A method for determining coordinates of each channel of a distributed seismic acquisition optical fiber

Abstract

The application discloses a kind of methods for determining the coordinates of each channel of distributed seismic acquisition optical fiber.The application adopts multiple seismic sources near the optical cable straight line and obtains intercept vector to the foot of optical cable straight line, multiple seismic sources excite seismic signal, optical fiber receives seismic signal to obtain first arrival channel vector, linear fitting is carried out to intercept vector and first arrival channel vector, and the coordinates of each channel on the optical fiber in the optical cable are obtained;By the application, the coordinates of each channel on the optical fiber in the optical cable of any structure can be obtained, whether the optical fiber in the optical cable is arranged in a straight line or in a spiral or in other shapes;When the optical cable is moved along the optical cable straight line, it is not necessary to know where the optical cable is moved to, and the coordinates of each channel on the optical fiber in the optical cable can be obtained by the application;The application has good application prospect in two-dimensional or three-dimensional seismic exploration and surface towed exploration.

Description

Technical Field

[0001] This invention relates to optical fiber technology, and more specifically to a method for determining the coordinates of each trace of a distributed seismic acquisition optical fiber. Background Technology

[0002] Distributed acoustic sensing (DAS) technology enables high-density acquisition of seismic wave signals using a single optical fiber cable, and is increasingly being applied in fields such as oil and gas field exploration and geophysical exploration. The sensor in a DAS system is an optical fiber cable containing one or more optical fibers arranged linearly or spirally. Using DAS technology, the optical fiber itself acts as a spatially continuous distributed acoustic sensor. After digital discretization, it can achieve high-density acquisition with a channel spacing of less than 1 meter. Each channel on the fiber is equivalent to a detector. For seismic data interpretation, the coordinates of each detector are needed, i.e., the coordinates of each channel of the distributed acoustic sensor. Although meter marks can be inscribed on the outside of the optical fiber cable to indicate its different positions, there is not a one-to-one correspondence between the optical fiber and the cable. For linearly arranged optical fibers, there is usually a certain margin, meaning the length of the optical fiber is greater than the length of the cable. Therefore, determining the position of the internal optical fibers using the cable is inaccurate. For helical optical fibers, the fiber length is much greater than the cable length because the fiber is helical. In addition, due to process errors during production, the pitch and helix angle of the fiber at different positions are different, making it more difficult to determine the location of the internal fiber directly from the external dimensions of the cable. Summary of the Invention

[0003] To address the technical problem of inaccurate determination of the coordinates of each track on the optical fiber in distributed seismic acquisition optical cables, this invention proposes a method for determining the coordinates of each track on the optical fiber in distributed seismic acquisition optical cables. For optical cables of any structure, the coordinates of each track on the internal optical fiber can be obtained.

[0004] The method for determining the coordinates of each trace of a distributed seismic acquisition fiber optic cable according to the present invention includes the following steps:

[0005] 1) The optical cable is laid in a straight line. The straight line in which the optical cable is laid is called the optical cable straight line. The optical cable can move arbitrarily along the optical cable straight line.

[0006] 2) N seismic sources are deployed near the optical cable, namely the first to the Nth seismic source, where N is a natural number ≥ 2;

[0007] 3) Select any two points on the straight line of the optical cable as the first coordinate point and the second coordinate point, and obtain the coordinates (x, y) of the first coordinate point using a measuring instrument. o1 ,y o1 ) and the coordinates of the second coordinate point (x)o2 ,y o2 The equation of the straight line of the optical cable is calculated from the coordinates of the first and second coordinate points.

[0008] y = k o x+b o (1)

[0009] Where, k o Let be the slope of the straight optical cable. b o This is the straight-line intercept of the optical cable. 4) The coordinates of the first to Nth earthquake sources were obtained using a position coordinate measuring instrument. The coordinates of the nth earthquake source were (x... sn ,y sn ), n=1,…N;

[0010] 5) Draw perpendicular lines from the first to the Nth seismic source to the straight line of the optical cable. The intersection point is called the foot of the perpendicular. Based on the equation of the straight line of the optical cable and the coordinates of the first to the Nth seismic source, calculate the coordinates of the first to the Nth feet of the perpendicular:

[0011]

[0012] y pn =k o x sn +b o (3)

[0013] Where, x pn Let y be the x-coordinate of the foot of the nth perpendicular. pn Let be the ordinate of the nth perpendicular foot;

[0014] 6) Calculate the intercepts of the first to Nth perpendiculars on the straight line of the optical cable, using the coordinates of the first to Nth perpendiculars.

