RU2498357C1 - System for microseismic probing earth's crust and seismic monitoring - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: disclosed method of detecting seismic signals when searching for underwater hydrocarbon deposits involves detecting seismic vibrations of the Earth's surface using seismic vibration detectors capable of detecting seismic vibrations in the range from 0.1 to 20 Hz. The method involves further detection of seismic vibrations in the 20-40 Hz range, the electromagnetic field in the frequency range from 300 to 0.0001 Hz with detection period of 0.033-10000 s. The method also involves detection of seismic vibrations in the 20-40 Hz range, the electromagnetic field in the frequency range from 300 to 0.0001 Hz with detection period of 0.033-10000 s to obtain simultaneous records of variations of the electromagnetic field and the seismic field. The geoelectric section and velocity section of the sedimentary cover are constructed and geologic interpretation of the sedimentary section is performed.

EFFECT: high accuracy of probing data.

Description

The invention relates to geophysics and can be used to control seismic processes by synchronous measurements of the electric and magnetic components of the field, as well as the seismic field, and can be used to study horizontally heterogeneous geoelectric sections in order to search and explore oil and gas underwater deposits.

The known method of marine seismic exploration (certificate of authorship SU No. 1766180 [1]) includes the excitation of elastic vibrations, registration of reflected waves along a profile with a multi-channel receiving device, and also accumulation of information at a fixed midpoint at which to achieve a technical result consisting in increasing the detail and informativeness of seismic exploration by increasing the resolution and noise immunity of seismic data, source movement and multichannel reception of the device is made along the profile with the direct and reverse heading of the ship (vessel) with a successive change in the distance between the source and the receiving device when changing course, while fixing the position of the first and last common midpoints on the profile, the multi-channel receiver is positioned vertically with a variable base, selected depending from the depth of the studied layer, and the accumulation of information is carried out at both midpoints and at the same time along vertical bases, while additionally moving the source of the multichannel receiving device along parallel profiles located at a distance from each other, selected from the condition of accumulation along a common deep point in space.

The known device for marine seismic exploration (patent RU No. 2032190 [2]) includes a linear group of working pneumatic emitters of seismic signals associated with floats fixed to the carrier rope by means of flexible elements connected by electric and gas lines to the control panel of the seismic station, and means for placement air emitters and floats on board the vessel, which is made in the form of a winch equipped with a drum for placement of a supporting rope on it, the side cheeks of the drum contain sockets for attaching evmoizluchateley and slots for placement of electrical and gazomagistraley sleeves before the winch drum fixed guide mechanism orienting pnevmoizluchateli and floats in the direction of the drum slots, and the emitters and the floats are connected to the carrier by means of a rope carbines.

The known seismic-acoustic detector (patent RU No. 2032222 [3]) contains an acoustic microphone connected to the input of the amplifier of the acoustic channel, and a seismic receiver connected to the input of the amplifier of the seismic channel, a power source and a transmitter, a logic processing unit, an interface unit and a control and control panel.

The known method of geoelectrical exploration (certificate of authorship SU No. 1770776 [4]) includes excitation of the electromagnetic field in the geological environment by current pulses, in the pauses between which the transient signal is received, filtered by n filters, amplified and recorded in digital form, based on which the structure of the medium under study, in which, in order to achieve a technical result, which consists in increasing the noise immunity, the transient signal f filter, discretely reducing the upper cutoff frequency of the filters with a uniform sampling step, the value of n is set not less than the number of determined parameters, and the maximum values are recorded in digital form in the transient signal obtained after each filtering, which are used to judge the parameters of the medium under study. In the known method of geoelectrical exploration and device for its implementation (copyright

certificate SU No. 1770774 [5]) excites an electromagnetic field in a test medium sequentially at two given frequencies using an adjustable source, receives at these frequencies at the measurement points and measures the first and second geometric potential differences of the electric field, according to which the mapped parameter is calculated, which, to achieve a technical result, which consists in increasing the sensitivity and selectivity of identifying earthquake precursors, the the phase component of the signal with the emf of the source, and the distance from the measurement points to the source is set at least 20 km, and the device for implementing the method comprises a horizontal dipole two-frequency alternating current source, a receiver, which includes sensors of the first and second electric potential differences, a recorder, wherein the receiver comprises a divider, a synchronous detector, a drive, and a control unit.

Known methods and devices [1-5] for performing marine seismic exploration include artificial excitation of a seismic wave with subsequent registration of an acoustic or electromagnetic signal by means of hydrophones, usually mounted on a trawl, towed by a vessel or receiver of electromagnetic waves. The acoustic signals measured by the hydrophone or the receiver, electromagnetic waves, the signals are further processed (amplification, filtering, etc.) with the selection of a useful signal that carries information about the possible propagation of seismic waves.

The main disadvantage of the known methods, and their implementation is that they have low information content, as they measure the parameters of only acoustic or only electromagnetic fields.

The increase in information content in the implementation of marine seismic exploration is achieved using the known method of marine seismic exploration (patent RU No. 2388023 [6]). This method of marine seismic exploration includes the excitation of elastic waves with subsequent registration of the acoustic signal through the receiver of acoustic signals, processing the measured signals, the excitation of the electromagnetic field by current pulses, in which the artificial excitation of elastic waves is carried out in a semi-enclosed space bounded by a metal frame on three sides, using a spark plug , to which voltage is applied, while additionally registering the potential gradient square field of electrochemical origin and the gradient of the potential of the electric field due to the movement of water in the Earth's magnetic field, while the excitation of elastic vibrations is carried out on the interval of rise, culmination and decline of the lunar tide of the earth's crust, the gradient of the electric field potential due to the movement of water in the Earth’s magnetic field, register in the infra-low-frequency range of the waveguide sea water - soil, the processing of the measured signals is carried out by building a binomial tree Shter and - Brokaw. Thanks to new distinguishing features of the known technical solution, such as: artificial excitation of elastic vibrations is carried out in a semi-enclosed space bounded by a metal frame on three sides, by means of a spark plug, to which voltage is applied, the gradient of the electric field potential of electrochemical origin and the gradient of electric potential are additionally recorded field due to the movement of water in the Earth's magnetic field, while the excitation of elastic vibrations about take place on the time interval of the rise, culmination and decline of the lunar tide of the earth's crust, the gradient of the electric field potential due to the movement of water in the Earth’s magnetic field is recorded in the infra-low-frequency range of the waveguide sea water-soil, the processing of the measured signals is carried out by constructing the Stern-Broco binomial tree, it is ensured expanding information content in seismic surveys. However, to implement this method, it is necessary to use seismic emitters and conduct a preliminary study of the geological section in the search area.

