SPEr Conducting COR Lab Study

8/18/2019 SPEr Conducting COR Lab Study

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est Praawaz M. Al-assi F. Al-Q

opyright 2012, Societ

his paper was prepare

his paper was selecteviewed by the Societ

fficers, or members.produce in print is res

bstractEnergy delimate changeerfect storm f

f this green h

or EOR or se

ery efficient

To designeservoir/fluid

ome thought

omprehensiveThe essenti

teractions. Fl

roperties of

ock interactioermeability, c

light of their

ntroductionEOR (tertia

re many appl

articular reser hermal EOR

OR methods

The best

equestration,welling, and l

e reservoir pterface and h

rocess of enh

The term “ixed in any

riginal fluids.

immiscible.”iscible fluids

ith the reser

ultiple-conta

termediate cy condensing

26

tices fotaibi, SPE,

htani, SPE,

of Petroleum Engine

d for presentation at t

d for presentation byy of Petroleum Enginelectronic reproductiotricted to an abstract

and has been

has the worlor the use of c

use gas. Each

uestration. T

echanism for

CO2-EOR orsystem. Wher

nd effort. A s

experimentalal components

uid-fluid stud

O2-oil or CO

studies typiritical gas satu

best practice.

ry recovery) ied EOR tech

voir dependsmethods invol

nd it involves

as for injecti

nd higher oilwering oil vi

ressure, displence the inter

nced oil reco

iscibility” isroportion. A

If an interfa

n petroleum r . They form a

oir oil can be

t or dynamic

mponents frothe intermedia

Conducaad M. Al-Maudi Aramc

ers

he SPE EOR Confere

n SPE program comers and are subject to, distribution, or storaf not more than 300 w

escalating an

abuzz on tharbon dioxide

oil company (

e injection of

increasing oil

CO2 sequestr does one sta

earch of the lit

design for con of a laborator

es include mi

-brine mixtur

ally include cration, gas tra

The ultimate g

s a process toiques includi

n a number ove the injectio

the injection

on is CO2 fo

recoveries. Ccosity. The in

cing the oil,facial forces, i

ery by gas inj

referred to the important co

ce is formed

eservoirs, CO2single phase

made miscib

iscibility. Th

reservoir oiltes from the in

ting CO2utairi, SPE,

ce at Oil and Gas We

ittee following reviewcorrection by the aut

ge of any part of thisords; illustrations ma

is predicted

primary greefor enhanced

and others) ha

CO2 into a re

recovery.

tion project, ot? Even if the

erature reveal

ducting a CO2 study for C

scible displac

s including v

oreflooding te ping and wett

oal is to establ

recover the oilg thermal, g

f factors. Then of heat and

f gases such a

r several rea

O2 increasescrease in reco

and by elimint is possible t

ction, it is firs

ability of twosideration in

at some prop

that is miscibith the reserv

e (for certain

is process can

) or the conde jected solvent

EOR Launil L. Kokal

st Asia held in Muscat

of information containhor(s). The material d paper without the w not be copied. The a

to increase fu

n house gas,oil recovery.

s therefore ste

servoir is not

ne requires adata have to

no best pract

laboratory stu

2 injection inc

ment tests,

scosity and d

sts for determability change

ish a procedu

left behind as injection, c

screening critare the most

s CO2, N2 or h

ons: lower

il recovery tery by CO2 in

ating the inteo theoretically

t necessary to

or more fluidmiscible proc

ortion of one

le with the reoir fluid. An i

compositions

be either the

nsing gas drivinto the oil).

Studyl, SPE, Jame

, Oman, 16–18 April 2

ed in an abstract suboes not necessarily r ritten consent of thestract must contain c

rther in the co

carbon dioxidhe petroleum

ped up its eff

new. Indeed

arge set of ap be generated i

ices for gener

dy.lude measurin

easurement o

ensity, asphal

ining the oils. Each of the

e for generati

ter primary ahemical, etc.

eria is mostlycommon. Gas

ydrocarbons.

iscibility pre

rough its fav jection is also

rface between recover most

understand th

s (CO2 and oiesses is the el

fluid in the

ervoir fluid i jection gas (

only) with th

aporizing gas

e (the reservoi

s J. Funk, S

012.

mitted by the author(sflect any position of t

Society of Petroleumonspicuous acknowled

ming decades

. Both of theindustry is id

orts in carbon

O2 injection

propriate expen a service la

ating this data

g fluid-fluid i

f minimum m

ene precipitat

ecovery potee sets of expe

g a reliable a

d secondary r Selecting an a

based on theinjection is o

ssures, better

rable propertiattained by m

the oil andof the oil in

concepts of

) to form a siimination of t

other, then t

any proportiO2) which is

e reservoir oil

drive (CO2 c

r oil at the mi

E and

. Contents of the paphe Society of PetroleuEngineers is prohibitegment of SPE copyrig

