A high-precision borehole-to-ground electromagnetic inversion device and method

Abstract

The application belongs to the technical field of geophysical oil and gas exploration, and particularly discloses a high-precision borehole-ground electromagnetic inversion device and method. The device comprises a data acquisition module, a data calculation module, a difference module, an inversion module and an analysis module. The method comprises the following steps: first, designing parameters and obtaining borehole-ground electromagnetic original data; then, calculating normalized electric field component real part and imaginary part data of a ground observation point; then, performing difference on the obtained data to obtain the difference electric field component real part and imaginary part of each ground observation point; then, performing three-dimensional resistivity inversion to obtain three-dimensional resistivity data volume of a target layer; finally, combining the three-dimensional resistivity data volume of the target layer and the induced polarization anomaly to complete three-dimensional spatial distribution of oil and gas in the excited section in the ground observation area. The application is used for the exploration and development of oil and gas, can effectively improve the precision of resistivity, and provides a more reliable basis for the exploration and development of oil and gas reservoirs.

Description

Technical Field

[0001] This invention belongs to the field of geophysical oil and gas exploration technology, specifically relating to a high-precision well-to-surface electromagnetic inversion device and method. Background Technology

[0002] With the continuous deepening of oil and gas exploration and development, deep and ultra-deep oil and gas targets have become key exploration areas. Resistivity is a crucial indicator in oil exploration. Various methods exist for resistivity testing, among which well-to-surface electromagnetic (BTS) is a commonly used method. BTS involves supplying a high-power alternating current to a finite-length conductor in the well and receiving the electromagnetic response at the surface. Compared to surface electromagnetic methods, the transmitter is located in the well, making the response in the lower half of the reservoir more pronounced and facilitating exploration. BTS technology can better identify the existence and distribution range of oil and gas reservoirs in deep and ultra-deep oil and gas exploration and development.

[0003] However, when using the well-to-ground electromagnetic method to invert resistivity in deep and ultra-deep layers, the resistivity inversion resolution of the geological targets is still insufficient because the deep and ultra-deep geological targets are far from the observation point. Although the resolution of the geological target resistivity inversion is higher than that of the ground-based artificial source electromagnetic method, it is still difficult to meet the resolution requirements of the actual geological targets, and the obtained resistivity is still not accurate enough. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a high-precision well-to-surface electromagnetic inversion device to improve the resistivity inversion resolution of geological targets and effectively identify the existence and distribution range of oil and gas reservoirs.

[0005] Another objective of this invention is to provide a high-precision well-to-surface electromagnetic inversion method, which is implemented using the aforementioned high-precision well-to-surface electromagnetic inversion device. This method can effectively improve the accuracy of resistivity and provide a more reliable basis for the exploration and development of oil and gas reservoirs.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A high-precision well-to-surface electromagnetic inversion device includes a data acquisition module, a data calculation module, a differential module, an inversion module, and an analysis module;

[0008] The data acquisition module acquires raw well-to-surface electromagnetic data of different excitation signal cycles in the target layer and outputs it to the data calculation module.

[0009] The data calculation module calculates the real and imaginary parts of the normalized horizontal radial electric field of each ground observation point during each excitation signal cycle based on the received raw well-to-ground electromagnetic data, and outputs the data to the differential module.

[0010] a difference module, which calculates the real part and imaginary part data of the normalized horizontal radial electric field of each ground observation point, obtains the real part and imaginary part of the differential horizontal radial electric field of each ground observation point in each excitation signal period, and outputs to the inversion module;

[0011] the inversion module, which performs three-dimensional resistivity inversion on the real part and imaginary part of the differential horizontal radial electric field to obtain a three-dimensional resistivity data body of the target layer section, and outputs to the analysis module;

[0012] the analysis module, which is used for combining the three-dimensional resistivity data body of the target layer section and the induced polarization anomaly of the target layer section to complete the three-dimensional spatial distribution of the oil and gas content in the excited section in the well in the ground observation area.

