A formation interface far detection system and method

Abstract

The application discloses a stratum interface far detection system, characterized in that comprising: a transmitting device for continuously transmitting a detection current to a stratum during a drilling process; a receiving device located between the transmitting device and a drill bit and installed outside a drill rod, for measuring electromotive force parameters in multiple directions; a signal processing device for integrating the electromotive force parameters in multiple directions to form corresponding stratum interface boundary information; and a boundary generating device for obtaining complete boundary distribution characteristics of a current stratum interface according to the stratum interface boundary information generated by the receiving device in real time. The application realizes far detection of the stratum interface boundary under the conditions of a short source distance and non-rotation, and effectively improves the stratum description accuracy of the front, rear and side of the downhole drilling tool.

Description

Technical Field

[0001] This invention belongs to the field of petroleum exploration and development, and particularly relates to a system and method for remote detection of formation interfaces. Background Technology

[0002] Geological steering while drilling is an important means of oil and gas reservoir exploration and development. This technology is crucial for achieving accurate target entry into the target layer, real-time avoidance of drilling risks, and maximizing the oil and gas production capacity of horizontal wells. Among them, the key to geological steering while drilling is whether it can achieve logging foresight and timely detection of formation interfaces or anomalies. In the process of realizing this invention, the inventors found that the existing electromagnetic wave foresight logging instruments involved in the drilling technology usually rely on the combination of multi-component magnetic field signals and modular structural design, and the detection range can reach tens of meters. However, the existing technology also has the following problems: (1) the source distance between the transmitting and receiving antennas of the foresight logging instrument is too long, which makes it difficult to synchronize the signals between different short sections; (2) the scattered signal of the measurement magnetic field caused by the formation interface in front is weak and the signal-to-noise ratio is low.

[0003] Currently, forward-looking long-range detection mainly relies on tilted or orthogonally closed transmitting and receiving antennas, essentially measuring the magnetic field components excited by a magnetic dipole source. Long-range detection instruments designed based on this principle suffer from numerous problems, including weak measurement signals, excessively long source distances, and poor azimuth sensitivity. Furthermore, some long-range detection instruments use semi-circular antennas (open-loop half-coils) as transmitting antennas. The response information obtained using this method is easily affected by the environment, resulting in poor measurement performance. Additionally, the measurement results obtained using semi-circular antennas involve magnetic field information, which can only be extracted by rotating the instrument.

[0004] Therefore, how to achieve long-range detection (>15m) of geological anomalies ahead of the drill bit using shorter instrument sizes (<5m) is an inevitable requirement for the development of logging-while-drilling and a key issue that urgently needs to be addressed. At the same time, solving this problem is of great significance for broadening the geological steering field of view. Summary of the Invention

[0005] To address the above problems, embodiments of the present invention provide a long-range detection system for formation interfaces, comprising:

[0006] The system includes a transmitting device for continuously transmitting probe current into the formation during drilling; a receiving device located between the transmitting device and the drill bit and mounted on the outside of the drill pipe for measuring electromotive force parameters in multiple directions; a signal processing device for integrating the electromotive force parameters in multiple directions to form corresponding formation interface boundary information; and a boundary generation device for obtaining the complete boundary distribution characteristics of the current formation interface based on the formation interface boundary information generated in real time by the receiving device.

[0007] Preferably, the receiving device includes: a measurement module, wherein the measurement module includes: an axially closed measuring antenna, which surrounds the outside of the drill rod in a direction perpendicular to the drill rod axis, for measuring a first electromotive force of the longitudinal position of the receiving device; and a plurality of electromagnetic sensors, which are mounted on the axially closed measuring antenna, for measuring a second electromotive force of the receiving device in a plurality of circumferential directions.

[0008] Preferably, the plurality of electromagnetic sensors are arranged at 90° intervals along the circumferential direction.

[0009] Preferably, the signal processing device is further configured to calculate the potential difference between two pairs of sensors with symmetrical positional relationships, and obtain an intermediate electromotive force representing the electromotive force of the receiving device using the following expression, thereby generating the formation interface boundary information based on the intermediate electromotive force combined with the first electromotive force:

[0010] Ve = sqrt(△V1) 2 +△V2 2 )

[0011] Where Ve represents the intermediate electromotive force, ΔV1 and ΔV2 represent the two potential differences respectively, and sqrt represents the square root symbol.

[0012] Preferably, the signal processing device is further configured to combine the first electromotive force and the intermediate electromotive force using the following expression to obtain the amplitude variation relationship characteristics between the two, and then obtain the formation interface boundary information based on the amplitude variation relationship characteristics:

[0013] Att = abs(Ve / Vh)

[0014] Where Att represents the amplitude ratio, Vh represents the first electromotive force, and abs represents the absolute value sign.

