Inter-well time-frequency electromagnetic data acquisition system and acquisition method based on downhole current source

Abstract

This invention discloses an inter-well time-frequency electromagnetic data acquisition system and method based on a downhole current source. A time-frequency electromagnetic transmitter emits low-frequency time-frequency electromagnetic signal current between two or more wells. An array-type multi-component time-frequency electromagnetic data acquisition sub is used in the receiving well to acquire the inter-well time-frequency electromagnetic signals. Since one end of the time-frequency electromagnetic transmitter is downhole in the transmitting well, and the other end is grounded at the wellhead of the receiving well or connected to the metal casing, the time-frequency electromagnetic current emitted by the transmitter passes through the rock formations or reservoirs between the two or more wells, reaching the wellhead or casing of the receiving well, and simultaneously stimulating a low-frequency excitation polarization effect within the reservoir. Because this invention acquires low-frequency inter-well time-frequency electromagnetic data, the resistivity, polarizability, and IPR distribution of the rock formations between the two or more wells can be calculated through constrained inversion, enabling accurate evaluation of the oil and gas resources in the underground reservoirs.

Description

Technical Field

[0001] This invention relates to the field of time-frequency electromagnetic detection technology, and more specifically, to an inter-well time-frequency electromagnetic data acquisition system and acquisition method based on a downhole current source. Background Technology

[0002] Ground-based electromagnetic methods are largely limited by detection depth and resolution in practical applications. To overcome these shortcomings, cross-well electromagnetic methods emerged. Cross-well electromagnetic methods refer to geophysical methods that transmit or receive electromagnetic wave signals in two or more boreholes, using these signals for imaging and probing of the physical properties between boreholes. Because the transmitter and receiver can be placed in very deep boreholes, it features large transmission distance and large detection depth, and is therefore widely used in engineering environmental geophysics, mineral exploration, and oil exploration. For different applications, several specialized methods have been developed, including cross-well radio wave imaging, cross-hole radar, and cross-well electromagnetic imaging. Currently, cross-well radio wave imagers only measure electric field strength data, operate at low frequencies (generally single-frequency electromagnetic waves), typically in the range of 1kHz to 10MHz. Due to the lack of travel time data to correct ray paths, cross-well radio wave imaging mainly performs attenuated tomography based on straight ray tracing. Cross-well radio wave imaging can be used in engineering and environmental geophysics as well as mineral exploration. Cross-hole radar (CBAR) is a type of borehole radar that uses high-frequency electromagnetic pulses to detect changes in the dielectric constant and conductivity between two boreholes. Inter-well electromagnetic imaging (IEI) uses even lower frequencies to measure complex electromagnetic signals, making it suitable for monitoring oil and gas reservoirs. It is a cutting-edge geophysical technology. Practical application in multiple work areas has demonstrated that IIE is an effective tool for reservoir research, capable of analyzing the distribution of remaining oil and identifying oil and gas enrichment areas, thereby improving the success rate of drilling high-efficiency wells and enhancing oil recovery.

[0003] Inter-well electromagnetic logging is a logging method developed based on single-well electromagnetic logging. It places a transmitter in one well to emit electromagnetic waves into the formation, while placing a receiver in another or multiple wells to receive the electromagnetic waves propagating through the formation. By measuring these electromagnetic waves and performing forward and inverse modeling and tomographic imaging, two-dimensional or three-dimensional resistivity (or conductivity) images reflecting the reservoir structure and oil, gas and water distribution between wells or in the region are obtained. This enables the measurement and description of the electrical properties of the formation between wells or in the region, thereby obtaining information on the distribution of oil, gas and water between wells or in the region. This information is used to study the reservoir structure and the spatial distribution patterns of oil, gas and water, reveal underground geological characteristics, and improve the accuracy of reservoir description.

[0004] Current inter-well electromagnetic technology utilizes high-frequency electromagnetic waves, which have limited penetration distance and significant attenuation. Due to the strong shielding effect of metal casing on high-frequency electromagnetic waves, inter-well electromagnetic detection technology cannot be performed inside wells with metal casing. Furthermore, inter-well electromagnetic detection systems based on high-frequency electromagnetic waves can only measure the resistivity parameters of the rock formations between two wells, and cannot measure the low-frequency excitation polarization effect of the underground inter-well medium. This results in non-uniqueness of the data processing results, making it impossible to accurately assess the oil and gas saturation of oil and gas reservoirs. Summary of the Invention

[0005] The purpose of this invention is to provide an inter-well time-frequency electromagnetic data acquisition system and method using a high-power downhole current source. A high-power time-frequency electromagnetic transmitter is used to emit a high-power low-frequency time-frequency electromagnetic signal current between two or more wells. An array-type multi-component time-frequency electromagnetic data acquisition sub is used in the receiving well to acquire the inter-well time-frequency electromagnetic signals. By performing special processing on the acquired inter-well time-frequency electromagnetic data, multiple parameters (resistivity, polarizability, IPR) can be used to accurately and comprehensively evaluate the oil and gas reservoirs between wells.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution:

[0007] The well-to-well time-frequency electromagnetic data acquisition system based on downhole current source includes a first current source transmitting antenna deployed in the transmitting well and a second current source transmitting antenna deployed at the wellhead of the receiving well. Both the first current source transmitting antenna and the second current source transmitting antenna are connected to a time-frequency electromagnetic controllable current transmitting source.

