A flume experiment method for analyzing the controlling factors of sediment collapse and retransportation process.

Abstract

This invention discloses a flume experiment method for analyzing the controlling factors of sediment caving and retransportation processes, belonging to the field of sedimentary experimental technology. The method includes the following steps: identifying the controlling factors of a specific sediment caving and retransportation process based on literature review; designing flume experiment parameters according to the principle of equivalent experiments; conducting single-factor flume experiments with different controlling factors as single variables to simulate the sediment caving and retransportation process under different controlling factors; obtaining the initiation conditions and distribution characteristics of sediment caving and retransportation under different controlling factors; and quantitatively summarizing the control effects of different controlling factors on the sediment caving and retransportation process. This invention effectively solves the problem that traditional flume simulation experiments for simulating delta formation and subsequent triggering of sediment caving and retransportation processes are complex and cannot achieve quantitative comparative analysis of controlling factors, thus improving the applicability and accuracy of flume simulation experiments analyzing the controlling factors of sediment caving and retransportation processes.

Description

Technical Field

[0001] This invention relates to the field of sedimentation experimental technology, specifically a flume experimental analysis method for controlling factors in the sediment collapse and retransport process. Background Technology

[0002] Since 2010, global deepwater oil and gas exploration has achieved a series of groundbreaking breakthroughs, becoming the most important area for oil and gas discovery. Deepwater gravity sand bodies are widely distributed, found in marine and terrestrial strata, across different geological ages and depths; more than 1,300 oil and gas fields have been discovered in deepwater basins worldwide. These deepwater gravity sand bodies, due to their proximity to source rocks and superior reservoir conditions, are rich in oil and gas, making them the most realistic, promising, and widespread area for onshore oil and gas exploration in my country for a considerable period to come.

[0003] The formation of deep-water gravity flows involves multiple genetic mechanisms, including shallow-water sediment collapse and retransport, continuous flooding and density current replenishment, and unloading and settling by floating plumes. Sediments formed by different genetic mechanisms exhibit different sedimentary characteristics and sand body distribution patterns. In particular, deep-water gravity flow sediments formed by shallow-water sediment collapse and retransport are considered the primary formation mechanism, playing a crucial role in controlling the distribution of deep-water gravity flow sand bodies. Due to the sudden and destructive nature of the sediment collapse and retransport process, direct research on the sediment collapse and retransport process is extremely difficult. Therefore, the controlling factors of sediment collapse and retransport remain highly controversial, thus limiting the effective prediction of the distribution of deep-water gravity flow-induced sand bodies. Flume simulation experiments are one of the effective methods to reproduce the sediment collapse and retransport process under indoor experimental conditions. However, conventional experimental methods mainly involve simulating the formation of deltaic deposits and then triggering deltaic sediment collapse and retransport. Due to the complexity, difficulty, and numerous uncontrollable factors in the simulation process, it is extremely difficult to quantitatively study the controlling effect of a single factor on the landslide process. Therefore, current research on the controlling factors of sediment collapse and retransportation processes urgently requires the development of new, simple, feasible, and easily comparable flume simulation experimental methods. Summary of the Invention

[0004] To address the aforementioned issues, this invention, based on a thorough consideration of the operability and control factors of the sediment collapse and retransport process, and grounded in the principles of controlled variables and equivalent experiments, proposes a flume experiment method for analyzing the control factors of the sediment collapse and retransport process. This method employs a flume simulation experiment with more accurate process control to study the control factors of the sediment collapse and retransport process, thereby guiding the prediction of the distribution of deep-water gravity flow sedimentary sand bodies that are formed by sediment collapse and retransport.

[0005] The technical solution of the present invention is as follows:

[0006] A flume experiment method for analyzing the controlling factors of sediment collapse and retransportation processes includes the following steps:

[0007] S1. Based on literature review, analysis of actual geological conditions and material composition analysis, identify the controlling factors of a sediment collapse and retransport process.

