U.S. patent application number 16/536402 was filed with the patent office on 2020-06-11 for horizontal fracture prediction method, device and equipment.
This patent application is currently assigned to China University of Petroleum (Beijing). The applicant listed for this patent is China University of Petroleum (Beijing). Invention is credited to Bangrang Di, Pinbo Ding, Jianxin Wei.
Application Number | 20200183033 16/536402 |
Document ID | / |
Family ID | 66187342 |
Filed Date | 2020-06-11 |
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United States Patent
Application |
20200183033 |
Kind Code |
A1 |
Ding; Pinbo ; et
al. |
June 11, 2020 |
HORIZONTAL FRACTURE PREDICTION METHOD, DEVICE AND EQUIPMENT
Abstract
The present disclosure provides a horizontal fracture prediction
method, device and equipment. The method comprises: acquiring
primary wave velocities and shear wave velocities of first and
second incidence angle directions of seismic waves at a target
fracture location, wherein a first incidence angle is smaller than
a second incidence angle, and the incidence angles are included
angles between propagation directions of the seismic waves and a
surface normal direction of a target fracture; calculating a first
primary wave/shear wave velocity ratio and a first shear wave
splitting (SWS) coefficient of the first incidence angle direction;
calculating a second primary wave/shear wave velocity ratio of the
second incidence angle direction; and determining that the target
fracture is a horizontal fracture under the condition that the
first SWS coefficient is smaller than a first preset value and a
ratio of the first primary wave/shear wave velocity ratio to the
second primary wave/shear wave velocity ratio is smaller than a
second preset value. According to embodiments of the present
disclosure, whether the target fracture is the horizontal fracture
or not is determined through calculating the primary wave/shear
wave velocity ratio and the first SWS coefficient of the first
incidence angle direction and the primary wave/shear wave velocity
ratio of the second incidence angle direction, so that effective
data are provided for exploration and development of coal-bed gas
and shale gas.
Inventors: |
Ding; Pinbo; (Beijing,
CN) ; Di; Bangrang; (Beijing, CN) ; Wei;
Jianxin; (Beijing, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
China University of Petroleum (Beijing) |
Beijing |
|
CN |
|
|
Assignee: |
China University of Petroleum
(Beijing)
Beijing
CN
|
Family ID: |
66187342 |
Appl. No.: |
16/536402 |
Filed: |
August 9, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01V 1/303 20130101;
G01V 2210/6222 20130101; G01V 1/284 20130101; G01V 2210/646
20130101 |
International
Class: |
G01V 1/30 20060101
G01V001/30 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 10, 2018 |
CN |
201811502830.9 |
Claims
1. A horizontal fracture prediction method, comprising: acquiring a
primary wave velocity and a shear wave velocity of a first
incidence angle direction and a primary wave velocity and a shear
wave velocity of a second incidence angle direction of seismic
waves at a target fracture location, wherein a first incidence
angle is smaller than a second incidence angle, and the incidence
angles are included angles between propagation directions of the
seismic waves and a surface normal direction of a target fracture;
calculating a first primary wave/shear wave velocity ratio of the
first incidence angle direction according to the primary wave
velocity and shear wave velocity of the first incidence angle
direction; acquiring a fast shear wave velocity and a slow shear
wave velocity of the first incidence angle direction according to
the shear wave velocity of the first incidence angle direction;
calculating a first shear-wave splitting (SWS) coefficient of the
first incidence angle direction according to the fast shear wave
velocity and slow shear wave velocity of the first incidence angle
direction; calculating a second primary wave/shear wave velocity
ratio of the second incidence angle direction according to the
primary wave velocity and shear wave velocity of the second
incidence angle direction; and determining that the target fracture
is a horizontal fracture under the condition that the first SWS
coefficient is smaller than a first preset value and a ratio of the
first primary wave/shear wave velocity ratio to the second primary
wave/shear wave velocity ratio is smaller than a second preset
value.
2. (canceled)
3. The method according to claim 2, wherein the first SWS
coefficient of the first incidence angle direction is calculated
according to the fast shear wave velocity and slow shear wave
velocity of the first incidence angle direction according to a
formula as follows: SWS1=(Vs11-Vs21)/Vs21 wherein, Vs11 means the
fast shear wave velocity of the first incidence angle direction;
Vs21 means the slow shear wave velocity of the first incidence
angle direction; and SWS1 means the first SWS coefficient.
4. The method according to claim 1, wherein after the target
fracture is determined as the horizontal fracture, the method
further comprises: acquiring a fast shear wave velocity and a slow
shear wave velocity of the second incidence angle direction;
calculating a second SWS coefficient of the second incidence angle
direction according to the fast shear wave velocity and slow shear
wave velocity of the second incidence angle direction; taking the
second SWS coefficient as fracture density of the target fracture;
and determining the development degree of the target fracture
according to the fracture density.
5. The method according to claim 4, wherein the second SWS
coefficient of the second incidence angle direction is calculated
according to the fast shear wave velocity and slow shear wave
velocity of the second incidence angle direction according to a
formula as follows: SWS2=(Vs12-Vs22)/Vs22 wherein, Vs12 means the
fast shear wave velocity of the second incidence angle direction,
Vs22 means the slow shear wave velocity of the second incidence
angle direction, and SWS2 means the second SWS coefficient.
6. The method according to claim 4, wherein the step of determining
the development degree of the target fracture according to the
fracture density comprises: judging a preset range to which the
fracture density belongs; determining the development degree of the
target fracture as a fracture nondevelopment zone when the fracture
density belongs to a first preset range; determining the
development degree of the target fracture as a fracture
sub-development zone when the fracture density belongs to a second
preset range; and determining the development degree of the target
fracture as a fracture development zone when the fracture density
belongs to a third preset range.