[0008] The tail end of the first current source transmitting antenna gradually moves from the bottom of the transmitting well to the wellhead during the inter-well time-frequency electromagnetic data acquisition process;

[0009] The tail end of the second current source transmitting antenna is grounded at the wellhead of the open-hole receiving well or connected to the casing at the wellhead of the receiving well with a casing.

[0010] One end of the first current source transmitting antenna that extends into the well is connected to a copper power supply electrode rod, and the tail end of the copper power supply electrode rod is fitted with an insulating rubber ball to prevent the copper power supply electrode rod from directly contacting the inner wall of the metal sleeve.

[0011] The receiving well is equipped with a downhole array-type time-frequency electromagnetic data receiving section.

[0012] The downhole array-type time-frequency electromagnetic data receiving subsections are connected by armored optical cables or armored optoelectronic composite cables. The top of the downhole array-type time-frequency electromagnetic data receiving subsection is connected to an armored optical cable or armored optoelectronic composite cable, and the first end of the armored optical cable or armored optoelectronic composite cable is connected to the wellhead time-frequency electromagnetic data receiving terminal placed near the wellhead.

[0013] The downhole array-type time-frequency electromagnetic data receiving section includes three pairs of mutually orthogonal and perpendicular three-component non-polarized electric field sensor pairs or a three-component fiber optic electric field sensor, and also includes a mutually orthogonal and perpendicular three-component inductive or fluxgate magnetic field sensor or a three-component fiber optic magnetic field sensor.

[0014] Among the three pairs of mutually orthogonal and perpendicular three-component non-polarized electric field sensor pairs, the vertical non-polarized electric field sensor pair consists of two annular non-polarized electrodes, which are respectively installed at both ends of the metal shell of the downhole array-type time-frequency electromagnetic data receiving subsection, and are insulated from the metal shell of the downhole array-type time-frequency electromagnetic data receiving subsection by ceramic rings or high-temperature resistant rubber rings on both sides of the annular non-polarized electrodes.

[0015] The two pairs of horizontal non-polarized electric field sensor pairs are two pairs of circular non-polarized electrode plates that are orthogonal to each other in the horizontal orientation. They are respectively embedded in the outer shell of the downhole array-type time-frequency electromagnetic data receiving sub-section, and are insulated from the metal shell of the downhole array-type time-frequency electromagnetic data receiving sub-section by ceramic rings or high-temperature resistant rubber rings on the outside of the circular non-polarized electrode plates.

[0016] Each nonpolar electric field sensor in the three-component nonpolar electric field sensor pair is made of copper sulfate, silver chloride, or platinum-plated platinum nonpolar electrode pairs.

[0017] The downhole array-type time-frequency electromagnetic data receiving section includes three pairs of mutually orthogonal and perpendicular three-component non-polarized electric field sensor pairs and one mutually orthogonal and perpendicular three-component inductive or fluxgate magnetic field sensor. It also includes a high-temperature resistant three-component attitude sensor, a multi-channel signal amplifier, a multi-channel analog-to-digital converter, a solid-state memory, a data transmission drive module, and a photoelectric converter.

[0018] Alternatively, the downhole array-type time-frequency electromagnetic data receiving section includes a three-component fiber optic magnetic field sensor and a three-component fiber optic electric field sensor, as well as a three-component fiber optic attitude sensor.

[0019] The method for acquiring inter-well time-frequency electromagnetic data based on downhole current sources includes the following specific steps:

[0020] S1. A first current source transmitting antenna is installed in the transmitting well to the bottom of the well, and a second current source transmitting antenna is installed at the wellhead of the receiving well. A time-frequency electromagnetic controllable current transmitting source is connected between the first current source transmitting antenna and the second current source transmitting antenna.

[0021] S2. The second tail end of the second current source transmitting antenna installed at the wellhead of the receiving well is grounded at the wellhead of the receiving well (open hole well) or connected to the casing at the wellhead (metal casing well).

[0022] S3. Activate the ground-based time-frequency electromagnetic controllable current transmitter to transmit positive and negative high-power square wave currents with a duty cycle of 1 to the first tail end of the first current source transmitting antenna deployed in the transmitting well.

[0023] S4. Deploy downhole array-type time-frequency electromagnetic data receiving sub-sections to the bottom of the receiving well;

[0024] S5. Start the wellhead time-frequency electromagnetic data receiving terminal near the wellhead, control and start the downhole array time-frequency electromagnetic data receiving sub to start collecting inter-well time-frequency electromagnetic data;

[0025] S6. During the continuous acquisition of inter-well time-frequency electromagnetic data by the downhole array-type time-frequency electromagnetic data receiving sub, start the electric winch next to the receiving wellhead and slowly and uniformly raise the downhole array-type time-frequency electromagnetic data receiving sub until it reaches the wellhead.