[0008] S2. Based on the principle of equivalent experiment, design the parameters of the flume experiment, and conduct single-factor flume experiments with different control factors as single variables in turn to simulate the sediment collapse and retransport process under different control factors, and obtain the initiation conditions of sediment collapse and retransport and the distribution characteristics of sediment retransport under different control factors.

[0009] S3. Analyze the initiation conditions and distribution characteristics of sediment collapse and retransport under different control factors, and quantitatively summarize the control effects of different control factors on the sediment collapse and retransport process.

[0010] In one specific embodiment of the present invention, the control factors in step S2 include clay mineral content and sediment consolidation degree, and the corresponding flume experiment includes the following steps:

[0011] S21. Prepare sediment in a rectangular long tank, place the long tank at the bottom of a large water tank and fill the large water tank with water so that the liquid level reaches the preset first height;

[0012] S22. Raise one end of the long tank towards the liquid surface to tilt it until the sediment collapses. Record the horizontal height (slope) when the sediment collapses to characterize the initiation conditions of transport. Then continue to move the sediment to a preset second height, which is less than or equal to the first height, so that the sediment is immersed in the liquid in the large tank.

[0013] S23. After the fluid stops moving, record the distribution of the sediment.

[0014] In one specific embodiment of the present invention, the control factor in step S2 includes terrain slope, and the corresponding water tank experiment includes the following steps:

[0015] S31. Prepare sediments in a long tank by placing the long tank at the bottom of a large water tank and filling the large water tank with water to make the liquid level reach the preset third height.

[0016] S32. Raise one end of the long tank towards the liquid surface to tilt it until the sediment collapses. Then continue to move the sediment to a preset fourth height, which is less than or equal to the third height, so that the sediment is immersed in the liquid in the large tank.

[0017] S33. After the fluid stops moving, record the distribution of the sediments;

[0018] S34. Repeat steps S31 to S33 at different fourth altitudes to obtain the distribution of sediments under different fourth altitude conditions.

[0019] In one specific embodiment of the present invention, the control factors in step S2 include fault activity, and the corresponding water tank experiment includes the following steps:

[0020] S41. Prepare sediment in a long tank. Place the long tank at the bottom of a large water tank and fill the large water tank with water until the liquid level reaches the preset fifth height. When preparing sediment, add a towel to the sediment, with one end of the towel extending out of the sediment.

[0021] S42. Raise one end of the long tank to the liquid surface to a sixth height so that it is tilted. The sixth height is less than or equal to the fifth height, so that the sediment is immersed in the liquid in the large tank. The sixth height is less than the initiation condition for sediment collapse, that is, the sediment does not collapse at the sixth height.

[0022] S43. Pull the towel at a predetermined rate to simulate the impact of fault activity on the collapse and retransport of sediments.

[0023] S44. After the fluid stops moving, record the distribution of the sediment.

[0024] Furthermore, the effect of different fault intensities on the sediment collapse and retransport process can be simulated by changing the rate at which the towel is pulled.

[0025] Furthermore, towels can be added to different locations in the sediment to simulate the impact of fault activity at different locations on the sediment collapse and retransport process.

[0026] The technical effects of this invention are:

[0027] This invention, based on a thorough consideration of the controlling factors in sediment collapse and retransportation, designs an experimental scheme based on the operability and controllability of flume simulation experiments. Employing the principle of equivalent experiments, it utilizes a dual-flume experimental system with a fixed initial sediment repose angle. By changing the experimental control conditions, it simulates the sediment collapse and retransportation process, thereby clarifying the experimental methods for controlling factors. This invention effectively solves the problem of the complexity of traditional flume simulation experiments for simulating delta formation and subsequent sediment collapse and retransportation, and the inability to achieve quantitative comparative analysis of controlling factors. It improves the applicability and accuracy of flume simulation experiments for analyzing the controlling factors in sediment collapse and retransportation, and can provide scientific guidance for predicting the distribution of deep-water gravity current sand bodies that contribute to the formation of sediment collapse and retransportation. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below.