7. The method according to claim 1, wherein the first incidence
angle is greater than or equal to 0.degree. and is smaller than or
equal to 20.degree.; and the second incidence angle is greater than
or equal to 70.degree. and is smaller than or equal to
90.degree..
8. A horizontal fracture prediction device, comprising: means for
acquiring a primary wave velocity and a shear wave velocity of a
first incidence angle direction and a primary wave velocity and a
shear wave velocity of a second incidence angle direction of
seismic waves at a target fracture location, wherein a first
incidence angle is smaller than a second incidence angle, and the
incidence angles are included angles between propagation directions
of the seismic waves and a surface normal direction of a target
fracture; means for, calculating a first primary wave/shear wave
velocity ratio of the first incidence angle direction according to
the primary wave velocity and shear wave velocity of the first
incidence angle direction; means for acquiring a fast shear wave
velocity and a slow shear wave velocity of the first incidence
angle direction according to the shear wave velocity of the first
incidence angle direction; means for calculating a first shear-wave
splitting (SWS) coefficient of the first incidence angle direction
according to the fast shear wave velocity and slow shear wave
velocity of the first incidence angle direction; means for
calculating a second primary wave/shear wave velocity ratio of the
second incidence angle direction according to the primary wave
velocity and shear wave velocity of the second incidence angle
direction; and means for determining that the target fracture is a
horizontal fracture under the condition that the first SWS
coefficient is smaller than a first preset value and a ratio of the
first primary wave/shear wave velocity ratio to the second primary
wave/shear wave velocity ratio is smaller than a second preset
value.
9. (canceled)
10. The device according to claim 9, wherein the first SWS
coefficient is calculated according to a formula as follows:
SWS1=(Vs11-Vs21)/Vs21 wherein, Vs11 means the fast shear wave
velocity of the first incidence angle direction; Vs21 means the
slow shear wave velocity of the first incidence angle direction;
and SWS1 means the first SWS coefficient.
11. The device according to claim 8, further comprising: means for
acquiring a fast shear wave velocity and a slow shear wave velocity
of the second incidence angle direction after the target fracture
is determined as the horizontal fracture; means for, calculating a
second SWS coefficient of the second incidence angle direction
according to the fast shear wave velocity and slow shear wave
velocity of the second incidence angle direction; means for, taking
the second SWS coefficient as fracture density of the target
fracture; and means for, determining the development degree of the
target fracture according to the fracture density.
12. The device according to claim 11, wherein the second SWS
coefficient is calculated according to a formula as follows:
SWS2=(Vs12-Vs22)/Vs22 wherein, Vs12 means the fast shear wave
velocity of the second incidence angle direction, Vs22 means the
slow shear wave velocity of the second incidence angle direction,
and SWS2 means the second SWS coefficient.
13. The device according to claim 11, wherein the means for
determining the development degree of the target fracture according
to the fracture density comprises: means for judging a preset range
to which the fracture density belongs; means for determining the
development degree of the target fracture as a fracture
nondevelopment zone when the fracture density belongs to a first
preset range; means for determining the development degree of the
target fracture as a fracture sub-development zone when the
fracture density belongs to a second preset range; and means for
determining the development degree of the target fracture as a
fracture development zone when the fracture density belongs to a
third preset range.
14. A horizontal fracture prediction equipment, comprising a
processor and a memory for storing processor executable
instructions, wherein steps of the method according to claim 1 are
achieved when the instructions are executed by the processor.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Chinese Patent
Application No. 201811502830.9, filed Dec. 10, 2018, which is
incorporated by reference as if fully set forth herein.
FIELD OF THE INVENTION
[0002] The present disclosure relates to the technical field of
geophysical exploration and development and particularly relates to
a horizontal fracture prediction method, device and equipment.
BACKGROUND OF THE INVENTION
[0003] Fractures are extensively distributed in underground rocks,
have all-important influence on propagation of seismic waves and
also play a critical role in storing and migrating subsurface
fluids. Therefore, feature description of formation fractures is an
important research content of fractured oil and gas reservoirs.
Under the action of tectonic movement, rocks will generate
high-angle fractures, also called vertical fractures, which are
major research objects in conventional oil-gas exploration.
Besides, in shale and coal beds, horizontally-distributed natural
fractures, also called horizontal fractures, are developed under
the influence caused by factors such as oriented arrangement of
minerals and action of geostress. Wherein, the horizontal fractures
provide reservoir spaces for shale gas and coal-bed gas and play an
all-important role in gas content of reservoir beds, so that the
prediction of the horizontal fractures has an important
significance in exploration and development of the shale gas, the
coal-bed gas, etc.
[0004] The existing fracture prediction methods, for example a
shear-wave splitting (SWS) based formation fracture prediction
method can only be used for effectively predicting the vertical
fractures and cannot be used for identifying the horizontal
fractures during the prediction of the fractures.
[0005] In view of how to predict the horizontal fractures, an
effective solution is not proposed yet at present.
SUMMARY OF THE INVENTION
[0006] Embodiments of the present disclosure provide a horizontal
fracture prediction method which is used for solving the problem in
the prior art that a horizontal fracture cannot be effectively
predicted.
[0007] The horizontal fracture prediction method provided by the
embodiments of the present disclosure comprises: acquiring a
primary wave velocity and a shear wave velocity of a first
incidence angle direction and a primary wave velocity and a shear
wave velocity of a second incidence angle direction of seismic
waves at a target fracture location, wherein a first incidence
angle is smaller than a second incidence angle, and the incidence
angles are included angles between propagation directions of the
seismic waves and a surface normal direction of a target fracture;
calculating a first primary wave/shear wave velocity ratio and a
first shear-wave splitting (SWS) coefficient of the first incidence
angle direction according to the primary wave velocity and shear
wave velocity of the first incidence angle direction; calculating a
second primary wave/shear wave velocity ratio of the second
incidence angle direction according to the primary wave velocity
and shear wave velocity of the second incidence angle direction;
and determining that the target fracture is a horizontal fracture
under the condition that the first SWS coefficient is smaller than
a first preset value and a ratio of the first primary wave/shear
wave velocity ratio to the second primary wave/shear wave velocity
ratio is smaller than a second preset value.
