A method and system for radially remote high-precision exploration of a reservoir

Abstract

The present application relates to a kind of post-casing reservoir radial long-distance high-precision detection method and system, comprising: the joint detection mechanism of electromagnetic induction method and line source method is analyzed, and the layered columnar model of post-casing reservoir joint detection of electromagnetic induction and line source combination is established;Based on the layered columnar model of post-casing reservoir joint detection, the excitation of electromagnetic probe and line source is designed, and the radial long-distance detection result of post-casing reservoir under different detection depths is obtained;The radial long-distance detection result of post-casing reservoir obtained under different detection depths is imaged, and the injection breakthrough front and oil-water interface distribution are obtained.The present application explains the reservoir resistivity by the way of electromagnetic induction and line source combination, eliminates the limitations in the reservoir detection in the prior art, improves the reliability of reservoir detection system inversion interpretation, provides a new idea for downhole casing post-casing reservoir medium online identification and oil-water interface distinction.Therefore, it can be widely applied in oil reservoir detection technical field.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of electromagnetic induction and linear source combination's post casing reservoir radial remote high-precision detection method and system, belong to oil reservoir detection technical field. BACKGROUND

[0002] In the process of oil exploitation, due to a large number of water injection, oil layer will appear different degree of water flooding, water injection layer subsidence or wellbore collapse and other problems, which seriously affect the recovery efficiency. Therefore, for the post casing well in the later stage of exploitation, it is necessary to timely grasp the reservoir information outside the casing, especially the oil-water distribution and water injection front, and accurately interpret and evaluate it, to provide theoretical guidance for further development of reservoir, and then increase the oil production efficiency and reduce the oil production cost.

[0003] At present, there are many technical researches on the monitoring of post casing reservoir at home and abroad, which are introduced as follows:

[0004] Tracer method is the earliest method applied to the dynamic monitoring of post casing reservoir. This method needs to inject fluid containing tracer, and by analyzing the arrival time and concentration of tracer in the water sample of each production well in the whole test area, the direction, speed and direction of water injection are determined. Then, according to certain sampling regulations, the surrounding production wells are sampled to monitor the production and reservoir heterogeneity.

[0005] Seismic monitoring method uses the difference of acoustic attenuation characteristics in gas, liquid and solid, and identifies the gas swept area by detecting the acoustic attenuation and time delay characteristics caused by the intersection interface of gas enrichment area and sandstone and carbonate containing oil and water pores, which is mainly used for monitoring the gas injection front during gas injection to analyze the displacement effect and its influence on reservoir.

[0006] Potential measurement method supplies high-power current to the downhole through casing, establishes a stable artificial electric field in the reservoir, and realizes reservoir monitoring by measuring the change of surface potential. Due to the huge resistivity difference between the detected target body, injected liquid and reservoir surrounding rock, this resistivity difference will show strong repulsion or attraction to the surrounding leakage current path, so that the artificial electric field in the measured range will be distorted. If this distortion field reaches a sufficient strength to spread to the ground surface, the underground oil and gas distribution area and water swept range can be inverted by observing the change of ground potential around the well, combined with the corresponding processing technology, so as to realize the dynamic monitoring of underground reservoir.

[0007] Cross-well electromagnetic monitoring is conducted by continuously moving a high-power electromagnetic transmitter in one well and placing a series of receivers statically from top to bottom in another well. Under the excitation of low-frequency signals, a magnetic or electric dipole transmitter coil transmits electromagnetic fields into the formation. The primary field causes eddy currents to generate a secondary alternating field in turn, the strength of which is inversely proportional to the formation resistivity. The primary field and the secondary alternating field are detected at the receiver array.

[0008] Radioactive logging is currently the main means of production well logging. By testing some elements and their corresponding contents in the formation, the producing layers and non-producing layers can be determined, the remaining oil distribution in the block can be understood, the fluid interface can be detected, and the porosity can be obtained, which is an indispensable means for re-understanding the formation near the wellbore.

