Reservoir Rock Properties Analysis, Mohsen Masihi Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 1 Sharif University of Technology Reservoir Rock Properties Analysis 2010 Laboratory Work Book No. 26504 Mohsen Masihi Department of Chemical and Petroleum Engineering Sharif University of Technology, Tehran, Iran [email protected]
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Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 1
and xylene. Toluene and benzene are most frequently used to remove oil and methanol and water is
used to remove salt from interstitial or filtrate water. The cleaning procedures used are specifically
important in special core analysis tests, as the cleaning itself may change wettabilities. The core sample
is dried for the purpose of removing connate water from the pores, or to remove solvents used in
cleaning the cores. When hydratable minerals are present, the drying procedure is critical since
interstitial water must be removed without mineral alteration. Drying is commonly performed in a
regular oven or a vacuum oven at temperatures between 50°C to 105oC. If problems with clay are
expected, drying the samples at 60°C and 40 % relative humidity will not damage the samples.
2-1 Dean Stark The distillation extraction (Dean stark) method for determination of the fluid saturation depends upon
the distillation of the water fraction, and the solvent extraction of the oil fraction from the sample. The
sample is weighed and the water fraction is vaporized by boiling solvent. The water is condensed and
collected in a calibrated receiver. Vaporized solvent also condenses, soaks the sample, and extracts the
oil. The sample is oven dried and weighed. The oil content is determined by gravimetric difference.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 28
Machine Description This consists of a distillation / extraction glassware unit and a heating mantle with thermostatic
controller. The glassware for one sample is composed of boiling flask with extractor, a sample support
screen, volumetrically graduated water receiving tube of 5 or 10 ml, condenser and desiccant drying
tube. A soft tubing is also used to connect the condenser to the water cooling unit. All these devices are
mounted on a frame rack (Fig.16).
Figure 16: Dean Stark apparatus model (left) DS_1.5”x6 and (right) DS_4”x3
Experiment operation: The objective of the experiment is to determine the oil, water and gas saturation of a core sample. The
procedure is as foolow:
1. Weigh a clean, dry cellulose thimble. Use tongs to handle the thimble.
2. Place the cylindrical core plug inside the thimble, then quickly weigh the thimble and sample.
3. Fill the extraction flask two-thirds full with toluene. Place the thimble with sample into the long
neck flask.
4. Tighten the ground joint fittings. Start circulating cold water in the condenser.
5. Turn on the heater and adjust the rate of boiling so that the reflux from the condenser is a few
drops of solvent per second. The water circulation rate should be adjusted so that excessive
cooling does not prevent the condenser solvent from reaching the core sample.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 29
6. Continue the extraction until the solvent is clear.
7. Read the volume of collected water in the graduated tube. Turn off the heater and cooling water
and place the sample into the oven (from 105°C to 120°C), until the sample weight does not
change. The dried sample should be stored in a desiccater.
8. Obtain the weight of the thimble and the dry core.
9. Calculate the loss in weight Wl , of the core sample due to the removal of oil and water.
10. Measure the density of a separate sample of the oil.
11. Calculate the oil, water and gas saturations after the pore volume Vp of the sample is
determined.
Table 2: Data sheet for Dean Stark experiment
Worg
gr
Wdry
gr wρ
gr/cc
oρ
gr/cc
Vw
cc
Wo
gr
Vo
cc
Vp
cc So Sw Sg
Worg = Weight of original saturated sample
Wdry = Weight of desaturated and dry sample
2-2 Retort Oven The retort oven is used to determine the porosity and total saturation of water (Sw) as well as the
residual saturation of oil (Sro) in the fresh or preserved core samples (Fig. 17). Note that the saturations
which are determined in a laboratory are generally different from the field saturations. These
differences come from:
• Invasion of drilling mud, or of mud filtrate
• Expansion of gas due to pressure drop during upraise of core to surface
• To some errors of manipulations, as core sample washing with water or drying without cares
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 30
Figure 17: A retort oven device
Machine Description The retort oven is composed of following items:
• Insulated oven with heat control with a maximum operating temperature of 700 °C.
• 12 traps and stainless steel screens
• stainless steel tank for condensed water
The procedure of the test is as follow:
• Install water supply to each end of bath which has a baffle in centre, ie each end independent of
other end.
• Set required temperature using UP and DOWN arrows buttons only.
• Heat the chamber (cover closed) to 540-650 °C (1000–1200 °F). When retort cups are placed in
the heated enclosure, the temperature will fall down about 400 °C, and then will go up again.
• The fresh sample is roughly crushed, weight = 125 grams, and placed in the retort cup.
• Volume of the crushed sample = VT with VT = Weight / Natural density
Note : measurement must be realized on an another piece of core whatever is its form, about 30
cm3, weighed with its fluids, water, oil, gas and with total volume will have been determined
with a volumetric pump.
• Place all the retort cups (12 max) in the retort, even there is no sample to analyze in each of
them and close the retort which is under voltage. The receiving graduated 20 cc tubes clean are
in place.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 31
• Read the volume of water “INI.W” collected after “T” minutes. This time “T” corresponds
exclusively to the water contained into the pores of the sample and not to the water contained
into the clays. It is determined in pointing out according to the time (or to the temperature) the
volume of water collected into the receiving tubes. It is the value of the time which corresponds
with the middle of the plateau, or of the inflection point (in case of clayey samples).
• Read the volume of water “FINAL W” collected when temperature reaches 650 °C.
• Read the volume of oil “OBS.O” collected when the temperature reaches 650 °C. This quantity
of oil collected is by default because oil is lost by cracking during heating, from which a
calibration is needed.
Calibration In sands samples contained in retort cups, one places growing known quantities of oil from Occ to
10cc. Using normally the retort oven, one notes the “OBS.O” volumes. Then plot working curves of
correction: see correction table (for example a retort oven and crude oil 45° API)
Table 3: calibration table
Reading observed,
“OBS.O” cc
Reading corrected,
“CORR.O” cc
0
traces
0.05
0.1
0.2
1.0
0
0.1
0.15
0.25
0.35
1.40
For reading higher then 1.0 cc, add 0.4 to determine the corrected volume. Correction of the volume of
oil collected. Use the precedent table. It is determined “CORR.O”.
Calculation Amount of oil in the sample:
. 100CORR OObVT
= ×
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 32
Amount of water in the sample:
. 100INIT WWbVT
= ×
Amount of gas contained in the sample Gb is determined by volumetric mercury pump.
Porosity : Ob Wb Gbφ = + +
Total saturation of water : 100TWWbSφ
=
Residual saturation of oil :
100ROObSφ
=
2-3 Core Saturator Prior to perform any core flood experiment, we need a saturated rock sample. Automatic saturator is
a device used to prepare samples for such experiments. The automatic saturator is used to inject water
or brine into the sample.
Machine Description This machine can either work on automatic mode and semi-automatic mode. Although standard
parameters fulfil most of applications, the operator can easily change the duration steps of the
automated mode. Furthermore, it is possible to shift to semi-auto or manual mode for any specific
process. In the semi automated mode the operator controls the Electro-Valves, as in the manual mode
where the operator work with the manual valves. In semi-auto and manual mode the steps duration and
valve sequence is custom. For very low permeability samples, you can increase the "additional sample
evacuation" step to evacuate the samples longer than the saturant (and avoid vaporization and salt
concentration change or precipitation). This system is composed of the following items as shown in
Fig. 18 and its main feature is summarized in Table 4.
• A console with injection pump, valves and PLC (Programmable Logical Controller)
• 2 jars (one saturant TANK, one vacuum TRAP)
• A pressure vessel
• A vacuum pump
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 33
Figure 18: Main components of the automatic saturator
Table 4: Main features of automatic saturator
psi 2000 Maximum saturating pressure
mm 58 Cell diameter
mm300 Cell height
VAC, 50 Hz 220 Power supply
To achieve a good quality saturation on a low permeability sample, thoroughly evacuation (sample and
test brine) is followed by saturation at pressure controlled via a turn-key unattended program.
