Interwell time-frequency electromagnetic data acquisition system and method based on underground current source

Abstract

The invention discloses an inter-well time-frequency electromagnetic data acquisition system and method based on an underground current source, and the method comprises the steps: employing a time-frequency electromagnetic emission source to emit low-frequency time-frequency electromagnetic signal current among two wells or multiple wells, and employing an array type multi-component time-frequency electromagnetic data acquisition short section in a receiving well, inter-well time-frequency electromagnetic signals of two wells or multiple wells are collected; as one end of the time-frequency electromagnetic emission source is arranged under the emission well, and the other end of the time-frequency electromagnetic emission source is grounded at the mouth of the receiving well or is connected to the mouth of the metal sleeve, the time-frequency electromagnetic current emitted by the time-frequency electromagnetic emission source under the emission well passes through rock stratums or reservoirs among two wells or multiple wells to reach the mouth of the receiving well or the sleeve of the receiving well; and meanwhile, a low-frequency induced polarization effect is excited in the inter-well reservoir. Due to the fact that inter-well low-frequency and time-frequency electromagnetic data are collected, the resistivity, the polarizability and the IPR distribution of rock strata between two wells or multiple wells can be calculated through constraint inversion, and accurate evaluation on oil and gas resources of underground reservoirs is achieved.

Description

Technical Field

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

[0002] In actual work, the ground electromagnetic method is largely limited by the detection depth and resolution. In order to overcome these shortcomings, the interwell electromagnetic method has emerged. The interwell electromagnetic method refers to a geophysical method that transmits or receives electromagnetic wave signals in two or more boreholes, uses electromagnetic wave signals to perform imaging and detect the physical properties between the wells. Since the transmitter and receiver can be placed in very deep boreholes, it has the characteristics of large penetration and large detection depth, and is therefore widely used in engineering environmental geophysical prospecting, mineral exploration, petroleum exploration, etc. For different applications, some special methods with their own characteristics have been produced, including interwell radio wave imaging, cross-hole radar, and interwell electromagnetic imaging. At present, interwell radio wave imagers only measure electric field intensity data, with a low operating frequency, generally single-frequency electromagnetic waves, and the frequency range is usually 1kHz to 10MHz. Due to the lack of travel time data to correct the ray path, interwell radio wave imaging mainly performs attenuation tomography based on direct ray tracing. Interwell radio wave imaging can be used for both engineering and environmental geophysics and prospecting. Cross-hole radar is a detection method of borehole radar, which uses high-frequency electromagnetic pulses to detect the changes in dielectric constant and conductivity between two wells. Inter-well electromagnetic imaging uses a lower frequency to measure complex electromagnetic signals, which is suitable for oil and gas reservoir monitoring. It is a frontier geophysical technology. Production practice in multiple work areas has shown that inter-well electromagnetic imaging is an effective means of reservoir research and can be used to analyze the distribution of remaining oil. Find oil and gas enrichment areas, thereby achieving the purpose of improving the success rate of drilling high-efficiency wells and improving recovery rates.

[0003] Cross-well electromagnetic logging is a logging method developed on the basis of single-well electromagnetic logging. It places a transmitter in a well to transmit electromagnetic waves to the formation, and places a receiver in another or more wells to receive the electromagnetic waves transmitted through the formation. By measuring these electromagnetic waves and performing forward, inverse and tomographic imaging, two-dimensional or three-dimensional resistivity (or conductivity) images reflecting the inter-well or regional reservoir structure and the distribution of oil, gas and water are obtained, thereby achieving the measurement and description of the electrical characteristics of the inter-well or regional formations, thereby obtaining inter-well or regional oil, gas and water distribution information, which is used to study the structure of the reservoir and the spatial distribution of oil, gas and water, reveal the underground geological characteristics, and improve the accuracy of reservoir description.

