CN101339252B - Directional lighting seismic exploration method based on single earthquake focus - Google Patents

Abstract

The invention relates to a seismic prospecting method based on a single seismic focus directional lighting. An offset distance and a track pitch are determined according to the traditional geologic prospecting method; a wave-detector array is arranged in a collinear way; according to the different offset distance of the shot-points in the same group and the same offset distance of the m shot-points in the different groups with the serial number differing in n, seismic data in a single shot on an entire cross-section is gathered; a uniformly-spaced time delay is made for the seismic data in the single-shot in the same group according to the sequence of the serial number; a linear superposition is made for the delayed seismic data in the single-shot so as to compose a directional lighting seismic signal with directivity, and the directional lighting seismic signal is corresponding to a directional seismic wave field; by adopting a routine seismic data processing method, a directional lighting seismic cross-section based on the single seismic focus can be obtained. After a test, the direction of the directional lighting seismic wave field that is composed can be controlled manually according to a target occurrence and has better prospecting effect to the target body of a steep dip, as compared with the common seismic prospecting method based on the single seismic focus; the seismic prospecting method of the invention also has the advantages of low operation cost and simple operation as compared with a phased seismic prospecting method.

Description

Directional illumination seismic exploration method based on single source

Technical field:

The invention relates to a seismic prospecting method, which is especially suitable for the seismic prospecting method of single seismic source directional illumination in areas with strong background noise and low signal-to-noise ratio.

Background technique:

The existing vibrator seismic exploration methods can be divided into two categories according to the number of seismic sources involved in the work. One is single vibrator seismic exploration; the other is array vibroseis seismic exploration. The seismic wavefield excited by a single vibroseis in the underground half-space can be approximated as a spherical wavefield with no directionality; the seismic wavefield excited by an array vibroseis has obvious directionality, and the main beam direction of the seismic wavefield excited by the combined vibrator is perpendicular to the ground. Under normal circumstances, the seismic wave field excited by the phase-controlled vibrator also has directionality, and the direction is controllable; generally speaking, the seismic wave direction can be reasonably controlled, and the seismic data with a higher signal-to-noise ratio can be obtained by using the phase-controlled vibrator. However, the phase-controlled seismic source seismic exploration method has high cost, complex control, and the inconsistency of multiple sources, which limit the promotion of the phase-controlled seismic source seismic exploration method. For this reason, it is still considered to use a single seismic source as the excitation source, and use the single-shot seismic signal based on the single seismic source as the data source, and use the directional illumination seismic signal synthesis method to synthesize the directional illumination single-channel seismic signal, and then synthesize the directional illumination single-shot seismic data similarly , the data correspond to a directional seismic wavefield. The similarity with the phased seismic wavefield is that both wavefields are directional wavefields, so both are effective for improving the signal-to-noise ratio of seismic data; the difference with the phased seismic wavefield is that the wavefield is artificially synthesized Wavefields, not physical wavefields. Therefore, the directional illumination seismic exploration method, on the basis of ensuring the directional characteristics of the wave field, overcomes the shortcomings of the inconsistency and high cost of the array source, and is bound to provide an effective method for high-resolution seismic exploration.

Invention content:

The purpose of the present invention is to provide a single-source directional lighting seismic exploration method that improves the signal-to-noise ratio of reflected wave signals by synthesizing directional seismic wavefields and aiming at the shortcomings and deficiencies of common single-source and array-source seismic prospecting methods.

The purpose of the present invention is achieved in the following manner:

The directional illumination seismic exploration method based on single source includes the following sequence and steps:

a. When carrying out exploration in the field, according to the geological data, determine the offset distance p, shot point distance d, trace spacing and the shot point position of each shot according to the traditional seismic prospecting method; here p refers to the distance between the first shot point and the first shot point The distance of the detector, that is, the offset p;

b. According to the geological background and exploration requirements, determine the number of directional lighting groups m and the number of single-source shot points n required to synthesize a directional lighting shot point. Therefore, the total number of shots included in the directional lighting seismic survey is N=n×m, that is, the directional lighting The total number of seismic exploration shots is divided into m groups, and each group contains n shots single-source seismic data;

c. According to the offset p set in step a, the shot distance d and the track spacing, arrange the detector array and the shot point on the survey line;