[0009] The through-casing resistivity logging technology for single wells started relatively late. At present, the more feasible resistivity logging technologies mainly include the leakage current method, the transient electromagnetic method and the line source method. These methods have different principles, and the common difficulty they face is how to correct the influence of the non-uniformity of the casing, cement sheath and formation on the through-casing resistivity measurement results.

[0010] The above casing reservoir resistivity test method has certain effect, but has some shortcomings in application. The tracer method has the shortcomings of complex test process, long test period and lagged test result. The seismic method is difficult to adapt to the monitoring of injected water because the influence of injected water and formation water on acoustic wave is basically the same. Therefore, the seismic reservoir monitoring is mainly used for monitoring the gas drive effect, and the drive front is determined by comparing the time delay amplitude attenuation before and after gas injection. The potential method requires the whole test to be carried out in stages, that is, the background potential is tested before water (gas) injection, and then the potential is measured in stages during the injection process, so the dynamic monitoring of the reservoir under study is realized by the change rule of the potential in different stages. Similar to the seismic method, the potential method requires the whole test to be carried out in stages, that is, the background potential is tested before water (gas) injection, and then the potential is measured in stages during the injection process, so the method is also difficult to adapt to the monitoring of injected water. The specific measurement parameters of the interwell electromagnetic measurement system are related to well spacing, transmitter and receiver interval, casing type, working frequency and noise and other factors. At present, the practical technology is still very limited. Among the single-well measurement methods, the more feasible resistivity logging technologies mainly include the leakage current method and the transient electromagnetic method. The two methods have different principles, and the common difficulty they face is how to correct the influence of the non-homogeneity of casing, cement ring and formation on the casing resistivity measurement results. The leakage current method mainly improves the accuracy of the interpretation results by studying complex interpretation methods, which is extremely difficult. The transient electromagnetic method uses non-contact electromagnetic induction, does not need focusing and can measure continuously, but the transient electromagnetic method is easily affected by casing damage, perforation and the like, which will make the formed magnetic field more disordered, especially for long-distance detection, the influence will be more obvious. The line source method has a longer detection distance, but has low resolution for the nearby reservoir. SUMMARY

[0011] In view of the above problems, the purpose of the present application is to provide a casing reservoir radial long-distance high-precision detection method and system combining electromagnetic induction and line source, which can further improve the accuracy of casing reservoir resistivity monitoring by combining electromagnetic induction and line source to interpret reservoir resistivity.

[0012] To achieve the above purpose, the present application adopts the following technical solutions:

[0013] In the first aspect, the present application provides a casing reservoir radial long-distance high-precision detection method, comprising the following steps:

[0014] The joint detection mechanism of electromagnetic induction method and line source method is analyzed, and a casing reservoir joint detection layered columnar model combining electromagnetic induction and line source is established;

[0015] The excitation of electromagnetic probes and line sources is designed based on the layered columnar model of the combined detection of the back-casing reservoir, and the radial long-distance detection results of the back-casing reservoir at different detection depths are obtained.

[0016] The radial long-distance detection results of the reservoir after casing at different detection depths were imaged to obtain the distribution of the water injection front and oil-water interface.

[0017] Furthermore, the combined shell-and-reservoir exploration stratigraphic model includes a casing, a cement sheath, and a reservoir arranged sequentially from the inside out. An electromagnetic induction module is located in the middle of the casing. This module includes a magnetic core and an array of electromagnetic transmitting and receiving coils wound around the outer wall of the magnetic core. The array of electromagnetic transmitting coils is used to apply a bipolar step signal, and the array of electromagnetic receiving coils is used to acquire a secondary field signal. A line source detection module is located on the inner wall of the casing. This module includes an excitation electrode, a grounding electrode, and an array of measuring electrodes. The excitation electrode is used to apply an alternating current, and the array of measuring electrodes is used to measure the electric field response along the formation direction.

