Geophysics Labs

Geophysical Exploration 2011-GE-56

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Lab#01

STATEMENT:

INTRODUCTION TO GEOPHYSICAL LAB EQUIPMENTS

SCOPE:

To know and familiar with the geophysical lab equipment’s and their uses in the field

THEORY:

GEOPHYSICS:

Geophysicists study a variety of natural phenomena, including the Earth's shape, the

dynamics of its interior, and atmospheric processes.

APPLICATIONS OF GEOPHYSICS:

Geophysics is a vast field and its uses are countless. The following are some of the

applications of geophysical exploration:

Mineral exploration

Oil and gas exploration

Civil engineering projects

Archeology

Unexploded ordnance detection

Interior of earth

Finding problematic zones in tunnels and mines

Specification and accessories of each of the equipment are given as:

1) TERRAMETER SAS 4000:

Terrameter SAS 4000 has the ability to measure Resistivity and Induced Polarization as

well as Self Potential, making the Terrameter SAS 4000 a highly competent and flexible solution

for near investigations. All measured data is stored into a database which allows for export or

other suitable programs for interpretation and analysis. A Borehole log option is also available.

ADVANTAGES:

- Groundwater resource management and vulnerability assessment,

- Mapping and monitoring of contaminated ground/groundwater

- Geotechnical pre-investigation

- Geological mapping

- Mapping/prospecting of natural resources

- Geothermal prospecting

- Sub-bottom mapping at sea and in lakes

http://en.wikipedia.org/wiki/Figure_of_the_Earth


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Figure 1.1

Figure 1.2

- Mapping of frozen ground/permafrost

- Archaeology

- Resistivity Imaging a Robust Method

ACCESSORIES OF TERRAMETER:

Electric cables:

Cables are used extensively in electronic

devices for power and signal circuits.

Connectors:

An electrical connector is an electro-

mechanical device for joining electrical circuits as

an interface using a mechanical assembly.

Connectors consist of plugs (male-ended) and jacks

(female-ended).

http://en.wikipedia.org/wiki/Electro-mechanical

http://en.wikipedia.org/wiki/Electro-mechanical

http://en.wikipedia.org/wiki/Electrical_circuit

http://en.wikipedia.org/wiki/Interface_(computing)


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Figure 1.3

Figure 1. 4

Figure 1.5

Polarized electrodes:

A metallic conductor behaves as a polarized electrode if it allows no movement of charge

between itself and the solution phase.

12 volt battery:

An electric battery is a device consisting of one or more electrochemical cells that

convert stored chemical energy into electrical energy.

Connecting cables:

Connecting cables are used to connect two or more devices.

http://en.wikipedia.org/wiki/Electrochemical_cell


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Figure 1.6

Figure 1.7

Steel electrodes:

A type of steel resistant to corrosion as a result of the presence of large amounts of

chromium (12 to 15 percent). The carbon content depends on the application.

Electrode Selector:

Resistivity imaging technique in which overall 64 resisters can be read out.

2) TERRALOC MK-6:

Terraloc MK-6 is an instrument used in geophysical exploration. It is used seismic survey

and is an old version. Terraloc MK-6 has the following specifications:

Up hole channel Channel 12 or 24, redirectable to a separate connector

Sampling Rate 25, 50, 100, 250, 500 µs, 1, 2 ms

Minimum Input Signal ±0.24 µV

Maximum Input Signal ±250 mV

Frequency Range 2-4000 Hz

Processor 386/486 (Depending on model)

Memory 4 to 32 MB RAM (Depending on model)

Power 10 to 30V DC External battery or internal battery


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Figure 1. 8

Figure 1. 9

Figure 1.10

ACCESSORIES FOR TERRALOC MK-6:

5-6kg hammer:

Hammer is used to produce seismic waves in the ground. The hammer is striked against

the rubber plate.

Rubber/metal/fiber plate:

Plate provide concentration to seismic waves. A hammer is used to hit it.

Explosives:

Explosive is used for the generation of seismic waves. The explosives are used in holes

and the length and diameter of the holes are calculated according to the geology and depth.

Explosives are mostly used in areas where seismic reflection survey is used. Extra care must be

taken while using explosives.


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Figure 1.11

Figure 1.12

Figure 1.13

Seismic cable:

It is used to connect all the geophones which record the seismic waves resulting from

either Vibroseis or dynamite when recording seismic data.

Geophones:

A geophone is a device that converts ground movement (displacement) into voltage,

which may be recorded at a recording station. Types of geophones w.r.t sensitivity:

- SG-5 (high-sensitive geophone)

- SG-10 (high performance geophone sensor)

- jF-20DX (conventional geophone sensor)

Triggering device:

It is used to initiate the whole system.

http://en.wikipedia.org/wiki/Voltage


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Figure 1.14

Figure 1.15

3) SHIELDED ANTENNA GPR:

GPR means Ground Penetrating Radar. It works on electromagnetism principle.

RAMAC/GPR shielded antennas are primarily used for medium to high resolution surveys. The

shielded antenna construction makes the antennas especially suitable for urban investigations or

at sites with a lot of background noise.

A GPR measurement system consists of a transmitter and a receiver antenna and a control

unit. In the system applied in this practical course both antennas are placed in one box. The main

part of the GPR system is the control unit which generates the GPR signal and also receives the

signals after their passage through the ground. The complete system is computer controlled. The

measurement wheel at the back of the antenna box measures the distance along the survey track

and triggers the emittance of the electromagnetic pulses.

SPECIFICATIONS:

The shielded 100MHz antenna is the lowest shielded antenna frequency commercially

available. It is used for medium to low resolution. It is suitable for geological and geotechnical

applications. Dimensions: 1.25 x 0.78 x 0.20 m, Weight: 25.5 kg.

ACCESSORIES FOR GPR:

Distance measuring wheel:

This small, lightweight distance-measuring wheel is designed with flexible mounts to

attach to most GSSI antennas with the mounting bolts. It measures distance.


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Figure 1.16

Figure 1.17

Figure 1.18

Single button monitor:

Single button monitor is an old type of monitor in which the whole process is controlled

by using a single button present on the monitor.

Rods/Extension Rods:

It is an instrument used to cause the sharpened sampler edge to cut through the soil.

4) GRAVIMETER:

It is used for gravity survey. It is easy to operate and has excellent field repeatability. It is

fully portable and it automatically rejects the noise. It transfers data quite easily.


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Figure 1.20

Figure 1.19

SPECIFICATIONS FOR GRAVIMETER:

ACCESSORIES FOR GRAVIMETER:

Tripod stands:

A stand with three geophones attached with it. It has a level bubble for leveling the

tripod.

5) MAGNETOMETER:

It is used for magnetic survey. It gives the magnetic information of the subsurface

formations. Magnetometers are measurement instruments used for two general purposes: to

measure the magnetization of a magnetic material like a Ferro magnet, or to measure the strength

and, in some cases, the direction of the magnetic field at a point in space.

