US 12,596,202 B2 · Direct well-tie method for depth-domain logging and seismic data

Abstract

A direct well-tie method for depth-domain logging and seismic data, including: removing null and outlier values from logging velocity data and logging density data to obtain valid logging velocity data and valid logging density data; calculating a logging reflection coefficient; estimating an initial zero-phase depth-domain seismic wavelet from seismic section; making a depth-domain synthetic seismogram; interpolating the depth-domain seismogram at the logging location; performing cross-correlating operation between the depth-domain synthetic seismogram and the interpolated depth-domain seismogram at the logging location; estimating a depth-domain seismic wavelet; updating the depth-domain synthetic seismogram; generating a corresponding depth deviation point set; subjecting elements in the set to interpolation to obtain a depth calibration curve; subjecting the depth calibration curve and depth axis to addition to obtain depth axis; generating a logging depth-seismic depth corresponding relationship and a depth-domain seismic wavelet.

A method for locating an oil-gas reservoir based on direct well-tie of depth-domain logging and seismic data, comprising:

(1) removing null values and outlier values from logging velocity data and logging density data to obtain valid logging velocity data and valid logging density data;
(2) based on the valid logging velocity data and the valid logging density data, calculating a logging reflection coefficient r at different depths, expressed as:
r=[r(1), . . . ,r(l), . . . ,r(L)];
wherein L indicates the number of sampling points for the valid logging velocity data and the valid logging density data;
(3) estimating an initial zero-phase depth-domain seismic wavelet from a seismic section S, wherein the seismic section S is within a target depth range and passes through a well location, and the initial zero-phase depth-domain seismic wavelet is estimated through steps of:
(3.1) calculating an average spectrum y of the seismic section S through the following equation:
y
=
1
N
⁢
∑
n
=
1
N
⁢
(
f
⁢
f
⁢
t
[
S
⁡
(
n
)
]
)
2
,
n
∈
[
1
,
2
,
…
,
N
]
;
wherein fft[⋅] represents vector's fast Fourier transform;
the seismic section S contains N seismograms in total;
and S(n) indicates an n-th seismogram in the seismic section S, and contains M sampling points;
(3.2) building an objective function
min
α
,
β

