Oil and gas accumulation analysis system based on multi-isotope synchronous monitoring

Abstract

The invention discloses an oil and gas accumulation analysis system based on multi-isotope synchronous monitoring, and belongs to the technical field of oil and gas accumulation, the system comprises a signal acquisition module, a signal processing module and a main control module which are connected in sequence, the main control module is connected with a DAC and a DDS, the DAC and the DDS are jointly connected to a driving module, and the driving module is connected with the signal processing module. The driving module and the temperature control module are jointly connected to the signal acquisition module; the signal acquisition module comprises an EC-QCL, a convergent lens group, an As2S3 optical fiber, an off-axis integral cavity, a convergent lens and a photoelectric detector; and the main control module performs data analysis on the second harmonic signal to obtain an isotope value, further calculates abundance of three isotopes of C, H and O, and analyzes the source, maturity, migration and reservoir forming processes of oil and gas by using a multi-isotope conjoint analysis oil and gas reservoir forming mechanism analysis model. The defect that the reservoir forming mechanism is not comprehensive enough when single isotope or double isotope analysis is adopted at present is overcome, and the vacancy of multi-element isotope joint analysis is made up.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrocarbon accumulation, and particularly relates to a hydrocarbon accumulation analysis system based on synchronous monitoring of multiple isotopes. Background Art

[0002] During the hydrocarbon exploration process, the shale gas exuded from rock formations contains various isotopes, among which C, H, and O isotopes are the most common. With the continuous in-depth research on hydrocarbon geochemistry, the detection of isotope abundances provides an effective basis for the traceability, migration, maturity, and accumulation process of chemical substances in hydrocarbon resources. Therefore, synchronously monitoring the abundances of C, H, and O isotopes (δ 13 C, δD, δ 18 O) and analyzing the hydrocarbon accumulation mechanism can provide key geochemical basis for the fine evaluation of complex hydrocarbon reservoirs.

[0003] In spectral logging, δ 13 C, δD, δ 18 O are important geochemical indicators that can provide key information about hydrocarbon sources, maturity, migration, and accumulation processes. However, existing research mostly focuses on single or dual isotope combination analysis. Huang Shipeng et al. from the Research Institute of Petroleum Exploration and Development, PetroChina explored the application of H isotope of alkane gas in natural gas origin, maturity identification, and indicating the sedimentary water environment of source rocks. Ni Yunyan et al. from China University of Petroleum comprehensively analyzed the carbon and hydrogen isotope characteristics of natural gas and explored the application of C and H isotopes in natural gas origin. Yang Yang from the School of Exploration and Surveying Engineering, Changchun Institute of Technology discussed the genetic mechanism of dolomite through geochemical means such as C and O isotope analysis. After investigation, there is no research that clearly analyzes the hydrocarbon accumulation mechanism by jointly using the ratios of C, H, and O isotopes simultaneously.

[0004] At present, the analysis techniques of gas isotopes at home and abroad are mainly divided into mass spectrometry and spectral analysis. Mass spectrometry technology detects isotope abundance through the difference in the mass-to-charge ratio of isotopes. It has high accuracy and precision and is an important means of laboratory isotope detection. However, in the analysis of shale gas components, mass spectrometry needs to be combined with gas chromatography. Limited by the efficiency of chromatographic separation, it leads to a long detection cycle, poor real-time performance, and large equipment, which makes it difficult to detect in situ. In addition, the operation is complicated and it is difficult to obtain continuous geochemical data, which limits subsequent mechanistic analysis. In recent years, spectral analysis technology has become an emerging isotope detection method with its fast, convenient, low-cost and non-destructive nature. At present, the spectral techniques commonly used for gas isotope detection can be divided into photoacoustic spectroscopy and absorption spectroscopy. Most spectral techniques use light sources that can only emit lasers with a narrow tunable range. Therefore, a single laser is difficult to achieve multi-component gas detection with a long gas absorption line distance. Multiple lasers will occupy more resources and are not conducive to system integration. If a laser with a wide tuning range is used, the requirements of synchronous monitoring and integration of multi-component gases can be taken into account. At present, quantum cascade laser frequency comb (QCL-FC) and external cavity quantum cascade laser (EC-QCL) have a wide tuning range. Since QCL-FC is relatively large, it is not conducive to downhole measurement, while EC-QCL has the characteristics of wide tuning, narrow linewidth, long life and fast tuning, and can provide up to 70 mW of optical output power. Based on these advantages, EC-QCL was finally selected as the light source for monitoring the isotope abundance of C, H, and O. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention proposes an oil and gas reservoir analysis system based on multi-isotope synchronous monitoring, which has a reasonable design, solves the shortcomings of the prior art and has good effects.

