Kamal Abdurahman

Group:B

2/5/2015

2015Multi Desaturator Cell

Supervised By : Mr.Ail Kamal Mr.Hiwa Mss.Sana

FACULTY OF ENGINEERING

SCHOOL OF PETROLEUM AND CHEMICAL

RESERVOIR ENGIEERING LAB

Contents

1 -Aim.

2-Inroduction.

3 -Theory.

4 -Apparatus.

5 -Procedure.

6-Calculation.

7 -discussion .

8 -references.

Aim of experiment:

In this test we are determined the curves of capillary pressure

Versus saturation water.

INTRODUCTION

The capillary pressure desaturation cell is dedicated to enable

generation of air-brine capillary curves on core samples.

Capillary curve is the relationship between pressure applied

and pressure stabilized, and water content in the core samples.

The equipment is mainly composed of a console (on left on

first page picture) and a sample extractor (blue vessel on right

on first page picture).

The console controls the air pressure supplied to the vessel. It

is possible to humidify the air used in the process.

In the extractor, core samples are installed on a capillary

(ceramic) pressure plate.

TheoryThe principle involved in the operation of the Capillary pressure

de-saturation cell is that water is removed from sample by

suction wherein a porous ceramic wall serves as a connecting

link and at the same time a means of maintaining a pressure

difference between the liquid phase of the water in the soil and

the water at lower pressure on the opposite side of the wall.

The illustration in Fig. 3 shows a magnified view of soil particles

in contact with the porous ceramic plate inside the Pressure

Extractor during an extraction run.

A wetted porous ceramic plate is backed by a fine mesh screen

which also provides a passage way for the extracted solution,

and is futher sealed by a rubber membrane backing.

The rock samples initially saturated with brine and weighted

individually are installed in the vessel on the ceramic plate

preliminary wetted to ensure good capillary contact.

After bolting the Extractor lid onto the Extractor, air pressure

may be increased to the value of the test (0.1 to 1500 kPa). As

soon as air pressure inside the chamber is raised above

atmospheric pressure, the higher pressure inside the chamber

forces excess water through the microscopic pores in the

ceramic plate. The high pressure air, however, will not flow

through the pores since they are filled with water and the

surface tension of the water at the gas-liquid interface at each

of the pores supports the pressure much the same, When the

air pressure is increased inside the Extractor, the radius of

curvature of this interface decreases (Fig.4). However, the

water films will not break and let air pass throughout the whole

pressure range of the Extractor.

At any given air pressure in the chamber, soil moisture will flow

from around each of the soil particles and out through the

ceramic plate until such time as the effective curvature of the

water films throughout the soil are the same as at the pores in

the membrane. When this occurs, equilibrium is reached and

the flow of moisture ceases. When the air pressure in the

Extractor is increased, flow of soil moisture from the samples

starts again and continues until a new equilibrium is reached.

At equilibrium, there is an exact but opposite relationship

between the air pressure (positive force) in the Extractor and

the soil suction (negative force).

Water content by weight or by volume can be determined for

the sample that was at equilibrium with the pressure in the

Extractor.

According to the pressure value and to the sample

characteristics, it spends from 1 hour to several days. Then, the

operator bleeds off pressure, open the vessel to determine

water production by weight.

Finally, the operator plots the water (or brine) content in

core versus the applied (capillary) pressure. The water

content is usually expressed in % of pore volume of the

sample.

Apparatus of experiment

Procedure

Test Preparation (humidifier filling)

The air in the extractor should be humidified to prevent sample

drying and cracking of the ceramic plate.

1. Unscrew four ¼`` fittings as shown in the nearby picture

2. Unscrew 3xCHC M6 screws with allen key provided

3. Open the top lid of the humidifier tank by hand. Maybe you

need pull off strongly to remove the top lid, due to the mounted

oring.

4. Fill 2/3 of height with water and tight the top lid of the

humidifier tank as was showing before

5. Connect the ¼’’ lines before the experience

6. Dry sample in oven not over 82°C (180 °F) so as not remove

water of hydratation.

7. Leach if necessary to remove salt:

a) Leach sample by flowing fresh or distilled water trough until

all salt is removed. Salt concentration can be detected in

effluent water by resistivity.

b) Do not leach if sample is suspected to contain clay, shale or

anhydrite.

8. Run air permeability measurements, and select sample to

cover desired permeability range.