[0013] The application further discloses a high-precision borehole-to-surface electromagnetic inversion method, which comprises the following steps performed in sequence:

[0014] S1. According to the resolution in the geological task, the well excitation point and the ground observation point of the target layer section are determined, and the data acquisition module is used to obtain the borehole-to-surface electromagnetic original data of different excitation signal periods of the target layer section;

[0015] S2. The borehole-to-surface electromagnetic original data is read, and the data calculation module is used to calculate the real part and imaginary part data of the normalized horizontal radial electric field of each ground observation point when each excitation point is excited in each excitation signal period;

[0016] S3. The difference module is used to perform data difference on the real part and imaginary part data of the horizontal radial electric field, so as to obtain the real part and imaginary part of the differential horizontal radial electric field of each ground observation point when each excitation point is excited in each excitation signal period;

[0017] S4. According to the real part and imaginary part of the differential horizontal radial electric field, the inversion module is used to perform three-dimensional resistivity inversion to obtain a three-dimensional resistivity data body of the target layer section;

[0018] S5. The analysis module is used to combine the three-dimensional resistivity data body of the target layer section and the induced polarization anomaly of the target layer section to complete the three-dimensional spatial distribution of the oil and gas content in the excited section in the well in the ground observation area.

[0019] As a limitation, the well excitation point and the ground observation point of the target layer section are determined according to the resolution in the geological task in the step S1; after the formation resistivity model of the work area is established according to the drilling logging resistivity information, three-dimensional forward analysis is performed to obtain the excitation signal period.

[0020] As a second limitation, the borehole-to-surface electromagnetic original data comprises the coordinate positions of the excitation point and the ground observation point, the transmission signal file of the well excitation and the observation signal file of the ground observation.

[0021] As a further limitation, the step S2 of calculating the real part and imaginary part data of the normalized horizontal radial electric field at all excitation points and ground observation points in each excitation signal cycle comprises:

[0022] a1) reading the well excitation current signal in the emission signal file and the horizontal radial electric field component signal in the observation signal file;

[0023] a2) converting the well excitation current signal into real part data and imaginary part data in the complex domain by Fourier transform; and converting the horizontal radial electric field component signal observed by the ground observation point into real part data and imaginary part data in the complex domain after polar distance normalization and Fourier transform;

[0024] a3) performing current normalization processing on the electric field component complex domain to obtain normalized horizontal radial electric field component complex domain real part and imaginary part data;

[0025] The current normalization processing is to divide the real part and imaginary part data of the electric field collected by the ground observation point by the real part and imaginary part data of the well excitation current, respectively;

[0026] a4) performing outlier removal and filtering denoising on the normalized horizontal radial electric field component real part and imaginary part data to obtain the real part and imaginary part data of the normalized horizontal radial electric field at each ground observation point when each excitation point is excited in each excitation signal cycle.

[0027] As a further limitation, the step S3 of obtaining the real part and imaginary part of the differential horizontal radial electric field comprises:

[0028] If there are n excitation points, n>2, the real part and imaginary part data of the normalized horizontal radial electric field obtained by the ground observation point when the two excitation points spaced by i, i∈[0,n-2] excitation points are excited in each excitation signal cycle are subtracted, respectively, wherein the real part and imaginary part data of the normalized horizontal radial electric field corresponding to each ground observation point when the excitation point close to the bottom of the target layer section is excited in the excitation signal cycle are subtracted from the real part and imaginary part data of the normalized horizontal radial electric field corresponding to each ground observation point when the excitation point close to the top of the target layer section is excited in the excitation signal cycle, and The real part and imaginary part of the differential horizontal radial electric field are obtained by fitting the new excitation source excitation ground observation point data, i.e. The real part and imaginary part of the differential horizontal radial electric field are obtained by fitting the new excitation source excitation ground observation point data, i.e.

[0029] As a third limitation, before performing the step S4, the target layer section needs to be three-dimensionally inverted and grid-encrypted sectioned according to the geological task, and the grid density of the grid-encrypted sectioning is determined by the resolution of the geological task, which is greater than or equal to the resolution of the geological task;

[0030] The target segment of the densification is greater than or equal to the ground observation area on the horizontal plane, and extends beyond the planes of the uppermost and lowermost excitation points in the vertical direction.

