Core plugging

Reservoir lab. Core plugging
Date: Nov 19th
2015 Group:B lab. No:1
Koya University
Faculty of Engineering
Petroleum Engineering Department
Reservoir lab
Third stage
Lab. No:1
Core plugging
Prepared by: Sarwar Salam
Supervised by:
Mr. Barham–Mr.haval

Date: Nov 19th
Aim of experiment:
The purpose of this particular experiment is to plug or
prepare a core sample in a non-uniform rock sample of
about adequate size and smoothing the final core sample
and preparing it for further reservoir test, measurements
as well in the lab.

Date: Nov 19th
Introduction to Experiment:
Coring and core analysis form an integral part of
formation evaluation and provide vital information
unavailable from either log measurements or
productivity tests.
Core information includes detailed lithology,
microscopic and macroscopic definition of the
heterogeneity of the reservoir rock, capillary pressure
data defining fluid distribution in the reservoir rock
system, and the multiphase fluid flow properties of the
reservoir rock, including directional flow properties of
the system.
Also, selected core data are used to calibrate log
responses, such as acoustic, or neutron logs used to
determine porosity. As a result, core data becomes an
indispensable source in the collection of basic reservoir
data directed toward the ultimate evaluation of
recoverable hydrocarbons in the reservoir.
Core slabbing: Core slabbing is the first step in the
preparation of samples for core laboratory experiments.
The radial core slabbing saw is a machine for cutting
rocks into the smaller parts. This is basically for cutting a
big size outcrop rock into the smaller parts and/or cutting
the longer cores to the shorter ones. Radial core slabbing

Date: Nov 19th
saw is designed for diamond cutting discs only, which is
connected to the motor with a shaft and two pulleys and
the use of the cooling waters improves the slice quality
and cutting speed and reduces the heat which is produced
by sawing process.
Knowledge of petro-physical and hydrodynamic
properties of reservoir rocks are of fundamental
importance to the petroleum engineer, Samples are taken
at selected locations or at fixed intervals and are
subsequently used for a wide variety of analyses
performed to determine physical, chemical and
geological parameters important for the evaluation of
the (potential) reservoir. Plugs of standard length and
diameter are taken either “horizontal” (perpendicular to
the core axis and parallel to the inclination) or “vertical”
(parallel to the core axis).
These plugs are obtained by drilling cylinders from the
Core using lubricants such as Water, brine or oil and
trimming the ends of these cylindrical samples. Standard
plugs are used for the determination of oil and water
saturation, porosity, permeability and grain density
measurements (at ambient pressure or at higher pressures
to mimic sub-surface conditions) and for a variety of
Special Core Analysis tests.

Date: Nov 19th
Theory:
The task of the reservoir geoscientist is to describe the
reservoir as completely and accurately as possible using
a variety of methods, from seismic and well testing to
logging, cuttings analysis and coring. These methods
present the engineers with a valuable range of scales
from photomicrograph of a single filament of illite, to the
log investigating up to several feet around the borehole,
to the well test probing hundreds to thousands of feet
into the formation.
Many of these methods allow the engineer to estimate
three key formation descriptorsporosity, fluid saturation,
and permeability. But different methods may lead to
different values. Porosity, for example, measured on a
core, which is removed from in situ pressure,
temperature and fluid, then cleaned, dried and re-
saturated may not become close to porosity determined
from log measurement.
To form a commercial reservoir of hydrocarbons, a
formation must exhibit two essential characteristics.
There must be a capacity for storage and transmissibility
to the fluid concerned, i.e. the reservoir rock must be
able to produce and maintain fluids, when development
wells are drilled.

Date: Nov 19th
In general, several objectives must be met when taking
core samples.
But in the prime place, a careful on-site examination for
hydrocarbon traces is desirable (e.g. gas bubbling or oil
seeping from the core, core fluorescence on a freshly
exposed surface, fluorescence and staining in solvent
cuts etc.).
Advances in technology continuously make new
improved measurements and experiments available to the
industry. Today this process seems to move faster and
there is a demand for new standards both for coring and
core analysis.
Even with the current possibilities in computer
technology, much energy is used in the process of
transporting data between different software systems and
different formats.
A potential for improving acquisition and analysis at
reduced cost is obvious. In this paper, the basic concepts
of coring and core analysis were reviewed and used the
developmental advances as the main goal.

Date: Nov 19th
Equipment and machines:
Device description:
1-Core Slabbing Cross Cut Saw: this device is used in
preparing the core sample to cut a non-uniform rock into
pieces that can be plugged by plugging machine.
The machine has a motor which supplies the rotational
motion for sawing. The main machine parts are:
· Radial saw
· Electro motor
· Shaft, pulleys and rim
· Adjustable tilting table
· Cooling system, including pumps, water supply,
flexible pipes The rotational motion transmitted by two
pulleys from electro motor.
At either side, there are three different stepped pulley
couples. The speed of motion can be adapted by
positioning the compound diamond rim on the suitable
stepped pulley couple on the electro motor and saw
system. The dimension of rock sample should be smaller
than the max height of saw from table to be cut
electively. Bigger rocks should be broken to a proper
part with other methods. One drawback of this machine

Date: Nov 19th
is its noise. The machine noise level is around 70 dBa.
During the cutting process, the noise level depends on
the material to be cut, the type of disc used, the rotation
speed and the cooling.
2- Core plugging machine:
This machine having a drillable bit installed inside a
wide pit in which a rock specimen is tided carefully, in
which a bit having its teeth in the around it to drill a
cylindrical core plug.
The core cutting machine is designed to cut specimens
from cores of between 4 to 6 inches, or from blocks of a
similar size. The produced plugs are in two different size
of 1 and 1.5 inches. This machine can be installed on any
table. By screwing down of a hollow plug drill, plugs are
cut from the samples.
However, students should considered the following
safety notices:
-The core cutting machine should only be used by
qualified operators or students under supervision of the
teacher who have been suitably trained in how to
produce the quality of cut required under the prescribed
safety conditions.

