Hydraulic fracturing is a method to estimate initial stresses by pressurizing a sealed borehole section until it fractures. The fracture orientation indicates the minimum stress direction. This provides the orientation of the maximum horizontal stress for vertical boreholes. The breakdown pressure estimates the minimum principal stress, while the reopening pressure estimates the maximum principal stress. This allows estimating the 2D stress field in the horizontal plane, making it suitable for deep measurements where no underground access exists. However, it requires space for equipment and is best suited to vertical boreholes.
ground control in coal mines, stress regime, pressure arch concept, ground reaction curve, mechanics of strata failure, caving mechanism in bord & pillar, longwalls, roof falls, cavability, ground control practices or techniques in coal mines or metal mines
ground control in coal mines, stress regime, pressure arch concept, ground reaction curve, mechanics of strata failure, caving mechanism in bord & pillar, longwalls, roof falls, cavability, ground control practices or techniques in coal mines or metal mines
Rock Mass Classification and also a brief description of Rock Mass Rating (RMR), Rock Structure Rating (RSR), Q valves and New Austrian Tunneling method(NATM)
Subsidence is one of the major environmental issues related to underground mining industry. This presentation gives an insight to causes, nature, effect of subsidence and some mitigation measures.
is one of the first steps in
searching for oil and gas resources that directly
affects the land and the landowners Seismic surveys are like sonar on steroids They are based on recording the time it takes for sound waves generated by controlled energy sources .The survey usually requires people and machinery
to be on private property and may result in
disturbances of the land such as the clearing of
trees
Rock Mass Classification and also a brief description of Rock Mass Rating (RMR), Rock Structure Rating (RSR), Q valves and New Austrian Tunneling method(NATM)
Subsidence is one of the major environmental issues related to underground mining industry. This presentation gives an insight to causes, nature, effect of subsidence and some mitigation measures.
is one of the first steps in
searching for oil and gas resources that directly
affects the land and the landowners Seismic surveys are like sonar on steroids They are based on recording the time it takes for sound waves generated by controlled energy sources .The survey usually requires people and machinery
to be on private property and may result in
disturbances of the land such as the clearing of
trees
Polymer road technology is about innovations in road construction leading to technological development of nation. It's an innovative platform which combines Civil and Polymer engineering for better economic outcomes.
Quantitative and qualitative seismic attributes interpretationmohamed Shihata
Seismic attribute is the only way that can enable interpreter to understand seismic data very well and generate new view for his model, but there are hundreds of seismic attributes and there are many classes that make interpreters afraid of using new thing so in this course explain both theoretical and application for each one and try to generate workflow to help interpretation for different geological environment.
In this course, we will gain an intuitive understanding of the kinds of seismic features that can be identified by 3-D seismic attributes, the sensitivity of seismic attributes to seismic acquisition and processing, and of how ‘independent’ seismic attributes can are coupled through geology. We will also discuss alternative workflows using seismic attributes for reservoir characterization as implemented by modern commercial software and practiced by interpretation service companies. Participants are invited to bring case studies from their workplace that demonstrates either the success or failure ofseismic attributes to stimulate class discussion.
The extensive slide-pack starts with introducing physics and basics on geomechanics. A lot of stress and rock strength concepts are explored. Then it moves on to explain the importance of the discipline for drilling, injection, sanding. Apart from giving theory to understand more difficult content that follow, it throws in practical application and prepares good ground for further study of geomechanical literature.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Salas, V. (2024) "John of St. Thomas (Poinsot) on the Science of Sacred Theol...Studia Poinsotiana
I Introduction
II Subalternation and Theology
III Theology and Dogmatic Declarations
IV The Mixed Principles of Theology
V Virtual Revelation: The Unity of Theology
VI Theology as a Natural Science
VII Theology’s Certitude
VIII Conclusion
Notes
Bibliography
All the contents are fully attributable to the author, Doctor Victor Salas. Should you wish to get this text republished, get in touch with the author or the editorial committee of the Studia Poinsotiana. Insofar as possible, we will be happy to broker your contact.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
The ability to recreate computational results with minimal effort and actionable metrics provides a solid foundation for scientific research and software development. When people can replicate an analysis at the touch of a button using open-source software, open data, and methods to assess and compare proposals, it significantly eases verification of results, engagement with a diverse range of contributors, and progress. However, we have yet to fully achieve this; there are still many sociotechnical frictions.