[0004] The current interwell electromagnetic technology uses high-frequency electromagnetic waves, which have limited penetration distance and large attenuation. Due to the strong shielding effect of metal casing on high-frequency electromagnetic waves, interwell electromagnetic detection technology cannot be used in metal casing wells. In addition, the interwell electromagnetic detection system based on high-frequency electromagnetic waves can only measure the resistivity parameters of the rock formation between the two wells, and cannot measure the low-frequency induced polarization effect of the underground interwell medium, resulting in the non-uniqueness of its data processing results and the inability to accurately evaluate the oil and gas saturation of oil and gas reservoirs. Summary of the invention

[0005] The purpose of the present invention is to provide a high-power downhole current source inter-well time-frequency electromagnetic data acquisition system and acquisition method, using a high-power time-frequency electromagnetic emission source to transmit a high-power low-frequency time-frequency electromagnetic signal current between two or more wells, and using an array-type multi-component time-frequency electromagnetic data acquisition short section in the receiving well to collect the inter-well time-frequency electromagnetic signals of the two or more wells. By performing special processing on the collected inter-well time-frequency electromagnetic data, multiple parameters (resistivity, polarizability, IPR) can be used to accurately and comprehensively evaluate the inter-well oil and gas reservoir.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions:

[0007] An inter-well time-frequency electromagnetic data acquisition system based on a downhole current source includes a first current source transmitting antenna arranged in a transmitting well and a second current source transmitting antenna arranged at a wellhead of a receiving well, wherein 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 in a receiving well with a casing;

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

[0011] A downhole array type time-frequency electromagnetic data receiving short section is arranged in the receiving well;

[0012] The downhole array-type time-frequency electromagnetic data receiving short sections are connected by armored optical cables or armored optoelectronic composite cables. The top of the downhole array-type time-frequency electromagnetic data receiving short section is connected to the armored optical cable or armored optoelectronic composite cable. The head end of the armored optical cable or armored optoelectronic composite cable is connected to the wellhead time-frequency electromagnetic data receiving terminal installed near the wellhead.

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

[0014] The vertical non-polarized electric field sensor pair among the three pairs of mutually orthogonal and perpendicular three-component non-polarized electric field sensor pairs is 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 short section, and are insulated from the metal shell of the downhole array-type time-frequency electromagnetic data receiving short section 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 sheets orthogonal to each other in the horizontal direction, which are respectively embedded in the outer shell of the downhole array type time-frequency electromagnetic data receiving short section, and are insulated from the metal shell of the downhole array type time-frequency electromagnetic data receiving short section by ceramic rings or high-temperature resistant rubber rings on the outside of the circular non-polarized electrode sheets.

[0016] The material of each non-polarizable electric field sensor of the three-component non-polarizable electric field sensor pair is a pair of platinum non-polarizable electrodes made of copper sulfate or silver chloride or platinum-plated platinum.

[0017] The downhole array time-frequency electromagnetic data receiving short 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, and 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 short section includes a three-component optical fiber magnetic field sensor and a three-component optical fiber electric field sensor, and also includes a three-component optical fiber attitude sensor.

[0019] The method for collecting time-frequency electromagnetic data between wells based on downhole current source includes the following specific steps:

[0020] S1, a first current source transmitting antenna is arranged in the transmitting well to the bottom of the well, a second current source transmitting antenna is arranged at the wellhead of the receiving well, and a time-frequency electromagnetic controllable current transmitting source is connected in the middle of 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 arranged 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 cased well);

[0022] S3, start the time-frequency electromagnetic controllable current transmitting source on the ground, and transmit the forward and reverse high-power square wave current with a duty cycle of 1 to the first tail end of the first current source transmitting antenna arranged in the transmitting well;

[0023] S4. Arrange a downhole array type time-frequency electromagnetic data receiving short section in the receiving well to the bottom of the well;

