06_spe_haneffect Of Alkaline Preflush In An Alkaline-surfactant-polymer Flood.pdf

SPE 102564 The Effect of Wettability on Oil Recovery of Alkaline/Surfactant/Polymer Flooding Han Dong, Yuan Hong, and Weng Rui, Research Inst. of Petroleum Exploration and Development, PetroChina, and Dong Fan，Huabei Oilfield，PetroChina Copyright 2006, Society of Petroleum Engineers This paper was prepared for presentation at the 2006 SPE Annual Technical Conference and Exhibition held in San Antonio, Texas, U.S.A., 24–27 September 2006. This paper was selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax 01-972-952-9435.

Abstract The present paper summarizes the laboratory studies of the effect of wettability on oil recovery of Alkaline/Surfactant/Polymer flooding. The wettability of water-wet Berea sandstone was altered into neutral-wet and oil-wet conditions by using organic reactants. The wettability index of each core sample was determined using a modified Amott imbibition method. The displacement efficiency of Alkaline/Surfactant/Polymer flooding and Polymer flooding at the different wetting conditions was evaluated by laboratory coreflood experiments. The experiment results indicate that the displacement efficiency of water flooding and ASP flooding is markedly affected by the wettability of the core. The wettability is one of the important factors to determine the oil recovery of water and ASP flooding. Water-wet and oilwet conditions are favorable to obtain high enhanced oil recovery for ASP flooding. Contrast to ASP flooding, the influence of wetttability on oil recovery of polymer flooding was found to be minor for the three different wetting conditions. These results provide a guide to applying the ASP flooding and polymer flooding to the reservoirs with different wettability.

the end of 1980s and at the beginning of 1990s, numerous literatures reported the experimental work relating to the role of wettability in various aspects of oil recovery of water flooding . 3-9 In recent years, the laboratory studies of the effect of wettability on oil recovery of imbibition of aqueous surfactant solution concerning the spontaneous oil expulsion from oil- and water –wet low permeable chalk material, and low permeability fractured sandstone reservoirs were reported.10-14 In China, eight pilot tests of Alkaline-surfactant-polymer (ASP) flooding have been carried on since 1992. The enhanced oil recovery of these pilots is about 15～25%OOIP. The application of ASP flooding will play an important role in improving the oil recovery and keeping the stable production of Daqing Oilfield, the largest oilfield in east of China. Laboratory experiments have shown that microscopic flooding mechanism of ASP at the water-wet condition is obviously different from that at oil-wet condition.15 Unfortunately, the investigation of effect of wettability on the displacement efficiency of ASP flooding remains unexplored. The purpose of this paper is to quantify the effect of wettability on oil recovery of ASP flooding.

EXPERIMENTAL FLUIDS Two oil samples, a degassed crude oil of free water and a simulation oil, were used in these studies. The degassed crude oil was a single well sample collected from Daqing Oilfield. The simulation oil with the viscosity close to the reservoir crude viscosity in Daqing Oilfield was prepared by adding some kerosene into the degassed crude oil. The physical properties of the two oil samples are listed in the Table 1. Brine used in these studies was prepared in the lab according to the average composition of the produced water in Daqing Oilfield. The composition of the brine is listed in Table 2.

INTRODUCTION There is an important influence of wettability on multiphase flow in porous medium and hence on oil recovery. Consequently, there is a necessity for the oil industry to better understand the effect of wettability on oil recovery of water flooding and chemical flooding. The evaluation of reservoir wettability and its effects on oil recovery has been investigated extensively since 1950s.1-2 In

CORES Berea sandstone was widely used as a model rock in petroleum research. All cores used in these experiments were Berea sandstone purchased from USA, dried at 105℃. Core plugs were 3.79cm diameter and about 20cm in length. Air permeability of the cores was approximately 300-400md. The mineral composition of the cores is listed in Table 3. This sandstone is composed primarily of quartz, but also contains

