experimentalevaluationoflignosulfonate asa sacrificial ... a... ·...
Post on 08-Mar-2018
226 Views
Preview:
TRANSCRIPT
Experimental Evaluation of Lignosulfonate as a Sacrificial
Agent in COa-Foam Flooding
by
Andy Eka Syahputra
Thesis
Submitted in Partial Fulfillment of the Requirements for the Degree ofMaster of Science in Petroleum Engineering
Department of Petroleum EngineeringNew Mexico Institute of Mining and Technology
Socorro, New Mexico 87801
August 1999
ABSTRACT
Lignosulfonates are abundant wood-based chemicals obtained as by products in
the sulfite process of wood pulping. They are relatively inexpensive compared to most
polymers and surfactants. An effort to improve the economics of tertiary oil recovery
operations by using lignosulfonates, a mixture of a lignosulfonate reagent with
surfactants was studied. Three sets of laboratory experiments were performed: (1) to
quantify interfacial tension and foam durability; (2) to quantify the sweep efficiency
when using lignosulfonate mixedwith a good foaming surfactant in COi-foam flooding
in heterogeneous core; and (3) to investigate lignosulfonate as a sacrificial agent to
minimize the loss of surfactant by adsorption on reservoir rock. All of the experiments
except the adsorption measurements were conducted at elevated pressures.
Quantification of interfacial tension and foam durability using a high-pressure
foam durability apparatus was performed as the first set of laboratory experiments to
screen lignosulfonate as a sacrificial agent in C02-foam flooding. The foam durability
test demonstrates the potential of using lignosulfonate solutions at various concentrations
as sacrificial agents to be mixed with other surfactants, such as alpha olefin sulfonate and
alkyl phenol ethoxylate for C02-foam flooding. We found that the lignosulfonate solution
was a weak foam former. When the lignosulfonate solution was added to different
surfactant solutions, foam stability was affected by the lignosulfonate concentration. The
results of the foam durability test show that a strong foam could be formed by some
lignosulfonate solutions mixed with surfactant CD1045; thus, lignosulfonate can be
tested as a sacrificial agent in CO2-foam flooding processes.
The second set of laboratory experiments was to determine the sweep efficiency
using lignosulfonate as a sacrificial agent mixed with a good foaming surfactant in CO2-
foam flooding in heterogeneous reservoirs. A noncommunicating composite core sample
of two different permeability regions (ratio 1:10) in parallel was used. The high
permeability region was located in the centerof the core and the low permeability region
in the annulus. In order to reduce mobility and increase sweep efficiency of CO2
injection, lignosulfonate mixed with surfactant CD1045 was coinjected into a C02-foam
core flooding apparatus. The results indicate that lignosulfonate mixed with surfactant
CD1045 significantly improved the nonuniformity in displacement associated with rock
heterogeneity and reduce the channeling of CO2 in a heterogeneous core. Coinjection of
CO2 and lignosulfonate as sacrificial agent at 5000 ppm mixed with two concentrations
of surfactant CD1045 (250 ppm or 500 ppm) are effective for diverting displacing fluid
into the low permeability region. Thus, oil from the low permeability region was
displaced and oil production was increased.
The third and final set of experiments was to investigate the degree of retention of
the injected components. The loss of injected surfactant is a major factor causing poor
efficiencyof C02-foam flooding. In this study, we performed experiments to investigate
lignosulfonate as the sacrificial agent to minimize the loss of the good foaming
surfactant. A single core sample of Berea sandstone was used to investigate the
adsorption by a circulation method. Solutions were circulated through the core using
surfactant CD1045 and a sacrificial agent (lignosulfonate) with different initial conditions
to establish the adsorption isotherm under equilibrium conditions with constant flow rate
at a specific confining pressure. Experimental results show that using surfactant CD1045,
the amount of adsorption onto therockincreases as concentration increases andby using
lignosulfonate mixed with surfactant reduces the adsorption of surfactant CD1045.
ACKNOWLEDGEMENTS
I would like to express my sincere appreciation and gratitude to my advisor Dr.
ReidB. Griggfor his valuable guidance, advice, patience, and encouragement throughout
the course of this study.
Many thanks are due to my coadvisor Dr. Jyun Syung Tsau for comments,
suggestions, encouragement, useful discussions and guidance in the set up of foam
durability experiments apparatus and adsorption measurement apparatus during the
course of this research. I also express my appreciation to the other members of my
advisory committee. Dr. LarryTeufel, Dr. Her Yuan Chen for their advice and time spent
on this thesis.
I wish to express my gratitude to the Petroleum Recovery Research Center
(PRRC) for the financial support through research assistantship grant.
Appreciation is also extended to Dr. Hossein Yaghoobi for his guidance in the set
up of the C02-foam coreflooding experiment apparatus. I also wish to thank Liz
Bustamante for her help in correction of the thesis manuscript. I would like to thank to
the entire staff of the PRRC for their kindness and assistance.
Finally, I am greatly indebtedto my parents, my brother Dr. Erwinsyah putra, my
wife Afrin Aulia, my beloved daughter Navira Alifa, my family and my friends for their
patience, moral support, understanding and encouragement during this study.
11
TABLE OF CONTENTS
Abstract
Acknowledgments ii
List ofTables
List of Figures ix
Chapter 1 Introduction 1
Chapter 2 Literature Review 5
2.1 Characteristics of Lignosulfonate 5
2.2 CO2 Breakthrough 6
2.3 C02-Foam Flow Behavior 8
2.4 Adsorption Effects 9
Chapter 3 Experimental Descriptions 12
3.1 Foam Durability Test 12
3.1.1 Foam Durability Apparatus 12
3.1.2 Foam Durability Experiments and Procedure 13
3.2 C02-Foam Coreflooding Test 21
3.2.1 COa-Foam Coreflooding Apparatus 21
3.2.1-a Core unit assembly 21
3.2.1-b A foam generator 26
3.2.1 -c Differential pressure transducers 26
3.2.1-d Backpressure regulators (BPR) 26
3.2.1-e Floating piston accumulators (FPA) 27
iii
3.2.1-f Positive displacement pumps 27
3.2.1-g Data acquisition system 28
3.2.1-h Effluent collection 29
3.2.2 COa-Foam Coreflooding Experiments and Procedure 29
3.3 Adsorption Measurement Test 30
3.3.1 Adsorption Measurement Apparatus 30
3.3.2 Adsorption Measurement Experiments and Procedure 30
Chapter 4 Discussion of Results 34
4.1 Foam Durability Results 34
4.2 C02-Foam Coreflooding Results 43
4.3 Adsorption Measurements Results 55
Chapter 5 Conclusions and Recommendations for Future Work 66
5.1 Conclusions 66
5.1.1 Foam Durability Experiments 66
5.1.2 C02-Foam Coreflooding Experiments 67
5.1.3 Adsorption Measurement Experiments 68
5.2 Recommendations for Future Work 68
References 70
Appendix - A Foam Durability Experimental Data 76
Appendix - B C02-Foam Coreflooding Experimental Data 82
Appendix - C Adsorption Measurements Experimental Data 101
iv
LIST OF TABLES
Table 3.1 Surfactant and Brines Properties 20
Table 3.2 Lignosulfonate Properties 20
Table 3.3 Properties of Isolated Coaxial Composite Core 25
Table 4.1 Sununary of Isolated Coaxial CompositeCore Experiments 44
Table 4.2 Cost Savings Using a Sacrificial Agent, Based on Adsorption Results
(Ib/acre-ft) 65
Table A.1 Foam Durabilty Experimental Data:
Decay of Calcium Lignosulfonate Data 77
Table A.2 Foam Durability Experimental Data:
Interfacial Tension (IFT) Calculation 79
Table B.l COi-Foam Coreflooding Experimental Data:
CO2 Displacing Oil at Center 83
Table B.2 COi-Foam Coreflooding Experimental Data:
CO2/ Brine Displacing Oil at Center 83
Table B.3 COa-Foam Coreflooding Experimental Data:
CO2 / Surfactant @500 ppm Displacing Oil at Center 84
Table B.4 COa-Foam Coreflooding Experimental Data:
CO2/ Surfactant @2500 ppm Displacing Oil at Center 84
Table B.5 C02-Foam Coreflooding Experimental Data:
CO2/ Surfactant @2500 ppm Displacing Oil at Annulus 85
Table B.6 C02-Foam Coreflooding Experimental Data:
C02 / (500 ppm Surfactant + 5000 ppm Lignosulfonate) Displacing
Oil at Center 85
Table B.7 COz-Foam Coreflooding Experimental Data:
CO2 / (500 ppm Surfactant + 5000 ppm Lignosulfonate)Displacing
Oil at Annulus 86
Table B.8 C02-Foam Coreflooding Experimental Data:
CO2/ (250 ppm Surfactant + 5000 ppm Lignosulfonate) Displacing
Oil at Center 86
Table B.9 C02-Foam Coreflooding Experimental Data:
CO2/ (250 ppm Surfactant + 5000 ppm Lignosulfonate) Displacing
Oil at Annulus 87
Table B.IO C02-Foam Coreflooding Experimental Data:
CO2/ (5000 ppm Lignosulfonate) Displacing Oil at Center 87
Table B.ll C02-Foam Coreflooding Experimental Data:
Total Oil Recovery from Both Region at CO2 / (Surfactant @2500 ppm) 88
Table B.12 C02-Foam Coreflooding Experimental Data:
Total Oil Recovery from Both Region at CO2/(250 ppm Surfactant
+ 5000 ppm Lignosulfonate) 88
Table B.13 C02-Foam Coreflooding Experimental Data:
Total Oil Recovery from Both Region at CO2/(500 ppm Surfactant
+ 5000 ppm Lignosulfonate) 89
Table B.14 C02-Foam Coreflooding Experimental Data:
Pressure Difference at The Core versus Time for CO2 /(500 ppm
vi
Surfactant CD1045) 90
Table B.15 C02-Foam Coreflooding Experimental Data:
Pressure Difference at The Core versus Time for CO2/(2500 ppm
Surfactant CD1045) 92
Table B.16 COa-Foam Coreflooding Experimental Data:
Pressure Difference at The Core versus Time for CO2/(250 ppm
Surfactant CD1045 + 5000 ppm Lignosulfonate) 95
Table B.17 C02-Foam Coreflooding Experimental Data:
Pressure Difference at The Core versus Time for CO2/(500 ppm
Surfactant CD1045 + 5000 ppm Lignosulfonate) 98
Table C.1 Adsorption Measurement Experimental Data:
CD1045 & Lignosulfonate Standard Curve with Different
Wavelengths 102
Table C.2 Adsorption Measurement Experimental Data:
Adsorption of Surfactant CD1045 onto Berea Sandstone
(The core was flushed with brine followed by injecting the different con
centrations of CD1045) 102
Table C.3 Adsorption Measurement Experimental Data:
Adsorption of Lignosulfonate onto Berea Sandstone
(The core was flushed with brine followed by injecting the different con
centrations of lignosulfonate) 103
Table C.4 Adsorption Measurement Experimental Data:
Adsorption of Surfactant CD1045 Mixed with Lignosulfonate Using
Vll
Surfactant Strandard Curve. (The core was flushed with brine followed by
injecting the three different concentrations of surfactant mixed with ligno-
Sulfonate) 104
Table C.5 Adsorption Measurement Experimental Data:
Adsorption of Surfactant CD1045 onto Berea Sandstone (The core was
flushed with brine prior to injecting each concentrations of surfactant) 105
