Spermiogenesis or Spermateleosis or metamorphosis of spermatid
subsurface[1].pptx
1. KUVEMPU UNIVERSITY
DEPARTMENT OF P.G STUDIES AND RESEARCH IN
APPLIED GEOLOGY
EARTH SCIENCE AND RESOURCE MANAGEMENT
SEMINAR ON:
Sub-Surface Investigation of Ground water
SUBMITTED TO:
Ms Smitha T.L
Guest Lecturer
DEPARTMENT OF P.G STUDIES AND RESEARCH IN
APPLIED GEOLOGY
Kuvempu University,
Shankaraghatta
SUBMITTED BY:
Mallikarjun A.H
2nd SEM MSc, ESRM
DEPARTMENT OF P.G STUDIES AND RESEARCH IN
APPLIED GEOLOGY
Kuvempu University,
Shankaraghatta
2. Introduction
Water is one of the mankind's most vital
resources.
In areas where surface water is not available,
Ground water constitutes significant part of
active fresh water resources of the world and is
dependable source for all the needs.
Water is one of the mankind's most vital
resources.
In areas where surface water is not available,
Ground water constitutes significant part of
active fresh water resources of the world and is
dependable source for all the needs.
3. Subsurface methods
The subsurface methods of groundwater exploration includes both
Test Drilling & Borehole Geophysical Logging techniques.
When compared to the surface methods, the subsurface methods
are very expensive.
4. Subsurface investigation of ground
water
Test drilling
1. Geological log
2. Drilling time log
3. water level measurements
Geophysical logging
Resistivity logging
Spontaneous potential logging
Radiation logging
1. Natural gamma logging
2. gamma logging
3. Neutron logging
Temperature logging
Calliper logging
Fluid conductivity logging
Fluid velocity logging
Miscellaneous logging techniques
1. Television logging
2. Acoustic logging
3. Casing logging
5. Test drilling
drilling small diameter holes that furnish information on substrata in a vertical
line from the subsurface
:-useful in
(i) verifying other means of investigation
(ii) confirm groundwater conditions prior to well drilling
(iii) serving as observation wells for measuring groundwater levels
and for conducting pumping tests
f found fruitful, many a times the test holes are redrilled or enlarged to form
pumping or production wells.
6. Geological log
constructed from the drill-cutting samples
collected at frequent intervals during the
drilling of a well. (samples are utilized for
laboratory determinations of their hydrologic
properties)
Furnishes a description of the geologic
character and the thickness of each stratum
encountered as a function of depth, thereby
enabling aquifers to be delineated.
Preparation of proper geologic map may be
difficult because of interference of drilling fluid
with fine particles, and lack of proper
knowledge to interpret the findings.
7. Geological log (conti)
useful supplement to test drilling
consists of an accurate record of the time, in minutes and seconds,
required to drill each unit of depth of the hole.
Because the texture of a stratum being penetrated largely governs
the drilling rate, a drilling time log may be readily interpreted in
terms of formation types and depths.
8. Drilling time log
A drilling-time log is a useful
supplement to test drilling.
It consists of an accurate record of the
time, in minutes and seconds, required
to drill each unit depth of the hole.
The technique is most practical with
hydraulic rotary drilling although it is
applicable to other methods as well.
9. Water level measurement
One of the most common measurements in groundwater investigations is the
determination of the depth to groundwater.
In both existing and new wells, such data are needed to define groundwater flow
directions, changes in water levels over time, and effects of pumping tests.
A simple and accurate method for obtaining water depth is lowering a steel tape
into a well. By adding chalk to the end of the tape, the length of submersion
becomes apparent, thus giving the distance from the top of the well to the water
surface.
A unique and convenient method for measuring water levels in deep wells is the
rock tech nique developed by Stewart. He determined empirically the time
required for a common 1.55-cm glass marble fall to the water surface plus the
time for the sound of the splash to return to ground surface. Measuring the
elapsed time by stop watch, the depth to water can be read directly from table
10.
11. Geophysical logging
is a set of borehole investigation methods that are based on special
logging tools.
Geophysical logging involves lowering sensing devices in a borehole
and recording a physical parameter that may be interpreted in
terms of formation characteristics; groundwater quantity, quality,
and movement; or physical structure of the borehole
It is doubtful if more than a few percent of the new water wells
drilled each year are logged by geophysical equipment.
The primary reason for this is cost. Most water wells are shallow,
small-diameter holes for domestic water supply; logging costs
would be relatively large and usually unnecessary.
But for deeper and more expensive wells, such as for municipal,
irrigation, or injection purposes, logging can be economically
justified in terms of improved well construction and performance.
12. A wide variety of logging techniques are available; Table lists the
types of information that can be obtained from various logging
techniques
13. Resistivity logging
Within an uncased well, current and potential electrodes can be
lowered to measure electric resistivities of the surrounding media
and to obtain a trace of their variation with depth.
The result is a resistivity (or electric) log. Such a log is affected by
fluid within a well, by well diameter, by the character of
surrounding strata, and by groundwater.