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minor amounts of feldspar, dolomite and clay minerals. CHEMICAL REAGENT The surfactant (Commercial code: SY) used in the ASP formula is sodium alkyl benzene sulfonate with special structure. NaOH used in the ASP formula is commercial reagent.(A.R.) The polymer is modified partly hydrolysis polyarylamide (Commercial code: KY-26) made in China. The average molecular weight of the polymer is approximately 26 million. The wettability altering reagents employed in these studies were silicone oil and organochlorosilane (DCDMS and DCMPS). The silicone oil (SOI) was purchased in China. The organochlorosilane reagents were purchased in the USA. MEASUREMENT OF WETTABILIT The wettability of representative core samples were determined by modified Amott test. The Values of wettability index to water is Iw. The Values of wettability index to oil is Io. The relative wettability index is Iw-o (Iw-o=Iw―Io). MEASUREMENT OF IFT IFT between ASP system and oil was measured at 45℃ using a Texas model 500(II ) spinning drop interfacial tension meter. The change of IFT with time in two hours was recorded. The equilibrium IFT is the IFT value which the IFT is hardly changed with time. CORE FLOOD EXPERIMENT The core sample was inserted into a Hassler-type core holder at a confining pressure of 3.0MPa. After vacuumed, the core was saturated with simulation brine. The core permeability to brine was then measured using a constant rate pump and then flooded with oil at 45℃.After that the core was aged for 48hr. The water flooding was conducted until the water cut is approximately 98%. Then the slug of ASP or polymer was injected. The brine was injected again until the oil was not produced.

RESULTS AND DISCUSSION The formula of ASP and polymer flooding The formula of ASP flooding is composed of 0.2%(wt) SY, 1.0%(wt) NaOH and 0.15%(wt) polymer KY-26. The formula of polymer flooding is 0.1%(wt) KY-26. The basic properties of the ASP and polymer solution are listed in Table 4. The equilibrium IFT between the ASP solution and crude oil is about 2.3×10-3mN/m. The equilibrium IFT between the ASP solution and simulation oil is 3.4×10-3mN/m. The methods of altering the wettability of cores The wettability evaluation results of cores listed in Table 5 indicate that the wettability of Berea sandstone used in this

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research is water-wet. There are many methods that can be used to alert the wettability of core. In several investigations, the crude oil is used to control the wettability of Berea sandstone.4-9 The advantage of this technique is the active component adsorbed on the solid surface is much more close to the actual reservoir status. Its obviously disadvantage is that the degree of interaction between surface-active constituent in crude oil and the solid surface may depend on numerous factors, such as the choice of the crude oil, mineral composition, brine composition, aging temperature, initial water saturation, and pressure. It is very difficult to obtain the reproducible wetting conditions and to alert the water-wet Berea sandstone into oil-wet. The long aging time (at least ten days) and long research period is also a fatal shortcoming for this technique.4 The wettability of cores and other porous media was often altered by chemical treatment, usually with silicon oil and oganochlorosilane.7 The advantage of this method is that the special wettability conditions can be generated in short time. In this paper, the method of applying chemical treatment to alter the wettability was adopted. The water-wet Berea cores were treated by a kind of silicon oil (SOI) and two oganochlorosilane (DCDMS and DCMPS) reagents. The evaluation results of relative wettability index (Iw-o) of the cores treated by the 3% SOI in light hydrocarbon and the 33%DCDMS and 33%DCMPS in light hydrocarbon are listed in Table 4. The relative wettability Index (Iw-o) of the untreated Berea sandstone is 0.54. The Iw-o of the Berea sandstone treated with the silicon oil-SOI is 0.0. The Iw-o of the Berea sandstone treated with DCDMS is -0.39. The r Iw-o of the Berea sandstone treated with DCMPS is -0.51. It means that the water-wet Berea sandstone can be altered into neutral-wet by using silicon oil (SOI), and oil-wet by using the oganochlorosilane (DCDMS and DCMPS).

