SPE-184746-STU Application of Nanotechnology in EOR, Polymer-Nano Flooding the Nearest Future of Chemical EOR Mohammed Elkady, Al-Azhar University Copyright 2016, Society of Petroleum Engineers This paper was prepared for presentation at the SPE international Student Paper Contest at the SPE Annual Technical Conference and Exhibition held in Dubai, UAE, 26–28 September 2016. This paper was selected for presentation by merit of placement in a regional student paper contest held in the program year preceding the International Student Paper Contest. 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. Electronic reproduction, distribution, or storage of any part of this paper 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 SPE copyright. Abstract Oil reserve is the commercial oil which can be produced with current technology. Nanotechnology can enhance the ultimate oil recovery factor as we will show in many pervious experimental works such as improving CO2 flooding, improving heat transfer for heavy oil, interfacial tension reduction, wettability alteration through contact angle, reducing oil viscosity, Nano fluid flooding at reservoir condition and using Nano fluid slug. In this paper we will show experimental work related to using Aluminum Oxide Nanoparticles with polyacrylamide to make a new technique in chemical EOR methods called (Polymer-Nano flooding). Polymer-Nano flooding after polymer flooding can increase R.F with more than 2% of OOIP. Polymer-Nano flooding on a sample saturated with oil gave a R.F 66.29 %of OOIP slightly below the value of R.F (67.16 %of OOIP) of polymer flooding but with more than 40% cost reduction. Polymer-Nano flooding can alter the wettability through decreasing the value of Kw@Sor and that made the value of the intersection point of Kro & Krw curves increase which means that the rock became more water wet. Introduction The General mechanism of oil recovery is movement of the oil from reservoir to the production well, due to the pressure difference between this reservoir and this production well. Oil recovery is divided into three main types 1. Primary recovery: oil is forced out of the reservoir by existing natural pressure in this reservoir (without human being interference), such as water drive, gas cap drive, rock and fluid expansion drive, etc. 2. Secondary recovery: it refers to injecting water into aquifer or reservoir or injecting gas into gas cap zone to restore or maintain pressure, hence driving the oil to producing well (without changing the rock and fluid properties). 2 SPE-184746-STU 3. EOR (tertiary recovery): It refers to processes in porous medium that recover oil which is not recovered by the conventional methods (primary and secondary) by reducing the remaining oil saturation (residual oil and by-passed oil) ◦ ◦ Residual oil: oil trapped in the flooded area by capillary forces. By passed oil: oil in areas not flooded by the injected fluid. EOR categorized into three major recovery methods • • • Chemical recovery methods: Those in which additional chemical components are added to the injection fluid to improve mobility control through increasing the displacing fluid viscosity, reduce IFT, wettability alteration and to improve conformance in heterogeneous reservoir. These methods are polymer flood, surfactant flood, micellar flood and alkaline flood. Thermal recovery methods: They refer to introducing heat into heavy oil reservoir to reduce oil viscosity, enhance oil thermal expansion and in some reservoirs to cause distillation and thermal cracking. These methods are steam flooding, in-situ combustion or cyclic steam injection (huff & puff). Miscible recovery methods: They refer to using gas miscible with oil as CO2, N2 or LPGs to generate miscibility, increase oil volume (swelling) and reduce oil