[0008] In one embodiment, the step of calculating the first SWS
coefficient of the first incidence angle direction according to the
primary wave velocity and shear wave velocity of the first
incidence angle direction comprises: acquiring a fast shear wave
velocity and a slow shear wave velocity of the first incidence
angle direction according to the shear wave velocity of the first
incidence angle direction; and calculating the first SWS
coefficient according to the fast shear wave velocity and slow
shear wave velocity of the first incidence angle direction.
[0009] In one embodiment, the first SWS coefficient is calculated
according to the fast shear wave velocity and slow shear wave
velocity of the first incidence angle direction according to a
formula as follows:
SWS1=(Vs11-Vs21)/Vs21
[0010] Wherein, Vs11 means the fast shear wave velocity of the
first incidence angle direction; Vs21 means the slow shear wave
velocity of the first incidence angle direction; and SWS1 means the
first SWS coefficient.
[0011] In one embodiment, after the target fracture is determined
as the horizontal fracture, the method further comprises: acquiring
a fast shear wave velocity and a slow shear wave velocity of the
second incidence angle direction; calculating a second SWS
coefficient of the second incidence angle direction according to
the fast shear wave velocity and the slow shear wave velocity of
the second incidence angle direction; taking the second SWS
coefficient as fracture density of the target fracture; and
determining the development degree of the target fracture according
to the fracture density.
[0012] In one embodiment, the second SWS coefficient of the second
incidence angle direction is calculated according to the fast shear
wave velocity and slow shear wave velocity of the second incidence
angle direction according to a formula as follows:
SWS2=(Vs12-Vs22)/Vs22
[0013] Wherein, Vs12 means the fast shear wave velocity of the
second incidence angle direction, Vs22 means the slow shear wave
velocity of the second incidence angle direction, and SWS2 means
the second SWS coefficient.
[0014] In one embodiment, the step of determining the development
degree of the target fracture according to the fracture density
comprises: judging a preset range to which the fracture density
belongs; determining the development degree of the target fracture
as a fracture nondevelopment zone when the fracture density belongs
to a first preset range; determining the development degree of the
target fracture as a fracture sub-development zone when the
fracture density belongs to a second preset range; and determining
the development degree of the target fracture as a fracture
development zone when the fracture density belongs to a third
preset range.
[0015] In one embodiment, the first incidence angle is greater than
or equal to 0.degree. and is smaller than or equal to 20.degree.;
and the second incidence angle is greater than or equal to
70.degree. and is smaller than or equal to 90.degree..
[0016] Embodiments of the present disclosure further provide a
horizontal fracture prediction device, comprising: an acquisition
module, which is used for acquiring a primary wave velocity and a
shear wave velocity of a first incidence angle direction and a
primary wave velocity and a shear wave velocity of a second
incidence angle direction of seismic waves at a target fracture
location, wherein a first incidence angle is smaller than a second
incidence angle, and the incidence angles are included angles
between propagation directions of the seismic waves and a surface
normal direction of a target fracture; a first calculation module,
which is used for calculating a first primary wave/shear wave
velocity ratio and a first shear-wave splitting (SWS) coefficient
of the first incidence angle direction according to the primary
wave velocity and shear wave velocity of the first incidence angle
direction; a second calculation module, which is used for
calculating a second primary wave/shear wave velocity ratio of the
second incidence angle direction according to the primary wave
velocity and shear wave velocity of the second incidence angle
direction; and a processing module, which is used for determining
that the target fracture is a horizontal fracture under the
condition that the first SWS coefficient is smaller than a first
preset value and a ratio of the first primary wave/shear wave
velocity ratio to the second primary wave/shear wave velocity ratio
is smaller than a second preset value.
[0017] In one embodiment, the first calculation module comprises: a
first acquisition unit, which is used for acquiring a fast shear
wave velocity and a slow shear wave velocity of the first incidence
angle direction according to the shear wave velocity of the first
incidence angle direction; and a first calculation unit, which is
used for calculating the first SWS coefficient according to the
fast shear wave velocity and slow shear wave velocity of the first
incidence angle direction.
[0018] In one embodiment, the first SWS coefficient is calculated
by the first calculation unit according to a formula as
follows:
SWS1=(Vs11-Vs21)/Vs21
[0019] Wherein, Vs11 means the fast shear wave velocity of the
first incidence angle direction; Vs21 means the slow shear wave
velocity of the first incidence angle direction; and SWS1 means the
first SWS coefficient.
[0020] In one embodiment, the processing module further comprises:
a second acquisition unit, which is used for acquiring a fast shear
wave velocity and a slow shear wave velocity of the second
incidence angle direction after the target fracture is determined
as the horizontal fracture; a second calculation unit, which is
used for calculating a second SWS coefficient of the second
incidence angle direction according to the fast shear wave velocity
and the slow shear wave velocity of the second incidence angle
direction; a processing unit, which is used for taking the second
SWS coefficient as fracture density of the target fracture; and a
determination unit, which is used for determining the development
degree of the target fracture according to the fracture
density.
[0021] In one embodiment, the second SWS coefficient is calculated
by the second calculation unit according to a formula as
follows:
SWS2=(Vs12-Vs22)/Vs22
[0022] Wherein, Vs12 means the fast shear wave velocity of the
second incidence angle direction, Vs22 means the slow shear wave
velocity of the second incidence angle direction, and SWS2 means
the second SWS coefficient.
