Method for identifying shale deposited under turbulence hydrodynamic force condition

Abstract

The invention provides a method for identifying shale deposited under a turbulent hydrodynamic condition, and relates to the technical field of shale identification. The method for identifying the deposited shale under the turbulent hydrodynamic force condition comprises the following steps: S1, taking a consolidated shale rock sample, selecting one position to be cut along a strata, and cutting blocky bedding shale parallel to a strata series interface to obtain two rock blocks with sections of which the short axes are not less than 1cm; s2, the two rock blocks are soaked in the two beakers correspondingly; s3, the rock blocks are taken out and repeatedly washed with deionized water, and hydrochloric acid residues are removed. According to the invention, through a large number of water tank experiments, silt particles in silt-mud mixed fine particles deposited on a bottom bed under a turbulent flow condition can be gathered into plaques with different sizes on the bottom bed, and the characteristic does not appear in fine particle sediments deposited under laminar flow and still water hydrodynamic conditions. And the hydrodynamic conditions during deposition can be accurately judged by identifying the plaques.

Description

Technical Field

[0001] The invention relates to the technical field of shale identification, and in particular to a method for identifying shale deposited under turbulent hydrodynamic conditions. Background Art

[0002] Fine particles smaller than 62.5 microns can be deposited under turbulence, which has been repeatedly proven in flume experiments. People's understanding of the shale formation environment has expanded from the traditional static water and extremely low flow hydrodynamic environment to the turbulent environment with higher hydrodynamic intensity. Accurately judging the hydrodynamic conditions when shale was formed is a basic requirement for reconstructing the sedimentary environment and determining the sedimentary phase.

[0003] The limitations of using cross-bedding developed in shale to judge the hydrodynamic conditions during deposition are very obvious: (1) Not all shales deposited under turbulent conditions can produce cross-bedding. For shales with low silt content or turbulent flow with low flow rate, it is difficult to form cross-bedding even if the mud particles are deposited on the bed under turbulent conditions. (2) The angle of the inclined laminations in the cross-bedding of some shales is very low, and it is necessary to distinguish the inclined laminations from the parallel laminations over a very large field of view to determine whether the sedimentary structure is cross-bedding. For most shales deposited under turbulent flow, there is currently no suitable judgment method to distinguish them from shales formed under other hydrodynamic conditions. The existing shale hydrodynamic judgment methods are no longer able to meet the needs of shale oil and gas exploration. Summary of the invention

[0004] 1. Technical issues to be solved

[0005] In view of the shortcomings of the prior art, the present invention provides a method for identifying shale deposited under turbulent hydrodynamic conditions, which solves the problem that there is currently no suitable method to distinguish shale deposited under turbulent conditions from shale formed under other hydrodynamic conditions. The existing shale hydrodynamic identification method is difficult to meet the needs of shale oil and gas exploration.

[0006] (II) Technical solution

[0007] To achieve the above objectives, the present invention is implemented by the following technical scheme: a method for identifying shale deposited under turbulent hydrodynamic conditions, the method comprising the following steps:

[0008] S1. Take a consolidated shale block sample, select one position to cut along the lamination, and cut the massive bedding shale parallel to the interface of the strata to obtain two sections with a minor axis of not less than 1 cm;

[0009] S2. Soak two rocks in two beakers respectively;

[0010] S3, taking out the rock block, and repeatedly washing it with deionized water to remove the hydrochloric acid residue;

[0011] S4, drying the rock in a drying oven;

[0012] S5. Place the two rock blocks with the cut surface facing downward in a 50 ml quartz crucible, add 20 g potassium pyrosulfate, and place in a muffle furnace for heating;

[0013] S6. Take out the rock after cooling and soak it repeatedly in deionized water until the white chemical reagent on the surface is completely dissolved;

[0014] S7, drying the rock in a drying oven;

[0015] S8. Use the rock with more silt on the cut surface. If there are fewer authigenic quartz particles in the rock or the authigenic quartz particles are smaller than 10 microns, the distribution characteristics of silt particles larger than 10 microns on the cut surface can be directly observed. If they are relatively evenly dispersed, they were formed under laminar or still water conditions. If they are aggregated into patches, it can be determined that the shale was formed under turbulent flow.

[0016] S9. If the authigenic quartz particles in the rock are larger than 10 microns and have a high content, it is necessary to perform cathode luminescence analysis on the cross-section of the rock block and observe the distribution characteristics of the colored quartz particles. If the colored quartz particles larger than 10 microns are relatively evenly dispersed on the cross-section, it can be ruled out that the shale was formed under turbulent flow. If the colored quartz particles larger than 10 microns are concentrated in patches, it can be determined that the shale was formed under turbulent flow.

[0017] Preferably, in step 2, the two rock blocks are immersed in a 10% HCl solution at room temperature with the cut surfaces facing downwards for 24 hours.

[0018] Preferably, the temperature in the drying oven in step 4 is not higher than 100 degrees Celsius.

[0019] Preferably, the temperature in the muffle furnace is 650 degrees Celsius and the heating time is 1 hour.

[0020] Preferably, the temperature in the drying oven in step 7 is not higher than 100 degrees Celsius.

[0021] (III) Beneficial effects

[0022] The present invention provides a method for identifying shale deposited under turbulent hydrodynamic conditions. It has the following beneficial effects:

[0023] 1. The present invention, through a large number of flume experiments, found that in the silt-mud mixed fine particles deposited on the bottom bed under turbulent conditions, the silt particles will gather into patches of different sizes on the bottom bed, while this feature will not appear in the fine-grained sediments deposited under laminar flow and static water hydrodynamic conditions. By identifying these patches, the hydrodynamic conditions at the time of deposition can be more accurately determined.

