2 5217774511700575821

Chapter one
well logging
Well logging :Is the practice of making a detailed record(log) of the geologic formations
penetrated by a borehole. May have different names( borehole geophysics, petrophysics,
formation evaluation).
The log may be based on Visual inspection of samples brought to the surface(geological
logs, core logs) or physical measurements made by instruments lowered into the
hole(geophysical logs)
A log can refer to :
-The tool that makes the measurement .
-The paper (or digital) representation of those measurements.
-A single measurement(a curve or a trace).
Basic log types:
-Open wire line log.
-Wire line cased hole logging.
-Logging while drilling(LWD).
Uses of well logging:
1-Determination of reservoir parameters:
-Lithology, porosity, permeability, fluid saturation
2- Determination of formation fluids.

3-Recognize depositional systems or other geological features.
4-Correlation to geologic maps or seismic.
5-Detection of overpressure zones.
6-Detection and estimation of hydrocarbonzones:
-Oil in place.
-Reservoir managements.
-Reassessment .
Types of well logs:
-Electrical ( resistivity log, spontaneous potential log).
-Nuclear( gamma ray log, density log, neutron log).
-Acoustic(sonic log).
-Other categories (temperature log, caliper log, dipmeter log, image log).
1-Resistivity log: The first well log was a resistivity tool, measures resistance to the flow
of electrical current.
-It is used for:
1-Determination of water bearing versus hydrocarbonbearing zones .
2-Determination of water(oil) saturation in the porespaces of formation rock.
3-Determination of porosity in known water-filled formations.
-Apparent resistivity( Ra):Resistivity log measures apparent resistivity
.-Ra is based on :
1-Spherical flow of DC for electrode type devices.

2-Ra is resistivity of homogeneous , isotropic and infinitely extended medium that is
electrically equivalent to the medium surrounding the tool.
-Resistivity log depth of investigation :
-In flushed zone(Rxo) use (micro log(ML), micro laterolog(MLL), proximity log(PL),
micro spherically focused log(MSFL)).
- In invaded zone (Ri) use(short normal(SN), laterolog-8(LL8), spherically focused
log(SFL), medium induction log(ILm), shallow laterolog(LLs)).
-In un invaded zone(Rt) use( long normal (LN), lateral log , deep induction log(ILd), deep
laterolog (LLd), laterolog-3(LL3), laterolog-7(LL7)).
2-Spontaneous potential log (SP): Is measurements against depth of the potential
difference between the voltage at the surface and an electrode in the well bore.
-Interpretation goals:
1-Correlation of formations from well to well.
2-Gross lithology(reservoir vs. non reservoir ).
3-Estimate of formation water resistivity Rw.
4-Estimate of shale (clay) content.
5-Qualitative indication of permeability.
6-Identification of depositional environments.
3-Gamma ray log :Is a method of measuring naturally occurring gamma radiation to
characterize the rock or sediment in a borehole or drill hole.
4-Density log:
-Density log help to determine :

1-Measures formation bulk density( matrix density and fluid density need to be known)
2-Porosity can be derived.
3-PEF log is a lithology indicator: matrix density.
4-Borehole size (from attached caliper).
5-Gas indication (with the neutron).
6-Formation mechanical properties(with the sonic).
7-Clay content (shaliness) (with the neutron).
4-Neutron log: Neutron logs are porosity logs that measure the hydrogen concentration in
a formation .In a clean formation where porosity is filled with water or oil, the neutron
log measure the liquid filled porosity. Neutrons are created from a chemical sourcein the
neutron logging tool. The chemical sourceis usually a mixture of americium and
beryllium which continuously emit neutrons.
5-Sonic log: Measures interval transit times of a compressional sound wave travelling
through the formation along the axis of the borehole .The sonic transit time depends on
the lithology, porosity and fluids in the pore space.It also assumes a homogeneous
distribution of porosity.
-Sonic log application :
1-Porosity determination .
2-Rock properties determination .
3-Formation stress determination.
4-Abnormal pressure detection .
5-Fracture detection.
6-Caliper log

-Applications of caliper log:
1-Evaluate the borehole environment for logging measurements.
2-Identification of mud cake deposition , evidence of formation permeability.
3-Estimate hole volume to determine cement volume requirements.
4-Determine competent formations to set packers.
5-Provide position data for dip meter interpretation.
-Methods:
1-Mechanical .
2-Acoustic.
3-Electromagnetic.
The steps of this work:
step 1: this icon for log