[0023] In one embodiment, the determination unit is further used
for judging a preset range to which the fracture density belongs;
determining the development degree of the target fracture as a
fracture nondevelopment zone when the fracture density belongs to a
first preset range; determining the development degree of the
target fracture as a fracture sub-development zone when the
fracture density belongs to a second preset range; and determining
the development degree of the target fracture as a fracture
development zone when the fracture density belongs to a third
preset range.
[0024] Embodiments of the present disclosure further provide a
horizontal fracture prediction equipment, comprising a processor
and a memory for storing processor executable instructions, wherein
steps of the horizontal fracture prediction method are achieved
when the instructions are executed by the processor.
[0025] Embodiments of the present disclosure further provide a
computer readable storage medium storing computer instructions,
wherein steps of the horizontal fracture prediction method are
achieved when the instructions are executed.
[0026] In embodiments of the present disclosure, a horizontal
fracture prediction method is provided. A first primary wave/shear
wave velocity ratio and a first SWS coefficient of a first
incidence angle direction and a second primary wave/shear wave
velocity ratio of a second incidence angle direction are
calculated, and whether a target fracture is a horizontal fracture
or not is determined according to the obtained first SWS
coefficient, the first primary wave/shear wave velocity ratio and
the second primary wave/shear wave velocity ratio, so that
effective data are provided for exploration and development of
coal-bed gas and shale gas, and then, the yield of the coal-bed gas
and shale gas is effectively increased.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Drawings described herein are used for providing further
comprehension for the present disclosure, form part of the present
application, but not define the present disclosure. In the
drawings:
[0028] FIG. 1 is a schematic diagram of steps of a horizontal
fracture prediction method provided by embodiments of the present
disclosure;
[0029] FIG. 2 is a schematic diagram of a horizontal fracture
prediction method provided by specific embodiments of the present
disclosure;
[0030] FIG. 3 is a schematic diagram of a horizontal fracture
prediction device provided by embodiments of the present
disclosure;
[0031] FIG. 4 is a schematic diagram of horizontal fracture
prediction electronic equipment provided by embodiments of the
present disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0032] The principle and spirit of the present disclosure will be
described below with reference to a plurality of demonstrative
embodiments. It should be understood that presenting of these
embodiments is only intended to make those skilled in the art
better comprehend and then implement the present disclosure, rather
than limiting the scope of the present disclosure in any way.
Contrarily, the presenting of these embodiments is intended to make
the present application disclosure more thorough and complete, and
the scope of the present disclosure can be completely transferred
to those skilled in the art.
[0033] Those skilled in the art know that the embodiments of the
present disclosure may be implemented as a system, arrangement,
method or computer program product. Therefore, the present
application disclosure may be specifically implemented in a form as
follows: complete hardware, complete software (including firmware,
resident software, microcodes, etc.) or hardware and software
combinations.
[0034] In view of the existing fracture prediction methods, such as
a shear-wave splitting based formation fracture prediction method,
a propagation path of excited seismic waves is approximately
perpendicular to a horizontal fracture plane, and anisotropic
features of a horizontal fracture location are not represented, so
that the method can only be used for effectively predicting
vertical fractures and cannot be used for effectively predicting
horizontal fractures when fractures are predicted by using the
method.
[0035] Based on the above-mentioned problem that horizontal
fractures cannot be effectively predicted, embodiments of the
present disclosure provide a horizontal fracture prediction method,
referring to FIG. 1, and the method may comprise the following
steps.
[0036] Step S101: a primary wave velocity and a shear wave velocity
of a first incidence angle direction and a primary wave velocity
and a shear wave velocity of a second incidence angle direction of
seismic waves at a target fracture location are acquired, wherein a
first incidence angle is smaller than a second incidence angle, and
the incidence angles are included angles between propagation
directions of the seismic waves and a surface normal direction of a
target fracture.
[0037] Multiwave seismic exploration is a method for exploring
formations through comprehensively utilizing a variety of seismic
waves such as primary waves and shear waves (or converted waves),
accordingly, multiwave seismic data carry formation lithologic
information richer than components of separate waves (the primary
waves), particularly formation fracture information. Therefore, the
primary wave velocity and shear wave velocity of the first
incidence angle direction and the primary wave velocity and shear
wave velocity of the second incidence angle direction can be
obtained through performing preprocessing and velocity analysis on
the acquired multiwave seismic data of the target fracture
location. Wherein, the preprocessing comprises, but not limited to,
denoising, amplitude compensating and gaining; and the velocity
analysis comprises, but not limited to, acquiring a seismic wave
correcting velocity through velocity scanning.
[0038] The above-mentioned first incidence angle is smaller than
the second incidence angle, specifically, the first incidence angle
is greater than or equal to 0.degree. and is smaller than or equal
to 20.degree., and the second incidence angle is greater than or
equal to 70.degree. and is smaller than or equal to 90.degree..
Wherein, the above-mentioned incidence angles may be included
angles between the propagation directions of the seismic waves and
a plane normal direction of the fracture. Further, in seismic
exploration, numerous source points (locations of seismic focuses
exciting the seismic waves) and receiver points (locations of wave
detectors receiving the seismic waves) compose an observation
system. Therefore, seismic wave incidence-reflection paths of
different angles are present, and the propagation directions of the
seismic waves can be determined according to source point-receiver
point space locations in the observation system.
[0039] The incidence angles are in a range of 0.degree. (namely
perpendicular to a fracture plane) to 90.degree. (namely parallel
to the fracture plane); and in the multiwave seismic data, proper
spacing among the seismic wave incidence-reflection paths of all
the different angles can be selected, and thus, the condition that
multiwave seismic data of only one direction between 0.degree. and
20.degree. and between 70.degree. and 90.degree. are present is
guaranteed, namely, the first incidence angle and the second
incidence angle are unique.
