A method, device and system for analyzing the formation age of a natural gas hydrate reservoir

Abstract

The application discloses a natural gas hydrate reservoir formation age analysis method, device and system, relates to the technical field of marine natural gas hydrate exploration, and comprises the following steps: collecting marine sediment samples in a natural gas hydrate drilling core column; performing a photoelectric age test on the marine sediment samples; establishing an age-depth model of the natural gas hydrate samples according to the obtained photoelectric age and sediment depth of the marine sediment samples; calculating the sedimentation time of the natural gas hydrate reservoir according to the age-depth model of the natural gas hydrate drilling, and further determining the formation age of the natural gas hydrate. The method can accurately determine the formation age of the natural gas hydrate, avoids the interference caused by the uncertainty of the natural gas hydrate reservoir forming time, and lays a geological exploration foundation for further revealing the natural gas hydrate reservoir forming mechanism.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of marine natural gas hydrate exploration, and more particularly to a method, device and system for analyzing the formation age of a natural gas hydrate reservoir. BACKGROUND

[0002] Natural gas hydrate has the characteristics of wide distribution, large reserves, high calorific value and large energy density, and has attracted widespread attention from countries around the world as an energy resource.

[0003] The research area of natural gas hydrate in China is mainly in the northern South China Sea, and the hydrate system type is diverse and the accumulation process is complex.

[0004] A large number of studies on natural gas hydrate mainly include six elements: temperature and pressure conditions, gas source conditions, water source conditions, gas migration channels, reservoir conditions and time. In particular, the formation time of natural gas hydrate is the key to determining whether the first five elements can be reasonably matched in the entire accumulation system of the natural gas hydrate system. Previous studies have determined the static conditions of the accumulation system based on seismic, logging and geochemical analysis methods, but there have been few reports on the research of the accumulation and mineralization time of natural gas hydrate.

[0005] Due to the lack of sample carriers and methods for directly determining the formation age of natural gas hydrate, how to obtain more accurate hydrate formation time and further reveal the hydrate accumulation mechanism has been a research difficulty in the field of hydrate accumulation that needs to be addressed.

[0006] Therefore, how to determine the formation time of natural gas hydrate in the sea area and reveal the natural gas hydrate accumulation mechanism, a rapid, accurate and efficient analysis method is urgently needed. SUMMARY

[0007] Therefore, the purpose of the present application is to provide a method, device and system for analyzing the formation age of a natural gas hydrate reservoir to solve the technical problem that the formation age of natural gas hydrate cannot be directly determined in the prior art.

[0008] To achieve the above-mentioned purpose, the first purpose of the present application is to provide a method for analyzing the formation age of a natural gas hydrate reservoir, comprising the steps of:

[0009] Step S 100 : Collecting marine sediment samples in a natural gas hydrate drill core column;

[0010] Step S 200 : Performing a photoelectric age test on the marine sediment sample to obtain a photoelectric age of the marine sediment sample;

[0011] Step S 300: establishing an age-depth model of the natural gas hydrate sample according to the obtained optical luminescence age of the marine sediment sample and the sediment depth of the marine sediment sample, the age-depth model of the natural gas hydrate drill core column sample being:

[0012] ;

[0013] wherein: is a predicted age of the natural gas hydrate drill core column sample at depth x, is a measured age of the i-th drill core column sample, is a weight of the i-th drill core column sample at depth x;

[0014] Step S 400 : calculating a deposition time of the natural gas hydrate reservoir according to the age-depth model of the natural gas hydrate drill core column sample, and further determining the formation age of the natural gas hydrate reservoir.

[0015] Preferably, in the step S 100 , the specific step of collecting the marine sediment sample of the natural gas hydrate drill core column sample comprises:

[0016] Step S 110 : obtaining a core column sample of the natural gas hydrate drill core from a formation below the seabed by a drilling ship;

[0017] Step S 120 : cutting the core column sample into a plurality of core segments at certain length intervals under light-proof conditions, and sealing and storing the core segments in light-proof aluminum foil bags, and numbering the aluminum foil bags;

[0018] Step S 130 : placing the aluminum foil bags in a special light-proof sample box, and transferring the aluminum foil bags to a laboratory for light-proof storage.