viscosity. Nanotechnology • • Nanotechnology describes the usage of particles which have a size less than 100 nm (nanoparticles) to gain more benefits through their unique properties due to their small size and their type, such as very high mechanical strength, very large surface area, catalytic properties, super conductivity and penetrability through very small medium. Nowadays nanotechnology has proved its efficiency in most oil and gas fields as exploration, drilling fluid, drilling bit, cement, well logging, stimulation and reservoir characterization and management. Nanotechnology in EOR The aim of EOR is increasing R.F through improving overall oil displacement efficiency. The overall displacement efficiency can be increased by improving the mobility ratio or by increasing the capillary number or both. • Mobility ratio is improving through increasing the displacing fluid (water) viscosity and/or reducing the displaced fluid (oil) viscosity. • Capillary number is increasing through reducing capillary pressure, due to IFT reduction and/or wettability alteration through contact angle. SPE-184746-STU 3 Pervious experimental works The following Pervious experimental works show the good effect of nanoparticles on R.F through the mechanisms explained above and others which aim also to improve R.F. ❖ Shah's work 2009 (Effect of Nano fluid with CO2 flooding on R.F) Shah showed that R.F increased when using Nano fluid with CO2 flooding instead of using CO2 alone. See tables (1) Table 1—observed weights for EOR studies Dry weight of the Berea sandstone core 342.7 g Dry weight of the Berea sandstone core 349.2 g Weight of the core after water saturation 370.3 g Weight of the core after water saturation 367.8 g Porosity 15.86 % Porosity 10.68 % Weight of the core after ANS oil saturation 368.0 g Weight of the core after ANS oil saturation 367.1 g Water displaced by ANS heavy oil 18 g Water displaced by ANS heavy oil 12.2 g Irreducible water saturation (%Swi) 34.78 % Irreducible water saturation (%Swi) 34.4 % Initial oil in place for the core 15.7 g Initial oil in place for the core 11.5 g Oil removed by CO2 gas core flood 9.1 g Oil removed by CO2 gas core flood 8.2 g % Recovery 58 % % Recovery 71.30 % The R.F increased from 58% to 71%, due to increasing the viscosity and density of CO2. ❖ Hamed's work 2010 (Effect of NPs on Heat Transfer for Heavy Oil) The highest thermal conductivity appeared when adding metal NPs as iron 0.5wt% to the heavy oil sample, as we see in figure 1 Figure 1—result of heat transfer experiment There was faster distribution of heat during recovery process. So, this can be applied to thermal flooding methods. ❖ Ogolo's work 2012 (Enhancing oil recovery by using NPs) Ogolo concluded that when adding different types of NPs to different injected fluid types such as (Distilled water, brine or ethanol), the R.F becomes higher than when using the fluid injected alone without NPs. see figure 2 4 SPE-184746-STU Figure 2—results of various Nano fluids used for EOR experiments • Distilled water flooding (without NPs): R.F was 25% of OOIP When adding Fe2O3 NPS to distilled water, R.F increased to be 34.2% of OOIP, due to increasing the viscosity of the displacing fluid (water viscosity). • Brine flooding (without NPs): R.F was 35% of OOIP When adding AL2O3 NPS to brine, R.F increased to be 40% of OOIP, due to reduction in displaced viscosity (oil viscosity). • Ethanol flooding (without NPs): R.F was 46.7% of OOIP When adding SiO2 NPs to ethanol, R.F increased to be 51.7%, due to change of formation wettability (reducing contact angle). ❖ Lucy's work (2013) (effect of NPs concentration on IFT and contact angle) Lucy concluded that IFT and contact angle decrease when NPs concentration increas, as shown in figure 3 SPE-184746-STU 5 Figure 3—IFT and contact