[0006] A system for analyzing oil and gas reservoir formation based on multi-isotope synchronous monitoring, comprising a signal acquisition module, a signal processing module and a main control module connected in sequence, wherein the main control module is also connected to a DAC and a DDS respectively, the DAC and the DDS are connected to a driving module together, and the driving module and the temperature control module are connected to the signal acquisition module together; The signal acquisition module includes EC-QCL, a converging lens group, As 2 S 3 Optical fiber, off-axis integrating cavity, converging lens and photodetector are used to collect optical signals containing gas absorption information and convert the optical signals into electrical signals that are easy to process; The signal processing module includes a preamplifier circuit, a filter circuit, a phase-locked amplifier and an AD acquisition circuit, which are used to filter and demodulate the electrical signal to obtain a second harmonic signal that can reflect the gas concentration; The main control module is used to control DAC and DDS to generate driving voltage signals on the one hand, and to obtain isotope values ​​through data analysis of the second harmonic signal on the other hand, and then calculate the abundance of three isotopes of C, H and O, and use the multi-isotope joint analysis model of oil and gas accumulation mechanism to analyze the source, maturity, migration and accumulation process of oil and gas, predict the oil and gas sweet spot and assist in resource estimation; The driving module and the temperature control module are used to realize the current driving and temperature control of the EC-QCL, so that the output wavelength of the EC-QCL covers the three isotope absorption lines of C, H and O.

[0007] Furthermore, in the signal acquisition module, the EC-QCL output wavelength used is 3.26μm~3.55μm, and the laser output by the EC-QCL is converged to the mid-infrared optical fiber head through a converging lens group. 2 S 3 The optical fiber is coupled into the off-axis integrating cavity; The off-axis integrating cavity uses a high-reflection mirror and a sapphire window with a reflectivity of 99.98% in the target band, and the off-axis integrating cavity is connected to a gas sampling device, which includes an air pump and a filtering device. The air pump draws filtered shale gas into the cavity to absorb the laser. The optical signal output by the off-axis integrating cavity is converged by a converging lens to the photosensitive surface of the photodetector and is converted into an electrical signal by the photodetector.

[0008] Furthermore, in the main control module, the abundance of the three isotopes of C, H and O , , They are: ; ; ; in, To contain 13 CH 4 The second harmonic signal amplitude of the concentration information, for 12 CH 4 The absorption cross section at the center of the absorption line, for 12 CH 4 The incident light intensity corresponding to the absorption line is To contain 12 CH 4 The second harmonic signal amplitude of the concentration information, for 13 CH 4 The absorption cross section at the center of the absorption line, for 13 CH 4 The incident light intensity corresponding to the absorption line; Containing CH 3 D concentration information second harmonic signal amplitude, CH 4 The absorption cross section at the center of the absorption line, CH 4 The incident light intensity corresponding to the absorption line is Containing CH 4 The second harmonic signal amplitude of the concentration information, CH 3 D is the absorption cross section at the center of the absorption line, CH 3 D The incident light intensity corresponding to the absorption line; Contains OC 18 The second harmonic signal amplitude of O concentration information, For OC 16 The absorption cross section of O at the center of the absorption line, For OC 16 The incident light intensity corresponding to the O absorption line is Contains OC 16 The second harmonic signal amplitude of O concentration information, For OC 18 The absorption cross section of O at the center of the absorption line, For OC 18 The incident light intensity corresponding to the O absorption line.

[0009] Furthermore, the multi-isotope joint analysis oil and gas reservoir formation mechanism analysis model includes a four-layer structure of data input layer, data processing layer, isotope analysis layer, and prediction and evaluation layer; The data input layer inputs each isotope standard abundance value and detection geographical location information; The data processing layer filters and fuses abnormal data. The guidelines are: ; in, Representative Sample data, is the sample mean, is the standard deviation of the sample; the error is located in The extra data were removed to ensure the validity of the data; The isotope analysis layer analyzes the oil and gas sources, maturity, migration and accumulation process respectively; The prediction and assessment layer predicts exploration targets and estimates resource quantities.