[0029] Figure 1 This is a flowchart of the flume experiment analysis method for controlling factors in the sediment collapse and retransport process in Example 1;

[0030] Figure 2 This is a schematic diagram of the water tank experimental setup for controlling factors of sediment collapse and retransportation in Example 1;

[0031] Figure 3 This is a schematic diagram of the initial sediment accumulation state in Example 1;

[0032] Figure 4 A comparative graph showing the control effect of different clay contents on the sediment collapse and retransport process;

[0033] Figure 5 A comparative diagram showing the control effect of different degrees of sediment consolidation on the sediment collapse and retransport process;

[0034] Figure 6 A comparative diagram showing the control effect of different fault activities on the collapse and retransport of sediments. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment uses a flume simulation experiment to analyze the controlling factors of sediment collapse and retransportation in a certain area of ​​the Changqing Oil and Gas Field in the Ordos Basin as an example to illustrate the specific technical solution of the invention. The analysis method of this embodiment includes the following steps:

[0039] S1. Experimental prototype analysis: Taking sediments formed by sediment collapse and retransport in a certain area of ​​Changqing Oilfield as the research object, and integrating previous research results, 3D seismic data, drilling core data, logging data and analytical test data, the controlling factors of sediment collapse and retransport process are identified.

[0040] S11. Identify the types and characteristics of sediments formed by sediment collapse and retransport. Three-dimensional seismic analysis shows that sediment collapse and retransport sediments mainly form in areas with significant progradational structures at the delta front, with topographic slope being a crucial factor controlling their formation. Core observation and logging data analysis reveal that the study area primarily exhibits sedimentary processes closely related to sediment collapse and retransport, including sliding-slump deposits, sandy debris flow deposits, muddy debris flow deposits, low-density turbidity current deposits, and mixed event layer deposits. Sliding-slump deposits are dominated by muddy sandstone, with well-developed sedimentary structures such as shear slip surfaces, slump deformation, folding, and soft sediment deformation. They are located adjacent to the delta front, with a thickness ranging from 0.07 m to 7.22 m, averaging 1.17 m. Muddy debris flow deposits are dominated by muddy sandstone, with well-developed sedimentary structures such as massive bedding, floating mud gravel, mudstone rifts, and basal shear slip layers. They are mainly distributed on the delta front slopes, with a thickness ranging from 0.05 m to 5.82 m, averaging 0.6 m. Sandy clastic flow deposits are dominated by fine sandstone, with well-developed sedimentary structures such as massive bedding, floating mudstone gravel, mudstone rifts, and basal shear slip layers. They are mainly distributed on the delta front slopes, with a thickness of 0.07 m to 2.5 m, averaging 0.66 m. Mixed event layer deposits are dominated by silty fine sandstone and argillaceous sandstone, with well-developed sedimentary structures such as massive sandstone, bilayer structures, and floating mudstone clastics. They are mainly distributed in the basin center, with a thickness of 0.5 m to 1.2 m, averaging 0.99 m. Low-density turbidite deposits are dominated by siltstone, with well-developed sedimentary structures such as scour surfaces, channel patterns, positive gradations, incomplete Bouma sequences, and positive gradations of silt and mud rhythm layers. They are mainly distributed in the basin center, with a thickness of 0.01 m to 6.16 m, averaging 0.52 m.

[0041] S12. Analyze the material composition of sediments formed by the collapse and retransport of sediments. The average grain size of the sandstone is generally 0.06 mm to 0.20 mm, mainly composed of very fine to fine sand; the clastic grains are moderately to well sorted, with roundness mainly angular to sub-angular, and the structure is relatively mature. It mainly consists of feldspathic sandstone, lithic feldspathic sandstone, and feldspathic lithic sandstone, containing a small amount of lithic sandstone. The quartz content is generally less than 50%, and the average compositional maturity Q / (F+R) is 0.9. The main interstitial materials are illite, ferroalloy, ferroalloy, and silica. Illite has the highest content, accounting for 46.63% of the total interstitial materials; followed by ferroalloy and ferroalloy, accounting for 18.07% and 15.74% respectively; then silica, accounting for 11.88%; it also contains some chlorite and a small amount of kaolinite. The clay minerals are mainly rose petal-shaped chlorite films, hair-like illite, honeycomb-shaped illite / montmorillonite mixed-layer clay films, and dendritic kaolinite.