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

[0025] S6. When the downhole array-type time-frequency electromagnetic data receiving subsection continuously collects the time-frequency electromagnetic data between wells, the electric winch next to the receiving wellhead is started to slowly and evenly lift the downhole array-type time-frequency electromagnetic data receiving subsection to the wellhead;

[0026] S7, then the downhole array time-frequency electromagnetic data receiving subsection stops collecting the inter-well time-frequency electromagnetic data, and the electric winch next to the receiving wellhead lowers the downhole array time-frequency electromagnetic data receiving subsection to the bottom of the well again;

[0027] S8. According to the distance between two adjacent transmitting sources in the well determined by the construction design, the electric winch next to the well mouth lifts the first tail end of the first current source transmitting antenna arranged at the bottom of the well upward by a pre-designed distance;

[0028] S9, restarting the time-frequency electromagnetic controllable current transmitting source on the ground to transmit forward and reverse high-power square wave currents with a duty cycle of 1 to the first tail end of the first current source transmitting antenna arranged in the transmitting well;

[0029] S10, the downhole array time-frequency electromagnetic data receiving subsection starts to continuously collect inter-well time-frequency electromagnetic data again, starts the electric winch next to the receiving wellhead, and slowly and evenly pulls up the downhole array time-frequency electromagnetic data receiving subsection to the wellhead;

[0030] S11, repeating the operation flow from step S13 to step S10 until the first tail end of the first current source transmitting antenna arranged in the transmitting well is lifted upward to the wellhead, thereby completing the collection of a pair of inter-well time-frequency electromagnetic data;

[0031] S12, performing denoising, filtering, improving the signal-to-noise ratio and consistency processing of the emission current of the relative emission source on the inter-well time-frequency electromagnetic data collected from each pair of wells;

[0032] S13, using the three-dimensional ground or two-dimensional seismic data to interpret the occurrence of the interface between the underground rock layer and the reservoir to carry out geological modeling, and using the lithology model interpreted by the logging data of the transmitting well and the receiving well to carry out well-seismic calibration of the buried depth and thickness of each rock layer;

[0033] S14, smoothing the deep resistivity logging data of the transmitting well and the receiving well to obtain a model of average resistivity value 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 the reservoir between the two or more underground wells calibrated in step S13 and the average resistivity value of each layer of the transmitting well and the receiving well to strongly constrain the inversion processing of the inter-well time-frequency electromagnetic data pre-processed in step S12, to obtain the distribution and change data of the resistivity and polarizability along each rock stratum between the two or more underground wells;

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

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

[0037] S18. High resistivity, high polarizability, and high IPR abnormal reservoirs between two or more underground wells should be related to fluids with high hydrocarbon saturation in the reservoir;

[0038] S19, using the logging data of the transmitting well and the receiving well to calculate the porosity of each rock layer and reservoir between two or more underground wells;

[0039] S20, inverting the porosity of each rock layer and reservoir between wells using the attribute data of ground or well or inter-well seismic, and calibrating with the porosity of each rock layer and reservoir between two or more underground wells calculated in step S19;

[0040] S21, calibrating the oil and gas saturation of known reservoirs using resistivity data and polarizability data distributed along each reservoir between two or more wells and IPR data;

[0041] S22. Utilize the porosity of each reservoir calculated and calibrated by inversion in step S20 and the oil and gas saturation of the known reservoir calibrated in step S21, and combine the resistivity, polarizability and IPR data distribution in each reservoir between the wells obtained in steps S15 and S16 to calculate the total oil and gas content of each reservoir between two or more wells, thereby achieving accurate evaluation of the oil and gas resources in each reservoir between two or more wells.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows: in this scheme, a high-power time-frequency electromagnetic transmitting source is used to transmit a high-power low-frequency time-frequency electromagnetic signal current between two or more wells, and an array-type multi-component time-frequency electromagnetic data acquisition short section 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 transmitting source is located underground 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 transmitting source under the transmitting well passes through the rock formation or reservoir between the two or more wells from the bottom of the transmitting well, reaches the wellhead of the receiving well or the grounding electrode on the metal casing of the receiving well, and simultaneously excites a low-frequency induced polarization effect in the reservoir between the wells. Since the present invention collects inter-well low-frequency time-frequency electromagnetic data, the resistivity, polarizability and IPR distribution of the rock formation or reservoir between two or more wells can be calculated through constrained inversion, so as to accurately evaluate the oil and gas resources of the underground oil and gas reservoir. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

