AU2021107040A4 - A comprehensive method for deep geological exploration in urban areas - Google Patents
A comprehensive method for deep geological exploration in urban areas Download PDFInfo
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- AU2021107040A4 AU2021107040A4 AU2021107040A AU2021107040A AU2021107040A4 AU 2021107040 A4 AU2021107040 A4 AU 2021107040A4 AU 2021107040 A AU2021107040 A AU 2021107040A AU 2021107040 A AU2021107040 A AU 2021107040A AU 2021107040 A4 AU2021107040 A4 AU 2021107040A4
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- 238000000034 method Methods 0.000 title claims abstract description 67
- 230000005484 gravity Effects 0.000 claims abstract description 23
- 239000003245 coal Substances 0.000 claims abstract description 16
- 238000001514 detection method Methods 0.000 claims description 22
- 235000019738 Limestone Nutrition 0.000 claims description 17
- 239000006028 limestone Substances 0.000 claims description 17
- 230000008569 process Effects 0.000 claims description 8
- 239000011435 rock Substances 0.000 claims description 7
- 238000007405 data analysis Methods 0.000 claims 1
- 230000015572 biosynthetic process Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 6
- 238000012545 processing Methods 0.000 description 5
- 230000005684 electric field Effects 0.000 description 3
- 230000005672 electromagnetic field Effects 0.000 description 3
- 230000004044 response Effects 0.000 description 3
- 241000417893 Kania Species 0.000 description 2
- 235000019994 cava Nutrition 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000005284 excitation Effects 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000009933 burial Methods 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000012937 correction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000002500 effect on skin Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V11/00—Prospecting or detecting by methods combining techniques covered by two or more of main groups G01V1/00 - G01V9/00
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V1/00—Seismology; Seismic or acoustic prospecting or detecting
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V3/00—Electric or magnetic prospecting or detecting; Measuring magnetic field characteristics of the earth, e.g. declination, deviation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V7/00—Measuring gravitational fields or waves; Gravimetric prospecting or detecting
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- Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- Geophysics (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Geology (AREA)
- Remote Sensing (AREA)
- Acoustics & Sound (AREA)
- Geophysics And Detection Of Objects (AREA)
Abstract
The invention provides a comprehensive method for deep geological exploration
in urban areas. This method comprises: conducting preliminary exploration using a
gravity method to obtain the density information of the target body in the center of the
urban area, conducting supplementary exploration using the electromagnetic method
to obtain the electrical information of the target body; conducting fine exploration of
typical sections by the seismic method to obtain velocity information of the target
body. The comprehensive combination of gravity, electromagnetic, and seismic
methods can be applied in the deep exploration in urban areas, acquiring more
accurate and precise data of coal seam structure.
-1- / 1
Drawings
I.
boundary of
seismic and EM
boundary and --------- _
point of gravity
Fig. 1
60'
Fig. 2
-1- / 3
Description
Drawings
boundary of seismic and EM
boundary and --------- _ point of gravity
Fig. 1
60'
Fig. 2
-1- / 3
Description A comprehensive method for deep geological exploration in urban areas
The invention relates to the field of city, engineering environment and
geophysical exploration, in particular to a comprehensive method for deep detection
in urban environment.
Background technology
Underground targets such as cavities, water bodies and structures are
distributed in many cities in northern China, it is difficult to accurately locate
underground targets. Geophysical methods are commonly used to determine these
kind of special targets. However, due to large electromagnetic interference, dense
population and many buildings in urban areas, geophysical detection is limited
in many aspects. Therefore, it is very necessary to select appropriate geophysical
methods and their combinations, carry out effective exploration step by
step, make various achievements complement each other, and realize the
exploration of underground deep structures in urban areas.
Summary of the invention
In order to solve the above technical problems, the invention provides a
comprehensive method for deep detection in an urban environment. In order to have a
basic understanding of some aspects of the disclosed embodiments, a brief summary
is given below. This summary is not a general comment, nor is it intended to identify
key/important constituent elements or describe the scope of protection of these
embodiments. Its sole purpose is to present some concepts in a simple form as a
-1- / 12
Description preface to the detailed description later.
The invention adopts the following technical scheme:
In some optional embodiments, a comprehensive method for deep detection in
an urban environment is provided, including the following steps: conducting
preliminary detection by gravity method to obtain the density information of the
target body; conducting supplementary detection by electromagnetic method to
obtain the electrical information of the target body; conducting fine detection of
typical sections by seismic method to obtain the velocity information of the target
body.