[0010] Furthermore, in the isotope analysis layer, the oil and gas source analysis is specifically as follows: The value can distinguish the origin of coal-generated gas. If the value distribution range is between -94‰ and -55‰, it is caused by microbial chemical action; If the value distribution range is between -55‰ and -29‰, it is caused by pyrolysis maturity; The value is between -260‰~-150‰, and the oil-type gas Values ​​above -180‰; The specific analysis of oil and gas maturity is as follows: For oil-type gas, there is the following formula: ; For coal-derived gas, there is the following formula: ; In the formula, is the reflectance of organic vitrinite in source rocks, which is used to judge the maturity of oil and gas. When it is lower than 0.5%, it is in the immature stage; when it is between 0.5% and 1.3%, it is in the low-maturity to mature stage; when it is between 1.3% and 2.0%, it is in the high-maturity stage; when it is higher than 2.0%, it is in the over-mature stage.

[0011] Furthermore, in the isotope analysis layer, the oil and gas migration path analysis is specifically as follows: Calculate the migration direction gradient, Gradient = / distance, if If the gradient is greater than 1‰ / km, it indicates a short-distance rapid migration, which is a fault channel; If the gradient is less than 0.5 ‰ / km, it indicates long-distance diffusion and a homogeneous reservoir. If the value changes from high value in deep part to low value in shallow part, it indicates that there is a vertical migration channel; in horizontal direction, if The value decreases with the increase of exploration distance, which indicates that there is horizontal migration; during the migration process, if If the value is close to that of the surrounding rock, that is, the difference with the background value of the surrounding rock is within ±1%, it indicates that the migration path passes through a specific lithology section and water-rock interaction occurs; The specific analysis of reservoir-forming environment is as follows: when When the value is higher than -0.8‰, CO 2It comes from the dissolution of carbonate rocks. Its oxygen isotope fractionation is related to temperature. The paleotemperature can be obtained according to the carbonate-water oxygen isotope balance formula: ; In the formula The value needs to be input from outside the model. If it is marine sediments, ; Combination and The paleo-salinity during the reservoir formation period can be inferred collaboratively. The value is higher than -160‰, and If the value is higher than -0.8‰, it is a marine high-salinity environment; The value is less than -160‰, and If the value is negative, it is a continental low-salinity environment; The closure of the reservoir environment is indirectly reflected by isotope fractionation dynamics and gas adsorption behavior. The value change range does not exceed ±3% and CO 2 The content is higher than 50%, and The value change range is less than 10‰, indicating that the gas has not diffused significantly and has high sealing. High sealing means that the fractionation range is less than 10‰. On the contrary, if Above -0.8‰ and CO 2 The content is less than 20%, and The value change range is higher than 20‰, indicating that the gas diffuses significantly, and it is considered to be an open system. The open system has a fractionation range higher than 20‰; When it is negative, it means that the sealing is poor and CO 2 Preferentially escape or react with groundwater.

[0012] Furthermore, the prediction and assessment layer first integrates the isotope data and geological parameters based on the results of the isotope analysis layer, combines the data with visualization graphics, updates the data on the topographic map, and calculates along the potential migration path. Gradient: The steep gradient area indicates the main migration channel, and the steep gradient area is higher than 0.5 ‰ / km. Next, the exploration target is delineated, and the area that meets the comprehensive indicators is considered the sweet spot: ; In the formula, the calculation formula for hydrocarbon generation intensity is: ; In the formula, is the total organic carbon content, is the thickness of source rock, is the hydrogen index, for maturity; The calculation formula for oil and gas resources Q is: ; In the formula, Q is the oil and gas resources, A is the effective reservoir area, h is the effective thickness of the reservoir, is the porosity, is the hydrocarbon saturation, is the density of crude oil, is the volume coefficient of crude oil.

[0013] Beneficial technical effects brought by the present invention: The present invention adopts a single external cavity quantum cascade laser combined with off-axis integral cavity output spectroscopy technology to complete the in-situ synchronous monitoring of the abundance of three isotopes of carbon, hydrogen and oxygen in shale gas, and based on this, constructs a multi-isotope joint analysis model for oil and gas accumulation mechanism analysis, which makes up for the shortcoming that the current use of single isotope or dual isotope analysis of accumulation mechanism is not comprehensive enough, and fills the gap in multi-isotope joint analysis.

[0014] 1. Using a single EC-QCL as the light source, based on its wide tuning range and narrow linewidth, multiple isotope absorption peaks are scanned simultaneously to perform multi-isotope synchronous monitoring, instead of using multiple lasers for multi-gas detection in traditional spectroscopy, which reduces the size of the instrument and greatly improves the system integration.

[0015] 2. In order to adapt to the high temperature and vibration environment during drilling, the laser beam is coupled to the cavity using a high temperature resistant mid-infrared optical fiber, and the off-axis integrating cavity window is made of sapphire material, so as to adapt to the high temperature environment and solve the problem that the traditional reflector group is difficult to adapt to the bumpy environment, so as to ensure the smooth operation of the detection device.

