Indian Journal of Chemical Technology Vol. 19, September 2012, pp. 366-370

Use of an effluent for enhanced oil Na-lignosulfonate, which is chosen as an alternative recovery surfactant source because it is derived from Subrata Borgohain Gogoi* & Borkha Mech Das bamboo which is renewable and abundantly available Department of Petroleum Technology, Dibrugarh University, in this region. Na- lignosulfonate is available in Dibrugarh, 786 004, India effluent from and mills. Several studies of lignosulfonate showed increased interfacial activity Received 1 September 2011; accepted 27 February 2012 between oil and petroleum sulfonate upon the addition of lignosulfonate2,3. However, the quantity of This paper reports the effect of using black liquor and spent lignosulfonate required for lowering the IFT should sulfite liquors, which emanate as effluent from Nowgong Paper 4 5 Mill, Jagiroad, Assam, in enhanced crude oil recovery from be much smaller . In fact, De Groote and Monsoon Naharkotiya porous media. An attempt has been made to study the originated the idea of recovering oil from reservoirs effect of interfacial tension of black liquor and how it affects by means of spent liquors. The principal objective of the recovery of crude oil from the porous rock of Naharkotiya the work is to focus on the fundamental aspect of reservoir of Oil India Limited, Duliajan, Assam. The main surfactant flooding related to interfacial tension and constituent of black liquor is Na-lignosulfonate, an anionic water soluble surfactant. Addition of Na-lignosulfonate to crude oil enhanced oil recovery. emulsions gives rise to ultra-low inter-facial tensions between the oil and the aqueous phase, which are very much in demand in Experimental Procedure enhanced oil recovery projects. Reduction of interfacial tension leads to the release of residual oil droplets from the capillaries Materials in the porous media, thereby increasing substantially the amount The porous medium was obtained from a of petroleum obtainable from a given porous media. producing field of Deohal area obtained from a depth of 3856-3859m. The paraffin oil of viscosity (µo) Keywords: Black liquor, Critical micelle concentration, Enhanced 5.596×10-3 Pa-s and density (ρ ) 0.810 kg/m3 was col- oil recovery, Interfacial tension, Porous media, Residual o oil saturation, Sodium lignosulphonate lected from Digboi refinery. The brine solution is 3000 ppm of NaCl in DW having viscosity (µw) -3 3 It has been widely recognized that surfactant of 9.67×10 Pa-s and density (ρw) of 1 kg/m . flooding of petroleum reservoirs is an effective Analytical grade NaCl was procured from BDH means of recovering a fraction of the remaining oil, (Mumbai, India). Catflo-T (cationic polyelectrolyte) provided an ultra low IFT (interfacial tension) a deoiler, was supplied by Thermax, Pune, and used ( ≈ 0.001×10-3 N/m) between the oil and the aqueous to separate the emulsion. The surfactants used were solution containing surfactant is attained. Several BL (black liquer), anionic water soluble surfactant, types of petroleum sulfonate surfactants have been whose main constituent is Na-lignosulfonate from investigated for attaining such low interfacial Nowgong , Jagiroad; and TX (polyethyle- tensions. However, the high cost of petroleum neglycol 4-tert-octylphenol ether) a non-ionic sulfonate is one of the major drawbacks in surfactant water soluble surfactant, supplied from Research flooding processes. Laboratories Pvt. Ltd, Mumbai. Sodium lignosul- In this study, the IFT between surfactants fonate is stable at ambient temperature when kept BL(black liquor) and TX (Triton X 100) and open in the air, its instability temperature is not 6 co-surfactant IPA (isopropyl alcohol) in DW available . The density and viscosity of TX was (distilled water) and paraffin oil were calculated by 1.0694 kg/m3 and 1.076×10-3 Pa-s and that of IPA Hawkin’s Drop method1. It tries to investigate the was 0.8 kg/m3 and 1.091×10-3 Pa-s respectively. A possibilities of using BL alone and BL along with typical analysis of BL sample is given in Table.1. TX and IPA in EOR (enhanced oil recovery) Other constituents of BL are silica, lime, iron oxide, operations. The main constituent of BL is alumina, potash and sodium chloride in appreciable amounts, and organic matter varying within the limit —————— * Corresponding author. of 55-70 % of the total solids in BL. Sulphur and 3 E-mail: [email protected] water contents in BL are 6.04 kg/m and 79.41% NOTE 367

