Research Article Numerical Simulation and Optimization of...

Research ArticleNumerical Simulation and Optimization of Enhanced OilRecovery by the In Situ Generated CO

2Huff-n-Puff Process with

Compound Surfactant

Yong Tang1 Zhengyuan Su1 Jibo He1 and Fulin Yang2

1The State Key Laboratory of Oil amp Gas Reservoir Geology and Exploitation Engineering Southwest Petroleum UniversityChengdu 610500 China2The Institute of Petroleum Engineering Technology Jiangsu Oilfield Corporation Yangzhou Jiangsu 225009 China

Correspondence should be addressed to Yong Tang tangyong2004126com

Received 2 April 2016 Accepted 23 June 2016

Academic Editor Jean-Luc Blin

Copyright copy 2016 Yong Tang et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

This paper presents the numerical investigation and optimization of the operating parameters of the in situ generated CO2Huff-

n-Puff method with compound surfactant on the performance of enhanced oil recovery First we conducted experiments ofin situ generated CO

2and surfactant flooding Next we constructed a single-well radial 3D numerical model using a thermal

recovery chemical flooding simulator to simulate the process of CO2Huff-n-Puff The activation energy and reaction enthalpy

were calculated based on the reaction kinetics and thermodynamicmodelsThe interpolation parameters were determined throughhistory matching a series of surfactant core flooding results with the simulation model The effect of compound surfactant onthe Huff-n-Puff CO

2process was demonstrated via a series of sensitivity studies to quantify the effects of a number of operation

parameters including the injection volume and mole concentration of the reagent the injection rate the well shut-in time and theoil withdrawal rate Based on the daily production rate during the period of Huff-n-Puff a desirable agreement was shown betweenthe field applications and simulated results

1 Introduction

Enhanced oil recovery (EOR) is the practice of implementingdifferent techniques to increase crude oil production froma reservoir According to the literature the most commonlyapplied EOR techniques include thermal recovery chemicalinjection and gas injection In the Permian Basin CO

2EOR

and thermal methods continue to be the most dominantEOR field applications [1] Furthermore most oil fields areoperated under water flooding

It is well known that some oil will remain unproducedafter water flooding (termed residual oil) Even though poly-mer flooding may reduce residual oil saturation a significantportion of the oil will remain in the reservoirs Surfactantsthen have to be injected to produce the residual oil [2]Because acid and exothermic chemical reactions relieve deepreservoir damage surfactants reach places in the formationwhere many polymers cannot enter the injected surfactant

decreases interfacial tension in oil-water contact and CO2

dissolved in oil increases oil volume that subsequently affectsthe displacement of residual oil [3] Surfactant EOR is afundamental method for the recovery of this residual oil Anumber of factors impact the selection of the EOR techniqueand the resultant crude oil recovery Generally speakingthese factors include the consideration of both technologicalavailability and economic feasibility Bera and Babadagli[4] tested foamy oil flow for different types of EOR gasesdissolved and evolved at different conditions under pressuredepletion Their results showed that among the three gasesof CH

4 C3H8 and CO

2 CO2is a good candidate for foamy

oil Maximum oil recovery (more than 50 of the original oilin place [OOIP]) was obtained in the case of CO

2 Olsen [5]

compared CO2flooding with water flooding The test results

showed that water flooding leftmuchmore oil in the reservoirformation than CO

2flooding did

Hindawi Publishing CorporationJournal of ChemistryVolume 2016 Article ID 6731848 13 pageshttpdxdoiorg10115520166731848

2 Journal of Chemistry

Traditionally the CO2Huff-n-Puff technique is consid-

ered an effective technique and field tests have revealed thatthis technology is generally economically feasible in diversereservoir environments [6ndash9] The governing mechanismsof this technology are as follows a fraction of the injectedCO2will be dissolved in the water phase which increases

the water viscosity by 20ndash30 and its mobility 2-3 timesThe CO

2dissolved in oil decreases the interfacial tension

(IFT) in the oil-water contact and the CO2dissolved in oil

reduces the oil viscosity 15ndash25 times Also theCO2dissolved

in oil increases the oil volume [10] The dissolution of CO2

in the oil phase can also increase the total volume of oiland the vaporization of lighter hydrocarbon components [11ndash15] Martinez et al [16] investigated the use of CO

2as an

EOR solvent for heavy oil Due to multicontact miscibilitythe Huff-n-Puff simulation cases also indicate increased oilrecovery and reducedmatrix oil saturation by CO

2compared

to N2injection

Although the CO2Huff-n-Puff process has been deter-

mined to be able to improve oil recovery some negativeimpacts associated with the application of this techniquehave been reported For example some negative impactsare the reduction of CO

2concentration coagulation and

sedimentation of asphaltene in the oil phase due to changein the thermobaric conditions well and oil field equipmentcorrosion and issues with CO

2transportation [10] Thus

a considerable effort has been undertaken to develop thistechnology (in particular the in situ generated CO

2tech-

nique)This technique involves the injection of undergroundwater into a formation to allow injected chemicals to reactwith formation materials to release CO

2inside the reservoir

[3] The advantage of this technique is the elimination ofany surface facility and associated negative impacts on theenvironment In addition chemical enhanced oil recoveryhas recently focused on using surfactants to change oil-wetwettability into water-wet wettability to enhance water imbi-bition into matrix blocks in the oil reservoirs and to improvethe flowing property of crude oil by reducing interfacialsurface tension [17ndash24] The increase in recovery by CO

2

generation is also attained by maintaining (or increasing)the reservoir pressure displacing the oil and eliminating theinterface between the oil and CO

2

Jia et al [3] conducted a laboratory investigation on insitu CO

2generation and found that the proposed technology

can decrease the injection pressure of the damaged core by117MPa Furthermore the increase rates of the amount of thegenerated gas and the oil volume escalate with the increaseof temperature and system concentration In addition theoil volume and the oil viscosity reduction rates increase withthe increase of oil viscosity Under the condition of 60∘C10MPa and 2010mPasdots the oil volume increased by 25 theoil viscosity decreased by 527 and the recovery efficiencyimproved by 76ndash142

AlSofi et al [25] performed a series of surfactant coreflooding experiments in carbonate cores under typical reser-voir conditions The core flooding results showed significantoil recovery potential for surfactant flooding (SF) formula-tions under the investigated conditions The base SF resultedin a 234 incremental recovery after water flooding with

a combination of polymer and surfactant The results alsodemonstrated the effects of surfactant slug-size and concen-tration on the recovery performance Kumar andMandal [26]found experimentally that alkali-surfactant systems changethe wettability of an intermediate-wet quartz rock to water-wet and the change of wettability from oil-wet to water-wet increases the oil recovery significantly The solution ofC19H42BrN surfactant in the presence of sodium metaborate

changes the contact angle to 8-9∘ whereas the solutions ofC12H25NaO3S in the presence of Na

2CO3change the contact

angle to 4∘ An effective mobility ratio and a reduced IFTbetween the residual oil and displacing fluid are obtainedby the formed emulsion which is recognized as a potentialefficient chemical EOR process C

12H25NaO3S also forms

good emulsions in the presence or absence of alkali whichhave good stability compared to other surfactants Unlikenonionic surfactants ionic surfactant molecules containcharge and form a charged monolayer at the interface henceit is found to be comparatively more capable of reducing theinterfacial tension

Our literature review concludes that the in situ generatedCO2Huff-n-Puff process with chemical compound surfac-

tant could substantially improve oil recovery performance[27 28] However very limited research has been undertakenin this area especially for the parametric analysis of thekey operating variables for the improvement of oil recoveryTherefore we performed a numerical simulation and opti-mization study on the effect of the in situ generatedCO

2com-

pound surfactant Huff-n-Puffmethod on oil recovery perfor-mance for a low permeability fault-block reservoir located insoutheast ChinaThe objective of this paper is to examine theimportant parameters best practices and lessons learned thatcontribute to the success of the in situ generated CO

2Huff-

n-Puff process with compound surfactant Based on thesesuccesses the optimal operating parameters are analyzed andidentified and recommendations to improve related Huff-n-Puff projects further are presented

2 Experimental

21 In Situ Generated CO2

211 Materials The N2gas (purity 9999) was supplied by

Chengdu Dongfang Electric Gas Co Ltd The NaHCO3and

Na2CO3salts were supplied by SinopharmChemical Reagent

Co Ltd were of analytical grade with a purity of gt99 andare shown in Table 1 The specific details of the compoundacid made up of CH

3COOH and HCl are also shown in

Table 1 Distilled water was used to prepare the solutions

212 Apparatus and Procedures The auxiliary laboratoryequipment was purchased from Chengdu Kelong ChemicalReagent Co Ltd and included test tubes stopwatch sophis-ticated electronic balance rubber tubes glass tubes and acidburettes The main apparatus consisted of a reaction vessel(Taixing Xingjian Chemical and Machinery Plant) a highpressure manual metering pump (Jiangsu Huaan ScientificInstruments Co Ltd) and a N

2gas cylinder (Chengdu

Journal of Chemistry 3

Table 1 Source and purity of the reagents used

Compounds CAS number Source Molar mass(gmol)

Purity (massfraction)

N2

7727-37-9 Chengdu Dongfang Electric Gas Co Ltd 28013 09999NaHCO

3144-55-8 Sinopharm Chemical Reagent Co Ltd 8401 0999

Na2CO3

497-19-8 Sinopharm Chemical Reagent Co Ltd 10599 0999CH3COOH 64-19-7 Sinopharm Chemical Reagent Co Ltd 6005 099