[0042] S13. Identify the controlling factors of sediment caving and retransportation. Based on the analysis of sedimentary characteristics and material composition of sediments formed by sediment caving and retransportation in the study area, and combined with a literature review, it is believed that clay mineral content, topographic slope, degree of sediment consolidation, and fault activity intensity are the main factors controlling the sediment caving and retransportation process.

[0043] S2. Flume Experiment Design: Based on the principle of equivalent experiments, a fixed initial sediment repose angle was used. The sediment collapse and retransport process was simulated by changing the experimental control conditions (clay mineral content, topographic slope, sediment consolidation degree, and fault activity intensity). The initiation conditions and distribution characteristics of sediment collapse and retransport under different control factors were analyzed, and the control effects of different control factors on the sediment collapse and retransport process were quantitatively summarized.

[0044] The water tank experimental apparatus used in this embodiment is as follows: Figure 2 As shown, it is a double-water tank experimental system. The large water tank 100 is 6m long and 2m wide, with an inlet 101 at the front and two outlets 102 at the back. In the middle of the large water tank 100, a small water tank (a rectangular tank) 200 is set up. The small water tank is 2m long, 0.2m wide and 0.25m high.

[0045] This embodiment employs a fixed sediment repose angle experimental method to determine the amount of sediment and the repose angle. The sediment profile is shown below. Figure 3 As shown, the overall shape is trapezoidal, with a height of 20cm. When preparing the sediment, 16-32 mesh quartz sand is used. The dry quartz sand and clay minerals are mixed evenly in a certain proportion, and then a small amount of water is added to moisten it. Then, it is deposited underwater in a small water tank to form an initial sedimentary accumulation in the shape of a trapezoid with an accumulation angle of 30°. At this time, the slope of the small water tank is 0°.

[0046] The specific experimental procedure and analysis are as follows.

[0047] (1) The role of clay content in controlling the collapse and retransport of sediments.

[0048] A small trough filled with sediment was placed inside a large trough, and then the large trough was filled with water to a depth of 70 cm. The left side of the small trough was then slowly raised to tilt it, and the timing of sediment collapse was observed. Once collapse and sliding occurred, the raising of the small trough was stopped, and the initial collapse height (Table 1) was recorded. The left end of the small trough was then raised to 70 cm and maintained at this height. After the fluid stopped transporting the sediment, the left end of the small trough was slowly lowered, and finally, the water was drained, recording the transport distance of the sediment. This embodiment included six comparative experiments with chlorite clay mineral contents of 0%, 5%, 8%, 10%, 12%, and 15%. Specific experimental results are shown in Table 1.

[0049] Table 1. Statistical table of the controlling effect of clay content on sediment collapse and retransportation process.

[0050] Experimental group Clay content (chlorite) wt% Initial slump height / cm Transport distance / cm 1 0 52 27 2 5 47 38 3 8 46 39 4 10 43 42 5 12 39 46 6 15 48 36

[0051] Clay content significantly controls the sediment collapse and retransport process. When the clay content in the sediment is 0%, the required slope for sediment collapse is greater than that of sediments with lower clay content, resulting in a shorter transport distance at the same slope. A slight increase in clay content to 5% reduces the initial sediment collapse initiation height by 5 cm and increases the transport distance by 11 cm. Subsequent increases in clay content do not lead to the same increase in transport distance as when the clay content initially increases to 5%. The initial collapse initiation height is inversely proportional to the final transport distance; a lower initial collapse initiation height results in a greater final transport distance. The best simulation of sediment collapse and retransport is achieved when the clay content is 12%, resulting in the longest transport distance. Figure 4 When the clay content is less than 12%, the sediment is more likely to collapse and be transported as the mud content increases, and its transport distance also increases. When the clay content is greater than 12%, the sediment is less likely to collapse and be transported as the clay content increases, and its transport distance also decreases.

