Mud Density
Mud density is commonly measured with a mud balance capable of ±0.1 lb/gal accuracy. A mud bal- ance calibrated with fresh water at 70°±5° should give a reading of 8.3 lb/gal.
Step
1. Measure and record the temperature of the sample of mud to be tested.
2. Place the mud balance base on a flat, level surface.
3. Fill the clean, dry, mud balance cup with the sample of mud to be tested. Rotate cap until it is firmly seated. Ensure that some mud is expelled through the hole in the cap to remove any trapped air or gas.
4. Place thumb over hole in cap and hold the cap firmly on the cup. Wash or wipe the outside of the cup, and dry.
5. Place balance arm on the support base and balance it by moving the rider along the graduated scale until the level bubble is centered under the center line.
6. Read the density (weight) of the mud shown at the left-hand edge of the rider and report to nearest 0.1 lb/gal. Enter result on API Drilling Mud Report as Weight (lb/gal, lb/ft3) or Specific Gravity.
Marsh Funnel Viscosity
Marsh Funnel viscosity is the time required (seconds) for a quart of mud to flow through a 2-in. long, 3/16-in. diameter tube at the bottom of the Marsh Funnel. This viscosity measurement is used to peri- odically report mud consistency. One quart of water should flow through a Marsh Funnel in 26± 0.5 seconds.
Step
1. Hold one finger over the orifice at the tip of the funnel. Pour the mud sample through the funnel screen until mud reaches the bottom of the screen (1500 cm3). Place viscosity cup beneath funnel tip. Remove finger and start stop watch.
2. Stop the watch when the mud level reaches the 1 qt mark on the viscosity cup.
3. Record the number of seconds required to outflow 1 qt of mud. Enter on Drilling Mud Report as Funnel Viscosity (sec/qt) API.
4. Measure and record temperature of mud sample to ±1°F.
Mud Density is used to control subsurface pressures and stabilize the wellbore.
Rheology
A rotational viscometer is used to measure shear rate/shear stress of a drilling fluid - from which the Bingham Plastic parameters, PV and YP, are calculated directly. Other rheological models can be applied using the same data. The instrument is also used to measure thixotropic properties, gel strengths. The following procedure applies to a Fann Model 35, 6-speed VG Meter.
Plastic Viscosity (PV) and Yield Point (YP)
Step
1. Obtain a sample of the mud to be tested. Record place of sampling. Measurements should be made with minimum delay.
2. Fill thermal cup approximately 2/3 full with mud sample. Place thermal cup on viscometer stand. Raise cup and stand until rotary sleeve is immersed to scribe lie on sleeve. Lock into place by turn- ing locking mechanism (refer to Figure 1).
3. Place thermometer in thermal cup containing sample. Heat or cool sample to desired test temper- ature of 115°±2°F.
4. Flip VG meter toggle switch, located on right rear side of VG meter, to high position by pulling for- ward.
5. Position red knob on top of VG meter to the 600-rpm speed. When the red knob is in the bottom position and the toggle switch is in the forward (high) position -this is the 600-rpm speed (refer to Figure 2).
6. With the sleeve rotating at 600-rpm, wait for dial reading in the top front window of VG meter to stabilize (minimum 10 seconds. Record 600-rpm dial reading.
7. With red knob in bottom position, flip the VG meter toggle switch to low position by pushing the toggle switch away from you. Wait for dial reading to stabilize (minimum 10 seconds). Record 300-rpm dial reading. [See Step 8 to calculate the Plastic Viscosity and Yield Point].
8. The Plastic Viscosity and Yield Point are calculated from the 600-rpm and 300-rpm dial readings as follows:
Gel Strength (10-sec/10-min)
Step
1. With red knob in bottom position, flip toggle switch to 600-rpm position (forward position). Stir mud sample for 10 seconds.
Rheological properties measured with a rotational viscometer are commonly used to indicate solids buildup, flocculation or deflocculation of solids, lifting and suspension capabilities, and to calculate hydraulics of a drilling fluid.
PV,cP 600-rpm dial reading 300-rpm dial reading – = YP,lb/100 ft2 300-rpm dial reading Plastic
Viscosity
– =
2. Position red knob to the 3-rpm speed. When the red knob is in the middle position and the toggle switch is in low (rear) position - this is the 3-rpm speed. Flip toggle switch to off position. Allow mud to stand undisturbed for 10 seconds.
3. After 10 seconds, flip toggle switch to low (rear) position and note the maximum dial reading. This maximum dial deflection is the 10-second (initial) gel strength in lb/100 ft2. Record on the mud check sheet.