Table €.6 Adsorption Measurement Experimental Data;
Adsorption of Surfactant CD1045Mixed with Lignosulfonate Using
Surfactant Standard Curve (The core was flushed with brine prior to
injecting each concentrations of surfactant mixed with lignosulfonate) 105
Table C.7 Adsorption Measurement Experimental Data:
Adsorption of Surfactant CD1045 with Three Different Sequences of
Experiments onto Berea Sandstone (The core was flushed with brine prior
to injecting each concentrations of solutions) 106
vui
LIST OF FIGURES
Fig. 2.1 Structure of a section of lignosulfonate molecule 7
Fig. 3.1 Foam durability apparatus 15
Fig. 3.2 Sapphire tube 16
Fig. 3.3 IFTs between surfactant and dense CO2 19
Fig. 3.4 C02-Foam coreflooding apparatus 23
Fig. 3.5 Core unit assembly 24
Fig. 3.6 Adsorption measurement apparatus 32
Fig. 4.1 IFTs between lignosulfonate calcium in different brines and dense CO2 37
Fig. 4.2 IFTs between lignosulfonate solutions with surfactants and dense CO2 38
Fig. 4.3 Decay of C02-foam of lignosulfonate with brine 3 (base solution) 39
Fig. 4.4 Decay of C02-foam of lignosulfonate with 0.025 wt % CD1045 40
Fig. 4.5 Decay of C02-foam of lignosulfonate with 0.025 wt % CD1050 41
Fig. 4.6 Decay of C02-foam of lignosulfonate with 0.025 wt % CD1040 42
Fig. 4.7 Cumulative GOR observed from the high permeability (center) region 48
Fig. 4.8 Cumulative GOR observed from the low permeability (annulus) region 49
Fig. 4.9 Oil recovery through the high permeability region (center) 50
Fig. 4.10 Oil recovery through the low permeability region (annulus) 51
Fig. 4.11 Oil recovery through both regions 52
Fig. 4.12 Pressure drop profiles and oil recoveryfor the low permeability region
(annulus) with different concentrations of surfactant in CO2injection 53
Fig. 4.13 Pressure drop profiles and oil recovery for the low permeability region
ix
(aimulus) with different concentrations of surfactant mixed with 5000 ppm
lignosulfonate in CO2injection 54
Fig. 4.14 Surfactant CD1045 standard curve with wavelength 520 nm 58
Fig. 4.15 Lignosulfonate calcium standard curve with wavelength 283 nm 59
Fig. 4.16 Adsorption of surfactant CD1045 onto Berea sandstone core sample 60
Fig. 4.17 Adsorption of lignosulfonate onto Berea sandstone core sample 61
Fig. 4.18 Adsorption of surfactant CD1045 onto Berea sandstone cores sample as a
function of surfactant CD1045 concentration at lignosulfonate levels of
0 ppm and 500 ppm (The core was flushed with brine followed by
injecting the three different concentrations of surfactant) 62
Fig. 4.19 Adsorption of surfactant CD1045 onto Berea sandstone core sample as a
function of surfactant CD1045 concentration at lignosulfonate levels of
of 0 ppm and 500 ppm (The core was flushed with brine prior to injecting
each concentrations of surfactant) 63
Fig. 4.20 Adsorption of surfactant CD1045 with three different sequences of
Experiments onto Berea sandstone core sample 64
CHAPTER 1
INTRODUCTION
Despite the favorable characteristics of gas injections for displacing oil, gas injection
processes have major problems with poor sweep efficiency, due to viscous fingering,
gravity override, and reservoir heterogeneity. In CO2 injection, mobility is usually high
relative to that of other reservoir fluids because of the large viscosity contrast between the
reservoir and injected fluids. Therefore, CO2 sweep efficiency decreases and early gas
breakthrough occurs as a result of the unfavorable mobility ratio. Several alternatives
have been proposed to increase sweep efficiency of CO2 injection in the field or in
experimental work, such as injecting water alternating with gas (WAG) (Caudle and
Dyes, 1958), direct CO2 thickeners (Heller et al., 1983), and injecting surfactant solution
alternating with gas (SAG) (Bernard and Holm, 1964; Tsau and Heller, 1992). The
benefits of usingSAGto improve the efficiencyof CO2 displacement have been reported
by several investigators (Albrech and Marsden, 1970; Yang and Reed, 1989; Tsau and
Grigg, 1997; Yaghoobi etal, 1998).
-1-
-2-
Laboratory and field studies indicate that foam potentially presents an efficient
method of reducing CO2 mobility (Yang and Reed; 1989, Tsau et al., 1992, 1996, 1997,
1998; Yaghoobi et al, 1994, 1995, 1996; Prieditis et a/., 1992; Kuehne et al., 1992;
Bernard et aL, 1964). Foam inside porous medium is defined as a dispersion of gas in
liquid such that the liquid phase is continuous and at least some part of the gas is made
discontinuous by thin liquid films called lamellae (Falls et al.^ 1988). The foam occurs as
gas dispersed within a surfactant solution and the mobilites of gas and aqueous phase are
reduced.
The inherent advantage of foam over water for mobility improvement is that it
consists of 85 to 95% gas. This means that a relatively small amount of water is used to
decrease CO2 mobility. Foam has other properties that are favorable to oil recovery,
particularly by CO2 flooding. The apparent foam viscosity is greater than the viscosity of
its components. This factor is favorable for greater oil recovery because increased
viscosity is reflected in improved mobility ratio. Foam also increases trapped gas
saturation and decreases the oil saturation. In addition, high-trapped gas saturation
usually reduces gas mobility. All of these unique properties of foam indicate that it
should be useful in CO2 flooding. Foam properties may also cause unfavorable increased
in injectivity and increased chemical costs.
It has been found that surfactants can play an important role in controlling CO2
mobility, but surfactants are expensive. In order to find solutions that are less expensive,
lignosulfonate was tested as a sacrificial agent, mixed with the good foaming to form
C02-foam. The overwhelming appeal of lignosulfonate is the relative low cost (about
$0.03/lb) for calcium lignosulfonate compared to a good foaming agent (about $1.43/lb)
-3-
for Chaser™ CD1045 and is available as a byproduct from the pulp and paper industry.
The prices of CD1045 and lignosulfonate were quoted by Chevron Chemical (1991) and
Georgia Pacific (1998), respectively.
In this work the performance of foam using lignosulfonate was investigated with
three different sets of experiments. The first set of studies used the foam durability
apparatus (Tsau et al., 1992, 1996, 1997). The purposes of the first set of studies were
threefold. The first was to determine the foaming ability and stability of foam. The
second objective was to identify the optimum concentration of a lignosulfonate/surfactant
mixture. The final objective was to provide information about interfacial tension between
CO2 and lignosulfonate/surfactant mixture.
The second set of experiment was conducted using the C02-foam coreflooding
apparatus (Tsau et al, 1998; Yaghoobi et a/., 1994, 1995, 1996). In this study, we
examined the effectiveness of COa-foam flooding with lignosulfonate at 5000 ppm
concentration mixed with two different concentrations of surfactant CD1045 (250 ppm
and 500 ppm). The solution was injected simultaneously with CO2 into saturated
heterogeneous porous media to displace oil. We used lignosulfonate mixed with certain
concentrations of surfactant CD1045 because they formed a strong foam in previous
foam durability test experiments. The experiments were performed on a
nonconmiunicating composite core sample of two different parallel permeability regions.
The purposes of this study were twofold. The first was to determine the delay of CO2
breakthrough time. The second objective was to examine the effectiveness of
lignosulfonate/surfactant mixture on diverting displaced fluid to the lower permeability
-4-
region to improve oil recovery. The results were compared with the results from using
surfactant CD1045, lignosulfonate and brine (1.5 wt% NaCl and 0.5 wt% CaCla).
The third set of studies examined adsorption by the circulation method (Tsau et al.,
1999). The purpose of the third set of study was to assess both the loss of primary
foaming agent and of lignosulfonate for economic evaluation, and to design a surfactant
injection scheme to minimize the loss of the primary foaming agent onto sandstone.
CHAPTER 2
LITERATURE REVIEW
2.1 Characteristics of Lignosulfonate
Lignosulfonates are anionic polyelectrolytes that are soluble in water, tolerate
hard water (polyvalent ions, e.g. calcium and magnesium) and are derivatives of lignin
(Kalfoglou, 1977). The use of lignosulfonates as sacrificial agents for C02-foammobility
control is desirable because they are stable at high reservoir temperatures, plentiful, and
lower cost than either polymers or other surfactants. One variety of lignosulfonate
products is the lignosulfonic acids. These are calcium, magnesium, sodium or ammonium
salts of the lignosulfonic acids that are available under various tradenames including
Marasperse™, Lignosite™, Orzan™, Toranil™, and Rayflo™ (Kalfoglou, 1977). The
organicstructureof lignosulfonate has not been completelyelucidated but the basic lignin
monomer unit is substituted phenyl propane. The complex structure of lignosulfonates
make them completely insoluble in oils. The molecular weight and degree of sulfonation
govern the extent of electrical charge of the system under consideration. The type of
-5-
-6-
metallic ions in the lignosulfonate affects its properties. The structure of a section of
lignosulfonate can be seen in Fig. 2.1.
The lignosulfonate used in this study is Lignosite®100 calcium lignosulfonate,
which is produced by sulfonation of softwood lignin and provided by the manufacturer in
a powder form. Lignosite®100 calcium lignosulfonate is particularly effective because
alcohol fermentation and distillation purify it. This removes the hexose sugars and yields
a product with a high content of calcium lignin sulfonate. High purity calcium
lignosulfonate from softwood is the most effective composition for many applications
and is the most widely used of all lignosulfonates.
2.2 CO2 Breakthrough
Early CO2 breakthroughoccurs in most CO2 projects, especially in heterogeneous
reservoirs. Several methods have already been proposed to alleviate that problem. Rowe
et al. (1981) injected alternate slugs of water with CO2 for reducing injecting mobility.
The water decreases the relative permeability of the porous medium to CO2 and thus
lowers its mobility. When the porous medium is not strongly water-wet, this method
seems to work well, but in strongly water-wet fomations, CO2 may have difficulty in
contacting the residual oil left after the slug of injected water. Although water alternating
gas (WAG) seems to be successful in some field operations, it is not an ideal method,
because after water is injected and followed by CO2, the fronts formed around the
injection well are unstable. The CO2will tend to finger through the high water saturation
zones and may bypass regions of high oil saturation.