USES OF MAGNETOMETER:

SENSOR TYPE Fused quartz using electrostatic nulling

READING RESOLUTION 1microGal

POWER CONSUMPTION 4.5Watts at 25°C

WEIGHT 8kg (17.5lbs) including battery

GPS ACCURACY Standard

OPERATING RANGE Worldwide (8,000mGal without resetting)

STANDARD DEVIATION < 5microGal

http://en.wikipedia.org/wiki/Magnetization

http://en.wikipedia.org/wiki/Magnetic_field


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Figure 1.21

Magnetometers are widely used for measuring the Earth's magnetic field and

in geophysical surveys to detect magnetic anomalies of various types. They are also used

militarily to detect submarines.

In archaeology and geophysics, where the sensor sweeps through an area and many

accurate magnetic field measurements are often needed, cesium and potassium magnetometers

have advantages over the proton magnetometer.

6) PORTABLE WELL LOGGER:

It is used for well logging purposes for shallow depth. It is a portable well logger that can

be transported from one place to other easily.

FEATURES OF WELL LOGGER:

For upward logging, also for downward logging

Can receive digital / analog / pulse signal

Winch automatically stops upon reaching the logging termination depth

Indoor simulation logging, repeatability observation of instruments and probes

Integration of depth control system and data acquisition system

Digital real-time display of frequency, voltage for supply voltage

Real-time display of working voltage, working current for down hole probe

http://en.wikipedia.org/wiki/Earth%27s_magnetic_field

http://en.wikipedia.org/wiki/Geophysical_survey

http://en.wikipedia.org/wiki/Magnetic_anomalies


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Figure 1.22

Figure 1.23

ACCESSORIES OF WELL LOGGER:

Probe:

Probes used for gamma ray and SP resistivity logs. Different types of probes are used for

different purposes. Some of them are given as:

Natural Gamma Logging

Caliper Logging

Spontaneous Potential Logging

Nature Gamma Probe

Acoustic Wave Probe

Temperature and Liquid Resistance probe

7) MINI-SEIS:

The Mini-Seis is the very definition of a great blast monitoring seismograph for an

affordable cost. It is ideal for all kinds of blast vibration monitoring and for most continuous

vibration monitoring in bargraph mode. Rugged, reliable and very easy to use, the Mini-Seis sets

the standard for value in a seismograph. This device measures and detects surface waves, mostly

earthquake waves are detected.


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Figure 1.24

FEATURES OF MINI SEIS:

Lightweight and easy to use.

Costs much less than comparable seismographs.

Maintenance and calibration costs are also less.

Keypad and display for easy field setup and data review.

Selectable seismic and acoustic recording range, seismic and acoustic trigger level, sample

rate and record duration.

Can use either AC or DC power for long term monitoring.

Sophisticated, non-loss data compression results in small record sizes and fast data transfer.

REFERENCES:

- http://shop.modelis-gis.com/shop/product.php?id_product=273&id_lang=1

- Ebooks from google

- Wikipedia search

- http://en.wikipedia.org/wiki/Exploration_geophysics

- http://www.geophysicalmethodsofexploration.com/

- http://en.wikipedia.org/wiki/Reflection_seismology

- http://en.wikipedia.org/wiki/Magnetometer

http://shop.modelis-gis.com/shop/product.php?id_product=273&id_lang=1

http://en.wikipedia.org/wiki/Exploration_geophysics

http://www.geophysicalmethodsofexploration.com/

http://en.wikipedia.org/wiki/Reflection_seismology

http://en.wikipedia.org/wiki/Magnetometer


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LAB#02

INTRODUCTION TO TERRALOC MK-6

STATEMENT:

To study and describe Terraloc ABM Mk-6 and its reliability in the field

SCOPE:

It is used to conduct seismic refraction and reflection surveys.

Terraloc is a compact and complete seismograph with all we need to collect our seismic data

in single casing.

It is used to explore the sub-surface feature of the earth.

Ideal for all types of applications in shallow seismic as refraction, reflection, crosshole,

surface wave investigations.

THEORY:

TECHNICAL SPECIFICATIONS:

Up hole channel Channel 12 or 24, redirectable to a separate connector

Sampling Rate 25, 50, 100, 250, 500 µs, 1, 2 ms

Minimum Input Signal ±0.24 µV

Maximum Input Signal ±250 mV

Frequency Range 2-4000 Hz

Processor 386/486 (Depending on model)

Memory 4 to 32 MB RAM (Depending on model)

Data Storage 80 to 250 MB hard disk and 1.44 MB floppy disk drive 3.5 in.

Power 10 to 30V DC External battery or internal battery


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Figure 2.1 Terraloc MK-6

TYPES OF GEOPHONE SPREADS:

Split Spread:

Type of spread in which the source is in between regularly spaced receivers.

End-on Spread:

Type of spread in which the source is at one end of regularly spaced receivers.

In-line Offset:

In which the source away from the first receiver (i.e., Distance of source may vary).

Cross Spread:

In which two lines of geophones are laid out roughly at right angle and one source is fired at the

intersection point.

L Spread:

In which the source is at Centre and geophones are at sides,

forming an L shape.


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PROCEDURE:

Terraloc MK-6 is an instrument which records seismic waves generated by either hammer,

explosives, earth quake or any other source. The procedure is simple and easy. The connection is

being built between the Terraloc and seismic cables. The geophones are connected with the

cables and is recording the seismic waves being generated. The source may kept at either ends or

at the middle of the geophones. The battery is used to power the Terraloc. Before starting the

survey triggering is done which removes the error in the apparatus. The wiggles are recorded and

is saved in the system for further calculations.

APPLICATIONS OF TERRALOC MK-6:

Terraloc MK 6 is the best one instrument to find out the depth of bed rock.

It helps to locate the water table.

It also helps to determine the velocities of waves through different layers.

We can also compute depth of layer boundaries and so their thicknesses too.

Real time noise monitoring.

Frequency spectrum analysis.

Refractor velocity indication.

REFRENCES:

Terraloc-MK-6-Manual-1994-02-24


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LAB#03

STATEMENT:

SEISMIC REFLECTION SERVEY IN UET STADIUM GROUND

OBJECTIVE:

Main objective of this lab is to acquire data for 80 ft. subsurface depth

PRINCIPAL:

This test method is based on refraction of waves according to Snell’s Law. A refraction survey

uses refracted (or head) waves to deduce velocities of the layered-earth model. So called first

arrival information is used for the analysis. More generalized methods based on the turning

waves from an arbitrary velocity model have also been used in recent days. This is called seismic

refraction tomography.

APPARATUS:

Terraloc Mark 6

25 Geophones

12 V Battery

Seismic cable

Extension Cable


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Figure 3.1 Terraloc Setup

PROCEDURE:

Setup the geophones according to the acquisitive design.

Make all the connections with the help of seismic cables.

Also attach a trigging geophone with the Terraloc.