[0016] 3. Compared with single-isotope or dual-isotope analysis, this method analyzes key information such as oil and gas sources, maturity, migration paths, and accumulation processes more comprehensively based on the collected in-situ carbon, hydrogen, and oxygen isotope abundance information, and establishes an oil and gas accumulation mechanism analysis model based on multi-isotope joint analysis, revealing the full-chain isotope response of oil and gas generation-migration-accumulation, predicting the distribution of oil and gas resources, and thus guiding oil and gas development. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of an oil and gas reservoir analysis system based on multi-isotope synchronous monitoring in the present invention.

[0018] Figure 2 For the present invention 12 CH 4 , 13 CH 4 Graph showing changes in the infrared absorption intensity of a molecule.

[0019] Figure 3 In the present invention, CH4 , CH 3 Graph showing changes in infrared absorption intensity of molecule D.

[0020] Figure 4 OC in the present invention 16 O.OC 18 Graph showing changes in infrared absorption intensity of O molecules.

[0021] Figure 5 It is a schematic diagram of the multi-isotope joint analysis model for oil and gas accumulation mechanism analysis in the present invention.

[0022] Among them, 1-main control module; 2-digital-to-analog converter; 3-digital frequency synthesizer; 4-driving module; 5-temperature control module; 6-external cavity quantum cascade laser; 7-converging lens group; 8-As 2 S 3 Optical fiber; 9-off-axis integrating cavity; 10-air pump; 11-filtering device; 12-converging lens; 13-photoelectric detector; 14-signal processing module. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention is further described below in conjunction with specific embodiments: A hydrocarbon reservoir analysis system based on multi-isotope synchronous monitoring, such as Figure 1 As shown, it includes a signal acquisition module, a signal processing module and a main control module 1 connected in sequence, the main control module 1 is connected to a digital-to-analog converter 2 (DAC) and a digital frequency synthesizer 3 (DDS) respectively, the DAC and the DDS are connected to a driving module 4, and the driving module 4 and the temperature control module 5 are connected to the signal acquisition module; The signal acquisition module includes an external cavity quantum cascade laser 6 (EC-QCL), a converging lens group 7, and an As 2 S 3 The optical fiber 8, the off-axis integrating cavity 9, the converging lens 12 and the photodetector 13 are used to collect the optical signal containing the gas absorption information and convert the optical signal into an electrical signal that is easy to process; The EC-QCL output wavelength used is 3.26 μm~3.55 μm, which completely covers the absorption lines of C, H, and O isotopes (3.39 μm, 3.31 μm, and 3.34 μm). The absorption line positions of the three isotopes are as follows: Figure 2 , Figure 3 , Figure 4 As shown; the converging lens group consists of a convex lens and a concave lens, which are fixed at the laser output port of the EC-QCL to couple the laser beam into the optical fiber; As 2 S 3The optical fiber is a mid-infrared optical fiber that can transmit the laser emitted by the EC-QCL. The other end is connected to the off-axis integrating cavity to couple it into the cavity. The off-axis integrating cavity is the place where the laser and the gas absorb each other. A high-reflection mirror with a reflectivity of 99.98% in the target band is used. Its optical path can reach the kilometer level. In order to adapt to the high-temperature environment underground, a sapphire window is used. The off-axis integrating cavity is connected to a gas sampling device, which includes an air pump 10 and a filtering device 11. Due to the complex underground environment and the presence of many fine particles and other substances in the gas, a filtering device is required to avoid contaminating the lens in the cavity. The air pump draws the filtered shale gas into the cavity to absorb the laser. The signal processing module 14 includes a preamplifier circuit, a filter circuit, a phase-locked amplifier and an AD acquisition circuit, which are used to filter and demodulate the electrical signal to obtain a second harmonic signal that can reflect the gas concentration; The main control module 1 is embedded with digital noise reduction, concentration inversion and oil and gas accumulation mechanism analysis algorithms, and communicates with other modules. It is the core unit of the entire system. On the one hand, it is used to control DAC and DDS to generate driving voltage signals. On the other hand, it obtains isotope values ​​through noise reduction, inversion and other data analysis of the second harmonic signal, and then calculates the abundance of three isotopes of C, H and O. It also uses the multi-isotope joint analysis oil and gas accumulation mechanism analysis model to analyze the oil and gas source, maturity, migration and accumulation process, predict the oil and gas sweet spot and assist in resource estimation. The driving module includes a constant current source circuit and an overcurrent protection circuit. The constant current source circuit converts the driving voltage signal into a current signal to complete the current drive of the laser. The overcurrent protection circuit is to prevent excessive current from damaging the laser. The temperature control module integrates a temperature control chip, and uses a semiconductor cooler (TEC) controller to perform high-precision control of the TEC inside the EC-QCL to stabilize the laser temperature.