[0018] Furthermore, the method for designing the excitation of the electromagnetic probe and line source based on the stratigraphic columnar model of the combined detection of the back-casing reservoir, and obtaining radial long-distance detection results of the back-casing reservoir at different detection depths, includes:

[0019] 2.1) Obtain the medium radius r = r1, r2, ..., r at a certain detection depth in the reservoir behind the casing. t ,r t+1 ..., and the radius of the medium r = r1, r2, ..., r t The reservoir region near the casing is considered the near zone, r = r t ,r t+1 The reservoir region far from the casing of the casing is considered the far zone;

[0020] 2.2) Based on the layered columnar model of the combined detection of the reservoir after the casing, the electromagnetic probe and the line source excitation are designed, and the electromagnetic method is used to obtain the near-field resistivity and the line source method is used to obtain the far-field resistivity.

[0021] 2.3) Locate the interface between near-field resistivity and far-field resistivity, and stitch together the monitoring results of near-field resistivity and far-field resistivity to obtain the radial long-distance detection results of the reservoir after the casing at this detection depth.

[0022] 2.4) Repeat steps 2.1) to 2.3) to perform imaging based on the obtained radial long-distance detection results of the reservoir after casing at different detection depths, and obtain the distribution of the water injection front and oil-water interface.

[0023] Furthermore, the method for obtaining near-field resistivity using electromagnetic methods includes:

[0024] The emission mode of the array transmitting coil of the electromagnetic induction module is set so that its emitted magnetic field is focused at the set detection depth;

[0025] The weight vector corresponding to the array electromagnetic receiving coil is determined based on the different transmit and receive distances;

[0026] The time-domain induced electromotive force of a single electromagnetic receiving coil is calculated, and the induced electromotive force of all electromagnetic receiving coils is weighted based on its corresponding weight vector to obtain the average resistivity of the reservoir at different medium radii at the detection depth.

[0027] Furthermore, the time-domain induced electromotive force of the single electromagnetic receiving coil is:

[0028]

[0029] In the formula, t represents the observation time, and z n ρ represents the transmit / receive distance of the nth receiving coil. n denoted as the reservoir resistivity corresponding to the observation position of the nth receiving coil; p represents the order of the inverse Laplace transform of GS, and Dp represents the integral coefficient of the inverse Laplace transform of GS.

[0030] Furthermore, the method of obtaining far-field resistivity using the line source method includes:

[0031] The theoretical potential values ​​at different media radii were calculated;

[0032] The residual potential value is obtained by subtracting the theoretical potential value calculated at different media radii from the corresponding measured potential value. The residual resistivity is then calculated based on the residual potential value at different media radii.

[0033] Furthermore, the residual resistivity is:

[0034]

[0035] In the formula, W is the coefficient of the reservoir monitoring device based on the line source, and ΔV is the residual potential value.

[0036] Secondly, the present invention provides a high-precision radial long-range detection system for reservoirs after casing, comprising:

[0037] The model building module is used to analyze the joint detection mechanism of electromagnetic induction method and line source method, and to establish a layered columnar detection model for joint detection of back-cascade reservoirs combining electromagnetic induction and line source.

[0038] The reservoir interpretation module is used to design electromagnetic probes and line source excitation based on the stratigraphic columnar detection model of the combined detection of the back-casing reservoir, and to obtain radial long-distance detection results of the back-casing reservoir at different detection depths.

[0039] The results display module is used to image the radial long-distance detection results of the reservoir after casing at different detection depths, and to obtain the distribution of the water injection front and oil-water interface.

[0040] Thirdly, the present invention provides a processing device, which includes at least a processor and a memory, wherein the memory stores a computer program, and the processor executes the steps of the method for high-precision radial long-distance detection of the back-casing reservoir when running the computer program.

[0041] Fourthly, the present invention provides a computer storage medium storing computer-readable instructions that can be executed by a processor to implement the steps of the method for high-precision radial long-distance detection of the reservoir.

[0042] The present invention has the following advantages due to the adoption of the above technical solutions:

[0043] 1. This invention is the first to combine electromagnetic induction method with line source method, which can measure both near-field resistivity outside the casing and far-field reservoir resistivity. The combination of near and far-field measurement can realize long-distance reservoir monitoring outside the casing.