Inspired by David Donoho's vision, this talk aims to revisit the three crucial pillars of frictionless reproducibility (data sharing, code sharing, and competitive challenges) with the perspective of deep software variability.
Our observation is that multiple layers — hardware, operating systems, third-party libraries, software versions, input data, compile-time options, and parameters — are subject to variability that exacerbates frictions but is also essential for achieving robust, generalizable results and fostering innovation. I will first review the literature, providing evidence of how the complex variability interactions across these layers affect qualitative and quantitative software properties, thereby complicating the reproduction and replication of scientific studies in various fields.
I will then present some software engineering and AI techniques that can support the strategic exploration of variability spaces. These include the use of abstractions and models (e.g., feature models), sampling strategies (e.g., uniform, random), cost-effective measurements (e.g., incremental build of software configurations), and dimensionality reduction methods (e.g., transfer learning, feature selection, software debloating).
I will finally argue that deep variability is both the problem and solution of frictionless reproducibility, calling the software science community to develop new methods and tools to manage variability and foster reproducibility in software systems.
Exposé invité Journées Nationales du GDR GPL 2024
2. What Is Strain?
• Increase (or decrease) in
length resulting from a stress
acting parallel to the
longitudinal axis of the
specimen.
• strain is defined as extension
per unit length.
• Strain = extension / original
length
4. Typical regions that can be
observed in a stress-strain
curve are:
• Elastic region,
• Yielding,
• Strain Hardening,
• Necking and Failure
Stress-Strain Curve for Textile Fibre
5. Elastic Behavior
• If the specimen returns
to its original length
when the load acting on
it is removed, it is said
to response elastically
6. Yielding
• A slight increase in stress
above the elastic limit will
result in permanent
deformation. This
behavior is
called yielding
• The stress that causes
yielding is called yield
stress sy.
• The deformation that
occurs is called plastic
deformation
7. Strain Hardening
• When yielding has ended,
a further load can be
applied to the specimen,
resulting in a cure that
rises continuously but
becomes flatter until it
reaches a maximum
stress referred to
as ultimate stress, su.
• The rise in the curve is
called Strain Hardening
8. Necking & Fracture
• After the ultimate
stress, the cross-
sectional area begins to
decrease in a localized
region of the specimen,
instead of over its entire
length. The load (and
stress) keeps dropping
until the specimen
reaches the fracture
point.
9. Initial stress
Stress state in rock mass without
artificial disturbances.
One of the basic data in designing
rock structure.
Competence factor = Uniaxial
compressive stress / initial
vertical stress is a good index for
stability of an opening in
rock mass
Initial stress
10. Stress state near opening is
disturbed
Disturbed zone is avoided
for measurement of initial
stress
Disturbed stress is also
measured in some cases
where investigating
deformation and failure
behavior around the
opening
11. Primitive Estimation
σ V = γ h
stress σV is
weight of
rock
Initial vertical
equal to the
overburden
(overburden pressure)
γ is unit volume weight
(ex. 27 kN /m3)
h is the depth (m)
Ex. Initial vertical stress
at 500 m deep is 13.5
MPa
σ V = γ h
σ h = k2σ V
σ H = k1σ V
Initial stress value
12. Initial horizontal stress σH at a shallow depth.
Horizontal stress ε is assumed to be zero.H
Eε H = σ H −ν (σ H
σ H = kσ V
+ σ V ) = 0
ν
k =
1−ν
E is Young's modulus.
ν is Poisson's ratio
k is the coefficient for horizontal stress
k is assumed to be 1 at great depth.