To check the geophones send signals by hammering to the geophones.

See on Terraloc if we are getting signals on all geophones then ok otherwise check all the

connections of geophones and try again until u get signals on all geophones.

Send signals to the geophones by generating seismic by hammering.

We get a data of the subsurface read the data from the Terraloc or save it.

Then we have to plot the data

THEORY:

FARWARD SHOT:

In farward shot the source is near to the first geophone (may be at the last one. Actually farward

and reverse shot are opposite of each other).

MID SHOT:

When the source is placed in the middle of geophones then it is called mid shot.

REVERSE SHOT:

The source is placed in opposite to the

farward shot. (may be at the end of

geophones).


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Figure 3.2 Geophones Setup

COMMANDS OF TERRRALOC:

First of all <ARM> the apparatus.

Then for triggering press <Ctl + ARM> then <DISARM> the

apparatus

Then start the

hammering at any required point mid or farwad.

Then select the <file> and then the files as (File#00014.SG2).

Then enter and save the file and open the new file and repeat the

same procedure for next shot.

DATA ACQUIRED IN THE STADIUM:

FOR 3 ft. INTERVAL:

72 ft. Spread giving 36 ft. Subsurface Depth:

Farward Shot:

File #000142.SG2

Mid Shot:

File#000143.SG2

Reverse Shot

File#00044.SG2

FOR 5 ft. INTERVAL:

120 ft spread giving 60 ft. subsurface depth:

Farward Shot:

File #000145.SG2

Reverse Shot:

File #000146.SG2

FOR 7 ft. INTERVAL:

168 ft. spread giving 82 ft. subsurface depth:

Farward Shot:

File #000147.SG2 & File #000148.SG2

Reverse Shot:

File #000146.SG2


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Mid Shot:

File#000149.SG2

LAB#04

TO CALCULATE THE THICKNESS OF DIFFERENT LAYERS BY USING GRAPH

PAPER

GIVEN DATA:

GEOPHONE# TIME (ms)

12 8

11 14

10 22

9 24

8 28

7 30

6 31

5 36

4 38

3 40

2 42

1 44

Using Graph#01

Slope (m1) = 5 ms/m

Velocity (V1) = 1/5×1000 = 200 m/sec

Slope (m2) = 2 ms/m

Velocity (V2) = 500 m/sec

Intercept Time = 0.021 sec

XCross over = 7.7

THICKNESS OF LAYER:


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h1 =

√

h1 = 2.29m

GIVEN DATA:

USING GRAPH#02:

There are 3 layers and 2 interfaces in the given data.

Also we have calculated:

- Slope (m1) = 1×10-3

sec/m

- Velocity (V1) = 1000 m/sec

- Slope (m2) = 4×10-4

sec/m


- Slope (m3) = 2×10-4

sec/m


- Xcross-over for 1st = 40 m

- Xcross-over for 2nd

= 123 m

- Intercept Time T1 = 0.024 sec

DISTANCE

(meter)

TIME (sec)

10 0.010

20 0.020

30 0.030

40 0.040

50 0.045

75 0.055

100 0.065

125 0.075

150 0.080

175 0.085

200 0.090

250 0.100

300 0.110


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- Intercept Time T2 = 0.049 sec

THICKNESS OF 1ST

LAYER:

h1 =

√

h1 = 13.09 m

Another formula for finding thickness of layer:

h1 =

√

h1 = 13.10 m

THICKNESS OF 2ND

LAYER:

h =

√

h2 = 36.08 m

2nd

layer thickness can also be find from the following formula:

h2 = (

)

RESULTS:

Thickness for graph#01 = 2.29m

Thickness of 1st layer for graph#02 = 13.10m

Thickness of 1st layer for graph#02 = 36.08m


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Figure 5.125

LAB#05

STATEMENT:

SEISMIC REFLECTION DATA INTERPRETATION

SCOPE:

Time can be calculated from the seismic reflection data. Surfer is used to draw the contour map

by using time, latitude and longitude.

APPARATUS:

Final filtered migrated stack

Magnifying glass

Pencil

Scale

Base map

THEORY:

BASE MAP:

A base map contains seismic line and source points with coordinates (latitude and

longitude).

CONTOUR MAP:

A contour map uses contour lines which are often just called a "contour", to join points of

equal elevation (height) and thus this shows valleys and hills, and the steepness of slopes.

The relative spacing of the lines indicates the relative slope of the surface.


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Figure 5.2

STEPS FOR DRAWING CONTOUR MAP:

STEP 1:

COLLECT THE SEISMIC SECTIONS:

Example: Line= 915-MWI-81

From the above:

91= Year at which data is collected

5= Seismic party no.

MWI= Abbreviation for area

81= Seismic line no.

Full details are given at the header which are at the right side of the Final filtered migrated stack.

Like channels, source type, source interval etc.

STEP 2:

INTERPRETATION STEPS:

At Y-axis= Time ( Mostly in ms)

At X-axis= Source points (Shot points)

Source point no. = First shot no. and last shot no. should be given

Example: 318-110= 208 (Last shot - First shot)

Multiplying the shot no. difference with the interval

Example: 208×50 (Interval) = 10900

Check the parameters

1) Pick seismic time of different seismic horizons:


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- Continuous reflectors are called seismic horizons (Dark Lines)

- Pick times of horizons at different points

2) Seismic well tie:

Collect the data from well logs (Sonic and density). Comparing well log data with

synthetic seismogram by calculating its reflection coefficient and acoustic impedence.

R.C=

- Then making a graph between depth and R.C. A wiggle is generated from this graph. - This wiggle is compared with the seismic wiggle. - If the well is not present then the geological report which contains the extend of layers and

outcrops will help us.

- Then converting the seismic data to depth from time and velocity relation.

3) Mapping of the seismic Horizon:

- Note the latitude and longitude of the required seismic line from the base map.

- Entering the latitude, longitude and time into the surfer software.

- A contour map is drawn from that data.

OBSERVATION AND CALCULATIONS:

Data for Formation No.1:

SP # LATITUDE LONGITUDE TIME

480 71.3 32.65 -1.44

470 71.29 32.65 -1.46

460 71.285 32.65 -1.46

450 71.28 32.65 -1.45

440 71.275 32.65 -1.43

430 71.27 32.65 -1.42

420 71.26 32.65 -1.41

410 71.25 32.65 -1.38

400 71.245 32.65 -1.37

390 71.24 32.65 -1.35

380 71.235 32.65 -1.32

370 71.23 32.65 -1.30

360 71.225 32.65 -1.29

350 71.22 32.65 -1.26

340 71.215 32.65 -1.25

320 71.205 32.65 -1.14

310 71.2 32.65 -1.10

300 71.19 32.65 -1.07

290 71.185 32.65 -1.02


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Contour Map For Formation#01:

Contour Map (3D) For Formation#01:


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SP # LATITUDE LONGITUDE TIME

480 71.3 32.65 -1.93

470 71.29 32.65 -1.94

460 71.285 32.65 -1.94

450 71.28 32.65 -1.93

440 71.275 32.65 -1.91

430 71.27 32.65 -1.9

420 71.26 32.65 -1.87

410 71.25 32.65 -1.88

400 71.245 32.65 -1.84

390 71.24 32.65 -1.82

380 71.235 32.65 -1.79

370 71.23 32.65 -1.78

360 71.225 32.65 -1.77

350 71.22 32.65 -1.73

340 71.215 32.65 -1.68

330 71.21 32.65 -1.64

320 71.205 32.65 -1.61

310 71.2 32.65 -1.61

300 71.19 32.65 -1.61

Contour Map For Formation#02:


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Contour Map (3D) For Formation#02:


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LAB#06

STATEMENT:

INTRODUCTION TO RESISTIVITY SURVEY

SCOPE:

Resistivity survey is used to measure the depth and thickness of geologic strata.

