Sediment collapse re-carrying process control factor water tank experiment analysis method

Abstract

The invention discloses a water tank experiment analysis method for a control factor of a sediment collapse and re-carrying process, which belongs to the technical field of deposition experiments and comprises the following steps of: determining the control factor of a certain sediment collapse and re-carrying process based on literature investigation and the like; the method comprises the following steps: designing water tank experiment parameters according to an equivalent experiment principle, carrying out a single-factor water tank experiment by taking different control factors as single variables in sequence, simulating a sediment collapse and re-carrying process under different control factors, and obtaining sediment collapse and re-carrying starting conditions and sediment re-carrying distribution characteristics under different control factors; and quantitatively summarizing the control effects of different control factors on the collapse and carrying process of the sediments. The problems that the experimental process of simulating delta formation and then triggering to form sediment collapse and then carrying in a traditional water tank simulation experiment is complex, and quantitative contrastive analysis of control factors cannot be achieved are mainly solved, and the applicability and accuracy of water tank simulation experiment analysis of the control factors in the sediment collapse and then carrying process are improved.

Description

Technical Field

[0001] The invention relates to the technical field of sedimentation experiments, in particular to a flume experiment analysis method for control factors in a sediment collapse and re-transportation process. Background Art

[0002] Since 2010, global deepwater oil and gas exploration has made a series of major breakthroughs that shocked the world, becoming the most important field for oil and gas discovery. Deepwater gravity flow sand bodies are widely distributed, and have been found in marine strata, continental strata, different geological eras, and different burial depths; more than 1,300 oil and gas fields have been discovered in deepwater basin oil and gas exploration around the world, distributed in various regions of the world. These deepwater gravity flow sand bodies are close to source rocks, have excellent reservoir formation conditions, and are rich in a large amount of oil and gas. They are the most realistic, most potential, and most universal oil and gas exploration field on land in my country for a long period of time in the future.

[0003] The formation of deepwater gravity flow has many genetic mechanisms, such as shallow water sediment collapse and re-transportation, continuous recharge of flood hyperpycnal flow, floating plume unloading and sedimentation. Deepwater gravity flow sediments with different genetic mechanisms have different sedimentary characteristics and sand body distribution patterns. In particular, deepwater gravity flow deposition formed by shallow water sediment collapse and re-transportation is considered to be its main formation mechanism, which plays a very important role in controlling the distribution of deepwater gravity flow sand bodies. Due to the suddenness and destructiveness of the process of sediment collapse and re-transportation to form deepwater gravity flow, it is very difficult to directly carry out research on the process of collapsed sediment re-transportation; therefore, there are still many controversies about the control factors of sediment collapse and re-transportation process at this stage, which in turn restricts the effective prediction of the distribution of sand bodies caused by sediment collapse and re-transportation in deepwater gravity flow. Flume simulation experiment is one of the effective methods to reproduce the sediment collapse and re-transportation process under indoor experimental conditions, but the conventional experimental method is mainly to simulate the formation of delta deposition and then trigger the collapse and re-transportation of delta sediments. Due to the complexity and difficulty of the simulation process and the large number of uncontrollable factors, it is very difficult to achieve quantitative research on the control effect of a single control factor on the landslide process. Therefore, at this stage, the research on the control factors of sediment collapse and re-transport process urgently needs to develop a new flume simulation experimental method that is simple and feasible and convenient for comparative analysis of control factors. Summary of the invention

[0004] In view of the above problems, the present invention, on the basis of fully considering the operability and control factors of the sediment collapse and re-transportation deposition process, based on the control variables and equivalent experimental principles, proposes a flume experimental analysis method for the control factors of the sediment collapse and re-transportation process. It adopts a flume simulation experimental method with more accurate process control to study the control factors of the sediment collapse and re-transportation process, and then guides the distribution prediction of deep-water gravity flow sedimentary sand bodies caused by sediment collapse and re-transportation.