In the General case, the known methods of seismic exploration usually use the registration of the passage of seismic vibrations with a frequency of more than 10.0 Hz. During the use of similar frequencies in seismic exploration, the hardware design for generating and recording such oscillations, as well as a mathematical apparatus for processing data, have been quite widely developed. Either vibrators or explosions are predominantly used to generate such vibrations. For blasting, it is necessary to drill holes for laying explosives. This technique dramatically negatively affects the state of the environment in the search area. In addition, the success rate of prediction using known methods and techniques of seismic exploration does not exceed 0.5. Therefore, at least every second well drilled according to the conclusions of traditional seismic exploration of oil and gas deposits, is erroneously laid. In addition to funds spent in vain for drilling a well, irreparable and unreasonable damage to the environment is caused, especially when performing similar work on the shelf of the seas.

A number of hydrocarbon search methods (options) are also known, for example, (patent RU No. 2251716 [7]) and a method for determining the depth of productive formations (patent RU No. 2336541 [8]). In the known method [7], the technical problem to be solved is to increase the accuracy of determining hydrocarbon-productive formations, including determining the depth of their occurrence. The technical result obtained as a result of the implementation of the method [7] consists in reducing the number of erroneously drilled wells, as well as providing the ability to control the operation of production wells and gas storages during oil and gas production.

To achieve the indicated technical result, according to the first embodiment, it is proposed to use a hydrocarbon search method characterized by recording seismic vibrations of the Earth’s surface using seismic vibrations receivers capable of detecting seismic vibrations in the range from 0.1 to 20 Hz, and seismic vibration receivers located at a distance of 50 m to 500 m from each other, registration is carried out simultaneously for all measured components, dividing the time range of registration of the measured and the prospective area of the information signal, for discrete sections synchronized in time for all seismic receivers, calculate the spectral characteristic corresponding to each discrete section with the formation of a discrete sequence, analyze each discrete section for the presence of interference of anthropogenic nature, and for the presence of an event associated with by the arrival of a signal from the reservoir, those discrete sections that do not contain events associated with the signal from the reservoir in each of the records of the corresponding components of the seismic receivers, as well as discrete sections containing the indicated interference, and analyze the remaining discrete sections with a judgment on the presence or absence of hydrocarbons. When implementing the method, seismic oscillations are additionally measured in a place that is obviously not containing hydrocarbons, and the presence of oil or gas is judged by the appearance of deviations in the spectral characteristics, compared with a place that is obviously not containing hydrocarbons. The method can be implemented both on land and in the water area, with seismic receivers respectively being located on land, in the bottom of the water area, or deepened in the surface layer, in the aquatic environment, and / or on watercraft in places minimally prone to natural vibrations of the body of the craft moreover, the watercraft are removed at equal distances from the source of oscillation generation.

According to the second variant, in order to achieve the indicated technical result, the Earth’s microseismic noise is additionally measured and the presence of hydrocarbons is judged by the appearance of changes in the spectral characteristics of at least one of the components when recording a signal during oscillation generation and / or after oscillation generation in comparison with an information signal, measured before generation. The proposed method can also be implemented both on land and in the water area; therefore, seismic receivers are located on land, in the bottom of the water area and / or on watercraft in places that are minimally prone to natural vibrations of the body of the craft, and the craft are removed at equal distances from the source of oscillation generation. In all cases of the implementation of the proposed method, the receivers of seismic vibrations are usually grouped and synchronized. In addition, in the process of mathematical processing of the recorded results, the information signal is predominantly divided into temporary sections of at least 2-3 signal periods of the lowest frequency range.

As part of the implementation of the first and second options, the task of controlling the operation of a hydrocarbon deposit can be solved. To do this, control points are selected over the reservoir, preferably located near production wells. At selected points, receivers of seismic vibrations are located, capable of detecting seismic vibrations in the infrasonic frequency range by at least one of the components. Earth's microseismic noise is periodically recorded. By the disappearance of the anomaly in the spectral characteristics at frequencies of 0.1–20 Hz, the passage of the water – hydrocarbon contact under the control point is judged.

The anomalous behavior of the spectral characteristics is determined by any of the above options - without applying external influences, by analyzing the behavior of the spectral characteristics of each discrete section of the time range partition, or with respect to the spectral characteristic of the information signal recorded for the section that obviously does not lie above the reservoir, as well as in the variant using external influence, using the same oscillation processing algorithms, but applying them to the recorded signal during / after air The action of the source of seismic vibrations, or the transition of the water-hydrocarbon contact, is judged by the appearance of changes in the spectral characteristics of at least one of the components when recording a signal during oscillation generation and / or after oscillation generation in comparison with the spectral characteristics of the information signal measured before generation . It is preferable to record the spectral characteristics of the microseismic noise of the Earth for each point for 40-60 minutes. When controlling the degree of filling of the underground natural gas storage, points on the Earth's surface are selected that roughly determine the different degrees of filling of the gas storage, seismic vibration detectors are placed at selected points that are capable of recording infrasonic vibrations by at least one component, and the spectral characteristics of the Earth’s microseismic noise are periodically recorded, moreover the absence of an abnormal change in the spectral characteristics of the information signal at frequencies of 0.1-20 Hz stvuet the absence of natural gas under the control point. For comparison, a microseismic noise of the Earth is recorded by a similar receiver above a place obviously located outside the gas storage. It is preferable to select control points during the first filling of the gas storage, determining in which places above the gas storage the presence of natural gas is noted at various amounts of supplied gas. However, in any case, control points are determined empirically. It is possible to generate seismic vibrations during the registration process. In this case, registration is carried out both before the start of generation and during generation.

