Three-dimensional electromagnetic fracturing monitoring method

Abstract

The invention relates to the technical field of geophysical exploration, and provides a three-dimensional electromagnetic method fracturing monitoring method which comprises the following steps: collecting parameter data of a target well; establishing a target well work area geoelectric model, and performing forward modeling through the target well work area geoelectric model to select reasonable acquisition parameters; arranging a three-dimensional measuring net according to a fracturing construction scheme; collecting data of a natural field source and an artificial field source in the fracturing monitoring process; processing to obtain natural potential data before and after fracturing, induced polarization method data before and after fracturing, time-frequency electromagnetic method data before and after fracturing, and controllable source magnetotelluric method apparent resistivity data and controllable source magnetotelluric method phase data before and after fracturing; differential abnormal data are obtained through calculation, all the differential abnormal data are comprehensively analyzed, and fracturing fluid and fracture distribution form data in the complete fracturing process are obtained. According to the invention, multiplicity of solutions is reduced, precision and monitoring accuracy are improved, and construction cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of geophysical exploration, and particularly relates to a three-dimensional electromagnetic method for fracturing monitoring. Background Art

[0002] With the in-depth exploration and development of oil and gas, the fracturing technology of oil and gas wells has been widely applied. During the fracturing process of oil and gas wells, the propagation of fractures has an important impact on the productivity and development effect of oil and gas wells. Therefore, the monitoring of the fracture propagation situation is particularly important.

[0003] Currently, the electromagnetic method for fracturing monitoring mainly collects horizontal electric field components. The information obtained by observing single electromagnetic component data is less, and the ability to reflect anomalies caused by changes in fracturing fluid is insufficient. It is impossible to monitor various electromagnetic anomaly data reflecting the dynamic information of fracturing fluid during the fracturing process, which affects the monitoring of the fracture propagation situation. Summary of the Invention

[0004] In view of this, the present invention provides a three-dimensional electromagnetic method for fracturing monitoring to solve the problem in the prior art that various electromagnetic anomaly data reflecting the dynamic information of fracturing fluid during the fracturing process cannot be monitored, so that the characteristic data of the fracturing fluid and the fracture distribution pattern cannot be accurately obtained.

[0005] The present invention provides a three-dimensional electromagnetic method for fracturing monitoring, including:

[0006] S1. Collect parameter data of the target well, where the parameter data of the target well includes logging data, well trajectory data, and geological data of the target area;

[0007] S2. Establish a geoelectric model of the target well work area according to the parameter data of the target well, and select reasonable acquisition parameter data through forward simulation using the geoelectric model of the target well work area. Among them, the reasonable acquisition parameter data includes: excitation frequency in the emission frequency table, line spacing, point spacing, transmitter-receiver distance, and excitation electrode distance;

[0008] S3. According to the fracturing construction plan of the target well, deploy a three-dimensional survey network directly above the fracturing well section of the target well to monitor the entire fracturing process;

[0009] S4. During the fracturing monitoring process, transmit according to the frequency in the frequency table at a set time interval according to the fracturing construction plan of the target well, and collect natural field source data and artificial field source data;

[0010] S5. Intercept the natural field source data during the non-transmission time period to obtain the natural source electric field time series data before and after fracturing, and based on the natural source electric field time series data before and after fracturing, obtain the spontaneous potential data before and after fracturing;

[0011] During the artificial field source emission period, intercept the artificial field source data within the emission period to obtain the time-series data of the artificial source electric field and magnetic field before and after fracturing. Process the time-series data of the artificial source electric field and magnetic field before and after fracturing respectively to obtain the induced polarization method data before and after fracturing, the time-frequency electromagnetic method data before and after fracturing, the apparent resistivity data of the controlled-source magnetotelluric method before and after fracturing, and the phase data of the controlled-source magnetotelluric method before and after fracturing.

[0012] S6. Calculate respectively according to the natural potential data before and after fracturing, the induced polarization method data before and after fracturing, the time-frequency electromagnetic method data before and after fracturing, and the apparent resistivity data of the controlled-source magnetotelluric method and the phase data of the controlled-source magnetotelluric method before and after fracturing to obtain differential anomaly data, and comprehensively analyze all the differential anomaly data to obtain the characteristic data of the fracturing fluid and the fracture distribution pattern during the complete fracturing process.

[0013] Further, the layout of the three-dimensional measurement network includes:

[0014] Design the measurement network according to the known fracturing section and cluster information.