SOjM
IOCH,
C —C—C—
I I I ^H. H H OCH.
-7
H£OH
ICH
HiCOH
KC
HC
HC
Acs OH
OCH,
HiCOH
1
C•
1CH
MO^
H]CO
CHiOH
ICO
<1
OCH,
OCHi
HiC
KC
HjCO
OH
v4
CH
CH
HC CH,
- O
OCH,
OH
Fig. 2.1 - Structure of a section of lignosulfonate molecule.
\
-8-
Moreover, the solubility of CO2 in water would increase the overall CO2
consumption to make the CO2 project less economical.
One method to control CO2 viscous fingering is the use of C02-foam. Because the
foam has a muchhigher effective viscositythan CC)2, it tends to inhibit viscous fingering.
2.3 C02-foam flow behavior
Foam has the ability to block or minimize CO2 flow into high permeability
regions in C02-foam flooding. With an apparent viscosity greater than the CO2, foam
reduces gas mobility in a favorable way that corrects the nonuniformity flow problem in a
heterogeneous porous medium.
The flow behavior and the displacement mechanism of C02-foam were
investigated by several authors (Bernard et al, 1980; Wang, 1984). In 1980, Bernard
al. presented results of using three classes of surfactants (anionic, cationic and nonionic)
to improve the effectiveness of CO2 flooding. Oil recovery efficiency increased when
surfactant was used with CO2, and that efficiency further increased with flooding
pressure. One anionic surfactant was found to be superior for that purpose as it emulsified
CO2 well and greatly reduced CO2 mobility. Wang (1984) investigated the flow behavior
of C02-foam and the displacement mechanism in porous media glassbead pack using
SACROC and Rock Creek crude oils. He examined these models with varying CO2 slug
injection sequences and some surfactant concentration. His results showed that C02-foam
flooding slightly improved oil recovery and delayed gas breakthrough.
Several researchers have reported that some surfactants generated foams, which
selectively reduced mobility of CO2 by a greater firaction in higher than in lower
-9-
penneability regions (Moradi et aL, 1997; Yang and Reed, 1989; Yaghoobi et ai, 1994,
1996; Lee et al, 1991; Tsau and Heller, 1996; Tsau et al, 1998). The main purpose of
injecting COa-foam is to divert the injection fluid into the lower permeability region. The
oil in lower permeability regions is often by passed and often has a higher portion of
unrecovered oil compared with high permeabilityregions.
In 1996, Yaghoobi et al. conducted COa-foam core flooding experiments in core
samples without oil present. The experiments were performed in composite core samples
with two different permeability regions in capillary contact. They found that the
displacement of C02-foam delayed CO2 production and improved sweep efficiency in
bothregions. The experiment wascontinued by Tsau et al (1998) on two composite core
systems of a known heterogeneity with oil present. The first composite core system
consisted of two coaxial permeability layers in capillary contact. The second composite
system used a barrier embedded between two different permeability regions to prevent
flow communication between two parallel zones. They observed that foam was diverted
to lower permeability regions and delayed CO2 breakthrough, thus improving oil
recovery efficiency for both regions.
2.4 Adsorption Effects
Surfactant loss due to adsorption during C02-foam flooding is considered a major
factor in the inefficiency of tertiary oil recovery. Various experimental methods have
been used to measure the adsorption of surfactants on sample cores. One of those was
conducted by Mannhardt et al. (1990). They measured adsorption onto sandstone and
limestone cores for two types of surfactants (anionicand amphoteric surfactants) found to
- lo
be effective in forming mobility control foams under extremely high salinityconditions.
Theyfound that anionic surfactant adsorbed more strongly onto limestone core than onto
sandstone core, while the opposite behavior was observed with amphoteric surfactant.
Also, they found the presence of divalent ions increased adsorption levels of both
surfactants onto both rock types.
In order to minimize the loss of injected surfactant, several studies have been
conducted to optimize the cost of application (Trogus et al, 1977; Bae et aL, 1976;
Lawson, 1978). For economic reasons, it is desirable to find sacrificial agents that are less
expensive and that minimize the loss of surfactant.
Several researchers investigated the amount of sacrificial agent needed to allow
for adsorption onto reservoir rock. In 1976, Hobbs investigated the possibility that
sacrificial agents that adsorb in place of surfactants could be used in a preflush or as a
competitive additive to the surfactant slug, but effective agents were not identified.
Similar experimental results were reported by Hurd (1976).
A process using lignosulfonates as sacrificial agents during oil recovery by
surfactant flooding was patented by Kalfoglou (1977). His results showed that the
injection of lignosulfonates into the reservoir as a preflush reduces the loss of the costly
primary surfactant (petroleum sulfonate) by adsorption onto the reservoir rock. He
asserted that since lignosulfonates have strongly ionized sulfonate groups, they are
capable of covering the potential adsorption sites of the rock by means of electrostatic
attraction or hydrogen bonding and, as a consequence, impart a negative charge to the
surface. Afterward, the surface would have little or no affinity for anionic surfactants
such as petroleum sulfonates and their loss by adsorption would be minimized.
-11-
Novasad (1984) investigated the use of lignosulfonate as a sacrificial adsorbate in
surfactant flooding. The author found that lignosulfonate can improve oil recovery by
two possible ways. First, lignosulfonate reduced surfactant adsorption by being
preadsorbed on to reservoir rock surfaces and second, lignosulfonate acted together with
the surfactant at the liquid-liquid interface to further reduce interfacial tension between
oil and brine.
Somansundaran (1989) examined the adsorption of sodium dodecylsulfonate
(SDS) in the presence of lignosulfonate. The addition of 1000 ppm lignosulfonate
decreased sulfonate adsorption onto kaolinite by almost half an order of magnitude in the
premicellarregionbut it had no noticeable effect in the micellar region. The adsorption of
SDS onto kaolinite in the presence of varying concentrations of lignosulfonate (from
1000 ppm to 5000 ppm) was found to decrease with an increase in the lignosulfonate
level and SDS adsorption onto kaolinite was completely inhibited at an initial
concentration of 7500 ppm.
Hong et al (1987 and 1990) showed that surfactant loss could be reduced
significantly (>50% reduction) by pretreatment with a lignosulfonate preflush. However,
when the lignosulfonate was incorporated with the surfactant slug, no significant
reduction in adsorption of the surfactant was obtained. The investigation was continued
by injecting lignosulfonate as a sacrificial adsorbate in real-world situations at Glenn
Pool field. A lignosulfonate solution was injected as part of the preflush in one of the
patterns without any interruption of the surfactant flood project. Results of this
experiment testing the effect of lignosulfonate on sulfonate adsorption demonstrated that
almost half the injected lignosulfonatewas adsorbed, and more oil was produced.
CHAPTERS
EXPERIMENTAL DESCRIPTION
This chapter describes the experiments conducted in this study. Three different
sets of experiments were performed. The first set used the foam durability apparatus to
optimize the concentration of lignosulfonate mixed with surfactants. The second set of
experiments was conducted using the C02-foam coreflooding apparatus to investigate the
effectiveness of C02-foam for improving oil recovery by using lignosulfonate mixed
with surfactant for diverting displacingfluid from the high to the low permeability region
of the core. The third set investigated adsorption using a sacrificial agent such as
lignosulfonate to minimize the loss of surfactant. The adsorption experiments were
performed using a circulation method for establishing the adsorption isotherm under
equilibrium conditions with constant flow rate.
3.1 Foam Durabilty Test
3.1.1 Foam Durability Apparatus
-12-
-13-
The foam durability apparams is a device that is used for testing surfactant
properties at high pressure, thus allowing the evaluation of these surfactants for reservoir
use. The schematic view of the entire apparatus is shown in Fig. 3.1 with an enlarged
viewof the sapphire tube high-pressure cell shownin Fig. 3.2. The apparatus consists of
a CO2 source tank, a visual cell made from a transparent sapphire tube, a buffer solution
cylinder, a Ruska pump and a cathetometer for measuring the level of bubble decay
versus elapsed time. The CO2 tank and the sapphire tube high-pressure cell are major
parts of the system that are contained in a temperature-controlled water bath. The Ruska
pump and the buffer solution tank are installed outside of the water bath and their
temperatures are maintained at the test temperature through another temperature control
systemthat consisted of Exacal Circulator, Flowthru Coolerand tubing that wrap around
the pump and buffer solution tank.
3.1.2 Foam Durability Experiments and Procedure
During the durability experiment, the sapphire visual cell is first filled with the
solution to be tested. Once the system is brought to the desired pressure by means of the
Ruska pump, the dense CO2is introduced through a needle at the lower end of the cell.
Depending on the effectiveness of the lignosulfonate and lignosulfonate mixed surfactant,
the bubbles either formed a layer of foamlike dispersion at the top of the sapphire tube or
coalesced into a clear layer of dense CO2. After a standard volume of CO2 (1.75 cc) is
introduced into the sapphire tube, the pump is stopped and the duration of formed foam is
measured. The measure of foamability is the fraction of the bubbles that stay intact as a
foam layer at the top of the cell. The durability of the foam is obtained in terms of foam
-14-
decay by measuring the change of the percentage of foam or coalescence of the bubbles.
The screening tests on lignosulfonate solutions and the Iignosulfonate/surfactant mixtures
were conducted at 77° F (25® C) and 2000 psig.
To Ruska Pump
o
Buffer
Solution
Outlet
-15-
To Isco Pump
Water Bath
Sapphire Tube
CO^ Tank
Fig. 3.1 - Foam durability apparatus
h ' '. : '
'^'y.V ;.
'•/ •
, 3-».
A«
• 'W'
...w
•
..' ''-Tf-.; -^ «••"'- s '"k ''•»
-16-
•i
Bubbles
Needle
Fig. 3.2 - Sapphire tube
-17-
The measurement techniques for calculating the interfacial tension are analogous
to those of the drop-weight method. The rate of entry of the dense CO2 is known from the
pump settmgs and number of drops are recorded against time; thus, the volume and
radius of each drop can be calculated. The radius of the needle from which the bubbles
emerge, the density of the lignosulfonate solution, and the density of the CO2 are also
known. The following equation is used to calculate IFT:
|'''̂ 'k.surf-''ooJs=2"rTf (3.1)\ J
Where
R = average radius of the bubbles, cm.
r = radius of the needle from which the bubbles emerge, cm.
Y = interfacial tension between dense CO2and lignosulfonate,
dynes/cm.
f = dimensionless correction factor.
g = gravity, cm/sec^.
The correction factor is necessary because a portion of the CO2will remain on the
tip of the needle after the bubble is released. The correction factor for the drop weight
method was reported by Harkins and Brown (1919) and summarized by A.W. Adamson
(1990).
Stock solutions of Lignosite®100 calcium lignosulfonate at a concentration of 10
wt% were prepared by dissolving the product powders into distilled water and three types
-18-
of brines. The properties of three types of brine and surfactants are described in Table
3.1. The critical micelle concentration (CMC) values for surfactant solutions using
Chaser™ CD1040, Chaser™ CD1045, and Chaser™ CD1050 were determined to be
0.06%, 0.07% and 0.07%, respectively (Fig.3.3).
