Langmuir 1995,11, 1760-1767
1760
Competitive Interactions between Water and Organic Solvents onto Mineral Solid Surfaces Studied by Calorimetry Thierry Zoungrana, Abderrahim Berrada, Jean-Marc Douillard,” and Stanislas Partyka Laboratoire des Agrkgats Moleculaires et Matiriaux Inorganiques, URA 79, USTL, Place EugBne Bataillon, 34095 Montpellier Cedex 05, France Received May 19, 1994@ Investigations have been carried out on several systems to compare the strength of the solifliquid interactions. Possible industrial implications for the results have guided the choice of the studied systems beeing mineral oxidelwater and mineral oxidelpyridines systems. Immersional enthalpies of the solids in different solvents including water and pyridines as well as adsorption densities of pyridines from water onto solids have been measured. Each of these experiments proved that pyridines could be adsorbed preferentially to water on the studied solids. In order to establish if pyridine can also displace water from the oxide surface, immersion of the solid with preadsorbed water vapor in pyridine has been performed. The obtained results show a possible displacement of the water by the pyridine from the solid surface. The reverse experiment, i.e. immersion of the solid with preadsorbed pyridine vapor in water, has also been run showing that, apparently, water is able to displace pyridine from the solid surface.
Introduction Extraction of petroleum from a reservoir is a complex problem. For several years, scientists and engineers have made a lot of effort to understand the interactions between the natural or model rocks and crude oi11,2because, on the average, only 5-25% of the total oil in place in a n underground reservoir can be recovered by natural depletion. Another 10-20% more oil may be extracted by secondary recovery techniques such as waterflooding or gas injection. The last fraction of the recoverable reserves can be extracted by tertiary recovery techniques, also called Enhanced Oil Recovery techniques. The amount of recovered oil is closely linked to the wettability of the rocks. These rocks are essentially composed of carbonates, clays, and silicates. Initially, i n the absence of any organic species, these minerals a r e hydrophilic and thus totally wetted by water. But, surprisingly, many wells seem to be rather hydrophobic, which involves a lot of economical problems linked to oil recovery. The fact is that, in many cases, during the history of these wells, the rocks undergo a wettability inversion and become hydrophobic. One of the hypothesis put forward to explain this change is based on a physico-chemical process, i.e. the adsorption of a polar organic molecule able to migrate from the oil phase to the solid surface and to adsorb preferentially to water on this solid surface, giving to the latter a n hydrophobic naturea3 The aim of this work is to bring some informations which could explain the interfacial processes occurring i n t h a t kind of systems; this is a quite complex problem since the predicability of these phenomena is related to the heterogeneity ofthe real solid surface^.^,^ However, two basic questions can be distinguished, namely, the following. What are the minerals of the rocks involved in the oil retention phenomenon?
* To whom all correspondence should be addressed.
Abstract published in Advance ACS Abstracts, May 1, 1995. (1)Gonzalez, G.;Moreira, M. B. C. Colloids Su$. 1991,58, 293. (2) Buckles, J. S.: Takamura, K.: Morrow. N. R. SOC.of Pet. E m . 16964,1987,-317. (3) Van Olphen, H. J. J. Colloid Interface Sci. 1988,28, 370. Everett.D. H.AdsorDtion ofGases on Heterogeneous (4)Rudzinski,W.: ’ Surfaces;Academic Press: London, 1992. (5) Rudzinski, W.; Charmas, R.; Partyka, S. Colloids Surf. A 1993, @
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Which molecules from t h e oil phase are able to be responsible for the oil retention effect? This contribution consists to define, i n comparison with water, the relative affinity of polar molecules toward minerals contained in the reservoir. On one hand, as we said before, the minerals usually found in the reservoir rocks are carbonates, clays, and silicates. That is the reason why we chose silica, quartz, calcite, kaolinites, and illites as solids samples. On the other hand, according to a theoretical study of Binet and Toulhoat,6pyridines seem to be the kind of molecules possessing the ability to be at the origin of a wettability change. So, taking into account these data, we studied the interactions between solids such as silica, quartz, calcite, kaolinites, and illites and liquids such as water and pyridines by both adsorption and calorimetric methods.
Experimental section Materials. Silica is a synthetic precipitated silica supplied by RhBne-Poulenc-France. Quartz supplied by Sifraco is a crushed quartz. It was washed with boiling 2 N HC1 during 2 hours and rinsed with distilled water in order to remove the organic impurities which could screen the adsorption properties of the solid surface. Calcite has been supplied by Merck. The kaolinite from Ploemeur,France (kaolinite 11,is an hydrothermal, well-crystallized kaolinite. It is almost pure, i.e., there are only a few structural defects. The kaolinite from Charentes, France (kaolinite 21, is a sedimentary kaolinite. The kaolinite from Provins,France (kaolinite3), is a sedimentary and disorganized kaolinite coming from the alteration of chalk and containing 8% quartz. The illite from Hungary (illite 1) is an hydrothermal and interstratified illite 85%illite-15%beidellite. The illite from Brives-Charensac, France (illite 2), is generated by transformation (ions fixation) and is ferromagnesian. Kaolinites and illites have been supplied by the “Centre de Recherche sur la Physico-Chimie des Surfaces Solides” from Mulhouse, France. Pyridine has been supplied by Fluka. Its punty is over 99.8%. 2-Ethylpyridinehas been supplied by Aldrich. Its punty is over 97%. Benzene has been supplied by Fluka. Its purity is over 99.5%. Heptane has been supplied by SDS. Its purity is over 99%. (6) Binet, L.; Toulhoat, H . Adsorption de moliculespolaires sur des sites superficiels de la silice: modklisation par MOPAC via CHEM-X; IFP Report; IFP: Rueil-Malmaison, France, 1990.
1995 American Chemical Society
Competitive Interactions Studied by Calorimetry
Langmuir, Vol. 11, No. 5, 1995 1761
Table 1. Specific Surface Areas of the Solids
solids silica quartz calcite kaolinite 1
specific surface area (m2g-l) 15 6 0.7 15
solids kaolinite 2 kaolinite 3 illite 1 illite 2
Table 5. Mineralogical Impurities in the Clays
specific surface area (m2 g-l) 21 47 37 127
Table 2. Size Distribution of the Solid Particles
mean diameter Ocm)
limits solids silica 0.2 pm < d < 0.3 pm l p m < d < 10pm quartz l p m < d < 20pm calcite 6.35 0.35pm < d < 35pm kaolinite 1 0.8 0.15pm < d < 3pm kaolinite 2 0.74 0.15pm < d < 4pm kaolinite 3 2.61 0.25pm < d < 8pm illite 1 illite 2 3.3 0.15pm < d < 13pma a In fact, the particles of illite 2 are smaller but they are very associated. Table 3. Weight Percentage of the Chemical Elements in the Calcite
99.75
traces
0.02
0.06
0.1
