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Fuel Science and Technology International

ISSN: 0884-3759 (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/lpet19

ESTIMATING TEMPERATURE AND PRESSURE EFFECTS ON VISCOSITY OF SASKATCHEWAN HEAVY OILS B. Singh , A. Miadonye , S.S. Huang , R. Srivastava & V.R. Puttagunta To cite this article: B. Singh , A. Miadonye , S.S. Huang , R. Srivastava & V.R. Puttagunta (1994) ESTIMATING TEMPERATURE AND PRESSURE EFFECTS ON VISCOSITY OF SASKATCHEWAN HEAVY OILS, Fuel Science and Technology International, 12:5, 693-704, DOI: 10.1080/08843759408916202 To link to this article: http://dx.doi.org/10.1080/08843759408916202

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FUEL SCIENCE AND TECHNOLOGY INT'L., 12(5), 693-704 (1994)

Downloaded by [University Town Library of Shenzhen] at 10:39 18 October 2015

ESTIMATING TEMPERATURE AND PRESSURE EFFECTS ON VISCOSITY OF SASKATCHEWAN HEAW OILS

B. Singh*, A. Miadonye*. 5.5. Huang'*. R. Srivastava"

* **

Keywords:

and V.R.

Puttagunta'

School of Engineering, Lakehead U n i v e r s i t y Thunder Bay, O n t a r i o , Canada P7B SEl

Petroleum D i v i s i o n , Saskatchewan Research Council Regina, Saskatchewan, Canada S4N 5 x 1

Heavy o i l s , pressure, temperature, v i s c o s i t y c o r r e l a t i o n .

ABSTRACT P r e d i c t i o n s f o r v i s c o s i t y o f Saskatchewan heavy o i l s a r e v a l i d a t e d w i t h experimental d a t a a t v a r i o u s temperatures and a w i d e range o f pressures. Comparisons of p r e d i c t i o n s made w i t h a s i n g l e measured v a l u e and c u r v e - f i t v a l u e b o t h a t 30'C and 0 MPag p r e s s u r e showed t h a t r e s u l t s o b t a i n e d w i t h t h e l a t e r were i n b e t t e r agreement w i t h experimental values; w i t h o v e r a l l average a b s o l u t e d e v i a t i o n s o f 6.9% and 2.9%, r e s p e c t i v e l y . The r e s u l t s demonstrated t h a t extreme c a r e i s e s s e n t i a l i n measuring v i s c o s i t y a t t h e r e f e r e n c e temperature if a c c u r a t e p r e d i c t i o n i s t o be achieved w i t h t h e c o r r e l a t i o n ; and f u r t h e r m o r e t h a t t h e c o r r e l a t i o n can s u c c e s s f u l l y p r e d i c t heavy o i l s v i s c o s i t y .

INTRODUCTION

V i s c o s i t y data are required a t

reservoir

temperature and

v a r i o u s pressures f o r r e s e r v o i r performance and w e l l b o r e h y d r a u l i c s calculations.

Measurements

of

693 Copyright 0 1994 by Mamsl Dekkcr, lac.

viscosity

at

these

reservoir

SlNGH ET AL.

694

c o n d i t i o n s d u r i n g p r o d u c t i o n processes a r e n o t o n l y time-consuming b u t a l s o h i g h l y expensive.

Over t h e years, s e v e r a l workers have

proposed e m p i r i c a l methods f o r e s t i m a t i n g t h e v i s c o s i t y of heavy oils

and

bitumens


(Sanderson,

as

a function o f

1949; B r i g g s e t a l . ,

temperature

and

pressure

1984; Mehrotra and Svrcek, 1986,

1987; Q u a i l e t a l . , 1988). Most of these c o r r e l a t i o n s a r e based on p s e u d o c r i t i c a l parameters and t h u s y i e l d e d unacceptably h i g h average a b s o l u t e d e v i a t i o n s , w h i l e o t h e r s o n l y a p p l y t o s p e c i f i c samples o f bitumen.

I n o u r p r e v i o u s p u b l i c a t i o n s (Puttagunta e t a l . .

1989. 1993)

a p r e s s u r e t e r m based on t h e l i n e a r r e l a t i o n s h i p between v i s c o s i t y and p r e s s u r e was developed and i n c o r p o r a t e d i n t o o u r g e n e r a l i z e d one-parameter v i s c o s i t y - t e m p e r a t u r e c o r r e l a t i o n .

The p r e d i c t i o n s on

A l b e r t a heavy o i l s and bitumen y i e l d e d an average a b s o l u t e d e v i a t i o n below 5%.

T h i s paper presents d a t a f r o m Saskatchewan heavy o i l s a t

v a r i o u s temperatures and pressures n o t used i n t h e development o f t h e c o r r e l a t i o n parameters.