[0040] Step S102: a first primary wave/shear wave velocity ratio
and a first shear-wave splitting (SWS) coefficient of the first
incidence angle direction are calculated according to the primary
wave velocity and shear wave velocity of the first incidence angle
direction.
[0041] In respect that when seismic shear waves are propagated in a
fracture-containing anisotropic medium, an SWS phenomenon will
occur to form fast shear waves and slow shear waves, the degree of
difference between the fast shear waves and the slow shear waves is
proportional to the degree of development of formation fractures,
and the SWS phenomenon mainly embodies fracture information.
Therefore, a fast shear wave velocity and a slow shear wave
velocity of the first incidence angle direction can be acquired
from the multiwave seismic data of the target fracture location,
and the first SWS coefficient is calculated according to the fast
shear wave velocity and the slow shear wave velocity of the first
incidence angle direction. Wherein, the first SWS coefficient is
obtained through a formula below:
SWS1=(Vs11-Vs21)/Vs21
[0042] Wherein, Vs11 means the fast shear wave velocity of the
first incidence angle direction; Vs21 means the slow shear wave
velocity of the first incidence angle direction; and SWS1 means the
first SWS coefficient.
[0043] Further, the first primary wave/shear wave velocity ratio is
a value obtained by dividing the primary wave velocity by the shear
wave velocity of the first incidence angle direction of the target
fracture location.
[0044] Step S103: a second primary wave/shear wave velocity ratio
of the second incidence angle direction is calculated according to
the primary wave velocity and shear wave velocity of the second
incidence angle direction.
[0045] The second primary wave/shear wave velocity ratio is a value
obtained by dividing the primary wave velocity by the shear wave
velocity of the second incidence angle direction of the target
fracture location.
[0046] Step S104: it is determined that the target fracture is a
horizontal fracture under the condition that the first SWS
coefficient is smaller than a first preset value and a ratio of the
first primary wave/shear wave velocity ratio to the second primary
wave/shear wave velocity ratio is smaller than a second preset
value.
[0047] Wherein, the first preset value may be 0.02, and the second
preset value may be 0.8. When the first SWS coefficient is smaller
than 0.02 and the ratio of the first primary wave/shear wave
velocity ratio to the second primary wave/shear wave velocity ratio
is smaller than 0.8, it can be determined that the target fracture
is a horizontal fracture. It is understandable that the first
preset value and the second preset value may also be set as other
reasonable values according to actual situations and are not
defined in the present application.
[0048] Fracture density is a conceptual value representing a
fracture development degree and is used for reflecting the fracture
development degree. The target fracture can be divided into a
fracture development zone, a fracture sub-development zone or a
fracture nondevelopment zone according to the fracture density; and
in one embodiment, the second SWS coefficient can serve as the
fracture density of the target fracture to determine the
development degree of the target fracture.
[0049] Specifically, after the target fracture is determined as the
horizontal fracture, a fast shear wave velocity and a slow shear
wave velocity of the second incidence angle direction can be
acquired from the multiwave seismic data of the target fracture
location, and the second SWS coefficient is calculated according to
the fast shear wave velocity and slow shear wave velocity of the
second incidence angle direction. Wherein, the second SWS
coefficient is obtained through a formula below:
SWS2=(Vs12-Vs22)/Vs22
[0050] Wherein, Vs12 means the fast shear wave velocity of the
second incidence angle direction; Vs22 means the slow shear wave
velocity of the second incidence angle direction; and SWS2 means
the second SWS coefficient.
[0051] Then, the development degree of the target fracture is
determined according to the fracture density by taking the second
SWS coefficient as fracture density of the target fracture.
Firstly, a preset range to which the fracture density belongs is
judged; when the fracture density belongs to a first preset range,
the development degree of the target fracture is determined as a
fracture nondevelopment zone; when the fracture density belongs to
a second preset range, the development degree of the target
fracture is determined as a fracture sub-development zone; and when
the fracture density belongs to a third preset range, the
development degree of the target fracture is determined as a
fracture development zone. Wherein, the first preset range may be
smaller than 0.02, the second preset range may be greater than or
equal to 0.02 and smaller than or equal to 0.08, and the third
preset range may be greater than 0.08. It is explanatory that the
above-mentioned three preset ranges may be set as other reasonable
values according to actual situations and are not defined in the
present application.
[0052] The above-mentioned method is described below with reference
to one specific embodiment. However, it is noteworthy that the
specific embodiment is only used for better describing the present
application, but not improperly defining the present
application.
[0053] Embodiments of the present disclosure provide a horizontal
fracture prediction method, referring to FIG. 2, and the method may
comprise the following steps.
[0054] Step 201: multiwave seismic data are acquired from a target
fracture location, and preprocessing and velocity analysis are
performed on the multiwave seismic data to obtain primary wave
velocities Vp, shear wave velocities Vs, fast shear wave velocities
Vs1 and slow shear wave velocities Vs2 of different incidence angle
directions.
[0055] Wherein, the preprocessing comprises denoising, amplitude
compensating and gaining; and the velocity analysis specifically
comprises acquiring a seismic wave correcting velocity through
performing velocity scanning on the multiwave seismic data, and
performing analysis to obtain the primary wave velocities Vp, the
shear wave velocities Vs, the fast shear wave velocities Vs1 and
the slow shear wave velocities Vs2 of different incidence angle
directions.
[0056] Step 202: primary wave/shear wave velocity ratios and SWS
coefficients of different directions are calculated.
[0057] Wherein, the primary wave/shear wave velocity ratios are
values obtained by dividing the primary wave velocities Vp by the
shear wave velocities Vs.