[0015] Preferably, the signal processing device further employs a fast forward and inverse algorithm to pixelate the amplitude variation relationship, thereby converting the amplitude variation relationship into the stratigraphic interface boundary information.

[0016] Preferably, the system further includes an excitation device for providing the time-harmonic current required for the launch device to launch.

[0017] Preferably, the system is further configured with several transmitting devices and several receiving devices.

[0018] Preferably, the system further includes a resistivity measurement module, which is used to measure the apparent resistivity of the formation at the location where the drill bit arrives in real time.

[0019] Furthermore, this invention proposes a method for long-range detection of formation interfaces. This method utilizes the system described in this invention to achieve long-range detection of formation interfaces. The method includes: continuously transmitting a probe current into the formation during drilling; measuring electromotive force parameters in multiple azimuths using a receiving device positioned between the transmitting device and the drill bit; integrating the electromotive force parameters in multiple azimuths to form corresponding formation interface boundary information; and obtaining the complete boundary distribution characteristics of the current formation interface based on the formation interface boundary information generated in real time by the receiving device.

[0020] Compared with the prior art, one or more embodiments of the above solutions may have the following advantages or beneficial effects:

[0021] This invention proposes a long-range formation interface detection system and method. The system includes a transmitting device, a receiving device, a signal processing device, and a boundary generation device. First, both the transmitting and receiving devices are positioned outside the drill pipe. Then, during drilling, the transmitting device continuously transmits a detection current into the formation, while the receiving device measures electromotive force parameters in multiple azimuths in real time. Next, the signal processing device integrates the measured electromotive force parameters from multiple azimuths to form corresponding formation interface boundary information. Finally, the boundary generation device collects the formation interface boundary information generated in real time by the receiving device to generate the complete boundary distribution characteristics of the current formation interface. This invention resolves the contradiction between the detection depth and source distance (the distance between each transmitting device and each receiving device) of existing detection instruments, achieving long-range formation interface detection under shorter source distances and non-rotational conditions. This effectively improves the accuracy of formation description in front of, behind, and to the sides of the downhole drill string, and enhances the efficiency of oil and gas exploration and development.

[0022] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description

[0023] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0024] Figure 1 This is a schematic diagram of the overall structure of the formation interface remote detection system according to an embodiment of this application.

[0025] Figure 2 This is a schematic diagram of the specific structure of the formation interface remote detection system according to an embodiment of this application.

[0026] Figure 3This is a schematic diagram of a single-interface calculation model in the formation interface remote detection system according to an embodiment of this application.

[0027] Figure 4 This is a schematic diagram of the rotational orientation change of two sets of potential differences based on four directions in the formation interface remote detection system according to an embodiment of this application.

[0028] Figure 5 This is an example diagram showing the variation of the electromotive force parameter of the formation interface remote detection system according to an embodiment of this application with the measurement depth.

[0029] Figure 6 An example diagram illustrating the variation of the amplitude ratio of the formation interface remote detection system with measurement depth according to an embodiment of this application.

[0030] Figure 7 A schematic diagram illustrating the variation trend of the maximum detection edge distance under different conditions in the formation interface remote detection system of this application embodiment.

[0031] Figure 8 This is an example diagram of an arrayed transmitting and receiving device in a formation interface remote detection system according to an embodiment of this application.

[0032] Figure 9 This is a stratigraphic curtain map of the stratigraphic interface remote detection system according to an embodiment of this application.

[0033] Figure 10 This is a flowchart illustrating the steps of a remote detection method for formation interfaces according to an embodiment of this application. Detailed Implementation

[0034] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that, as long as there is no conflict, the various embodiments and features in the various embodiments of the present invention can be combined with each other, and the resulting technical solutions are all within the protection scope of the present invention.

[0035] Furthermore, the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0036] Geological steering while drilling is an important means of oil and gas reservoir exploration and development. This technology is crucial for achieving accurate target entry into the target layer, real-time avoidance of drilling risks, and maximizing the oil and gas production capacity of horizontal wells. Among them, the key to geological steering while drilling is whether it can achieve logging foresight and timely detection of formation interfaces or anomalies. In the process of realizing this invention, the inventors found that the existing electromagnetic wave foresight logging instruments involved in the drilling technology usually rely on the combination of multi-component magnetic field signals and modular structural design, and the detection range can reach tens of meters. However, the existing technology also has the following problems: (1) the source distance between the transmitting and receiving antennas of the foresight logging instrument is too long, which makes it difficult to synchronize the signals between different short sections; (2) the scattered signal of the measurement magnetic field caused by the formation interface in front is weak and the signal-to-noise ratio is low.