The effects of wettability on water flooding The simulation oil with the reservoir crude viscosity is also often used in core flooding experiments especially for water flooding and polymer flooding. But for the ASP flooding, in order to simulate the composition of the crude, degassed crude oil is often used for the formula study. For the same reason, degassed crude oil is also directly used in many core flooding experiments of ASP. Accurate evaluation of water flood recovery is the foundation to obtain accurate displacement efficiency of ASP. In this paper, the effects of wettability on water flooding recovery were investigated firstly by using the two oil samples. Laboratory water flooding experiment results in Berea core with water-wet, neutral-wet, and oil-wet wettability using crude oil and simulation oil are listed in Table 6 and Table 7. The data in Table 6 and Table 7 show that the effect of wettability oil recovery of water flooding is very obvious. For the two oil samples, the water flooding recovery at the neutralwet condition is much higher than that at the water-wet and oil wet conditions. Maximum oil recovery of water flooding was obtained at close to neutral wettability ( Iw-o=0). The result is consistent to that obtained in the core flood experiments that

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the wettability of core was controlled with crude oil.5 Comparing the water flood recovery of the two oil samples at same wetting condition, it can be found that the oil recovery of water flooding using simulation oil is higher than the oil recovery of water flooding using the degassed crude oil. It means that lower the viscosity ratio of oil and water is favorable to overcome the effect of viscous fingering and to obtain the higher water flood recovery.

The effects of wettability on ASP flooding Laboratory core flooding of ASP using crude oil The laboratory core flooding results of ASP using crude oil are summarized in Table 8. At the water-wet condition，the oil recovery of water flooding is 38.2%OOIP，the enhanced oil recovery of ASP is 28.6%OOIP, the total recovery of water and ASP flooding is 66.8%OOIP. At the neutral-wet condition, the oil recovery of water flooding is 44.3%OOIP， the enhanced oil recovery of ASP is 15.2%OOIP, the total recovery of water and ASP flooding is 59.5%. At the oil-wet condition，the oil recovery of water flooding is 37.4%OOIP ，the enhanced oil recovery Of ASP is 16.7%OOIP, the total recovery of water and ASP flooding is 54.1%. These results indicate that the oil recovery of ASP was remarkably affected by the wettability of core. The enhanced oil recovery at waterwet condition is the highest in the three wetting conditions. Laboratory of ASP using simulation oil Core flooding experiment results of ASP using simulation oil are presented in Table 9. The data in Table 8 further demonstrate that the oil recovery of water flooding and ASP flooding was affected by wettability of cores. Comparing the data in Table 9 with in Table 8, it was noticed that: (1) At water-wet condition, the enhanced oil recovery of ASP using simulation oil (approximately 17.4%OOIP) is much lower than the result obtained by using crude oil(28.6%OOIP), but the total recovery of water and ASP flooding (65.2%OOIP) is close to the result obtained by using crude oil (66.7)%. (2) At the neutral-wet condition, the enhanced oil recovery of ASP is only 12.3%OOIP, but the total recovery of water and ASP flooding (71.3%OOIP) is much higher than the result (59.5%OOIP) obtained by using crude oil. (3)At oil-wet condition, the enhanced oil recovery of ASP using simulation oil (approximately 17.6%OOIP) is close to the result obtained by using crude oil(16.7%OOIP), but the total recovery of water and ASP flooding using simulation oil (64.2%OOIP) is much higher than the result obtained by using crude oil (54.1%OOIP). These results can be served to indicate that the oil recovery of the reservoirs with different wettability can be improved by applying ASP flooding. The wettability of reservoir is one of the important factors to determine the water flooding recovery and the displacement efficiency of ASP flooding.