[0015] Design the point spacing, the transmitter-receiver distance, and the excitation electrode distance according to the reasonable parameters.

[0016] Further, the frequencies in the emission frequency table are the artificial field source emission frequencies.

[0017] Further, the acquisition of the natural potential data before and after fracturing includes:

[0018] During the non-emission period, intercept the natural field source data to obtain the time-series data of the natural source electric field before and after fracturing. Select the data of the time period with a signal-to-noise ratio higher than the set value in the time-series data of the natural source electric field before and after fracturing, and calculate its average value to obtain the natural potential data before and after fracturing.

[0019] Further, the acquisition of the induced polarization method data before and after fracturing includes:

[0020] Process the time-series data of the artificial source electric field before and after fracturing through DC drift correction, half-frequency folding superposition, and electrode distance correction, then intercept the long-period flat section data and calculate its average value to obtain the induced polarization method data before and after fracturing, where the long period refers to the period when the frequency is the lowest.

[0021] Further, the acquisition of the time-frequency electromagnetic method data before and after fracturing includes:

[0022] The time-series data of the artificial source electric field and the magnetic field before and after fracturing are subjected to DC drift correction, halved and superimposed at the same frequency, then Fourier-transformed and current-normalized to obtain the frequency-domain electric field data and magnetic field data before and after fracturing, wherein the frequency-domain electric field data are time-frequency electromagnetic method data.

[0023] Further, the acquisition of the apparent resistivity data and phase data of the controlled-source magnetotelluric method before and after fracturing includes:

[0024] According to the frequency-domain electric field data and magnetic field data before and after fracturing, the apparent resistivity and phase data of the controlled-source magnetotelluric method before and after fracturing are obtained by calculating according to the Cagniard apparent resistivity formula.

[0025] Further, the set range of the signal-to-noise ratio in S5 is higher than 30 decibels.

[0026] Further, the expression of the abnormal difference calculation is as follows:

[0027] dX = (X2 - X1) / (X2 + X1)

[0028] Wherein, dX represents the data difference anomaly, X2 represents the data after fracturing, and X1 represents the data before fracturing. Among them, the data before fracturing includes the spontaneous potential method data before fracturing, the induced polarization method data before fracturing, the time-frequency electromagnetic method data before fracturing, the apparent resistivity data of the controlled-source magnetotelluric method before fracturing, and the phase data of the controlled-source magnetotelluric method before fracturing; the parameter data after fracturing includes the spontaneous potential method data after fracturing, the induced polarization method data after fracturing, the time-frequency electromagnetic method data after fracturing, the apparent resistivity data of the controlled-source magnetotelluric method after fracturing, and the phase data of the controlled-source magnetotelluric method after fracturing.

[0029] Further, after S6, it further includes:

[0030] Through the differential anomaly data in the complete fracturing process, the characteristic data of the fracturing fluid in the complete fracturing process are obtained, and the characteristic data of the fracture distribution form are deduced from the characteristic data of the fracturing fluid. Among them, the characteristic data of the fracturing fluid includes volume, and the characteristic data of the fracture distribution form includes length, width, and height.

[0031] The beneficial effects of the present invention compared with the prior art are:

[0032] 1. By arranging a three-dimensional measurement network, the present invention collects the electric field component and the magnetic field component, and monitors the differential anomaly data reflecting the dynamic information of the fracturing fluid during the fracturing process;

[0033] 2. Compared with the traditional electrical monitoring method, the present invention obtains five types of abnormal data, and then obtains the distribution patterns of fracturing fluid and fractures, reducing the non-uniqueness, improving the accuracy and monitoring accuracy, and reducing the construction cost.

[0034] 3. According to the differential abnormal data, the present invention obtains the characteristic data of the fracturing fluid during the entire fracturing process, and infers the characteristic data of the fracture distribution pattern, thereby providing data for predicting the risks of fracturing channeling and casing deformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1 It is a flowchart of a three-dimensional electromagnetic method for fracturing monitoring provided by an embodiment of the present invention;

[0037] Figure 2 It is a schematic diagram of the layout of the on-site device for three-dimensional electromagnetic method for fracturing monitoring provided by an embodiment of the present invention;

[0038] Figure 3 It is a plan view of the amplitude difference anomaly of the time-frequency electromagnetic method provided by an embodiment of the present invention;

[0039] Figure 4 It is a plan view of the apparent resistivity difference anomaly of the controlled-source magnetotelluric method provided by an embodiment of the present invention;

[0040] Figure 5 It is a sectional view of the phase difference anomaly of the controlled-source magnetotelluric method provided by an embodiment of the present invention;

[0041] Figure 6 It is a plan view of the prediction of the height of the fracture network provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] In the following description, for the purpose of illustration rather than limitation, specific details such as specific system structures and technologies are proposed in order to thoroughly understand the embodiments of the present invention. However, those skilled in the art should clearly understand that the present invention can also be implemented in other embodiments without these specific details. In other cases, the detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present invention.

