synthetic records through the acoustic time difference logging curve, and the logging information was integrated with the three-dimensional seismic information to clarify the location of the gravity flow deposit development site in the seismic profile. According to the sedimentary structural background indicated by different seismic profiles, Niu110, a representative well for gravity flow deposits close to the delta front, with discontinuous and worm-like seismic reflection characteristics in the delta bottom accumulation layer, and Shi100, a representative well for gravity flow deposits, which has nothing to do with the delta front accumulation, is flat as a whole, and has significant downcut and upcut seismic reflection characteristics, were selected to carry out sedimentary characteristics and lithofacies analysis related to gravity flow sediment cores.

[0045] (2) The composition, grain size, sedimentary structure and other characteristics of the cores were studied, and further analysis of lithofacies, lithofacies combination types and lithofacies combination sequences was carried out. Based on the distribution characteristics and lithofacies analysis, the genetic mechanism of deep-water gravity flow deposition was clarified.

[0046] The cores in the range of 3000.5-3022.35m of Niu110 well and 3066.5-3093m of Shi100 well were analyzed in terms of composition, grain size, sedimentary structure and other characteristics. The gravity flow sediments in Niu110 well are mainly composed of fine sandstone, while the grain size of the gravity flow sediments in Shi100 well is large, including fine conglomerate, gravelly sandstone, medium-coarse sandstone and fine sandstone. The gravity flow sediments in the two wells are mainly composed of lithic feldspar sandstone.

[0047] The soft sediment deformation structure, massive structure and normal grain sequence are well developed in the gravity flow sediments of Well Niu110; the bottom scour structure, parallel bedding, reverse normal grain sequence, sand ripple bedding and massive structure are well developed in the gravity flow sediments of Well Shi100.

[0048] According to the combination relationship of sediment grain size and sedimentary structure, the deep-water gravity flow sediments in the study area can be divided into four main types: gravel-bearing sandstone phase, sandstone phase, muddy sandstone phase and mudstone phase. Then, according to the differences in sedimentary structure and contents, they can be further subdivided. The main types include: massive bedding gravel sandstone phase, massive bedding sandstone phase, normal grain sequence bedding sandstone phase, reverse grain sequence bedding sandstone phase, parallel bedding sandstone phase, ripple bedding sandstone phase, banded sandstone phase, deformation structure sandstone phase, clastic mudstone phase, rhythmic siltstone phase, mudstone phase and other main types. For example, Figure 3 shown.

[0049] Then, according to the vertical combination relationship of lithofacies reflected in the cores of Well Shi100 and Well Niu110, the lithofacies combination sequences were classified and summarized. Well Shi100 mainly develops three types of lithofacies combination sequences, namely, the vertical superposition of gravel-bearing coarse sandstone facies and normal-sequence medium-coarse sandstone facies developed at the scour interface, the vertical superposition of fine sandstone facies with sand-ribbed bedding, massive bedding sandstone facies and reverse normal-sequence sandstone facies, and the vertical superposition of fine sandstone facies with parallel bedding and normal-sequence bedding sandstone facies, which correspond to gravity flow channel deposits, embankment deposits, and lobe deposits, respectively. Well Niu110 mainly develops three types of lithofacies combination sequences, namely, the vertical superposition of sandstone facies with deformation structure development, the vertical superposition of massive bedding sandstone facies, and the vertical superposition of banded sandstone facies and clastic mudstone facies, which correspond to sliding slump deposits, tongue-shaped deposits, and tongue-shaped distal deposits, respectively. Figure 4 shown.

[0050] Based on the above different lithofacies combination sequences and distribution characteristics, different gravity flow genesis mechanisms are indicated. There is no obvious correlation between the gravity flow deposits of Shi100 Well and the delta. According to the lithofacies combination sequence and its planar distribution relationship, it is believed that it has the typical characteristics of gravity flow channel development, reverse normal grain sequence sandstone development, and carbonaceous debris development. Therefore, the deep-water gravity flow deposition mechanism in the area where Shi100 Well is located is mainly flood hyperpycnal flow deposition.

