UA54003C2 - Method for exploring hydrocarbon deposits by seismic prospecting - Google Patents

Abstract

The proposed method for exploring hydrocarbon deposits by seismic prospecting implies developing the optimal scheme of seismic observations at the monitored areas, presenting the dynamic section lines, plotting geological maps for all the explored profiles, and predicting the depth, dimensions, and type of the deposit by the exploration results. The method is distinctive by analyzing each longitudinal profile and a number of the lateral profiles within the three-dimensional spatial zone that is covered by the seismic prospecting, with a distance between seismic receivers reduced by 5 à 10 times and the length L of the base recording area equal to L = 4X, where X is the distance between the points of excitation of seismic vibrations along the X axis, matching the current measurement data for reflected and refracted seismic signals, determining the corresponding corrections for updating the analyzed profiles by using the data obtained, determining the dynamic section lines at the decreased distance between the routes and enhanced signal-to-noise ratio, and analyzing the distribution of reflected seismic signals at the upper pert of each dynamic section. The analysis results are used for predicting oil or gas deposits. The present invention allows the prediction accuracy to be increased.

Description

Description of the invention

The proposed method refers to seismic methods of mineral exploration and can be used, in particular, in the search and exploration of hydrocarbons (BB) concentrated in traps of both anticlinal and non-anticlinal types.

A well-known method of exploration for oil and gas deposits (1), which involves conducting profile seismic surveys in order to detect anticlinal explosive traps followed by drilling deep exploratory wells, while the success rate is about 3095. In the case of non-anticlinal traps, it decreases by 70 to 3-4 times , which is unacceptable given the high cost of drilling.

The well-known method of searching for hydrocarbons is more advanced, which involves carrying out profile seismic studies with the aim of identifying anticlinal traps of explosives, followed by prediction of deposits in these traps using the study of integral physical properties in the section interval, slightly larger than the thickness of the expected deposit (in the vast majority, it is about 200ms seismic section) |2). The method is based 12 on the fact that a trace of a diffusion flow (SDF) is observed above the explosive deposits, which leads to an epigenetic change in the physical properties of the rocks, and this also entails a change in the dynamic characteristics of seismic waves in a certain range of the seismic recording, which covers both the trap itself and and surrounding rocks.

The disadvantages of the method are limited depth (mainly up to 2-Zkm) and the use of a regular grid of profiles, where the level of interference may exceed the expected effects; study of only the productive part of the section; insufficient density of seismic profiles passing through the explosive deposit; decrease in efficiency in the case of studying deposits at great depths, where the reservoirs are characterized by high density and differ little in physical properties from the surrounding rocks.

The closest in technical essence and result is the method of searching for hydrocarbon deposits by seismic exploration

IZI, which provides for the use of reconnaissance and detailed seismic research on a liquid grid from longitudinal profiles, on which groups of seismographs are placed with a step equal to half the length of the seismic wave (3 waves, and sources of seismic oscillations using the method of a common deep point, where in geological regions promising for oil and gas, on large areas with traps of anticlinal and non-anticlinal types, create optimal grids of areal seismic studies, divide the system of parallel profiles for direct or inverted arrangement of areal observations with distances between adjacent profiles o along the Y axis, increased in comparison with the distances along the X axis between the receivers by 2-5 times, conduct excitation in the av medium and record seismic oscillations excited by the given field installation, move the observation field installations to neighboring positions with a given overlap along the X and Y axes, determine the reflection times and amplitudes of the reflected waves from seismograms, I will install trace the diffusion flow in the form of epigenetically altered 3o rocks on the area and on profile sections according to the relative amplitudes and other dynamic parameters, construct dynamic sections and maps based on the data of all investigated profiles and weathered reflective o horizons at a given site to depths of 5-7 km, where the expected deposit of hydrocarbons can be found, the reducing and oxidizing zones of the area of the trace of the diffusion flow above the predicted deposits along the entire section are determined, according to which the dimensions of the deposit, the estimated depth of its occurrence are determined, and the height of the "reducing zone" - the type of hydrocarbon - oil or gas. C 50 Disadvantages of the prototype: c 1. A decrease in the detail and reliability of the amplitude analysis in the upper part of the section is caused by the reduction of the area of observation of reflected waves; 2. The influence on the signal/interference ratio on the time section along the upper and deeper reflecting horizons of the angles of incidence of seismic waves and changes (expansion) of the area of monitoring of reflected waves with increasing research depth; i-th Z. Irregularity of the formation of bins during the implementation of area observation systems with significant source-seismic receiver distances, which leads to the appearance of false amplitude anomalies, especially in the upper part of the section. o The proposed invention is based on the task of improving the method of searching for hydrocarbon deposits av! 20 with three-dimensional (30) seismic exploration by conducting special observations on longitudinal profiles on a limited basis with a 5-10 times reduced distance between receivers and dynamic linking of seismic records, which allows to increase the detail and reliability of forecasting oil and gas deposits.