The invention relates to a comprehensive geophysical methods for deep
detection in an urban environment is further characterized by comprehensively
analyzing the three geophysical data obtained by the preliminary detection of the
gravity method, the supplementary detection of the electromagnetic method and the
fine seismic detection of the typical section, so as to determine the accurate
geological information of the deep structure in the urban area.
Furthermore, the gravity method preliminarily detects and obtains the density
information of the target body, including: in the urban area to be evaluated where
there are a lot of electromagnetic noise and dense buildings, the gravity detection
method is used to preliminarily infer the buried depth and fluctuation characteristics
of the upper interface of the limestone of the basement of the deep structure, as well
as the fault structure, so as to determine the preliminary geological information of the
deep structure.
-2- / 12
Description Furthermore, the process of supplementary detection of the electromagnetic
method to obtain the electrical information of the target body includes: in the
periphery of the urban area, the electromagnetic interference is relatively small. The
electromagnetic sounding method is used to detect and form the electromagnetic
apparent resistivity section. Based on the electrical difference between the deep
structure and the surrounding rock, the occurrence characteristics and deep structural
characteristics of the basement limestone in the urban area are estimated
supplementarily on the apparent resistivity section, and further supplementary
geological information of deep structure is given according to electromagnetic
results.
Further, the process of obtaining the velocity information of the target body by
fine seismic exploration of the typical section includes: the seismic exploration
method is used to detect in the periphery of the urban area to form a seismic section.
Using the elastic wave velocity difference between the deep structure and the
surrounding rock, the occurrence characteristics and deep structural characteristics of
the coal measure strata and the base limestone of the coal measure strata in the urban
area are finely estimated on the velocity section, and the further fine geological
information of the deep structure is obtained.
-3- / 12
Description
Beneficial effects brought by the invention: the three geophysical methods of
gravity, electromagnetic and seismic are used to cooperate in comprehensive
exploration, so that the high-precision data of coal seam structure and shape in the
exploration area with the best effect can be obtained, which is more accurate.
Description of diagrams
Fig. 1 is the layout of gravity method in the central urban area of the invention;
Fig.2 is a schematic diagram of the principle of frequency-domain
electromagnetic sounding of the invention;
Fig.3 is the layout of electromagnetic exploration outside the urban area of the
invention;
Fig.4 is the inference diagram of the Austrian roof interface;
Fig.5 is the seismic geological section.
Specific embodiments
The following description and the accompanying diagrams fully show specific
embodiments of the invention so that those skilled in the art can practice them. Other
embodiments may include structural, logical, electrical, process, and other changes.
The embodiments represent only possible changes. Unless explicitly required,
individual components and functions are optional and the order of operation can be
changed. Portions and features of some embodiments may be included in or replace
portions and features of other embodiments.
In some illustrative embodiments, the invention provides a comprehensive
-4-/12
Description method for deep detection in an urban environment, comprising the following steps:
First, conducting preliminary detection by gravity method to obtain the density
information of the target body;
The specific process is that in the urban area to be evaluated where there are a
lot of electromagnetic noise and dense buildings, the gravity detection method is used
to preliminarily infer the buried depth and fluctuation characteristics of the upper
interface of the limestone of the basement of the deep structure, as well as the fault
structure, so as to determine the preliminary geological information of the deep
structure.
Then, conducting supplementary detection by electromagnetic method to obtain
the electrical information of the target body;
The specific process is that using the electromagnetic sounding method to detect
and form the electromagnetic apparent resistivity section in the periphery of the urban
area. Based on the electrical difference between the deep structure and the
surrounding rock, the occurrence characteristics and deep structural characteristics of
the basement limestone in the urban area are estimated supplementarily on the
apparent resistivity section, and further supplementary geological information of deep
structure is given according to electromagnetic results.
Then, conducting fine detection of typical sections by seismic method to obtain
the velocity information of the target body.
The specific process is that using the seismic exploration method to detect in the
periphery of the urban area to form a seismic section. Using the elastic wave velocity
-5- / 12
Description
difference between the deep structure and the surrounding rock, the occurrence
characteristics and deep structural characteristics of the coal measure strata and the
base limestone of the coal measure strata in the urban area are finely estimated on the
velocity section, and the further fine geological information of the deep structure is
obtained.
-6- / 12
Description
Finally, three kinds of geophysical data obtained from preliminary detection by
gravity method, supplementary detection by electromagnetic method and fine seismic
exploration of typical sections are comprehensively analyzed to determine the
accurate geological information of deep structures in the urban area.
The survey area is located in Yangqu county, Taiyuan. There are dense buildings
in the urban area, and many caves are distributed around the urban area.
