(Steam-CO 2 Drive Experiments Using Horizontal and Vertical)

8/12/2019 (Steam-CO 2 Drive Experiments Using Horizontal and Vertical)

1/17

ELSEVIER

Journal o f Petroleum Science and E ngineering 18 (1997) 113 - 129

S t e a m C O 2 d r iv e e x p e r i m e n t s u s i n g h o r i z o n t a l a n d v e r ti ca l w e l l s

F Giim rah , S . Ba~ cl

Petroleum and Natural Gas Engineering Department Middle East Techmcal University 06531 Ankara Turkey

Rece wed 4 July 1996; accepted 17 January 1997

A b s t r a c t

R e s e a r c h i n t o t h e a p p l i c a t i o n o f a s i m u l t a n e o u s s t e a m - C O 2 d ri v e p r o c e s s a n d t h e e x a m i n a t i o n o f v e r t i c a l an d h o r i z o n t a l

i n j e c t i o n - p r o d u c t i o n w e l l c o n f i g u r a t i o n s w a s c o n d u c t e d i n a p h y s i c a l m o d e l o f 1 / 1 2 t h o f a n i n v e r t e d r e g u l a r s e v e n - s p o t

p a t t er n t o d e t e r m i n e t h e r e c o v e r y p e r f o r m a n c e o f 1 2 . 4 A P I h e a v y o i l . T h r e e g r o u p s o f w e l l c o n f i g u r a ti o n s w e r e m a i n l y

i n v e s t i g a te d : a v e r t i c a l i n je c t i o n a n d p r o d u c t i o n w e l l s s c h e m e ( g r o u p 1 ), a v e r t i c a l in j e c t i o n a n d h o r i z o n t a l p r o d u c t i o n w e l l s

s c h e m e ( g r o u p s 2 A a n d 2 B ) , a n d a h o r i z o n t a l i n j e c t i o n a n d p r o d u c t i o n w e l l s s c h e m e ( g r o u p s 3 C a n d 3 D ) . A t o t a l o f 1 7

e x p e r i m e n t s o f w h i c h h a v i n g f i v e s t e a m - a l o n e a n d t w e l v e s t e a m - C O 2 p r o c e s se s w e r e c o n d u c t e d f o r th e a b o v e w e l l

c o n f ig u r a t io n s .

I n s t e a m - a l o n e t e s t s , th e v e r t i c a l i n j e c t o r a n d h o r i z o n t a l p r o d u c e r s c h e m e ( g r o u p 2 B ) s u p p l i e d a h i g h e r r e c o v e r y t h a n t h a t

o f t h e o th e r s. T h e o i l re c o v e r y w a s 3 3 . 6 % o f o r ig i n a l o i l i n p l a c e ( O O I P ) i n g r o u p 2 B c o m p a r e d t o 7 . 8 % o f O O I P f o r t h e

v e r t i c a l i n j e c t i o n a n d p r o d u c t i o n w e l l s s c h e m e ( g r o u p 1 ) a t 1 p o r e v o l u m e ( P V ) o f s t e a m i n j e c t e d . T h e l o w e s t u l t im a t e

r e c o v e r y w a s o b t a i n e d f r o m t h e h o r i z o n t a l i n j e c t o r - h o r i z o n t a l p r o d u c e r w e l l c o n f i g u r a t i o n ( g r o u p 3 C ) .

F o r s t e a m - C O ~ t e s t s , o i l r e c o v e r i e s w e r e 5 8 . 3 % a n d 2 5 . 3 % o f O O I P f o r a C O 2 / s t e a m r a t io o f 1 4. 2 d m 3 / 1 i n g r o u p 2 A

a n d t h e h o r iz o n t a l i n j e c t o r a n d p r o d u c e r ( g r o u p 3 C ) w i t h a C O 2 / s t e a m r a t i o o f 1 3 .4 d m 3 / 1 , r e s p e c t i v e l y . T h e c o - i n j e c ta o n o f

C O 2 w i t h s t e a m i n c r e a s e d t h e u l t i m a t e o i l r e c o v e r y a n d t h e p r o d u c t i o n r a te o v e r s t e a m a l o n e . T h e r e c o v e r y e f f i c i e n c y o f

h o r i z o n t a l i n j e c t o r - h o r i z o n t a l p r o d u c e r ( g r o u p 3 C ) w a s a l s o t h e l o w e s t o n e , b u t v e r t i c al i n j e c t o r - h o r i z o n t a l p r o d u c e r ( g r o u p

2 A ) g a v e t h e b e s t p e r f o r m a n c e w h e n c o m p a r e d t o o t h e r t e s t s .

W h e n s t e a m - a l o n e a n d s t e a m - C O 2 t e st s w e r e c o m p a r e d , t h e o i l r e c o v e r y i n c re a s e d w i t h i n c r e a s i n g C O 2 / s t e a m r a t i o t i ll

a n o p t i m u m v a l u e w a s re a c h e d , a ft e r w h i c h a d i m i n i s h i n g e f f e c t w a s o b s e r v e d . T h e o p t i m u m C O 2 / s t e a m r a t io fo r

m a x i m i s i n g o i l r e c o v e r y w a s ~ 1 4 d m 3 / 1 f o r a ll w e l l c o n f i g u r a ti o n s . T h e r e f o r e t h e v a l u e o f C O 2 / s t e a m r a t io w a s o n e o f

t h e i m p o r t a n t f a c t o r s w h i c h a f f e c t e d th e p e r f o r m a n c e o f t h e p r o ce s s . T h e o t h e r f a c t o r w h i c h i n f l u e n c e d t h e o i l r e c o v e r y w a s

t h e w e l l t y p e o f i n j e c t o r a n d / o r p r o d u c e r w h e t h e r i t i s h o ri z o n t a l o r v e r ti c a l . T h e d i s ta n c e b e t w e e n t h e w e l l s a l s o a f f e c te d

t h e e f f i c i e n c y o f t h e p r o ce s s . T h e p r i m a r y m e c h a n i s m s f o r t h e m o b i l i s a t i o n o f o i l w e r e v i s c o s i t y r e d u c ti o n , s t e a m d i s t i l la t i o n ,

s t r ip p in g a n d g a s d r iv e e f f e c t o f C O 2 .

Keywords: stea m -CO 2 drive: physical model; vertical-ho rizontal wells , heavy-oil recovery

1 I n t r o d u c t i o n

* Correspo nding author. Fax:

Fevz i@ orqual.cc.metu.edu.tr

90-312-2101271; e-maih

H e a v y - o i l r e s e rv o i r s p re s e n t p r o d u c t i o n p r o b l e m s

b e c a u s e t h e h i g h o i l v i s c o s i t y a n d l o w r e s e r v o i r

e n e r g y r e s u l t i n l o w r e c o v e r y r a t e s a n d p o o r r e c o v -

092 0-41 05/ 97/ 17. 00 Copyright 1 997 Elsevier Science B.V. All r ights reserved.