Step 2 : this is track of well log
Chapter 2
Cross plot
dimensional plot with one variable scaled in the vertical
-
A two
-
Cross plot :
(Y) direction and the other in the horizontal (X) axis. The scales are usually
linear but may be other functions, such as logarithmic. Additional dimensions
may be represented by using color or symbols on the data points. These plots are
common tools in the interpretation of petrophysical and engineering data.
Cross plots are used in well log analysis to calculate from graphs or charts a
result based on two or more forms of data.
Neutron-Density Cross Plot :-
One of the earliest cross plots is the neutron-density cross plot. This cross plot is
used in log analysis for determination of porosityand lithology from neutron
porosity and bulk density.
The neutron logging tool is calibrated to provide accurate porosity in a
limestone, sandstone, or dolomite formation (matrix). Neutron porosity is only

valid after making appropriate corrections and when used in a specific limestone
matrix. The neutron-density cross plotis used to perform the final analysis.
To determine lithology or correct porosities for lithologic or gas effect from a
density-neutron cross plot, follow the steps listed below :-
1-use the table below to determine how to a neutron porosity value
2- Use the table below to determine how to enter a density porosity value.
Then
If
Find the density log percent
porosity value on the diagonal line
that matches the lithologic units
recorded on the log (use sandstone
line if the log was recorded in
sandstoneunits). Move left or right
to intercept the neutron projection.
Density log porosity is in
sandstone, limestone or dolomite
units
Enter the y-axis with the log bulk
density value and intercept the
neutron projection.
Density log scale is bulk density.
Then
If
Enter the chart along the x-axis
with neutron porosity. Project up to
density porosity.
Neutron porosity is in limestone
units.
Enter the chart on the sandstone or
dolomite line. Project up or down
to a density value.
Neutron porosity is in sandstoneor
dolomite units.

3- Use the table below to determine formation lithology and porosity.
Then
If
The point defines the lithology of
the formation by which line it falls
on and the porosity is the value
marked on the line at that point.
Point falls on a diagonal line
Move down and to the right parallel
to the nearest dashed line until a
diagonal line is intersected . Read
the value foe porosity at that point.
The lithology is a combination of
the lithologies of the lines on either
side of the point of intersection.
Gas is present if the original point
is northwest of the appropriate
diagonal lithology line.
Point falls away from appropriate
diagonal line.
‫فاات‬
The steps of this work
Step 1: this icon of cross plot

step 2 : here you should to choose the available logs (for examplein bu 15 we
choose the density log in x and neutron login y)
Step 3 : here you should add the top and bottom depthto the wellor to
required zone
Step 4 : this is the cross plot in 3D modelfor bu 15

chapter 3
Volume of clay
Clay minerals are generally crystalline in nature. The structure of the clay
crystals determines its properties. Typically, clays have a flaky ,mica-type
structure. Clay flakes are made up of a number of crystal plates (each plate
called a unit layer) stacked face-to-face. the surfaces of the unit layer are called
basal surfaces. . A unit layer is composed ofmultiple sheets with two types:-
: it is composed ofeither aluminum or magnesium atoms
Octahedral sheet
-
1
octahedrally coordinated with the oxygen atoms of hydroxyl groups.
: consists of silicon atoms tetrahedrally coordinated with
Tetrahedral sheet
-
2
oxygen atoms.
Swelling Mechanism
is a phenomenon in which water molecules surround a clay crystal structure and
position themselves to increase the structure's c-spacing thus resulting in an
increase in volume.
There are two types of swelling :
in which water molecules are adsorbed on crystal
-
:
Surface hydration
-
1
surfaces. Hydrogen bonding holds a layer of water molecules to the oxygen
atoms exposed on the crystal surfaces. Subsequent layers of water molecules
align to form a quasi-crystalline structure between unit layers which results in
an increased c-spacing. All types of clays swell in this manner.

Where the concentration of cations between unit layers
-
:
Osmotic swelling
-
2
in a clay mineral is higher than the cation concentration in the surrounding
water, water is osmotically drawn between the unit layers and the c-spacing is
increased. Osmotic swelling results in larger overall volume increases than
surface hydration. However, only certain clays, like sodium montmorillonite,
swell in this manner.
The effects of clay swelling
Clay swelling during the drilling of a well can have a tremendous negative
impact on drilling removal of cuttings from beneath the drill bit, increases
friction between the drill string and the sides of the borehole, and inhibits
formation of the mud cake . Clay swelling can also create other drilling
problems such as loss of circulation or stuck pipe that slow drilling and increase
drilling costs.
Step 1 : this is a volume of clay

step 2 : you should to add all of this log
Step3 : this is the (Vcl) for bu 15
Chapter 4
Porosity and water saturation
Porosityor void fraction is a measure of the void (i.e. "empty") spaces in
a material, and is a fraction of the volume of voids over the total volume,
between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking,
some tests measure the "accessible void", the total amount of void space
accessible from the surface (cf. closed-cell foam).