The task is solved in such a way that in the method of searching for hydrocarbon deposits, which involves the creation of an optimal grid of areal seismic observations with distances between adjacent profiles along the 29 Y axis, increased in comparison with the distances along the X axis between receivers by 2-5 times, and a step between in groups

GF) of seismographs along the X axis, equal to half the length of seismic waves in the environment, construction of dynamic sections and maps based on the data of all profile studies and forecasting the depth, size and type of deposit, according to the invention, each longitudinal profile of ZO-seismic exploration and two or more transverse profiles they additionally practice with a 5-10 times reduced distance between the seismic receivers and the registration base, equal to I -4АХdz, 60 where АХпз - the distance between the excitation pickets along the X axis, perform dynamic linking of seismic records by two types of waves - reflected and refracted, form arrays amplitude corrections along the developed profiles, the latter are introduced into the seismic records of additional (special) observations and data of longitudinal profiles

ZO-seismic surveys, after which dynamic time sections with a reduced distance between tracks and an increased signal/interference ratio are built and the distribution of relative amplitudes of reflected waves is studied in the upper part of the section and along deeper horizons, and oil and gas deposits are predicted based on the obtained results.

Compared to the prototype, the method has distinctive features: - additional processing of each longitudinal profile of ZO-seismic reconnaissance and two or more transverse profiles with a 5-10 times reduced distance between seismic receivers on a limited base (I-4АХдлз) ensures the connection of the corresponding seismic records through mutual points at neighboring points of excitation, as well as the introduction of a limited base allows you to monitor dynamically sustained horizons in the upper part of the section with a uniform signal/interference ratio and, thus, to refute possible false amplitude anomalies, including those related to the unevenness of the formation of bins during data processing ZO-seismic reconnaissance; - performance of dynamic linking of seismic records by two independent types of waves (refracted and reflected) 7/0 increases the accuracy of determining amplitude corrections; - the formation of arrays of amplitude corrections and their application in the process of building dynamic time sections with a reduced distance between tracks, as well as in the processing of ZO-seismic reconnaissance data, allows you to create a reference grid of profiles with an improved signal/noise ratio both along the horizons of the upper part of the section, and over deep horizons, which increases the accuracy of the study of seismic parameters, in particular, the relative 7/5 amplitudes of reflected waves, thanks to which the prediction of oil and gas deposits becomes more reliable.

All the above-mentioned signs are essential and allow solving the task.

The essence of the method is explained by the drawings, where Fig. 1 shows the scheme of conducting research and the course of rays from the points of excitation to the points of reception of oscillations and the dimensions of the traced sites from each point of excitation.

The following symbols are used for explanation: day surface 1; sole of low speed zone 2; reflective border in the upper part of section C; vibration excitation points 4; vibration registration points 5; rays 6, 8, 10 falling at a critical angle on boundary 2; rays 7, 9, 11 of refracted waves, respectively, from excitation points 0.4, O»5, Oz; rays of 12, 14, 16 incident waves, respectively, from excitation points O14, O5, Oz; rays 13, 15, 17 of reflected waves, respectively, from the excitation points 0.4, 05, Oz reflecting platforms 18, 19, 20 of the boundary Z at s Excitation of oscillations, respectively, at the points O., O", and Oz.