Experiment operation: To do the experiment, some pre-steps to prepare the system are necessary before using either
automatic, semi-auto or manual modes. These are four main steps to prepare the system:
i)Setting the target pressure. For setting the target pressure you can use the knob on the pressure gauge.
You can change the set point by rotating the knob to move the red tip needle to the requested value.
(Fig. 19)
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 34
Figure 19: Setting the target pressure
ii)Setting the pump. The pump panel is located at the right low corner of the console (Fig. 20left).
Screw the knob to reduce the flow rate. The setting must be at least higher than 30% of the range (Fig.
20right). Before starting an automatic process, switch “On” the pump. If you plan to run a semi-
automatic mode or manual mode, you will switch on the pump on request.
Figure 20: Illustration of: (left) setting the pump and (right) pump flow rate
iii)Sample loading. Discharge the pressure in the unit by setting the manual valves MV3 to by-pass and
MV2 to vent. Disconnect the tubing from the lid. Then open the cell by unscrewing the lid. After you
are checking the sample identification, install the sample with the tray into saturator cell. Eeventually
complete the volume with some plain plugs in order to reduce the volume of brine to inject (Fig. 21).
Figure 21: Illustration of sample loading
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 35
Check the lid seal. Screw the lid to the pressure vessel. Connect back the tubing. Install the tray with
samples into the saturator cell. Check the lid seal. Figure 22 shows a home-made hook to lift the tray.
Figure 22: Illustration of hooking to lift the tray
iv)Jars preparation. Poor the saturant (brine) into the tank jar (2 ports model). Let enough free space for
bubbling during degassing. Empty the water trapped in the jar (1 port) connected to the vacuum pump.
Close the two jars. (Fig. 23)
Figure 23: Illustration of jar preparation step
1-Automatic mode
• Switch the selector in horizontal position to Automatic option. The green bulb is lightening.
• Press on the button START, the green bulb "IN PROGRESS" is lightening.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 36
• There are six steps (sample and saturant evacuation, sample additional saturation, saturant to atm
pressure, by-pass opens, pump priming, saturation under pressure) that are processed automatically.
• Once the cycle is completed, the green bulb "COMPLETE" is lightening.
• You can abort the cycle at any time by pressing on the STOP button. Check the pressure and the
pumps status.
Figure 24 shows the switch time table with default time span. The global duration is about 3 1/2 hour.
The long durations are respectively T6 (saturation under pressure), T2 (additional saturation), T1
(sample and saturant evacuation) and for 2, 1½ and 1 hours. Others durations are similar to a
commutation time. Note that any of these durations can be modified. The sample and saturant
evacuation step start simultaneously with T2 but as soon as T2 is elapsed, the saturant is isolated while
the sample goes on to be evacuated until T1 is elapsed. This allows evacuating the saturant for a shorter
time T2 than the sample evacuated during T1 and to prevent from potential saturant evaporation (in
case of brine etc). Make sure that no manual valve is set open during semi-auto process.
Stop
End
of S
tep
# 1
End
of S
tep
# 2
End
of S
tep
# 3
End
of S
tep
# 4
End
of S
tep
# 5
End
of S
tep
# 6
Start
Sam
ple
and
Satu
rant
evac
uatio
n
CompletedIn progress
Sam
ple
addi
tiona
lev
acua
tion
Satu
rant
to a
tm. p
ress
.
By-
pass
ope
n
Pum
p Pr
imin
g
Satu
ratio
n @
pre
ssur
e
ONEV4 EV4ONEV5 EV5
ONEV6 EV6ONEV7 EV7
ONEV8 EV8Pump run Pump
T5 : 1'T4 : 2'T3 : 1' T6 : 120 '
afterabout3 1/2 h
T2 : 60 '
T1 : 90 '
Figure 24: The time duration of six steps used in the automatic mode
Step1: Samples and brine evacuation with T2 = 60 min (note that T1 starts simultaneously)
• The valves EV4 and EV5 are open to the vacuum pump during T2 (not T1)
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 37
• Check that the vacuum pump is running and bubbles appear immediately in the saturant jar (as for
boiling water). If no bubble comes after the first minute elapsed, stop the process and fix the leak.
• Check that no saturant (brine) is going out from the trap jar to the vacuum pump.
Step 2: Relieving vacuum in the brine jar with T1 = 90 min, ends 30 min after T2
• The valve EV5 is closed to isolate saturant brine jar from the vacuum pump. T2 (1 minute default
value) is devoted to these operations (see Fig. 25 for the steps 1 & 2)
Vacuum
Vent
85
6
7
4
By-Pass
Pump(stopped)
Vacuum
Vent
85(open)
6
7(closed)
4
By-Pass
Step#1 Sample & Saturant evacuation T2=60 min Step#2 Sample additional evacuation T1-T2=30 minT1=90min starts at same time as T2
Figure 25: Illustration of the schematic connections used in the steps 1 and 2
Step 3: Saturant to atmosphere pressure with T3 = 1 min
• The valve EV8 is open: the vacuum is relieved in the desaturant jar. The brine pressure builds up to
atmospheric but stay degassed.
• You can stop the vacuum pump.
step 4: By-pass opens with T4 = 2 min
• The by-pass EV6 is open, thus the saturant invades the sample vessel under push-pull action of
atmospheric pressure at valve EV8 and vacuum at valve EV4 (see Fig. 26 for the steps 3 & 4)
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 38
Vacuum
Vent
85
6
7
4
By-Pass
Vacuum
Vent
85
6
7
4
By-Pass
Step# 3 Saturant to atm. pressure T3 = 1 min Step#4 By-pass open T4 = 2 min Figure 26: Illustration of the schematic connections used in the steps 3 and 4
Step5: Pump priming with T5 = 1 min
• Ev7 is open to feed the pump with the saturant
• The pump starts and is primed.
Vacuum
Vent
85
6
7
4
By-Pass
Pump run
Vacuum
Vent
85
6
7
4
By-Pass
Step#6 Saturation @ pressure T6 = 120 minStep#5 Pump priming T5 = 1 min Figure 27: Illustration of the schematic connections used in the steps 5 and 6
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 39
Step6: Pressuring the sample vessel with T6 = 120 min.
• Ev6 is closed. The saturant path is through the pump only.
• The injection pump hold on (stops temporarily) as the pressure set point ("target") is reached.
If the pressure decreases before T6 is elapsed, the pump restarts to build-up the pressure up back to the
target value. This ensures the saturation of low permeability samples (see Fig. 27 for the steps 5 & 6)
2-semi automatic mode
Semi auto mode is a custom process where operator uses the appropriate switches, as in manual mode.
For this switch the selector to Manual. To operate the electro-valves: press once the button of a valve,
the green bulb switches lightening as the valves open. Press once again to close the valve. (Fig. 28)
Figure 28: button of valves panel from which the operating mode can be changed
Note that you run a single mode at once (e.g. semi-auto, automatic or manual). Also when an automatic
mode is running, just press the STOP button before starting a manual mode.
3-Manual mode
Manual mode is a custom process where operator adjusts the EV valves manually. Make sure that no
electro-valve is set open during manual process. Switch the selector to Manual. You can open as many
valves as you want at the same time and run any step of yours as long as required. Figure 29 shows the
various status of tank.
The valves and pump sequence to reproduce the automatic process in the manual mode is as follow:
• Check that the vacuum pump is running and bubbles appear immediately in the saturant jar (as if
the water was boiling). If no bubble comes within the first minute, stop the process and fix the leak.