Date: Nov 19th
Figure2: plugging machine

Date: Nov 19th
Experiment Procedure:
The procedure for cutting a given sample is as follows:
 If the rock is big then it should first be cut by
another method
 Put the sample on the table
 Check the tension on the pulleys
 Adjust the direction of water line on both saw and
sample
 Check water tanks and fill them if they are empty
 Start the water pump and check the direction of
water and check the flow
 Start the saw by pressing the start bottom
 Cut the sample by screwing up and down of the saw
and pushing the sample table of machine
 Press the stop button
Unclamp the core sample
However, in working with the machine consider the
following safety issues:
(i) prevent touching of saw with the machine
sample table, because of damaging of saw,
(ii) protect yourself from any splash and water
drops by wearing overall and safety glasses.

Date: Nov 19th
Core plugging test procedure:
 Check the tension on the pulleys
 Check the direction of the spindle
 Fill the recycling tank
 Screw down the core drill and lock it in place
 Close the core drill protective housing
 Press the power key
 Start the water circulation
 Start rotation for a few seconds before coming down
to the sample.
 Slowly come down to the sample and each (cm)
coming down go back to your start point and start
again until the maximum length that can be reached
drilled.
 Then if the plug come out of the rock, it can be
smoothed then, but if not use hummer to extract the
plug in the rock.
After plugging the core, it should be trimmed and
smoothed, this can be done using special devices or
also using slabbing device with same procedure of
slabbing but this time it is use for trimming so less
length of sample is put to the device.

Date: Nov 19th
Discussion:
1- Explain coring briefly?
 Retrieval and analysis of cores is essential to all
phases of the petroleum industry. Cores offer the
only opportunity to obtain intact, vertically
continuous samples that allow the visual
examination of depositional sequences and
variations in reservoir character. Properly analyzed
cores provide data available from no other source;
these data should provide direct evidence of the
presence, quantity, distribution, and deliverability
of hydrocarbons. Cores are essential to
understanding the nature of the pore system in the
potential reservoir unit. The knowledge gained
from cores enhances our ability to predict reservoir
performance and to select procedures to maximize
profitable hydrocarbon recovery.
2- Why it is crucial to take a plug as soon as possible
after getting the reservoir rock core?
 It is important to take plug samples within the first
24 hours after the core has arrived on surface in
order to isolate the centre section of core for
accurate invasion analysis data
3- What are the primary objectives of coring process?
 The primary objective of the coring process to
reduce uncertainty of the other Formation
Evaluation processes such as well logging.

Date: Nov 19th
4- Which type of data can be produced by coring?
 There are a lots of data that can be measured from
the reservoir rock sample, such as:
-Depositional environment
-Reservoir rock type
-Mineralogy and chemical composition of the rock.
-Porosity
-Permeability and Relative permeability
-Grain (matrix) geometry
And many other data can be measured either
directly or indirectly from the core sample.
5- What are the pre-main test preparations that should
be done to the sample?
 When a piece of rock or a core is wanted to be
used for analysis as a sample in the laboratory,
several steps, as per-processing steps, should be
considered on the sample to be prepared for
experiments. The main per-processing steps are as
follow: (i) slabbing; the cores need to be slabbed
with the aim of making the rock structure visible.
This can simply be done by sawning down the
middle of the core and cuting it at desired length.
(ii) plugging: one can drill the plugs at every one
foot of the core. (iii) trimming: both end of the
plugs and core samples can be trimmed in order to
produce high quality thin sliced samples without
disturbing the structure of the sample.

Date: Nov 19th
References:
 Donaldson, A., and Clydesdale, G. M.
(1990).: “Accurate reservoir evaluation
quality core samples—a good starting point,”
in P. F. Worthington, ed., Advances in core
evaluation: Gordon and Breach, New York, p.
35-53.
 Halvorson, C., and Hurst, A.(1990).: “
Principles, practice and applications of
laboratory mini-permeametry,” in P. F.
Worthington, ed., Advances in core
evaluation: Gordon and Breach, New York, p.
521-549
 American Petroleum Institute, 1960, RP-40
recommended practices for core analysis
procedures: Dallas, API, 55 p.
 Skopec, R. A.(1991).: “Rock characterization
in reservoirs targeted for horizontal drilling,”
paper SPE-22709 presented in Annual
Technical Conference and Exhibition
Proceedings, v. omega, p. 503-513.
 Dykstra, H., and Parsons, R. L., (1950).: “The
prediction of oil recovery by water flood,” in
Secondary recovery in the U.S.A., 2nd ed.:
American Petroleum Institute, New York, p.
160-174.

Core plugging

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Core plugging