[0051] The Niu110 gravity flow deposits are closely related to the delta foreset layers. According to the lithofacies combination sequence and its planar distribution relationship, it is believed that it has the typical characteristics of developed sliding and slump structures, massive sandstones and banded sandstones. Therefore, the deep-water gravity flow deposits in the area where the Niu110 well is located are mainly caused by sediment collapse and re-transportation.

[0052] Second, thin sections of typical samples of massive sandstone formed by different gravity flow mechanisms were ground and imaged and preprocessed using a microscope. The specific steps are as follows:

[0053] Based on the previous research on the mechanism of gravity flow, massive sandstones formed by gravity flow caused by sediment collapse and transportation and gravity flow caused by continuous supply of flood hyperpycnal flow were selected, and two groups of samples were taken from the middle and upper parts of massive sandstones and the middle and lower parts of massive sandstones and numbered. The massive sandstones formed by gravity flow caused by sediment collapse and transportation are numbered Niu110-1 and Niu110-2; the massive sandstones formed by gravity flow caused by continuous supply of flood hyperpycnal flow are numbered Shi100-1 and Shi100-2.

[0054] For the above four groups of blocky sandstone samples with different numbers, ordinary thin sections were ground respectively, and the thin sections of typical samples were observed under the microscope using a Zeiss AxioscopeA1APOL. digital transmission and reflection polarization microscope. In order to avoid damage and interference to the edge of the thin section caused by the manual grinding process, the following observation range was selected: Figure 5 The center of the slice shown in A was observed, and the slice was magnified 20 times to obtain an image using Axio Vision Software Rel. Image analysis software. After selecting a designated area, the following analysis was performed in the area: Figure 5 The nine-square grid format shown in B is divided into 9 adjacent pictures and numbered 1.1, 1.2, 1.3, 2.1, 2.2, 2.3, 3.1, 3.2, and 3.3 respectively. Reference objects are selected at the edge of each picture to ensure continuity, and the selected reference objects are overlapped when the pictures are spliced.

[0055] Afterwards, according to the actual Figure 5 The position shown in C is re-jigged, and the software image is reversed and spliced ​​corresponding to the actual position according to the actual position of the thin film, that is, the position of the two images in the alignment is exchanged respectively with the image numbered 2.2 as the central axis.

[0056] Then, combined with the optical characteristics of mineral crystals, the non-particle fillings, pores, bubbles formed during the slice production process, epoxy resin contamination, etc. in the 9 spliced ​​pictures were identified. The specific identification and classification examples are as follows: Figure 6 As shown. Figure 6 It can be seen that the filling material has no obvious particle morphology, including two types: cementing material and impurity matrix. It is colorless or brown under single polarized light and has certain interference colors under orthogonal light. The pores are mainly colorless and transparent under single polarized light and completely extinct under orthogonal light. Bubbles and epoxy resin contaminants are mostly round or ellipsoidal and obscure the debris particles.

[0057] Based on statistical analysis, under the premise of ensuring efficiency and accuracy, a single slice with a count of about 300 particles can represent the distribution characteristics of the debris particles in the entire slice. Therefore, more than 60 particles were selected from the areas selected in the 9 pictures, and about 550 particles were selected for the entire slice to draw the long axis direction. The long axis is the longest straight line that can exist in the plane of the debris particles, which is convenient for subsequent quantitative statistics of the long axis direction of the debris particles.

[0058] 3. Quantitative statistics of the long axis direction of clastic particles at the microscopic scale. Using a microscope and CorelDraw drawing software, quantitative statistics were performed on the long axis direction of particles in massive sandstone thin sections formed by gravity flow of different genetic mechanisms. When counting, the 9 pictures in the above-mentioned whole thin section were counted separately, so that the subsequent statistics of the same thin section from bottom to top, from left to right and overall trends can be counted.