P r e d i c t i o n s a r e made f r o m a s i n g l e

v i s c o s i t y measurement a t 30'C, as w e l l as f r o m t h e v a l u e s o b t a i n e d by c u r v e - f i t t i n g techniques, a t one atmosphere pressure.

V i s c o s i t v C o r r e l a t i o n f o r Temoerature and Pressure

Sanderson

(1949)

equation

was

developed

for

kinematic

v i s c o s i t y o f o i l ; b u t t h e equations t o represent t h e e f f e c t s o f temperature and pressure on a b s o l u t e v i s c o s i t y o f bitumen came much l a t e r ( B r i g g s e t a l . . 1984; Mehrotra and Svrcek, 1986, 1987).

The model presented by B r i g g s e t a l . Puttagunta correlation.

et

al.

(1989)

to

develop

(1984)

the

was m o d i f i e d by

following

empirical

SASKATCHEWAN HEAVY OILS

S.


where

8,

and

d

are

c h a r a c t e r i z a t i o n parameter b.

695

parameters

which

depend

on

the

C i s a constant, T i s temperature i n

'C, P i s pressure i n MPag, and N i s v i s c o s i t y i n Pa.s.

Equation (1)

i s an e x t e n s i o n of t h e v i s c o s i t y - t e m p e r a t u r e c o r r e l a t i o n (Miadonye et 1

1992) t o i n c l u d e pressure parameters whose values were

o b t a i n e d f r o m a n o n - l i n e a r r e g r e s s i o n o f v i s c o s i t y w i t h pressure values.

The value o f r' obtained from t h e r e g r e s s i o n method was

0.99. The values f o r t h e parameters and constant were found t o be as f o l l o w s :

The v i s c o s i t y c h a r a c t e r i z a t i o n parameter b i s d e r i v e d f r o m one v i s c o s i t y measurement a t

30'C and one atmosphere:

The v i s c o s i t y values a t

30'C used f o r t h e p r e d i c t i o n s were

o b t a i n e d by measurements on t h e

corresponding dead o i l s .

To

e l u c i d a t e p o s s i b l e e r r o r s i n t h e p r e d i c t i o n due t o measurements.

SINGH ET AL.

696 30'C

values

obtained

by

curve-fitting

were

also

used

for

predictions.


V i s c o s i t y Data

The d a t a used f o r t h i s work were p r o v i d e d by Saskatchewan Research C o u n c i l ,

Regina,

r e s e r v o i r s coded A#1.

and o b t a i n e d f r o m samples

A#2.

B and C,

from

four

l o c a t e d i n Saskatchewan.

R e s e r v o i r s A # l and A#2 samples were drawn f r o m t h e L l o y d m i n s t e r a r e a a t a depth of

about 790 meters,

and R e s e r v o i r B samples were

o b t a i n e d f r o m t h e K i n d e r s l e y area a t t h e depth o f about 825 meters. R e s e r v o i r C i s a medium o i l sample taken a t t h e depth of about 1350 meters f r o m S w i f t C u r r e n t area.

A t o t a l o f 44 d a t a p o i n t s were

correlated.

V i s c o s i t y measurements a t h i g h pressures were performed u s i n g a PYT c e l l equipped w i t h an o n - l i n e viscometer.

I n f o r m a t i o n on t h e

e x p e r i m e n t a l procedures and t h e apparatus used have been documented i n an e a r l i e r p u b l i c a t i o n by Puttagunta e t a l . (1991).

RESULTS AND DISCUSSION

P r e d i c t i o n s on t h e d a t a s e t s were based on a s i n g l e v i s c o s i t y measurement, as w e l l as on v i s c o s i t y v a l u e obtained by c u r v e - f i t t i n g technique,

b o t h a t 30'C

and one atmosphere pressure.

Results

p r e s e n t e d i n Tables 1 and 2 a r e f o r R e s e r v o i r Samples A#l and B which d e p i c t s examples of

the percent e r r o r s obtained w i t h t h e

correlation.

The

sumnary

of

the

average

absolute

deviations

between

p r e d i c t e d and experimental v i s c o s i t i e s a r e d e p i c t e d i n T a b l e 3.

For

SASKATCHEWAN HEAVY

OILS TABLE

Experimental Data and P r e d i c t i o n s Measured and C u r v e - f i t Values.