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

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

[0047] Figure 4 This is a schematic diagram of the external structure of a short section for collecting time-frequency electromagnetic data between wells according to an embodiment of the present invention;

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

[0049] Figure 6 The figure is a schematic diagram of the internal structure of a well-to-well time-frequency electromagnetic data acquisition sub using a three-component optical fiber electric field sensor and a three-component optical fiber magnetic field sensor according to an embodiment of the present invention.

[0050] Marks and corresponding parts names in the attached drawings:

[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 time-frequency electromagnetic data receiving short section, 9. Armored optical cable or armored optoelectronic composite cable, 10. Wellhead time-frequency electromagnetic data receiving terminal, 11. Receiving electric winch next to the wellhead, 12. Transmitting electric winch next to the wellhead, 81. Three-component induction 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 casing, 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 DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0053] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0055] In the description of the embodiments of the present invention, it should be noted that if the terms "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. appear, the orientation or position relationship indicated is based on the orientation or position relationship shown in the accompanying drawings, or is the orientation or position relationship in which the product of the invention is usually placed when used. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0056] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components must be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "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, "plurality" means at least 2.

[0058] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0059] Embodiment 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 arranged in a transmitting well, and a second current source transmitting antenna 2 arranged at the wellhead of a receiving well, wherein the first current source transmitting antenna 1 and the second current source transmitting antenna 2 are both connected to a time-frequency electromagnetic controllable current transmitting source 3. 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 during the inter-well time-frequency electromagnetic data acquisition process. 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 cased well).

[0061] Figure 1 Schematic diagram of the inter-well time-frequency electromagnetic data acquisition system based on downhole current source in an embodiment of the present invention. The end of the first current source transmitting antenna 1 extending into the well is connected to a copper power supply electrode rod 6, and the tail end of the copper power supply electrode rod 6 is sleeved with an insulating rubber ball 7 to prevent the copper power supply electrode rod 6 from directly contacting the inner wall of the metal casing. A downhole array-type time-frequency electromagnetic data receiving short section 8 is arranged in the receiving well.

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

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

[0064] The downhole array-type time-frequency electromagnetic data receiving short sections 8 are connected by armored optical cables or armored optoelectronic composite cables 9. The top of the downhole array-type time-frequency electromagnetic data receiving short sections 8 is connected to an armored optical cable or an armored optoelectronic composite cable 9. The head end of the armored cable or the armored optoelectronic composite cable is connected to a wellhead time-frequency electromagnetic data receiving terminal 10 installed near the wellhead.

[0065] Figure 4 The external structure diagram of the inter-well time-frequency electromagnetic data acquisition subsection of the embodiment of the present invention is shown in FIG. The downhole array-type time-frequency electromagnetic data receiving subsection 8 includes three pairs of mutually orthogonal three-component non-polarized electric field sensors 83 or a three-component optical fiber electric field sensor 84, and also includes a mutually orthogonal three-component inductive or fluxgate magnetic field sensor 81 or a three-component optical fiber magnetic field sensor 82.

[0066] The vertical non-polarized electric field sensor pair in the three-component non-polarized electric field sensor pair 83 is 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 short section 8, and are insulated from the metal shell 86 of the downhole array type time-frequency electromagnetic data receiving short 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 sheets 88 that are orthogonal to each other in the horizontal direction, and are respectively embedded in the metal shell 86 of the downhole array type time-frequency electromagnetic data receiving short section 8, and are insulated from the metal shell 86 of the downhole array type time-frequency electromagnetic data receiving short section 8 by the ceramic ring or high temperature resistant rubber ring 87 on the outside of the circular non-polarized electrode sheets 88.