[0058] In respect that when seismic shear waves are propagated in a
fracture-containing anisotropic medium, an SWS phenomenon will
occur to form fast shear waves and slow shear waves, the degree of
difference between the fast shear waves and the slow shear waves is
proportional to the degree of development of formation fractures,
and the SWS phenomenon mainly embodies fracture information.
Therefore, the SWS coefficient can be calculated according to the
fast shear wave velocity Vs1 and the slow shear wave velocity Vs2.
Wherein, the SWS coefficient is obtained through a formula
below:
SWS=(Vs1-Vs2)/Vs2
[0059] Step 203: a primary wave/shear wave velocity ratio and the
SWS coefficient of a direction of a relatively small incidence
angle are compared with a primary wave/shear wave velocity ratio
and the SWS coefficient of a direction of a relatively big
incidence angle, and a horizontal fracture is predicted according
to a comparison result.
[0060] Wherein, the above-mentioned incidence angles are included
angles between the propagation directions of the seismic waves and
a plane normal direction of the fracture and are in a range of
0.degree. (namely perpendicular to a fracture plane) to 90.degree.
(namely parallel to the fracture plane). In seismic exploration,
numerous source points (locations of seismic focuses exciting the
seismic waves) and receiver points (locations of wave detectors
receiving the seismic waves) compose an observation system.
Therefore, seismic wave incidence-reflection paths of different
angles are present, and the incidence angles can be determined
according to source point-receiver point space locations in the
observation system. Wherein, the direction of the relatively small
incidence angle is a direction of an incidence angle in a range of
0.degree.-20.degree., and the direction of the relatively big
incidence angle is a direction of an incidence angle in a range of
70.degree.-90.degree..
[0061] A judgment basis for predicting the horizontal fracture is
as follows: the target fracture is determined as the horizontal
fracture under the condition that the SWS coefficient of the
relatively small incidence angle is smaller than 0.02 and a ratio
of the primary wave/shear wave velocity ratio of the direction of
the relatively small incidence angle to the primary wave/shear wave
velocity ratio of the direction of the relatively big incidence
angle is smaller than 0.8.
[0062] Further, fracture density is a conceptual value representing
a fracture development degree and is used for reflecting the
fracture development degree. The target fracture can be divided
into a fracture development zone, a fracture sub-development zone
or a fracture nondevelopment zone according to the fracture
density; and in one specific embodiment, a mode for evaluating a
development degree of the horizontal fracture is as follows: the
SWS coefficient of the direction of the relatively big incidence
angle serves as the fracture density of the target fracture. The
development degree of the horizontal fracture is determined
according to the fracture density. Firstly, a preset range to which
the fracture density belongs is judged; when the fracture density
belongs to a first preset range, the development degree of the
target fracture is determined as a fracture nondevelopment zone;
when the fracture density belongs to a second preset range, the
development degree of the target fracture is determined as a
fracture sub-development zone; and when the fracture density
belongs to a third preset range, the development degree of the
target fracture is determined as a fracture development zone.
Wherein, the first preset range may be smaller than 0.02, the
second preset range may be greater than or equal to 0.02 and
smaller than or equal to 0.08, and the third preset range may be
greater than 0.08. It is explanatory that the above-mentioned three
preset ranges may be set as other reasonable values according to
actual situations and are not defined in the present
application.
[0063] Based on the same inventive concept, embodiments of the
present disclosure further provide a horizontal fracture prediction
device, described in an embodiment as follows. A problem solving
principle of the horizontal fracture prediction device is similar
to that of the horizontal fracture prediction method, so that the
implementation of the horizontal fracture prediction device refers
to that of the horizontal fracture prediction method, and
repetitions are not explained any more. Terms `unit` or `module`
used hereinafter can achieve a combination of software and/or
hardware of predetermined functions. Although the device described
in the embodiment as follows is preferably achieved by software,
realization by hardware or combinations of the software and the
hardware is also possible and is conceived. FIG. 3 is a structure
block diagram of a horizontal fracture prediction device of
embodiments of the present disclosure. Referring to FIG. 3, the
horizontal fracture prediction device comprises an acquisition
module 301, a first calculation module 302, a second calculation
module 303 and a processing module 304, and a structure is
described as follows.
[0064] The acquisition module 301 is used for acquiring a primary
wave velocity and a shear wave velocity of a first incidence angle
direction and a primary wave velocity and a shear wave velocity of
a second incidence angle direction of seismic waves at a target
fracture location, wherein a first incidence angle is smaller than
a second incidence angle, and the incidence angles are included
angles between propagation directions of the seismic waves and a
surface normal direction of a target fracture.
[0065] Multiwave seismic exploration is a method for exploring
formations through comprehensively utilizing a variety of seismic
waves such as primary waves and shear waves (or converted waves),
accordingly, multiwave seismic data carry formation lithologic
information richer than components of separate waves (the primary
waves), particularly formation fracture information. Therefore, the
primary wave velocity and shear wave velocity of the first
incidence angle direction and the primary wave velocity and shear
wave velocity of the second incidence angle direction can be
obtained through performing preprocessing and velocity analysis on
the acquired multiwave seismic data of the target fracture
location. Wherein, the preprocessing comprises, but not limited to,
denoising, amplitude compensating and gaining; and the velocity
analysis comprises, but not limited to, acquiring a seismic wave
correcting velocity through velocity scanning.
[0066] The above-mentioned first incidence angle is smaller than
the second incidence angle, specifically, the first incidence angle
may be greater than or equal to 0.degree. and smaller than or equal
to 20.degree., and the second incidence angle may be greater than
or equal to 70.degree. and smaller than or equal to 90.degree..
