Mixing cause type natural gas hydrate saturation calculation method and device

Abstract

The invention discloses a method for calculating saturation of mixed cause type natural gas hydrate. The method comprises the following steps: obtaining a lithologic geologic model of a research area; performing simulation prediction on formation temperature field distribution of the research area according to the lithologic geologic model of the research area to obtain a formation temperature field distribution diagram; dividing the formation temperature field distribution diagram to obtain a biological hydrocarbon generation window and a thermal hydrocarbon generation window; and according to the distribution range of the biological hydrocarbon generation window and the thermal hydrocarbon generation window, determining a reservoir forming numerical model for saturation calculation of the mixed cause type natural gas hydrate. According to the technical scheme, seismic data, logging data and hydrocarbon source rock organic carbon geochemical data in a research area are collected, a lithologic geological framework model is established, a formation temperature field is simulated, and a hydrocarbon generation numerical value is simulated; and simulating a reservoir forming process of the natural gas hydrate to calculate and obtain a saturation range and a distribution schematic diagram of the mixed cause type natural gas hydrate, thereby providing a basis for evaluating the resource quantity of the natural gas hydrate in a research area.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas hydrates, and in particular to a method and a device for calculating the saturation of mixed-genetic natural gas hydrates. Background Art

[0002] Natural gas hydrate is a cage-like crystalline substance composed of natural gas molecules wrapped by water molecules under high pressure and low temperature. It looks like ice and snow, so it is also called "combustible ice". The prediction of natural gas hydrate saturation is the basis for the evaluation of natural gas hydrate resources. The saturation prediction research is conducive to understanding the impact of natural gas hydrates on submarine ecosystems and climate change. It also has important guiding significance for understanding the accumulation law of natural gas hydrates and guiding the exploration and development of natural gas hydrates.

[0003] The gas sources of natural gas hydrates include thermogenic gas, biogenic gas and mixed gas. However, the types of mixed gas and the quantitative proportion of mixed gas have not yet been clarified, so the calculation of its saturation is relatively difficult. Summary of the invention

[0004] The object of the present invention is to provide a method and device for calculating the saturation of mixed-genetic natural gas hydrates to solve the above-mentioned problems.

[0005] To achieve the above object, the present invention provides a method for calculating the saturation of mixed-genetic natural gas hydrates, the method comprising:

[0006] Obtaining the lithologic geological model of the study area;

[0007] According to the lithology geological model of the study area, the formation temperature field distribution in the study area is simulated and predicted to obtain the formation temperature field distribution map;

[0008] Divide the formation temperature field distribution map to obtain biological hydrocarbon generation window and thermal hydrocarbon generation window;

[0009] According to the distribution range of biological hydrocarbon generation window and thermal hydrocarbon generation window, the reservoir numerical model for calculating the saturation of mixed genetic natural gas hydrate is determined.

[0010] Optionally, obtain a lithologic geological model of the study area, including:

[0011] Obtain a seismic profile through the target well in the study area;

[0012] According to the seismic profile through the target well in the study area, determine the lateral distribution of lithology and sedimentary facies corresponding to different strata;

[0013] According to the lateral distribution of lithology and sedimentary facies corresponding to different strata, the lithological geological model of the study area is obtained.

[0014] Optionally, the formation temperature field distribution in the study area is simulated and predicted based on the lithologic geological model of the study area to obtain a formation temperature field distribution map, including:

[0015] Obtain the initial values ​​of seafloor temperature and heat flow in the study area;

[0016] Using the lithology geological model and combining the seabed temperature and initial heat flow values, the formation temperature field distribution is simulated and predicted to obtain the initial formation temperature field distribution map;

[0017] The initial formation temperature field distribution map is corrected using the formation temperature measured at the well location of the seismic profile to obtain the formation temperature field distribution map.

[0018] Optionally, according to the distribution range of the biological hydrocarbon generation window and the thermal hydrocarbon generation window, a reservoir numerical model for calculating the saturation of mixed-genetic natural gas hydrate is determined, including:

[0019] According to the distribution range of biological hydrocarbon generation window and thermal hydrocarbon generation window, the numerical simulation parameters of each set of formations are determined;

[0020] According to the numerical simulation parameters of each set of formations and the gas hydrate phase equilibrium curves of the well locations through the seismic profile, a reservoir numerical model for calculating the saturation of mixed-genetic gas hydrates is obtained.

