Determination of Saybolt Viscosity of crude oil and liquid petroleum products. PDF

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The Pennsylvania State University College of Earth and Mineral Sciences Department of Energy and Mineral Engineering Petroleum and Natural Gas Engineering Program PNG 482 - Production Engineering Laboratory Experiment #3– Determination of Saybolt Viscosity of Crude Oil and Liquid Petroleum Products....

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The Pennsylvania State University College of Earth and Mineral Sciences Department of Energy and Mineral Engineering Petroleum and Natural Gas Engineering Program

PNG 482 - Production Engineering Laboratory Experiment #3– Determination of Saybolt Viscosity of Crude Oil and Liquid Petroleum Products. Instructor: Dr Luis F. Ayala Lab Assistant: Miao Zhang

BY

Alexander Ibojo

Alexander Ibojo Performed: 11/14/2013 Submitted: 11/15/2013

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INTRODUCTION The focus of this experiment involves measuring the viscosity of crude oil and liquid petroleum products by means of a Saybolt viscosimeter which measures the elapsed time, known as Saybolt seconds, for a volume of liquid, at specified temperature, to flow under gravity through the calibrated capillary of the viscosimeter. The time measured in Saybolt seconds would be converted to required viscosity unit by using set of e uatio s. I additio , the alidit of A d ade’s equation, which express viscosity as a function of temperature would be validated. What is viscosity? Viscosity is the quantity that describes a fluid's resistance to flow. Fluids resist the relative motion of immersed objects through them as well as to the motion of layers with differing velocities within them. A fluid that has no resistance to shear stress is known as an ideal fluid or in viscid fluid. Fluid with zero viscosity observed only at very low temperatures, are known as super fluids. Otherwise all fluids have positive viscosity. A liquid whose viscosity is less than that of water is sometimes known as a mobile liquid, while a substance with a viscosity substantially greater than water is called a viscous liquid. Fo

all , is osit

ep ese ted

the s

ol η "eta" is the atio of the shea i g st ess ƒ/A to the elo it

g adie t Δ /Δz o d /dz i a fluid. F ∆Vx =η A ∆Z

The more usual form of this relationship, called Newton's equation, states that the resulting shear of a fluid is directly proportional to the force applied and inversely proportional to its viscosity. The similarity to Newton's se o d la of F

=η

A ⇕

F =m

otio

Δ Δz

ƒ or

=η

A

Δ Δt

ƒ = ma) should be apparent in the expression below:

or

dvx dz

⇕

ƒ =m

dv dt

The SI unit of viscosity is the Pascal second [Pa s], which has no special name. The most common unit of viscosity is the dyne second per square centimeter [dyne s/cm2], which is given the name poise [P] after the French

physiologist Jean Louis Poiseuille (1799-1869). Ten poise equal one Pascal second [Pa s] making the centipoise [cp] and millipascal second [mPa s] identical (Glen E., 2013) 1 pascal second = 10 poise = 1,000 millipascal second 1 centipoise = 1 millipascal second There are actually two quantities that are called viscosity. The quantity defined above is sometimes called dynamic viscosity, absolute viscosity, or simple viscosity to distinguish it from the other quantity, but is usually just alled is osit . The othe

ua tit

alled ki e ati

is osit

ep ese ted

the s

ol ν " u" is the

ratio of the dynamic viscosity of a fluid to its density. ϑ =

μ

Where: µ is the dynamic viscosity and ρ is the density of the fluid

Kinematic viscosity is a measure of the resistive flow of a fluid under the influence of gravity. It is frequently measured using a device called a capillary viscometer which is the focus of our experiment. Before we dive fu the i to the e pe i e tal details, let’s e u e ate the ele a e of is osit to pet oleu

a d atu al gas

industries. In reservoir engineering, viscosity is of porous media has been used in conjunction with other petro-physical data to for reservoir characterization and saturations. Viscosity, which is a dynamic property does not directly influence the conductive capacity of petroleum reservoir rocks but is extensively used not only in petroleum engineering calculations to determine the absolute or effective permeability of reservoir rocks but also in reservoir estimation of hydrocarbon fluid in-situ. Q=− A μ