[0043] The following will describe in detail a three-dimensional electromagnetic method for fracturing monitoring according to the present invention with reference to the drawings.

[0044] Figure 1 It is a flowchart of a three-dimensional electromagnetic method for fracturing monitoring provided by an embodiment of the present invention.

[0045] As Figure 1 shown, the three-dimensional electromagnetic method for fracturing monitoring includes:

[0046] S1. Collect parameter data of the target well, where the parameter data of the target well includes logging data, well trajectory data, and target area geological data;

[0047] Among them, the target well is the well for which the fracturing process needs to be monitored. In addition to logging data, well trajectory data, and target area geological data, the parameters of the target well also include some auxiliary data.

[0048] S2. Establish a geoelectric model of the target well work area according to the parameter data of the target well, and select reasonable acquisition parameter data through forward simulation using the geoelectric model of the target well work area;

[0049] Among them, the reasonable acquisition parameter data includes: the excitation frequency in the emission frequency table, the survey line distance, the point distance, the transmitter-receiver distance, and the excitation electrode distance. For example, in the application scenario, the excitation frequency is 50 - 0.05 Hz, the survey line distance is 60 - 90 m, the point distance is 20 - 50 m, the transmitter-receiver distance is 2 - 5 km, and the excitation electrode distance is 4 - 6 km.

[0050] Figure 2 It is a schematic diagram of the layout of the three-dimensional electromagnetic method for fracturing monitoring field device provided by an embodiment of the present invention.

[0051] S3. According to the target well fracturing construction plan, arrange a three-dimensional survey network directly above the fracturing well section of the target well to monitor the entire fracturing process;

[0052] Among them, the fracturing construction plan is issued by the Party A or the fracturing operation party. The Party B fracturing monitoring operation team conducts fracturing monitoring operations according to the fracturing construction plan, including arranging a three-dimensional survey network, etc.

[0053] As Figure 2 shown, the high-power transmitter emits square wave signals of different frequencies to the ground through the transmitting electrode A and the transmitting electrode B according to the frequency in the emission frequency table. The electrodes and magnetic rods are arranged in a three-dimensional array above the fracturing well and are used to receive electric field signals and magnetic field signals respectively.

[0054] The arrangement of the three-dimensional survey network includes:

[0055] Design the survey network according to the known fracturing section and cluster information;

[0056] Among them, the survey network is a combination of survey lines in three dimensions.

[0057] Design the dot pitch, the transceiver distance, and the excitation electrode distance according to the reasonable parameters.

[0058] In the present invention, by arranging a three-dimensional survey network, the electric field component and the magnetic field component are collected, and electromagnetic anomaly data reflecting the dynamic information of the fracturing fluid during the entire process before and after fracturing is monitored.

[0059] S4. During the fracturing monitoring process, transmit according to the frequencies in the frequency table at a set time interval according to the fracturing construction plan of the target well, and collect natural field source data and artificial field source data;

[0060] Among them, the set time interval is set according to human needs, the frequencies in the emission frequency table are the artificial field source emission frequencies, and the collection of natural field source data and artificial field source data is to collect the electric field component parallel to the emission source and the magnetic field component perpendicular to the emission source.

[0061] S5. Intercept the natural field source data in the non-emission time period to obtain the natural source electric field time series data before and after fracturing, and based on the natural source electric field time series data before and after fracturing, obtain the spontaneous potential data before and after fracturing;

[0062] In S5, the obtaining of the spontaneous potential data before and after fracturing includes:

[0063] In the non-emission time period, intercept the natural field source data to obtain the natural source electric field time series data before and after fracturing, select the data of the time period higher than the set value of the signal-to-noise ratio in the natural source electric field time series data before and after fracturing, take its average value, and obtain the spontaneous potential data before and after fracturing.