[0015] The intercept of the nth perpendicular foot on the straight line of the optical cable is defined as the distance from the nth perpendicular foot to the first coordinate point on the straight line of the optical cable:

[0016]

[0017] Among them, L n Let L be the intercept of the nth perpendicular on the straight line of the optical cable; the intercepts of the first to Nth perpendiculars on the straight line of the optical cable are denoted as the intercept vector [L1, L2, ..., L]. N ];

[0018] 7) The first to the Nth source-excited seismic signals are excited, the excited seismic waves propagate on the optical cable, the optical fiber distributed acoustic sensor receives the seismic signals, and a seismic signal graph is obtained, on which the first to the Nth source-excited seismic signals obtained by the optical fiber distributed acoustic sensor are found out, the first to the Nth source-excited seismic signals are the first received seismic signals, and the first to the Nth source-excited seismic signals are denoted as T n , the first to the Nth source-excited seismic signals are denoted as a first to an Nth trace vector

[0019] [T1, T2, …, T N ];

[0020] 8) Linear fitting is performed on the first to the Nth trace vector [T1, T2, …, T N ] and the intercept vector [L1, L2, …, L N ], and a fitting straight line equation of the trace and the intercept is obtained:

[0021] L=kT+b (5)

[0022] , T is the serial number of the trace, L is the intercept of the foot on the optical cable straight line, k is the slope of the fitting straight line, and b is the intercept of the fitting straight line;

[0023] 9) The coordinates (x T , y T ) of the Tth trace on the optical fiber satisfy the following relationship:

[0024] (x T -x o1 ) 2 +(y T -y o1 ) 2 =L 2 (6)

[0025] y T =k o x T +b o (7)

[0026] 10) The coordinates of the Tth trace on the optical fiber are calculated by using the straight line equation of the optical cable straight line and the fitting straight line equation of the trace and the intercept:

[0027]

[0028]

[0029] In step 1), the arrangement form of the optical fibers in the optical cable can be any form, a straight line arrangement or a spiral arrangement or an arbitrary shape arrangement.

[0030] In step 2), the seismic source is positioned within the vertical range at both ends of the optical cable, ensuring that the foot of the plumb line falls on the optical cable. The distance between the seismic source and the optical cable is greater than 1 meter and less than 10 kilometers. The seismic source is an artificial seismic source, such as an explosive seismic source, a hammer seismic source, an electric spark seismic source, an air gun seismic source, or a controlled seismic source.

[0031] In step 3), the position coordinate measuring instrument is a GPS measuring instrument, a theodolite, or a navigator.

[0032] Advantages of this invention:

[0033] This invention can obtain the coordinates of each fiber inside an optical cable; it can also obtain the coordinates of each fiber inside an optical cable of any structure, regardless of whether the fibers are arranged in a straight line, spiral, or other shapes; when the optical cable moves arbitrarily along a straight line, without needing to know where the cable has moved, this invention can obtain the coordinates of each fiber inside the optical cable; this invention has excellent application prospects in two-dimensional or three-dimensional seismic exploration and surface towed exploration. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the method for determining the coordinates of each trace of a distributed seismic acquisition fiber according to the present invention;

[0035] Figure 2 A schematic diagram of the first arrival trace obtained from the seismic signal map, based on the method for determining the coordinates of each trace of a distributed seismic acquisition fiber according to the present invention. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0037] The method for determining the coordinates of each trace of a distributed seismic acquisition fiber in this embodiment includes the following steps:

[0038] 1) The optical cable is laid in a straight line. The arrangement of the optical fibers in the optical cable can be arbitrary. The straight line in which the optical cable is located is called the optical cable straight line. The optical cable can move arbitrarily along the optical cable straight line.