[0068] The material of the three-component non-polarized electric field sensor pair 83 is copper sulfate or silver chloride or platinum-plated platinum non-polarized electrode pair.

[0069] Figure 5The schematic diagram of the internal structure of the well-to-well time-frequency electromagnetic data acquisition short section of the embodiment of the present invention adopts a three-component non-polarized electric field sensor pair 83 and a three-component inductive or fluxgate magnetic field sensor 81. When the downhole array-type time-frequency electromagnetic data receiving short section 8 has 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 short section 8 also needs to have 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, a photoelectric converter 94, etc.

[0070] Figure 6 The internal structure diagram of the downhole array type time-frequency electromagnetic data receiving short section 8 using the three-component optical fiber electric field sensor 84 and the three-component optical fiber magnetic field sensor 82 in the embodiment of the present invention. When the downhole array type time-frequency electromagnetic data receiving short section 8 has the three-component optical fiber magnetic field sensor 82 and the three-component optical fiber electric field sensor 84, only one three-component optical fiber attitude sensor 95 is needed in the downhole array type time-frequency electromagnetic data receiving short section 8, and the downhole array type time-frequency electromagnetic data receiving short section 8 and the wellhead time-frequency electromagnetic data receiving terminal 10 only need to be connected with an armored optical cable or an armored optoelectronic composite cable 9.

[0071] The method for collecting time-frequency electromagnetic data between wells based on downhole current source includes the following specific steps:

[0072] S1, a first current source transmitting antenna 1 is arranged in the transmitting well to the bottom of the well, a second current source transmitting antenna 2 is arranged at the wellhead of the receiving well, and 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;

[0073] S2, the second tail end 5 of the second current source transmitting antenna 2 arranged 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 cased well);

[0074] S3, start the time-frequency electromagnetic controllable current transmitting source 3 on the ground, and transmit the forward and reverse high-power square wave current with a duty cycle of 1 to the first tail end 4 of the first current source transmitting antenna 1 arranged in the transmitting well;

[0075] S4, deploying a downhole array type time-frequency electromagnetic data receiving short section 8 to the bottom of the well in the receiving well;

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

[0077] S6, when the downhole array type time-frequency electromagnetic data receiving subsection 8 continuously collects the time-frequency electromagnetic data between wells, the electric winch 11 next to the receiving wellhead is started to slowly and uniformly lift the downhole array type time-frequency electromagnetic data receiving subsection 8 to the wellhead;

[0078] S7, then the downhole array type time-frequency electromagnetic data receiving subsection 8 stops collecting the inter-well time-frequency electromagnetic data, and the electric winch 11 next to the receiving wellhead lowers the downhole array type time-frequency electromagnetic data receiving subsection 8 to the bottom of the well again;

[0079] S8. According to the distance between two adjacent transmitting sources in the well determined by the construction design, the electric winch 12 next to the well mouth lifts the first tail end 4 of the first current source transmitting antenna 1 arranged at the bottom of the well upward by a pre-designed distance;

[0080] S9, start the time-frequency electromagnetic controllable current transmitting source 3 on the ground again to transmit forward and reverse 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 arranged in the transmitting well;

[0081] S10, the downhole array time-frequency electromagnetic data receiving subsection 8 starts to continuously collect inter-well time-frequency electromagnetic data again, starts the electric winch 11 next to the receiving wellhead, and slowly and uniformly pulls up the downhole array time-frequency electromagnetic data receiving subsection 8 to the wellhead;

[0082] S11, repeating the operation flow from step S13 to step S10 until the first tail end 4 of the first current source transmitting antenna 1 arranged in the transmitting well is lifted upward to the wellhead, completing the collection of a pair of inter-well time-frequency electromagnetic data;