∆P ∆

where µ is the liquid viscosity expressed in centipoises

Viscosity is also a very important fluid property put into consideration by engineers to develop and drilling fluids for oil and gas exploration and production as wrong choice of drilling fluids could cause formation damage, loss of down hole tools and possibly, blowout, translating to enormous loss of lives, properties and financial ruins to oil companies and investors. Last but not the least, equipment used in oil and gas operations, use petroleum and non-petroleum products as lubricants to operate optimally. These equipment are designed to operate optimally at certain product specification. There proper operation depends on the viscosity of these products. Hence, accurate determination of viscosity is essential.

In this experiment, a fixed volume of liquids are made to flow under gravity through the capillary of a calibrated viscosimeter at a controlled temperature and the time it takes these fluids to flow are measured. The measured time are converted to centipoise using these set of equations: µ = δt [ .

9t −

14 . t

]

where

δt = δto[ + α To − T ]

OBJECTIVES: 

The objectives of this experiment is to measure the Saybolt viscosity of crude oil and liquid petroleum product at specified temperature between 70 degF and 140 degF



To check the alidit of A d ade’s e uatio

hi h e p esses is osit as a fu tio of te pe atu e.

THEORY REVIEW As stated earlier, viscosity is a measure of fluid resistance to flow or the measure of its resistance to gradual deformation by shear stress or tensile stress. As stated earlier, the focus of this experiment involves measuring the viscosity of crude oil and liquid petroleum products by means of a Saybolt viscosimeter which measures the elapsed time, known as Saybolt seconds, for a volume of liquid, at specified temperatures of 70 0F and 140 0F, to flow under gravity through the calibrated capillary of the viscosimeter. Generally, viscosity is usually determined by measuring the fluid flow through a capillary or orifice (PNG 482, Lab manual, 2013). This is e p essed i Poiseuille’s la : Q=

r4P

Where : Q = Liquid volume that flows per unit of time

μ

P = differential pressure between the capillary ends R = Radius of the capillary L = Length of the capillary µ = Fluid viscosity (dynamic viscosity)

The quantity defined above called dynamic viscosity, absolute viscosity, or simple viscosity to distinguish it from the other quantity, but is usually just called viscosity. The other quantity called kinematic viscosity ep ese ted ϑ =

μ

the s

ol ν

u is the atio of the is osit of a fluid to its de sit .

Where: µ is the dynamic viscosity And ρ is the density of the fluid.

Kinematic viscosity is a measure of the resistive flow of a fluid under the influence of gravity. It is frequently measured using a device called a capillary viscometer (Saybolt viscosimeter) which is the focus of our experiment. The concept of its measurement is based on the fact that when two fluids of equal volume are placed in identical capillary viscometers and allowed to flow under the influence of gravity, a viscous fluid takes longer than a less viscous fluid to flow through the tube. The time elapsed is then measured in Saybolt seconds (SUS), which can then be converted to absolute or kinematic viscosities using the equation above. The steps of conversion are shown below in equation 1 and 2: µ = δt [ .

9t −

14 . t

----------------------------------------------- equ 1

Where µ = Liquid viscosity, in centipoises δt = Specific gravity of liquid at temperature of liquid

T = Liquid viscosity, Saybolt seconds

δt = δto[ + α To − T ] ------------------------------------------ equ 2

Where δto = Specific gravity of liquid at (To) used as a reference point

α = Coefficient of thermal expansion of liquid with respect to To.

Values of α are provided for the samples under test.

