Static Filtration Tests
Control of filtration properties of a drilling fluid can be useful in reducing tight hole conditions and fluid loss to formations.
Static filtration tests are used to indicate filter cake quality and filtrate volume loss for a drilling mud under specific testing conditions. Filtration characteristics are affected by the types and quantities of solids and their physical and chemical interactions. Temperature and pressure further affect these solids and their interactions.
The following instructions for Low-Pressure/Low-Temperature Filtration and High-Pressure/High-Temperature Filtration will be applicable only to equipment used at DTC's training lab. To operate any other units, manufacturer's instructions should be carefully read before attempting to perform testing.
- Open main air valve by turning handle (located on lab bench) counter clockwise. Adjust regulator to read 100 psi.
- Be sure cell components, especially the screen, are clean and dry. Check gaskets and discard any that are worn or distorted.
- Assemble filtration cell (as illustrated in Figure 3). Lock cell bottom into position by turning cell body until peg locks into J slot.
- Pour mud sample to within 1/2 in. of top of cell. Place cell onto filter press rack.
- Position cell lid onto top of cell body. To seal, turn filter press handle clockwise until hand-tight.
- Place a clean, dry graduated cylinder under the drain tube of the filtration cell assembly.
- Close bleeder valve. Maintain in the closed position while test is running (refer to Figure 4).
- Set interval timer for 30 minutes. Open valve located on filter press manifold by turning black knob counterclockwise. Pull timer arm down and begin timing immediately.
- 6/94 3-44
- At the end of 30 minutes, remove graduated cylinder. Measure and record filtrate volume collected. Volume is measured in cm3/30 minutes. Close valve by turning black knob clockwise. Open bleeder valve and release trapped line pressure.
- Turn filter press handle counterclockwise to remove filtration cell assembly from frame. Pour mud back into viscosity cup, then carefully disassemble mud chamber.
- Remove filter paper from screen, being careful not to disturb mud cake. Gently wash excess mud from cake with a stream of water.
- Measure and report thickness of filter cake to nearest 1/32 of an inch. Describe cake (i.e., soft, tough, rubbery, firm, etc.).
High-Temperature/High-Pressure Filtration (HTHP)
To operate this or any other unit, manufacturer's instructions should be carefully read before attempting to perform testing. Extreme caution should be used in running this test. Equipment should be cleaned and maintained in good working condition (refer to Figure 5).
- Plug heating jacket cord into correct voltage for the unit.
- Place metal thermometer in hole on outside from of heating jacket. Adjust thermostat and preheat jacket to 10°F above desired test temperature.
- While jacket is heating, check o-rings (3) on the following components and replace if worn or distorted:
- High-Pressure Regulator
- Cell Body
- Refer to Figures 6, 7, and 8 for details.)
- Stir mud sample 10 minutes with a high-speed mixer.
- Close Valve A by turning black knob clockwise.
- Turn handle counterclockwise on high pressure regulator, then load CO2 cartridge into chamber (refer to Figure 6).
- Close valve B and pour stirred mud sample into cell, leaving 1/2 in. from the top lip to allow for expansion. Position o-ring in groove inside cell body. Place filter paper on top of o-ring (refer to Figure 7).
- Open valve C and seat lid/valve assembly. Lubricate threads of allen screws with silicone grease and tighten (refer to Figure 8).
- Close valve C low-pressure shut-off valve.
- 6/94 2-32
- Invert cell. (The lid/valve assembly is now at the bottom.) Carefully, install cell assembly into heating jacket.
^Caution: The Heating Jacket is hot!
Transfer thermometer from the jacket to the thermometer well located on top of HTHP cell body (refer to Figure 9).
- Slip high-pressure regulator (0-1500 psi) onto top of valve B and lock into place with steel ring.
- Slip low-pressure regulator (0-200 psi) on bottom of valve C. Lock into place with steel ring. Be sure bleeder valve on low-pressure regulator is in the horizontal (closed) position.
- With valves B and C closed, apply 100 psi to both the high-pressure regulator and the low-pressure regulator by turning regulator handles clockwise.
- Open valve B. This is done to maintain 100 psi back pressure in the cell body while heating to the desired temperature. Heating time should not exceed 1 hour (refer to Figure 10).
- When desired temperature is reached, increase pressure on high-pressure regulator to 600 psi by turning regulator handle clockwise.
Note: If pressure on low-pressure regulator rises above 100 psi during the test, cautiously reduce pressure by drawing off a portion of filtrate using valve D located on bottom of filtrate collection chamber.
- Open valve C. Start timer immediately at this point! Collect filtrate for 30 minutes, maintaining test temperature within ±5°F (refer to Figure 11).
- At the end of 30 minutes close valve C. Carefully open valve D and collect filtrate. Leave valve open until low-pressure gauge reads 0 psi.
- Note the total volume of filtrate, test temperature and pressure, and cell heat-up time. Because most HTHP filter presses have a filter area of 3.5 in.2, the filtrate volume collected must be doubled to correct to API standard 7.1 in.2 Calculate and record the API HTHP filtrate as follows: API HTHP Filtrate = (2) (cm3 filtrate collected).
- Unplug unit and allow cell and contents to cool to room temperature before proceeding to disassembly procedure.
Note: CAUTION — Throughout the disassembly procedure, Always assume there could be trapped high pressure in the HTHP unit.
- After HTHP cell assembly and contents are cooled to room temperature, proceed with disassembly and cleaning procedure. Valves B and C should already be in the closed positions (refer to Figure 12).
- 6/94 3-46
- To bleed pressure from the high-pressure (top) regulator, be sure Valve B is closed. Turn regulator handle clockwise and carefully open Valve A. Bleed pressure until CO2 cartridge is expended and high-pressure gauge reads 0 psi (refer to Figure 13).
- To bleed pressure from the low-pressure (bottom) regulator, be sure that valve C is closed. Turn regulator handle clockwise and carefully open valve D. Bleed pressure until CO2 cartridge is expended and low-pressure gauge reads 0 psi (refer to Figure 14). The pressure on the high-pressure gauge and the low-pressure gauge should now read 0 psi. If not, carefully bleed pressure until both gauges read 0 psi, then remove regulators.
- Remove cell from heating jacket and place in sink. Carefully open valve C and bleed pressure trapped in the cell. Now, open valve B. All pressure should now be released (refer to Figure 14).
- Remove Allen Screws, being careful to point the top assembly away from your body in case any pressure may be trapped (refer to Figure 15).
Note: If Allen Screws are tight, DO NOT attempt to remove them because the cell may contain trapped pressure! This requires special procedures to unplug valves C and B.
- Open cell and carefully remove filter paper and cake from screen, being careful not to disturb the filter cake. Wash excess mud from cake with a small, gentle stream of base oil.
- Measure and report thickness of filter cake to nearest 1/32 of an inch. Describe condition of the cake.
- Discard the mud. Clean the cell. Cleaning includes removal of Valves B and C to prevent mud from drying in the cell assembly, which could cause valves to plug in future tests.
Was this article helpful?
Get All The Support And Guidance You Need To Be A Success At Understanding Waste Management. This Book Is One Of The Most Valuable Resources In The World When It Comes To The Truth about Environment, Waste and Landfills.
Get My Free Ebook