[0083] S12, performing denoising, filtering, improving the signal-to-noise ratio and consistency processing of the emission current of the relative emission source on the inter-well time-frequency electromagnetic data collected from each pair of wells;

[0084] S13, using the three-dimensional ground or two-dimensional seismic data to interpret the occurrence of the interface between the underground rock layer and the reservoir to carry out geological modeling, and using the lithology model interpreted by the logging data of the transmitting well and the receiving well to carry out well-seismic calibration of the buried depth and thickness of each rock layer;

[0085] S14, smoothing the deep resistivity logging data of the transmitting well and the receiving well to obtain a model of average resistivity value 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 the reservoir between the two or more underground wells calibrated in step S13 and the average resistivity value of each layer of the transmitting well and the receiving well to strongly constrain the inversion processing of the inter-well time-frequency electromagnetic data pre-processed in step S12, to obtain the distribution and change data of the resistivity and polarizability along each rock stratum between the two or more underground wells;

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

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

[0089] S18. High resistivity, high polarizability, and high IPR abnormal reservoirs between two or more underground wells should be related to fluids with high hydrocarbon saturation in the reservoir;

[0090] S19, using the logging data of the transmitting well and the receiving well to calculate the porosity of each rock layer and reservoir between two or more underground wells;

[0091] S20, inverting the porosity of each rock layer and reservoir between wells using the attribute data of ground or well or inter-well seismic, and calibrating with the porosity of each rock layer and reservoir between two or more underground wells calculated in step S19;

[0092] S21, calibrating the oil and gas saturation of known reservoirs using resistivity data and polarizability data distributed along each reservoir between two or more wells and IPR data;

[0093] S22. Utilize the porosity of each reservoir calculated and calibrated by inversion in step S20 and the oil and gas saturation of the known reservoir calibrated in step S21, and combine the resistivity, polarizability and IPR data distribution in each reservoir between the wells obtained in steps S15 and S16 to calculate the total oil and gas content of each reservoir between two or more wells, thereby achieving accurate evaluation of the oil and gas resources in each reservoir between two or more wells.

[0094] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

[0095] Embodiment 2:

[0096] Embodiment 2 of the present invention is to arrange a first current source transmitting antenna 1 to the bottom of a transmitting well, arrange a second current source transmitting antenna 2 in multiple receiving wells within a certain distance around the transmitting well, and connect a ground time-frequency electromagnetic controllable current transmitting source 3 in the middle of each pair of the first current source transmitting antenna 1 and the second current source transmitting antenna 2. An underground array-type time-frequency electromagnetic data receiving short section 8 is arranged to the bottom of the well in all receiving wells.

[0097] All ground-based time-frequency electromagnetically controllable current transmitting sources 3 are started to transmit forward and reverse 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.

[0098] The wellhead time-frequency electromagnetic data receiving terminal 10 is started, and all downhole array-type time-frequency electromagnetic data receiving subsections 8 are controlled and started to collect inter-well time-frequency electromagnetic data.

[0099] The operation flow from step S6 to step S11 in Example 1 is repeated to complete the collection of inter-well time-frequency electromagnetic data of all pairs of wells.

[0100] Repeat the inter-well time-frequency electromagnetic data flow from step S12 to step S22 in 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, thereby achieving accurate evaluation of the oil and gas resources in the inter-well reservoirs of multiple pairs of wells.

[0101] The total amount of oil and gas in the interwell reservoirs of multiple pairs of wells and the accurate evaluation results of oil and gas resources in the interwell reservoirs of multiple pairs of wells are interpolated and fused to obtain the total amount of oil and gas in the area of ​​multiple receiving wells, thereby realizing the accurate evaluation of the total oil and gas resources in the area of ​​multiple receiving wells.