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

[0006] A flume experimental analysis method for controlling factors in a sediment collapse and re-transportation process comprises the following steps:

[0007] S1. Based on literature research, analysis of actual geological conditions and material composition, clarify the controlling factors of a sediment collapse and re-transportation process;

[0008] S2. Design the flume experiment parameters according to the equivalent experiment principle, conduct single-factor flume experiments with different control factors as single variables, simulate the sediment collapse and re-transportation process under different control factors, and obtain the sediment collapse and re-transportation start-up conditions and sediment re-transportation distribution characteristics under different control factors;

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

[0010] As a 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, preparing sediment in a rectangular long trough, placing the long trough at the bottom of a large water tank and filling the large water tank with water to make its liquid level reach a preset first height;

[0012] S22, lifting one end of the long trough toward the liquid surface to tilt it until the sediment collapses, recording the horizontal height (slope) when the sediment collapses, and using this to characterize the start condition of the transport, and then continuing to move the sediment up 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 water tank;

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

[0014] As a specific implementation of the present invention, the control factor in step S2 includes the terrain slope, and the corresponding flume experiment includes the following steps:

[0015] S31, preparing sediment in the long trough, placing the long trough at the bottom of the large water tank and filling the large water tank with water so that its liquid level reaches a preset third height;

[0016] S32, lifting one end of the long trough toward the liquid surface to tilt it until the sediment collapses, and then continuing to move the sediment upward 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 water tank;

[0017] S33, after the fluid stops transporting, record the distribution of the sediment;

[0018] S34, changing the fourth height and repeating steps S31 to S33 to obtain the distribution of sediments under different fourth height conditions.

[0019] As a specific implementation of the present invention, the control factor in step S2 includes fault activity, and the corresponding flume experiment includes the following steps:

[0020] S41, preparing sediment in the long trough, placing the long trough at the bottom of the large water tank and filling the large water tank with water to make its liquid level reach a preset fifth height; when preparing the sediment, adding a towel into the sediment, with one end of the towel extending out of the sediment;

[0021] S42, lifting one end of the long trough to the liquid surface to a sixth height to make it tilted, the sixth height being less than or equal to the fifth height, so that the sediment is immersed in the liquid in the large water tank, and the sixth height is less than the starting condition for sediment collapse, that is, the sediment does not collapse at the sixth height;

[0022] S43, pulling the towel at a predetermined rate to simulate the effect of fault activity on the sediment collapse and re-transport process;

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

[0024] Furthermore, the effect of different fault strengths on the sediment collapse and re-transport process can be simulated by changing the towel pulling rate.

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

[0026] The technical effects of the present invention are:

[0027] The present invention fully considers the control factors of the sediment collapse and re-transportation process, designs an experimental scheme based on the operability and controllability of the flume simulation experiment, adopts the equivalent experimental principle, uses a double flume experimental system, and adopts a fixed initial sediment repose angle to simulate the sediment collapse and re-transportation process by changing the experimental control conditions, thereby clarifying the experimental method of the control factors. The focus is on solving the problem that the traditional flume simulation experiment simulates the formation of deltas and then triggers the formation of sediment collapse and re-transportation process, which is complicated in experimental procedures and cannot realize quantitative comparative analysis of control factors. It improves the applicability and accuracy of the flume simulation experiment analysis of the control factors of the sediment collapse and re-transportation process, and can provide scientific guidance for the distribution prediction of deep-water gravity flow sand bodies caused by sediment collapse and re-transportation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below.

[0029] Figure 1 This is a flow chart of the flume experiment analysis method for controlling factors in the sediment collapse and re-transportation process in Example 1;

[0030] Figure 2 This is a schematic diagram of the structure of the water tank experimental device for controlling factors in the sediment collapse and re-transportation process in Example 1;

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

[0032] Figure 4 A comparison of the control effects of different clay contents on the sediment collapse and re-transport process;

[0033] Figure 5 A comparison of the control effects of different sediment consolidation degrees on the sediment collapse and re-transport process;

[0034] Figure 6 This is a comparison chart showing the control of different fault activities on the sediment collapse and re-transport process. DETAILED DESCRIPTION

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

[0036] 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. 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.

[0037] Example 1

[0038] This embodiment takes the analysis of the control factors of sediment collapse and re-transportation process in a certain area of ​​Changqing Oil and Gas Field in 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 the sediments formed by sediment collapse and re-transportation in a certain area of ​​Changqing Oilfield as the research object, integrating the previous research results, 3D seismic, drilling core, logging data and analysis and test data, to clarify the control factors of sediment collapse and re-transportation process.