σ V = γ h
σ h = k2σ V
σ H = k1σ V
13. Measured initial stress values
Initial vertical
stress is roughly equal to the
primitive estimation
Initial horizontal
stress is different from the primitive
estimation
14. Average initial horizontal stress
σHavLower limit of (2.7 + 0.0081 h)
σHavUpper limit of (40.5 + 0.0135 h)
0
200
Average initial horizontal
stress = depth independent
value + depth proportional
value for 0.25 - 0.33 of
poisson's ratio
400
600
800
1000
0 10 20 30 40 50 60
Stress (MPa)
Depth(m)
σV
15. Depth independent value?
Movement of the tectonic plates
Spherical shell subsidence model
"Reprinted from http://pubs.usgs.gov/gip/earthq1/fig1.gif with permission from USGS".
16. Orientation of the maximum horizontal stress measured by
hydraulic fracture method (Goodman, 1980)
Average focal
mechanism of deep earthquakes in and around Japan projected on
the upper hemisphere. Arrows show tension and compression axes
(Kasahara, 1983)
17. Spherical shell subsidence model
The earth shrinks by
gravity force.
Compressive strain
appears by the spherical
geometry.
18. Need for initial stress measurement
Initial stress can roughly estimated by the primitive
method
Measurement is required for precise values
Initial stress can be affected by such geological phenomena as fold,
faults, intrusion of magma etc.
Method to measure initial stress
19. Method Description Feature
Stress relief method A borehole is drilled to desired depth. A
probe is installed in the hole. Stress
around he probe is relieved by usually
overcoring.
Three dimensional stress state can be
estimated by one overcoring in most
methods. It takes costs and time. There
are many results. The hole is drilled
usually from a roadway.
Stress compensation method Stress is relieved measuring displacement
or strain. Stress is applied until the
displacement or strain recovers to the
values before the stress relief. Necessary
stress is regarded as initial stress.
Measurement is usually carried out at
rock surface. It is difficult to estimate
three dimensional stress state. Elastic
constants are not required to estimate
rock stress.
Hydraulic fracturing method A borehole is drilled from the ground
surface or a roadway. Initial stress is
estimated from hydraulic fracturing data.
Only horizontal stresses are usually
estimated. It can be apllied up to
several km deep. There are any results.
Methods using oriented core Material tests in laboratory are carried out
for rock cores. Initial stress is estimated
from such data as stress-strain curves.
Results similar to other methods are
often obtained although the
mechanisms are not well understood.
Method based on fault
earthquake data
Orientation of initial stress is estimated
based on the focal mechanism of fault
earthquakes.
Enormous data can be used although
the stress magnitude can't be estimated.
20. Stress relief method
(1)
A borehole is drilled usually
from a roadway. The borehole
should be longer than the
roadway width to avoid areas
where stress concentrates.
A pilot hole is drilled from the
borehole top.
A probe is installed in the pilot
hole.
Overcoring is carried out
measuring deformation and/or
strains.
(2)
(3)
(4)
Stress relief methods
21. Principle of stress relief method
No stress exists in the hollow cylinder formed by
overcoring.
Magnitude of strain and/or deformation with overcoring
are equal to that when the pilot hole is drilled under the
initial stress state with an inverted sign.
The strains and/or deformations can be obtained by analytical
methods or numerical methods assuming an elastic medium.
Initial stress can be estimated by solving the simultaneous
equations.
22. Example
2
y
1
Overcoring
σ α = σ cos2
α+ σ sin 2
α + 2τ xycosα sinα
x y
x
3
A rosette gage was
atacched to a rock
surface and overcoring
was carried out around
the gage. Represent
change in strains of the
gauges 1, 2 and 3 by E,
ν, σx, σy τxy.
Conical bottom strain
method (Sakaguchi et al.,
1994)
23. Hydraulic fracturing method
Often used method.
Originally developed for
wells for petroleum and
geothermal energy to
measure stress and to
enhance the prodcution
Fracture
There are some cases in
which hydraulic fracturing
p
is carried out from an
existed roadway.