[0064] The set value of the signal-to-noise ratio is 30 decibels.

[0065] During the artificial field source emission time period, intercept the artificial field source data in the emission time period to obtain the artificial source electric field time series data and magnetic field time series data before and after fracturing, and respectively process the artificial source electric field time series data and magnetic field time series data before and after fracturing to obtain the induced polarization method data before and after fracturing, the time-frequency electromagnetic method data before and after fracturing, the apparent resistivity data of the controlled-source magnetotelluric method before and after fracturing, and the phase data of the controlled-source magnetotelluric method;

[0066] Among them, the artificial field source emission time period refers to the time period of emitting according to the frequencies in the emission frequency table.

[0067] In S5, the obtaining of the induced polarization method data before and after fracturing includes:

[0068] The artificial source electric field time series data before and after fracturing are subjected to DC drift correction, same-frequency half-superposition and electrode distance correction processing, and then the long-period straight section data are intercepted and the average value is calculated to obtain the induced polarization method data before and after fracturing, wherein the long period refers to the period when the emission frequency is the lowest.

[0069] Figure 3 It is a plan schematic diagram of the amplitude difference anomaly of the time-frequency electromagnetic method provided by an embodiment of the present invention.

[0070] like Figure 3 As shown in the figure, after processing the time-frequency electromagnetic method data collected before and after the fracturing operation, the time-frequency electromagnetic method amplitude difference anomaly plane map is obtained. Figure 3 Obvious amplitude difference abnormal areas appeared on both sides of the horizontal well. The black cross is the midpoint of each fracturing section of the horizontal well. The range of the abnormal area can be used to predict the distribution range of the fracturing fluid.

[0071] In S5, obtaining the time-frequency electromagnetic method data before and after fracturing includes:

[0072] The artificial source electric field time series data and magnetic field time series data before and after fracturing are subjected to DC drift correction, half-frequency superposition, Fourier transformation and current normalization to obtain frequency domain electric field data and magnetic field data before and after fracturing, wherein the frequency domain electric field data is time-frequency electromagnetic method data.

[0073] Figure 4 It is a plan schematic diagram of apparent resistivity differential anomaly of the controlled source magnetotelluric method provided by an embodiment of the present invention.

[0074] After processing the controlled source magnetotelluric data collected before and after the fracturing operation, the amplitude difference anomaly plane map of the controlled source magnetotelluric method was obtained. Figure 4 Obvious apparent resistivity differential anomaly areas appeared on both sides of the horizontal well. The black cross is the midpoint of each fracturing section of the horizontal well. The range of the anomaly area can be used to predict the distribution range of the fracturing fluid.

[0075] Figure 5 It is a cross-sectional schematic diagram of the phase difference anomaly of the controlled source magnetotelluric method provided by an embodiment of the present invention.

[0076] After processing the controlled source magnetotelluric data collected before and after the fracturing operation, the controlled source magnetotelluric phase difference anomaly profile was obtained. In the figure, obvious phase difference anomaly areas appeared above and below and on the left and right sides of the horizontal well circle. The range of the anomaly area can be used to predict the distribution range of the fracturing fluid.

[0077] In S5, the acquisition of the apparent resistivity data and phase data of the controlled-source magnetotelluric method before and after fracturing includes:

[0078] According to the frequency-domain electric field data and magnetic field data before and after fracturing, by calculating according to the Cagniard apparent resistivity formula, the apparent resistivity data and phase data of the controlled-source magnetotelluric method before and after fracturing are obtained.

[0079] The existing electrical monitoring methods can only obtain single abnormal data. Compared with the traditional electrical monitoring methods, the present invention obtains five kinds of abnormal data, and then obtains the distribution patterns of fracturing fluid and fractures, reduces the non-uniqueness, improves the accuracy and monitoring accuracy, and reduces the cost.

[0080] Figure 6 It is a schematic plan view of predicting the height of a fracturing crack network provided by an embodiment of the present invention.

[0081] By comprehensively analyzing and interpreting the differential anomalies of various different data, a schematic plan view of predicting the height of the fracturing crack network is obtained. Figure 6 The colors in it describe the height of the fracturing crack network in different regions.

[0082] S6. According to the natural potential data before and after fracturing, the induced polarization method data before and after fracturing, the time-frequency electromagnetic method data before and after fracturing, and the apparent resistivity data and phase data of the controlled-source magnetotelluric method before and after fracturing, calculate respectively to obtain differential anomaly data, and comprehensively analyze all the differential anomaly data to obtain data on the distribution patterns of fracturing fluid and fractures during the entire fracturing process.