[0031] By adopting the above-described technical solution, the beneficial effects achieved by this invention compared to the prior art are as follows:

[0032] (1) The device of the present invention obtains more accurate three-dimensional resistivity data by repeatedly exciting the target layer in the well and collecting data from the ground observation point, and by performing differential analysis on the multiple excitation electric field data through the differential module, so as to provide a more reliable basis for oil and gas exploration and development.

[0033] (2) The method of the present invention performs differential analysis on the multiple excitation electric field data collected from ground observation points to eliminate the influence of the strata above the excitation point on the target layer. By densifying and subdividing the target layer segment, the high-precision three-dimensional inversion is completed using the three-dimensional resistivity inversion and the differential data volume, and a high-precision resistivity data volume is obtained. The resistivity data volume and other information are used to complete a more accurate three-dimensional oil and gas evaluation of the target layer.

[0034] In summary, this invention can effectively improve the accuracy of resistivity, providing a more reliable basis for the exploration and development of oil and gas reservoirs. Attached Figure Description

[0035] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0036] Figure 1 This is a principle block diagram of Embodiment 1 of the present invention;

[0037] Figure 2 This is a schematic diagram of the ground observation network density in Embodiment 2 of the present invention;

[0038] Figure 3 This is a schematic diagram of the inversion target model and ground observation points in Embodiment 2 of the present invention;

[0039] Figure 4 This is a planar schematic diagram of the resistivity after three-dimensional inversion in Embodiment 2 of the present invention. Detailed Implementation

[0040] To better explain and facilitate understanding of the present invention, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0041] Example 1: High-precision well-to-ground electromagnetic inversion device

[0042] like Figure 1 As shown, this embodiment includes a data acquisition module, a data calculation module, a difference module, an inversion module, and an analysis module.

[0043] a data acquisition module, which acquires the original data of the borehole-ground electromagnetic method of the target layer section in different excitation signal periods and outputs the data to a data calculation module.

[0044] the data calculation module, which calculates the real part and the imaginary part of the normalized horizontal radial electric field of each ground observation point when each excitation point is excited in each excitation signal period according to the received original data of the borehole-ground electromagnetic method, and outputs the data to a difference module.

[0045] the difference module, which calculates the real part and the imaginary part of the normalized horizontal radial electric field of each ground observation point to obtain the real part and the imaginary part of the differential horizontal radial electric field of each ground observation point in each excitation signal period, and outputs the data to an inversion module.

[0046] the inversion module, which performs three-dimensional resistivity inversion on the real part and the imaginary part of the differential horizontal radial electric field to obtain a three-dimensional resistivity data volume of the target layer section, and outputs the data to an analysis module;

[0047] the analysis module, which is used to complete the three-dimensional spatial distribution of the oil and gas content in the excited section in the well in the ground observation area by combining the three-dimensional resistivity data volume of the target layer section and the excitation polarization anomaly of the target layer section.

[0048] Example 2: High-precision borehole-ground electromagnetic inversion method

[0049] This embodiment is realized by using the high-precision electromagnetic inversion device in Example 1. This embodiment includes the following steps performed in sequence:

[0050] S1. According to the geological task, the excited points in the well, the ground observation area, the ground observation points and the excitation signal periods of the target layer section are designed, and the data acquisition module is used to acquire the original data of the borehole-ground electromagnetic method of the target layer section in different excitation signal periods;

[0051] S2. The original data of the borehole-ground electromagnetic method is read, and the data calculation module is used to calculate the real part and the imaginary part of the normalized horizontal radial electric field of each ground observation point when each excitation point is excited in each excitation signal period;

[0052] S3. The real part and the imaginary part of the horizontal radial electric field are subjected to data difference by using the difference module to obtain the real part and the imaginary part of the differential horizontal radial electric field of each ground observation point when each excitation point is excited in each excitation signal period;

[0053] S4. According to the real part and the imaginary part of the differential horizontal radial electric field, the inversion module is used to perform three-dimensional resistivity inversion to obtain a three-dimensional resistivity data volume of the target layer section;

[0054] S5. The analysis module is used to complete the three-dimensional spatial distribution of the oil and gas content in the excited section in the well in the ground observation area by combining the three-dimensional resistivity data volume of the target layer section and the excitation polarization anomaly of the target layer section.