[0026] S7. Subsequently, the downhole array-type time-frequency electromagnetic data receiving sub-section stops collecting time-frequency electromagnetic data between wells, and the electric winch next to the wellhead lowers the downhole array-type time-frequency electromagnetic data receiving sub-section to the bottom of the well again.

[0027] S8. Based on the distance between two adjacent transmitters in the well as determined by the construction design, the electric winch next to the wellhead will lift the first tail end of the first current source transmitter antenna that is laid at the bottom of the well upward by a pre-designed distance.

[0028] S9. Re-start the ground-based time-frequency electromagnetic controllable current transmitter to transmit positive and negative high-power square wave currents with a duty cycle of 1 to the first tail end of the first current source transmitting antenna deployed in the transmitting well.

[0029] S10. The downhole array-type time-frequency electromagnetic data receiving sub begins to continuously collect time-frequency electromagnetic data between wells again. The electric winch next to the receiving wellhead is started, and the downhole array-type time-frequency electromagnetic data receiving sub is slowly and uniformly raised to the wellhead.

[0030] S11. Repeat the work process from step S13 to step S10 until the first tail end of the first current source transmitting antenna deployed in the transmitting well is lifted upward to the wellhead, thus completing the acquisition of a pair of time-frequency electromagnetic data between wells.

[0031] S12. Denoise, filter, improve signal-to-noise ratio, and ensure consistency of the emission current of the relative emission source for the time-frequency electromagnetic data collected from each pair of wells.

[0032] S13. Geological modeling is performed using the occurrence of the interfaces between underground rock strata and reservoirs interpreted from surface three-dimensional or well-through two-dimensional seismic data, and well-seismic calibration of the burial depth and thickness of each rock stratum is performed using lithological models interpreted from launch and receiving well logging data.

[0033] S14. Smooth the deep resistivity logging data of the launch well and the receiving well to obtain the average resistivity value model of each layer of the rock layer or reservoir corresponding to the lithology model interpreted by the logging data.

[0034] S15. Using the layered geological model of the interface between the rock strata and reservoir of the two or more underground wells calibrated in step S13 and the average resistivity value of each layer of the launching well and receiving well, the inversion processing of the time-frequency electromagnetic data between the wells after the preprocessing in step S12 is strongly constrained to obtain the distribution and variation data of resistivity and polarizability between the two or more underground wells along each rock stratum.

[0035] S16. Multiply the resistivity and polarizability data distributed along each rock layer between two or more underground wells retrieved in step S15 to obtain the distribution of resistivity multiplied by polarizability (IPR) between the two or more wells.

[0036] S17. To comprehensively interpret the resistivity, polarizability, and IPR data distributed along each rock layer between two or more underground wells, and to accurately evaluate the oil and gas reservoirs between wells.

[0037] S18. High resistivity, high polarizability, and high IPR anomaly reservoirs between two or more underground wells should be related to fluids with high oil and gas saturation within the reservoir.

[0038] S19. Calculate the porosity of each rock layer and reservoir between two or more underground wells using logging data from the launch well and the receiving well;

[0039] S20. Use the attribute data of ground, well or inter-well seismic events to invert the porosity of each rock layer and reservoir between wells, and use the porosity of each rock layer and reservoir between two or more underground wells calculated in step S19 for calibration.

[0040] S21. Use resistivity and polarizability data distributed along each reservoir between two or more wells, as well as IPR data, to calibrate the oil and gas saturation of a known reservoir.

[0041] S22. Using the porosity of each reservoir calculated and calibrated in step S20 and the known oil and gas saturation of the reservoir after calibration in step S21, combined with the resistivity, polarizability and IPR data distribution of each reservoir between wells obtained in steps S15 and S16, the total oil and gas content of each reservoir between two or more wells is calculated, thereby achieving an accurate evaluation of the oil and gas resources of each reservoir between two or more wells.

[0042] Compared with the prior art, the beneficial effects of this invention are as follows: In this solution, a high-power time-frequency electromagnetic transmitter is used to transmit a high-power low-frequency time-frequency electromagnetic signal current between two or more wells. An array-type multi-component time-frequency electromagnetic data acquisition sub is used in the receiving well to collect the time-frequency electromagnetic signals between the two or more wells. Since one end of the high-power time-frequency electromagnetic transmitter is located downhole in the transmitting well, and the other end is grounded at the wellhead of the receiving well or connected to the metal casing of the receiving well, the high-power low-frequency time-frequency electromagnetic current emitted by the high-power time-frequency electromagnetic transmitter in the transmitting well passes through the rock strata or reservoir between the two or more wells from downhole in the transmitting well, reaching the wellhead of the receiving well or the grounding electrode on the metal casing of the receiving well, and simultaneously stimulating a low-frequency excitation polarization effect in the reservoir between the wells. Since this invention collects low-frequency time-frequency electromagnetic data between wells, the resistivity, polarizability, and IPR distribution of rock formations or reservoirs between two or more wells can be calculated through constrained inversion, so as to accurately evaluate the oil and gas resources of underground oil and gas reservoirs. Attached Figure Description

[0043] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0044] Figure 1 This is a schematic diagram of an inter-well time-frequency electromagnetic data acquisition system based on a downhole current source in an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of the field layout of the inter-well time-frequency electromagnetic data acquisition system based on a downhole current source in an embodiment of the present invention;

[0046] Figure 3 This is a schematic diagram of the field layout of the inter-well time-frequency electromagnetic data acquisition system based on a downhole current source for single-well excitation and multi-well reception in an embodiment of the present invention.