• Check that no desaturant (brine) is going out from the trap jar to the vacuum pump.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 40
Figure 29: Illustration of tank status by setting it to: the vent, the vacuum pump, be isolated
There are 7 steps with various the ellipse(s), point(s) and the valve(s) actions. You can set custom
duration for each step. The default duration is summarized in Table 5:
Table 5: A summery of the default durations for 7 steps
Step Duration
(min)
Process
1 30 Global evacuation,
2 60 Sample additional evacuation
3 1 Relieving vacuum in saturant tank
4 2 By-pass open
5 1 Pump priming
6 120 Sample saturation at pressure
7 ∝ Release vessel pressure
These are the description of various steps. Also Fig. 30 show the connections at each step.
step 1: set V2 to the vacuum (global evacuation).
step 2: set V2 to the close and set V1 to the vacuum (sample additional evacuation).
step 3: set V3 to the vent (relieving vacuum in saturant tank)
step 4: set V3 to the By-pass (by-pass open)
step 5: set V3 to the pump (pump priming)
step 6: stop the vacuum pump and set V1 to the close (pump brine into core vessel for 120 min)
step 7: Finally, cycle is completed.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 41
Manual Step 2:Sample Evacuation
Manual Step 1:Global Evacuation
Vent 2 1
3
Vent2 1
3
Vacuum
Closed
Closed
Stop
Vacuum Vacuum
(Action )
Vent 2 1
3
Manual Step 3: Relievingvacuum in the brine tank
Vent 2 1
3
Manual Step 4:By-pass open
Vent
Vacuum Vacuum
By-pass
Pump
Manual Step 5:Pump priming
Vacuum
Vent2 1
3Run
Vent2 1
3
Manual Step 6:Sample saturation @pressure
Vacuum
Vent2 1
3
Manual Step 7:Release the vessel pressure
By-passStop
Vacuum
Figure 30: Illustration of the schematic connections used in the steps 1-7
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 42
3-Porosity From the viewpoint of petroleum engineers one of the most important property of a reservoir rock is
porosity. Porosity is a measure of storage capacity of a reservoir. It is defined as the ratio of the pore
volume to bulk volume, and it may be expressed as either a percent or a fraction,
In the static method the plate is held at the position shown in Fig. 47b and the equation will be
( ) θσ cos2 yxbWF P ++−=
Where b is buoyancy force of immersed part of the plate in the liquid and θ is contact angle.
This instrument can be calibrated such that the interfacial tension reads directly.
3-Ring Method The ring (or Nouy) method of measuring surface and interfacial tension is commonly used and the
apparatus is called a ring tensiometer. To measure interfacial tension, a platinum ring is placed in the
test liquid. The force necessary to withdraw it front the liquid is determined (Fig. 48).
Figure 48: Ring method
When the ring is completely wetted by the liquid (θ = 0), this equation is obtained from
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 63
)2(2 σπrbWF r +−=
where F is measured force, r is radius of the ring at centre (the radius of the platinum thread is
negligible compared to r), Wr is weight of the ring in air and b is buoyancy force of the ring immersed
in the liquid. For interfacial measurements, the ring is placed in the interface and the force necessary to
break the interfacial film with the ring is determined.
The instrument can be regulated in such a way that the ring weight and buoyancy effect are taken care
of with a correction factor C given by,
)2(2 rFCπ
σ =
4-Drop Weight Method The drop weight method of measuring the interfacial tension of liquid with respect to air consists in
determining the number of drops falling from a capillary. The drops are allowed to fall into a container
until enough have been collected so that the weight per drop can be determined accurately. The
principle of the method is that the size of the drop falling from a capillary tube depends on the surface
tension of the liquid (Fig. 49).
Figure 49: Drop weight method
The maximum amount of liquid W, which can hang from a capillary tube with radius r without falling
depends on the surface tension as
σπrmgW 2==
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 64
where m is the mass per drop. Observations of falling drops show that a considerable portion of the
drop (up to 40%) may remain attached to the capillary end. This effect will be compensated with a
correction factor f.
rmgfπ
σ2
=
The correction factor f varies in the region of 0.5 to 1.0. The drop method can be used for the
determination of both gas-liquid and Iiquid-liquid interfacial tensions.
5-Pendant Drop Method Small drops will tend to be spherical because surface forces depend on area. In principle, one can
determine the interface tension from measurements of the shape of the drop. In the case of the pendant
drop, the most convenient and measurable shape dependent quantity is es ddS = indicated in Fig. 50,
de is the equatorial diameter and ds is the diameter measured distance de, from the bottom of the chop.
The interfacial tension can be calculated by the following equation,
Hgd e
2ρσ =
where H is a shape determining variable. The relationship between the shape dependent quantity H and
the experimentally measured shape dependent quantity S is determined empirically. A set of 1/H versus
S values is obtained in form of tables (Table 9). The quantity of S is calculated after measuring de and
ds from shape of the pendant drop, and then 1/H can be determined from Table 9.
Figure 50: Relationship between dimensions of a pendant drop
The pendant drop method is widely used and has good accuracy.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 65
Table 9: Values of 1/H versus S
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 66
6-Spinning Drop
In this method, a drop of a less dense fluid is injected into a container of the denser fluid, and the whole
system is rotated as shown in Fig. 51. In the resulting centrifugal field, the drop elongates along the
axis of rotation. The interfacial tension opposes the elongation because of the increase in area and a
configuration which minimizes system free energy is reached. The method is similar to that for the
pendant drop with the gravitational acceleration g replaced by the appropriate acceleration term for a
centrifugal field.
If the fluid densities are aρ and bρ , and the angular velocity ω of rotation are known, then interfacial
tension can be calculated from the measured drop profile. When drop length is much greater than the
radius rm the following approximate expression holds
4)( 32
mBA rωρρσ
−=
Figure 51: Schematic diagram of spinning drop
The spinning drop device has been widely used in recent years to measure very low interfacial tensions.
Unlike the other methods, no contact between the fluid interface and a solid surface is required.
5-1 IFT 700 instrument The IFT 700 provides the determination of the interfacial tension, contact angle and also the
observation of heat and mass transfer phenomena. The experiment can be conducted at high pressure
(up to 69 MPa, 10000 psi) and high temperature (up to 180°C).
The flow sheet of this machine is illustrated in Fig. 52. The IFT 700LL includes basically:
• Two pressure generators (PG1 and PG2)
• Temperature indicator (TI)
• Pressure indicator (PI)
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 67
• Rupture disc and support (RD); the (safety) burst pressure is given on the plate attached to the
support. Actual burst pressure may vary by ± 5%.
• Two supply tanks for liquid (TL1, TL2).
• Capillary tubes (CT): dosage of liquid for pendant drop, type “CT-A” and another one for
standing bubble/drop, type “CT-B”, outer diameter 1/16” (1.59 mm), inner diameter 0.8 mm.
• Video system: 1 CCD camera
Figure 52: Flow sheet of IFT 700 machine
Gas-liquid systems: For generating liquid drops in gas atmosphere, the view chamber needs to be filled with the desired gas
up to the designated pressure. Therefore, the gas supply needs to be connected to valve G.
• shut all valves.
• open all suitable valves of the gas supply line (not belonging to the IFT 700).
• open G shortly and shut right away (allowing a small amount of gas to enter).
• open D for venting the system and displacing the air inside the view chamber (Purging).
• shut valve D.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 68
• open G carefully. Listen for whistling noises indicating escaping gas. In case of leakage,
depressurize respective part of the equipment. Fasten connection. Eventually replace damaged
pieces.
Pressure increase must be taken into account when filling the chamber prior raising the temperature.
You can fill the capillary with liquid before pressurizing the chamber to ensure that no gas is trapped in
the capillary. For this purpose, follow the dedicated instructions for filling liquid (in a separate
chapter), then open valve B while valve C is closed. The pressure generator PG1 is operated clockwise
until liquid appears at the capillary tip inside the chamber. Then close valve B and proceed to fill the
chamber with gas. Note that previous filling of the capillary or liquid being present elsewhere in the
chamber may cause fog when gas enters the view cell.
1-View cell heating A thermocouple measures the temperature inside the wall of the view cell. A second one is installed as
safety probe. In case the first thermocouple fails or breaks, the second one will prevent the system
temperature from rising excessively.
It is recommended to adjust the temperature prior to pressurizing the system.
Adjust temperature stepwise. Allow some time for temperature stabilization and watch the pressure
carefully before setting further temperature increase.