respectively as calculated by gravimetric analysis. The drop number and the number of houses the Total organic solids comprise mainly since the volume of drops occupy on the graph paper were raw material of this paper mill is bamboo. The BL recorded after 300, 600 and 900s. The number of oil contains sodium salts which also help in reducing the drops that passes from the nozzle of the capillary tube IFT of oil and water. But in this case, small amount through the aqueous phase of the external reservoir of liquor used contains only a negligible amount of when 1cc of oil was allowed to pass was recorded. Na salts. Therefore, some other component of the It was also observed that oil being lighter occupies liquor possibly the lignosulfonate must be responsible the top portion of the aqueous phase and the number in lowering the IFT. The co-surfactant chosen was of houses that the oil occupies was counted from iso-propyl-alcohol (IPA) [CH3 (CH2)5CH3] supplied the graph paper. IFT calculation was done using from Central Drug House (P) Ltd., Mumbai, India. the balance of IFT and buoyancy force equation, VF ∆ρg = 2πrσ F. The concentrations of surfactants Methods (BL and TX) on the X-axis and IFT on the Y-axis

Interfacial Tension were plotted to determine the critical micelle concen- Modified Hawkin’s Drop Weight method7 was tration (CMC) for each different surfactant. Above used to determine IFT (Fig. 1). The apparatus used a critical concentration depending on the structure of comprises a precision bore capillary tube attached surfactant molecules as well as the physicochemical to a stop cork and reservoir at the left hand end, condition, the surfactant molecule form aggregates terminating in a precision ground glass nozzle at called micelles. This characteristic concentration the right hand end. A small sample bottle was placed is the CMC. IFT was also measured for different over the precision nozzle and sealed in position. concentrations of co-surfactant (IPA).

After about 172800 s (2 days) of equilibration, the Permeability test IFT was determined. Initially the capillary tube and The permeability test was conducted in a the reservoir were filled with the oil phase, which was cylindrical section of 0.3048m length and 0.0381m done by pouring the oil through a funnel into the open and operated vertically as shown in Fig. 2. The setup end of the capillary tube till it reaches the nozzle end essentially comprises a cylinder packed with crushed keeping the stop cork open. The stop cork was closed and the oil phase was kept stable inside the capillary tube. The aqueous phase was poured into the sample bottle attached at the right hand end. Oil droplets were released from the open nozzle into the sample bottle through the aqueous phase and occupy the top portion of the aqueous phase in the sample bottle. A series of oil droplets were released from the nozzle, the volume of each being directly calculated from the air solvent movement in the external reservoir, with the help of a graph paper attached (Fig. 1).

Fig. 1—Apparatus for determination of IFT Table 1—Composition of black liquor Composition Amount (in %) Density (289 K) 1090 kg/m3 Total solids 16.1-16.5% 3 NaO 2C 3 as Na2O 29.04 kg/m (2.904) 3 Na 2S as Na2O 5.83 kg/m (0.583) 3 NaOH as Na2O 3.63 kg/m (0.363) 3 NaO 2S 4 as Na2O 1.16 kg/m (0.116) 3 Other compounds as Na2O 9.57 kg/m (0.957) 3 Fig. 2—Permeability apparatus [1- Stirrer, 2- Sample reservoir, Total Sodium as Na2O 49.23 kg/m (4.923) 3 3- Pump, 4 & 5- Pressure gauge, 6- Porous media, 7- By-pass, Na-lignosulfonate (approx) 132.58 mol/m 8- Sample collector] 368 INDIAN J. CHEM. TECHNOL, SEPTEMBER 2012