[0019] Preferably, in the step S 200 , the step of performing optical luminescence age testing on the marine sediment sample comprises:

[0020] Step S 210 : preparing a quartz grain sample from the core segment;

[0021] Step S 220 : placing the quartz grain sample on an aluminum sheet for machine testing;

[0022] Step S 230 : performing equivalent dose measurement on the quartz grain sample on a luminescence analyzer by using a single-plate regenerative dose method to obtain a sediment sample;

[0023] Step S 240: measuring the environmental dose rate of the sediment sample by a high-purity germanium gamma spectrometer, and simultaneously measuring the water content of the sediment sample;

[0024] Step S 250 : calculating the optically stimulated age of the sediment sample to obtain the absolute geological age of the sediment sample, wherein the optically stimulated age = equivalent dose / environmental dose rate.

[0025] Preferably, in step S 210 Among them, the step of preparing the quartz grain sample from the core section includes:

[0026] Step S 211 : in the laboratory, taking a sediment sample with a mass m0 from the middle part of each core section, and obtaining a core grain sample after removing organic matter and carbonate minerals in the sediment sample using a 30% H2O2 solution and a 10% HCl solution;

[0027] Step S 212 : extracting a fine grain sample of 4-11 μm from the core grain sample according to the Stokes sedimentation principle;

[0028] Step S 213 : placing the fine grain sample into a centrifuge tube, adding 35 ml of 30% H2SiF6 fluorosilicic acid, and continuously stirring on a homogenizer for 3-5 days to remove feldspar minerals to obtain a core sample mixed solution;

[0029] Step S 214 : washing the core sample mixed solution with a 30% HCl solution for 30-120 min to completely remove fluorides and obtain a core sample solution;

[0030] Step S 215 : washing the core sample solution to neutral with clean water, and drying in an oven to obtain a quartz grain sample.

[0031] Preferably, in step S 300 Among them, the method for establishing the age-depth model of the gas hydrate drilling core column sample specifically includes:

[0032] Calculating the bandwidth;

[0033]

[0034] wherein: represents a smoothing parameter, represents the difference between the maximum depth and the minimum depth of the sample, , is the maximum depth of the sample, ​the minimum depth of the sample;

[0035] calculating the kernel function value of each data point at a specific x depth; the kernel function value of the i-th sample at x depth, the depth value of the i-th gas hydrate borehole core column sample;

[0036] calculating the weight sum:

[0037] the weight of the i-th borehole core column sample at x depth;

[0038] calculating the weight sum:

[0039] W

[0040] W the weight sum, n is the total number of samples;

[0041] calculating the weight of each data point at a specific x depth:

[0042]

[0043] the weight of the i-th borehole core column sample at x depth;

[0044] According to the measured age, the predicted age and their depth relationship, an age-depth model of the gas hydrate borehole core column sample is established.

[0045] Preferably, in the step S 400 , the specific step of calculating the deposition time of the gas hydrate reservoir and further determining the formation age of the gas hydrate comprises:

[0046] Step S 410 : combining the age-depth model of the gas hydrate borehole core column sample and the depth of the gas hydrate reservoir, the deposition time of the gas hydrate reservoir is calculated;

[0047] Step S 420 : according to the deposition time of the gas hydrate reservoir, the formation age of the gas hydrate is determined.

[0048] The second object of the present application is to provide a formation age analysis device of a gas hydrate reservoir, which adopts the formation age analysis method of the gas hydrate reservoir as described above, and the analysis device comprises:

[0049] a sample collection module for collecting and analyzing core data;

[0050] ​A sample testing module is configured to perform a photoluminescence age test analysis based on the prepared marine sediment sample;

[0051] A model establishing module is configured to establish an age-depth model of the gas hydrate sample according to the obtained photoluminescence age and the sediment depth of the marine sediment sample;

[0052] An analysis module is configured to calculate a gas hydrate reservoir deposition time according to the age-depth model of the gas hydrate borehole, and further determine the formation age of the gas hydrate.