[0044] 2. In this invention, the electromagnetic induction probe adopts a multi-transmitter-multi-receiver mode. Multiple transmitters can be used to achieve magnetic field focusing, and multiple receivers can be used for array weighting. This can solve the problems of low resolution in close-range line source measurement and weak signal strength in long-range electromagnetic induction measurement, and realize high-precision radial long-range inversion interpretation of the reservoir after the casing.

[0045] In summary, this invention can further improve the accuracy of the post-casing reservoir resistivity monitoring system. By combining electromagnetic induction with line sources to interpret reservoir resistivity, it eliminates the limitations of existing reservoir detection technologies. More importantly, it improves the reliability of the reservoir detection system's inversion interpretation, providing a new approach for online identification of reservoir media and oil-water interface differentiation after casing. Therefore, it can be widely applied in the field of reservoir exploration technology. Attached Figure Description

[0046] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0047] Figure 1 This is a flowchart of the method for high-precision radial long-distance detection of reservoirs after casing provided in an embodiment of the present invention;

[0048] Figure 2This is the detection model combining electromagnetic induction and line source provided in the embodiments of the present invention;

[0049] Figure 3 This is a flowchart illustrating the joint interpretation of electromagnetic line sources provided in an embodiment of the present invention;

[0050] Figure 4 This is a monitoring data processing flow based on the electromagnetic induction method provided in an embodiment of the present invention;

[0051] Figure 5 This is a line source detection model and schematic diagram provided in an embodiment of the present invention. 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, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0053] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0054] In some embodiments of the present invention, a method for high-precision radial long-distance detection of reservoirs behind casing using a combination of electromagnetic induction and line source methods is disclosed. First, electromagnetic induction is used to measure the reservoir resistivity near the casing. However, since the electromagnetic received signal is an exponential signal that decays over time, its late-stage signal is usually very weak. Even if the late-stage signal contains information about distant reservoirs, it is difficult to extract effective test information. To address this problem, a line source detection method is used to measure the medium information at a distance outside the casing. The casing body is used as a line current source, and the oil-water distribution characteristics in the underground reservoir are obtained by measuring the downhole potential distribution. Finally, the near-field resistivity measured by electromagnetic induction and the far-field resistivity measured by the line source method are jointly interpreted to solve the problems of low resolution in near-field line source measurements and weak signal strength in far-field electromagnetic induction measurements, thus achieving high-precision radial long-distance inversion interpretation of the reservoir behind casing.

[0055] Correspondingly, some other embodiments of the present invention provide a high-precision radial long-distance detection system for reservoirs that combines electromagnetic induction with a line source.

[0056] Example 1

[0057] like Figure 1 As shown, this embodiment provides a method for high-precision radial long-distance detection of reservoirs after casing, including the following steps:

[0058] 1) The joint detection mechanism of electromagnetic induction method and line source method is analyzed, and a layered columnar model of combined detection of back-cascade reservoir using electromagnetic induction and line source is established.

[0059] 2) Based on the layered columnar model of the combined detection of the back-casing reservoir, the excitation of the electromagnetic probe and the line source is designed, and the radial long-distance detection results of the back-casing reservoir at different detection depths are obtained.

[0060] 3) The radial long-distance detection results of the reservoir after casing at different detection depths are imaged to obtain the distribution of the water injection front and oil-water interface.

[0061] Preferably, in step 1) above, such as Figure 2 As shown, the stratigraphic columnar model for combined casing and reservoir exploration includes a casing, a cement sheath, and a reservoir arranged sequentially from the inside out. An electromagnetic induction module is located in the middle of the casing. This module includes a magnetic core and arrayed electromagnetic transmitting and receiving coils wound around the outer wall of the magnetic core. The arrayed electromagnetic transmitting coils are used to apply a bipolar step signal, and the arrayed electromagnetic receiving coils are used to acquire secondary field signals. A line source detection module is located on the inner wall of the casing. This module includes an excitation electrode, a grounding electrode, and an arrayed measuring electrode. The excitation electrode is used to apply an alternating current, and the arrayed measuring electrode is used to measure the electric field response along the formation direction.

