RU2814806C1 - Seismic data collection method and system - Google Patents

Abstract

FIELD: physics; measurement.

SUBSTANCE: invention relates to seismic exploration and can be used for prospecting and exploration of mineral deposits and studying the structure and physical and mechanical properties of near-surface strata of the earth's crust. Disclosed is a method of collecting seismic data, characterized by exposing the investigated surface to sources of seismic signals following predetermined trajectories, mounting the sources on a platform placed in contact with the investigated surface, continuous movement of sources, synchronization of clocks of sources with clocks of seismic data collection system and continuous recording of signals issued by receivers. Signal sources are launched simultaneously and move along predetermined trajectories with a given speed, pulse repetition time interval T of signal sources is set on each signal source, pulse repetition interval at each source is selected based on the required recording time by the receivers of the subsoil response to the pulse supplied by the source to obtain all information about the studied area of the medium, coordinates of the source x_n, y_n, h_n and time of pulse supply t_sn are recorded into the storage module at the moment of pulse supply, where n is the number of the source; continuous recording is prepared for further use by dividing it into separate intervals.

EFFECT: invention makes it possible to multiply the productivity of geological exploration by seismic exploration methods and volumes of geophysical data per unit area of the investigated section of the earth's crust, detailed construction of geological and geophysical models, minimization of errors when placing exploration and production wells.

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Description

The proposed technical solution relates to seismic exploration and can be used for searching and exploring mineral deposits and studying the structure and physical and mechanical properties of the near-surface strata of the earth's crust.

Since the 2000s, geophysical companies have begun to actively use high-resolution seismic exploration. The work has shown that increasing the density of traces makes it possible to expand the frequency content of the recording, identify discontinuities in more detail, etc. In addition, the use of surface sources, which are inferior in power to explosions in wells, did not prevent the identification of deep-seated objects in seismic sections. A large volume of seismic data leads to the preservation of the useful signal and the suppression of various types of interference, and helps to identify small faults and cracks to which oil deposits are confined. The use of high-density techniques leads to an increase in the units of geophysical equipment, technology (including sources of seismic waves) used in the work area, and the volume of information obtained (from a route density of 102-256 thousand/km to at least 1-10 million/km ² ), which requires the use of high-performance excitation technologies.

There is a known method and high-performance seismic sources (US 20130163381 A1, publ. 06/27/2013, analogue), which includes the following steps: placing a plurality of vibrators at given points on the earth's surface; generation and configuration of the corresponding (unique) sweep signal on each vibrator to prepare them for operation; asynchronous excitation of seismic signals by vibrators; continuous recording of seismic signals. In this case, sweep signals from each vibrator are pseudo-random sequences weakly correlated with each other.

The disadvantage of the analogue is the low productivity of technological operations, due to the need to stop the vibrator at a given point, the long preparation time for work and the generation of sweep signals with a duration exceeding the time of recording the subsoil response.

There is a known method and system for collecting seismic data (RU 2745481 C1, published March 25, 2021, prototype), which uses one or more sources of seismic signals moving along predetermined trajectories and a given speed. The speed of movement V of the signal source is calculated by the formula V=(1/T _ready )/n, where n is the required excitation density (imp/km), T _ready is the readiness period of the sources (sec). The sources send pulses and begin to move one by one, after receiving a command from the control station controller, the pulse repetition interval is selected based on the time of arrival of the reflected seismic wave from the extremely deep horizon of the underground structure being studied, which limits the number of signal sources used. The maximum number of sources N _max can be found from the expression N _max = _Δ x/(V⋅t), where _Δ x is the step between the pulse repetition points, V is the speed of movement of the sources, t is the pulse repetition interval. For example, the required excitation density is 200 imp/km, while _Δ x=5 m, T _ready =10 sec, V=0.5 m/s, t - 5 sec, then N _max =5/(0.5⋅5)=2, otherwise, the source signals will intersect in time and interfere with the seismic record.