[0047] Figure 4 This is a schematic diagram of the external structure of the inter-well time-frequency electromagnetic data acquisition sub according to an embodiment of the present invention;

[0048] Figure 5 This is a schematic diagram of the internal structure of the well-to-well time-frequency electromagnetic data acquisition section using a three-component non-polarized electrode pair and a three-component inductive or fluxgate magnetic field sensor, as described in an embodiment of the present invention.

[0049] Figure 6 This is a schematic diagram of the internal structure of the well-to-well time-frequency electromagnetic data acquisition section using a three-component fiber electric field sensor and a three-component fiber magnetic field sensor, as described in an embodiment of the present invention.

[0050] The attached diagram shows the markings and corresponding component names:

[0051] 1. First current source transmitting antenna; 2. Second current source transmitting antenna; 3. Time-frequency electromagnetic controllable current transmitting source; 4. First tail end; 5. Second tail end; 6. Copper power supply electrode rod; 7. Insulating rubber ball; 8. Downhole array-type time-frequency electromagnetic data receiving section; 9. Armored optical cable or armored optoelectronic composite cable; 10. Wellhead time-frequency electromagnetic data receiving terminal; 11. Electric winch next to the receiving wellhead; 12. Electric winch next to the transmitting wellhead; 81. Three-component inductive or fluxgate magnetic field sensor; 8 2. Three-component fiber optic magnetic field sensor; 83. Three-component non-polarized electric field sensor pair; 84. Three-component fiber optic electric field sensor; 85. Ring-shaped non-polarized electrode; 86. Metal housing; 87. Ceramic ring or high-temperature resistant rubber ring; 88. Circular non-polarized electrode sheet; 89. High-temperature resistant three-component attitude sensor; 90. Multi-channel signal amplifier; 91. Multi-channel analog-to-digital converter; 92. Solid-state memory; 93. Data transmission drive module; 94. Photoelectric converter; 95. Three-component fiber optic attitude sensor. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0053] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0054] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0055] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, they are only for the convenience of describing the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0056] Furthermore, the use of terms such as "horizontal," "vertical," and "sag" does not imply that the component must be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0057] In the description of the embodiments of the present invention, "multiple" means at least two.

[0058] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0059] Example 1:

[0060] This embodiment provides an inter-well time-frequency electromagnetic data acquisition system based on a downhole current source, including a first current source transmitting antenna 1 deployed in the transmitting well and a second current source transmitting antenna 2 deployed at the wellhead of the receiving well. Both the first and second current source transmitting antennas are connected to a time-frequency electromagnetic controllable current transmitting source 3. During the inter-well time-frequency electromagnetic data acquisition process, the first tail end 4 of the first current source transmitting antenna 1 gradually moves from the bottom of the transmitting well to the wellhead. The second tail end 5 of the second current source transmitting antenna 2 is grounded at the wellhead of the receiving well (open hole well) or connected to the casing at the wellhead (metal casing well).

[0061] Figure 1 This is a schematic diagram of an inter-well time-frequency electromagnetic data acquisition system based on a downhole current source in an embodiment of the present invention. One end of the first current source transmitting antenna 1, extending into the well, is connected to a copper power supply electrode rod 6, and an insulating rubber ball 7 is fitted onto the tail end of the copper power supply electrode rod 6 to prevent direct contact between the copper power supply electrode rod 6 and the inner wall of the metal casing. Downhole array-type time-frequency electromagnetic data receiving sections 8 are deployed inside the receiving well.

[0062] Figure 2 This is a schematic diagram of the field layout of the inter-well time-frequency electromagnetic data acquisition system based on a downhole current source in an embodiment of the present invention. Figure 3 This is a schematic diagram of the field layout of the inter-well time-frequency electromagnetic data acquisition system based on a downhole current source for single-well excitation and multi-well reception in an embodiment of the present invention.

[0063] The downhole array-type time-frequency electromagnetic data receiving section 8 includes a three-component inductive or fluxgate magnetic field sensor 81 or a three-component fiber optic magnetic field sensor 82, a three-component non-polarized electric field sensor pair 83 or a three-component fiber optic electric field sensor 84.

[0064] The downhole array-type time-frequency electromagnetic data receiving subsections 8 are connected to each other by armored optical cables or armored optoelectronic composite cables 9. The top of the downhole array-type time-frequency electromagnetic data receiving subsection 8 is connected to an armored optical cable or armored optoelectronic composite cable 9, and the first end of the armored cable or armored optoelectronic composite cable is connected to the wellhead time-frequency electromagnetic data receiving terminal 10 placed near the wellhead.