[0039] 2) Install N seismic sources within the perpendicular range at both ends of the optical cable, ensuring that the foot of the plumb line falls on the optical cable. The distance between the seismic sources and the optical cable should be greater than 1 meter, and can reach several kilometers or even ten kilometers in some cases. The seismic sources are explosive sources, designated as the first to the Nth seismic sources, where N is a natural number ≥ 2. Figure 1 As shown;

[0040] 3) Select any two points on the straight line of the optical cable as the first coordinate point and the second coordinate point, and obtain the coordinates (x, y) of the first coordinate point using a GPS measuring instrument. o1 ,y o1 ) and the coordinates of the second coordinate point (x)o2 ,y o2 ), and by the coordinates of the first coordinate point and the second

[0041] The equation of the optical cable is obtained by calculating the coordinates of the two coordinate points:

[0042] y = k o x+b o (1)

[0043] Where, k o Let be the slope of the straight optical cable. b o This is the straight-line intercept of the optical cable. 4) The coordinates of the first to Nth earthquake sources were obtained using a GPS measuring instrument. The coordinates of the nth earthquake source are (x... sn ,y sn ), n=1,…N; 5) Draw perpendicular lines from the first to the Nth seismic source to the optical cable line respectively, and the intersection point is called the foot of the perpendicular, thus obtaining the first to the Nth feet of the perpendicular.

[0044] Based on the equation of the optical cable and the coordinates of the first to Nth seismic sources, the coordinates of the first to Nth perpendicular feet are calculated as follows:

[0045]

[0046] y pn =k o x sn +b o (3)

[0047] Where, x pn Let y be the x-coordinate of the foot of the nth perpendicular. pn Let be the ordinate of the nth perpendicular foot;

[0048] 6) Calculate the intercepts of the first to Nth perpendiculars on the straight line of the optical cable, using the coordinates of the first to Nth perpendiculars.

[0049] The intercept of the nth perpendicular foot on the straight line of the optical cable is defined as the distance from the nth perpendicular foot to the first coordinate point on the straight line of the optical cable:

[0050]

[0051] Among them, L n Let L be the intercept of the nth perpendicular on the straight line of the optical cable; the intercepts of the first to Nth perpendiculars on the straight line of the optical cable are denoted as the intercept vector [L1, L2, ..., L]. N ];

[0052] 7) The first to Nth earthquake sources generate seismic signals, and the generated seismic waves propagate onto the optical cable. The fiber optic distributed acoustic wave sensor receives the seismic signals and obtains a seismic signal map. The first arrival traces of the seismic signals generated by the first to Nth earthquake sources, as obtained by the fiber optic distributed acoustic wave sensor, are located on the seismic signal map. Figure 2 As shown, Figure 2 The horizontal axis represents the trace number, and the vertical axis represents time. The first arrival trace is the trace that received the seismic signal first. The first arrival trace corresponding to the nth source is denoted as T. n The first to Nth source earthquakes are denoted as the first to Nth source earthquake vectors [T1, T2, ..., T]. N ];

[0053] 8) For the intercept vector [L1,L2,…,L…] N ] and the initial arrival vector [T1,T2,…,T N By performing linear fitting, the equation of the fitted line between the trace and the intercept is obtained:

[0054] L=kT+b (5)

[0055] Where T is the channel number, L is the intercept of the perpendicular on the straight line of the optical cable, k is the slope of the fitted line, and b is the intercept of the fitted line.

[0056] 9) The coordinates (x, y) of the T-th channel on the optical fiber T ,y T ), satisfying the following relationship:

[0057] (x T -x o1 ) 2 +(y T -y o1 ) 2 =L 2 (6)

[0058] y T =k o x T +b o (7)

[0059] 10) Using the linear equation of the optical cable and the fitted linear equation of the channel and intercept, the coordinates of the T-th channel on the optical fiber are calculated:

[0060]

[0061]

[0062] Finally, it is to be understood that the embodiments are for purposes of illustration only and that various changes and modifications can be made by those skilled in the art without departing from the scope of the application as disclosed in the specification and appended claims. Therefore, the scope of the application is not to be limited to the embodiments disclosed but is to be accorded the full scope permissible by the appended claims.