Seismic data acquisition is controlled manually by transmitting commands to supply pulses to the sources from the control station controller. In the process of supplying pulses, each signal source must move at a certain, strictly regulated speed, deviation from which will lead to the intersection of seismic signals from neighboring groups of sources and distortion (manufacturing defects) of the obtained geophysical information and errors in constructing models of the geological environment. To prevent the intersection of signals, sources can be separated at distances at which signals from neighboring sources will attenuate and not create interference, but the number of sources and the reliability of reception and transmission of control commands will depend on the parameters of the surveillance network (length, width of the survey area) and the limits of possibility radio communications. Also, this approach will require a multiple increase in seismic signal receivers, which will negatively affect the overall productivity and cost of geological exploration.

The objective of the proposed technical solution is to eliminate the shortcomings of the prototype, namely to develop a method for collecting seismic data that makes it possible to implement the use of an unlimited number of signal sources that are autonomous and independent of seismic data recording complexes.

The technical result of the invention consists in a multiple increase in the productivity of geological exploration by seismic exploration methods and the volume of geophysical data per unit area of the studied area of the earth's crust, the detail of constructing geological and geophysical models, and minimizing errors when laying exploration and production wells.

This technical result is achieved by the fact that the method is based on the use of an unlimited number of surface pulsed non-explosive sources of seismic vibrations due to the fact that the seismic data recording complex and signal sources perform their functions autonomously and are synchronized by the clock. The use of an unlimited number of sources ensures that a large amount of data is obtained in less time, i.e. increases the productivity of seismic exploration and ensures the detailed construction of geological and geophysical models, and the pulse repetition interval containing a random variable eliminates distortion of the received geophysical information when crossing signals from neighboring groups, weakening the latter by √n times, where n is the density of seismic recording traces per unit area of the studied area of the environment. The method ensures continuous movement of signal sources along predetermined trajectories with a given speed V, affecting the studied environment with pulses following at a certain interval T=t ₀ ±x _i , where t ₀ is the interval common to all sources, x _i is a random variable. The pulse repetition interval at each source is selected based on the required time for the receivers to record the response of the subsoil t _asq to the signal supplied by the source in order to obtain all the information about the area of the medium being studied, with T≥t _asq . The time the pulse is supplied by the source t _sn and the coordinates of the point on the earth's surface x _n , y _n , h _n coming from the GNSS receiver are recorded in the storage module. Seismic signals are recorded by receivers as a continuous recording. The division of a continuous recording occurs by determining the time t _sn on a continuous recording and excluding the recording intervals obtained before the moment t _sn and after the moment t _sn +t _asq -Δ, where Δ is the time quantization step of the recording. The trajectory of the source and its speed are controlled by the navigation module. After the next pulse is applied, the control device transmits the time and coordinates of the point where the pulse was given, data on the technical condition of the source to the storage module and to the control center to the remote control and storage device, where the compliance of the data with the specified values is assessed. If the values deviate from the specified ones, the operation of the source is suspended.

The invention is illustrated in Fig. 1 and fig. 2.

In fig. Figure 1 shows a block diagram of a method for collecting seismic data containing signal sources on which a GNSS receiver 1, a navigation module 2, a control device 3, a storage module 4, a signal emitter 5, a communication device 6 are mounted. The control center in which the communication device 6 is installed, the device remote control and storage 7, processing device 8. Seismic data recording complex consisting of a data recording control station 9 and signal receivers 10.

In fig. 2. The processes of accumulation and suppression of signals intersecting in time are schematically depicted: time scale 1, signals from single impacts of sources N ₁ , N ₂ and N ₃ and total signals ΣN ₁ and ΣN ₂ , N ₃ from sources N ₁ N ₂ and N ₃ . The indices 1, 2 and 500 indicate the number of impacts of each source, as well as the number (density) of traces per unit area of the studied area of the environment.

Implementation of the invention.