d. If n=3 single-source shot point data are selected to synthesize single-shot directional lighting shot point data, the first to nth shot points are arranged first, and these n shot points can be regarded as the first group of shot points for directional lighting exploration , arrange the geophone array according to the traditional geological exploration method, and set the first shot point according to the specified offset p, the distance between the shot point and the first geophone is: p ₁ = p, and the vibroseis For the seismic data of the first shot, keep the position of the geophone array unchanged, install the second shot point, the distance between the shot point and the first geophone is p ₂ =p ₁ -d, obtain the vibrator and get the second shot Seismic data: keep the location of the geophone array unchanged, install the third shot point, the distance between the shot point and the first geophone is p ₃ =p ₂ -d=p ₁ -2d, and obtain the third vibroseis Shot seismic data. At this time, the seismic data acquisition of the first group of n shot points has been completed;

e. According to the traditional seismic exploration method, roll the geophone array, and then arrange the n+1th to 2nth shot points. These n shot points can be regarded as the second group of shot points for directional lighting exploration. During the data acquisition process of , the track spacing of the geophone array remains unchanged, and the n+1th shot point is set at a distance from the 1st geophone: p ₁ =p, that is, the distance from the 1st geophone of the 1st group The offsets of the two shot points are the same, and the seismic data of the fourth shot of the vibrator are obtained; the n+2th shot point is set at a distance from the first geophone: p ₂ =p ₁ -d, that is, the same as The offset distance of the second shot point in the first group is the same, and the seismic data of the fifth shot of the vibrator is obtained; the n+3th shot point is set at a distance from the first geophone: p ₃ =p ₂ - At the position of d=p ₁ -2d, the seismic data of the sixth shot of the vibrator is obtained; at this time, the seismic data acquisition of n shot points in the second group is completed; that is, the offset distances of each shot point in the same group are different, and the The offset distances of the m shot points whose sequence numbers differ by n are the same;

f, and so on, continue to scroll the detector array;

g, arranging the n shot points of the next group, assuming that the group number is i, the sequence number of the n shot points corresponding to the i group in the total shot points is (i-1)×n+1 to For the (i-1)×n+n shot point, arrange the (i-1)×n+1 shot point, the distance between the shot point and the first geophone is p ₁ =p; then arrange the ( i-1)×n+2 shot points, the distance between the shot point and the first geophone is p ₂ =p ₁ -d; ..., then arrange the (i-1)×n+nth shot point , the distance between the shot point and the first geophone is:

p _n ＝p _n-1 -d＝p ₁ -(n-1)×d; obtain the (i-1)×n+1th to (i-1)×n+nth shots at the above n shot points Seismic data of the shot point;

h. Repeat steps f and g until all N shot seismic data are obtained

i. Divide the obtained single-shot seismic data into m groups, perform equal-interval time delay on the single-shot seismic data belonging to the same group according to the order of numbering, do linear superposition of the n single-shot seismic data after the delay, and synthesize a direction The directional illumination seismic signal corresponds to the directional seismic wave field, and the directional illumination seismic section based on a single source can be obtained by using the conventional seismic data processing method.

The purpose of the present invention can also be achieved in the following ways:

The shot pitch d is equal to or not equal to the track pitch; m in step b is an odd number >1.

Beneficial effects: After testing, compared with the ordinary single source seismic exploration method, the directional illumination seismic exploration method can improve the signal-to-noise ratio of the reflected wave signal from the target body; because the direction of the synthetic directional illumination seismic wave field can be adjusted according to the occurrence of the target Artificial control is better for the exploration of objects with steep dip angles; compared with the phase-controlled seismic method, it has the advantages of low work cost and simple control.

Description of drawings

Figure 1: Layout of different groups of shot points and geophones for directional illumination seismic exploration

Figure 2: Layout of the same set of shot points and detectors for directional lighting

m: the number of directional lighting groups, that is, the grouping number of the total shot number in the directional lighting seismic method

n: the number of single-source shot points required to synthesize a directional lighting shot point, that is, the number of shot points per directional lighting synthesis group in the total shot number group

N: total number of shot points on the survey line

d: shot point distance

P: Offset

Detailed ways:

Below in conjunction with accompanying drawing and embodiment describe in further detail:

The directional illumination seismic exploration method based on single source includes the following sequence and steps:

a. When carrying out exploration in the field, according to the geological data, determine the offset distance p, shot point distance d, trace spacing and the shot point position of each shot according to the traditional seismic prospecting method; here p refers to the distance between the first shot point and the first shot point The distance of the detector, that is, the offset p;

b. According to the geological background and exploration requirements, determine the number of directional lighting groups m and the number of single-source shot points n required to synthesize a directional lighting shot point. Therefore, the total number of shots included in the directional lighting seismic survey is N=n×m, that is, the directional lighting The total number of seismic exploration shots is divided into m groups, and each group contains n shots single-source seismic data;

c. According to the offset p set in step a, the shot distance d and the track spacing, arrange the detector array and the shot point on the survey line;

d. If n=3 single-source shot point data are selected to synthesize single-shot directional lighting shot point data, the first to nth shot points are arranged first, and these n shot points can be regarded as the first group of shot points for directional lighting exploration , arrange the geophone array according to the traditional geological exploration method, and set the first shot point according to the specified offset p, the distance between the shot point and the first geophone is: p ₁ = p, and the vibroseis For the seismic data of the first shot, the position of the geophone array remains unchanged, and the second shot point is placed. The distance between the shot point and the first geophone is p ₂ =p ₁ -d, and the vibroseis is obtained to obtain the second shot Seismic data: keep the location of the geophone array unchanged, install the third shot point, the distance between the shot point and the first geophone is p ₃ =p ₂ -d=p ₁ -2d, and obtain the third shot point of the vibroseis Shot seismic data. At this time, the seismic data acquisition of the first group of n shot points has been completed;

e. According to the traditional seismic exploration method, roll the geophone array, and then arrange the n+1th to 2nth shot points. These n shot points can be regarded as the second group of shot points for directional lighting exploration. During the data acquisition process of , the track spacing of the geophone array remains unchanged, and the n+1th shot point is set at a distance from the 1st geophone: p ₁ =p, that is, it is the same as the 1st The offsets of the two shot points are the same, and the seismic data of the fourth shot of the vibrator is obtained; the n+2th shot point is set at a distance from the first geophone: p ₂ =p ₁ -d, that is, the same as The offset distance of the second shot point in the first group is the same, and the seismic data of the fifth shot of the vibrator is obtained; the n+3th shot point is set at a distance from the first geophone: p ₃ =p ₂ - At the position of d=p ₁ -2d, the seismic data of the sixth shot of the vibrator is obtained; at this time, the seismic data acquisition of n shot points in the second group is completed; that is, the offsets of each shot point in the same synthetic group are different, The offset distances of the m shot points with a difference of n in the synthesized group numbers are the same;

f, and so on, continue to scroll the detector array;

g, arranging the n shot points of the next group, assuming that the group number is i, the sequence number of the n shot points corresponding to the i group in the total shot points is (i-1)×n+1 to For the (i-1)×n+n shot point, arrange the (i-1)×n+1 shot point, the distance between the shot point and the first geophone is p ₁ =p; then arrange the ( i-1)×n+2 shot points, the distance between the shot point and the first geophone is p ₂ =p ₁ -d; ..., then arrange the (i-1)×n+nth shot point , the distance between the shot point and the first geophone is:

p _n ＝p _n-1 -d＝p ₁ -(n-1)×d; obtain the (i-1)×n+1th to (i-1)×n+nth shots at the above n shot points Seismic data of the shot point;

h. Repeat steps f and g until all N shot seismic data are obtained

i. Divide the obtained single-shot seismic data into m groups, perform equal-interval time delay on the single-shot seismic data belonging to the same group according to the order of numbering, do linear superposition of the n single-shot seismic data after the delay, and synthesize a direction The directional illumination seismic signal corresponds to the directional seismic wave field, and the directional illumination seismic section based on a single source can be obtained by using the conventional seismic data processing method.

m: the number of directional lighting groups, that is, the grouping number of the total shot number in the directional lighting seismic method

n: the number of single-source shot points required to synthesize a directional lighting shot point, that is, the number of shot points per directional lighting synthesis group in the total shot number group

N: total number of shot points on the survey line

d: shot point distance

P: Offset

The purpose of the present invention can also be achieved in the following ways:

The shot pitch d is equal to or not equal to the track pitch; m in step b is an odd number >1.

