CN102393533A

CN102393533A - Processing method for correcting uplink converted wave of vertical seismic profile (VSP) by using drilling track

Info

Publication number: CN102393533A
Application number: CN2011102169595A
Authority: CN
Inventors: 何晓冬; 吴永栓; 赵群; 王跃; 周枫; 刘路佳
Original assignee: China Petroleum and Chemical Corp; Sinopec Geophysical Research Institute
Current assignee: China Petroleum and Chemical Corp; Sinopec Geophysical Research Institute
Priority date: 2011-07-29
Filing date: 2011-07-29
Publication date: 2012-03-28

Abstract

The invention provides a processing method for correcting an uplink converted wave of a vertical seismic profile (VSP) by using a drilling track, and belongs to the field of geophysical exploration. In the method, a travel path and a travel speed of the uplink converted wave of the VSP are corrected by an actual petroleum drilling track and a deviation distance and an azimuth angle of a central vertical line, so that the processing error of the uplink converted wave of the VSP due to deviation of the drilling track from the central vertical line is eliminated. By the method, the error of uplink converted wave data of the VSP due to deviation of drilling track data from the central vertical line is corrected, the problem that the conventional VSP data is unsuccessfully processed due to large deviation from a central track is solved, the waste of exploration expenditure is reduced, and seismic exploration accuracy is improved.

Description

Processing method for correcting VSP (vertical seismic profile) uplink converted wave by using drilling track

Technical Field

The invention belongs to the field of geophysical exploration, and particularly relates to a method for correcting VSP (vertical seismic profile) uplink converted waves by using a drilling track.

Background

VSP (vertical seismic profile) data is typically processed assuming that the petroleum borehole is considered 90 degrees from the vertical, and substantially regardless of the deviation of the borehole from the central vertical due to construction considerations. With the increasing of the oil exploration degree, the requirements on the acquisition and processing precision of the VSP data are also increased, for example, the sensitivity of the VSP data to the speed requirement in the lithology exploration and the small-amplitude structure exploration is higher, and the speed precision requirement is high, so that the exploration effect is easily influenced when the speed has an error. Generally, the velocity obtained by the VSP and the logging velocity are both used as reference velocities to correct the seismic velocity, so that the VSP travel time path error can be caused by no correction when the drilling track deviates from a central vertical line and is processed, and the travel time path error further causes the velocity error obtained by the path calculation, thereby further influencing the exploration precision.

The existing VSP up-converted wave processing technology is processing under the assumption of vertical oil drilling. The travel time path calculation formula is as shown in formula (1):

s_{p} = \sqrt{x_{p}^{2} + H^{2}}

s = \sqrt{x_{p}^{2} + H^{2}} + \sqrt{{(x - x_{p})}^{2} + {(H - H_{R})}^{2}} - - - (1)

when the drilling trajectory deviates significantly from the central vertical line, a relatively large error occurs. The error is formula (2):

FIGS. 1 and 2 are examples of actual drilling trajectories that deviate from the central vertical line, where FIG. 1 is a plot of a well drilling trajectory that deviates significantly from the vertical line below 4200 meters, and the processed VSP data for this well below 4200 meters are unusable. Figure 2 is a plot of the drilling trajectory of another well, with the drilling trajectory deviating relatively large from the perpendicular bisector below 2000. The depth is larger, the target layer of exploration is provided, and the VSP time error is caused when the drilling track deviates from the central vertical line, so that the VSP data processed conventionally has larger error in the deep layer, and the VSP data cannot be explained if the VSP data is not corrected, and the seismic data explanation is influenced.

Also, instances where VSP data cannot be interpreted without correction, or affects seismic data interpretation, occur frequently because the well trajectory is too far off the central vertical line.

Disclosure of Invention

The invention aims to solve the problems in the prior art, and provides a processing method for correcting VSP uplink converted waves by using a drilling track, so that the time precision and the speed precision of the VSP are improved, the failure of conventional VSP data processing is reduced, the exploration expenditure efficiency is improved, and accurate VSP processing data are provided for lithological exploration, small-amplitude structure exploration and complex area exploration.

The invention is realized by the following technical scheme:

a method for correcting VSP up-conversion waves by using a drilling track corrects a travel time path and a travel time speed of the VSP up-conversion waves by using a deviation distance and an azimuth angle between an actual petroleum drilling track and a central vertical line, and eliminates an error of VSP up-conversion wave processing caused by deviation of the drilling track from the central vertical line; the method comprises the steps of firstly obtaining all actual travel time paths and theoretical travel time paths, then calculating each depth to obtain travel time path errors, and then adding or subtracting the travel time path errors by the actual travel time paths to obtain accurate travel time paths, so that all errors are corrected to a reference line, namely a central vertical line of a well mouth of a drilling well.