HCl 7647-01-0 Sinopharm Chemical Reagent Co Ltd 3646 370C12H25NaO3S 2386-53-0 Chengdu Kelong Chemical Reagent Co Ltd 27238 099

C18H29NaO3S 25155-30-0 Chengdu Kelong Chemical Reagent Co Ltd 34848 099

Dongfang Electric Gas Co Ltd) The experiments wereperformed inside the apparatus based on the static approachA schematic of the experimental setup for in situ generatedCO2is shown in Figure 1The temperature of the thermostatic

air bath was controlled by a temperature controllerIn this experiment the reaction vessel and lines were

evacuated using a vacuum pump prior to introducing theaqueous solution which consisted of Na

2CO3 NaHCO

3 and

compound acid (HCl + CH3COOH) The concentration of

the NaHCO3solution was the same as that of the Na

2CO3

solution (20wt) The concentration of compound acid was1270

The reaction vessel was placed in the air bath and thetemperature in the bath was controlled with an immersedthermocouple by an electric furnace to the desired temper-ature of 60∘C Initially the desired amounts of the Na

2CO3

and NaHCO3solutions were injected into the reaction vessel

Then the compound acid was injected Subsequently N2

was discharged into the system using the pressure amplifierand the reaction vessel was controlled to reach the desiredpressure of 1000MPa

The aqueous phase in the vessel was stirred using amagnetic stirrer The stirring of the aqueous phase ensureda homogeneous reaction temperature inside the vessel Thetemperature was detected by a thermometer within plusmn01∘Cscale and the pressure was monitored by a transducerwith a precision of 001MPa Finally the pressure and thetemperature of the system were recorded

22 Surfactant Flooding

221 Materials The oil sample was collected from the fault-block formation of Chinarsquos northeast region The composi-tional analysis of dead oil is presented in Table 4 For allHuff-n-Puff tests the core was saturated with dead oil atwhich viscosity is 15530mPasdots and density is 90850 gcm3 at25∘C In addition to the reagents previously described in thein situ generated CO

2experiment we used the surfactants

of C12H25NaO3S and C

18H29NaO3S supplied by Chengdu

Kelong Chemical Reagent Co Ltd which were of analyticalgrade with a purity of gt99 (see Table 1)

222 Apparatus and Procedures A schematic diagram of thesurfactant flooding experimental setup used in this study isshown in Figure 2

A sand pack measuring approximately 50 cm in lengthand 35 cm in diameter was prepared with 80ndash120mesh sandsin a sleeve The sand was wet-packed with a pneumaticvibrator and the pack was vibrated for about 20min Thepacked core was then triaxially loaded and subjected to anoverburden pressure to seal the assembly Once the coreholder was fully wet-packed the vibrator continued at arelatively high rate for two hours to ensure a tight sand packThe core holder was placed in a thermostatic air bath andconnected to the fluid injection system and sample collectionsystemThewet-packed sand pack was flooded with crude oiluntil irreducible water saturation was achievedThe details ofthe sand pack are presented in Table 2

The flood tests were conducted horizontally at an ambienttemperature of 60∘C After establishing the above conditionsthe sand pack was ready for water flooding as an initialoil recovery process Water was injected at a constant rateof 10mLmin and was continued to one pore volumeFollowing the water flooding the next stage was the processof surfactant flooding (in situ generated CO

2Huff-n-Puff

with compound surfactant) In this primary Huff-n-Puffprocess the concentrations of the compound acid Na

2CO3

and NaHCO3were all 08molL and the concentration of the

surfactant was 03The method of slug injection formula was selected and

conducted as follows initially a surfactant solution slugwith a specified size of 02 pore volume was injected at aconstant rate of 10mLmin Then the compound acid andthe Na

2CO3solution were injected at the rate of 10mLmin

At the same time the NaHCO3solution was injected at

a constant rate of 10mLmin Subsequently we cycled theinjection of the compound acid together continually with theNa2CO3solution and NaHCO

3solution until the volume

of injection reached the 01 pore volume After a 2 h shut-in period the oil recovery process was initiated The backpressure was established at 6MPa When the shut-in timereached 2 h we used a measuring cylinder to collect andrecord the volumes of effluent from the outlet

The specific procedures of the secondary and tertiaryHuff-n-Puff processes were the same as those of the primaryHuff-n-Puff process The oil recovery rate (119864

119863) of the three

cycles of CO2Huff-n-Puff with compound surfactant was

calculated using

119864119863=sum119881oi119878oi119881119875times 100 (1)


(9) (10) (11)(2)

(2)

(7)

(8)

(6)

(3)

(4) (5)

(1)

(12)

Figure 1 Schematic diagram of the in situ generated CO2apparatus (1) Gas cylinder (2) vacuum pump (3) pressure amplifier (4) pressure

gauge (5) temperature transducer (6) reaction vessel (7) magnetic stirrer (8) thermostatic air bath (9) Na2CO3solution (10) NaHCO

3

solution (11) compound acid and (12) pump

Table 2 Sand pack filling conditions and properties

PermeabilitymD Porosity () Oil saturation () Water saturation () Temperature (∘C)

59423 3977 6887 3113 60

where 119881oi is the oil volume collected from outlet 119878oi is theoriginal water saturation and 119881

119875is the pore volume

3 Numerical Simulation

31 Reservoir Modeling Parameters In this numerical studya typical low permeability fault-block oil reservoir is taken asan example A single-well radial plane model was establishedusing STARS Ver 2012 from the Computer ModelingGroup (CMG) (Figure 3(a)) Although this process cannotcharacterize the whole reservoir the reaction of gas-forming

in the formation and change of components can be preciselydescribed The computational domain contains a total of14616 active grid blocks (29times 24times 21) In the 119868 direction fromthe center of wellbore to the edge there are three 2m stepgrids ten 5m ones and sixteen 9m ones In the 119869 directiona 360∘ wellbore circle is divided into 24 equal parts with each15∘ In the 119870 direction the grid is constructed according tothe thickness of the real reservoir The property parametersof porosity permeability and thickness are obtained fromthe well logging data which are shown in Figures 3(b)ndash3(d)respectively The initial oil saturation is about 45 and theOOIP is about 354 times 105 tons The other reservoir modeling


(2) (3) (4) (5)

(1)

(1)

(6) (6)(6)

(6)

(7)

(8) (9)

(10)

(11)

Figure 2 Schematic diagram of the core flooding apparatus (1) Pump (2) Na2CO3solution (3) NaHCO

3solution (4) acid (5) compound

surfactant (6) pressure gauge (7) thermostatic air bath (8) sand pack tube (9) back pressure regulator (10) oil and water collector and (11)gas meter

parameters are shown in Table 3 The detailed properties ofthe sand-rock layer for the oil reservoir are as follows thevolumetric thermal capacity is 235 times 106 J(m3sdot∘C) and thethermal conductivities are 66 times 105 J(msdotdsdotC) and 8305 times103 J(msdotdsdotC) for the rock and oil samples respectively

32 Phase Equilibrium and Properties of Fluids In order todevelop PVT thermodynamic equations for the reservoirfluids the fluids were characterized by analytical tests ofconstant composition expansion saturation pressure deter-mination and single flash tests The original composition ofcrude oil is shown in Table 4 Subsequently the key stateparameters for establishing PVT equationswere derived fromthe CMG Winprop Ver 2012 phase behavior simulatorThe final results of flash tests and saturation pressure deter-mination fitting are shown in Table 5 and the constantcomposition expansion results are given in Figure 4 Asshown in Table 6 fluid property analysis allowed the lumpingof nonaqueous components into five pseudo-componentsThe mole fractions of each component were CO

2 25 N

2ndash

C1 159 C

2ndashC6 3 C

7ndashC20 308 and C

21ndashC32 478

Table 3 Characteristic parameters of the reservoir (at a reservoirtemperature of 59∘C)

Reservoir depth (m) 1212Total thickness (m) 979Porosity () 5ndash28Permeability (mD) 15ndash90Drainage radius (m) 200Original water saturation 055Original formation pressure (MPa) 1134Reservoir temperature (∘C) 59Saturation pressure (MPa) 425Viscosity of crude oil (mPasdots) 7001Density of crude oil (gcm3) 08218

33 Parameters of In Situ Generated CO2 Thekey parametersfor the reaction of in situ CO

2generation in reservoir layers

include the gas generation rate the activation energy reactionenthalpy and breakdown temperature [29 30] These keyreaction parameters can influence the accuracy and reliability


1256

1247

1238

1230

1221

1212

1203

1194

1186

1177

1168

(a)

028

026

023

021

019

016

014

012

010

007

005

(b)

90

83

75

68

60

53

45

38

30

23

15

(c)

124

112

101

89

78

67

55

43

32

20

09

(d)

Figure 3 Single-well radial plane model of the southeast oilfield (CMG STARS Ver 2012) (a) 3D sectional view of depth (b) grid porosity(c) grid permeability (mD) and (d) grid thickness (m)

Table 4 The original composition of crude oil

Component CO2

N2

C1

C2

C3

iC4

nC4

iC5

nC5

C6

C7

C8

C9

C10

C11+

Composition 248 037 1802 128 052 024 027 020 015 053 036 027 043 037 7451

Table 5 The fitted results of single flash tests and saturation pressure (at a reservoir temperature of 59∘C)

Index Experiment Simulation Absolute error Relative errorGas oil ratio (m3m3) 16850 16610 minus0240 minus142Crude oil density (gcm3) 0909 0899 minus001 110Viscosity (cp) 70010 70006 minus010 minus0002Saturation pressure (MPa) 4250 4249 minus0001 minus002