To implement the method, the following apparatus and equipment is used. Signal sources towed by means of a hitch to a vehicle. A GNSS receiver 1 is installed in the source or vehicle, providing continuous receipt of source location coordinates and time, which are transmitted to the navigation module 2 and control device 3 (Fig. 1). The navigation module, receiving coordinates from the GNSS receiver, monitors the speed and trajectory of the source and displays them on the screen. The control device 3, after a given time interval, sends a command to the emitter of the sources 5 to initiate a seismic signal; during the initiation of the seismic signal, the control device 3 transmits the current coordinates of the source, the time of the impulse and data on the technical condition of the sources to the storage module 4 and through communication devices 6 to remote monitoring device 7. Remote monitoring device 7 receives the received information and, if the parameter/parameters deviate from the specified ones, through communication devices 6 sends a command to stop the sources until the malfunction is eliminated. The seismic data recording complex consists of a data recording control station 9 and signal receivers 10. The data recording control station 9 is equipped with a clock for synchronization with sources and performs three main functions - at a given time, sending commands to signal receivers 10 to start recording, monitoring the technical condition of the receivers 10 signals and storage of continuous recording received from receivers. In particular, the data recording control station 9 and the signal receivers 10 can also be independent, in which case each signal receiver 10 assumes the functions of the data recording control station. The stored record of seismic signals is transmitted to the processing device 8 via external storage media. The processing device 8 ensures that the continuous recording is divided into separate intervals.

The seismic data collection method is carried out as follows.

Based on the structure and area of the studied area of the environment, the depth and detail of the study of the geological structure, as well as the time required to conduct research, the number of signal sources, the trajectories of their movement, the step between the points of pulse repetition and the installation points of signal receivers 10 are selected. The recording interval is selected based on from the required depth of study of a section of the earth's crust. The step between the pulse repetition points and the interval between the receiver installation points are selected based on the required density of seismic recording traces per unit area of the studied area of the environment. The signal sources and seismic data recording complex are clock-synchronized and perform their functions autonomously. Once the signal sources are ready, the signal receivers begin recording. Signal sources are launched simultaneously and begin to move at a given speed, influencing the surface of the studied area of the medium with pulses following at certain intervals. The speed of movement of signal sources can be found from the expression V= _Δ x/T, where _Δ x is the step between the pulse repetition points, T is the pulse repetition time interval. The pulse repetition time interval T of the signal sources is set on each signal source; the pulse repetition interval on each source is selected based on the required time for the receivers to record the response of the subsoil to the signal supplied by the source in order to obtain all the information about the area of the environment being studied. The pulse repetition time interval is a random variable T=t ₀ ±X _i , where t ₀ is the interval common to all sources, while T≥t _asq , x _i is a random variable. Since the pulse repetition interval is a random variable, then on the record received from the source N _i , seismic records intersecting in time, received from sources N _i+b N _i+2 ...N _i+n , will be presented as random noise, and when After further processing, the noise intensity will be reduced by √n times, where n is the density of seismic recording traces per unit area of the studied area of the environment.

In particular, the number of sources can be unlimited.

While moving, the source sends pulses through the signal emitter into the medium under study through the interval T.

In particular, the source moves continuously and has constant contact with the surface under study.

In particular, the signal emitter is made in the form of a pulsed non-explosive source of seismic signals.

In particular, the method can be applied on various surfaces, such as soil, snow, ice, water.

Example.

Let it be required to carry out geological exploration using seismic methods in the amount of 1500 linear meters. km within a period not exceeding 30 days. At the same time, work is limited to t _shifts = 10 hours per day. The density of seismic recording traces per unit area of the studied area of the environment is equal to 500. The signal pulse repetition step _Δ x should not exceed 5 m, the recording time of the subsoil response receivers is 7 seconds, t ₀ is 8 seconds, the recording time quantization step Δ is 1 millisecond . The pulse repetition time interval T is 8 seconds, the speed of the sources will be V= _Δ x/T=5/8=0.625 m/s (2.3 km/h). In a day, one group of sources can work out L=V⋅t _shift =2.3⋅10=23 km in a 10-hour shift, and 690 linear kilometers in 30 days. km. Thus, to work out a volume of 1500 linear. km. you will need N _sources =1500/690≈2.7=3 groups of sources. In the case of the prototype, using the formula N _max = _Δ x/(V⋅t), the maximum number of sources will be equal to N _max = _Δ x/(V⋅t)=5/(0.625⋅8)=l, which will not allow work within the specified time frame.

Before starting work, signal receivers 10 are installed at predetermined points on the earth's surface, ice, and the bottom of reservoirs; For signal sources, their movement routes are determined.

The work is performed as follows.