[0065] Figure 4 This is a schematic diagram of the external structure of the downhole time-frequency electromagnetic data acquisition sub-section according to an embodiment of the present invention. The downhole array-type time-frequency electromagnetic data receiving sub-section 8 includes three pairs of mutually orthogonal and perpendicular three-component non-polarized electric field sensor pairs 83 or a three-component fiber optic electric field sensor 84, and also includes a mutually orthogonal and perpendicular three-component inductive or fluxgate magnetic field sensor 81 or a three-component fiber optic magnetic field sensor 82.

[0066] The vertical non-polarized electric field sensor pair in the three-component non-polarized electric field sensor pair 83 consists of two annular non-polarized electrodes 85, which are respectively installed at both ends of the metal shell 86 of the downhole array-type time-frequency electromagnetic data receiving sub-section 8, and are insulated from the metal shell 86 of the downhole array-type time-frequency electromagnetic data receiving sub-section 8 by ceramic rings or high-temperature resistant rubber rings 87 on both sides of the annular non-polarized electrodes 85.

[0067] The two pairs of horizontal non-polarized electric field sensor pairs in the three-component non-polarized electric field sensor pair 83 are two pairs of circular non-polarized electrode plates 88 that are orthogonal to each other in the horizontal orientation. They are respectively embedded on the metal shell 86 of the downhole array-type time-frequency electromagnetic data receiving sub-section 8, and are insulated from the metal shell 86 of the downhole array-type time-frequency electromagnetic data receiving sub-section 8 by ceramic rings or high-temperature resistant rubber rings 87 on the outside of the circular non-polarized electrode plates 88.

[0068] The three-component nonpolarized electric field sensor pair 83 is made of copper sulfate, silver chloride, or platinum-plated platinum nonpolarized electrode pairs.

[0069] Figure 5This is a schematic diagram of the internal structure of the downhole time-frequency electromagnetic data acquisition sub-section using a three-component non-polarized electric field sensor pair 83 and a three-component inductive or fluxgate magnetic field sensor 81, as described in an embodiment of the present invention. When the downhole array-type time-frequency electromagnetic data receiving sub-section 8 contains three pairs of mutually orthogonal and perpendicular three-component non-polarized electric field sensor pairs 83 and one mutually orthogonal and perpendicular three-component inductive or fluxgate magnetic field sensor 81, the downhole array-type time-frequency electromagnetic data receiving sub-section 8 also needs to include a high-temperature resistant three-component attitude sensor 89, a multi-channel signal amplifier 90, a multi-channel analog-to-digital converter 91, a solid-state memory 92, a data transmission drive module 93, and a photoelectric converter 94, etc.

[0070] Figure 6 This is a schematic diagram of the internal structure of the downhole array-type time-frequency electromagnetic data receiving section 8, which employs a three-component fiber optic electric field sensor 84 and a three-component fiber optic magnetic field sensor 82, according to an embodiment of the present invention. When the downhole array-type time-frequency electromagnetic data receiving section 8 contains a three-component fiber optic magnetic field sensor 82 and a three-component fiber optic electric field sensor 84, only one three-component fiber optic attitude sensor 95 is needed within the downhole array-type time-frequency electromagnetic data receiving section 8. The downhole array-type time-frequency electromagnetic data receiving section 8 and the wellhead time-frequency electromagnetic data receiving terminal 10 can be connected only by an armored optical cable or an armored optoelectronic composite cable 9.

[0071] The method for acquiring inter-well time-frequency electromagnetic data based on downhole current sources includes the following specific steps:

[0072] S1. A first current source transmitting antenna 1 is installed in the transmitting well to the bottom of the well, and a second current source transmitting antenna 2 is installed at the wellhead of the receiving well. A time-frequency electromagnetic controllable current transmitting source 3 is connected between the first current source transmitting antenna 1 and the second current source transmitting antenna 2.

[0073] S2. The second tail end 5 of the second current source transmitting antenna 2 installed at the wellhead of the receiving well is grounded at the wellhead of the receiving well (open hole well) or connected to the casing at the wellhead (metal casing well).

[0074] S3. Start the ground-based time-frequency electromagnetic controllable current transmitter 3 and transmit positive and negative high-power square wave currents with a duty cycle of 1 to the first tail end 4 of the first current source transmitting antenna 1 deployed in the transmitting well.

[0075] S4. Deploy downhole array-type time-frequency electromagnetic data receiving sub-section 8 to the bottom of the receiving well;

[0076] S5. Start the wellhead time-frequency electromagnetic data receiving terminal 10 near the wellhead, control and start the downhole array time-frequency electromagnetic data receiving section 8 to start collecting inter-well time-frequency electromagnetic data.

[0077] S6. During the continuous acquisition of inter-well time-frequency electromagnetic data by the downhole array-type time-frequency electromagnetic data receiving section 8, start the electric winch 11 next to the receiving wellhead and slowly and uniformly raise the downhole array-type time-frequency electromagnetic data receiving section 8 until the wellhead.

[0078] S7. Subsequently, the downhole array-type time-frequency electromagnetic data receiving section 8 stops collecting inter-well time-frequency electromagnetic data, and the electric winch 11 next to the wellhead lowers the downhole array-type time-frequency electromagnetic data receiving section 8 back to the bottom of the well.

