2. CORING
PURPOSE OF CORING
TYPES OF CORING
1 CONVENTIONAL CORING
2 SIDE WALL CORING
DIFFERENCE BETWEEN CONVENTIONAL AND
SIDE WALL CORING
CORE HOLDER
3. Cores which extract from the formation /reservoir
using special coring tools. Once the cores is cut ,they
are captured and retrieved to the surface for
analysis of different physical parameters.
A core sample is a cylindrical section of (usually)
a naturally occurring substance. Most core samples
are obtained by drilling with special drills into the
substance, for example sediment or rock, with a
hollow steel tube called core drill.
The hole made for the core sample is called the "core
bowling".
4. CONTD…..
In the coring process,
the sample is pushed
more or less intact into
the tube.
Removed from the
tube in the laboratory,
it is inspected and
analyzed by different
techniques and
equipment depending
on the type of data
desired.
5. The purpose of getting cores is to obtained rock samples
of sufficient size for :
1. Making reservoir analysis test to determined
porosity, permeability, residual oil and water
saturation (primary purpose of coring).
2. To establish the physical character of formation
boundary.
3. To furnish paleontological data for age and facies
correlation
4. To determined the structural attitude of the beds
6. There are two types of coring which are
1 Conventional coring
2 Side wall coring
7. Conventional coring is a methed of drilling and
acquiring rock samples to retrieve the core
samples.
The complete rod string and core barrel has to be
removed from the hole.
When the bit is about to enter a formation of
special interest. A service company may be
brought in to take barrel cores.
The coring tools consist of an annular diameter
bit to cut the core and a hollow barrel to catch it.
8. Core samples may be of any length .but cores o f
over 90 feet are hard to handle. A 60 feet core is
average cores, which can be handle easily.
A core diameter range from 11/8 to 5 inches with
4 inches being the most popular size for core
analysis.
Since it is costly and time consuming, also
removing the cores is some time dangerous. since
it is possible to swab the well and cause a
blowout.
So sidewall coring is most commonly used than
conventional coring
11. Side wall coring is a methed used in zones
where core recovery by conventional methed
was less than expected or whereas cores were
not obtained as drilling progressed.
Side wall coring is useful in paleontological
work.
A side wall coring device is lowered into the
hole on a wire line cable and a sample of the
formation is taken at the desire depth.
12. This done by shooting a hollow bullet into the
bore hole wall, then pulling it out of the well
and bring up to the surface.
There are as many as 30 bullets per guns and
since two guns can be used.
Up to sixty cores can be obtained during one
run.
If electric logs have been run previously , a
spontaneous potential or gamma ray curve is
used to determined gun position by direct log
correlation
15. Conventional coring:
Conventional coring provides large samples
It is more better and more consistent
representation of formation.
It is better for heterogeneous rocks or for more
complex lithology.
Sidewall coring :
Side wall coring provides smaller samples.
It is less representative of heterogenous
formation..
16. MINIMIZING CORE LOSSES DUE TO EROSION OF
MATERIAL FROM FLUID CIRCULATION
Bit discharge directed away from core
Drilling fluid use kept to a minimum
Polymer compounds added to drilling fluid
Vibration of drill rod minimized
Controlled advancement of the drill rod
Core-catching devices installed
17. ROCK CORE LOGS
To record all relevant information about the core
and to make a field description Contains……
Percent core recovery
Amount and location of core loss
Depth of the beginning and ending of each
core run
18. CORE HANDLING PROCEDURES
Properly label and identify all samples
Sample packaging depends on sample types
Samples for chemical analysis should remain
undisturbed, subsampled in the field and sealed
immediately
Chain of custody forms
19. ROCK CORE SAMPLES
Rigid container required for transport
Core placed into box left to right like top to bottom so
it reads like a book
Mechanical breaks in core should be distinguished
from fractures
Core can be labeled on core surface
Depth, core loss points, fractures
21. WHAT IS A CORE HOLDER? WHY IS IT
USED?
“A portable apparatus provide on-site permeability
measurements and formation evaluation by a core
sample extracted from an underground reservoir.”
CORE SAMPLE: A cylindrical rock (1-1/8“ to 5-
1/4" diameter and 30 to 60 ft long) sample taken
from the formation for geological analysis to
perform laboratory evaluation of basic properties.
22. TYPES OF CORE HOLDERS
According to geometry:
---Vertical core holder
---horizontal core holder
According to test:
--resistivity core holder
--acidizing core holder
--Steam Flooding core holder
For Permeability Measurements:
--Gas (or Air) permeability measurement core holder
--water (or brine, polymer) permeability measurement core
holder
23. CORE HOLDERS FOR ROUTINE &
SPECIAL CORE ANALYSIS
(A) Hassler Type Core Holders
(B) Biaxial Type Core Holders
(C) Triaxial Type Core Holders
24. BIAXIAL TYPE CORE HOLDERS
Biaxial type core holders
are defined as core holders
that have common radial
and axial pressure applied
to the core sample.
These core holders are
routinely used for gas and
liquid permeability and
other core flooding
experiments.
25. TRIAXIAL TYPE CORE HOLDERS
TCH Series core holders
are triaxial type core
holders.
A triaxial type core holder
is defined as a core holder
in which the axial and
radial pressures are
independent of each other
and can be varied during
the test.
26. HASSLER TYPE CORE HOLDERS
Core holders that have radial
pressure applied to the core
sample.
Routinely used for gas and liquid
permeability and other core
flooding experiments.
Spacers are provided to
accommodate undersized cores.
Distribution plugs are provided
with a single inlet and outlet.
The volume of all ports and flow
lines are kept to a minimum so
that accurate flow data can be
determined.
27. LIMITATIONS IN MEASUREMENT
Core sample may not be representative of the reservoir
rock because of reservoir heterogeneity.
Core recovery may be incomplete.
Permeability of the core may be altered when it is cut,
or when it is cleaned and dried in preparation for
analysis. This problem is likely to occur when the rock
contains reactive clays.
Sampling process may be biased. There is a temptation
to select the best parts of the core for analysis.