Packer
Hydraulic fracturing
24. Hydraulic fracturing
A borehole is drilled.
Packer and a water pipe is
installed.
Water is injected measuring Fracture
pressure and flow rate.
p
Packer
25. Hydraulic fracturing
Water valve is closed after
breakdown which is a decrease of
water pressure and represents that a
fracture appears at the borehole wall. Breakdown
The pressure at the breadown is
called pb.
Water is injected again.
Decrease of the slope of the water
pb
pr
Down-hole pressure
ps
pressure-time curve represent
reopening, namely, the fracture is
opened again. The pressure at re-
opening
pressure pr.
is called re-opening
Injection
and then
pressure
is continued for a while
the valve is shut.Water
Flow rate
will converge. The
converged pressure is called shut-in
pressure ps.
Time
26. Hydraulic fracturing
Packer etc. are removed and
fracture orientation is
observed by a borehole
Breakdown
camera or impression packer. pb
pr
Down-hole pressure
ps
Flow rate
Time
27. Principle of hydraulic fracturing
Tangential stresses σA, σB at points A and B when internal
pressure p acts to a circular hole under maximum principal
stress σH and minimum principal
ignored for convenience).
σh
σ
stress (pore pressure is
H
A
σ A
σ
= 3σ h − σ H − p
σh
= 3σ −σ − pB H h p
B
28. principle of hydraulicfracturing
σA is smaller than σB. A fracture
initiate and grows from point A
when the following criterion
satisfied.
T0 is tensile strength.
is
σH
A
T0 ≤ −σ A = −3σ h + σ H + p
σh
The following equation is
derived for the breakdown
pressure pb.
T0 = −3σ h +σ H + pb
p
B
29. Principle of hydraulic Fracturing
Reopening occurs when the
tangential stress at point A
becomes tensile.
0 ≥ 3σ h − σ H − p
σH
A
Consequently, for reopening
pressure,
σh
0 = 3σ h − σ H − pr
p
B
30. Principle of hydraulic fracturing
It is said that shut-in
pressure is roughly
σh.
σ h = ps
equal to
σH
A
σh
p
B
31. Procedure to estimate initial stress
Minimum principal stress is estimated from the shut-in pressure
σ h = ps
Maximum principal stress is estimated from the minimum principal
stress and the re-opening pressure.
0 = 3σ h − σ H − pr
Orientation of the maximum principal stress is equal to that of the
fracture observed by a borehole camera or an impression packer.
33. Criterion for horizontal fracture
Vertical stress σv at borehole wall is
σ v = σ V − 2 p
Criterion for horizontal fracture is
σ v < 3σ h − σ H
Another method has to be used in
fracture occurs.
he case where horizontal
34. More detail
Consideration on pore pressure and fracture mechanics
(Nihon Kikai Gakkai, 1989)
Determination of three dimensional stress state based on
data from one borehole (Nihon Kikai Gakkai, 1989)
Statistical consideration (Shin & Okubo, 1999)
Estimation of initial stress measuring strains (Sato et
1999b、Itoh et al., 2001)
Detailed consideration on re-opening pressure (Ito et
1999b)
al.,
al.,
35. Estimation of initial stress from laboratory test on oriented cores (Ex.
Nihon Kikai Gakkai, 1989)
AE mehod (Lavrov, 2003)
DSCA method (Oikawa et al.,1995, Yamaguchi et al., 1991, Matsuki et al.,
1995)
DRA mehod
ASR method
Mehod utilizing P-wave velocity
Results similar to such reliable methods as stress relief method and
hydraulic fracturing method are often obtained.
Principle is not well known. There are many points which should be
clarified. For example, how long rock core maintain the stress memory
is not well known.
Methods using oriented cores
37. Sign and amplitude of elastic wave from fault slip depends
on orientation to the observatory.
Compressional and dilatational wave can be observed for
P-wave, for example.