[0079] S8. According to the distance between two adjacent transmitters in the well determined by the construction design, the electric winch 12 next to the wellhead lifts the first tail end 4 of the first current source transmitter antenna 1, which is laid to the bottom of the well, upward by a pre-designed distance.

[0080] S9. Re-start the ground-based time-frequency electromagnetic controllable current transmitter 3 to transmit positive and negative high-power square wave currents with a duty cycle of 1 to the first tail end 4 of the first current source transmitting antenna 1 deployed in the transmitting well.

[0081] S10. The downhole array-type time-frequency electromagnetic data receiving section 8 resumes continuous acquisition of time-frequency electromagnetic data between wells. The electric winch 11 next to the receiving wellhead is started and slowly and uniformly raised up the downhole array-type time-frequency electromagnetic data receiving section 8 until it reaches the wellhead.

[0082] S11. Repeat the work process from step S13 to step S10 until the first tail end 4 of the first current source transmitting antenna 1 deployed in the transmitting well is lifted upward to the wellhead, thus completing the acquisition of a pair of time-frequency electromagnetic data between wells.

[0083] S12. Denoise, filter, improve signal-to-noise ratio, and ensure consistency of the emission current of the relative emission source for the time-frequency electromagnetic data collected from each pair of wells.

[0084] S13. Geological modeling is performed using the occurrence of the interfaces between underground rock strata and reservoirs interpreted from surface three-dimensional or well-through two-dimensional seismic data, and well-seismic calibration of the burial depth and thickness of each rock stratum is performed using lithological models interpreted from launch and receiving well logging data.

[0085] S14. Smooth the deep resistivity logging data of the launch well and the receiving well to obtain the average resistivity value model of each layer of the rock layer or reservoir corresponding to the lithology model interpreted by the logging data.

[0086] S15. Using the layered geological model of the interface between the rock strata and reservoir of the two or more underground wells calibrated in step S13 and the average resistivity value of each layer of the launching well and receiving well, the inversion processing of the time-frequency electromagnetic data between the wells after the preprocessing in step S12 is strongly constrained to obtain the distribution and variation data of resistivity and polarizability between the two or more underground wells along each rock stratum.

[0087] S16. Multiply the resistivity and polarizability data distributed along each rock layer between two or more underground wells retrieved in step S15 to obtain the distribution of resistivity multiplied by polarizability (IPR) between the two or more wells.

[0088] S17. To comprehensively interpret the resistivity, polarizability, and IPR data distributed along each rock layer between two or more underground wells, and to accurately evaluate the oil and gas reservoirs between wells.

[0089] S18. High resistivity, high polarizability, and high IPR anomaly reservoirs between two or more underground wells should be related to fluids with high oil and gas saturation within the reservoir.

[0090] S19. Calculate the porosity of each rock layer and reservoir between two or more underground wells using logging data from the launch well and the receiving well;

[0091] S20. Use the attribute data of ground, well or inter-well seismic events to invert the porosity of each rock layer and reservoir between wells, and use the porosity of each rock layer and reservoir between two or more underground wells calculated in step S19 for calibration.

[0092] S21. Use resistivity and polarizability data distributed along each reservoir between two or more wells, as well as IPR data, to calibrate the oil and gas saturation of a known reservoir.

[0093] S22. Using the porosity of each reservoir calculated and calibrated in step S20 and the known oil and gas saturation of the reservoir after calibration in step S21, combined with the resistivity, polarizability and IPR data distribution of each reservoir between wells obtained in steps S15 and S16, the total oil and gas content of each reservoir between two or more wells is calculated, thereby achieving an accurate evaluation of the oil and gas resources of each reservoir between two or more wells.

[0094] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0095] Example 2:

[0096] Embodiment 2 of the present invention involves deploying a first current source transmitting antenna 1 to the bottom of a single transmitting silo, and deploying second current source transmitting antennas 2 in multiple receiving silos within a certain distance around the transmitting silo. A ground-based time-frequency electromagnetic controllable current transmitting source 3 is connected to the middle of each pair of first current source transmitting antennas 1 and second current source transmitting antennas 2. Downhole array-type time-frequency electromagnetic data receiving sub-sections 8 are deployed to the bottom of all receiving silos.

[0097] All ground-based time-frequency electromagnetic controllable current transmitters 3 are activated to transmit high-power square wave currents with a duty cycle of 1 to the first tail end 4 of the first current source transmitting antenna 1 in both positive and negative directions.

[0098] Start the wellhead time-frequency electromagnetic data receiving terminal 10, control and start all downhole array-type time-frequency electromagnetic data receiving sections 8 to begin collecting inter-well time-frequency electromagnetic data.

[0099] Repeat the operation process from steps S6 to S11 in Example 1 to collect all well-to-well time-frequency electromagnetic data.

[0100] Repeat steps S12 to S22 of Example 1 to complete the time-frequency electromagnetic data processing and interpretation work for each pair of wells, calculate the total oil and gas content of the reservoir between each pair of wells, and thus achieve accurate evaluation of the oil and gas resources of the reservoir between multiple pairs of wells.

