PET ENG 313 L4-Drilling Fluids 1

7/21/2019 PET ENG 313 L4-Drilling Fluids 1

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Lecture #4 PET ENG 313

Drilling fluids 1

Drilling fluids 1

1. The fluid circulation system

2. Types of mud

3. Functions of drilling fluids

4. Rheological properties of drilling mud

5. Weight of drilling mud

6. Drilling mud additives

7. Selection of drilling mud additives



Covered in Lecture 4

Concepts

• Circulation system

• Functions of drilling fluid

• Rheological properties and models ofdrilling fluids

• Viscosity and Apparent Viscosity

Calculations

• Viscosity

• Apparent viscosity for differentreadings

• PV and YP for Bingham Plastic model

• n ,K for Power law

The fluid circulation system

CuttingsShale shaker

Stand

pipe

Reserve pit

Mud in annulus

Mud

pump



Mud system

Mud tanks Mud tanks or pits is us ed by the crew to prepare the mud for circulation

Mud pumps One or more pumps t hat circulate the mud up t he standpipe and down the

drill stri ng. Duplex pumps are most common. Triplex pumps is in use but less

common.

Standpipe &

Rotary hose

The standpipe takes the mud halfway up the Derrick. The rotary hose is a

flexible hose that moves with t he swivel as it goes up and dow n in the mast.The rotary hose is connected to t he standpipe and to th e Kelly.

Standpipe pressure is the point where the fluid pr essure is measured when

the fluid is entering the well.

Drill string & bit The mud pump moves the mud down the drill st ring to the bit. At the bit the

mud goes thr ough the nozzles. The mud cleans the cuttin gs around the bit.

Annulus Mud is transports th e cuttings up in th e annulus, first in the open holeannulus and then in the cased section of t he annulus.

Flow line Mud goes through the flow line /return line to the shale shaker.

Shale shaker The shale shaker has screen that removes cutting and th e mud falls into t he

mud tanks where the mud tanks can pump it up again for next circ ulation cycle.

Mud tanks

Centrifuge Shale shaker The mud pass

mesh sieves with a

certain size

200 mesh =

200 holes per in2

De-Sander

De-Gasser

Removes gas from

the mud

A hydrocyclone that

remove larger particles

in the mud with a

centrifugal force

(remove particles

larger than 40 microns)

De-Silter

Removes particles in

the size range of 2-5

microns

A hydrocyclone like the

de-sander but with

smaller cones (remove

particles larger than 20

microns)

Suction mud tank

Where the pump take

the mud to be

circulated in the hole

Mud pump

mponents of the Mudks



Three main types of base fluids for drilling

Water based Fresh water, seaw ater, salt water

etc.

Oil based

NADF (Non Aqueous

Drilling Fluids)

Diesel, high on aromatics

Mineral oil

Synthetics, low on aromatics

Air or gas

based

Air, n it rogen, mis t, foam.

Functions of drilling fluids

Remove cuttings

Cool, lubricate, and lower friction for bit and

drill string

Prevent formation fluids from entering well

Keep wellbore walls from collapsing

Create filter cake in permeable formation to

prevent wellbore walls from caving in

Maintain stability of open hole – chemicallye.g. shale swelling

Transmit information from tools

Create weight/torque on bit

Power down hole directional tools to drilldirectional wells

Functions Desired properties

Keep cutting in suspension when

tripping

Clean bit

Low friction between drill string and

hole

Be as non damaging as possible to

producing formations

Be as environmentally friendly as

possible

Be pumpable at high densities

Be stable at high temperatures andpressures



Laminar Flow

• Rheological Models

• Newtonian

• Bingham Plastic

• Power-Law

• Herschel-Bulkley

• Rotational Viscometer

• Laminar Flow in Wellbore

Laminar Flow of Newtonian Fluids

vF

large t

Fv

v

Fluid initially at restUpper plate set in

motion

Velocity build up

in unsteady flow

Final velocity

distribution in

steady flow

L

time<0 time = 0

small t



Newtonian Fluid Model

Fluid Shear stress = viscosity * shear rate

A

F

L

V

vF

Large t

Final velocity

distribution in

steady flow

5 5 2

210 10 /F dyne N g cm s

A cm

Newtonian Fluid Model

In a Newtonian fluid the shear stress is directly proportional to the

shear rate (in laminar flow):

i.e.,

The constant of proportionality, is the viscosity of the fluid and

is independent of shear rate.

sec

12

cm

dyne .







Bingham Plastic Model

Bingham Plastic Model

-if

-if 0

if

yyp

yy

yyp

and y (yield point) are often expressed in

lb/100 sq.ft





Apparent Viscosi ty

Is not constant for a pseudoplastic fluid

The apparent viscosity decreases with increasing shear

rate

(for a power-law fluid)

(and also for a

Bingham Plastic fluid)

Rheological Models

1. Newtonian Fluid:

2. Bingham Plastic Fluid:

rateshear

viscosityabsolute

stressshear

*)( p y

viscosity plastic pointyield

p

y

What if y



3. Power Law Fluid:

• When n = 1, fluid is Newtonian and K = m

• We shall use power-law model(s) to calculate pressure losses

(mostly).

n

)(K

K = consistency index

n = flow behavior index

Rheological Models

Typical Drilling Fluid Vs. Newtonian, Bingham and Power Law

Fluids

(Plotted on linear paper)



Figure 3.6Rotating

Viscometer

Rheometer

We

determine

rheological

properties

of drilling

fluids in

this device

Infinite

parallel

plates

Rheometer (Rotational Viscometer)

Shear Stress = Dial Reading

Shear Rate = Sleeve RPM

)(f BOB

sleeve

fluid

RateShear the(GAMMA),of value

theondependsStressShear the),TAU(





Example

A rotational viscometer containing a Bingham plastic fluid gives a dial

reading of 12 at a rotor speed of 300 RPM and a dial reading of 20 at arotor speed of 600 RPM

Compute plastic viscosity and yield point

12-20

300600 p

cp8 p

= 20

= 12

Example

8-12

p300y

2y ftlbf/1004

= 20

= 12



Rotational Viscometer, Power-Law Model

Example: A rotational viscometer containing a non-Newtonianfluid gives a dial reading of 12 at 300 RPM and 20 at 600 RPM.

Assuming power-law flu id, calculate the flow behavior index and the

consistency index.

Example

cpeq.67.61511

12*510

511

510

7370.0

12

20 log322.3log322.3

7372.0

300

300

600

nK

n

n

= 20

= 12



Gel Strength

0 300 600

= shear stress when fluid movement begins

τ

γ

τ y

RPM

Actual

readings of τ y

The yield strength, extrapolated from

the 300 and 600 RPM readings is not a

good representation of the gel strength

of the fluid

Gel strength may be measured by

turning the rotor at a low speed and

noting the dial reading at which the gel

structure is broken (usually at 3 RPM)

Gel Strength

2ft100/lbf

The gel strength is the maximum dial reading when theviscometer is started at 3 rpm.

g = max,3



Just a reminder for this week

• HW 1 due tomorrow - Friday.• HW 2 will be posted today and due next Thursday.

• Lab 1 Due in two weeks! Note! follow the lab report

format.

• Remember and register your clickers this week.

• Next week no lab (Labor day), The following weeks the lab

will be in McNutt 115 drilling fluids lab.

Documents

PET ENG 313 L4-Drilling Fluids 1