[0083] The expression for the abnormal difference calculation is as follows:

[0084] dX = (X2 - X1) / (X2 + X1)

[0085] Wherein, dX represents the differential anomaly of the data represented, X2 represents the data after fracturing, and X1 represents the data before fracturing. Among them, the data before fracturing includes the natural potential method data before fracturing, the induced polarization method data before fracturing, the time-frequency electromagnetic method data before fracturing, the apparent resistivity data of the controlled-source magnetotelluric method before fracturing, and the phase data of the controlled-source magnetotelluric method before fracturing; the parameter data after fracturing includes the natural potential method data after fracturing, the induced polarization method data after fracturing, the time-frequency electromagnetic method data after fracturing, the apparent resistivity data of the controlled-source magnetotelluric method after fracturing, and the phase data of the controlled-source magnetotelluric method after fracturing.

[0086] After S6, it further includes:

[0087] Obtain the characteristic data of the fracturing fluid during the complete fracturing process through the differential anomaly data during the complete fracturing process, and inversely deduce the characteristic data of the fracture distribution pattern from the characteristic data of the fracturing fluid. Among them, the characteristic data of the fracturing fluid includes volume, and the characteristic data of the fracture distribution pattern includes length, width, and height.

[0088] The present invention collects the electric field component parallel to the emission source and the magnetic field component perpendicular to the emission source by arranging a three-dimensional measurement network, monitors the electromagnetic anomaly data of the dynamic information of the fracturing fluid during the complete process before and after fracturing, obtains the characteristic data of the fracturing fluid during the complete fracturing process, and inversely deduces the characteristic data of the fracture distribution pattern, thereby providing data for predicting the risks of fracturing channeling and casing deformation. Compared with the traditional electrical method monitoring method that can only obtain single anomaly data, the present invention obtains five kinds of anomaly data, and then obtains the fracturing fluid and the fracture distribution pattern, reducing the non-uniqueness, improving the accuracy and monitoring accuracy.

[0089] Embodiment 1

[0090] Step 1. Collect the parameter data of the target well, where the parameter data of the target well includes logging data, well trajectory data, and geological data of the target area.

[0091] Step 2. Establish a geoelectric model of the target well work area according to the parameter data of the target well, and perform forward simulation through the geoelectric model of the target well work area to select reasonable acquisition parameter data: point spacing 25m, line spacing 85m, transmitter-receiver distance 4.5km, excitation electrode distance 4km, excitation frequency range 64 - 0.1Hz.

[0092] Step 3. According to the fracturing construction plan, arrange a three-dimensional measurement network directly above the fracturing section of the target well to monitor the complete fracturing process; specifically as follows:

[0093] The measurement network is designed according to the known fracturing section and cluster information, with a point spacing of 25m. The emission source is arranged parallel to the measurement line, the transmitter-receiver distance is 4.5km, the excitation electrode distance is 4km, the acquired component is the electric field component parallel to the emission source, the electrode distance is 25m, and the magnetic field component perpendicular to the emission source.

[0094] Step 4. Start transmitting at a certain time interval half an hour before the start of fracturing and during the fracturing process according to the frequencies in the frequency table, and the frequencies in the emission frequency table are determined by selecting reasonable acquisition parameter data from the forward simulation results.

[0095] Step 5. Perform time-sharing interception on the data collected in Step 4, intercept the artificial field source data during the emission time period, and obtain the artificial source electric field time series data and magnetic field time series data before and after fracturing.

[0096] Step 6. Perform time-sharing interception on the data collected in Step 4, intercept the natural field source data during the non-transmission time period, obtain the natural field source electric field time series data before and after fracturing, select the time period with less electromagnetic interference, calculate its average value, and obtain the spontaneous potential data before and after fracturing, denoted as A1 and A2 respectively, where A1 represents the spontaneous potential data before fracturing and A2 represents the spontaneous potential data after fracturing.