Lower concentrations of lignosulfonate solution, ranging from 0.5 to 7.5 wt%,
were prepared by dilution of the 10 wt% batch solution with a brine solution. The values
of pH and density were measured for 0.5 wt% to 10 wt% concentrations of
lignosulfonate,see Table 3.2. The summaryof the foam durability test data are presented
in Tables A.1-A.2, Appendix A.
u 12
c 10
0.001
-19-
OCD1040 ACD1050 XCD1045
0.01 0.1 1
Concentration (wt%)
Fig. 3.3 - IFTs between surfactants and dense CO2.
10
-20-
Table 3.1 - Surfactants and Brines Properties
Solution Concentration
(PPM)pH Density, (p)
(gm/cc)Type Active
(wt%)Formula Manufacture
Chaser™CD1040
250 6.3 1.033 Anionic 40.0 Alpha OlefinSulfonate
Chaser Inter-
National
Chaser™CD1045
250 6.8 1.024 Not avai
lable
46.7 Not available Chaser Inter
national
Chaser™CD1050
250 5.98 1.026 Nonionic 70.0 Alkyl PhenolEthoxylate
Chaser Inter
national
Brine 1 10000 6.59 1.016 * 100.0 1.0Wt%CaC12 *
Brine 2 10000 6.92 1.017 * 100.0 1.0Wt%NaCl *
Brine 3 20000 6.72 1.013 * 100.0 1.5Wt%NaCl
&0.5Wt%
CaC12
*
(*): Not applicable.
Table 3.2 - Lignosulfonate Properties
Lignosulfonate pH Density, (p )wt% (gm/cc)
10 4.80 1.069
7.5 4.83 1.061
5.0 4.90 1.056
2.5 4.96 1.045
1.0 5.21 1.034
0.5 5.93 1.024
-21-
3.2 COi-Foam Coreflooding Test
3.2.1 C02-Foam Coreflooding Apparatus
The C02-foam coreflooding experiments were performed by using a high-
pressure coreflood apparatus, which is shown in Fig. 3.4. The major elements of this
apparatus are a core unit assembly, a foam generator, differential pressure transducers,
back pressure regulator (BPR), floating piston accumulators (FPA), positive displacement
pumps, data acquisition system and effluent collection.
3.2.1-a Core unit assembly
Thecore unitassembly comprised of a nonconmiunicating composite coresample
with a large permeability contrast of 1 to 10. A brass sleeve was used between the two
regions of the cores to prevent communication between them. The annulus was a fired
Berea core with length 6.7 cm, diameter 3.56cm and 500 md permeability. The core was
epoxied to the brass sleeve. A central hole with a diameter of 1.6 cm was drilled and
filledwith 90-120 microndiameterglassbeadshaving5000 md permeabiUty. The core
unit assembly of a heterogeneous core is shown in Fig 3.5 and the properties of the
isolated coaxial composite core are listed in Table 3.3.
The core holder consisted of one upstream distribution plate within an end cap
and a downstream dual end cap. Both ends were secured by six long bolts to sustain
pressure. The inlet distribution plate was used to share fluid across the surface of the two
sections equally. An 0-ring was put on the edge of this distribution plate to seal;
preventing fluid invasion. A dual outlet end cap was designed such that the effluent fluids
of the center and annulus sections can be collected separately. In this end cap, fluid
-22-
sealedby an 0-ring on its edge. A one millimeterseparatorbarrier machined in the center
of the end cap sat on the center hole sand pack to prevent the central effluent fluid from
beingmixed with the fluidexiting the annulus section. This dual outletendcap was added
as a special feature to the core unit assembly so that the effluent fluids from the central
and annulus sections wouldenter independently into separateoutlet paths.
-23-
Notes:
A. COi-Tank.B. Nz-Tank.C. Brine, Surfactant
<M- Lignosulfonate.
) D. Oil.
mm E. CO2.F. Distilled Water.
* B G. Foam Generator.
H. Core Holder.
I. PressureTransduco*.
3. PressureTransducer.
K. BPR for Annuius.
L. BPR for Center.
M. To Computer.N. To Temco Pump.O. To Milton-Roy Pump.P. To Dry Gas Meter.
Q- To Wet Test Meter.
R. To Strip ChartP
Q -• R
Fig. 3.4 - COi-Foam coreflooding apparatus.
-'''A.-
'''•-Mf'-. ^
"••^•5i4:. V .-• • •,0.
^ ^"T J$• -/f^••#SI:
Inlet Endcap
T
B
-24-
Core Holder
Outlet Endcap
I
Bnina
Distribution grooves O-ring
Stainless
steel sleeve
Glass beads
Fig. 3.5 - Core unit assembly.
Epoxy
Berea sandstone
-25
Table 33 - Properties of Isolated Coaxial Composite Core.
CompositeCore sample (isolated)
K
(md)Area
(cm^)
Center Region(Glass bead 90-120 mm) 5000 0.42 1.27
Annulus Region(Fired Berea sandstone) 500 0.23 7.58
-26-
3.2.1-b A foam generator
The foam generator was a 2.5-cm long, and 3.7-cm diameter consolidated, fired
Berea sandstone core, inline with the core unit assembly. It was epoxy-mounted in a 304-
grade stainless steel holder designed to sustain pressure up to 3000 psi, in a manner
similar to that described for the core itself. COa/brine, C02/surfactant, C02/lignosulfonate
and C02/lignosulfonate mixed with surfactantwere coinjected into it to generate the foam
or bubbles, which propagated to the core.
3.2.1-c Differential pressure transducers
Differential pressure transducers, Validyne models DP-215 and DP-303, were
used to measure the pressure drops between different areas of the system. Appropriate
diaphragm sizes were used in the transducers to meet the anticipated pressure range in
each location. The transducers were calibrated with a dead-weight tester before they were
used. The low-pressure diaphragms (< 5-psi) were calibrated using a mercury
manometer. A threeway testing valve was mounted for each transducer to make sure that
a zero reading can be initially achieved prior to recording the data and can be rechecked
periodically during the run.
3.2.1-d Backpressure regulators (BPR)
Backpressure regulators, modified Temco model BPR-50, were used to maintain
the system pressure. The high pressure BPRs were connected to the center and annulus
outlet ports at the core exit while the domes were both connected to a nitrogen cylinder
from which they could be pressurized simultaneously. The low-pressure outlets from the
-27-
BPRs were connected to two separator vessels. The performance of the BPRs was very
critical, as it affected the flow velocities of the two high and low permeability sections.
The BPRs-50consists of two major sectionsthat areboltedtogether on each side of a thin
stainless steel diaphragm. The first part is the dome body, in which an empty volmne of
about 40 cc canbe filled withinertgas in order to pressurize the system. The second part
is a unit in which a diaphragm and a pencilshaped piece called the stem are attached
together via a seal bar. The stem moved freely within a 5-nmi hole in the center of the
unit and allowed fluid to flow when the dome pressure is equal to the inlet fluid pressure.
The seat and stem designs were modified to improve their ability to maintain identical
backpressure.
3.2.1-e Floating piston accumulators (FPA)
Three floating piston accumulators were employed as the transfer vessels with
volumetric capacity of a few liters for oil, brine or surfactant or lignosulfonate mixed
with surfactant, and CO2. The sealed pistons in these accumulators kept the solutions and
distiUed water isolated from each other. Distilled water was used as a displacing fluid for
advancing their pistons via the pump.
3.2.1-f Positive displacement pumps
A Milton-Roy HI metering pump and a TEMCO 1000-1-10-MP pump used
distilled water to drive the fluid inputs of aqueous phase and high pressure CO2 into the
system through floating piston accumulators. When saturating the core with oil, a Milton-
Roy in metering pump was used to drive water into the floating piston accumulators of
-28-
oil. The maximum flow rates in the Milton Roy HI pump and the TEMCO pump were
200 cc/hr and 21.95 cc/hr, respectively. However, for this experiment the core was
injected with a constant injection rate with the volumetric ratio of CO2 to aqueous
solution of 4 to 1. Therefore, the constant injection rate for CO2 was 13.16 cc/hr and 3.29
cc/hr for the aqueous phase. The total flow rate for these experiments were 16.45 cc/hr or
1.3 ft/d (Darcy velocity). When CO2 was injected alone, the flow rate was 16 cc/hr or 1.2
ft/d.
3.2.1-g Data acqiusition system
The data acquisition system consisted of a PCL-711S PC-Multilab Card (B & C
Microsystem Inc., Sunnyvale, CA.) mounted in a windows operated personal computer
and a MCl-20carrier demodulator(Validyne Engineering Corporation), receiving voltage
signals from the Validyne transducers. Several channels were used for transforming the
input signal, corresponding to each transducer, into DC voltages for the PC-LabCard. In
1995, Yaghoobi wrote an interactive program in Turbo Pascal to monitor, record and
convert the raw data to a usable form such as the pressure unit (psi), and to carry out
further computations for plotting and data processing. The voltage signals, produced by
each Validyne transducer, were transformed through a designated channel into the
demodulator and then to the computer for data acquisition. These data points were
averaged with a time delay of ten seconds. Rearranged data was saved mstantaneously in
four independent data files.
-29-
3.2.1-h Effluent collection
A special dual outlet end cap was designed to collect the effluent fluid separately
from the centerand annulus sections of the composite core. The output flowed from the
two regions, which were separated by a circular barrier of the same diameter as the
central zone of the composite core. The two output regions had their own exit plumbing
so that each was lead to a modified backpressure regulator (BPR) in which the dome
pressure was maintained at the test pressure (2100 psi). The two low-pressure liquid
outputs from the BPRs flowed into receiving flasks, while the outputs of atmospheric
pressure gas flowed through a wet test meter or a dry gas meter. The oil from the core
was collected in sample vials for the elapsed time of 30, 45 and 60 minutes during each
displacement run.
3.2.2 COi-Foam Coreflooding Experiments and Procedure
The experiments were conducted on a core saturated with crude oil. The crude oil
was degassed separator oil from the Sulimar Queen field. Lea County, New Mexico. We
used CO2, C02/brine, CO2/CDIO45 at concentrations of 500 ppm or 2500 ppm, CO2/
lignosulfonate at the concentration of 5000 ppm, COyClignosulfonate @ 5000 ppm mixed
with CD1045 @ 500 ppm) or COz/Clignosulfonate @ 5000 ppm mixed with CD1045 @
250 ppm) as the displacing agents. All tests were conducted at a constant injection rate of
CO2 to aqueous phase of 4 to 1 through core that already saturated with oil. Tests were
performed at a typical Permian Basin reservoir pressure and temperature (101° F and
2100 psig). The breakthrough time and incremental oil recovery were recorded for each
-30-
nin. The summary of C02-foam Coreflooding experiments are presented in Tables B.l-
B.17, Appendix B.