[0062] In this embodiment, in the electromagnetic induction module, since the secondary field signal exhibits an exponential decay trend over time and contains a large amount of information related to the outer medium, the relevant physical parameters of the outer reservoir can be interpreted by analyzing the secondary field signal. In the line source detection module, when an alternating current is applied to the transmitting sleeve (i.e., the excitation electrode) via a cable, electromagnetic waves propagate through the uniform formation according to the principle of electromagnetic induction. The electric field response along the formation direction is measured by the array of measuring electrodes. Since the measured electric field signal contains rich information about the outer reservoir, the purpose of reservoir detection can be achieved by analyzing the measured potential.

[0063] Preferably, in step 2) above, such as Figure 3 As shown, the method for obtaining radial long-range detection results of the reservoir at different detection depths includes the following steps:

[0064] 2.1) Obtain the radius of the medium at a certain detection depth of the reservoir behind the casing.

[0065] The radii of different media are related to the medium information of the detected reservoir section, and can be represented as r = r1, r2, ..., r from the inner layer to the outer layer. t ,r t+1 In this embodiment, r = r1, r2, ..., r t The region is considered as the reservoir near the casing, i.e., the near-zone, where r = r t ,r t+1 The area is considered as the reservoir far from the casing, i.e., the far zone.

[0066] 2.2) Based on the stratigraphic columnar model of the combined exploration of the reservoir after the casing, the electromagnetic probe and the line source excitation are designed, and the near-field resistivity is obtained by electromagnetic method and the far-field resistivity is obtained by line source method.

[0067] 2.3) Locate the interface between near-field resistivity and far-field resistivity, and stitch together the monitoring results of near-field resistivity and far-field resistivity to obtain the radial long-distance detection results of the reservoir after the detection depth.

[0068] 2.4) Repeat steps 2.1) to 2.3) to perform imaging based on the obtained radial long-distance detection results of the reservoir after casing at different detection depths, and obtain the distribution of the water injection front and oil-water interface.

[0069] Preferably, in step 2.2) above, obtaining the near-field resistivity using the electromagnetic method refers to obtaining the reservoir near the casing using the electromagnetic method, i.e., the medium with radii r1, r2, ..., r. t The average resistivity of the regional reservoir is used as the near-field resistivity. Since the received response of the electromagnetic coil exhibits an exponentially decaying curve over time, and the diffusion time of the electromagnetic eddy current corresponds to different reservoir radii, and the signals at different observation times correspond to medium information at different reservoir radii, r can be determined based on the signal changes corresponding to different observation times. t .

[0070] like Figure 4 As shown, it includes the following steps:

[0071] 2.2.1) Set the emission mode of the array transmitting coil of the electromagnetic induction module so that its emitted magnetic field is focused at the set detection depth to improve the longitudinal monitoring resolution;

[0072] 2.2.2) Determine the weight vector corresponding to the array electromagnetic receiving coil according to the different transmit and receive distances, that is, array weighting, in order to improve the monitoring signal-to-noise ratio;

[0073] 2.2.3) Calculate the induced electromotive force of a single electromagnetic receiving coil, and then weight the induced electromotive forces of all electromagnetic receiving coils based on their corresponding weight vectors to obtain the average resistivity of the reservoir at different medium radii at the detection depth.