[0055] In this embodiment, a new drilling well is selected, and the target interval is 5990m-6500m. The geological task in step S1 is to determine the oil and gas content in the interval 5990m-6500m in the well including the shooting well, and the horizontal resolution is required to be 12.5m and the vertical resolution is required to be 5m.

[0056] According to the geological task, the interval of the shooting points in the well is twice the vertical resolution, and the distance between the ground observation points is twice the horizontal resolution. In this embodiment, the interval of the shooting points is 10m, and there are 52 shooting points. The observation network of 25m x 25m is selected for the ground observation points, and the observation area includes the range of 1100m x 1700m including the shooting well. The total number of observation points is 45 x 69, i.e. 3105. The shooting signal period is obtained by three-dimensional forward analysis after establishing the formation resistivity model of the work area through the drilling well logging resistivity information, wherein the drilling well logging resistivity information is known information collected before construction.

[0057] The well-to-ground electromagnetic raw data includes the coordinate positions of the shooting points and the ground observation points, the transmission signal file of the shooting in the well, and the observation signal file of the ground observation.

[0058] Table 1 shows the positions of the shooting points in the well and the corresponding numbers in the target interval of this embodiment, and Table 2 shows the shooting signal period of this embodiment.

[0059] Table 1 shows the positions of the shooting points in the well and the corresponding numbers in the target interval of this embodiment, and Table 2 shows the shooting signal period of this embodiment.

[0060] Sequence number Well depth Sequence number Well depth Sequence number Well depth Sequence number Well depth AB01 6500 AB14 6370 AB27 6240 AB40 6110 AB02 6490 AB15 6360 AB28 6230 AB41 6100 AB03 6480 AB16 6350 AB29 6220 AB42 6090 AB04 6470 AB17 6340 AB30 6210 AB43 6080 AB05 6460 AB18 6330 AB31 6200 AB44 6070 AB06 6450 AB19 6320 AB32 6190 AB45 6060 AB07 6440 AB20 6310 AB33 6180 AB46 6050 AB08 6430 AB21 6300 AB34 6170 AB47 6040 AB09 6420 AB22 6290 AB35 6160 AB48 6030 AB10 6410 AB23 6280 AB36 6150 AB49 6020 AB11 6400 AB24 6270 AB37 6140 AB50 6010 AB12 6390 AB25 6260 AB38 6130 AB51 6000 AB13 6380 AB26 6250 AB39 6120 AB52 5990

[0061] Table 2 shows the shooting signal period.

[0062] Sequence number Excitation signal period Excitation signal frequency 1 0.32600 3.06748 2 0.40000 2.50000 3 0.46000 2.17391 4 0.51200 1.95313 5 0.68000 1.47059 6 0.82000 1.21951 7 1.02400 0.97656

[0063] Figure 2 The figure shows the observation network density diagram of the ground observation, wherein the smaller diameter dots are the ground observation points, and the larger diameter dots are the shooting wells.

[0064] In step S2 of this embodiment, the well-to-ground electromagnetic raw data is read, and the data calculation module is used to calculate the real part and the imaginary part of the normalized horizontal radial electric field of 3105 ground observation points when 52 shooting points are shot in 7 shooting signal periods. The specific calculation process includes the following steps in turn:

[0065] a1) reading the well shooting current signal in the transmission signal file and the horizontal radial electric field component signal in the observation signal file;

[0066] a2) converting the excited current signal in the well into real part data and imaginary part data in the complex domain by Fourier transform, and converting the horizontal radial electric field component signal observed by the ground observation point into real part data and imaginary part data in the complex domain by Fourier transform after polar distance normalization;

[0067] a3) performing current normalization on the electric field component in the complex domain to obtain normalized real part and imaginary part data of the horizontal radial electric field component; the current normalization is to divide the real part and imaginary part data of the electric field collected by the ground observation point by the real part and imaginary part data of the excited current in the well, respectively;

[0068] a4) performing outlier elimination and filter denoising on the normalized real part and imaginary part data of the horizontal radial electric field component to obtain the normalized real part and imaginary part data of the horizontal radial electric field of each ground observation point at each excited signal period.