9. Obtain dry weight of sample.

10. Place sample in saturator and evacuate for at least four

hours, longer evacuation will be necessary for tight samples.

11. Pressurize sample in saturator with degassed evacuated

brine at 2,000 psi. Unless otherwise specified, use brine of

91,000 ppm NaCl. As a general rule, allow sample to remain at

2000 psi in brine for a period of 8 to 16 hours, depending on the

permeability of the sample.

12. Remove sample from depressurized saturator, wipe excess

brine from sample with hand only, taking care to rub off any of

the sample grains. Determine saturated weight.

Operation

It is assumed that:

- One type of test is selected:

a. maximum desaturation and

b. desaturation step by step

- Flush the ceramic with brine to be used before placing sample

in desaturator.

- The core sample (s) is loaded in the single / multi desaturator

cell and prepared for the test.

- The humidifier is filled with 2/3 of water

- Air connection is done

- All fittings are tight

These detailed procedure and calculation instruction are

based on Dr R. MONICARD work.

a. For a maximum desaturation:

1. Close the low pressure gas regulator valve

2) Open all other valves (HV01, HV02 and HV03)

3) Extract fresh sample by centrifuge or Dean Stark method.

4) Set the air supply. Close low pressure gas regulator and

open the high pressure gas regulator to perform maximum

desaturation experience.

5) Turn clockwise progressively the regulator knob until the cell

pressure display monitors the required operating pressure.

6) Start with a capillary pressure step of 1 psi for a period of at

least 48 hours. Open gently the valve HV04 to pressurize the

desaturator cell.

7) After this time length in desaturator cell, isolate the pressure

regulator by setting HV02 in mid position.

8) Open gently the fitting on desaturator cell to depressurize the

vessel.

9) Open the desaturator, remove sample.

b. Step by step:

Repeat the previous steps, using different pressures and using

the same 48 hours interval (remember you have a maximum

ceramic pressure plate of 250psi). This time interval is the

minimum required for searching equilibrium. Tighter samples

may require a longer time for reaching equilibrium.ecord

weight.

6.5 Shutoff procedure:

After the last step:

1. Isolate the air supply.

2. Isolate the pressure regulators by closing HV02 (in the mid

position).

3. Turn anticlockwise both regulators knob.

4. Open gently the valve HV03 to depressurize the vessel.

5. Open HV05 to release gas

6. Open desaturator cell.

7. Place the sample(s) in a tare container(s) and dry in an oven

temperature of 71 - 82°C (160 - 180 °F) for a period of at least

2 4 hours, and again longer for tighter samples. The use of a

tare container in the drying step will eliminate the grain loss.

The tare will retain for final weight measurement any particle

which is displaced from the sample during drying.

8. Remove sample and tare from oven and measure final dry

weight of sample after it reaches room temperature in

desiccator.

9. Run gas expansion porosity. Unless the samples are

leached, the salt from the water displaced during the capillary

test will be left in the sample, and must be considered as part of

the porosity in the calculation.

5. Drying the Cell after the Run

When a Pressure Cell is to be dried for storage after a run, it is

very important to keep evaporation deposits on the surface

to a minimum.

To do this, cover the surface of the ceramic plate with a thin

layer of fine dry soil and allow it to set for several days until dry.

After it is dry, remove the soil and store the cell.

This procedure forms the evaporation deposits on the soil

particles rather than on the surface of the cell.

After a period of time, if the flow rate of a Cell drops due to

deposits, they should be replaced.

Discussion

-In this test the main effect is time because there are many

cores samples need to a many weeks to saturated.

-The ceramics plate resistant to the 3bar pressure we are must

be takes less than 3bar pressure if higher than 3bar this plate

cracked or broken.

-In this test the De-saturation of the core decrease when you

have a capillary pressure, then the saturation decrease when

you takes another capillary pressure .

Pc

Sw

-If the core has low permeability to saturated this core need

usually one week, If the core has high permeability to saturated

this core need to two or three or more days.

Reference

http://www.malvern.com/en/products/measurement-type/

desaturation/default.aspx

Jiao, D. and M.M. Sharma, “desaturation,” Journal of Colloidal

and Interfacial Science, 1994. 162:p. 454-462.

http://www.glossary. desaturation .slb.com/en/Terms/m/

mudcake.aspx

Fisk, J.V., and Jamison, D.E., SPE Reservoir Engineering,

December 1989, pp. 341-46.