Table 6 Characteristic parameters of formation of nonaqueous fluid pseudo-components

Components Molecular weight Critical pressure Critical temperature Critical volume Acentric factor Coefficient 119886 Coefficient 119887(gmol) (atm) (K) (m3) mdash mdash mdash

CO2

440100 72800 30420 00940 022500 0457236 0077796N2to C1

162863 43083 18923 00988 000865 0457236 0077796C2to C6

509499 29588 39460 02209 016607 0457236 0077796C7to C20

2619422 14612 78338 07529 068937 0457236 0077796C21to C32

4016392 10786 78839 12247 097418 0365791 0077796


0

05

1

15

2

25

0 2 4 6 8 10 12

Rel

ativ

e vo

lum

e

Pressure (MPa)

Numerical simulation

Experiment data

Saturation pressure

Figure 4The fitted results of constant composition expansion (at areservoir temperature of 59∘C)

of the numerical simulation results considerably The gasgeneration rate is the reaction rate of CO

2generation at a

given pressure and temperature in the reservoir layers whichis obtained through the experimental results The activationenergy and reaction enthalpy are then calculated based onthe established reaction kinetics model and thermodynamicmodel [31] According to thermodynamic calculations theactivation energy and the reaction enthalpy are 38150 Jgmoland 45140 Jgmol respectively

Typically two methods are employed for self-generatingCO2Huff-n-Puff the single-fluid method and the double-

fluid method In the single-fluid method a salt solution withlow thermal stability is injected into the formation At thereservoir temperature the salt will decompose and generateCO2and some byproductsThe double-fluidmethod involves

mixing two miscible liquids Normally a salt solution anda low-concentration acid solution are mutually injected intothe reservoir to react to generate CO

2

In this paper we adopt the double-fluid method anddefine Na

2CO3and NaHCO

3as the main reagents because

of their simple reaction low environmental impact and easeof purchase The reaction of the reagents occurs with thegeneration of CO

2and byproducts as shown in

Na2CO3+NaHCO

3

H+997888rarr

CO2uarr +H

2O + NaCl + CH

3COONa

(2)

34 Parameters of Surfactant Flooding The primary controlparameters of surfactant flooding include oil-water interfacialtension the relative permeability curves and the interpo-lation parameters at low and high interfacial tensions [32ndash36] Without the addition of any surfactants the IFT of thecrude oil against its water was measured to be 1973mNmusing the axisymmetric drop shape analysis technique [37]When the surfactants and salts were added to the water themeasured IFTs decreased to 096mNm A numerical modelfor a long core sample was first established to extrapolatekey parameters from the lab data Consequently the inter-polation parameters (used in the relative permeability curveto reflect its trend) at low and high interfacial tensions for

0

02

04

06

08

1

05 06 07 08 09

Rel

ativ

e p

erm

eab

ilit

y

Sw

Krw (with surfactants)

Kro (with surfactants)

Krw (without surfactants)

Kro (without surfactants)

After interpolation

Figure 5 Relative permeability curves (with surfactants withoutinterpolation)

the nonwetting phase were determined to be minus301 and minus810respectively based on the best matching with experimentalmeasurements With the changes in interpolation parame-ters the changing interfacial tensions were reflected in therelative permeability curves (Figure 5)

35 Operating Parameters on Key Oil Recovery PerformanceIndicators Following the establishment of the proposedmodel the total simulation time period for oil recoverywas about 12 months A number of key parameters for thein situ CO

2generation reaction and surfactant properties

were obtained based on curve fitting with the experimentalresults Subsequently simulation studies were conducted toinvestigate the influences of in situ CO

2Huff-n-Puff operat-

ing parameters on key oil recovery performance indicatorssuch as the injection volume and mole concentration of thereagent injection rate well shut-in time and oil withdrawalrate Accordingly the optimal values of these parameterswere obtained by using the single control variable methodto quantify the effects of a number of operation parametersThe primary evaluation indexes included the cumulative oilproduction incremental oil production and the oil exchangerate

4 Results and Discussion

41 In Situ Generated CO2 The analytical model for thegas generation rate was developed based on the experimen-tal data [38] The corresponding transient pressures andtemperatures of the gas self-generation system from modelsimulations and lab measurements were compared (Figures6 and 7) Figure 6 shows that the model results have areasonable agreement with the lab data except for those atthe later stages of the reaction with a low system pressureThis is mainly because the generated byproduct is dissolved


10

12

14

16

18

20

0 20 40 60 80 100 120 140

Time (min)


Experimental data

(MP

a)

Ave

rage

sys

tem

op

erat

ing

pre

ssu

reP

Figure 6 Comparison of the average system operating pressurepredicted by the model and the laboratory measurements


Experimental data

60

65

70

75

80

85

90

0 20 40 60 80 100 120 140

Time (min)

Rea

ctio

n t

emp

erat

ure

(∘C

)

Figure 7 Comparison of the reaction temperature predicted by themodel and the laboratory measurements

in the water therefore resulting in a lower average systempressure than the model prediction

In the process of experiment the pressure increasedsignificantly from an initial 1000MPa to 1903MPaThis willresult in higher effectiveness in exploiting underground oilbecause with the depletion of natural energy the reservoirpressure will drop lower than a certain value and thus willno longer push the trapped oil toward producing wellsMeanwhile the generated CO

2gas will increase andmaintain

the existing pressure in the reservoirThe temperature of the reaction vessel rose to 845∘C an

increase of 245∘C above the original 600∘CThe exothermicreaction for heat stimulation based on Na

2CO3 NaHCO

3

and the compound acid is unique as the heat generatedin the process is used for reducing the viscosity of crudeoil In addition the byproducts are CO

2 NaCl H

2O and

CH3COONa which are nondamaging to the reservoir

42 Surfactant Flooding Figure 8 shows the detailed com-parison of the oil recovery rate measured from the lab datawith that predicted from the numerical model An excellent

0

02

04

06

08

1

0 05 1 15 2

Oil

rec

ove

ry r

ate R

(

)

Pore volume injected


Experimental data

Chemical injection

Water injection

PrimaryHuff-n-Puff Huff-n-Puff

TertiaryHuff-n-Puff Secondary

Figure 8The oil recovery rate of surfactant flooding (at a tempera-ture of 60∘C)

agreement is evident between the experimentally measuredand numerically simulated profiles with respect to oil recov-ery rate

By considering the financial loss caused by surfactantadsorption and the interfacial tension reductionC18H29NaO3S was found to be the most appropriate

candidate for surfactant flooding among the tested materials[32] During the lab test three Huff-n-Puff cycles wereperformed The procedure was as follows the water floodingwas first carried out on the long core sample Next thereagent solution was mixed with the chemical surfactantsAfter a certain shut-in period the oil recovery process wasinitiated The overall oil recovery rate increased by 1069in which the primary Huff-n-Puff increased by 693 thesecondary Huff-n-Puff increased by 271 and the tertiaryHuff-n-Puff increased by 105

This clear enhancement of oil recovery occurred mainlybecause by contacting surfactants and CO

2 the crude oil

volume was swollen its viscosity was decreased and inter-facial tension was reduced Crude oil is driven by solutiongas as light-components are extracted to the injected CO

2

phase the mechanisms of solution gas driving and light-components extraction play important roles in recoveringoil production [39] The desirable outcomes achieved inthese experiments provided fundamental proof for studyingthe operating parameters on key oil recovery performanceindicators in the next step

43 Effect of Volume and Mole Concentration of Reagent Thereagent injection volume directly affects the quantity of in situgenerated CO

2 and the quantity of generated CO

2further

determines the effectiveness of the Huff-n-Puff process onoil recovery In this analysis the mole concentration of thereagent was fixed at 50 and seven different injection vol-umes from 250 t up to 800 t were selected during a fixed timeperiod of 12 months to evaluate the effect of injection volumeon oil recovery performances Figure 9 shows the variation ofthe cumulative oil production at different injection volumesIt is clear that the cumulative oil production increases with


3700

3800

3900

4000

4100

4200

4300

4400

0 50 100 150 200 250 300 350 400

Production time (day)

Natural depletion

Injection volume = 250 t







Cu

mu

lati

ve o

il p

rod

uct

ionΔQ

oil

(t)

Figure 9 Cumulative oil production at different injection volumes

the reagent injection volume The reason for this is thatmore CO

2with higher pressure will be generated in the

oil-rich layer and thus more oil is recovered However theoil exchange rate (120572) would not necessarily follow the samevariation trend 120572 is defined as the ratio of increased oilproduction during the recovery period (Δ119876oil) to the totalinjection volume of the reagent (119876reag) as shown in

120572 =Δ119876oil119876reag (3)

Figure 10 presents the variations of the increased oil produc-tion and the associated 120572 with different injection volumes ofthe gas reagent The oil exchange rate first increases with theinjection volume to a maximum value of about 157 tt Nextit decreases with a further increase of the injection volumeThis occurs mainly because the increase in the injectedreagent volume reduces the relative fraction of the surfactantand thus decreases the effect of the surfactant on alternatingthe wettability and spontaneous imbibition of water into theoil-containing matrix [40] This results in lower effectivenessin driving oil out of the matrix Based on considerationsof technical feasibility and economic practice the optimalinjection volume of the reagent should be maintained ataround 250 t

In addition to injection volume chemical reagent con-centration also is a critical parameter governing oil recoveryTypically to generate sufficient CO

