CN102411155A - Processing method for correcting VSP (vertical seismic profile) downgoing transmission converted wave by drilling path - Google Patents

Abstract

The invention provides a processing method for correcting a VSP (vertical seismic profile) downgoing transmission converted wave by a drilling path, and belongs to the field of geophysical exploration. The method is characterized in that the travel route and travel speed of the VSP downgoing transmission converted wave are corrected according to the offset distance and azimuth angle between an actual petroleum drilling path and a centre vertical line, which eliminates the processing error of the VSP downgoing transmission converted wave caused by deviation of the drilling path from the centre vertical line. The processing method provided by the invention has the beneficial effects of correcting the data error of the VSP downgoing transmission converted wave caused by data deviation of the drilling path from the centre vertical line, solving the problem of failure in processing the conventional VSP data caused by partial excessive deviation of the drilling path from the centre vertical line, reducing waste of exploration expenditure, and improving seismic exploration precision.

Description

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

Technical Field

The invention belongs to the field of geophysical exploration, and particularly relates to a processing method for correcting VSP (vertical seismic profiling) downlink transmission 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 downlink transmission converted wave processing technology is to process under the condition of assuming that an oil well is vertical. The travel time path calculation formula is as shown in formula (1):

$s=\sqrt{x_p^2+H^2}+\sqrt{{(x-x_p)}^2+{(H-H_R)}^2}---\left(1\right)$

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

<math> <mrow> <mi>&Delta;s</mi> <mo>=</mo> <msub> <mi>s</mi> <mn>1</mn> </msub> <mo>-</mo> <mi>s</mi> <mo>=</mo> <msqrt> <msubsup> <mi>x</mi> <mrow> <mi>p</mi> <mn>1</mn> </mrow> <mn>2</mn> </msubsup> <mo>+</mo> <msup> <mi>H</mi> <mn>2</mn> </msup> </msqrt> <mo>+</mo> <msqrt> <msup> <mrow> <mo>(</mo> <msub> <mi>x</mi> <mn>1</mn> </msub> <mo>-</mo> <msub> <mi>x</mi> <mrow> <mi>p</mi> <mn>1</mn> </mrow> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <msub> <mi>H</mi> <mi>R</mi> </msub> <mo>-</mo> <mi>H</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> <mo>-</mo> <mrow> <mo>(</mo> <msqrt> <msubsup> <mi>x</mi> <mi>p</mi> <mn>2</mn> </msubsup> <mo>+</mo> <msup> <mi>H</mi> <mn>2</mn> </msup> </msqrt> <mo>+</mo> <msqrt> <msup> <mrow> <mo>(</mo> <mi>x</mi> <mo>-</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <msub> <mi>H</mi> <mi>R</mi> </msub> <mo>-</mo> <mi>H</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow> </math>

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. Generally, the drilling depth is larger, the drilling depth is a target layer of exploration, and a VSP time error is caused when a drilling track deviates from a central vertical line, so that the conventional processing of VSP data has larger errors in a deep layer, and if the VSP data is not corrected, the VSP data cannot be explained, 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 downlink transmission 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 processing method for correcting VSP downlink transmission converted waves by using a drilling track corrects a travel path and a travel speed of the VSP downlink transmission converted waves by using a deviation distance and an azimuth angle of an actual petroleum drilling track and a central vertical line, and eliminates errors of VSP downlink transmission converted 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 angle γ and an azimuth α, wherein the well angle γ is well-to-verticalAngle of line, azimuth alpha being at drilling depth point H_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 d, x₁、s、s₁、x_pAnd x_p1：

d＝H_R·tgγ；

<math> <mrow> <msubsup> <mi>x</mi> <mn>1</mn> <mn>2</mn> </msubsup> <mo>=</mo> <msup> <mi>d</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mi>x</mi> <mn>2</mn> </msup> <mo>-</mo> <mn>2</mn> <mi>xd</mi> <mi>cos</mi> <mi>&theta;</mi> </mrow> </math>

$s=\sqrt{x_p^2+H^2}+\sqrt{{(x-x_p)}^2+{(H_R-H)}^2}$

${\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="HDA0000079748460000072.png"\; state="\{\{state\}\}">s</figure-callout>}}_1=\sqrt{x_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HDA0000079748460000072.png"\; state="\{\{state\}\}">p</figure-callout>}1}^2+H^2}+\sqrt{{(x_1-x_{p1})}^2+{(H_R-H)}^2}$

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

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;

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;