Electromagnetic method and seismic exploration cannot be carried out normally. The
exploration with one geophysical method is obviously restricted, and the combination
of multiple methods must be used to effectively detect the undulating shape of the
basement of underground coal measures.
In this exploration, three geophysical methods of gravity, electromagnetic and
seismic are used for collaborative exploration. First, gravity exploration is used to
find out the undulating shape and buried depth of the fixed interface of Ordovician
limestone in the urban area of Yangqu county. Then, the electromagnetic exploration
is carried out to obtain the form and buried depth of Ordovician limestone outside the
urban area. From the gravity exploration results in the urban area and the
electromagnetic exploration results outside the urban area, the fluctuation form and
buried depth information of the fixed interface of Ordovician limestone in the whole
area are obtained. Finally, the exploration area is identified by seismic method, the
detailed information of the coal seam above the fixed interface of Ordovician
limestone is obtained, and the high-precision data of coal seam structure and shape in
-7- /12
Description the exploration area with the best effect are obtained by integrating the results of the
above three methods.
First, gravity exploration is carried out in the urban area of Yangqu county,
Shanxi Province, to understand the fluctuation of Ordovician limestone top interface.
The strata in the urban area of Yangqu county from old to new are Ordovician,
Benxi Formation of Middle Carboniferous, Taiyuan Formation of Upper
Carboniferous, Shanxi formation of Lower Permian and Lower Shihezi Formation of
Lower Permian, in which the coal seams are mainly distributed in Taiyuan formation.
The density of coal seam is the lowest in Yangqu area, generally 1.2-1.5g/cm 3. The
second is mudstone density of 2.0-2.2g/cm 3, Tertiary conglomerate 2.2-2.4g/cm 3. The
density of limestone is relatively high, generally above 2.7g/cm 3. It can be seen that
there is an obvious density difference interface between Ordovician limestone and
overlying strata, which provides an interpretation basis for gravity exploration in this
area. The layout of the gravity method in the urban area is shown in Fig. 1.
CG-3M automatic gravimeter produced by SCINTREX, a Canadian company,
was used to test at obstacles. It was found that the response of the building was 40
pgal, the response of the cave was 25 pgal, and the abnormal value caused by the
bottom interface of deep coal seam is 3419mgal3425mgal. The interference
anomaly is very small compared with the effective anomaly. Thus, the impact of
buildings and caves can be ignored.
Then, supplementary exploration was carried out by electromagnetic method to
determine the burial depth of coal seam bottom interface.
-8- / 12
Description
CSAMT adopts a controllable artificial source, which is connected to two
grounded electrodes through a certain length of wire to supply alternating current to
the earth for transmission. For the horizontal layered earth, the transmitted waves are
TE and TM mixed waves. Observe the electromagnetic response excited by the
source at an appropriate distance from the source, and judge the underground
geological structure through the analysis and interpretation of data with geological
information. The high frequency corresponds to the shallow part and the low
frequency corresponds to the deep part. CSAMT has the advantages of high
efficiency, large exploration depth, high resolution, flexible device, convenient
construction, multiple parameters, little influence by terrain, strong ability to
penetrate high-resistivity layer and so on. The schematic diagram of
frequency-domain electromagnetic sounding principle is shown in Figure 2.
CSAMT follows the Kania formula of MT. By observing a pair of orthogonal
electric field component and magnetic field component in the far field and calculating
the ratio between them, it is called the impedance of electromagnetic wave, so as to
obtain the resistivity p, of the earth in uniform half space, as follows:
Pa - Z = wP wp H, Wp H,
In the above formula, c is the frequency, p is the permeability of the earth,
E, and H, is the orthogonal electric field component and magnetic field component
respectively.
The formula of apparent resistivity p, defined by electric field component E0
is as follows: -9- / 12
Description 4xr3 E, Ia 3cos2O-1
In the above formula, Ia is the horizontal harmonic electric dipole and r is
the polar distance.
In the case of far field, the apparent resistivity defined is basically the same for
all frequency sounding curves of the same geoelectric section, whether according to
Kania ratio method or single component method. However, due to the use of artificial
source excitation, it can't ensure that all sounding data are in the far field. When the
low-frequency data is in the near field, the apparent resistivity data is distorted and
can't reflect the deep geological information.
According to the theory of electromagnetic field, after the source is established,
the electromagnetic field is distributed in any range of depth underground. However,
for convenience, it is necessary to define the depth of the electromagnetic field. The
skin effect of electromagnetic wave propagation in the earth medium is used, that is,
the detection depth is determined by the different skin depth of electromagnetic
waves with different frequencies in the stratum. The skin depth is calculated as
follows:
15= 503;
In the above formula, A represents the formation resistivity and f represents
the working frequency.