3.3 Adsorption Measurement Test
3.3.1 Adsorption Measurement Apparatus
The experiments were conducted using the circulationmethod apparatus shown in
Fig. 3.6. The confining pressure of the core holder in this apparatus was 200 psi. A
minipump was used to deliver fluid at a constant flow rate. The Berea sandstone core was
cut into a single core sample with length 2.3 in, diameter 1.5 in, porosity 14.7%, pore
volume 9.75 cc and permeability of 300-md. The core was inserted into rubber sleeve to
separate core from confining fluid and then into a stainless steel core holder. The stirrer
was used to mix the solution (surfactant, lignosulfonate and lignosulfonate mixed with
surfactant) in the flask during experiments. All adsorption measurements were conducted
at 77° F and ambient outlet pressure.
33.2 Adsorption Measurement Experiments and Procedure
To allow for equilibrium, at beginning of the experiments, brine from a flask
filled with a known weight of 102.5 cc was circulated through the core for 24 hours at a
flow rate of 10 cc/hr. After 24 hours of circulation, a known weight of brine was removed
from the system and was replaced with a known amount having a known of surfactant
solution concentration. After another 24 hours of circulation, another sample was
removed from the system and more surfactant having a different concentration was
added. Each removed sample was tested to determine the concentration change.
-31-
consequently the amount adsorbed onto the core. The cycle of sampling and adding was
repeated until no significant additional surfactant was adsorbed and the surfactant
adsorption isotherm was established. In a second series of experiments, the same
circulation rate and time were applied but with a different circulation scheme. A detailed
description of the circulation sequence will be given in the results and discussions.
The concentrations ofsolution components were analyzed spectrophotometrically.
The solution preparation methods to be used in a UV/visible wavelength
spectrophotometer to determine the unknown concentrations for CD1045 and
lignosulfonate were suggested by the sample providers (Chaser International and Georgia
Pacific Corporation).
A colorimetric method was used to analyze the unknown concentrations of
surfactant CD1045. This method relies on the formation of an ion pair by the anionic
surfactant component and a cationic dye (dimidium bromide). The ion pair is extractable
into anorganic solvent (chloroform) and changes its color from transparent to pink while
the dye alone is not. The mixed solution consisted of 1 cc surfactant, 7 cc chloroform and
7 cc dimidium bromide disulfine blue indicator. The surfactant dissolved into chloroform
was extracted into a square cuvette holding about 2.5 cc and measured with the
spectrophotometer at the wavelength of 520 nm.
For determining the unknown concentration of lignosulfonate, the dye and
organic solvent were not necessary, as the unknown concentrations of lignosulfonate
were directly measured using a spectrophotometer at a wavelength of 283 nm, which is
also minimal interference from CD1045.
Pump
-32-
MagneticStirrer
ConfiningPressure
Core Holder
Stainless Steel
Rubber
^ Berea Sandstone
Fig. 3.6 - Adsorption measurement apparatus.
-33-
The amount of adsorbed substance was determined based on the following
equation:
(V.dC,+V.C„+VpvC„)' V +v +v *
^ad ^ ^tv ^ *PV
_10-^V,(C.Vb(l-^)
where
Ci* = average initial concentration of system, ppm.
Ci = concentration of flask, ppm.
Cn = equilibrium concentration after last circulation, ppm
Cn+i = new equilibrium concentration, ppm.
Vad = volume of flask, (102.5 cc).
Vtv = tubing volume, (2.5 cc).
Vpv = pore volume of rock, (9.75 cc).
Vb = bulk volume, (66.57 cc).
Vt = total system volume, cc.
Vt =Vad+Vtv + Vpv
Mad = mass adsorption onto the rock, mg/ccrock-
(|) = porosity, (14.7%).
Summary of the adsorption measurements are presented in Tables C.1-C.7,
Appendix C.
CHAPTER 4
DISCUSSION OF RESULTS
The results of the experiments conducted in this study are presented and discussed.
Three types of experiments were performed. They were foam durability, C02-foam
coreflooding and adsorption measurement experiments. The data sets discussed in this
section can be found in Appendix A through C.
4.1 Foam Durability Results
Figure 4.1 shows the results of interfacial tension (IFT) between CO2 and
lignosulfonate solutions with diflerent base solutions (distilled water. Brine 1, Brine 2,
Brine 3, see Table 3.1). The IFT values in this graph were calculated using Eq. 3.1. The
results show that the IFTs increase with decreasing concentration of lignosulfonates.
Adding monovalent or divalent cations (Na"^, Ca^^ into distilled water lower the
interfacial tension slightly.
-34-
-35-
When lignosulfonate solutions were mixed with different 0.025 wt% surfactant
solutions, the result showed that IFTs increase with the lignosulfonate concentration (as
shown in Fig. 4.2) which is different from what was observed in Fig 4.1. The IFT
measurements were terminated at a concentration of 10 wt% because the solution of
lignosulfonate was too dark to see the bubbles. The results show that the IFT of
lignosulfonate solutions mixed with CD1045 is the lowest followed by mixtures with
CD1050 and CD1040, respectively. Lower IFTs favor foam generation and bubbles
stabilization.
Figure. 4.3 presents the result of static decay of COa-foam using lignosulfonate
solution as a foam former withBrine 3 as the base solution. The percentage of foam in
this graph indicates the persistence of foam remaining inside the sapphire cell after a
standardvolumeof CO2 hasbeen injected. The percentages of foam generated from these
solutions are very small, less tiian 20%. This indicates that this solution is a weak
foaming agent. The bubbles formed at 0.5 wt% concentration of lignosulfonate coalesced
in less than a minute. At higherconcentrations, the percentage of foam increased and the
bubbles formed lasted more than five minutes.
A very different trend was found when 0.025 wt% surfactant CD1045 was mixed
with lignosulfonate solutions at different concentrations, as shown in Fig. 4.4. Very
strong bubbles were formed (100% foam) at low concentrations (0.25 and 0.5 wt%) and
did not coalesce for at least90 minutes. At a concentration of 1.25 wt% of lignosulfonate,
a lower percentage of foam was formed (72%) but the bubbles also lasted for at least 90
minutes. At concentration above 2.5 wt% of lignosulfonate, the percentages of foam
became smaller and the bubbles coalesced in less than 20 minutes.
-36-
Lower concentrations of lignosulfonate showed higher percentages of foam
formed and longer decay times. The foaming ability of a surfactant increases as the
interfacial tension between CO2 and surfactant solution decreases. At a concentration of
lignosulfonate of 0.25 and 0.5 wt% with 0.025 wt% CD1045, the system was as stable
and as good foaming agent as CD1045 alone at high concentration.
The higher percentage of foam with lower percentage of lignosulfonate
concentrations were also found when 0.025 wt% CD1050 was mixed with lignosulfonate
at different concentrations. However, the percentages of foam formed at 0.25 and 0.5
wt% were lower than CD1045 and decreased with the time; but still had some foam
remaining after 90 minutes as shown in Fig. 4.5.
Similar trends are also shown in Fig. 4.6 when 0.025 wt% surfactant CD1040 was
mixed with lignosulfonate at different concentrations. However, at concentrations of 0.25
and 0.5 wt%, the percentage of foam formed was lower than in either CD1045 or
CD1050 and the bubbles coalesced in less than 20 minutes. But it should be noted that
CD1040 with no lignosulfonate decays much faster than CD1045 or CD1050.
These results show that lignosulfonate solutions mixed with 0.025 wt% CD1045
at concentrations of 0.25 and 0.5 wt% are the most stable compared to other solution of
CD1045 as well as solutions of CD1050 and CD1040. These results support earlier
finding that the Chaser™ CD1045 is one of the best foaming agents (Tsau and Heller,
1992; Preditis and Paulett, 1992; Kuehne, etal, 1992).
27
e22o
w<uc>»
2,17
12
0.1
-37-
-O-LC+DW
-O-LC+Brinel
LC+Brine2
-O- LC-<-Brine3
I I I I 1,1, • • • ' ' i-
1 10Concentration (wt%)
I I I I I >.
Fig.4.1 - IFTs between calcium lignosulfonate
in different brines and dense CO2.
100
25
20
115CO0)c>«
T3
hIO11.
5
0.1
• • ' • • •
-38-
+-
1 10Concentration (wt%)
-0-LC+CD1045
-^s-LC+CD1050
-0-LC+CD1040
I I I 1 I 111
100
Fig. 4.2 - BFTs between lignosulfonate solutions with surfactants and dense CO2.
30
25
20
-39-
—H-10wt% -0-7.5wt%
-i!^5.0wt% -^2.5 Wt%
1.0 Wt% -X- 0.5 Wt%
5 10
Elapsed Time (minutes)
Fig. 4.3 - Decay of C02-foamof lignosulfonate with Brine3 (basesolution).
—f
15
120
100 S—9
80
.? 60
-40-
-X- -X- -x- -X
-+-5.00wt% -0-3.75wt%
-i5t-2.50wt% -X-1.25wt%
-0-0.25wt% -0-0.50 wt%
- 0.00 wt%
20 40 60
Elapsed Time (minutes)
80 100
Fig. 4.4 - Decay of C02-foam of lignosulfonate with 0.025 wt% CD1045.
120
100 X—X—X ^x-
-41-
•X- —X
-+-5.00wt%
-^2.50 wt%
-O-0.25 wt%
-X-0.00 wt%
40 60
Elapsed Time (minutes)
-0-3.75wt%
-X-1.25wt%
-0-0.50wt%
Fig. 4.5 - Decay ofCOi-foam of lignosulfonate with 0.025 wt% CD1050.
-42-
h- 5.00 wt% -O-3.75 wl%
-j2s-2.50 wt% -O-1.25 wt%
-•-0.25 wt% -)K-0.50 wt%
X 0.00 wt%
10 15
Elapsed Time (minutes)
20
Fig. 4.6 - Decay ofC02-foam of lignosulfonate with 0.025 wt% CD1040.
25
-43-
4.2 C02-Foain Coreflooding Results
Table 4.1 summarizes observed CO2 breakthrough time in both permeability
regions. When pure COa was used as a displacing agent in the noncommunicating
composite core (run #1), breakthrough occurred in the high permeability region (center)
after 0.26 PV of CO2 was injected but no breakthrough had been observed in the low
permeability zone (aimulus) when the test was terminated after 2.78 PV of total fluid was
injected. Coinjection of CO2 with brine, CD1045 @500 ppm and lignosulfonate @5000
ppm (runs #2, #3 and #4) simulated short cycles of WAG or SAG and delayed CO2
breakthrough was observed at 0.42 PV, 0.42 PV and 0.49 PV, respectively in the center.
CO2 breakthrough had not occurred in the low permeability region (annulus) at
termination which was after 5.31 PV, 6.46 PV and 13.72 PV injected, respectively. The
CO2 channeled through the highpermeability region andcontinued to flow preferentially
due to the high permeability contrast between the two layers.