. The dialogu

e factors havally suited fo

dioxide utiliza

as established

rimental data, a good desi

et. This paper

teractions and

scibility pres

on, and swell

tial, three-phiments will b

d accurate dat

ecovery meth ppropriate m

luid and rocke of the most

solvent prop

es includingaintaining (or

O2. By elimilace. To und

iscibility.

gle phase whhe interface b

e fluids are

n are called finot first-conta

by a process

n extract or v

xing front is

r have not beenm Engineers, itsd. Permission toht.

on global

e created adisposing

tion, either

itself as a

for a givenn requires

presents a

fluid-rock

ures, fluid

ing. Fluid-

se relativedescribed

aset.

ds. Therethod for a

properties. promising

rties, CO2

iscibility,ncreasing)

nating thiserstand the

en they areetween the

considered

rst-contactct miscible

known as

aporize the

ade richer


2/12

2 SPE 151126

CO2-EOR is a well-known method that has been applied in the field extensively. The initial pilots were conducted in the

US in the late 1940s. The first full scale immiscible carbon dioxide flooding process was conducted in Bartlesville in

Oklahoma in 1958 (Dyer and Farouq, 1989). The first pure carbon dioxide gas injection was conducted in the Ritchie field ofsouthern Arkansas in 1969 (Khatib and Earlougher, 1981). Today, most of the CO2-EOR commercial projects are located in

the Permian Basin of west Texas. CO2-EOR has added increasing amounts of oil production capacity in the US (Jarrell et al.,

2002). The American Petroleum Institute stated that the oil and gas industry has over 35 years of continuously developing

experience in transporting and injecting CO2 for enhanced oil recovery (EOR). CO2-EOR is now being commercially

exploited in the rest of the world including Canada, Europe, Asia, Middle East and the Far East. Immiscible carbon dioxideflooding has been conducted in the Bati Raman in Turkey in 1980 (Khatib and Earlougher 1981, Karaoguz et al. 1989, Sahin

et al. 2007). This project is considered one of the most successful EOR applications in the history for heavy oil fracturedcarbonate reservoirs. In recent years, a lot of interest in CO2 injection is stemming from the CO2 sequestration in reservoirs.

Due to the recent interest in CO2 from environmental issues, the interest in CO2-EOR has grown substantially. CO2-EOR

is being field tested around the world. There are numerous pilots and commercial field projects either in the implementation

phase or on the drawing board. Many other companies are contemplating CO2-EOR. Before a further decision can be madeon whether to apply it in field or not, generally some laboratory experiments are needed to be done. The lab experiments or

studies generally cover fluid-fluid and fluid-rock interactions. To generate a reliable and accurate CO2-EOR dataset we have

to establish a procedure for conducting such lab studies. A complete set of data for a CO2-EOR lab study includes MMP

measurements, fluid properties of CO2-oil mixtures, asphaltene precipitation, swelling, oil recovery potential, three-phase

relative permeability, critical gas saturation, gas trapping and wettability changes. These data are critical input for anyreservoir simulation that follows the initial laboratory study to evaluate the feasibility of the process for a given reservoir.

Experimental StudiesTwo sets of experimental studies need to be conducted for any given CO2-EOR prospect: fluid-fluid and fluid-rock

interactions. Fluid-fluid studies involve the oil and CO2 interactions while fluid-rock studies involve reservoir fluids and rock

samples. The first and perhaps the most important step towards getting accurate and reliable experimental data is acquiring

representative samples. The representative fluid sample for a CO2-EOR study is generally a recombined sample of the pressurized separator gas and liquid samples targeting the average fluid composition of the original well stream. The other

important parameters in the experimental study are procedures, and calibrated and reliable instruments. These will be

discussed under each laboratory experiment. Specific experiments that are generally conducted in any CO2-EOR studies

involve minimum miscibility pressure (MMP) measurements, fluid properties of CO2-oil mixtures, asphaltene precipitation,swelling, oil recovery potential, three-phase relative permeabilities, critical gas saturation, gas trapping and wettability

changes. These will be discussed in the following sections.