[0040] S11. Clarify the types and characteristics of sediments formed by sediment collapse and re-transportation. Through three-dimensional seismic analysis, sediment collapse and re-transportation sediments are mainly formed in areas with significant progradational structures at the delta front, and the terrain slope is an important factor controlling its formation. Through core observation and analysis of well logging data, the study area mainly develops sliding slump deposits, sandy debris flow deposits, muddy debris flow deposits, low-density turbidity current deposits and mixed event layer deposits, which are closely related to the sediment collapse and re-transport process. Sliding slump deposits are mainly muddy sandstone deposits, and sedimentary structures such as shear sliding surface, sliding deformation, wrinkling, and soft sediment deformation are developed. They are close to the delta front, with a sediment thickness of 0.07m to 7.22m and an average of 1.17m. Muddy debris flow deposits are mainly muddy sandstone, and sedimentary structures such as massive bedding, floating mud gravel, mudstone tear debris, and bottom shear sliding layer are developed. They are mainly distributed on the slope of the delta front, with a sediment thickness of 0.05m to 5.82m and an average of 0.6m. The sandy debris flow deposits are mainly fine sandstone, with sedimentary structures such as massive bedding, floating mud gravel, mudstone tear debris, and bottom shear sliding layer. They are mainly distributed in the slope of the delta front, with a sedimentary thickness of 0.07m to 2.5m and an average of 0.66m. The mixed event layer deposits are mainly fine sandstone and mud sandstone deposits, with massive sandstone, double-layer structure, floating mud debris and other sedimentary structures. They are mainly distributed in the center of the basin, with a sedimentary thickness of 0.5m to 1.2m and an average of 0.99m. The low-density turbidity current deposits are mainly siltstone, with sedimentary structures such as scour surface, trough mold, normal grain sequence, incomplete Bouma sequence, normal grain sequence silt and mud rhythmic layer, mainly distributed in the center of the basin, with a sedimentary thickness of 0.01m to 6.16m and an average of 0.52m.

[0041] S12. Analysis of the composition of sediments formed by sediment collapse and re-transportation. The average grain size of sandstone is generally 0.06mm-0.20mm, mainly fine sand-fine sand; the sorting of debris particles is medium-good, the roundness is mainly angular-sub-angular, and the structural maturity is relatively high. It is mainly feldspar sandstone, lithic feldspar sandstone and feldspar lithic sandstone, containing a small amount of lithic sandstone. The quartz content is generally less than 50%, and the composition maturity Q / (F+R) is 0.9 on average. The main filling materials are illite, ferrocalcite, ankerite, and siliceous. Among them, illite has the highest content, accounting for 46.63% of the total filling materials; followed by ferrocalcite and ankerite, accounting for 18.07% and 15.74% of the total filling materials, respectively, and then siliceous, accounting for 11.88% of the total filling materials; it also contains some chlorite and a small amount of kaolinite. The clay minerals are mainly rose-petal-shaped chlorite film, hair-like illite, honeycomb-like illite / montmorillonite mixed-layer clay film and dendritic kaolinite.

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

[0043] S2. Flume experiment design: Based on the equivalent experimental principle, the initial sediment repose angle is fixed, and the sediment collapse and re-transport process is simulated by changing the experimental control conditions (clay mineral content, terrain slope, sediment consolidation degree, and fault activity intensity). The sediment collapse and re-transport initiation conditions and sediment re-transport distribution characteristics under different control factors are analyzed, and the control effects of different control factors on the sediment collapse and re-transport process are quantitatively summarized.

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

[0045] This embodiment adopts the experimental method of fixing the sediment repose angle, fixing the amount of sediment and the repose angle, and the cross-section of the sediment is as follows: Figure 3 As shown, the whole is a trapezoid with a height of 20 cm. When preparing the sediment, quartz sand of 16 to 32 mesh is used. After the dry quartz sand and clay minerals are mixed evenly in proportion, a small amount of water is added to moisten them, and then they are piled up underwater in a small water tank to form a trapezoidal initial sediment accumulation body with a stacking angle of 30°. At this time, the slope of the small water tank is 0°.

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

[0047] (1) The control effect of clay content on the sediment collapse and transport process.

[0048] Put the small water tank with accumulated sediment into the large water tank, and then drain the large water tank to a depth of 70 cm; then slowly raise the left side of the small water tank to make it tilted, and observe when the sediment begins to collapse. Once collapse and sliding occur, stop lifting, and record the lifting height of the small water tank when the sediment begins to slide, that is, the initial sliding height in Table 1; then lift the left end of the small water tank to 70 cm high and maintain this height. After the fluid stops being transported, slowly lower the left end of the small water tank, and finally drain the water, and record the transport distance of the sediment. This embodiment sets up six comparative experiments with chlorite clay mineral content of 0%, 5%, 8%, 10%, 12% and 15%, and the specific experimental results are shown in Table 1.

