A method for extracting seismic fluid velocity anomaly information in a geothermal field

Abstract

The application provides a geothermal field area seismic electric fluid velocity anomaly information extraction method, comprising the following steps: a, using a seismic electric exploration instrument to measure a measurement area to obtain original seismic electric data; b, obtaining seismic electric data after input parameters; c, obtaining fluid data containing relative permeability corresponding to different depths; d, drawing a relative permeability profile curve graph and a relative permeability section graph according to the relative permeability data obtained in step c; e, obtaining a relative permeability profile curve graph, a water-bearing layer inference interpretation result graph and a relative permeability water-bearing layer inference interpretation section graph. The anomaly information extraction method of the application finds out the distribution characteristics of underground fluid, and comprehensively interprets the results of the wide frequency magnetotelluric method, so that good survey effect can be achieved for searching for geothermal fluid.

Description

Technical Field

[0001] This invention relates to the field of geological exploration technology, specifically a method for extracting seismic current velocity anomaly information in geothermal fields. Background Technology

[0002] With the development of society and economy, energy shortages are becoming increasingly urgent. Against this backdrop, the development and utilization of geothermal resources have gradually come into the public eye. In my country, the geophysical methods commonly used for geothermal exploration include: Controlled-Source Audio-Frequency Magnetotelluric (CSAMT), Broadband Magnetotelluric (BMT), or Magnetotelluric (MT). However, conventional electromagnetic methods only roughly determine the geoelectric structure within a 3km depth of the geothermal zone, revealing the undulating morphology of the basement and the spatial distribution characteristics of hidden faults. They are unlikely to yield good results for directly locating geothermal water, meaning that conventional electromagnetic methods struggle to extract accurate spatial locations of geothermal fluids and their distribution characteristics from the obtained information. Summary of the Invention

[0003] The purpose of this invention is to provide a method for extracting geothermal fluid velocity anomaly information in geothermal fields, so as to solve the problem that conventional electromagnetic methods alone cannot obtain the accurate spatial location of geothermal fluids.

[0004] This invention is implemented as follows: A method for extracting seismic current velocity anomaly information in geothermal fields, comprising the following steps:

[0005] a. Select the geothermal area to be measured as the measurement area, and use a seismoelectric probe to measure the measurement area to obtain the raw seismoelectric data;

[0006] b. Input the deep water layer relative permeability parameter Dem1, water layer thickness parameter Dem2, and formation lithology velocity parameter into the seismoelectric probe to obtain the seismoelectric data after inputting the parameters;

[0007] c. Perform noise reduction filtering on the seismic data after input parameters to obtain fluid data containing fluid velocity and relative permeability corresponding to different depths;

[0008] d. Based on the fluid data obtained in step c, plot the relative permeability profile curve and the relative permeability cross section.

[0009] e. Based on the relative permeability profile curve and relative permeability cross section obtained in step d, and combined with data including geological and borehole logging curves, information is extracted from the seismic anomaly area to obtain the relative permeability profile curve, aquifer inference and interpretation result map, and relative permeability aquifer inference and interpretation cross section map.

[0010] Furthermore, the present invention can be implemented according to the following technical solution: In step a, the center point of the measurement area is determined, and the four copper electrodes of the seismoelectric exploration instrument are buried in the soil at intervals of 1 m with the center point as the center, with a depth of more than 70 cm.

[0011] In step a, before measuring the original seismic data, the grounding resistance is checked and made to be less than 2KΩ. If it is greater than 2KΩ, water is poured to make the grounding resistance less than 2KΩ.

[0012] In step b, the relative permeability parameter Dem1 of the deep water layer is set to 0 or 0.4, and the water layer thickness parameter Dem2 is set to 0.001, 4, 40, 80 or 160.

[0013] In step c, the interference electromagnetic signals in the seismoelectric data after input parameters are denoised by bandpass filtering to obtain fluid data containing fluid velocities corresponding to different depths.

[0014] In step d, the obtained depth and relative permeability data are used to plot the relative permeability profile curve and the relative permeability cross section.

