Multi desaturator cell
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This document describes an experiment to determine the capillary pressure-saturation curves for a core sample using a multi-desaturator cell apparatus. The apparatus applies varying pressures to the core sample to remove water from the pores and measure the resulting saturation levels. The procedure involves saturating core samples with brine, placing them in the cell on a ceramic plate, increasing the air pressure to remove water, then measuring water production and plotting capillary pressure versus saturation. The goal is to understand how capillary pressure affects water saturation in porous rock cores at different pressures.
Multi desaturator cell
- 1. 2015 Kamal Abdurahman Group:B 2/5/2015 Multi Desaturator Cell Supervised By : Mr.AilKamal Mr.Hiwa Mss.Sana
- 2. Contents 1- Aim. 2-Inroduction. 3- Theory. 4- Apparatus. 5- Procedure. 6-Calculation. 7- discussion. 8- references. Aim of experiment:
- 3. In this test we are determined the curves of capillary pressure Versus saturation water.
- 4. 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.
- 5. Theory The 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.
- 6. 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
- 7. 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.
- 9. 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.
- 10. 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.
- 11. 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.
- 12. 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
- 13. 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.
- 14. 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
- 15. -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.
- 16. 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.