2in the oil matrix the

solution with a lower concentration of reagent will requirea higher injection volume which in turn would be limitedby the capability of the existing field facility In the case ofa higher concentration the injected less solution tends tobe concentrated in the near wellbore area Therefore theeffective radius of the Huff-n-Puff region will be reducedsignificantly and the self-generated CO

2will not displace the

oil from the matrix deep in the toe of the reservoir effectivelyFigures 11 and 12 demonstrate and compare the effect

of solution concentration on oil recovery The reagent moleconcentration varies in a relatively large range from 2 to

0

02

04

06

08

1

12

14

16

18

0

50

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600 700

Reagent injection volume Qreag (t)

Oil

exc

han

ge r

ate120572

(tt

)

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)

Figure 10 Variations of the incremental oil production and oilexchange rate at different reagent injection volumes

3700

3800

3900

4000

4100

4200

4300

4400

0 100 200 300 400


Natural depletion

2

3

4

5

6

8

10

Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)

Figure 11 The variation of the cumulative oil production withinjected solution at different reagent solution mole concentrations

10 As expected Figure 11 shows that the cumulative oilproduction first increases with the solution concentrationand then decreases with further concentration elevationThemaximum oil production occurs at approximately 5 moleconcentration Figure 12 shows the effect of reagent concen-tration on the increased oil production and the oil exchangerate It is clear that both terms reach their maximum at theoptimal concentration of about 5 At higher concentrationsthe increased oil production decreases from a peak value of390 t to about 330 t at the concentration of 10 while theexchange rate is reduced by almost 16 (ie from 16 to 11)

44 Effect of the Injection Rate The injection rate of thereagent solution is an important operational variable that hasa significant impact on the cost safety duration and ultimatesuccess of in situHuff-n-Puff oil recovery [12 41]The reagentsolution injection rate directly determines the total mass ofreagent available in the oilmatrix to generateCO

2throughout

the overall duration of chemical injection Additionally thereagent injection rate can effectively impact the rate of


125

13

135

14

145

15

155

16

310

320

330

340

350

360

370

380

390

0 2 4 6 8 10 12

Concentration of the reagent solution ()

Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)

Figure 12 Variations of the incremental oil production and oilexchange rate at different reagent solution mole concentrations

0

04

08

12

16

2

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800

Injection rate of the reagent solution Vinj (m3d)

Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)

Figure 13 The incremental oil production and oil exchange rate atdifferent reagent solution injection rates

the generation of CO2bubbles in the vicinity of the injector

Figure 13 shows the effect of different injection rates (119881inj)on the increased oil production and the oil exchange rateconsidering a fixed injection amount of about 250 t As 119881injincreases from 300 to 700m3d the reduced oil productionis about 150 t in total and the oil exchange rate considerablydecreases from 15 to 10 (a reduction of approximately33) This observation indicates that the injection rate ofthe reagent solution can substantially affect Huff-n-Puff oilrecovery compared with parameters However it is not oftenoperationally feasible to inject reagent solution at a high ratedue to operational limits on the injection pressure (and hencethe injection rate) to avoid matrix fracture or well blowoutTherefore considering the feasibility and existing capabilityof the oil well the optimal injection rate of interest in thisstudy is recommended to be about 300m3d

45 Effect of Well Shut-In Time The shut-in time is anotherimportant operating factor for the oil recovery performanceTypically a certain reaction time is required for the generatedCO2to diffuse so that it will be fully dissolved in the crude

14

145

15

155

16

350

355

360

365

370

375

380

385

390

0 5 10 15 20

Well shut-in time (day)

Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)

Figure 14 The incremental oil production and oil exchange rates atdifferent well shut-in time periods

oil within the matrix This is because a certain time period isrequired for the diffusion and spread of the in situ generatedCO2through the low permeability layer Therefore the well

should be shut in for a certain time period During thisperiod pressure dissipation and fluid diffusion dominatethe fluid flow process behind the flood front leading tomore efficient displacement of the hydrocarbon by the CO

2

Huff-n-Puff approach However if an extended shut-in timeis applied [42] the long soaking period causes the in situgenerated CO

2to spread into the deep layer of the formation

boundary of the oil well weakening the elastic driving energyand reducing the miscible condition of the CO

2with the oil

in the main recovery regionFigure 14 illustrates the effects of different well shut-in

times (from 2 to 15 d) between two consecutive recoverycycles on the performance of Huff-n-Puff oil recovery Boththe incremental oil production and the oil exchange rateclearly increase with a shut-in period of up to 8 d They startto decrease after a longer period because of the excessivediffusion of CO

2towards the formation boundaries of the

oil well Considering the practical operating feasibility theoptimal shut-in time for effective Huff-n-Puff oil recovery isrecommended to be around 8 d

46 Effect of the Oil Withdrawal Rate Figure 15 showsthe variation in Huff-n-Puff oil recovery with different oilwithdrawal rates As withdrawal increases the incrementaloil production and the exchange rate initially increase sig-nificantly but they eventually reach their asymptotes whenthe withdrawal rate exceeds 7m3d This occurs mainlybecause the excessive withdrawal rate causes a considerabledepression of the CO

2pressure within the formation layer

and consequently lowers the oil displacement effect from thein situ generated CO

2 Based on this analysis the practical oil

withdrawal rate in the context of this study is recommendedto be around 7m3d

47 Comparison of Different Exploitation Modes Severalcritical operating variables for Huff-n-Puff CO

2oil recovery


05

07

09

11

13

15

200

250

300

350

400

0 5 10 15 20

Withdrawal rate Vwd (m3d)

Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)

Figure 15 The incremental oil production and oil exchange rate atdifferent oil withdrawal rates

0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50

Oil production time (month)

Field oil production

Model prediction for natural depletion mode

Effects of site construction

35 gas generation efficiency for CO2 Huff-n-Puff mode

Dai

ly o

il p

rod

uct

ion

rat

eQ

oild

(t)

Figure 16The daily oil production rate in different recoverymodes

were identified based on the above comprehensive parametricanalysis Therefore for the oil well studied in this case thebenefits of in situ generated CO

2Huff-n-Puff on the oil

production are now evaluated Based on the results of thereaction efficiency of gas generation in the undergroundthe value of actual reaction efficiency is equal to 35 of thetheoretical value Thus the gas generation efficiency of themodel is now amended by 35 of the theoretical value toprovide an accurate prediction Figures 16 and 17 compare thecumulative and daily oil production under a natural depletionscenario with those in the Huff-n-Puff recovery process Forthe Huff-n-Puff process the operating parameters includethe injection volume of reagent 250 t the mole concentrationof 50 the injection rate of 300m3d and the well shut-intime of 8 d Figure 16 shows that in the natural depletionscenario the daily oil production rate decreases with theproduction time Since the onset of the 35thmonth the Huff-n-Puff recovery mode is initiated with the injection of areagent to generate high pressureCO

2within the oil layerThe

corresponding production rate is boosted instantaneously upto 22 td and then the rate gradually declines over the course

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50




In situ generated CO2


Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)

Figure 17 The cumulative oil production in different recoverymodes

of the remainder of the recovery process Overall the dailyproduction rate is increased by more than 100 relative tothe production at the end period of the natural depletionmode Consequently Figure 17 shows that the incremental oilproduction during the 12-month time period is about 610 tin the Huff-n-Puff recovery mode which is almost 37 timeshigher than the incremental oil production in the naturaldepletion mode Therefore we conclude that in this regionsubstantial oil production increase is achieved by the in situgenerated CO

2compound surfactant Huff-n-Puff method

5 Conclusions

(i) The in situ generated CO2Huff-n-Puff method with

compound surfactant is a new technology to enhanceoil recovery in a low permeability fault-block reser-voir This method mitigates a number of negativeimpacts of external CO

2injection on the environ-

ment the lack of field equipment reliability costissues well corrosion and the transportation of CO

2

(ii) In the numerical model the key parameters ofreaction and surfactant flooding are experimentallydetermined The laboratory results agree with thesimulated results for the daily production rate in theperiod of Huff-n-Puff

(iii) The results indicate that (a) the injection volume andmole concentration of the reagent and the oil fluidwithdrawal rate have important effects comparedwithother parameters and (b) optimal values exist tomaximize the incremental oil production We foundthat for the low permeability fault-block reservoirstudied in this paper the optimal range of theseoperating parameters is 250 t for the injection volume5 for the mole concentration of the reagent 7m3dfor the oil fluid withdrawal rate 300m3d for theinjection rate of the reagent and 8 d for the well shut-in time


Competing Interests

The authors declare that they have no competing interests

Acknowledgments

This work was supported by the National Science Foundationof China (no 51274173) and the Sichuan Provincial Innova-tion Team (no 16TD0010)

References

[1] E Manrique C Thomas R Ravikiran et al ldquoEOR currentstatus and opportunitiesrdquo in Proceedings of the SPE ImprovedOilRecovery Symposium SPE-130113-MS Tulsa Okla USA April2010

[2] J J Sheng ldquoStatus of surfactant EOR technologyrdquo Petroleumvol 1 no 2 pp 97ndash105 2015

[3] X Jia K Ma Y Liu B Liu J Zhang and Y Li ldquoEnhanceheavy oil recovery by in-situ carbon dioxide generation andapplication in China offshore oilfieldrdquo in Proceedings of the SPEEnhanced Oil Recovery Conference pp 68ndash73 Kuala LumpurMalaysia July 2013

[4] A Bera and T Babadagli ldquoRelative permeability of foamy oil fordifferent types of dissolved gasesrdquo SPE Reservoir Evaluation ampEngineering 2016

