Petroleum Sulfonates as Oil Displacement Agent and Application Shengchun Xiong 1, a Ying He 1, b and Maolei Cui 2, c

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1 Advanced Materials Research Online: ISSN: , Vol. 529, pp doi: / Trans Tech Publications, Switzerland Petroleum Sulfonates as Oil Displacement Agent and Application Shengchun Xiong 1, a Ying He 1, b and Maolei Cui 2, c 1 Research Institute of Petroleum Exploration and Development-Langfang, Langfang, China 2 Research Institute of Petroleum Exploration and Development, SINOPEC, Beijing, China a xshch0000@sina.com, b @qq.com, c @qq.com Keywords: Polymer Flooding; Petroleum Sulfonate; Oil Displacement Agent; Interfacial Tension Isogram; Dynamic Interfacial Tension; EOR Abstract. In terms of the condition of injection water after polymer flooding of Gudao oilfield, the following water quickly broke though the bank to the production wells, while most of residual oil remains in the formation. To solve the problem, two kind of petroleum sulfonates made in China are selected to form oil displacement agent (ODA) solution. The petroleum sulfonate available for crude oil of Gudao oilfield with the ultra-low interfacial tension is found by drawing an oil/water interfacial tension contour diagram. The results show that the interfacial tension can be lower than mn/m when the active agent contained with 0.25%KPS+0.225%APS, and the agent reduces water resistance of entering the hole to improve sweep coefficient and oil displacement efficiency. The existence of the polymer has no influence on the balanced value of interfacial tension, but just delays the interfacial tension to reach the balance. Pouring into 0.3 pore volume (PV) high-efficient ODA can improve 17% oil recovery. Synergistic effect of two kind of petroleum sulfonate with low cost to enhance oil recovery will have a great prospect for enhanced oil recovery (EOR) Introduction Producing ultra-low interfacial tensions is one of the most important mechanisms for enhancing oil recovery with respect to surfactant flooding. Surfactant flooding aims at producing the residual oil remained after secondary recovery with water flooding or gas injection. The petroleum sulfonate can be used as surfactant for making the water/oil interfacial tension reach ultra-low value and driving crude oil out to improve oil recovery. The oil composition of raw materials for producing petroleum sulfonate is complicated, and the sources for sulfonate are different, so the petroleum sulfonate is made up of complicated mixture and different molecular structure. And it is difficult to take sulfonate as the single component to combine and study on its interface chemical property of sulfonate. When designing a prescription of sulfonate at present for strengthening EOR efficiency, the average molecular weight and active component of the sulfonate are usually concerned. Petroleum sulfonate is widely and inexpensive. It is suitable for temperature below 120 and formation water salinity lower than mg/l.gudao oil field layer 3-4 oil reservoir temperature is about 70 and the water salinity is up to 6049mg/L. The petroleum sulfonate can be chosen as the oil displacement agent for Gudao oilfield. Experimental Apparatus and Reagents KPS provided by Kelamayi Chemical plant is a kind of petroleum sulfonate. Average relative molecular weight is 485, Effective content is 44.56%, Kraft value is about 40, aromatic ring is less but more alkyl radical base Figs in hydrocarbon radical. The average relative molecular weight of APS made in An'qing Chemical plant is 540. The effective content is 35.20%, Kraft value is about 27, aromatic ring is more but less alkyl radical base Figs in hydrocarbon radical (Guo et al., 2003). Crude oil of Gudao oilfield includes bitumen 12.42% with acid value mgKOH/g, colloid 20.65%, density g/cm3, and 70 viscosity 237mPa.s. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (# , Pennsylvania State University, University Park, USA-18/09/16,22:30:12)