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The mechanism of the influence of wettability on oil recovery of ASP flooding remains to be investigated further. The effect of wettability on Polymer flooding Laboratory core flooding experiments of Polymer using crude oil The core flooding results of polymer using the crude oil in three different wettability conditions, such as water-wet, neutral-wet, and oil-wet, are listed in Table 10. Contras to the results of ASP flooding, it can be found that the effects of wettability on oil recovery of polymer are minor. At the water-wet, neutral-wet and oil-wet conditions, the corresponding oil recovery of water flooding is 39.5%OOIP， 48.9%OOIP and the 38.7%OOIP, and the enhanced oil recovery of polymer is 14.5%OOIP, 10.6%OOIP and 13.7%OOIP, the total recovery of water and polymer flooding is 54.0 %OOIP, 59.5%OOIP, and 52.4%OOIP. In a word, the difference of the enhanced oil recovery of polymer at the three wetting conditions is less. It means that polymer flooding is not sensitive to reservoir wettability. The results are accordance with the mechanism of polymer flooding. Core flooding experiments of Polymer using simulation oil The core flooding results of polymer flooding using the simulation oil in three different wettability conditions are listed in Table 11. The similar trend that displacement efficiency of polymer is not sensitive to the wettability of core was also observed in these experiments. CONCLUSIONS 1. The core flooding experiment results indicate that the displacement efficiency of water flooding is remarkably affected by the wettability of the core. The oil recovery of water flooding is optimum at close to neutral wettability(I=0.0). 2. The displacement efficiency of ASP flooding is also remarkably affected by the wettability of the core. The water-wet and oil-wet conditions are favorable to obtain high enhanced oil recovery for ASP flooding. 3. Contrast to the ASP flooding, the effect of wetttability on polymer flooding recovery was found to be minor for the three different wetting conditions. It can be concluded that displacement efficiency of polymer flooding is not sensitive to reservoir wettability. 4. For the laboratory core flooding experiment of ASP, it is necessary to reproduce the wettability of the reservoir in order to obtain the reliable evaluation results of water flooding recovery and enhanced oil recovery. ACKNOWLEDGEMENT This study is a part of the National Basic Research Program of China，“Fundamental Study on Enhanced Oil Recovery by

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Chemical Flooding and Microbial Flooding 2005CB221300” . The authors wish to thank the Department of Science and Technology of the P.R. China and Development Department of Science and Technology of PetroChina for providing fund for this work and permission to publish this paper.

REFERENCES 1.

Anderson,W.G.: ″ Wettability Literature Survey-Part6: The effect of wettability on Water Flooding, ″ JPT(Dec.1987) 1605-22.

2.

Cuiec, L.E. Anderson,B.: ″ Evaluation of Reservoir Wettability and Its Effects on Oil Recovery, ″ Interfacial Phenomena in Oil Recovery, N.R. Morrow(ed.), Marcell Dekker , New York (1990) P319-75.

3.

Morrow, N.R.: ″Wetabbility and Its Effect on Oil Recovery,″ JPT (Dec.1990) 1476-84.

4.

Anderson,W.G.: ″ Wettability Literature Survey-Part6: The Effect of Wettability on Waterflooding ″ JPT (Dec. 1987) P1605-22. P.P. Jadhunandan, Inst. Teknologi Bandung, and N. R. Morrow,: ″Effect of Wettability on Water flood Recovery for Crude-Oil/Brine/Rock System″, Paper SPE 22597, presented at the 66th Annual Technical Conference and Exhibition of SPE held in Dallas, TX, October, 1991.

5.

6.

Dou Jia, J. S. Buckley, and N.R. Morrow: ″Control of Core Wettability with Crude Oil, ″Paper SPE 21041, presented at the SPE International Symposium on Oilfield Chemistry held in Anahaim, California, 18-21 February, 1991.

7.

Anderson, B.: ″Wettability Literature Survey-Part1: Rock-OilBrine Interactions and Effects of Core Handing on Wettability, ″ JPT (Oct.1986) P1125-1143. Dubey, S.T. and Waxman , M.H.: “Asphaltene Adsorption and Desorption From Mineral Surfaces, “paper SPE 18462 presented at the 1989 SPE International Symposium on Oilfield Chemistry, Houston, TX, Feb . 8-10. Buckley, J.S. and Morrow N.R.,: “Characterization of Crude Oil Wetting Behavior by Adhesion Tests,” SPE paper 20263 presented at the 1990 SPE/DOE Seventh Symposium on Enhanced Oil Recovery, Tulsa, April 21-25.

8.

9.

10.

11.

T. Austad, and J. Milter: ″Spontaneous Imbibition of Water into Low Permeable Chalk at Different Wettabilities Using Surfactant, ″Paper SPE37236, presented at the International Symposium on Oil Field held in Houston, Texas, 18-21 Feb. 1997. Austad T., Matre B.,Milter J, Seavare A., OYNO L: “Chemical Flooding of oil Reservoir: PT8: Spontaneous Oil expulsion from Oil-and Water-wet Low Permeable Chalk Material by Imbibition of Aqueous Surfactant Solution, ” Colloids Surfaces, Sect A V137, Nos1-3, PP 117-129, 6/15/98 (ISSN09277757, 15 Refs.)