It is used to detect changes and locate the anomalous geologic conditions.

It measures the soil resistivity and soil corrosion rates and designing the grounding girds.

It maps salt water intrusion and contaminant plumes

It locates buried wastes e.g. locates landfill boundaries.

APPARATUS:

Terrameter SAS 4000

ACCESSORIES:

Electrodes

Measuring tape

Crocodile connectors

Electric cables

Connecting cables

External battery

Jumpers

THEORY:

RESISTIVITY SURVEY:

Electrical resistance survey (also called earth resistance or resistivity survey) is one of a number of

methods used in archaeological geophysics. In this type of survey electrical resistance meters are

used to detect and map subsurface archaeological features and patterning.

TYPES OF RESISTIVITY SURVEY ARRANGEMENTS:

The types of electrode arrays that are most commonly used in resistivity survey are

Schlumberger, Wenner, and dipole-dipole. There are other electrode configurations that are used

experimentally or for non-geotechnical problems or are not in wide popularity today. Some of

these include the Lee, half-Schlumberger, polar dipole, bipole dipole, and gradient arrays. The

description of these configurations are given below.

Techniques:

1. Vertical Electrical Sounding (VES)

2. Vertical Electrical Profiling (VEP)


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Figure 6.1 Wenner onfiguration

Figure 6.2 Schlumberger Configuration

VERTICAL ELECTRICAL SOUNDING (VES):

Vertical electrical sounding (VES) is a geophysical method for investigation of a geological

medium. The method is based on the estimation of the electrical conductivity or resistivity of the

medium. The estimation is performed based on the measurement of voltage of electrical field

induced by the distant grounded electrodes (current electrodes).

CONFIGURATION:

There are four types of configurations used in electrical resistivity survey. They are:

1. Wenner Configuration

2. Schlumberger Configuration

3. Pole-dipole Configuration

4. Dipole-dipole Configuration

Mostly the first two configurations are widely used

WENNER CONFIGURATION:

This array consists of four electrodes in line, separated by equal intervals, denoted a. By using

the formula of apparent resistivity the user will find that the geometric factor K is equal to a, so

the apparent resistivity is given by:

SCHLUMBERGER CONFIGURATION:

The Schlumberger array consists of four collinear electrodes. The outer two electrodes are

current (source) electrodes and the inner two electrodes are the potential (receiver) electrodes.

The potential electrodes are installed at the center of the electrode array with a small separation,

typically less than one fifth of the spacing between the current electrodes.


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Figure 6.4 Double Dipole Configuration

Figure 6.3 Pole dipole Configuration

Pole-dipole Configuration:

The pole-dipole array contains four collinear electrodes. One of the current (source)

electrodes is installed at an “effective infinity” distance, which is approximately five to ten times

the survey depth. The other current electrode is placed in the vicinity of the two potential

(receiver) electrodes. This geometry is utilized because it reduces the distortion of equipotential

surfaces.

DOUBLE DIPOLE:

The dipole-dipole electrode array consists of two sets of electrodes, the current (source) and

potential (receiver) electrodes. A dipole is a paired electrode set with the electrodes located

relatively close to one another; if the electrode pair is widely spaced it is referred to as a

bipole. The convention for a dipole-dipole electrode array is to maintain an equal distance for

both the current and the potential electrodes (spacing = a), with the distance between the current

and potential electrodes as an integer multiple of a. The electrodes do not need to be located

along a common survey line.

APPLICATION OF RESISTIVITY SURVEY:

There are different applications of resistivity survey such as;

It measures bedrock & water table depth.

It detects sinkholes & hidden voids.

It geophysical maps buried alluvial channels.

It profiles landslip geometry.


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It characterizes fracture zones & discontinuities.

It defines landfill sites and leachate contamination.

REFERENCES:

http://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity

http://www.epa.gov/esd/cmb/GeophysicsWebsite/pages/reference/methods/Surface

Class Notes

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html


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LAB#07

STATEMENT:

TO PERFORM THE RESISTIVITY SURVEY IN UET GROUND

SCOPE:

Resistivities and no. of layers can be calculated from resistivity survey

APPARATUS:

Terrameter SAS 4000

ACCESSORIES:

Electrodes

Measuring tape

Crocodile connectors

Electric cables

Connecting cables

External battery

Jumpers

TECHNIQUES USED:

VERTICAL ELECTRICAL SOUNDING:

Wenner

Schlumberger

PROCEDURE:

The following procedure is generic and will work with all meters. The meter’s manual should be

consulted for operational details.

Verify that the metal strip between the meter’s C1 and P1terminals is disconnected (used for

3-Point testing)

Install the 4 test probes in the ground equally spaced in straight line. Generally the shorter

spacing is done first.

Using the conductors, connect the C1, P1, P2 and C2terminals to the electrodes. The

electrodes must be connected in order from the end, to the C1, P1, P2 and C2 terminals. The

test results will be invalid if the electrodes are not connected properly.

Press the test button and read the digital display. Record the reading on the worksheet at the

appropriate location. If the reading is not stable or displays an error indication, double check

the connections. For some meters, the RANGE and TEST CURRENT settings may be

changed until a combination that provides a stable reading without error indications is


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Figure 7.1

reached. The addition of moisture is insignificant for the reading; it will only achieve a better

electrical connection and will not influence the overall results. Also a longer probe or

multiple probes (within a short distance) may help.

Place the probes at each of the spacing indicated above and record the readings on the

worksheet

All above steps of this procedure must be repeated at multiple locations on the site to obtain a

reliable soil profile.

OBSERVATION AND CALCULATIONS:

LOCATION MAP:

Figure 7.2 UET Lahore


34 | P a g e

Figure 6.2

TARGET DEPTH:

40 ft.

CONFIGURATION:

1) WENNER CONFIGURATION:

Spacing (a) = 5,10,15,20,25,30,35,40

TABLE#6.1

Spacing (a) meter Resistivity (Ω-m)

1 99

2 110

3 112

4 118

5 130

6 155

7 165

8 200

9 215

10 235


35 | P a g e

WENNER GRAPH:

LOG GRAPH FOR WENNER:

INTERPRETATION FROM GRAPH:

Two layers and single interface.