Electrical heating is fast and may overshoot the set temperature. Never exceed specified maximum
operating temperature.
Be careful when touching surfaces around the view cell: it might be very hot.
2-Filling the capillary with liquid Prior to metering liquid, and generate droplets into the view chamber, the tubing needs to be filled with
the test liquid. Proceed as follow:
• displace the lid of the liquid supply tank (TL1).
• shut the valve B.
• open the valve A (liquid inlet valve) carefully. Be aware of pressure remaining in the system!
• operate the pressure generator (PG1) clockwise to drive the piston into the chamber, until
reaching the end of stroke IN.
• fill the supply tank (TL1) with the test liquid and wait for bubbles to rise.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 69
• operate pressure generator PG1 anti-clockwise to withdraw the piston until reaching the end of
stroke OUT. This load the cylinder with the test liquid.
• operate pressure generator clockwise until no bubbles rise anymore at the liquid supply tank.
• Eventually drive the piston IN and OUT until the tubing is completely filled with liquid and no
gas remains trapped. Finally, withdraw the piston to the end of stroke OUT to get the cylinder
completely filled with liquid.
• shut the valve A
• open the valve C
• operate the pressure generator clockwise until the liquid is discharged through valve C. Collect
the liquid with a small glass beaker or similar.
• shut valve C.
3-Generating a Pendant Drop Allow some time for pressure and temperature stabilization.
• Operate PG1 clockwise until the pressure reading at PI1 raises up to the pressure in the view
cell read at PI2.
• Open carefully B while watching simultaneously both pressure gauges.
(If the pressure PI2 clearly drops while opening B, this means that some gas has entered the
liquid capillary tubing.)
• Operate clockwise the pressure generator PG1 until the first liquid droplet appears at the
capillary outlet.
• Once the suitable droplet is generated, close the valve B during video recording.
Liquid-liquid systems: For measuring either liquid-liquid interfacial tension by the pendant-drop method or for measuring gas-
liquid interfacial tension by the standing-bubble method, the chamber must be filled with a second
liquid in the following named “liquid C”. The liquid forming the drop is called “liquid D”. Fill the view
chamber with liquid according to the following instruction:
• Shut all valves.
• Fill the tank TL2 with liquid C: open the valve E and operate the pressure generator PG2 anti-
clockwise until the piston reaches the end of stroke OUT.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 70
• Operate the pressure generator clockwise until no bubble rises anymore in the liquid supply
tank.
• Eventually drive the piston IN and OUT until the tubing is completely filled with liquid and no
gas remains trapped. Finally, withdraw the piston to the end of stroke OUT to get the cylinder
completely filled with liquid.
• Close the valve E.
• Open the valves F and D.
• Hold a container (glass beaker) at the outlet of the valve D.
• Operate PG2 clockwise to inject the liquid C into the view chamber until producing at valve D
outlet.
• Go on to operate PG2 clockwise, and follow liquid level in the view chamber.
• Watch for leakages inside the support.
• Close the valve D.
• Go on to operate the pressure generator PG2 clockwise until reaching the required pressure
controlled at the pressure indicator.
Note: If PG2 is easy going and no change in pressure is recorded; air may be trapped. Open the
valve D shortly for venting and restart at f.
If PG2 is increasingly hard-going but no change in pressure is recorded, look for closed valves,
or disconnected pressure indicators.
Evaluation of drop shapes pendant/sessile drop Run the program PAT by selecting “Main_PAT1-11-04_D.exe” or from the desktop shortcut to
“C/programs/PAT_exe”. The “Start- Window” appears.
The PAT software features some options especially for automatic drop generation that do not apply for
the high pressure equipment IFT-E700.
From the start window, general options can be set. For experiments using the high pressure equipment
all symbols “Check Opt.” and “Ctrl Options” should be deactivated (crossed out). This can be done
directly by clicking the mouse or by pressing the “Check/Ctrl” icon depending on the version released.
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 71
Figure 53: Start window
Select the pendant drop mode in the Start-Window when working with captured bubbles. The
“Camera” window can be selected in "portrait" or "landscape" orientation. The drop icon “Exper.”
allows for selection pendant/sessile drop or standing bubble (see Fig. 53).
The “CALIB.” icon opens the “Device Parameters” window for checking calibration of the complete
camera system. This calibration is checked automatically when starting a measurement from the main
window. Notice that the aspect ratio should be closed to 1.
Figure 54: Camera calibration
In the usual case the user carries out calibration by using the capillary (nozzle) diameter. For this
purpose, press the “PRGM” icon, choose “New/Edit” and select nozzle. Now, close the “Device
Parameters” window by clicking on “OK” and return to the start window. The position of the capillary
(nozzle) for calibrating is selected in the window opened by choosing the “FOCUS” icon.
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 72
A new window called “Focus &Light” opens containing a life image of the actual drop at the capillary
tip. This window should be checked frequently for right adjustment of light, focus and nozzle
calibration. The graph “light intensity” shows the gray values of the image ranging between 0 and 255.
The focusing marker must be positioned at the drop surface. Then, the graph shows the transition from
outside (high value=light) to inside the drop (low value = dark). By adjusting the values given in the
boxes called “white” and “black” the graph must be adjusted in order to show values of 200 – 250
outside the drop (white) and 0 – 50 inside the drop once the adjustments are completed, press “OK” to
return to the start window.
Figure 55: Illustration of the calibration method
Now, you can press the “START” button to display the main measurement window.
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 73
Figure 56: Main measurement window
Measurement window and determination procedure Before starting the measurement, the experimental parameters need to be set. This includes drop phase
(internal phase) and external phase densities, the measurement procedure and the calibration
parameters. For this purpose, select “PRGM” to open the following window:
Figure 57: Profile analysis system window
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 74
Click the “New or Edit” icon to open the “Time Line” window:
Figure 58: Time line window
The time program must be set. For example T = 0.00 sec …. dT=1.0, which means that starting at 0
seconds a measurement is carried out every second. With the high pressure equipment “CONTROL
Vol/Area” is not applicable. The “CALIBR.” cursor must be switched toward “NOZ.”
(nozzle/capillary).
Settings can be saved or loaded as ~.prg files. By choosing “Done” you can return to the parameter
window. After having chosen a file name to save the image data (~.prf), the parameter window is
closed and the main window appears once you click “OK”. Now, you can start the measurement by
selecting “START”. The calibration data is used during the interfacial tension determination. (Fig. 58)
The diagrams in the lower part of this window show the interfacial tension (as a rough estimate) and
the drop area in real time. These data are given for information only and are not saved.
A small picture at the right side of the life drop image named “Drop Dim.” Indicates whether the drop
has a suitable dimension (green) or is too small (red) for determination of the interfacial tension.
The symbol below named “Ctrl Loop” is not applicable with the high pressure equipment and should
be switched off.
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 75
Figure 59: Illustration of determination procedure
The data acquisition in the “Main Measurement” window is stopped by pressing the “ABORT” button.
Afterwards, press “EXIT”. In case “Fitting Auto-Start” was switched on in the “Experimental
Parameter” window, the fitting procedure starts automatically. Otherwise, press “FITTING” in the
start window.
Press “LOAD” in the appearing “Fitting” window and select the ~.prf file containing the data of an
experiment performed earlier. All the available measurement points are computed to match the Laplace
equation, and then to determine the interfacial tension as a function of time. Data of the interfacial
tension, the drop volume and area etc. are saved in a ~.fit file to the hard disk. This file can be imported
to an excel sheet.
However, students should consider the following safty notices:
• Operation and maintenance may only be carried out after all necessary steps have been taken to
ensure the safety of people and equipment.
• Make sure that samples involved (liquids, gases, fluids and solids) do not interact with parts of
the equipment to which they are in contact.
• Aggressive organic solvents, e.g. aromatic substances can lead to a leakage in the view cell.
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 76
• Handling highly volatile or toxic liquids requires suitable ventilation.
• Working at high pressure requires wearing safety glasses.