When CD1045 @2500 ppm or lignosulfonate mixed with CD1045 (runs #5
through #7) were coinjected with CO2, foam displacement diverted fluid to the low
permeability region. In C02/CD1045@2500 ppm, CO2 breakthrough occurred after 0.48
PV of fluid injected in the high permeability region and 3.32 PV fluid injected in the low
permeability region. Even though using CD1045 @2500ppm (run #5) diverts the foam to
the lower permeability region, it is more expensive than using lignosulfonate mixed with
surfactant, as seen in run # 6 and #7. CO2 breakthrough in the high permeability region
occurred at 0.35 PV and in the low permeability region at 0.86 PV and 0.75 PV,
respectively.
-44-
Table 4.1 - Summaiy of Isolated Coaxial Composite Core Experiments
Run
#
ExperimentalConditions
Flow
rate
(cc/hr)
Ratio Bieakduough inAnnulus Region
(PV)
BrealdiroughTime in
Annulus Region( minutes)
Breakthrough inCenter Region
(PV)
BreakthroughHmein
Center Region( minutes)
1 CO2displaced oil 16 1 2.78 (♦*) (*) 0.26 14
2 COi/brine displacedoil
16.45 4:1 5.31 (••) (*) 0.42 22
3 COj/suif.(@SOO ppm)displaced oil
16.45 4:1 6.46 (♦♦) (*) 0.42 22
4 COj/lignosulfonate(©SOOOppm)displac^ oil
16.45 4:1 13.72 (♦») (*) 0.49 23
5 COi/surf. (@2500ppm) displaced oil
16.45 4:1 3.32 173 0.48 25
6 C02/(sarf.-flig-nosulfonate) (@S00iq>m + @5000 ppm)displaced oil
16.45 4:1 0.86 45 0.35 18
7 C02/(surf.+lig-nosulfonate) (@2S0ppm + @5000 ppm)displaced oil
16.45 4:1 0.75 39 0.35 18
(*): No breakthrough was observed. (**): End of the experiment
-45-
The production of CO2 in the low permeability regions indicated that foam
diverted part of the injected CO2 from the high to the low permeability region. When
lignosulfonate was used with surfactant CD1045, foam displacement becomes more
uniformin the two different permeabilityregions.
Figures 4.7 and4.8show theresults ofplotting thecumulative gas oil ratio(GOR)
as a function of total pore volume injected. The highest cumulativeGOR occurred in the
high permeability region when CO2 only was used as the displacmg agent. Coinjected
CO2 with brine or foam reduced the cumulative GOR. When surfactant @2500 ppm or
lignosulfonate mixed with surfactant were coinjected with CO2, foam was displaced
through the core, substantially reducing the GOR in the high permeability region while
detectable CO2 was produced fromthe low permeability region (Fig. 4.8).
This illustrated that surfactant @2500 ppm or lignosulfonate mixed surfactant
reduces the problem of nonuniformity in a displacement associated with the rock
heterogeneity and reduce the channelingof CO2 in a heterogeneouscore.
Figures4.9 and 4.10 present the results of the amount of oil produced (fractional
oil recovery) from the high and low permeability regions as a fimction of total pore
volume of displacing fluid injected. As mentioned earlier, the low permeability region
had a higher portion of recoverable oil compared with the high permeability regions;
therefore, it is hoped that the fluid injection will displace the oil from both, the high and
low permeability regions. About 100% of the oil in the high permeability region was
produced for each displacing agents usedin this study, as shownin Fig.4.9.
However, there was no oil production from the annulus Gow permeability) region
when CO2, C02-brine, C02-surfactant @500 ppm and C02-lignosulfonate @5000 ppm
-46-
were injected, as shown in Fig. 4.10. The mixture injection systems of surfactant @2500
ppm and lignosulfonate mixed with surfactant successfully depleted the low permeability
region (annulus). The displacement efficiency of surfactant @500 ppm with
lignosulfonate @5000 ppm at about 8.0 total PV injected in this region had the highest
efficiency (97%), followed by surfactant @2500 ppm (94%), surfactant @250 ppm, and
lignosulfonate @5000 ppm (68%). The production occurred earlier for surfactant @250
ppm with lignosulfonate at 5000 ppm than CD1045@2500 ppm and was not surpassed
until after more than 3 PV of fluid had been injected.
Further evidence to support this assertion is presented in Fig. 4.11 where
fractional oil recovery is plotted through both regions. The displacement of surfactant
@2500 ppm can recover all oil left from both regions, but surfactant at this concentration
is expensive as previous explanation. In order to find the cheaper solution, lignosulfonate
@5000 ppm wasmixedwith surfactant @250 ppm and @500 ppm.The sweep efficiency
at about 8.0 total PV injected from lignosulfonate mixed with surfactant @250 ppm was
not as effective for both regions, because the foam was not strong enough to divert as
much fluid to the low permeability region. Therefore, to make the lignosulfonate mixed
with surfactant more effective and recover all oil left from both regions, the concentration
of surfactant mixed with lignosulfonate was increased to 500 ppm. This mixture
performed better than CD1045 alone at the high concentration.
Figure 4.12 shows the pressure drop profiles and oil recovery for the low
permeability region with different concentrations of CD1045. The pressure drop using
CD1045 at 500 ppm are very low. That result indicates there was no oil produced from
the low permeability region. In order to increase the sweep efficiency from this region.
-47-
the concentration of surfactant was increased to 2500 ppm. No oil was produced during
the first two hours of the test. Foam started to form in the center section and gradually
diverting displacing fluid into the annulus section; thus displacing oil from this section
and increasing the oil production.
Pressure drop profiles and oil recovery for the low permeability region (annulus)
with different concentrations of CD1045 mixed with 5000 ppm Iignosulfonate in CO2
injection can be seen in Fig. 4.13. The pressure drop of CD1045 @500 ppm and
Iignosulfonate @5000 ppm is higher than that of CD1045 @250 ppm and Iignosulfonate
@5000 ppm; hence increasing the oil recovery.
-48-
12.00 1
10.00
6.00 -
i 4.00
0.00 1.00 2.00 3.00 4.00 5.00
Total Pore Volume Injected
-X-C02
-O C02/surfactant@ 500 ppm C02/surfactant@2500 ppm-O- C02/(surf@500 ppm + lig @ 5000ppm) -O-C02/(surf@250 ppm+ lig @ 5000ppm)-X- C02/lignosulfonate@5000 ppm
C02/Brine
6.00
Fig. 4.7- Cumulative GOR observed from the high permeability (center) region.
7.00
OCOO 10.00 -
16.00
14.00 •
12.00
8.00
c 6.00
" 4.00-
0.00 1.00 2.00
-49-
3.00 4.00 5.00 6.00
Total Pore Volume Injected
7.00 8.00 9.00
-£r-C02/surfactant @2500 ppm -O-C02/(surf@500 ppm + lig @ 5000ppm)HD- C02/(surf@250 ppm + lig @ 5000 ppm)
Fig. 4.8- Cumulative GrOR observed from the low permeability (amiulus) region.
-50-
1.20
o 0.80
O 0.60CO
o 0.40
0.00 1.00 2.00 3.00 4.00 5.00
Total Pore Volume Injected
•x—ffl:
6.00 7.00
-X-C02 -l-C02/Brine
-O C02/surfactant@ 500 ppm -o- C02/surfactant@2500 ppm-O- C02/(surf@500 ppm + lig @ 5000 ppm) -A- C02/(surf@250 ppm + lig@ 5000 ppm)-X- C02/lignosulfbnate@ 5000 ppm
Fig. 4.9 - Oil recoverythrough the high permeability region (center).
1.20
^ 1.00 -
IS 0.80 ^
6 0.60 -
.2 0.40 -
0.20 -
0.00
-51-
2.00 4.00 6.00
Total Pore Volume Injected
8.00 10.00
-£s-C02/surfactant @2500 ppm -O- C02/(surf@500 ppm + Hg @ 5000 ppm)-O- C02/(surf@250 ppm + lig @ 5000 ppm)
Fig. 4.10 - Oil recoverythrough the low permeability region (amiulus).
1.20
P 0.80
O 0.60
.2 0.40
0.20
-52-
3 4 5 6
Total Pore Volume Injected
C02/surfactant @2500 ppm -o- C02/(surf@500 ppm + Iig @ 5000ppm)-•-C02/(surf@250 ppm + iig @ 5000 ppm)
Fig. 4.11 - Oil recovery through both regions.
S.
sQ
£S 10.00CO
25.00
20.00
15.00
5.00
0.00
-53-
100 200 300
Time, minute
400
—O—Pressure drop of CD1045 @ 2500 ppmA Pressure drop of CD1045 @ 500 ppm
- -O- -Oil recovery of CD1045 @ 2500 ppm
1.20
1.00
0.80 ^
0.60 S
0.40
0.20
0.00
500
Fig. 4.12 - Pressure dropprofilesandoil recovery for the low permeability region(annulus) with different concentrations of CD1045 in CO2 injection.
30.00
25.00
j£ 20.00
15.00
S 10.00
-54-
1.20
O 1.00
0.80 C
0.40 o
0.20
0.00
0 50 100 150 200 250 300 350 400 450
Time, minute
—A—Pressuredrop of C02/(CD1045@500 ppm + lig@5000 ppm)-O-Pressure drop for C02/(CD1045@250 ppm + lig@5000 ppm)- O- -Oil recovery for C02/(CD1045@500 ppm + lig@5000 ppm)- -X- -Oil recovery for C02/(CD1045@250 ppm + lig@5000 ppm)
Fig. 4.13 - Pressuredrop profiles and oil recoveryfor lowpermeabilityregion (annulus)with different concentrations of CD1045 mixedwith5000ppm lignosulfonate in CO2
injection.
-55-
4.3 Adsorption Measurements Results
The standard calibration curves of lignosulfonate and CD1045 were established (as
shown in Figs. 4.14 and4.15) to determine the concentrations of CD1045, lignosulfonate
or lignosulfonate mixed with CD1045 in the later analysis. An explanation of standard
curves relatedto using the wavelengths for lignosulfonate andCD1045 (283 and 520 nm,
respectively) has already been given in the adsorption measurement experiments and
procedure.
Figure 4.16 shows the amount of surfactant adsorbed onto Berea sandstone rock
samples. The adsorption isotherm of CD1045 indicates that the mass adsorbed onto the
rock increases as the final (equilibrium) concentration of surfactant increases. Similar
results (as shown in Fig. 4.17) were obtained when lignosulfonate wascirculated through
the core sample, where increasing the amount of final concentration of lignosulfonate
increased the adsorption of lignosulfonate. The adsorption quantity reaches a maxiiriiim
of 3 mg/ccrock at lignosulfonate concentration of 15000 ppm, then it decreases to 2.5
mg/cciock at a high concentration (20000 ppm).