[0053] A third object of the present application is to provide a formation age analysis system of a gas hydrate reservoir, which adopts the formation age analysis method of the gas hydrate reservoir.

[0054] One or more processors;

[0055] A storage device configured to store one or more programs;

[0056] When the one or more programs are executed by the one or more processors, the one or more processors are caused to implement the formation age analysis method of the gas hydrate reservoir.

[0057] Compared with the prior art, the present application has the following advantages and effects:

[0058] The formation age analysis method of the gas hydrate reservoir in the present application takes the light-avoiding collected marine sediment as the target, collects the marine sediment sample in the core column of the gas hydrate borehole, performs a photoluminescence age test on the marine sediment sample, obtains the photoluminescence age of the marine sediment sample, applies the luminescence chronology test method to establish the age-depth model of the gas hydrate borehole, combines the reservoir depth of the gas hydrate, further determines the gas hydrate reservoir deposition time, and finally determines the formation age of the gas hydrate. The method can quickly determine the age of the Quaternary deep stratum sediment, accurately determine the Quaternary gas hydrate reservoir deposition time in the sea area, and effectively determine the formation age of the gas hydrate. BRIEF DESCRIPTION OF DRAWINGS

[0059] Figure 1 FIG. 1 is a flowchart of the formation age analysis method of the gas hydrate reservoir in the embodiment of the present application;

[0060] Figure 2 FIG. 2 is a detailed flowchart of step S 100 in the embodiment of the present application;

[0061] Figure 3 FIG. 3 is a detailed flowchart of step S 200 in the embodiment of the present application;

[0062] Figure 4 Structure diagram of the device for analyzing the formation age of the natural gas hydrate reservoir in the embodiment of the present application;

[0063] Figure 5 Structure diagram of the system for analyzing the formation age of the natural gas hydrate reservoir in the embodiment of the present application;

[0064] Figure 6 Curve diagram of the relationship between the drilling age and the depth of the natural gas hydrate in the Qiongdongnan Basin in the embodiment of the present application;

[0065] Figure 7 Well logging-seismic comprehensive interpretation diagram of the natural gas hydrate in the Qiongdongnan Basin in the embodiment of the present application. DETAILED DESCRIPTION

[0066] The technical solutions of the present application will be described clearly and completely below with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0067] In the description of the present application, it should be noted that the terms "comprise" and "include" used herein should be understood as inclusive and open, and not exclusive. Specifically, when the terms "comprise" and "include" and their synonyms are used in the specification and claims, it means that the specified features, steps or components are included. These terms cannot be understood as excluding the presence of other features, steps or components.

[0068] Optically stimulated luminescence dating is the determination of the age of the last exposure (or heat) event of the sediment, and the test object is mainly quartz and feldspar minerals. The energy accumulated by the sediment mineral crystals since the last burial from the irradiation of the surrounding radioactive substances is released in the form of light through the excitation of the light beam, that is, the luminescence signal, and the intensity of the luminescence signal can be measured to obtain the age of the last burial of the sample. The dating range is tens to hundreds of thousands of years, and the dating accuracy is 5-10%. The optically stimulated luminescence dating technology is one of the most widely used and most recognized dating technologies, and it is widely used in archaeological, active tectonic, paleoseismic and other researches.

[0069] Referring to Figures 1-5 As shown in the drawings, in one embodiment, the present application provides a method for analyzing the formation age of a natural gas hydrate reservoir, which comprises the following steps:

[0070] Step S 100: collecting marine sediment samples in a natural gas hydrate drill core column;

[0071] In this step, it needs to be explained that the natural gas hydrate drill core column refers to the core column sample obtained by the marine drilling ship in the formation below the seabed, which is formed in the drilling plastic casing.

[0072] Step S 200 : performing a light emission age test on the marine sediment sample to obtain the light emission age of the marine sediment sample;

[0073] In this step, it needs to be explained that luminescence is a physical phenomenon that quartz, feldspar and other crystal minerals release energy in the form of photons from the mineral lattice after being subjected to high temperature or light. In the luminescence dating of geological samples, the main minerals determined are quartz and feldspar.