[0037] Currently, forward-looking long-range detection mainly relies on tilted or orthogonally closed transmitting and receiving antennas, essentially measuring the magnetic field components excited by a magnetic dipole source. Long-range detection instruments designed based on this principle suffer from numerous problems, including weak measurement signals, excessively long source distances, and poor azimuth sensitivity. Furthermore, some long-range detection instruments use semi-circular antennas (open-loop half-coils) as transmitting antennas. The response information obtained using this method is easily affected by the environment, resulting in poor measurement performance. Additionally, the measurement results obtained using semi-circular antennas involve magnetic field information, which can only be extracted by rotating the instrument.

[0038] Therefore, how to achieve long-range detection (>15m) of geological anomalies ahead of the drill bit using shorter instrument sizes (<5m) is an inevitable requirement for the development of logging-while-drilling and a key issue that urgently needs to be addressed. At the same time, solving this problem is of great significance for broadening the geological steering field of view.

[0039] To address the aforementioned problems, this invention proposes a long-range formation interface detection system and method. The system includes a transmitting device, a receiving device, a signal processing device, and a boundary generation device. During drilling, the transmitting device continuously transmits a probe current into the formation, thereby creating a changing electric potential field within the current formation. The receiving device, located between the transmitting device and the drill bit and mounted on the outside of the drill pipe, measures electromotive force parameters in multiple orientations. The signal processing device integrates the electromotive force parameters measured by the receiving device to form corresponding formation interface boundary information (formation layering interface information). Finally, the boundary generation device summarizes the formation interface boundary information generated in real time by the receiving device to generate the complete boundary distribution characteristics of the current formation interface.

[0040] This invention resolves the contradiction between the detection depth and source distance (the distance between each transmitting device and each receiving device) of existing detection instruments, and achieves the goal of long-range detection of formation interfaces under conditions of shorter source distance and non-rotation. It effectively improves the accuracy of formation description in front of, behind and on the sides of downhole drilling tools, and improves the efficiency of oil and gas exploration and development.

[0041] Example 1

[0042] Figure 1 This is a schematic diagram of the overall structure of the formation interface remote detection system according to an embodiment of this application. Figure 2 This is a schematic diagram of the specific structure of the formation interface remote detection system according to an embodiment of this application. The following is in conjunction with... Figure 1 and Figure 2 The geological interface remote detection system described in this invention will be described in detail.

[0043] like Figure 1 The aforementioned formation interface remote detection system includes at least: a transmitting device 11, a receiving device 12, a signal processing device 13, and a boundary generation device 14. The transmitting device 11 continuously transmits a detection current into the formation during drilling. The receiving device 12 is located between the transmitting device 11 and the drill bit and is mounted on the outside of the drill pipe. The receiving device 12 measures electromotive force parameters in multiple azimuths. The signal processing device 13 integrates the electromotive force parameters measured by the receiving device 12 in multiple azimuths to form corresponding formation interface boundary information. The boundary generation device 14 obtains the complete boundary distribution characteristics of the current formation interface based on the formation interface boundary information generated in real time by the receiving device 12.

[0044] During drilling exploration, the transmitter 11 and receiver 12 of the formation interface remote detection system are both installed on the drill pipe near the drill bit. Therefore, the combination of the transmitter 11 and receiver 12 constitutes the probe of the formation interface remote detection system in this embodiment of the application.

[0045] The structure and function of the formation interface remote detection system according to the embodiments of this application will be described in detail below.

[0046] like Figure 2 In this embodiment of the invention, both the transmitting device 11 and the receiving device 12 are disposed on the outside of the drill pipe. The receiving device 12 is located between the transmitting device 11 and the drill bit. (See reference...) Figure 2 The drill bit is located on the right side of the drill pipe (not shown). The transmitting device 11 mainly includes a transmitting coil. The transmitting coil is used to excite current into the formation. The receiving device 12 mainly includes a receiving coil. The receiving coil is used to measure the current returning to the formation after the excitation current enters, thereby obtaining the resistivity information of the formation at a certain distance from the drill bit based on the returning current.

[0047] In this embodiment, an excitation device is used to provide the time-harmonic current required for transmission to the transmitting device 11. First, a low-frequency alternating current is emitted using a current excitation source, and the current is injected into the downhole metal casing to obtain a conductive metal casing. Then, the conductive metal casing is used as a quasi-steady-state excitation source. Further, the current quasi-steady-state excitation source is used as the excitation device of this invention to provide the time-harmonic current required for transmission to the transmitting device 11, thereby making the excitation position of the excitation device in the current formation near the downhole electrical anomaly (formation interface). The formation interface has a high conductivity compared to the non-formation interface region in the current formation.