[5] D Olsen ldquoCO2EOR production properties of chalkrdquo in

Proceedings of the SPE EUROPECEAGEAnnual Conference andExhibition SPE Vienna Austria May 2011

[6] W Wan and S Wang ldquoDetermination of residual oil saturationand connectivity between injector and producer using interwelltracer testsrdquo Journal of PetroleumEngineeringampTechnology vol3 no 3 pp 18ndash24 2013

[7] J Ma X Wang R Gao et al ldquoEnhanced light oil recovery fromtight formations through CO

2huff lsquonrsquo puff processesrdquo Fuel vol

154 pp 35ndash44 2015[8] A Q Firouz and F Torabi ldquoUtilization of carbon dioxide and

methane in huff-and-puff injection scheme to improve heavyoil recoveryrdquo Fuel vol 117 no 2 pp 966ndash973 2014

[9] D S Rivera KMohanty andM Balhoff ldquoReservoir simulationand optimization of Huff-and-Puff operations in the BakkenShalerdquo Fuel vol 147 pp 82ndash94 2015

[10] K K Gutnersky A K Shakhverdiev and Y G MamedovldquoIn-situ generation of carbon dioxide new way to increaseoil recoveryrdquo in Proceedings of the SPE European PetroleumConference SPE-65170-MS Paris France October 2000

[11] F Torabi A Q Firouz A Kavousi and K Asghari ldquoCom-parative evaluation of immiscible near miscible and miscibleCO2huff-n-puff to enhance oil recovery from a single matrix-

fracture system (experimental and simulation studies)rdquo Fuelvol 93 pp 443ndash453 2012

[12] Z Li and Y Gu ldquoSoaking effect on miscible CO2flooding in

a tight sandstone formationrdquo Fuel vol 134 no 9 pp 659ndash6682014

[13] F Torabi and K Asghari ldquoEffect of operating pressure matrixpermeability and connate water saturation on performanceof CO

2huff-and-puff process in matrix-fracture experimental

modelrdquo Fuel vol 89 no 10 pp 2985ndash2990 2010[14] F Yang J Deng and Y Xue ldquoJiangsu oil field carbon dioxide

cyclic stimulation operations lessons learned and experiencesgainedrdquo in Proceedings of the SPE International Conference on

CO2 Capture Storage and Utilization New Orleans La USANovember 2010

[15] C Chen M Balhoff and K K Mohanty ldquoEffect of reservoirheterogeneity on improved shale oil recovery by CO

2huff-

n-puffrdquo in Proceedings of the SPE Unconventional ResourcesConference pp 410ndash425 April 2012

[16] J N F Martinez M Abbaszadeh R P Olguin E P Martinezand A R Figueroa ldquoEvaluation of CO2-EOR gas injection ina heavy-oil naturally fractured reservoirrdquo in Proceedings of theSPE Heavy and Extra Heavy Oil Conference SPE-171054-MSMedellın Colombia September 2014

[17] J J Sheng ldquoComparison of the effects of wettability alterationand IFT reduction onoil recovery in carbonate reservoirsrdquoAsia-Pacific Journal of Chemical Engineering vol 8 no 1 pp 154ndash1612013

[18] K Rai R T Johns M Delshad L W Lake and A GoudarzildquoOil-recovery predictions for surfactant polymer floodingrdquoJournal of Petroleum Science and Engineering vol 112 pp 341ndash350 2013

[19] J J Sheng ldquoReview of surfactant enhanced oil recovery incarbonate reservoirsrdquo Advances in Petroleum Exploration andDevelopment vol 6 no 1 pp 1ndash10 2013

[20] W Wan A Raj T-P Hsu P Lohateeraparp J H Harwell andB-J B Shiau ldquoDesigning surfactant-only formulations for ahigh salinity and tight reservoirrdquo International News on FatsOils and Related Materials vol 24 no 10 pp 622ndash627 2013

[21] A A Dehghan M Masihi and S Ayatollahi ldquoPhase behaviorand interfacial tension evaluation of a newly designed surfac-tant on heavy oil displacement efficiency effects of salinitywettability and capillary pressurerdquo Fluid Phase Equilibria vol396 pp 20ndash27 2015

[22] K Babu N Pal A Bera V K Saxena and A MandalldquoStudies on interfacial tension and contact angle of synthesizedsurfactant and polymeric from castor oil for enhanced oilrecoveryrdquo Applied Surface Science vol 353 pp 1126ndash1136 2015

[23] H Pei G Zhang J Ge L Jin and L Ding ldquoStudy on thevariation of dynamic interfacial tension in the process ofalkaline flooding for heavy oilrdquo Fuel vol 104 pp 372ndash378 2013

[24] M M F Hasan E L First F Boukouvala and C A FloudasldquoA multi-scale framework for CO

2capture utilization and

sequestration CCUS and CCUrdquo Computers and ChemicalEngineering vol 81 no 8 pp 2ndash21 2015

[25] A M AlSofi J S Liu M Han and S Aramco ldquoNumericalsimulation of surfactantndashpolymer coreflooding experiments forcarbonatesrdquo Journal of Petroleum Science and Engineering vol111 no 11 pp 184ndash196 2013

[26] S Kumar and A Mandal ldquoStudies on interfacial behaviorand wettability change phenomena by ionic and nonionicsurfactants in presence of alkalis and salt for enhanced oilrecoveryrdquo Applied Surface Science vol 372 pp 42ndash51 2016

[27] Q Liu M Dong S Ma and Y Tu ldquoSurfactant enhanced alka-line flooding forWestern Canadian heavy oil recoveryrdquoColloidsand Surfaces A Physicochemical and Engineering Aspects vol293 no 1ndash3 pp 63ndash71 2007

[28] V Mirchi S Saraji L Goual and M Piri ldquoDynamic interfacialtension and wettability of shale in the presence of surfactants atreservoir conditionsrdquo Fuel vol 148 pp 127ndash138 2015

[29] B Y Jamaloei R Kharrat and F Torabi ldquoAmechanistic analysisof viscous fingering in low-tension polymer flooding in heavy-oil reservoirsrdquo Journal of Petroleum Science and Engineering vol78 no 2 pp 228ndash232 2011


[30] S Carroll Y Hao M Smith and Y Sholokhova ldquoDevelop-ment of scaling parameters to describe CO

2mdashrock interactions

within Weyburn-Midale carbonate flow unitsrdquo InternationalJournal of Greenhouse Gas Control vol 16 pp S185ndashS193 2013

[31] B J B Shiau T-P Hsu B L Roberts and J H HarwellldquoImproved chemical flood efficiency by in situ CO

2generationrdquo

in Proceedings of the 17th SPE Improved Oil Recovery Symposium(IOR rsquo10) pp 1077ndash1086 Tulsa Okla USA April 2010

[32] S Park E S Lee andW RW Sulaiman ldquoAdsorption behaviorsof surfactants for chemical flooding in enhanced oil recoveryrdquoJournal of Industrial and Engineering Chemistry vol 21 no 1pp 1239ndash1245 2015

[33] W Hongyan C Xulong Z Jichao and Z Aimei ldquoDevelopmentand application of dilute surfactant-polymer flooding systemfor Shengli oilfieldrdquo Journal of Petroleum Science and Engineer-ing vol 65 no 1-2 pp 45ndash50 2009

[34] A Mehranfar and M H Ghazanfari ldquoInvestigation of themicroscopic displacement mechanisms and macroscopicbehavior of alkaline flooding at different wettability conditionsin shaly glass micromodelsrdquo Journal of Petroleum Science andEngineering vol 122 pp 595ndash615 2014

[35] L Chen G Zhang J Ge P Jiang J Tang and Y LiuldquoResearch of the heavy oil displacement mechanism by usingalkalinesurfactant flooding systemrdquo Colloids and Surfaces APhysicochemical and Engineering Aspects vol 434 no 19 pp63ndash71 2013

[36] Y Zhu Q Hou G Jian D Ma and Z Wang ldquoCurrent devel-opment and application of chemical combination floodingtechniquerdquo PetroleumExploration andDevelopment vol 40 no1 pp 96ndash103 2013

[37] P Cheng D Li L Boruvka Y Rotenberg and AW NeumannldquoAutomation of axisymmetric drop shape analysis for measure-ments of interfacial tensions and contact anglesrdquo Colloids andSurfaces vol 43 no 2 pp 151ndash167 1990

[38] F Yang J Deng andWZhu ldquoLab experimental study on in-situcarbon dioxide generation to enhance oil recoveryrdquo ComplexHydrocarbon Reservoirs vol 5 no 4 pp 70ndash72 2012

[39] C Song and D Yang Performance Evaluation of CO2Huff-n-

Puff Processes in Tight Oil Formations Society of PetroleumEngineers 2013

[40] P Bikkina J Wan Y Kim T J Kneafsey and T K TokunagaldquoInfluence of wettability and permeability heterogeneity onmiscible CO

2flooding efficiencyrdquo Fuel vol 166 pp 219ndash226

2015[41] R Safi R K Agarwal and S Banerjee ldquoNumerical simulation

and optimization of CO2utilization for enhanced oil recovery

from depleted reservoirsrdquo Chemical Engineering Science vol144 pp 30ndash38 2016

[42] J Ma X Wang R Gao et al ldquoStudy of cyclic CO2injection

for low-pressure light oil recovery under reservoir conditionsrdquoFuel vol 174 pp 296ndash306 2016