[0049] Table 1 Statistical table of the control effect of clay content on the sediment collapse and re-transport process

[0050] Experimental groups Clay content (chlorite) wt% Initial landslide 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] The control effect of clay content on the sediment collapse and re-transport process is very significant. When the clay content in the sediment is 0, the slope required for sediment collapse is larger than the initial sliding slope of the sediment with a lower clay content, and the transportation distance at the same slope is shorter. When the clay content increases slightly to 5%, the initial sediment collapse starting height decreases by 5cm and the transportation distance increases by 11cm. With the subsequent increase in clay content, the increase in transportation distance is less than when the clay content first increases to 5%. The initial collapse starting height of the sediment is inversely proportional to the final transportation distance. The lower the initial collapse starting height, the greater the final transportation distance. When the clay content is 12%, the simulation effect of sediment collapse and re-transport is the best, and the transportation distance is the longest ( Figure 3 ). When the clay content is less than 12%, as the mud content increases, the sediments are easier to collapse and transport, and the transportation distance will increase accordingly. When the clay content is greater than 12%, as the clay content increases, the sediments are more difficult to collapse and transport, and the transportation distance will decrease accordingly.

[0052] (2) The controlling effect of terrain slope on the sediment collapse and transport process.

[0053] When the clay content, sediment dosage, sediment height, sediment composition and other conditions are the same, change the slope of the small water tank and observe the sediment transportation and deposition process. The specific operation is as follows: put the small water tank with accumulated sediment into the large water tank, and then drain the large water tank to a depth of 70 cm; then slowly raise the left side of the small water tank to make it tilted, observe when the sediment begins to collapse, stop lifting once collapse and slide, and record the lifting height of the small water tank when the sediment begins to slide; then lift the left end of the small water tank to different heights to simulate different terrain slopes, and after the fluid stops being transported, slowly lower the left end of the small water tank, and finally drain the water, and record the sediment transportation distance. The specific experimental results are shown in Figure 4 .

[0054] from Figure 4 It can be seen that as the terrain slope increases from 0° to 20°, the sediment collapse and re-transport distance also increases, that is, the greater the terrain slope, the more conducive it is to the sediment collapse and re-transport process.

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

[0056] The experimental operation steps of the experiment with the degree of consolidation as the control factor are the same as those of the experiment with the clay content as the control factor, except that the composition of the sediment is different. Figure 5 a) Loosely deposited sand-mud interlayer sedimentary fabric ( Figure 5 b) and loosely deposited pure sand sedimentary fabric ( Figure 5 The three sediments with different consolidation degrees were simulated to determine the entire sediment transportation process after the left end of the small water tank was raised by 70 cm. The results are shown in Figure 5 shown.

[0057] Depend on Figure 5 It can be seen that the experiment of compacted sand-mud interlayer sedimentary fabric failed to trigger the sediment collapse and re-transport process, indicating that the compacted state of dense stacking is not conducive to the collapse and re-transport of sediments. The loosely stacked sand-mud interlayer sedimentary fabric and the loosely stacked pure sand sedimentary fabric collapsed and re-transported sediments under external triggering, forming sandy debris flows and turbidity currents, but the transportation of sediments stopped immediately after the triggering stopped. The loosely stacked pure sand sedimentary fabric is most likely to collapse and re-transport to form sandy debris flow deposits. Therefore, the more developed the sand-mud interlayer sedimentary structure of the sediment and the higher the degree of consolidation, the more difficult it is to collapse and re-transport, and the less conducive it is to the formation of sandy debris flow deposits.

[0058] (4) The controlling effect of fault activity on the sediment collapse and transport process.

[0059] The control effect of fault activity on sediment collapse and re-transportation mainly simulates fault activity at different locations, and compares the transport distance and thickness of sediment formed by its collapse. In this embodiment, towels were added to the bottom and middle of the sediment, respectively, to simulate the activity of the fault at the bottom of the sediment and the activity of the fault in the middle of the sediment. The sediment was raised to 50 cm underwater, at which time the sediment did not collapse and re-transport. The towel was quickly pulled at a rate of 10 cm / s to simulate the effect of fault activity on the sediment collapse and re-transport process, and then the distribution of the sediment was observed. The results of the two experiments are shown in Figure 2. Figure 6 shown.