The offset distance of each shot point in the same group is different, the offset distance of the first shot is p, the offset distance of the second shot is p2=p-d, the offset distance of the third shot is p3=p-2d, The offset of the fourth shot is p4=p-3d. The offset distance of each shot point in different groups is the same, the offset distance of the first shot in the first group is p, the offset distance of the first shot in the second group is also p, and the offset distance of the second shot in the first group is p2 =p-d, the offset distance of the second group of second guns is also p2=p-d, the offset distance of the first group of third guns is p3=p-2d, the offset distance of the second group of third guns is p3=p -2d.......

Design the offset and trace spacing according to the conventional reflection seismic exploration method; roughly estimate the depth and shape of the target with reference to the geological data of the survey area, and roughly determine the value range of the directional lighting delay control parameter τ; select the directional lighting superposition control parameter n, generally The value of n is related to the noise intensity of the survey area. The stronger the noise is, the larger the value of n is, and with the increase of the value of n, the computational complexity of the original single-shot records and synthetic directional illumination seismic signals that need to be acquired increases accordingly. It can be seen that the value of n should be considered as a compromise between the requirements of seismic exploration resolution and workload and cost.

Set up m groups of shot points on the survey line, each group contains n shots, that is, it contains N=n×m shot points in total, and each shot point is numbered 1, 2, ..., N in turn. The geophones are arranged collinearly and evenly, and the geophone array and the shot point are collinear. The position of the geophone array in the same synthesis group remains unchanged, the distance between the shot point and the first geophone is variable, and the offset distances of each shot point in the same synthesis group are different, that is, the offset distance of n shot points in the same group In turn, p, p-d, p-2d, ..., p-(n-1)d. The positions of shot points and geophone arrays of different synthesis groups are scrolled according to the set shot point distance d and track spacing. The offset distances of the m shot points with a difference of n in different groups of serial numbers are the same, that is, the offset distance of the m shot points of the 1st, n+1, 2n+1, ..., (m-1)×n+1 is p ; The 2nd, n+2, 2n+2, ..., (m-1) × n+2 the offset distance of the m shot points is p-d; the 3rd, n+3, 2n+3, ..., (m -1)×n+3, the offset distance of the m shot points is p-2d; ..., and so on, the offset distance of the nth, 2n, 3n, ..., m×n shot points is p -(n-1)d.

Specifically, single-vibrator single-shot seismic records with a total of N shots in m groups were obtained using the single-vibrator according to the above arrangement method. Using the directional illumination seismic signal synthesis method, using the first group of n single-source single-shot records labeled 1 to n to synthesize the first shot directional illumination single-shot record, the corresponding equivalent directional illumination shot point position of the record is (n +1)/2 The position of the shot point is the position of the middle shot point of the first group; use the n single-source single-shot records labeled n+1 to 2n in the second group to synthesize the second shot directional illumination single-shot record, The position of the equivalent directional lighting shot point corresponding to this record is the position of the n+(n+1)/2 shot point, that is, the position of the middle shot point of the second group; ...; similarly, using the m group label as (m -1) n single-source single-shot records from n+1 to m×n are combined to synthesize the m-th shot directional lighting single-shot record, and the corresponding equivalent directional lighting shot point position of the record is (m-1)n+(n+ 1)/2 The position of the shot point, that is, the position of the middle shot point of the m group; according to the above method, the m group of directional illumination single shot records can be synthesized. Its synthesis method has been disclosed by CN200810050992.3.

Seismic sections can be obtained by performing cross-correlation detection on seismic signals with directional illumination and using conventional seismic data processing methods and software.

Directional Lighting Seismic Wavefield Direction Calculation method:

According to the geological data of the survey area or the seismic data of a single source, the direction of directional lighting can be estimated. For an approximately horizontal target layer, set the offset as x and the depth of the target as h, and at this time the directional lighting direction can be estimated by

(公式1)，

(Formula 1),

Estimation method of directional lighting seismic delay control parameter τ:

Assuming that the shot distance is d, for an approximately horizontal target layer, when the average velocity of the overlying medium of the target layer is v, the delay parameter can be estimated by the following formula.

(公式2)

(Formula 2)

Synthesis method of single-shot seismic records with directional illumination:

Synthesize 1-shot directional illumination seismic data by using n-shot single-source data, and the synthesis method has been disclosed by CN200810050992.3.

Firstly, single source data of n shots are used to synthesize 1 shot directional illumination seismic data, and the quality of directional illumination seismic signal is analyzed. If the signal meets the expected signal-to-noise ratio requirements, determine n-shot single source data as a composite group, and synthesize 1-shot directional illumination seismic data; otherwise, adjust the parameters to re-determine the number of directional illumination shots required for a composite group. Finally, using the synthesized m-shot directional illumination seismic data, the conventional seismic data processing method is used to synthesize the seismic section.