There are many ways to test porosity in a substanceor part, such as industrial
CT scanning.
The term porosityis used in multiple fields
including pharmaceutics, ceramics, metallurgy, materials, manufacturing, hydrol
ogy, earth sciences, soil mechanics and engineering.
In gas-liquid two-phase flow, the void fraction is defined as the fraction of the
flow-channel volume that is occupied by the gas phase or, alternatively, as the
fraction of the cross-sectionalarea of the channel that is occupied by the gas
phase.[1]
Void fraction usually varies from location to location in the flow channel
(depending on the two-phase flow pattern). It fluctuates with time and its value
is usually time averaged. In
Porosityof rocks
Consolidated rocks (e.g., sandstone, shale, granite or limestone) potentially have
more complex "dual" porosities, as compared with alluvial sediment. This can
be split into connected and unconnected porosity. Connected porosity is more
easily measured through the volume of gas or liquid that can flow into the rock,
whereas fluids cannot access unconnected pores.
Porosity is the ratio of pore volume to its total volume. Porosity is controlled by:
rock type, pore distribution, cementation, diagenetic history and composition.
Porosity is not controlled by grain size, as the volume of between-grain spaceis
related only to the method of grain packing.
Rocks normally decrease in porositywith age and depth of
burial. Tertiary age Gulf Coast sandstones are in general more porous
than Cambrian age sandstones. There are exceptions to this rule, usually because
of the depth of burial and thermal history.
Watersaturation

space. It is expressed in volume/volume,
pore
The fraction of water in a given
units. Unless otherwise stated, water saturation is the
saturation
percent or
. The saturation is known as
undisturbed zone
in the
ter
formation wa
fraction of
, but is known as
total porosity
the total water saturation if the pore spaceis the
. If used
effective porosity
effective water saturation if the pore spaceis the
usually refers to the effective water saturation.
without qualification, the term
Step1 this icon is for porosity and water saturation
Step 2 : you should to full these information include (logs , temperature and water
equation )

Step 3 this is track for porosity and water saturation
Chapter 5
Cutoff
Upper or lower limiting value of a reservoir parameter. Values outside
Cutoff:
these limits are not used in computation or other data handling manipulation.
-
Types of cutoff:
*
1. Shale content (Vsh) : eliminate the portion of the formation which contains
large quantities of shale (maximum shale content tolerable to be productive).
Vsh cutoff ≈ 20 to 30 %
2. Porosity : eliminate the portion of the formation which is low porosity (and
low permeability) and therefore would be non-productive.
Carbonates
Sandstones
Φcutoff ≈ 7% gas Øcutoff≈ 4%
Φcutoff ≈ 8% oil
3. Water saturation: eliminate the portion of the formation which contains large
volumes of water in the pore space. The water saturation cutoff ensures
sufficient effective permeability to be productive.

Carbonates
Sandstones
Swcutoff ≈ 60% Swcutoff ≈ 50%
is defined as the interval from the top to the bottom of the
Gross thickness
reservoir including both reservoir rocks and non-reservoir rocks such as shales,
anhydrites, salts etc.
-
is defined as the portion of the reservoir which excludes the non
Gross sand
reservoir rock and is thus subject to a shale cutoff.
is defined as the fraction of the gross sand which is porous, permeable
Net sand
and contains hydrocarbons and water and is subject to a porosity cutoff.
ains enough hydrocarbons
is defined as the portion of the net sand that cont
Net pay
and is subject to a water saturation cutoff.
The step of this work

Step 1 : this icon is cutoff
Step2 : you should to full the information include (porosity cutoff , water
saturation , and clay volume )
Step 3: this track is cutoff

This is a finally result of net pay
Discussion
Interactive petrophysics is one of the best petrophysical software in the industry
. But there are a number of problem that accompany this program , including
that lack of activation of options , not all logs are available , when loading data
there are similar data such as gamma ray and caliper so we will give overwrite
to replace it , the files may be compressed , also opening Wi-Fi in laptop affects
the program ,may be logs with one file and this is also a problem accompanying
the program , when choosing the wrong depth or not adding all files also affects
our work one of the problems that accompanies our work there are unaccounted
cutoff porosity wells for them the solution is to take a cutoff for the closest well
also there are errors in the program or not all the logs in a certain well are
available

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