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;

h: indicating the depth of the transmission point;

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

<math> <mrow> <mi>&Delta;s</mi> <mo>=</mo> <msub> <mi>s</mi> <mn>1</mn> </msub> <mo>-</mo> <mi>s</mi> <mo>=</mo> <msqrt> <msubsup> <mi>x</mi> <mrow> <mi>p</mi> <mn>1</mn> </mrow> <mn>2</mn> </msubsup> <mo>+</mo> <msup> <mi>H</mi> <mn>2</mn> </msup> </msqrt> <mo>+</mo> <msqrt> <msup> <mrow> <mo>(</mo> <msub> <mi>x</mi> <mn>1</mn> </msub> <mo>-</mo> <msub> <mi>x</mi> <mrow> <mi>p</mi> <mn>1</mn> </mrow> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <msub> <mi>H</mi> <mi>R</mi> </msub> <mo>-</mo> <mi>H</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> <mo>-</mo> <mrow> <mo>(</mo> <msqrt> <msubsup> <mi>x</mi> <mi>p</mi> <mn>2</mn> </msubsup> <mo>+</mo> <msup> <mi>H</mi> <mn>2</mn> </msup> </msqrt> <mo>+</mo> <msqrt> <msup> <mrow> <mo>(</mo> <mi>x</mi> <mo>-</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <msub> <mi>H</mi> <mi>R</mi> </msub> <mo>-</mo> <mi>H</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> <mo>)</mo> </mrow> </mrow> </math>

(4) and (3) error analysis: and (4) after correcting the VSP downlink transmission converted wave path by using the VSP downlink transmission converted wave travel time path error obtained in the step (3), correcting the speed of the downlink transmission shear wave part, and analyzing the speed error of the downlink transmission shear wave part.

The method for correcting the VSP downlink transmission converted wave path in the step (4) comprises the following steps: 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 view of VSP down-going transmittance converted travel time.

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

FIG. 5 is a schematic diagram of the downward transmission converted wave travel time in the present invention.

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 path of the conventional method (theoretical travel path) and the travel path of the drilling trajectory (accurate travel path) for a downward transmitted converted wave with a certain well offset of 120 m, an azimuth angle of 340 degrees and a depth of a reflecting layer of 2000m in the embodiment of the invention. Data are from columns 6 and 7 of table 1.

FIG. 8 is a comparison graph of the conventional method travel time (theoretical travel time) and the travel time (accurate travel time) of a downhole transmitted converted wave at a certain well offset distance of 120 m, an azimuth angle of 340 degrees and a reflection layer depth of 2000m in an embodiment of the invention. Data are from columns 8 and 9 of table 1.

FIG. 9 is a graph of the downward transmitted converted wave travel time error for a well offset of 120 meters, an azimuth of 340 degrees, and a depth of reflection of 2000 meters in an embodiment of the present invention, the data being 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) for a certain well offset distance of 2400 m, an azimuth angle of 140 degrees and a depth of a reflecting layer of 2000m in the embodiment of the invention. Data are from table 2, columns 6 and 7.

FIG. 11 is a comparison graph of the conventional method travel time (theoretical travel time) and the travel time (accurate travel time) of a downhole transmitted converted wave at a certain well offset distance of 2400 m, an azimuth angle of 140 degrees and a reflection layer depth of 2000m in an embodiment of the invention. Data are from columns 8 and 9 of table 2.

FIG. 12 is a diagram of the transit converted wave travel time error for a well with offset of 2400 m, azimuth 140 degrees, and depth of the reflector of 2000m in the embodiment of the present invention. Data are from table 2, column 10.

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 downward transmission converted wave with a certain well offset distance of 2400 m, an azimuth angle of 220 degrees and a depth of a reflecting layer of 2000m in the embodiment of the invention. Data are from columns 6 and 7 of table 5.

FIG. 14 is a comparison graph of the conventional method travel time (theoretical travel time) and the travel time (accurate travel time) of a downhole transmitted converted wave at a certain well offset distance of 2400 m, an azimuth angle of 220 degrees and a reflection layer depth of 2000m in an embodiment of the invention. Data are from columns 8 and 9 of table 5.

FIG. 15 is a diagram of the transit converted wave travel time error for a well with offset of 2400 m, azimuth of 220 degrees, and depth of the reflector of 2000m in an embodiment of the present 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 downlink transmission converted waves by using a drilling track corrects a travel path and a travel speed of the VSP downlink transmission converted waves by using a deviation distance and an azimuth angle of an actual petroleum drilling track and a central vertical line, and eliminates errors of VSP downlink transmission converted wave processing caused by deviation of the drilling track from the central vertical line.