[0048] In addition, based on the high conductivity of the formation interface, this invention preliminarily determines the formation interface region. Therefore, an array of ground-based multi-component electromagnetic receivers is arranged directly above the formation interface region. The electromagnetic signals generated by the excitation device received by these receivers are then used to analyze the influence of the metal bushing on different components of the electromagnetic signal, thereby eliminating the influence of the metal bushing on the electromagnetic signal generated by the excitation device and obtaining an accurate electromagnetic signal. It should be noted that the embodiments of this application do not specifically limit the intensity of the time-harmonic current. Those skilled in the art can set the various parameters of the excitation device according to actual needs to obtain the required current intensity.

[0049] Furthermore, the transmitting device 11 is used to continuously transmit a probe current into the formation during drilling. Specifically, a closed multi-turn coil is used as the transmitting coil of the transmitting device 11, wherein the closed multi-turn coil is wrapped around the outside of the drill pipe in a direction perpendicular to the drill pipe axis (see reference). Figure 2 During drilling exploration, a closed multi-turn coil continuously transmits the time-harmonic current (probe current) provided by the excitation device into the formation, thereby creating a changing potential field in the current formation. In this embodiment, the transmitting device 11 is preferably a closed axial magnetic source antenna containing a closed coil. It should be noted that this embodiment does not specifically limit the number of turns of the closed coil in the transmitting device 11 or the orientation of the closed axial magnetic source antenna; those skilled in the art can set it according to actual needs.

[0050] Next, the receiving device 12 is used to measure the electromotive force in multiple directions. During the drilling exploration process, the receiving device 12 moves with the drill pipe and measures the electromotive force parameters in multiple directions around itself in real time during the movement.

[0051] Furthermore, the receiving device 12 includes a measurement module. The measurement module includes an axially closed measurement antenna and multiple electromagnetic sensors. The axially closed measurement antenna is wound around the outside of the drill pipe in a direction perpendicular to the drill pipe axis, and is used to measure the first electromotive force (EMF) at the longitudinal position of the receiving device. Multiple electromagnetic sensors are uniformly mounted on the axially closed measurement antenna. The multiple electromagnetic sensors are used to measure the second EMF at multiple circumferential positions. In this embodiment, the receiving coil of the receiving device 12 uses an axially closed measurement antenna, and the axially closed measurement antenna is wound around the outside of the drill pipe in a direction perpendicular to the drill pipe axis, that is, the axially closed measurement antenna is parallel to the closed multi-turn coil in the transmitting device 11. The axially closed measurement antenna is used to measure the first EMF at the longitudinal position of the receiving device 12, which is the EMF V of the receiving coil. h Each electromagnetic sensor has one end fixedly connected to the drill pipe, and the other end protruding from the outside of the axially closed measuring antenna. Each electromagnetic sensor has a corresponding measuring electrode at its outer end on the outside of the axially closed measuring antenna. The measuring electrodes measure the potential intensity information in space, while the electromagnetic sensors convert this potential intensity information to generate corresponding electromotive force parameters, thereby obtaining a second electromotive force in multiple circumferential directions. In this embodiment, the receiving device 12 has a fiberglass housing, and the axially closed measuring antenna and multiple measuring sensors are all located within the fiberglass housing.

[0052] In the receiving device 12, multiple electromagnetic sensors are arranged at 90° intervals along the circumferential direction of the drill pipe. For example... Figure 2 As shown, multiple electromagnetic sensors are distributed orthogonally to each other along the circumferential direction, with each electromagnetic sensor located at 0 degrees, 90 degrees, 180 degrees, and 270 degrees along the circumferential direction, respectively. In the embodiments of this application, the second electromotive forces corresponding to the circumferential directions of 0 degrees, 90 degrees, 180 degrees, and 270 degrees are denoted as V1, V2, V3, and V4, respectively.

[0053] Furthermore, the signal processing device 13 integrates electromotive force parameters from multiple azimuths to form corresponding stratigraphic interface boundary information. Specifically, the signal processing device 13 first acquires the first electromotive force measured by the axially closed measuring antenna in the receiving device 12 and the second electromotive force measured by multiple electromagnetic sensors. Then, it processes the second electromotive force measured by the multiple electromagnetic sensors. Finally, it integrates the processed second electromotive force with the first electromotive force to obtain an integrated result from which the azimuth and distance information of the stratigraphic interface boundary can be extracted. Based on the extracted azimuth and distance information, the corresponding stratigraphic interface boundary information is formed.