[0021] Optional numerical simulation parameters include: total organic carbon TOC, hydrogen index I H 2. Select different hydrocarbon generation kinetic models for different formations;

[0022] Among them, the hydrocarbon generation kinetic models include: Biogenic-Reaction-01 biological hydrocarbon generation kinetic model, Type II thermal hydrocarbon generation kinetic model under Burnham and Type III thermal hydrocarbon generation kinetic model.

[0023] Optionally, the method further includes: verifying the numerical model of reservoir formation.

[0024] Optionally, validation of the reservoir numerical model is performed, including:

[0025] According to the reservoir formation numerical model, the initial gas hydrate stability zone range is simulated;

[0026] The initial gas hydrate stable zone range is compared with the measured gas hydrate stable zone range of the well location through the seismic profile. If the comparison result meets the preset requirements, the initial gas hydrate stable zone range is used as the final gas hydrate stable zone distribution range; if the comparison result meets the preset requirements, the initial gas hydrate stable zone range is adjusted, and the adjusted gas hydrate stable zone range is used as the final gas hydrate stable zone distribution range.

[0027] The present invention also provides a mixed-genesis natural gas hydrate saturation calculation device, the device comprising:

[0028] Acquisition unit, used to obtain the lithological geological model of the study area;

[0029] A prediction unit is used to simulate and predict the formation temperature field distribution in the study area according to the lithology geological model of the study area to obtain a formation temperature field distribution map;

[0030] A division unit is used to divide the formation temperature field distribution map to obtain the biological hydrocarbon generation window and the thermal hydrocarbon generation window;

[0031] A determination unit is provided for determining a reservoir-forming numerical model for calculating the saturation of mixed-genetic natural gas hydrates according to the distribution range of the biological hydrocarbon generation window and the thermal hydrocarbon generation window.

[0032] The present invention also provides an electronic device, comprising: a processor, the processor is coupled to a memory; the processor is used to read and execute a computer program stored in the memory to implement the above method.

[0033] The present invention also provides a computer-readable storage medium, in which a program or instruction is stored, and when the program or instruction is executed by a processor, the above method is implemented.

[0034] Technical effects and advantages of the present invention:

[0035] The present invention provides a method for calculating the saturation of mixed-genetic natural gas hydrates, the method comprising: obtaining a lithologic geological model of a study area; simulating and predicting the distribution of a formation temperature field in the study area according to the lithologic geological model of the study area to obtain a formation temperature field distribution map; dividing the formation temperature field distribution map to obtain a biological hydrocarbon generation window and a thermal hydrocarbon generation window; and determining a reservoir-forming numerical model for calculating the saturation of mixed-genetic natural gas hydrates according to the distribution ranges of the biological hydrocarbon generation window and the thermal hydrocarbon generation window.

[0036] This technical solution will simulate the formation process of natural gas hydrates by collecting seismic data, well logging data, organic carbon geochemical data of source rocks in the study area, establishing a lithological geological framework model, simulating the formation temperature field, and numerical simulation of hydrocarbon generation. It will calculate the saturation range and distribution diagram of mixed-genetic natural gas hydrates, thereby providing a basis for the evaluation of natural gas hydrate resources in the study area.

[0037] Other features and advantages of the present invention will be described in the following description, and partly become obvious from the description, or be understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flow chart of the method for calculating the saturation of mixed-genesis natural gas hydrates;

[0039] Figure 2 It is the structural evolution characteristics and stratigraphic framework of the Pearl River Mouth Basin;

[0040] Figure 3 It is the lithology geological model map;

[0041] Figure 4 This is the simulated formation temperature field diagram;

[0042] Figure 5 Gas hydrate stability zone map predicted for numerical simulations;

[0043] Figure 6 This is the simulated hydrate saturation distribution diagram under mixed gas source conditions. DETAILED DESCRIPTION

[0044] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings provided by the present invention, and the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0045] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0046] In order to solve the shortcomings of the prior art, the present invention discloses a method for calculating the saturation of mixed-genetic natural gas hydrates. Figure 1 The method is introduced as follows:

[0047] 1. Obtain the lithological geological model of the study area.

[0048] Specifically: select a seismic profile passing through a certain well in the study area, interpret the strata, faults and gas chimneys on the seismic profile, and determine the sedimentary phase type, lithology type and content ratio of each set of strata, and on this basis determine the lateral distribution of lithology and sedimentary phases and then establish a lithological geological model of the study area.