Calculation and Report: Use the notations given in Fig. 60 along with the following equations to fill Table 10.
HgDe
2ρσ
Λ= where g=981 cm/s2, and De (real size of de) = de (1.1/ d IMG), mm
Figure 60: pendant drop imaging picture
Table 10: Data sheet for IFT 700 experiment
1ρ 2ρ ρ∆ Image Picture Sizes Sample de
( mm)
ds
( mm) dIMG
( mm)
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 77
6-Capillary pressure The coexistence of two or more immiscible fluids within the voids of a porous medium, such as a
reservoir rock, gives rise to capillary forces. As interfacial tension exists on the boundary between two
immiscible fluids in a pore space, the interface is curved and there is a pressure difference across the
interface. The pressure difference is termed the capillary pressure and can be expressed as:
PC = Po - Pw
where:
Po is the oil pressure (non-wetting phase)
Pw is the brine pressure (wetting phase)
Capillary pressure as a function of surface tension and radii of curvature r (for spherical cap) is,
( ) 2 coswoc w oP gh
rσ θ
ρ ρ= − =
Note that the free water level, FWL is the point where Pc=0. Oil-water contact OWC above FWL has
Sw=100% due to the capillary action. The zone of varying water saturation with height above OWC is
called the transition zone (Fig. 61).
Figure 61: Illustration of saturation distribution above OWC
The size of the transition zone depends on pore size distribution (PSD), grain sorting, interfacial
tension, rock characteristics (porosity/permeability) and also difference in fluid density. The saturation
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 78
history of the rock can also affect the capillary pressure. Two processes usually considered are
drainage which is the replacement of the wetting phase (e.g. water) with non wet phase (saturation of
wet phase decreases). In this case, the saturation level is dictated by the capillary pressure associated
with the narrow pores and it is able to maintain water saturation in the large pore below. The second is
imbibition where wetting phase saturation increases by the expulsion of the non wet phase. The level
of saturation is determined by the large pore reducing the capillary pressure effect and preventing
water entering the larger pore. Figure 62 shows different process of this kind in a water wet system
where A, B, C shows respectively the primary, negative secondary and positive secondary drainage and
D and E shows positive and negative imbibition respectively.
Figure 62: Typical capillary pressures for in various stages of drainage and imbibition processes
Capillary pressure measurements are essential for the complete characterization of a hydrocarbon
reservoir. A plot of capillary pressure versus fluid saturation for a core plug can be used:
• to calculate reserves
• in reservoir simulation computer routines
• provides data on the irreducible water saturation of a reservoir rock
• shows the entry pressure of fluid into a water saturated reservoir or cap rock.
6-1 CAPRI instrument The The CAPRI system is dedicated to the determination of the capillary pressure curves (positive
and negative) and the electrical resistivity index as a function of core sample saturation at reservoir
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 79
conditions. Knowledge of the water-oil capillary pressure and resistivity index vs. saturation
relationship is necessary for many reservoir-engineering tasks:
(1) assess connate water saturation to calculate oil in place;
(2) calibrate resistivity logs;
(3) determine the height of the transition zone;
(4) model oil displacement either by free water imbibition and /or water injection.
The equipment measures the resistivity of core plugs at different brine saturations by a precise
resistivity meter having 4 electrode measurement system. The core plug is placed in a core holder
subjected to confining pressure and pore pressure equivalent to reservoir conditions. Temperature of
the core plug is raised to the reservoir condition. The brine saturation is changed from 100 % to lower
values by gradually increasing the pressure of an upstream metering pump which injects oil into the
core plug and displace the brine. The volume of the displaced brine is accurately determined by a
downstream metering pump which accumulates the displaced brine at a constant pressure. Both the
pumps are attached to the core holder through semi porous membrane saturated with respective fluid.
The resistivity of the pure brine used for the saturation of the core plug is determined with the help of a
Rw cell subjected to the reservoir pressure and temperature condition. The resistivity measurement of
a core plug at 100% brine allows for the evaluation of the Formation Factor (FF) whereas the
resistivity of a core sample at different saturations allows for the determination of the Resistivity Index
(RI) at simulated reservoir pressure and temperature conditions. The equipment has also the provision
for estimation of Resistivity of brine (Rw) at simulated reservoir temperature and pressure condition.
The user can run tests either in manual mode or in sequenced mode. In automatic mode, the operator
fills a table of pressure increments. Test data is graphically displayed on the screen and is logged on the
hard disk as a table file. Printouts of the input and test data are done using a printer.
Machine Description Sample Diameter 1” or 1” ½ or 30 mm (according to customer’s selection)
Sample Length from 2" to 3"
Sample: Square edge, Parallel faces and consolidated
Pressure:
Overburden: up to 10,000 psi
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 80
Pore: up to 9,000 psi
Capillary pressure: up to 150 psi
Ceramic pressure breakthrough: 150 psi
Temperature: ambient up to 150°C
A schematic connection diagram is shown in Fig. 63.
Figure 63: A schematic connection diagram of CAPRI instrument
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 81
Experiment operation: During the test, the temperature of the core plug is raised to the reservoir condition. The brine
saturation is changed from 100 % to lower values by gradually increasing the pressure of an upstream
metering pump which injects oil into the core plug and displaces the brine. The volume of the displaced
brine is accurately determined by a downstream metering pump which accumulates the displaced brine
at a constant pressure. Both the pumps are attached to the core holder through semi porous membrane
saturated with respective fluid. For this the following is done.
After setting up the core holder, the first step is to fill the pumps. This can be done through the panel
available in the software. Note that the pumps should be calibrated so that the volumes shown on the
panel is the true one. At the next step it is time to give the core holder some confining pressure. An
starting pressure on 500 psi should be sufficient. It is highly recommended that before any process the
air probably contained within the core holder and the pumps are removed. This should be done for the
three pressures. The two filled pumps then should be started one at each time with almost the same
pressure in order to make sure the core is intimately saturated with the fluids. The pressure of oil pump
is a little less then the brine pressure so that no flow into core occurs.
When all the steps are performed correctly it is time to start the test. The brine pump is always on and
the run mode is pressure. In this case the brine pressure is set to some value. The set mode on oil pump
is delta pressure and the test begins by setting a small delta pressure. It is good to check to see if the
delta pressure shown by the software is calculated correctly. The first steps of changing the delta
pressure should be done by care cause it might affect the accuracy of the result curve. The steps are
changed if the resistivity has become constant or if the displaced volumes of oil and brine pumps are
showing the same value. At the end of the experiment decrease the pore pressure by setting the water
pump in constant pressure with 15 psi set value with a pressure ramp of -50 psi/min and the oil pump in
constant delta pressure at zero psi set value. As the pore pressure decreases, the confining pressure by
opening slowly the isolating confining valve. Keep a difference of 300 psi between the confining
pressure and the pore pressure and decrease the temperature to room condition.
The process body is schematically composed of 5 stages. The end of a step is determined from
stabilisation of electrical measurement and volume in the pumps. Water pump is pressure controlled at
pore pressure set point. Oil pump is DeltaP controlled at capillary pressure.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 82
1. Starting from a sample 100% saturated with brine, Primary drainage is applied by increasing
DeltaP in small steps. DeltaP is going positive. The maximum final DP can be 150 psi. Practically,
the drainage is completed when no more water production happens for an increase in DeltaP. Each
step can need from a few hours up to several days to reach equilibrium. When reaching equilibrium,
DP and pumps volume are recorded. From the reading of the pumps volume, the balance with the
sample content ("saturation" in oil and water) is determined. The DeltaP is the capillary pressure. A
graph can be plot of DeltaP vs water saturation.
2. Spontaneous imbibition is then conducted by reducing DeltaP in small steps, down to DeltaP
equal zero. There is an hysterisis, and the curve of DeltaP vs water saturation is different from the
curve obtained before. The saturation curve does not cross the pressure axis at for 100% water.