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal ofPhotoenergy


Carbohydrate Chemistry

International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


Chromatography Research International


Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


Traditionally the CO2Huff-n-Puff technique is consid-

ered an effective technique and field tests have revealed thatthis technology is generally economically feasible in diversereservoir environments [6ndash9] The governing mechanismsof this technology are as follows a fraction of the injectedCO2will be dissolved in the water phase which increases

the water viscosity by 20ndash30 and its mobility 2-3 timesThe CO

2dissolved in oil decreases the interfacial tension

(IFT) in the oil-water contact and the CO2dissolved in oil

reduces the oil viscosity 15ndash25 times Also theCO2dissolved

in oil increases the oil volume [10] The dissolution of CO2

in the oil phase can also increase the total volume of oiland the vaporization of lighter hydrocarbon components [11ndash15] Martinez et al [16] investigated the use of CO

2as an

EOR solvent for heavy oil Due to multicontact miscibilitythe Huff-n-Puff simulation cases also indicate increased oilrecovery and reducedmatrix oil saturation by CO

2compared

to N2injection

Although the CO2Huff-n-Puff process has been deter-

mined to be able to improve oil recovery some negativeimpacts associated with the application of this techniquehave been reported For example some negative impactsare the reduction of CO

2concentration coagulation and

sedimentation of asphaltene in the oil phase due to changein the thermobaric conditions well and oil field equipmentcorrosion and issues with CO

2transportation [10] Thus

a considerable effort has been undertaken to develop thistechnology (in particular the in situ generated CO

2tech-

nique)This technique involves the injection of undergroundwater into a formation to allow injected chemicals to reactwith formation materials to release CO

2inside the reservoir

[3] The advantage of this technique is the elimination ofany surface facility and associated negative impacts on theenvironment In addition chemical enhanced oil recoveryhas recently focused on using surfactants to change oil-wetwettability into water-wet wettability to enhance water imbi-bition into matrix blocks in the oil reservoirs and to improvethe flowing property of crude oil by reducing interfacialsurface tension [17ndash24] The increase in recovery by CO

2

generation is also attained by maintaining (or increasing)the reservoir pressure displacing the oil and eliminating theinterface between the oil and CO

2

Jia et al [3] conducted a laboratory investigation on insitu CO

2generation and found that the proposed technology

can decrease the injection pressure of the damaged core by117MPa Furthermore the increase rates of the amount of thegenerated gas and the oil volume escalate with the increaseof temperature and system concentration In addition theoil volume and the oil viscosity reduction rates increase withthe increase of oil viscosity Under the condition of 60∘C10MPa and 2010mPasdots the oil volume increased by 25 theoil viscosity decreased by 527 and the recovery efficiencyimproved by 76ndash142

AlSofi et al [25] performed a series of surfactant coreflooding experiments in carbonate cores under typical reser-voir conditions The core flooding results showed significantoil recovery potential for surfactant flooding (SF) formula-tions under the investigated conditions The base SF resultedin a 234 incremental recovery after water flooding with

a combination of polymer and surfactant The results alsodemonstrated the effects of surfactant slug-size and concen-tration on the recovery performance Kumar andMandal [26]found experimentally that alkali-surfactant systems changethe wettability of an intermediate-wet quartz rock to water-wet and the change of wettability from oil-wet to water-wet increases the oil recovery significantly The solution ofC19H42BrN surfactant in the presence of sodium metaborate

changes the contact angle to 8-9∘ whereas the solutions ofC12H25NaO3S in the presence of Na

2CO3change the contact

angle to 4∘ An effective mobility ratio and a reduced IFTbetween the residual oil and displacing fluid are obtainedby the formed emulsion which is recognized as a potentialefficient chemical EOR process C

12H25NaO3S also forms

good emulsions in the presence or absence of alkali whichhave good stability compared to other surfactants Unlikenonionic surfactants ionic surfactant molecules containcharge and form a charged monolayer at the interface henceit is found to be comparatively more capable of reducing theinterfacial tension

Our literature review concludes that the in situ generatedCO2Huff-n-Puff process with chemical compound surfac-

tant could substantially improve oil recovery performance[27 28] However very limited research has been undertakenin this area especially for the parametric analysis of thekey operating variables for the improvement of oil recoveryTherefore we performed a numerical simulation and opti-mization study on the effect of the in situ generatedCO

2com-

pound surfactant Huff-n-Puffmethod on oil recovery perfor-mance for a low permeability fault-block reservoir located insoutheast ChinaThe objective of this paper is to examine theimportant parameters best practices and lessons learned thatcontribute to the success of the in situ generated CO

2Huff-

n-Puff process with compound surfactant Based on thesesuccesses the optimal operating parameters are analyzed andidentified and recommendations to improve related Huff-n-Puff projects further are presented

2 Experimental

21 In Situ Generated CO2

211 Materials The N2gas (purity 9999) was supplied by

Chengdu Dongfang Electric Gas Co Ltd The NaHCO3and

Na2CO3salts were supplied by SinopharmChemical Reagent

Co Ltd were of analytical grade with a purity of gt99 andare shown in Table 1 The specific details of the compoundacid made up of CH

3COOH and HCl are also shown in

Table 1 Distilled water was used to prepare the solutions

212 Apparatus and Procedures The auxiliary laboratoryequipment was purchased from Chengdu Kelong ChemicalReagent Co Ltd and included test tubes stopwatch sophis-ticated electronic balance rubber tubes glass tubes and acidburettes The main apparatus consisted of a reaction vessel(Taixing Xingjian Chemical and Machinery Plant) a highpressure manual metering pump (Jiangsu Huaan ScientificInstruments Co Ltd) and a N

2gas cylinder (Chengdu





N2



Na2CO3







2CO3 NaHCO

3 and



2CO3



2CO3














2Huff-n-Puff


2CO3












calculated using

119864119863=sum119881oi119878oi119881119875times 100 (1)


(9) (10) (11)(2)

(2)

(7)

(8)

(6)

(3)

(4) (5)

(1)

(12)



3




59423 3977 6887 3113 60







(2) (3) (4) (5)

(1)

(1)

(6) (6)(6)

(6)

(7)

(8) (9)

(10)

(11)






2 25 N

2ndash

C1 159 C

2ndashC6 3 C

7ndashC20 308 and C

21ndashC32 478







1256

1247

1238

1230

1221

1212

1203

1194

1186

1177

1168

(a)

028

026

023

021

019

016

014

012

010

007

005

(b)

90

83

75

68

60

53

45

38

30

23

15

(c)

124

112

101

89

78

67

55

43

32

20

09

(d)



Component CO2

N2

C1

C2

C3

iC4

nC4

iC5

nC5

C6

C7

C8

C9

C10

C11+

Composition 248 037 1802 128 052 024 027 020 015 053 036 027 043 037 7451





CO2

440100 72800 30420 00940 022500 0457236 0077796N2to C1

162863 43083 18923 00988 000865 0457236 0077796C2to C6

509499 29588 39460 02209 016607 0457236 0077796C7to C20

2619422 14612 78338 07529 068937 0457236 0077796C21to C32

4016392 10786 78839 12247 097418 0365791 0077796


0

05

1

15

2

25

0 2 4 6 8 10 12

Rel

ativ

e vo

lum

e

Pressure (MPa)


Experiment data

Saturation pressure



2generation at a





2


2CO3and NaHCO




Na2CO3+NaHCO

3

H+997888rarr

CO2uarr +H

2O + NaCl + CH

3COONa

(2)


0

02

04

06

08

1

05 06 07 08 09

Rel

ativ

e p

erm

eab

ilit

y

Sw





After interpolation











10

12

14

16

18

20

0 20 40 60 80 100 120 140

Time (min)


Experimental data

(MP

a)

Ave

rage

sys

tem

op

erat

ing

pre

ssu

reP



Experimental data

60

65

70

75

80

85

90

0 20 40 60 80 100 120 140

Time (min)

Rea

ctio

n t

emp

erat

ure

(∘C

)







2CO3 NaHCO

3


2 NaCl H

2O and



0

02

04

06

08

1

0 05 1 15 2

Oil

rec

ove

ry r

ate R

(

)



Experimental data

Chemical injection

Water injection








2 the crude oil


2




2further



3700

3800

3900

4000

4100

4200

4300

4400

0 50 100 150 200 250 300 350 400


Natural depletion








Cu

mu

lati

ve o

il p

rod

uct

ionΔQ

oil

(t)





120572 =Δ119876oil119876reag (3)








0

02

04

06

08

1

12

14

16

18

0

50

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600 700


Oil

exc

han

ge r

ate120572

(tt

)

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


3700

3800

3900

4000

4100

4200

4300

4400

0 100 200 300 400


Natural depletion

2

3

4

5

6

8

10

Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




2throughout



125

13

135

14

145

15

155

16

310

320

330

340

350

360

370

380

390

0 2 4 6 8 10 12


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

04

08

12

16

2

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)





14

145

15

155

16

350

355

360

365

370

375

380

385

390

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)




2




2with the oil











2oil recovery


05

07

09

11

13

15

200

250

300

350

400

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50






Dai

ly o

il p

rod

uct

ion

rat

eQ

oild

(t)







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50






Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




5 Conclusions





2




Competing Interests


Acknowledgments


References
























2huff-























2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





N2



Na2CO3







2CO3 NaHCO

3 and



2CO3



2CO3














2Huff-n-Puff


2CO3












calculated using

119864119863=sum119881oi119878oi119881119875times 100 (1)


(9) (10) (11)(2)

(2)

(7)

(8)

(6)

(3)

(4) (5)

(1)

(12)



3




59423 3977 6887 3113 60







(2) (3) (4) (5)

(1)

(1)

(6) (6)(6)

(6)