rock sample, pressure gauges, sample reservoir, Catflo (catalytic polyelectrolyte) supplied from sample collector, stirrer and a pump all connected by Thermax, Pune, India, with constant agitation by pipes of 0.0127 and 0.022225m outside diameter. means of a stirrer. Secondary brine flooding was The core sample was crushed in such a way that the carried out till residual oil saturation (Sor) was grains were not broken. The crushed grains were reached. It was discontinuous. Finally, surfactant made into a pack by using emseal, purchased locally flooding was done till residual oil saturation after and compressed uniformly in order to obtain a pack surfactant flooding (Sors) was reached and there was of uniform packing characteristics 8 and kept into the no further production of oil from the test sample. test cylinder. The permeability experiment was not carried out with the actual core obtained from the oil Results and Discussion field because the clay minerals in the actual core Interfacial Tension samples encountered problems like swelling and IFT between aqueous phase and oil phase was 9.10 also to gain further understanding of the physical measured with and without surfactant in the mechanisms of emulsion flow in porous media. The aqueous phase (Fig. 3). It is observed that the addition measured effective porosity by saturation method of surfactants reduces the IFT between the two before flooding was found to be 18.78 - 21.90%. phases. For a system the ratio of aqueous phase to The pack was covered with a sieve of 320 mesh size oleic phase is one, the IFT is 0.422×10-3 N/m when at the top and the bottom. Flooding solutions were the aqueous phase is DW and the oleic phase is stirred in the reservoir and injected at the bottom dodecane2. The IFT between DW and paraffin oil is of the cylindrical section at a constant volumetric found to be 0.861×10-3 N/m. When varying amounts flow rate of 0.0002m/s by self priming monoblock of BL is added to the aqueous phase the IFT is 186.425watt (0.25HP) pump supplied by Telco, 0.012×10-3 N/m at CMC of 0.34% BL in DW Coimbatore, India. The inlet and outlet pressure (Fig. 3). It is observed that when the aqueous phase valves of the cylindrical section were recorded from contains TX in DW, it has the lowest IFT and the pressure gauges. A constant superficial velocity of lowest CMC value compared to the others. The IFT -5 -6 -6 7.3×10 m/s+1.62×10 m/s and 3.472×10 m/s was and CMC values when 0.34%BL is mixed with TX maintained during the brine and surfactant flooding and IPA are shown in Fig. 4. The aqueous phase 1,2 steps respectively . Experiments were conducted comprises 0.34% BL and different % of TX or IPA at room temperature of 301.15+275.15K. The perme- in DW and the oil phase is paraffin oil. The CMC ability of the porous media was varied by adjusting values are represented graphically in Fig. 4. It is again the sand grain distribution using clay mineral through observed that when the aqueous phase contains washing and settling. The absolute permeability (Ko) TX in 0.34% BL it has the lowest IFT and the lowest of the porous media to brine was measured during CMC value compared to the others. initial brine flooding flow rate and pressure was constant. Paraffin oil was injected into the test sample saturated with brine and brine was displaced until the initial brine saturation (Swc) was reached. Finally, the relative permeability (Kro) of oil at Swc (intial brine saturation) was calculated. Towards the end of paraffin oil flooding the core sample will be saturated with Swc and Soi and then flooded by secondary brine. During secondary brine flooding the breakpoint (i.e. the point at which the first drop of brine comes out) was noted and the brine with oil, that flows out from the test sample, was collected in graduated test tubes. The difference in pressure was noted at about 5×10-6 m3, 10×10-6 m3, 20×10-6 m3, 40×10-6 m3, 80×10-6 m3, 130×10-6 m3 and 260×10-6 m3 effluent emulsion collection. Simultaneously, the relative Fig. 3—IFT between aqueous phase containing varying conc. permeabilities of the test sample to oil and water were of TX, IPA and BL in DW and oleic phase containing also calculated. Oil was separated by adding deoiler paraffin oil NOTE 369

Fig. 4—IFT in 10-3(N/m)vs amount of TX & IPA in 0.34% Fig. 6—Oil recovery by different surfactants

BL and BL in DW saturation of the wetting and the non-wetting phases.

The imbibition i.e. water seems to displace oil as in this case, the shapes of the curves (Fig. 5) describes how oil relative permeability (Kro) reduces from a minimum value of Swc and maximum value of Soi to Sor. The drainage i.e. oil seems to displace water as in this case, the shapes of the curves (Fig. 5) describes how water relative permeability (Krw) reduces from a minimum value of Swc to a maximum value. The values of maximum water permeability, and the shape of Kro and Krw curves depend on a number of factors. In these cases, Kro remains high and Krw remains low as water saturation increases. This means that water velocity remains lower than oil velocity until the point at which Kro and Krw are equal at crossover. This means that the ability of water