[0024] The working principle of the device is as follows: the main control module controls DAC and DDS to generate low-frequency sawtooth wave and high-frequency sine wave respectively. The superposition of the two is used as a driving voltage signal and converted into a current signal by the driving module. The temperature control module is combined to realize the current drive and temperature control of the laser, so that the laser output wavelength covers the three isotope absorption lines of C, H, and O. The laser output laser is converged to the mid-infrared fiber head through the converging lens group and the As 2 S 3The optical fiber is coupled to the off-axis integrating cavity. Shale gas is pumped into the cavity by the gas pump and fully absorbed by the laser. The optical signal output by the off-axis integrating cavity is converged by the converging lens to the photosensitive surface of the photodetector, and is converted by the detector into an electrical signal that is easier to process. The signal processing module filters and demodulates the detector signal to obtain a second harmonic signal that can directly reflect the gas concentration. After being collected by the main control module, the isotope value is obtained after noise reduction, inversion and other data analysis, and then the isotope abundance is calculated. The oil and gas source, maturity, migration and accumulation process are analyzed through the internal integrated analytical algorithm.

[0025] When laser absorption spectroscopy is used to measure gas concentration, the Beer-Lambert law is expressed as follows: ; in, is the laser input intensity when there is no gas absorption, is the intensity of the transmitted light of the laser through the absorbed gas; The wavelength is The absorption cross section of the medium per unit concentration per unit length is also called the absorption coefficient. is the concentration of the measured gas, It is the optical path of the laser through the gas being measured.

[0026] Assume that the initial light intensity entering the integrating cavity is I in , the cavity length is L 0 The integrating cavity consists of an input mirror and an output mirror, both with a reflectivity of R and a transmittance of T=1-R. The total loss of light propagating once in the cavity (including gas absorption, scattering or off-axis diffraction, etc.) is d. When light enters the cavity, a portion of it will be transmitted and output each time it is reflected. The path length of each transmitted light and the ratio of the intensity of the transmitted portion are shown in Table 1: Table 1 Path length of each transmitted light and ratio of transmitted light intensity ; Total effective optical path L eff It is the weighted average of the path length of each transmitted light and its light intensity contribution. Since the light intensity decays with the number of reflections, the total optical path can be expressed as: ; The driving current of the laser is sinusoidally modulated, and the corresponding light intensity and frequency of the light source are also modulated and are proportional to the injection current.

[0027] ; ; in is the light intensity modulation coefficient, is the center frequency of the light source when it is not modulated, is the frequency modulation amplitude (usually on the same order of magnitude as the absorption half-width), is the sinusoidal modulation frequency, ; The Beer-Lambert law can be written in frequency form as follows: ; The light intensity modulation coefficient and the gas absorption coefficient are both very small, that is, and , and make an approximate calculation to obtain the following formula: ; Absorption line shape of gas It can be described by the normalized Lorentz line shape, namely: ; in is the absorption cross section of pure gas at the center of the absorption line, is the center frequency of the absorption peak, is the half width of the absorption line.

[0028] You can get: ; When the center frequency of the light source output is precisely locked on the gas absorption peak, ,but: ; in, ; Expand the above formula into a Fourier series. Since the amplitude of higher harmonics is small, they are not expanded one by one. The coefficients of the first harmonic (f) and the second harmonic (2f) are as follows: ; ; in , the size of k is related to w, ,Right now When , the amplitude of the second harmonic reaches a maximum of 3.43. The first harmonic signal is mainly caused by light intensity modulation, and its magnitude is proportional to the average power of the light source. The magnitude of the second harmonic signal is related to the initial light intensity and the concentration of the gas. The gas concentration information can be obtained by extracting the second harmonic signal. The concentration can be expressed as: ; The effective absorption path length of the off-axis integrating cavity Substituting into the above formula, we can get the expression of concentration C: ; Isotope abundance Indicates the ratio of heavy isotope to light isotope content in the substance to be tested The ratio of heavy isotope to light isotope content in the standard material The relative deviation between: ; The calculation method of isotope abundance can be obtained: ; When measuring isotope abundance, the selected standard substances are shown in Table 2: Table 2 Standard substances ; Therefore, δ can be calculated 13 C.δ 2 D. δ 18 O: ; ; ; After obtaining the standard abundance values ​​of the three isotopes, a multi-isotope joint analysis model for oil and gas accumulation mechanism was constructed, such as Figure 5 As shown in the figure, it includes four layers: data input layer, data processing layer, isotope analysis layer, and prediction and evaluation layer. First, establish the data input layer to input the standard abundance values ​​of each isotope and the detection geographical location information; establish the data processing layer to filter abnormal data and merge data to make the data more reliable; enter the isotope analysis layer to identify the source of oil and gas, calculate maturity, reconstruct migration paths, and infer the reservoir environment based on isotope data; finally, in the prediction and evaluation layer, based on isotope analysis, predict exploration targets and assist in estimating resource volume to guide oil and gas development.