[0054] Next, the signal processing device 13 is further used to calculate the potential difference between two pairs of sensors with symmetrical positional relationships to obtain an intermediate electromotive force (EMF) representing the EMF of the receiving device 12. Based on this intermediate EMF and the first EMF, formation interface boundary information is generated. Specifically, according to the axisymmetric rule, multiple pairs of electromagnetic sensors symmetrical about the drill string axis are identified, and the potential information corresponding to each pair of electromagnetic sensors is grouped into a set. The signal processing device 13 identifies the potential signal corresponding to each electromagnetic sensor and calculates the potential difference corresponding to each set of potential information. Then, the signal processing device 13 integrates the potential differences corresponding to each set of potential information to obtain the intermediate EMF representing the EMF of the receiving device 12. Finally, the signal processing device 13 combines the intermediate EMF with the first EMF to obtain the formation interface boundary information.

[0055] Figure 3 This is a schematic diagram of a single-interface calculation model in the formation interface remote detection system according to an embodiment of this application. For example... Figure 3 As shown, the resistivity of the upper and lower strata are 10 Ωm and 1 Ωm, respectively, and the stratigraphic interface remote detection system (detection instrument) described in this invention is... Figure 3 The stratigraphic interfaces shown are parallel. Using, for example... Figure 3 The computational model shown simulates the rotational detection process of a remote detection system for formation interfaces. It then obtains the relationship between the potential difference and the rotation angle for each set of potential information. Figure 4 ( Figure 4 This diagram illustrates the potential difference variation characteristics in the formation interface remote detection system based on the rotational orientation change of two sets of potential differences in four directions, according to an embodiment of this application. Analysis of the potential difference variation characteristics reveals that when the formation interface remote detection system is located in a high-resistivity layer, at a distance of 1.0 m from the formation interface boundary, with the transmitting device 11 having 10 coil turns and an operating frequency of 100 kHz, and under rotational detection conditions, the potential difference between the two pairs of sensors with symmetrical positions follows cosine and sine variation laws respectively during drilling. Therefore, the formation interface can be detected using each set of potential differences. Furthermore, further calculations show that there is a numerical relationship between the two sets of potential differences where the sum of their squares is a constant.

[0056] In one embodiment of this application, the signal processing device 13 calculates the following two sets of potential differences: ΔV1 = (V3 - V1) and ΔV2 = (V4 - V2). Based on the periodic variation law satisfied by the two sets of potential differences, the intermediate electromotive force Ve is extracted. The intermediate electromotive force representing the electromotive force of the receiving device 12 is obtained using the following expression:

[0057] Ve = sqrt(△V1) 2 +△V2 2(1)

[0058] Where Ve represents the intermediate electromotive force, ΔV1 and ΔV2 represent the two potential differences respectively, and sqrt represents the square root symbol.

[0059] Furthermore, the signal processing device 13 is also used to combine the first electromotive force (EMF) with the intermediate EMF to obtain the amplitude variation relationship characteristics between the two, and then obtain the formation interface boundary information based on the amplitude variation relationship characteristics. Specifically, the signal processing device 13 combines the first EMF with the intermediate EMF, and by synthesizing the two, converts the EMF into an amplitude ratio Att that characterizes the amplitude variation relationship characteristics between the two. After obtaining the amplitude ratio, the signal processing device 13 uses the change in the amplitude ratio to represent the distance between the receiving device 12 and the formation interface boundary. The change in the amplitude ratio represents the distance of the drill bit from the formation interface boundaries in front, behind, and on the side of the drill bit. Additionally, the sign of the amplitude ratio represents the orientation of the formation interface boundary. The first EMF and the intermediate EMF are combined using the following expression:

[0060] Att=abs(Ve / Vh) (2)

[0061] Where Att represents the amplitude ratio, Vh represents the first electromotive force, and abs represents the absolute value sign.

[0062] Furthermore, the signal processing device 13 employs a fast forward and inverse algorithm to pixelate the amplitude variation relationship, thereby converting the amplitude variation relationship into stratigraphic interface boundary information. In this embodiment, based on the aforementioned conversion relationship between the amplitude ratio and the stratigraphic interface boundary, the signal processing device 13 uses a fast forward and inverse algorithm to extract the azimuth and distance information of the stratigraphic interface boundary in real time from the amplitude ratio data, and performs one-dimensional pixelation processing on the amplitude ratio data, thereby achieving the purpose of converting the amplitude variation relationship between the first electromotive force and the intermediate electromotive force into stratigraphic interface boundary information.

[0063] After the signal processing device 13 generates the formation interface boundary information, the boundary generation device 14 is used to obtain the complete boundary distribution characteristics of the current formation interface based on the formation interface boundary information generated in real time by the receiving device 12. During the drilling exploration process, the boundary generation device 14 collects the formation interface boundary information generated by the signal processing device 13 in real time, and integrates all the formation interface information in the entire drilling exploration process into a two-dimensional curtain map including the information of each formation interface, so as to use the two-dimensional curtain map to intuitively reflect the complete boundary distribution characteristics of the current formation interface.