The adsorption results of CD1045 in the presence of 5000 ppm of lignosulfonate
and the adsorption result of lignosulfonate (5000 ppm) are plotted as fimctions of the
final concentration of CD1045 in Figs. 4.18 and 4.19, with different initial conditions
(using brine) of the core sample. In Fig. 4.18, the core was flushed with brine followed by
injecting the three different concentrations of surfactant. For Figure 4.19, the core was
flushed with brine prior to injecting each concentrations of CD1045. Adsorption results
of CD1045 in the absence of lignosulfonate are also included in these figures. In Figures
4.18, 4.19 and 4.20 were presented the final concentrations of CD1045 that they were
-56-
based on initial concentrations of CD1045 with three different concentrations of 250
ppm, 500 ppm and 1000 ppm.
Figure 4.18 presents the adsorption results when 5000 ppm of lignosulfonate was
coinjected with different final concentrations of CD1045. The adsorption of CD1045
increases as the final concentrationincreases. However, the adsorption amount is reduced
by adding lignosulfonate into surfactant solutions from 1.28 to 0.69 mg/cc rock (46%) at
1000 ppm and from 0.61 to 0.31 mg/cc rock (49%) at 500 ppm initial concentrations of
CD1045. No significant reductionwas found at 250 ppm initial concentrationof CD1045.
Similar results were obtained using different initial conditions, as shown in
Fig.4.19. The adsorption amount is reduced from 0.97 to 0.81 mg/cc rock (17%) at 1000
ppm, 0.32 to 0.20 mg/cc rock (37%) at 500 ppm and 0.20 to 0.14 mg/cc rock (30%) at 250
ppm initial concentration of CD1045. This indicates that initial conditions are important
in the adsorption of CD1045.
Figure 4.20 depicts the adsorption of surfactant CD1045 in three different
sequences of experiments. The first sequence used CD1045, where the core was flushed
with brine before injecting the different concentrations of surfactant. The second
sequence used lignosulfonate as the sacrificial agent; the core was first flushed with
brine, then lignosulfonate was injected followed by injecting CD1045. The third
sequence coinjected lignosulfonate with CD1045, where the core was flushed with brine
before injecting the different concentration of CD1045 mixed with lignosulfonate. The
results show that coinjecting 5000 ppm of lignosulfonate with CD1045 (500 ppm and
lOOO ppm initial concentrations) reduces the adsorption of CD1045 by 38% and 17%,
respectively, whereas preflushing the core with 5000 ppm lignosulfonate reduces the
-57-
adsorption of CD1045 (500 ppm and 1000 ppm initial concentrations) by 56% and 30%,
respectively.
In order to demonstrate the cost effectiveness of using lignosulfonate as sacrificial
agent, an example calculation is presented in Table 4.2. The expense due to CD1045
adsorption was determined based on the model consisting of a 15 feet pay thickness
formation with 12% average porosity in a 25 acre field. Coinjection of lignosulfonate
with CD1045 reduced the loss of CD1045 from 870 to 544 Ib/acre-ft at 500 ppm and
from 2638 to 2203 Ib/acre-ft at 1000 ppm CD1045. The cost savings wouldbe $153,992
and $230,988, respectively. On the other hand, prefiushing the core with 5000 ppm
lignosulfonate reduced the adsorption of CD1045 from 870 to 381 Ib/acre-ft at 500ppm
and from 2638 to 1849 Ib/acre-ft at 1000 ppm CD1045. The cost savings would be
$205,323 and $372,147, respectively.
The results show that prefiushing with 5000 ppm lignosulfonate is more effective
in reducing the loss of surfactant CD1045 and more money could be saved than by
coinjecting 5000 ppm of lignosulfonate with CD1045.
« 0.08
-58-
y = 0.0006X + 0.0012
100 150 200
Concentration, ppm
250 300
Fig. 4.14 - Surfactant CD1045 standard curve with wavelength520 nm.
8CO
I 1.60^
3.50
3.00
2.50
2.00
1.00
0.50
0.00 —1—
50
-59-
y = 0.0094X + 0.0895
100 150 200 250
Concentration, ppm
300 350
Fig. 4.15- Lignosulfonate calcium standard curvewith wavelength 283 nm.
o>
Eco
e-S
<
3.50
2.50
-60-
200 400 600 800
Final concentration of surfactant CD1045,ppm
r •• i !•
1000 1200 1400 1600 1800
Fig. 4.16 - Adsorption ofsurfactant CD1045 onto Berea sandstone core sample.
9 2.50
2.00
s 1.50
•P 1.00
-61-
5000 10000 15000 20000
Final concentration of lignosulfonate, ppm
Fig.4.17 - Adsorption oflignosulfonate onto Berea sandstone core sample.
25000
1.20 -
^ 1.00
0.20 -
5 0.00
-62-
200 400 600 800
Final concentrations of surfactant, ppm
1000
-O-O ppm of lignosulfoante -^5000 ppm of lignosulfonate
Fig. 4.18 - Adsorption of surfactant CD1045 onto Berea sandstone coresample asa function ofsurfactant CD1045 concentration at lignosulfonate levels of0 ppm and 5000
ppm (The core was flushed with brine followed by injecting the three differentconcentrations ofsurfactant).
1.20
I
-63-
100 200 300 400 500
Concentrations of surfactant, ppm600
-O-O ppm of lignosulfoante -^5000 ppm of lignosulfonate
Fig. 4,19 - Adsorption ofsurfactant CD1045 onto Berea sandstone core sample asa function ofsurfactant CD1045 concentration atlignosulfonate levels of0 ppm and 5000
ppm (The corewas flushed with brine prior to injecting each concentrations ofsurfactant).
o E 0.40
-64-
Final concentration of surfactant, ppm
-O-CD1045 alone -O-Ugnosulfonate first Mixed
600
Fig. 4.20 - Adsorption ofsurfactant CD1045 with three different sequences ofexperiments ontoBereasandstone core sample.
-65-
Table 4.2 - CostSaving Using a Sacrificial Agent, Based on Adsorption Results
(Ib/acre-ft).
Adsorption results in (Ib/acre-ft) Cost saving with a sacrificial agent ($)
Initial con-. CD1045 Mixture Pie-flush with Mixture Pie-flash with
centradon 001045+ 5000 ppm CD1045+ 5000 ppm
(ppm) Ugnosulfonate Lignosulfonate Lignosulfonate lignosulfonate
500 ppm 870 544 381 $ 153,992 $ 230.988
1000 ppm 2638 2203 1849 $205^23 $ 372,147
CHAPTERS
CONCLUSIONS
AND
RECOMMENDATIONS FOR FUTURE WORK
5.1 Conclusions
Conclusions were drawn based on the three different sets of laboratory
experiments. These studies investigated the feasibility of using Ugnosulfonate as a
sacrificial agent to mix with surfactants in C02-foamflooding application.
5.1.1 Foam Durability Experiments
Based on the results of a series of foam durability experiments, the following
conclusions can be drawn:
1. Ugnosulfonate in a brine solution (1.5 wt% NaCL + 0.5 wt% CaCl2) is a weak
foaming agent for generating COa-foam bubbles.
2. Lower interfacial tension is favorable to generating more stable foam in the
mixture of lignosulfonate/surfactant mixture.
-66-
-67-
3. The BFTs of lignosulfonate solutions decrease with the increase of the
concentration of lignosulfonate.
4. The IFTs of the mixtures of surfactant and lignosulfonate increase with the
concentration of lignosulfonate.
5. When a low concentration (0.25 and 0.5 wt%) of lignosulfonate was mixed with
0.025 wt% of other surfactants, CD1045 generated the strongest foam followed
byCD1050andCD1040.
5.1.2 COi-Foam Corefloodjng Experiments
Based on COa-foam coreflooding experiments, the following conclusions were
made:
1. Lignosulfonate mixed with CD1045 could improve the problem ofnonuniformity in
displacement associated with rock heterogeneity and reduce the channeling of CO2
in a heterogeneous core.
2. Coinjection of CO2 and lignosulfonate at 5000 ppm as sacrificial agent mixed with
various concentration of surfactant CD1045 (250 ppm or 500 ppm) is effective for
delaying CO2 breakthrough time in the high permeability region and diverting
displacing fluid into the low permeability region. Thus, oil in the low permeability
region was displaced andoil production was significantiy increased.
3. The displacement efficiency ofCD1045 @500 ppm and lignosulfonate @5000 ppm
at about 8.0 total PV injected had the highest oU recovery (97%) in the low
permeability region, foUowed by CD1045 @ 2500 ppm (94%), and CD1045 @250
ppm and lignosulfonate @5000ppm (68%).
-68-
4. The pressure drop of CD1045 @500 ppm and lignosulfonate @5000 ppm is higher
than that of CD1045 @250 ppm and lignosulfonate @5000 ppm; producing a higher
oil recovery.
5.1.3 Adsorption Measurement Experiments
Based on adsorption measurement experiments, the following conclusions can be
drawn:
1. The adsorption of surfactant CD1045 on Berea sandstone increases as the
concentration of CD1045 increases.
2. CD1045 adsorption is dependent on the initial core conditions.
3. The addition of lignosulfonate reduces the adsorption of surfactant CD1045.
4. Coinjecting 5000 ppm of lignosulfonate with CD1045 (500 ppm and 1000 ppm)
reduces the adsorption of CD1045 by 17% to 38%, respectively, whereas
preflushing the core with 5000 ppm lignosulfonate reduces the adsorption of
CD1045 (500 ppm and 1000ppm) by 30% to 56%, respectively.
5. Preflushing with 5000 ppmlignosulfonate is more effective in reducing the lossof
CD1045 and more money could be saved than by coinjecting 5000 ppm of
lignosulfonate with CD1045.
5.2 Recommendations for Future Work
1. Besides using calcium lignosulfonate as sacrificial agent, other types of
lignosulfonate such as ammonium lignosulfonate and sodium lignosulfonate
mixed with different types of surfactants such as CD1045, Dowfax8390 and
CD128 should be examined.
-69-
2. Using different types of rock such as limestone and carbonate in COi-foam
corefloodingexperiments and adsorption measurement experiments are necessary
to be performed to investigate the effectiveness of lignosulfonate as a sacrificial
agent in different types of reservoir rocks.
REFERENCES
Adamson, A.W.: Physical Chemistry ofSurfaces, FifthEdition, John Wiley & Sons, Inc.,
1990.
Albrecth, R.A., and Marsden, S.S.: "Foams as Blocking Agents in Porous Media," SPEJ
(March, 1970) 51-55.
Bae, J. H. and Petrick, C.B.: "Adsorption/Retention of Petroleum Sulfonates in Berea
Cores," paper SPB 5819 presented at the 1976 SPE Symposium on Improved
Methods for Oil Recovery, Tulsa, March 22-24.
Bernard, G.G., and Holm, L.W.: "Effect of Foam on Permeability of Porous Media to
Gas," SPEJ (Sept1964) 267-274.
Bemard, G.G., Holm, L.W., and Harvey, C.P.: "Use of Surfactant to Reduce CO2
Mobility in Oil Displacement," SPEJ (1980), 281-292.
Burman, J.W. and Hall, B.E.: "Foam-Diverting Technique Improved Sandstone Acid
Jobs," World Oil, (Nov. 1987) 31-36.