angle mersuement Decreasing of IFT and contact angle leads to decreasing the capillary pressure, hence increasing the capillary number and hence increasing the R.F. ❖ Afzal's work 2015 (reducing the oil viscosity by using NPs) Afzal concluded that NPs can decrease the oil viscosity rapidly when added to oil at certain temperature and concentration, due to the catalytic effect of NPs on breaking of c-s and c=c bonds in big molecules as aqua-thermolysis process, as shown in figure 4 Figure 4—deviation of oil viscosity vs nano concentration When adding 0.2wt% Fe2O3 to the oil, viscosity reduced from 169.74 cp to 104.04 cp at 40 °c (oil viscosity reduced by more than38%) and reduced from 29.59 cp to 9.01 cp at 100 °c (oil viscosity reduced by more than 64%). 6 SPE-184746-STU ❖ Osamah's work 2015 (effect on NPs on R.F even at reservoir condition) Osamah found that when using mixture of NPs at certain concentration the R.F increased, even at reservoir condition (P=1600 psi, T= 1750F and salinity 160,000 ppm), as shown in fig.5 Figure 5—NPs oil recovery under reservoir condition Because of the chemicals which are used in chemical recovery methods are less effective at high water salinity and high temp, Osamah expected that NPS will be the best type of chemical flooding due to its good stability at reservoir condition. ❖ Mohamed Tarek's work 2015 (Effects of Nano fluid Mixtures on R.F) Tarek used mixture of NPs (40% Fe2O3+ 35% Al2O3 + 25% SiO2) suspended in brine water (3 wt. % NaCl). He conducted (Continuous injection after Nano-fluid slug). See figure 6 Figure 6—using nano fluid slug SPE-184746-STU 7 Using drive water after injecting a Nano-fluid slug (of 1 PV) showed nearly the same oil recovery trend; so Tarek concluded that using Nano-Fluid slug (instead of continuous injection) may be better for economical matters. Experimental work (Polymer-Nano flooding) The author has chosen the polymer flooding because it's more common and applicable in flooding projects. ❖ Materials ▪ Polyacrylamide had been chosen because it is most extensively used in polymer flooding projects, due to its good effect on R.F. fig.7 ▪ Aluminum oxide (Al2O3) NPs had been chosen due to its good effect on R.F through IFT reduction and wettability alteration, as shown at previous experimental work. And it's cheaper than most NPs which have also a good effect on R.F. The size of alumina NPs used in the experiments was 50nm according to Scanning & Transmission Electron Microscopy images (SEM &TEM). fig.7 Figure 7—Polyacrylamide (Left), NPs SEM Scan (Middle), NPs TEM Scan (Right) ❖ Experimental Devices Figure 8—Porosimeter (Left), Permeameter (Middle), Saturator (Right) 8 SPE-184746-STU Figure 9—Flooding system ❖ Core preparation ▪ The following procedures were used to prepare the two core samples for the experiments: ➢ Sample Cleaning: • Hydrocarbons were extracted from the plug samples in a cool solvent reflux soxhlet using toluene. • Any salt present was leached from the samples using methyl alcohol in a solvent reflux soxhlet extractor. • The samples were dried in a regular oven at 85°C. ➢ Gas permeability measurements • The gas permeability was measured using a calibrated steady state permeameter with nitrogen gas as the flowing medium. • Gas permeability measurements were performed on the clean, dry samples in a Hassler core holder with an applied overburden pressure of 400 psig. Nitrogen gas was flowed through each sample and the differential pressure (across the sample) was measured using a transducer. The permeability value was calculated by application of Darcy's law. ➢ Porosity and Grain Density measurements • The grain volumes of the samples were measured using a calibrated helium gas volume expansion meter. • Bulk volumes were measured by mercury displacement using Archimedes principle. The samples were placed in an oven to let any possible surface mercury evaporate. • Pore Volume (ccs) = Bulk Volume (ccs) - Grain Volume (ccs) ▪ Porosity (%) = (pore volume/bulk volume) x100 ▪ Grain Density (g.cc-1) = Sample Dry Weight (g) / Grain Volume (ccs) ➢ Sample saturation • The selected samples were initially loaded into a saturation cell and evacuated for 3 hours. The cell was then filled with brine (3 wt.