[0064] Furthermore, the formation interface long-range detection system is also equipped with several transmitting devices and several receiving devices. These transmitting and receiving devices are arranged in an array on the outside of the drill pipe, and the transmitting and receiving devices are arranged sequentially along the drill pipe axis according to a preset interleaving order. Therefore, using the formation interface long-range detection system described in this invention, an array-based detection range can be obtained.

[0065] Next, the configuration methods of the transmitting device and the receiving device according to the embodiments of this application will be described in detail.

[0066] Specifically, in the formation interface long-range detection system described in this invention, multiple first combinations, including transmitting and receiving devices, are generated for the current formation. The ratio of transmitting to receiving devices in each first combination is different, and each transmitting and receiving device in each first combination forms a corresponding arrayed detection instance. Furthermore, the number of receiving devices that can be set between each transmitting device in different first combinations varies. Then, a corresponding source distance array (the distance between each transmitting device and each receiving device) is set for each first combination, forming multiple source distance setting schemes for each first combination. Further, based on the source distance setting schemes for all first combinations, a corresponding operating frequency is set for the transmitting devices in each source distance setting scheme, forming multiple operating frequency configuration schemes for each source distance setting scheme. Thus, a corresponding transmitting and receiving setting scheme is formed for each operating frequency configuration scheme.

[0067] Next, using numerical simulation technology, for each set of transmission and reception settings, the thresholds (including intermediate electromotive force threshold, first electromotive force threshold, and amplitude ratio threshold) of the measurement data used to convert into formation interface boundary information are calculated. Using the thresholds of the measurement data, the detection range corresponding to each working frequency configuration is obtained. Then, the transmission and reception settings corresponding to the maximum detection range are determined as the optimal settings, and the current optimal settings are put into the actual logging-while-drilling process.

[0068] Furthermore, the formation interface remote detection system described in this invention also utilizes, for example... Figure 3 The single-interface calculation model shown simulates the relationship between the intermediate electromotive force and the first electromotive force in the measurement data as a function of the detection depth. Under non-rotational conditions, it utilizes methods such as... Figure 3 The single-interface calculation model shown simulates the detection process of a formation interface remote detection system traversing a single interface from top to bottom, obtaining the relationship between the intermediate electromotive force and the first electromotive force in the measurement data as a function of the detection depth, as shown below. Figure 5 ( Figure 5The diagram (showing an example of the variation of the electromotive force parameter of the formation interface remote detection system according to an embodiment of this application) illustrates the relationship between measurement depth and the intermediate electromotive force. It shows that the closer the intermediate electromotive force is to the formation interface, the greater its amplitude variation, reaching its highest value at the interface. Furthermore, near the interface, the intensity of the intermediate electromotive force is significantly higher than that of the first electromotive force. The intermediate electromotive force also decays more slowly on the low-resistivity layer side, while the first electromotive force changes relatively smoothly in both high-resistivity and low-resistivity layers, with a slight decrease in value in the low-resistivity layer. Based on this, the formation interface remote detection system, using the varying decay patterns of the intermediate and first electromotive forces in the measurement data obtained through numerical simulation technology, determines the threshold values ​​of the intermediate and first electromotive forces in the measurement data as the measurement thresholds for acquiring the boundary characteristics of the formation interface.

[0069] Next, the formation interface remote detection system described in this invention also utilizes, as... Figure 3 The single-interface calculation model shown simulates the relationship between the amplitude ratio and the depth of the probe data. Under non-rotation conditions, it utilizes, as shown in the example... Figure 3 The single-interface calculation model shown simulates the detection process of a formation interface remote detection system traversing a single interface from top to bottom, obtaining the relationship between the amplitude ratio in the measurement data and the detection depth, as shown below. Figure 6 ( Figure 6 The amplitude ratio of the formation interface remote detection system according to an embodiment of this application varies with measurement depth, as shown in the example diagram. This reveals that the amplitude ratio is essentially zero when the system is far from the interface, while it increases sharply as the system approaches the interface. Furthermore, the anomaly range of the system in high-resistivity layers is significantly greater than that in low-resistivity layers. Therefore, it is determined that the current formation interface remote detection system has a stronger detection capability in high-resistivity layers.

[0070] In one specific embodiment of this application, under the condition that the potential intensity corresponding to the measurement threshold is 0.2dB, the detection distances of the current formation interface remote detection system in high resistivity formation and low resistivity formation are 2.5m and 1.75m, respectively.