4. Pull toggle switch to high and position red knob to 600-rpm speed. Stir mud for 10 seconds.
5. After 10 seconds, and while mud is still stirring, position red knob to the 3-rpm speed. Flip toggle switch to off position and allow mud to stand undisturbed for 10 minutes.
6. After 10 minutes, flip toggle switch to low (rear) position and note the maximum dial reading. This maximum dial deflection is the 10-minute gel strength in lb/100 ft2. Record on the mud check sheet.
Static Filtration Tests
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 sol- ids and their interactions.
The following instructions for Low-Pressure/Low-Temperature Filtration and High-Pressure/High-Tem- perature 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.
Low-Temperature/Low-Pressure Filtration
Step
1. Open main air valve by turning handle (located on lab bench) counter clockwise. Adjust regulator to read 100 psi.
2. Be sure cell components, especially the screen, are clean and dry. Check gaskets and discard any that are worn or distorted.
3. Assemble filtration cell (as illustrated in Figure 3). Lock cell bottom into position by turning cell body until peg locks into J slot.
4. Pour mud sample to within 1/2 in. of top of cell. Place cell onto filter press rack.
5. Position cell lid onto top of cell body. To seal, turn filter press handle clockwise until hand-tight.
6. Place a clean, dry graduated cylinder under the drain tube of the filtration cell assembly.
7. Close bleeder valve. Maintain in the closed position while test is running (refer to Figure 4). 8. 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.
Control of filtration properties of a drilling fluid can be useful in reducing tight hole conditions and fluid loss to formations.
9. At the end of 30 minutes, remove graduated cylinder. Measure and record filtrate volume col- lected. Volume is measured in cm3/30 minutes. Close valve by turning black knob clockwise. Open
bleeder valve and release trapped line pressure.
10. Turn filter press handle counterclockwise to remove filtration cell assembly from frame. Pour mud back into viscosity cup, then carefully disassemble mud chamber.
11. Remove filter paper from screen, being careful not to disturb mud cake. Gently wash excess mud from cake with a stream of water.
12. 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 attempt- ing 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).
Step
1. Plug heating jacket cord into correct voltage for the unit.
2. Place metal thermometer in hole on outside from of heating jacket. Adjust thermostat and preheat jacket to 10°F above desired test temperature.
3. While jacket is heating, check o-rings (3) on the following components and replace if worn or dis- torted:
•
High-Pressure Regulator•
Lid/Valve•
Cell Body(Refer to Figures 6, 7, and 8 for details.)
4. Stir mud sample 10 minutes with a high-speed mixer.
5. Close Valve A by turning black knob clockwise.
6. Turn handle counterclockwise on high pressure regulator, then load CO2 cartridge into chamber
(refer to Figure 6).
7. 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).
8. Open valve C and seat lid/valve assembly. Lubricate threads of allen screws with silicone grease and tighten (refer to Figure 8).
10. Invert cell. (The lid/valve assembly is now at the bottom.) Carefully, install cell assembly into heat- ing jacket.
Transfer thermometer from the jacket to the thermometer well located on top of HTHP cell body (refer to Figure 9).
11. Slip high-pressure regulator (0-1500 psi) onto top of valve B and lock into place with steel ring.
12. 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.
13. With valves B and C closed, apply 100 psi to both the high-pressure regulator and the low-pres- sure regulator by turning regulator handles clockwise.
14. 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).
15. When desired temperature is reached, increase pressure on high-pressure regulator to 600 psi by turning regulator handle clockwise.
16. Open valve C. Start timer immediately at this point! Collect filtrate for 30 minutes, maintaining test temperature within ±5°F (refer to Figure 11).
17. 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.
18. 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 dou- bled 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).
19. Unplug unit and allow cell and contents to cool to room temperature before proceeding to disas- sembly procedure.
20. After HTHP cell assembly and contents are cooled to room temperature, proceed with disassem- bly and cleaning procedure. Valves B and C should already be in the closed positions (refer to Figure 12).
Caution: The Heating Jacket is hot!
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 col- lection chamber.
Note: CAUTION — Throughout the disassembly procedure, Always assume there could be
21. 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).
22. 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-pres- sure 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.
23. 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). 24. 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).
25. 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.
26. Measure and report thickness of filter cake to nearest 1/32 of an inch. Describe condition of the cake.
27. 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.
Retort - Water, Oil and Solids
The volume percent of liquid phase (water and oil) are measured by heating a known volume of whole mud in a retort unit. The liquid is evaporated from the mud, vapor is condensed and measured as oil and fresh water in a graduated glass tube. Suspended solids are calculated by difference of liquid col- lected subtracted from whole mud volume (retort cup volume).