PII S 0 9 2 0 - 4 1 0 5 ( 9 7 ) 0 0 0 0 3 - X


2/17

4 F. Gf imrah , S. Ba~c t / Journa l o f Pe t ro leum Sc ience and Engm eermg 18 11997 113- 129

ery efficiency when compared to those of conven-

tional oil reservoirs. The most widely used thermal

technique to extract residual oil from heavy-oil fields

is steam injection (Chu, 1985). There is an interest in

using CO 2 gas as immiscible phase for recovering

heavy oil (Roadifer, 1986). In heavy-oi l reservoirs, a

combination of steam and non-condensable gases

can be used to increase heavy-oil production. In

Turkey 80 of the oil reservoirs are heavy-oil reser-

voirs (Kantar and Topkaya, 1983). These heavy oils

are usually mobile at reservoir conditions and most

can be produced with primary production but recov-

ery is very low. The Bat1 Kozluca Field which has

98 106 stb crude oil with 12.4API is located in

the southeastern region of Turkey. The presence of

the Dodan natural gas field having 93 of CO~

close to the oil field may favour the use of the CO 2

injection process with steam. In the following para-

graphs, the results of field tests, simulation studies

and laboratory experiments for the combined use of

steam and gases are reviewed.

Steam-air stimulation f ield tests were reported

by Rintoul (1979) and Meldau et al. (1981). The

improvement in oil recovery over conventional steam

stimulation was recorded in these applications. Sperry

(1981) reported the results of the Vapour Therm

system in three different fields in the U.S. mid-conti-

nent region. An improvement in oil/steam ratio was

achieved. The steam-generating systems such as

downhole steam generators (Fox et al., 1981), the

Vapour Therm process (Sperry, 1981). and the

wet-air oxidation technique (Wilhelmi and Knopp,

1979) consider the injection of produced non-con-

densable gases with high-quality steam into the

reservoirs. The injection of gases together with steam

is believed to benefit the recovery process by the

presence of non-condensing gas phase. Schirmer and

Eson (1985) reported the concept of using a direct

fired downhole steam generator in thermal oil recov-

ery projects in the Kern River Field, California. The

oil/steam ratio and peak production rate obtained

from downhole the steam generator were higher

compared to previous responses with conventional

steam injection.

Numerical reserL oir simulato rs have been used to

predict the effect of various conditions on the use of

non-condensable gases with steam for oil recovery

(Weinstein, 1974; Fox et al., 1981; Meldau et al.,

1981; Balog et al., 1982; Leung, 1982; Claridge and

Dietrich, 1983; Stone and Malcolm, 1985a,b). Co-in-

jection of a non-condensable gas with steam acceler-

ated the oil production compared to the steam-only

case. The ultimate recovery in a certain period was

about the same for both cases, or higher for the

co-injection case, depending on operating and reser-

voir conditions. This indicates that an interpretation

of simulation studies should be made with awareness

of the conditions studied.

The results of l abora to~ experimen ts which have

been conducted to study the expected beneficial ef-

fect of co-injecting a non-condensable gas together

with steam are summarised in the following para-

graphs. Ozen (1967) conducted a laboratory experi-

ment to test the effect of co-injection of nitrogen gas

on steam flood residual oil saturation. It was found

that N2-steam flooding increased the oil recovery by

~ 4- 5 more compared to the steam-only case.

This result was attributed to the presence of gas in

the core which would aid in the distillation of crude

leading to increased oil recovery. Slobod and Mer-

riam (1969) investigated the contribution of factors

as gas drive and vaporisation to improve the effi-

ciency of displacement o f oil by steam flooding. But,

hot water was used to introduce heat into the system,

and nitrogen was used to provide a vapour space in

the porous system to isolate the actions produced by

heat alone and vaporisation alone. Pursley (1975)

carried out experiments to investigate the effect of

injecting air, methane, or CO 2 on steam stimulation.

A dramatic improvement in the oil/steam ratio was

observed as a result of injecting methane or air. The

addition of CO~ was somewhat less effective be-

cause of its high solubility in water. Fox et al. (1981)

conducted laboratory experiments to examine recov-

ery with soluble gas-steam drive using core sam-

ples. It was found that soluble gas-steam drive

recovered more rapidly than the steam-only case.

Redford (1982) reported the effects of adding CO 2

or ethane to steam in a 3-D physical model. Adding

of CO 2 or ethane to steam greatly improved the

recovery of Athabasca tar sand over that recovered

with other additives. This was attributed to a solution

gas drive effect which produced the fluid from the

cooler portion of the reservoir. Briggs et al. (1982)

presented the results of a 1-D physical simulator of

cyclic steam injection with CO~ and naphtha addi-


3/17

F. Giimrah, S. Ba~ct / Journal of Petroleum Sctence and Engineering 18 1997) 113-129

115

rives. The experiments were done with Athabasca tar

sand. The use of CO 2 with steam improved recovery

primarily by providing additional drive energy on the

depletion portion o f the cyclic process. Harding et al.

1983) reported results of a physical model study of

steam flooding with nitrogen and CO 2 additives

which were injected into a linear porous medium

saturated with a moderately viscous refined oil and

water. It was observed that the simultaneous injec-

tion of the gases with steam resulted in a significant

improvement in the ultimate recovery of the crude

oil. Paracha 1985) studied the effects of CO~ addi-

tion to steam in a 1-D laboratory model on heavy

oils. The results indicated that although CO: with

steam increased the rate o f recovery significantly, the

oil viscosity and hence the API gravity were en-

larged. Stone and Malcolm 1985b) conducted high-

pressure steam-C O, co-injection experiments in a

1-D physical model with Athabasca tar sand. The

results from the experiments were compared with

results from a numerical model study. Both models

gave results that co-injection of CO z and steam

increased ultimate recovery. Stone and Nasr 1985)

analysed the use of s tea m-CO 2 and s tea m-N 2 mix-

tures in a set of continuous injection experiments in

a test bed. The addi tion of CO 2 to the steam resulted

in a significant change in the displacement mecha-

nism. An enhanced bitumen stripping and the forma-

tion of a gas zone around the injection well resulted

in increased conformance in the test bed and in-

creased bitumen production, as well as in bitumen

viscosity reduction due to d issolved CO 2 and an

increased pressure gradient between the injection and

production wells. Stone and Ivory 1987) carried out

steam-C O 2 experiments in a large pressure oil sand

vessel. CO 2 pre-soak followed by steam injection,

steam-C O 2 co-injection and steam, CO, and solvent

co-injection experiments were employed to under-

stand the mechanisms behind recovery processes. In

all cases investigated, the addition of CO~_ to steam

resulted in improved utilisation of injected energy

and improved the oil recovery over that from steam

alone. Nasr et al. 1987) studied the effects of steam,

ste am-C O 2, ste am-N 2 and stea m-CO R-N 2 mix-

tures on bitumen recovery from oil sands by using a

3-D physical model. The test results showed that the

addition of flue gas to steam substantially improved

both rate and ultimate recovery of bitumen as com-

pared to that obtained by steam alone. The steam-

CO 2 mixture was superior to either the steam-N 2 or

steam-flue gas combinations. Giimrah and Okandan

1987) studied simultaneous steam-CO, injection

processes in a 1-D physical limestone pack model

with heavy oils. The results indicated that an opti-

mum COJsteam injection ratio was present. The

ste am-C O 2 process accelerated production of heavy

oil above that of the steam-only case. Doscher et al.

1988) conducted scaled physical model experiments

to investigate the advantage of using high-velocity

gas injection for recovering reservoir fluids, the in-

jection of gas and steam after steam breakthrough for

increasing the profitability of some steam drives and

the use of specially fractured horizontal wells to aid

in the profitable production of viscous hydrocarbons.