[0097] Step 7. Perform DC drift correction, same-frequency superposition processing, and electrode distance correction processing on the artificial source electric field time series data and magnetic field time series data obtained in Step 5 to obtain the artificial source electric field data before and after fracturing;

[0098] Step 8. Perform half-overlap superposition on the artificial source electric field time series data before and after fracturing in Step 7, then intercept the long-period flat segment data, calculate its average value, and obtain the induced polarization method data before and after fracturing, denoted as B1 and B2 respectively. B1 represents the induced polarization method data before fracturing, and B2 represents the induced polarization method data after fracturing;

[0099] Step 9. Perform Fourier transform on the data after superposition in Step 7 and perform current normalization to obtain the frequency-domain electric field data and magnetic field data before and after fracturing;

[0100] Among them, the frequency-domain electric field data is time-frequency electromagnetic method data, denoted as C1 and C2 respectively, where C1 represents the time-frequency electromagnetic method data before fracturing, and C2 represents the time-frequency electromagnetic method data after fracturing;

[0101] Step 10. Calculate the controlled-source magnetotelluric apparent resistivity and controlled-source magnetotelluric phase data before and after fracturing according to the Cagniard apparent resistivity formula for the frequency-domain electric field data and magnetic field data obtained in Step 9, denoted as Dr1, Dr2, Dp1, and Dp2 respectively. Among them, Dr1 represents the controlled-source magnetotelluric apparent resistivity data before fracturing, Dr2 represents the controlled-source magnetotelluric apparent resistivity data after fracturing, Dp1 represents the controlled-source magnetotelluric phase data before fracturing, and Dp2 represents the controlled-source magnetotelluric phase data after fracturing;

[0102] Step 11. Perform differential calculations on the spontaneous potential method data before and after fracturing, the induced polarization method data before and after fracturing, the time-frequency electromagnetic method data before and after fracturing, the controlled-source magnetotelluric apparent resistivity data before and after fracturing, and the controlled-source magnetotelluric phase data before and after fracturing respectively. The calculation formula is dX = (X2 - X1) / (X2 + X1), and obtain the spontaneous potential method differential anomaly, induced polarization method differential anomaly, time-frequency electromagnetic method differential anomaly, controlled-source magnetotelluric apparent resistivity differential anomaly, and controlled-source magnetotelluric phase differential anomaly respectively.

[0103] Among them, dX represents the differential anomaly of the represented data, X2 represents the data after fracturing, and X1 represents the data before fracturing. Among them, the data before fracturing includes the spontaneous potential method data before fracturing, the induced polarization method data before fracturing, the time-frequency electromagnetic method data before fracturing, the apparent resistivity data of the controlled-source magnetotelluric method before fracturing, and the phase data of the controlled-source magnetotelluric method before fracturing; the parameter data after fracturing includes the spontaneous potential method data after fracturing, the induced polarization method data after fracturing, the time-frequency electromagnetic method data after fracturing, the apparent resistivity data of the controlled-source magnetotelluric method after fracturing, and the phase data of the controlled-source magnetotelluric method after fracturing.

[0104] Any combination of the above optional technical solutions can form an optional embodiment of the present application, which will not be elaborated one by one here.

[0105] It should be understood that the magnitudes of the sequence numbers of the steps in the above embodiments do not mean the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present invention.

[0106] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A three-dimensional electromagnetic method for fracturing monitoring, characterized in that Including: S1. Collect parameter data of the target well, where the parameter data of the target well includes logging data, well trajectory data, and geological data of the target area; S2. Establish a geoelectric model of the target well work area based on the parameter data of the target well, and perform forward modeling through the geoelectric model of the target well work area to select reasonable acquisition parameter data. Among them, the reasonable acquisition parameter data includes: excitation frequency in the emission frequency table, line spacing, point spacing, transmitter-receiver distance, and excitation electrode distance; S3. According to the target well fracturing construction plan, deploy a three-dimensional measurement network directly above the fracturing section of the target well to monitor the entire fracturing process; S4. During the fracturing monitoring process, transmit according to the frequency in the frequency table at a set time interval according to the target well fracturing construction plan to collect natural field source data and artificial field source data; S5. Intercept the natural field source data during the non-transmission time period to obtain the natural source electric field time series data before and after fracturing, and based on the natural source electric field time series data before and after fracturing, obtain the natural potential data before and after fracturing; During the artificial field source emission time period, intercept the artificial field source data during the emission time period to obtain the artificial source electric field time series data and magnetic field time series data before and after fracturing. After processing the artificial source electric field time series data and magnetic field time series data before and after fracturing respectively, obtain the induced polarization method data before and after fracturing, the time-frequency electromagnetic method data before and after fracturing, the apparent resistivity data of the controlled-source magnetotelluric method before and after fracturing, and the phase data of the controlled-source magnetotelluric method; S6. Calculate respectively according to the natural potential data before and after fracturing, the induced polarization method data before and after fracturing, the time-frequency electromagnetic method data before and after fracturing, and the apparent resistivity data of the controlled-source magnetotelluric method and the phase data of the controlled-source magnetotelluric method before and after fracturing to obtain differential anomaly data, and comprehensively analyze all differential anomaly data to obtain the characteristic data of the fracturing fluid and fracture distribution pattern during the entire fracturing process.