3. Going further, we run the Forced imbibition by reducing DeltaP in small steps, getting negative
values of DeltaP. The maximum final DeltaP can be -150 psi (theoretical value). Practically, the
imbibition is completed when no more water enters the sample for a change in DeltaP.
4. In the next step, we increase DeltaP by steps during Spontaneous drainage, until DeltaP is back
again to zero. There is an hysterisis, and the curve of DeltaP vs water saturation is different from
the curve obtained at previous stage.
5. Going on to increase DeltaP in positive value, we run the Secondary drainage. DeltaP is build up to
the previous maximum value during Primary drainage.
The process schematic to get whole pc curve is shown in Fig. 64.
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 83
Figure 64: Schematic illustration of various stages of the process of getting whole pc curve
Calculations and Report: The type of summarized information along with the formation factor results obtained from CAPRI is
shown in Fig. 65. Note: the core holder factor refers to the sample size 1" ½; with electrodes spaced
by 25.4mm (2 / 4
25.4 1000dm π
=× ). In red are the experimental data, in black are the calculated values.
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 84
Figure 65: Summarized report of the formation factor results obtained from CAPRI
The type of report of Pc, Ir and n with core partially or totally desaturated is shown in Fig. 66.
Figure 66: A typical summarized report of Pc, Ir and n of a core partially or totally desaturated
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 85
The equation used to calculate the parameters are shown in Fig. 67.
Figure 67: Illustration of equations used to calculate the parameters in CAPRI instrument
Moreover, a typical capillary pressure curve obtained is shown in Fig. 68.
PC curve
-5000
-4000
-3000
-2000
-1000
0
1000
2000
3000
4000
5000
0 10 20 30 40 50 60 70 80 90 100
Brine Saturation (Sw), %PV
Cap
illar
y Pr
essu
re (P
o - P
w),
mba
r
Figure 68: Illustration of a typical capillary pressure curve obtained from CPAR instrument
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 86
7-Permeability Permeability is a property of a porous medium which shows the ability of porous media to
transmit fluids. The reciprocal of permeability represents the viscous resistivity. The effective
permeability of a porous medium is a measure of the rock conductivity to a particular phase of a multi-
phase fluid system residing within the porous medium, where the saturation of each phase is specified.
Relative permeability is the ratio of the effective permeability of a particular fluid phase to some
arbitrary reference permeability (i.e. absolute permeability). Permeability has the unit of m2 in SI
system or Darcy in field unit with a conversion factor of -12 21D 0.986923 10 m≡ × . Note that a rock
sample has a permeability of one meter squared when it permits 1 m3/s of fluid of 1 Pa.s viscosity
through an area of 1 m2 under a pressure gradient of 1 Pa/m. Permeability is calculated using the
following equation:
Where:
k = permeability (Darcy)
q = flow rate (cm3/S)
= viscosity (mPa.s)
x = length (cm)
A = cross sectional area (cm2)
p = differential pressure across flow section (atm).
One of the quick methods to measure permeability is the “transient method”, which is used in KeyPhi
device. Transient measurements employ fixed-volume reservoirs for the gas. These may be located
upstream of the sample from which the gas flows into the sample being measured. The pressure falloff
apparatus (Fig. 69) employs an upstream gas manifold that is attached to a sample holder capable of
applying hydrostatic stresses to a cylindrical plug of diameter D and length L. An upstream gas
reservoir of calibrated volume can be connected to the calibrated manifold volume by means of a valve.
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 87
Figure 69: schematic of pressure-falloff gas Permeameter.
Multiple reservoir volumes are used to accommodate a wide range of permeabilities. The
downstream end of the sample is vented to atmospheric pressure. An accurate pressure transducer is
connected to the manifold immediately upstream of the sample holder. The reservoir, manifold and
sample are filled with gas. After a few seconds for thermal equilibrium, the outlet valve is opened to
initiate the pressure transient. When the upstream pressure has decayed to about 85% of the fill
pressure, data collection is started. Pressures and times are recorded. This technique has a useful
permeability range of 0.001 to 20,000 md.
The use of liquids for permeability measurements eliminates the problem of gas slippage, and at
reasonable and usual flow rates, inertial resistance is generally negligible. Thus, Darcy’s Law can be
used directly to calculate permeability from a single flow rate measurement. However, potential
permeability alteration from interaction of rock constituents and liquids (especially aqueous solutions),
fines movement, and microbial plugging requires special attention. Also, the liquid remaining in a
sample may have to be removed before other measurements can be performed. Because of these
problems, most routine permeability measurements have been made using gases. However, for some
samples, such as those sensitive to drying techniques, liquid permeability measurements are considered
to be the only acceptable alternative. BRP-350 is a device which can be used for absolute and relative
permeability measurement using both gas and liquids. The description of this instrument is given in
section 7.2.
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 88
Klinkenberg effect: Klinkenberg (1941) has reported that there are variations in the permeability determined by using gases
as the flowing fluid compared to those obtained when using liquids. This has the following relation,
L
1
g
m
kk
bP
=
+
where Pm is the mean pressure, kg is the gas permeability and kL is the equivalent liquid permeability.
These variations were considered to be due to slippage, a phenomenon well known with respect to gas
flow in capillary tubes. The phenomenon of gas slippage occurs when the diameter of the capillary
openings approach the mean free path of the gas. Note that the mean free path of a gas is a function of
molecular size and the kinetic energy of the gas. Therefore, permeability of gas depends on factors
which influence the mean free path, such as temperature, pressure and the molecular size of the gas.
Figure 70 is a plot of the permeability of a porous medium as determined at various mean pressures
using three different gases. Note that for each gas a straight line is obtained for the observed
permeability as a function of the reciprocal of the mean pressure of the test. All the lines when
extrapolated to infinite mean pressure (1/Pm = 0) intercept to the same point kL.
Figure 70: Variation in gas permeability with mean pressure and type of gas
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 89
7-1 KeyPhi instrument As described before KEYPHI instrument is able to measure directly the gas permeability as well as
calculating important parameters such as Klinkenberg slip factor "b", Klinkenberg corrected
permeability and Inertial coefficient. The gas permeability determination is based on the unsteady state
method (pressure falloff ). As can be seen in Table 8 the range of permeability measurement is from
0.001 md to more than 20d.
The detail conditionings and the operation procedures are as those described in chapter 3 (porosity).
7-2 Benchtop Relative Permeameter (BRP 350) The Benchtop Relative Permeameter system is designed to perform tests on core plug samples
in order to determine monophasic permeability, liquid/liquid relative permeability and optionally
liquid/gas relative permeability.
The determination of relative permeability allows comparison of the different abilities of fluids to flow
in the presence of each other. In many instances, relative permeability data selected to represent the
subsurface of reservoir fluid behavior have more effect on the ultimate answer than any other
parameter used in reservoir engineering equations.
These tests are performed at ambient temperature with the unsteady-state technique. Confining
and pore pressure can go up to 350 bars (5000 psi) maximum. All wetted components are made of
Stainless Steel 316 for chemical compatibility and corrosion resistance. This system includes a fluid
delivery pump, 2 piston accumulators, a core-holder, a back pressure regulator, a confining pressure
system, a pressure measurement system, and optionally a video tracker and a gas meter. Operation of
the system is controlled through a computer interface. The Applilab software included with the system
is designed to allow for automated data acquisition and pump control. Finally, the Cydar software
enables calculation of relative permeability. Table 15: General properties of BPR 350 instrument.
Working Confining Pressure Up to 5000 psi (option 10000 psi)
Working Pore Pressure Up to 5000 psi (option 10000 psi)
Core Sample Diameter 1’’ (option 1.5’’)
Core Sample Length 1’’ to 3’’
Confining Pump Pressure Up to 10000 psi
Video Tracker burette External Diameter 18.00 mm
Gas Meter Capacity per Revolution 250 cc
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 90
Working Procedure The Applilab software has been developed by the programmers from VINCI in order to control the
process parameters simultaneously from one central unit. The graphical interface of Applilab is shown
below.
Figure 71: The graphical interface of the Applilab software.