12.

Xie X., Morrow N.R.: ″ Oil Recovery by Spontaneous Ambition from Weak Water-wet Rocks, ″ Petrophysics Vol. 42, No. 4, PP313-322, July-Aug. 2001.

13.

Standnes D. C., Austad T.: ″Wettability Alteration in Chalk: Part 2: Mechanism for Wettability Alteration from Oil-wet to Water-wet Using Surfactant, ″J Petro. Sci. Eng., Vol. 28, No.3, PP123-143, Nov. 2000.

14.

Graue A., Bogno T.: ″Wettability Effects on Oil Recovery

Mechanism in Fractured Reservoirs, ″ Paper SPE 56672, presented at the Annul. SPE Tech. Conference held in Huston, Texas, 3-6 Oct. 1999. 15.

Tong Zhengxin, Yang Chengzhi, Yuan Hong: ″A study of Microscopic mechanisms of Surfactant/Alkali/Polymer, ″ Paper SPE 39662, presented at the annual symposium of SPE held in Tulsa, Oklahoma, 19-22, April 1998.

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Table 1 Property of Oil Samples Oil

Viscosity (45℃), mPa.s

Density (45℃),g/cc

Crude oil (Daqing Oilfield)

35.2

0.8524

Simulation Oil(Crude+ Kerosene)

9.0

0.8273

Table 2 Composition of Brine Composition

NaCl

KCl

CaCl2

MgCl2•6H2O

Na2SO4

NaHCO3

Total

Concentration (g/L)

2.294

0.13

0.042

0.017

0.075

1.860

4.456

Table 3 Mineral Composition of Berea Sandstone-- Analysis Results of X-ray Diffraction Mineral type and content（%） Core No. Quartz

Potash

Sodium

feldspar

feldspar

Total Content of Clay Calcite

Dolomite

Siderite

pyrite

Mineral（%）

B1-1

81.5

4.7

2.3

/

1.6

/

/

10.2

B2-1

82.5

3.5

1.3

/

1.9

/

/

10.8

Relative content of clay（%）

Ratio （%S）

Core No. S

I/S

I

K

C

C/S

I/S

B1-1

/

31

20

44

5

/

25

B2-1

/

23

9

48

20

/

20

S：montmorillonite

I：Illite K：Kleit C：Chlorite

Table 4 the Basic Properties of ASP Solution and Polymer Solution Oil ASP solution (0.2%SY-1.0%NaOH-0.15%KY-26 Polymer solution (0.1%KY-26)

IFT, mN/m

Viscosity, mPa.s

(45℃)

(45℃)

2.3×10

-3

33.2

3.1×10

-3

32.5

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Table 5 the Wettability Evaluation Results of Core Samples Core sample serial number

1-1

Wettability treatment reagent

untreated

Porosity， %

2-2-1 Treated

2-2-2 with

Treated

2-2-3 with

Treated

with

3%SOI

33% DCDMS

33% DCMPS

21.7

21.2

17.7

19.8

456

430

340

414

Oil saturation， %

73.4

73.6

75.8

77.8

Index of water-wet（Iw）

0.54

0.00

0.00

0.00

Index of oil-wet（Io）

0

0

0.39

0.50

Relative wettability Index（I ）

0.54

0.00

-0.39

-0.50

Wettability distinction standard

0.3≤I<0.7

-0.1≤I<0.1

-0.7≤I<0.3

Evaluation Results

Water-wet

Neutrality

Oil-wet

-3

Air permeability，×10 μm

2

Table 6 Laboratory water flooding experiment results using crude oil Core No.

2-5

Wettability Treatment

2-1

2-5-2

R2-6

2-9

R2-5

Untreated

Treated with SOI

Treated with DCMPS

Wettability

Water-wet

Neutral-wet

Oil-wet

Porosity， %

19.9

21.5

19.7

20.1

19

20.2

414

359

507

356

344

410

70.1

70.6

71.6

73.8

74.9

72.2

38.2

39.5

44.3

46.9

37.4

38.3

Reagent

-3

Air Permeability，×10 μm

2

Oil Saturation， % Oil Recovery of Water Flooding ，OOIP%

Table 7 Laboratory water flooding experiment results using simulation oil Core No.