Wherein, the above-mentioned incidence angles may be included
angles between the propagation directions of the seismic waves and
a plane normal direction of the fracture. Further, in seismic
exploration, numerous source points (locations of seismic focuses
exciting the seismic waves) and receiver points (locations of wave
detectors receiving the seismic waves) compose an observation
system. Therefore, seismic wave incidence-reflection paths of
different angles are present, and the propagation directions of the
seismic waves can be determined according to source point-receiver
point space locations in the observation system.
[0067] The incidence angles are in a range of 0.degree. (namely
perpendicular to a fracture plane) to 90.degree. (namely parallel
to the fracture plane); and in the multiwave seismic data, proper
spacing among the seismic wave incidence-reflection paths of all
the different angles can be selected, and thus, the condition that
multiwave seismic data of only one direction between 0.degree. and
20.degree. and between 70.degree. and 90.degree. are present is
guaranteed, namely, the first incidence angle and the second
incidence angle are unique.
[0068] The first calculation module 302 is used for calculating a
first primary wave/shear wave velocity ratio and a first shear-wave
splitting (SWS) coefficient of the first incidence angle direction
according to the primary wave velocity and shear wave velocity of
the first incidence angle direction.
[0069] In respect that when seismic shear waves are propagated in a
fracture-containing anisotropic medium, an SWS phenomenon will
occur to form fast shear waves and slow shear waves, the degree of
difference between the fast shear waves and the slow shear waves is
proportional to the degree of development of formation fractures,
and the SWS phenomenon mainly embodies fracture information. In one
embodiment, the first calculation module may comprise: a first
acquisition unit, which is used for acquiring a fast shear wave
velocity and a slow shear wave velocity of the first incidence
angle direction from the multiwave seismic data of the target
fracture location; and a first calculation unit, which is used for
calculating the first SWS coefficient according to the fast shear
wave velocity and slow shear wave velocity of the first incidence
angle direction. Wherein, the first SWS coefficient is obtained
through a formula below:
SWS1=(Vs11-Vs21)/Vs21
[0070] Wherein, Vs11 means the fast shear wave velocity of the
first incidence angle direction; Vs21 means the slow shear wave
velocity of the first incidence angle direction; and SWS1 means the
first SWS coefficient.
[0071] Further, the first primary wave/shear wave velocity ratio is
a value obtained by dividing the primary wave velocity by the shear
wave velocity of the first incidence angle direction of the target
fracture location.
[0072] The second calculation module 303 is used for calculating a
second primary wave/shear wave velocity ratio of the second
incidence angle direction according to the primary wave velocity
and shear wave velocity of the second incidence angle
direction.
[0073] The second primary wave/shear wave velocity ratio may be a
value obtained by dividing the primary wave velocity by the shear
wave velocity of the second incidence angle direction of the target
fracture location.
[0074] The processing module 304 is used for determining that the
target fracture is a horizontal fracture under the condition that
the first SWS coefficient is smaller than a first preset value and
a ratio of the first primary wave/shear wave velocity ratio to the
second primary wave/shear wave velocity ratio is smaller than a
second preset value.
[0075] Wherein, the first preset value may be 0.02, and the second
preset value may be 0.8. When the first SWS coefficient is smaller
than 0.02 and the ratio of the first primary wave/shear wave
velocity ratio to the second primary wave/shear wave velocity ratio
is smaller than 0.8, it can be determined the target fracture is a
horizontal fracture. It is understandable that the first preset
value and the second preset value may also be set as other
reasonable values according to actual situations and are not
defined in the present application.
[0076] Fracture density is a conceptual value representing a
fracture development degree and is used for reflecting the fracture
development degree. The target fracture can be divided into a
fracture development zone, a fracture sub-development zone or a
fracture nondevelopment zone according to the fracture density; and
in one embodiment, the second SWS coefficient can serve as the
fracture density of the target fracture to determine the
development degree of the target fracture.
[0077] Specifically, after the target fracture is determined as the
horizontal fracture, the processing module further may comprise a
second acquisition unit, which is used for acquiring a fast shear
wave velocity and a slow shear wave velocity of the second
incidence angle direction from the multiwave seismic data of the
target fracture location; and a second calculation unit, which is
used for calculating the second SWS coefficient according to the
fast shear wave velocity and slow shear wave velocity of the second
incidence angle direction. Wherein, the second SWS coefficient is
obtained through a formula below:
SWS2=(Vs12-Vs22)/Vs22
[0078] Wherein, Vs12 means the fast shear wave velocity of the
second incidence angle direction; Vs22 means the slow shear wave
velocity of the second incidence angle direction; and SWS2 means
the second SWS coefficient.
[0079] After the second SWS coefficient is obtained through
calculation, the second SWS coefficient serves as the fracture
density of the target fracture in a processing unit, and the
development degree of the target fracture is determined through a
determination unit according to the fracture density of the target
fracture location.
[0080] Further, the determination unit is further used for judging
a preset range to which the fracture density belongs; determining
the development degree of the target fracture as a fracture
nondevelopment zone when the fracture density belongs to a first
preset range; determining the development degree of the target
fracture as a fracture sub-development zone when the fracture
density belongs to a second preset range; and determining the
development degree of the target fracture as a fracture development
zone when the fracture density belongs to a third preset range.
Wherein, the first preset range may be smaller than 0.02, the
second preset range may be greater than or equal to 0.02 and
smaller than or equal to 0.08, and the third preset range may be
greater than 0.08. It is explanatory that the above-mentioned three
preset ranges may be set as other reasonable values according to
actual situations and are not defined in the present
application.