[0015] In step e, based on the relative permeability profile curve, positive and negative associated anomalies are delineated in the curve. The relative permeability profile curve is compared with the borehole logging curve. Within the delineated range of positive and negative associated anomalies, the low-resistivity area in the logging resistivity curve and the corresponding small amplitude area in the sonic transit time curve are extracted as fluid velocity anomaly areas, and the aquifer is preliminarily delineated, resulting in the relative permeability profile curve and the aquifer inference interpretation result map. Then, based on the high permeability areas of the aquifer delineated on the seismoelectric relative permeability profile, these areas are compared with the aquifer areas preliminarily delineated in the relative permeability profile curve and the aquifer inference interpretation result map, and the high permeability areas of the aquifer delineated on the seismoelectric relative permeability profile. The matching areas are finally extracted as fluid velocity anomaly areas. The aquifer is comprehensively inferred and delineated, resulting in the relative permeability aquifer inference interpretation profile map.

[0016] In step e, the low-resistivity region is a region with resistivity ≤ 20 Ω∙m, the high-permeability aquifer area is a region with aquifer permeability > 0.113, and the small amplitude region of the acoustic transit curve is a region with an amplitude of acoustic transit curve less than 600 μs / m.

[0017] This invention employs seismoelectric measurement to probe the measurement area, obtaining raw seismoelectric data. By studying the seismoelectric anomaly characteristics of known underground fluids, interpretative markers are established, and all survey cross-sections are manually analyzed to determine the distribution characteristics and location of underground fluids. The method of this invention can accurately detect underground fluids and has broad application prospects, suitable for widespread application in geological exploration in areas with geothermal mineralization conditions. The anomaly information extraction method of this invention clarifies the distribution characteristics of underground fluids, and when combined with the results of broadband magnetotelluric methods, it can achieve good exploration results in the search for geothermal fluids. Attached Figure Description

[0018] Figure 1 This is a flowchart of the present invention.

[0019] Figure 2 This is a schematic diagram of the setting of the deep water layer relative permeability parameter Dem1 according to the present invention.

[0020] Figure 3 This is a schematic diagram of the water layer thickness parameter Dem2 setting of the present invention.

[0021] Figure 4 This is a schematic diagram of the formation lithology velocity parameter settings of the present invention.

[0022] Figure 5 This is a schematic diagram of the seismoelectric data denoising and filtering after input parameters in this invention.

[0023] Figure 6 This is a profile curve of the relative permeability of the electrostatics of the present invention.

[0024] Figure 7 This is a cross-sectional view of the relative permeability of the seismoelectric field in this invention.

[0025] Figure 8 This is a schematic diagram illustrating the relationship between the porosity of geological bodies and positive and negative associated anomalies according to the present invention.

[0026] Figure 9 This is a schematic diagram comparing the relative permeability profile curve and the borehole logging curve of the present invention.

[0027] Figure 10 This is a relative permeability profile curve and an aquifer inference and interpretation result diagram of the present invention.

[0028] Figure 11 This is a cross-sectional diagram illustrating the inference and interpretation of the relative permeability of aquifers according to the present invention. Detailed Implementation

[0029] like Figure 1 As shown, the method for extracting geothermal fluid velocity anomaly information in geothermal fields according to the present invention includes the following steps:

[0030] a. Select the geothermal area to be measured as the measurement area, and use a DC-2500 seismoelectric probe to measure the measurement area to obtain the raw seismoelectric data.

[0031] Determine the center point of the measurement area. Bury the four copper electrodes of the seismoelectric probe sequentially along a straight line passing through the center point, spaced 1 m apart, in the soil to a depth of at least 70 cm. Then compact the soil to ensure good grounding. Keep the probe away from tree roots, flowing water, busy roadsides, and villages, and avoid burying it near ditches or embankments. The copper electrode wires should not be suspended in the air; compact them along the ground to prevent swaying interference. The seismoelectric probe's vibration sensor is sensitive to horizontal vibrations; it should be placed horizontally, and its wires should be compacted to prevent swaying interference. The seismic source should be buried at a depth of 20-30 cm, and the source sleeve should be firmly buried to ensure concentrated energy and reduce surface wave effects.

[0032] Before each acquisition of raw seismic data, the grounding resistance must be measured to ensure it is less than 2 kΩ. If it is greater than 2 kΩ, water should be poured on the ground to reduce the resistance to less than 2 kΩ.

[0033] Set the point number, line number, and acquisition parameters, excite the seismic source to acquire data, and continuously observe the shape of the measurement data curve during the measurement process. If any abnormalities appear in the shape of the measurement data curve during the observation process, promptly check the observation and find the root cause of the problem, arrange relevant technical personnel to conduct targeted inspections and report the situation around the measurement point, and take appropriate measures; if the interference is significant, increase the number of observations; at key parts of the curve, such as extreme points, repeat the observations to ensure data accuracy.