Fluid-Fluid Interactions

An understanding of reservoir oil and CO2 interactions is perhaps the most important for any CO2-EOR project. Itinvolves the measurement of miscibility of CO2 with the reservoir oil, PVT phase behavior, swelling, enrichment, reduction

in viscosity and mixing. Another important aspect of these interactions is the precipitation of asphaltenes from live crude oil

when it comes in contact with CO2. Fluid-fluid interactions should also include reservoir brine and CO2 behaviors. Thesemeasurements and procedures to measure them are outlined below, and should constitute an important part of any CO2-EOR

laboratory study.

MMP Measurements:

MMP is an important parameter for the design of gas injection-EOR processes and is defined as the lowest pressure at

which a gas can develop miscibility, through a multicontact process, with reservoir oil at reservoir conditions. When theMMP is above the reservoir pressure, the gas injection flood will be immiscible with generally lower ultimate oil recoveries.

Conversely, when the MMP is below the reservoir pressure, the gas flood will be miscible with higher oil recoveries.

Miscibility can be achieved through a vaporizing process, a condensing process, or a combined vaporizing-condensing

process. The MMP can be obtained experimentally either by the slim tube system (Danesh, 1998), a rising bubble apparatusor through the use of correlations. The gold standard for MMP measurement in the industry is the slim tube apparatus. Aschematic representation of the slim tube apparatus is given in Fig. 1. The tubing is tightly packed with glass beads and

coiled to give a certain permeability and porosity. The specifications for slim tube are rather stringent and are provided

elsewhere (Elsharkawy, Suez, Poettmann and Christiansen, 1992).


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PE 151126

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PE 151126

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PE 151126

CO2 injecti

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ystem (SDS)ystem is give

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on reduces th

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egh, 1995). T

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Figure 7: S

oil viscosity.

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Figure 8:

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il viscosity

reservoir, esp

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an find the vi

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unt of CO2

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measured fro

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d magneticall

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c representati optic bundle

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6/12

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Figure 9: So

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int B). As mo

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ents describ

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on apparatus

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resenting res

e experimentd. The experi

d (Fig. 12).

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lids Detecti

oil is charged

the onset of a

ge, 1995). A

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re CO2 is add

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Fi

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phaltene preci

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ir oil with C

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is shown in

after ~0.75 cm

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berger)

titrated slowly

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in as the bub

t quantify the

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sembly that a

pm or as a perecipitated me

PE 151126

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7/12

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PE 151126

luid-Rock IFluid-rock

pical, but we

ater-gas) rela

Another co

issolution of plugging of p

teraction bet

cid (H2CO3):

he weak carb

ollowed by se

he deposition

ifferent CO2-

jection of C

AppropriatO2 injection

O2/rock inte

ublications (I

Fig

teractionsinteractions a

l thought out

ive permeabil

cern during

rock can havres, scale pre

een CO2/bri

nic acid react

ondary precip

of interactio

OR operatio

2 in limestone

studies shoulCO2-EOR). It

actions. This

sever et al. 19

re 11: Bulk

Figure 12:

e equally imp

oreflooding e

ity, critical gas

O2 injection is

e both positivcipitation). Be

e and carbon

s with carbona

itation of calci

CaMg(

products of

s. According

cores, while n

d be conducteshould invest

aspect of flu

93, Stalkup 19

Asphaltene

ulk Asphal

ortant in a C

periments. O

saturation me

its interactio

e (increase isides the pote

te rock is cru

CO2 +

H2CO3 + H2

HCO3- + H

te rocks releas

um carbonate

aCO3 + H2

O3)2 + H2C

O2/brine/rock

to Grigg and

o deposition

d that addressgate factors (

id-rock intera

78, Simon an

Precipitatio

ene Precipi

2-EOR proje

her experime

asurements, a

with reservoi

injectivity, r tial benefits

cial. Carbon d

2O ↔ H2

O↔ H3O+

O ↔ H3O+

ing calcium a

due to increas

O3 ↔ Ca2+

3 ↔ Ca2+ +

has been fou

vec (2003), s

as observed i

the impact of.g., pressure,

ctions is not

Graue 1965,

Apparatus

ation Data (

t. The oil rec

ts that need to

d wettability

r rock and the

educed pressut of the CO

ioxide dissolv

O3

HCO3-

CO32-

d magnesium

e in pH value:

2HCO3-

Mg2+ + 2H

nd to cause a

ignificant calc

dolomite cor

CO2 on carboflow rate, wat

covered and

Mungan 1991,

(Schematic)

typical)

overy potentia

be conducted

alteration mea

subsequent di

re for injecti flooding in t

es in water to

ions. This ini

O3-

decrease in t

ium carbonate

es.

nate (or sandser saturation,

the reader is

Hadlow 1992

l should be si

include three-

urements.

solution of th

n) and negaterms of oil re

form the wea

tial dissolutio

e well injecti

was noted du

tone) rocks asand other) tha

referred to t

).