In the periphery of the urban area, the electromagnetic interference is relatively
small. The electromagnetic sounding method was used to detect and form the
-10- / 12
Description electromagnetic apparent resistivity section. Based on the electrical difference
between the deep structure and the surrounding rock, the occurrence characteristics
and deep structural characteristics of the basement limestone in the urban area were
supplementarily estimated on the apparent resistivity section. Further supplementary
geological information of deep structure is obtained according to electromagnetic
results. The layout of electromagnetic exploration outside the urban area is shown in
Figure 3, and the inference diagram of Austrian roof interface is shown in Figure 4.
Finally, the typical section is explored by seismic method to find out the
basement fluctuation.
The seismic exploration was carried out on the basis of gravity exploration and
electromagnetic exploration, and seismic exploration laid 1000mx2000m survey
network to cover the whole area. Based on the principle that the main survey line
should be perpendicular to the stratum and structural trend as far as possible and the
connecting line should be perpendicular to the main survey line, the survey line in
NW direction should be determined as the main survey line with a line distance of
1000m, and the survey line in NE direction should be the connecting line with a line
distance of 2000m. Using vibrator as the excitation, DFS-V type and corresponding
supporting equipment as the receiving, and geophones of 60Hz natural frequency
were used; sampling interval: 1ms; record length: Is; preamplifier gain: 28; record
format: SEG-D; recording density: 1600; driving capacity of vibrator equipment:
%; scanning length: 14 seconds; scanning frequency: 12-110Hz; scanning type:
nonlinear; nonlinear compensation coefficient: 0.15dB/Hz; vertical stacking times: 12
-11- / 12
Description times for single set and 5-8 times for double sets. A total of 20 survey lines, 7263
qualified physical points and 131.93km section length have been completed in
seismic exploration.
The key processing links such as static correction, velocity interpretation,
improvement processing, special processing and VSP data processing are focused,
analyzed and studied, and high-quality processing results were obtained.
As shown in Figure 5, through seismic exploration, the structure in the area is
further controlled and the depth of coal seam bottom interface is further determined.
Those skilled in the art should also understand that various illustrative logic
blocks, modules, circuits and algorithm steps described in connection with the
embodiments herein can be implemented into electronic hardware, computer software
or a combination thereof. In order to clearly illustrate the interchangeability between
hardware and software, various illustrative components, frames, modules, circuits and
steps are generally described around their functions. Whether this function is
implemented as hardware or software depends on the specific application and the
design constraints imposed on the whole system. Skilled technicians may implement
the described functions in a flexible manner for each specific application, but such
implementation decisions should not be interpreted as departing from the scope of
protection of the present disclosure.
- 12- /12
EDITORIAL NOTE 2021107040
There are 2 pages of claims only.
Claims (5)
- Claims 1. A comprehensive method for deep geological exploration in urban areas,comprises:Conducting preliminary exploration using a gravity method to obtain thedensity information of the target body in the center of the urban area;Conducting supplementary exploration using the electromagnetic methodto obtain the electrical information of the target body;Conducting fine exploration of typical sections using seismic method toobtain the velocity information of the target body.
- 2. The method according to claim 1, wherein a fine data analysis isperformed after the data acquisition;
- 3. The method according to claim 2, wherein the preliminary explorationusing the gravity method further includes:In the dense urban area with a high level of electromagnetic interference,the gravity detection method is used to preliminarily examine the faultstructure, buried depth, and fluctuation characteristics of the upperinterface of the limestone at depth, as well as the fault structure, so as todetermine the preliminary geological information of the deep structure;
- 4. The method according to claim 3, wherein the process of thesupplementary exploration of the electromagnetic method furthercomprises:On the periphery of urban areas with low electromagnetic interference, theelectromagnetic method is used to generate electromagnetic apparentClaims resistivity sections. Based on the electrical difference between the deepstructure and the surrounding rocks, the occurrence characteristics anddeep structural characteristics of the basement limestone in the urban areaare evaluated, and therefore, further supplementary geological informationof deep structure is acquired.
- 5. The method according to claim 4, wherein the process of fine explorationof typical sections using seismic method further comprises:The seismic exploration method is used to explore the periphery of theurban area and generate seismic sections. Using the elastic wave velocitydifference between the deep structure and the surrounding rocks, theoccurrence characteristics and deep structural characteristics of the coalmeasure strata and the base limestone of the coal measure strata in theurban area are finely determined in the velocity section, and therefore,further fine geological information of the deep structure is obtained.
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