drilliung engineering Lab

1. Drilling Engineering-I
Pet-E-211L
Lab Instructor :
Engr. Muhammad Awais Qureshi
Department of Petroleum &
Gas Engineering 5/5/2021

2. Experiment # 07
• Objective:
1) Measurement of gel strength of drilling mud sample by
Rheometer.
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3. Apparatus
• Rotational Rheometer,
• Bentonite,
• Water,
• Graduated Cylinder,
• Stirring Rod,
• Balance,
• Beakers
• PPE’s (Personal Protective Equipments)
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4. Related Theory
• Thixotropy :
• The characteristic of a liquid, such as a drilling mud, to form a gelled
structure over the time at static condition and then to liquefy when agitated.
• Gel Strength :-
• The shear stress measured at low shear rate after a mud has set
quiescently for a period of time
(10 seconds and 10 minutes in the standard API procedure. Although measurements after 30 minutes
or 16 hours may also be taken)
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5. • The time-dependent forces in the drilling mud cause an
increase in viscosity as the fluid remains quiescent for a
certain period.
• The gel strength is a measurement of the electrochemical
forces within the fluid under static conditions.
• Its field unit is the same as that of the yield strength.
• The strength is a function of suspended solids, solid contents,
temperature, chemical content and time.
• Usually it is caused by the high concentration of clay.
• Functions of gel strength:
• Gel Strength decreases the settling rate of cuttings when
circulation is stopped/ interrupted.
• Units are lbf/100 sq. ft
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6. 1) More pump pressure required
for "Break Circulation's
2) Lost circulation by pressure
surges.
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Problems Attributed To
High Gel Strength

7. Rheometer
• Rheometer is a laboratory device used to measure
the way in which a liquid, suspension or slurry flows
in response to applied forces.
• It is used for those fluids which cannot be defined by
a single value of viscosity and therefore require more
parameters to be set and measured than is the case
for a viscometer.
• It measures the rheology of the fluid.
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8. Rotational Rheometer
• In rotational Rheometer, the
liquid is placed within the
annulus of one cylinder inside
another. One of the cylinders is
rotated at a set speed. This
determines the shear rate
inside the annulus.
• The liquid tends to drag the
other cylinder round and the
force it exerts on that cylinder
(torque) is measured, which can
be convened to a shear stress.
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9. • One version of this is the Fann V-G viscometer, which runs at
two speeds, (300 and 600 rpm) and therefore only gives two
points on the flow curve. This is sufficient to define a Bingham
plastic model which used to be widely used in the oil industry
for determining the flow character of drilling fluids.
• In recent years Rheometer at 600, 300, 200, 100, 6 & 3 RPM
have been used. This allows for more complex fluids models
such as Herschel-Bulkley to be used.
• Some models allow the speed to be continuously increased
and decreased in a programmed fashion, which allows the
measurement of time-dependent properties.
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10. Measurement Procedure
1) Stir the sample for 15 sec and lower the rotor assembly
into beaker up to the scribed line on the rotor, allow the
mud to rest for 10 sec and then turn to gel strength
knob slowly and note the max reading on the dial.
2) Allow the mud to rest for 10 min and take the reading, in
previous manner.
3) Reading should he in lbf/ 100 sq. ft.
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11. Demonstration
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12. Observation and
Calculations
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Time Gel Strength Readings
(lbf/100 sq. ft )
t ( 10 sec)
T (after 10 mins)

13. Precautions
1. The rotor bob assembly should be lowered slowly into
the beakers up to the mark.
2. Wear relevant Personal Protective Equipment (PPE)
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14. Viva Voce
Q1) Which role does Gel Strength play in the drilling
process?
Q2) What type of fluids does drilling fluid belong to?
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