Signal sources reach specified positions. At the appointed time, the signal receivers 10 begin recording, and the sources, having also received a signal at the appointed time, from the control device 3 begin to move along a predetermined route and at a certain speed. Navigation module 3 receives the coordinates of the source from GNSS receiver 1 and controls the trajectory of the signal source and its speed. The command to supply pulses is given by the control device 3 and, at the same time, transmits the coordinates of the pulse supply point x _n , y _n , h _n received from the GNSS receiver 1, the pulse supply time t _sn , data on the technical condition of the emitter, the speed of movement V of the signal source into the storage module 4 and communication devices 6 at the moment the pulse is applied. Data from the communication device 6 in the control center is transmitted to the remote control device 7 where the compliance of the data with the specified values is assessed. If the values deviate from the specified values, the remote control and storage device transmits a command to the control device to suspend the operation of the source through communication devices. Signal receivers 10 record seismic signals (response of the subsurface to a signal supplied by the source), which are transmitted and stored in the data recording control station 9. The continuous recording stored in the data recording control station 9 is transmitted to the processing device 8 where it is divided into separate intervals. The division of a continuous recording occurs by determining the impulse delivery time t _sn on the continuous recording and excluding the recording intervals obtained before the moment t _sn and after the moment t _sn +t _asq -Δ, where Δ is the time quantization step of the recording. Since three sources N ₁ N ₂ and N ₃ make impacts through the interval T=t ₀ ±X _i , where to is the interval common to all sources, x _i is a random variable, then after dividing the continuous recording, the pulse supply time t _sn for the source n _i will be equal to zero, at _sn for sources n ₂ and n ₃ will take the values t _sn ±x _i . For example, the value x _i takes values of ±50 milliseconds and is distributed according to the normal (Gaussian) law, then the beginning of the recording of the subsoil response after its separation from source N ₁ will begin at time 0 milliseconds and the subsurface response will represent a constant signal, and the response records the depths of sources N ₂ and N ₃ originate from a time of 0±50 milliseconds, represent random interference and will be suppressed at √n, i.e. √n=√500=22 times, while the signal from the Ni source remains unchanged (Fig.). The same is true for the source N ₂ and N ₃ .

Thus, the proposed method allows you to simultaneously use three groups of signal sources to complete the volume of work within the specified time frame without separating the sources at distances that exclude the overlap of seismic recording in time and the involvement of additional equipment, in particular, signal receivers, which allows you to increase the productivity of geological exploration work by multiples seismic surveys and volumes of geophysical data per unit area of the studied section of the earth's crust, detail in the construction of geological and geophysical models, minimizing errors when laying exploration and production wells.

Claims (4)

1. A method for collecting seismic data, characterized by the impact on the surface under study of seismic signal sources that are autonomous and independent of the data acquisition system, following predetermined trajectories, mounting the sources on a platform placed in contact with the surface under study, continuous movement of the sources, synchronizing the source clocks with the clock systems for collecting seismic data and continuous recording of signals issued by receivers, characterized in that the signal sources are launched simultaneously, the sources move along predetermined trajectories and at a given speed, the pulse repetition time interval T of the signal sources is set on each signal source, the pulse repetition interval on each the source is selected based on the required time of recording by receivers of the response of the subsoil t _asq to the pulse supplied by the source to obtain all information about the studied area of the medium, the coordinates of the source x _n , y _n , h _n and the pulse supply time t _sn are recorded in the storage module at the moment the pulse is supplied, where n is the source number, a continuous record is prepared for further use by dividing it into separate intervals. 2. The method according to claim 1, characterized in that the pulse repetition time interval is a random variable T=t ₀ ±X _i , where t ₀ is the interval common to all sources, while T≥t _asq , x _i is a random variable . 3. The method according to claim 1, characterized in that on the record received from source N _i, seismic records intersecting in time, received from sources N _i+1 , N _i+2... N _i+n , are presented as random noise, and with further processing, the noise intensity decreases by a factor of √n, where n is the density of seismic recording traces per unit area of the studied area of the environment. 4. The method according to claim 1, characterized in that the division of continuous recording into separate intervals occurs by determining time t _sn on the continuous recording and excluding recording intervals obtained before the moment t _sn and after the moment t _sn +t _asq -Δ, where Δ - time quantization step of the recording.

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