Fig. 5—Results of the permeability test on Naharkotiya to bypass oil is suppressed, as water breakthrough porous media during permeability experiment is delayed. As the cross over point is reached at water saturation of less Permeability than 50% in NH2 it is assumed to be oil-wet porous The results of permeability experiment when the medium12. The plot of relative permeability against porous media is flooded by brine are shown in water saturation (Fig. 5) resembles to that reported Fig. 5. The permeability tests were conducted from in literature13,14. the test data using JBN method in unsteady – state displacements. JBN method is essentially direct Oil recovery test calculation method stemming from the simplified Different surfactants are flooded through NH2 theory and formulation of immiscible displacement in (depth 3856-3859m) core sample after brine flooding porous media according to Buckley and Leverett11. in the permeability experiment. The relation between Figure 5 shows water saturation (Sw) in the forward surfactant and co-surfactant injected oil recovery is direction and oil saturation (So) in the backward shown in Fig. 6 and calculations are done applying 15 direction. The initial brine saturation (Swc) is about JBN (Johnson-Bossler-Naumann) method in unsteady 9.26% and initial oil saturation (Soi) is about 90.72% state displacements based on K= µLQ . It is observed in the porous media. Relative permeability is the ∆PA direct consequence of the different proportions of that the lower the IFT, the higher is the oil recovery. each fluid present in the porous medium and as Figure 6 shows that when injecting different such is directly dependent upon the percentage surfactant solutions the oil recovery is different. It is 370 INDIAN J. CHEM. TECHNOL, SEPTEMBER 2012

maximum when surfactant solution contains TX and lignin is mixed with petroleum based surfactants; least when it contains BL. The total pore volumes about 40-60% of lignin is added. of oil recovered during surfactant flooding are 9.04%, 22.02% and 15.58% when the surfactants Acknowledgement are 0.34%BL in DW, 0.34%BL, 0.305%TX in DW The author acknowledges thankfully the financial and 0.34%BL, 0.313%IPA in DW respectively. support by the University Grants Commission, India in the form a Research Project to carry out the study. Conclusion The properties of the emulsions used for the present study has been characterized in terms of References 1 Harkins W D & Brown F E, J Am Chem Soc, 41 (1919) IFT and are found to be suitable for enhanced oil 499-524. recovery. The interfacial tension is the lowest 2 Babu D R, Hornof V & Neale G, J Can Pet Tech, 23 (2) when the aqueous phase contains Triton X 100 either (1984), 48-53. in distilled water or in black liquor, followed by 3 Boon J A, J Can Pet Tech, 23 (1) (1984) 59-65. isopropyl alcohol and black liquor. Oil recovery 4 Son J E, Neale G & Honrof V, Can J Chem Engg, 60 (1982) 684. experiments are done and it is found that when the 5 De Groote M & Monson L T, US Pat 1823440 (Justia aqueous phase contains Triton X 100 at critical Company), 1931. micelle concentration the recovery is maximum 6 Material Safety Data Sheet Sodium Lignosulfonate MSDS, (6.75×10-6 m3) compared to the recovery by 0.34% 4, ScienceLab.com (accessed on 5.5.11). 7 Weatherley L R & Wilkinson D T, Process Biochem, 23 (5) black liquor alone and a combination of black (1988) 149-155. liquor and Isopropyl alcohol which are 2.66×10-6 m3 8 Pope G A, Lake W & Helfferich F G, Soc Pet Engr J, 18 and 5.06×10-6 m3 respectively. Compared to the (1978) 418-434. petroleum based surfactants for enhanced oil 9 Adamson A W, Physical Chemistry of Surfaces (John Wiley & Sons, New York), 1982, 649. recovery, lignin based surfactant systems combine 10 Shah D O, Surface Phenomena in Enhanced Oil Recovery the advantage of low cost and high brine tolerance. (Plenum Press. New York), 1977, 675-694. Lignin and are byproducts of pulp 11 Leverett M C, Trans Am Inst Min Metall Ret Eng, 142 and paper mills, thus are low priced and abundant (1942) 152-169. 12 Core Analysis, Application of Petrophysics and Reservoir throughout the world. A typical tree contains half a ton Engineering (Edinberg Petroleum Service Ltd), 2000, Chap of lignin for every ton of (paper component). 5, 51-53. Since lignin is produced from a source unrelated from 13 Morrow N R, Chatzis I & Lim H, J Can Pet Tech, 24(4) petroleum, the price of lignin is not tied directly to the (1985) 62-68. price of crude oil. And this decoupling is a significant 14 Al-Futaisi A & Patzek T W, J Contaminated Hydrology, 75 (2004) 61-81. advantage for enhanced oil recovery formulations. So 15 Johnson E F, Bossler D P & Naumann V O, Trans Am Inst far for enhanced oil recovery surfactant formulation, Min Metall Ret Eng, 216 (1959) 370-372.