Frauenfeld et al. 1988) conducted physical model

experiments to study the effects of a steam injection

process. For oils without an initial gas content, co-in-

jection of CO 2 with steam was capable of improving

oil recovery over that obtained with steam alone.

When an initial dissolved gas was present, co-injec-

tion of CO 2 was not beneficial. Injection o f CO 2 or

CH slugs just before steam injection was beneficial

in increasing oil recovery for experiments where an

initial dissolved gas was present. Metwally 1990)

conducted a laboratory program for the Lindbergh

Field, Alberta, to investigate the effect of CO~ and

methane on the performance of steam processes. The

results indicated that the presence of a non-con-

densable gas improved steam injectivity. Injectivity

improvement was most pronounced when a gas slug

was injected prior to steam injection, but the pres-

ence of a non-condensable gas with steam did not

improve recovery and resulted in much higher resid-

ual oil saturation compared to steam injection alone.

Hornbrook et al. 1991) carried out a high-pressure

1-D laboratory displacement study to evaluate the

effects of adding CO 2 to steam on the recovery of

West Sak crude oil. It was found that adding CO 2 to

steam improved the recovery and recovery rate of

the crude over conventional steam flooding. Giimrah

and Okandan 1992) conducted steam-C O 2 experi-

ments in 1-D and 3-D laboratory models to evaluate

the benefits o f CO 2 addition to steam on the recov-

ery of heavy oils. The linear tests indicated that the

oil recovery increased with increasing CO2/steam

ratios until an optimum value was reached. Light-oil


4/17

116 F . G i im r a h , S . B a ~ c t / J o u r n a l o f P e t r o l e u m S c i e n c e a n d E n g i n e e r i n g 1 8 1 9 9 7 ) 1 1 3 - 1 2 9

r e c o v e r y w a s r e l a t i v e l y l e s s i mp r o v e d b y t h e a d d i -

t i o n o f C O 2 to t h e i n j e c t e d s t e a m ; h o w e v e r , t h e o i l

p r o d u c t i o n r a t e w a s i n c r e a s e d c o n s i d e r a b l y f o r a l l

o i ls . T h e p r o d u c t i o n o f l i g h te r - o i l f r a c t io n s i n c r e a s e d

w i t h i n c r e a s i n g CO 2 c o n c e n t r a t i o n a n d A P I g r a v i t y .

N a s r a n d P i e r c e 1 9 9 5 ) u s e d a h i g h - p r e s s u r e a n d

h i g h - t e mp e r a t u r e s c a l e d mo d e l t o e v a l u a t e o i l r e c o v -

e r y p r o c e s s e s b y a s e r i e s o f e x p e r i m e n t s o n s t e a m -

CO 2 i n j e c ti o n s t r a te g i e s f o r b o t t o m w a t e r r e s e r v o i r s .

T h e c o - i n j e c t i o n o f CO 2 w i t h s t e a m a c c e l e r a t e d a n d

i m p r o v e d o i l r e c o v e r y r a t e s a s c o m p a r e d t o s t e a m -

o n l y i n j e ct i on . T h e s t e a m - C O 2 c o n t i n u o u s i n j e c t i o n

r e s u l t e d i n a b e t t e r p e r f o r ma n c e t h a n t h a t f r o m

s t e a m - o n l y o r s t e a m - C O 2 s e q u e n t ia l i n je c t io n .

S t e a m- o n l y i n j e c t i o n r e s u l t e d i n a d r a ma t i c i mp r o v e -

m e n t i n o il r e c o v e r y a s c o m p a r e d t o h o t w a t e r - C O 2

in jec t ion .

N o e x p e r i m e n t a l d a t a k n o w n t o u s h a v e b e e n

p u b l i s h e d o n s t e a m f l o o d i n g i n th e p r e s e n c e o f C O 2

f o r Ba t l K o z l u c a c r u d e o i l . A l s o , t h e r e h a s n o c o m-

p a r a t i v e s t u d y b e e n m a d e o n t h e p e r f o r m a n c e o f

s t e a m - C O 2 p r o c e s s e s b y t h e u s e o f h o r i zo n t a l a n d

v e r t i c a l i n j e c t i o n - p r o d u c t i o n w e l l s . Be c a u s e o f th e

a mo u n t o f h e a v y o i l i n r e s e r v e a n d t h e p r e s e n c e o f a

n a t u r a l C O 2 s o u r c e , i t w a s d e c i d e d t o s t u d y t h e

e f f e c ts o f a d d i ng C O 2 t o s t e a m o n t h e r e c o v e r y o f

Ba t1 K o z l u c a h e a v y o i l a t l a b o r a t o r y c o n d i t i o n s .

2 Ex per i menta l a ppa ra tus a nd pro cedure

2 1 Laboratory model

I n r e c o v e r y p r o c e s s e s , t h e i n j e c t io n a n d p r o d u c i n g

w e l l s c a n b e a r r a n g e d i n s o m e t y p e o f p a t t e rn . F r o m

d .

@

p r o d u c l n g w i l l s

l l n m o f

_ _ l ~ l la rn o u n d ~ l ~

d v ~ l l p a e l n g

F i g . 1 . I n v e r t e d r e g u l a r s e v e n - s p o t w e l l a r r a y .

t h i s p a t t e r n a s ma l l e l e me n t c a n b e d e r i v e d b y s y m-

me t r y t o r e p r e s e n t t h e f l o o d i n a mo d e l s t u d y . T h e

f l o o d p e r f o r ma n c e f o r t h e e n t i r e p a t t e r n c a n b e d e -

v e l o p e d b y r e p r o d u c i n g t h e p e r f o r m a n c e o f t h e p r o -

c e s s i n t h i s s ma l l e l e me n t . T h e s ma l l e s t e l e me n t

f r o m t h e p a t t e r n t h a t c a n b e u s e d a s a mo d e l i s

d e r i v e d b y c o n s t r u c t i n g l i n e s t h r o u g h a l l p l a n e s o f

s y m m e t r y . T h e s e l i n e s o f s y m m e t r y r e p r e s e n t i nv a r i-

an t l i nes across which there i s no f low. In th i s work ,

t h e i n v e r t e d r e g u l a r s e v e n - s p o t p a t t e r n i s s t u d i e d .