[0069] The process of obtaining the real part and imaginary part of the differential horizontal radial electric field of each ground observation point in step S3 of the embodiment is as follows:

[0070] If there are n excited points, the normalized real part and imaginary part data of the horizontal radial electric field obtained by the ground observation point at each excited signal period of the two excited points with an interval i, i∈[0, 50] are subtracted, respectively, wherein the normalized real part and imaginary part data of the horizontal radial electric field corresponding to each ground observation point at each excited signal period of the excited point close to the bottom of the target layer are subtracted from the normalized real part and imaginary part data of the horizontal radial electric field corresponding to each ground observation point at each excited signal period of the excited point close to the top of the target layer, and a total of The real part and imaginary part of the differential horizontal radial electric field are fitted to the approximate new excited source ground observation point data, i.e. each ground observation point obtains The real part and imaginary part of the differential horizontal radial electric field are fitted to the approximate new excited source ground observation point data, i.e. each ground observation point obtains

[0071] In this embodiment, the target layer section is three-dimensionally inverse to encrypt the grid profile of the target layer before step S4 according to the geological task. The grid density of the grid encryption profile is determined by the resolution of the geological task, and is greater than or equal to the resolution of the geological task. In this embodiment, the grid density is 12.5m×12.5m×5m, which is the same as the resolution of the geological task. The encrypted target layer section is greater than or equal to the ground observation area in the horizontal plane, and is greater than or equal to the plane where the uppermost excitation point is located and the plane where the lowermost excitation point is located in the vertical direction. When performing three-dimensional resistivity inversion, the influence of the casing must be considered. If there is three-dimensional seismic wave impedance data in the study area, the wave impedance data can be used to convert the conductivity according to the relationship between the wave impedance and the conductivity to establish the initial model for inversion. If not, a uniform layer model can be used as the initial model for inversion.

[0072] Figure 3 The figure shows the plane schematic diagram of the inversion target model and the ground observation point. The three black boxes represent three three-dimensional target bodies. Figure 4 The figure shows the plane diagram of the resistivity after three-dimensional inversion. The deeper the color in the three boxes in the figure, the greater the resistivity. After obtaining the three-dimensional target body inversion resistivity data body, the three-dimensional spatial distribution of the oil and gas content in the excitation section in the well in the ground observation area is completed according to the excitation polarization anomaly of the target layer section obtained by the prior art.

Claims

1. A high-precision well-to-surface electromagnetic inversion device, characterized in that, It includes a data acquisition module, a data calculation module, a difference module, an inversion module, and an analysis module; The data acquisition module acquires raw well-to-surface electromagnetic data of different excitation signal cycles in the target layer and outputs it to the data calculation module. The data calculation module calculates the real and imaginary parts of the normalized horizontal radial electric field of each ground observation point during each excitation signal cycle based on the received raw well-to-ground electromagnetic data, and outputs the data to the differential module. The differential module calculates the real and imaginary parts of the normalized horizontal radial electric field at each ground observation point, obtains the real and imaginary parts of the differential horizontal radial electric field at each ground observation point in each excitation signal cycle, and outputs them to the inversion module. The inversion module performs three-dimensional resistivity inversion on the real and imaginary parts of the differential horizontal radial electric field to obtain the three-dimensional resistivity data volume of the target layer, and outputs it to the analysis module. The analysis module is used to combine the three-dimensional resistivity data of the target layer and the induced polarization anomaly of the target layer to complete the three-dimensional spatial distribution of oil and gas content in the induced section of the well in the surface observation area.