[0074] Preferably, in step 2.2.3) above, the method for calculating the induced electromotive force of a single electromagnetic receiving coil includes:

[0075] First, calculate the frequency domain induced electromotive force of the nth electromagnetic receiving coil, which can be expressed as:

[0076]

[0077] Where, f(λ,r,ω,ρ) n Let ξ be a variable related to the information of the measured medium, and let ξ be a constant variable, expressed as:

[0078] f(λ,r,ω,ρ n )=x1C1I0(x1r) (2)

[0079] ξ=μ1N R N T I T / π (3)

[0080] In the formula, ω is the angular frequency, z n For the transmit / receive distance, ρ n Let be the reservoir resistivity corresponding to the observation position of the nth receiving coil, i be the imaginary unit, r1 be the radius of the transmitting coil, μ1 be the permeability of the transmitting coil, r be the radius of the measured medium outside the casing, x1 and λ be introduced variables, C1 be undetermined coefficients, I0() be the first-order 0th-order corrected Bessel function, and N be the reservoir resistivity corresponding to the observation position of the nth receiving coil, i be the imaginary unit, r1 be the radius of the transmitting coil, μ1 be the permeability of the transmitting coil, r be the radius of the measured medium outside the casing, x1 and λ be introduced variables, C1 be the undetermined coefficients, I0() be the first-order 0th-order corrected Bessel function, and N be the radius of the measured medium outside the casing. T and N R The number of turns of the electromagnetic transmitting coil and the electromagnetic receiving coil are respectively, I T This is the emission current.

[0081] Secondly, assume the turn-off time of the oblique step signal is t. of Then, by using the P-order GS inverse Laplace transform, equation (1) can be transformed to the time domain, and the time-domain induced electromotive force of the nth electromagnetic receiving coil can be obtained as:

[0082]

[0083] In the formula, iω=pln2 / t, t and D p Let z represent the observation time and the integral coefficients of the inverse Laplace transform of GS, respectively. n ρ represents the transmit / receive distance of the nth receiving coil. n denoted as the reservoir resistivity corresponding to the observation position of the nth receiving coil; p is the order of the inverse Laplace transform of GS, and Dp is the integral coefficient of the inverse Laplace transform of GS.

[0084] Preferably, in step 2.2) above, obtaining the far-field resistivity using the line source method refers to obtaining the reservoir far from the casing using the line source method, i.e., the medium radius is r. t,r t+1 The stratified resistivity of the reservoir in the region is used as the far-field resistivity.

[0085] like Figure 5 The diagram shown is a simplified representation of the wire source detection module. Since the casing diameter is much smaller than the casing length, the casing can be treated as a wire current source. For a single measuring electrode, the measured potential value mainly consists of two parts: first, a dominant uniform electric field formed around the casing well, which is cylindrically symmetrical and can be calculated based on fundamental electric field theory; second, the abnormal electric field distribution caused by the non-uniform resistivity of the oil-bearing layer, specifically the repulsion of current lines by high-resistivity regions and the attraction of current lines by low-resistivity regions, both of which cause anomalies in potential measurement.

[0086] 2.2.1) Calculate the theoretical potential value at each medium radius.

[0087] The theoretical potential value V is decomposed into the sum of the normal field (background field) potential value Vn and the abnormal value Va, i.e.

[0088] V = Vn + Va (5)

[0089] The normal field potential value Vn can be calculated based on the normal value of the vertical line current source in the half-space medium, that is:

[0090]

[0091] In the formula, ρ is the average resistivity of the monitoring area, and I L For the supply current, l L s is the length of the line source, d is the radial distance from the measuring electrode to the line source, and d is the depth of the measuring electrode.

[0092] The abnormal potential Va can be obtained numerically, for example, by constructing a sparse linear system of equations, i.e.

[0093] HVa=Q (7)

[0094] In the formula, H is a sparse matrix and Q is the residual potential vector, both of which are known quantities.

[0095] 2.2.2) The residual potential value is obtained by subtracting the theoretical potential value and the measured potential value at different media radii. The residual resistivity, i.e., the far-field resistivity, is then calculated based on the residual potential value at different media radii.

[0096] Based on the relationship between potential and resistivity, the residual potential value ΔV can be converted into the residual resistivity Δρ, as follows:

[0097]

[0098] In the formula, W is the coefficient of the reservoir monitoring device based on the linear source.