Using, in particular, the second option (with generation), it is possible to determine the depth of the reservoir productive for hydrocarbons. To do this, use at least 4 receivers of seismic vibrations, capable of detecting infrasound vibrations by 3 mutually perpendicular components, placing them at the vertices of the quadrangle.

In all of the above embodiments of the invention, a fundamental and important step is the process of filtering the recorded time series from surface noise and extracting the information signal. For this purpose, a grouping (arrangement) of seismic oscillation receivers and cross-correlation processing of the recorded signal are used.

To implement the above options, a seismic oscillation detector is used that is capable of detecting vibrations in the infrasonic range, containing at least one seismic oscillation sensor capable of detecting infrasound vibrations, all the sensors used are located on a rigid base so that the sensitivity axes of the sensors are located at fixed angles relative to flat rigid base and relative to each other, with each sensor connected to the registration unit, and the main The sensors are housed in a rigid, sealed enclosure. Angular and / or linear vibration sensors that can detect vibrations in the infrasonic frequency range can be used. Advantageously, the recording unit of each sensor comprises a pre-connected signal amplifier, an amplitude-frequency response driver and a terminal amplifier, each terminal amplifier being configured to be connected to a common recorder. However, the known method [7] is based on the hypothesis of an oil deposit as the only possible source of the observed anomaly in the low-frequency range of the seismic spectrum. However, practice shows (patent RU No. 2336541 [8]) that abnormal signals are observed in the presence of other significant heterogeneities in the section, in particular in the form of active tectonic disturbances or in the presence of underground rivers. An abnormal signal is also observed in the target range with a shallow basement at the point of study, commensurate with the depth of hydrocarbons.

In addition, when placing seismic oscillation receivers on boats or at deep horizons, it is necessary to exclude from the observation results the signal component due to noise of navigation and the speed of underwater currents. In this case, all the sensors used must be located on a rigid base in such a way that the sensitivity axes of the sensors are located at fixed angles with respect to the flat rigid base and with respect to each other, which is practically impossible to provide under the hydrosphere.

Judging hydrocarbon deposits according to the characteristics of microseismic waves alone is associated with a very large volume of measurements, which is a serious problem for bottom seismology. When passing random signals through linear chains, it is necessary to consider the transformation of these characteristics for each argument separately, which leads to cumbersome expressions. These characteristics are not visual and difficult to imagine in the form of graphs, which complicates their visual processing, which is the main one in modern seismology.

In addition, since microseismic waves are non-stationary processes, their correlation functions and spectral densities depend not only on the corresponding parameters (period and frequency), but also on time, which in the process of practical determination of their estimates involves a very large volume of measurements, and taking into account the fact that the bottom stations for registration at the water - soil boundary have a limited resource for the autonomy of their use, this significantly increases the duration of the studies, and accordingly material and material costs.

In the known method of low-frequency seismic sounding for the search and exploration of hydrocarbon deposits (options) [8], the problem is solved by the method of low-frequency seismic sounding for the search and exploration of hydrocarbon deposits, including the determination of at least one observation point in the search area, placement at the observation point of the receiver seismic vibrations, registration of information signals by their measured components for a period of time sufficient to record statistically significant a noise signal in the infra-low-frequency range, calculating the spectral characteristics using the Fourier transform of the received signals, analyzing them for the presence of false signals and signals from the reservoir with natural hydrocarbons, excluding false signals from the analysis, analyzing the remaining signals with a judgment on the presence or the absence of hydrocarbons, in which, unlike the known method, registration and recording are carried out on the vertical components of information signals, Fu rye conversion of the vertical components of information signals is carried out according to their first derivative, the maximum is determined on the obtained spectra, which is characterized by the location on the spectrum in the frequency range

V _S / H <F <Vp / H,

where V _S - average sedimentary cover velocity of transverse seismic waves at the point of observation;

V _P - average sedimentary cover velocity of propagation of longitudinal seismic waves at the observation point;

H is the known depth of the foundation at the observation point, a signal with a given maximum is taken for the corresponding resonance between the day surface and the foundation; a false signal is a signal from the foundation, a point with a spectrum at which a signal from the foundation is present with a monotonic decrease in the spectrum amplitude at side of large frequencies from the maximum of the signal from the foundation, the observation point, in the signal spectra of which there are maxima at frequencies higher than the frequency of the maximum of the signal from pounds The ententa, with their uniform arrangement with a shift relative to other measurements less than half the width of their maximum, is accepted as promising for the presence of deposits from natural hydrocarbons. In this case, when identifying a uniform arrangement of signals, it is possible to compare them relative to signals of other measurements from one observation point, or relative to signals from other channels of their recording from this observation point with a multi-channel observation method, or relative to signals from their recordings from neighboring observation points with a single-channel observation method. If there are more observation points in the study area, the signal from the foundation additionally characterizes its presence at most observation points.

In general, known methods for measuring seismic signals [7, 8] include recording seismic signals, determining the instant of measurement, determining geographic coordinates, determining the oscillation of seismic signals by analyzing the results of observations on periodic components in the time series of the observation results.

A disadvantage of the known methods is that when determining the fluctuation of the level of seismic signals at the measurement point, the main waves of the oscillatory process are distinguished, according to the amplitudes and phases of which complete harmonic analysis is performed with the allocation of harmonic constants. However, in marine conditions, the acoustic noise of the sea and the noise of shipping have a significant impact on the results of the analysis of recorded seismic signals. To take into account the influence of these waves in the amplitudes and phases of the main seismic waves, it is necessary to introduce corrections that depend on astronomical conditions. In addition, in the known methods, the solution to the problem of converting time intervals is based on methods for converting the time parameters of the processes under study that take place when analyzing the results

observations.