[0074] The principle of luminescence dating is to use the accumulated radioactive dose in the quartz particles of the sample and the annual dose rate provided by the sample burial environment to calculate the burial age of the sample.

[0075] Step S 300 : establishing an age-depth model of the natural gas hydrate drill core column sample according to the obtained light emission age of the marine sediment sample and the sediment depth of the marine sediment sample, the age-depth model of the natural gas hydrate drill core column sample being:

[0076]

[0077] Wherein: is the predicted age of the natural gas hydrate drill core column sample at depth x, is the measured age of the i-th drill core column sample, is the weight of the i-th drill core column sample at depth x.

[0078] Step S 400 : calculating the deposition time of the natural gas hydrate reservoir according to the age-depth model of the natural gas hydrate drill core column sample, and further determining the formation age of the natural gas hydrate reservoir.

[0079] It should be noted that natural gas hydrate is a solid crystalline substance formed by water and natural gas under specific temperature and pressure conditions.

[0080] Further, please refer to Figure 2 , in one embodiment, step S 100 , the specific steps of collecting marine sediment samples in a natural gas hydrate drill core column include:

[0081] Step S 110 : Core column samples of natural gas hydrate borehole cores obtained from strata below the seabed by drilling vessels;

[0082] Step S 120 Under light-protected conditions, the core column sample is cut into several core segments at certain length intervals and sealed in light-protected aluminum foil bags. The aluminum foil bags are then numbered.

[0083] Step S 130 Place the aluminum foil bag in a dedicated light-proof sample box and transport it to the laboratory for light-proof storage.

[0084] During the process of obtaining marine sediment samples, natural gas hydrate cores are obtained through drilling operations in the ocean using drilling vessels or drilling platforms, with the use of drilling plastic casing and aluminum foil bags. The purpose of these operations is to obtain undisturbed natural gas hydrate samples or cores of reservoirs containing natural gas hydrates.

[0085] It should be explained that marine sediments refer to the general term for seabed sediments formed by various marine sedimentary processes. They are substances deposited on the seabed using seawater as the medium.

[0086] Further, please refer to Figure 3 As shown, in one embodiment, step S 200 The step of performing optically stimulated luminescence (OSL) dating on the marine sediment samples includes:

[0087] Step S 210 Quartz grain samples were prepared from core sections;

[0088] Step S 220 The quartz particle sample is placed on an aluminum sheet for testing.

[0089] Step S 230 The sediment sample was obtained by equivalent dose measurement of the quartz particle sample using a single-piece regenerative dosimetry method on an luminescent spectrometer.

[0090] Step S 240 The environmental dose rate of the sediment sample was determined using a high-purity germanium gamma spectrometer, and the water content of the sediment sample was also determined simultaneously.

[0091] Step S 250 Calculate the luminescence age of the sediment sample to obtain the absolute geological age of the sediment sample, wherein the luminescence age = equivalent dose / environmental dose rate.

[0092] Further, in one embodiment, step S 210Among them, the step of preparing the quartz grain sample from the core section includes:

[0093] Step S 211 : In the laboratory (dark room), a marine sediment sample with a mass m0 is taken from the middle of each core section, and after removing the organic matter and carbonate minerals in the marine sediment sample using a 30% H2O2 solution and a 10% HCl solution, a core grain sample is obtained.

[0094] In this step, since the sediments stored at both ends of the drilling plastic casing pipe may be affected by exposure during sampling, a marine sediment sample is taken from the middle of each core section, and the marine sediment sample is pretreated.

[0095] By using a 30% hydrogen peroxide solution (H2O2) and a 10% hydrochloric acid (HCl) to remove organic matter and carbonate minerals in the marine sediment sample, pure quartz is extracted.

[0096] Step S 212 : According to the Stokes sedimentation principle, a fine particle sample of 4-11 μm is extracted from the core grain sample.

[0097] It needs to be explained here that the so-called Stokes sedimentation principle is a physical phenomenon based on Stokes' law, which describes the relationship between the settling velocity of particles in a viscous fluid and the size, density of particles and fluid viscosity. This principle is important for understanding and analyzing many natural phenomena and industrial processes.