0

50

100

150

200

250

0 2 4 6 8 10 12

ap

pare

nt

resi

stiv

ity

(ρ

a)

Ὡm

spacing (a) m

Electrode spacing (a) VS Apparent resistivity (ρa)

10

100

1000

1 10

resi

stiv

ity

(ρ

a)

Ὡm

spacing (a) m

Electrode spacing (a) VS apparant resistivity (ρa)

wenner configration (VES)


36 | P a g e

Figure 7.4

2) SCHLUMBERGER CONFIGURATION:

Spacing b/w potential electrodes= a= 3,6,9,12,15,18,21,24

Total spread is = 5a

Investigated depth = 5a/3

TABL#6.2

Spacing (a) Effective depth

(5a/2)

Resistivity

1 2.5 95

2 5 105

3 7.5 110

4 10 115

5 12.5 120

6 15 145

7 17.5 165

8 20 185

9 22.5 200

10 25 225


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GRAPH FOR SCHLUMBURGER:

LOG GRAPH FOR SCHLUMBURGER:

INTERPRETATION:

Two layers and a single interface.

0

50

100

150

200

250

0 5 10 15 20 25 30

Res

isti

vit

y (

ρa)

Ὡm

Effective depyh (5a/2) m

Effective depth (5a/2) VS apparent resistivity (ρa)

schlmbergr configration (VES)

10

100

1000

1 10

Res

isti

vit

y (

ρa)

Ὡm

Effective depyh (5a/2) m

Effective depth VS Apprent resistivity of Schlumberger


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BOREHOLE DATA:

The above data are collected from the borehole that were taken in UET ground.

COMMENTS:

The borehole data doesn’t coincides with the field data which shows that there exist some

problem in the field data.

10

m


39 | P a g e

Figure 8.1

LAB#08

STATEMENT:

INTRODUCTION TO 2D AND 3D RESISTIVITY SURVEY

SCOPE:

To perform and understand the layout of 2D and 3D Resistivity Survey.

APPARATUS:

Terrameter SAS 4000

ACCESSORIES:

Electrodes

12 V battery

Imaging Cable

Electrode Selector

Hammer

Tape

Connectors

THEORY:

The purpose of electrical surveys is to determine the subsurface resistivity distribution by

making measurements on the ground surface. From these measurements, the true resistivity of

the subsurface can be estimated. The ground resistivity is related to various geological

parameters such as the mineral and fluid content, porosity and degree of water saturation in the

rock. Electrical resistivity surveys have been used for many decades in hydrogeological, mining

and geotechnical investigations. More recently, it has been used for environmental surveys.

We have seen the greatest limitation of the resistivity sounding method is that it does not take

into account horizontal changes in the subsurface resistivity. In many situations, particularly for

surveys over elongated geological bodies, this is a reasonable assumption. In theory, a 3-D

resistivity survey and interpretation model should be even more accurate. However, at the

present time, 2-D surveys are the most practical economic compromise between obtaining very

accurate results and keeping the survey costs down.


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Figure 8.2

1D SURVEY:

It is along a single axis y i.e, this survey measure only reading of resistivity with depth along a

straight line in y-axis direction. In order to locate a water supply tube-well that can serve the

congregation of thousands of worshippers patronizing the camp on weekly basis, a major

geophysical mapping of the camp was carried out. This involved both 1D and 2D surveys. 1D

electrical method using Vertical Electrical Sounding has been employed over the years to

characterize aquifer in different geologic environments and to map fractures in basement areas.

2D SURVEY:

It is along the two axis x, y. recently, attention is shifting to a more accurate method of imaging

the subsurface. 2D resistivity images are created by inverting hundreds to thousands of

individual resistivity measurements to produce an appropriate model of the subsurface resistivity.

3 D SURVEY:

It is along the three axis x, y and z. Since all geological structures are 3-D in nature, a fully 3-D

resistivity survey using a 3-D interpretation model (Figure 3c) should in theory give the most

accurate results. At the present time 3-D surveys is a subject of active research. However it has

not reached the level where, like 2-D surveys, it is routinely used. The main reason is that the

survey cost is comparatively higher for a 3-D survey of an area which is sufficiently large. There

are two current developments that should make 3-D surveys a more cost-effective option in the

near future.


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PROCEDURE:

Select the suitable site for the experiment of resistivity survey.

42 electrodes are placed at 5 ft interval depth..

Instrument is attached with the battery.

Instrument is started and readings are taken.

INTERPRETATION:

2D = we make simple contour map of resistivity.

3D = volumetric based map is formed for interpretation

COMMENTS:

The configuration were spread to know about the survey but due to the fault in battery the survey

were not done.


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LAB#09

STATEMENT:

TO PERFORM 2D RESISTIVITY SURVEY USING LUND IMAGING SYSTEM AT

UET AUDITORIUM GROUND

SCOPE:

To identify the different soil layers in UET auditorium ground

APPARATUS:

Terrameter

Battery

Electrode

Wires

Connectors

Jumper

Crocodile connector

Lund imaging selector

Lund imaging wire

RELATED THEORY:

TERRAMETER SAS 4000 WITH LUND IMAGING SYSTEM:

It provides a system for automatic Resistivity and IP Imaging. ABEM Terrameter SAS 4000

with LUND Imaging System provides optimum versatility in infrastructure projects and

environmental studies.

FEATURES OF LUND IMAGING:

It allows number of arbitrary cable arrangements and electrode arrays for Resistivity and

Induced Polarization survey (like Wenner, Schlumberger, gradient, dipole-dipole, pole-

dipole, pole-pole, square array, borehole etc.).

It is also provided with some supporting softwares like software for data transfer from

instrument to PC, protocol generation software, file conversion software and pseudo section

plotting.

Terrameter SAS 4000 allows number of geo-electrical surveys which include Resistivity

Sounding and Profiling (with different arrangements) and IP Survey and Subsurface Imaging.


43 | P a g e

FIELD APPLICATIONS:

Ground water resource management vulnerability assessment

Mapping and monitoring of contaminated ground/groundwater

Geotechnical pre-investigation

Geological mapping

Mapping/prospecting of natural resources

Geothermal prospecting

Sub-bottom mapping at sea and in lakes

Mapping of frozen ground/permafrost.

Archaeology

MAJOR ADVANTAGE:

A major advantage of the electrical imaging method is that it produces continuous images of the

variation in properties in the subsurface. This method can serve as an excellent basis for planning

detail investigations via for example a drilling and sampling programme with optimized

sampling locations. The detail investigation results can then in turn be used as a base for a

refined interpretation of the electrical imaging data, leading to a comprehensive and reliable

model of the underground.

Figure 9.26


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PROCEDURE:

41 electrodes are connected at 5 ft. distances.