(a)

S i n g l e Measurement:

I {(B I

Pressure Wag)

I

I for

Reservoir A # l

Based on

Measured V i s c o s i t y @ 30'C = 1.3101 Pa.s

Experimental Viscosity (Pa,s)

Predicted Jiscosity (Pa, s)

Error

Average Absolute D e v i a t i o n = 12.94%

(b)

C u r v e - f i t Technique:

Pressure

C u r v e - f i t V i s c o s i t y @ 30'C = 1.5070 Pa.s

Experimental Viscosity (Pa ,s)

Predicted Viscosity (Pa.s)

20 28 40 60 28 28 28 28 28 28 28

Average Absolute D e v i a t i o n = 3.92%

SlNGH FT AL. TABLE I1 E x p e r i m e n t a l D a t a and P r e d i c t i o n s f o r R e s e r v o i r B based on Measured and C u r v e - f i t V a l u e s .


(a)

S i n g l e Measurement:

Measured V i s c o s i t y @ 30'C = 1.3900 P a . s redicted iscosi t y (Pa.s)

Average A b s o l u t e D e v i a t i o n = 3.30%

(b)

C u r v e - f i t Technique:

-

C u r v e - f i t V i s c o s i t y @ 30'C

Tem

(T?

Viscosity

redicted iscosity (Pa,s)

Average A b s o l u t e D e v i a t i o n = 2.75%

-

1.3743 P a . s

SASKATCHEWAN HEAVY OILS TABLE I11


Summary o f P r e d i c t e d and Experimental V i s c o s i t y f o r t h e V a r i o u s Saskatchewan Heavy O i l s .

Tem

('cY

Samples

Pressure Range (MPag)

Viscosity @ 30'C (Pa, s) Measured

Reservoir A#l

I

Reservoir A#2

Reservoir B

I

Curve -fit

'AAD

I

Measured

I

Curve -fit

28

28

I

26

*Average Absolute D e v i a t i o n (AAD) =

p r e d i c t i o n s based on s i n g l e v i s c o s i t y measurement, t h e c o r r e l a t i o n y i e l d e d an o v e r a l l average absolute d e v i a t i o n o f 6.7%.

The h i g h e s t

average a b s o l u t e d e v i a t i o n s between p r e d i c t e d and experimental v i s c o s i t i e s were o b t a i n e d w i t h Samples A # l and C.

Conversely,

p r e d i c t i o n s based on c u r v e - f i t values a t 30'C showed s i g n i f i c a n t l y l o w e r magnitude o f d e v i a t i o n s from experimental values, o v e r a l l average absolute d e v i a t i o n o f 2.9%.

w i t h an

SINGH ET AL.

3


2.5 -

* 2

-

1.5 1.5

I

I

2

2.5

Experimental Viscosity, Pa.s. Figure 1

P r e d i c t e d v s Experimental Values

The reasons f o r t h e r e l a t i v e l y l a r g e r d i s c r e p a n c i e s o b t a i n e d when p r e d i c t i o n s a r e based on a s i n g l e v i s c o s i t y measurement c o u l d be due t o a combination o f several f a c t o r s .

Inconsistency i n the

experimental d a t a due t o l o s s o f v o l a t i l e components i n t h e sample f o r i n s t a n c e , can r e s u l t i n h i g h e r r o r s i n p r e d i c t e d values; u s u a l l y i n c r e a s i n g i n a s y s t e m a t i c manner.

F i g u r e 1 showed t h a t t h e e r r o r s

i n Sample A # l may be due t o i n c o n s i s t e n c y i n experimental values. P r e d i c t i o n s made w i t h c u r v e - f i t values a t 30'C a r e s c a t t e r e d about t h e d i a g o n a l l i n e , i n d i c a t i n g a c l o s e match w i t h t h e e x p e r i m e n t a l values.

Conversely, t h e p r e d i c t i o n s made from a s i n g l e v i s c o s i t y

measurement a t 30.C a r e c h a r a c t e r i z e d by l a r g e d e v i a t i o n s f r o m t h e


SASKATCHEWAN HEAVY OILS

PA -

A

...

Experimental viscosity Predictions with curve-fit value Predictions with measured value

- 9 . 1 4

0

8

12

Pressure, MPag. Figure 2

Conparison o f P r e d i c t e d and Experimental V i s c o s i t i e s a t D i f f e r e n t Pressures f o r R e s e r v o i r Sanple B

d i a g o n a l l i n e (Figure 1).

S i m i l a r r e s u l t s were o b t a i n e d f o r t h e

v a r i a t i o n o f v i s c o s i t y w i t h pressure f o r Samples 6 and C (Figures 2 and 3).

However,

f o r Sample 6 (Figure 2) b o t h p r e d i c t e d values

c l o s e l y match t h e experimental v i s c o s i t y , which i n d i c a t e s t h a t t h e data set i s very consistent. Furthermore, i n a c c u r a t e t e m p e r a t u r e a n d v i s c o s i t y m e a s u r e m e n t s a t t h e r e f e r e n c e c o n d i t i o n s , can i n t r o d u c e unsystematic e r r o r s i n t h e p r e d i c t e d values, (Miadonye e t a l . .

as documented i n our p r e v i o u s p u b l i c a t i o n

1992).

