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



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.



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



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.



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.



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.



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



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.



Figure2: plugging machine



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.



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.



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.

http://wiki.aapg.org/Core_description

http://wiki.aapg.org/Petroleum



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.



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.