Moreover, on the basis of observational data, to analyze the observational results, periodic components are revealed in the time series of the data for which the measurement moments are “asynchronous” with the detected oscillation period, i.e. the time intervals between the moments of measurements are not regular and significantly exceed the detected period of oscillations, using the Fourier analysis, i.e. the studied processes are presented as a superposition of harmonic oscillations in the form of a Fourier series, which, for example, when determining the oscillation of seismic waves can introduce an additional error, since the sum of two periodic oscillations can be a non-periodic function, for example, when two sinusoidal oscillations with incommensurable frequencies are added when As a result of their addition, a complex non-periodic oscillation can be obtained. In this case, the time course is represented in the form of functions of the process values from time to time, and time is determined from the condition that time is a strictly increasing real variable. In this case, the structure of the cycle of time intervals with the allocation of the time standard is established and the cyclic frequency is selected. The choice of the cyclic frequency includes determining the protective time interval, providing carrier recovery, clock synchronization by elements and addressing information, setting signal levels in time intervals. However, due to the fact that the periods of the measurement time system and the periods of harmonics of the oscillatory process can be incommensurable, additional operations are required to ensure high-quality synchronization. To do this, when determining the periodic components in the time series of data obtained by observing the oscillatory process, in which the measurement times are asynchronous with the detected oscillation period, use the periodicity property of the detected signal based on the properties of the periodic function F (t + T) = f (t ), where t is the time; T is the period of the function f (t). To analyze harmonic oscillations, the time axis is divided into equal segments, which are subsequently combined with each other. In the cyclic time obtained in this way, the measurement moments describe changes in the function over one period, which provides a connection between the continental (solar) and oceanic (tidal) time in accordance with the dependence x = y-y _m , where x is the tidal time (the number of tidal days the beginning of the tidal year); y is the date of solar time (the number of days from the beginning of the year); y _m is the number of days between solar and tidal times, i.e. this determines the average solar time, which is cyclic time with a constant period of one day. The connection between these times is carried out by scanning the cyclic average solar time in a linear sequential series by introducing numbered time intervals.

However, true solar time and true lunar days change their duration in a relatively wide range, which leads to errors in determining the periodic component in marine conditions, in asynchronous hydrological observations, due to the difference in the nature of the periodicity of real and measured processes due to the measurement of the average solar time in a cyclic system. At the same time, the main energy-carrying harmonics are associated with lunar periods, as a result of which the periods of the measurement time system and the periods of the process harmonics can be incommensurable. In this case, in a phase space built on time systems incommensurable with the process, the trajectories of the oscillatory process behave randomly. Depending on the dimension of the phase space, the trajectories can be quasiperiodic with intermittency, and even, moreover, have the structure of a strange artifact. The nonstationarity of the process can also be a consequence of the non-ergodicity of the trajectories in the phase space.

In addition, the implementation of the known method [8] provides for a total analysis of longitudinal and transverse microseismic waves, which significantly complicates the analysis process, as well as in obtaining the final reliable research results.

The identified shortcomings lack a way to register seismic signals in the sea during the search for submarine hydrocarbon deposits (patent RU No. 24342500 C1, 11/20/2011 [9]), which solves the problem of increasing the information content and reliability of seismic studies in the search for underwater hydrocarbon deposits.

The problem, in the known method [9], is solved due to the fact that in the method of recording seismic signals in the sea when searching for submarine hydrocarbon deposits, by recording seismic vibrations of the Earth’s surface using seismic vibration receivers capable of detecting seismic vibrations in the range from 0 , 1 to 20 Hz, with the placement of seismic oscillation receivers at a fixed distance from each other, in which the registration of seismic signals is carried out simultaneously for all measured components, dividing the time range of registration of the information signal measured on the prospective area, into discrete sections synchronized in time for all seismic receivers, calculate the spectral characteristic corresponding to each discrete section with the formation of a discrete sequence, analyze each discrete section for interference of anthropogenic nature, and the presence of an event associated with the arrival of a signal from the reservoir is excluded from further consideration I discrete sections that do not contain events associated with the arrival of a signal from the reservoir in each of the records of the corresponding components of the seismic receivers, as well as discrete sections containing the indicated interference, and analyze the remaining discrete sections with a judgment on the presence or absence of hydrocarbons, in which, unlike the known method [7], seismic receivers are placed in the coastal zone of the shelf and on the border of the foot of the continental slope, a gradient is placed in the coastal zone of the shelf seismic oscillometric detectors that record seismic vibrations in the range from 0.1 to 20 Hz, which are placed in pairs in each studied discrete section, while the sensitive elements of each pair of seismic receivers are rotated relative to each other in azimuth of 45 degrees, each pair of seismic receivers is tuned to receiving signals from a specific area where the directions of reception of elastic vibrations intersect, based on measurements not exceeding 50-100 km in middle latitudes and 8-10 km in high and equatorial latitudes, and at frequencies from 0.003 to 0.1 Hz, microseismic oscillations are recorded, starting from frequencies from 0.003 Hz, by means of broadband digital seismic receivers located at the boundary of the foot of the continental slope in pairs as well, when analyzing each discrete section, harmonics from two seismic receivers reflected simultaneously with almost equal amplitudes, to detect interference for each discrete section, measure the variation of the magnetic field at frequencies of 0.01-1.0 Hz, the magnetic induction of the electromagnetic field I at frequencies of 1-200 Hz, the electric component of the electromagnetic field at frequencies of 1-500 Hz, acoustic noise at frequencies of 5-50000 Hz, hydrodynamic noise of the sea at frequencies of 0.01-100 Hz in the zones of tectonic faults, take into account the time course of the level of the underlying earth surface under the influence of the tidal forces of the Earth's crust, according to the measured parameters, a factor analysis is performed at the levels of the natural geophysical background and geophysical background during the phase of the sun and moon being on the same sky line, by plotting the gradient amplitude graph eysmicheskih, geodeformation, geochemical, hydro-physical characteristics, in the analysis of harmonic oscillations of seismic wave is performed in conversion of cyclic time linear analysis for the microseismic waves with judging the presence or absence of hydrocarbons is performed for transverse microseismic waves.