The place where the electrodes are connected should be sprayed with water.

Pocket multimeter may be used to check the error.

The total spread was 210 ft. and the subsurface depth was 28 ft.

After the connection the apparatus is started.

The no. of cycles were 190.

Electrode test is set to run for the whole electrodes.

When the cycles are completed, the whole file is loaded to the software.

PROCEDURE TO LOAD THE DATA:

Softwares:

1) Res 2D inv.

2) SAS 4000

The file is first loaded to the PC with a USB connecter from the terrameter.

This file is in S4K extension.

To convert the S4K file to .dat file, we will use the Res 2D inv. software.

In this software go to the File menu and select New and then select Lund conversion

Now press F8 to convert it to the .dat file extension

After conversion load the same file to SAS 4000 software.

Three models will be created, select the one that the last and least final model.


45 | P a g e

FINAL MODELS FOR RESISTIVITY SURVEY IN UET GROUND:

INTERPRETATION:

There are four layers identified from the data (from 3.7m to 6m), The different colour in the

image shows different resistivity levels. Also with the increase in depth the resistivity is

increasing which shows that either there exists lower moisture content or anomalies are present.

There is an error of 9% which shows that the data is not a good one but may be acceptable.

PRECAUTIONS:

The surface should not be too dry or too wet

The electrodes should be connected properly

Battery should be fully charged

REFRENCES:

Instruction manual of ABEM Terrameter SAS 4000 / SAS1000


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LAB#10

STATEMENT:

INTRODUCTION TO GPR SURVEY

SCOPE:

GPR uses electromagnetic wave propagation and scattering to image and identify changes in

electrical and magnetic properties in the ground.

SHIELDED ANTENNA GPR:

GPR means Ground Penetrating Radar. It works on electromagnetism principle. RAMAC/GPR

shielded antennas are primarily used for medium to high resolution surveys. The shielded

antenna construction makes the antennas especially suitable for urban investigations or at sites

with a lot of background noise.

A GPR measurement system consists of a transmitter and a receiver antenna and a control unit.

In the system applied in this practical course both antennas are placed in one box. The main part

of the GPR system is the control unit which generates the GPR signal and also receives the

signals after their passage through the ground. The complete system is computer controlled. The

measurement wheel at the back of the antenna box measures the distance along the survey track

and triggers the emittance of the electromagnetic pulses.

Figure 270.1 GPR Bag Figure10.28 GPR with Accessories


47 | P a g e

SPECIFICATIONS:

The shielded 100MHz antenna is the lowest shielded antenna frequency commercially

available. It is used for medium to low resolution. It is suitable for geological and geotechnical

applications.

GPR SPECIFICATIONS

Antenna Frequency

MHZ

Radial Resolution

m/µs

Maximum Penetration Depth

m

25 100 50

50 50 40

100 25 25

200 12.5 12

250 10 8

500 5 6

800 3 2.5

1000 2.5 1.5

1200 2.1 1

1600 1.6 0.5

2000 1.3 0.4

PARTS OF GPR

Distance measuring wheel

Monitor

7.5 V 2 batteries

Transmitter

Receiver

Cables

Wear plate

Pulling handles

Figure10. 3 Battery place Figure 10.4 Wheel


48 | P a g e

HOW GPR WORKS:

When a wave impinges on interface, it scatters the energy according to the shape and roughness

of the interface and the contrast of electrical properties between the host material and the object.

Part of the energy is scattered back into the host material, while the other portion of the energy

may travel into the object. The portion of the wave that propagates into the object is said to be

refracted. The angle that the wave enters into the object is determined by Snell’s law, which can

be stated as follows:

V1 / V2 = sin Φ1 / sinΦ2

Where,

V1 and V2 are the velocities of the wave through the upper and lower materials, respectively,

and Φ1and Φ2 are the angles of the ray path for the incident and refracted waves, respectively.

FIELD APPLICATIONS:

The system supports a number of subsurface investigations. Some of which are given below:

- Archeological site assessment

- Measuring bridge deck thickness

- Underground mining mapping

- Underground storage tank location

- Excavation planning

- Utility detection

- Hazardous waste site assessment

- Void detection and location

LIMITATIONS:

The most significant performance limitation of GPR is in high-conductivity materials such as

clay soils and soils that are salt contaminated.

Considerable expertise is necessary to effectively design, conduct, and interpret GPR

surveys.

Relatively high energy consumption can be problematic for extensive field surveys.

REFRENCES:

- http://en.wikipedia.org/wiki/Ground-penetrating_radar

- http://www.geophysical.com/whatisgpr.htm

- http://www.geophysical.com/

- http://mysite.du.edu/~lconyers/SERDP/variablesaffecting2.htm

http://en.wikipedia.org/wiki/Ground-penetrating_radar

http://www.geophysical.com/whatisgpr.htm

http://www.geophysical.com/


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LAB#11

STATEMENT:

GPR DATA PROCESSING AND INTERPRETATION

SOFTWARE USED FOR THE INTERPRETATION:

GV (GROUND VISION) RAMAC

MALÅ Ground Vision Software is a data acquisition software platform designed by MALÅ

Geoscience for MALÅ GPR systems with Ethernet communication. This softwares primary

function is data acquisition, but also includes tools for filtering, printing of GPR data

and includes support for multi-channel operation.

Ground Vision is the dedicated data acquisition software platform for MALÅ's single or multi-

channel GPR systems. As Window based software (running under W2000 or later), Ground

Vision offers an easy-to-use user interface with file management, printing and other key features.

Each measurement and its associated settings are stored in files. Filtering can be performed

during data acquisition measurements, or afterwards during post-processing. Ground Vision

software supports GPS coordinate logging during measurement. All radar grams can be printed

as such, or post-processed by further software.

DATA FROM GPR SURVEY:

File # DAT_0101

Frequency= 500 MHZ (6m penetration depth)

Velocity= 100 m/µs

STANDARD CHART FOR THE DIELECTRIC CONSTANT VALUES:


50 | P a g e

GPR DATA FILE IN MALA SOFTWARE:

FROM THE FIRST PICK UP TIME THE FOLLOWING DATA IS COLLECTED:

Distance Time

3.5 10.2

20 9.8

25 9.9

59.5 10.1

64 10.2

92 9.5

129 10.5

144.5 9.8

145 10

147.5 10.2

178.5 11

186 10.5

194.5 10.8

195 9

195.5 9.9

227 10.5

248 12

260.5 10.8

262 10.5

267 10.6

278 10.5

286 10.2


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Graph#11.1 Graph B/W Time and Distance:

Graph 11.29

Velocity can be calculated using:

V=

9

9.5

10

10.5

11

11.5

12

0 50 100 150 200 250 300 350

Tim

e

Distance

Figure 10.30Borehole data


52 | P a g e

Depth of specific layer can be calculated by using:

S= vt

INTERPRETATIONS:

There are 4 layers that is mostly found from the GPR data. There is a change in data from 120m

to 200m which shows that there exist some anomalies. The anomaly may be pipe or concrete

slab present near the cricket ground.

