find porosity of core samples by saturating it with water by manual device

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Petroleum department
3rd stage
Group (A4)
Reservoir Lab
3rd
Experiment:
Porosity by Saturation
Date of experiment: December 17th
2015
Supervised by:
Mr. Haval Hawez
Prepared by:
Muhammad Faisal

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Aim of experiment:
The main objective of this experiment is to calculate the effective
porosity of the interconnected pores of a core plug by saturating
it with water using a manual saturating device.

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Theory:
There are many methods to calculate porosity. Boyle’s Law porosity meter
as shown in consists of two sample chambers. The first step is to calibrate
the volumes of the sample chambers by injecting inert gas such as helium
or nitrogen and recording the pressure differences when the valve
between the two chambers is open and equalization occurs. The next
step is to place the core sample in one chamber at some pressure, p1,
which is isolated from the second chamber at p2. When the valve is
opened pressure equilibrium occurs at some final pressure, pf. The pore
space of the sample is penetrated by the gas; therefore the gas volume
difference between the two tests is a measure of the grain volume.
0.5% of
the grain volume (Jenkins,1960).
Several methods have been developed to measure the pore volume of a
sample. The original mercury injection methods such as Washburn-
Bunting and Kobe are obsolete and seldom used. Their elimination was
due to the destructive nature of mercury and the lack of accurate results.
A second method is called the fluid saturation method. A clean and dried
sample is weighted, saturated with a liquid of known density, and then
reweighed. The weight change divided by the density of the fluid results
in the pore volume.
This technique also yields effective porosity; however, complete saturation
is seldom obtained and therefore porosity is commonly lower than that
determined from the Boyle’s Law method. Furthermore, if the sample is
water sensitive then oil should be used as the saturating fluid. The
procedure is slow, however numerous samples can be run simultaneously
(Helander,1983).

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Introduction:
The manual saturator permits to perform a sequence of vacuum
and saturation cycles on plug size samples. The standard
apparatus includes a plug sized core cell, a vacuum pump, and
hand operated pressure pump (2,000 psi output), a saturant
vacuum tank and necessary hand operated valves and plumbing.
A larger capacity cell to accommodate full size core samples is
also available.
Instruments and devices:

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Test procedures:
1- Record the temperature in the laboratory.
2- Measure each dimension three times to take the average
dimensions of the core samples and record.
3- Measure the weight of the dry core sample.
4- Wait till the weight reading will stabilize, and record.
5- Put the core plug in the core cell chamber sample.
6- Turn on valve No.1 between the vacuum pump and core sample
container.
7- Close the valve No.2 between the core sample container and the
brine reservoir.
8- Turn on the vacuum pump.
9- When the vacuum pressure will be stable, wait for 2 minute and
then turn off vacuum pump.
10- Open valve No.2 to allow brine to flow to the core sample
container.
11- Once the liquid level in the saturant vacuum tank takes it is stabile
level, then turn off valve No.2 and vacuum pump.
12- Start to pressurize the core chamber cell manually and slowly up
to 2000 psi.
13- Monitor and keep the pressure on 2000psi till it will stabilize on
this value.
14- Waite for 5 minute.

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15- Open valve. No.2 and wait for the pressure gauge to go back to
Zero pressure reading.
16- Gently take out the core sample and wipe out the liquid on the
sample surface by rolling it on a piece of paper.
17- Measure and record the weight of the saturated core sample.
18- Measure the difference and find the pore volume and Porosity.
Discussion:
Q1) how can we find porosity by saturation?
A1) after the core sample is cleaned we place it in the sample
container and we inject it with water by considerable amounts of
pressure and the volume of the injected water is equal to the pore
volume of the interconnected pores and the porosity can be
calculated.
Q2) what are the advantages of and limitations of manual saturator?

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A2) Advantages:
 Rapid and efficient saturation.
 Samples can be used for further testing.
 Can accommodate plug size sample and full sized core sample in
option.
 Manual operations Load carrier for easy loading.
 Dead volume sets to minimize volume of saturant.
Disadvantages:
 Wetting the rock surfaces with either brine or hydrocarbon
saturants is difficult.
 Incomplete saturation causes erroneously low porosity values.
Q3) why are the dead volume sets used in this experiment?
A3) they are used to reduce the exposed area to the compressible
pressure by water, and that allows the core sample to get more
saturated with water (depending on the rocks porosity).

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References:
Cosentino, L., 2001. Integrated Reservoir Studies. Paris: Editions
TECHNIP.
Dandekar, A. Y., 2013. Petroleum Reservoir Rock and Fluid
Properties, Second Edition. 2nd ed. New York: CRC Press.

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