Fig. 2 shows the scheme of ZO-seismic reconnaissance with six observation lines in the strip, where a dynamic (primarily, amplitude) coupling of longitudinal profiles is provided. The following marks were adopted: vibration reception lines 21, 22, 23, respectively, of the first, second, and third observation bands of З3О-seismological reconnaissance; vibration excitation pickets 24 at ZO-seismological survey; common pickets for excitation of oscillations 25 during ZO-seismic survey and so with additional (double) observations along the X axis; vibration excitation pickets 26 with additional observations along the U axis, the line of receiving oscillations 27 along the U axis. o

As can be seen from Fig. 1, when oscillations are excited at point O. and registration of oscillations according to the given condition (1-4 АХпз) о should be carried out in the interval from point A to point Oz, which will make it possible to follow the reflective border in the interval from point K to point M. Z

The path reflected from the boundary of the Z wave to the point O" will be: yuyu 81-01ММО5 (1)

Accordingly, when oscillations are excited at point О" and their registration at point 0. and a similar path will be equal to " - с 82-О02МаМО1 (2) from Here it is clear that point M is a mutual point of reflection of waves on boundary 3, and it is used in kinematic seismic for connecting wave hodographs of two adjacent excitation points.

However, the amplitude of the reflected waves registered during excitation of oscillations at points O. and O5 will be determined 75 not only by the properties of the boundary З at point M, but also by the conditions of excitation of oscillations (the force E of the impact of the i-th source on the soil and the properties of the soil O at the excitation point ). Therefore, if the amplitude at point О" upon excitation of oscillations t" at point 04 and will be AZ(E4101), then, accordingly, at point ОО upon excitation of oscillations at point О5 it will be equal to AZ(GB202).

In this way, the amplitude correction that must be made to the seismic record at point O" is calculated in relation to (ав) 50 of the seismic record at point O. and mini AA-ACETO1UA(B2) (3)

A similar correction is calculated for the refracted wave. 59 The path that the refracted wave will travel when the oscillations are excited at point О1 will be about 811501ЕЖЭОн0О" (4) name)

When the oscillations are excited at the point O», it is possible to write down 60 821-0200 EEOh (5)

Examination of expressions (4) and (5) shows that these points on the hodographs of refracted waves are also reciprocal and can be used not only for kinematic, but also for dynamic (amplitude) connection of records. 65 The amplitude of the refracting horizon in this case will also be determined by the force E of the influence of the source of vibrations on the soil and the properties of the soil 0.

To determine the amplitude correction, we use an expression similar to (3).

AA AH E1941)-A2 Ego) (6)

I I I - I

A similar amplitude connection is made between seismic records from the excitation point O 4 and Oz. If the amplitude of the reflected or refracted wave at mutual points from the point of excitation О4 and at the point О5" is denoted by Ао40", at the point Oz - through Ао40з, from the point of excitation О» at the point О»z - through Аогоз, from the point of excitation О» at point O4 - through

Aogo4 from the point of excitation О» at the point Ф. - through Aozoi, then you can write the following:

ААо102-А0102-АО201 (7)

AAo102-LAo103-DAozo1 (8)

ААогоз:ЛАог03-лаозоз (9) here ААо10», ДАОо103, ДЛАОо»з is the amplitude correction between the corresponding excitation points (0.4, О»5, Оз).

Analysis of expressions (7-9) allows to write down

AAotozAAogoz- DAO 103 (10)

In this way, the magnitude of the amplitude correction in the seismic record upon excitation of oscillations at the Oz point is calculated in two ways (in relation to the seismic record from the first point of excitation).

In the first case, expression (8) is used, and in the second case, the calculation is performed according to (10), where the correction is the sum of two corrections lAo40" and dAogoz.