2. A high-precision well-to-surface electromagnetic inversion method, implemented using the high-precision well-to-surface electromagnetic inversion device described in claim 1, characterized in that, The method includes the following steps performed sequentially: S1. Based on the geological task, design the excitation point in the well, the ground observation area, the ground observation point and the excitation signal period of the target layer, and use the data acquisition module to obtain the raw well-to-ground electromagnetic data of different excitation signal periods of the target layer; S2. Read the raw well-to-ground electromagnetic data, and use the data calculation module to calculate the real and imaginary parts of the normalized horizontal radial electric field of each ground observation point during each excitation signal cycle at each excitation point; S3. The real and imaginary parts of the horizontal radial electric field data are differentially divided using a differential module to obtain the real and imaginary parts of the differential horizontal radial electric field at each ground observation point during each excitation signal cycle at each excitation point. S4. Based on the real and imaginary parts of the differential horizontal radial electric field, the three-dimensional resistivity inversion is performed using the inversion module to obtain the three-dimensional resistivity data volume of the target layer. S5. Using the analysis module, the three-dimensional spatial distribution of oil and gas content in the well-induced polarization anomaly of the target layer is completed by combining the three-dimensional resistivity data volume of the target layer and the induced polarization anomaly of the target layer.

3. The high-precision well-to-ground electromagnetic inversion method according to claim 2, characterized in that, In step S1, the excitation point in the well and the ground observation point of the target layer are determined according to the resolution of the geological task; after establishing the formation resistivity model of the work area based on the drilling logging resistivity information, three-dimensional forward modeling analysis is carried out to obtain the excitation signal period.

4. The high-precision well-to-ground electromagnetic inversion method according to claim 2 or 3, characterized in that, The raw well-to-ground electromagnetic data includes the coordinates of the excitation point, the coordinates of the ground observation point, the transmission signal file generated in the well, and the observation signal file from the ground observation.

5. The high-precision well-to-ground electromagnetic inversion method according to claim 4, characterized in that, The calculation of the real and imaginary parts of the normalized horizontal radial electric field at each ground observation point in step S2 includes the following steps performed sequentially: a1) Read the well excitation current signal from the transmitted signal file and the horizontal radial electric field component signal from the observed signal file; a2) The in-well excitation current signal is converted into real and imaginary data in the complex domain by Fourier transform; the horizontal radial electric field component signal observed at the ground observation point is normalized by pole moment and then converted into real and imaginary data in the complex domain by Fourier transform. a3) The complex domain of the electric field component is normalized to obtain the real and imaginary parts of the complex domain of the horizontal radial electric field component after normalization. The current normalization process involves dividing the real and imaginary parts of the electric field data collected from the ground observation points by the real and imaginary parts of the excitation current in the well, respectively. a4) Perform fly-point removal and filtering noise reduction operations on the real and imaginary parts of the normalized horizontal radial electric field components to obtain the normalized real and imaginary parts of the horizontal radial electric field of each ground measuring point during each excitation signal cycle.

6. The high-precision well-to-ground electromagnetic inversion method according to claim 5, characterized in that, In step S3, the method for obtaining the real and imaginary parts of the differential horizontal radial electric field is as follows: If there are n excitation points, n>2, for each excitation point with an interval of i, i∈[0,n-2], subtract the real and imaginary parts of the normalized horizontal radial electric field obtained from the ground observation point during each excitation signal cycle. Specifically, for the excitation point near the bottom of the target layer, the real and imaginary parts of the normalized horizontal radial electric field corresponding to each ground observation point during excitation signal cycle are subtracted from the real and imaginary parts of the normalized horizontal radial electric field corresponding to the excitation point near the top of the target layer during excitation signal cycle. A total of [number missing] normalized horizontal radial electric fields are obtained for each excitation signal cycle. The data from ground observation points are excited by an approximate new excitation source, meaning that each ground observation point receives data during each excitation signal cycle. The real and imaginary parts of the differential horizontal radial electric field.

7. The high-precision well-to-surface electromagnetic inversion method according to any one of claims 2, 3, 5, and 6, characterized in that, Before performing step S4, the target layer needs to be meshed into a three-dimensional inversion target layer according to the geological task. The mesh density of the meshing is determined by the resolution of the geological task and is greater than or equal to the resolution of the geological task. The target segment of the densification is greater than or equal to the ground observation area on the horizontal plane, and extends beyond the planes of the uppermost and lowermost excitation points in the vertical direction.

Images