7

mulated in

phase (oil-

rock. The

ive effectsovery, the

k carbonic

is usually

ity during

ring WAG

a result oft affect the

he several


8/12

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The oil rec

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arts should b

nd CO2 are gumps. System

s equipped wi

laced inside t

ne of which is

The core fl

outine analysis to make sur

acro porosit

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art water floo

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Figure 1

ure starts wit

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selecting a l

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the correct

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constant flo

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on experiment

in fraction col

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injection. T

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eservoir con

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1991) has c

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PE 151126

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9/12

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PE 151126

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Figure 1

ettability C

Wettability

lteration are oistory (Buckl

resent in the

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llect the data

AG type core

4: Cumulati

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portant aspects, oil, gas a

tensive resea

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lso noted thatrelative perm

ther two phas

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: Experime

anges:

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eability:

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ch has been c

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ld be wetting

the relative peability of the

s (Pejic, Drag

eability dataxpensive leadi

i et al., 1990,

lab experimen

viewed a wid

lection of pre

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that overcome

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tal and por

effective app

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alter most

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e recovery cal

iments results

jected vers

ab studies anld be consid

nducted on th

ection. The lit

or intermediat

meability of tintermediate-

an and Maini,

an be obtaineng to limited

Larsen and S

ts, predictive

e range of exp

ictive models

e-phase predithese predic

s the experim

s for both caatform for opt

network si

roach to enha

try, rock surf n of polar co

f the rock’s

tion collector no more flui

culations.

are shown in

us cumulati

experimentsered in gas i

ree-phase rela

erature revie

wetting (Lev

he wetting anetting phase

2003).

d by conductinumber of lab

auge, 1995,

odels have b

erimental res

for generation

tive model thive models

ental difficult

bonate and saimal sensitivit

ulated thr

ce oil recover

ce mineralog pounds and/

surface chem

s at atmosphe is produced.

ig. 14.

e % OOIP r

is three-phasenjection, gas

tive permeabil

shows that t

erett and Lewi

non-wettingis strongly aff

g special SC experiments

leri et al., 19

een used wid

lts reported o

of three-phas

at can be conave been de

is the use o

ndstones prov testing. An

e phase rel

y significantl

and the syster the depositi

istry. Polar c

ic conditions.

covered an

relative permcap expansio

ity to understa

e gas always

s, 1940, Core

phase is primaected by the s

L experimentreported in th

95 and Baker

ely to estimat

n three-phase

e relative per

idered reliableloped base

pore network

de quantifiablexample is sho

tive permea

. The main fa

m temperatur n of organic

mpounds co

The collected

d pressure

ability data.n and therm

nd the hydrod

ehaves as a n

et al., 1956,

rily a functionaturation histo

s. The naturee literature fo

1999). To ov

the three ph

elative perme

eability isope

e and compre on two-pha

models (Piri

e data includiwn in Fig. 15.

bility (SPE9

tors affecting

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tain a polar

9

oil here is

rop

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namics of

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araf et al.,

of its ownry and the

of such labthe three-

rcome the

se relative

ability and

ms. It was

ensive forse relative

and Blunt,

g trapping

594)

wettability

saturationoriginally

end and a


10/12

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ressure and dtructure, the s

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ettability bef

975; Tiffin a

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n conventiona

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Figure 17:

onclusionThe design

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Fluid-fluid

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uch experimexperiments w

Fluid-rock

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d. The polar6). Brine che

the charge of

ged when thering compoun

nce is seen ne

2007). Zones

estabilize thelid surfaces

alteration du

re and after

d Yellig, 198

lts showed tha. Also, it was

riments study

ed three types bility were e

anges in rela

action of the r

experimentset. CO

2 flood

h results sho

s if the media

ettability forettability alte

tion of wettab

s brine whichvoirs to study

ed, wettabilit

ding to higher

changes duriT2 relaxation

l testing, repe

do more sophi

ater distrib

of a CO2-EO

system. Theseuch a project.