New distinctive features are that seismic receivers are located in the coastal zone of the shelf and at the border of the foot of the continental slope; gradiometric seismic receivers are recorded in the coastal zone of the shelf, which record seismic oscillations in the range from 0.1 to 20 Hz, which are. placed in pairs on each discrete section under study, while the sensitive elements of each pair of seismic receivers are rotated relative to each other in azimuth by 45 degrees, each pair of seismic receivers is configured to receive signals from a certain area where the directions of reception of elastic vibrations intersect, based on measurements not exceeding 50-100 km at middle latitudes and 8-10 km at high and equatorial latitudes, microseismic oscillations are recorded at frequencies from 0.003 to 0.1 Hz, starting from frequencies from 0.003 Hz, by means of wide in pairs of digital seismic receivers located at the foot of the continental slope, harmonics from two seismic receivers reflected simultaneously with almost equal amplitudes are selected in the analysis of each discrete section, to detect interference for each discrete section, measurements of magnetic field variations at frequencies of 0.01 -1.0 Hz, magnetic induction of the electromagnetic field at frequencies of 1-200 Hz, electric component of the electromagnetic field at frequencies of 1-500 Hz, acoustic noise at h frequencies 5–50000 Hz, hydrodynamic noise of the sea at frequencies of 0.01–100 Hz in the zones of tectonic faults, take into account the time course of the level of the underlying Earth’s surface under the influence of the tidal forces of the Earth’s crust, factor analysis is performed on the measured parameters at the levels of the natural geophysical background and geophysical background during the phase of finding the sun and moon on one celestial line, by plotting the amplitudes of the gradients of seismic, geodeformation, geochemical, hydrophysical characteristics, in the analysis of harmonic oscillations of seismic waves converts cyclic time to linear, analysis of recorded microseismic waves with the judgment of the presence or absence of hydrocarbons is performed for transverse microseismic waves, can increase the information content and reliability of seismic studies when searching for submarine hydrocarbon deposits, compared to analogues [1-8] as well as by known methods such as patent RU 2251716 C1, 05/10/2005 [10], patent RU 2276388 C1, 05/10/2006 [11], patent RU 2348950 C1, 03/10/2009 [12], patent US 6175809 Bl, 16.01 .2001 [13], in which are based on the most common method of seismic research at frequencies of 30-120 Hz with a resolution of up to 12-24 m or the high-frequency method, at frequencies from 250-650 to 1200 Hz with a resolution of up to 1-2 m.

The numerous experimental data obtained in this case indicate a more or less pronounced layering of the sedimentary layer, which is violated by heterogeneous, localized or spatially distributed inhomogeneities (cavities and inclusions) of various nature and properties. The study of such a medium by acoustic methods requires the preliminary construction of developed structural-acoustic models of the medium, which fully take into account all the indicated structural and physical features. And the determination of gas resources in subsea deposits, in addition to seismic sensing, requires deep drilling with coring and a full range of geophysical studies, which significantly increases the complexity of work and material costs.

The objective of the proposed technical solution is to reduce the complexity of seismic research in the search for underwater hydrocarbon deposits.

The problem is solved due to the fact that in the method of recording seismic signals in the sea when searching for submarine hydrocarbon deposits, by recording seismic vibrations of the Earth’s surface using seismic vibration receivers capable of detecting seismic vibrations in the range from 0.1 to 20 Hz, with the placement receivers of seismic vibrations at a fixed distance from each other, in which the registration of seismic signals is carried out simultaneously for all measured components, dividing into the recording time range of the measured information signal measured in the prospective area, for discrete sections synchronized in time for all seismic receivers, calculate the spectral characteristic corresponding to each discrete section with the formation of a discrete sequence, analyze each discrete section for interference of anthropogenic nature events associated with the arrival of a signal from the reservoir, exclude from those further consideration those discrete sections that do not contain events associated with the arrival of a signal from the reservoir in each of the records of the corresponding components of the seismic receivers, as well as discrete sections containing the indicated interference, and analyze the remaining discrete sections with a judgment on the presence or absence of hydrocarbons in which the seismic receivers in the coastal zone of the shelf and on the border of the foot of the continental slope, in the coastal zone of the shelf, gradientometric seismic receivers are placed that record the cosmic oscillations in the range from 0.1 to 20 Hz, which are placed in pairs in each studied discrete section, while the sensitive elements of each pair of seismic receivers are rotated relative to each other in azimuth by 45 degrees, each pair of seismic receivers is configured to receive signals from a certain zone where the directions of reception of elastic vibrations intersect, on the basis of measurements not exceeding 50-100 km at middle latitudes and 8-10 km at high and equatorial latitudes, microseismic signals are recorded at frequencies from 0.003 to 0.1 Hz oscillations, starting from frequencies from 0.003 Hz, by means of broadband digital seismic receivers located at the foot of the continental slope also in pairs, when analyzing each discrete section, harmonics from two seismic receivers reflected simultaneously with practically equal amplitudes are selected to detect interference for each discrete section measure the variation of the magnetic field at frequencies of 0.01-1.0 Hz, the magnetic induction of the electromagnetic field at frequencies of 1-200 Hz, the electrical component of the electromagnet of the magnetic field at frequencies of 1-500 Hz, acoustic noise at frequencies of 5-50000 Hz, hydrodynamic noise of the sea at frequencies of 0.01-100 Hz in the zones of tectonic faults, take into account the time course of the level of the underlying earth's surface under the influence of tidal forces of the Earth's crust, according to the measured the parameters are performed by factor analysis at the levels of the natural geophysical background and geophysical background during the phase of the sun and moon being on the same celestial line, by plotting the amplitudes of the seismic, geodeformation, geochemical, and hydrophysical gradients In the analysis of harmonic oscillations of seismic waves, cyclic time is converted to linear, analysis of registered microseismic waves with the judgment of the presence or absence of hydrocarbons is performed for transverse microseismic waves, in which, unlike the prototype [9], seismic oscillations in the range are additionally recorded 20-40 Hz, the electromagnetic field in the frequency range from 300 to 0.0001 Hz with recording periods from 0.033 to 10000 seconds.