[0049] 2. Based on the lithological geological model of the study area, simulate and predict the distribution of the formation temperature field in the study area to obtain the formation temperature field distribution map.

[0050] Specifically, the lithologic geological model obtained in step 1 is used to simulate and predict the formation temperature field distribution in combination with the heat flow value of the current formation in the study area and the initial temperature value of the seabed. The simulation results of the initial formation temperature field distribution are compared with the formation temperature measured at the well position of the seismic profile, and the simulation results of the current formation temperature field are reasonably corrected based on the comparison results to obtain the final formation temperature field distribution.

[0051] 3. Divide the formation temperature field distribution map to obtain the biological hydrocarbon generation window and thermal hydrocarbon generation window.

[0052] Specifically, based on the temperature range of 75°C representing biological hydrocarbon generation and the temperature range of 100-300°C representing thermal hydrocarbon generation, the temperature fields of biological hydrocarbon generation and thermal hydrocarbon generation are divided on the simulated profile of the formation temperature field distribution obtained in step 2, and then the distribution ranges of natural gas hydrates of different origins are divided.

[0053] 4. According to the distribution range of biological hydrocarbon generation window and thermal hydrocarbon generation window, determine the reservoir numerical model for calculating the saturation of mixed genetic natural gas hydrate.

[0054] Specifically, the numerical simulation parameters of each set of strata are determined by using the division results to predict and simulate the range of the natural gas hydrate stability zone, the range of natural gas hydrate saturation and its distribution. The numerical simulation parameters include: total organic carbon TOC (%), hydrogen index I H (mg / g TOC), and different hydrocarbon generation kinetic models are selected for different formations (including Biogenic-Reaction-01 biological hydrocarbon generation kinetic model, Type II thermal hydrocarbon generation kinetic model under Burnham, and Type III thermal hydrocarbon generation kinetic model);

[0055] The determined simulation parameters and the simulation results of the current formation temperature field distribution are used to establish a numerical reservoir model in combination with the natural gas hydrate phase equilibrium curve of the well location through the seismic profile. According to the numerical reservoir model finally determined after the above correction, the saturation range and distribution diagram of the mixed-genetic natural gas hydrate are calculated, and the simulation results are compared with the measured average saturation of the well location, which is used for the evaluation of the saturation and spatial distribution of mixed-genetic natural gas hydrates.

[0056] The method also includes verifying the reservoir formation numerical model, specifically: simulating the range of the gas hydrate stability zone and determining the simulated bottom boundary of the gas hydrate stability zone; and comparing and reasonably correcting the range of the gas hydrate stability zone measured by the well position through the seismic profile, so as to obtain the final distribution range of the gas hydrate stability zone;

[0057] In order to better explain the present scheme, examples are also provided below.

[0058] The Pearl River Mouth Basin has the characteristics of both passive and active continental margins, and the regional geological background is complex. The Wenchang Formation of the Eocene and the Enping Formation of the Oligocene are considered to be the main mature-high mature source rocks, which can generate abundant thermogenic gas. Although the organic matter deposited in the Zhujiang Formation and the Hanjiang Formation is in the immature-low mature stage, it can be used as a source rock to produce a large amount of biogenic gas. Both thermogenic gas from deep formations and biogenic gas from shallow formations provide gas sources for the formation of natural gas hydrates in the Shenhu area.

[0059] 1. A seismic profile through the W19 well in the study area was selected. Based on the interpretation of the seismic sedimentary facies, nine sets of sequence interfaces were identified in the two-dimensional seismic profile, including the seafloor, T2 (2.6Ma), T3 (5.33Ma), T4 (11.6Ma), T5 (15.5Ma), T6 (23.8Ma), T7 (33.9Ma), T8 (38Ma) and Tg (49Ma). From top to bottom, they are divided into eight layers, namely the Quaternary, Wanshan Formation, Yuehai Formation, Hanjiang Formation, Zhujiang Formation, Zhuhai Formation, Enping Formation and Wenchang Formation. At the same time, according to the interpretation of the two-dimensional seismic data, several faults and gas chimneys were identified. The sedimentary facies type, lithology type and content ratio of each set of strata were determined (see Table 1). On this basis, the lateral distribution of lithologies of different strata was determined, and then the lithological geological model of the study area was established, such as Figure 2 and 3 shown.