% NaCl). The pressure was increased to 2000 psi and maintained for about 24 hours. The brine-saturated samples were removed from the cell SPE-184746-STU 9 and weighed. The gravimetric saturated pore volume was calculated and compared to the gas expansion pore volume to verify complete saturation. • The cores were drained with the mineral oil (21c.p) until reaching the irreducible water saturation (Swi). The oil in place was then calculated. The properties and measurements of core plugs which were used in the experiments Table 2—core samples properties & measurements Core 1 2 Type Well sorted Sandstone Sandstone Length (cm) 5.53 4.27 Diameter (cm) 3.76 3.76 Porosity (%) 25.2 13.4 Permeability (md) 8266 1317 Swi (%PV) 20.2 15.1 Ko @ Swi 5292.9 715 Figure 10—core sample 1 (left) & core sample 2 (right) Experimental procedures ➢ For core sample 1 1. Water (brine) flooding and measuring relative permeability. 2. Normal polymer flooding (2000 PPM polymer) and measuring relative permeability. 3. Polymer-Nano flooding after step (2). Concentration of NPs (0.02 wt.%) with polymer (1000 PPM). 4. Polymer-Nano flooding after saturating the sample with oil. Concentration of NPs (0.02 wt.%) with polymer (1000 PPM) and measuring relative permeability. ➢ For core sample 2 10 SPE-184746-STU To check some of the results we repeated some steps on core sample 2 as follows: 1. Normal polymer flooding (2000 PPM) and measuring relative permeability. 2. Polymer-Nano flooding after step (5). Concentration of NPs (0.02 wt.%) with polymer (1000 PPM). ❖ Results Figure 11—Result of R.F after water, polymer and Polymer-Nano flooding on sample 1 Figure 12—Results of R.F after various flooding on core sample 2 SPE-184746-STU 11 Figure 13—values of Kro&Krw intersection after various flooding on core sample 1 Figure 14—values of Kw at Sor after polymer and Polymer-Nano flooding on sample 1 12 SPE-184746-STU • • • • • From the previous figures, we see that at sample 1, after the sample was saturated with oil it was flooded with brine; the R.F was 60.65 % of OOIP and the Kw @ Sor was 931 md; this made the intersection of Kro & Krw at 56.5 (%PS).(See table 5 & fig. 15) After that the sample was saturated again with oil and flooded the core with polymer (2000 PPM polymer); the R.F increased to be 67.16 % of OOIP and the Kw @ Sor was 189.03 md; this made the intersection of Kro & Krw at 68.8 %PS. (See table 6 & fig.16) Then when the core was flooded with Polymer-Nano flooding (2000 PPM polymer+ 0.02wt% NPs) after the last normal polymer flooding, the R.F increased to 69.3 % of OOIP (R.F increased by 2.14 % of OOIP). The sample was resaturated afterwards with oil and the last solution of Polymer-Nano was used as the same concentrations of polymer and NPs to flood the sample directly. In this flooding the R.F was 66.29 % of OOIP (R.F increased by 5.64% when compared with R.F of water flooding and decreased by 0.87 % when compared with the R.F of normal polymer flooding) and the Kw @ Sor was 170.3 md (Kw @ Sor decreased by 18.73 md when compared with the Kw @ Sor of normal polymer flooding). This made the intersection of Kro & Krw at 70 %PS (intersection of Kro & Krw increased by 1.2 % when compared with normal polymer flooding). (See table 7 & fig.17) To check the results; another sample (sample 2) was used for normal polymer flooding followed by Polymer-Nano flooding at the same concentrations as in sample 1. The R.F due to PolymerNano was found to be 2.12 % of OOIP more than normal Polymer flooding (nearly the same value of sample1 in which R.F also increased by more than 2% if OOIP). Table 3—Summary of the results are shown in the following tables sample Sor (% PS) R.F (% of OOIP) Kw @ Sor Intersection of Kro @ Krw(PV) Table. No Fig. No At water (brine) flooding 1 31.4 60.65 931 56.5 Table 6 Fig.19 At polymer flooding (2000 ppm) polymer. 