The method comprises the following steps:

(1) data entry, comprising:

(11) inputting drilling track data: drilling depth H_RA well inclination angle gamma and an azimuth angle alpha, wherein the well inclination angle gamma is the angle between the well and the vertical line, and the azimuth angle alpha is the depth point H of the well_RAzimuth from the central vertical;

(12) VSP data input: offset x, azimuth angle β of the wellhead to the surface seismic source VSP shot, where offset x is the distance from the drilling wellhead to the surface seismic source VSP shot; the azimuth angle beta of the well mouth and the ground seismic source VSP shot point is the azimuth angle of the well mouth and the ground seismic source VSP shot point by taking the well mouth as an origin;

(2) calculating x₁、d、s、s₁、x_pAnd x_p1：

d＝H_R·tgγ；

s = \sqrt{x_{p}^{2} + H^{2}} + \sqrt{{(x - x_{p})}^{2} + {(H - H_{R})}^{2}}

s_{1} = \sqrt{x_{p 1}^{2} + H^{2}} + \sqrt{{(x_{1} - x_{p 1})}^{2} + {(H - H_{R})}^{2}}

Wherein,

d is the depth H of the VSP detector in the well_RDistance from the perpendicular bisector;

x is the distance from the well mouth to the ground seismic source VSP shot point;

H_Rfor the depth of the point of acceptance of the VSP receiver in the well, i.e. the borehole depth H_R；

s: the travel time path from a ground seismic source VSP shot point to a VSP wave detector in a theoretical vertical well drilling is defined;

s₁the travel time path from the ground seismic source VSP shot point to the VSP wave detector wave in the actual drilling well is defined;

theta is an included angle of a horizontal plane projected by a VSP wave detector and a ground seismic source VSP shot point by taking the well mouth as an original point; when the angle is less than or equal to 180 degrees, theta is equal to alpha-beta, and when the angle is more than 180 degrees, theta is equal to alpha-beta-180 degrees;

x_prepresenting the distance between the horizontal position of the vertical projection of the theoretical reflection point to the ground and the shot point of the ground seismic source VSP;

x_p1representing the distance between the horizontal position of the vertical projection of the actual reflection point to the ground and the shot point of the ground seismic source VSP;

(3) computing depth H of VSP detector_RThe travel time path error when the depth of the reflecting interface is H:

(4) and (3) error analysis: and (4) after correcting the VSP up-converted wave path by using the travel time path error of the VSP up-converted wave obtained in the step (3), correcting the speed of an up-going transverse wave part, and analyzing the speed error of the up-going transverse wave part.

The method for correcting the VSP up-converted wave path in step (4) is as follows: when the actual travel time path is larger than the theoretical travel time path at the corrected depth point by taking the theoretical vertical well drilling perpendicular bisector as a reference, subtracting the travel time path error from the actual travel time path to obtain an accurate travel time path; and when the actual travel time path is smaller than the theoretical travel time path, adding the actual travel time path and the travel time path error to obtain the accurate travel time path.

The speed correction method in the step (4) comprises the following steps: the corrected speed is the precise travel path/travel time.

The method for analyzing the speed error in the step (4) comprises the following steps: the original speed is the theoretical travel path/travel time, the corrected speed is the accurate travel path/travel time, and the two are compared to obtain the speed error.

Compared with the prior art, the invention has the beneficial effects that:

(1) the method solves the problem of VSP exploration, and improves the time precision and speed precision of VSP data processing;

(2) the method reduces the failure of conventional VSP data processing and reduces the waste of exploration expenditure;

(3) the method provides accurate VSP processing data for lithology exploration, small-amplitude structure exploration and complex area exploration;

(4) the method of the invention combines the well drilling data and the VSP data to be applied, and also expands the application range of exploration data.

Drawings

FIG. 1 is a prior art well trajectory diagram.

FIG. 2 is a prior art well trajectory diagram.

FIG. 3 is a schematic graph of VSP up-conversion travel time.

FIG. 4 is a projection of the wellhead, VSP receivers and seismic source onto a horizontal plane.

FIG. 5 is a schematic view of the drilling trajectory travel time

Fig. 6 is a block diagram of the steps of the method of the present invention.