(7)

(8) (9)

(10)

(11)






2 25 N

2ndash

C1 159 C

2ndashC6 3 C

7ndashC20 308 and C

21ndashC32 478







1256

1247

1238

1230

1221

1212

1203

1194

1186

1177

1168

(a)

028

026

023

021

019

016

014

012

010

007

005

(b)

90

83

75

68

60

53

45

38

30

23

15

(c)

124

112

101

89

78

67

55

43

32

20

09

(d)



Component CO2

N2

C1

C2

C3

iC4

nC4

iC5

nC5

C6

C7

C8

C9

C10

C11+

Composition 248 037 1802 128 052 024 027 020 015 053 036 027 043 037 7451





CO2

440100 72800 30420 00940 022500 0457236 0077796N2to C1

162863 43083 18923 00988 000865 0457236 0077796C2to C6

509499 29588 39460 02209 016607 0457236 0077796C7to C20

2619422 14612 78338 07529 068937 0457236 0077796C21to C32

4016392 10786 78839 12247 097418 0365791 0077796


0

05

1

15

2

25

0 2 4 6 8 10 12

Rel

ativ

e vo

lum

e

Pressure (MPa)


Experiment data

Saturation pressure



2generation at a





2


2CO3and NaHCO




Na2CO3+NaHCO

3

H+997888rarr

CO2uarr +H

2O + NaCl + CH

3COONa

(2)


0

02

04

06

08

1

05 06 07 08 09

Rel

ativ

e p

erm

eab

ilit

y

Sw





After interpolation











10

12

14

16

18

20

0 20 40 60 80 100 120 140

Time (min)


Experimental data

(MP

a)

Ave

rage

sys

tem

op

erat

ing

pre

ssu

reP



Experimental data

60

65

70

75

80

85

90

0 20 40 60 80 100 120 140

Time (min)

Rea

ctio

n t

emp

erat

ure

(∘C

)







2CO3 NaHCO

3


2 NaCl H

2O and



0

02

04

06

08

1

0 05 1 15 2

Oil

rec

ove

ry r

ate R

(

)



Experimental data

Chemical injection

Water injection








2 the crude oil


2




2further



3700

3800

3900

4000

4100

4200

4300

4400

0 50 100 150 200 250 300 350 400


Natural depletion








Cu

mu

lati

ve o

il p

rod

uct

ionΔQ

oil

(t)





120572 =Δ119876oil119876reag (3)








0

02

04

06

08

1

12

14

16

18

0

50

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600 700


Oil

exc

han

ge r

ate120572

(tt

)

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


3700

3800

3900

4000

4100

4200

4300

4400

0 100 200 300 400


Natural depletion

2

3

4

5

6

8

10

Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




2throughout



125

13

135

14

145

15

155

16

310

320

330

340

350

360

370

380

390

0 2 4 6 8 10 12


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

04

08

12

16

2

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)





14

145

15

155

16

350

355

360

365

370

375

380

385

390

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)




2




2with the oil











2oil recovery


05

07

09

11

13

15

200

250

300

350

400

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50






Dai

ly o

il p

rod

uct

ion

rat

eQ

oild

(t)







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50






Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




5 Conclusions





2




Competing Interests


Acknowledgments


References
























2huff-























2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(9) (10) (11)(2)

(2)

(7)

(8)

(6)

(3)

(4) (5)

(1)

(12)



3




59423 3977 6887 3113 60







(2) (3) (4) (5)

(1)

(1)

(6) (6)(6)

(6)

(7)

(8) (9)

(10)

(11)






2 25 N

2ndash

C1 159 C

2ndashC6 3 C

7ndashC20 308 and C

21ndashC32 478







1256

1247

1238

1230

1221

1212

1203

1194

1186

1177

1168

(a)

028

026

023

021

019

016

014

012

010

007

005

(b)

90

83

75

68

60

53

45

38

30

23

15

(c)

124

112

101

89

78

67

55

43

32

20

09

(d)



Component CO2

N2

C1

C2

C3

iC4

nC4

iC5

nC5

C6

C7

C8

C9

C10

C11+

Composition 248 037 1802 128 052 024 027 020 015 053 036 027 043 037 7451





CO2

440100 72800 30420 00940 022500 0457236 0077796N2to C1

162863 43083 18923 00988 000865 0457236 0077796C2to C6

509499 29588 39460 02209 016607 0457236 0077796C7to C20

2619422 14612 78338 07529 068937 0457236 0077796C21to C32

4016392 10786 78839 12247 097418 0365791 0077796


0

05

1

15

2

25

0 2 4 6 8 10 12

Rel

ativ

e vo

lum

e

Pressure (MPa)


Experiment data

Saturation pressure



2generation at a





2


2CO3and NaHCO




Na2CO3+NaHCO

3

H+997888rarr

CO2uarr +H

2O + NaCl + CH

3COONa

(2)


0

02

04

06

08

1

05 06 07 08 09

Rel

ativ

e p

erm

eab

ilit

y

Sw





After interpolation











10

12

14

16

18

20

0 20 40 60 80 100 120 140

Time (min)


Experimental data

(MP

a)

Ave

rage

sys

tem

op

erat

ing

pre

ssu

reP



Experimental data

60

65

70

75

80

85

90

0 20 40 60 80 100 120 140

Time (min)

Rea

ctio

n t

emp

erat

ure

(∘C

)







2CO3 NaHCO

3


2 NaCl H

2O and



0

02

04

06

08

1

0 05 1 15 2

Oil

rec

ove

ry r

ate R

(

)



Experimental data

Chemical injection

Water injection








2 the crude oil


2




2further



3700

3800

3900

4000

4100

4200

4300

4400

0 50 100 150 200 250 300 350 400


Natural depletion








Cu

mu

lati

ve o

il p

rod

uct

ionΔQ

oil

(t)





120572 =Δ119876oil119876reag (3)








0

02

04

06

08

1

12

14

16

18

0

50

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600 700


Oil

exc

han

ge r

ate120572

(tt

)

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


3700

3800

3900

4000

4100

4200

4300

4400

0 100 200 300 400


Natural depletion

2

3

4

5

6

8

10

Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




2throughout



125

13

135

14

145

15

155

16

310

320

330

340

350

360

370

380

390

0 2 4 6 8 10 12


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

04

08

12

16

2

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)





14

145

15

155

16

350

355

360

365

370

375

380

385

390

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)




2




2with the oil











2oil recovery


05

07

09

11

13

15

200

250

300

350

400

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50






Dai

ly o

il p

rod

uct

ion

rat

eQ

oild

(t)







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50






Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




5 Conclusions





2




Competing Interests


Acknowledgments


References
























2huff-























2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


(2) (3) (4) (5)

(1)

(1)

(6) (6)(6)

(6)

(7)

(8) (9)

(10)

(11)






2 25 N

2ndash

C1 159 C

2ndashC6 3 C

7ndashC20 308 and C

21ndashC32 478







1256

1247

1238

1230

1221

1212

1203

1194

1186

1177

1168

(a)

028

026

023

021

019

016

014

012

010

007

005

(b)

90

83

75

68

60

53

45

38

30

23

15

(c)

124

112

101

89

78

67

55

43

32

20

09

(d)



Component CO2

N2

C1

C2

C3

iC4

nC4

iC5

nC5

C6

C7

C8

C9

C10

C11+

Composition 248 037 1802 128 052 024 027 020 015 053 036 027 043 037 7451





CO2

440100 72800 30420 00940 022500 0457236 0077796N2to C1

162863 43083 18923 00988 000865 0457236 0077796C2to C6

509499 29588 39460 02209 016607 0457236 0077796C7to C20

2619422 14612 78338 07529 068937 0457236 0077796C21to C32

4016392 10786 78839 12247 097418 0365791 0077796


0

05

1

15

2

25

0 2 4 6 8 10 12

Rel

ativ

e vo

lum

e

Pressure (MPa)


Experiment data

Saturation pressure



2generation at a





2


2CO3and NaHCO




Na2CO3+NaHCO

3

H+997888rarr

CO2uarr +H

2O + NaCl + CH

3COONa

(2)


0

02

04

06

08

1

05 06 07 08 09

Rel

ativ

e p

erm

eab

ilit

y

Sw





After interpolation











10

12

14

16

18

20

0 20 40 60 80 100 120 140

Time (min)


Experimental data

(MP

a)

Ave

rage

sys

tem

op

erat

ing

pre

ssu

reP



Experimental data

60

65

70

75

80

85

90

0 20 40 60 80 100 120 140

Time (min)

Rea

ctio

n t

emp

erat

ure

(∘C

)







2CO3 NaHCO

3


2 NaCl H

2O and



0

02

04

06

08

1

0 05 1 15 2

Oil

rec

ove

ry r

ate R

(

)



Experimental data

Chemical injection

Water injection








2 the crude oil


2




2further



3700

3800

3900

4000

4100

4200

4300

4400

0 50 100 150 200 250 300 350 400


Natural depletion








Cu

mu

lati

ve o

il p

rod

uct

ionΔQ

oil

(t)





120572 =Δ119876oil119876reag (3)








0

02

04

06

08

1

12

14

16

18

0

50

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600 700


Oil

exc

han

ge r

ate120572

(tt

)

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


3700

3800

3900

4000

4100

4200

4300

4400

0 100 200 300 400


Natural depletion

2

3

4

5

6

8

10

Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




2throughout



125

13

135

14

145

15

155

16

310

320

330

340

350

360

370

380

390

0 2 4 6 8 10 12


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

04

08

12

16

2

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)