New distinctive features, which include the additional registration of seismic vibrations in the range of 20-40 Hz, the electromagnetic field in the frequency range from 300 to 0.0001 Hz with recording periods from 0.033 to 10000 seconds, allow simultaneous recording of variations in the electromagnetic and seismic fields, construct a geoelectric section of the sedimentary cover and a velocity section of the sedimentary cover, as well as perform a geological interpretation of the sections of the sedimentary cover. The proposed method in terms of the implementation of the restrictive features of the claims is similar to the technical implementation of the prototype [9]. As in the prototype, the means for receiving and recording seismic signals are located, which are autonomous bottom stations (patents RU No. 2276388, No. 229400) or underwater observatories (patent RU No. 2348950), which are equipped with multi-channel receivers of seismic signals, recording and storage units, a block of linear and angular displacement sensors, sensors for recording geophysical and hydrological parameters.

In this case, seismic receivers are placed in the coastal zone of the shelf and on the border of the foot of the continental slope; gradiometric seismic receivers are placed in the coastal zone of the shelf, recording seismic vibrations in the range from 0.1 to 20 Hz, which are placed in pairs in each studied discrete section, while sensitive the elements of each pair of seismic receivers are deployed relative to each other in azimuth by 45 degrees, each pair of seismic receivers is configured to receive signals from a certain zone, g the directions of receiving elastic vibrations do not intersect, based on measurements not exceeding 50-100 km at middle latitudes and 8-10 km at high and equatorial latitudes. Each pair of gradiometric seismic receivers in this case plays the role of a directional antenna.

Gradient seismic receiver is a three-tensor gradient meter for underwater research, in which five independent tensiometers of the gradiometer allow to obtain a qualitative and quantitative picture of the physical data of discrete sections, including obtaining preliminary information about the geological structure.

At frequencies from 0.003 to 0.1 Hz, microseismic oscillations are recorded, starting from frequencies from 0.003 Hz, by means of broadband digital seismic receivers located at the boundary of the foot of the continental slope in pairs as well, when analyzing each discrete section, harmonics from two seismic receivers reflected simultaneously with almost equal amplitudes. Since microseismic waves are unsteady processes, when processing signals of microseismic waves, time-averaged correlation and spectral characteristics of non-stationary processes are used. At the same time, when random non-stationary signals pass through the linear chains of broadband signal recorders, the time-averaged correlation and spectral functions are transformed by these chains in the same way as the corresponding characteristics for stationary processes. The registered signals during processing are divided into frequency subbands, which gives a significant gain in reducing the required memory size of the information storage device and the amount of computation in determining the correlation and spectral functions of random processes.

In the practical implementation of the proposed method, the entire frequency range of the broadband seismic receiver was divided into two sub-bands (0.003-0.2 Hz and 0.1-0.2 Hz). The “crosslinking” region of the 0.1-0.2 Hz subrange was selected in the region of a stable maximum of microseismic waves, in which earthquakes are practically not recorded. In the low-frequency subband, digital recording was carried out with a quantization frequency of 1 Hz in each of the four recording channels. In the high-frequency subband, analog recording was performed on magnetic tape, followed by quantization and calculation of correlation functions and spectra. This technical solution allows you to approximately 100 times increase the operating time of the seismic receiver at the bottom in the continuous recording of microseismic waves; To identify interference for each discrete section, measurements are made of the variation of the magnetic field at frequencies of 0.01-1.0 Hz, the magnetic induction of the electromagnetic field at frequencies of 1-200 Hz, the electrical component of the electromagnetic field at frequencies of 1-500 Hz, acoustic noise at frequencies of 5 -50000 Hz, hydrodynamic noise of the sea at frequencies of 0.01-100 Hz in the zones of tectonic faults, which are taken into account when analyzing the recorded signals.

When analyzing the recorded signals, the time course of the level of the underlying earth's surface under the influence of the tidal forces of the Earth's crust is also taken into account.

In this case, according to the measured parameters, factor analysis is performed at the levels of the natural geophysical background and geophysical background during the phase of the sun and moon being on the same sky line by plotting the amplitudes of the gradients of seismic, geodeformation, geochemical, and hydrophysical characteristics. When analyzing harmonic vibrations of seismic waves, cyclic time is converted into linear time.

Using a block of linear and angular displacement sensors, signals are recorded that characterize the tidal oscillations of the Earth's crust (soil). The solid crust of the Earth also experiences tidal fluctuations, as well as the water masses of the oceans. The tidal oscillations of the Earth's crust are also harmonic, i.e. the oscillation phase is a smooth function. However, due to the fact that the crust is a more rigid medium, phase shifts accumulate in adjacent areas of the crust with different elastic characteristics, which are not removed by the formation of amphidromic points, but are removed by the formation of earthquakes. The analysis of the spatiotemporal distribution of the phases of tidal oscillations in the Earth's crust is performed in the following sequence.

Measurement of sea ground vibrations is performed in discrete sections of the sea at different times so that the measurements obtained at each measurement point have different time intervals relative to the last moment of the upper culmination of the moon at the fixed geographical meridian closest to the time of measurement.