Compressional wave
Dilatational wave
Method based on fault earthquakes
38. Compression and
tensile axes can be obtained by projecting polarity of P-wave on the
direction of observatory.
Directions of compression and tension axes are sometimes regarded as those
of the maximum and minimum principal stress, respectively.
39. Compression and tension axes represents stress change due
to fault slip and their directions should not be always
coincides to those of initial stress. However, similar results
to stress relief method and hydraulic fracturing method are
often obtained.
The directions of initial stress can be easily estimated from
enormous fault earthquake data although the magnitude of
initial stress can't be estimated.
40. Borehole breakout
Failure phenomena which are
observed at sidewall of
petroleum and geothermal wells
Failure zones of dog ear-shape
grow in the direction of the
minimum principal stress
Initial stress magntude can be
estimated from the shape of the
failure zone.
For detail, refer Brudy &
Zoback (1999), Cuss et al.
(2003), Haimson & Lee (2004)
σH
σh
Other methods
41. Core discing
Rock core breaks in a
many discs when a
borehole is drilled to a
high pressure zone.
Relationship between
stress state and disc
shape is investigated
(ex. Obara et al., 1998).
Initial stress state can
be roughly estimated. Core discing which was
observed at Kamaishi Mine
42. Other other other
Calcite twins (Kang et al., 1999)
Sub-crater of volcano (Karino and Murata, 1998)
Electric resistivity (Ito et al., 1999a)
etc.........................
43.
44. Magnitude and orientation of Insitu stresses vary considerably within
geological systems.
2. The pre-existing stress state changes dramatically due to
excavation/construction therefore load must be redistributed.
3. Stress is not familiar – it is a tensor quantity and tensors are not
encountered in
everyday life.
4. It is a means to analyze mechanical behaviors of rock.
5. It serves as boundary conditions in rock engineering problems as a
stress state
is applied for analysis and design.
6. It helps in understanding groundwater fluid flow.
7. At large scale shed some light on the mechanism causing tectonic
plates to
move or fault to rupture with the added uncertainty in that there is no
constraint
on the total force, as is the case with gravity loads.
55. A section, normally less than 1m in length, of a borehole is sealed off with a straddle
packer.
The sealed-off section is then slowly pressurized with a fluid, usually water.
This generates tensile stresses at the borehole wall. Pressurization continues
until the borehole wall ruptures through tensile failure and a hydro fracture is
initiated.
The fracture plane is normally parallel to the borehole axis, and two fractures are
initiated simultaneously in diametrically opposite positions on the borehole
periphery.
The hydro fracture will initiate at the point, and propagate in the direction, offering
the least resistance. The fracture will therefore develop in a direction perpendicular
to the minimum principal stress.
The orientation of the fracture is obtained from the fracture traces on the borehole
wall –it coincides with the orientation of the maximum horizontal stress, in a vertical
or subvertical
hole where it is assumed that one principal stress is parallel to the borehole.
The fracture orientation may be determined either by use of an impression packer
and a compass or by use of geophysical methods such as a formation micro-scanner
or a borehole televiewer.
56. In its conventional form, the method is 2D: only the maximum and minimum normal
stresses in the plane perpendicular to the borehole axis are established.
For a vertical borehole, these components are the maximum and minimum horizontal
stresses.
Since the principal stress directions in tectonically passive and topographically at areas
areusually close to horizontal and vertical, it can often be assumed that the components
measured in a vertical borehole are two of the principal stresses.
Hydraulic fracturing is an efficient method for determining the 2D stress field, normally
inthe horizontal plane, and is therefore suitable at the early stages of projects when no
underground access exists.
Due to its efficiency, it is especially advantageous for measurements at great depth. . The
method is also not significantly affected by the drilling processes.
Hydraulic fracturing normally includes large equipment, which requires space.
Furthermore,the theoretical limitations normally imply that the measurements should
be done in vertical
holes. Hence, the method is most suited for surface measurements in vertical or
subvertical
boreholes.
Applied packer pressure – 2-4 MPa