[0034] b. Use the GroundWater Locator 2500 software built into the seismoelectric exploration instrument to read the seismoelectric data. Input the deep water layer relative permeability parameter Dem1, water layer thickness parameter Dem2, and formation lithology velocity parameter into the seismoelectric exploration instrument to obtain the seismoelectric data after inputting the parameters.

[0035] GroundWater Locator 2500 software reads seismic and electrical data, inputs the deep water layer relative permeability parameter Dem1 and water layer thickness parameter Dem2, model parameters, and formation lithology velocity.

[0036] The relative permeability parameter Dem1 for deep aquifers is set to 0 or 0.4, and the aquifer thickness parameter Dem2 is set to 0.001, 4, 40, 80, or 160. The formation lithology velocity parameter refers to the rock wave velocity value, which is set based on the rock wave velocity values ​​distributed in the measurement area. Each type of rock has a different wave velocity value. Sandstone was collected on-site, and its rock wave velocity value was measured using existing methods.

[0037] like Figure 2 , Figure 3 , Figure 4 As shown, enter the main interface of the software, click the "file" menu in the menu bar, and then enter the "read" drop-down menu to read the data. Click the "Depth Options" button and enter the deep water layer relative permeability parameter Dem1, the water layer thickness parameter Dem2, and the formation lithology velocity. Based on the characteristics of the data curves collected in the working area and combined with the geological conditions, enter 0 for the deep water layer relative permeability parameter Dem1, and enter 160, 4, and 0.001 for the water layer thickness parameter Dem2.

[0038] After obtaining the seismic data with the input parameters, observe whether the shape of the seismic data curve is consistent with the known well logging curve. If they are consistent, the data quality is considered reliable.

[0039] c. Perform noise reduction filtering on the seismic data after input parameters to obtain fluid data containing fluid velocity and relative permeability corresponding to different depths.

[0040] Interference electromagnetic signals in the seismoelectric data after input parameters are filtered by bandpass filtering to reduce noise. The data is then saved to obtain fluid data containing fluid velocities corresponding to different depths. For example... Figure 5 As shown, enter the "FDoman" menu to filter the data. View the curves for channels 1 and 2, select the one with the most interference, click the curve, right-click to zoom in, and select appropriate maximum and minimum frequencies. If there is interference around 50 Hz, perform a 50 Hz linear filter. Click the "Famed" button, enter the minimum and maximum frequencies, and perform bandpass filtering. View the curve for channel 3; once the noise is suppressed and removed, click "Save".

[0041] d. Based on the fluid data obtained in step c, plot the relative permeability profile curve and the relative permeability cross section.

[0042] like Figure 6 and Figure 7 As shown, the relative permeability profile curve was drawn using Grapher software based on the processed depth and relative permeability values; the relative permeability cross section was drawn using Geosoft software based on the processed depth and relative permeability values.

[0043] e. Based on the relative permeability profile curve and relative permeability cross section obtained in step d, and combined with data including geological and borehole logging curves, information is extracted from the seismic anomaly area to obtain the relative permeability profile curve, aquifer inference and interpretation result map, and relative permeability aquifer inference and interpretation cross section map.

[0044] Based on the relative permeability profile, first identify the positive and negative associated anomalies in the graph, such as... Figure 8 As shown, since the amplitude of the seismoelectric effect is proportional to the porosity of the porous medium in the fluid reservoir, the magnitude and location of the porosity of underground oil and gas or water-bearing reservoirs can be directly detected by measuring the amplitude of the seismoelectric effect signal. The positive and negative associated anomalies in the delineation map are delineated based on the locations of the peaks and troughs with larger amplitudes in the curve.

[0045] Combining geological and borehole logging data, an interpretation marker for fluid velocity anomalies is established: The relative permeability profile curve is compared with existing borehole logging curves. Within the delineated positive and negative associated anomaly range, low-resistivity regions (generally ≤20Ω∙m) in the logging resistivity curves are selected, along with areas where the amplitude of the sonic transit time curve corresponding to the low-resistivity anomaly is small (less than 600μs / m). These areas are used as the approximate range of the initially inferred velocity anomaly region, extracted as the fluid velocity anomaly region, and the aquifer is preliminarily delineated, resulting in the relative permeability profile curve and the aquifer inference interpretation map. Figure 9 As shown;

[0046] By combining the interpretation indicators of fluid velocity anomalies with the extraction of fluid velocity anomaly regions from the relative permeability profile, the aquifer is preliminarily delineated, resulting in a relative permeability profile and an aquifer inference interpretation map, as shown below. Figure 10 As shown.