14. Spontaneous potential logging
The spontaneous potential method measures
natural electrical potentials found within the earth.
Measurements, usually in millivolts, are obtained
from a recording potentiometer connected to two
like electrodes. One electrode is lowered in an
uncased well and the other is connected to the
ground surface,.
as illustrated by electrodes M and N in Figure
measures differences in the voltages of an
electrode at the land surface and an electrode in
the borehole
15. Sp logging (conti)
Deflections of the SP curve occurs due to the development of a
liquid junction potential, i.e. potential difference across the junction
from mud filtrate to formation water.
If water in permeable bed is more saline than drilling mud, SP is
generally more-ve in the permeable bed than in the adjacent clay &
vice versa.
useful in determining water quality
The right hand boundary generally indicates impermeable beds
(e.g. clay, shale, and bedrock)
Left-hand boundary indicates sandand other permeable layers
16.
17. Radiation logging
also known as nuclear or radioactive logging
Generally two types:
(i) measures the natural radioactivity
(ii) detects radiation reflected from an artificial source
radiation Logs having application to groundwater are
1.Natural-gamma logging
2.Gamma-gamma logging
3.Neutron logging
These are promising but not widely used hydrogeologic tools. An important
advantage of these logs over most others is that they may be recorded in
either cased or open holes that are filled with any fluid.
18. Natural gamma logging
all rocks emit natural gamma radiation originating from unstable
isotopes of potassium, uranium, and thorium
Clayey formations (shale, clay) emit more rays than gravels and
sands.
Can be used to differentiate between sand, clay and gravel (this is
identifying lithology, the primary application)
19. Gamma gamma logging
Gamma rays from a source in the probe (cobalt-
60 or cesium-137) are scattered and diffused
through formation.
Part of the scattered rays re-enter the hole and
are remeasured.
The higher the bulk density of formation, the
smaller the number of gamma-gamma rays that
reach the detector.
Primary applications:
(i) identifying lithology
(ii) measurement of bulk density and porosity of
rocks.
20. Neutron logging
Useful in determining the porosity of formations
A fast neutron source is used to bombard the
rock
When any individual neutron collides with a
hydrogen ion (of a water molecule), some of the
neutron's energy is lost and it slows down.
A large number of slow neutrons, as recorded by
a slow neutron counter, indicates a large
number of fluid (i.e. high porosity)
Results are influenced by hole size. Therefore, in
large uncased holes, information on hole
diameter is required for proper interpretation.
21. Temperature logging
A vertical measurement of groundwater temperature in a well by a
resistance thermometer
Normally Temperature will increase according to geothermal gradients
(roughly 30C for each 100 m depth)
Departures from this normal gradient may provide information on
circulation (hydrologic Cycle) or geologic conditions in the well.
Abnormally cold water may indicate recharge from ground surface (in
deep well)
Abnormally warm water may indicate water of deep-seated origin.
Geothermal gradient is usually steeper in rocks with low permeability
22. Temperature logging(conti)
Applications:
(i) identify aquifers contributing water to a well.
(ii) Provide data on the source of water
(iii) identify rock types
(iv) calculate fluid viscosity and specific conductivity from fluid
resistivity logs
(v) distinguish moving and stagnant water
23. Caliper logging
Provides a record of average hole diameter of a borehole◆Hole
diameter will be equal to drilling bit when a hard sandstone is
traversed.
Diameter becomes larger for shales/clays as they become wet with
mud fluid, slough off and cave into the hole.
Applications:
(i) identification of lithology and stratigraphic correlation
(ii) Locating fractures and other rock openings
(iii) Correcting other logs for hole-diameter effects
24. Fluid velocity logging
Measurement of fluid movement
within a borehole constitutes a fluid-
velocity log.
Such data reveal strata contributing
water to a well, flow from one stratum
to another within a well, hydraulic
differences between aquifers
intersected by a well, and casing leaks.
26. Television logging
A convenient tool with increasing use is a television camera lowered in a
well.
Specially designed wide-angle cameras, typically less than 7 cm in
diameter,
are quipped with lights and provide continuous visual inspection of a
borehole;
with videotape a record of the interior can be preserved.
Among the variety of applications are locating changes in geologic strata,
pinpointing large pore spaces, inspecting the condition of the well casing
and screen, checking for debris in wells, locating zones of sand entrance,
and searching for lost drilling tools.
27. Acoustic lighting
Acoustic, or sonic, logging measures the velocity of sound through
the rock surrounding an uncased, fluid-filled hole.
Chief applications of the acoustic log include determining the depth
and thickness of porous zones, estimating porosity, identifying
fracture zones, and determining the bonding of cement between
the casing and the formation.
28. Casing logging
A casing-collar locator is a useful device for recording locations of
casing collars, perforations, and screens.
The instrument consists of a magnet wrapped with a coil of wire;
voltage fluctuations caused by changes in the mass of metal cutting
the lines of flux from the magnet are recorded to form the log.