[0101] Data interpolation and fusion processing are performed on the total oil and gas content of the reservoirs between multiple pairs of wells and the accurate evaluation results of the oil and gas resources of the reservoirs between multiple pairs of wells to obtain the total oil and gas content within the area of ​​multiple receiving wells, thereby achieving an accurate evaluation of the total oil and gas resources within the area of ​​multiple receiving wells.

Claims

1. A method for acquiring time-frequency electromagnetic data between wells based on downhole current sources, applied to an inter-well time-frequency electromagnetic data acquisition system based on downhole current sources, the inter-well time-frequency electromagnetic data acquisition system based on downhole current sources includes a first current source transmitting antenna (1) deployed in the transmitting well and a second current source transmitting antenna (2) deployed at the wellhead of the receiving well, the first current source transmitting antenna (1) and the second current source transmitting antenna (2) being connected to a time-frequency electromagnetic controllable current transmitting source (3); The tail end of the first current source transmitting antenna (1) moves gradually from the bottom of the transmitting well to the wellhead during the inter-well time-frequency electromagnetic data acquisition process; The tail end of the second current source transmitting antenna (2) is grounded at the wellhead of the open-hole receiving well or connected to the casing at the wellhead of the receiving well with a casing. The first current source transmitting antenna (1) is connected to a copper power supply electrode rod (6) at one end of its extension into the well, and an insulating rubber ball (7) is fitted to the tail end of the copper power supply electrode rod (6) to prevent the copper power supply electrode rod (6) from directly contacting the inner wall of the metal sleeve. The receiving well is equipped with a downhole array-type time-frequency electromagnetic data receiving section (8). The downhole array-type time-frequency electromagnetic data receiving subsections (8) are connected to each other by armored optical cables or armored optoelectronic composite cables (9). The top of the downhole array-type time-frequency electromagnetic data receiving subsections (8) is connected to an armored optical cable or armored optoelectronic composite cable (9), and the head end of the armored optical cable or armored optoelectronic composite cable (9) is connected to the wellhead time-frequency electromagnetic data receiving terminal (10) placed near the wellhead. Its features are, The method includes the following specific steps: S1. A first current source transmitting antenna (1) is installed in the transmitting well to the bottom of the well, and a second current source transmitting antenna (2) is installed at the wellhead of the receiving well. A time-frequency electromagnetic controllable current transmitting source (3) is connected in the middle of the first current source transmitting antenna (1) and the second current source transmitting antenna (2). S2, the second tail end (5) of the second current source transmitting antenna (2) installed at the wellhead of the receiving well is grounded at the wellhead of the open-hole receiving well or connected to the casing at the wellhead of the receiving well with a casing. S3. Start the ground-based time-frequency electromagnetic controllable current transmitter (3) and transmit positive and negative high-power square wave currents with a duty cycle of 1 to the first tail end (4) of the first current source transmitting antenna (1) deployed in the transmitting well. S4. Deploy downhole array-type time-frequency electromagnetic data receiving subsection (8) to the bottom of the receiving well; S5. Start the wellhead time-frequency electromagnetic data receiving terminal (10) near the wellhead, control and start the downhole array time-frequency electromagnetic data receiving section (8) to start collecting inter-well time-frequency electromagnetic data; S6. During the continuous acquisition of inter-well time-frequency electromagnetic data by the downhole array-type time-frequency electromagnetic data receiving section (8), start the electric winch (11) next to the receiving wellhead and slowly and uniformly raise the downhole array-type time-frequency electromagnetic data receiving section (8) until the wellhead. S7. Subsequently, the downhole array-type time-frequency electromagnetic data receiving section (8) stops collecting time-frequency electromagnetic data between wells, and the electric winch (11) next to the wellhead lowers the downhole array-type time-frequency electromagnetic data receiving section (8) to the bottom of the well again. S8. According to the distance between two adjacent transmitters in the well determined by the construction design, the electric winch (12) next to the wellhead lifts the first tail end (4) of the first current source transmitter antenna (1) laid in the well to the bottom of the well by a pre-designed distance. S9. Restart the ground-based time-frequency electromagnetic controllable current transmitter (3) to transmit positive and negative high-power square wave currents with a duty cycle of 1 to the first tail end (4) of the first current source transmitting antenna (1) deployed in the transmitting well. S10, the downhole array-type time-frequency electromagnetic data receiving section (8) starts to continuously collect time-frequency electromagnetic data between wells again, and starts the electric winch (11) next to the receiving wellhead, slowly and uniformly raising the downhole array-type time-frequency electromagnetic data receiving section (8) until the wellhead. S11. Repeat the operation process from step S3 to step S10 until the first tail end (4) of the first current source transmitting antenna (1) installed in the transmitting well is lifted upward to the wellhead, thus completing the acquisition of a pair of time-frequency electromagnetic data between wells. S12. Denoise, filter, improve signal-to-noise ratio, and ensure consistency of the emission current of the relative emission source for the time-frequency electromagnetic data collected from each pair of wells. S13. Geological modeling is performed using the occurrence of the interfaces between underground rock strata and reservoirs interpreted from surface three-dimensional or well-through two-dimensional seismic data, and well-seismic calibration of the burial depth and thickness of each rock stratum is performed using lithological models interpreted from launch and receiving well logging data. S14. Smooth the deep resistivity logging data of the launch well and the receiving well to obtain the average resistivity value model of each layer of the rock layer or reservoir corresponding to the lithology model interpreted by the logging data. S15. Using the layered geological model of the interface between the rock strata and reservoir of the two or more underground wells calibrated in step S13 and the average resistivity value of each layer of the launching well and receiving well, the inversion processing of the time-frequency electromagnetic data between the wells after the preprocessing in step S12 is strongly constrained to obtain the distribution and variation data of resistivity and polarizability between the two or more underground wells along each rock stratum. S16. Multiply the resistivity and polarizability data distributed along each rock layer between two or more underground wells retrieved in step S15 to obtain the distribution of IPR data multiplied by resistivity and polarizability between the two or more wells. S17. To comprehensively interpret the resistivity, polarizability and IPR data distributed along each rock layer between two or more underground wells, and to accurately evaluate the oil and gas reservoirs between wells. S18. High resistivity, high polarizability, and high IPR anomalies between two or more underground wells are associated with fluids with high oil and gas saturation within the reservoir. S19. Calculate the porosity of each rock layer and reservoir between two or more underground wells using logging data from the launch well and the receiving well; S20. Use the attribute data of ground, well or inter-well seismic events to invert the porosity of each rock layer and reservoir between wells, and use the porosity of each rock layer and reservoir between two or more underground wells calculated in step S19 for calibration. S21. Use resistivity and polarizability data distributed along each reservoir between two or more wells, as well as IPR data, to calibrate the oil and gas saturation of a known reservoir. S22. Using the porosity of each reservoir calculated and calibrated in step S20 and the known oil and gas saturation of the reservoir after calibration in step S21, combined with the resistivity, polarizability and IPR data distribution of each reservoir between wells obtained in steps S15 and S16, the total oil and gas content of each reservoir between two or more wells is calculated, thereby achieving an accurate evaluation of the oil and gas resources of each reservoir between two or more wells.