COMMENTS:

In actual field we know that there is a pipe and a concrete slab present near the cricket ground so

we have a clue from the real data. By comparing it with the GPR data we are sure that there is

anomaly present. Also the data shows that the GPR is working great.

REFRENCES:

- http://www.malags.com/products/mala-groundvision-2

- http://hyperphysics.phy-astr.gsu.edu/hbase/tables/diel.html

http://www.malags.com/products/mala-groundvision-2


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LAB#12

STATEMENT:

INTRODUCTION TO GRAVITY SURVEY

SCOPE:

To understand the gravity survey and to familiar with its applications

EQUIPMENT:

CG-5 Autograv (Gravimeter)

RELATED THEORY:

CG-5 AUTOGRAV (GRAVIMETER):

A gravimeter is an instrument used in gravimetry for measuring the local gravitational field of

the Earth. A gravimeter is a type of accelerometer, specialized for measuring the constant

downward acceleration of gravity, which varies by about 0.5% over the surface of the Earth.

The CG-5 is the latest, gravity meter. It offers all of the features of the low noise industry

standard CG-3M micro-gravity, but is lighter and smaller, has a larger screen which gives a

superior user interface. The CG-5 can be operated with minimal operator training, and automated

features significantly reduce the possibility of reading errors.

Data down load bottlenecks have been eased with the provision of a fast USB interface and

flexible data formats. Noise rejection has been improved.

TYPES OF GRAVIMETER:

ABSOLUTE GRAVIMETER:

Absolute gravimeters, which nowadays are made compact so they too can be used in the field,

work by directly measuring the acceleration of a mass during free fall in a vacuum, when the

accelerometer is rigidly attached to the ground.

Figure 12.1 Gravimeter

http://en.wikipedia.org/wiki/Gravimetry

http://en.wikipedia.org/wiki/Gravitational_field

http://en.wikipedia.org/wiki/Accelerometer

http://en.wikipedia.org/wiki/Acceleration_of_gravity

http://en.wikipedia.org/wiki/Free_fall

http://en.wikipedia.org/wiki/Vacuum


54 | P a g e

RELATIVE GRAVIMETERS:

Most common relative gravimeters are spring-based. They are used in gravity surveys over large

areas for establishing the figure of the geoid over those areas. A spring-based relative gravimeter

is basically a weight on a spring, and by measuring the amount by which the weight stretches the

spring, local gravity can be measured. However, the strength of the spring must be calibrated by

placing the instrument in a location with a known gravitational acceleration.

SPECIFICATION OF CG-5 AUTOGRAV:

Sensor Type Fused Quartz using electrostatic nulling

Reading Resolution 1 microGal

Standard Field

Repeatability

<5 microGal

Operating Range 8,000 mGal without resetting

Residual Long-Term Drift : Less than 0.02 mGal/day (static)

Tares Typically less than 5 microGals for shocks up to 20 G

Automated Corrections Tide, Instrument Tilt, Temperature, Drift, Near Terrain,

Noisy Sample, Seismic

Noise Filter

Operating Temperature -40°C to +45°C

Ambient Temperature

Coefficient

0.2 microGal/°C

Pressure Coefficient 0.15 microGal/kPa

Magnetic Field Coefficient 1 microGal/Gauss

Power Consumption : 4.5 W at +25°C

Standard System CG-5 Console, Tripod base, 2 rechargeable batteries,

Battery Charger

110/240 V, External Power Supply 110/240 V, RS-232 and

USB Cables

GRAVITY OBSERVATIONS AND LEVELLING:

When performing manual gravity observations with relative gravimeters different circumstances

have to be considered. Important aspects relate to the actual measuring site, the specific

instrument and handling of it, natural conditions and of course, since the reading is carried out

manually, the observer himself. Because gravity measurements are normally conducted in loop

sequences higher order stations (as a minimum) are normally measured several times during a

working day.

It is essential that the gravimeter is kept strictly levelled during each observation sequence. This

requires continuous monitoring and frequent adjusting of the instrument level. The procedure

associated with most manually operated gravimeters may be rather demanding with respect to

http://en.wikipedia.org/wiki/Spring_(device)

http://en.wikipedia.org/wiki/Geoid

http://en.wikipedia.org/wiki/Calibrate


55 | P a g e

time and mental concentration of the observer. Especially during hot summer days when stations

are located on asphalt-paved ground this task are often really cumbersome and time-consuming

while the “legs“ of the meter base “pan“ may slowly sink into the warm asphalt thereby

distorting the measurements. Similar problems may arise if the underground is wet. With

automatic gravimeters like the Scintrex CG-5 Autograv the problem of levelling the instrument

are automatically handled by electronic tilt sensors. Along with automatic reading and logging of

the data into the gravimeters memory measuring becomes less demanding as regards the

involvement and skills of the observer.

STEPS TO FOLLOW:

STEP#01

GEOLOGICAL REPORT OF AN AREA:

Includes tectonic setting, outcrop mapping, topography, structure and stratigraphy. From these

values we can prepare the geological report.

STEP#02

3D GEOLOGICAL MODEL:

For 3D model we have to know about the orientation, structure etc. The geological report is

necessary for 3D model. From these features the 3D geological model is prepared.

STEP#03

PLOTTING GRAVITY LINES:

Perform proper grids and acquire data from grids. The grids are easy to read and give accurate

readings.

STEP#04

DEFINE GRAVITY BASE STATION:

Point of known coordinates and from IGSN71 taking a base station and define gr value. The

values of the base stations are already known.

IGSN71: International gravity standardization network.

STEP#05

PREPARE EQUIPMENT:

Time is very important (day/night).


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Tide correction:

Tide correction is applied for time. The apparatus have its own tide correction in it.

Drift Correction:

It is also called mechanical correction. As the equipment is used for a long time so the apparatus

starts to show error. This error can be removed by applying the drift correction.

STEP#06

DEFINE THE READING INTERVAL:

On the base of experience and geology define the intervals. The coordinates can also be defined.

STEP#07

ELEVATION OF AREA WITH RESPECT TO MEAN SEA LEVEL:

The values are feeded in the instrument country wise.

Latitude adjustment:

It can be calculated by subtracting the normal gravity values from the observed gravity values.

USES:

- Basement rock identification

- Igneous body on regional scale

- Anticline structures

- Mineral ores identification

- Also used for the contrast of sedimentary and igneous body


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LAB#13

STATEMENT:

SURFER GRAVITY CONTOUR MAP

SCOPE:

To draw the surfer map and to interpret the gravity and density changes in different zones from

the surfer map.

PROCEDURE:

1) Copy the data from surfer to the New work sheet in the surfer.

2) The data consists of longitude, latitude and bouguer gravity values. The grid file can be

created from this data by using the same file saved in .bln extension.

3) After it go to the contour map option and select the

same grid file that is generated and contour map is drawn.