Claims

1. The inter-well time-frequency electromagnetic data acquisition system based on downhole current source is characterized by: It comprises a first current source transmitting antenna (1) arranged in the transmitting well, and a second current source transmitting antenna (2) arranged at the wellhead of the receiving well, wherein the first current source transmitting antenna (1) and the second current source transmitting antenna (2) are both connected to a time-frequency electromagnetically controllable current transmitting source (3); The tail end of the first current source transmitting antenna (1) gradually moves 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 an open hole receiving well or connected to the casing at the wellhead of a receiving well with a casing; 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 the tail end of the copper power supply electrode rod (6) is sleeved with an insulating rubber ball (7) to prevent the copper power supply electrode rod (6) from directly contacting the inner wall of the metal casing; A downhole array-type time-frequency electromagnetic data receiving short section (8) is arranged in the receiving well; The downhole array-type time-frequency electromagnetic data receiving short sections (8) are connected to each other via armored optical cables or armored photoelectric composite cables (9); the top of the downhole array-type time-frequency electromagnetic data receiving short sections (8) is connected to the armored optical cables or armored photoelectric composite cables (9); the head end of the armored optical cables or armored photoelectric composite cables (9) is connected to a wellhead time-frequency electromagnetic data receiving terminal (10) installed near the wellhead.

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

3. The inter-well time-frequency electromagnetic data acquisition system based on downhole current source according to claim 2 is characterized in that: The vertical non-polarized electric field sensor pair among the three pairs of mutually perpendicular and orthogonal three-component non-polarized electric field sensor pairs (83) is two annular non-polarized electrodes (85), which are respectively installed at two ends of a metal shell (86) of a downhole array type time-frequency electromagnetic data receiving short section (8), and are insulated from the metal shell (86) of the downhole array type time-frequency electromagnetic data receiving short 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 sheets (88) orthogonal to each other in the horizontal direction. Each pair of circular non-polarized electrode sheets (88) are respectively embedded in the outer shell of the downhole array type time-frequency electromagnetic data receiving short section (8) at an orientation of 90 degrees, and are insulated from the metal outer shell (86) of the downhole array type time-frequency electromagnetic data receiving short section (8) by ceramic rings or high temperature resistant rubber rings (87) on the outer sides of the circular non-polarized electrode sheets (88).

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

5. The inter-well time-frequency electromagnetic data acquisition system based on downhole current source according to claim 1 is characterized in that: The downhole array-type time-frequency electromagnetic data receiving short section (8) includes three pairs of mutually perpendicular and 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), and 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 downhole current source-based time-frequency electromagnetic data acquisition system according to claim 1, characterized in that: The downhole array-type time-frequency electromagnetic data receiving short section (8) comprises a three-component optical fiber magnetic field sensor (82) and a three-component optical fiber electric field sensor (84), and also comprises a three-component optical fiber attitude sensor (95).