[0029] The specific construction steps are as follows: The data input layer inputs the standard abundance values ​​of each isotope and the detection geographical location information; The data processing layer filters and fuses abnormal data based on The guidelines are: ; in, Representative Sample data, is the sample mean, is the standard deviation of the sample; the error is located in The extra data were removed to ensure the validity of the data; Isotope analysis layer, first of all, oil and gas source analysis, using - The collaborative discrimination method. The value can distinguish the origin of coal-generated gas. If the value distribution range is between -94‰ and -55‰, it is a typical microbial chemical cause; If the value distribution range is between -55‰ and -29‰, it is caused by pyrolysis maturity. It is difficult to distinguish between oil-type gas and coal-generated gas. Value-assisted identification, coal-derived gas The value is usually lighter, ranging from -260‰ to -150‰; oil-type gas The values ​​are heavier, above -180‰.

[0030] The second is the oil and gas maturity analysis. The initial carbon isotope composition of different organic matter types is significantly different, so it is necessary to select an appropriate maturity calculation formula based on the parent material type. For oil-type gas (sapropelic natural gas), the following formula is used: ; For coal-generated gas (humic natural gas), there is the following formula: ; Next, the migration path is reconstructed using and Combined tracing method. There is diffusion fractionation in the migration process. The light isotope molecules diffuse faster. The methane at the far end of the migration path So according to The value and the measurement location can determine the direction of the migration path. gradient( / distance), if If the gradient is greater than 1‰ / km, it indicates a short-distance rapid migration, which is a fault channel; If the gradient is less than 0.5 ‰ / km, it indicates long-distance diffusion and a homogeneous reservoir. The transition of the value from high value in deep part to low value in shallow part indicates the existence of vertical migration channel. The value decreases with the increase of exploration distance, indicating the existence of horizontal migration. The value is close to that of the surrounding rock, that is, the difference with the background value of the surrounding rock is within ±1%, indicating that the migration path passes through a specific lithology section and water-rock interaction occurs.

[0031] Next is the speculation of reservoir-forming environment. and Combined speculation method. High temperature will enhance the fractionation effect of hydrogen isotopes in methane molecules, resulting in It becomes more positive (heavier) as the temperature increases. When the value is higher than -0.8‰, CO 2It comes from the dissolution of carbonate rocks, and its oxygen isotope fractionation is related to temperature. The paleotemperature can be obtained according to the carbonate-water oxygen isotope balance formula: ; In the formula The value needs to be input from outside the model. If it is marine sediments, . Combined and The paleo-salinity during the reservoir formation period can be inferred collaboratively. The value is higher than -160‰, and If the value is higher than -0.8‰, it can be inferred to be a marine high-salinity environment; The value is less than -160‰, and If the value is negative, it can be inferred that it is a continental low-salinity environment. The closure of the reservoir-forming environment is indirectly reflected by isotope fractionation dynamics and gas adsorption behavior. The value change range does not exceed ±3% and CO 2 The content is higher than 50%, and The value change range is less than 10‰, indicating that the gas has not diffused significantly and has high closure (fractionation range is less than 10‰); on the contrary, if Above -0.8‰ and CO 2 The content is less than 20%, and The value variation is higher than 20‰, indicating that the gas diffuses significantly and it is considered to be an open system (fractionation amplitude is higher than 20‰). 2 The adsorption capacity is significantly higher than that of CH 4 , so when When it is negative, it means that the sealing is poor and CO 2 Preferentially escape or react with groundwater.