As shown in fig. 6, the method comprises the steps of: (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; (H, γ, α) the set of data is the position of the drill bit in the well (columns 1-3 in tables 1-5 are the set of data), and the (x, y, z) coordinates of the drill bit in the well in three-dimensional space can be transformed; correcting the travel path or travel speed of the VSP downlink transmission converted wave, and eliminating the error of VSP downlink transmission converted wave processing caused by deviation of a drilling track from a central vertical line.

The VSP downlink transmission converted wave travel time path error correction is similar to static correction of ground longitudinal wave seismic exploration, and when the actual travel time path is larger than the theoretical travel time path (the travel time path error values in the 4 th column of tables 1-5 are positive values) at the corrected depth point, the value is subtracted by taking the theoretical vertical well drilling perpendicular bisector as a reference, 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.

(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 d, x₁、s、s₁、x_pAnd x_p1：

d＝H_R·tgγ；

<math> <mrow> <msubsup> <mi>x</mi> <mn>1</mn> <mn>2</mn> </msubsup> <mo>=</mo> <msup> <mi>d</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mi>x</mi> <mn>2</mn> </msup> <mo>-</mo> <mn>2</mn> <mi>xd</mi> <mi>cos</mi> <mi>&theta;</mi> </mrow> </math>

$s=\sqrt{x_p^2+H^2}+\sqrt{{(x-x_p)}^2+{(H_R-H)}^2}$

${\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="HDA0000079748460000072.png"\; state="\{\{state\}\}">s</figure-callout>}}_1=\sqrt{x_{\mathrm{<figure-callout\; id="1"\; label="p"\; filenames="HDA0000079748460000072.png"\; state="\{\{state\}\}">p</figure-callout>}1}^2+H^2}+\sqrt{{(x_1-x_{p1})}^2+{(H_R-H)}^2}$

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

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 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;

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;

h: indicating the depth of the transmission point;

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

<math> <mrow> <mi>&Delta;s</mi> <mo>=</mo> <msub> <mi>s</mi> <mn>1</mn> </msub> <mo>-</mo> <mi>s</mi> <mo>=</mo> <msqrt> <msubsup> <mi>x</mi> <mrow> <mi>p</mi> <mn>1</mn> </mrow> <mn>2</mn> </msubsup> <mo>+</mo> <msup> <mi>H</mi> <mn>2</mn> </msup> </msqrt> <mo>+</mo> <msqrt> <msup> <mrow> <mo>(</mo> <msub> <mi>x</mi> <mn>1</mn> </msub> <mo>-</mo> <msub> <mi>x</mi> <mrow> <mi>p</mi> <mn>1</mn> </mrow> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <msub> <mi>H</mi> <mi>R</mi> </msub> <mo>-</mo> <mi>H</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> <mo>-</mo> <mrow> <mo>(</mo> <msqrt> <msubsup> <mi>x</mi> <mi>p</mi> <mn>2</mn> </msubsup> <mo>+</mo> <msup> <mi>H</mi> <mn>2</mn> </msup> </msqrt> <mo>+</mo> <msqrt> <msup> <mrow> <mo>(</mo> <mi>x</mi> <mo>-</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <msub> <mi>H</mi> <mi>R</mi> </msub> <mo>-</mo> <mi>H</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow> </math>

the point of processing of VSP downlink transmission converted wave is permanently at H_RAbove, i.e. H is always less than H_RProcessed and transmitted waves.

(4) And (3) error analysis: and (4) obtaining a VSP uplink converted wave error through the step (3), and after correcting the VSP downlink transmission converted wave path, correcting the transverse wave speed and analyzing the transverse wave speed error. After correcting the VSP down-traveling converted wave path, it is possible to perform velocity correction of the down-traveling transmitted shear wave portion (referred to as down-traveling transmitted converted wave because the incident is a longitudinal wave and the transmission is a shear wave, and referred to as down-traveling transmitted shear wave because the velocity correction of the shear wave portion is mentioned)) and also perform velocity error analysis of the down-traveling transmitted shear wave portion.

The VSP downlink transmission converted wave travel time path error correction is similar to static correction of ground longitudinal wave seismic exploration, and when the actual travel time path is larger than the theoretical travel time path (the travel time path error values in the 4 th column of tables 1-5 are positive values) at the corrected depth point, the value is subtracted by taking the theoretical vertical well drilling perpendicular bisector as a reference, 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 mature technique, and few analyses.