The method is implemented by the following sequence of operations. When implementing ZO-seismic exploration (Fig. 2) on each line of reception of vibrations (21, 22, 23) in the case of the approach to it by the excitation point 25 (with the working out scheme of the "cross" type), an additional arrangement (o) of seismic receivers is carried out (with point grouping) on the basis of I - 4АХдлз, where АХпз - the distance between excitation pickets along the X axis at ZO-seismic survey. The distance between the seismic receivers is set 5-10 times smaller than the AHpdz value. со со Registration of oscillations is carried out in case of installation of sources of oscillations on the receiving lines 21, 22, 23. At the same time, different schemes of excitation and registration can be used. The simplest scheme is when the excitation o is performed once per profile, and the registration is carried out simultaneously for all channels of the ZUO-observation system and o channels of a special arrangement. Other excitation schemes can be used, for example, using the minimum possible distance between sources of oscillations, or even with point excitation by one source. "

However, in such a case, a separate recording of oscillations is performed, which will lead to a certain decrease in the rate of development of the square system. In order to maintain high labor productivity during ZO-observations, it is necessary to have 2-3 scythes in stock (with a reduced step between seismic receivers) to implement the conveyor system of works.

The development of transverse profiles 27 for linking ZUO-observations along the U axis is carried out separately, although from a methodological point of view, simultaneous development is more appropriate. For this, it is necessary to have an appropriate stock of equipment (scythes, seismographs, recording systems). Transverse profiles 27 must be worked out at the beginning and at the end of the area observation system (Fig. 2), however, if necessary, intermediate profiles are set as well (with a large variation of relative amplitudes along the horizons and complex surface or depth conditions ).

In the process of data processing, seismic records are compiled along the longitudinal profiles of the ZO-observation system and c along the Y axis (on transverse profiles). Then, one-time dynamic sections are formed and the amplitudes of reflected and refracted waves at mutual points are determined. The next step is to determine the amplitude corrections at each picket in relation to the previous one according to (7-9) and check these corrections according to (10). The received amplitude corrections are entered into the seismic records by profiles, which makes it possible to construct time sections with the Sustained amplitude characteristic along the seismic horizons in the upper part of the section. The lack of multiple overlaps is compensated by the high signal/noise ratio in this part of the section on these primary seismograms.

Amplitude corrections are also used in the processing of ZO-observation data in order to improve the quality of deep horizons on time sections and increase the reliability of studying relative amplitudes based on them. 5B Example of implementation of the method.

As an example of the implementation of the proposed method, we will give arbitrary amplitude characteristics (Ф) of seismic recordings along one of the longitudinal profiles of the ZO-observation system (at mutual points) of the developed technology, which involves linking seismic recordings, under the following conditions:

The length of the observation profile is 1km. The distance between the excitation profiles (АХпз) with the square observation system of the "cross" type (between the excitation pickets on the longitudinal profiles - 0.2kmM)

The number of excitation pickets on the longitudinal profile is -6

Oscillation registration base - I -4АХлЗ - ВВ0Ом 65 Amplitude A of the reflected wave at mutual points:

first and second seismic records, respectively -1.0;

OA of the first and third seismic records, respectively -1.0; 0.5 9 of the second and third seismic records, respectively - 0.4; 0.5 of the second and fourth seismic records, respectively - 0.4; 0.7 of the third and fourth seismic records, respectively - 0.5; 70 o'clock of the third and fifth seismic records, respectively - 0.5; 1.0 of the fourth and fifth seismic records, respectively -0.7; 1.0 of the fourth and sixth seismic records, respectively -0.7; 0.3 of the fifth and sixth seismic records, respectively -1.0; 0.3

To connect seismic records of the first and second excitation points, we use expression (7):

АКАог0о2-Ао105-АО2О. or dАo40о25-1-1.4-0.6, that is, the amplitude of the seismic recording at the second excitation point should be increased by 0.6.