14

145

15

155

16

350

355

360

365

370

375

380

385

390

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)




2




2with the oil











2oil recovery


05

07

09

11

13

15

200

250

300

350

400

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50






Dai

ly o

il p

rod

uct

ion

rat

eQ

oild

(t)







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50






Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




5 Conclusions





2




Competing Interests


Acknowledgments


References
























2huff-























2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


1256

1247

1238

1230

1221

1212

1203

1194

1186

1177

1168

(a)

028

026

023

021

019

016

014

012

010

007

005

(b)

90

83

75

68

60

53

45

38

30

23

15

(c)

124

112

101

89

78

67

55

43

32

20

09

(d)



Component CO2

N2

C1

C2

C3

iC4

nC4

iC5

nC5

C6

C7

C8

C9

C10

C11+

Composition 248 037 1802 128 052 024 027 020 015 053 036 027 043 037 7451





CO2

440100 72800 30420 00940 022500 0457236 0077796N2to C1

162863 43083 18923 00988 000865 0457236 0077796C2to C6

509499 29588 39460 02209 016607 0457236 0077796C7to C20

2619422 14612 78338 07529 068937 0457236 0077796C21to C32

4016392 10786 78839 12247 097418 0365791 0077796


0

05

1

15

2

25

0 2 4 6 8 10 12

Rel

ativ

e vo

lum

e

Pressure (MPa)


Experiment data

Saturation pressure



2generation at a





2


2CO3and NaHCO




Na2CO3+NaHCO

3

H+997888rarr

CO2uarr +H

2O + NaCl + CH

3COONa

(2)


0

02

04

06

08

1

05 06 07 08 09

Rel

ativ

e p

erm

eab

ilit

y

Sw





After interpolation











10

12

14

16

18

20

0 20 40 60 80 100 120 140

Time (min)


Experimental data

(MP

a)

Ave

rage

sys

tem

op

erat

ing

pre

ssu

reP



Experimental data

60

65

70

75

80

85

90

0 20 40 60 80 100 120 140

Time (min)

Rea

ctio

n t

emp

erat

ure

(∘C

)







2CO3 NaHCO

3


2 NaCl H

2O and



0

02

04

06

08

1

0 05 1 15 2

Oil

rec

ove

ry r

ate R

(

)



Experimental data

Chemical injection

Water injection








2 the crude oil


2




2further



3700

3800

3900

4000

4100

4200

4300

4400

0 50 100 150 200 250 300 350 400


Natural depletion








Cu

mu

lati

ve o

il p

rod

uct

ionΔQ

oil

(t)





120572 =Δ119876oil119876reag (3)








0

02

04

06

08

1

12

14

16

18

0

50

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600 700


Oil

exc

han

ge r

ate120572

(tt

)

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


3700

3800

3900

4000

4100

4200

4300

4400

0 100 200 300 400


Natural depletion

2

3

4

5

6

8

10

Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




2throughout



125

13

135

14

145

15

155

16

310

320

330

340

350

360

370

380

390

0 2 4 6 8 10 12


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

04

08

12

16

2

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)





14

145

15

155

16

350

355

360

365

370

375

380

385

390

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)




2




2with the oil











2oil recovery


05

07

09

11

13

15

200

250

300

350

400

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50






Dai

ly o

il p

rod

uct

ion

rat

eQ

oild

(t)







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50






Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




5 Conclusions





2




Competing Interests


Acknowledgments


References
























2huff-























2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0

05

1

15

2

25

0 2 4 6 8 10 12

Rel

ativ

e vo

lum

e

Pressure (MPa)


Experiment data

Saturation pressure



2generation at a





2


2CO3and NaHCO




Na2CO3+NaHCO

3

H+997888rarr

CO2uarr +H

2O + NaCl + CH

3COONa

(2)


0

02

04

06

08

1

05 06 07 08 09

Rel

ativ

e p

erm

eab

ilit

y

Sw





After interpolation











10

12

14

16

18

20

0 20 40 60 80 100 120 140

Time (min)


Experimental data

(MP

a)

Ave

rage

sys

tem

op

erat

ing

pre

ssu

reP



Experimental data

60

65

70

75

80

85

90

0 20 40 60 80 100 120 140

Time (min)

Rea

ctio

n t

emp

erat

ure

(∘C

)







2CO3 NaHCO

3


2 NaCl H

2O and



0

02

04

06

08

1

0 05 1 15 2

Oil

rec

ove

ry r

ate R

(

)



Experimental data

Chemical injection

Water injection








2 the crude oil


2




2further



3700

3800

3900

4000

4100

4200

4300

4400

0 50 100 150 200 250 300 350 400


Natural depletion








Cu

mu

lati

ve o

il p

rod

uct

ionΔQ

oil

(t)





120572 =Δ119876oil119876reag (3)








0

02

04

06

08

1

12

14

16

18

0

50

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600 700


Oil

exc

han

ge r

ate120572

(tt

)

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


3700

3800

3900

4000

4100

4200

4300

4400

0 100 200 300 400


Natural depletion

2

3

4

5

6

8

10

Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




2throughout



125

13

135

14

145

15

155

16

310

320

330

340

350

360

370

380

390

0 2 4 6 8 10 12


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

04

08

12

16

2

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)





14

145

15

155

16

350

355

360

365

370

375

380

385

390

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)




2




2with the oil











2oil recovery


05

07

09

11

13

15

200

250

300

350

400

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50






Dai

ly o

il p

rod

uct

ion

rat

eQ

oild

(t)







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50






Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




5 Conclusions





2




Competing Interests


Acknowledgments


References
























2huff-























2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


10

12

14

16

18

20

0 20 40 60 80 100 120 140

Time (min)


Experimental data

(MP

a)

Ave

rage

sys

tem

op

erat

ing

pre

ssu

reP



Experimental data

60

65

70

75

80

85

90

0 20 40 60 80 100 120 140

Time (min)

Rea

ctio

n t

emp

erat

ure

(∘C

)







2CO3 NaHCO

3


2 NaCl H

2O and



0

02

04

06

08

1

0 05 1 15 2

Oil

rec

ove

ry r

ate R

(

)



Experimental data

Chemical injection

Water injection








2 the crude oil


2




2further



3700

3800

3900

4000

4100

4200

4300

4400

0 50 100 150 200 250 300 350 400


Natural depletion








Cu

mu

lati

ve o

il p

rod

uct

ionΔQ

oil

(t)





120572 =Δ119876oil119876reag (3)








0

02

04

06

08

1

12

14

16

18

0

50

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600 700


Oil

exc

han

ge r

ate120572

(tt

)

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


3700

3800

3900

4000

4100

4200

4300

4400

0 100 200 300 400


Natural depletion

2

3

4

5

6

8

10

Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




2throughout



125

13

135

14

145

15

155

16

310

320

330

340

350

360

370

380

390

0 2 4 6 8 10 12


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

04

08

12

16

2

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)





14

145

15

155

16

350

355

360

365

370

375

380

385

390

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)




2




2with the oil











2oil recovery


05

07

09

11

13

15

200

250

300

350

400

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50






Dai

ly o

il p

rod

uct

ion

rat

eQ

oild

(t)







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50






Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




5 Conclusions





2




Competing Interests


Acknowledgments


References
























2huff-























2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


3700

3800

3900

4000

4100

4200

4300

4400

0 50 100 150 200 250 300 350 400


Natural depletion








Cu

mu

lati

ve o

il p

rod

uct

ionΔQ

oil

(t)





120572 =Δ119876oil119876reag (3)








0

02

04

06

08

1

12

14

16

18

0

50

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600 700


Oil

exc

han

ge r

ate120572

(tt

)

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


3700

3800

3900

4000

4100

4200

4300

4400

0 100 200 300 400


Natural depletion

2

3

4

5

6

8

10

Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




2throughout



125

13

135

14

145

15

155

16

310

320

330

340

350

360

370

380

390

0 2 4 6 8 10 12


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

04

08

12

16

2

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)





14

145

15

155

16

350

355

360

365

370

375

380

385

390

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)




2




2with the oil











2oil recovery


05

07

09

11

13

15

200

250

300

350

400

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50






Dai

ly o

il p

rod

uct

ion

rat

eQ

oild

(t)







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50






Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




5 Conclusions





2




Competing Interests


Acknowledgments


References
























2huff-























2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


125

13

135

14

145

15

155

16

310

320

330

340

350

360

370

380

390

0 2 4 6 8 10 12


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

04

08

12

16

2

0

50

100

150

200

250

300

350

400

450

0 200 400 600 800


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)





14

145

15

155

16

350

355

360

365

370

375

380

385

390

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)




2




2with the oil











2oil recovery


05

07

09

11

13

15

200

250

300

350

400

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50






Dai

ly o

il p

rod

uct

ion

rat

eQ

oild

(t)







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50






Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




5 Conclusions





2




Competing Interests


Acknowledgments


References
























2huff-























2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


05

07

09

11

13

15

200

250

300

350

400

0 5 10 15 20


Oil

exc

han

ge r

ate120572

(tt

)

ΔQoil

120572

Incr

emen

tal

oil

pro

du

ctio

nΔQ

oil

(t)


0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50






Dai

ly o

il p

rod

uct

ion

rat

eQ

oild

(t)







0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 10 20 30 40 50






Cu

mu

lati

ve o

il p

rod

uct

ionQ

oil

(t)




5 Conclusions





2




Competing Interests


Acknowledgments


References
























2huff-























2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Competing Interests


Acknowledgments


References
























2huff-























2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of






2generationrdquo



























Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Research Article Numerical Simulation and Optimization of...

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