[0098] In the same fluid, larger and heavier particles will settle faster than smaller and lighter particles. In addition, if the viscosity of the liquid is larger, the settling velocity of the particles will slow down, resulting in longer settling time of the particles.

[0099] After a period of settling treatment of the core grain sample, a fine particle sample with a particle size of 4-11 um can be obtained.

[0100] Step S 213 : The fine particle sample is placed in a centrifuge tube, 35 ml of 30% fluorosilicic acid (H2SiF6) is added, and constant stirring is performed on a homogenizer for 3-5 days to remove feldspar minerals and obtain a core sample mixed solution.

[0101] In this step, the feldspar particles in the fine particle sample are dissolved by fluorosilicic acid to remove feldspar minerals.

[0102] Step S 214The core sample mixture was then washed with 30% HCl for 30-120 minutes to completely remove fluoride and obtain the core sample solution.

[0103] In this step, the core sample mixture is neutralized with 30% hydrochloric acid (HCl) more than twice to remove fluoride.

[0104] Step S 215 The core sample solution was washed with water until neutral and then dried in an oven to obtain a quartz particle sample.

[0105] Therefore, before conducting equivalent dose measurements, experiments on luminescence properties such as quartz purity testing, preheating plate, and dose recovery are performed to determine the luminescence analysis parameters and procedures.

[0106] Further, in one embodiment, step S 300 The method for establishing the age-depth model of natural gas hydrate borehole core samples specifically includes:

[0107] Step 1: Calculate bandwidth;

[0108]

[0109] in: Represents the smoothing parameter. The difference between the maximum and minimum depths of the core sample from the borehole representing natural gas hydrate. = , This represents the maximum depth of the core sample from the natural gas hydrate borehole. This represents the minimum depth of the core sample from the borehole containing natural gas hydrates.

[0110] Step 2: Calculate the specific depth The kernel function value of the core sample from the i-th borehole;

[0111]

[0112] in: This represents the kernel function value of the i-th sample at depth X. denoted as the depth value of the core sample from the i-th natural gas hydrate borehole.

[0113] Step 3: Calculate the weighted sum:

[0114] W

[0115] in: W is the total weighted sum, and n is the total number of samples.

[0116] Step 4: Calculate the weight of each data point at a specific x-depth:

[0117]

[0118] where: Wi is the weight of the ith borehole core sample at x-depth.

[0119] Finally, based on the measured ages, predicted ages, and their depth relationships, an age-depth model for the gas hydrate borehole core samples is established.

[0120] It is important to note that the equivalent dose refers to the cumulative radiation dose since the last sufficient exposure (or thermal event) experienced by the sample. This dose comes from radioactive materials in the sample's environment, such as natural radioactive elements like uranium (U), thorium (Th), and potassium (K), as well as cosmic rays, etc.

[0121] Measurement methods of equivalent dose:

[0122] Single-aliquot regenerative dose method: This is a commonly used method for measuring equivalent dose, suitable for quartz and feldspar grains. In this method, each sample is divided into multiple aliquots (or test pieces), and each aliquot is measured for its natural luminescence signal and a series of regenerative dose signals at different doses. By establishing a dose recovery curve, the natural luminescence signal is projected onto this curve to obtain the equivalent dose.

[0123] Factors affecting the measurement of equivalent dose:

[0124] Purity of the sample: Impurities in the sample may affect the stability and intensity of the luminescence signal.

[0125] Thermal history of the sample: If the sample has experienced high temperatures or exposure events, it may affect its luminescence signal.

[0126] Laboratory conditions: Preheating temperature, intensity and duration of the excitation light source during the measurement process will affect the measurement results.

[0127] Environmental factors: The environment in which the sample is located, such as humidity, temperature, and chemical conditions, may affect the accumulation of radiation dose.

[0128] Further, in an embodiment of step S 400 , the specific steps for calculating the deposition time of the gas hydrate reservoir and determining the formation age of the gas hydrate include:

[0129] Step S 410 : Calculate the deposition time of the gas hydrate reservoir by combining the age-depth model of the gas hydrate borehole and the depth of the gas hydrate reservoir.​

[0130] Step S 420 : According to the natural gas hydrate reservoir deposition time, the natural gas hydrate formation age can be determined.