FIG. 7 is a comparison graph of the travel time path of the conventional method (theoretical travel time path) and the travel time path of the drilling trajectory (accurate travel time path) of the converted wave at a certain well offset distance of 120m, an azimuth angle of 340 degrees and a reflecting layer depth of 6000m in the embodiment of the invention. Data are from columns 6 and 7 of table 1.

FIG. 8 is a comparison of the conventional method travel time (theoretical travel time) and the travel time (accurate travel time) of the converted wave up to a certain well offset of 120 meters, azimuth angle of 340 degrees and depth of reflection layer of 6000 meters in an embodiment of the invention. Data are from columns 8 and 9 of table 1.

FIG. 9 is a plot of the converted wave travel time error for a well at 120 meters offset, 340 degrees azimuth, and 6000 meters depth of reflector in an embodiment of the invention. Data are from column 10 of table 1.

FIG. 10 is a comparison graph of the travel time path of the conventional method (theoretical travel time path) and the travel time path of the drilling trajectory (accurate travel time path) of the converted wave at a certain well offset distance of 2400 m, an azimuth angle of 140 degrees and a reflection layer depth of 6000m in the embodiment of the invention. Data are from columns 6 and 7 of table 2.

FIG. 11 is a comparison graph of the conventional method travel time (theoretical travel time) and the travel time (accurate travel time) of the converted wave at a certain well offset distance of 2400 m, an azimuth angle of 140 degrees and a reflecting layer depth of 6000m in the embodiment of the invention. Data source table 2 columns 8 and 9.

FIG. 12 is a diagram of the travel time error of the up-converted wave at a well offset distance of 2400 m, an azimuth angle of 140 degrees and a reflection depth of 6000m in the embodiment of the invention. Data are from column 10 of table 2.

Fig. 13 is a comparison graph of the travel time path of the conventional method (theoretical travel time path) and the travel time path of the drilling trajectory (accurate travel time path) of the converted wave at a certain well offset distance of 2400 m, an azimuth angle of 220 degrees and a reflecting layer depth of 6000m in the embodiment of the invention. Data are from columns 6 and 7 of table 5.

FIG. 14 is a graph comparing the conventional method travel time (theoretical travel time) and the travel time (accurate travel time) of the converted wave at a certain well offset distance of 2400 m, an azimuth angle of 220 degrees and a reflecting layer depth of 6000m in the embodiment of the invention. Data are from columns 8 and 9 of table 5.

FIG. 15 is a diagram of the travel time error of the up-converted wave at a well offset distance of 2400 m, an azimuth angle of 220 degrees and a reflection depth of 6000m in the embodiment of the invention. Data are from column 10 of table 2.

Detailed Description

The invention is described in further detail below with reference to the accompanying drawings:

a processing method for correcting VSP up-converted waves by using a drilling track, wherein the method can convert (x, y, z) coordinates of a three-dimensional space drilling bit in a well by using the deviation distance and azimuth angle of an actual petroleum drilling track from a central vertical line, wherein the group (H, gamma, alpha) of data is the position of the drilling bit in the well (the 1-3 columns in the table 1-5 are the group of data); correcting the travel path or travel speed of the VSP up-converted wave, and eliminating the error of VSP up-converted wave processing caused by deviation of a drilling track from a central vertical line.

As shown in fig. 6, the method comprises the steps of:

(1) data entry, comprising:

(2) calculating d, x₁、s、s₁、x_pAnd x_p1Wherein

d＝H_R·tgγ；

s = \sqrt{x_{p}^{2} + H^{2}} + \sqrt{{(x - x_{p})}^{2} + {(H - H_{R})}^{2}}

s_{1} = \sqrt{x_{p 1}^{2} + H^{2}} + \sqrt{{(x_{1} - x_{p 1})}^{2} + {(H - H_{R})}^{2}} - - - (3)

wherein:

theta is an included angle of a projection of a VSP wave detector and a shot point of a ground seismic source VSP on a horizontal plane by taking a well head as an original point, when the angle is less than or equal to 180 degrees, the angle is alpha-beta, and when the angle is more than 180 degrees, the angle is alpha-beta-180 degrees;

the point of processing in the up-converted wave correction method is always below HR, i.e. H is always greater than the depth of HR processing and is the reflected wave.

(4) And (3) error analysis: after the VSP up-converted wave error is obtained in step (3), the up-converted wave path is corrected, so that the speed correction of the up-converted wave portion (the up-converted wave is also called up-converted wave because the incident is longitudinal wave and the reflection is transverse wave, and the up-converted wave is also called up-converted wave because the speed correction of the transverse wave portion is mentioned) can be performed, and the speed error analysis of the up-converted wave portion can also be performed.