[0071] Next, under the condition that the potential intensity corresponding to the measurement threshold is 0.2dB, and further assuming that the resistivity on both sides of the formation interface is 100m and 10m respectively, the relationship between the source distance and the operating frequency of the transmitting device 11 and the maximum probe edge distance is simulated, and the results are as follows: Figure 7 ( Figure 7 The diagram illustrates the variation trend of the maximum detection distance under different conditions in the formation interface remote detection system of this application embodiment, showing the relevant relationships. Analysis shows that the larger the source distance, the stronger the detection capability of the formation interface remote detection system; and the higher the frequency, the shorter the detection distance of the formation interface remote detection system.

[0072] Therefore, the embodiments of this application are designed as follows: Figure 8 ( Figure 8 As shown in the example diagram of the arrayed transmitting and receiving device in the stratigraphic interface remote detection system of this application embodiment, it has a source distance array with four source distances (0.4m, 0.6m, 0.8m and 1.8m) and a combination of three multi-transmit and multi-receive antennas with three operating frequencies (100kHz, 500kHz and 2MHz), which enables the stratigraphic interface remote detection system to have a wide detection range in the current stratigraphic layer, and the detection range can fully cover all stratigraphic interface boundaries in the current stratigraphic layer.

[0073] Furthermore, the formation interface remote detection system also includes a resistivity measurement module, used to measure the apparent resistivity of the formation at the location where the drill string reaches in real time. In actual logging-while-drilling operations, the terrain within the formation is uneven, and the underground medium is also heterogeneous, with various rocks overlapping, faults and fractures crisscrossing, or the formation filled with ore bodies. The resistivity measurement module, by measuring the apparent resistivity of the formation at the location where the drill string reaches in real time, reflects the electrical inhomogeneities and terrain undulations within the formation, thus assisting in the detection of formation interface boundaries.

[0074] In one specific embodiment of this application, the formation interface remote detection system is based on, as follows: Figure 8 The array structure shown yields the following results: Figure 9 ( Figure 9 This is a stratigraphic curtain map (as shown in the embodiment of the stratigraphic interface remote detection system of this application). The light colors represent high-resistivity layers, and the dark colors represent low-resistivity layers. The current two-dimensional curtain map demonstrates that the stratigraphic interface remote detection system can accurately locate the boundary of the stratigraphic interface even when far from the underlying interface.

[0075] Example 2

[0076] On the other hand, based on the above-mentioned far-field detection system for stratigraphic interfaces, this embodiment of the invention also proposes a far-field detection method for stratigraphic interfaces, which utilizes the above-mentioned far-field detection system for stratigraphic interfaces to effectively realize the far-field detection function of stratigraphic interfaces. Figure 10 This is a flowchart illustrating the steps of a remote detection method for formation interfaces according to an embodiment of this application. Figure 10As shown, the formation interface remote detection method of the present invention includes the following steps: Step S101: Continuously transmit a detection current to the formation during drilling; Step S102: Measure the electromotive force parameters in multiple azimuths using a receiving device disposed between the transmitting device and the drill bit; Step S103: Integrate the electromotive force parameters in multiple azimuths measured in Step S102 to form corresponding formation interface boundary information; Step S104: Obtain the complete boundary distribution characteristics of the current formation interface based on the formation interface boundary information generated in real time by the receiving device in Step S103.

[0077] This invention proposes a long-range formation interface detection system and method. The system includes a transmitting device, a receiving device, a signal processing device, and a boundary generation device. First, both the transmitting and receiving devices are positioned outside the drill pipe. Then, during drilling, the transmitting device continuously transmits a detection current into the formation, while the receiving device measures electromotive force parameters in multiple azimuths in real time. Next, the signal processing device integrates the electromotive force parameters measured by the receiving device in multiple azimuths to form corresponding formation interface boundary information. Finally, the boundary generation device summarizes the formation interface boundary information generated in real time by the receiving device to generate the complete boundary distribution characteristics of the current formation interface. This invention solves the problems of short detection distance of existing detection instruments and dependence on drill collar rotation, achieving long-range formation interface detection under shorter source distances and non-rotational conditions. This effectively improves the accuracy of formation description in front of, behind, and to the sides of the downhole drill string, and enhances the efficiency of oil and gas exploration and development. Simultaneously, the use of array acquisition significantly improves signal strength and signal-to-noise ratio.

[0078] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0079] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should be extended to equivalent substitutions of these features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0080] The phrase "an embodiment" or "an embodiment" used in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Therefore, the phrase "an embodiment" or "an embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0081] While the embodiments disclosed in this invention are as described above, the content is merely for the purpose of facilitating understanding of the invention and is not intended to limit the invention. Any person skilled in the art to which this invention pertains may make any modifications and changes in form and detail of the implementation without departing from the spirit and scope disclosed herein; however, the scope of patent protection of this invention shall still be determined by the scope defined in the appended claims.