[0052] (2) The role of topographic slope in controlling the collapse and retransport of sediments.

[0053] Under the condition that the clay content, sediment quantity, sediment height, and sediment composition are all consistent, the slope of the small flume was varied to observe the sediment transport and deposition process. The specific operation was as follows: A small flume containing sediment was placed in a large flume, and then the large flume was filled with water to a depth of 70 cm. Next, the left side of the small flume was slowly raised to tilt it, and the timing of sediment collapse was observed. Once collapse and sliding occurred, the raising of the small flume was stopped, and the height of the raised flume at the start of sediment sliding was recorded. Then, the left end of the small flume was raised to different heights to simulate different terrain slopes. After the fluid transport stopped, the left end of the small flume was slowly lowered, and finally, water was drained, and the transport distance of the sediment was recorded. Specific experimental results can be found in [link to experimental results]. Figure 4 .

[0054] from Figure 4 As can be seen, as the terrain slope increases from 0° to 20°, the distance of sediment collapse and retransportation also increases. That is, the greater the terrain slope, the more conducive it is to the collapse and retransportation process of sediments.

[0055] (3) The degree of consolidation controls the process of sediment collapse and retransport.

[0056] The experimental procedures for using the degree of consolidation as the control factor are the same as those for using clay content as the control factor, the difference being the composition of the sediments. This embodiment uses compacted, interbedded sand-mud sedimentary structures (…) Figure 5 a) Loose sedimentary structure consisting of interbedded sand and mud layers ( Figure 5 (b) and loosely deposited pure sand sedimentary textures ( Figure 5 (c) Simulations were performed on sediments with three different degrees of consolidation to determine the sediment transport process after the left end of the small flume was raised by 70 cm. The results are as follows: Figure 5 As shown.

[0057] Depend on Figure 5 The experiments on compacted sand-mud interbedded sedimentary structures failed to trigger sediment collapse and retransport, indicating that compacted sedimentary structures are unfavorable for sediment collapse and retransport. Loose sand-mud interbedded sedimentary structures and loose pure sand sedimentary structures, when triggered by external factors, underwent sediment collapse and retransport, forming sandy debris flows and turbidity currents; however, sediment transport ceased immediately upon cessation of the triggering process. Loose pure sand sedimentary structures are most prone to collapse and retransport, forming sandy debris flow deposits. Therefore, the more developed and consolidated the sand-mud interbedded sedimentary structure, the greater the difficulty of collapse and retransport, and the less favorable it is for the formation of sandy debris flow deposits.

[0058] (4) The role of fault activity in controlling the collapse and retransport of sediments.

[0059] The control effect of fault activity on sediment collapse and retransportation was mainly simulated by examining fault activity at different locations and comparing the transport distance and sediment thickness resulting from collapse. In this embodiment, towels were placed at the bottom and middle of the sediment to simulate fault activity at the bottom and middle of the sediment, respectively. The sediment was then raised to 50 cm underwater, at which point no collapse and retransportation occurred. The towels were then pulled rapidly at a rate of 10 cm / s to simulate the effect of fault activity on the sediment collapse and retransportation process. The distribution of the sediment was then observed. The results of the two experiments are as follows: Figure 6 As shown.

[0060] Figure 6 In the simulation, (①) when the fault was deep, the amount of sandy debris flow and turbidity flow formed by sediment collapse was relatively large and the transport distance was relatively far. (②) when the fault was shallow, the amount of sandy debris flow and turbidity flow formed by sediment collapse was relatively small and the transport distance was relatively short. The comparison showed that the fault activity at the bottom of the sediment triggered a larger range of sediment collapse and re-transport, and the transport distance of the sediment was longer. This indicates that the intensity and range of fault activity have a significant controlling effect on the sediment re-transport process. The stronger the fault activity and the wider the range of action, the more conducive it is to trigger sediment collapse and re-transport, and the longer the transport distance.