[0059] After drawing the long axis direction of a sufficient number of particles in the thin slice image, statistical analysis of the long axis tendency is performed. In order to facilitate statistics, CorelDraw drawing software is still used for counting. First, draw a statistical base map with a 180° semicircle, copy the long axis of the particles in each area to the statistical base map, and use the "Object-Alignment and Distribution-Vertical Center Alignment, Horizontal Center Alignment" in the software toolbar to fix the center of all long axes. Use the horizontal and vertical coordinate values ​​of the auxiliary lines to magnify the long axes of all particles by appropriate multiples and align the center with the center point of the base map circle. The effect after alignment is as follows Figure 7 As shown, the direction of the long axis of each particle is counted in the semicircular statistical base map, and the statistical range is 0-180°. When counting, each sector surface of 10° is a statistical range, and the integers with range boundaries are counted to the adjacent smaller range, such as 20° is counted within 10-20°, and 0 or 180° are counted within 0-10°. The above statistical operations are performed on a total of 4 thin slices of Niu110-1, Niu110-2, Shi100-1, and Shi100-2, that is, a total of 36 statistical areas.

[0060] Fourth, the results of the statistical analysis of the orientation of particles observed under a microscope were used to draw and analyze the plates to clarify the deposition mechanism of massive sandstone and the gravity flow deposition mechanism. According to the results of the statistical analysis of the orientation of particles observed under a microscope, the distribution diagram of the long axis direction of particles in three directions, namely the overall direction of the thin section, the horizontal partition of the thin section, and the vertical partition of the thin section, was drawn. The division was based on the dominant inclination angle and quantity of the particles, so as to achieve an accurate division of the dynamic mechanisms of the deposition of massive sandstones of different origins.

[0061] Based on the quantitative overall statistical results of the long axis direction of the massive sandstone (Niu110 well) formed by the gravity flow caused by sediment collapse and transport and the massive sandstone (Shi100 well) formed by the gravity flow caused by the continuous supply of flood hyperpycnal flow observed under the microscope, the quantitative statistical rose diagrams of the long axis direction of the thin section grains of the two massive sandstone samples were drawn respectively, as shown in the following figure. Figure 8 and Fig. 9 shown.

[0062] Depend on Figure 8 It can be seen that the long-axis arrangement characteristics of the debris particles in the two samples of Well Niu110 are very similar. Debris particles with different inclinations are all developed, and there is no obvious dominant direction of the long-axis inclination of the particles. The overall indication is that the arrangement of the debris particles is relatively disordered and has no obvious directionality. Therefore, the deep-water gravity flow deposition cause of the samples with such long-axis arrangement characteristics is associated with the sediment collapse and re-transport cause.

[0063] According to Fig. 9 It can be seen that there are great differences in the long-axis arrangement characteristics of the debris particles in the two samples of Well Shi100. There is an obvious dominant direction of the long-axis inclination of the particles, and there are certain differences in the dominant directions of the long-axis inclination of particles in different samples, indicating that the arrangement of debris particles has obvious directionality. Therefore, the deep-water gravity flow deposition origin of samples with such long-axis arrangement characteristics is associated with the flood hyperpycnal flow deposition origin.

[0064] For other areas, after thin-section sampling, the same quantitative statistics of the long-axis distribution of the debris particles as in the above steps are carried out. If the long-axis arrangement characteristics of the debris particles of the sample match the above-mentioned correlation results, the deep-water gravity flow deposition cause associated with the long-axis arrangement characteristics can be used as the deep-water gravity flow deposition cause of the sampling area.