Another focus of this experiment was to validate A d ade’s e uatio

hich expresses viscosity as a function

of temperature. During enhanced oil recovery process, especially in the prediction of oil recoveries in thermal recovery process, oil viscosity as a function of temperature is a very important physical quantity to consider for designing the appropriate techniques and transportation, storage and handling through high pressured pipelines. In general, the viscosity of a simple liquid decreases with increasing temperature (and vice versa). As temperature increases, the average speed of the molecules in a liquid increases and the amount of time they spend "in contact" with their nearest neighbors decreases. Thus, as temperature increases, the average intermolecular forces decrease. Hence using Andrade’s e uatio , o e a show that the relationship between liquid viscosity and temperature is a linear one when graph of viscosity is plotted against the reciprocal of the temperature on a semi-log paper or Log µ vs 1/T on Cartesian paper.

Andrade’s e uatio is µ = AeB/T Or

Logµ = LogA + B1/T1

Where T1 = Temperature of liquid, in degree absolute (Kelvin or Rankie) A & B a e o sta ts of A d ade’s E uatio a d B1= B. Log e EXPERIMENTAL SET-UP AND PROCEDURE         

All personal protective equipment were worn The cooling line was opened before beginning experiment and stopper was placed at the bottom of the cooling line. The chamber of the equipment was rinsed with isopropanol and emptied thereafter Crude oil was poured unto the chamber The viscosimeter was set to desired temperature and the fluid was allowed to reach this desired temperature. A stop watch was prepared, cork removed, timing was started. Once the liquid reached the 60ml mark line, timer was stopped. Temperature and time were recorded. Experiment was repeated for baby oil.

LIST OF MATERIALS AND EQUIPMENTS:    

An automated viscosimeter Thermometers Safety gloves, respirators and goggles Glassware (funnel, 60ml flask, 100ml pipet)

LIST OF SUBSTANCES USED DURING THIS EXPERIMENT: 

Sample crude oil or liquid petroleum products

ANSWER TO PRE-LAB QUESTION: 1). Viscosity: viscosity is a measure of fluid resistance to flow or the measure of its resistance to gradual deformation by shear stress or tensile stress. The SI unit of viscosity is the Pascal second Pa s (1 Pa s = 1 Kg/ms = 1 Ns/m2). The most common unit of viscosity is the dyne second per square centimeter [dyne s/cm2 ] = 1 g/cm s which is given the name poise [P]. Since Poise can be a large unit, a much smaller unit is used called the centipoise (cp) where 1 poise = 100 cp 2. The unit of Saybolt viscosity measurement is Saybolt seconds. Yes it can be converted to centipoises using the units of conversions: 1 Pa s = 1 Kg/m-s = 1 Ns/m2= 103 cp 3. Temperature and Liquid viscosity: In general, the viscosity of a simple liquid decreases with increasing temperature (and vice versa). As temperature increases, the average speed of the molecules in a liquid increases and the amount of time they spend "in contact" with their nearest neighbors decreases. Thus, as temperature increases, the average intermolecular forces decrease. Temperature and gas viscosity: While liquids get runnier as they get hotter, gases get thicker. The viscosity of gases increases as temperature increases and is approximately proportional to the square root of temperature. This is due to the increase in the frequency of intermolecular collisions at higher temperatures. Since most of the time the molecules in a gas colliding with one another and with the wall of the container in which they are enclosed, anything that increases the number of times one molecule is in contact with another will decrease the ability of the molecules as a whole to engage in the coordinated movement. The more these molecules collide with one another, the more disorganized their motion becomes, the higher the resistance to flow, hence the higher the viscosity. 4. Temperature of the measured fluid/liquid in degree Fahrenheit or Celsius Time in Saybolt seconds

REFERENCES: 1) A ala. L. F; Determination of Saybolt Viscosity of Crude Oil and Liquid Petroleum Products , Pennsylvania State University, PNG-482-006, Fall 2013 2) Gle Ele t: The Ph si s H pe te t ook, Viscosity. , 1998-2013

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