[0061] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A flume experiment method for analyzing the controlling factors of sediment collapse and retransportation processes, characterized in that, Includes the following steps: S1. Based on literature review, analysis of actual geological conditions and material composition analysis, identify the controlling factors of a sediment collapse and retransport process. S2. Based on the principle of equivalent experiment, design the parameters of the flume experiment, and conduct single-factor flume experiments with different control factors as single variables in turn to simulate the sediment collapse and retransport process under different control factors, and obtain the initiation conditions of sediment collapse and retransport and the distribution characteristics of sediment retransport under different control factors. S3. Analyze the initiation conditions and distribution characteristics of sediment collapse and retransport under different control factors, and quantitatively summarize the control effects of different control factors on the sediment collapse and retransport process. The control factors mentioned in step S2 include fault activity, and the corresponding flume experiment includes the following steps: S41. Prepare sediment in a long tank. Place the long tank at the bottom of a large water tank and fill the large water tank with water until the liquid level reaches the preset fifth height. When preparing sediment, add a towel to the sediment, with one end of the towel extending out of the sediment. S42. Raise one end of the long tank to the liquid surface to a sixth height so that it is tilted. The sixth height is less than or equal to the fifth height, so that the sediment is immersed in the liquid in the large tank. The sixth height is less than the initiation condition for sediment collapse, that is, the sediment does not collapse at the sixth height. S43. Pull the towel at a predetermined rate to simulate the impact of fault activity on the collapse and retransport of sediments. S44. After the fluid stops moving, record the distribution of the sediment.

2. The method for analyzing the controlling factors of sediment collapse and retransportation process using a flume, as described in claim 1, is characterized in that... The control factors in step S2 include clay mineral content and sediment consolidation degree, and the corresponding flume experiments include the following steps: S21. Prepare sediment in a rectangular long tank, place the long tank at the bottom of a large water tank and fill the large water tank with water so that the liquid level reaches the preset first height; S22. Raise one end of the long trough towards the liquid surface to tilt it until the sediment collapses. Record the horizontal height of the sediment when it collapses. Then continue to raise the raised end of the long trough so that the sediment continues to move upward to a preset second height. The second height is less than or equal to the first height, so that the sediment is immersed in the liquid in the large water tank. S23. After the fluid stops moving, record the distribution of the sediment.

3. The method for analyzing the controlling factors of sediment collapse and retransportation process using a flume, as described in claim 1, is characterized in that... The control factors in step S2 include topographic slope, and the corresponding flume experiment includes the following steps: S31. Prepare sediments in a long tank by placing the long tank at the bottom of a large water tank and filling the large water tank with water to make the liquid level reach the preset third height. S32. Raise one end of the long trough towards the liquid surface to tilt it until the sediment collapses. Then continue to raise the raised end of the long trough so that the sediment continues to move upward to the preset fourth height. The fourth height is less than or equal to the third height, so that the sediment is immersed in the liquid in the large water tank. S33. After the fluid stops moving, record the distribution of the sediments; S34. Repeat steps S31 to S33 at different fourth altitudes to obtain the distribution of sediments under different fourth altitude conditions.

4. The method for analyzing the control factors of sediment collapse and retransportation process using a flume as described in claim 1, characterized in that, In step S43, the effect of different fault intensities on the sediment collapse and retransport process is simulated by changing the rate at which the towel is pulled.

5. The method for analyzing the controlling factors of sediment collapse and retransportation process using a flume, as described in claim 1, is characterized in that... In step S41, towels are added to different locations on the sediment to simulate the effect of fault activity at different locations on the sediment collapse and retransport process.

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