[0065] It can be seen that the directional arrangement characteristics of the long axis direction of the debris particles inside the massive sandstone can be used as an important basis for identifying the genetic mechanism of deep-water gravity flow. Specifically, the massive sandstone formed by the gravity flow caused by sediment collapse and transportation is mainly formed by sandy debris flow deposition. Due to the plastic rheological properties of sandy debris flow, the transported sediments are unloaded as a whole in the form of block consolidation, resulting in the internal debris particles not having time to be oriented and directly settling, so the long axis direction of the debris particles does not have an obvious directional advantage. The massive sandstone formed by the gravity flow caused by the continuous supply of flood hyperpycnal flow is mainly formed by the hyperpycnal flow deposition dominated by the bed load. Due to the transportation form of the bed load of the hyperpycnal flow, the debris particles are rapidly stacked and settled layer by layer. The debris particles will have obvious directional arrangement in the process of friction and migration with the bed. Therefore, the macroscopic massive sandstone formed by it has obvious directional arrangement in the long axis direction of microscopic debris particles, and the similarity of the directional arrangement of the long axis tendency of debris particles in different regions indicates that it is an inherent property inside the sediment, which can be used as a reliable identification mark of the sedimentary dynamics and formation process, and will not be destroyed by compaction and chemical diagenesis. Therefore, the quantitative statistical identification of the arrangement of the long axis direction of massive sandstone debris particles can be used as an effective basis for the discrimination of the genetic mechanism of deep-water gravity flow.

[0066] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for identifying the origin of deep-water gravity flow based on the directional arrangement of debris particles, characterized in that: The following steps are involved: Step S1: extracting actual geological data of the area to be tested and analyzing the deep-water gravity flow deposition mechanism of the sample; Step S2: Select typical sandstone samples with different gravity flow genesis mechanisms to prepare sample slices, acquire images and perform preprocessing to obtain processed images; Step S3: quantitatively counting the distribution of the long axis direction of the debris particles in the image after the sample thin slice processing, and establishing the relationship between the statistical results of the long axis direction distribution of the debris particles in different sample thin slices and the cause of deep-water gravity flow deposition; Step S4: Collect thin sections of samples from other areas, quantitatively calculate the distribution of the long axis direction of the debris particles, and derive the deep-water gravity flow deposition causes of samples from other areas based on the relationship described in step S3.

2. A method for identifying the cause of deep-water gravity flow based on the directional arrangement of debris particles according to claim 1, characterized in that: The step of analyzing the deep-water gravity flow deposition mechanism of the sample in step S1 includes: 1) Using actual geological data and combining basic core observation and analysis, summarize the location, stratigraphic structure, and distribution characteristics of deepwater gravity flow deposits. The actual geological data include core, well logging, and 3D seismic data; 2) Conduct analysis on the composition, grain size, and sedimentary structural characteristics of the cores, and further analyze the lithofacies, lithofacies combination types, and lithofacies combination sequences. Based on the distribution characteristics and lithofacies analysis, clarify the genetic mechanism of deep-water gravity flow deposition.

3. The method for identifying the cause of deep-water gravity flow based on the directional arrangement of debris particles according to claim 1, characterized in that: The deep-water gravity flow deposition mechanism described in step S1 includes flood hyperpycnal flow deposition and sediment collapse and re-transportation deposition.

4. The method for identifying the cause of deep-water gravity flow based on the directional arrangement of debris particles according to claim 1, characterized in that: The steps of preprocessing the image in step S2 are: 1) Obtaining an enlarged image of the sample slice, selecting 9 pictures distributed in a nine-square grid in the center of the image, and performing inverted splicing on the pictures, wherein the inverted splicing method is to use the center picture of the nine-square grid as the axis and exchange the positions of the two pictures located at the axis positions respectively; 2) Identify no less than 60 debris particles in each grid area of ​​the inverted nine-grid image.

5. A method for identifying the cause of deep-water gravity flow based on the directional arrangement of debris particles according to claim 4, characterized in that: The sample slice image has a magnification of 5 to 40 times.

6. The method for identifying the cause of deep-water gravity flow based on the directional arrangement of debris particles according to claim 4, characterized in that: The step of quantitatively counting the distribution of the long axis direction of the debris particles in the image after the sample slice is processed in step S3 is: 1) Observe the longest straight line that can exist on the plane of the debris particles identified in each grid area of ​​the nine-grid image, and use it as the long axis of the debris particles; 2) Then draw a semicircular base map in the drawing software, overlap and intersect the center of the long axis of all debris particles with the center of the semicircular base map, take the 10° sector surface in the semicircular base map as one grid, and count the number of long axes of debris particles contained in each grid within the range of 0 to 180°.

Images