Retort Test Procedure
Step
1. Clean and dry the retort assembly and condenser. Condenser passage should be cleaned using a pipe cleaner.
2. Mix the mud sample thoroughly to ensure homogeneity, being careful not to entrain any air, and that no solids remain on the bottom of container. Air or gas entrapment will cause erroneously high retort solids due to reduced mud sample volume.
3. Use a clean syringe to obtain a sample of the mud to be tested.
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.
Accurate measurement of water, oil and solids content provides fundamental information for con- trol of mud properties and is essential for evaluating solids control equipment.
4. Fill retort cup slowly to avoid air entrapment. Lightly tap side of cup to expel air. Place lid on the cup. Rotate lid to obtain a proper fit. Be sure a small excess of mud flows out of the hole in the lid. Wipe off any excess mud without wicking any of the sample from inside the cup. Wipe the cup clean with towel.
5. Pack retort body with steel wool.
6. Apply Never-Seez to threads of retort cup. With lid in place, hand tighten retort cup onto retort body (refer to Figure 16).
7. Apply Never-Seez to threads on retort stem and attach the condenser.
8. Place the retort assembly inside the heating jacket and close the lid.
9. Place the clean, dry, liquid receiver below the condenser discharge tube. The length of the receiver may require that it be angled out from the retort and supported off the edge of the work table.
10. Plug cord into 110-volt outlet. Allow the retort to run for a minimum of 45 minutes.
11. Allow the receiver to cool. Read and record: (1) total liquid volume, (2) oil volume, and (3) water volume in the receiver.
12. Unplug retort and allow to cool. Disassemble and clean the retort assembly and condenser.
13. Calculate volume percent water (VW), volume percent oil (VO), and volume percent retort solids
(VS), as follows:
(See Retort Cup Verification Procedure)
Retort Cup Verification Procedure
Step
1. Allow retort cup, lid and distilled water to reach ambient temperature. Record the temperature.
2. Place the clean, empty retort cup and lid on a balance (precision of 0.01 g) and tare to zero.
3. Fill retort cup with distilled water. Place lid on the cup. Rotate lid to obtain proper fit. Be sure a small excess of water flows out of hole in lid. Wipe excess water from lid; avoid wicking out water.
Note: If mud boils over into the receiver, the test must be rerun. Pack the retort with a larger amount of steel wool and repeat the test.
VO 100 volume of oil, cm( 3) VR C --- = VW 100 volume of water, cm( 3) VRC --- = VS = 100–(VW+VO)
4. Place filled retort cup and lid on the previously tared balance. Read and record weight of water to 0.01 g.
5. Calculate the retort cup Volume, VRC, using density of water at measured temperature from
Table 1 as follows:
Whole Mud Alkalinity (VSA) and Lime Content (LimeOM)
To measure oil mud alkalinity, the emulsion is broken with a solvent and diluted with water and then titrated with 0.1N H2SO4 to the phenolphthalein endpoint.
Step
1. Add 100 cm3 of 50-50 xylene/isopropanol solvent to a 1000-cm3 Erlenmeyer flask.
2. Fill a 5-cm3 syringe past the 3-cm3 mark with mud to be tested.
3. Displace 2 cm3 mud into the flask; swirl until the mixture is homogenous.
4. Add 200 cm3 of de-ionized water to the mixture; then add 15 drops of phenolphthalein indicator
solution.
5. While stirring rapidly with a magnetic stirrer, slowly titrate with 0.1N sulfuric acid until pink color dis- appears; continue stirring. If no pink color reappears within 1 minute, stop stirring.
6. Let sample stand 5 minutes; IF NO PINK COLOR REAPPEARS, the endpoint has been reached. IF A PINK COLOR RETURNS, titrate a second time with sulfuric acid. If pink color returns again, titrate a third time. If, after the third titration a pink color returns, call this the endpoint anyway. Record the cm3 of 0.1N sulfuric acid required to reach endpoint. Save the mixture for Whole Mud
Chloride test.
7. Calculate Whole Mud Alkalinity (VSA); then, calculate Lime Content (LimeOM) as follows:
VRC Weight of water, g Density of water, g/cm3
--- =
The alkalinity of an oil mud is used to calculate the pounds per barrel of excess lime. Excess alka- line materials, such as lime, help stabilize the emulsion and also neutralize acid gases such as hydrogen sulfide and carbon dioxide.
Note: It may be necessary to stop the stirring to allow the phases to separate in order to see the endpoint. VSA cm3 0.1N Sulfuric Acid cm3 of mud --- = LimeOM, lb/bbl = (VSA)(1.295)