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

because seismic and VSP data processing are based on a homogeneous cap layer (i.e., a horizontal reflection interface) model, the VSP utility formula is also based on this model.

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

<math> <mrow> <mi>&gamma;</mi> <mo>=</mo> <mfrac> <msub> <mi>v</mi> <mi>s</mi> </msub> <msub> <mi>v</mi> <mi>p</mi> </msub> </mfrac> <mo>=</mo> <mfrac> <mrow> <mi>sin</mi> <mi>&beta;</mi> </mrow> <mrow> <mi>sin</mi> <mi>&alpha;</mi> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>5</mn> <mo>)</mo> </mrow> </mrow> </math>

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

Observed VSP dataH can be determined after processing_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

<math> <mrow> <mi>H</mi> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <msub> <mi>v</mi> <mi>p</mi> </msub> <mo>&CenterDot;</mo> <msub> <mi>t</mi> <mn>0</mn> </msub> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>6</mn> <mo>)</mo> </mrow> </mrow> </math>

v_s

Then X_pCan be obtained by a numerical method.

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

<math> <mrow> <mi>sin</mi> <mi>&beta;</mi> <mo>=</mo> <mfrac> <mrow> <mi>x</mi> <mo>-</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> </mrow> <msqrt> <msup> <mi>h</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <mi>x</mi> <mo>-</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> </mfrac> </mrow> </math>

<math> <mrow> <mi>sin</mi> <mi>&alpha;</mi> <mo>=</mo> <mfrac> <msub> <mi>x</mi> <mi>p</mi> </msub> <msqrt> <msup> <mi>H</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <msub> <mi>x</mi> <mi>p</mi> </msub> <mn>2</mn> </msup> </msqrt> </mfrac> </mrow> </math>

Order to <math> <mrow> <mi>&gamma;</mi> <mo>=</mo> <mfrac> <mrow> <mi>sin</mi> <mi>&beta;</mi> </mrow> <mrow> <mi>sin</mi> <mi>&alpha;</mi> </mrow> </mfrac> <mo>=</mo> <mfrac> <mrow> <mi>x</mi> <mo>-</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> </mrow> <msqrt> <msup> <mi>h</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <mi>x</mi> <mo>-</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> </mfrac> <mo>&CenterDot;</mo> <mfrac> <msqrt> <msup> <mi>H</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <msub> <mi>x</mi> <mi>p</mi> </msub> <mn>2</mn> </msup> </msqrt> <msub> <mi>x</mi> <mi>p</mi> </msub> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>7</mn> <mo>)</mo> </mrow> </mrow> </math>

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

Squaring two sides of the formula (7) to obtain

<math> <mrow> <msup> <mi>&gamma;</mi> <mn>2</mn> </msup> <msubsup> <mi>x</mi> <mi>p</mi> <mn>2</mn> </msubsup> <mo>[</mo> <msup> <mi>h</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <mi>x</mi> <mo>-</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>]</mo> <mo>=</mo> <msup> <mrow> <mo>(</mo> <mi>x</mi> <mo>-</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mrow> <mo>(</mo> <msup> <mi>H</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <msub> <mi>x</mi> <mi>p</mi> </msub> <mn>2</mn> </msup> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>8</mn> <mo>)</mo> </mrow> </mrow> </math>

Through simple and convenient arrangement

<math> <mrow> <mo>(</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <msup> <mi>&gamma;</mi> <mn>2</mn> </msup> <mo>)</mo> </mrow> <msubsup> <mi>x</mi> <mi>p</mi> <mn>4</mn> </msubsup> <mo>-</mo> <mn>2</mn> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <msup> <mi>&gamma;</mi> <mn>2</mn> </msup> <mo>)</mo> </mrow> <mi>x</mi> <mo>&CenterDot;</mo> <msubsup> <mi>x</mi> <mi>p</mi> <mn>3</mn> </msubsup> <mo>+</mo> <mrow> <mo>(</mo> <msup> <mi>x</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mi>H</mi> <mn>2</mn> </msup> <mo>-</mo> <msup> <mi>&gamma;</mi> <mn>2</mn> </msup> <msup> <mi>x</mi> <mn>2</mn> </msup> <mo>-</mo> <msup> <mi>&gamma;</mi> <mn>2</mn> </msup> <msup> <mi>h</mi> <mn>2</mn> </msup> <mo>)</mo> </mrow> <msup> <msub> <mi>x</mi> <mi>p</mi> </msub> <mn>2</mn> </msup> <mo>-</mo> <mn>2</mn> <mi>x</mi> <msup> <mi>H</mi> <mn>2</mn> </msup> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>+</mo> <msup> <mi>x</mi> <mn>2</mn> </msup> <msup> <mi>H</mi> <mn>2</mn> </msup> <mo>=</mo> <mn>0</mn> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>9</mn> <mo>)</mo> </mrow> </mrow> </math>