[0060] Table 1 Sedimentary facies, lithology, TOC, I of each stratum in the model H and hydrocarbon generation kinetics

[0061]

[0062]

[0063] 2. Use the current stratum heat flow value and the initial seafloor temperature value in the study area to establish a stratum temperature field model. The current stratum heat flow value is 70Mw·m -2The initial seabed temperature value is 4.5℃, and the formation temperature field distribution is simulated and predicted. The simulation results are compared with the formation temperature measured at the well position of the seismic profile, and the current formation temperature field simulation results are reasonably corrected until the simulated temperature (line) is compared with the measured temperature (point) of hydrate drilling W19, and the two results are basically consistent. The formation temperature field profile shows a law of increasing temperature from the seabed downward. The highest temperature of the profile can reach 400℃, and the temperature in the hydrate layer is about 20℃. Figure 4 shown.

[0064] 3. Using the results of formation temperature field simulation, the temperature fields of biological hydrocarbon generation and thermal hydrocarbon generation are divided on the simulated section of the temperature field. Generally speaking, the temperature range of biological hydrocarbon generation is within 75°C, and the temperature range of thermal hydrocarbon generation is 100-300°C. Therefore, the temperature fields of biological hydrocarbon generation and thermal hydrocarbon generation are divided on the simulated section of the temperature field. Figure 4 As shown by the middle dotted line, within a depth range of about 1,300 m below the seabed, the strata for hydrocarbon generation are mainly biological, and within a depth range of about 1,800 to 5,800 m below the seabed, the strata for hydrocarbon generation are mainly thermal.

[0065] 4. Using the division results, determine the numerical simulation parameters of each set of strata to carry out prediction simulation of the range of natural gas hydrate stability zone, natural gas hydrate saturation range and distribution. The numerical simulation parameters include: total organic carbon TOC (%), hydrogen index I H (mg / g TOC), and different hydrocarbon generation kinetic models (including Biogenic-Reaction-01 biological hydrocarbon generation kinetic model, Burnham type II thermal hydrocarbon generation kinetic model and type III thermal hydrocarbon generation kinetic model) are selected for different formations (see Table 1).

[0066] 5. Using the above parameters and the simulation results of the current formation temperature field, combined with the natural gas hydrate phase equilibrium curve of the well location through the seismic profile, a numerical model of reservoir formation is established to simulate the range of the natural gas hydrate stability zone and compare it with the measured natural gas hydrate stability zone range at the well location; since the numerical simulation only considers the formation of methane hydrate, the thickness of the methane hydrate stability zone is calculated, so the actual stability zone thickness is greater than the thickness of the pure methane hydrate stability zone, such as Figure 5 shown.

[0067] 6. Using the above-mentioned reservoir numerical model, the state of the fault is set to open, and the fault activity time is set to 10Ma to the present. The final mixed-genesis natural gas hydrate saturation distribution model is calculated. The results show that the hydrate layer distributed in the hydrate stability zone has a continuous or semi-continuous lateral distribution. The hydrate saturation value is approximately between 10% and 50%, and the closer to the bottom of the hydrate stability zone, the higher the saturation value. The simulation results are compared with the measured average saturation of the W19 well for the evaluation of the saturation and spatial distribution of mixed-genesis natural gas hydrates, such as Figure 6 shown.

[0068] The present invention also provides a mixed-genesis type natural gas hydrate saturation calculation device, the device comprising: an acquisition unit, used to obtain a lithological geological model of a study area; a prediction unit, used to simulate and predict the formation temperature field distribution of the study area according to the lithological geological model of the study area, and obtain a formation temperature field distribution map; a division unit, used to divide the formation temperature field distribution map, and obtain a biological hydrocarbon generation window and a thermal hydrocarbon generation window; a determination unit, used to determine a reservoir numerical model for mixed-genesis type natural gas hydrate saturation calculation according to the distribution range of the biological hydrocarbon generation window and the thermal hydrocarbon generation window.

[0069] Since the content protected by this device is similar to that protected by the above method, no further introduction will be given here. Please refer to the discussion section of the above method for details.

[0070] The present invention also provides a device. The electronic device includes: at least one processor, at least one communication interface, at least one memory and at least one communication bus; optionally, the communication interface may be an interface of a communication module, such as an interface of a GSM module; the processor may be a processor CPU, or an application specific integrated circuit ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement an embodiment of the present invention. The memory may include a high-speed RAM memory, and may also include a non-volatile memory, such as at least one disk memory. The memory stores a program, and the processor calls the program stored in the memory to execute the method provided in the above embodiment of the present application.