The VSP up-conversion wave travel time path error correction is similar to static correction of ground longitudinal wave seismic exploration, and based on a theoretical vertical well drilling perpendicular bisector, when an actual travel time path is larger than a theoretical travel time path (the travel time path error value in the 4 th column of tables 1-5 is a positive value), the value is subtracted at a corrected depth point, namely: s- □ s; when the actual travel time path is smaller than the theoretical travel time path (the error value of the travel time path in the 4 th column of tables 1-5 is a negative value) at the corrected depth point, the value is added, namely: s + □ s.

And (3) analyzing a speed error: that is, the original speed before correction is: theoretical travel path/travel time; the speed after the travel time path correction analysis is as follows: the travel time path/travel time is accurate, and error analysis and correction can be carried out by comparing the two speeds; the VSP velocity analysis method is a well-established technique.

In step (2), x_pAnd x_p1The solving method of (2) is as follows:

because seismic and VSP data processing are based on homogeneous medium (i.e., a horizontal reflection interface) models, the VSP utility formula is based on such models.

The P-wave reflection angle and the SV-wave reflection angle, x, are represented by alpha and beta, respectively_pRepresenting the distance between the horizontal position of the vertical projection of the reflection point to the ground and the shot point of the ground seismic source VSP, H representing the depth of the reflection point, H_RIndicating the depth of the detector, H-H_RRepresenting the distance of the detector from the reflecting surface (as shown in FIG. 5), from Snell's law

Give γ, where v_p V_pIs the velocity of longitudinal wave, v_sIs the shear wave velocity.

Processing observed VSP data allows determination of H_R、x、v_pEquivalently, H in FIG. 5 can be the velocity v in the seismic data on the ground_pAnd two-way travel time t₀To represent

X is then_pCan be obtained by a numerical method.

From FIG. 5, assume that H is known_R、x、x_pH is equal to

Order to

Wherein H is H-H_RThen x can be solved by the following equation (8)_p。

Squaring two sides of the formula (7) to obtain

Through simplification and arrangement, the product is obtained

The algebraic equation is solved by a Newton-Rayleigh method, namely the formula (9) is expressed as F (xp) ═ 0, and then the first derivative of F (xp) is expressed as the following formula

Iterative formula

With an initial value of iteration of

Thus obtaining x_pThe value of (c).

For the same reason x_p1And x_pThe calculation method is the same.

Tables 1 through 5 are VSP actual data and well trajectory data for a well and error analysis using these data, and tables 1 through 5 are comparative analysis results of the prior art method and the present invention method. When the average speed of the longitudinal wave is 3000 m/s, the converted wave is transmitted upwards when the longitudinal wave speed is 1.73 times of the transverse wave speed, and errors of different reflection depths of 3000 m, 4500 m and 6000m, and when the azimuth angle is 340 degrees at the offset distance of 120m, the azimuth angle is 2400 m, the azimuth angle is 140 degrees and the azimuth angle is 220 degrees at the offset distance of 2400 m are analyzed.

Fig. 7 to 15 are graphs showing the results of comparative analysis of the conventional method and the method of the present invention, based on the travel time path analysis, the travel time analysis, and the travel time error analysis shown in tables 1, 2, and 5.

From the above data analysis, it can be concluded that there are errors in the observation depth segments that are all different in size. The data corrected with the non-drilling trajectory data for actual production is erroneous:

1, the VSP up-converted wave error is relatively small at zero offset (120 meters), as shown in fig. 9, the travel time error is 8.4ms at an offset of 120m and an azimuth angle of 340 degrees and a depth of 5075 meters. This shows that the VSP up-converted wave error is small at zero offset (120 meters).

2, when there is an offset, the VSP up-converted wave error is large, as shown in fig. 12 and fig. 15, fig. 12 is an error analysis with an offset of 2400 meters, an azimuth angle of 140 degrees, and a reflection depth of 6000m, and the maximum error range is-55.5 ms to 19.5ms, and the maximum error amplitude difference is 75 ms. FIG. 15 shows the error analysis of the reflection depth of 6000m at the azimuth angle of 220 degrees at the offset distance of 2400 m, the maximum error range is-11.1 ms-34.1ms, and the maximum error amplitude difference is 45.2 ms. This shows that the errors generated by excitation at different azimuth angles of the seismic source are different; when the offset distance is large, the uplink converted wave error of the VSP is large.