Applilab allows to:
Ø Switch on/off the pump (A)
Ø Control the flow rate of the pump (A)
Ø Display the set parameters (pressure, volume,...) during remote control (B)
Ø Show the evolution of process graphically by trends display (C)
Ø Offset the pressure sensors (D)
Ø Log data (E)
Dead Volume Measurement The dead volume should be measured using a specific caliber, by the following procedure:
A
C
D
B
E
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 91
1. Check that the caliber is mounted on the core holder. Saturate the tubing from the oil
accumulator to the core holder with oil. Then inject brine to saturate all the lines until the
burette with brine. Refer to the above picture to open/close the burette valves.
2. Inject oil (drainage) and simultaneously open the top burette valve and close the bottom burette
valve. When only oil is produced in the burette, measure the Volume of water produced. The
first drainage dead volume is equal to this volume minus the caliber void volume, i.e. 0.1 cc.
3. Inject brine (imbibition) and simultaneously close the top burette valve and open the bottom
burette valve. When only brine is produced in the burette, measure the Volume of oil produced.
The first imbibition dead volume is equal to this volume minus the caliber void volume, i.e. 0.1
cc.
4. Repeat the same operations until getting the same volumes (typically after 3 or 4 cycles). Dead
volume measurements for gas-liquid experiments are similar except that gas is injected instead
of brine.
Figure 72: Hydraulic schematic of the assembly with a caliber sample.
Preparation of the Test In order to perform any test using BPR 350, the following steps should be done carefully.
1. Select a suitable core sample Select a homogeneous core with square edges and parallel faces. Make sure that the length is greater
than 24 mm and smaller than 77 mm. (Write down all information about the core, especially the length,
diameter, dry weight and gas permeability. Then saturate the core with brine in case of liquid-liquid
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 92
permeability, or oil in case of gas-liquid permeability. The saturation of the core can be done with a
saturator or with a vacuum bell connected to a vacuum pump. Then write down the wetted weight.)
2. Load the sample in the core-holder
3. Initiate the confining pressure Close the hand pump release valve. Open the confining valve HV06 and close the buffer valve HV08.
Operate the handle to increase the pressure up to around 700 psi. If needed, you can decrease the
pressure by opening the hand pump release valve. Close the confining valve HV06. Wait for stability
and adjust if necessary.
4. Initiate the back pressure Set the nitrogen pressure at your facility to around 250 psi, open back pressure valve HV07 and close
buffer valve HV08. Wait until back pressure reaches roughly 200 psi. If needed, you can decrease the
pressure by opening buffer valve HV08 and opening the hand pump release valve. When the set point
pressure is reached, close back pressure valve HV07 and close buffer valve HV08.
5. Purge the lines Before performing a test, you have to ensure that the inlet and outlet lines are correctly saturated and
that no gas is remaining in these lines. For the following explanations, refer to the below picture
concerning the mentioned numbers.
6. Pressure Control Open process valve HV01, open brine valve HV03 and close oil valve HV02. Start injection pump and
control that outlet pressure increases up to back pressure. Wait until inlet and outlet pressure are
stabilized.
At any time you must control the following relations true:
Back P < Outlet P < Inlet P < Confining P < 5000 psi
In the case Inlet P > Confining P, you can spoil the core by getting invasion of confining oil into the
core sample. Typically, Back P = 200 psi and Confining P = 700 psi.
I. Monophasic Permeability Once the different steps to prepare a test are realized, you can start the monophasic permeability
measurement. Refer to Darcy’s law for permeability calculation. Darcy’s law can be applied under the
following assumptions:
Ø The core plug is 100% saturated with the flowing fluid.
Ø The flowing fluid is incompressible.
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Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 93
Ø The flow is horizontal, steady state and under the laminar regime.
Ø The flow of fluid through the porous medium takes place under viscous regime (i.e. the rate of flow is sufficiently low so that it is directly proportional to the pressure differential or the hydraulic gradient).
Ø The flowing fluid does not react with the porous medium because it may alter the characteristics of the porous medium thereby changing its permeability as flow continues.
Once the system is stabilized you can run brine injections at different flow rates. For each flow rate,
wait stabilization of the ΔP and complete the excel file “Permeability-template” provided with the
Applilab software as in the below picture.
Figure 73: software excel sheet during a monophasic permeability measurement.
On this excel sheet, monophasic permeability is automatically calculated once the data cells are filled.
II. Relative Permeability The gas, oil and water relative permeabilities are normally denoted by Krg, Kro and Krw, respectively.
Relative permeabilities are usually expressed by the ratio of effective permeability to absolute
permeability. Effective permeability is a relative measure of the conductance of the porous medium for
one fluid phase when the medium is saturated with multiple fluid phases. Absolute permeability can be
expressed as monophasic permeability or usually the effective oil permeability at irreducible water
saturation.
The Unsteady State Method for relative permeability is based on the Buckley-Leverett two phases flow
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 94
model. This model can be applied under the following assumptions:
Ø Immiscible and uncompressible fluids
Ø No capillary pressure
Ø No gravity
Ø Unidirectional flow along the core axe. Preparation of the diphasic test
Ø Adjust the camera to the fluid interface. Use the video tracker software to calibrate the volume
and detect the interface.
Ø Turn the ΔP valve HV05 on bypass position. Then offset the ΔP thanks to the Applilab
software. Make sure that the actual Delta P is within the transmitter range (0-500 psi), then turn
the ΔP valve HV05 on measure position.
Ø Start data logging. You can adjust the time interval to your needs.
a) Oil injection (Drainage)
Reset the camera volume thanks to the Applilab software. Run the injection pump at medium flow rate
(example: 0.5 cc/min) and simultaneously open oil valve HV02 and close brine valve HV03. Refer to
the below picture concerning the position of the burette valves. Wait until ΔP and Vw stabilization.
Then complete the excel file “Permeability-template” provided with the Applilab software, especially
the “Drainage” part. From the pump flow rate, ΔP and Vw, the excel file will calculate automatically
the initial water saturation (Swi) and the permeability of oil at Swi, i.e. Ko(Swi).
Figure 74: Drainage configuration.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 95
b) Brine injection (Imbibition)
When the drainage is over, i.e. the ΔP and Vw are stabilized, you can prepare the imbibition. This is the
most important phase of the test. Before injecting brine, check the following points:
Ø Decrease the flow rate of the pump (example: 0.1 cc/min).
Ø Check that historical collect is running.
Ø Reset the camera volume thanks to the Applilab software.
Ø Offset the ΔP (refer to section 3.7).
Then do the following operations simultaneously:
Ø Start the Applilab chronometer
Ø Close oil valve HV02
Ø Open water valve HV03
Ø Close the top burette valve
Ø Open the bottom burette valve
Ø Write down the imbibition start time
Figure 75: Imbibition configuration.
On Applilab trend curves, you can control the evolution of the ΔP and oil production. The typical shape
of these curves is shown in the below picture.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 96
Figure 76: Typical curves for Delta P and Oil Production.
Stabilization usually occurs after 5 pore volume injections. Now, we can proceed to the treatment of
data to calculate the relative permeability curves using CYDAR software.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 97
8- Other Rock Properties
8-1 Acoustic Velocity System (AVS 700)
The measurement of the speed of sound through a rock yields an index called velocity. This velocity
depends upon both the elastic modulus and density of the rock. If the rock is isotropic, homogeneous
and linearly elastic then there are only two possible types of waves which can travel through the rock:
o a compressional, acoustic or sonic wave,
o a shear wave.
Vinci Technologies’ AVS 700 measure both compressional (Vp) and shear wave (Vs) velocities in the
borehole which are used to calculate Young’s modulus and Poisson’s ratio required in hydraulic
fracture design, to detect hydrocarbons and to estimate formation porosity.
Seismic exploration uses both compressional and shear waves to define and map reservoir boundaries,
detect hydrocarbons in place and monitor changes during production (4D-seismic reservoir
management). These technologies have the attractive feature of mapping petrophysical and fluid
variations on the scale of the reservoir. Elastic properties, moduli and velocities are also used to model
reservoir subsidence and assess borehole stability and sanding potential.