[0071] Corresponding to the above method of the present application, the present application further provides a computer storage medium. The computer storage medium stores a computer program, which is executed by a processor to execute the method provided in the above embodiment of the present application.

[0072] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the saturation of mixed-genetic natural gas hydrates, characterized in that: The method comprises: Obtaining the lithologic geological model of the study area; According to the lithology geological model of the study area, the formation temperature field distribution in the study area is simulated and predicted to obtain the formation temperature field distribution map; Divide the formation temperature field distribution map to obtain biological hydrocarbon generation window and thermal hydrocarbon generation window; According to the distribution range of biological hydrocarbon generation window and thermal hydrocarbon generation window, the reservoir numerical model for calculating the saturation of mixed genetic natural gas hydrate is determined.

2. The method according to claim 1, characterized in that Obtain the lithologic geological model of the study area, including: Obtain a seismic profile through the target well in the study area; According to the seismic profile through the target well in the study area, determine the lateral distribution of lithology and sedimentary facies corresponding to different strata; According to the lateral distribution of lithology and sedimentary facies corresponding to different strata, the lithological geological model of the study area is obtained.

3. The method according to claim 2, characterized in that According to the lithologic geological model of the study area, the formation temperature field distribution in the study area is simulated and predicted to obtain the formation temperature field distribution map, including: Obtain the initial values ​​of seafloor temperature and heat flow in the study area; Using the lithology geological model and combining the seabed temperature and initial heat flow values, the formation temperature field distribution is simulated and predicted to obtain the initial formation temperature field distribution map; The initial formation temperature field distribution map is corrected using the formation temperature measured at the well location of the seismic profile to obtain the formation temperature field distribution map.

4. The method according to claim 3, characterized in that According to the distribution range of biological hydrocarbon generation window and thermal hydrocarbon generation window, the reservoir numerical model for mixed genetic natural gas hydrate saturation calculation is determined, including: According to the distribution range of biological hydrocarbon generation window and thermal hydrocarbon generation window, the numerical simulation parameters of each set of formations are determined; According to the numerical simulation parameters of each set of formations and the gas hydrate phase equilibrium curves of the well locations through the seismic profile, a reservoir numerical model for calculating the saturation of mixed-genetic gas hydrates is obtained.

5. The method according to claim 4, characterized in that Numerical simulation parameters include: total organic carbon TOC, hydrogen index I H 2. Select different hydrocarbon generation kinetic models for different formations; Among them, the hydrocarbon generation kinetic models include: Biogenic-Reaction-01 biological hydrocarbon generation kinetic model, Type II thermal hydrocarbon generation kinetic model under Burnham and Type III thermal hydrocarbon generation kinetic model.

6. The method according to claim 5, characterized in that The method further comprises: verifying the reservoir forming numerical model.

7. The method according to claim 6, characterized in that Verification of the reservoir numerical model, including: According to the reservoir formation numerical model, the initial gas hydrate stability zone range is simulated; The initial gas hydrate stable zone range is compared with the measured gas hydrate stable zone range of the well location through the seismic profile. If the comparison result meets the preset requirements, the initial gas hydrate stable zone range is used as the final gas hydrate stable zone distribution range; if the comparison result meets the preset requirements, the initial gas hydrate stable zone range is adjusted, and the adjusted gas hydrate stable zone range is used as the final gas hydrate stable zone distribution range.

8. A mixed origin natural gas hydrate saturation calculation device, characterized in that: The device comprises: Acquisition unit, used to obtain the lithological geological model of the study area; A prediction unit is used to simulate and predict the formation temperature field distribution in the study area according to the lithology geological model of the study area to obtain a formation temperature field distribution map; A division unit is used to divide the formation temperature field distribution map to obtain the biological hydrocarbon generation window and the thermal hydrocarbon generation window; A determination unit is provided for determining a reservoir-forming numerical model for calculating the saturation of mixed-genetic natural gas hydrates according to the distribution range of the biological hydrocarbon generation window and the thermal hydrocarbon generation window.

9. An electronic device, comprising: a processor coupled to the memory; The processor is used to read and execute the computer program stored in the memory to implement the method as described in 1-7.

10. A computer-readable storage medium storing a program or instruction, wherein the program or instruction implements the method described in 1-7 when executed by a processor.

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