Claims (3)

1. A method for directional illumination seismic exploration based on a single source, characterized in that it comprises the following sequence and steps: a. When carrying out exploration in the field, according to the geological data, determine the offset distance p, shot point distance d, trace spacing and the shot point position of each shot according to the traditional seismic prospecting method; here p refers to the distance between the first shot point and the first shot point The distance of the detector, that is, the offset p; b. According to the geological background and exploration requirements, determine the number of directional lighting groups m and the number of single-source shot points n required to synthesize a directional lighting shot point. Therefore, the total number of shots included in the directional lighting seismic survey is N=n×m, that is, the directional lighting The total number of seismic exploration shots is divided into m groups, and each group contains n shots single-source seismic data; c. According to the offset p set in step a, the shot distance d and the track spacing, arrange the detector array and the shot point on the survey line; d. Synthesize single-shot directional lighting shot point data by using n=3 single-source shot point data, and first arrange the 1st to nth shot points, and these n shot points can be regarded as the first group of shot points for directional lighting exploration, The geophone array is arranged according to the traditional geological prospecting method, and the first shot point is set according to the specified offset p. The distance between the shot point and the first geophone is: p ₁ = p. For the seismic data of the first shot, keep the position of the geophone array unchanged, arrange the second shot point, the distance between the shot point and the first geophone is p ₂ =p ₁ -d, and obtain the seismic data of the second shot of the vibrator; Keep the location of the geophone array unchanged, arrange the third shot point, the distance between the shot point and the first geophone is p ₃ =p ₂ -d=p ₁ -2d, and obtain the seismic data of the third shot of the vibrator, At this point, the seismic data acquisition of the first group of n shot points is completed; e. According to the traditional seismic exploration method, roll the geophone array, and then arrange the n+1th to 2nth shot points. These n shot points can be regarded as the second group of shot points for directional lighting exploration. During the data acquisition process of , the track spacing of the geophone array remains unchanged, and the n+1th shot point is set at a distance from the 1st geophone: p ₁ =p, that is, the distance from the 1st geophone of the 1st group The offset distances of the two shot points are the same, and the seismic data _of the fourth shot of the vibrator are obtained _; the n+2th shot point is set at a distance from the first geophone: The offset distance of the second shot point in group 1 is the same, and the seismic data of the fifth shot of the vibrator is obtained; the n+3th shot point is set at a distance from the first geophone: p ₃ =p ₂ -d= At the position of p ₁ -2d, the seismic data of the sixth shot of the vibrator is obtained; at this time, the seismic data acquisition of the second group of n shot points is completed, that is, the offset distances of each shot point in the same group are different, and the sequence numbers of different composite groups The offsets of the m shot points with a difference of n are the same; f, and so on, continue to scroll the detector array; g, arranging the n shot points of the next group, assuming that the group number is i, the sequence number of the n shot points corresponding to the i group in the total shot points is (i-1)×n+1 to For the (i-1)×n+n shot point, arrange the (i-1)×n+1 shot point, the distance between the shot point and the first geophone is p ₁ =p; then arrange the ( i-1)×n+2 shot points, the distance between the shot point and the first geophone is p ₂ =p ₁ -d; ..., then arrange the (i-1)×n+nth shot point , the distance between the shot point and the first geophone is: p _n ＝p _n-1 -d＝p ₁ -(n-1)×d; obtain the (i-1)×n+1th to (i-1)×n+nth shots at the above n shot points Seismic data of the shot point; h, repeating steps f and g until all N shot seismic data are obtained; i. Divide the obtained single-shot seismic data into m groups, perform equal-interval time delay on the single-shot seismic data belonging to the same group according to the order of numbering, do linear superposition of the n single-shot seismic data after the delay, and synthesize a direction The directional illumination seismic signal corresponds to the directional seismic wave field, and the directional illumination seismic section based on a single source can be obtained by using the conventional seismic data processing method. 2. The single-source-based directional illumination seismic exploration method according to claim 1, characterized in that the shot distance d is equal to or not equal to the trace distance. 3. The single-source-based directional illumination seismic exploration method according to claim 1, characterized in that m in step b is an odd number >1.

Images