2. The method for inter-well time-frequency electromagnetic data acquisition based on a downhole current source according to claim 1, characterized in that, The downhole array-type time-frequency electromagnetic data receiving section (8) includes three pairs of mutually perpendicular or orthogonal three-component non-polarized electric field sensor pairs (83) or a three-component fiber optic electric field sensor (84), and also includes a mutually perpendicular or orthogonal three-component inductive or fluxgate magnetic field sensor (81) or a three-component fiber optic magnetic field sensor (82).

3. The method for inter-well time-frequency electromagnetic data acquisition based on a downhole current source according to claim 2, characterized in that, The vertical non-polarized electric field sensor pair (83) consists of two annular non-polarized electrodes (85), which are respectively installed at both ends of the metal shell (86) of the downhole array-type time-frequency electromagnetic data receiving sub-section (8), and are insulated from the metal shell (86) of the downhole array-type time-frequency electromagnetic data receiving sub-section (8) by ceramic rings or high-temperature resistant rubber rings (87) on both sides of the annular non-polarized electrodes (85); The two pairs of horizontal non-polarized electric field sensor pairs are two pairs of circular non-polarized electrode plates (88) that are orthogonal to each other in the horizontal orientation. Each pair of circular non-polarized electrode plates (88) is embedded in the shell of the downhole array-type time-frequency electromagnetic data receiving sub-section (8) at a 90-degree angle. They are insulated from the metal shell (86) of the downhole array-type time-frequency electromagnetic data receiving sub-section (8) by ceramic rings or high-temperature resistant rubber rings (87) on the outside of the circular non-polarized electrode plates (88).

4. The method for inter-well time-frequency electromagnetic data acquisition based on a downhole current source according to claim 3, characterized in that, The material of each non-polarized electric field sensor in the three-component non-polarized electric field sensor pair (83) is copper sulfate or silver chloride or platinum-plated platinum non-polarized electrode pair.

5. The method for inter-well time-frequency electromagnetic data acquisition based on a downhole current source according to claim 1, characterized in that, The downhole array-type time-frequency electromagnetic data receiving section (8) includes three pairs of mutually perpendicular or orthogonal three-component non-polarized electric field sensor pairs (83) and a mutually orthogonal and perpendicular three-component inductive or fluxgate magnetic field sensor (81). It also includes a high-temperature resistant three-component attitude sensor (89), a multi-channel signal amplifier (90), a multi-channel analog-to-digital converter (91), a solid-state memory (92), a data transmission drive module (93), and a photoelectric converter (94).

6. The method for inter-well time-frequency electromagnetic data acquisition based on a downhole current source according to claim 1, characterized in that, The downhole array-type time-frequency electromagnetic data receiving section (8) includes a three-component fiber optic magnetic field sensor (82) and a three-component fiber optic electric field sensor (84), as well as a three-component fiber optic attitude sensor (95).

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