Bharat, B.B., Homof, V., and Neale, G.: "Enhanced Oil Recovery Using
Lignosulfonate," The Canadian Joumal of Chemical Engineering, 57, (April,
1979).
Caudle, B.H., and Dyes, A.B.: Improving Miscible Displacement by Gas-Water
Injection," Trans., AIME (1958) 213,281-284.
Chiwetelu, C., Neale, G, and Homof, V.: "Effects of Addition of Lignosulfonate on Oil
RecoveryEfficacyof PetroleumSulfonates," paper SPE 8786, Nov 5,1979.
Falls, A.H., Hirasaki, G.J., Patzek, T.W., Gaugliz, D.A., Miller, D.D., and Ratulowski,
T.: "Development of a Mechanistic FoamSimulator: The Population Balance and
Generation by Snap-Off,"SPEKE (Aug. 1988) 884.
Felber, J.B and Dauben, D.L.: "Laboratory Development of Lignosulfonate Gels for
Sweep Improvement," SPEJ., (Dec 1977) 391.
-70-
Harkins, W.D. and Brown, F.E., J. Amer. Chem. Soc. (1919) 41,499.
Harwell, J.F.: "Surfactant Adsorption and Chromatographic Movement with Application
in Enhanced Oil Recovery", Ph.D. dissertation,U. of Texas, Austin, (1993).
Hill,A.D. andGalloway, P.J.: "Laboratory andTheoretical Modeling of Diverting Agent
Behavior," (July 1984) 1157-1162.
Heller, J.P., et al.: "Direct Thickeners for Mobility Control in CO2 floods," paper SPE
11789 presented at the 1983 International Symposium on Oilfield and Geothermal
Chemistry, Denver, June 1-3.
Hoefner, M.L., Evans, E.M., Buckles, J.J., and Jones, T.A.: "CO2 Foam: Results From
Four Developmental Field Trials," paper SPE/DOE 27787 presented at the 1994
Symposium on Improved Oil Recovery, Tulsa, April 17-20.
Homof v.: "Applications of Lignosulfonates in Enhanced Oil Recovery," Cellulose
Chemistry ondTechnology, (1990), 24,407-415.
Hong, S.A, Bae, J.H and Lewis, G.R.: "An Evaluation of Lignosulfonateas a Sacrificial
Adsorbate in Surfactant Flooding," SPERE (Feb.1987) 17-27.
Hong, S.A, Bae, J.H and Lewis, G.R.: 'Tield Experiment of Lignosulfonate Preflushing
for Surfactant Adsorption Reduction," SPERE (Nov. 1990) 467-474.
Hobbs, L. R.: "Adsorption of Alkylphenol Surfactants on Kaolinite in the Presence of
OrganicCompounds," MS thesis, U. of Texas, Austin, TX (May 1976).
Hurd, B.G.; "Adsorption and Transport of Chemical Species m Laboratory Surfactant
Waterflooding Experiments," paper SPE 5818 presented at the 1976 SPE
Symposium on Improved Oil Recovery, Tulsa, March 22-24.
Jonas, T.M., Vasicek, S.L., and Chou, S.I.:"Evaluation of CO2 Foam Field Trial-Rangely
Weber Sand Unit," paper SPE20468 presented at the 1990 Annual Technical
Conference, New Orleans, September 23-26.
Lawson, J.B.: 'The adsorption of Non-Ionic and Anionic Surfactants on Sandstone and a
Carbonates," paper SPE 7052 presented at the 1978 SPE Symposium on
Improved Methods for Oil Tulsa, Apr. 16-19.
-71-
Kalfoglou et al.: "Ugnosulfonate-Acrylic Acid Graft Copolymers as Sacrificial Agents
For CarbonDioxideFoaming Agents," US PatentNo. 08/562,927(1995).
Kalfoglou, M. and Monson, L.T.: "Lignosulfonate as Sacrificial Agents in Oil Recovery
Processes," US Patent No. 4,006,779 (1977).
Kovarik, F.S., Heller, J.P., and Martin, F.D.: "Improvement of CO2 Flood Performance,"
Fifth Annual Report, New Mexico Petroleum Recovery Research Center, PRRC
Report 89-22 (February 1990).
Kuehne, D.L., Frazier, R.H, Cantor, J., and Horn, WJr.: "Evaluation of Surfactants for
CO2 Mobility in Dolomite Reservoirs," paper SPE 24177 presented at the 1992
SPE/DOE Symposium on Enhanced OilRecovery, Tulsa, April22-24.
Kuhlman, M. I, Lau, H.C and Falls, A.H.: "Carbon Dioxide Foam With Surfactants Used
BelowTheir CriticalMicelle Concentrations," paper SPE 28952 presented at the
SPE International Symposium on Oilfield Chemistry, San Antonio, TX, USA, 14-
17 February 1995.
Kuhlman, M. I, Falls, A.H, Hara, S.K., Monger-McClure, T.G and Borchardt, J.K.: "C02
Foam with Surfactants Used Below Their Critical Micelle Concentration," SPERE
(November 1992) 445.
Lee, H.O., Heller, J.P., and Hoefer, A.M.W.: "Change in Apparent Viscosity of CO2-
Foam with Rock Permeability," SPERE (November 1991)421-428.
Mannhardt, K., Schramm, L.L., and Novosad, J.J.: "Effect of Rock Type and Brine
Composition on Adsorption of Two Foam-Forming Surfactants," paper SPE
20463 presented at the 1990 SPE Annual Technical Conference and Exhibition,
New Orleans, Sept. 23-26.
Martin, F.D., and Heller, J.P., F.D.: "Improvement of CO2 Flood Performance," Final
Report, NewMexico Petroleum Recovery Research Center, (1991).
Moradi-Araghi, A., Johnston, E.L., Zomes, D.R., and Harpole, K.J.: "Laboratory
Evaluation ofSurfactants InC02-Foam Application atthe South Cowden," paper
SPE 37218 presented at the 1997 SPE International Symposium on Oilfield
Chemistry, Houston, Feb. 18-21.
-72-
Novasad, JJ., and lonescu, E.F.: "Foam Forming Surfactants for Beaverhill Lake
Carbonates and Gilwood Sands Reservoirs," CIM Paper #87-38-80, presented at
the 1987 Annual Technical Meeting of the Petroleum Society of CIM, Calgary,
June 7-10.
Parlal, M., Pairis, M., and Jasinski, R.: "An Experimental Study of Foam Flow Through
Berea Sandstone With Application to Foam Diversion in Matrix Acidizing,"
paper SPE 29678 presented at the 1995 Westem Regional meeting, Bakersfield,
March 8-10.
Prieditis, J. and Paulett, G.S.: "C02-Foam Mobility Tests at Reservoir Condition in San
Andres Cores," paper SPE 24178 presented at the 1992 SPE/Doe Symposium on
Enhanced Oil Recovery, Tulsa, April 22-24.
Rowe, H.G., York, S.D. and Ader, J.C.: "Slaughter Estate Unit Tertiary Pilot
Performance," paper SPE 9796 presented at the 1981 SPE EOR Symposium,
Tulsa, April 5-8.
Scamehom, J. F., Schecter, R. S. and Wade, W. H.: "Adsorption of Surfactants on
Mineral Oxide Surfaces from Aqueous Solution. I: Isometrically Pure
Surfactants", J. Colloid and Interface Science, (1982) 85, No. 2,463.
Siddiqui, S., Talabani, S., Yang, J., Saleh, S. and Islam, M.R.: "An Experimental
Investigation of the Diversion Characteristic of Foam in Berea Sandstone Cores
of Contrasting Permeabilities," paper SPE 37463 presented at the 1997 SPE
ProductionOperationsSymposium, OklahomaCity, March 9-11.
Somasundaran. P.: " Adsorption from Flooding Solutions in Porous Media," Second
Annual Report submitted to DOE, NSF, and a Consortium of supporting
Industrial Organizations, Columbia University, New York, NY(March 1988).
Stevens, J. E., and Martin, F. D.: "CO2 Foam Field Verification Pilot Test at EVGSAU:
Phase fflB-Project Operations andPerformance Review," paper SPE/DOE 27786
presented at the 1994 Symposium onImproved Oil Recovery, Tulsa, April 17-20.
ThomasM. S., "Analysis of Surfactant," SurfactantScienceSeries40,1992.
-73-
Tsau, J.S., and Heller, J.P.: "How Can Selective Mobility Reduction of C02-Foam Assist
in Reservoir Floods," paper SPE 35168 presented at the 1996 Permian Basin Oil
and Gas Recovery Conference, Midland, March 27-29.
Tsau, J.S., Yaghoobi, H. and Grigg, R.B.: "Smart Foam to Improve Oil Recovery in
Heterogeneous Porous Media," paper SPE 39677 presented at the 1998 SPE/DOE
Improved Oil Recovery Symposium, Tulsa, April 19-22.
Tsau, J.S. and Heller, J.P.: **Evaluation of Surfactants For COa-Foam Mobility Control,"
paper SPE 24013presentedat the 1992SPE PermianBasin Oil and Gas Recovery
Conference, Midland, March 18-20.
Tsau, J.S., Yaghoobi, H., and Grigg, R.B.: "Use of Mixed Surfactants to Improve
Mobility Control in CO2 Flooding," paper SPE 39792 presented at the 1998 SPE
Permian Basin Oil and Gas Recovery Conference, Midland, March 25-27 1998.
Tsau, J.S. and Grigg, R.B.: "Assessment of Foam Properties and Effectiveness in
Mobility Reduction for C02-Foam Floods," paper SPE 37221 presented at the
1997 SPE International Symposium on Oilfield Chemistry, Houston, Feb. 18-21.
Tsau, J.S., Syahputra, A.E., Yaghoobi, H. and Grigg, R.B.: "Use of Sacrificial Agents in
CO2 Foam Flooding Application," paper SPE 56609 presented at the 1999 SPE
Annual Technical Conference and Exhibition, Houston, Texas, October 3-6.
Trogus, F.J., Sophany, T., Schecter, R.S., and Wade, W.H.: "Static and Dynamic
Adsorption of Anionic and Nonionic Surfactants," SPEJ (Oct. 1977) 337-344.
Wang, G.C.: "A Laboratory of CO2 Foam Properties and Displacement Mechanism,"
paper SPE/DOE 12645presented at the 1984SPE/DOESymposium on Enhanced
Oil Recovery, Tulsa, April 15-18.
Yang, S.H. and Reed, R.L.: "Mobility Control Using CO2 Foams," paper SPE 19689
presented at the 1989 Annual Technical Conference and Exhibition, San Antonio,
October 8-11.
Yaghoobi, H., Tsau, J.S., andGrigg, R.B.: "Effect of Foam on CO2 Breakthrough: Is this
Favorable to Oil Recovery?" paper SPE 39789 presented at the 1998 SPE
Permian Basin Oil and Gas Recovery Conference, Midland, March 23-26.
-74-
top related