T h i s p a t t e r n c o n s i s t s o f o n e i n j e c t i o n w e l l s u r -

r o u n d e d b y s i x p r o d u c i n g w e l l s . F i g . I s h o w s t h e

a r r a n g e me n t o f w e l l s i n a h e x a g o n a l a r r a y . T h e u s e

o f t h i s s y mme t r y t o d i v i d e t h e p a t t e r n i n t o s ma l l e r

e l e me n t s i s a l s o s h o w n i n F i g . 1 . T h e s h a d e d a r e a i s

t h e s ma l l e s t mo d e l l i n g e l e me n t o b t a i n e d f r o m t h i s

p a t t e r n a n d r e p r e s e n t s t h e mo d e l s h a p e u s e d . T h e

i n j e c t i o n w e l l o f t h e mo d e l a c t u a l l y r e p r e s e n t s 1 / 1 2

of an in j ec t ion wel l i n the pa t t e rn , where as the

T a b l e 1

T h e p r o p e r t i e s o f p h y s i c a l a n d p r o t o t y p e m o d e l s

P a t t e r n S c a l i n g p a r a m e t e r P r o t o t y p e P h y s i c a l m o d e l

1 / 1 2 t h o f i n v e r te d r e g u l a r 7 - s p o t 1 / 1 2 t h o f i n v e r te d r e g u l ar 7 - s p o t

D i s t a n c e b e t w e e n i n j e c t i o n L p / L m = a = 250 202 . 5 m

a n d p r o d u c i n g w e l l s

T h i c k n e s s H p / H m = a 2 5 . 0 m

P e r m e a b i l i t y K p / K m = l / a 4 0 .0 m D

P o r o s i t y 1 2 5 . 4

T e m p e r a t u r e - 5 0 . 0 C

O i l v i s c o s i t y 1 6 0 7 . 0 m P a s

T i m e

t p / t m = a z

4 3 . 4 d a y s

P r e s s u r e d r o p A p p / A P m = a 3 4 4 7 . 5 k P a

In jec t ion r a t e Q p / Q m = a 1 4.4 m 3 / d a y

8 1 . 0 c m

1 0 . 0 c m

10 . 0 D

3 8 . 0

5 0 . 0 C

6 0 7 . 0 m P a s

1 rn in

2 0 . 7 k P a

4 0 .0 c m 3 / m i n


5/17

F. Giimrah, S. Ba~cl / Journal of Petroleum Science and Engineering 18 1997) 113-129 117

WET TEST HEATER

METER HEAT ER ONTROLLER TEMPERATURECA NNE R CONT ROLLE R

~ i i - ~ ; 1 ~ 1 I ] 1 , ' t ' [ I ~ -ROTAMETER ~,J2 )~

',I .- ' ,', ,/ i k ,:,:,,','.~..... : co

r - - T - T _ l . . . . . . . . . o o L _ J

b : - . : : : -'/ - . . . . . . . . . . . . . . . . . . . . . J STEAM

SEPARATORS 3-D MOD EL GENERATOR

F i g . 2 . A s c h e m a t i c r e p r e s e n t a t io n o f t h e e x p e r i m e n t a l s e t u p .

G rou p 1 :vert ical in ject ion-vert ical production

Injection we ll (vertical)

. ~ T l e n g t h = 9 .7 cm

a = 40.5 cm ~ per fo ra tion= 4 x5 mm

P r o d u c t i o n e l l

vert ical) ~l~ _ , , / ~'~

length = 9 ,7 om

pe r fo r a ti on= 4 x5 mm h = 10o re

produotlon c = 81 m Injection

Well well

G rou p 2 : vert ical in ject ion-hor izon tal production

G r o u p 2 A P~

le ng th = 40,5 m / ~ ~ T

per fora t ion= 10 x 2 .5 mm f / -

r.5 ~ A I~ li l

~roduot lon InJeot lon

w e l l / . ~ w e l l

G r o u p 2 B . , / ~ ~

7.5

~ ~ o d u ~ o n Inj~=tlon

Well well

G r o u p 3 : horizontal in ject ion-hor izontal production

/ - In ject ion we l l (hor izontal)

j ~ l eng th =39 , 2 cm

G r o u p 3 C , / / ~ p e r f o r e t l o n = 10 x 2 .5 m m

inj~ tion

/

Group 3D. / / ~ o~ ,,~

7 .5 ~ L ~

produo~on inJeo~on

well w~l

F i g 3 . W e l l c o n f i g u r a t i o n s .


6/17

[ 18 F. Giimrah, S. Ba~,cl/Journal of Petroleum Science and Engineering 18 1997) 113-129

p r o d u c t i o n w e l l o f t h e m o d e l r ep r e s en t s 1 / 6 o f a

p r o d u c t i o n w e l l . T h e m o d e l w a s t r i a n g u l a r i n s h a p e .

A s c a l in g f a c t o r o f 2 5 0 w a s a s c e r t a i n e d t o c o r re -

s p o n d t o t h e p r o t o t y p e s i n t h e f i e l d . P u j o l a n d

B o b e r g ' s ( 1 9 7 2 ) t h e r m a l s c a l i n g a p p r o a c h w a s u s e d

i n th e d e s i g n o f t h e s c a le d m o d e l . T h e p r o p e r t i e s o f

t h e s c a l e d m o d e l a n d i t s c o r r e s p o n d i n g p r o t o t y p e a r e

g i v e n i n T a b l e 1 .

A s c h e m a t i c r e p r e s e n t a t i o n o f t h e e x p e r i m e n t a l

s e t - u p i s i l l u s t r a t e d i n F i g . 2 . T h e s e t - u p i s c o m p r i s e d

o f f o u r m a i n p a r t s : a s t e a m a n d C O 2 i n j e ct i o n s y s -

t e m , a p h y s i c a l m o d e l , a d a t a r e c o r d i n g s y s t e m a n d a

p r o d u c t i o n s y s t e m . T h e w e l l c o n f i g u r a t i o n s a r e d e -

l i n e a te d i n F i g . 3 . T h e m o d e l h a s a d i m e n s i o n o f 8 1

c m 7 0 . 1 c m x 4 0 . 5 c m w i t h a t h i c k n e s s o f l 0

c m . T h e t o p o f th e m o d e l w a s r e m o v a b l e a n d a c ts a s

a f l a n g e s o t h a t w a t e r , o i l a n d c r u s h e d l i m e s t o n e

m i x t u r e c a n b e p a c k e d e a s i l y . T o m e a s u r e t h e t h r e e -

d i m e n s i o n a l t e m p e r a t u r e d i s t r i b u t i o n i n s i d e t h e

m o d e l , 6 2 t h e r m o c o u p l e s w e r e i n s t a l l e d a t t h e t o p ,

c e n t r e a n d t h e b o t t o m p l a n e s o f th e m o d e l . I n s u l a t i n g

m a t e r i a l s a n d h e a t e r s w e r e a l s o u s e d i n t h e m o d e l .

2 2 Experimental procedure

T h e p r e m i x i n g m e t h o d w a s u s e d i n p r ep a r i n g t h e

u n c o n s o l i d a t e d l i m e s t o n e p a c k m i x t u r e s f o r t h e e x -

p e r i m e n t s . T h e w a t e r a n d c l e a n c r u s h e d l i m e s t o n e

w e r e m i x e d i n i ti a ll y t o m e e t t h e c o n d i t i o n s o f a

w a t e r - w e t s y s t e m . T h e n t h e o i l w a s m i x e d h o m o g e -

n e o u s l y w i t h t h e m t o y i e l d t h e d e s i r e d f l u i d s a t u r a -

t i o n s a n d c a r e f u l l y p a c k e d i n t o t h e m o d e l . T h e o i l

a n d w a t e r s a t u r a ti o n s w e r e c h o s e n a s 7 5 a n d 2 5 ,

r e s p e c t i v e l y , a n d k e p t t h e s a m e f o r e a c h e x p e r i m e n t .

T h e l im e s t o n e p a c k w i t h p o r e v o l u m e o f 5 3 7 3 c m 3

g i v e s 3 8 p o r o s i t y a n d a b s o l u t e l i q u id p e r m e a b i l i t y

o f 1 0 d a rc i es . A f t e r p a c k i n g , t he m o d e l w a s m o v e d

h o r i z o n t a l l y i n s i d e t h e i n s u l a t i o n j a c k e t , t h e s e t - u p

w a s t h e n p r e p a r e d f o r t h e t e s t a n d t h e m o d e l w a s

h e a t e d a p p r o x i m a t e l y t o 5 0 C w h i c h w a s t h e d e s i r e d

r e s e r v o i r t e m p e r a t u r e . T o i n i t i a t e a n e x p e r i m e n t , t h e

s t e a m g e n e r a t o r w a s b r o u g h t t o i t s m a x i m u m t e m -

p e r a t u r e a n d t h e m a s s f l o w c o n t r o l l e r w a s s e t t o t h e

d e s i r e d C O 2 f lo w r a t e. T h e s i m u l t a n e o u s i n j e c ti o n o f

s t e a m a n d C O 2 w a s s t ar te d . T e m p e r a t u r e d i s t r ib u t i o n

i n s i d e t h e m o d e l w a s c o n t i n u o u s l y r e g i s t e r e d . T h e

o t h e r p a r a m e t e r s t h a t w e r e r e c o r d e d t h r o u g h o u t t h e

t e s t s w e r e f l u i d i n j e c t i o n a n d p r o d u c t i o n p r e s s u r e s

O_

g

O

o

o

>

J

o

1 0 0 0 0

1

1O 0

0

BATI KOZLUCACRUDEOIL

1 0 2 0 3 0 4 0 g o 6 0 i o

8

T E M P E R A T U R E ( C )

F i g . 4 . V l sc o s i u e s f B a t lK o z lu c a r u d eo i l 12 . 4AP I) .

a n d o i l , w a t e r a n d g a s p r o d u c t i o n d a t a . T h e e f f l u e n t s

f r o m t h e m o d e l w e r e c o l l e c t e d in a t w o - s t a g e s e p a r a -

t i o n s y s te m . B o t h o f t h e m a r e o p e r a t in g a t a t m o -

s p h e r ic p r e s s u r e . T h e t o p o f t h e s e c o n d s e p a r a t o r w a s

c o n n e c t e d t o a w e t t e s t m e t e r t o m e a s u r e t h e a m o u n t

o f g a s p r o d u c e d . T o c o n t r o l t h e p r e s s u r e o f t h e

p r o d u c t i o n w e l l , b a c k p r e s s u r e r e g u l a t o r s w e r e l o -

c a t e d a t t h e f lu i d s t r e a m e n d o f th e f i rs t s e p a r a t o r

a n d a t t h e u p s t r e a m e n d o f th e f i r s t se p a r a to r . T h e

b a c k p r e s s u r e r e g u l a t o r s w e r e a d j u s t e d t o a p r e s s u r e

w h i c h w a s ~ 1 3 .8 k P a ( A p = 2 p s i ) l o w e r t h a n t h e

v a l u e o f i n j e c t i o n p r e s s u r e . T h e l i g h t e r - o i l f ra c t i o n s ,

w h i c h w e r e t e r m e d c o n d e n s a t e d u r i n g t h i s w o r k ,

w e r e p r o d u c e d f r o m t h e s e c o n d s e p a r a t o r . B a t 1 K o -

z l u c a c r u d e o i l ( 1 2 . 4 A P I ) f r o m s o u t h e a s t e r n T u r k e y

w a s u s e d . T h e v i s c o s i t y o f t h e o il s a m p l e i s il l u s -

t r a t e d i n F i g . 4 .

3 R e s u l t s a n d d i s c u s s i o n

A t o t a l o f 1 7 e x p e r i m e n t s w e r e c o n d u c t e d w i t h a

p h y s i c a l m o d e l r e p r e s e n ti n g 1 / 1 2 t h o f a n in v e r te d

r e g u l a r s e v e n - s p o t p a tt e rn . T h e a i m o f t h e p r e s e n t

s t u d y w a s t o i n v e s t ig a t e t h e p e r f o r m a n c e o f s te a m

f l o o d i n g i n t h e p r e s e n c e o f C O 2 f o r h e a v y - o i l r e c o v -

e r y b y u s i n g v e r t i c a l a n d h o r i z o n t a l w e l l c o n f i g u r a -

t i o n s . T h e e x p e r i m e n t a l c o n d i t i o n s a r e p r e s e n t e d i n

T a b l e 2 .

T h e e x p e r i m e n t s w e r e c o n d u c t e d u n d e r t h re e m a i n


7/17

F. Gi~mrah, S. Ba~ct / Journal of Petroleum Science and Engineering 18 1997) 113-129

119

Tab le 2

E x p e r i m e n t a l c o n d i t i o n s

STEAM NJECTION STEAM C0 2 INJECTION

ell

c o n f i g u r a t i o n c o = / , . ~ . ~ c o = c o = . . = o . ~ c o = ~ , . ~ = ~ . = . . . . c o = c o = / , .~ = ~o . = . . . c o =

P r m l J m R i ce R i t e : St wr n P r l ll l Jr e R l a R J I ~ p r u i J r l R i l l ~ ~ P r l l i J r l R a l R i m

(1112thof inverted egular7-s po t pa ttern) , a-,*o R-,,o ~=o Rmo

[dm3,4. ] [kP I] [c. tmin] [c/mtn] l [dm3/~] [kP i] [/~ ln] [c, 'mk' l ] fdm3/I . ] [kP I] [c/mt~][cc#n ln] . [~] [ I


8/17

1 2 0

F. Giimrah, S. Ba~cl / Journal of Petroleum Sctence and Engmeermg 18 1997) 113-129

dm3/1 were carried out. Fig. 5 compares the experi-

mental recoveries as a function of pore volumes of

injected steam as cold water equivalent (cwe). The

highest recovery was obtained with the CO2/steam

ratio of 22.3 din3/1. The oil recovery was the same

for the CO2/steam ratio of 84.3 dm3/l when com-

pared to the steam-only case. This result was at-

tributed to the highest amount of injected gas with

steam. As a result it might prevent the movement of

oil through the production well because of higher

mobility of gas. For the steam-alone test, the recov-

ery was increased after 1 PV of steam injection. The

22.3-dm3/1 CO~-st eam mixture recovered 34.4 of

OOIP and the steam-only case recovered 7.8 of

OOIP when 1 PV of steam was injected into the

model. The recovery of the steam-only case was

reached to 33.6 of OOIP when the injected amount

of steam was 1.68 PV. The steam/oil ratios were

6.83 cm 3/ cm 3 for the steam-only case, 18.83

cm 3/ cm 3 for the CO2/ ste am ratio of 84.3 dm3/1,

and 4.31 cm 3/ cm 3 for the CO 2/s tea m ratio of 22.3

dm3/l at the end of the tests. Therefore, a lower

amount of steam was required to produce the same

amount of crude at the CO2/steam ratio of 22.3

dm3/1.

3.1.2. Group 2; t erticaI injection-horizontal produc-

tion scheme

In this group of tests, a horizontal production well

was placed at two different locations of the model.

Therefore the experiments were done under two

subgroups, 2A and 2B. Scheme A includes a hori-

zontal production well along the shorter side of the

model and scheme B has a horizontal well located at

the longer side of the model (Fig. 3).

3.1.2.1. Group 2A. A total of four experiments were

conducted. The CO2/steam ratios were 14.2, 29.8

and 36.4 din3/1, and a steam-alone test was done to

compare the performance of the steam -CO 2 experi-

ments. Fig. 6 shows the results of these experiments.

The highest recovery was obtained for the

CO2/steam ratio of 14.2 dm3/I. The steam-only

case supplied the lowest recovery. The recoveries of

other tests were ranged between them. Oil recoveries

were 58.3 of OOIP for the CO2/ stea m ratio of

14.2 dm3/1, 43.2 of OOIP for 29.8 dm3/1, 41.9

of OOIP for 36.4 dm3/l , and 23.8 of OOIP for the

100

9 0 G R O U P 2 A

~ 8 0

oO 7 0 [ CO.STEAM~T[

6

[ u 5 0 -

0 4 0

0 _ , ~

w

r r 3 0 -

O 2 0 -

10-

0

0 0.5 1 1.5 2 2 5 3 5

S T E A M I N JE C T E D ( P V o f c w e )

F i g 6 . O i l r e c o v e r i e s f o r v e r t i c a l i n J e c t i o n - h o r i z o n t a l p r o d u c t i o n

s c h e m e g r o u p 2 A )

steam-only case. The steam/oil ratios at 1 PV of

steam injection were 5.6 cm3 /c m 3 for the steam-

alone test and 2.32 cm3 /c m 3 for the 14.2-dm3/1

CO2/steam ratio test. In all CO2-steam experi-

ments, the oil production rates were high and tapered

off rapidly after 1 PV of steam injection. The pres-

ence of a horizontal producer prevented the early

production of CO 2 gas which was accumulated at

the top of the model. Then, it exerted an extra force

to drive the heated oil through the production well.

The contact area of the horizontal production well is

four times larger than that of the vertical well. This

effect is also an important factor for higher oil

production rate.

3.1.2.2. Group 2B.

In this group, the production well

was placed along the longer side of the model, it has

the same length of the production well of group 2A.

A total of four experiments were done. One of them

is steam alone and the others are CO2-steam experi-

ments in which the CO2/steam ratios were 14.1,

24.3 and 140 din3/1. Fig. 7 shows the oil recoveries

of these tests. For the 14.1-dm3/1 test, the highest oil

recovery was obtained as 52.4 of OOIP. The re-

coveries were 36.0 of OOIP for 24.3 dm3/k 28.8

of OOIP for 140 dm3 /l, and 33.6 of OOIP for the

steam-only case. The highest COJsteam ratio case

recovered lower oil than that of the steam-only case.

The presence of a larger amount of CO 2 supplied

worst performance than the other cases. For higher

CO2/s tea m ratio, a larger amount of CO 2 was pro-


9/17

F. Giimrah, S. Ba~ct / Journal of Petroleum Science and Engineering 18 1997) 113-129

121

1 0 0 -

9o

E 8 o -

O 7 0 -

uJ 50-

O 4 0 - / ~

O _ - - - - - I ~ [o I

L _ J

r r 3 0 -

---_1

O 2 0

1 0 ~ . + . ~ , , ,

0

0 0 . 5 1 1 . 5 2 2 . 5

S T E A M I N J E C T E D ( P V o f c w e )

F i g . 7 . O l l r e c o v e r i e s f o r v e r t i c a l i n j e c U o n - h o r i z o n t a l p r o d u c t i o n

s c h e m e g r o u p 2 B )

1 0 0

G R O U P 3 C

9 0

~ 8 0 -

0 7 0 -

6 0 -

> .

r r

5 0 -

>

0 40 - ~

W

~ 3 0

2 0 ~

10-

0 : .~-~-- ~

0 0 . 5 1 1 . 5 2 2


F i g . 8 . O l l r e c o v e r i e s f o r h o r i z o n t a l i n j e c t i o n - h o r i z o n t a l p r o d u c -

t ion schem e g roup 3C).

duced, and as a result, steam followed the path

already swept by the CO 2. This result has also

pointed out the importance of using optimum mix-

ture of steam and COt in the tests. The ste am/ oi l

ratios at 1 PV of steam injection were 2.60 and 3.97

cm 3/ cm 3 for the stea m-CO 2 (14.2 dm3/1) and

steam-alone tests, respectively. The co-injection of

CO 2 with steam supplied better performance till a

certain CO2/steam ratio was reached.

3.1.3. Group 3; horizontal injection horizontal pro

duction scheme

3.1.3.1. Group 3C. The horizontal production well

was placed along the shorter side of the model. The

location is 2.5 cm higher than the bottom of the

model. In this group, two s team- CO 2 tests and one

steam-alone test were carried out to investigate the

performance of CO2-steam mixture in horizontal

well combinations (Fig. 8). Oil recoveries were

30.3 of OOIP for the CO2/ ste am ratio of 49.7

din3/1, 25.3 of OOIP for 13.4 dm3/1, and 8.8 of

OO1P for the steam-alone test. If the recovery of the

test of 49.7 dm3/1 CO2/steam ratio is compared

with the 13.4-dm3/1 case, a 3.7 times higher amount

of CO 2 had to be injected to attain only 20 incre-

mental oil recovery over the 13.4-dm3/1 case. There-

fore, the cost effect of injecting larger amounts of

CO 2 gas should be considered. Both st eam-C O,

tests recovered more oil than the steam-only case.

These results were also observed for the values of

steam/oil ratios. The steam/oil ratio was 16.6

cm 3/ cm 3 for the steam-only case, 5.8 c m3 /c m 3 for

the CO2/steam ratio of 49.7 dm3/l, and 5.2

cm 3/ cm 3 for the CO2/ ste am ratio of 13.4 din3/1.

3.1.3.2. Group 3D. The horizontal production well

was placed along the longer side of the model. The

location of horizontal injection well is the same as in

group 3C and its position is 2.5 cm higher than the

bottom of the model. Fig. 9 compares the recoveries

of two steam-C O 2 tests and one steam-alone test.

Recoveries were 51.1 of OOIP and 8.9 of OOIP

for the CO2/steam ratios of 11.7 and 38.1 din3/1,

respectively. For the steam-only case, it was 18.4

1 0 0

O

>-

t r

IaJ

>

o

o

w

rc

90

80-

7 0 -

60-

50-

40-

30-

20

10-

0 - . 4 -

0

G R O U P D ]

[ ' : ' ~ - ' ~ - ~ ' ~ = I ~ [ ]

]

]

0 . 5 1 1 . 5 2 2 . 5

S T E A M I N J E C T E D ( P V o f cw e )

F i g . 9 . O i l r e c o v e r i e s f o r h o r i z o n ta l i n j e c t i o n - h o r i z o n t a l p r o d u c -

t i o n s c h e m e g r o u p 3 D ).


10/17

122 F. Gi imrah , S . Ba~c t / Journa l o f Pe t ro leum Sc ience and Engineer ing 18 1997) 11 3-1 29

S T E A M O N L Y G R O U P 3 D

A IN JEC T ED ST E AM =O .0 4 5 PV A '

INJECTION

A I N J E C T E D S T E A M = l . 2 3 0 P V A

I N J E C T I O N

A I N J E C T E D S T E A M = 1 . 6 8 0 P V A '

I N JE C T IO N T e m p e r a t u r e s in C

P R O D U C T I O N I N J E C T I O N

Fig. 10. Temp erature distribution of steam-alone test for horizontal injec tion -ho rizo ntal production group 3D).

S T E A M - C O 2 G R O U P 3D

C 0 2 / S T E A M R A T I O = 3 8 . 1 d m 3 1 L

A I N JE C T E D S T E A M = 0 . 2 9 0 P V A '

f -d

INJE TION

A I N J E C T E D S T E A M = 1 , 2 9 0 P V A

I N J E C T I O N

A IN JEC T ED ST EAM = 2 .0 5 0 PV A '

I N J E C T I O N

T e m p e r a t u r e s in C

P R O D U C T I O N I N J E C T I O N

F i g . | 1 . T e mp e r atu re d i s t r i b u t io n o f s te a m- C O ~ te st f o r h o r i zo n ta l i n j e c t i o n - h o r i zo n ta l p r o d u c t i o n ( g r o u p 3 D ) ,


11/17

F. Gi~mrah, S. Ba~ct Journal of Petroleum Science and Engineering 18 1997) 113-129 123

o f O O I P . T h e s t e a m / o i l r a ti o s w e r e 8 .5 c m 3 / c m 3

f o r th e s t e a m- o n l y c a s e , 1 9 .8 c m 3 / c m 3 f o r t he 3 8 . 1 -

d i n 3 /1 c a s e, a n d 3 . 8 c m 3 / c m 3 f o r th e l l . 7 - d m 3 / 1

c a s e . I n t h i s s c h e me , t h e d i s t a n c e b e t w e e n t h e h o r i -

z o n t a l p r o d u c e r a n d t h e h o r i z o n t a l i n j e c t o r w a s t h e

o t h e r f a c t o r i n f l u e n c i n g t h e r e c o v e r y o f o i l f r o m t h e

m o d e l . T w o r e p r e s e n t a t i v e e x p e r i m e n t s , s t e a m o n l y

a n d s t e a m - C O z 3 8. 1 d m 3 / 1 ) a r e s e le c t e d t o s h o w

t h e t y p i c a l b e h a v i o u r o f t h e t e mp e r a t u r e d i s t r i b u t i o n

in the mo del tes t s F igs . 10 and 11). Te m pera tu re

d a t a w e r e t a k e n f r o m t h r e e l e v e l s : t o p , c e n t r e , a n d

b o t t o m o f t h e mo d e l . S t e a m t e n d s t o r e a c h t h e

p r o d u c i n g e n d b y f l o w i n g t h r o u g h t h e u p p e r p a r t s o f

t h e mo d e l . T h i s w a s d e mo n s t r a t e d b y t h e h i g h e r

t e mp e r a t u r e s b e i n g r e c o r d e d a t t h e t o p r a t h e r t h a n a t

t h e c e n t r e a n d b o t t o m o f th e m o d e l . E f f e c t i v e h e a t i n g

o c c u r r e d a f t e r s t e a m b r e a k t h r o u g h i n t h e v e r t i c a l l y

d o w n w a r d d i r e c t i o n a l o n g t h e mo d e l , i n d i c a t i n g

s t e a m- z o n e e n l a r g e me n t . A l a r g e r p o r t i o n o f t h e

m o d e l w a s t h e n h e a t e d b y s t e a m . T h e t e m p e r a t u r e s

o f t h e b o t t o m o f t h e mo d e l w e r e l o w e r i n t h e s t e a m-

a l o n e t e s t a s c o mp a r e d t o t h e s t e a m - C O 2 t es t.

3.1.4. Comparison between the runs

3.1.4.1. Steam-alone tests. A c o mp a r i s o n o f t h e r e -

c o v e r y e f f i c i e n c i e s o f d i ff e r e n t w e l l c o n f i g u r a t i o n s i s

s h o w n i n F i g . 1 2 . F r o m t h e c o m p a r i s o n o f o i l r e c o v -

e r i e s f o r s t e a m- a l o n e t e s t s o f f i v e w e l l c o n f i g u r a -

t ions , a ver t i ca l i n j ec to r and a hor i zon ta l p roducer

w e l l sc h e m e g r o u p 2 B ) g a v e a b e t t er p e r f o r m a n c e

t h a n t h e o t h e r te s ts . T h e r e c o v e r i e s w e r e t h e s a me f o r

t h e v e r t i c a l i n j e c t i o n - p r o d u c t i o n w e l l s s c h e me g r o u p

1 ) a n d t h e h o r i z o n t a l i n j e c t i o n - p r o d u c t i o n w e l l s

s c h e m e g r o u p 3 C) t i ll 1 .1 PV o f s t e a m i n j e c t io n i s

r e a c h e d . T h e n mo r e o i l w a s p r o d u c e d f o r g r o u p 1 .

A l t h o u g h t h e u l t i ma t e r e c o v e r i e s o f t h e v e r t i c a l i n -

j e c t i o n - h o r i z o n t a l p r o d u c t io n w e ll s s c h e m e g r o u p

2 A ) a n d g r o u p 1 w e r e t h e s a m e u p t o 2 P V o f s t e a m

i n j e c t i o n , t h e r e c o v e r y w a s mu c h h i g h e r u p t o 1 . 2

PV o f s t e a m i n j e c t i o n i n g r o u p 2 A . T h i s w a s a t -

t r i b u t e d t o t h e b e n e f i c i a l e f f e c t o f t h e h o r i z o n t a l

p r o d u c e r w h i c h a c c e l e r a t e d t h e o i l p r o d u c t i o n . T h e

l o w e s t u l t i ma t e r e c o v e r y w a s o b t a i n e d f o r g r o u p 3 C ,

t h e d i s ta n c e b e t w e e n t h e h o r i z o n t a l i n j e c t o r a n d h o r i -

1 0 0 -

9 0 -

8 0

0_

O 7 0

O

6 0

>-

n

LU 50-

>

O

j 4 0 -

LLI

r r

3 0 -

O

2 0 -

1 0 -

0 :

I S T E A M O N L Y

i v e r t J c a l l r t j - h o r i z o r r t a l p r o d g r o u p ? A ) I

_ _

I I I l I [

0 . 5 1 1 . 5 2 2 . 5


Fig. 12. Com parisonof oil recoveries or steam-alone ests.

3 3 . 5


12/17

124 F. Gi imrah , S . Ba~c t / Jo urna l o f Pe t ro leum Sc ience and Engineer ing 18 1997) 11 3-12 9

1 0 0

13..

0

0

>-

n,-

IJJ

>

0

0

HJ

r

0

9 0 - [ S T E A M - C O 2

I(C02/steam ra tio) I

8 0 - [ v o ~ . ,o , ~ o . = ~ r o d . o r o o ~ . 4 ~ , ]

~ 0 - I ~ . . . . ~ , ,o , -~ . . . . O , o r * .o ~ o o o ~ D , , ,~

6 0 , / ~ . ~ - E ~ . . . . . . . ~ . x

, . > , ~ , .. X ' [ v e ~ c a lm -hor i zonta l rod ,g roup2B 14.1

4 0 - ..~ > ~-c - - j m

~ u ..':~ r - - - -

. ~ ~ , l l I l - - . ~ ~ p r od . ,g r o u p (2 2 ..3 )]

2 0 4 j ~ ~ ~ -

, , ,

0 . 5

1 1 . 5 2


Fig. 13. Comparison of oil recoveries for steam CO~ tests.

2.5

zontal producer was another important factor for the

displacement of oil. At 1 PV of steam injection, the

recovery of group 2B was 33.6 of OOIP compared

to 7.8 of OOIP for group 3C.