We will connect the seismic records of the second and third excitation points according to expression (9):

AKAoOgo3 DAOg2053-LAOz02 Ha

AAogo3-0.4-0.5--0.1 o

By analogy with the previous one, we define:

ААозо4-0.5-0.7--0.2

AAodovB-O,7-1,0--0,3

ААовОов-1-0.3-0.7 i)

According to (10), we find the total correction for each subsequent seismic record in relation to the first o

ААо103-0.6-0.1-0.5 lАо-оу-0.6-0.1-0.2-0.3 о

AAoio5-0.6-0.1-0.2-0.3-0 "I

AAoio6-0.6-0.1-0.2-0.3-0.7-0.7

The introduction of amplitude corrections to seismic records at each point will give: ю

A2-0,40,6-1

Az-0.580.5-1

A-0,70,3-1 « 20 AB-1,0-0,3-1 with

Av-0,30,7-1 s, which will lead to equalization of amplitudes of seismic records along the profile relative to the first record. :z" For control, we will define corrections between seismic records on remote channels:

ААо103Ао103-АОоз04-1-0.5-0.5

AKAogoAog0,-ALAOdog-0.4-0.7--0.3 g AKAozovB-:DAOzov-LAoBOoz-0.5-1--0.5

AAodovyDAodov-LAovbod-0.7-0.3-0.4 e The amplitude of seismic records after the introduction of corrections will be: av! a) for odd pickets:

Az-0.580.5-1 o AB-1.040.5-0.5-1 s" b) for paired pickets:

A,-0.7-0.30,6-1

Av-0,30,4-0,30,6-1

The obtained results indicate the correctness of the previously defined amplitude corrections.

The connection of the longitudinal profiles of the ZO-observation system in the transverse direction is carried out in a similar way

F, schemes. The calculation of corrections using refracted waves does not differ from the calculation using reflected waves. Thus, the implementation of the proposed method makes it possible to determine dynamic, first of all, amplitude corrections in ZO-seismic exploration with sufficiently high accuracy with a small increase in funds for field work.

Taking into account corrections when constructing dynamic time sections based on the materials of special observations and

ZO-seismological prospecting significantly increases the accuracy and reliability of seismoparametric analysis, especially when studying the properties of the seismic horizons of the upper part of the section, which significantly increases the efficiency of the search for hydrocarbon deposits by reflecting the trace of the effusion-diffusion flow in the form of epigenetically altered rocks in seismic wave fields.

Bibliographic data of sources of information. 1. Sheriff R., Geldart L., Seismorazvedka, vol. 1, M., Mir, 1987, p. 21. 2. Kyry P., Brooks M., Introduction to geophysical prospecting. M., Mir, 1988, p. 320-325. 3. Patent for the invention OA Mo21783, MKI 501M1/00, 1/28, 1/30. published 30.09.98 (prototype).

The method of searching for hydrocarbon deposits by seismic exploration 5

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The method of searching for hydrocarbon deposits, which involves the creation of an optimal grid of area seismic observations with distances between adjacent profiles along the Y axis, increased in comparison with the distances along the X axis between receivers by 2-5 times, and a step between groups of seismic receivers along the X axis equal to half the length of seismic waves in the environment, the construction of dynamic sections and maps based on the data of all investigated profiles, and the prediction of the depth, size and type of the deposit, which is distinguished by the fact that each longitudinal profile of the ZO-seismic survey and two or more transverse profiles are additionally tested at a reduced 5 - 10 times "» the distance between the seismic receivers and the registration base, which is equal to 1, - АХ in where АХ in - the distance between pickets: 15 excitations along the X axis, perform dynamic linking of seismic records by two types of waves - reflected and sl refracted, form arrays of amplitude corrections along the developed profiles, the latter are entered into seismic records of special observations and data of longitudinal n profiles of ZO-seismic reconnaissance, after which they build dynamic time sections with a reduced distance between tracks and an increased signal/interference ratio, and study the distribution of the amplitudes of reflected waves in the upper part of the section and along deeper horizons, and based on the obtained results, oil and gas deposits are predicted. ((c) syu) Official Bulletin "Industrial Property". Book 1 "Inventions, useful models, topographies of integrated microcircuits", 2005, M 8, 15.08.2005. State Department of Intellectual Property of the Ministry of Education and Science of Ukraine. name) 60 b5