Claims

1. A long-range detection system for stratigraphic interfaces, characterized in that, include: The transmitting device is used to continuously transmit probe current into the formation during drilling; An excitation device is used to provide the time-harmonic current required for the launch device. The excitation device is formed by using a current excitation source to emit low-frequency alternating current and injecting the current into the downhole metal casing to obtain a conductive metal casing, which is further used as a quasi-steady-state excitation source. A ground-based multi-component electromagnetic receiver is arranged in an array directly above the geological interface region to receive the electromagnetic signals generated by the excitation device, analyze the influence of the metal bushing on different components of the electromagnetic signals, and eliminate the influence of the metal bushing on the electromagnetic signals generated by the excitation device. A receiving device, located between the transmitting device and the drill bit and mounted on the outside of the drill rod, is used to measure electromotive force parameters in multiple directions. The receiving device includes a measurement module, wherein the measurement module includes: an axially closed measuring antenna, which surrounds the outside of the drill rod in a direction perpendicular to the drill rod axis, for measuring a first electromotive force at the longitudinal position of the receiving device; and a plurality of electromagnetic sensors arranged at 90° intervals in the circumferential direction, mounted on the axially closed measuring antenna, for measuring a second electromotive force at multiple circumferential positions of the receiving device. A signal processing device is used to integrate the electromotive force parameters from multiple azimuths to form corresponding stratigraphic interface boundary information. Specifically, it calculates the potential difference between two pairs of sensors with symmetrical positional relationships and obtains an intermediate electromotive force representing the electromotive force of the receiving device using the following expression. Based on this intermediate electromotive force and the first electromotive force, the stratigraphic interface boundary information is generated. Ve =sqrt(△ V 1 2 +△ V 2 2 ) in, Ve Denotes the intermediate electromotive force, Δ V 1 and △ V 2 These represent two sets of potential differences, and sqrt represents the square root symbol. A boundary generation device is used to obtain the complete boundary distribution characteristics of the current stratigraphic interface based on the stratigraphic interface boundary information generated in real time by the receiving device.

2. The system according to claim 1, characterized in that, The signal processing device is further configured to combine the first electromotive force and the intermediate electromotive force using the following expression to obtain the amplitude variation relationship characteristics between the two, and then obtain the formation interface boundary information based on the amplitude variation relationship characteristics: That=abs( Ve / Vh ) Where Att represents the amplitude ratio, Vh denoted by , abs represents the first electromotive force, and abs represents the absolute value symbol.

3. The system according to claim 2, characterized in that, The signal processing device also employs a fast forward and inverse algorithm to pixelate the amplitude variation relationship, thereby converting the amplitude variation relationship into the stratigraphic interface boundary information.

4. The system according to claim 3, characterized in that, The system is also equipped with several transmitting devices and several receiving devices.

5. The system according to claim 4, characterized in that, The system also includes: The resistivity measurement module is used to measure the apparent resistivity of the formation at the location where the drill bit arrives in real time.

6. A method for long-range detection of stratigraphic interfaces, characterized in that, The method is implemented using the system as described in any one of claims 1 to 5, and the method includes: During the drilling process, a probe current is continuously emitted into the formation; The excitation device provides the time-harmonic current required for the launch device to launch. The excitation device emits low-frequency alternating current by using a current excitation source and injects the current into the downhole metal casing to obtain a conductive metal casing. The conductive metal casing is then used as a quasi-steady-state excitation source to form the device. The electromagnetic signals generated by the excitation device are received to analyze the influence of the metal bushing on different components of the electromagnetic signals, so as to eliminate the influence of the metal bushing on the electromagnetic signals generated by the excitation device. A receiving device positioned between a transmitting device and a drill bit is used to measure electromotive force parameters in multiple directions. Specifically, the receiving device uses a measurement module to measure the first electromotive force at the longitudinal position of the receiving device by using an axially closed measuring antenna that surrounds the outside of the drill rod in a direction perpendicular to the drill rod axis, and multiple electromagnetic sensors mounted on the axially closed measuring antenna and spaced 90° apart in the circumferential direction to measure the second electromotive force at multiple circumferential positions of the receiving device. The electromotive force parameters from multiple azimuths are integrated to form corresponding stratigraphic interface boundary information. Specifically, the potential difference between two pairs of sensors with symmetrical positions is calculated, and an intermediate electromotive force representing the electromotive force of the receiving device is obtained using the following expression. Based on this intermediate electromotive force and the first electromotive force, the stratigraphic interface boundary information is generated. Ve =sqrt(△ V 1 2 +△ V 2 2 ) in, Ve Denotes the intermediate electromotive force, Δ V 1 and △ V 2 These represent two sets of potential differences, and sqrt represents the square root symbol. Based on the stratigraphic interface boundary information generated in real time by the receiving device, the complete boundary distribution characteristics of the current stratigraphic interface are obtained.

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