Drilling Hydraulics 2

8/12/2019 Drilling Hydraulics 2

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D

rilling E

ngineering 2

Course (

1

st

Ed.)
http://bit.ly/Q921-DE2http://bit.ly/Q921-DE2mailto:[email protected]://bit.ly/Q921-DE2mailto:[email protected]


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1. Mud Weight Planning

2. drilling hydraulics:

A.

the hydrostatic pressure


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1. drilling hydraulics:

A.

types & criteria of fluid flowB.

fluid Rheology and models

a. Bingham

plastic & Power

-

law models


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Parameters influence rheologicalproperties of drilling fluidSince multiple aspects of drilling and completion

operations require the understanding of how fluidmoves through pipes, fittings and annulus, theknowledge of basic fluid flow patterns is essential.

Generally, fluid movement can be described as laminar,turbulent or in transition between laminar andturbulent.

It should be understood that rotation and vibrationsinfluence the rheological properties of drilling fluids.

Also the pulsing of the mud pumps cause variations inthe flow rates as well as the mean flow rates.Furthermore changing solid content influences theactual mud density and its plastic viscosity.

Fall

13

H. AlamiNia Drilling Engineering

2

Course (

1

st Ed.) 5


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Laminar vs. turbulent flowFluid movement, when laminar flow is present, can

be described as in layers or laminae.

Here at all times the direction of fluid particle movementis parallel to each other and along the direction of flow.

In this way no mixture or interchange of fluid particlesfrom one layer to another takes place.

At turbulent flow behavior,

which develops at higher average flow velocities,

secondary irregularities such as vortices and eddys areimposed to the flow.

This causes a chaotic particle movement andthus no orderly shear between fluid layers is present.

Fall

13

H. AlamiNia Drilling Engineering

2

Course (

1

st Ed.) 6


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Ideal laminar flow animation)Ideal laminar

flow in a tube

(note that theparticles tothe center ofthe tubemove faster,as affected to

a lesser extentdissipativeeffect of thewalls)

Fall 13 H. AlamiNia Drilling Engineering 2 Course (1st Ed.) 7


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Laminar, transitional, and turbulentflow

Laminar vs. turbulent flow Laminar, transitional, and turbulent flow from a faucetFall 13 H. AlamiNia Drilling Engineering 2 Course (1st Ed.) 8


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Laminar vs. turbulent flow

Laminar and turbulent water flow Laminar vs. turbulent flow of smokeFall 13 H. AlamiNia Drilling Engineering 2 Course (1st Ed.) 9


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Reynolds numberThe so called Reynolds number is often used to

distinguish the different flow patterns.

After defining the current flow pattern,different equations are applied

to calculate the respective pressure drops.

For the flow through pipes, the Reynolds number isdetermined with:

and for the flow through annuli:



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Reynolds number rangeThe different flow patterns are then characterized

considering the Reynolds number.

Normally the Reynolds number 2,320 distinguishesthe laminar and turbulent flow behavior,

for drilling purposes a value of 2,000 is applied instead.

Furthermore it is assumed that turbulent flow is fullydeveloped at Reynolds numbers of 4,000 and above,

thus the range of 2,000 to 4,000 is named transition flow:



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Rheological Classification of FluidsAll fluids encountered in drilling and production

operations can be characterized as eitherNewtonian fluids or Non-Newtonian ones.

Newtonian fluids,like water, gases and thin oils (high API gravity)show a direct proportional relationship betweenthe shear stress and the shear rate,assuming pressure and temperature are kept constant.

They are mathematically defined by:

[dyne/cm2] ... shear stress

[1/sec] ... shear rate for laminar flow within circular pipe

[p] ... absolute viscosity [poise]



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Newtonian flow modelA plot of

vs.

produces a

straight linethat passesthrough theorigin and has

a slop of .



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Non-Newtonian fluidsMost fluids encountered at drilling operations

like drilling muds, cement slurries, heavy oil and gelledfracturing fluids do not show thisdirect relationship between shear stress and shear rate.

They are characterized as Non-Newtonian fluids.

To describe the behavior of Non-Newtonian fluids,various models like

Time-independent fluid model including

the Bingham plastic fluid model,

the Power law fluid model and

Time-dependent fluid models were developed



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Non-Newtonian fluidstime depended modelsThe time dependence mentioned here concernsthe change of viscosity by the duration of shear.

It is common to subdivide the time dependedmodels intoThixotropic fluid models and

The Rheopectic fluid models.

It shall be understood that all the modelsmentioned above are based on

different assumptions that arehardly valid for all drilling operations,thus they are valid to a certain extend only.



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Bingham plastic fluid modelBingham plastic fluid

model

y[lbf/100 ft2]yield point

p [cp]plastic viscosity

Sketch of Bingham fluid modelFall 13 H. AlamiNia Drilling Engineering 2 Course (1st Ed.) 19


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Bingham fluidsIn contrary to Newtonian fluids,

Bingham fluids do have a yield point and

it takes a defined shear stress () to initiate flow.

Above , and are proportional defined by theviscosity, re-named to plastic viscosity p



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Power-law fluid modelPower-law fluid model

n [1]flow behavior index

K [1]consistency index

Sketch of Power-law fluid modelFall 13 H. AlamiNia Drilling Engineering 2 Course (1st Ed.) 21


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Power-law fluid modelWhen the characteristics of the Power-law fluid model

is done on a log-log scale, the results is in a straight line.

Here the slope determines the flow behavior index n and

the intercept with the vertical,

the value of the consistency index (logK).

The flow behavior index (n), that ranges

from 0 to 1.0 declares the degree of Non-Newtonian behavior,

where n = 1.0 indicates a Newtonian fluid.

The consistency index K on the other handgives the thickness (viscosity) of the fluid where,

the larger K, the thicker (more viscous) the fluid is.



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rheological properties determinationTo determine the rheological

properties of a particular fluid,a rotational viscometer withsix standard speeds and variable

speed settings is used commonly.In field applications, out of these

speeds just two are normally used

(300 and 600 [rpm])

since they are sufficient todetermine the required properties.

rotational ViscometerFall 13 H. AlamiNia Drilling Engineering 2 Course (1st Ed.) 23


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individual fluid parametersdeterminationNewtonian fluid model

Bingham plastic fluid model

Power-law fluid model

r2 [in] rotor radius, r1 [in] bob radius, r [in] any radius betweenr1 and r2, N [1] dial reading of the viscometer at speed N,N [rpm] speed of rotation of the outer cylinder



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1. Dipl.-Ing. Wolfgang F. Prassl. Drilling

Engineering.

Master of PetroleumEngineering. Curtin University of Technology,

2001. Chapter 4


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Drilling Hydraulics 2

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