2 Advanced Materials Research Vol HPAM parameters: content 91.37%, hydrolysis degree 32.48%, relative molecular weight The experimental water is formation water produced by Gudao oilfield, and its analysis result of sample is tabulated in Table 1. Texas500 interface-tension instrument, Model DDSⅡA Type conductivity instrument, Abe refract light instrument, purple-outside spectrophotometer, PHS-2A type accurate acidity instrument, 1/10000 electronic balance and flow device. Water type PH Table 1.Experimental Water Analysis. Ion Concentration mg/l Na + Mg 2+ Ca 2+ Cl SO 4 HCO 3 Total salinity mg/l Formation water Flooding water 8.0cm Test Method Determination of the effective content surfactant: Take Regard Hyamine1622 as the standard liquid, and the mixed solution of Disulphine blue V and Dimidium bromide as indicator. Apply the titrimetric law to test the effective content of sulfonate surfactant. Determination of the oil/water interfacial tension. Adopt the Texas500 interface-tension instrument to determine the interfacial tension value under the temperature the same as formation zone. Measure the column diameter of oil in the capillary after it is stable. Calculate the equilibrium interfacial tension through the diameter data of the oil column. Drawing isogram of the interfacial tension. Regard quality mark in the prescription of two kinds of petroleum sulfonate as x-axis and y-axis. Points in the graph stand mass fraction of two petroleum sulfonate, mass fraction for this point corresponding x-axis and y-axis value. Finally, obtain the interfacial tension isogram. Results and Discussion Oil/Water Interfacial Tension Oil/Water Interfacial Tension without HPAM Use the Texas500 interface-tension instrument at 70 to test interface-tension of crude oil and petroleum sulfonate surfactant (ODA) solution contained with different mass fraction of KPS and APS. Mark the test values at different mass fraction in the graph, print the contour line, finally form the isogram graph. Fig.1. Crude oil/oda interfacial tension isogram graph. Apparently in Fig 1, mn/m isopleth forms a closed circle. In theory, any point in the circle area can produce ultra-low interfacial tension of crude oil and ODA aqeuous solution, and can be used as efficiency oil displacement agent. The minimum equilibrium interfacial tension ( mn/m) corresponding concentration is 0.25% KPS+0.225% APS. Interfacial tension is a major parameter for evaluating the interfacial performance of ODA flooding.

3 514 Optical, Electronic Materials and Applications II Because ODA is of mixture with different relative molecular weight, petroleum sulfonate with the same total mass fraction can be regarded as a kind of mixing surfactant. Fig1 is about oil/water balance interfacial tension (BIT) with different mass fraction. Fig.2. Relation between the surfactant and balance interfacial tension In Fig2, with the increase in the total mass fraction of ODA in the solution, oil/water balance interfacial tension value reduce first, and when mass fraction of ODA is up to 0.47%, the interfacial tension value reaches minimum. With the continual increase in the mass fraction of ODA, the interfacial tension value increases gradually. For mixing surfactant, the minimum of the interfacial tension corresponds to critical intermicellar concentration of surfactant in the solution. At the moment, surfactant monomer concentration is up to the highest value, forming the high interface density of surfactant, and making the interfacial tension reach the minimum value. Oil/water interfacial tension with HPAM In Fig2, when HPAM exists in the solution, 0.005mN/m isopleth forms an enclosed circle. As the one in Fig1, any point in the circle area of the graph can reach ultra-low interfacial tension between crude oil and ODA solution. The mass concentration corresponding to minimum equilibrium interfacial tension ( mn/m) is 0.25%KPS+0.225% APS. Compared Fig1 with Fig2, with the same concentration, the interfacial tension is identical. In the range that the error allows, the existence of HPAM will not change the equilibrium value of the interfacial tension. Dynamic interfacial tension The existence of the HPAM will not affect the equilibrium interfacial tension, but HPAM will influence the dynamic interfacial tension. Test dynamic interfacial tension (DIT) value of the crude oil and surfactant with 1750mg/L polymer or no polymer at different time. In Fig 3, two curves show that whether the HPAM exists or not, the final interfacial tension value is about mn/m. Without HPAM, the time to reach the final value about 52min is shorter than the solution with 1750mg/L HPAM about 132min. Because the existence of HPAM increases the viscosity of the solution, decreases the speed of the surfactant spreading to the surface of solution. When being applied to oilfield, the high-efficiency displacement agent will keep a long time in the oil reservoir, and the existence of the polymer will not affect the final interfacial tension in the formation. ODA Physical Flow Test ODA Optimum Consumption The experiment is divided into 7 groups with the physical modeling: Saturate the sandy model with water, then fill the model with crude oil, and flood water through the model, pour into ODA (0.25% KPS % APS) 0.02PV, 0.05PV, 0.1PV, 0.15PV, 0.20PV, 0.25PV, 0.3PV, 0.35PV and 0.4PV separately after HPAM flooding, then cease water-flooding until output water ratio up to 98%. Note down the change of the oil recovery during whole course. As we can see from Fig 4, pouring ODA into the model after polymer flooding, the final oil recovery will further increase up to 18%. When Polymer flooding, most of the crude oil of swept region is displaced by polymer, but the crude oil of the tiny narrow hole stay in the former place, because polymer can't enter the tiny narrow hole. The ODA can change the properties of the interface of oil and water, reduce the interfacial tension and decrease the polymer aqueous solution resistance of entering the tiny porous passage. With constant growth of ODA consumption from 0.02PV to 0.4PV, oil recovery increase continuously from 0.8% to 18%. After the consumption of ODA was more than 0.3PV, the increasing degree of the oil recovery reduced. When the consumption increase