3.1.5. St ea m CO 2 tests

3.1.5.1. Oil recoveries. Fig. 13 shows the compari-

son of the results of tests which were conducted at

13_

O

O

> -

r r

u J

>

O

O

U J

r r

O

1 0 0

9 0 -

8 0 -

7 0 -

S T E A M - C O 2

~ , e r t ic a l n j . - h o r i z o n t a lp r o d , g ro u p 2 A ]

6 0 -

~ . ~

5 0 ~ , ........... ~ e r t ic a l n j - h o r i z o n t a l p r o d . , g r o u p 2 B

~ : ~ '- . ~ - .. ~ p , . ~ v en a l in j .- v e r ti c a l p r o d , g r o u p I [

2 0 ' - . ~ - - -

~ ' ~ Z ' ' . ~ [ h o r iz o n ta ln j -hor i zonta l rod , g roup 3D

l o ~ ( ~ , ~ - ~ - - ~ . . . .

I I hor i zonta ln j .-h . . . . ~ p rod , g roup 30 I

0 l , T , ; , , ,

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0

C O 2 / S T E A M R A T I O ( d m 3 / L )

Ftg. 14. Oil recoveries as a fund]on of CO2/steam ratio.


13/17

F. Giimrah. S Ba~,ct Journal of Petroleum Sctence and Engmeering 18 1997) 113-129 1 2 5

a b o u t th e s a m e C O 2 / s t e a m r a t io s a n d d if f e r e n t w e l l

c o n f i g u r a t i o n s . T h e r e s u lt s o f t e st s h a v i n g t h e h i g h e s t

r e c o v e r i e s w e r e p l o t t e d i n t h i s f i g u r e . T h e r e c o v e r y

e f f i c i e n c y o f g r o u p 3 C w a s a l s o t h e l o w e s t o n e

a m o n g t h e s t e a m - C O 2 t es ts , b u t g r o u p 2 A g a v e t h e

b e s t p e r f o r m a n c e w h e n c o m p a r e d t o o t h e r t e s t s . O i l

r e c o v e ri e s w e r e 5 8 . 3 o f O O I P a n d 2 5 . 3 o f O O I P

f o r t h e C O 2 / s t e a m r a ti o o f 1 4 .2 d m 3 / 1 ( g r o u p 2 A )

a n d 1 3 .4 d m 3 / 1 ( g r o u p 3 C ) , r e s p e c t i v e l y . F i g . 1 4

c o m p a r e s t h e e x p e r i m e n t a l r e c o v e r i e s a s a f u n c t i o n

o f C O 2 / s t e a m r a ti o a t 1 P V o f s te a m i n je c te d . T h e

C O 2 / s t e a m r a ti o w a s ra n g e d f r o m z e r o t o 1 4 0 d m 3 / 1 .

T h e r e c o v e r y w a s i n c r e a s e d u p t o a c e r t a i n p o i n t

w i t h i n c r e a s i n g C O 2 / s t e a m r a t i o , a f t e r w h i c h a d i -

m i n i s h i n g e f f e ct w a s o b s e r v e d . T h e u s e o f to o m u c h

C O 2 c a n h a v e u n d e s i r a b l e e f f e c t s . F i r s t ly , t h e g a s

o c c u p i e s v o l u m e a n d r e d u c es t h e a m o u n t o f s te a m

i n j e c t e d . S e c o n d l y , i f t o o m u c h g a s i s i n j e c t e d , i t

i n c r e a s e s t h e g a s s a t u r a t i o n f l o w i n g b e t w e e n t h e

i n j e c t i o n a n d p r o d u c t i o n w e l l s a n d c a u s e s c h a n -

n e l l in g o f t h e s t e a m t o t h e p r o d u c t i o n p o i n t . T h i s

e f f e c t i s n o t e d i n t h e e x p e r i m e n t a l r e s u l t s p r e s e n t e d

h e r e b y t h e r e d u c e d r e c o v e r y a n d l o w e r s t e a m i n j e c -

t i v it y a t h i g h e r a m o u n t s o f C O 2 . H e n c e b y t h is

a n a l y s i s , i t b e c a m e a p p a r e n t t h a t a n o p t i m u m

C O 2 / s t e a m r a t io e x i s te d , w h i c h i s ~ 14 d m 3 / 1 f o r

B a u K o z l u c a c r u d e o i l ( 1 2 . 4 A P I ) w h i c h c a u s e d t h e

b e s t p e r f o r m a n c e i n te r m s o f h i g h e s t o i l r e c o v e r y .

T h e C O 2 / s t e a m r a t i o t h a t r e s u l t e d i n t h e m a x i m u m

o i l r e c o v e r y w a s t h e s a m e v a l u e f o r a l l w e l l c o n f i g u -

r a t i o n s e x c e p t i n g r o u p 3 C . T h e i n c r e m e n t a l o i l

r e c o v e r y o v e r t h e s t e a m - o n l y c a s e d e c r e a s e d w i th

i n c r e a s i n g C O ~ / s t e a m r a t i o . T h e r e f o r e t h e v a l u e o f

C O 2 / s t e a m r a ti o w a s o n e o f th e i m p o r t a n t fa c t o rs

w h i c h a f f e c t e d th e p e r f o r m a n c e o f t h e p r o c e s s . T h e

o t h e r f a ct o r w a s t h e t y p e o f in j e c to r a n d / o r p r o -

d u c e r , w h e t h e r t h e w e l l w a s p l a c e d i n h o r i z o n t a l o r

v e r t i c a l p o s i t i o n . T h e d i s t a n c e b e t w e e n t h e w e l l s a l s o

a f f e c t e d t h e e f f i c ie n c y o f p ro c e s s . I f th e y w e r e c l o s e

t o e a c h o t h e r , b e c a u s e o f h i g h e r f l u i d m o b i l i t y , e a r l y

b r e a k t h r o u g h o c c u r r e d . A s a r e s u l t , t h e m a j o r i t y o f

s u b s e q u e n t l y i n j e c te d f l u i d s f o l l o w e d t h is e s t a b l i s h e d

p a t h o f l e a st r e s i s ta n c e a n d p r o c e s s e f f i c i e n c y w a s

i m p a i r e d .

2 0 0

1 8 0 -

2 1 6 0 -

E

o 1 4 0 -

co

(3_

O 1 2 0 -

uJ

r r l O 0 -

z

O

r - - 80-

C.)

-3

(3

O 6 0 -

E

0 .

.J

5

s team-CO2 , (OPR)

4 0 - - i ~/ ,-

20 - ...i ~

O '

0

v e r t i c a l i n j e c t i o n - h o r i z o n t a l p r o d u c t i o n , g r o u p 2 B

CO2/ste~'n atio= 141 dm3/L ]

~.. t lW_:~,.-stea. , I , - - - o n ly , ( SO R )

, ,~ A ' k ~ . , ~ - - - - - - - I ID ~ s te a m - C O 2 , ( S O R )

I s team on ly , (OPR)

~] i-

... ~ ..... F i ........

5. 5 1 . 2


Fig. 15. Production data for vertical rejection-horizontal production (group 2B).

1 0

- 9

- 8

- 7

- 6

- 5

- 4

- 3

-2

-1

0

2 . 5

-

o

o,9_,

O

O

V--

(Steam-CO 2 Drive Experiments Using Horizontal and Vertical)

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