RU2682135C1 - Method of seismic exploration for direct search of hydrocarbon reserves - Google Patents

Abstract

FIELD: physics.SUBSTANCE: invention relates to methods of seismic exploration, and in particular to methods of direct search for hydrocarbon deposits by their own microseismic oscillations emitted by them after external wave action. Seismic survey method is proposed for direct search for hydrocarbon deposits, which includes multiple excitation in the studied medium by elastic oscillations of geodynamic noise induced by hydrocarbon (HC) deposits and reflected from seismic wave boundaries, registration of seismic oscillations according to the common point depth method (CPD) and subsequent digital processing of microseisms with the allocation of sections of anomalous values of their low-frequency component. At the same time, according to the invention, at each point of the excitation, on the area under study or along the profile, before the seismic oscillations are excited, a common source gather microseism gather is recorded during time t of at least 1 s where, for any source of oscillation, there are no signals of direct and surface waves, their correlation noise and distortions in the dynamics of microseism signals. Then, elastic oscillations are excited and a standard common source gather seismogram of reflected and other regular waves is recorded. Next, separate digital processing of the obtained seismograms of the common source gather microseisms and reflected waves and the joint integrated geological interpretation of geodynamic noise and reflected waves are carried out.EFFECT: improving the accuracy and reliability of exploration data by creating a method of seismic exploration, providing a direct search for hydrocarbon deposits by induced geodynamic noise with any type of seismic source.1 cl, 2 dwg

Description

The invention relates to methods for seismic exploration, and in particular to methods for a direct search for hydrocarbon deposits (HC) emitted by them after an external wave action of their own microseismic vibrations (artificially induced geodynamic noise).

Among such methods, the method of vibro-seismic exploration when searching for oil and gas fields is best known, including exposure to hydrocarbon deposits by seismic vibrations from a seismic vibrator in the frequency range from 1 to 20 Hz with a session duration of at least 3 minutes (RF patent No. 2045079, G01V 1/00). Seismic signals are recorded twice: for at least 20 minutes before excitation of vibrations by the seismic vibrator and 5 minutes after the end of their excitation. For registration of seismic signals, highly sensitive three-component sensor modules specially created for these purposes are used, which are located at two (for profile surveying) or four (for areal surveying) reception points (PP) of oscillations that are 600- away from the point of their excitation (PV) 800 meters. The presence of hydrocarbon deposits is judged by the criterion for increasing the amplitude-frequency spectrum of the recorded microseismic vibrations (microseisms) on the records of the same name components in the frequency band of 2-7 Hz after excitation of the oscillations compared with the records before their excitation.

The disadvantages of this method include the implementation of only a single wave action on hydrocarbon deposits, the need to perform special field work for the excitation and registration of induced geodynamic noise, the use of unique equipment for recording signals, the low density of reception points in the observation system of oscillations and the absence of registration on these points of reception (PP) of reflected seismic waves, which, in general, leads to insufficient information and the effectiveness of this technologist and.

There is also a known method of seismic exploration, in which there are no the above disadvantages and which we adopted as a prototype of the invention. This is a standard active seismic exploration method using the common depth point method (MOGT), supplemented by author processing using spectral analysis technology of microseisms ("SAM") simultaneously recorded on seismograms of a common point of excitation (OPV) from artificially induced geodynamic noise emitted by hydrocarbon deposits (RF patent 2263932, G01V 1 / 00, prototype). The excitation of such noise is carried out by repeated exposure to hydrocarbon deposits of regular waves created by the source of elastic vibrations of the seismic exploration of the MOGT. Noise is recorded repeatedly using the same telemetry equipment and at the same points of reception (PP) of profile (2D) or area (3D) multiple overlap systems that are used and optimized for the extraction and analysis of reflected waves.

As part of the additional processing of the MOGT data using the indicated SAM technology, the time fields of microseisms are formed on the seismograms of the OPV, common reception point (OP) and at sections of equal distances (RU) of the receiver from the source from the tracks from sections 1, 2 of the standard seismograms of the OPV observations of the MOGT, which free from recording regular waves (Fig. 1). Then, on these seismograms and sections of RU, filtering operations remove the signals of various surface, technogenic and natural-climatic interference (electrical interference, traffic, soil vibrations from the wind, etc.). Next, the energy and amplitude-frequency spectra of microseisms at each BOP are determined , identify areas of the presence of induced geodynamic noise according to the criterion of the anomalous low-frequency component and carry out a geological interpretation of the dynamic parameters of these noises in combination with wave features fields of reflected waves in sections of open-cut deposits and with a priori geological and geophysical information according to the data of drilling deep wells.

The disadvantages of this method include its limited functionality: it is effective only with an explosive source of excitation of oscillations and ineffective with shock or vibration sources. This is due to the fact that on the summations of the OPV with the shock source before the arrival of the direct wave there are often “tails” of surface waves, and on the correlograms of the OPV with the vibration source there is always also a correlation noise of the direct and surface waves, which are not observed on the gathers of the OPV with the shock source Therefore, it is practically impossible to establish the presence or absence of induced geodynamic noise according to the data of the MOGT with a vibration source.

A significant drawback of the MOGT data when working with shock and vibration sources is also the fact that the intensity and frequency spectrum of geodynamic noise are not true on the resulting summograms and correlograms of the OPV, due to the non-phase summation of the recorded single seismograms and the OPV vibrograms.

In modern MOGT seismic exploration, vibration and shock sources of vibration excitation are increasingly used. Therefore, it is relevant to implement such a method of seismic exploration of MOGT, which will be effective for studying induced geodynamic noise using data from such sources. The present invention is directed to solving this technical problem.

The technical result of the invention is the creation of a method of seismic exploration for the direct search for hydrocarbon deposits, providing a direct search for hydrocarbon deposits by induced geodynamic noise at any source of excitation of vibrations used in active seismic exploration.

The specified technical result is achieved due to the fact that in the seismic exploration method for direct search for hydrocarbon deposits, including repeated excitation by the source of active seismic exploration in the test medium of geodynamic noise induced in the hydrocarbon deposits and reflected from the seismic boundaries of the waves, registration of seismic vibrations using the OGT technique and subsequent digital processing of microseisms with the allocation of areas of abnormal values of their low-frequency component, according to the invention, at each point of excitation in the study of the area or along the profile prior to the initiation of seismic vibrations, the seismogram of the OPV microseismic is recorded for a time t of at least 1 s, on which for any source of excitation of vibrations there are no direct and surface wave signals, their correlation noise and distortions in the dynamics of the microseismic signals, then they produce excitation oscillations and record the standard gather of the optical waveform of the reflected and other regular waves, separate digital processing of the received gathers of the optical waveform of the microseisms and reflected waves and the Joint Integrated geological interpretation of geodynamic noise and reflected waves.

In FIG. 1 shows a view of the seismogram of the OPW seismic survey of the MOGT and its sections 1, 2, used in the prototype for the analysis of microseismic records.

FIG. 2 illustrates the gathers of the OPV method of the invention.

The method according to the invention is carried out in the following sequence of operations.

1. At the stage of field work of the MOGT at each receiver, first, before the excitation of vibrations, in the passive seismic mode, the OPV microseismic seismogram is recorded with a recording time of at least 1 s (Fig. 2A), and then the oscillations are excited and recorded in the active seismic mode standard seismogram of OPV of reflected and other regular waves (Fig. 2B, Fig. 2B).

2. At the stage of data processing, the MOGT carry out separate processing, for example, according to the above-mentioned “SAM” technology, seismograms of OPV microseisms and reflected waves. In this case, the OPP seismograms and RC sections of the microseism are formed from all the traces of their OPV seismograms (Fig. 2A), and not from the tracks of sections 1, 2 (Fig. 1, Fig. 2B, Fig. 2B) of the OPV seismograms of regular waves, as is done in the prototype. After that, the energy and amplitude-frequency spectra of microseisms at each PP are estimated.

3. At the stage of interpreting the results of processing the MOGT data according to the criterion of the anomalous low-frequency component of the microseisms, areas of possible registration of induced geodynamic noise in the area under study are distinguished. Within each such section, a joint analysis of microseismic parameters, reflected waves and a priori geological and geophysical information is carried out according to the data of drilling deep wells and outlines the possible location zones of oil and gas deposits with higher accuracy than by the prototype method.

The proposed method is more effective than the prototype for a direct search for hydrocarbon deposits at any source of excitation of vibrations.

With shock and vibration sources, it is more effective because, firstly, there are no direct and surface wave signals and their correlation noise in the microseismic seismograms obtained before excitation of vibrations, and, secondly, there are no distortions in the dynamics of geodynamic noise signals having place on the summograms and correlograms of the OPV of active seismic exploration of the MOGT. In addition, for any source of excitation of oscillations (including explosive), the estimates of the parameters of geodynamic noise in this case are always more accurate than in the prototype, since they are estimated from the totality of all the tracks of the seismograms of the OPW microseisms, and not from the tracks of sections 1, 2 (Fig. 1, Fig. 2B, 2C) of the OPV seismograms that are free from recording regular waves, the number of which is always 25-30% less,

Thus, the method according to the invention, in contrast to the known methods, has broader functional capabilities, since it provides an effective solution to the problem of direct search for oil and gas fields by the artificially induced geodynamic noise emitted by them at any source of excitation of seismic vibrations.

Claims (1)

A seismic exploration method for direct search for hydrocarbon deposits, including multiple excitation by a source of active seismic exploration in the test medium of geodynamic noise induced in the hydrocarbon deposits and reflected from the seismic boundaries of the waves, registration of seismic vibrations using the OGT technique and subsequent digital processing of microseisms with the allocation of sections of anomalous values of their low-frequency component characterized in that at each point of excitation in the studied area or along the profile before the excitation of seismic vibrations there is registration of an OPV microseismic seismogram for a time t of at least 1 s, at which there are no direct and surface wave signals, any correlation noise and distortions in the dynamics of the microseismic signals for any source of vibrational excitation, then excitation of vibrations is generated and a standard OPV seismogram of reflected and other of regular waves, they carry out separate digital processing of the obtained seismograms of the OPV microseism and reflected waves and a joint complex geological interpretation by geodynamics noise and reflected waves.

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