1 26.2 67.16 189.03 68.8 Table 7 Fig.20 2 27.1 68.08 49.2 67 _________ At polymer-Nano flooding: (1000 ppm) polymer + (0.02 wt. %) NPs. 1 24.5 69.3 _________ 2 25.3 70.2 _________ ____________ At Polymer-Nano flooding: (1000ppm) polymer + (0.02 wt. %) NPs. 1 26.9 66.29 170.3 70 Table 4—comparison of the cost of materials used in polymer and Polymer-Nano flooding Normal polymer flooding Polymer-Nano flooding Materials used at 1 liiter 2gm polymer 1gm polymer + 0.2gm NPs Cost per USD 0.0688 0.0404 Table 8 Fig. 21 SPE-184746-STU 13 Table 5—water (brine) flooding relative permeability measurments Brine Saturation (% Pore Space) Kro* Krw* Krw/Kro 20.2 1.000 - - 25.4 0.671 0.005 0.01 30.2 0.506 0.012 0.02 34.0 0.404 0.019 0.05 37.9 0.331 0.031 0.09 40.9 0.268 0.039 0.15 45.3 0.203 0.054 0.27 48.7 0.164 0.067 0.41 51.3 0.136 0.078 0.57 53.9 0.115 0.087 0.76 55.9 0.101 0.096 0.95 57.8 0.088 0.104 1.18 59.4 0.075 0.111 1.48 60.4 0.064 0.116 1.82 61.4 0.056 0.122 2.16 62.3 0.051 0.128 2.51 63.2 0.045 0.135 2.98 64.1 0.037 0.141 3.82 65.0 0.031 0.146 4.80 65.8 0.025 0.153 6.24 66.8 0.016 0.161 9.85 67.6 0.009 0.167 19.20 68.6 - 0.176 - * Relative to Ko @ Swi Table 6—polymer flooding relative permeability measurments Brine Saturation (% Pore Space) Kro* Krw* Krw/Kro 20.2 1.00 - - 23.7 0.80 0.0015 0.00 27.3 0.65 0.0019 0.00 32.3 0.48 0.0028 0.01 38.1 0.33 0.0041 0.01 41.7 0.26 0.0052 0.02 44.8 0.22 0.0064 0.03 47.5 0.19 0.0078 0.04 49.9 0.16 0.0092 0.06 52.3 0.14 0.0105 0.07 54.5 0.12 0.0120 0.10 57.1 0.10 0.0136 0.14 59.0 0.08 0.0149 0.18 14 SPE-184746-STU Brine Saturation (% Pore Space) Kro* Krw* Krw/Kro 60.8 0.07 0.0162 0.23 62.6 0.06 0.0179 0.30 63.7 0.053 0.0190 0.36 65.1 0.045 0.0205 0.45 66.6 0.036 0.0224 0.63 68.2 0.027 0.0245 0.92 69.6 0.019 0.0274 1.42 70.9 0.014 0.0301 2.14 72.4 0.007 0.0330 4.45 73.8 - 0.0357 - * Relative to Ko @ Swi Table 7—Polymer-Nano flooding relative permeability measurments Brine Saturation (% Pore Space) Kro* Krw* Krw/Kro 20.2 1.00 - - 25.4 0.80 0.0005 0.00 30.0 0.64 0.0009 0.00 34.0 0.53 0.0018 0.00 39.7 0.40 0.0031 0.01 45.3 0.29 0.0042 0.01 49.2 0.23 0.0054 0.02 53.1 0.18 0.0058 0.03 56.1 0.15 0.0072 0.05 58.7 0.12 0.0101 0.08 61.9 0.09 0.0123 0.13 64.1 0.074 0.0152 0.20 65.8 0.061 0.0181 0.30 67.2 0.049 0.0204 0.42 68.7 0.035 0.0225 0.64 70.4 0.022 0.0253 1.17 71.9 0.009 0.0289 3.07 73.1 - 0.0322 - * Relative to Ko @ Swi SPE-184746-STU 15 Figure 15—water flooding relative permeability curve 16 SPE-184746-STU Figure 16—polymer flooding relative permeability curve SPE-184746-STU 17 Figure 17—Polymer-Nano flooding relative permeability curve 18 SPE-184746-STU ❖ Discussion • • • • At normal polymer flooding the main mechanism was mobility control, due to polymer fluid viscosity which improved the mobility ratio through increasing the displacing fluid. When Polymer-Nano flooding was performed it was found that there was more than one mechanism affecting the R.F as wettability alteration due to the presence of Al2O3 NPs and mobility control due to the presence of polyacrylamide. These experiments were conducted to show the effect of NPs with polymer in flooding. it was found that the R.F increased by more than 2 % of OOIP through two experiments not due to the improving mobility ratio enhancement only but due to wettability alteration caused by the presence of NPs. Comparing