2. The three-dimensional electromagnetic method for fracturing monitoring according to claim 1, wherein In S3, the deployment of the three-dimensional measurement network includes: Design the measurement network according to the known fracturing section and cluster information; Design the point spacing, the transmitter-receiver distance, and the excitation electrode distance according to the reasonable parameters.

3. The three-dimensional electromagnetic method for fracturing monitoring according to claim 1, wherein In S4, the frequency in the emission frequency table is the artificial field source emission frequency.

4. The three-dimensional electromagnetic method for fracturing monitoring according to claim 1, wherein In S5, the obtaining of the natural potential data before and after fracturing includes: During the non-transmission time period, intercept the natural field source data to obtain the natural source electric field time series data before and after fracturing. Select the data of the time period with a signal-to-noise ratio higher than the set value in the natural source electric field time series data before and after fracturing, and calculate its average value to obtain the natural potential data before and after fracturing.

5. The three-dimensional electromagnetic method for fracturing monitoring according to claim 1, characterized in that In S5, the obtaining of the induced polarization method data before and after fracturing includes: The time-series data of the artificial source electric field before and after fracturing are processed by DC drift correction, half-frequency folding superposition, and electrode spacing correction, and then the flat section data of the long period are intercepted, and their average value is obtained to obtain the induced polarization method data before and after fracturing, where the long period refers to the period at the lowest frequency.

6. The three-dimensional electromagnetic method for fracturing monitoring according to claim 1, wherein In S5, the acquisition of the time-frequency electromagnetic method data before and after fracturing includes: The time-series data of the artificial source electric field and the magnetic field before and after fracturing are subjected to DC drift correction, half-frequency folding superposition, then Fourier transform and current normalization to obtain the frequency-domain electric field data and magnetic field data before and after fracturing, where the frequency-domain electric field data are the time-frequency electromagnetic method data.

7. The three-dimensional electromagnetic method for fracturing monitoring according to claim 1, wherein In S5, the acquisition of the apparent resistivity data and phase data of the controlled-source magnetotelluric method before and after fracturing includes: According to the frequency-domain electric field data and magnetic field data before and after fracturing, the apparent resistivity and phase data of the controlled-source magnetotelluric method before and after fracturing are obtained by calculating according to the Cagniard apparent resistivity formula.

8. The three-dimensional electromagnetic method for fracturing monitoring according to claim 1, wherein In S5, the set range of the signal-to-noise ratio is higher than 30 dB.

9. The three-dimensional electromagnetic method for fracturing monitoring according to claim 1, wherein The expression of the abnormal difference calculation is as follows: dX = (X2 - X1) / (X2 + X1) where dX represents the data differential anomaly, X2 represents the data after fracturing, and X1 represents the data before fracturing. Among them, the data before fracturing include the spontaneous potential method data before fracturing, the induced polarization method data before fracturing, the time-frequency electromagnetic method data before fracturing, the apparent resistivity data of the controlled-source magnetotelluric method before fracturing, and the phase data of the controlled-source magnetotelluric method before fracturing; the parameter data after fracturing include the spontaneous potential method data after fracturing, the induced polarization method data after fracturing, the time-frequency electromagnetic method data after fracturing, the apparent resistivity data of the controlled-source magnetotelluric method after fracturing, and the phase data of the controlled-source magnetotelluric method after fracturing.

10. The three-dimensional electromagnetic method for fracturing monitoring according to claim 1, wherein After S6, it further includes: Through the differential anomaly data in the complete fracturing process, the characteristic data of the fracturing fluid in the complete fracturing process are obtained, and the characteristic data of the fracture distribution pattern are deduced from the characteristic data of the fracturing fluid. Among them, the characteristic data of the fracturing fluid include volume, and the characteristic data of the fracture distribution pattern include length, width, and height.

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