R8

Wettability Treatment Reagent

Untreated

Treated with SOI

Treated with DCMPS

Wettability

Water-wet

Neutral-wet

Oil-wet

Porosity， %

20.3

20.6

20.1

19.3

19.1

18.6

396

414

356

344

436

381

Oil Saturation， %

74

67.8

73.9

73.3

72.8

74.2

Oil Recovery of Water Flooding ，OOIP%

47.6

45.7

59

58.3

46.6

45.9

-3

Air Permeability，×10 μm

2

2-3

R7

R2-9

R2-1

R2-10

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Table 8 Effect of Wettability on Oil Recovery of ASP Flooding for crude oil sample Core No.

2-5

2-5-2

2-9

Wettability treatment reagent

untreated

Treated with SOI

Treated with DCMPS

Wettability

Water-wet

Neutrality

Oil-wet

Porosity， %

19.9

19.7

19

414

507

344

Oil saturation， %

70.1

71.6

74.9

Composition of ASP Slug

0.2%1SY-1.0%NaOH-0.15%KY-26

Injection Volume of ASP， PV

0.3

Composition of Polymer Protection Slug

0.1%KY-26

Injection Volume of Polymer Protection Slug， PV

-3

Air permeability，×10 μm

2

0.3

0.3

0.2

0.2

0.2

Water Flooding Recovery ，OOIP%

38.2

44.3

37.4

Enhanced Oil Recovery of ASP，%OOIP

28.6

15.2

16.7

Total Recovery of Water and ASP Flooding ，%OOIP

66.8

59.5

54.1

Table 9 Effect of Wettability on Oil Recovery of ASP Flooding for Simulation Oil Core No.

R8

R7

2-1

Wettability treatment reagent

untreated

Treated with SOI

Treated with DCMPS

Wettability

Water-wet

Neutrality

Oil-wet

Porosity， %

20.3

20.1

19.1

396

356

436

Oil saturation， %

74

73.9

72.8

Composition of ASP Slug

0.2%1SY-1.0%NaOH-0.15%KY-26

Injection Volume of ASP， PV

0.3

Composition of Polymer Protection Slug

0.1%KY-26

Injection Volume of Polymer Protection Slug， PV

-3

Air permeability，×10 μm

2

0.3

0.3

0.2

0.2

0.2

Oil recovery of Water Flooding ，OOIP%

47.6

59.0

46.6

Enhanced Oil Recovery of ASP，%OOIP

17.4

12.3

17.6

Total Recovery of Water and ASP Flooding ，%OOIP

65.0

71.3

64.2

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Table 10 Effect of Wettability on Oil Recovery of Polymer Flooding for Crude Oil Core No.

R2-1

R2-6

R2-5

Wettability treatment reagent

untreated

Treated with SOI

Treated with DCMPS

Wettability

Water-wet

Neutrality

Oil-wet

Porosity， %

21.5

19.0

20.2

Air permeability，×10-3μm2

359

422

410

Oil saturation， %

70.6

73.8

72.2

Injection Volume of Polymer， PV

0.5

0.5

0.5

Oil recovery of Water Flooding ，OOIP%

39.5

46.9

38.3

Enhanced Oil Recovery，%OOIP

14.5

10.6

13.8

Total Recovery ，%OOIP

54.0

59.5

52.0

Table 11 Effect of Wettability on Oil Recovery of Polymer Flooding for Simulation Oil Core No.

2-3

R2-9

R2-10

Wettability treatment reagent

untreated

Treated with SOI

Treated with DCMPS

Wettability

Water-wet

Neutrality

Oil-wet

Porosity， %

20.6

19.3

18.6

Air permeability，×10-3μm2

414

344

381.0

Oil saturation， %

67.8

73.3

74.2

The Composition of Polymer Slug

0.1%KY-26

0.1%KY-26

0.1%KY-26

Injection Volume of ASP， PV

0.5

0.5

0.5

Oil recovery of Water Flooding ，OOIP%

45.7

58.3

45.9

Enhanced Oil Recovery，%OOIP

10.7

7.9

12.6

Total Recovery，%OOIP

56.4

66.2

58.5