The algebraic equation is solved by a Newton-Rayleigh method, namely, the formula (10) is expressed as F (xp) which is 0, and the first derivative of F (xp) is

<math> <mrow> <msup> <mi>F</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>)</mo> </mrow> <mo>=</mo> <mn>4</mn> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <msup> <mi>&gamma;</mi> <mn>2</mn> </msup> <mo>)</mo> </mrow> <msubsup> <mi>x</mi> <mi>p</mi> <mn>3</mn> </msubsup> <mo>-</mo> <mn>6</mn> <mrow> <mo>(</mo> <mn>1</mn> <mo>-</mo> <msup> <mi>&gamma;</mi> <mn>2</mn> </msup> <mo>)</mo> </mrow> <mi>x</mi> <mo>&CenterDot;</mo> <msup> <msub> <mi>x</mi> <mi>p</mi> </msub> <mn>2</mn> </msup> <mo>+</mo> <mn>2</mn> <mrow> <mo>(</mo> <msup> <mi>x</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mi>H</mi> <mn>2</mn> </msup> <mo>-</mo> <msup> <mi>&gamma;</mi> <mn>2</mn> </msup> <msup> <mi>x</mi> <mn>2</mn> </msup> <mo>-</mo> <msup> <mi>&gamma;</mi> <mn>2</mn> </msup> <msup> <mi>h</mi> <mn>2</mn> </msup> <mo>)</mo> </mrow> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>-</mo> <mn>2</mn> <mi>x</mi> <msup> <mi>H</mi> <mn>2</mn> </msup> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>10</mn> <mo>)</mo> </mrow> </mrow> </math>

Iterative formula

<math> <mrow> <msubsup> <mi>x</mi> <mi>p</mi> <mrow> <mi>n</mi> <mo>+</mo> <mn>1</mn> </mrow> </msubsup> <mo>=</mo> <msubsup> <mi>x</mi> <mi>p</mi> <mi>n</mi> </msubsup> <mo>-</mo> <mfrac> <mrow> <mi>F</mi> <mrow> <mo>(</mo> <msubsup> <mi>x</mi> <mi>p</mi> <mi>n</mi> </msubsup> <mo>)</mo> </mrow> </mrow> <mrow> <msup> <mi>F</mi> <mo>&prime;</mo> </msup> <mrow> <mo>(</mo> <msubsup> <mi>x</mi> <mi>p</mi> <mi>n</mi> </msubsup> <mo>)</mo> </mrow> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>11</mn> <mo>)</mo> </mrow> </mrow> </math>

With an initial value of iteration of <math> <mrow> <msubsup> <mi>x</mi> <mi>p</mi> <mn>0</mn> </msubsup> <mo>=</mo> <mfrac> <mi>x</mi> <mrow> <mn>1</mn> <mo>+</mo> <msup> <mi>&gamma;</mi> <mn>2</mn> </msup> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>12</mn> <mo>)</mo> </mrow> </mrow> </math>

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 reflected downwards when the longitudinal wave speed is 1.73 times of the transverse wave speed, and the errors of azimuth angles of 2000m, 3000 m and 4500 m with different transmission depths are analyzed, wherein the errors occur when the azimuth angle is 340 degrees at an offset distance of 120 m, the azimuth angle is 2400 m, the azimuth angle is 140 degrees and the azimuth angle is 220 degrees at an offset distance of 2400 m.

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, at zero offset (120 m), the VSP downward transmitted converted wave error is relatively small, and as shown in fig. 9, the travel time error at the depth of 4725 m of the receiving point is 11 ms. This shows that the VSP down-going transmitted converted wave error is small at zero offset (120 meters).