[0131] In another aspect, referring to Figure 4 , in one embodiment, the present application further provides a natural gas hydrate reservoir formation age analysis device, which comprises:

[0132] A sample collection module is configured to collect and analyze core data.

[0133] A sample testing module is configured to perform optical luminescence age testing analysis based on the prepared marine sediment sample.

[0134] A model establishing module is configured to establish an age-depth model of the natural gas hydrate borehole core column sample according to the optical luminescence age and the sediment depth of the obtained marine sediment sample.

[0135] An analysis module is configured to calculate the natural gas hydrate reservoir deposition time according to the age-depth model of the natural gas hydrate borehole core column sample, and further determine the formation age of the natural gas hydrate.

[0136] In another aspect, in one embodiment, referring to Figure 5 , in one embodiment, the present application further provides a natural gas hydrate reservoir formation age analysis system, which comprises: Figure 5 The structural diagram of the natural gas hydrate reservoir formation age analysis system provided by an embodiment of the present application.

[0137] The natural gas hydrate reservoir formation age analysis system comprises a processor, a memory and a bus. The memory stores machine readable instructions executable by the processor. When the analysis system is running, the processor and the memory communicate through the bus. When the machine readable instructions are executed by the processor, the steps of the natural gas hydrate reservoir formation age analysis method in the method embodiment shown in Figure 1 The specific implementation can be referred to the method embodiment, and will not be repeated here.

[0138] In another aspect, in one embodiment, the present application further provides a computer readable storage medium, which stores a computer program. When the computer program is run by the processor, the steps of the natural gas hydrate reservoir formation age analysis method in the method embodiment shown in Figure 1 The specific implementation can be referred to the method embodiment, and will not be repeated here.

[0139] In the embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and other division methods may be used in actual implementation. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the functional units in the various embodiments of this application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0140] like Figure 6 , 7 As shown, taking the Qiongdongnan Basin in the northern South China Sea as an example, the formation age of the natural gas hydrate reservoirs in the Qiongdongnan Basin in the northern South China Sea was determined by the above-mentioned method for analyzing the formation age of natural gas hydrate reservoirs.

[0141] The specific implementation process is as follows:

[0142] Step 1: Collect marine sediment samples;

[0143] Step 1: After the drilling vessel obtains deep-sea core samples of natural gas hydrate borehole cores from the strata below the seabed in the Qiongdongnan Basin in the northern South China Sea, it is necessary to ensure that the samples are protected from light. Then, the core samples, along with the drilling plastic casing, are cut into 20 cm long core segments at intervals of more than 1 meter, for a total of 14 segments. These segments are then sealed in light-proof aluminum foil bags and labeled with sample numbers from 1H-1 to 11H-4c. The samples are placed in a special light-proof sample box to avoid accidental exposure during transportation and are immediately transferred to a laboratory (darkroom) for light-proof storage.

[0144] Step 2: Optical Stimulated Luminescence Age Testing and Analysis of Marine Sediment Samples;

[0145] Step 2: In a darkroom, take about 150 g of sediment samples from the middle part of each of the 14 core sample tubes, and use 30% H2O2 solution and 10% HCl to remove organic matter and carbonate minerals from each sample in turn.

[0146] Step 3: Extract 4-11μm fine particles from each sample based on the Stokes sedimentation principle.

[0147] Step 4: Place the 4-11μm fine particles from each sample into centrifuge tubes, add 35ml of 30% H2SiF6 fluorosilicic acid, and continuously stir the samples on a mixer for 3-5 days to remove feldspar minerals from each sample.

[0148] Step 5: Clean the samples with 30% HCl for 30 minutes to 2 hours to remove fluoride from each sample.

[0149] Step 6: Wash each sample to neutral with clean water and dry in an oven at 40 °C.

[0150] Step 7: Place the purified quartz grain samples in the order of samples on a round aluminum sheet with a diameter of about 1 cm for machine testing.

[0151] Step 8: Measure the equivalent dose of the treated pure quartz grain samples using the single-aliquot regenerative-dose method on a luminescence analyzer (RISØ-TL / OSL-DA-20C / D model).