AVS 700 uses high frequency signals. To calculate velocities one then divides the sample length (m)
by the travel time (sec) to arrive at a velocity in m/sec. The speed of the P-wave is about twice that of
S-wave. The ramifications of this are that the shear wave arrives amidst reverberations of the earlier P-
wave making its detection more difficult.
AVS 700 uses transducers on both sides of the core. One transducer acts as a source and at the opposite
end, a second acts as a receiver.
Figure 77: General schematic of the AVS parts.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 98
AVS 700 uses three piezoelectric crystals. The crystals generate:
o Compressional wave (P)
o Polarized shear waves (S1 and S2)
The shear waves are orthogonally polarized. A matched set of transducers acts as a receiver array.
Transducers are activated such that five waveforms can be recorded at each pressure point. The five
waveforms are:
1) P wave;
2) S wave (S1 transmits and S1 receives)
3) S wave (S2 transmits and S2 receives)
4) S wave (S1 transmits and S2 receives)
5) S wave (S2 transmits and S1 receives)
If a material is isotropic, then there should be no signal recorded on the cross coupled transmitter /
receiver pairs. Signal is a positive indication of anisotropy. If a material is isotropic, then the signals
recorded on S1 and S2 should be equivalent. A difference between S1 and S2 signals shows the
anisotropy of the sample. If a rock is isotropic and linearly elastic then one can relate the velocities and
moduli through the following relationships:
Where:
VP: Velocity of P wave (in m/s)
VS: Velocity of S wave (in m/s)
ρ: Density (in kg/m3)
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 99
ν: Poison’s ratio
E: Young’s modulus (in Pa)
K: Bulk modulus (in Pa)
μ: Shear modulus (in Pa)
λ: Lame’s constant (in Pa)
K: Compressibility (in Pa−1)
Al: Acoustic impedance (in kg·m−2·s−1)
Operational Parts
1. Core Holder AVS is provided with two core holders one to accommodate plugs of 1’’ diameter and one to
accommodate plugs of 1.5’’ diameter. The core holders are tri-axial and can accommodate cores of 1 to
3’’ length. It is made of stainless steel. Radial pressure, Axial pressure and Pore pressure can be applied
independently. The design of the vessel is so that when Radial and Axial pressures are identical the
core holder is hydrostatic.
The different elements of the vessel are shown on the pictures below. The main features of the device
are as follows:
o Core diameter: 1 & 1.5”
o Core length: 1 to 3”
o Material: stainless steel
o Pore pressure: up to 10,000 psi
o Confining pressure: up to 10,000 psi
o Radial pressure: up to 10,000 psi
The scheme below shows the 1.5’’ core holder.
Figure 78: Different elements of the vessel.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 100
2. Accumulator AVS includes a 100 cc pore fluid accumulator. This accumulator is connected to the hand pump and
permits to apply a pore pressure up to 10,000 psi. The accumulator is located on the rear side of the
panel. The process fluid is on the top side of the accumulator.
The accumulator is isolated on the pump side by the valve V5 and on the process side by the valve V1.
Figure 79: The fluid accumulator.
3. Electrical Connections The connections between the acoustic core holder, the switch box, the impulser and the oscilloscope
are shown below. The Oscilloscope is connected to the impulser via 2 BNC female / female cables. The
impulser is connected to the Switch box via 2 BNC female / female cables. The switch box is
connected to the core holder via 6 SMA male to BNC female cables.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 101
Figure 80: Type of connections between different parts.
Measurement 1. Overburden Set-up
1.1. Building up step by step procedure o Check the connection from the panel ports RADIAL and AXIAL to the core holder.
o Open Valve 3 “RADIAL INLET” and Valve 4 “AXIAL INLET".
o Check the oil level in the manual pump. Refill if necessary with specific oil (refer to specific
manual).
o Check the built-in valve of the manual pump: it must be closed.
o Operate the pump to build up the pressure in both radial and axial direction.
o Check the pressure on the 2 dedicated displays: upper central for RADIAL, upper right for
AXIAL.
o Optionally, close Valve 3 RADIAL INLET and operate the pump to build-up more axial
pressure.
o Once you have reached the axial and radial pressure, close Valve 3 and Valve 4 to isolate the
pump.
o When building up the process fluid pressure, it may interact with the axial and radial pressure.
Adjust them if necessary.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 102
1.2. Pressure Release o Before relieving the radial or the axial pressure, be sure to open the build-in valve of the manual
pump. Then, relieve the radial / axial pressure by opening the Valve ¾.
o Do not forget to close the build-in valve of the manual pump if you need to increase the axial
or/and radial pressure.
o Always check the pressure at RADIAL and AXIAL displays.
2. Transducers’ Orientation Whatever the relative positions of the transducers are, the signal of the P-waves displayed on the
oscilloscope should remain constant. The intensity of the signal of S waves should be maximum when
S1 transducers are parallel. If this is not the case, it means that the core is anisotropic (refer to the
“Theory” chapter). To adjust the relative positions of the transducers, the operator may rotate them
thanks to the tube guides H02-213 (long) and H02-224 (short).
The correct position is determined by a constant checking of the oscilloscope signal.
Figure 81: Adjusting the relative position of the transducers.
3. Time of Flight Determination The “time of flight” is the duration between the emission of the signal by one transducer and the
reception of this signal by another one. at the opposite end of the core. This time of flight should be
corrected since it includes the propagation in the core itself but also in the spreader (see Chapter
“Calibration”).
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 103
3.1. P Waves Using an oscilloscope, calculating the time of flight of P-waves is very easy. It is possible to trig the
signal of the impulse. The time of flight is the difference between the pulse and the first detected signal
following the pulse. On the following screen copies, the time of flight of P-waves is of about 28.6 μs.
Figure 82: Schematic screen showing a P-wave time.
3.2. S Waves Calculating the time of flight of S waves is far more difficult than the one of P waves. S-waves will
generate P waves each time they encounter an interface (transducer /spreader, speader/core,
core/sleeve, etc.). Since the velocity of P waves is about twice as much as the one of S waves, the P
waves will reach the receiving transducer before the S-waves and blur the signal. The amplitude of the
unwanted P waves is usually lower than the one of the S waves. Another possible way to discriminate P
waves and S waves is to slightly modify the relative positions of the transducers. The amplitude of P
waves should remain almost constant while the amplitude of S waves should decrease. On the
following screen copies, the time of flight of S-waves is of about 42. μs.
Figure 83: Schematic screen showing a S-wave time.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 104
4. Calibration The instrument is provided with some calibration plugs: Two aluminum plugs of 1.5’’ diameter (1 and
3’’ of length respectively) and two nylon plugs of 1.5’’ diameter (1 and 3’’ of length respectively).
Those plugs can be used to calibrate the AVS system and to get the propagation
speed of S and P waves via the time of flight of those waves. The table below gives the propagation
speed of P and S waves in aluminum and nylon at ambient temperature.
Parameter Aluminium Nylon
Propagation speed of P waves (m/s) 6300 2700
Propagation speed of S waves (m/s) 3100 1700
The propagation speed of P and S waves can be calculated via the following equations:
With:
VPwave & VSwave : Propagation speed of P/S waves (m/s)
TPwave & TSwave : Time of flight of P/S waves (s)
CFPwave & CFSwave : Correction factor of P/S waves (s)
The correction factors correspond to the time of flight of the waves without any plug. They can be
directly measured by pressing the two spreaders one against each other. To get an accurate
measurement of those correction factors it is possible to measure the time of flight of the waves in a
calibration plug. Thus the correction factor can be calculated using the equations below:
The calibration factors of the AVS system should be of about 10 μs for P waves and 16 μs for S waves.
Reservoir Rock Properties Analysis, Mohsen Masihi
Department of Chemical & Petroleum Engineering, Sharif University of Technology, Tehran, IRAN 105