the intersection of Kro & Krw in Polymer flooding versus Polymer-Nano flooding, an increase of 0.2% is found at at Polymer-Nano flooding. This means that the rock was more water wet and this made the water flow more difficult and the flow of oil freer than before. The values of R.F in polymer and Polymer-Nano flooding were found near each other (67.16% of OOIP at polymer flooding and 66.29% of OOIP at Polymer-Nano flooding). It was also found that the difference was lower than 1%. However, the Polymer-Nano technique required materials were cheaper than normal polymer technique materials by more than 40 %. ▪ Polyacrylamide According to actual polymer flooding project in Egypt, the actual price of polyacrylamide used was 92,700 euro per 3000 kg. So 3000kg = 103,202.91 dollar (1 EUR= 1.1133 USD, at 05/07/16); so 1kg= 34.401 USD. ▪ AL2O3 NPs The average price of Aluminium Oxide Nano powder (50nm) is 30 USD per 1kg. So, when using Polymer-Nano flooding instead of normal polymer flooding, nearly half the amount of polymer can be saved by adding only a small amount of NPs, due to its low concentration (0.02 wt. %). which will be more cost efficient. Finally, Polymer-Nano flooding is a new technique in chemical EOR methods which has many advantages like polymer flooding technique and additional advantages due to presence of Alumina NPs as follows: ▪ ▪ ▪ ▪ ▪ Higher recovery factor (very near to polymer flooding recovery factor values). Having two main mechanisms: mobility control and wettability alteration. Cheaper than polymer flooding method and other expensive EOR methods. Not complex (easy to be applied in oil fields). Environmental and no fire hazards. ❖ future work More experimental work is currently conducted to understand the different factors affecting the new technology and to optimize all the parameter which include: • • • Flooding Polymer-Nano with various concentrations to show the highest R.F this technique can reach. Using Polymer-Nano slug flooding after water flooding to approach reality. Trying to show the stability of Polymer-Nano method at reservoir condition (high salinity, high temperature and high overburden pressure) SPE-184746-STU • 19 Crashing the polyacrylamide to become powder (nm in size), using it alone in flooding in various concentrations and then mixing it with Alumina NPs in order to show the effect of these processes on R.F. Conclusions ➢ Increasing the R.F by a few percentages will provide billions of dollars as additional profit. ➢ Nanotechnology can be chosen as one alternative method to unlock the remaining oil resources. ➢ Polymer-Nano flooding can be chosen to be the nearest future of the chemical EOR methods. Acknowledgements The author would like to thank: • • • Prof. Dr. Abdel Wahab Bayoumi, Dr. Sayyed Gomaah, Dr. Amir Mahdy, assistant lecturer Eng. Wael Hoziefa and Special thanks to Research Assistant Eng. Mohamed Tarek. The Egyptian Petroleum Research Institute (EPRI) and Belayim petroleum company (petrobel). Prof.Dr. Mohamed Hassan Elkady, Eng. Mahmoud Younis, eng. Zeyad Obaia and all who have helped me in this work. Nomenclature Krw Kro μo ρ v θ μ Ka Swi Ko @Swi Sor Kw@Sor = Water relative permeability = Oil relative permeability = Oil viscosity = Interfacial tension (IFT) = Darcy velocity = Contact angle = Water viscosity : Gas Permeability (mD) : connate Water Saturation (% pore volume) : Oil Permeability at connate Water Saturation : 0Residual Oil Saturation (% pore space) : Water Permeability at Residual Oil Saturation References 1. 2. 3. 4. Shah, R. D., (2009) "application of NANOPARTICLES saturated injection Gasses for EOR OF heavy oils" SPE paper-129539-STU presented at The SPE technical conference and exhibition held in New Orleans Louisiana, October 2009. 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