[0047] Finally, based on the high-permeability areas of the aquifer delineated on the seismic relative permeability profile map—that is, areas exhibiting gradient zones, beaded high-permeability zones, or anomaly zones—these areas are compared with the initially delineated aquifer regions in the relative permeability profile curve and aquifer inference interpretation map. The matching areas are ultimately extracted as fluid velocity anomaly zones. Through comprehensive inference and delineation, the aquifer is obtained, resulting in the relative permeability aquifer inference interpretation profile map, as shown below. Figure 11 As shown.

Claims

1. A method for extracting seismic current velocity anomaly information in a geothermal field, characterized in that, Includes the following steps: a. Select the geothermal area to be measured as the measurement area, and use a seismoelectric probe to measure the measurement area to obtain the raw seismoelectric data; b. Input the deep water layer relative permeability parameter Dem1, water layer thickness parameter Dem2, and formation lithology velocity parameter into the seismoelectric probe to obtain the seismoelectric data after inputting the parameters; c. Perform noise reduction filtering on the seismic data after input parameters to obtain fluid data containing fluid velocity and relative permeability corresponding to different depths; d. Based on the fluid data obtained in step c, plot the relative permeability profile curve and the relative permeability cross section. e. Based on the relative permeability profile curve and relative permeability cross section obtained in step d, and combined with data including geological and borehole logging curves, information is extracted from the seismic anomaly area to obtain the relative permeability profile curve, aquifer inference and interpretation result map, and relative permeability aquifer inference and interpretation cross section map.

2. The method for extracting seismic current velocity anomaly information in geothermal fields according to claim 1, characterized in that, In step a, the center point of the measurement area is determined, and the four copper electrodes of the seismoelectric probe are buried in the soil at intervals of 1 m from the center point, with a depth of more than 70 cm.

3. The method for extracting seismic current velocity anomaly information in geothermal fields according to claim 1, characterized in that, In step a, before measuring the original seismic data, the grounding resistance is checked and made to be less than 2KΩ. If it is greater than 2KΩ, water is poured to make the grounding resistance less than 2KΩ.

4. The method for extracting seismic current velocity anomaly information in geothermal fields according to claim 1, characterized in that, In step b, the relative permeability parameter Dem1 of the deep water layer is set to 0 or 0.4, and the water layer thickness parameter Dem2 is set to 0.001, 4, 40, 80 or 160.

5. The method for extracting seismic current velocity anomaly information in geothermal fields according to claim 1, characterized in that, In step c, the interference electromagnetic signals in the seismoelectric data after input parameters are denoised by bandpass filtering to obtain fluid data containing fluid velocities corresponding to different depths.

6. The geothermal field seismic current velocity anomaly information extraction technology according to claim 1, characterized in that, In step d, the obtained depth and relative permeability data are used to plot the relative permeability profile curve and the relative permeability cross section.

7. The method for extracting seismic current velocity anomaly information in geothermal fields according to claim 1, characterized in that, In step e, based on the relative permeability profile curve, positive and negative associated anomalies are delineated in the curve. The relative permeability profile curve is compared with the borehole logging curve. Within the delineated range of positive and negative associated anomalies, the low-resistivity area in the logging resistivity curve and the corresponding small amplitude area in the sonic transit time curve are extracted as fluid velocity anomaly areas, and the aquifer is preliminarily delineated, resulting in the relative permeability profile curve and the aquifer inference interpretation result map. Then, based on the high permeability areas of the aquifer delineated on the seismoelectric relative permeability profile, these areas are compared with the aquifer areas preliminarily delineated in the relative permeability profile curve and the aquifer inference interpretation result map, and the high permeability areas of the aquifer delineated on the seismoelectric relative permeability profile. The matching areas are finally extracted as fluid velocity anomaly areas. The aquifer is comprehensively inferred and delineated, resulting in the relative permeability aquifer inference interpretation profile map.

8. The method for extracting seismic current velocity anomaly information in geothermal fields according to claim 7, characterized in that, In step e, the low-resistivity region is a region with resistivity ≤ 20 Ω∙m, the high-permeability aquifer area is a region with aquifer permeability > 0.113, and the small amplitude region of the acoustic transit curve is a region with an amplitude of acoustic transit curve less than 600 μs / m.

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