At the same time, the measured values of the ground level at the points of the sea water area, which are arranged in increasing order of time between the nearest previous point in time of the upper culmination of the Moon on a fixed meridian and the moment of measurement, allow us to establish the time course of the level under the influence of the tidal forces of the Earth’s crust, due to the fact that tidal fluctuations at some point in the water area, the sea has an almost constant phase shift relative to the time of the upper climax of the moon on a fixed geographical meridian e. Since the combinations of the phases of the Moon’s movement around the Earth and the phases of the fluctuation of the sea ground level at some point are repeated with the period of the Moon’s movement around the Earth, the measured values of the sea ground level at some point in the sea’s area are arranged according to the increase in the time interval between the nearest previous time point of the upper climax The moons on a fixed geographical meridian and the moment of measurement, represent a change in the phase of the tide, and therefore the temporal course of the level at the measurement point under the action of ilivnyh forces.

According to the measured instrumental values, sea level fluctuations form observation series.

The tide height values of the specific harmonic component of the wave h (t) are determined, which is determined by the amplitude A, the angle of position g (A and g are harmonic constants) and the period T, in accordance with the dependence h (t) = Acos (qt-g), where q is the angular velocity of the harmonic wave in one hour of average time, t is a fixed point in time.

The amplitudes of the harmonic component of the tidal height of the Earth's crust are determined. To analyze harmonic oscillations, the time axis is divided into equal segments, which are subsequently combined with each other. In the cyclic time obtained in this way, the measurement moments describe changes in the function over one period, which provides a connection between the continental (solar) and oceanic (tidal) time in accordance with the dependence x = y-y _m , where x is the tidal time (the number of tidal days beginning of the tidal year), y is the date of solar time (the number of days from the beginning of the year), y _m is the number of days between solar and tidal time (the number of days from the beginning of the year).

Due to the fact that the periods of the measurement time system and the periods of harmonics of the oscillatory process can be incommensurable, the cyclic time is converted to linear, in accordance with the known dependence (see, for example, patent RU No. 2343415).

Further processing is performed taking into account the converted time. The values of the tidal height of the Earth's crust h = h (x, y) are determined for a sequential set of discrete time values h = h (x, y, t), for example, by the grid method (see, for example, Lavrentiev M.A., Shabat B. B. Methods of the theory of functions of a variable. M.-L. GITTL, 1958).

From the obtained values of the tide height for a sequential set of discrete values of time, the oscillation amplitudes of the harmonic component are determined, for example, at grid nodes (see, for example, Lavrent'ev MA, Shabat BV Methods of the theory of variable functions. M.-L. GITTL , 1958).

According to the obtained values of the tidal height of the Earth's crust, the time of the onset of the maximum level is determined.

In the analysis of the periodic component of the oscillatory process, many real numbers are used, which allows us to determine the real variability of the oscillatory process.

The determination of the time interval between the nearest previous moment of time of the upper culmination of the Moon and the moment of the upper culmination of the Moon allows us to determine the temporal course of tidal fluctuations of the earth's crust at various points in the sea and to obtain the spatial course of tidal fluctuations in this water area at any astronomical moment in time. The measured values of the Earth’s crust level at some points of the sea area, arranged by increasing the time interval, allow us to determine the time course of the level at the measurement point under the influence of tidal forces by changing the tidal phase.

Due to the fact that the oscillatory process q of the level of the Earth’s crust at each fixed moment of time is a function of two frequencies, and at each moment of time the value of the oscillatory process will be a function of two independent variables, which are the coordinates of the phase space, the probability of a reliable separation of the periodic component of the oscillatory process increases . In this case, harmonic constants are determined on the basis of a set of real numbers, which allows us to determine the real variability of the oscillatory process of the Earth's crust level. When performing operations to approximate the results, the numerical values of the measurements are recorded in the Stern-Broco symbol system (1. Graham R., Knut D., Patashnik O. Concrete mathematics. - M.: Mir; BINOM. Laboratory of knowledge, 2006. - 703, p. 2. Aigner M., Ziegler G. Evidence from the Book. - M.:

Mir, 2006 .-- 256 p.). The hierarchical graph structure of the Stern-Brokaw system makes it possible to quickly search for close numbers represented with different errors due to primary measurement sensors, since this corresponds to a different number of characters in the Stern-Brokaw representation. Fewer characters in the view are a sign of a large margin of error. This property of the Stern-Brocko system allows a simple way to represent a number given or measured with some error, a number with a larger error by simply reducing the rejection of the last characters. In decimal notation, what takes place in known methods cannot be carried out. The record of a number in the Stern-Broco symbol system contains information not only about the measured value, but also contains information about the error in representing the number, since the sequence of characters in the representation of the number is determined by all the corresponding nodes in the Stern-Broco tree. For the lowest node, you can find its neighbors, both vertically and horizontally, which allows you to evaluate the accuracy of the representation of the number and go to the representation with a different accuracy. The algorithms for finding the nearest and next numbers are known and very efficient from a computational point of view. The representation of a symbolic record of a number in the Stern-Broco system in binary form requires less memory than with the interval representation of numbers, which is the case in the known methods of marine seismic exploration.

An analysis of the recorded microseismic waves with a judgment on the presence or absence of hydrocarbons is performed for transverse microseismic waves.

Moreover, for all radiating microseismic points of a discrete section, all harmonics are selected from two broadband seismic receivers, reflected simultaneously with almost equal amplitudes and lying within the angle of arrival of the reflected waves.

The value of the angle of arrival of the reflected waves, in a particular implementation of the method is 7 degrees, which is due to the following restrictions.

On the one hand, the angle should not be more than 10 degrees due to the high velocity of the longitudinal wave, which can lead to errors due to the geometry of the location of the emitted signals along the rays of their propagation. On the other hand, the angle should not be less than 1 degree, since the necessary accuracy of the signal fixation time will not be sufficient and, in combination with the existing sensitivity of seismic sensors, the measurement error may increase.

To extract from the results of processing the longitudinal component of microseismic waves in the signal processing circuit, a phase amplitude filter is provided that extracts longitudinal microseismic waves and eliminates transverse microseismic waves.