From the above analysis it can be concluded that: the method can find out the error between the travel time path (theoretical travel time path) of the common method and the travel time path (accurate travel time path) of the drilling track; with static correction similar to ground longitudinal wave seismic exploration, based on a theoretical vertical well drilling perpendicular bisector, when an actual travel time path is larger than a theoretical travel time path (the error value of the travel time path in the 4 th column of tables 1-5 is a positive value) at a corrected depth point, subtracting the value to obtain: s- □ s; when the actual travel time path is smaller than the theoretical travel time path (the error value of the travel time path in the 4 th column of tables 1-5 is a negative value) at the corrected depth point, the value is added, namely: s + □ s. Correcting errors in the VSP process caused by the deviation of the drilling trajectory from the central vertical line; the effect is more obvious particularly when the drilling track deviates from the central vertical line by a large distance, and the method can solve the practical production problem.

After the VSP up converted wave path is corrected, the up transverse wave speed correction can be carried out, and the transverse wave speed error analysis can also be carried out.

The method can correct the error of the uplink converted wave data of the VSP of the drilling track data deviating from the central vertical line, solves the problem of processing failure of the conventional VSP data caused by too much deviation of part of the drilling track, reduces the waste of exploration expenditure, and improves the seismic exploration precision. The correction method is used for correcting the VSP uplink converted wave data under the condition of an isotropic medium by using the azimuth and deviation data of the drilling track, and the accuracy degree is high. There is a certain error in using under the assumption of anisotropic heterogeneous media.

The above-described embodiment is only one embodiment of the present invention, and it will be apparent to those skilled in the art that various modifications and variations can be easily made based on the application and principle of the present invention disclosed in the present application, and the present invention is not limited to the method described in the above-described embodiment of the present invention, so that the above-described embodiment is only preferred, and not restrictive.

Claims

1. A method for correcting VSP up-converted waves by using a drilling track is characterized by comprising the following steps: the method corrects the travel path and the travel speed of the VSP uplink converted wave by using the deviation distance and the azimuth angle of the actual petroleum drilling track and the central vertical line, and eliminates the error of VSP uplink converted wave processing caused by the deviation of the drilling track from the central vertical line; the method comprises the steps of firstly obtaining all actual travel time paths and theoretical travel time paths, then calculating each depth to obtain travel time path errors, and then adding or subtracting the travel time path errors by the actual travel time paths to obtain accurate travel time paths, so that all errors are corrected to a reference line, namely a central vertical line of a well mouth of a drilling well.

2. The method of processing to correct VSP upconverted waves using well trajectory of claim 1, wherein: the method comprises the following steps:

(1) data entry, comprising:

(2) calculating x₁、d、s、s₁、x_pAnd x_p1：

d＝H_R·tgγ；

s = \sqrt{x_{p}^{2} + H^{2}} + \sqrt{{(x - x_{p})}^{2} + {(H - H_{R})}^{2}}

s_{1} = \sqrt{x_{p 1}^{2} + H^{2}} + \sqrt{{(x_{1} - x_{p 1})}^{2} + {(H - H_{R})}^{2}}

Wherein,

s is a theoretical travel path, namely the travel path from a ground seismic source VSP shot point to a VSP wave detector in a theoretical vertical drilling well;

s₁the method comprises the following steps of (1) obtaining an actual travel time path, namely the travel time path from a ground seismic source VSP shot point to a VSP wave detector wave in an actual well;

3. The method of processing to correct VSP upconverted waves using well trajectory of claim 2, wherein: the method for correcting the VSP up-converted wave path in step (4) is as follows: when the actual travel time path is larger than the theoretical travel time path at the corrected depth point by taking the theoretical vertical well drilling perpendicular bisector as a reference, subtracting the travel time path error from the actual travel time path to obtain an accurate travel time path; and when the actual travel time path is smaller than the theoretical travel time path, adding the actual travel time path and the travel time path error to obtain the accurate travel time path.

4. The method of claim 3, wherein the step of correcting the VSP upconverted wave using the well trajectory comprises the steps of: the speed correction method in the step (4) comprises the following steps: the corrected speed is the precise travel path/travel time.

5. The method of processing to correct VSP up-converted waves using well trajectory of claim 4, wherein: the method for analyzing the speed error in the step (4) comprises the following steps: the original speed is the theoretical travel path/travel time, the corrected speed is the accurate travel path/travel time, and the two are compared to obtain the speed error.