Rheology

Rheological properties measured with a rotational viscometer are commonly used to indicate solids buildups flocculation or deflocculation of solids, lifting and suspension capabilities, and to calculate hydraulics of a drilling fluid.

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 turning locking mechanism (Figure 1).

Figure 1

Fann Model 35 6-Speed Viscometer

Figure 1

Fann Model 35 6-Speed Viscometer

Meter Speed
  1. Place thermometer in thermal cup containing sample. Heat or cool sample to desired test temperature of 115° ±2°F.
  2. Flip VG meter toggle switch, located on right rear side of VG meter, to high position by pulling forward.
  3. 6/94 3-2
  4. 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

Figure 2 Speed Selection Knob (Caution: Change gears only when motor is running.)

Figure 2 Speed Selection Knob (Caution: Change gears only when motor is running.)

Methylene Blue Mbt Drilling
  1. With the sleeve rotating at 600-rpm, wait for dial reading in the top window of VG meter to stabilize (minimum 10 seconds). Record 600-rpm dial reading.
  2. 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). Records 300-rpm dial reading. [See Step 8 to calculate the Plastic Viscosity and Yield Point].
  3. The Plastic Viscosity and Yield Point are calculated from the 600-rpm and 300-rpm dial readings as follows:

PV,cP YP,lb/100 ft2

600-rpm ö dial readingj

300-rpm ö dial readingj

300-rpm ö dial readingj

Plastic ö ViscosityJ

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.
  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 ontrol of filtration properties of a drilling fluid can be useful in reducing tight hole conditions a

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.

To operate any equipment, manufacturer's instructions should be carefully read. The following are general instructions for a possible configuration of Low-Pressure/Low-Temperature Filtration and High-Pressure/High-Temperature Filtration equipment. To operate any other units, manufacturer's instructions should be carefully read before attempting to perform testing.

Low-Temperature/Low-Pressure Filtration

  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 (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.
  9. At the end of 30 minutes, remove graduated cylinder. Measure and record filtrate volume collected. Volume is measured in cm3 per 30 minutes. Close valve by turning black knob clockwise. Open bleeder valve and release trapped line pressure.

sheet.

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Responses

  • BONNIE
    How the rheology of drilling mud changes when the speed of dial is chnaged from 3rpm to 100 rpm?
    8 years ago
  • peter loewe
    What is 6 rpm dial reading mud?
    7 years ago
  • Nora Ferrari
    How to increase low end rheology in drilling fluids?
    7 years ago
  • dylan
    How to calculate 6 rpm reading in drilling mud?
    7 years ago
  • caradas bolger
    How to measure gel strength in fann vg viscometer?
    3 years ago
  • luisa
    How to cal apperant viscosity usng V G meter?
    2 years ago
  • Kenneth
    How to do rheology and gel strength of a drilling mud?
    2 years ago
  • Hagosa
    How to calculate plastic viscousity and yield point using rheology readings?
    2 years ago
  • Sara
    What temperature to heat mud before rhelogy testing?
    11 months ago
  • peregrin
    How do bentonite affect the rheology of the drilling mud?
    6 months ago
  • Demsas Girma
    How to operate fann 35 rheometer?
    3 months ago
  • ambretta
    How to get viscosity of 600rpm from a machine having maximum of 100rpm?
    27 days ago

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