[0032] The prediction and assessment layer first integrates the isotope data and geological parameters based on the results of the isotope analysis layer, combines the data with visualization graphics, updates the data on the topographic map, and calculates along the potential migration path. Gradient: steep gradient areas (above 0.5‰ / km) indicate the main migration channel; Next, we will define the exploration targets, and the areas that meet the comprehensive indicators will be considered as sweet spots: ; In the formula, the calculation formula for hydrocarbon generation intensity is: ; In the formula, is the total organic carbon content, is the thickness of source rock, is the hydrogen index, for maturity; To assist in resource estimation, the calculation formula for oil and gas resource Q is: ; In the formula, Q is the oil and gas resources, 10,000 tons; A is the effective reservoir area, km 2 ; h is the effective thickness of the reservoir, m; is the porosity; is the hydrocarbon saturation; is the density of crude oil g / cm 3 ; is the crude oil volume coefficient. Although the isotope abundance value is directly used as a factor in the resource calculation, it plays an auxiliary role in the parameter determination. Indicating high-mature source rocks (R o >1.0%), indicating a large hydrocarbon generation potential; The decay gradient can delineate the effective reservoir area (A); A change of less than 5‰ indicates good preservation conditions and increases hydrocarbon saturation ( ) reliability.

[0033] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A system for analyzing oil and gas reservoir formation based on multi-isotope synchronous monitoring, characterized in that: It includes a signal acquisition module, a signal processing module and a main control module connected in sequence, wherein the main control module is also connected to a DAC and a DDS respectively, the DAC and the DDS are connected to a driving module together, and the driving module and the temperature control module are connected to the signal acquisition module together; The signal acquisition module includes an EC-QCL, a converging lens group, an As2S3 optical fiber, an off-axis integrating cavity, a converging lens and a photodetector, and is used to collect optical signals containing gas absorption information and convert the optical signals into electrical signals that are easy to process; The signal processing module includes a preamplifier circuit, a filter circuit, a phase-locked amplifier and an AD acquisition circuit, which are used to filter and demodulate the electrical signal to obtain a second harmonic signal that can reflect the gas concentration; The main control module is used to control DAC and DDS to generate driving voltage signals on the one hand, and to obtain isotope values ​​through data analysis of the second harmonic signal on the other hand, and then calculate the abundance of three isotopes of C, H and O, and use the multi-isotope joint analysis model of oil and gas accumulation mechanism to analyze the source, maturity, migration and accumulation process of oil and gas, predict the oil and gas sweet spot and assist in resource estimation; The driving module and the temperature control module are used to realize the current driving and temperature control of the EC-QCL, so that the output wavelength of the EC-QCL covers the three isotope absorption lines of C, H and O.

2. The oil and gas reservoir analysis system based on multi-isotope synchronous monitoring according to claim 1 is characterized in that: In the signal acquisition module, the EC-QCL output wavelength used is 3.26μm~3.55μm, and the laser output by the EC-QCL is converged to the mid-infrared optical fiber head through a converging lens group, and coupled to the off-axis integrating cavity by the As2S3 optical fiber; The off-axis integrating cavity uses a high-reflection mirror and a sapphire window with a reflectivity of 99.98% in the target band, and the off-axis integrating cavity is connected to a gas sampling device, which includes an air pump and a filtering device. The air pump draws filtered shale gas into the cavity to absorb the laser. The optical signal output by the off-axis integrating cavity is converged by a converging lens to the photosensitive surface of the photodetector and is converted into an electrical signal by the photodetector.

3. The oil and gas reservoir analysis system based on multi-isotope synchronous monitoring according to claim 2 is characterized in that: In the main control module, the abundance of three isotopes of C, H and O , , They are: ； ； ； in, To contain 13 The second harmonic signal amplitude of CH4 concentration information, for 12 The absorption cross section of CH4 at the center of the absorption line, for 12 The incident light intensity corresponding to the CH4 absorption line is To contain 12 The second harmonic signal amplitude of CH4 concentration information, for 13 The absorption cross section of CH4 at the center of the absorption line, for 13 The incident light intensity corresponding to the CH4 absorption line; is the amplitude of the second harmonic signal containing CH3D concentration information, is the absorption cross section of CH4 at the center of the absorption line, is the incident light intensity corresponding to the CH4 absorption line, is the amplitude of the second harmonic signal containing CH4 concentration information, is the absorption cross section of CH3D at the center of the absorption line, is the incident light intensity corresponding to the CH3D absorption line; Contains OC 18 The second harmonic signal amplitude of O concentration information, For OC 16 The absorption cross section of O at the center of the absorption line, For OC 16 The incident light intensity corresponding to the O absorption line is Contains OC 16 The second harmonic signal amplitude of O concentration information, For OC 18 The absorption cross section of O at the center of the absorption line, For OC 18 The incident light intensity corresponding to the O absorption line.