[0024] 2. The present invention does not need to identify a specific sedimentary structure type, and only requires a small amount of shale rock samples to complete the process, thereby overcoming various major defects of the prior art. This method is a summary based on a large number of experimental analyses, with extremely high recognition accuracy and good reliability. At the same time, this method can also avoid the compaction effect and mineral transformation during the shale diagenesis process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0027] Example:

[0028] like Figure 1 As shown, an embodiment of the present invention provides a method for identifying shale deposited under turbulent hydrodynamic conditions, the method comprising the following steps:

[0029] S1. Take a consolidated shale block sample, select one position to cut along the lamination, and cut the massive bedding shale parallel to the interface of the strata to obtain two sections with a minor axis of not less than 1 cm;

[0030] S2. Place two rock blocks in two beakers with the cut surface facing downward and immerse them in a 10% HCl solution at room temperature for 24 hours.

[0031] S3, taking out the rock block, and repeatedly washing it with deionized water to remove the hydrochloric acid residue;

[0032] S4, drying the rock in a drying oven at a temperature not higher than 100 degrees Celsius;

[0033] S5. Place the two rock blocks with the cut surface facing downward in a 50 ml quartz crucible, add 20 g potassium pyrosulfate, and heat them in a muffle furnace at 650 degrees Celsius for 1 hour.

[0034] S6. Take out the rock after cooling and soak it repeatedly in deionized water until the white chemical reagent on the surface is completely dissolved;

[0035] S7, drying the rock in a drying oven at a temperature not higher than 100 degrees Celsius;

[0036] S8. Use the rock with more silt on the cut surface. If there are fewer authigenic quartz particles in the rock or the authigenic quartz particles are smaller than 10 microns, the distribution characteristics of silt particles larger than 10 microns on the cut surface can be directly observed. If they are relatively evenly dispersed, they were formed under laminar or still water conditions. If they are aggregated into patches, it can be determined that the shale was formed under turbulent flow.

[0037] S9. If the authigenic quartz particles in the rock are larger than 10 microns and have a high content, it is necessary to perform cathode luminescence analysis on the cross-section of the rock block and observe the distribution characteristics of the colored quartz particles. If the colored quartz particles larger than 10 microns are relatively evenly dispersed on the cross-section, it can be ruled out that the shale was formed under turbulent flow. If the colored quartz particles larger than 10 microns are concentrated in patches, it can be determined that the shale was formed under turbulent flow.

[0038] In the present invention:

[0039] 1) Using the aggregation characteristics of silt particles on the shales to judge the hydrodynamic state of shale during deposition is a conclusion obtained through a large number of experimental analyses and is highly reliable.

[0040] 2) For some shale samples with significant diagenetic effects, using terrigenous quartz particles larger than 10 microns instead of silt particles can greatly reduce the impact of diagenesis.

[0041] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprising a reference structure" do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0042] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for identifying shale deposited under turbulent hydrodynamic conditions, characterized by: The method comprises the following steps: S1. Take a consolidated shale block sample, select one position to cut along the lamination, and cut the massive bedding shale parallel to the interface of the strata to obtain two sections with a minor axis of not less than 1 cm; S2. Soak two rocks in two beakers respectively; S3, taking out the rock block, and repeatedly washing it with deionized water to remove the hydrochloric acid residue; S4, drying the rock in a drying oven; S5. Place the two rock blocks with the cut surface facing downward in a 50 ml quartz crucible, add 20 g potassium pyrosulfate, and place in a muffle furnace for heating; S6. Take out the rock after cooling and soak it repeatedly in deionized water until the white chemical reagent on the surface is completely dissolved; S7, drying the rock in a drying oven; S8. Use the rock with more silt on the cut surface. If there are fewer authigenic quartz particles in the rock or the authigenic quartz particles are smaller than 10 microns, the distribution characteristics of silt particles larger than 10 microns on the cut surface can be directly observed. If they are relatively evenly dispersed, they were formed under laminar or still water conditions. If they are aggregated into patches, it can be determined that the shale was formed under turbulent flow. S9. If the authigenic quartz particles in the rock are larger than 10 microns and have a high content, it is necessary to perform cathode luminescence analysis on the cross-section of the rock block and observe the distribution characteristics of the colored quartz particles. If the colored quartz particles larger than 10 microns are relatively evenly dispersed on the cross-section, it can be ruled out that the shale was formed under turbulent flow. If the colored quartz particles larger than 10 microns are concentrated in patches, it can be determined that the shale was formed under turbulent flow.

2. The method for identifying shale deposited under turbulent hydrodynamic conditions according to claim 1, characterized in that: In step 2, the two rock blocks are immersed in a 10% HCl solution at room temperature with the cut surfaces facing downwards for 24 hours.

3. The method for identifying shale deposited under turbulent hydrodynamic conditions according to claim 1, characterized in that: The temperature in the drying oven in step 4 is not higher than 100 degrees Celsius.

4. The method for identifying shale deposited under turbulent hydrodynamic conditions according to claim 1, characterized in that: The temperature in the muffle furnace is 650 degrees Celsius and the heating time is 1 hour.

5. The method for identifying shale deposited under turbulent hydrodynamic conditions according to claim 1, characterized in that: The temperature in the drying oven in step 7 is not higher than 100 degrees Celsius.

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