Ingenieria

S PE
S ociety o f P etroleLm E ngineers o f AIM E

SPE 12171
Low Interfacial Tension Relative Permeability
by L.W. Harbert, A moco Production Co.
Member SPE-AIME
Copyright 1983 Society of Petroleum Engineers of AIME
This paper was presented at the 58th Annual Technical Conference and Exhibition held in San Francisco. CA, October 5 -8, 1983. The material is subject
to correction by theauthor. Permission to copy is restricted to an abstract of not more than 300 words. Write SPE, 6200 North Central Expressway,
Drawer 64706, Dallas, Texas 75206 USA. Telex 730989 SPEDAL.

ABSTRACT
EOR p rocesses t hat f eature a n ear m iscible p rocess, CO 2 i njected b elow t he minimum m iscibility
p ressure o r m icellar f luids, r equire r elative p ermeability d ata t o c alculate t he flow b ehavior o f t he
l ow i nterfacial t ension ( low 1FT) f luids. The f low
b ehavior o f l ow 1FT f luids d iffers f rom t hat o f c onventional g as a nd o il o r w ater a nd o il; i t d epends
u pon 1 FT, v iscosity, a nd f low r ate a s w ell a s t he
r ock p roperties o f p ore s ize d istribution a nd w ettability. The r esults o f l aboratory c ore t ests u sing
a n a lcohol, brine, a nd o il f luid s ystem i n o utcrop
a nd r eservoir r ock s amples a re p resented. B oth
w ater a nd o il r elative p ermeability c urves w ere
f ound t o s hift u pward, i ndicating t he two p hases
i nterfere l ess w ith e ach o ther a s 1FT i s r educed.
F or a g iven r eservoir r ock t ype, t he f low b ehavior
i s a dequately c haracterized b y a c apillary n umber
d efined b y combined ( total) f luid v elocity, a verage
v iscosity, a nd i nterfacial t ension. I t was a lso
f ound t hat f low t ests o n r epresentative r eservoir
r ock s amples a re n ecessary t o d escribe l ow i nterfacial t ension r elative p ermeability f or f ield p rocess
p erformance c alculations.

d irection o f b etter u nderstanding o f l ow 1FT
r elative p ermeability.
THEORY ANDDEFINITIONS
The s caling p arameters r elating l aboratory c ore
t est r esults t o f ield p erformance m ust i nclude a ll
t he m ajor v ariables c ontrolling l ow 1FT f low
b ehavior. I f p ore s ize d istribution a nd w etting
p reference a re c onsidered r ock p roperties,l t he
r emaining v ariables a re f low r ate, v iscosity; a nd
i nterfacial t ension. S ince t he c ombined viscosities
o f t he f luids i n t he s ystem p roduce t he v iscous
f orce, t he a verage o f t he o il a nd w ater p hase v iscosities i s u sed i n t his s tudy. L ikewise, t he
v elocity o f t he p hases i s c onsidered t o b e r epresented b y t he c ombined ( total) v elocity; t hat i s,
t he t otal f low r ate d ivided b y t he t otal c rosssectional a rea. 2 T he p roduct o f t he a verage viscosity a nd t he t otal v elocity o f t he f luids
r epresents t he v iscous f orces. The c apillary f orces
a re r epresented b y t he i nterfacial t ension,3 a nd t he
q uotient o f t he v iscous a nd c apillary f orces i s
d efined a s t he c apillary n umber, N.

INTRODUCTION
Low i nterfacial t ension d isplacement t ests h ave
b een c onducted i n r eservoir r ocks a nd r eported, a ndsome o f t he e ffects o f l ow i nterfacial t ension o n
r elative p ermeability h ave b een known s ince t he
1 950's. O nly i n t he p ast f ew y ears h as t he u nderstanding o f t he c ombined e ffects o f f luid v elocity,
v iscosity, a nd i nterfacial t ension b een p ublished.
T oday, m ore e xperimental w ork t han e ver b efore i s
b eing c onducted t o q uantify t he e ffects o ff luid
1 FT, v elocity, a nd v iscosity a nd r ock w etting p reference a nd p ore s ize d istribution. I n s ystems
w here t he d isplacing a nd d isplaced p hases a re m iscible a nd v elocity i s l ow e nough s o t hat t he p rocess
i s c ontrolled b y d iffusion, t he f ractional f low v s
s aturation c urve i s a 4 5° l ine. B ut, w here 1FT i s
f inite a nd t here i s no mass t...