T h i s i s why extreme care i s e s s e n t i a l i n

SlNGH ET AL. -

r Experimental viscosi - Predicted with curve. 11v a l ~ o ... Preacled wltn measurea value

1


...'...' ,..'...'

,,.

Pressure, MPag Figure 3

Conparison o f P r e d i c t e d and Experimental V i s c o s i t i e s a t D i f f e r e n t Pressures f o r R e s e r v o i r Sanple C

making t h e s i n g l e measurement and t o make sure t h a t v a p o r i z a t i o n o f v o l a t i l e compounds i s avoided.

From t h e r e s u l t s o b t a i n e d i t i s obvious t h a t t h e c o r r e l a t i o n can a c c u r a t e l y p r e d i c t t h e combined e f f e c t s o f temperature and p r e s s u r e on t h e v i s c o s i t y of heavy o i l s , based on a s i n g l e v i s c o s i t y measurement a t

30'C.

The c o r r e l a t i o n accuracy i s c o n s i d e r a b l y

improved i f measurement e r r o r i n t h e d a t a o r r e f e r e n c e c o n d i t i o n s , i s nominal.

T h i s was e v i d e n t i n t h e r e s u l t s where p r e d i c t i o n s based

30'C.

on a s i n g l e v i s c o s i t y measurement and c u r v e - f i t

value a t

yielded

6.9% and 2.9%.

overall

respectively.

average a b s o l u t e d e v i a t i o n s

of

SASKATCHEWAN HEAVY OILS NOMENCLATURE

AAD = average a b s o l u t e d e v i a t i o n b = v i s c o s i t y c h a r a c t e r i z a t i o n parameter


B,

-

pressure parameter which depends on b

C = c o n s t a n t i n v i s c o s i t y - t e m p e r a t u r e term d

pressure parameter which depends on b

N = number o f d a t a p o i n t s P = pressure i n MPag r = regression c o e f f i c i e n t

s T

-

temperature parameter which depends on b temperature i n 'C

v = a b s o l u t e v i s c o s i t y i n Pa,s ACKNOWLEDGEMENTS

The a u t h o r s g r a t e f u l l y thank Saskatchewan Research C o u n c i l . Canada, f o r p r o v i d i n g t h e data.

F i n a n c i a l support was p r o v i d e d by

N a t u r a l Sciences and Engineering Research C o u n c i l , and A l b e r t a O i l Sands Technology and Research A u t h o r i t y , Canada.

REFERENCES

B r i g g s , I . P . . V.R. Puttagunta and N.B. Khjamel, 1984. The V i s c o s i t y of Heavy O i l and Bitumen which Contain Subsaturated Concentrations o f Carbon D i o x i d e . WRI-WE Tar Sand Symposium, V a i l Colorado. Mehrotra, A.K. and W.Y. Athabasca Bitumen.

Svrcek. 1986. V i s c o s i t o f Compressed Can. 1 . Chem. Eng.. 64: i44-7.

Mehrotra, A.K. and W.Y. Svrcek, 1987. V i s c o s i t y of Compressed Cold Lake Bitumen. Can. I.Chem. Eng.. 65: 672-5. Miadon e, A. 8. Singh and V.R. Puttagunta. 1992. M o d e l l i n g t h e h s c o s i t y - ~ e m p e r a t u r e Relationship of A l b e r t a Bitumens. Fuel S c i . and Techn. I n t e r . , i n p r i n t . P u t t a g u n t a , V.R., 5. Singh and E. Cooper, 1989. A G e n e r a l i z e d V i s c o s i t y C o r r e l a t i o n of A l b e r t a Heavy O i l s and Bitumens. Proceedina 4 t h UNITAR/UNDP I n t e r . Conf. on Heavv Crudes and T a r Sands; Edmonton, A l b e r t a , Canada.

704

SlNGH ET AL.

Puttagunta, V.R., A. Miadonye and B. Singh, 1993. C o r r e l a t i o n o f Bitumen V i s c o s i t y w i t h Temperature and Pressure, Can. I.Chem. Eng., i n p r i n t .


Q u a i l , B., G.A. H i l l and K.N. I h a , 1988. C o r r e l a t i o n s o f V i s c o s i t y , Gas S o l u b i l i t y and Density of Saskatchewan Heavy O i l s . I n d . Eng. Chem. Res.. 27: 519-23. Sanderson, R.T., 1949. Lubricating Oils.

RECEIVED: ACCEPTED:

May 18, 1993 June 8, 1993

V i s c o s i t y , Temperature and Pressure o f I n d . Eng. Chem.. 41: 2059-61.