Claims

1. A method of determining coordinates of each channel of a distributed seismic acquisition optical fiber, characterized in that, The method comprises the following steps: 1) arranging the optical cable in a straight line, the straight line where the optical cable is arranged being referred to as an optical cable straight line, and the optical cable being capable of being moved arbitrarily along the optical cable straight line; 2) arranging N seismic sources on one side or both sides of the optical fiber, the N seismic sources being respectively referred to as a first seismic source to an Nth seismic source, N being a natural number greater than or equal to 2; 3) Select any two points on the straight line of the optical cable as the first coordinate point and the second coordinate point, respectively, and obtain the coordinates (x o1 ,y o1 ) of the first coordinate point and the coordinates (x o2 ,y o2 ) of the second coordinate point through the measuring instrument, and calculate the straight line equation of the optical cable straight line from the coordinates of the first coordinate point and the coordinates of the second coordinate point: y = k o x + b o (1) wherein k o is the slope of the optical cable straight line, b o is the intercept of the optical cable straight line, 4) get the first to the Nth seismic source coordinates by position coordinate measuring instrument, the nth seismic source coordinate is (x sn ,y sn ), n = 1, … N; 5) respectively drawing a perpendicular line from the first seismic source to the Nth seismic source to the optical cable straight line, the intersection point being referred to as a foot point, and first to Nth foot points being obtained, and the first to Nth foot point coordinates being calculated according to the straight line equation of the optical cable straight line and the coordinates of the first to Nth seismic sources; y pn = k o x sn + b o (3) where x pn is the horizontal coordinate of the nth foot, y pn is the vertical coordinate of the nth foot; 6) the intercepts of the first to Nth foot points on the optical cable straight line are calculated in sequence according to the first to Nth foot point coordinates, the intercept of the nth foot point on the optical cable straight line being defined as the distance from the nth foot point to the first coordinate point on the optical cable straight line: wherein L n is the intercept of the nth foot on the optical cable straight line; the intercepts of the first to the Nth foot on the optical cable straight line are denoted as intercept vector [L1, L2, …, LN] N ]. 7) the first to the Nth seismic source excitation seismic signals, the excited seismic waves propagate on the optical cable, the optical fiber distributed acoustic sensor receives the seismic signals, and obtains a seismic signal graph, and the first to the Nth seismic source excitation seismic signals obtained by the optical fiber distributed acoustic sensor are found on the seismic signal graph The first arrival trace is the first received seismic signal, and the first arrival trace corresponding to the nth seismic source is denoted as T n , the first to the Nth seismic source corresponding to the first arrival trace is denoted as the first arrival trace vector [T1, T2, …, T N ] 8) Linear fitting of the first arrival vector [T1, T2, …, T N ] and intercept vector [L1, L2, …, L N ] to obtain the fitting straight line equation of the trace and intercept. L = kT + b (5) wherein T is the serial number of the channel, L is the intercept of the foot point on the optical cable straight line, k is the slope of the fitting straight line, and b is the intercept of the fitting straight line; 9) coordinates (x T ,y T ) of the Tth track on the optical fiber, satisfying the following relation: (x T -x o1 ) 2 +(y T -y o1 ) 2 = L 2 (6) y T = k o x T + b o (7) 10) the coordinates of the Tth channel on the optical fiber are calculated according to the straight line equation of the optical cable straight line and the fitting straight line equation of the channel and the intercept; 2. The method of claim 1, wherein, In the step 1), the arrangement form of the optical fiber in the optical cable can be any form.

3. The method of claim 1, wherein, In the step 2), the seismic sources are arranged within the perpendicular line range of the two ends of the optical cable, the foot point falls on the optical cable, and the distance between the seismic source and the optical cable is greater than 1 meter and less than 10 kilometers.

4. The method of claim 1, wherein, In the step 2), the seismic source is an artificial seismic source.

5. The method of claim 1, wherein, In the step 3), the position coordinate measuring instrument is a GPS measuring instrument, a theodolite or a navigator. In the step 4), the seismic source is an artificial seismic source. In the step 5), the position coordinate measuring instrument is a GPS measuring instrument, a theodolite or a navigator.

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