7. A method for collecting time-frequency electromagnetic data between wells based on a downhole current source, characterized in that: The inter-well time-frequency electromagnetic data acquisition system based on a downhole current source applied to any one of claims 1 to 6 comprises the following specific steps: S1, a first current source transmitting antenna (1) is arranged in the transmitting well to the bottom of the well, a second current source transmitting antenna (2) is arranged at the wellhead of the receiving well, and a time-frequency electromagnetically 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) arranged 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, starting the time-frequency electromagnetic controllable current transmitting source (3) on the ground, transmitting a forward and reverse high-power square wave current with a duty cycle of 1 to the first tail end (4) of the first current source transmitting antenna (1) arranged in the transmitting well; S4, deploying a downhole array-type time-frequency electromagnetic data receiving short section (8) to the bottom of the well in the receiving well; S5, starting the wellhead time-frequency electromagnetic data receiving terminal (10) near the wellhead, controlling and starting the downhole array-type time-frequency electromagnetic data receiving subsection (8) to start collecting inter-well time-frequency electromagnetic data; S6, while the downhole array-type time-frequency electromagnetic data receiving short section (8) continuously collects the time-frequency electromagnetic data between wells, start the electric winch (11) next to the receiving wellhead, and slowly and evenly lift the downhole array-type time-frequency electromagnetic data receiving short section (8) to the wellhead; S7, the downhole array type time-frequency electromagnetic data receiving short section (8) then stops collecting the inter-well time-frequency electromagnetic data, and the electric winch (11) next to the receiving wellhead lowers the downhole array type time-frequency electromagnetic data receiving short section (8) to the bottom of the well again; S8. According to the distance between two adjacent transmitting sources in the well determined by the construction design, the electric winch (12) next to the well mouth lifts the first tail end (4) of the first current source transmitting antenna (1) arranged at the bottom of the well upward by a pre-designed distance; S9, restarting the time-frequency electromagnetically controllable current transmitting source (3) on the ground to transmit a forward and reverse high-power square wave current with a duty cycle of 1 to the first tail end (4) of the first current source transmitting antenna (1) arranged in the transmitting well; S10, the downhole array type time-frequency electromagnetic data receiving short section (8) starts to continuously collect the time-frequency electromagnetic data between wells again, starts the electric winch (11) next to the receiving wellhead, and slowly and evenly pulls up the downhole array type time-frequency electromagnetic data receiving short section (8) to the wellhead; S11, repeating the operation flow from step S13 to step S10 until the first tail end (4) of the first current source transmitting antenna (1) arranged in the transmitting well is lifted upward to the wellhead, thereby completing the collection of a pair of inter-well time-frequency electromagnetic data; S12, performing denoising, filtering, and improving the signal-to-noise ratio and consistency processing of the emission current of the relative emission source on the inter-well time-frequency electromagnetic data collected from each pair of wells; S13, using the three-dimensional ground or two-dimensional seismic data to interpret the occurrence of the interface between the underground rock layer and the reservoir to carry out geological modeling, and using the lithology model interpreted by the logging data of the transmitting well and the receiving well to carry out well-seismic calibration of the buried depth and thickness of each rock layer; S14, smoothing the deep resistivity logging data of the transmitting well and the receiving well to obtain a model of average resistivity value 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 the reservoir between the two or more underground wells calibrated in step S13 and the average resistivity value of each layer of the transmitting well and the receiving well to strongly constrain the inversion processing of the inter-well time-frequency electromagnetic data pre-processed in step S12, to obtain the distribution and change data of the resistivity and polarizability along each rock stratum between the two or more underground wells; S16, multiplying the resistivity and polarizability data distributed along each rock layer between two or more underground wells inverted in step S15 to obtain the distribution of IPR data of resistivity and polarizability multiplied between the two or more wells; S17. Comprehensively interpret the resistivity data, polarizability data and IPR data distributed along each rock layer between two or more underground wells to accurately evaluate the oil and gas reservoirs between the wells; S18. High resistivity, high polarizability, and high IPR abnormal reservoirs between two or more underground wells should be related to fluids with high hydrocarbon saturation in the reservoir; S19, using the logging data of the transmitting well and the receiving well to calculate the porosity of each rock layer and reservoir between two or more underground wells; S20, inverting the porosity of each rock layer and reservoir between wells using the attribute data of ground, well or inter-well seismic, and calibrating with the porosity of each rock layer and reservoir between two or more underground wells calculated in step S19; S21, calibrating the oil and gas saturation of known reservoirs using resistivity data and polarizability data distributed along each reservoir between two or more wells and IPR data; S22. Utilize the porosity of each reservoir calculated and calibrated by inversion in step S20 and the oil and gas saturation of the known reservoir calibrated in step S21, and combine the resistivity, polarizability and IPR data distribution in each reservoir between the wells obtained in steps S15 and S16 to calculate the total oil and gas content of each reservoir between two or more wells, thereby achieving accurate evaluation of the oil and gas resources in each reservoir between two or more wells.

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