4. The oil and gas reservoir analysis system based on multi-isotope synchronous monitoring according to claim 3 is characterized in that: The multi-isotope joint analysis oil and gas accumulation mechanism analysis model includes a four-layer structure of data input layer, data processing layer, isotope analysis layer, and prediction and evaluation layer; The data input layer inputs each isotope standard abundance value and detection geographical location information; The data processing layer filters and fuses abnormal data. The guidelines are: ； in, Representative Sample data, is the sample mean, is the standard deviation of the sample; the error is located in The extra data were removed to ensure the validity of the data; The isotope analysis layer analyzes the oil and gas sources, maturity, migration and accumulation process respectively; The prediction and assessment layer predicts exploration targets and estimates resource quantities.

5. The oil and gas reservoir analysis system based on multi-isotope synchronous monitoring according to claim 4 is characterized in that: In the isotope analysis layer, the oil and gas source analysis is specifically as follows: The value can distinguish the origin of coal-generated gas. If the value distribution range is between -94‰ and -55‰, it is caused by microbial chemical action; If the value distribution range is between -55‰ and -29‰, it is caused by pyrolysis maturity; The value is between -260‰~-150‰, and the oil-type gas Values ​​above -180‰; The specific analysis of oil and gas maturity is as follows: For oil-type gas, there is the following formula: ； For coal-derived gas, there is the following formula: ； In the formula, is the reflectance of organic vitrinite in source rocks, which is used to judge the maturity of oil and gas. When it is lower than 0.5%, it is in the immature stage; when it is between 0.5% and 1.3%, it is in the low-maturity to mature stage; when it is between 1.3% and 2.0%, it is in the high-maturity stage; when it is higher than 2.0%, it is in the over-mature stage.

6. The oil and gas reservoir analysis system based on multi-isotope synchronous monitoring according to claim 5 is characterized in that: In the isotope analysis layer, the oil and gas migration path analysis is specifically as follows: Calculate the migration direction gradient, Gradient = / distance, if If the gradient is greater than 1‰ / km, it indicates a short-distance rapid migration, which is a fault channel; If the gradient is less than 0.5 ‰ / km, it indicates long-distance diffusion and a homogeneous reservoir. If the value changes from high value in deep part to low value in shallow part, it indicates that there is a vertical migration channel; in horizontal direction, if The value decreases with the increase of exploration distance, which indicates that there is horizontal migration; during the migration process, if If the value is close to that of the surrounding rock, that is, the difference with the background value of the surrounding rock is within ±1%, it indicates that the migration path passes through a specific lithology section and water-rock interaction occurs; The specific analysis of reservoir-forming environment is as follows: when When the value is higher than -0.8‰, CO2 comes from carbonate rock dissolution, and its oxygen isotope fractionation is related to temperature. The paleotemperature can be obtained according to the carbonate-water oxygen isotope balance formula: ； In the formula The value needs to be input from outside the model. If it is marine sediments, ; Combination and The paleo-salinity during the reservoir formation period can be inferred collaboratively. The value is higher than -160‰, and If the value is higher than -0.8‰, it is a marine high-salinity environment; The value is less than -160‰, and If the value is negative, it is a continental low-salinity environment; The closure of the reservoir environment is indirectly reflected by isotope fractionation dynamics and gas adsorption behavior. The value change range does not exceed ±3% and the CO2 content is higher than 50%. The value change range is less than 10‰, indicating that the gas has not diffused significantly and has high sealing. High sealing means that the fractionation range is less than 10‰. On the contrary, if Higher than -0.8‰ and CO2 content is lower than 20%, and The value change range is higher than 20‰, indicating that the gas diffuses significantly, and it is considered to be an open system. The open system has a fractionation range higher than 20‰; When it is negative, it indicates that poor sealing causes CO2 to escape preferentially or react with groundwater.

7. The oil and gas reservoir analysis system based on multi-isotope synchronous monitoring according to claim 6 is characterized in that: The prediction and assessment layer first integrates the isotope data and geological parameters based on the results of the isotope analysis layer, combines the data with visual graphics, updates the data on the topographic map, and calculates along the potential migration path. Gradient: The steep gradient area indicates the main migration channel, and the steep gradient area is higher than 0.5 ‰ / km. Next, the exploration target is delineated, and the area that meets the comprehensive indicators is considered the sweet spot: ； In the formula, the calculation formula for hydrocarbon generation intensity is: ； In the formula, is the total organic carbon content, is the thickness of source rock, is the hydrogen index, for maturity; The calculation formula for oil and gas resources Q is: ； In the formula, Q is the oil and gas resources, A is the effective reservoir area, h is the effective thickness of the reservoir, is the porosity, is the hydrocarbon saturation, is the density of crude oil, is the volume coefficient of crude oil.

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