2, when there is an offset distance, the VSP downlink transmission converted wave error is relatively large, as shown in fig. 12 and fig. 15, fig. 12 is an error analysis with an offset distance of 2400 meters, an azimuth angle of 140 degrees, and a transmission depth of 2000 m. The maximum error range is-73 ms-39ms, and the maximum error amplitude difference is 112 ms. FIG. 15 shows an error analysis of a 220 degree transmission depth of 2000m at different azimuth angles, offset from 2400 meters. The maximum error range is-11 ms-47ms, and the maximum error amplitude difference is 58 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 VSP downlink transmission converted wave error is large.

The method of the invention can find 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, and the tables 1 to 5, the 4 th column is the error numerical value 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 correcting the VSP down-traveling converted wave path, it is possible to perform velocity correction of the down-traveling transmitted shear wave portion (referred to as down-traveling transmitted converted wave because the incident is a longitudinal wave and the transmission is a shear wave, and referred to as down-traveling transmitted shear wave because the velocity correction of the shear wave portion is mentioned)) and also perform velocity error analysis of the down-traveling transmitted shear wave portion.

From the above analysis it can be concluded that: the method can correct the error of VSP treatment caused by deviation of the drilling track from the central vertical line, has obvious effect especially when the distance of the drilling track from the central vertical line is large, and can solve the practical production problem.

The method can correct the error of the downward transmission converted wave data of the drilling track data deviating from the central vertical line VS, solves the problem of processing failure of the conventional VSP data caused by too much deviation of part of the central track, reduces the waste of exploration expenditure and improves the seismic exploration precision. The correction method is used for correcting the VSP downlink transmission 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 higher. 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 (5)

1. A processing method for correcting VSP downlink transmission 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 downlink transmission 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 downlink transmission 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 down-going transmission converted waves using well trajectory of claim 1, wherein: 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 d, x₁、s、s₁、x_pAnd x_p1：

d＝H_R·tgγ；

<math> <mrow> <msubsup> <mi>x</mi> <mn>1</mn> <mn>2</mn> </msubsup> <mo>=</mo> <msup> <mi>d</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mi>x</mi> <mn>2</mn> </msup> <mo>-</mo> <mn>2</mn> <mi>xd</mi> <mi>cos</mi> <mi>&theta;</mi> </mrow> </math>

$s=\sqrt{x_p^2+H^2}+\sqrt{{(x-x_p)}^2+{(H_R-H)}^2}$

$s_1=\sqrt{x_{p1}^2+H^2}+\sqrt{{(x_1-x_{p1})}^2+{(H_R-H)}^2}$

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

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;

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;

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;

h: indicating the depth of the transmission point;

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

<math> <mrow> <mi>&Delta;s</mi> <mo>=</mo> <msub> <mi>s</mi> <mn>1</mn> </msub> <mo>-</mo> <mi>s</mi> <mo>=</mo> <msqrt> <msubsup> <mi>x</mi> <mrow> <mi>p</mi> <mn>1</mn> </mrow> <mn>2</mn> </msubsup> <mo>+</mo> <msup> <mi>H</mi> <mn>2</mn> </msup> </msqrt> <mo>+</mo> <msqrt> <msup> <mrow> <mo>(</mo> <msub> <mi>x</mi> <mn>1</mn> </msub> <mo>-</mo> <msub> <mi>x</mi> <mrow> <mi>p</mi> <mn>1</mn> </mrow> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <msub> <mi>H</mi> <mi>R</mi> </msub> <mo>-</mo> <mi>H</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> <mo>-</mo> <mrow> <mo>(</mo> <msqrt> <msubsup> <mi>x</mi> <mi>p</mi> <mn>2</mn> </msubsup> <mo>+</mo> <msup> <mi>H</mi> <mn>2</mn> </msup> </msqrt> <mo>+</mo> <msqrt> <msup> <mrow> <mo>(</mo> <mi>x</mi> <mo>-</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <msub> <mi>H</mi> <mi>R</mi> </msub> <mo>-</mo> <mi>H</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> <mo>)</mo> </mrow> </mrow> </math>

(4) and (3) error analysis: and (4) after correcting the VSP downlink transmission converted wave path by using the VSP downlink transmission converted wave travel time path error obtained in the step (3), correcting the speed of the downlink transmission shear wave part, and analyzing the speed error of the downlink transmission shear wave part.

3. The method of processing to correct VSP down-going transmission converted waves using well trajectory of claim 2, wherein: the method for correcting the VSP downlink transmission converted wave path in the step (4) comprises the following steps: 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 processing to correct VSP downlrojection converted waves using a well trajectory of claim 3, wherein: 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 claim 4, wherein the step of correcting the VSP down-going transmission converted wave using the well trajectory comprises: 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.

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