[0152] Step 9: The environmental dose rate of each sediment sample will be mainly determined by a high-purity germanium gamma spectrometer (HPGe Gamma Spectrometer).

[0153] Step 10: The determination of the water content of each sample will be based on the measured water content and the saturated water content, taking into account the sediment burial process, to ensure the accuracy of the environmental dose rate measurement.

[0154] Step 11: Calculate the optical luminescence age of the sediment samples: luminescence age = equivalent dose / environmental dose rate, which is the absolute geological age of the sediment (Table 1).

[0155] Table 1 Optical luminescence dating results of gas hydrate drill holes in Qiongdongnan Basin

[0156]

[0157] Step 3: Based on the optical luminescence age of the marine sediments obtained in Step 2, establish an age-depth model for the drill hole;

[0158] Step 12: Based on the depth of the sediment and the optical luminescence age, combined with the gas hydrate drill core column, use the local weighted regression calculation method to establish the age-depth model of the drill core column samples, the specific process is as follows:

[0159] Select a suitable smoothing parameter SPAN value such as 0-0.5; through computer operation, for example, the predicted age at 22 meters below the seabed is about 47.5 ka, and the predicted age at 70 meters below the seabed is about 116.2 ka; based on the relationship between the measured age and the predicted age and their depths, an age-depth model of the drill core column samples can be established;

[0160] Step 4: Based on the age-depth model of the drill core column samples obtained in Step 3, determine the deposition time of the gas hydrate reservoir, and then determine the formation age of the gas hydrate.

[0161] Step 13: Combined with the age-depth model of the drill core column samples and the depth of the gas hydrate reservoir, the deposition time of the gas hydrate reservoir can be determined. Combined with the logging-seismic data (Fig. 4), it can be known that the drill hole gas hydrate mainly exists in the intervals of 22 mbsf-70 mbsf, 78 mbsf-106 mbsf and 122 mbsf-136 mbsf. Figure 7

[0162] According to the age-depth model of the drill core column samples established in this study, the deposition time of the upper section of the gas hydrate reservoir is about 47.5 ka-116.2 ka; the deposition time of the middle section and the lower section is unknown.

[0163] Step 14: Since the gas hydrate is formed after the deposition of the gas hydrate reservoir, according to the deposition time of the gas hydrate reservoir, the formation age of the gas hydrate can be determined.

[0164] According to the deposition time of the drill hole gas hydrate reservoir, the upper section is mainly 47.5 ka-116.2 ka, so it can be determined that the latest formation age of the drill hole gas hydrate is 47.5 ka to now.

[0165] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited to this. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present disclosure.​

Claims

1. A method for analyzing the formation age of natural gas hydrate reservoirs, characterized in that, Including the following steps: Step S 100 Collect marine sediment samples from the core column of the natural gas hydrate borehole; Step S 200 The optically stimulated luminescence (OSL) age of the marine sediment samples was determined by performing an OSL age test. Specifically, it includes: Step S 210 Quartz grain samples were prepared from core sections; Step S 211 In the laboratory, sediment samples with a mass of m0 were taken from the middle part of each core segment. Organic matter and carbonate minerals in the sediment samples were removed using a 30% H2O2 solution and 10% HCl to obtain core particle samples. Step S 212 Fine particles of 4-11 μm were extracted from the core sample based on the Stokes sedimentation principle. Step S 213 The fine particle sample was placed in a centrifuge tube, and 35 ml of 30% H2SiF6 fluorosilicic acid was added. The mixture was stirred continuously on a mixer for 3-5 days to remove feldspar minerals and obtain a core sample mixed solution. Step S 214 The core sample mixture was then washed with 30% HCl for 30-120 minutes to completely remove fluoride and obtain the core sample solution. Step S 215 The core sample solution was washed with water until neutral and then dried in an oven to obtain a quartz particle sample. Step S 220 The quartz particle sample is placed on an aluminum sheet for testing. Step S 230 The sediment sample was obtained by equivalent dose measurement of the quartz particle sample using a single-piece regenerative dosimetry method on an luminescent spectrometer. Step S 240 The environmental dose rate of the sediment sample was determined using a high-purity germanium gamma spectrometer, and the water content of the sediment sample was also determined simultaneously. Step S 250 : Calculate the luminescence age of the sediment sample to obtain the absolute geological age of the sediment sample, wherein the luminescence age = equivalent dose / environmental dose rate; Step S 300 Based on the optically stimulated luminescence (OSL) age and sediment depth of the obtained marine sediment samples, an age-depth model for natural gas hydrate borehole core samples is established. The age-depth model for the natural gas hydrate borehole core samples is as follows: in: The predicted age of the core sample from the borehole containing natural gas hydrate at depth x. Let x be the weight of the core sample from the i-th borehole at depth x. Let be the measured age of the core sample from the i-th borehole; Step S 400 Based on the age-depth model of the core samples from the natural gas hydrate borehole, the deposition time of the natural gas hydrate reservoir is calculated, thereby determining the formation age of the natural gas hydrate reservoir.