Unlike the prototype [9], in the proposed method, seismic vibrations in the range of 20-40 Hz are additionally recorded by means of a highly sensitive seismic sensor of the type "SM-ZKV1" located on a gimbal in the lower hemisphere of the underwater station, which allows you to save the vertical location of the sensor in the nutria of an underwater station with seabed inclinations of up to 25 degrees, as well as an electromagnetic field in the frequency range from 300 to 0.0001 Hz with recording periods from 0.033 to 10000 seconds, by means of an electromagnetic sensor module The system consists of two induction sensors of the magnetic field and two sensors of the electric field located on the sturdy case of the underwater station. In this case, two components of the electric (Ex, Eu), two components of the magnetic (Hx, Well) field and the vertical component Z of the seismic field are recorded.

Based on the measurement results, for example, the simplest model of an underwater hydrocarbon reservoir is constructed, which can be represented as a homogeneous reservoir with a reduced density and an increased speed of elastic waves. In such a model of an underwater deposit, two contrasting boundaries must correspond - at the bottom surface, associated with the top of the deposit, and at the lower boundary depth. A change in the density of precipitation and the speed of propagation of elastic waves in them creates the prerequisites for identifying underwater deposits by seismic and acoustic methods. Since the submarine deposits are distributed in the sedimentary sequence extremely unevenly and the structural anomalies encountered are of different sizes, the use of much more complex structural-acoustic models of the submarine hydrocarbon deposits may be required. Additional registration of seismic vibrations in the range of 20–40 Hz, of an electromagnetic field in the frequency range from 300 to 0.0001 Hz with recording periods of 0.033 to 10,000 seconds, allows simultaneous recording of variations in electromagnetic and seismic fields, and the construction of a geoelectric section of the sedimentary cover and velocity section sedimentary cover, as well as perform a geological interpretation of sections of the sedimentary cover, which allows you to determine the lower and upper boundaries of hydrocarbon rocks, as well as their concentration in the rocks, based on In addition, it is possible to estimate gas resources and choose a place for drilling exploration wells for an initial assessment of a deposit. Detailed exploration of subsea deposits is carried out through geophysical exploration in drilled wells, as well as by coring followed by their comprehensive analysis.

The proposed method is implemented on devices having industrial applications, which leads to the absence of technical risks in its application. In contrast to the known methods of marine seismic exploration for the search for hydrocarbons, the proposed method allows to obtain a wider range of signals about the state of geophysical fields, which increases the reliability of judgments about the presence of discrete sections of underwater hydrocarbon deposits.

Information sources

1. Copyright certificate SU No. 1766180.

2. Patent RU No. 2032190.

3. Patent RU No. 2032222.

4. Copyright certificate SU No. 1770776.

5. Copyright certificate SU No. 1770774.

6. Patent RU No. 2388023.

7. Patent Ри№2251716.

8. Patent Ри№23 36541.

9. Patent RU No. 24342500 C1, 11/20/2011.

10. Patent RU 2251716 C1, 05/10/2005.

11. Patent RU 2276388 C1, 05/10/2006.

12. Patent RU 2348950 C1, 03/10/2009.

13. Patent US 6175809 B1, 16.01.2001.

Claims (1)

A method for recording seismic signals by recording seismic vibrations of the Earth’s surface using seismic oscillation receivers capable of detecting seismic vibrations in the range from 0.1 to 20 Hz, with the placement of seismic oscillation receivers at a fixed distance from each other, in which seismic signals are recorded simultaneously all measured components, dividing the time range of registration of the information signal measured on the prospective area into synchronized discrete sections that are time-dependent for all seismic receivers, calculate the spectral characteristic corresponding to each discrete section with the formation of a discrete sequence, analyze each discrete section for the presence of interference of anthropogenic nature, and for the presence of an event associated with the arrival of a signal from the reservoir, exclude from further consideration, those discrete sections that do not contain events associated with the arrival of a signal from the reservoir in each of the records, respectively components of seismic receivers, as well as discrete sections containing the indicated interference, and analyze the remaining discrete sections with a judgment on the presence or absence of hydrocarbons, in which gradiometric seismic receivers are recorded that record seismic oscillations in the range from 0.1 to 20 Hz, which placed in pairs on each studied discrete section, while the sensitive elements of each pair of seismic receivers are rotated relative to each other in azimuth by 45 °, each The seismic receiver array is configured to receive signals from a specific area where the directions of reception of elastic vibrations intersect, based on measurements not exceeding 50-100 km at middle latitudes and 8-10 km at high and equatorial latitudes, at frequencies from 0.003 to 0.1 Hz record microseismic oscillations starting from frequencies from 0.003 Hz, using broadband digital seismic receivers; in the analysis of each discrete section, harmonics from two seismic receivers are taken, reflected simultaneously with almost equal amplitudes In order to detect interference for each discrete section, measurements are made of the variation of the magnetic field at frequencies of 0.01-1.0 Hz, the magnetic induction of the electromagnetic field at frequencies of 1-200 Hz, the electrical component of the electromagnetic field at frequencies of 1-500 Hz, acoustic noise at frequencies of 5-50000 Hz, hydrodynamic noise of the sea at frequencies of 0.01-100 Hz in the zones of tectonic faults, take into account the time course of the level of the underlying earth's surface under the influence of the tidal forces of the Earth's crust, factor measurements are performed at the EU levels according to the measured parameters natural geophysical background and geophysical background during the phase the sun and moon are on the same sky line, by plotting the amplitudes of the gradients of seismic, geodeformation, geochemical, hydrophysical characteristics, when analyzing harmonic vibrations of seismic waves, cyclic time is converted into linear, analysis of recorded microseismic waves with judging the presence or absence of hydrocarbons is performed for transverse microseismic waves, characterized in that additionally record seismic vibrations in the range of 20-40 Hz, the electromagnetic field in the frequency range from 300 to 0.0001 Hz with recording periods from 0.033 to 1000 s.