nents of mea

studies inclu

O2-oil or CO2nts should bell to obtain ac

nteraction stu

bility, critical

nd adsorbs oistry plays a

the rock surf

pH is increasds. In an oil-

ar the bottom

higher in the

water film, alostly retain th

ing CO2 floo

O2 flooding to

3). Schneider

t oil bypassedfound that w

ing the effects

of wettabilityamined initial

tive permeabi

ock surface ca

were conducing was perfo

ed that CO2 di

were interme

tight limestoration. The re

ility, i.e., mor

was a favorabthe effects so

y alteration d

oil recovery f

g and afterime distributi

at measureme

sticated obser

ution and in

or CO2 sequ

data are criti. A comprehe

uring fluid-flu

e miscible di

-brine mixtur

conductedcurate and rep

dies typically

gas saturation

the rock sur ajor role in

ce. The rock

ed. Also, raisiearing forma

f the transitio

structure hav

lowing surface water film (

ing process i

track any cha

nd Owens (1

by the solventater mobility

of CO2 flood

states: intermly before and

lity behaviors

used by CO2.

ted on a car rmed in glass

d not contact

iate-wet. Ze

e cores. Chaults suggeste

water-wet co

le effect. Gue of the fluid

ecreased. Als

om fractured

O2 injectionsn and calcula

ts of the Am

ations based o

ermediate

(S

stration proje

al input for ansive experim

id interactions

placement in

s including vi

ith live reser esentative dat

include corefl

, gas trapping

ace, exposingltering the we

surface beco

ng the temper tion, the wett

n zone and a

a greater ca

e-active compil and Gas Jo

s investigated

nges (Lin and

976) conducte

bank increaseas reduced

ing on the we

diate oil-wet,after CO2 flo

. The results

Chalbaud et a

bonate reserv micro-model

he solids for

ri et al. (2007

ges in relati that CO2 floo

ndition. Also,

ta and Moha properties on

o, it was fou

carbonate rese

are difficult ttion of surfac

tt our USBM

n ESEM imag

etting char

E 105114)

t requires a la

y reservoir siental design

and fluid-roc

luding the m

scosity and d

oir fluids ata that can be u

oding tests f

and wettabilit

the hydrocarbttability of the

es positively

ature and presability can va

reater oil-wet

illary pressur

onents in thernal, summer

extensively i

Huang, 1990;

d laboratory e

d the gas satuuring later pe

tability of W

intermediateding. Then, r

showed that

l. (2007) addr

oir for twos to trace the

ater-wet med

conducted a l

e permeabilitding changed

CO2 flooding

ty (2008) testwettability al

d that the

rvoirs.

o determinerelaxavity ca

before and a

es (Okasha, 2

cteristics o

rge set of exp

mulation studor conductin

interactions.

easurement o

nsity, asphalt

reservoir consed in simulat

r determining

changes. Th

on end and m rock where t

charged when

sure tends tory with depth

ing preferenc

e, which can

oil to contact2007).

the literatur

Stalkup, 197

xperiments on

ation trappedriods of wate

st Texas dolo

nd intermediaock wettabilit

the cores be

ssed the role

ettability codistribution o

ia. On the oth

aboratory stud

y due to CO2the water-wet

reduced the I

ed oil sampleseration. The t

ettability alte

uantitatively.n often be use

ter CO2 inject

07).

grains, Ara

erimental and

that may bea CO2 labor

minimum mi

ene precipitati

ditions. It isors and fluid c

the oil recov

se tests provi

aking the surf e brine’s salin

the pH is dec

romote the s where a gre

is observed n

counteract the

the solid. Lo

. Researchers

; Shelton and

more than 19

during the late injection. Po

itic cores. T

te water-wet.was monitor

came slightly

f wettability

nditions: watf fluids unde

r hand, the C

y evaluating t

injection we limestone co

T between th

obtained frost results sho

ation increas

With NMRd for wettabil

ion provide o

b-D carbona

modeled data

conducted toatory study r

scibility pres

on, and swelli

important toharacterizatio

ry potential, t

e the key co

PE 151126

ace oil wetity and pH

reased and

lubility ofter water-

ear the top

disjoining

wer in the

measured

Schneider,

preserved

r period oftter (1987)

e selected

hanges ined through

water-wet

uring CO2

r-wet andthe same

2 partially

e possible

re used toes to more

employed

fractureded that as

ed at high

echniques,ty indices.

e point of

te rocks

for a given

xplore thequires the

ures, fluid

ng. Ideally

design the.

hree-phase

ponents to


11/12

SPE 151126 11

address flow regime and displacement sensitivities. An accurate set of data is key to successfully modeling and validation

larger pilot and field scale projects.

AcknowledgementsThe authors would like to thank Saudi Aramco for permission to publish this paper. Special thanks go to Ali Al-Meshari

for his help in the development of experimental procedure.

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SPEr Conducting COR Lab Study

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