2. The method for analyzing the formation age of natural gas hydrate reservoirs according to claim 1, characterized in that, In step S 100 The specific steps for collecting marine sediment samples from the borehole core of natural gas hydrate include: Step S 110 Core samples of natural gas hydrates were obtained from boreholes in strata below the seabed using a drilling vessel. Step S 120 Under light-protected conditions, the core column sample is cut into several core segments at certain length intervals and sealed in light-protected aluminum foil bags. The aluminum foil bags are then numbered. Step S 130 Place the aluminum foil bag in a dedicated light-proof sample box and transport it to the laboratory for light-proof storage.

3. The method for analyzing the formation age of natural gas hydrate reservoirs according to claim 1, characterized in that, In step S 300 The method for establishing the age-depth model of natural gas hydrate borehole core samples specifically includes: Calculate bandwidth; in: Represents the smoothing parameter. The difference between the maximum and minimum depths of the core sample from the borehole representing natural gas hydrate. = , This represents the maximum depth of the core sample from the natural gas hydrate borehole. The minimum depth for drilling core samples of natural gas hydrates; Calculate specific Core sample from the i-th borehole at depth The kernel function value; This represents the kernel function value of the i-th sample at depth x. Let be the depth value of the core sample from the i-th natural gas hydrate borehole. Calculate the total weights: W W The sum of weights is n, where n is the total number of samples. Calculate each data point at a specific x depth Weights: Let x be the weight of the core sample from the i-th borehole at depth x; An age-depth model for natural gas hydrate samples is established based on measured age, predicted age, and their depth relationship.

4. The method for analyzing the formation age of natural gas hydrate reservoirs according to claim 1, characterized in that, In step S 400 The specific steps for calculating the deposition time of natural gas hydrate reservoirs and thus determining the formation age of natural gas hydrates include: Step S 410 The deposition time of natural gas hydrate reservoirs was calculated by combining the age-depth model of the drill core samples and the depth of the natural gas hydrate reservoir. Step S 420 The formation age of natural gas hydrates is determined based on the deposition time of the natural gas hydrate reservoir.

5. An apparatus for analyzing the formation age of natural gas hydrate reservoirs, employing the method for analyzing the formation age of natural gas hydrate reservoirs according to any one of claims 1-4, characterized in that, include: The sample acquisition module is used to collect and analyze core data; The sample testing module is used for optically stimulated luminescence (OSL) age analysis based on the prepared marine sediment samples. The model building module is used to build an age-depth model for natural gas hydrate borehole core samples based on the optically stimulated luminescence age and sediment depth of the obtained marine sediment samples. The analysis module is used to calculate the deposition time of natural gas hydrate reservoirs based on the age-depth model of the drill core samples of natural gas hydrates, and thus determine the formation age of natural gas hydrates.

6. A system for analyzing the formation age of natural gas hydrate reservoirs, employing the method for analyzing the formation age of natural gas hydrate reservoirs according to any one of claims 1-4, characterized in that, The analysis system includes: One or more processors; A storage device for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the method for analyzing the formation age of natural gas hydrate reservoirs as described in any one of claims 1-4.

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