[0099] Example 2

[0100] Embodiment 1 above provides a method for high-precision radial long-range detection of back-casing reservoirs. Correspondingly, this embodiment provides a system for high-precision radial long-range detection of back-casing reservoirs. The system provided in this embodiment can implement the high-precision radial long-range detection method for back-casing reservoirs of Embodiment 1. The system can be implemented through software, hardware, or a combination of both. For example, the system may include integrated or separate functional modules or units to perform the corresponding steps in the methods of Embodiment 1. Since the system in this embodiment is basically similar to the method embodiment, the description process in this embodiment is relatively simple. For relevant details, please refer to the description of Embodiment 1. The system embodiment provided in this embodiment is merely illustrative.

[0101] This embodiment provides a high-precision radial long-range detection system for reservoirs after casing, comprising:

[0102] The model building module is used to analyze the joint detection mechanism of electromagnetic induction method and line source method, and to establish a layered columnar detection model for joint detection of back-cascade reservoirs combining electromagnetic induction and line source.

[0103] The reservoir interpretation module is used to design electromagnetic probes and line source excitation based on the stratigraphic columnar detection model of the combined detection of the back-casing reservoir, and to obtain radial long-distance detection results of the back-casing reservoir at different detection depths.

[0104] The results display module is used to image the radial long-distance detection results of the reservoir after casing at different detection depths, and to obtain the distribution of the water injection front and oil-water interface.

[0105] Example 3

[0106] This embodiment provides a processing device corresponding to the high-precision radial long-distance detection method for back-casing reservoirs provided in Embodiment 1. The processing device can be a client-side processing device, such as a mobile phone, laptop, tablet computer, desktop computer, etc., to execute the method of Embodiment 1.

[0107] The processing device includes a processor, a memory, a communication interface, and a bus. The processor, memory, and communication interface are connected via the bus to enable communication between them. The memory stores a computer program that can run on the processor. When the processor runs the computer program, it executes the radial long-range high-precision detection method for back-casing reservoirs provided in Embodiment 1.

[0108] In some embodiments, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0109] In other embodiments, the processor can be a general-purpose processor of various types, such as a central processing unit (CPU) or a digital signal processor (DSP), and is not limited thereto.

[0110] Example 4

[0111] The high-precision radial long-distance detection method for the back-casing reservoir described in Embodiment 1 can be specifically implemented as a computer program product. The computer program product may include a computer-readable storage medium on which computer-readable program instructions for executing the high-precision radial long-distance detection method for the back-casing reservoir described in Embodiment 1 are loaded.

[0112] A computer-readable storage medium can be a tangible device that holds and stores instructions for use by an instruction execution device. A computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination thereof.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for high-precision radial long-distance detection of reservoirs after casing, characterized in that, Includes the following steps: The joint detection mechanism of electromagnetic induction and line source methods is analyzed, and a layered columnar model for joint detection of back-cascade reservoirs combining electromagnetic induction and line source methods is established. The excitation of electromagnetic probes and line sources was designed based on a layered columnar model for joint detection of back-casing reservoirs, and radial long-range detection results of back-casing reservoirs at different detection depths were obtained, including: 2.1) Obtain the medium radius r = r1, r2, ..., r at a certain detection depth in the reservoir behind the casing. t ,r t+1 ..., and the radius of the medium r = r1, r2, ..., r t The reservoir region near the casing is considered the near zone, r = r t ,r t+1 The reservoir region far from the casing of the casing is considered the far zone; 2.2) Based on the layered columnar model of the combined exploration of the reservoir after the casing, the electromagnetic probe and the line source excitation are designed, and the electromagnetic method is used to obtain the near-field resistivity and the line source method is used to obtain the far-field resistivity. 2.3) Locate the interface between near-field resistivity and far-field resistivity, and stitch together the monitoring results of near-field resistivity and far-field resistivity to obtain the radial long-distance detection results of the reservoir after the casing is installed at this detection depth; 2.4) Repeat steps 2.1) to 2.3) to obtain the radial long-distance detection results of the reservoir after casing at different detection depths; The radial long-distance detection results of the reservoir after casing at different detection depths were imaged to obtain the distribution of the water injection front and oil-water interface.