4 Advanced Materials Research Vol from 0.3PV to 0.4PV, the oil recovery just rise 1%. When there is less ODA consumption, agent will be diluted and consumed by the stratum, can't play an active role to sweep the oil. On the contrary, excessive ODA can not fundamentally solve the problem. Proper ODA consumption can change property of interface, and excessive ODA is unreasonable in economy. In the laboratory experiment, the optimum consumption is 0.3PV. Fig.3. Relation between the surfactant and balance interfacial tension. Fig.4. Relation between the surfactant and balance interfacial tension Pressure, Water Ratio and Oil Recovery Curves Based on the optimized ODA consumption, select the 0.3PV as the optimum consumption to pour into the model. At first, pump the model to vacuum, then saturate the formation salinity water, and oil later. Drive with water until the out water ratio at 98%, pour HPAM 0.3PV 1750mg/L into the model, then input 0.2PV gels, wait and congeal 50h under 70. Change water drive again after freezing the glue and totally becoming and freezing until the out water content rises again to 98%, then inject 0.3PV ODA, finally, transfer to water drive until the out water recovery up to 98% again. Record the change of the oil recovery, water ratio and injection pressure in the whole course. The curves about injected fluid and water ratio or oil recovery are shown in Fig 5, and relation between volume injection fluid and pressure are shown in Fig 6. Fig.5. Relation between injection fluid pressure and oil recovery Fig.6. Relation between injection fluid porous volume and pressure

5 516 Optical, Electronic Materials and Applications II As can be seen in Fig5, from water-flooding beginning to water ratio up to 98% in the first stage, the oil recovery only reached 27% and the injection pressure gradually reduced to 0.01MPa. The residual oil remained in the formation without water swept. Due to improper mobility ratio between oil and water, following water flowed along the high permeability layer to the producing outlet, which caused water cut in a short time and reduced the sweep coefficient of water flooding. From the data of the injection pressure, less effective circulation of water caused the low injection pressure. After polymer flooding and gels injection, 0.3PV ODA was injected. The enhanced oil recovery reached 17% and final recovery was up to 75% under laboratory situation. The ODA can reduce the interfacial tension between oil and water. Synergistic effect of gels and ODA can simultaneously increase the sweep coefficient and oil displacement efficiency. Conclusion KPS and APS as ODA possess excellent capacity and efficiency in reducing the interfacial tension of the aqueous solution and the dynamic interfacial tension between oil and water and can decrease the tension of crude oil-water interface to ultra-low at very low mass concentration, 0.25% KPS % APS. The existence of the polymer wouldn t exert an influence on the balanced interfacial tension, but delay interfacial tension of the solution to reach the balance value. Injecting 0.3 PV high-efficient ODA could improve crude oil 17% recovery. Synergism effect of petroleum sulfonates, decreasing the cost of oil recovery, would have a great prospect for enhanced oil recovery. References [1] Zhongkui Zhao, Fei Liu, Zongshi Li..Dynamic interfacial tension between crude oil and novel surfactant flooding systems without alkali. Petroleum science and technology. (2006), p: [2] Qing You, Fulin Zhao et al. Research and application of deep plugging water in oil well. Drilling and Producing Technology (2007) p: [3] Caili Dai, Yefei Wang, Qiang Leng..Studies on Profile-control Oil-displacement Agent with Long Gelation Time for the Formation Far from Wellborn. Journal of Xi an Petroleum Institute (Natural Science Edition) (2003) p: [4] Smith J E..Performance of Polymers in Aluminum Citrate Colloidal Dispersion Gels. SPE (1995) p: [5] Mack J C, Smith E.Depth Colloidal Dispersion Gels improve Oil Recovery efficiency, SPE/DOE 27780, presented at the SPE/DOE 9th Symposium on Improved Oil Recovery, Tulsa, April 17-20(1994) p: [6] Fielding RC, Gibbons D H, LeGrand F P.In-Depth Drive Fluid Diversion Using an Evolution of Colloidal Dispersion Gels and New Bulk Gels: An Operational Case History of North Rainbow Ranch Unit, SPE/DOE 27773, presented at the SPE/DOE 9th Symposium on Improved Oil Recovery, Tulsa, OK, April 17-20(1994) p: [7] Bo Ye, Wei Xiong, Jing Xu..Study on suspend cross-liking system for deep profile control. Drilling and Production Technology (2005) p: [8] Caili Dai, Fulin Zhao, Jianhong Xiao..Studies on the reutilization techniques of the residual polymer information after polymer flooding.journal of Xian Shiyou University (Natural Science Edition) (2006) p: