RU2132075C1 - Process of search for hydrocarbon deposits - Google Patents

Abstract

FIELD: search for hydrocarbon deposits by nontraditional methods. SUBSTANCE: points corresponding to values of oxidation-reduction potential maximal by absolute value and negative by sign are determined in area of search as well as points of sudden rise of amplitude in amplitude-frequency characteristic of seismic background of ground taken on infrafrequencies with usage of electrodynamics geophone after generation of seismic vibrations in infrafrequency range. EFFECT: increased prediction accuracy and simplification of process. 2 dwg

Description

 The invention relates to the field of geophysical methods for searching for minerals, and in particular to unconventional methods for searching for mineral deposits, and can be used in the search for oil and gas fields.

 There is a method of searching for oil and gas fields (RU, patent 204579 G 01 1/00, 1993), according to which, using three-channel sensors, the natural seismic background of the earth is recorded at infra-frequencies, oscillations are generated at infra-low frequencies, while the seismic background is continued to be recorded during and after the oscillations. . By increasing the amplitude of the amplitude-frequency characteristics, the presence of an oil and gas field is judged. The disadvantage of this method is the lack of accuracy in predicting the presence of an oil and gas field, the complexity of working with three-channel electrochemical sensors.

 The technical problem to which the present invention is directed is to develop a multifactorial method for searching for oil and gas fields.

 The technical result obtained by the implementation of the invention consists in increasing the accuracy of forecasting while simplifying the work.

 According to the invention, the method of searching for hydrocarbon deposits is as follows. At least two electrodynamic geophones, capable of detecting infra-frequency vibrations, are placed above the proposed oil and gas field. Preferably, seismic vibrations of the earth’s natural background are recorded over a period of 10-20 minutes, preferably in the range of 1 to 6 Hz, then infrared waves, preferably in the range of 4 to 12 Hz, are generated over a period of 10 to 15 seconds, and re-register the natural seismic background, mainly in the range from 1 to 6 Hz. Seismic background registration can be carried out both on one, and on two or three channels. Registration and generation of oscillations can be carried out repeatedly. Sensors can work both in velocimetric and seismometric modes. During the installation of geophones at the points of their installation, rock samples are taken from a depth of 0.5 - 1.0 m. At the same time, a rock sample can be taken from under the vibrator. After the end of the generation of seismic vibrations from under the vibrator, the rock sample can be taken again. According to experimental data, the presence of an oil and gas field corresponds to a sharp increase in the amplitude-frequency characteristic of the natural seismic background of the earth at frequencies from 2 to 4 Hz. The soil samples taken are crushed to a particle size of 0.1 to 0.2 mm and the values and sign of the redox and electrokinetic potential are determined by known methods. The presence of a deposit is indicated by the highest in absolute value and negative in sign values of the measured potentials. The total conclusion about the presence or absence of an oil and gas field, made on the basis of geochemical and geophysical low-frequency methods, increases the accuracy of the forecast to 0.85.

 The applicant notes that according to the information available to him, the use of electrodynamic geophones in the field is not known.

 The invention is illustrated by the research scheme (Fig. 1) of a known test site, where red spots indicate promising places (places of known deposits) determined by infra-frequency seismic prospecting, and blue points indicate perspective points according to geochemical research. Asterisks mark known domes of hydrocarbon deposits. The scheme convincingly shows that, together, the data of infra-frequency seismic exploration and geochemical studies unambiguously correspond to the domes of the deposits. In FIG. Figure 2 shows the amplitude-frequency characteristic of a seismic background above a hydrocarbon field before generating oscillations (1) and the amplitude-frequency characteristic of a seismic background above a field after generating oscillations (2). It clearly follows that over the field at 2-4 Hz the signal amplitude increases sharply.

 The invention can be illustrated by the following example. A station containing an electric power supply unit and a device for recording signals from electrodynamic geophones was installed above the proposed field. Three or four electrodynamic sensors of the SMZ-KV type were placed at a distance of up to 300 meters from the station, connecting them with cables to the device for recording seismic signals. Prepared sensors for operation according to the instructions for use. For 10-20 minutes, the earth's seismic background was recorded in the frequency range 1-6 Hz. Then, the source of seismic vibrations (vibrator CB - 10/100) created vibrations in the following mode: for 10 sec, vibrations were created with a frequency sweep from 6 to 12 Hz, then they paused for 20 sec and oscillations were generated again under the same conditions. The total generation time was 10-20 minutes. In the process of excitation of oscillations, and also after that, the seismic background of the earth was recorded at the same frequencies of 1-6 Hz. In FIG. 2 shows that the ratio of signal amplitudes in the frequency range 2-4 Hz is of the order of 5-6. From each seismic receiver, rock samples were taken from a depth of about 0.8 m and placed in clean bags, marking the place where the sample was taken. The time taken for sampling (before or after the generation of oscillations), as found experimentally, does not matter. The geophones and recording equipment are transferred to new points in the search area and the entire procedure is repeated. In the laboratory, the imported samples are ground to a particle size of 0.1 to 0.2 mm, and the magnitude and sign of the electrokinetic potential and the magnitude and sign of the redox potential are determined by any known method. Points corresponding to a sharp increase in the amplitude of the amplitude-frequency value and negative in sign of the values of the redox and electrokinetic potential are noted on the structural map of the search area.

 The coincidence of the three points indicates with maximum probability the promising places for laying exploratory wells.

 In 1996-97, in the Krasnodar Territory, the proposed method was used to study the Varavenskaya (Fig. 1), South Grivenskaya and East Cheburgolskaya squares.

 Tests showed an 85% match of the forecast results.

Claims (1)

 A method of searching for hydrocarbon deposits, including generating seismic oscillations in the infra-frequency range, recording the amplitude-frequency characteristics of the earth's seismic background at infra-low frequencies before and after generation, and determining, using the obtained amplitude-frequency characteristics, the location of the hydrocarbon deposits, characterized in that for recording the amplitude-frequency characteristics use electrodynamic geophones, moreover, at the points of determining the amplitude-frequency of different characteristics, samples of subsoil soil are taken, crushed, and the magnitude and sign of the electrokinetic and oxidation-reduction potential are determined, and the location of the hydrocarbon deposits is determined by the coincidence of points with the maximum absolute value and negative sign of the values of redox and electrokinetic potentials, as well as a sharp increase amplitude-frequency characteristics after the generation of seismic oscillations in the infra-frequency range.

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