4) Now selecting the same grid make a 3D surface map and overlay the contour map and the 3d

surface map. Colour can changed from its properties. The final results will be:

INTERPRETATION FROM GRAVITY CONTOUR MAP:


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ZONE 1: (N-E DIRECTION)

There is a decrease in density but overall density doesn’t changes. This shows that either there is

a loose material, limestone cavity or sink hole present.

ZONE 2: (N-W DIRECTION)

The density contrast increases and decreases rapidly, so there is a change in the density at this

zone. This shows that there is an anomaly present in this zone.

ZONE 3: (S-E DIRECTION)

There is a high density contrast at this zone. The density increases rapidly in this zone. This

shows that either there is an igneous intrusion or mineral ore etc. present.

ZONE 4: (S-W DIRECTION)

The variation doesn’t seem to be high at this zone. There is no abrupt change happen here. This

shows that there is a continuous strata deposited here.

SURFER GRAVITY CONTOUR MAP:

Figure 13.31 Surfer Gravity Contour Map


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LAB#14

STATEMENT:

INTRODUCTION TO PORTABLE WELL LOGGER AND MAGNETOMETER

RELATED THEORY:

WELL LOGGING:

Well logging, also known as borehole logging is the practice of making a detailed record (a well

log) of the geologic formations penetrated by a borehole. The log may be based either on visual

inspection of samples brought to the surface (geological logs) or on physical measurements made

by instruments lowered into the hole (geophysical logs). Some types of geophysical well logs

can be done during any phase of a well's history: drilling, completing, producing, or abandoning.

Well logging is performed in boreholes drilled for the oil and gas, groundwater, mineral and

geothermal exploration, as well as part of environmental and geotechnical studies.

TYPES OF LOGS:

Resistivity logs

Porosity logs

Sonic logs

Gamma ray log

Density log

Neutron log

Figure 14.32 Well Logging software

http://en.wikipedia.org/wiki/Formation_(stratigraphy)

http://en.wikipedia.org/wiki/Borehole

http://en.wikipedia.org/wiki/Hydrocarbon_exploration

http://en.wikipedia.org/wiki/Groundwater

http://en.wikipedia.org/wiki/Mineral_exploration

http://en.wikipedia.org/wiki/Geothermal_exploration

http://en.wikipedia.org/wiki/Geotechnical


60 | P a g e

PORTABLE WELL LOGGER:

Borehole logging provides in situ measurements of the physical properties of the subsurface

layers. The Mount Sopris MGX II borehole logging system is a portable system controlled by a

notebook computer that allows for the acquisition of up to 9 logs simultaneously, using Poly

probe technology. The motorized winch, efficiency of data acquisition, and the amount of

information available from one logging run make this a very economical survey tool. The system

logs include natural gamma, self-potential, single point resistance, normal resistivity (using 8,

16, 32 and 64 inch arrays), a lateral log, induced polarization, magnetic susceptibility, acoustic

velocity, temperature, fluid resistivity, electromagnetic induction, flow meter, caliper, and

borehole deviation.

DATA ACQUISITION:

The software used for the data acquisition is Ms Well. This software shows proper reading when

the logger is moving in the well bore. It also shows that either any of the error is present in the

connection of the apparatus.

DATA INTERPRETATION:

The software used for the data acquisition is Well cad. It consists of different modules like core

and cutting module, 3D module and many others which can be used to interpret the data from it.

Figure 14.33 MS Well


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APPLICATIONS:

- In environmental and groundwater investigations, locations of greatest groundwater flow are

determined using temperature and/or self-potential logs, flow meters and caliper logs.

Natural gamma, electrical, and magnetic logs characterize the lithology in terms of grain size

and clay volume.

- Fluid and formation resistivity logs are used to delineate areas of groundwater contamination.

An acoustic velocity log provides information on porosity and well completion to help

minimize cross-contamination in remediation programs. The determination of exact depths

and the physical characteristics of each layer decrease the uncertainties in groundwater

modeling and allow for the accurate placement of well screens for sampling, or groundwater

extraction.

- In geotechnical investigations, borehole logs provide a direct measure of the physical

properties of the subsurface with accurate delineation of each horizon. The full waveform

sonic log provides compressional wave velocities, and the sonic porosity of each layer.

Companion surveys provide shear wave velocities for dynamic moduli determinations.

- In mining applications, a variety of tools are used to determine petrophysical properties and

physical boundaries not visible in the drill core. The sonic log is used in conjunction with

seismic reflection surveys to provide accurate interval velocities of subsurface layers for

interpretation.

- The natural gamma log is a standard parameter used in coal evaluation, and uranium

exploration, as well as in geological mapping of igneous and metamorphic environments.

This log shows variations in natural radioactivity which are correlated with changes in

lithology.

Figure 14.34 Well cad


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INTRODUCTION TO MAGNATOMETER:

- TAGS-6 (click on the above image for a detailed view) represents the latest development in a

long line of LaCoste-based airborne gravity systems, stretching back to the first successful

airborne gravity flights in 1958 and building on the success of the TAGS System. For over

50 years, LaCoste gravimeters have acquired hundreds of thousands of line kilometers of

gravity data during academic, government, and commercial surveys. TAGS-6 blends the

latest in GPS and data acquisition technology with the solid foundation of the LaCoste

dynamic gravimeter.

- TAGS-6 is an upgrade to the TAGS/Air III gravity meter, and is designed specifically for

airborne operations. The system incorporates a time-tested, low-drift, zero-length-spring

gravity sensor mounted on a gyro-stabilized gimbal platform. The sensor has a worldwide

gravity measuring range (no reset necessary) of 500,000 milliGals.

Figure 14.35 Magnetometer

HISTORY:

The first magnetometer was invented by Carl Friedrich Gauss in 1833 and notable developments in

the 19th century included the Hall Effect which is still widely used.

THEORY:

Magnetometers are measurement instruments used for two general purposes: to measure

the magnetization of a magnetic material like a ferromagnet, or to measure the strength and, in

some cases, the direction of the magnetic field at a point in space.

http://en.wikipedia.org/wiki/Carl_Friedrich_Gauss

http://en.wikipedia.org/wiki/Hall_Effect


http://en.wikipedia.org/wiki/Ferromagnet



63 | P a g e

USES:

Magnetometers are measurement instruments used for two general purposes: to measure

the magnetization of a magnetic material like a ferromagnet, or to measure the strength and, in

some cases, the direction of the magnetic field at a point in space.

COMMENTS:

The apparatus were out of order so we did not get any readings.

REFRENCES:

- http://scintrexltd.com/internal.php?storeCategoryID=4&s_page=airborne

- http://www.geomatrix.co.uk/products/land-geophysical-equipment/gravity/cg5/


http://en.wikipedia.org/wiki/Ferromagnet


http://scintrexltd.com/internal.php?storeCategoryID=4&s_page=airborne

Engineering

Geophysics Labs