exp
[
-
(
K
-
α
β
)
2
]
-
y

2
,
and solving the objective function by using least squares method to obtain a fitting parameter α and a fitting parameter β;
wherein ∥⋅∥2 represents a vector L2 norm;
exp[⋅] represents a vector exponent;
and a seismic wavenumber vector K is expressed as K=[K(1), . . . , K(m), . . . , K(M)];
wherein
K
⁡
(
m
)
=
(
m
-
1
)
M
⁢
Δ
⁢
D
;
and ΔD indicates a depth sampling interval of the seismic section S;
(3.3) constructing the initial zero-phase depth-domain seismic wavelet w0 based on the fitting parameter β and a logging wavenumber vector k, expressed as follows:
w
0
=
(
4
⁢
5
⁢
π
-
1
⁢
2
⁢
8
)
⁢
k
2
9
⁢
π
⁢
β
2
⁢
exp
[
-
(
(
4
⁢
5
⁢
π
-
1
⁢
2
⁢
8
)
⁢
k
2
1
⁢
8
⁢
π
⁢
β
2
)
+
1
]
;
wherein k=[k(1), . . . , k(l), . . . , k(L)];
k
⁡
(
l
)
=
(
l
-
1
)
L
⁢
Δ
⁢
d
and Δd cates a depth sampling interval of logging data;
(4) making a depth-domain synthetic seismogram A based on the initial zero-phase depth-domain seismic wavelet w0 and a logging reflection coefficient r, expressed as follows:
A=real{P[rP)⊙w0]};
wherein real{⋅} denotes an operation of taking a vector real part;
⊙ represents a vector Hadamard product;
P is an L-order matrix;
P is a conjugate matrix of the P;
and an element P(l,l) in the P is expressed as follows:
P
⁡
(
l
,
l
)
=
P
⁡
(
l
-
1
,
l
)
L
⁢
exp
[
-
i
⁢
2
⁢
π
⁡
(
l
-
1
)
⁢
v
max
v
⁡
(
l
)
⁢
L
]
;
wherein i=√{square root over (−1)} is an imaginary unit;
and vmax is a maximum value in the valid logging velocity data;
at this time, a depth axis DA corresponding to the depth-domain synthetic seismogram A is expressed as:
DA=[DA(1), . . . , DA(l), . . . , DA(L)];
wherein DA(1) is an initial depth of a depth-domain seismogram at the well location;
(5) according to the depth sampling interval Δd of the logging data, subjecting the depth-domain seismogram at the well location to interpolation by using a cubic spline interpolation method to obtain an interpolated depth-domain seismogram at the well location;
(6) performing cross-correlation operation between the depth-domain synthetic seismogram A and the interpolated depth-domain seismogram at the well location to obtain a cross-correlation result;
updating the depth axis DA corresponding to the depth-domain synthetic seismogram A into DA′=DA+[D0−DA(1)] according to a depth position D0 corresponding to a maximum value in the cross-correlation result;
at the same time, starting from D0, extracting L sampling points from the interpolated depth-domain seismogram at the well location to obtain a depth-domain seismogram segment B;
wherein a depth axis DB corresponding to the depth-domain seismogram segment B is expressed as DB=[DB(1), . . . , DB(l), . . . , DB(L)];
(7) based on the depth-domain seismogram segment B and the logging reflection coefficient r, estimating a depth-domain seismic wavelet by using a direct depth-domain seismic wavelet estimation method;
based on the depth-domain seismic wavelet and the logging reflection coefficient r, updating the depth-domain synthetic seismogram A by using a direct depth-domain seismogram synthesis method to obtain a depth-domain synthetic seismogram A′;
(8) selecting a wave peak or trough position from the depth-domain seismogram segment B, wherein the wave peak or trough position is similar to the depth-domain synthetic seismogram A′ in waveform characteristic;
compressing or stretching the depth-domain seismogram segment B to align the wave peak or trough position with the depth-domain synthetic seismogram A′, and generating a corresponding depth deviation point set E, expressed as follows:
E={E(1), . . . ,E(j), . . . ,E(J)},J<L;
wherein E(j)=DB(j)−DA′(j), representing a depth axis difference between the depth-domain seismogram segment B and the depth-domain synthetic seismogram A′ at a j-th point;
and
subjecting elements in the depth deviation point set E to interpolation by using the cubic spline interpolation method to obtain a depth calibration curve C;
(9) subjecting the depth calibration curve C and the depth axis DA′ to addition to obtain a depth axis DA″=DA′+C, and subjecting the depth calibration curve C and the depth axis DB to addition to obtain a depth axis DB′=DB+C;
according to the depth axis DB′, intercepting a corresponding depth-domain seismogram segment B′ from the interpolated depth-domain seismogram at the well location;
and repeating step (7);
(10) determining whether the depth-domain seismogram segment B′ is aligned with the depth-domain synthetic seismogram A′ at the wave peak or trough position, and a correlation coefficient between the depth-domain seismogram segment B′ and the depth-domain synthetic seismogram A′ is higher than a correlation coefficient in a previous calibration process;
if yes, completing a calibration operation, and generating a logging depth-seismic depth corresponding relationship and a depth-domain seismic wavelet;
otherwise, repeating steps (8)-(9);
and
(11) projecting a Gamma Ray logging curve onto the seismic section S based on the logging depth-seismic depth corresponding relationship to output a first image;
subjecting the depth-domain seismic wavelet to seismic inversion to output a second image, wherein the second image is an elastic impedance image of an underground medium;
and
locating, for a user, the oil-gas reservoir based on the first image and the second image.

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Direct well-tie method for depth-domain logging and seismic data

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Direct well-tie method for depth-domain logging and seismic data

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Abstract

Claims1