2. The method for high-precision radial long-distance detection of reservoirs after casing as described in claim 1, characterized in that, The combined shell-and-reservoir exploration stratigraphic model includes a casing, a cement sheath, and a reservoir arranged sequentially from the inside out. An electromagnetic induction module is located in the middle of the casing. This module includes a magnetic core and an array of electromagnetic transmitting and receiving coils wound around the outer wall of the magnetic core. The array of electromagnetic transmitting coils is used to apply a bipolar step signal, and the array of electromagnetic receiving coils is used to acquire a secondary field signal. A line source detection module is located on the inner wall of the casing. This module includes an excitation electrode, a grounding electrode, and an array of measuring electrodes. The excitation electrode is used to apply an alternating current, and the array of measuring electrodes is used to measure the electric field response along the formation direction.

3. The method for high-precision radial long-distance detection of reservoirs after casing as described in claim 2, characterized in that, The method for obtaining near-field resistivity using electromagnetic methods includes: The emission mode of the array electromagnetic emission coil of the electromagnetic induction module is set so that its emission magnetic field is focused at the set detection depth; The weight vector corresponding to the array electromagnetic receiving coil is determined based on the different transmit and receive distances; The time-domain induced electromotive force of a single electromagnetic receiving coil is calculated, and the induced electromotive force of all electromagnetic receiving coils is weighted based on its corresponding weight vector to obtain the average resistivity of the reservoir at different medium radii at the detection depth.

4. The method for high-precision radial long-distance detection of reservoirs after casing as described in claim 1, characterized in that, The method of obtaining far-field resistivity using the line source method includes: The theoretical potential values ​​at different media radii were calculated; The residual potential value is obtained by subtracting the theoretical potential value calculated at different media radii from the corresponding measured potential value. The residual resistivity is then calculated based on the residual potential value at different media radii.

5. A high-precision radial long-range detection system for reservoirs after casing, characterized in that, include: The model building module is used to analyze the joint detection mechanism of electromagnetic induction method and line source method, and to build a layered columnar model of joint detection of back-cascade reservoir by combining electromagnetic induction and line source. The reservoir interpretation module is used to design electromagnetic probes and line source excitation based on a stratigraphic columnar model of the combined exploration of the back-cascade reservoir, and to obtain radial long-range exploration results of the back-cascade reservoir at different exploration depths, including: 2.1) Obtain the medium radius r = r1, r2, ..., r at a certain detection depth in the reservoir behind the casing. t ,r t+1 ..., and the radius of the medium r = r1, r2, ..., r t The reservoir region near the casing is considered the near zone, r = r t ,r t+1 The reservoir region far from the casing of the casing is considered the far zone; 2.2) Based on the layered columnar model of the combined exploration of the reservoir after the casing, the electromagnetic probe and the line source excitation are designed, and the electromagnetic method is used to obtain the near-field resistivity and the line source method is used to obtain the far-field resistivity. 2.3) Locate the interface between near-field resistivity and far-field resistivity, and stitch together the monitoring results of near-field resistivity and far-field resistivity to obtain the radial long-distance detection results of the reservoir after the casing is installed at this detection depth; 2.4) Repeat steps 2.1) to 2.3) to obtain the radial long-distance detection results of the reservoir after casing at different detection depths; The results display module is used to image the radial long-distance detection results of the reservoir after casing at different detection depths, and to obtain the distribution of the water injection front and oil-water interface.

6. A processing apparatus, the processing apparatus comprising at least a processor and a memory, the memory storing a computer program, characterized in that, When the processor runs the computer program, it implements the steps of the method for high-precision radial long-distance detection of the reservoir behind the casing as described in any one of claims 1 to 4.

7. A computer storage medium, characterized in that, It stores computer-readable instructions that can be executed by a processor to implement the steps of the radial long-range high-precision detection method for back-casing reservoirs according to any one of claims 1 to 4.

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