[0060] Figure 6 In the simulation, (①) when simulating deep fault activity, the amount of sandy debris flows and turbidity currents formed by sediment collapse is large, and the transportation distance is relatively long. (②) when simulating shallow fault activity, the amount of sandy debris flows and turbidity currents formed by sediment collapse is small, and the transportation distance is relatively short. By comparison, it is found that the fault activity at the bottom of the sediment triggers a larger range of sediment collapse and re-transport, and the formed sediment is transported over a longer distance. This shows that the intensity and range of fault activity play a significant control role in the sediment re-transport process. The stronger the fault activity and the wider the range of action, the more conducive it is to triggering sediment collapse and re-transport, and the longer the transportation distance.

[0061] 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 flume experimental analysis method for controlling factors in sediment collapse and re-transportation process, characterized in that: The following steps are involved: S1. Based on literature research, analysis of actual geological conditions and material composition, clarify the controlling factors of a sediment collapse and re-transportation process; S2. Design the flume experiment parameters according to the equivalent experiment principle, conduct single-factor flume experiments with different control factors as single variables, simulate the sediment collapse and re-transportation process under different control factors, and obtain the sediment collapse and re-transportation start-up conditions and sediment re-transportation distribution characteristics under different control factors; S3. Analyze the initiation conditions of sediment collapse and re-transportation and the distribution characteristics of sediment re-transportation under different control factors, and quantitatively summarize the control effects of different control factors on the sediment collapse and re-transportation process.

2. A flume experimental analysis method for controlling factors in sediment collapse and re-transportation process according to claim 1, characterized in that: The control factors in step S2 include clay mineral content and sediment consolidation degree, and the corresponding flume experiment includes the following steps: S21, preparing sediment in a rectangular long trough, placing the long trough at the bottom of a large water tank and filling the large water tank with water to make its liquid level reach a preset first height; S22, lifting one end of the long trough toward the liquid surface to tilt it until the sediment collapses, recording the horizontal height of the sediment when it collapses, and then continuing to move the sediment up 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 water tank; S23. After the fluid stops being transported, record the distribution of the sediment.

3. A flume experimental analysis method for controlling factors in sediment collapse and re-transportation process according to claim 1, characterized in that: The control factor in step S2 includes the terrain slope, and the corresponding flume experiment includes the following steps: S31, preparing sediment in the long trough, placing the long trough at the bottom of the large water tank and filling the large water tank with water so that its liquid level reaches a preset third height; S32, lifting one end of the long trough toward the liquid surface to tilt it until the sediment collapses, and then continuing to move the sediment upward 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 water tank; S33, after the fluid stops transporting, record the distribution of the sediment; S34, changing the fourth height and repeating steps S31 to S33 to obtain the distribution of sediments under different fourth height conditions.

4. A flume experiment analysis method for controlling factors in sediment collapse and re-transportation process according to claim 1, characterized in that: The control factors in step S2 include fault activity, and the corresponding flume experiment includes the following steps: S41, preparing sediment in the long trough, placing the long trough at the bottom of the large water tank and filling the large water tank with water to make its liquid level reach a preset fifth height; when preparing the sediment, adding a towel into the sediment, with one end of the towel extending out of the sediment; S42, lifting one end of the long trough to the liquid surface to a sixth height to make it tilted, the sixth height being less than or equal to the fifth height, so that the sediment is immersed in the liquid in the large water tank, and the sixth height is less than the starting condition for sediment collapse, that is, the sediment does not collapse at the sixth height; S43, pulling the towel at a predetermined rate to simulate the effect of fault activity on the sediment collapse and re-transport process; S44. After the fluid stops being transported, record the distribution of the sediment.

5. A flume experiment analysis method for controlling factors in sediment collapse and re-transportation process according to claim 4, characterized in that: In step S43, the influence of different fault strengths on the sediment collapse and transport process is simulated by changing the towel pulling rate.

6. A flume experiment analysis method for controlling factors in sediment collapse and re-transportation process according to claim 4, characterized in that: In step S41, towels are added to different positions of the sediment to simulate the influence of fault activities at different positions on the sediment collapse and transport process.

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