[0081] From descriptions above, it is observed that the embodiments
of the present disclosure achieve the following technical effects
that: whether a target fracture is a horizontal fracture or not is
determined through calculating a primary wave/shear wave velocity
ratio and a first SWS coefficient of a first incidence angle
direction and a primary wave/shear wave velocity ratio of a second
incidence angle direction by using seismic anisotropy and physical
features of rocks, and a development degree of the horizontal
fracture is further determined through the SWS coefficient, so that
horizontal fractures in reservoir beds such as coal beds and shale
and development degrees thereof can be effectively predicted,
effective data are provided for exploration and development of
coal-bed gas and shale gas, and then, the yield of the coal-bed gas
and shale gas is effectively increased.
[0082] Embodiments of the present application further provide
electronic equipment, specifically referring to a composition
structural schematic diagram of the electronic equipment based on
the horizontal fracture prediction method provided by the
embodiments of the present application shown in FIG. 4, and the
electronic equipment specifically may comprise input equipment 41,
a processor 42 and a memory 43. Wherein, the input equipment 41
specifically may be used for inputting a primary wave velocity and
a shear wave velocity of a first incidence angle direction and a
primary wave velocity and a shear wave velocity of a second
incidence angle direction of seismic waves at a target fracture
location, wherein a first incidence angle is smaller than a second
incidence angle, and the incidence angles are included angles
between propagation directions of the seismic waves and a surface
normal direction of a target fracture. The processor 42
specifically may be used for calculating a first primary wave/shear
wave velocity ratio and a first shear-wave splitting (SWS)
coefficient of the first incidence angle direction according to the
primary wave velocity and shear wave velocity of the first
incidence angle direction; calculating a second primary wave/shear
wave velocity ratio of the second incidence angle direction
according to the primary wave velocity and shear wave velocity of
the second incidence angle direction; and determining that the
target fracture is a horizontal fracture under the condition that
the first SWS coefficient is smaller than a first preset value and
a ratio of the first primary wave/shear wave velocity ratio to the
second primary wave/shear wave velocity ratio is smaller than a
second preset value. The memory 43 specifically may be used for
storing parameters such as a primary wave velocity, a shear wave
velocity, a fast shear wave velocity and a slow shear wave velocity
of the first incidence angle direction and a primary wave velocity,
a shear wave velocity, a fast shear wave velocity and a slow shear
wave velocity of the second incidence angle direction.
[0083] In the present embodiment, the input equipment specifically
may be one of main devices for information exchange between a user
and a computer system. The input equipment may comprise a keyboard,
a mouse, a camera, a scanner, a light pen, a handwriting tablet, a
voice input device, etc.; and the input equipment is used for
inputting raw data and programs for processing these data into a
computer. The input equipment also can be used for acquiring and
receiving data transmitted from other modules, units and equipment.
The processor may be implemented in any appropriate manner. For
example, the processor may be in the form of a microprocessor or
processor, a computer readable medium storing computer readable
program codes (for example software or firmware) capable of being
executed by the (micro)processor, a logic gate, a switch, an
application specific integrated circuit (ASIC), a programmable
logic controller or an embedded microcontroller. The memory
specifically may be a memory device for storing information in
modern information technologies. The memory may comprise a
plurality of hierarchies, and in digital systems, any device which
can save binary data can be called a memory; in integrated
circuits, a circuit, which is free of a real object form and has a
storing function, is also called a memory, such as RAM and FIFO;
and in systems, a storage device with a real object form is also
called a memory, such as a memory bank and a TF card.
[0084] In the present embodiment, functions and effects
specifically achieved by the electronic equipment can be explained
in a manner of being compared with other embodiments and are not
explained any more.
[0085] Embodiments of the present application further provide a
computer readable storage medium based on the horizontal fracture
prediction method. The computer readable storage medium stores
computer programmed instructions, and the effects of determining
whether the target fracture is a horizontal fracture or not and
further determining a development degree of the horizontal fracture
if the target fracture is determined as the horizontal fracture are
achieved when the computer programmed instructions are
executed.
[0086] In the present embodiment, the storage medium comprises, but
not limited to, a random access memory (RAM), a read-only memory
(ROM), a cache, a hard disk drive (HDD) or a memory card. The
memory can be used for storing the computer programmed
instructions. A network communication unit may be an interface set
according to standards specified by communication protocols and
used for performing network communication.
[0087] In the present embodiment, functions and effects
specifically achieved by the programmed instruction stored by the
computer storage medium can be explained in a manner of being
compared with other embodiments and are not explained any more.
[0088] Apparently, those skilled in the art should understand that
all modules or steps of the above-mentioned embodiments of the
present disclosure may be implemented with general calculating
devices, may be centralized on a single calculating device or
distributed on a network composed of a plurality of calculating
devices, and optionally, may be implemented with calculating device
executable program codes, so that the modules or steps can be
stored in memory devices and executed by a calculating device; and
under certain circumstances, the steps shown or described may be
executed in a sequence different from that herein, or are
implemented through separately making the steps into each
integrated circuit module or making a plurality of modules or steps
thereof into single integrated circuit modules. Thus, the
embodiments of the present disclosure are not restricted to any
specific hardware and software combination.
[0089] It should be understood that descriptions above are intended
for graphic illustration rather than restriction. Through reading
the above-mentioned descriptions, many embodiments and many
applications, besides the provided examples, would be obvious to
those skilled in the art. Accordingly, the scope of the present
application should not be determined referring to the
above-mentioned descriptions, but should be determined referring to
full coverage of the fore-mentioned claims and equivalents occupied
by these claims.
[0090] The above mentioned are only preferred embodiments of the
present disclosure and are not intended to restrict the present
disclosure; and for those skilled in the art, the embodiments of
the present disclosure may have various modifications and
variations. Any modification, equivalent replacement, improvement
and the like made within the spirit and principle of the present
disclosure shall fall within the scope of protection of the present
disclosure.
* * * * *