Preparation and Characterization of Nanopolymeric Particles using Polymerizable Surfactants for Rock Wettability Alteration and Oil Production Improvement

Abstract

Improved oil recovery by polymer flooding involves injection of a mobility control agent (e.g. polyacrylamide and its hydrophobically associated derivatives) in order to displace the mobilized oil to the producing well, and improve seeping efficiency. In this study the authors reported about synthesis of hydrophobically associating polyacrylamide (HAPAM) prepared by free radical emulsion polymerization and its modified nanocomposite derivative. Chemical structure of the prepared latexes were proven through different techniques such as FTIR, 1H-NMR, 13C-NMR, Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), X-ray diffraction, while particle size and particle size distribution were characterized by dynamic light scattering (DLS) and thermal properties characterized by thermal gravimetric analysis(TGA) and differential scanning Calorimetry(DSC). Rheological solution properties for the prepared composites were investigated under various conditions such as polymer concentration, salinity, temperature and shear rate at simulated severe reservoir conditions of high temperature and high ionic strength to test their compatibility for enhanced oil recovery (EOR) applications. Flooding experiments carried out through one-dimensional sandstone packed semi-pilot model at simulated reservoir conditions. Based on the experimental results, the following conclusions can be drawn; 1. The optimum polymerization conditions were estimated through single factor and orthogonal experiments. 2. HAPAM-SiO2 nanocomposite prepared by introducing silica nanoparticles through one shot synthesis via aza Michael addition reaction, so we can overcome shortages arising from agglomeration and coagulation of modified silica particles during emulsion polymerization reactions.

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Conclusions 3. Dynamic light scattering analysis confirmed the presence of nano- sized silica particles in the system and TEM micrographs showed the core/shell morphology of nanoparticles. This illustrates that the polymerization reaction will progress certainly in the presence and on the surface of silica nanoparticles. 4. The prepared HAPAM copolymer and HAPAM-SiO2 nanocomposite had the perfect property of retaining the viscosity and strong non-Newtonian behaviors (i.e. exhibit shear thinning behaviour); so they can be considered as a promised EOR candidates for polymer flooding projects.

5. They respond to in situ reservoir stimuli (temperature, ionic strength, pH, and shear stress) also, show good thermal, rheological and salt resistant properties even at reservoir conditions, and consequently improve sweeping efficiency. 6. HAPAM copolymer and HAPAM-SiO2 nanocomposite show resistance factor (RF) of 14.2 and 12.0 respectively, so they are suitable for producing improved shearing behavior and sweeping volume in EOR applications. Also, its observed that, adsorbed polymer layer thickness (e), are 1.4 µm and 1.3 µm for HAPAM and HAPAM-SiO2 respectively, which are thin layers so, low slug loss by stratum adsorption and will not cause pores plugging. 7. They effectively reduce interfacial tension to ultra low values, so increase mobilization of residual crude oil which resemble the behaviour of interfacial tension agents.

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Conclusions 8. In the core flood test, the recovered oil amount reach to nearly 48% and 60% of residual oil saturation (%SOr) in case of HAPAM and HAPAM-SiO2 respectively at concentration of 2000mgL-1and salinity of 40,000 ppm NaCl equivalent at flooding temperature of 90oC. 9. Wettability assessment by static sessile drop method indicate that HAPAM copolymer and HAPAM-SiO2 nanocomposite can alter rock wettability from oil-wet to water-wet, which in turn will increase recovery factor as there is a consensus in petroleum engineering that water-wet reservoirs recover more oil than oil-wet ones. 10. The preliminary feasibility study indicates positive economics for enhanced oil recovery through application of HAPAM and HAPAM-SiO2, as net profit per bbl of incremental oil reach to $ 38.16 and $ 42.21 per bbl in case of HAPAM and HAPAM-SiO2 respectively. 11. Since limitation of any chemical flooding process is the cost of chemicals required to achieve significant recovery. In this study, chemical cost per barrel of oil reach to $1.17 and $ 0.96 in case of HAPAM and HAPAM-SiO2 respectively, while slug efficiency reach to 8.0 and 6.4 lb /bbl oil in case of HAPAM and HAPAM- SiO2 respectively. This indicates high profits and high efficiency during flooding processes using these novel latexes. In addition to the aforementioned aspects, and to the best of our knowledge, no polymers had previously reported to alter sandstone rock wettability, consequently the novel copolymer and nanocomposite considered as a promised candidates for EOR applications as a wettability modifying agent in

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Conclusions

high temperature and high-mineralization oil fields as compared to currently applied commercial polyacrylamides. On industrial scale, there is a big hope that the novel latexes can play an important role in increasing recovered oil amount to bring out all of us from the current energy crisis, since applications of polymer flooding in the enhanced oil recovery (EOR) field has shown some successes to recover more than 26% additional oil from original oil in place (OOIP).